The 23rd International Meeting on Lithium Batteries

All-solid-state sodium batteries (ASSSB) are emerging as a viable energy storage technology due to the cost-effectiveness and high energy density. Halide-based electrolytes have shown potential due to their compatibility with high-voltage cathodes. However, most efforts to improve their sluggish ionic transport have focused on inducing amorphization via mechanochemical processes, leaving the direct impact of defect formation relatively unexplored. We demonstrate that introducing Schottky defects, specifically Na and Cl vacancies in NaTaCl₆, significantly increases ionic conductivity to 4.77 × 10^-4 S/cm without amorphization. Comprehensive experimental analyses and first-principles calculations reveal that these vacancies diversify the local Na environments, thereby lowering energy barriers. Furthermore, while high-energy ball milling effectively promotes partial amorphization, it also triggers unregulated defect formation, resulting in a wide range of conductivities. Our findings highlight the importance of defect engineering as both an alternative and complementary strategy to amorphization, offering a new route to designing high-performance sodium-based solid electrolytes.

Lithium metal batteries (LMB) are promising candidates for next-generation energy storage, however, their application is hindered by lithium (Li) dendritic growth, electrolyte degradation, and poor interface incompatibility. While composite solid polymer electrolytes (CSPEs) have been developed to mitigate these issues, but traditional CSPEs often, suffer from filler aggregation, inherent isotropy, and weak interfacial integrity, which limit efficient ion transport.

To overcome these challenges, we designed a ferroelectric nanoparticle decorated core–shell 3D nanoweb–reinforced composite solid polymer electrolyte (CSrCSE) that simultaneously stabilizes both the Li metal anode and the high-voltage LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode. The 3D framework consists of barium titanate (BaTiO₃, BTO) nanoparticles uniformly encapsulating a PVDF-HFP core, fabricated through coaxial electrospinning. By embedding these nanowebs were integrated within an in situ cross–linked poly (ethylene glycol) dimethyl ether (PEGDME)–based polymer matrix, forming a mechanically robust film that enables polarization-enhanced directional ion transport.

To develop a long-life energy storage system such as Li ion batteries is desired for solving the problems caused by intermittent nature of solar cells and wind mills. It has been well known that a long-cycle life Li ion batteries is desired for growing renewable applications such as solar cells and wind mills. Furthermore, the transportation electrification such as electric vehicles have been widely adopted in order to achieve 2050 net-zero carbon goals effectively. Recently, the fast-growing AI data centers push the high demand for battery cathode with high specific capacity and extended life. Thus, Ni-rich layered-oxide cathodes with grain size in µm range, namely single-crystal NMC, have been demonstrated and received great attention due to their superior performance in comparison to the nanosized polycrystalline NMC. 

For the grains of Ni-rich layered oxides to grow in µm range, several approaches have been demonstrated such as molten salt (flux) synthesis, high temperature calcination, and salt-assisted spray pyrolysis. Based on the grain-growth theory, larger grains grow by consuming smaller grains, caused by the thermodynamic driving force to minimize total surface energy in this oxide. The thermal energy is also needed for atoms to diffuse across the grain boundaries resulted in the boundary to migrate toward its center of curvature. 

In this study, the main objective is to investigate the influence of processing variables such as temperature and holding time period during solid state reaction. Through the understanding of crystallization and grain-growth mechanism, the single-crystal process may be optimized. Ni-rich layered oxides, namely NMC 811 or [Ni2+]>80% will be selected and prepared. The crystal structure and microstructure of cathodes are examined using XRD and SEM. The electrochemical properties are measured and conducted using CV, EIS and charge/discharge tests.

Intense efforts are deployed on conventional Li-ion battery technology to increase energy density. However, this technology is reaching its limit despite tremendous development of new more ‘energetic’ electroactive materials, such as high-voltage positive electrodes and silicon dopped graphite negative electrodes. The bottleneck stems particularly from the use of liquid electrolyte that can form unstable passivation layer (SEI, CEI, etc.) with these new electrode materials¹.

All solid-state battery emerged as a promising technology to enhance energy density offering potentially safer usage and more electrochemically stable solid electrolytes. The goal is to replace the flammable liquid electrolyte by a solid electrolyte that will act as ionic charge carrier media as well as electrical separator between the electrodes. On the one hand, the safety improvement of solid-state electrolyte relies on the (partial) suppression of flammable liquid while energy density gain mainly depends on solid-electrolyte-electrode interface compatibility. However, it seems evident that replacing a liquid electrolyte with a solid equivalent brings its own set of challenges². Among the challenges often mentioned is the wetting of composite electrodes porosity and interface contact quality including interfacial degradation.

Different solutions are being studied to ensure suitable electrode wetting with solid electrolyte including gel electrolyte (e.g. quasi-solid), electrolyte where liquid plasticizer(s) and lithium salt are trapped in a solid polymer matrix. The quasi-solid-state electrolyte should offer high ionic conductivity, large electrochemical stability window, suitable transference number and easy processing while ensuring safety. For the elaboration of the polymer matrix, two approaches are currently being investigated by ARKEMA i) one from polymer ex situ manufactured and ii) from a polymer that has been synthesized in situ starting from a liquid monomer/oligomer. The proposed in situ polymerization strategy provides a step toward effective electrode porosity wetting while keeping equivalent battery cell assembly procedure³. On the other hand, the ex situ gel polymer electrolyte approach offers various chemical components combinations⁴.

Through this study, we will detail the two approaches while highlighting their respective specificities in terms of processability. The resulting quasi-solid electrolyte will be investigated by means of physico-chemical characterization techniques (SEM, NMR, DSC, etc.) and electrochemical characterizations (EIS, CV, cycling, etc.). This study aims to evaluate the electrochemical performance of a gel polymer electrolyte and examining the impact of electrolyte elaboration, cell assembly procedure as well as electrolyte composition. The results showed that ARKEMA’s products are perfectly suitable for developing next generation of quasi-solid state batteries⁵.

Li-metal batteries (LMBs), based on Li-metal anode (LMA), can theoretically boost the cell energy density and specific energy, up to 500 Wh Kg⁻¹ and 1000 Wh L⁻¹.¹ However, LMA suffers instability issues with carbonate electrolytes especially at lower concentration (≤ 1.2 M), leading to low plating/stripping coulombic efficiency, lithium dendrite formation, and persisting safety concerns.² To address these challenges, ceramic and polymer solid-state electrolytes have been developed but their commercial realization is quite challenging due to inferior electrochemical performance driven by low ionic conductivity and high resistance at solid-solid interfaces.^3,4 In-situ processed gel polymer electrolytes (GPEs), encompassing liquid components immobilized within a polymer matrix, represent an industrially viable alternative by simultaneously providing superior performance, enhanced safety, possibility to use an existing commercial Li-ion manufacturing line.^5,6 We design herein a in-situ processed GPE, impregnated within a localized high-concentration electrolyte (LHCE)^7–9, having a total molarity ≈ 2.5 M, composed of non-fluorinated solvents and polymeric components, to optimally balance between performance and safety while maintaining significantly lower environmental footprints. The LHCE ensures high ionic conductivity and superior plating-stripping performance, while absence of non-coordinated/free solvents molecules ensures high voltage oxidative stability. In addition, its incorporation into a gelled matrix reduces electrolyte leakage, slows down parasitic reactions, and increases cyclability. This electrolyte system demonstrates 90% capacity retention in NMC811||Li cell over 200 cycles at charge-discharge rate of C/3 and 25 °C, while using active cathode loading of 3 mAh cm⁻² and positive electrode combination of 96: 2: 2 (wt.%). The Li||Li symmetric cells exhibited outstanding performance, cycling over 1500 hours at 0.33 mA cm⁻² current density and a fixed capacity of 1 mAh cm⁻², additionally it shows a critical current density (CCD) of 1 mA cm^-2 at 3 mAh cm⁻².

The widespread adoption of high-energy-density all-solid-state batteries demands solid electrolytes that combine broad electrochemical stability, fast ionic transport, and scalable processability. While halide-based solid electrolytes offer high oxidative stability, their commercial viability is hindered by high material costs and poor reduction stability, which precludes direct integration with low-voltage anodes. Here, we introduce a novel, low-cost family of aluminum-based oxychloride (Li-Al-O-Cl) solid electrolytes synthesized via a scalable mechanochemical route. Through systematic tuning of the oxygen-to-chlorine ratio, we elucidate a fundamental mechanistic tradeoff governing the reduction stability of amorphous halides. While increased oxygen incorporation delays the intrinsic reduction onset, excessive oxygen induces the segregation of a nanocrystalline LiCl impurity phase. Our structural and electrochemical analyses reveal that this residual LiCl acts as a nucleation site that prematurely triggers reductive decomposition. Guided by this insight, we identified an optimal composition, Li_1.1AlO_1.1Cl₃, which minimizes LiCl segregation while maximizing oxygen content. This optimized SE exhibits a high ionic conductivity of 3.77 × 10^-4 S cm^-1 and an extended intrinsic reduction onset of 0.9 V (vs. Li⁺/Li). Strikingly, Li_1.1AlO_1.1Cl₃ enables stable cycling below this intrinsic limit without requiring a secondary anolyte or protective coatings. When paired with a coating-free high-nickel cathode (NCM811), the full cell demonstrated robust operation with both 0.6 V-class and 0.3 V-class Li-In alloy anodes. The 0.3 V-class anode cell achieved an outstanding 91.5% capacity retention after 100 cycles, representing one of the most stable cycle performances reported for halide-based solid electrolytes paired with low-voltage anodes. Ultimately, this work establishes new design principles for solid electrolytes, demonstrating that rational anion tuning can redefine the anode compatibility of halide solid electrolytes, providing a viable pathway to realize high-energy-density solid-state batteries.

All-solid-state batteries (ASSBs) operate through electrochemical reactions that require efficient transport pathways for both electrons and ions within the electrode. In composite cathodes, the electron conduction network critically influences the power capability and initial capacity of the battery[1]. However, conventional electrochemical characterization methods provide only averaged electrical information and have limited capability to directly visualize electron transport pathways inside the electrode microstructure.

In this study, the electron conduction network in sulfide-based ASSB composite cathodes (NCM + Li₆PS₅Cl) was directly visualized using SEM-EBAC (Electron Beam Absorbed Current) in the RCI (Resistive Contrast Imaging) mode, which enables spatial mapping of electrical connectivity and resistance distribution[2]. Furthermore, the structural evolution of the conduction network was systematically investigated by varying the conductive additive content (0, 1.5, and 5 wt.%).

In the absence of conductive additives, electron transport was primarily governed by direct contacts between NCM particles, while the presence of Li₆PS₅Cl particles separated the active material and limited the formation of continuous conduction pathways. When conductive additives were introduced, electrical connectivity between NCM particles improved significantly across the solid electrolyte matrix, leading to the formation of cluster domains with similar resistance characteristics. These domains were distributed discontinuously within the electrode but became electrically connected to form a percolation-cluster-type electron conduction network.

With sufficient conductive additive content, clusters with relatively low resistance ranging from several hundred kΩ to tens of MΩ interconnected across the electrode, resulting in the formation of long-range conduction pathways corresponding to an infinite percolation cluster. These observations indicate that electron transport in ASSB composite cathodes is governed not by a homogeneous continuous network but by the connectivity of discrete clusters forming a percolation-based conduction structure.

This work provides direct experimental evidence of percolation-cluster-based electron transport in sulfide-based ASSB composite cathodes. Moreover, it demonstrates that EBAC/RCI is an effective technique for visualizing electron conduction networks within composite electrodes. The results further suggest that conductive additive content plays a crucial role in determining cluster formation and connectivity, offering new insights for designing electron transport pathways in ASSB cathodes from a percolation perspective.

Achieving Ah-class all-solid-state batteries (ASSBs) that combine high energy density with low cost remains a key barrier to practical deployment. Here we report dry-processed 2.5 Ah pouch ASSBs that deliver 20 mAh cm⁻², 555 Wh kg⁻¹, and a projected cost of 88 USD kWh⁻¹ under a mild stack pressure of 0.5 MPa, reaching critical energy–cost benchmarks in an Ah-class format. This advance is enabled by a monomer-in-salt polymer catholyte (MPC) derived from an inexpensive precursor. In its precursor state, high mixing entropy promotes uniform dispersion of active materials and conductive additives during solvent-free electrode fabrication. Subsequent in-situ polymerization within the cathode locks this homogeneity into a solid, single-phase catholyte network enriched in AGG/AGG⁺ coordination motifs, creating ionically percolated and mechanically robust Li⁺ pathways that are largely decoupled from polymer segmental motion. The resulting architecture improves through-thickness utilization and interfacial stability at high-mass-loadings, establishing a scalable route to high-energy, low-cost Ah-class ASSBs.

Stack pressure plays a critical role in the electrochemical performance of all-solid-state batteries (ASSBs) by governing interfacial contact as well as ionic and electronic transport within composite electrodes [1]. To date, ASSBs have predominantly been studied in pelletized press-cell setups operated at pressures exceeding 25 MPa [2]. In these systems, stainless-steel plungers act as current collectors, while rubber O-rings provide sealing. However, friction between plungers and sealing elements introduces uncertainties in the effective stack pressure, limiting their reliability for systematic investigations. In addition, these configurations differ significantly from practical battery architectures [3], highlighting the need for application-relevant sheet-type cell formats.

Here, we investigate the pressure-dependent cycling performance of composite cathodes in sheet-type ASSB pouch cells based on the argyrodite solid electrolyte (SE) Li₆PS₅Cl. Composite cathodes were fabricated via wet processing using LiNi₀.₈₂Co₀.₁₁Mn₀.₀₇O₂ (NCM82) as cathode active material (CAM). The CAM:SE ratio was systematically varied to tune the microstructure and transport pathways within the composite. The assembled cells consist of a composite cathode sheet, a solid electrolyte separator, and an intermetallic In/(InLi)_x counter electrode. Pressure-dependent behavior was evaluated by galvanostatic cycling while systematically adjusting the applied stack pressure.

The electrochemical performance strongly depends on cathode composition. Galvanostatic measurements at stack pressures between 0 and 25 MPa reveal that lower CAM fractions reduce overpotentials and improve discharge capacities, particularly at low pressures. Electrochemical impedance spectroscopy (EIS) at different states of charge and at 1 and 25 MPa indicates increased interfacial and transport resistances at low pressure, which are significantly mitigated with higher SE content. These results suggest that enhanced ionic percolation and improved interfacial contact govern the superior low-pressure performance of SE-rich cathodes. However, increasing the SE fraction reduces the achievable energy density.

Overall, these findings highlight a fundamental trade-off between electrochemical performance and energy density in composite cathode design. This study provides practical guidance for optimizing sheet-type cathodes for argyrodite-based ASSBs operated at low stack pressures and contributes to bridging the gap between fundamental pressure studies and application-oriented cell architectures.

Anode-free lithium batteries offer promising advantages, including increased energy density and the ability to address common mechanistic failures within the cell, thus increasing safety. One way that can make this possible is to control lithium nucleation. This could be achieved by reducing the overpotential required and implanting lithophilic nucleation sites in an anodic interlayer to aid in lithium ion transport and plating. The concept has been utilized in solid-state battery systems where electrolytes are solids with further improved safety and structural longevity. In this presentation, we discuss the use of a silver-holey graphene-based anodic interlayer that can be fabricated via direct dry compression without the use of solvent or binder. The addition of silver to the holey graphene matrix creates a route to lithium plating via a lower-energy intermediate. This idea is supported by the presence of a lithium-silver alloy that forms during the activation step. It is understood that the embedded silver acts as a nucleation site for lithium ions, thereby assisting in even plating. This control, combined with the added cushion of the holey graphene itself, can help reduce dendrite formation, ultimately increasing the safety and lifetime of the solid-state batteries. 

Research into halide solid electrolytes for all-solid-state batteries has intensified owing to their high ionic conductivity, oxidative stability, and mechanical ductility. However, the close-packed anion frameworks of conventional halides offer limited structural tunability, restricting further enhancement of bulk Li⁺ conduction. Here, we elucidate the fundamental mechanism of divalent-anion-driven framework modification in halide solid electrolytes and extend it through a universal oxychlorination strategy that enables controlled oxygen incorporation into diverse LiₓMCl₆ (M = Zr, Y, Er, and In) lattices. Structural analyses using synchrotron X-ray techniques, depth-resolved spectroscopy, and vibrational characterization confirm the formation of oxygen-containing polyhedral units within the halide lattice while preserving overall structural integrity. First-principles calculations reveal that the introduced oxygen locally distorts the anionic framework, destabilizes Li sites, and diversifies the Li–anion bonding environment, effectively widening Li⁺ conduction channels and flattening the migration energy landscape. As a result, Li⁺ transport is significantly enhanced. In addition, oxygen incorporation alleviates the thermodynamic driving force for hydrolysis, improving air and moisture stability while enabling improved electrochemical performance. These findings establish a broadly applicable lattice-level design principle for halide electrolytes, demonstrating that oxygen-anchored framework regulation can simultaneously enhance ionic conductivity and environmental stability in next-generation all-solid-state batteries.

All-solid-state batteries (ASSBs) require stable solid–solid interfacial contact, yet repeated volume changes of active materials often induce contact loss, interfacial delamination, and rapid capacity decay. While the mechanical stability of solid electrolytes has been commonly discussed using averaged properties such as Young’s modulus or hardness, the role of particle-derived microstructure in determining the effective mechanical response of separator pellets remains insufficiently understood. Here, we investigate how the particle size and particle size distribution of solid-electrolyte separators affect pellet microstructure, local mechanical heterogeneity, and ultimately cycling stability in Sn-composite ASSBs. Sn composite anodes were prepared using a fine solid electrolyte (D50 = 0.64 μm), while separator electrolytes with different particle sizes (D50 = 13, 1, and 0.64 μm) were comparatively evaluated. The submicron separator exhibited a sharper particle size distribution, more uniform cross-sectional microstructure, and the smallest standard deviation in local mechanical properties obtained from 100 picoindentation measurements. These results indicate that the effective mechanical response of separator pellets is governed not only by intrinsic material properties but also by particle-derived microstructure and surface uniformity. Cells employing the 0.64 μm separator showed improved cycling stability, along with reduced crack formation and better intimate contact at the composite separator interface after cycling. This study highlights microstructure-derived mechanical homogeneity as a key descriptor for interfacial stability and provides a practical design strategy for long-life ASSBs.

Solid-state batteries (SSBs) emerge as a highly promising alternative to conventional lithium-ion batteries (LIBs) that use liquid electrolytes, since they offer the potential for increased energy density and enhanced safety.[1] A key challenge limiting the adoption of SSBs is their need to operate under significantly higher stack pressures compared to LIBs.

Recent research has demonstrated the crucial role of the cathode microstructure with respect to reduced stack pressure requirements of SSBs.[2] This suggests an important interdependence between charge transport within the cathode and the performance of SSBs at lower stack pressures. Especially, the determination of effective electronic and ionic conductivities has been found to provide valuable insights into the charge transport properties of composite cathodes demonstrating that, e.g. volume fractions and the particle size distributions of the constituents heavily impact it.[3,4] Although the stack pressure can be expected to have a substantial impact on the microstructure, a systematic determination of charge transport properties in composite cathodes as a function of the stack pressure has not been reported.

We have determined effective electronic and ionic conductivities of composite cathodes consisting of a LiNi_0.82Mn_0.07Co_0.11O₂ and a Li₆PS₅Cl solid electrolyte at different stack pressures. To investigate how a change of the composite microstructure affects the pressure dependence of charge transport, we used solid electrolyte powders with different particle size distributions as catholyte. Our results show that the effective electronic conductivity is highly sensitive to pressure. While the effective ionic conductivity is less sensitive to pressure, it also diminishes at low stack pressures required for practical applications of SSBs. A reduced solid electrolyte particle size leads to higher ionic conductivity, but it has no influence on the pressure dependence as such. This demonstrates the need for solid electrolytes that do not only have an optimized particle size distribution but also tailored mechanical properties. Considering the strong pressure dependence of electronic charge transport, we tested SSBs cells with and without conductive carbon. The addition of carbon led to particularly pronounced performance improvements at lower stack pressure.

TiNb₂O₇ (TNO) exhibits a theoretical capacity of 387 mAh g^-1 and a redox potential of 1.55 V vs. Li⁺/Li. However, electrochemical properties and charge–discharge mechanisms of TNO in all-solid-state batteries (ASSB) remain unclear. In this study, we comprehensively evaluated the electrochemical properties of sulfide-based ASSBs using TNO, Furthermore, Li-ion diffusion behavior was investigated using operando scanning electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS).

The ASSBs were fabricated using composite electrodes consisting of TNO, carbon black and 70Li₂S･30P₂S₅ (LPS), along with an LPS solid electrolyte and an In–Li counter electrode. Electrochemical properties were evaluated by charge–discharge tests and electrochemical impedance spectroscopy. TEM samples were attached to a current collector and thinned to approximately 120 nm using a focus ion beam system. The thinned samples were mounted on a TEM holder and inserted into a TEM system (JEM-ARM300F2, JEOL). The holder was connected to a potentiostat, and EEL spectra were acquired during charge–discharge operation at 303 K.

Fig. 1(a) shows the cycling performance of the ASSBs at 333 K. The capacity retention and coulombic efficiency after 100th cycle were both 99%, demonstrating that TNO functions as a high-capacity active material ASSBs. Fig. 1(b) presents the dQ/dV profiles at various current densities, where the Nb-related peak shifted significantly with increasing current density, suggesting insufficient Nb redox reaction. Fig. 1(c) and (d) show annular dark-field (ADF)-STEM image and Li map during Li insertion and extraction. The Li concentration increased from the particle surface toward the center during Li insertion and decreased from the surface during Li extraction, indicating the formation of a core-shell structure. This behavior is attributed to the low Li diffusion in the core region, originating from Li–Li repulsion [1] and insufficient Nb redox activity. Therefore, the slow Li-diffusion in the core region also contributes to the limited charge–discharge performance under the high current densities.

Single‑ion conducting polymer electrolytes (SICPEs) are highly promising solid‑state electrolytes due to their ability to suppress concentration polarization and support stable Li‑metal cycling. Inspired by recent advances in COF‑based single‑ion conductors, this work aims to design a sulfonated β‑ketoenamine COF (TpPa‑SO₃H) integrated with a poly(ethylene glycol) diacrylate (PEGDA) matrix for solid‑state lithium metal batteries. The SO₃H‑functionalized COF is intended to act as an active single‑ion‑conducting scaffold, providing rigid, ordered nanochannels where fixed SO₃⁻ groups anchor the anion and promote exclusive Li⁺ migration. By infiltrating PEGDA into the COF pores and polymerizing it in-situ, we expect to form continuous Li⁺ transport pathways supported by synergistic ion-dipole interactions. This study focuses on optimizing COF synthesis, Li⁺ loading, PEGDA infiltration, and membrane fabrication to maximize Li⁺ transference numbers, enhance ionic conductivity, and improve Li‑metal interfacial stability. Overall, the proposed SO₃H‑COF/PEGDA hybrid SICPEs aim to enable safe, high‑performance solid‑state lithium metal batteries.

The widespread use of electric vehicles, energy storage systems, and wearable electronics has driven significant demand for rechargeable battery technologies that combine lightweight construction, high energy density, and robust mechanical stability. Wearable and deformable electronic devices, in particular, require battery architecture that can reliably operate under repeated mechanical deformations such as bending and folding [1]. Conventional copper and aluminum metal foil current collectors in lithium-ion batteries (LIBs) are prone to cracking, delamination, and electrode damage under such conditions due to their low yield strain and high stiffness. These factors are primary contributors to performance degradation and reduced cycle life. Additionally, although metal current collectors are electrochemically inactive, they constitute a significant portion of the total cell weight, thereby limiting improvements in gravimetric energy density.

To overcome these limitations, conductive polymer-based current collectors were developed, comprising ultrathin metal layers deposited on flexible polymer substrates. Compared to conventional metal foils, these current collectors provide substantially lower areal weight while maintaining stable electrical performance and superior mechanical flexibility. Pouch-type LIB cells with these current collectors demonstrated stable charge–discharge behavior and favorable cycling performance under bending and folding conditions, indicating their potential as a practical, scalable design strategy for next-generation flexible LIBs.

Solid-state batteries are widely regarded as a transformational technology for next-generation electric vehicles, offering the potential for higher energy density, faster charging, enhanced intrinsic safety, and reduced long-term costs. Among the various solid electrolyte chemistries under investigation, sulfide-based electrolytes are particularly promising due to their exceptional room-temperature ionic conductivity and compatibility with scalable, ambient-pressure manufacturing processes. In response, several battery manufacturers and OEMs have announced development timelines indicating that sulfide-based all-solid-state batteries (ASSBs) could reach early-stage production in the near future.

However, the commercial deployment of sulfide-based ASSBs remains constrained by unresolved interfacial challenges, most notably the chemical and electrochemical instability of sulfide electrolytes in direct contact with lithium metal anodes. Although lithium–sulfide combinations enable very high energy density and favorable high-rate performance, recurrent issues such as lithium dendrite formation, electrolyte cracking, and interfacial degradation have been observed, even under elevated stack pressures. These degradation mechanisms compromise cycling stability, safety, and long-term durability, underscoring the need for improved electrolyte film design and interface engineering.

This contribution addresses key remaining barriers associated with sulfide electrolyte films and their interfaces with lithium metal. We report the development of novel binder systems specifically tailored for sulfide ceramic electrolytes, and systematically examine the roles of electrolyte composition, binder chemistry, film density, and mechanical flexibility. The results demonstrate how these parameters jointly determine ionic conductivity, processability, and interfacial stability, while enabling mechanically robust electrolyte films suitable for scalable manufacturing.

By integrating optimized sulfide electrolyte films with a stabilized lithium metal interface, we demonstrate pouch cells achieving over 700 galvanostatic cycles at moderate temperature under industry-relevant stack pressures. Safety characteristics are further evaluated using Accelerating Rate Calorimetry (ARC) and controlled internal short-circuit testing. These measurements reveal a substantial reduction in thermal runaway severity compared with liquid electrolyte systems, as well as enhanced tolerance to internal faults enabled by a ceramic-leaning composite electrolyte architecture.

Overall, this work highlights the critical interplay between binder design, slurry processing, film fabrication, and interfacial engineering in advancing sulfide-based ASSB technology toward safe, manufacturable, and commercially viable implementation.

Despite major progress, today’s Li‑ion batteries still fall short in energy and power density for longer EV range and faster charging. All‑solid‑state batteries (ASSBs) present a promising alternative, offering higher energy and power, longer cycle life, and improved safety through inorganic solid electrolytes that conduct Li⁺ without volatile liquids. Among them, sulfide electrolytes combine high room‑temperature conductivity with mechanical compliance, enabling low‑impedance operation. However, performance and durability ultimately depend on carefully engineered interfaces—particularly with lithium metal anodes and high‑voltage cathodes—and strict control of H₂S generation during scale‑up.

Lithium metal remains the benchmark anode because of its high capacity and low potential. Although sulfide and other ceramic electrolytes are often proposed to suppress dendrites, dendrite prevention is primarily an interfacial, electrochemomechanical challenge. Contact quality, local stress, and interphase chemistry dictate whether Li plates uniformly. Resistive interphases, stripping‑induced voids, and space‑charge layers can distort current distribution, making electrolyte composition, microstructure, and mechanical response central to stabilizing the Li|electrolyte interface under realistic stack pressures.

At the cathode, sulfides may react with high‑voltage materials, carbon, binders, or current collectors, increasing impedance. Effective triple‑phase‑boundary engineering is essential: ionic networks must wet active particles, while electronic pathways deliver electrons without triggering parasitic reactions. Conformal interlayers, protective coatings, and graded designs help stabilize the cathode|electrolyte interface and enhance rate performance, especially for 5‑V‑class materials.

Stack pressure further complicates design: enough pressure ensures contact, but too much promotes fracture and densification.

Hydro‑Québec’s ceramic‑leaning composite strategy leverages polymer processing with sulfide conductivity, yielding stable cathode architectures and electrolyte films optimized for conductivity, flexibility, and Li compatibility. This approach enables >700 cycles in pouch cells at moderate temperature and practical pressures.

The resulting design rules emphasize compliant interlayers, ultrathin protective chemistries, synchronized ionic/electronic percolation, robust yet flexible electrolyte films, and optimized stack pressure—treating interfaces as engineered assets that unlock viable sulfide‑based ASSBs.

All-solid-state batteries are expected to be a next-generation battery technology because they can offer improved energy density and safety by replacing organic liquid electrolytes with inorganic solid electrolytes. Oxide-based solid electrolytes are attractive because they are stable in air; however, their ionic conductivity is lower than that of other solid electrolytes, such as sulfides and oxychlorides. Pyrochlore-type oxyfluoride solid electrolytes are promising high-ionic-conductivity materials because they exhibit the highest ionic conductivity among previously reported oxide-based solid electrolytes.^[1] However, they suffer from poor densification, which results in high grain-boundary resistance. Therefore, optimizing the sintering method is important for improving their ionic conductivity. In this study, spark plasma sintering (SPS) was applied to densify pyrochlore-type solid electrolytes.^[2]

SPS was used to synthesize and sinter pyrochlore-type electrolytes with the nominal composition Li_1.25La_0.58Nb₂O₆F and 91% excess LiF. Starting materials (Li_0.5La_0.5Nb₂O₆, LiF, and LaF₃) were mixed and annealed at 1000 °C for 5 min. The prepared powders were then sintered at 1000 °C for 5 min under a uniaxial pressure of 50 MPa.

The pyrochlore samples prepared by SPS showed XRD patterns similar to those reported previously. SPS enables rapid synthesis within a few minutes compared with conventional solid-state synthesis. Cross-sectional images of the sintered pellets showed almost no voids. The resulting dense pellets exhibited a high relative density of 98%. The densely sintered pyrochlore-type Li_1.25La_0.58Nb₂O₆F solid electrolyte exhibited the highest bulk conductivity (15 mS cm⁻¹ at 300 K) and total conductivity (11 mS cm⁻¹ at 300 K) reported to date for oxide-based lithium-ion conductors, owing to reduced grain-boundary resistance. Furthermore, its activation energy was lower than that of existing highly ion-conductive materials.

This study demonstrated that SPS is useful for synthesizing and sintering pyrochlore-type solid electrolytes. For the first time, an ionic conductivity of over 10 mS cm⁻¹ was achieved in an oxide-based solid electrolyte. These results significantly advance the development of oxide-based solid electrolytes, opening new opportunities in a field long dominated by sulfide-, chloride-, and oxychloride-based systems.

Lithium-ion transport and mechanical properties in solid-state electrolytes (SSEs) are critical for enabling high-performance all-solid-state batteries (ASSBs). A novel viscoplastic lithium-aluminum oxychloride (LAOC) electrolyte was reported recently to exhibit a high ionic conductivity (1 mS cm^-1 at RT).¹ However, understanding the origin of the fast Li-ion transport mechanism at the atomic-level and long-range scale in such amorphous material is non-trivial.

In this work, solid-state nuclear magnetic resonance (ssNMR) is employed to probe site-specific lithium environments and dynamics in LAOC, from atomic-scale Li hopping to long-range micron-level Li transport. ⁶Li and ⁷Li magic-angle spinning (MAS) NMR spectra reveal the presence of multiple Li coordination environments, corresponding to 4-, 5-, and 6-coordinated Li environments.^{1, 2} Variable-temperature ⁷Li relaxometry and line shape analysis provide insight into the fast Li mobility within the mixed (O/Cl) 5-coordinated Li sites involving O dative bonds, with a measured activation energy of 0.23 eV from ⁷Li relaxometry.² In contrast, Cl-only coordinated Li sites (4- and 6-coordinated) exhibit slower dynamics, whereas the 4-coordinated site contributing minimally to Li-ion transport, as evidenced by ⁷Li selective-inversion (SI)-NMR.^{2 7}Li pulse-field-gradient (PFG)-NMR reveals the similar activation energy (0.49  0.02 eV) and diffusivity for long-range Li-ion diffusion² as those obtained from EIS (0.47 eV).¹

These findings provide direct experimental evidence that the mixed anion coordination plays a key role in enabling fast Li-ion dynamics.^{1, 2} Moreover, the bulk Li-ion conduction is not limited by grain-boundary resistance, supporting the viscoplastic nature of LAOC.² Finally, the 6-coorinated Li corresponds to deeper-energy sites that dictate the overall activation energy (0.47 – 0.49 eV) of long-range Li-ion transport within LAOC.² This work demonstrates the power of ssNMR in resolving Li-ion transport mechanisms across different length scales for amorphous materials, and offers important insights for developing SSEs for the next generation of ASSBs.

All-solid-state batteries (ASSBs) are emerging as a leading technology for next‑generation electrochemical energy storage owing to their intrinsic safety, high energy density, and compatibility with lithium metal anodes. These advantages originate from inorganic solid electrolytes, which provide high lithium‑ion transference numbers and eliminate risks associated with flammable organic liquids. Among these systems, sulfide-based solid electrolytes have attracted substantial interest due to their low-temperature synthesis routes, high deformability enabling intimate interfacial contact, and ionic conductivities approaching those of liquid electrolytes. However, their practical implementation remains limited by moisture sensitivity leading to H₂S release, interfacial reactivity with both lithium metal and high-voltage composite cathodes, and the reliance on costly and hazardous Li₂S precursors.

Within the sulfide family, argyrodites (Li₆PS₅X, X = Cl, Br, I) represent a particularly promising class because of their high ionic conductivity, structural tunability, and absence of rare elements. Nonetheless, their stability toward lithium metal, electronic conductors, and oxide-based cathode materials remains insufficient, and significant degradation is observed under moderate humidity. Oxygen incorporation into the argyrodite framework has been reported as an effective approach to improve electrochemical and humidity stability while partially mitigating interfacial reactivity.

Hydro‑Québec has therefore undertaken systematic research aimed at developing oxysulfide argyrodite electrolytes synthesized via a one‑step high‑energy ball‑milling route. This approach employs Li₂SO₄ as a low‑cost oxygen‑containing precursor to partially replace Li₂S and reduce material cost without compromising functional performance. The present study focuses on (1) compositional optimization to balance cost, ionic conductivity, and electrochemical and moisture stability; (2) characterization of reactivity and degradation mechanisms across controlled dew‑point conditions; and (3) assessment of long‑term behavior in dry‑room environments. Comprehensive structural and physicochemical analyses—including solid‑state NMR, XRD, Raman spectroscopy, impedance spectroscopy, electrochemical stability measurements, and safety testing—will be presented to elucidate the structure–property relationships governing the performance of oxysulfide argyrodite electrolytes synthesized at Hydro‑Québec.

All-solid-state batteries (ASSBs) have attracted significant attention due to their improved safety and potential for high energy density. However, their practical application is limited by the relatively low ionic conductivity of solid electrolytes and large interfacial resistance. In this study, a composite solid electrolyte was developed by incorporating two types of electrospun nanofiber fillers into a polyethylene oxide (PEO) matrix. Lithium aluminum titanium phosphate (LATP, Li_1.4Al_0.4Ti_1.6(PO₄)₃) nanofibers were used to enhance ionic conductivity, while polyvinylidene fluoride (PVDF) nanofibers were introduced to provide a structural framework, improve mechanical stability, and enhance the flame resistance of the electrolyte. PEO was selected as the polymer matrix due to its good Li-ion coordination ability and excellent processability. The composite electrolyte was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The results indicate that the incorporation of dual nanofiber fillers effectively improves ionic transport in the composite electrolyte.

Employing high-voltage LiCoO₂ (LCO) in all-solid-state batteries constitutes a critical pathway toward higher energy density. However, the two irreversible phase transitions occurring above 4.5 V induce cleavage cracks at the twin boundary defects of commercial LCO. These cracks propagate and accumulate, ultimately rupturing the particles and generating voids that cannot be refilled by the solid-state electrolyte, thereby causing permanent contact loss. In this work, a dispersion toughening coating design strategy is proposed, in which rotary-bed ALD ternary conformal co-deposition coupled with high temperature post annealing is employed to construct on the surface of commercial LCO a hybrid interfacial architecture composed of a Ti doped MO continuous matrix with ZrO₂ nanocrystals dispersed therein, while during the sintering process the incorporation of Zr further induces the formation of Ti, MO, and Zr co-enriched nano island protrusions. Transmission X-ray Microscopy (TXM) reveals the pronounced suppression of intraparticle crack propagation enabled by this design, and complementary systematic characterizations further confirm the effective inhibition of interfacial side reactions between the cathode and the electrolyte by the coating. Stable long-term cycling over 1800 cycles at 4.7 V is achieved in a halide-based ASSLB system. By exploiting a mechanical toughening strategy, this work overcomes the intrinsic brittleness limitation of conventional chemical passivation layers and offers a new perspective for the interfacial design of high-voltage cathodes.

Developing high-energy solid-state batteries (SSBs) requires a fundamental understanding of the complex solid-solid percolation networks within composite cathodes. However, practical electrode design guidelines that seamlessly bridge theoretical models and empirical multi-component systems remain scarce. In this study, we present a comprehensive electrode design framework for high-energy solid-state batteries, extending from binary to ternary composite cathode systems. First, we propose foundational design principles for binary composite cathodes comprising cathode active material (CAM) and solid electrolyte (SE). By defining 3 thresholds (balance, percolation, and loading thresholds), we systematically propose the optimal composition regimes and identify the distinct boundaries of electronic and ionic percolation limits. Moreover, building upon this binary framework, we further elucidate the critical role of conductive additives (CAs) in practical ternary systems. Using 3D digital twin microstructural modeling combined with localized Transmission X-ray Microscopy (TXM) analysis, we reveal how CAs systematically regulate the internal percolation network. In electronic-percolation-limited systems, CAs effectively reconnect isolated active material particles to enhance electronic pathways. More importantly, in ionic-percolation-limited high-loading systems, we demonstrate that the addition of CAs paradoxically lowers the ionic tortuosity. This multidimensional network regulation mitigates local reaction heterogeneity, leading to highly uniform electrochemical utilization across the thick cathode. Ultimately, this work establishes a unified design guideline offering a practical roadmap for the rational design of high-performance solid-state batteries.

Batteries are becoming increasingly important for applications in electric vehicles, portable electronics, etc. Among the different technologies, solid-state batteries are especially attractive because of their potential for higher safety and energy density. However, the performance of solid electrolytes (SEs), particularly halide-based systems, still poses challenges for real-world applications. Challenges such as poor structural control, difficulty in scaling up synthesis, and instability during processing and operation remain key issues. In this work, we develop a supersaturation-driven co-precipitation method to synthesize halide SEs.^[1] This approach enables improved control over the material structure while remaining compatible with large-scale production. With this method, we successfully prepared Li₃InCl₆ and characterized its structure using neutron powder diffraction to clearly distinguish the main phase and possible impurities. In addition, we carried out atmosphere-dependent synchrotron in situ X-ray diffraction to track how the material responds under different environments (dry Ar, dry O₂, and humid conditions), giving insight into its chemical stability and reaction behavior. The synthesized Li₃InCl₆ shows an ionic conductivity on the order of 10⁻³ S cm⁻¹, which is comparable to reported state-of-the-art values. Extending this method to Na-based systems, we obtain a Na₃InCl₆ SEs with much higher phase purity than what is typically achieved using conventional solution-based routes.^[2] As a result, its ionic conductivity improves by about two orders of magnitude compared to samples prepared by traditional wet methods. Overall, this work provides a scalable way to produce high-quality halide SEs and offers useful insights into their structural evolution under different conditions, helping guide the design of more stable and high-performance solid-state battery systems.

Halide solid electrolytes are promising candidates for all-solid-state lithium batteries because of their wide electrochemical stability and compatibility with high-voltage cathode materials. However, the structural diversity of halide-based lithium-ion conducting frameworks remains relatively limited. In this work, we demonstrate that lithium incorporation into a barium aluminum chloride precursor induces a reconstructive phase transformation, generating a previously unreported Li–Ba–Al–Cl halide framework with monoclinic symmetry. Structural analysis using X-ray and neutron diffraction reveals that lithium insertion is accompanied by framework reconstruction, lithium occupation at tetrahedral sites, and partial barium vacancy formation. Bond valence energy landscape analysis further suggests an anisotropic lithium-ion migration network, with the most favorable percolating pathway occurring along one crystallographic direction. Electrochemical impedance spectroscopy confirms measurable lithium-ion conduction after mechanochemical processing. Although the conductivity remains modest, the results show that lithium insertion can serve not only as a compositional modification strategy but also as a route to access new halide frameworks. This study expands the structural landscape of halide solid electrolytes and provides insight into structure-guided discovery of new inorganic lithium-ion conductors. Halide solid electrolytes are promising candidates for all-solid-state lithium batteries because of their wide electrochemical stability and compatibility with high-voltage cathode materials. However, the structural diversity of halide-based lithium-ion conducting frameworks remains relatively limited. In this work, we demonstrate that lithium incorporation into a barium aluminum chloride precursor induces a reconstructive phase transformation, generating a previously unreported Li–Ba–Al–Cl halide framework with monoclinic symmetry. Structural analysis using X-ray and neutron diffraction reveals that lithium insertion is accompanied by framework reconstruction, lithium occupation at tetrahedral sites, and partial barium vacancy formation. Bond valence energy landscape analysis further suggests an anisotropic lithium-ion migration network, with the most favorable percolating pathway occurring along one crystallographic direction. Electrochemical impedance spectroscopy confirms measurable lithium-ion conduction after mechanochemical processing. Although the conductivity remains modest, the results show that lithium insertion can serve not only as a compositional modification strategy but also as a route to access new halide frameworks. This study expands the structural landscape of halide solid electrolytes and provides insight into structure-guided discovery of new inorganic lithium-ion conductors.

Reducing the material cost of inorganic solid-state electrolytes is crucial to advancing all-solid-state batteries (ASSBs) for next-generation energy storage applications. The halospinel Li₂Sc_2/3Cl₄ solid electrolyte (SE) possesses a high ionic conductivity of 1.5 mS cm–1 and good cycling stability up to 4.6 V. However, the high cost of Sc limits its practical application. In this study, we combine M3GNET universal machine learning interatomic potential (UMLIP) and density functional theory (DFT) for efficient screening of lower-cost cation-substituted halospinel compositions for synthesis. As a cost-mitigation strategy, predicted Mg²⁺-, Al³⁺-, and Zr⁴⁺-substituted Li₂Sc_2/3Cl₄ spinels with substitution fractions ranging from 20.9% to 37.5% were experimentally synthesized with only minor impurities, achieving room-temperature ionic conductivities as high as 1.85 mS cm^–1. Substitution of Fe³⁺ was also achieved, albeit with a 7% Fe²⁺ impurity. Molecular dynamics simulations (MD) using highly accurate moment tensor potentials (MTPs) indicate that Li⁺/Sc³⁺/Mⁿ⁺ ordering plays a crucial role in determining the conductivity of disordered substituted compositions. ASSBs operating at 3.8 mAh cm^–2 capacity with Li_1.75Sc_0.416Zr_0.25Cl₄ at a high current density of 2 mA cm^–2 exhibited 80% of the capacity of more moderately loaded ASSBs cycled at a low rate. This work provides a foundational methodology for predicting the thermodynamic stability and ion transport of disordered lithium solid electrolytes and accelerating the discovery of novel materials for a range of applications.

All-solid-state batteries have attracted considerable attention as next-generation energy-storage systems owing to their intrinsic safety advantages and their potential to surpass the energy-density limits of conventional lithium-ion batteries.^[1] However, the practical implementation of Li metal anodes remains fundamentally hindered by the infinite volume change associated with repeated Li plating and stripping. To address this challenge, various strategies, including Ag–C composite-based anode-free configurations and functional protective interlayers, have been extensively investigated to stabilize the electrolyte/anode interface.^[2] Although these approaches improve electrochemical stability, they remain inherently limited in controlling the macroscopic volume expansion of the anode. At the module and pack levels, such unmitigated expansion necessitates bulky pressure-maintenance systems and additional buffering components, ultimately compromising system-level energy density.

Herein, we report a three-dimensional host architecture based on a mixed ionic-electronic conducting (MIEC) Li–Si framework that enables negligible macroscopic volume change during cycling. By precisely tailoring the pore network and regulating the lithiation-induced sintering of Si particles, we construct a robust 3D Li–Si skeleton with internal void space for Li⁰ accommodation. This engineered framework enables deposited Li to be stored within the internal host volume while maintaining continuous solid–solid interfacial contact during cycling. Operando pressiometry reveals negligible macroscopic volume change of the 3D Li–Si host under repeated cycling, supporting its ability to effectively accommodate Li0 within the framework without substantial external expansion. This work provides a practical design strategy for high-energy-density all-solid-state batteries by fundamentally addressing the mechanical instability of Li metal anodes.

Sulfide-based all-solid-state Li metal batteries are promising candidates for high-energy-density energy storage systems; however, their practical implementation is hindered by the chemical instability of sulfide catholytes toward polar solvents, moisture, and high-voltage cathode environments.[1,2] In particular, slurry-processed composite cathodes require catholytes that are chemically robust during wet processing while maintaining interfacial integrity under low stack pressure.

Here, we present a fluorocarbon-terminated self-assembled monolayer strategy for stabilizing Li₆PS₅Cl (LPSCl) catholytes. The resulting –CF₃@LPSCl forms a conformal and chemically inert surface layer that suppresses solvent- and moisture-induced degradation. Even after exposure to a polar solvent, ethyl acetate, –CF₃@LPSCl retained a high ionic conductivity of 1.44 mS cm⁻¹. Under 10% relative humidity, pristine LPSCl generated 34 ppm H₂S within 2 h, whereas the SAM-coated LPSCl reduced H₂S evolution to approximately one-third of that of pristine LPSCl.

The SAM-coated catholyte also improved electrochemical durability in slurry-cast NCM811 composite cathodes. Under a low stack pressure of ≈0.3 MPa, –CF₃@LPSCl-based cells delivered an initial discharge capacity of 156.6 mAh g⁻¹ and an initial Coulombic efficiency of 95.4%, outperforming cells based on bare LPSCl. Furthermore, full cells using 20 μm Li metal with a low N/P ratio of 1.68 retained 90.5% of their initial capacity after 300 cycles at 0.5 C. These results demonstrate that catholyte surface stabilization is an effective strategy for enabling scalable, slurry-processable, and low pressure-tolerant sulfide-based all-solid-state Li metal batteries.

Poor rate capability remains a significant challenge for practical applications of solid-state batteries (SSBs). One of the causes of the poor rate capability is spatially inhomogeneous charge-discharge reactions within and between the numerous active material particles in composite electrodes, reducing active material utilization. To suppress this inhomogeneity and improve rate performance, observing individual particle reactions and understanding their governing factors is essential. Previously, we have developed a 3D X-ray absorption fine structure (3D-XAFS) imaging technique to three-dimensionally visualize the reaction distributions of hundreds of particles before and after charging[1]. In this study, we extended this methodology into an operando scheme to simultaneously track the temporal evolution of reaction distribution in each individual particle during charge-discharge, aiming to clarify the factors governing the inhomogeneous reaction formation.

A composite cathode was fabricated by mixing and sintering LiCoO₂ (LCO) active material and Li_2.2C_0.8B_0.2O₃ (LCBO) solid electrolyte (40:60 vol%). A model SSB was constructed using this cathode, an LCBO electrolyte, and a Li-metal anode. For 3D-XAFS measurements, CT scans (rotation: –90° to 90°, 0.1° step, 12.5 ms exposure) were repeatedly performed while scanning the incident X-ray energy in 0.1 eV increments near the Co-K absorption edge (7724.3-7729.2 eV). The state of charge (x in Li_xCoO₂) at each voxel was evaluated based on the peak energy shift of the XAFS spectra. The cell was charged at 0.2C up to 100 mAh/g, with measurements conducted at seven stages (0, 8, 25, 43, 59, 76, and 100 mAh/g).

Figure 1 shows the 3D reaction distribution maps of individual particles at each stage. The observation region was an approximately 47 µm cubic volume with 277 nm voxels in the composite cathode. Blue and red regions represent fully discharged (x = 1.0) and deeply charged (x = 0.45) states, respectively. The temporal state-of-charge variation in each individual particle during charging was successfully tracked via operando 3D-XAFS, revealing substantial inter-particle inhomogeneity in reaction progression.

In the presentation, we will perform time-series analyses of these data to identify the factors governing inhomogeneous reaction among active material particles in composite SSB electrodes.

Sulfide-based solid electrolytes (SSEs) are considered key enablers for high-energy-density all-solid-state batteries (ASSBs).^[1],[2] However, despite their immense promise, Li argyrodite type (e.g., Li₆PS₅Cl) often fail to realize their full potential due to several intrinsic limitations, including poor moisture stability, inferior mechanical ductility compared to glass-ceramic analgos (e.g., Li₃PS₄), and a narrow electrochemical stability window. These inherent challenges are further exacerbated by the presence of trace impurities particularly residual carbon which remains a critical yet underappreciated factor governing the overall stability and reliability of these systems. 

In this study, LPSCl was synthesized via a straightforward dry-milling process using low-grade and high-grade precursors to systematically evaluate the influence of residual carbon. To assess air stability, the synthesized electrolytes were subjected to dry-room exposure, followed by comprehensive analysis of surface impurity formation via XPS an EIS. The mechanical and electrochemical robustness were evaluated through critical current density (CCD) measurements in Li-symmetric cells and long-term cyclability testing in Li-In/NCM811 full-cell configurations. 

LPSCl derived from high-grade precursors exhibited significantly suppressed H₂S evolution and superior air stability compared to the conventional counterpart prepared from low-grade precursors. Furthermore, the high-purity electrolyte demonstrated a denser and more ductile microstructure, which was instrumental in sustaining a high critical current density (CCD) of 2.4 mA cm^-2 a significant improvement compared to the 1.7 mA cm^-2 observed in the low-grade-derived system. These optimized properties enabled approximately 80% capacity retention over 400 cycles in Li-In/NCM811 full cell, whereas the system using low-grade precursors showed a much lower retention of 63%. Such performance is on par with state-of-the-art benchmark electrolytes. 

Our findings establish that controlling precursor-level purity-specifically the elimination of residual carbon-is a primary design lever for securing the environmental, mechanical, and electrochemical stability of sulfide electrolytes.

All-solid-state lithium metal batteries (ASSLBs) offer the potential of high-energy density and safety attracting strong research interest around the world, with emphasis put on high conductivity as key metric.[1] However, in our pursuit for the development of high-conductivity solid electrolytes often we neglect the imperatives of scaling-up and manufacturability.[1,2] Another significant challenge is poor interfacial coupling with the electrodes that has driven development efforts towards “semi-solid” battery architectures incorporating liquid electrolyte.[1] To address these issues, the HydroMET Laboratory has developed a hybrid solid‑state electrolyte (HSE) composed of a porous Li_6.1Al_0.3La₃Zr₂O₁₂ (LLZO) garnet membrane infiltrated with ~5% ion‑conductive polymer (patents pending).[3-4] This composite architecture improves interfacial contact, reduces impedance, and enhances mechanical strength. The developed HSE membranes have been successfully integrated with commercial cathodes and tested in Li‑metal coin cells, without the use of any liquid electrolyte or application of pressure, demonstrating stable cycling performance (over 1000 cycles) and fast-rate (2C) capability.[3-4] Building on these innovations, our ongoing efforts focus on scaling-up the technology toward a >400 Wh/kg all‑solid‑state lithium‑metal pouch‑cell prototype. Herein, we report a reproducible scalable synthesis route for size-tunable LLZO powders, increasing batch size from 1 g to 25 g, and describing its rendering into highly conductive porous garnet membrane via doctor-blade deposition, sintering, and polymer infiltration.

Among various battery systems, all-solid-state lithium batteries (ASSLBs) employing solid electrolytes have attracted significant attention owing to their enhanced safety and high energy density. Sulfide-based solid electrolytes exhibit high ionic conductivity (~10-2 S cm-1) at room temperature, comparable to that of conventional liquid electrolytes.[1] In addition, their ductile nature enables intimate solid–solid contact without requiring high-temperature sintering. In ASSLBs, composite cathodes are typically composed of active materials, solid electrolyte, conductive carbon, and polymer binders to establish continuous Li⁺-ion and electron transport pathways. However, despite the ductile nature of solid electrolyte, their intrinsically solid-state characteristics inevitably lead to the formation of internal pores within composite cathodes. These pores disrupt interfacial contact, induce localized polarization, and deteriorate the interfacial stability of composite cathodes during cycling.[2] Furthermore, the volume changes of cathode active materials, such as LiNixCoyMn1-x-yO2 (NCM), during cycling further aggravate pore formation. In addition, the narrow electrochemical stability window of solid electrolyte results in oxidative decomposition at high operating voltages, leading to the continuous formation of resistive byproducts within composite cathodes.[3] To address these challenges, surface modification and additive strategies have been explored to stabilize solid electrolyte interfaces by suppressing oxidative degradation and improving interfacial contact within composite cathodes. In this work, we introduce a novel liquid-like polymer–lithium salt complex (PLC) as a coating material for solid electrolyte to enhance the interfacial properties of composite cathodes. The effects of PLC-coated solid electrolyte on the electrochemical performance of composite cathodes are systematically investigated and discussed.

All-solid-state sodium batteries are attracting growing attention as cost-effective and high-energy-density energy storage systems. Among solid electrolytes, halide-based materials are promising because of their oxidative stability and compatibility with high-voltage cathodes. However, their ionic conductivity often remains limited, and conventional approaches have largely relied on mechanochemical amorphization rather than controlled defect formation. Here, we investigate how Schottky defect formation enhances Na⁺ transport in NaTaCl₆ halide solid electrolytes.

Structural relaxation was performed using density functional theory calculations with the PBE-GGA functional, PAW method, and VASP program. Ab initio molecular dynamics simulations were conducted under an NVT ensemble with a Nosé–Hoover thermostat to evaluate Na⁺ diffusion behavior. Bonding characteristics were analyzed using crystal orbital Hamilton population analysis with LOBSTER, while topological analysis using pymatgen and Zeo⁺⁺ was used to examine Na⁺ migration pathways.

The introduction of Na/Cl Schottky vacancies significantly improves ionic conductivity without requiring full amorphization. First-principles calculations reveal that Cl vacancies induce local structural distortion, shorten Ta–Cl bonds, and strengthen Ta–Cl interactions. These changes weaken and diversify Na–Cl bonding environments, leading to distorted Na coordination polyhedra and the formation of additional octahedral-like Na sites. As a result, the local Na environment becomes more diverse, flattening the Na⁺ migration energy landscape. AIMD simulations further show that defect-induced lattice expansion and local disorder reduce the migration barrier and enable more connected Na⁺ diffusion pathways.

All-solid-state lithium–sulfur batteries (ASSLSBs) with sulfide-based solid electrolyte offer promising advantages such as high safety, high energy density, and cost-effectiveness. However, maximizing sulfur utilization while increasing the areal loading level of sulfur remains challenging due to the difficulty of forming a well-connected triple-phase interface and Li-ion conduction pathways. [1,2]

We developed a high-performance ASSLSBs using a simple two-step mixing process: high-energy ball milling followed by gentle mixing of a sulfur/carbon composite with Li6PS5Cl (LPSCl). This method reduces particle size, improves mixing uniformity, and activates the redox behavior of LPSCl while preserving its superionic conductivity. As a result, continuous and well-distributed ion/electron pathways are established within thick cathodes. The effects of varying ball-milling energies on the chemomechanical and structural changes at the cathode are examined. As a result, our ASSLSB achieves a high areal capacity with good cycle retention at 30 °C.

This approach is simple, scalable, and applicable to other sulfur-based cathodes, offering a practical route toward high-energy solid-state batteries. When Se-doped sulfur was used as the active material, the ASSLSB with a high loading cathode (20 mg cm–2) delivered an areal capacity exceeding 20 mAh cm–2. Furthermore, it is successfully fabricated into a large-area dry electrode using a PTFE binder, demonstrating the feasibility for practical applications. [1]

All-solid-state lithium-ion batteries employing inorganic solid electrolytes have attracted much attention as next-generation batteries because of their high safety and energy density. While chemical degradation at cathode-electrolyte interfaces has been extensively investigated, mechanical degradation, including electronic contact loss between cathode active materials, has been largely overlooked, because it cannot be adequately captured by conventional topographical or morphological analyses. To date, although an electrochemical impedance spectroscopy analysis based on the transmission line model implied the possibility of electronic contact resistance between lithium nickel cobalt manganese oxide (NCM) particles in cathode composites, its effects on battery performance remain unclear. Scanning spreading resistance microscopy (SSRM), a type of conductive atomic force microscopy, is a powerful technique for acquiring microscopic electrical information at the sample surface. However, previous SSRM-based local resistance studies have relied on ex situ measurements, which obscure the evolution under mechanically constrained battery conditions. This limitation makes it difficult to obviously track the evolution of identical microscopic regions during battery operation, highlighting the need for in situ techniques under constrained states. In this study, we developed an in situ SSRM technique for all-solid-state batteries using sulfide solid electrolytes that enable direct visualization of the evolution of local electronic resistance in NCM-based cathode composites during charging. Using this approach, we revealed that some NCM particles become electrically isolated already at the early stages of charging, followed by a pronounced increase in interparticle contact resistance at higher charging potentials, even in the absence of obvious morphological changes. Therefore, mechanical degradation related to electronic contact between NCM particles emerges as the dominant mechanism governing the degradation of electrochemical performance across a wide operating voltage range. These findings provide a new mechanistic picture of battery degradation by identifying interparticle electronic contact loss as a critical failure pathway that has been largely overlooked in studies focused primarily on interfacial chemical degradation.

 Li-S batteries are promising candidates for next-generation batteries because of their high energy densities. In particular, all-solid-state Li-S batteries have attracted attention. Employing non-flammable solid electrolytes instead of organic liquid electrolytes improves safety and enhances cycling stability because dissolution of polysulfides from the cathode active material (CAM) is suppressed. However, all-solid-state Li–S batteries typically require a stack pressure of several tens of MPa to achieve and maintain their capacity, due to the significant volume change of CAM during charge-discharge cycling, which induces chemo-mechanical degradation [1]. Therefore, it is desirable to achieve both a small volume change of the CAM, which can suppress chemo-mechanical degradation of cathode, and a high capacity.

 For all-solid-state Li-S batteries, we developed Argyrodite cathode active material (Argyrodite-CAM). Our Argyrodite-CAM is made from solid electrolyte, conductive carbon and additives. By ball-milling them together, they change into a cathode active material composite, with high electronic and ionic conductivity. Argyrodite-CAM exhibits reversible capacity of 1000 mAh g^-1 based on the CAM weight, and it is estimated that a pouch cell with Argyrodite-CAM can reach 400 Wh kg^-1 based on the battery components excluding casing. Our Argyrodite-CAM is promising material for high energy density batteries.

 In this work, we demonstrated the pouch-type cells employing Argyrodite-CAM operation under low stack pressure. Figure 1(a) shows a photograph of the pouch cell. The cell is composed of a cathode electrode sheet, a separator sheet, an In-Li layer and current collectors. The cathode sheets and solid electrolyte sheets were made by a wet-coating process. Ni tabs were connected to the current collectors. Figure 1(b) shows that our pouch cells with Argyrodite-CAM cycled and maintained their capacity for 50cycles even under low stack pressure. In addition, in-situ SEM observations revealed that the volume changes of the Argyrodite-CAM during charge-discharge cycle was smaller than that of Li2S-LiI-VGCF [2]. We consider that this small volume change suppresses chemo-mechanical degradation and enables stable operation under low stack pressure. This presentation will discuss the detailed results of the in-situ SEM observation and effects of cathode loading and stack pressure on the charge-discharge performance of our pouch cells.

The growing demand for high-energy-density energy storage systems has accelerated research on all-solid-state batteries (ASSBs) employing sulfide solid electrolytes. Lithium metal is considered a key anode material for next-generation sulfide-based ASSBs owing to its high theoretical capacity (3860 mAh g-1) and low electrochemical potential (–3.04 V vs. SHE). In particular, lithium electrodeposition on lithium-free current collectors during charging can further enhance energy density. However, interfacial instability between lithium and sulfide electrolytes remains a critical challenge. Direct contact between electrodeposited lithium and the solid electrolyte induces electrolyte decomposition, interfacial void formation, and dendritic lithium penetration through grain boundaries, ultimately leading to rapid performance degradation and short circuits. To address these limitations, interlayer engineering strategies on current collectors have been extensively explored to regulate lithium nucleation and stabilize the interface. Although various carbon-based interlayers have been reported, the sluggish diffusion of lithium ions within the interlayer still induces unstable lithium growth toward the sulfide electrolyte layer. In this study, we introduce a surface engineering strategy to construct a chemically regulated carbon surface through a solution-based modification. A reaction derivative enables the introduction of functional moieties and lithiophilic domains, thereby promoting stable solid electrolyte interphase (SEI) formation and enhanced interfacial stability during electrochemical reactions. XPS, XRD, and TEM analyses confirmed the formation of lithiophilic domains within the conductive interlayer, while LSV, CV, and XPS results verified the formation of a stable SEI layer after electrochemical cycling. Half-cell tests demonstrated improved cycling stability under practical current densities. This work highlights that precise surface tuning of conductive interlayers provides an effective strategy for stabilizing interfaces in sulfide-based ASSBs under high-current-density conditions. Moreover, the proposed approach offers a scalable and cost-effective alternative to conventional carbon coating strategies.

１．Introduction

 All-solid-state lithium batteries with lithium metal anodes are promising candidates for high-energy-density batteries, since lithium metal exhibits the lowest electrode potential and the highest theoretical capacity among anode materials. However, dimensional stability of the lithium metal during cycling critically affects battery lifetime [1]; thus, minimizing thickness change is essential for long-life batteries. In this study, we applied a high-precision dilatometer to measure thickness changes of sheet-type all-solid-state lithium-metal batteries during charge-discharge cycling.

２．Experimental

 Sheet type batteries were fabricated with a high-Ni NMC cathode (LiNi_xCo_yMn_zO₂, x > 0.8) composed of sulfide argyrodite-type solid electrolyte, conductive additive, and binder. A carbon-based buffer sheet was employed on the anode side. Galvanostatic charge-discharge was performed between 4.25 and 2.5 V. Cell thickness changes were recorded continuously using a high-precision dilatometer equipped with a Keyence AT2-51 displacement sensor [2].

３．Results and Discussion

 Fig. 1 shows the thickness changes of the battery during cycling, which is caused by reversible deposition and dissolution of lithium metal anode. The lithium metal anode exhibited repeatable deposition and dissolution of approximately 25 μm per cycle. The area-specific deformation (ASD) corresponding to the change in thickness per unit capacity for lithium metal anode agreed well with the theoretical value of 4.88 μm/(mAh cm⁻²). This demonstrates that deposited lithium metal is highly dense, reversible dissolution and deposition in the all-solid-state battery from the perspective of thickness change. Importantly, no progressive abnormal expansion which is commonly observed in liquid-electrolyte lithium-metal batteries due to SEI and/or dendrite formation was detected. These findings indicate substantially improved dimensional stability of lithium metal anodes in all-solid-state batteries and support the viability of lithium metal as an anode material for long-life solid-state batteries.

The surge in electric vehicle adoption and the growing demand for large-scale energy storage systems have intensified the need for lithium-ion batteries (LIBs) capable of operating reliably under extreme thermal conditions. However, conventional liquid electrolytes suffer from severe degradation at elevated temperatures. A major challenge arises from the thermal instability of conventional LiPF6-based electrolytes, which readily undergo hydrolysis at high temperatures to generate corrosive hydrofluoric acid (HF) and PF5 species. These reactive byproducts accelerate transition metal dissolution from Ni-rich cathodes and degrade electrode–electrolyte interfaces, ultimately leading to rapid capacity fading. In this work, we developed a multifunctional gel polymer electrolyte (GPE) employing a novel cross-linker, siloxy-pentaerythritol triacrylate (SiO-PETA), to enhance the high-temperature cycling stability and safety of LIBs. The trimethylsilane groups in SiO-PETA effectively scavenge corrosive HF, thereby suppressing cell degradation induced by transition metal dissolution. In addition, the chemically cross-linked polymer matrix effectively confines the liquid electrolyte within the GPE, minimizing parasitic side reactions and suppressing electrolyte volatilization at elevated temperatures. The HF-scavenging capability and the resulting interfacial stabilization were systematically investigated by 19F NMR, TOF-SIMS, and TEM analyses. A graphite/LiNi0.6Co0.2Mn0.2O2 pouch-type cell incorporating the SiO-PETA-based GPE exhibited outstanding capacity retention at 70 °C, significantly outperforming cells using conventional liquid electrolytes. These findings demonstrate that the SiO-PETA-based GPE effectively suppresses electrolyte and electrode degradation, enabling stable LIB operation under high-temperature conditions.

  All-solid-state batteries (ASSBs) are a promising next-generation system to address the safety and energy density limitations of conventional Li-ion batteries. However, Li-based ASSBs face a fundamental cost barrier due to Li's scarcity. Na is far more earth-abundant, yet Na-based solid electrolytes remain poorly understood in terms of structure-conductivity relationships. 

  Previous study for new Na-ion conductors have relied on structural similarities to known conductors, with limited success, highlighting the need for new physical descriptors and broader structural exploration. To enable large-scale screening, we employed machine-learning interatomic potentials (MLIPs) to overcome the spatiotemporal constraints of DFT. We found that existing universal MLIPs (uMLIPs), trained on well-explored crystal databases, show poor accuracy for underrepresented Na-O configurations. By introducing largest cluster maximum distance (LCMD) sampling to augment the training set in underexplored compositional regions, we developed a Na-O MLIP achieving state-of-the-art accuracy for this chemical space. 

  Using this model, we screened approximately 8,900 Na-O frameworks from the Materials Project via MLIP molecular dynamic (MD), identifying 263 promising compositions across 79 distinct frameworks, more than 10 of which exceed 1 mS cm⁻¹, well beyond previously reported values for Na-O solid electrolytes outside the NASICON family. To elucidate transport mechanisms, we fine-tuned structure-specific MLIP models and performed 2 ns MLIP-MD on supercells exceeding 500 atoms. Beyond diffusion coefficients, we quantified framework dynamics, Na-framework correlations, and Na-Na concerted migration. A key finding is that bottleneck sites that appear narrow in static structures can transiently widen during ion migration. Statistical analysis shows that conductivity increases systematically when bottleneck openings exceed approximately 1.5 Å, and that this dynamic widening is governed by the connectivity of corner-sharing non-Na cation polyhedra. Based on these findings, we propose a design principle for high Na-ion conductivity centered on corner-sharing polyhedral connectivity and free volume, offering a rational basis for the discovery of Na-based solid electrolytes for next-generation ASSBs.

All-solid-state batteries (ASSBs) using sulfide-based solid electrolytes (SE) are expected to provide improved thermal safety compared to conventional lithium-ion batteries and are therefore actively developed for electric vehicle applications. However, sulfide-based ASSBs have also been reported to exhibit self-discharge and accelerated degradation at elevated temperatures [1], indicating that further improvement in thermal stability is required. Moreover, the influence of battery degradation on the thermal behavior of ASSBs remains insufficiently understood.

In this study, the thermal behavior of laminate-type sulfide-based ASSBs was investigated by differential scanning calorimetry (DSC), focusing on differences in exothermic behavior between fresh and degraded cells. DSC measurements were performed on electrode–electrolyte multilayer stacks extracted from the cells.

In general, if the reaction process is identical, the total heat evolution is independent of the heating rate. In contrast, as shown in Fig. 1, the ASSB samples exhibited an increase in total heat evolution with decreasing heating rate. Slower heating rates allow kinetically slow reactions to proceed, and their contribution is reflected in the measured heat evolution. This behavior is particularly pronounced in degraded cells, where kinetically slow reactions become more significant in the low- to intermediate-temperature range. X-ray photoelectron spectroscopy (XPS) revealed chemical-state changes in the SE of the cathode layer after degradation, suggesting that thermal decomposition of degraded SE species may be associated with these slow exothermic reactions.

Under rapid self-heating conditions relevant to thermal runaway, these kinetically slow reactions are likely to contribute only marginally. Thermal safety of lithium-ion batteries is commonly evaluated using accelerating rate calorimetry (ARC), which is also considered applicable to ASSBs. However, because ARC involves stepwise heating and waiting periods, slow reactions occurring at low to intermediate temperatures may not directly reflect the rapid self-heating processes that govern thermal runaway.

This study demonstrates that degradation alters the heat-generation processes in ASSBs and highlights that the appropriate heating rate and time scale in DSC measurements depend on whether the target of evaluation is battery degradation or thermal runaway.

This work is supported by SOLiD-Next project (JPNP23005), subsidized by NEDO.

The rate capability of Li insertion electrodes used in Li-ion batteries strongly depends on electrode architecture, such as electrode thickness and porosity. This dependence indicates that the rate-limiting process is not determined solely by Li-ion diffusion within the active material particles. In our previous studies on liquid-electrolyte-based Li-ion batteries, we demonstrated that the dilute-electrode method can be used to evaluate the intrinsic rate capability of electrode materials under conditions where solid-state Li-ion transport in the active material becomes the dominant rate-limiting process [1]. In the present study, we applied the dilute-electrode method to all-solid-state cells using lithium titanium oxide (LTO) as the active material and analyzed the kinetics of oxidation and reduction reactions in all-solid-state composite electrodes.

Fig. 1 shows the rate capability of a dilute all-solid-state LTO electrode containing 3 wt% LTO, 89 wt% solid electrolyte, and 8 wt% acetylene black. In the Li insertion reaction, the capacity of the dilute all-solid-state LTO electrode decreased to approximately 100 mAh g⁻¹ at 8 C-rate. In contrast, in the Li extraction reaction, a capacity of approximately 100 mAh g⁻¹ was retained even at 90 C-rate. These results clearly indicate that Li extraction proceeds much faster than Li insertion in the all-solid-state LTO electrode.

Fig. 2 compares the capacity retention of dilute and conventional all-solid-state LTO electrodes as a function of the current density normalized by the mass of LTO. In the conventional electrode, no pronounced difference in capacity retention was observed between Li extraction and Li insertion. By contrast, the dilute electrode exhibited a marked difference in capacity retention between the oxidation and reduction reactions. This result demonstrates that the reaction kinetics of Li extraction and Li insertion are highly asymmetric in dilute all-solid-state LTO electrodes.

All-solid-state batteries (ASSBs) have garnered significant attention for their potential to improve energy density and safety over conventional lithium-ion batteries, which rely on organic liquid electrolytes. Among various solid electrolyte candidates, sulfide-based solid electrolytes (SEs) are considered particularly promising because of their high ionic conductivity, mechanical deformability, composition flexibility, and favorable processability, making them key materials for ASSB applications. However, sulfide SEs are highly sensitive to moisture and therefore generally require handling in inert environments. Although Ar-filled glove boxes are widely adopted for laboratory-scale processing, their high operational cost and limited scalability remain obstacles for large-scale processing. Consequently, handling sulfide SEs in dry room environments with controlled humidity has emerged as a practical alternative. Nevertheless, even trace amounts of moisture accumulated during prolonged exposure can induce material degradation, leading to reduced ionic conductivity. This issue has led to extensive investigations into the atmospheric stability and degradation behavior of sulfide SEs. In parallel, many sulfide SEs are synthesized via solvent-mediated processes, such as liquid-phase synthesis and wet-milling, which inevitably introduce residual organic species originating from solvent treatments. Yet, existing studies on atmospheric degradation mechanisms and subsequent heat treatment processes have largely overlooked the effects of these residual organics. 

In this presentation, we investigate the surface degradation behavior of sulfide SEs induced by solvent-mediated processes and exposure to dry-air environments. In addition, we present a regeneration strategy for moisture-degraded sulfide SEs (Fig. 1), addressing a key challenge in improving the long-term stability and performance of ASSBs.

In solid-state battery (SSB) composite electrodes, vast numbers of active material and solid electrolyte particles, together with pores, form complex microstructures and interfaces. Under high-rate operation in particular, ions and electrons cannot reach each particle uniformly, causing three-dimensionally heterogeneous reactions within and between active material particles, lowering capacity and power. However, probing the reaction of each of many particles embedded in such complex microstructures has remained difficult, obscuring how particle arrangement and interfacial structure affect individual reactivity. In this study, we combined computed tomography–X-ray absorption fine structure (CT-XAFS) imaging, which yields the reaction state of several hundred individual particles, with offset-phase CT, which provides the 3D distribution, shape, and interfacial area of each particle, to clarify the correlation between electrode microstructure and per-particle reaction behavior.

LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) primary particles and Li_2.2C_0.8B_0.2O₃ (LCBO) solid electrolyte were mixed at 5:5 by weight to form a composite cathode. A model SSB was assembled with this cathode, a Li-foil and an LCBO separator, and charged up to 100 mAh/g. CT-XAFS was performed across the Ni K-edge (0.2 eV steps; –90 to 90°, 0.1° steps, 20 ms/projection), and the local Li content of NMC111 was extracted from the peak-top energy of the spatially resolved Ni K-edge spectra. Offset-phase CT (30 keV, 0.1° step, 125 ms) was then performed on the same specimen to observe electrode microstructure.

Figure 1(a) shows the 3D Li distribution after 0.1 C charging within a ~40 µm cubic region, revealing a coexistence of deeply charged and nearly fully discharged regions and thus pronounced reaction heterogeneity. Figure 1(b) shows the corresponding microstructure obtained by offset-phase CT (~50 µm cube), encompassing the CT-XAFS field of view and enabling quantitative evaluation of solid-electrolyte and pore interfacial areas of each particle as well as their 3D connectivity. By integrating these microstructural descriptors with the per-particle reaction states, we will discuss the origin of the in-electrode reaction heterogeneity from a microstructural perspective.

Sulfide solid-state electrolytes (SSEs) are among the most promising candidates for next-generation lithium metal batteries due to their high ionic conductivity and favorable mechanical properties [1]. However, their practical implementation is critically hindered by interfacial instability against lithium metal, leading to continuous electrolyte decomposition, impedance growth, and poor cycling performance [2]. Addressing these challenges is essential for enabling safe, high energy density systems for applications such as electric vehicles.

In this work, we introduce a flowable polymer–salt protective interlayer based on Jeffamine and LiTFSI, designed to stabilize the Li/SSE interface by avoiding direct contact, while still enabling fast ionic conduction. The interlayer composition is systematically optimized to enhance ionic transport and interfacial compatibility. Symmetric lithium cells incorporating sulfide SSEs and the protective layer in a sandwich configuration are used to evaluate interfacial stability under repeated cycles of stripping and deposition of lithium, while comparative studies with unprotected interfaces are performed to highlight the role of the interlayer.

The introduction of the Jeffamine–LiTFSI interlayer leads to a significant reduction in interfacial resistance evolution and enables more stable lithium plating/stripping over extended cycling, with lower overpotentials compared to bare sulfide electrolytes. The optimized system mitigates typical degradation phenomena observed in direct Li/SSE contact.

These results demonstrate that polymer interlayers represent an effective strategy to stabilize lithium metal interfaces in sulfide-based solid-state batteries. This approach provides a pathway toward improving the durability of solid-state lithium metal systems and offers design guidelines for interfacial engineering in next-generation battery architectures.

InoBat is a European technology leader in advanced battery solutions. It combines intellectual property, cutting-edge research, and vertically integrated manufacturing to help address key challenges facing Europe, such as the development of customized batteries for sustainable e- mobility applications. 

InoBat utilized high-throughput screening (HTP) to accelerate the development of optimized chemical composition for cathodes, anodes, and electrolytes in collaboration with Wildcat Discovery Technologies (WDT).

 InoBat has successfully scaled up highly optimized chemistry from a coin cell to a pilot-scale production of large-format cells (10Ah–60Ah). So far, four different generations (Gen1 - Gen4 on Fig.1) with increasing energy density have been developed, covering a wide range of applications with a focus primarily on niche, high-performance-oriented customers. 

Our most significant achievement is the production of fully functional prototype of a Gen4 33Ah cell, which utilizes a high-nickel NMC cathode and a medium-silicon anode. This cell approaches 1000 cycles at 80 % SOH and supports discharge rates up to 10C. The battery ranks among the current physical limits of conventional lithium-ion cells with an energy density of 330 Wh/kg and has successfully passed UN38.3 certification. 

As part of our efforts to continuously improve the chemical composition, power and safety, we aim to explore the development of all-solid-state batteries that will meet all safety requirements and has higher energy density (350–500 Wh/kg) and will be capable to operate over a wider temperature range. As evidenced by our successful collaboration with many partners, we believe that finding the right R&D partner and seeking suppliers of new materials suitable for all-solid-state batteries is the key to overcoming challenges currently associated with this type of battery.

 All-solid-state batteries using non-flammable solid electrolytes are a promising next-generation technology. However, their practical application requires the establishment of efficient ionic conduction pathways within the electrode layer. Liquid-phase processing of solid electrolytes is effective in enhancing ionic conduction pathways and forming a large contact area between the electrolyte and the active material. In this study, we focused on the chloride-based solid electrolyte Li₃InCl₆, which possesses both high ionic conductivity and high-voltage stability [1]. We aimed to improve battery performance by coating Li₃InCl₆ solid electrolyte onto a cathode active material using liquid-phase synthesis process. 

 Li₃InCl₆ was coated on LiCo_1/3Ni_1/3Mn_1/3O₂ (NMC111) powder via liquid-phase synthesis using tetrahydrofuran (THF) as a solvent. The electrochemical performance of the resulting cathode composite, comprising the coated powder and vapor-grown carbon fibers (VGCF), was evaluated in an all-solid-state battery. For comparison, a reference cathode composite was prepared by mixing the same components (Li₃InCl₆, NMC111, and VGCF) using an agate mortar.

 SEM observations revealed the formation of a uniform Li₃InCl₆ layer on the active material surface. The all-solid-state battery fabricated using the composite electrode synthesized via the liquid-phase process exhibited an initial discharge capacity of 121 mAh g⁻¹ (Figure 1), surpassing the performance of the battery constructed via the conventional hand-mixing process.

 We successfully fabricated a cathode composite that demonstrates higher charge-discharge capacity than that of composite produced by the hand-mixing process. This approach represents a promising strategy for achieving high energy density in all-solid-state batteries.

All-solid-state batteries (ASSBs) have emerged as a leading candidate for next-generation energy storage, offering potential improvements in safety and energy density over conventional liquid electrolyte systems. Among solid electrolyte (SE) families, argyrodite-type sulfide electrolytes have attracted particular attention owing to their high ionic conductivity and mechanical ductility, which enables intimate electrode-electrolyte contact via cold-pressing. However, achieving high ionic conductivity in sulfide electrolytes conventionally requires high-temperature annealing, which compromises mechanical flexibility, promotes grain growth, and introduces undesirable side effects such as sulfur loss — collectively increasing processing complexity and cost. Borohydride (BH₄^-), a pseudo-halogen anion with an ionic radius intermediate between Br^- and I^- yet significantly lighter, has recently emerged as a promising substituent in argyrodite frameworks, offering lattice expansion and enhanced Li-ion transport without the drawbacks of heavy halogen incorporation. Nevertheless, the structural origins of ionic transport in BH₄-containing argyrodites and their interfacial compatibility with both Li-metal anodes and high-voltage cathodes remain poorly understood.

Here, we report the synthesis and characterization of borohydride–fluoride argyrodite electrolytes, prepared via an annealing-free two-step mechanochemical process. Structural, mechanical, and electrochemical analyses reveal how dual anion substitution governs ionic transport and interfacial stability, demonstrating that this materials system simultaneously addresses the key challenges of Li-metal compatibility and high-voltage cathode stability in practical ASSBs.

     Oxide-based inorganic solid electrolytes are promising candidates for all-solid-state batteries (ASSBs) because of their high safety and chemical stability. However, grain-boundary resistance and poor electrode/electrolyte interfacial contact remain major challenges. In this study, grain-boundary resistance was eliminated and electrode/electrolyte interfacial contact was improved by coating inorganic solid electrolyte particles with Li mixed salts that are liquid at room temperature. This approach enabled pellet fabrication through a simple pressing process without the need for high-temperature sintering. Herein, we report the fundamental properties, local compositional, and battery application of this novel composite electrolyte, termed ionic clay. 

     The ionic clay consisted of the oxide-based inorganic solid electrolyte LLZO (Li₇La₃Zr₂O₁₂) and an equimolar LiFSA/LiTFSA molten salt, Li[(FSA)_0.5(TFSA)_0.5], with mixing ratio (Li[(FSA)_0.5(TFSA)_0.5] : LLZO = 1 : x). The resulting mixtures were hot-pressed into pellets at 423 K under 36.9 N mm^-2 without sintering. The obtained pellets were characterized by AC impedance spectroscopy, DC polarization measurements, and SEM–EDS analysis to evaluate the ionic conductivity (σ), Li⁺ transference number (t_Li+), and elemental distribution, respectively. 

     Figure 1 shows representative Nyquist plots of ionic clay measured at 333 K for two compositions: a Li mixed salt-rich composition (x = 0.5) and an LLZO-rich composition (x = 1.5). The sample with x = 0.5 exhibited a paste-like morphology, whereas the x = 1.5 sample showed a powdery appearance. Despite differences in physical appearance, only bulk resistance was observed for both compositions, which also exhibited high peak frequencies in the impedance spectra, suggesting rapid ionic response. These results indicate that favorable electrode/electrolyte interfacial contact can be achieved even in the powdery state and that grain-boundary resistance can be effectively eliminated. Figure 2 shows cross-sectional SEM images of ionic clay with x = 1.5 at different magnifications. The pellet exhibited a dense microstructure, and magnified images revealed that the LLZO particles were uniformly coated with the Li mixed salt. These observations suggest the formation of effective Li⁺ conduction pathways in the ionic clay. The Li⁺ conduction mechanism will be discussed in the presentation.

      This study proposes a new materials design strategy toward the practical implementation of oxide-based ASSBs.

Halide solid electrolytes are considered promising candidates for all-solid-state batteries thanks to their high ionic conductivity and enhanced oxidative stability against high-voltage cathodes compared with many sulphide-based electrolytes.¹ Their compatibility with layered oxide cathodes such as LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC) makes them attractive for high-energy-density applications, including electric vehicles. Despite significant progress, the mechanisms governing lithium transport within the composite cathode and at the buried cathode–electrolyte interface remain unclear, which demonstrates the need for techniques sensitive to different experimental lengths and time scales.^2,3 This study investigates lithium transport in a dual-electrolyte composite consisting of halide and sulphide solid electrolytes and NMC cathode active material. Electrochemical analysis and ⁷Li solid-state Nuclear Magnetic Resonance (ssNMR) are combined to correlate macroscopic electrochemical responses with interfacial lithium dynamics.

The galvanostatic intermittent titration technique (GITT) is used to probe polarisation and relaxation behaviour under near-equilibrium conditions during (de-)lithiation, offering time-resolved insights into electrochemical transport within the solid-state assembly. In parallel, ⁷Li ssNMR exchange spectroscopy (EXSY) is used to investigate local lithium environments and interfacial exchange processes at halide-NMC and halide-sulphide interfaces, capturing dynamic lithium-exchange phenomena recently reported at solid–solid electrolyte interfaces.⁴

GITT measurements indicate that apparent lithium mobility depends on the state of charge, reaching a maximum at intermediate values, analogous to the behaviour observed in liquid electrolyte systems. Relaxation behaviour remains consistent across the entire state-of-charge range, suggesting that the response is not exclusively governed by bulk diffusion in NMC. Complementary ⁷Li ssNMR 2D EXSY provides evidence of lithium exchange between the two solid electrolytes. In addition, 1D exchange measurements between NMC and the halide phase show signal attenuation consistent with interfacial lithium exchange.

Together, the GITT and ssNMR observations exhibit macroscopic and interfacial contributions to lithium transport in the dual-electrolyte assembly, each operating on distinct length and time scales. This integrated approach establishes a framework for understanding transport limitations in complex solid-state battery systems.

 All-solid-state lithium-ion batteries (ASSLBs) are expected to be next-generation energy storage devices due to their high safety and energy density. Recently, oxyhalide solid electrolytes, such as LiTaOCl₄, have attracted attention for their high ionic conductivity and wide electrochemical oxidation window [1]. However, the conventional mechanochemical synthesis from TaCl₅ and LiOH generates HCl gas, leading to significant equipment corrosion and environmental concerns. In this study, we developed a novel HCl-free mechanochemical synthesis route for LiTaOCl₄ using Ta₂O₅ as a strategic oxygen source. The effects of the milling conditions were investigated by comparing a single-step process, in which LiCl, TaCl₅, and Ta₂O₅ were simultaneously milled for 40 h, and a two-step process in which LiCl and Ta₂O₅ were pre-milled for 10 h followed by additional milling for 30 h with TaCl₅. For comparison, a LiTaOCl₄ sample was also synthesized from TaCl₅ and LiOH. 

 X-ray diffraction (XRD) patterns (Figure 1) revealed that the two-step mechanochemical process resulted in lower intensity peaks for residual LiCl and Ta₂O₅ compared to the single-step mechanochemical process, indicating a more complete reaction. The LiTaOCl₄ sample synthesized via the two-step process exhibited the highest ionic conductivity of 8.5 mS cm^-1, among the synthesized samples. These results demonstrate that HCl-free synthesis using metal oxides is useful for developing high-performance oxyhalide electrolytes for ASSLBs.

Halide-based Li-conducting inorganic solid electrolytes are emerging for their better high-voltage stability and potentially lower cost compare to sulfide counterparts. Especially, Li₂ZrCl₆ is considered one of the most promising candidates due to relatively low cost of Zr precursors than the others such as In, Sc, Y, Er, and Yb. However, its relatively low ionic conductivity around 10^-4 S cm^-1 is subjected to improve. Achieving (Electro-)chemical stability are also important for practical all-solid-state battery applications. In this consideration, herein, we conduct anion substitutions of oxygen, sulfur and fluorine to Li₂ZrCl₆ and investigated their influences in terms of ionic conductivity and structural aspect. As for structure, the chalcogenide substitutions (oxygen and sulfur) induced trigonal-to-monoclinic structure transformation accompanying anions sublattice change from hcp to ccp while the fluorine substitution preserved the original trigonal structure. Surprisingly, the oxygen substitution was only effective for improving ionic conductivity of Li₂ZrCl₆ where the highest ionic conductivity was 1.3 mS cm^-1 at 25 ^oC for Li_3.1ZrCl_4.9O_1.1 while the other substitutions lowered the ionic conductivity. The improved ionic conductivity is explained by combining the 3D connectivity among Li and interstitial sites and the energetically stabilized Li tetrahedral sites by hard-base substitution in the trigonal structure. In contrast, this stabilization effect was suggested marginal in the trigonal structure in BVSE analysis. Also, its feasibility for practical all-solid-state Li batteries were examined.

1. Introduction

Ionic conductivity in solid polymer electrolytes (SPEs) is commonly evaluated by AC impedance spectroscopy1,2). However, AC impedance measurements are performed under small-signal AC conditions, which differ from the DC charge-discharge conditions of practical batteries. Therefore, evaluating ion transport under DC operation is important for understanding SPE behavior in working cells. In this work, [Na/SPE/Na] symmetric coin cells using a polyether-based SPE were fabricated, and the ionic conductivity under DC conditions was evaluated by DC polarization measurements and compared with that obtained by AC impedance measurements.

2. Experiment 

100 μL of a polyether solution in THF (1 wt%) was coated onto sodium foil and dried to prepare sodium electrodes. An SPE precursor solution consisting of polyether (6.91%, OSAKA SODA CO., LTD.), sodium bis(trifluoromethanesulfonyl)imide (2.84%), crosslinking agent (0.24%), and benzoyl peroxide (0.03%) was coated onto a PET film and heat-treated at 100°C for 5 h under an argon atmosphere to obtain a free-standing SPE film. SPE films of various thicknesses were prepared to assemble [Na/SPE/Na] CR2032 coin cells. These cells were characterized at 60 °C by DC polarization and AC impedance measurements. For the DC polarization, a constant current was applied for 3 h, followed by a 10-minute rest period. Subsequently, the AC impedance was measured from 1 MHz to 10 mHz with an amplitude of 30 mV.

3. Results and Discussion

Figure 1 shows the DC polarization results for the polyether-based SPE at 60°C. The charge-discharge responses were nearly symmetric, and the cell voltage increased approximately linearly with the applied current. The voltage was plotted against the applied current, and the resistance was calculated from the slope. The ionic conductivity in polyether-based SPE was estimated from the change in resistance as a function of the polymer film thickness. In this presentation, we will discuss the ionic conductivities evaluated from both DC polarization and AC impedance measurements.

Acknowledgments 

This work was supported by the Japan Science and Technology Agency (JST), K Program, Grant Number, JPMJKP24P1, Japan.

All-solid-state lithium–sulfur batteries have received a great attention as next-generation energy storage systems owing to the high theoretical capacity of sulfur and the improved safety of nonflammable solid electrolytes. Nevertheless, their practical application is still limited by the insulating nature of elemental sulfur, sluggish solid–solid conversion kinetics, high interfacial resistance, and insufficient ionic contact between sulfur-based cathodes and sulfide solid electrolytes. To address these issues, we prepared sulfur/mesoporous carbon composite cathodes by uniformly encapsulating 65 wt% sulfur into mesoporous carbon with an optimized pore size of approximately 10 nm through a combined solution-impregnation and melt-diffusion process [1]. Multi-walled carbon nanotubes (MWCNT) were further incorporated to construct continuous electronic conduction pathways. A solution-assisted wet-mixing using weakly polar isopropyl acetate was carried out to enhance the interfacial contact between sulfur/carbon and the Li₆PS₅Cl solid electrolyte, The wet-mixing process promoted the formation of polysulfido-intermediate species at the sulfur/Li₆PS₅Cl interface, as confirmed by X-ray photoelectron spectroscopy. This interfacial tailoring enabled intimate solid–solid ionic contact, suppressed internal void formation, and reduced triple-phase interfacial resistance. Compared with the liquid Li–S cell showing a two-step discharge process, the wet-mixed all-solid-state Li–S cell exhibited a one-step solid–solid conversion behavior between sulfur and Li₂S (Fig. 1a). As a result, all-solid-state Li–S cell delivered a near-theoretical initial discharge capacity of 1621 mAh g⁻¹ (based on sulfur) at 0.1C and 60 °C. It also exhibited improved cycling stability, retaining 67.9% of its capacity after 300 cycles at 0.5C while maintaining a high Coulombic efficiency of over 99.98% (Fig. 1b) (no lithium polysulfide shuttle effect). These results strongly suggest that solution-mediated sulfur-loading and interface tailoring of sulfur/mesoporous carbon cathodes is an effective strategy for achieving high sulfur utilization and durable cycling performance in sulfide-based all-solid-state Li–S batteries [2].

Introduction

Oxide-type all-solid-state sodium batteries are promising energy-storage devices because oxide solid electrolytes exhibit high chemical stability and improved safety. However, increasing the cell size while maintaining uniform sintering, low interfacial resistance, and stable charge–discharge performance remains a key challenge for practical development.

In this study, the influence of cell diameter on the electrochemical performance and structural uniformity of oxide-type all-solid-state sodium batteries was investigated.

Experimental

Na₃V₂(PO₄)₃, Na₃Zr₂Si₂PO₁₂, and carbon were mixed at a weight ratio of 35:60:5 and used as the composite of positive and negative electrode layers. Oxide-type all-solid-state sodium batteries with diameters of 10 mm and 25 mm were fabricated by spark plasma sintering at 850 ^oC. Charge–discharge tests were conducted at 60 ^oC. To evaluate the origin of performance differences between the two cell sizes, two-dimensional X-ray diffraction analysis and two-dimensional thickness mapping were performed.

Results and discussion

The 10 mm cell delivered a discharge capacity of approximately 100 mAh g⁻¹ based on the mass of the positive electrode active material. In contrast, the discharge capacity of the 25 mm cell decreased to approximately 77 mAh g⁻¹ (Fig. 1). Two-dimensional X-ray diffraction and thickness mapping revealed spatial variations in the degree of sintering and densification within the enlarged cell. These results suggest that in-plane nonuniformity and possible side reactions slightly reduce the electrochemical performance of the 25 mm cell. Nevertheless, the enlarged 25 mm cell exhibited excellent cycling stability and maintained charge–discharge operation for more than 1000 cycles. These findings indicate that oxide-type all-solid-state sodium batteries can be scaled up to 25 mm while retaining high cycle durability, and that controlling two-dimensional structural uniformity is essential for further improving the performance of enlarged sintered cells.

Acknowledgments

I would like to acknowledge the support of GteX Program Japan Grant Number JPMJGX23S2.

Electrolytes for rechargeable batteries must simultaneously satisfy several demanding requirements, including high ionic conductivity, wide electrochemical stability, thermal and chemical stability, and compatibility with electrode interfaces. These properties are often competing, and the design space spanned by salts, solvents, and concentrations is vast, making data-driven approaches indispensable. However, existing molecular databases cover only individual molecules and lack the structural and physicochemical information of electrolytes as integrated solutions. Here, we developed the Open Electrolyte Database for Batteries (OEDB), an electrolyte-level database based on high-throughput molecular dynamics (MD) simulations.¹

We constructed a fully automated MD simulation framework spanning charge and force-field assignment, initial structure generation, equilibration, production runs, and property analysis, executed on the ARIM mdx high-performance computing platform.² The target compositional space comprised 5,616 electrolytes formed from 3 cations (Li⁺, Na⁺, K⁺), 9 anions, 26 solvents, and 8 concentration levels (0.5–4.0 mol/kg in 0.5 mol/kg increments). For each composition, radial distribution functions, coordination numbers, ionic conductivity, diffusion coefficients, viscosity, and density were computed.

The framework achieved a throughput more than 100 times higher than that of conventional manual approaches, enabling approximately 16 million CPU hours of MD calculations to be organized into a systematic dataset. Correlations among the calculated properties were consistent with known physical trends over a broad compositional range, supporting the physical consistency of the database. To facilitate data use, we developed a web-based graphical user interface, publicly available at https://oedb.jp, that allows users to browse and search compositions, electrolyte structure and physicochemical properties in an integrated manner. We also linked OEDB with a large language model, enabling natural-language queries on target applications, desired properties, and constraints to retrieve candidate electrolyte compositions and summarize property trends.

The OEDB is the first-of-its-kind open electrolyte-level database and provides a foundation for data-driven electrolyte design. Ongoing work focuses on expanding the compositional space and integrating higher-fidelity simulation results and experimental measurements to further improve comprehensiveness and reliability.

Current lithium-ion battery (LIB) electrolyte systems have been largely dominated by a limited range of standardized components, typically consisting of ethylene carbonate (EC), linear carbonates, and lithium hexafluorophosphate (LiPF₆). These components are widely employed owing to their well-balanced physicochemical properties and electrochemical stability. In particular, EC is regarded as an essential component for forming a stable solid electrolyte interphase (SEI) on graphite anodes. However, as LIB applications expand toward extreme operating conditions, such as low temperatures and fast-charging environments, conventional electrolyte formulations are approaching their performance limits. In particular, the de-solvation of Li⁺ ions from the solvation sheath becomes a major kinetic bottleneck, leading to significant capacity loss and lithium plating. To address these limitations, various strategies have been explored, including the use of low-viscosity ester-based solvents and alternative lithium salts. Although these approaches can effectively enhance ionic conductivity and low-temperature kinetics, they often involve inherent trade-offs in terms of cycle life and electrochemical stability. In this work, we propose an electrolyte design strategy that overcomes these limitations through the incorporation of a multi-component solvent and salt system. The combination of ester and fluorinated ester solvents was engineered to simultaneously reduce viscosity and lower the de-solvation energy barrier. In addition, a dual-salt strategy employing lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluoro(oxalato)borate (LiDFOB) was introduced to synergistically enhance the electrochemical performance of LIBs. While LiFSI provides high ionic conductivity, its inherent limitations at low temperatures, arising from its strong dissociation characteristics, are effectively mitigated by the incorporation of LiDFOB, which promotes improved low-temperature kinetics.

Water-in-salt electrolytes (WiSE) have emerged as an important class of aqueous electrolyte compositions that can significantly expand the electrochemical stability window (ESW). These highly concentrated systems can suppress water decomposition, mitigate active-material dissolution, and enhance the stability of battery anodes by forming a solid electrolyte interphase (SEI), thereby enabling the use of aqueous electrolytes in metal-ion batteries. In recent years, extensive research has sought to elucidate the mechanisms underlying WiSE's enhanced stability. The expansion of ESW is commonly attributed to SEI formation, while other proposed explanations include reduced water activity and disruption of hydrogen-bonded water network. In this work, polarisation is measured by linear sweep voltammetry and analyzed with appropriate potential corrections to the RHE scale through a concentration-dependent mathematical model. The relative contributions of these factors are subsequently examined by Tafel analysis. The analysis indicates that the apparent widening of the ESW in WiSE systems predominantly arises from kinetic suppression of water decomposition reactions induced by the unique solvation environment of these highly concentrated electrolytes. This perspective provides a clearer understanding of the governing mechanisms and offers guidance for the rational design of next-generation aqueous electrolytes.

Fluorination of electrolytes remains the key strategy to stabilize plating/stripping in lithium metal batteries (LMB). However, a switch to fluorine-free electrolytes is desirable given the safety and environmental challenges associated with fluorinated materials. Moreover, recent findings also point to Li₂O being the stronger driver of coulombic efficiency in LMBs than LiF.[1] Designing electrolytes without fluorine requires a comprehensive understanding of the solvation structures surrounding Li⁺, which in turn influence both  the bulk transport  the solid electrolyte interface (SEI) properties. Among fluorine-free Li salts, lithium nitrate (LiNO₃) is often employed as an additive to generate ion-conductive SEI components such as Li₂O and Li₃N. However, its poor ion dissociation and rapid consumption during cycling currently limit its use as the main electrolyte salt.

In this work, we employ lithium bis(oxalato)borate (LiBOB) as the secondary salt in LiNO₃/diglyme electrolytes, and show that the resulting modification of Li⁺ inner solvation structures synergistically improves both bulk Li⁺ transport and SEI properties.[2] The weakening of Li⁺-NO₃^- interactions in the presence of BOB^- ions significantly enhances ion dissociation, which increases the ionic conductivity of the electrolyte. We also observed the presence of LiBOB-derived outer SEI components over the LiNO₃-derived ion-conductive inner SEI layer, resulting in low-surface-area Li deposits and lower Li⁺/anion consumption during cycling. The dual-salt fluorine-free electrolytes enable stable, long-term cycling in Li/Cu cells with high coulombic efficiencies (>98%), and show promising capacity retention in Li/LFP full cells at 25 °C. Our work proposes a dual-salt pathway for future fluorine-free electrolyte development where borate salts could act as functional alternatives to fluorinated ones, and  highlights the importance of tuning the Li⁺ solvation structures for optimizing bulk and interface properties in these systems.

Ionic transport mechanisms within the electrolyte play a crucial role in governing the electrode processes and charge transfer kinetics in rechargeable battery systems. This has particularly garnered widespread attention in recent years, as high voltage for metal ion batteries (MIBs) and solid-state batteries (SSMBs) are key areas of growing interest, driven by their potential future applications. Despite their importance, the electrolytes in MIBs and SSMBs lead to multiple bottleneck challenges. SSMBs based on polymer-state electrolytes (SPEs) are relatively new research hotspots that exhibit higher ionic transport and greater energy density while addressing issues like flammability and low energy density often encountered with liquid electrolytes (LEs) in lithium-ion (LIBs) and sodium-ion (SIBs) batteries. However, owing to their high crystallinity, poly (ethylene oxide) - PEO, SPEs suffer from reduced ionic conductivity at room temperature. A possible remedy is provided by gel polymer electrolytes (GPEs), which, decrease crystallinity, thus improving the ionic conductivity as well as improving the electrode-electrolyte contact. This review covers the synthesis processes and characterization of lithium and sodium salts, which are key to electrolyte design. It then summarizes the recent progress in electrolyte formulations for high-voltage MIBs and SSMBs. Finally, the critical contribution of understanding ionic conductivity the stability of electrolytes-electrodes interfaces and electrolyte structures is highlighted, as these factors directly impact the performance and lifespan of these battery systems.

Accurately modeling the concentration-dependence of ionic conductivity in lithium-ion battery (LIB) electrolytes remains challenging, particularly at high concentration regime with prominent ion-pairing and ion-solvent interactions. Classical models such as Kohlrausch’s law and the Debye–Hückel–Onsager (DHO) theory exhibit bias with experimental data at the high concentration regime. While various theoretical and empirical extensions have tackled this problem, there remains substantial bias and the augmented parameters often lack physical meaning. Fuoss–Kraus theory includes ion-pairing equilibrium but treated the mean activity coefficient (γ_±) as constant, which is incompatible with the strong concentration dependence of γ_± and the corresponding free Li⁺ concentration that emerges in highly concentrated electrolytes. We note that the DHO and Fuoss–Kraus models are fundamentally based on charge density, which is best represented by the free Li+ concentration (i.e., equilibrium concentration). To determine the free Li+ concentration, it is essential to introduce actual γ_±, which determines the ion-pairing equilibrium. Herein, an activity-corrected Fuoss–Kraus model is developed by quantifying the concentration-dependent γ_± that provides the accurate equilibrium concentrations of Li⁺ ions. 

This activity-corrected Fuoss–Kraus model accurately described the concentration-dependent conductivity of nonaqueous Li-ion electrolytes up to the solubility limit, using a compact set of five fitting parameters. This conductivity model may enable more exact physicochemical parameterization for the design of advanced electrolytes and battery management systems towards highly safe and fast-charging Li-ion batteries. 

Developing safe and sustainable electrolytes remains a critical bottleneck for next-generation batteries. Commercial electrolytes rely on flammable organic solvents and fluorinated salts, such as LiPF₆ and NaPF₆, which contribute to forming a stable solid/cathode electrolyte interphase (SEI/CEI). However, the presence of these components also poses fire risks and releases toxic hydrofluoric acid (HF).^[1] Furthermore, increasing regulatory restrictions on PFAS compounds and the high energy costs associated with dry-room manufacturing create a strong motivation for developing PFAS-free and moisture-tolerant alternatives.^[2] In this work, we address these challenges by exploring PFAS-free aqueous electrolytes. While aqueous systems offer intrinsic safety and low cost, they typically suffer from a narrow electrochemical stability window (ESW). To overcome this, we apply the concept of high-entropy electrolytes (HEEs), where the complex interaction of multiple salts creates unique solvation structures that widen the ESW while maintaining sufficient ionic conductivity.^[3] Given the vast, high-dimensional design space of HEEs, manual optimization becomes impractical. Therefore, we developed an automated electrolyte development platform which integrates high-fidelity electrochemical characterization with Bayesian Optimization (BO). This cost-effective automated platform enables the efficient navigation of experimental parameters that are otherwise impractical for manual methods. Specifically, this platform enables automated ionic conductivity and ESW profiling of 24 electrolytes per day within a controlled temperature range of 0 – 40°C. By utilizing a three-electrode electrochemical cell with glassy carbon electrodes and an Ag/AgCl reference electrode, the system performs autonomous Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) measurements to respectively determine the electrolyte's ionic conductivity (mS cm^-1) and ESW (V). Using high-throughput screening, we demonstrate that optimized combinations of NaAc, NaNO₃, and Na₂SO₄ achieve the stability necessary for practical galvanostatic cycling based on PFAS-free aqueous electrolytes. The electrolyte development platform enables the rapid identification of PFAS-free electrolyte formulations, bridging the gap between environmental sustainability and the rigorous electrochemical demands of next-generation batteries.

A promising approach for overcoming the safety issue of Li-ion and Na-ion batteries is replacement of electrolyte organic solvents with a new class of poorly flammable and/or flame-retardant components, called ionic liquids (ILs) [1]. Despite these favorable characteristics, the ion conductivity of IL-based electrolytes is, however, still lower than that of organic solutions with negative effect on the high-rate performance especially at low temperatures. In this scenario, the combination of suitable co-solvent with ILs may represent a good compromise among fast ion transport properties and improved safety of the resulting electrolyte.

In the present work, we have developed hybrid electrolyte technologies based on bis(fluorosulfonyl)imide ionic liquids and glyme co-solvents. The IL materials were synthesized through an eco-friendly route developed at ENEA whereas glymes were selected for their favorable behavior in Li-ion and Na-ion systems [2].

The hybrid electrolytes were investigated in terms of thermal and ion transport properties, and electrochemical stability. Ignition tests allow to optimize the optimal glyme content. The results obtained have evidenced better conductivity and comparable oxidation with respect to pure IL electrolytes, but without depleting the safety issue.

To summarize, the hybrid electrolyte technologies open for applications in Li-ion and Na-ion battery systems requiring operating in safe conditions at low temperatures.

Electrolyte motion induced salt inhomogeneity (EMSI) is a failure mechanism in cylindrical and prismatic lithium-ion batteries that can lead to rapid capacity loss at high rates and eventually Li plating and cell failure. If a cell displaying EMSI is allowed to rest for several weeks before the onset of Li plating, capacity recovery is possible. This work studies the relationship between electrolyte fill volume and EMSI in a set of 18650 cells containing a mid-nickel cathode and a 20% chemical Si-C/80% graphite anode. The chemical Si-C is 50% by weight Silicon. Long-term cycling performance at 40°C and 55°C is performed to assess the trade-offs between EMSI resistance and long-term cycle life across a wide range of electrolyte fill volumes. Figure 1a shows 1C cycling of cells with a rest after 10 and 40 cycles to assess the severity of EMSI. Figure 1b shows C/3 cycling performance of similar cells at 40°C to assess cycle life. 

Cells containing less electrolyte are resistant to EMSI. Medium fill volumes (~4.0 mL) are the most susceptible to EMSI, while the highest fills show moderate EMSI resistance. Strong capacity recovery after 2-week rests (after 40 cycles) are observed in all cells experiencing EMSI. The presence of EMSI in these cells is further validated using rotational inertia measurements to ensure electrolyte motion, as well as electrochemical impedance spectroscopy measurements to ensure generation of salt imbalances. At C/3, electrolyte fill volumes below 3.4 mL show the worst cycle life of all cells. This is attributed to electrolyte depletion and resulting electrode dry-out in these underfilled cells. Cells with more electrolyte are less susceptible to electrode dry-out. Identical trends are observed at 55°C. A moment of inertia-based model is presented to quantify the amount of electrolyte depletion in aged cylindrical cells.

High-entropy electrolytes (HEEs), inspired by high-entropy materials design, have emerged as a popular strategy to enhance the performance of lithium metal batteries by using multiple electrolyte components to tune solvation structure and thermodynamics.^1,2 These systems are often assumed to benefit from increased configurational entropy, which is hypothesized to suppress ion pairing, enhance ion transport, and facilitate desolvation kinetics.¹ However, the thermodynamic basis of this “high-entropy” designation remains largely unvalidated experimentally, particularly in non-lithium systems. Sodium-based batteries offer a sustainable and cost-effective pathway to grid-scale energy storage, yet electrolyte design remains the key bottleneck for enabling practical, high-performance Na metal batteries. In this work, we investigate the role of solvation entropy in multicomponent Na electrolytes on ionic conductivity and interfacial exchange kinetics. We further critically assess whether such multicomponent electrolytes can be meaningfully described as “high-entropy.” Using the ionic Seeback effect, we directly measure the interfacial reaction entropy, as previously demonstrated by our group,³ across a series of electrolytes with systematically varied compositions, including mixtures of salts with different dissociation energies and solvents spanning a range of donor numbers and dielectric constants. We compare the experimentally measured solvation entropy with the nominal configurational entropy, as typically estimated in the literature using the Gibbs entropy formula. We examine whether increasing the number and diversity of salt and/or solvent components leads to measurable increases in solvation entropy, and whether these changes correlate with improved ionic conductivity or interfacial kinetics. Preliminary results suggest that increasing solvation entropy, achieved by lowering the solvent dielectric constant in a single-salt, single-solvent electrolyte, is correlated to faster interfacial exchange kinetics. Building on these findings, this work further investigates the key physicochemical descriptors that govern solvation entropy in multicomponent electrolytes. This work challenges the assumption that multicomponent electrolytes are inherently “high-entropy” and highlights the need for rigorous experimental quantification of entropy to guide electrolyte design for the development of stable, fast-charging Na metal batteries for next-generation energy storage technologies.

Flame-retardant electrolytes have attracted much attention because conventional lithium-ion batteries (LIBs) pose risks such as fire due to their flammable organic electrolytes. Recently, our group has developed flame-retardant methylurea-based electrolytes with LiN(SO₂F)₂ (LiFSA) (e.g., LiFSA:urea (1:4 mol/mol), LiFSA:1,3-dimethylurea (1:2)) and demonstrated their applications in LIBs and lithium metal batteries. However, these electrolytes are contaminated with large amounts of water (300~400 ppm), thus, it is expected that removing water from them will lead to further improved performance of LIBs.^1,2 In this study, we dried methylurea under optimal conditions and investigated the differences in electrochemical properties resulting from variations in water content.

To remove water, we dried urea for more than 15 hours with a glass tube oven connected to a diaphragm vacuum pump. Please note that “urea-X” represents “urea dried at X °C”. Thereafter, urea-based electrolytes were prepared by combining LiFSA (Lithium Battery Grade) and dried urea-X powders in a molar ratio of 1:4 with stirring overnight at room temperature. We quantified the water content of the LiFSA:urea-X (1:4) electrolytes using Karl Fischer titration. The water content was effectively reduced via drying with LiFSA:urea-110 (1:4) exhibiting a low value of 52 ppm (Figure 1a) approaching levels comparable to conventional organic electrolytes.

To investigate the impact of water content on LIBs performance, we evaluated the electrochemical cycling of the Li₄Ti₅O₁₂ electrodes in LiFSA:urea-X (1:4). LiFSA:urea (1:4) (black) and LiFSA:urea-110 (1:4) (orange) showed initial reversible capacities (186 mAh g^-1 and 205 mAh g^-1, respectively) near the theoretical capacity. On the other hand, the LiFSA:urea-110 (1:4) cell demonstrated higher initial Coulombic efficiency (CE, 76%) than the undried LiFSA:urea (1:4) cell (66%). In addition, the LiFSA:urea-110 (1:4) cell’s capacity retention after 50 cycles (95%) was superior to the LiFSA:urea (1:4) cell (86%) (Figure 1b.) These results indicate that decreasing the amount of water impurities in urea-based electrolytes effectively suppresses side reaction and capacity decay. In the presentation, we will also talk about 1,3-dimethylurea-based electrolytes.

Lithium-ion batteries are essential energy storage systems for EVs and large-scale ESS due to their high energy density and long cycle life. Among their components, electrolyte plays a critical role in transporting Li⁺ ions between the cathode and anode. Electrolytes are formulated from salts, solvents, and additives, creating a vast number of possible combinations depending on their components and ratios.^[1] These formulations strongly influence electrochemical stability, ionic conductivity, and SEI/CEI stability, all of which directly affect battery lifetime and safety. However, conventional trial-and-error experimental approaches are increasingly bottlenecked by the labor-intensive nature of manual preparation, cell assembly, and subsequent performance testing. To address these limitations, self-driving laboratories have emerged as a promising approach to automate repetitive experimental workflows and accelerate materials discovery.^[2] Building on this concept, we developed ALBATROSS (Automated Li-ion BAttery Testing RObot SyStem), an automated system for coin cell fabrication and evaluation.^[3] To build the system, we used a robotic arm, liquid dispenser, coin cell crimper, stepper motors, and linear actuators. Additionally, a PLC (Programmable Logic Controller) was employed as an intermediate control unit to manage the operation of motors and sensors and to facilitate communication with the main computer. All grippers and supporting structures were designed through iterative prototyping using a 3D printer, allowing for repeated testing and optimization to achieve the most efficient form. ALBATROSS fully automates the entire workflow from electrolyte mixing and cell assembly to electrochemical characterization, including charge-discharge and EIS (Electrochemical Impedance Spectroscopy). The system can fabricate 48 coin cells within just 3 hours without human intervention. Remarkably, ALBATROSS achieves superior reproducibility compared to manual assembly; the relative standard deviation (RSD) of cell capacity improved from 2.375% to 1.292% in the formation cycle, and from 2.310% to 1.365% after 50 cycles. These results demonstrate that ALBATROSS can serve as a tool for accelerating the development of electrolytes and contributing to the widespread adoption of renewable energy.

Ionic liquid electrolytes are attractive candidates for safer lithium-ion and lithium-metal batteries because of their negligible vapor pressure, intrinsic non-flammability, and wide electrochemical stability windows. However, their practical use remains limited by high viscosity, modest room-temperature conductivity, and low Li⁺ transference numbers. In ether-functionalized imidazolium ionic liquids, the molecular role of anion identity in controlling Li⁺ coordination and ion transport remains incompletely understood.

Here, we investigate 1-methoxyethyl-3-methylimidazolium, [MOEmim]⁺, paired with bis(trifluoromethanesulfonyl)imide, [TFSI]^-, and bis(fluorosulfonyl)imide, [FSI]^-, with added lithium salt at battery-relevant concentration. Atomistic polarizable molecular dynamics simulations using the APPLE&P force field in AMS were used to compute density, radial distribution functions, Li⁺ coordination structure, and diffusion coefficients. Complementary COSMO-RS calculations were performed to analyze σ-profiles and Li⁺ solvation thermodynamics [1,2].

Consistent with experimental literature for related imidazolium systems [3], [FSI]⁻-based electrolytes exhibit lower viscosity and higher ionic conductivity than their [TFSI]^- counterparts. MD analysis shows Li⁺ coordinated primarily by anion oxygen atoms in both systems, with the [FSI]^- coordination shell adopting a more compact geometry. COSMO-RS σ-profiles reveal that [FSI]^- presents a more localized region of high negative-screening-charge density than [TFSI]^-, and predict a modest thermodynamic preference (~1 kJ mol⁻¹) for Li⁺ solvation in [MOEmim][FSI], at the resolution limit of the method for monatomic cations and consistent with the σ-profile result.

These results indicate that the transport advantage of [FSI]^--based [MOEmim] ionic liquids has a molecular origin in the more localized anion charge distribution and corresponding Li⁺ coordination geometry. The combined MD + COSMO-RS approach provides design guidelines for selecting anions in safer, higher-conductivity ionic-liquid electrolytes for lithium battery applications.

Spinel LiMn1.5Ni0.5O4 (LMNO) is a promising high-voltage (4.7V) cathode material for high energy density lithium-ion batteries (LIBs). However, at high operating voltages, conventional carbonate-based electrolytes decompose significantly and form a thick cathode electrolyte interface (CEI), which mitigates Li-ion transport. Using lithium polyacrylate (LiPAA) as a binder instead of conventional binders, can develop a protective coating on the cathode material, create a more stable CEI, and improve ionic transport [1]. Moreover, at high voltages, conventional carbon additives become primary sites for electrolyte oxidation due to their large surface areas[2]. Thermally treating carbon black leads to the graphitization of carbon which can minimize oxidation reactions, thus improving oxidation stability. Unfortunately, at voltages >4.5 V, graphitized carbon enables anion (Li⁺) intercalation into the layered structure, causing irreversible structural damage to the carbon. In order to prevent the anion intercalation, using an electrolyte with LiBF₄ salt in the liquid electrolyte can offer a high activation barrier to anion intercalation. Moreover, using sulfolane in the electrolyte has been found to form a sulfur-containing, anion-blocking CEI on the conductive carbon and improve interfacial stability [3]. However, sulfolane has low ionic conductivity due to its high viscosity, which can be compensated for by using organic carbonate solvents like fluorobenzene and dimethylcarbonate (DMC) as a co-solvent [4], [5].

In this work, cathodes have been prepared using aqueous LiPAA binder to help accelerate Li⁺ transport and improve rate capability of LMNO-based cathodes. Additionally, carbon black that has been thermally treated at 2700^oC has been employed to improve oxidation stability and sulfolane-based electrolytes are explored to enhance the interfacial stability of the electrolyte. A major improvement in capacity is observed at high C-rates with cathodes prepared with LiPAA achieving more than a 100% increase in capacity at high C-rates and >99% capacity retention after 100 cycles in Li-half cells. 

Developing cost-effective and durable alternatives to platinum (Pt)-based oxygen reduction reaction (ORR) catalysts is essential for advancing next-generation energy conversion and storage systems, including metal-air batteries. Carbon-based materials are promising candidates; however, achieving high ORR activity requires precise control over heteroatom doping and hierarchical porosity to facilitate efficient mass transport.

Herein, we report a salt-protected carbonization strategy to synthesize highly active nitrogen-doped porous carbon from a metal–organic framework (MOF). A MOF-5/urea composite encapsulated within a sodium chloride (NaCl) shell undergoes one-step pyrolysis. The NaCl shell plays two pivotal roles: (1) preventing the premature loss of nitrogen precursors, thereby enabling effective nitrogen incorporation, and (2) acting as a nanoreactor that traps evolved gases during pyrolysis, which serve as in-situ templates to enhance surface area and pore volume.

The resulting porous carbon exhibits excellent ORR performance, with a high surface area and optimized nitrogen active sites. Notably, the catalyst outperforms commercial Pt/C in terms of electrochemical activity and long-term stability. These results highlight the potential of salt-protected MOF-derived carbon as an efficient ORR catalyst and suggest its applicability as a promising cathode material for metal-air battery systems.

Next-generation rechargeable batteries that surpass the energy-density and safety limits of conventional lithium-ion technology are critical for long-duration grid storage and zero-emission transport. Rechargeable lithium-hydrogen (Li-H) gas batteries have recently emerged as a promising candidate, coupling Li/Li⁺ redox at a lithium-metal or anode-free negative electrode with catalytic H₂/H⁺ redox at a gas-diffusion positive electrode. This chemistry offers a theoretical specific energy of 2825 Wh kg⁻¹, an operating voltage of 3 V, and round-trip efficiencies approaching 99.7%. The objective of this review is to consolidate the fundamentals, design principles, and industrial outlook of Li-H batteries to support their translation from laboratory demonstrations to deployable energy storage technology.

We trace the chemical lineage of Li-H batteries from Ni-H₂ aerospace cells through aqueous hydrogen-gas batteries and proton batteries to the 2025 proof-of-concept Li-H cell, and then move from chemistry to engineering by examining the working principles, materials design strategies, and interfacial behavior of three critical sub-systems: the lithium-metal/anode-free negative electrode, the LATP solid electrolyte, and the gas-diffusion hydrogen electrode. Safety and manufacturability are treated as a coupled, system-level problem, because combining lithium metal with hydrogen gas behind a ceramic separator creates hazards that cannot be addressed independently.

 Three dominant failure pathways are identified as gating practical reversibility: inactive lithium and LiH formation at the negative electrode, LATP interfacial decomposition in contact with Li and H₂, and three-phase-boundary disruption at the gas-diffusion electrode. The first techno-economic analysis (TEA) of Li-H batteries is also presented, benchmarking capital cost, Levelized Cost of Storage (LCOS), and dominant cost drivers against state-of-the-art Li-ion and Ni-H₂ systems and identifying catalyst loading and ceramic-electrolyte cost as the principal levers for cost reduction. 

By integrating chemistry, materials engineering, safety, and economics into a single framework, this review establishes a technology-readiness roadmap to move Li-H batteries from the current TRL 2-3 toward commercial deployment and outlines the materials- and interface-design priorities most likely to enable that transition.

Lithium-sulfur (Li-S) batteries offer a significantly ultra-high theoretical capacity (1675 mA h g^-1) and excellent energy density (~2500 W h kg^-1) compared to conventional Li-ion batteries.[1] However, numerous studies have revealed significant and formidable practical challenges associated with Li-S batteries, including severe shuttle effect, low electrical conductivity of sulfur, and large volume expansion and contraction during battery cycling.[2] To overcome these challenges, researchers have focused on designing polar sulfur host materials aiming to effectively suppress the shuttle effect.[3] In the present study, a polar transition metal oxide such as NiCo₂O₄ nanowire is chosen as a sulfur host material owing to its high density, strong polarity for anchoring the LiPS, and good electrical conductivity. The NiCo₂O₄ nanowires were directly grown on carbon cloth (CC) via a facile hydrothermal method. Importantly, nanowires serve as a polar electrocatalyst, promoting strong adsorption and conversion of lithium polysulfides (LiPSs), thereby effectively suppressing the shuttle phenomenon.[4] SEM confirms the nanowire morphology on carbon cloth, while EDAX mapping detects the coexisting nickel, cobalt, and oxygen elements. The resultant NiCO₂O₄/CC@S composite cathode achieves an initial capacity of 1066 mAh g^-1 at 0.2C with a sulfur loading of 4 mg cm^-2. Although additional experiments and modifications are required to corroborate these preliminary results, our finding suggest that the metal polar oxide/sulfur composite sulfur host cathode shows great synergistic potential for overcoming the practical challenges of Li-S batteries.    

Elemental sulfur is a key component in lithium–sulfur batteries (LSBs), serving as the cathode active material and enabling the high theoretical performances of LSBs. Beyond electrochemical performance, sulfur significantly reduces cathode raw material costs while mitigating the environmental and social challenges associated with the mining and processing of critical metals required by conventional battery chemistries. These attributes position LSBs as a promising technology for future e-mobility applications, especially in sectors where lightweight energy storage is essential. LSBs are therefore widely regarded as one of the most promising "beyond lithium-ion". Nevertheless, the practical commercialization of LSBs remains hindered by both the polysulfide shuttle effect and sluggish redox kinetics. 

This study aims to address these limitations through the engineering of composite cathode materials incorporating sulfur hosts capable of immobilizing lithium polysulfides (Li2Sx) and accelerating both the sulfur reduction reaction (SRR: S8 -> Li2S) and the sulfur oxidation reaction (SOR: Li2S -> S8), thereby unlocking the full potential of LSB cathode active materials[1,2]. Two carbon-based host matrices were investigated. First, biomass-derived carbon was optimized to achieve the structural features required for effective sulfur hosting. Second, a graphene-based host material was modified to enhance polysulfide anchoring capability. Sulfur composite materials were prepared by melt diffusion to incorporate sulfur within each host, followed by cathode processing via slurry coating on carbon-coated Al foil and cell assembly in 2032 coin cell configuration. 

Physicochemical characterizations were performed to identify the chemical phases, structural properties, and morphology of both host and composite materials, while electrochemical testing was conducted to evaluate cycling stability and capacity. Both materials demonstrated good cycling stability, with a capacity retention of 80% after more than 300 cycles at a sulfur loading around 1.5-2 mg/cm², confirming that both hosts effectively accommodate volume changes and mediate polysulfide redox reactions during cell operation. These results establish bio-based and graphene-derived carbon composites as viable sulfur cathode frameworks for LSBs. Further improvements targeting higher sulfur loadings will be pursued to maximize sulfur utilization and enable the high energy density that makes LSBs a promising candidate for next-generation energy storage systems.

Lithium-sulfur battery (LSB) is one of the most promising next-generation energy storage technologies with high theoretical specific capacity (1675 mAh g⁻¹) and gravimetric energy densities (up to 2600 Wh kg⁻¹) as well as cost-effective and eco-friendly nature. However, commercialisation is still hindered by low electronic conductivity of sulfur and its discharge products, dissolution and shuttling of intermediate lithium polysulfide species, and severe chemo-mechanical degradation caused by ~80% volume change of the cathode during cycling. These issues become even more problematic in practically relevant conditions (thick electrode and lean electrolyte), where high tortuosity and inhomogeneous charge distribution result in incomplete sulfur utilisation and more severe mechanical degradation.

This work introduces, for the first time, dual-strategy cathode architecture for LSBs combining femtosecond laser microstructuring with MOF-derived electrocatalysts. Two MOF precursors, MIL-101(Fe) and NH₂-MIL-101(Fe), are carbonised and sulfurised to yield Fe_xS_y@C and Fe_xS_y@NC catalytic hosts with sulfur loadings ≥70 wt%. Controlled microchannels are ablated into this MOF derived electrocatalyst loaded thick sulfur cathodes using a high-power femtosecond laser (Lasea LS5), keeping active material loss to ≤10%.

Laser structuring results of commercial LSB cathodes already show that it is feasible to generate uniform hole and hexagon channel architectures without causing any observable chemical changes to the electrode materials. The laser-structured architecture showed improved capacity and rate capability (up to 5C) compared to the unstructured electrodes due to reduced tortuosity and homogeneous Li+ transport throughout the cathode thickness. In future work, the MOF-derived catalysts are expected to complement these physical benefits through chemical adsorption and accelerate redox conversion. By combining this dual strategy, the target is to achieve a capacity of ≥800 mAh g⁻¹ after ≥500 cycles at 0.5 C with minimal capacity fade, under lean-electrolyte conditions (≤ 3 µL mg⁻¹), and high sulfur loading (~10 mg cm⁻²).

This work provides a scalable, cost-effective, and mechanistically validated electrode design approach towards practical LSBs by bridging the gap between high sulfur loading and electrochemical properties such as high energy density and improved cyclic stability. The insights from this work can be transferred to industrial electrode manufacturing, advancing next-generation heavy-duty and aviation energy storage systems.

The lithium-ion battery (LIB) underpins the wireless electronic age. However, the theoretical energy density and practical performance of current technology is limited.¹ Moreover, elements such as lithium, cobalt, silicon, and carbon (graphite) have been marked by the European Union as critical raw materials,² which has resulted in an increase in their price and rising environmental concerns.¹ Therefore, there is a need for new energy storage technologies that circumvent the rising economic and environmental factors that surround the current inorganic LIB systems.¹ Organic electrodes are composed of abundant elements^{1, 3} and may be accessible through biomass¹ or green synthetic routes.^1-3 Bipolar organic materials are capable of acting as both the anode and the cathode in a solid-state system,⁴ or as the anolyte and catholyte in a flow-battery setup.⁵ Examples of this class of compounds in the literature have typically consisted of tethering or fusing two redox centres to provide the oxidative and reductive couples but this may negatively impact the stability or physical properties of the resulting species.

This work consists of an exploration of bipolar organic electroactive materials where the redox reactions take place on the same framework and where the oxidation and reduction processes are separated by up to 2.76 V. The compounds were synthesised in a one-pot reaction from cheap and abundant starting materials and screened via both solid-state and solution-state electrochemical techniques to identify their electrochemical reversibility and stability. The compounds were further characterised using single-crystal x-ray diffraction to identify any structure-property relationship that may be prudent for further molecular design. Of the substrates tested, the best candidate was then further characterised for energy storage applications using both solid and solution-based cell formats. Spectral analyses (UV-Vis, NMR, and EPR) were used to characterise the compounds formed during charge and to investigate their stability and any potential causes of capacity fade. Experimental work was further supported, in both design and explanation of the physico-chemical phenomena, by density functional theory calculations. As tuneable electrical energy storage media, these compounds hold much promise as a platform technology for the new world.

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation high-energy-density storage systems, but practical deployment is limited by lithium polysulfide (LiPS) dissolution and shuttling, sluggish sulfur redox kinetics, and insufficient electronic transport within sulfur cathodes. Herein, we report an HCl-doped polyaniline (PANI)-encapsulated cobalt-iron Prussian blue analogue (CoFe PBA@PANI-HCl) as a multifunctional cathode catalyst for Li-S batteries with accelerated sulfur redox kinetics. This design integrates the cooperative catalytic features of bimetallic CoFe PBA with the electronically conductive and structurally tunable PANI coating.

CoFe PBA nanocubes were synthesized as open-framework transition-metal cyanides and subsequently encapsulated with HCl-doped PANI through in situ oxidative polymerization. This integrated catalyst was designed to provide accessible Co and Fe catalytic sites for polysulfide regulation and an acid-doped PANI coating that facilitates charge transport. The effect of dopant size on PANI-mediated charge transport was assessed by comparing CoFe PBA@PANI-HCl with CoFe PBA encapsulated with p-toluenesulfonic acid-doped PANI (CoFe PBA@PANI-pTSA). To this end, LiPS adsorption tests, electrochemical kinetic analyses, Li₂S nucleation measurements, and structural/spectroscopic characterizations were combined to correlate catalyst composition, PANI interchain arrangement, charge transport, and sulfur redox behavior.

CoFe PBA@PANI-HCl exhibited stronger LiPS immobilization and faster bidirectional sulfur conversion than uncoated CoFe PBA and CoFe PBA@PANI-pTSA. Combined XPS, XANES, WT-EXAFS, and electrochemical kinetic analyses suggest that Fe sites contribute to LiPS anchoring, whereas adjacent Co sites facilitate S-S bond cleavage and redox conversion. In addition, compared with bulky pTSA, the smaller HCl dopant induces a shorter PANI interchain distance, thereby enhancing electron-transfer pathways, reducing polarization, and supporting diffusion-favorable Li₂S nucleation. As a result, Li-S cells containing CoFe PBA@PANI-HCl delivered stable long-term cycling with a low capacity-decay rate of 0.047% per cycle over 1000 cycles at 0.5 C, and maintained robust areal capacity under a high sulfur loading of 5.4 mg cm^-2.

This work demonstrates that combining bimetallic PBA catalysis with dopant-regulated polymer interchain control enables the rational design of multifunctional cathode catalysts capable of mitigating LiPS shuttling and accelerating sulfur redox kinetics. These findings provide design principles for practically relevant Li-S battery cathodes and highlight PBA/polymer composites as promising catalytic platforms.

The air stability and moisture sensitivity of manganese-based layered electrode materials are critical factors governing their practical utilization in sodium-ion battery technologies. Nevertheless, the effects of moisture exposure on their structural stability and electrochemical performance, along with the feasibility of recovering their properties through post-calcination treatment, remain insufficiently understood. In this work, we systematically examine the influence of high-humidity exposure and direct water-soaking treatment on the crystal structure and sodium-storage characteristics of manganese-based layered oxides. Interaction with water molecules leads to proton incorporation through Na⁺/H⁺ ion-exchange processes, accompanied by the formation of sodium hydroxide species that can subsequently react with atmospheric carbon dioxide. Post-calcination treatment at relatively moderate temperatures effectively removes the incorporated water species and restores the structural framework. Furthermore, the correlation between moisture-induced structural evolution and electrochemical behaviour is comprehensively analyzed to provide deeper insights into enhancing the air stability and practical viability of manganese-based layered positive materials for sodium-ion battery applications.

High-energy lithium batteries are essential for electric vehicles, grid storage, and portable electronics, but conventional Li-ion systems face increasing demands for higher energy density, lower cost, and improved safety.¹ All-solid-state sulfur batteries (ASSLSBs) are attractive because sulfur provides high theoretical capacity and solid electrolytes suppress polysulfide dissolution and flammable liquid electrolyte risks. However, sulfur is electronically and ionic insulating, and its immobile solid-solid conversion in all-solid-state cathodes makes the initial arrangement of sulfur, host material, and solid electrolyte critically important. This work aims to overcome this triple-phase-interface limitation by designing a hierarchical nanowire host that can simultaneously deliver electrons and Li ions to sulfur and SeS₂ active materials.² CoMoS₂@CNT host was synthesized through a hydrothermal route, in which Co-doped MoS₂ nanosheets were grown on one-dimensional carbon nanotubes (CNT). Sulfur or SeS₂ was then incorporated into the host by melt diffusion and combined with Li₆PS₅Cl to form composite cathodes. The CNT core was designed to maintain continuous electronic conduction, while the porous CoMoS₂ shell provided chalcogen-affinitive interfaces, short transport pathways, and intimate contact with the surrounding solid electrolyte. By comparing zero-dimensional carbon, bare CNT, and CoMoS₂ modified CNT hosts, the role of host dimensionality and interfacial chemistry in solid-state chalcogen conversion was clarified. The hierarchical CoMoS₂@CNT architecture suppressed sulfur agglomeration, improved sulfur to Li₂S conversion, lowered polarization, and maintained charge transport pathways under high active material loading. An all-solid-state Li-S cell delivered 4.5 mAh cm^–2 at 2.5 mA cm^–2 with 79.4 % capacity retention after 300 cycles. When sulfur was replaced with SeS₂, the enhanced charge conduction and reversible chalcogen conversion enabled 16.3 mAh cm^–2 with 99.3 % retention over 60 cycles at 60 ℃, exceeding representative ASSLSBs’ benchmarks. A wet-slurry-method based pouch-type SeS₂ cell further demonstrated over 4 mAh cm^–2 under 3 MPa at 30 ℃. These results show that coupling one-dimensional electronic percolation with chalcogen-affinitive mixed-conducting interfaces provides a practical design strategy for high-areal-capacity, safer all-solid-state Li-S/SeS₂ batteries.

Fast-charging batteries with high energy density are critical for extending the driving range and reducing the charging time of electric vehicles. Lithium–sulfur batteries are attractive next-generation energy-storage systems owing to their high theoretical specific capacity of 1673 mAh g⁻¹, yet the mechanisms governing their charging kinetics remain insufficiently understood. Liquid sulfur has been proposed to facilitate fast charging through rapid liquid-phase reactions and dynamic renewal of active interfaces.^1,2 However, because the oxidation of Li₂S₈ to sulfur contributes only one-eighth of the total charging capacity, this process alone cannot explain the high rate charging capability of Li–S batteries.

To understand how sulfur phase influences the charging process, we introduced MoS₂ nanodots into a carbon film matrix to induce solid sulfur formation, whereas liquid sulfur forms on the pristine carbon film.  By regulating the sulfur phase during oxidation, we reveal that liquid sulfur reacts readily with solid Li₂S₂/Li₂S, whereas solid sulfur shows limited reactivity through optical microscopy and in situ Raman. Besides, electrodes (carbon nanofiber) that favor liquid sulfur formation exhibit superior capacity retention than favor solid sulfur (carbon nanofiber/MoS₂ nanodots) when the charging rate is increased from 0.2C to 4C under a fixed 0.2C discharge rate. After 4C charging, XPS confirms the absence of residual Li₂S₂/Li₂S on carbon nanofiber current collectors, while Li₂S₂/Li₂S remains on MoS₂-modified carbon nanofibers

These findings reveal liquid sulfur can act as an active mediator for solid sulfide oxidation, establishing a mechanistic foundation for designing high-energy Li–S batteries with fast-charging capability.

Lithium–sulfur batteries are promising next-generation energy-storage systems for electric vehicles, grid storage, and portable electronics because of their high theoretical capacity, high energy density, and the abundance of sulfur. However, their practical deployment is hindered by poor sulfur conductivity and the lithium polysulfide shuttle effect, which cause rapid capacity fading and low cycling efficiency. Designing sulfur hosts that can confine active species while chemically suppressing polysulfide migration is therefore essential for developing durable Li–S cathodes. In this work, polymer of intrinsic microporosity, PIM-1, was investigated as a functional sulfur host. PIM-1 contains intrinsic micropores below 2 nm that can physically confine sulfur species, while its polar nitrile groups can interact with lithium polysulfides and reduce their dissolution. Sulfur–PIM composites with 0, 15, and 50 wt% PIM-1 were prepared using melt diffusion to promote sulfur infiltration into the microporous polymer framework. The cathodes were then evaluated in Li–S cells to determine how polymer loading affects sulfur utilization, capacity retention, and Coulombic efficiency. The results reveal that PIM-1 content strongly governs the balance between initial capacity and long-term stability. Lower PIM-1 loading S-PIM (15) improves initial sulfur utilization but leads to faster capacity decay. In contrast, S-PIM (50) undergoes an initial stabilization period during the first approximately 20 cycles, followed by highly stable cycling. Compared with S-PIM (0), which retains only about 36% of its capacity after 400 cycles, S-PIM (50) achieves more than 90% capacity retention with nearly 100% Coulombic efficiency. This improvement is attributed to the combined physical confinement of sulfur species within the microporous network and chemical adsorption of polysulfides by nitrile groups, which together suppress shuttle-driven active-material loss. These findings demonstrate that intrinsically microporous polymers can serve as effective, lightweight, and processable hosts for sulfur cathodes. The work provides a molecular design strategy for stabilizing sulfur redox chemistry and advancing high-energy Li–S batteries toward practical applications.

Lithium–sulfur (Li–S) batteries have attracted considerable attention as next-generation lightweight energy storage systems, particularly for urban air mobility applications, because the use of sulfur as an abundant and lightweight cathode active material enables exceptionally high theoretical energy density.^[1,2] However, their practical implementation remains limited by the dissolution and shuttling of lithium polysulfides, which cause active-material loss, sluggish sulfur redox kinetics, and severe corrosion of the lithium metal anode.^[3,4] In this work, we propose a low-polarity solvent-mediated electrolyte design to simultaneously regulate polysulfide solubility and stabilize the lithium metal interface.

Diethyl ether (DEE) was selected as a low-polarity solvent because of its weak interaction with lithium polysulfides and high compatibility with lithium metal. Since DEE alone excessively suppresses polysulfide dissolution and limits sulfur redox kinetics, 1,2-dimethoxyethane (DME) was introduced as a co-solvent to balance polysulfide solubility and interfacial stability. The solvation environment and interfacial chemistry of the DEE/DME electrolyte were examined to clarify its role in regulating polysulfide behavior and lithium metal stability. Notably, operando optical microscopy enabled real-time visualization of electrolyte stability and dendrite evolution, which was further quantified using a normalized hue index and contour image mapping.

The optimized DEE/DME electrolyte promoted the formation of a LiF- and Li₃N-rich solid-electrolyte interphase, enabling uniform lithium deposition and suppressing parasitic reactions between lithium metal and polysulfides. Compared with the conventional DOL/DME electrolyte, the DEE/DME electrolyte exhibited enhanced sulfur conversion kinetics, lower shuttle current, and superior long-term cycling stability. The cell retained 80.14% of its initial capacity after 300 cycles at 3 C and maintained stable performance under practical conditions with high sulfur loading and a low electrolyte-to-sulfur (E/S) ratio.

These results demonstrate that rational control of solvent polarity is an effective strategy for balancing sulfur redox kinetics and lithium metal protection. This study provides useful design principles for high-energy-density Li–S batteries and broader lithium metal battery systems.

Currently, concerns regarding sustainability of LIBs are increasing, as lithium resources are geographically concentrated in limited regions, leading to issues such as price volatility and potential supply risks. Consequently, the development of cost-effective rechargeable batteries that do not rely on lithium becomes urgent. Among the promising candidates, aqueous proton batteries (APBs) have attracted considerable attention as lithium-free energy storage systems. Unlike LIBs that employ flammable organic electrolytes, APBs utilize non-flammable aqueous electrolytes, thereby enhancing operational safety. A representative example of practical APBs is nickel-metal hydride (Ni-MH) battery; however, both the positive and negative electrode materials of Ni-MH batteries contain nickel, which is relatively scarce and increasingly costly. In this study, manganese-based oxides, which are abundant in the Earth’s crust and inexpensive, are studied as positive electrode materials for APBs. First, Mn(OH)₂ was synthesized by a precipitation method. Mn(NO₃)₂ and KOH aqueous solutions were mixed and the resulting precipitate was filtered and washed with deionized water. The obtained Mn(OH)₂ was then oxidized to MnOOH under an O₂ flow. The MnOOH derived from Mn(OH)₂ exhibited a layered structure. The electrode was prepared by slurry method. MnOOH, acetylene black (AB) and aramid resin binder¹ were mixed, and the slurry was cast onto Ni foil and dried. To evaluate the electrochemical properties, the three-electrode cells were employed, using hydrogen storage alloy and NiOOH_x as the counter electrode and the reference electrode, respectively. 3 M KOH aqueous solution was used as the electrolyte and charge/discharge tests were conducted. For comparison, commercial γ-MnO₂, which has a tunnel structure, was also examined the electrochemical performance. The electrode preparation procedure and charge/discharge tests were the same as those used for MnOOH. When the charge capacity was limited to 300 mA h g⁻¹, the discharge capacity of MnOOH were less than 100 mA h g⁻¹. In contrast, γ-MnO₂ exhibited a discharge capacity exceeding 200 mA h g⁻¹ at a slow rate. At the conference, detailed discussions will be presented on the crystal structure changes after charge/discharge cycling, the effects of charge/discharge conditions on the electrochemical properties, and comparisons with Ni(OH)₂.

Lithium–oxygen secondary batteries (Li–O₂ batteries) possess the highest theoretically gravimetric energy density among next-generation secondary battery systems. During the charging process, Li₂O₂, the primary discharge product, must be oxidatively decomposed. However, its poor oxidative decomposability leads to an increase in charging voltage resulting in reduced energy efficiency and poor cycling performance. We have previously found that the oxidative decomposition activity of Li₂O₂ is enhanced when a mixed electrolyte solvent composed of amide and fluorinated amide is used^[1,2]. However, the underlaying mechanism by which this electrolyte lowers the charging voltage remains unclear.

In this study, we aimed to elucidate the origin of the enhanced decomposition activity of Li₂O₂ in this electrolyte by investigating the effect of the concentration ratio of fluorinated amide to amide in the charge-discharge characteristics. N,N-dimethylacetamide (DMA) and N,N-diethyl-2,2,2-trifluoroacetamide (DETFA) were selected as electrolyte solvents. LiNO₃ was employed as the lithium salt. LiNO₃ is reduced at the Li negative electrode to generate the NO₂/NO₂^－ redox couple, which functions as a redox mediator for Li₂O₂ decomposition during charging^[3].

The figure shows the charging profiles obtained under constant-current conditions (0.1 mA cm⁻²). The charging voltage decreased with increasing DETFA concentration. Synchrotron XRD analysis of the discharge products revealed that the crystallinity of Li₂O₂ decreases in electrolytes with high DETFA concentration. This suggests that highly decomposable Li₂O₂ is formed in the presence of high concentration of DETFA. Furthermore, it was found that the oxidation potential of NO₂^－ to NO₂ decreases with increasing DETFA concentration. This result indicates that the NO₂/NO₂^－ redox couple functions more efficiency as redox mediator under high DETFA concentration condition. These findings demonstrate that the reduction in charging voltage achieved by mixing fluorinated amide arises from both enhanced oxidative decomposability of Li₂O₂ and improved reactivity of the redox mediator.

Zinc–iodine flow batteries are promising candidates for safe, low-cost, and scalable stationary energy storage because they combine aqueous operation with high theoretical energy density and earth-abundant active materials. However, practical operation remains limited by unstable zinc plating/stripping, cell polarization, crossover-induced self-discharge, and capacity fade. Supporting electrolytes are often discussed mainly in terms of suppressing zinc dendrite formation, while the broader role of spectator cations and anions in regulating anolyte chemistry remains underexplored.

In this work, we investigate how spectator-ion identity influences the electrochemical behavior of zinc–iodine flow batteries. By systematically varying cations and anions in the anolyte, we examine their effects on zinc plating/stripping reversibility, charge–discharge voltage profiles, polarization, voltage efficiency, Coulombic efficiency, and cycling stability. Our results show that spectator ions are not passive background species. Instead, both cation and anion identity strongly affect the separation between charge and discharge curves, indicating a direct influence on cell polarization and voltage efficiency. The optimized supporting electrolyte shows reduced charge–discharge voltage separation and improved voltage efficiency compared with baseline anolytes. These effects are coupled with changes in zinc deposition behavior, electrolyte transport, and interfacial stability.

The results suggest that anolyte performance cannot be optimized solely by targeting dendrite suppression. Rather, spectator ions should be treated as active electrolyte-design parameters that regulate zinc reversibility, overpotential, transport resistance, and long-term flow-cell durability. This work provides new insight into cation–anion selection for aqueous zinc–iodine systems and highlights an electrolyte-design strategy for improving the efficiency and stability of next-generation redox flow batteries.

Aqueous Zn–I₂ batteries are attracting significant attention as next-generation energy storage systems due to their inherent safety, low cost, and high energy density. Despite these advantages, their practical application remains limited by severe interfacial instabilities at the Zn anode, including hydrogen evolution, corrosion, and dendritic growth, as well as sluggish I₂/I⁻ redox kinetics and polyiodide shuttling at the cathode. Overcoming these dual challenges is essential for enabling long-life, high-performance Zn–I₂ batteries suitable for grid-scale energy storage.

In this study, we introduce a molecular design strategy employing 4-aminobutyric acid (AB), a commercially available amino acid derivative with a push–pull dipolar structure, as a functional electrolyte additive. Unlike conventional additives with folded conformations, AB maintains an extended dipolar structure that maximizes polarizability and dipole moment. This unique conformation enables strong binding with Zn²⁺ ions, lowers the desolvation barrier, and promotes preferential (002)-oriented Zn deposition, thereby suppressing parasitic reactions such as hydrogen evolution and zinc corrosion. Simultaneously, AB interacts selectively with iodine species, mitigating polyiodide formation and shuttling while accelerating redox kinetics.

To elucidate these mechanisms, we employed density functional theory (DFT) calculations, FT-IR and Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and in-situ characterization techniques including XRD, SEM, Raman, and laser confocal scanning microscopy (LCSM). Comparative analysis with β-alanine (AL) highlighted the critical role of extended molecular conformation in achieving interfacial stability and enhanced charge transfer dynamics.

The incorporation of AB led to remarkable electrochemical improvements. Zn||Zn symmetric cells demonstrated stable cycling for over 1000 hours at 3 mA cm⁻² and 3 mAh cm⁻², while Zn–I₂ full cells with high-capacity cathodes (5 mAh cm⁻²) retained 95.8% of their initial capacity after 900 cycles. These results confirm that AB effectively suppresses dendritic growth, stabilizes electrode interfaces, and enhances overall battery kinetics.

This work establishes that controlling intramolecular interactions to maintain extended dipolar conformations represents a universal strategy for interfacial stabilization in aqueous Zn–I₂ batteries. The findings provide a pathway toward safer, longer-lasting, and higher-performance energy storage systems, offering valuable insights for the design of next-generation batteries supporting renewable energy integration and grid applications.

Lithium–sulfur batteries (LSBs) have attracted considerable attention due to their high theoretical specific capacity (1675 mAh g⁻¹) and energy density (2600 Wh kg⁻¹), as well as their low cost and environmental friendliness. However, their practical application is hindered by the severe volume expansion of the sulfur cathode (up to ~80%) during lithiation, which leads to structural degradation and rapid performance decay. Three-dimensional (3D) printing provides a promising strategy to address this issue by enabling the design of tailored electrode patterns and architectures.

This study systematically investigates the influence of filament width and electrode patterns/architectures on the electrochemical performance of 3D-printed cathodes. The filament width directly affects the transport of Li⁺ ions and electrons, as well as the ability to accommodate volume expansion. Notably, the filament width obtained using a 23G needle achieves an optimal balance between efficient charge transport and structural stability. Furthermore, the electrode architecture plays a crucial role in accommodating volume expansion and maintaining structural integrity. Various 3D-printed sulfur cathode architectures were designed, and their electrochemical performance was systematically compared.

The results demonstrate that the concentric circle architecture effectively mitigates structural degradation induced by volume expansion. At a sulfur loading of 3 mg cm⁻², after five activation cycles at a low current density, the electrode delivers an initial discharge capacity of 935.4 mAh g⁻¹ at 0.1 C and retains 783.89 mAh g⁻¹ after 100 cycles, corresponding to a capacity retention of 83%. This cycling performance is notably higher than that of the conventional waffle-patterned electrode and the doctor-blade electrode, indicating the advantage of the concentric circle design in maintaining electrode stability under high sulfur loading. Post-cycling SEM characterization further confirms the improved structural integrity of this architecture.

Overall, this study provides practical guidance for the scalable fabrication of 3D-printed sulfur cathodes and other electrode materials that undergo large volume expansion. It also offers useful insights into the practical application and future commercialization of 3D-printed lithium–sulfur batteries.

Lithium–air batteries have the potential to reach system-level energy densities of 500–1000 Wh kg⁻¹, making them a key enabling technology for the electrification of new sectors. During discharge, molecular oxygen is reduced to peroxide at the positive electrode. The reduction of oxygen to peroxide involves the formation of other reactive oxygen intermediates, such as superoxide. These reactive oxygen intermediates react with the electrolyte, limiting cell lifetimes to fewer than 10 cycles and severely hampering the energy-density promise of lithium–air batteries. This work examines the chemical stability of electrolyte solvents in the presence of superoxide.

By considering possible organic chemical transformations that the electrolyte solvent may undergo, this study identifies likely degradation mechanisms and the expected products of these degradation reactions. Using potassium superoxide as a chemical substitute for superoxide in the battery, reaction routes are confirmed using nuclear magnetic resonance spectroscopy (NMR), gas chromatography–mass spectrometry (GC–MS), and differential electrochemical mass spectrometry (DEMS). The presence of these products is then confirmed within the battery. This mechanistic perspective enables solvent instability to be linked directly to molecular structure and reactivity. The findings provide insight into the factors that govern electrolyte durability in lithium–air batteries and highlight broader design principles for improving solvent stability.

Aqueous zinc-ion batteries (AZIBs) offer a safe, cost-effective, and high-capacity energy storage solution, yet their performance is hindered by interfacial challenges at the Zn anode, including hydrogen evolution, corrosion, and dendritic Zn growth. While most studies focus on regulating Zn²⁺ solvation structures in bulk electrolytes, the evolution of interfacial solvation—where Zn²⁺ undergoes desolvation and deposition—remains insufficiently explored. Here, we introduce sulfated nanocellulose (SNC), an anion-rich biopolymer, to tailor the interfacial solvation structure without altering the bulk electrolyte composition. Using in situ attenuated total reflection Fourier transform infrared spectroscopy and fluorescence interface-extended X-ray absorption fine structure, we reveal that SNC facilitates the formation of a low-coordinated Zn²⁺ solvation shell at the interface by weakening H₂O coordination. This transformation is driven by electrostatic interactions between Zn²⁺ and anchored sulfate groups, thereby reducing water activity, improving interfacial stability during charge/discharge, and suppressing parasitic reactions. Consequently, a high average coulombic efficiency of 99.6% over 500 cycles in Zn|Ti asymmetric cells and 1.5 Ah pouch cells (13.4 mg cm⁻² loading, remained stable over 250 cycles) was achieved in SNC-induced AZIBs. This work underscores the importance of interfacial solvation structure engineering—beyond traditional bulk electrolyte design—in enabling practical, high-performance AZIBs.

Lithium iron phosphate (LFP, LiFePO₄) is already a key material in lithium-ion battery research due to its outstanding characteristics such as excellent electrochemical stability, intrinsic safety, non-toxicity, and low cost. In addition to its commercial success as a cathode material, LFP shows promising results as a reference material due to its stable potential in non-aqueous lithium-based electrochemical systems. In conventional electrochemical measurements, metallic lithium is most commonly used as the reference electrode. However, metallic lithium suffers from significant drawbacks, including high chemical reactivity toward certain electrolytes and additives such as acetonitrile, a very low electrochemical potential that can unintentionally reduce many substances, and the occurrence of spikes in potential profiles that are readily observable in the differential capacity (Fig. 1). These effects can lead to limitations in material selection and unintended measurement deviations.

This research focuses on partially delithiated LiFePO₄ as a reliable and chemically stable alternative to metallic lithium. By chemically removing lithium from the LFP structure, a well-defined potential can be achieved, providing a stable internal reference within the operating window of most battery materials. This work investigates the synthesis and long-term stability of partially delithiated LFP under working conditions (Fig. 1), with the aim of establishing it as a reliable and stable reference electrode for lithium-based systems, thereby improving the safety, reproducibility, and precision of measurements for next-generation battery materials and ultimately supporting the development of safer, more efficient, and high-performance energy storage technologies.

Aqueous zinc-ion batteries have attracted significant attention as promising alternatives to conventional lithium-ion batteries owing to their low cost, the abundance of zinc resources, and the intrinsic safety of non-flammable aqueous electrolytes.^[1] In addition, the inherent stability of zinc enables simpler and more cost-effective manufacturing without requiring stringent dry-room conditions.^[2]

However, their commercialization is hindered by poor cycling stability and rapid capacity fading, which originate from the highly unstable zinc anode–electrolyte interface.^[3] This thermodynamic instability triggers parasitic reactions, such as the hydrogen evolution reaction (HER) and chemical corrosion, which continuously consume active zinc and electrolyte. Moreover, the intrinsic surface heterogeneities of practical Zn foils give rise to spatially non-uniform reaction kinetics and local galvanic microcells. This inhomogeneous interfacial chemistry induces localized HER and interfacial alkalization, thereby promoting the precipitation of insulating byproducts and the formation of passivation layers. Consequently, these interfacial issues lead to uneven zinc deposition and uncontrolled dendrite growth, thereby causing electrochemical performance deterioration and increasing the risk of internal short circuits.^[4]

Herein, we present an interfacial design strategy based on a hybrid electrolyte system. We utilize the localized chemical environment generated by spontaneous reactions at the Zn–electrolyte interface as a controllable chemical trigger for the formation of an engineered interphase. Our findings suggest that the favorable electrochemical performance arises from the combined effects of the hybrid electrolyte and the regulated initial interphase, which together influence subsequent Zn plating/stripping dynamics and long-term cycling stability.

Electrochemical dissolution of metal anodes such as Li, Na, and Zn in reactive liquid electrolytes is of contemporary interest for applications in high energy density batteries. The tendency of metal anodes to undergo uneven dissolution – driven by the thermodynamic instability of the anode when in contact with reactive liquid electrolytes, has emerged as fundamental barrier to rechargeable metal batteries. Using low-cost Zinc (Zn) anodes as a proof of concept, we report that ordered dissolution of metals at electrochemical interfaces in reactive liquid electrolytes offers a new approach for improving reversibility of metal anodes. The electrochemical criterion for ordered metal electrodissolution is defined: analogous to crystallographically-induced directed electrodeposition at metal substrates, metal substrates are found to preferentially dissolve along a direction that exposes the atomic planes with highest surface energies. We leverage this phenomenon to fabricate Zn anodes with 3D-nanoarchitectured channels oriented along the (110) and (101) atomic planes and show that such nanochannels are effective hosts in suppressing mossy and dendritic metal deposition under ultrahigh charging capacities via a confined epitaxial electrocrystallization process within the nanochannels. The anodes maintain stable cycling over repeated cycles of charge and discharge at capacities as high as ~ 20 mAhcm^-2 in coin cell formats using I₂ cathodes (10 mAhcm^-2 in Zn||CC half cells and 6 mAhcm^-2 in Zn||MnO₂ full cells) with near unity reversibility, confirming the utility of our findings in practical applications. We further extend our findings to more challenging anode systems: HCP Mg, BCC Li, and show that oriented dissolution is universal across a variety of metal anodes, all of which are relevant for developing next generation metal batteries.

Aqueous rechargeable batteries are emerging as a promising alternative to conventional lithium-ion batteries for large-scale energy storage. This is especially true for zinc-ion batteries since they are considered safer and more stable due to their non-flammable electrolyte and reduced risk of thermal runaway. Various manganese oxide MnO₂ polymorphs, including α, b and δ have been studied as cathode materials for zinc-ion batteries; however, the low capacity and the poor stability issues limited their large-scale application. However, spinel-type MnO₂ is still rarely reported since the Zn²⁺ intercalation in the spinel lattice is assumed to be limited by the narrow three-dimensional tunnels, which limit its energy density.

Herein, we evaluate the electrochemical performance of various spinel-type manganese oxides synthesized through the leaching of metal ions (Mⁿ⁺) from MMn₂O₄ compounds, resulting in cathode materials optimized for ZIBs.

The synthesized materials demonstrate distinct structural features optimized for enhanced electrochemical performance. Notably, the pristine MMn₂O₄ materials exhibit limited specific capacities, below 140 mAh g⁻¹. However, after acid leaching, the capacities increase significantly, reaching 346 mAh g⁻¹at a current density of 50 mA g⁻¹. Moreover, MnO₂ displays excellent cycling stability, maintaining over 95% of its capacity after 110 cycles at 200 mA g⁻¹.

In addition, an in-depth study using ex-situ XRD and a distribution of relaxation time (DRT) analysis was conducted to elucidate the underlying mechanisms of the synthesized materials.

Structural instability remains the primary challenge limiting the practical application of iron- and manganese- based layered oxide cathodes for sodium-ion batteries. In the O3-type NaFe_0.5Mn_0.5O₂ material, coupled Jahn-Teller distortion, transition metal migration, and anisotropic lattice strain induce complex phase evolution during cycling, resulting in sluggish reaction kinetics and progressive capacity fading. Addressing these intrinsic instabilities requires regulation of the electronic structure and lattice dynamics at the atomic scale. ^[1]

In this work, a dual-doping strategy is employed to modify the transition metal framework of NaFe_0.5Mn_0.5O₂ through co-doping with Ti/Zn and Ti/Mg. The introduction of these dopants regulates the local electronic environment and stabilizes the layered structure during sodium ion extraction and insertion. Structural and electrochemical analyses reveal that dual-substitution significantly enhances electrochemical reversibility and suppresses structural degradation compared with the pristine material. The modified cathodes exhibit higher specific capacity, stable voltage profiles, reduced polarization and improved capacity retention, indicating enhanced Na⁺ diffusion and favorable reaction kinetics.

To further elucidate the role of dopant incorporation, density functional theory calculations were conducted to investigate changes in electronic structure and Na⁺ transport. The results indicate that titanium substitution stabilizes the transition metal-oxygen framework, while zinc or magnesium modifies the local charge distribution and mitigates Jahn-Teller distortion. Consequently, the co-doped systems exhibit more stable configurations, reduced Na⁺ diffusion barriers, and enhanced ionic transport. Furthermore, ab initio molecular dynamics simulations demonstrate that co-doping improves structural stability during Na⁺ extraction at elevated temperatures, reducing volume variation from more than 4.05% in the undoped material to less than 0.05% in doped systems.

Overall, this experimental and theoretical study shows that dual-doping tunes electronic and structural properties, stabilizing layered Fe/Mn oxides and guiding rational cathode design for SIBs.

O3-type layered cathodes for sodium-ion batteries have emerged as promising candidates because of their high theoretical capacity and low cost. Nevertheless, their practical deployment is hindered by insufficient cycling stability, primarily caused by unfavorable phase transitions and structural degradation during repeated sodiation and desodiation processes. To overcome these inherent limitations, we employed a high-entropy design strategy by incorporating multiple metal ions into the NaNi_0.4Fe_0.25Mn_0.35O₂ (NFM) framework, leading to the development of a series of compositionally engineered cathode materials. Such compositional modulation enhances structural stability and promotes more efficient Na-ion transport during cycling. Consequently, the high-entropy cathodes exhibit superior electrochemical performance, including higher reversible capacity, improved long-term cycling stability, and better rate capability than the pristine NFM material. Their enhanced Na-ion diffusion kinetics are supported by galvanostatic intermittent titration technique, cyclic voltammetry, and electrochemical impedance spectroscopy analyses, while in situ X-ray diffraction analysis confirms reduced lattice strain and mitigated structural instability during phase transitions. Moreover, full-cell evaluations with a hard carbon anode demonstrate excellent rate capability and prolonged cycling stability. These findings highlight the effectiveness of the high-entropy strategy in reinforcing the structural integrity and electrochemical performance of O3-type layered cathodes, providing a viable pathway for the development of durable, high-performance sodium-ion batteries.

Aqueous Zn-ion batteries are well regarded among the next-generation energy storage technologies due to their low cost and high safety. However, the unstable stripping/plating process leading to severe dendrite growth under high current density and low temperature impede their practical application. Herein, we demonstrate that the addition of 2-propanol can regulate the outer solvation shell structure of Zn2+ by replacing water molecules to establish a “eutectic solvation shell”, which provides strong affinity with the Zn (101) crystalline plane and fast desolvation kinetics during the plating process, rendering homogeneous Zn deposition without dendrite formation. As a result, the Zn anode exhibits promising cycle stability over 500 hours under an elevated current density of 15 mA cm-2 and high depth of discharge of 51.2%. Furthermore, remarkable electrochemical performance was achieved in a 150 mAh Zn|V2O5 pouch cell over 1000 cycles at low temperature of -20 °C. This work not only offers a new strategy to achieve excellent performance of aqueous Zn-ion batteries under harsh conditions but also reveals electrolyte structure designs that can be applied in related energy storage and conversion fields.

Metal batteries have attracted substantial attention for next-generation high-energy storage systems because of their ultrahigh theoretical energy densities and low redox potentials. However, their practical implementation remains limited by uncontrolled dendritic nucleation, unstable solid-electrolyte interphase formation, large nucleation overpotentials, and poor cycling stability. Conventional MXene synthesis predominantly relies on concentrated hydrofluoric acid (HF) etching of MAX precursors. Although HF etching is widely adopted due to its high efficiency and strong selectivity for A-layer removal, it suffers from severe drawbacks including hazardous handling, excessive –F terminations, structural over-etching, and significant environmental concerns. These limitations necessitate the exploration of sustainable etching strategies that can precisely tailor surface terminations while minimizing structural damage. Herein, we comparatively investigate the synthesis of Mo₂Ti₂C₃T_x via multiple etching pathways: (i) concentrated HF etching (fast kinetics; F-rich surfaces), (ii) mild HF-containing etching (controlled reaction; reduced defects and balanced terminations), (iii) Lewis acidic molten salt (LAMS) etching (fluorine-minimized route; alternative halide terminations), and (iv) Te-assisted etching (chalcogen-mediated modification; expanded interlayers with possible impurity incorporation). Each strategy induces distinct surface chemistries (–F, –O, –Cl, –Te), defect densities, and interlayer architectures, thereby modulating metal binding energies, ion diffusion pathways, and interfacial stability. During nucleation, the optimized MXene host enables homogeneous metal deposition and reversible stripping with suppressed dendrite growth and low polarization. Among the investigated routes, the mild etching strategy yields Mo₂Ti₂C₃T_x with favourable NaF rich surface terminations, enlarged interlayer spacing, and preserved structural integrity, resulting Coulombic efficiency of 99.2% at high current density (3 mA cm^-2) a fixed cutoff capacity of 3 mA h cm^-2. Thus, this study highlights the decisive role of synthesis-route engineering in tailoring Mo₂Ti₂C₃T_x surface terminations and structural properties by unlocking the full potential of Mo₂Ti₂C₃T_x MXene by correlating etching chemistry with nucleation thermodynamics and plating/stripping kinetics.

With the rapid expansion of electric vehicles, stationary grid storage, and renewable energy integration, the demand for rechargeable battery technologies continues to increase. Although lithium-ion batteries (LIBs) remain the dominant commercial platform, their long-term scalability is increasingly challenged by the high cost, limited reserves, and geographically concentrated supply of critical elements such as lithium, cobalt, nickel, and copper. These limitations raise broader concerns regarding supply-chain stability, geopolitical dependence, and sustainability, thereby motivating the development of alternative battery chemistries based on earth-abundant and cost-effective elements.

Among these alternatives, sodium-ion batteries (SIBs) have attracted considerable attention as promising candidates for next-generation energy storage. In particular, full cells combining Prussian Blue (PB) cathodes with hard carbon (HC) anodes are highly attractive owing to their low material cost and compositional abundance. However, the practical implementation of PB–HC full cells is hindered by the intrinsic mismatch between sodium storage and irreversible sodium consumption at the two electrodes, making rational cell balancing a critical issue.

PB cathodes possess an open three-dimensional framework that enables fast Na⁺ diffusion and favorable reaction kinetics. However, residual crystal water remaining after synthesis can trigger side reactions, accelerate structural degradation, and impair long-term cycling stability. In contrast, HC anodes experience substantial irreversible sodium loss during the initial cycle due to solid electrolyte interphase formation and sodium trapping in nanopores, leading to low initial coulombic efficiency (ICE) and depletion of the available sodium reservoir in the full cell.

To address these challenges, this study proposes an integrated sodium inventory engineering strategy for PB–HC sodium-ion batteries. In this work, sodium inventory refers to the total amount of cyclable sodium available in the full cell, which is strongly influenced by irreversible sodium consumption at both electrodes. Residual crystal water in PB is minimized to suppress irreversible capacity loss and improve cycling durability, while presodiation of the HC anode is employed to compensate for initial sodium loss and tune the operating voltage window. These results demonstrate that effective cell balancing in PB–HC full cells requires deliberate control of cyclable sodium inventory beyond conventional electrode mass matching.

Recently, environmental issues have attracted increasing attention from society, sustainable development have become important objectives for researchers. In response to this issue, we utilize plant waste as precursor for HC (HC) materials, aiming to mitigate carbon emissions during the production of anode materials. Furthermore, with the increasing performance demands of the energy devices, traditional energy storage systems are gradually falling short of these requirements. Graphite is the most common anode material applied in traditional lithium-ion batteries, due to the stable cycle life. However, limited by the physical structure, the theoretical specific capacity of graphite is only 372 mAh g^-1. Additionally, the highly crystalline structure and narrow interlayer spacing (d₀₀₂=0.335 nm) severely resulting in lower ion conductivity and C rate capability.

Consequently, HC has recognized as a potential alternative owing to the superior specific capacity and excellent ion storage capability for sodium/potassium-ion batteries. Generally, HC precursors can be classified into three main categories: resins, polymers, and biomass. This study focuses on BC (BC) owing to its environmentally friendly nature. However, BC typically contain highly heteroatoms and functional groups. Due to the intrinsic defects ^[1], BC often suffer from low initial Coulombic efficiency (ICE) and poor cycling stability.

To enhance the electrochemical performance, this study employs metal-catalyzed graphitization strategy. Although previous works ^[2]. indicate transition metal compound as a catalyst allows graphitization to proceed at low temperature (approximately 800 ℃), it inevitably leaves residual metal compounds within the HC matrix. In this work, transition metals compound is employed and the thermal processing temperature is maintained below 1200 ℃. Our results reveal absence of residual metal compounds in the HC when the thermal processing temperature is at or above 1000 ℃. The metal-catalyzed graphitization HC anode features reduced specific surface area and short ordered structure, resulting in excellent electrochemical performance. As shown in Fig. 1, the optimized HC anode in lithium/sodium-ion batteries deliver superior discharge capacity of 478/241 mAh g^-1 at 0.1 C, and initial coulombic efficiency (ICE) is 72.5/74.2 %, respectively. This study successfully developed a metal-catalyzed graphitization strategy for BC anodes for application in both lithium/sodium-ion batteries.

Rechargeable Mg-ion batteries (MIBs) represent a possible candidate for next-generation energy storage systems owing to the high abundance of Mg, dendrite-suppressed Mg metal deposition, and high volumetric capacity enabled by divalent Mg²⁺. Despite these advantages, practical application remains limited by sluggish and interphase-sensitive Mg deposition/dissolution, in which electrolyte-derived surface layers govern reversibility and interfacial kinetics. A detailed understanding of such dynamic interphase evolution is therefore essential for the rational design of advanced Mg electrolytes. Among the electrolyte systems developed for MIBs, all-phenyl complex (APC) electrolytes are widely recognized as benchmark chloride-based electrolytes because they enable relatively reversible Mg electrochemistry. In addition, cationic additives such as 1-butyl-1-methylpyrrolidinium chloride (PY14Cl) have been introduced into APC-based electrolytes to mitigate corrosion-related issues and improve electrochemical performance [1, 2]. Nevertheless, while the beneficial effects of PY14Cl have been reported, its precise influence on the dynamic interfacial evolution during Mg deposition/dissolution remains insufficiently understood. In this work, an electrochemical quartz crystal microbalance (EQCM) was used to probe operando mass evolution and motional resistance changes on Mg electrodes in pure APC and APC containing cationic additives during electrochemical cycling. The EQCM results reveal clear additive-induced changes in mass evolution and interfacial resistance, demonstrating that the cations alter the nature of the surface layer formed during Mg deposition/dissolution. As an example, the PY14Cl-containing electrolyte shows lower mass accumulation and reduced motional resistance compared with pure APC, indicating less resistive surface layer with suppressed interphase growth. Furthermore, higher mass-per-electron than ideal Mg deposition indicates reversible accumulation of complex interfacial species during the electrochemical cycling, whereas the additive moderates the accumulation. Overall, this study clarifies the role of PY14Cl in regulating interphase evolution in APC-based electrolytes and highlights EQCM as a powerful operando tool for probing additive-controlled interfacial phenomena. These findings provide useful guidance for the design of more stable Mg electrolytes.

Sodium-ion is a promising alternative to lithium-ion batteries, with potentially lower material costs due to reducing the use of critical materials. [1] Independent measurement of commercial sodium-ion battery performance and cycle life is important to ensure reliability. This study focuses on ageing tests of HAKADI 10 Ah sodium-ion cylindrical cells (33140-format) with an energy density of 110 Wh/kg. A tab-less design with aluminium current collectors compacted at both terminals was observed during cell disassembly, which reduces material costs and eliminates internal stresses due to the presence of an inner tab. Voltage curves, capacity fade, and temperature rise are shown in Figure 1. The cells were cycled at a 1C charge/discharge current and SOC 0-100% (1.5-4V) at 25°C, for 300 cycles with check-ups every 100 cycles. The cells likely have a nickel-iron-manganese (NFM) positive electrode, since the voltage curves are similar to those for layered transition metal oxides. [2] The voltage curves show an increase and decrease in the starting voltage during charge and discharge, respectively. Cell capacity increases during the first 50 cycles, followed by gradual capacity loss. Internal resistance increased during cycling, from 5.0 mΩ initially to 13.5 mΩ after 200 cycles, as measured by direct current pulse (1C, 10s) at SOC 50%. The maximum temperature rise during discharge increased from 7 to 11°C, also indicating an internal resistance increase. The cells had a reasonably high capacity retention (SOH 92%/300 cycles). The datasheet indicates a cycle life of 3000 cycles to reach SOH 70%. However, extrapolating the linear trend in capacity loss results in 970 cycles to reach SOH 70%. This significant difference could be explained by the fact that in the datasheet, the cell was cycled between 2-4V and with only a 5 min rest after charging and discharging. In contrast, in this ageing study the cell was cycled at full DOD (1.5-4V) with a 1h rest. This suggests that long rest times at both low and high SOCs significantly degrades cycle life.

Acknowledgement: The authors acknowledge support from the French National Research Agency (ANR) under France 2030 program and reference ANR-22-PEBA-0006 (project SENSIGA) [3]

As alternatives to lithium-ion batteries, sodium-ion batteries (SIBs) are gaining increasing attention because of the lower cost and higher abundance of sodium. In the hard carbon (HC) anode, the main limitations are low Na⁺ transport rate and poor Na⁺ storage capability because of narrow interlayer spacing and ineffective defect structure design.

In this research, we demonstrate a simple but scalable upcycling process that utilizes post-consumer polyethylene terephthalate (PET) waste to produce nitrogen doped HC (NHC) via potassium hydroxide (KOH)-assisted pyrolysis and further nitrogen doping through urea treatment. In particular, this combination promotes expansion of interlayer spacing and tuning of defect chemistry in NHC materials. After optimization, we acquire the NHC-800 with an expanded interlayer spacing (~0.408 nm) and a balanced ratio between disordered carbon and pseudo-graphite regions, together with rich amounts of electroactive pyridinic and pyrrolic nitrogen species.

Thus, NHC-800 shows a high specific capacity of 310.7 mAh g⁻¹ at a current density of 20 mA g⁻¹ with capacity retention of 80.3% after 874 cycles. Such high electrochemical performances are owing to the beneficial synergistic effect between the expanded interlayer spacing, optimized defect density and surface area, leading to high capacity of intercalating Na⁺, strong capacity of ion adsorption, and the prevention of thickening of the solid electrolyte interphase layer. Moreover, the kinetic test results prove the significant improvement of capacitance contribution and Na⁺ diffusion coefficient, showing the enhancement of Na⁺ intercalation.

Furthermore, the assembled full cell (NHC-800//Na₃V₂(PO₄)₃) exhibits remarkable stability and a high capacity retention of 84.5% after over 200 cycles, revealing the potential applicability of NHC-800 in the practical application of SIBs. This study provides a valuable insight into the correlation between the interlayer spacing and defect engineering in the hard carbon material for the first time and will guide us in developing an environmentally sustainable approach for producing next-generation electrode materials using plastic waste.

Aqueous zinc-ion batteries (AZIBs) have garnered significant attention as a sustainable and safe alternative to lithium-ion batteries. Despite their potential, the slow diffusion kinetics of divalent zinc ions and the structural degradation of cathode materials remain critical bottlenecks. While vanadium-based compounds offer high theoretical capacity, achieving simultaneous high-rate capability and long-term cycling stability is still a major challenge.

In this study, we developed a series of vanadium sulfide-based composites with tailored microstructures to enhance electrochemical performance. By controlling the chemical composition and the integration of carbonaceous frameworks, we systematically investigated the correlation between material architecture and Zn²⁺ storage behavior. Our findings reveal that the optimized composite exhibits a unique electrochemical activation process that significantly boosts energy density and charge transfer kinetics.

Comprehensive characterizations were conducted to evaluate the structural evolution and Zn²⁺ migration pathways. The results demonstrate that the rational design of the sulfide-based host can effectively mitigate structural strain and improve interfacial stability during repetitive cycling. This work provides a versatile strategy for designing advanced cathode materials, offering new insights into the development of high-power aqueous energy storage systems.

Mechanical instability and rapid capacity fading caused by the severe volumetric expansion of alloy-type anodes remain key barriers to their practical implementation in potassium-ion batteries. Here, we demonstrate that electrolyte formulation plays a decisive role in controlling both the electrochemical performance and structural integrity of a high-capacity Sb/graphite composite anode with a 70:30 wt% composition. A localized high-concentration electrolyte (LHCE), consisting of KFSI, glyme solvents, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether as a diluent, enables markedly enhanced durability, sustaining more than 300 cycles at 400 mAh g⁻¹, corresponding to 1.5 mAh cm⁻². In contrast, a conventional carbonate-based electrolyte (CBE) undergoes rapid degradation. Operando Raman spectroscopy, operando energy-dispersive X-ray diffraction, operando electrochemical dilatometry, and ex situ XPS and TEM reveal that this improvement originates from a dual electrolyte effect on both the surface chemistry and bulk structural evolution of the electrode. The CBE promotes crystalline multiphase K–Sb alloying, substantial graphite participation, and the formation of a thick, organic-rich SEI, resulting in large, poorly reversible swelling and mechanical damage. By contrast, the LHCE favors predominantly amorphous KₓSb formation, suppresses deep K⁺ intercalation into graphite, and generates a thin, inorganic, KF-rich interphase that mitigates internal strain. These findings establish a direct link between solvation structure, interphase chemistry, and chemo-mechanical stability, providing guidance for electrolyte design toward durable alloy-type anodes.

Anionic redox is a key route to high-energy sodium-ion batteries (SIBs), but its practical use is hindered by structural instabilities arising from irreversible phase transitions and cation migration. In Mn-Li-based layered oxides, lithium migration from the transition-metal layer to the alkali slab during charging triggers detrimental phase transformations that compromise oxygen-redox reversibility. Herein, we propose a kinetically induced thermodynamic non-equilibrium (TnE) strategy that exploits current density as a control variable to suppress Li migration and stabilize anion redox in a P3-type Na0.6[Li0.2Mn0.8]O2 (P3-NLMO) cathode.

P3-NLMO was synthesized via solid-state calcination, and its rate-dependent behavior was investigated by combining first-principles calculations with electrochemical analyses (GITT, CV, EIS), Mn K-edge X-ray absorption spectroscopy (XAS), O K-edge mapping resonant inelastic X-ray scattering (mRIXS), and operando synchrotron X-ray diffraction (XRD). Decoupling experiments using a 1C-charge / variable rest / 1C-discharge protocol were further designed to separate the contributions of charging kinetics and high-voltage dwell time.

P3-NLMO exhibits a striking anomalous rate behavior, retaining 63.7% of its capacity after 30 cycles at 1C versus only 41.2% at 0.1C. DFT calculations identify a thermodynamic equilibrium (TE) pathway in which spontaneous Li migration drives a deleterious P3-to-Z biphasic transition under slow cycling, while rapid charging kinetically outruns this migration along a TnE pathway, preserving a "zero-strain" P3 framework as confirmed by operando XRD. XANES/EXAFS and mRIXS confirm pure oxygen-driven redox at all rates, isolating the kinetic effect from any cationic contribution. Critically, capacity declines progressively with longer high-voltage rest, and operando XRD captures the P3-to-Z transformation proceeding even without current, establishing that degradation is intrinsically time-dependent rather than electrochemically driven.

These findings reframe fast charging as a deliberate stabilization strategy and establish kinetically induced TnE operation as a generalizable design principle for anion-redox layered oxide cathodes in next-generation high-energy SIBs.

The global move to net zero economies requires suitable energy storage solutions. Lithium-ion batteries (LIBs) lead the way in battery technology but the low abundance and uneven distribution of lithium deposits, along with their dependency on resource critical materials, such as nickel and cobalt, causes concerns regarding their long-term sustainability. Sodium-ion batteries (SIBs) are an attractive alternative that have significant cost and sustainability advantages over LIBs. Unlike lithium, sodium is widely abundant and evenly distributed across the globe. The sustainability of SIBs is further improved as they allow cobalt-free cathodes to be used and the copper current collectors at the anode (used in LIBs) to be replaced by aluminium.[1]

This poster focuses on the electrolyte for SIBs, where the benchmark salt is NaPF6.[1] Although NaPF6 affords stable long-term cycling,[2] there are safety concerns surrounding the PF6- anion due to its ability to undergo hydrolysis and form toxic HF.[3] The presence of HF causes severe safety concerns, corrosion to cell components and adds challenges to battery recycling. Consequently, it would be desirable to use electrolyte salts which do not decompose to give harmful products.

This poster will discuss using sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as a safer alternative electrolyte salt to NaPF6 (on account of the lower likelihood of forming HF due to strong C-F bonds) in cells containing an inexpensive Prussian white cathode and hard carbon anode. Interestingly, when comparing the air stability of NaTFSI to NaPF6, both salts were found to be stable to atmospheric air for one month. The remarkable high air stability of NaPF6 contrasts to the low air stability of LiPF6 and this poster gives detailed reasons for the difference.[4] Lastly, this poster will showcase using sodium tetraphenylborate (NaBPh4) as a fluorine-free electrolyte salt for SIBs. The challenges in developing fluorine-free electrolytes will be discussed and results of using NaBPh4 in Prussian white vs. hard carbon cells shown. Long-term stable galvanostatic cycling was observed with this electrolyte but required a low operating voltage.  

Advances in next-generation battery technologies are essential to address the increasing global demand for high-performance, sustainable, and cost-effective energy storage systems. Aluminum-ion batteries (AIBs) represent a promising alternative to conventional lithium-ion batteries, offering potential advantages in terms of material abundance, domestic production capability, cost reduction, and supply chain security. This work highlights ongoing research at the National Research Council of Canada (NRC) focused on the development of AIBs, leveraging NRC’s established expertise in materials science, electrochemistry, and battery engineering to advance beyond Li-ion technologies. The high theoretical volumetric capacity of aluminum, derived from its trivalent nature, combined with its abundance and low reactivity under ambient conditions, positions it as a compelling anode material for next-generation energy storage systems. Its favorable environmental profile and safer handling characteristics further enhance its suitability for large-scale applications.

In this study, a free-standing graphite-based cathode was developed to address compatibility challenges of cathode current collector in a deep eutectic electrolyte composed of AlCl3 and urea. Systematic optimization of the anode, cathode, electrolyte composition and purity, and separator materials was carried out using a two-electrode configuration. Complementary three-electrode measurements employing a platinum working electrode, aluminum counter electrode, and leakless silver reference electrode confirmed the reversible electrodeposition and stripping of aluminum. 

Figure 1 presents scanning electron microscopy (SEM) images of the free-standing cathode, revealing a highly porous morphology conducive to efficient ion transport. The Al/Al symmetric cell with a high‑purity electrolyte exhibited stable plating/stripping over 300 cycles, while the low‑purity counterpart showed initial voltage noise due to impurity‑induced side reactions and uneven Al deposition. The early cycles promote interfacial reconstruction and formation of a stable passivation layer, which is more uniform in high‑purity electrolytes, enabling smoother and more reversible Al plating/stripping thereafter.

The practical realization of high-power potassium-ion hybrid capacitors (PIHCs) is fundamentally limited by the restricted accessibility and underutilization of active sites in carbonaceous anodes. Here, we report a strategically engineered hierarchical macro–mesoporous carbon (hC) designed to overcome these kinetic bottlenecks. By employing a dual-templating approach—integrating homopolymer-assisted macropore modulation with block copolymer-directed mesostructuring—we achieved precise and independent control over multiscale porosity. Crucially, this methodology enables the isolated tuning of macropore dimensions while maintaining other structural parameters constant, providing a rigorous platform to elucidate the specific role of macroporosity in potassium storage. The optimized hC architecture features highly interconnected macroporous networks that accelerate electrolyte infiltration and shorten K⁺ diffusion pathways, facilitating rapid ion transport kinetics. Consequently, the hC anode exhibits superior specific capacity and an enhanced pseudocapacitive response, essential for high-rate performance. When integrated into a PIHC device, it delivers a remarkable energy density of 102 Wh kg⁻¹ and an exceptional power density of 8,347 W kg⁻¹. Furthermore, the device demonstrates robust long-term reliability, maintaining 85.5% capacity retention over 20,000 cycles at 2.0 A g⁻¹. This work highlights the pivotal role of hierarchical pore connectivity in enabling capacitive K⁺ storage. By establishing a clear structure-performance relationship through independent structural tailoring, this study offers a sophisticated design principle for next-generation, high-rate electrochemical energy storage systems.

The internal accessibility of active sites plays a critical role in achieving high-power potassium-ion hybrid supercapacitors (PIHCs). Here, mesopore-orientation-controlled carbon spheres were synthesized via a multiscale phase separation strategy combining block copolymer microphase separation with homopolymer macrophase separation. This approach enables the formation of two distinct structures: open-end (oe-MCS) and closed-end mesoporous carbon spheres (ce-MCS). By selectively controlling mesopore openings without altering other structural parameters, we demonstrate that open mesopores significantly enhance K⁺ adsorption, shorten ion diffusion pathways, and facilitate rapid ion transport. As a result, oe-MCS exhibits higher capacity and a dominant capacitive contribution compared to ce-MCS. Consequently, the assembled PIHC delivers a high energy density of 103 Wh kg⁻¹, a power density of 12,300 W kg⁻¹, and excellent cycling stability with 86.1% capacity retention over 20,000 cycles. This work identifies mesopore orientation as a critical structural parameter for designing high-power potassium-ion energy storage systems.The internal accessibility of active sites plays a critical role in achieving high-power potassium-ion hybrid supercapacitors (PIHCs). Here, mesopore-orientation-controlled carbon spheres were synthesized via a multiscale phase separation strategy combining block copolymer microphase separation with homopolymer macrophase separation. This approach enables the formation of two distinct structures: open-end (oe-MCS) and closed-end mesoporous carbon spheres (ce-MCS). By selectively controlling mesopore openings without altering other structural parameters, we demonstrate that open mesopores significantly enhance K⁺ adsorption, shorten ion diffusion pathways, and facilitate rapid ion transport. As a result, oe-MCS exhibits higher capacity and a dominant capacitive contribution compared to ce-MCS. Consequently, the assembled PIHC delivers a high energy density of 103 Wh kg⁻¹, a power density of 12,300 W kg⁻¹, and excellent cycling stability with 86.1% capacity retention over 20,000 cycles. This work identifies mesopore orientation as a critical structural parameter for designing high-power potassium-ion energy storage systems.

Na-ion batteries are receiving growing attention as sustainable energy storage systems, and a wide variety of electrode materials, electrolytes, and cell components have been actively investigated. Despite this progress, half-cell evaluations that conventionally employ Na metal counter electrodes suffer from severe parasitic reactions with commonly used ester-based electrolytes.[1,2] Such instability results in poor experimental reproducibility and distorted electrochemical parameters, including apparent capacity, Coulombic efficiency, and cycling performance, ultimately disturbing the intrinsic properties of the electrode materials and electrolytes.

In this presentation, we systematically address the limitations associated with Na metal-based half-cell measurements and propose a more reliable and facile evaluation strategy using NASICON-type counter electrodes, specifically Na₃V₂(PO₄)₃ and NaTi₂(PO₄)₃.[3] Owing to their structurally robust nature and flat voltage plateaus at moderate redox potentials, these NASICON-type counter electrodes effectively suppress artifacts originating from Na metal and enable accurate and reproducible electrochemical characterization of targeted materials. This approach provides a practical pathway toward standardized and trustworthy evaluation of Na-ion battery materials, thereby enabling rational material screening for SIBs.

Acknowledgement

This study was supported by the Japan Science and Technology Agency (JST, GteX Grant Number JPMJGX23S4).

The formation of a stable solid electrolyte interphase (SEI) in sodium-ion batteries is challenging due to the higher solubility of SEI species than in lithium-ion batteries.^1–3 The stability and efficiency of SEI is usually improved by introducing film-forming electrolyte additives.⁴ The functions and decomposition of common additives like vinylene carbonate (VC) and fluoroethylene carbonate (FEC) are not fully understood and yield different results in full- and half-cells. This study reveals that the electrochemical reduction of an electrolyte solution based on 1 M NaPF₆ dissolved in ethylene carbonate and diethyl carbonate (EC:DEC) with no additive yields a lower charge loss (see figure 1), while electrolytes containing 2 wt.% VC or FEC additives suffer from higher charge consumption for the formation and reformation of SEI due to higher solubility. To solely investigate stability and dissolution of the SEI in the absence of other ageing mechanisms, a model cell consisting of a carbon-coated aluminium foil working electrode and Prussian white counter and reference electrodes was used. Three different electrochemical techniques of cyclic voltammetry, chronoamperometry and galvanostatic were employed to investigate the SEI formation and stability. Additionally, the results showed a cross-talk when using sodium metal. This cross-talk influences the stability in positive and negative ways, depending on the salt (NaClO₄ vs NaPF₆). This work sheds light on the insufficiency of VC and FEC electrolyte additives in forming an efficient SEI in a carbonate-based sodium electrolyte. However, further investigations are required to account for additional ageing mechanisms to provide a comprehensive understanding of the role of VC and FEC in practical sodium-ion batteries.

Hard carbon is considered one of the most promising anode materials for sodium-ion batteries owing to its low cost, structural tunability, and favorable sodium storage capability. Since sodium storage in hard carbon is strongly governed by its local carbon structure, including interlayer spacing, defect concentration, and pore structure, the molecular design of carbon precursors is a critical factor in achieving high electrochemical performance. In this study, aminophenol isomers, 2-aminophenol and 3-aminophenol, were employed as model precursors to investigate how the position of functional groups in precursor molecules influences the structural evolution and sodium storage behavior of hard carbon.

Although 2-aminophenol and 3-aminophenol possess the same hydroxyl and amine functional groups, their different substitution positions lead to distinct polymerization and carbonization behaviors. Compared with 3-aminophenol, 2-aminophenol forms a relatively less cross-linked precursor network, which allows greater structural rearrangement during carbonization. This less constrained carbonization pathway promotes the formation of a more disordered carbon framework and pore structures favorable for sodium-ion storage. In contrast, the higher cross-linking degree of the 3AP-derived precursor restricts structural rearrangement during heat treatment, resulting in a more constrained carbon framework that is less favorable for effective pore filling.

Structural and electrochemical analyses revealed that the 2AP-derived hard carbon exhibited a more suitable microstructure for sodium-ion storage. The relatively disordered carbon framework of the 2AP-derived sample facilitated the development of pores that can accommodate sodium ions through a pore-filling mechanism, thereby enhancing the low-voltage capacity. In addition, this optimized pore structure and carbon framework contributed to stable cycling performance and superior rate capability compared with the 3AP-derived counterpart.

These results demonstrate that the molecular structure of aminophenol precursors significantly affects the polymerization behavior, carbonization pathway, and final sodium storage properties of hard carbon. In particular, 2-aminophenol is identified as a promising precursor for high-performance hard carbon anodes because its relatively low cross-linking degree enables the formation of a disordered carbon framework and pore structure favorable for sodium-ion pore filling. This work provides molecular-level insight into precursor design strategies for advanced hard carbon anodes in sodium-ion batteries.

1. Introduction 

Due to high potassium abundance and low redox potential, potassium-ion batteries (KIBs) are alternatives to Li-ion and Na-ion systems. However, the flammability of conventional organic electrolytes poses significant safety risks. Single-cation ionic liquids (SCILs) offer enhanced (electro)chemical stability and safety, but their development is largely restricted to binary systems because identifying eutectic composition in a multinary systems is labor-intensive. Consequently, current binary SCILs often operate above ambient temperature. This work employs Bayesian optimization (BO) to efficiently identify a ternary SCIL eutectic composition with an expanded operating temperature range to address the challenge of high melting points. 

2. Experimental

 Ternary mixtures of KFSI, KFTFSI, and KTFA were prepared in an argon-filled glovebox. Differential scanning calorimetry (DSC) was used to determine eutectic and liquidus temperatures (0 °C to 150 °C at a heating rate of 1 °C min^–1). A Python-based BO program iteratively predicted optimal compositions based on measured liquidus temperatures until the prediction matched experimental results within 1%. DFT calculations (B3LYP/aug-cc-pvdz) via Gaussian 09 and Multiwfn were used for structural optimization and electrostatic potential (ESP) analysis. MD simulations (AMBER) estimated liquid structures and K⁺ transport properties. 

Layered transition-metal oxide cathodes such as O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM) are promising for sodium-ion batteries but degrade rapidly in ambient air. Moisture and CO2 drive Na+/H+ exchange and surface reconstruction, depositing insulating carbonates and hydroxides that further accelerate parasitic HF reactions with NaPF6 electrolytes and shorten cycle life. Mitigating this air sensitivity is essential for low-cost, scalable cell manufacturing. We report a strategy that uses initiated chemical vapor deposition (iCVD) to grow an ultrathin (~100 nm), conformal pPFDA film directly on pre-cast NFM electrodes. The solvent-free, all-dry process preserves microstructure and produces a fluorinated barrier that simultaneously acts as an artificial cathode-electrolyte interphase. The water contact angle rises from 50° on bare NFM to 149° on pPFDA-NFM, confirming superhydrophobicity. After 12 hours at 90% relative humidity, SEM and EDS show that bare NFM develops extensive surface cracking and Na-rich carbonate phases, while pPFDA-NFM retains pristine morphology and homogeneous elemental distribution. Following the same exposure, bare NFM can no longer charge or discharge reversibly, whereas pPFDA-NFM retains normal cycling behavior. Even without humid pre-aging, pPFDA-coated cathodes also deliver markedly improved capacity retention in Na || NFM half-cells at both 4.0 V and 4.3 V cutoffs under ~1C cycling. This work establishes iCVD polymer coatings as a versatile, manufacturable platform for protecting moisture-sensitive cathodes and enabling high-energy sodium-ion batteries with robust air and electrolyte stability.

With growing demand for sustainable energy storage technologies, sodium-ion batteries (SIB) are emerging as a promising complementary technology to the widely used lithium-ion batteries. This is primarily due to the high availability and low cost of the necessary raw materials. A key challenge remains the development of suitable anode materials capable of effectively and reversibly accommodating sodium ions. Hard carbon appears to be the most suitable candidate, as it possesses a disordered structure. A major advantage is the possibility of producing hard carbon from renewable and sustainable sources, such as biomass. [1]

This paper presents the preparation and characterization of hard carbon derived from lignocellulosic biomass, specifically walnut shells. This precursor was chosen because of its wide availability, naturally dense structure, and high carbon content, which are ideal conditions for achieving and optimal morphology of the resulting hard carbon [2]. In this study, walnut shells were first ground in a ball mill to reduce the shells to 1–2 mm in size. In the second step, acid leaching was performed to remove subtractive substances. After pH neutralization, high-temperature carbonization was performed at 1000 °C in the presence of an inert nitrogen atmosphere. Final grinding was then performed in a planetary mill, and negative electrodes were prepared using the water-soluble binder carboxymethylcellulose (CMC). The active material content in the electrodes was 85 wt.%, and the average active material loading was 4.49 mg·cm^-2.

Structural analysis using X-ray diffraction (XRD) confirmed the formation of a disordered structure with an increased interlayer spacing. Electrochemical characterization using cyclic voltammetry demonstrated reversible sodiation and de-sodiation peaks. The cycling results revealed a specific capacity of approximately 236 mAh·g^-1 with an initial Coulombic efficiency of 84 %.

By valorising walnut shell waste into a high-quality hard carbon precursor, this approach effectively minimizes the environmental impact of SIB while maintaining competitive storage capabilities.

Acknowledgements: This work was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Comenius, call Excellent Research and specific graduate research of the Brno University of Technology No. FEKT-S-26-8946.

The rapid growth of electrochemical energy storage technologies has increased interest in sustainable battery materials and end-of-life management strategies for next-generation systems. Sodium-ion batteries are attracting attention for large-scale energy storage applications due to the potential use of abundant and lower-cost materials. However, further understanding of material stability, degradation behaviour, and post-use considerations remains important for the long-term implementation of these technologies. 

This work investigates the environmental stability and lifecycle considerations of sodium iron sulphate (Na2.5Fe1.75(SO4)3) cathode materials, focusing on the influence of environmental exposure on structural evolution and electrochemical functionality. A combination of time-resolved gravimetric analysis, quantitative XRD, and complementary chemical, and electrochemical characterization are employed to evaluate material behaviour under representative storage and handling conditions.

The results demonstrate systematic changes in material structure and electrochemical response following environmental exposure, while subsequent characterization and lifecycle assessment are used to evaluate broader economic and environmental performance. Correlations between phase evolution, environmental stability and electrochemistry are identified, highlighting the importance of considering environmental interactions during electrode material development and evaluation.

This work contributes to a broader understanding of sustainability considerations in sodium-ion battery materials research and supports ongoing efforts toward the development of durable and resource-conscious energy storage materials for widespread applications.

 Lithium-ion batteries (LIBs) are widely used as high-energy-density energy storage devices. To meet the increasing demand for rechargeable batteries, sodium-ion batteries (SIBs) are attracted considerable attention as next-generation energy-storage systems owing to their low cost and abundant resources [1]. For electrochemical characterization of individual electrodes in SIBs, three-electrode measurements are commonly employed. In these measurements, Na metal is generally used as the reference electrode. However, its high reactivity can induce side reactions with the electrolyte, resulting in reference potential instability and safety concerns [2]. Therefore, this study aimed to develop a three-electrode cell configuration that does not require a Na metal reference electrode.

 In this study, Na₃V₂(PO₄)₃ (NVP) was investigated as a reference electrode material. NVP is a promising candidate because of its chemical stability and flat potential plateau. To function as a reference electrode, the NVP should be maintained within a flat-potential region where the potential changes minimally with state of charge (SOC) variations. Accordingly, the NVP electrode was adjusted to 50% SOC, and a hard carbon (HC) electrode was introduced as an auxiliary electrode to maintain this state. The resulting cell was termed a Na-metal free four-electrode cell. The electrode potentials in the [NVP/HC] full cell were evaluated using the NVP reference electrode. Figure 1 shows the charge–discharge profiles and electrode potentials. The developed cell enabled independent analysis of the positive and negative electrode potentials while maintaining stable charge-discharge over 100 cycles. Linear regression of the average charging voltage of the NVP electrode as a function of cycle number yielded a slope of 0.354 mV cycle^-1. By comparison, a slope of 0.284 mV cycle^-1 was obtained using a Na metal reference electrode. Although the potential drift was slightly larger than that observed with the Na metal reference electrode, the values were comparable. These results suggest that an NVP electrode maintained at 50% SOC can function effectively as a reference electrode.

 These Na-metal free cell configuration provides a promising platform for accurately evaluating individual electrode reactions in SIBs and enables use of wider variety of electrolyte systems by eliminating concerns associated with the high chemical reactivity of Na metal.

The growing demand for sustainable and cost-effective energy storage systems has intensified research on sodium-ion batteries (SIBs) as a complementary technology to established lithium-ion batteries (LIBs). Despite significant progress in active material development, the drop-in ability of electrode manufacturing processes from LIB to SIB systems remains insufficiently understood. In particular, the interaction between various properties of different raw materials, slurry formulation, viscosity and the resulting percolation network.

This work investigates the influence of electrode porosity on the structural, mechanical and electrochemical properties of SIB electrodes produced from different cathode active materials. The study focuses on three representative sodium-based cathode materials: layered oxide NaNi_0.33Fe_0.33Mn_0.34O₂, Sodium Ferric Phosphate Pyrophosphate Na₄Fe₃(PO₄)₂(P₂O₇), and Prussian Blue Analogue Na_1.79Mn[Fe(CN)₆]_0.95. To enable a comparable processing route, slurry formulations were adjusted by varying the solids content in order to maintain similar viscosities across the different material systems. The materials were processed using a standardized, industry-relevant formulation to assess the influence of raw material properties on slurry behaviour and electrode manufacturing. Electrodes were manufactured under standardized coating and drying conditions and subsequently calendered to defined porosity levels. Material and electrode characterization included rheological investigations as well as structural and morphological analysis. Furthermore, structure-defining electrode properties such as adhesion strength, electronic conductivity, and ionic resistivity were systematically evaluated as a function of porosity.

The results reveal strong correlations between electrode porosity and the resulting transport and mechanical properties, with distinct differences depending on the active material class. Lower porosities generally improved electronic conductivity due to enhanced particle contact but also increased ionic transport limitations within the porous electrode network. Significant variations in adhesion behaviour and electrode homogeneity were observed, indicating material-dependent processing windows. The comparative analysis demonstrates that optimizing slurry composition and porosity is essential for balancing ionic and electronic transport in SIB electrodes and cannot be directly transferred from established LIB manufacturing strategies.

These results highlight the relationships between the process, structure, and properties of electrodes for SIBs manufactured with different material systems and provide a baseline for the development of scalable manufacturing processes for next-generation sodium-based energy storage systems.

In recent years, the widespread adoption of lithium-ion batteries has brought problems such as uneven resource distribution and increasing material costs. As an alternative, sodium-ion batteries (SIBs), which have fewer resource constraints, have attracted attention. In this study, we developed binder-free SIBs (BF-SIBs) with the aim of reducing costs and improving performance. BF batteries enable the fabrication of thicker electrodes and eliminate several manufacturing processes, including drying, crimping, winding, and electrolyte injection.

AC impedance measurements and distribution of relaxation times (DRT) analysis were performed to determine the optimal electrolyte composition [1]. Based on these results, a full cell was fabricated using Na₃V₂(PO₄)₃ (NVP) as the positive electrode and hard carbon (HC) as the negative electrode. Constant-current charge-discharge tests were performed at 303 K and 0.05 C within a voltage range of 0.7–3.8 V.

Figure 1 shows the DRT results and SEM images of the prepared electrodes. At an electrolyte content of 20 wt%, an electron-conducting pathway was identified from the resistance component associated with a short relaxation time, as confirmed by the relaxation-time peak at 3.19×10^-6 s in the DRT results. In contrast, at 100 wt%, the presence of an ion-conducting pathway was indicated by the long relaxation time, supported by the relaxation-time peak at 4.58 s. For electrolyte contents from 30 to 50 wt%, both electron- and ion-conducting peaks were observed in the relaxation-time range from 3.53×10^-5 to 1.56×10^-4 s. SEM observations revealed significant aggregation in the electrode slurry at 20 wt%. Although bonding among active material particles mediated by the electrolyte was observed near the aggregate surface, limited bonding was observed in the central region of the cross-section. Compared with 20 wt% sample, more uniform bonding throughout the electrode was observed at 30 to 40 wt%, which was found to be optimal because it provided both electron- and ion-conducting pathways while maintaining a physically stable electrode structure. Charge-discharge profiles of BF-SIBs will be presented at the conference.

BF-SIBs are expected to provide higher energy density and reduced resource constraints compared with conventional battery systems.

Polyanionic compounds are a promising class of cathode materials for sodium-ion batteries. Among them, sodium iron phosphate has attracted particular interest because of its thermal stability, operating voltage, and environmental friendliness [1]. Challenges such as limited electrochemical performance, rate capability, and low operating voltage have motivated efforts to improve these materials through compositional modification. Because of the inherent material limitation, studies are being made to improve stability, and electrochemical performance by synthesizing ferro-manganese cathodes. Such batteries would serve as a valid alternative to lithium-ion batteries for large-scale energy storage technologies [2]. 

In this work, a synthetic route for obtaining stable olivine-structured iron–manganese phosphates with varying iron/manganese ratios is reported. The synthesized materials were then electrochemically tested and measured in operando with X-Ray diffraction, while using an ECC-Opto-10 (EL-CELL). 

The obtained phases exhibited a high chemical purity, good capacity retention, and satisfactory specific capacity. The synthetic procedure was found to be highly reproducible and required only minor adjustments when varying the iron-to-manganese ratio. The synthesis relies on an indirect route, passing through a lithiated intermediate, which is subsequently chemically delithiated. This preserves the olivine structure of the material, without causing the material to degrade to the maricite-phase. This approach is superior to other direct methods, which successfully guarantee olivine structure only at high manganese content [3]. 

The present work aims at improving the stability and performance of sodium polyanionic compounds by studying the structural evolution of different types of phospho-olivines upon cycling. The proposed synthesis results in a stable phospho-olivine that delivers good performance and can be the base for more complex synthetic routes by incorporating other ions, such as cobalt and nickel.

Although hard carbons (HCs) are commonly used as negative electrode material for commercial sodium-ion batteries¹ and high-power-type lithium-ion batteries, the improvement of input rate-capability has remained challenging due to unclear impact of rate-limiting factors attributed to not only the active material property but also the composite electrode structure, i.e., ion depletion/saturation in the electrode.² To address this issue, we have previously reported the fast sodium-insertion capability of HCs evaluated by the diluted-electrode method,² which allows us to identify the accurate rate-performance of insertion materials without concentration overvoltage in composite electrode^.3,4 Here, we studied the fast sodiation/lithiation of HCs via diluted electrode method, rate-capability test, and chronoamperometry to find the rate-limiting factor attributes to HC structure, and propose a synthetic guideline towards high-power HCs, maintaining good capacity and operation potential. HC, aluminum oxide, and sodium polyacrylate were used as active material, diluent, and binder, respectively. The powders were mixed at a volumetric ratio of x : (95−x) : 5, with total volume of 0.1 cm³, and 0.8 mg of single-walled carbon nanotube was added as a conductive additive. The loading of HC in the electrode was proportional to HC concentration. Galvanostatic charge-discharge and chronoamperometry were carried out to evaluate the electrochemical properties. We compared fast sodiation abilities of commercial and lignin-derived HCs¹ in diluted electrodes. Figure 1a shows galvanostatic sodiation profile of a diluted electrode. Although the HC concentration in the electrode is only 5 vol.%, identical voltage slope and plateau are observed, which are respectively attributed to sodium storage at interlayer and pore in HCs. Its rate-capability was comparable to diluted-graphite electrode in Li-cell.⁴ Figure 1b shows a chronoamperogram collected after potential step from 100 to 2 mV vs. Na⁺/Na, and obtained curve was deconvoluted to three factors: nucleation, contraction of boundary, and diffusion based on solid-state reaction.⁵ The nucleation current was dominant, and it can be the rate-limiting for full sodiation as shown in Fig. 1c. Finally, diluted-electrode analysis using various HCs led us to conclude that HCs with smaller nanopores exhibit better rate-capabilities. This finding contributes to the development of high-rate sodium-ion batteries.

O3-type Na-ion layered oxides have emerged as one of the most practically relevant cathode chemistries for sodium-ion batteries.² However, their air instability limits manufacturing tolerance and electrochemical performance.³ Here, to address these issues, Zn²⁺ doping in the MO₂ slabs is introduced to regulate crystal structure, cationic valence states, and electrochemical properties.

Zn²⁺ substitution for Ti⁴⁺ in Na_0.94Ca_0.03Fe_0.2Mn_0.3Cu_0.08Ni_0.26Ti_0.16-xZn_xO₂ (0 ≤ x ≤ 0.08) preserves the O3-phase lattice structure. This substitution causes the NaO₂ and MO₂ interlayer spacings to linearly vary, which is associated with substitution of Ti⁴⁺ (66.1 nm^-1) by the lower ionic potential Zn²⁺ (27.0 nm^-1). Simultaneously, the charge-neutrality process induces a surface-to-bulk gradient in Mn and Ni oxidation states when x = 0.05, with Mn⁴⁺/Ni³⁺ enriched at the particle surface and Mn³⁺/Ni²⁺ concentrated in the bulk region. This cationic distribution is considered as a key origin of the preserved material stability after water immersion relative to the undoped, x = 0, sample. As a result, Zn doping significantly enhances both electrochemical cycling stability and moisture resistance, with the x = 0.05 sample outperforming the undoped sample in all respects.

In moisture-stability investigations, after 14-days atmospheric exposure, both cathode materials retain the characteristic O3-type diffraction features without additional impurity signals. For air-exposed materials, the x = 0.05 sample exhibits a lower average content of sodium residues and smaller standard error in replicate chemical titration measurements than the undoped sample. As a result of 30-min water immersion, the undoped sample shows segregation of a NiO phase from the O3 phase domain, whereas the x = 0.05 sample demonstrates stronger moisture resistance and structural stability. Moreover, electrochemical cycling results show that after air-exposure and water-immersion, the undoped materials only attain 85.9 and 81.8 mAh g^-1 after 100 cycles, whereas the x = 0.05 materials achieve higher capacities (near 102 mAh g^-1). The final cycled capacity of the air-exposed and water-immersed x = 0.05 samples correspond to about 91.9% capability of the fresh x = 0.05 material, demonstrating improved structural and compositional stability. These outcomes provide valuable insights into the development of moisture resistance, cycling stability, and cost-effective cathode materials for SIBs.

Sodium-ion batteries are emerging as a promising alternative to lithium-ion systems, particularly for large-scale and cost-sensitive energy storage, owing to the abundance and low cost of sodium resources. Among the possible cathode materials, alluaudite-type sodium iron sulfates are especially attractive as high-voltage, Co-free and Ni-free polyanionic compounds based on earth-abundant elements [1]. However, their electrochemical behavior is strongly governed by the complex interplay between sodium-site occupancy, electronic structure and structural evolution during Na extraction and reinsertion.

In this work, we investigate alluaudite Na_2.5Fe_1.75(SO₄)₃ as a cathode material for sodium-ion batteries, with particular emphasis on the relationship between electronic structure and the mechanism of sodium deintercalation/intercalation [2]. The material was characterized using X-ray diffraction, SEM/EDS, Mössbauer spectroscopy, Raman and FTIR spectroscopy, as well as operando and in situ X-ray diffraction during electrochemical cycling.

Density functional theory calculations using the KKR-CPA method revealed an unusual contribution of sodium states to the electronic density of states near the Fermi level. This behavior, not typically observed in layered transition-metal oxide cathodes, depends strongly on the crystallographic position of Na ions. The calculated electronic structure indicates different binding strengths for Na1, Na2 and Na3 sites, explaining the site-selective sodium extraction sequence, in which Na3 ions are removed first, followed by Na2, while Na1 remains the most strongly bound and contributes to structural stabilization.

Operando and in situ XRD show that the first charge involves partial irreversible reconstruction related to Fe migration, whereas deep sodium extraction leads to reversible structural disordering. Despite these structural changes, the optimized Na_2.5Fe_1.75(SO₄)₃ cathode exhibits excellent cycling stability, with only 2.5% capacity loss after 300 cycles at C/2.

These results demonstrate that site-dependent alkali-metal electronic states, residual Na acting as structural pillars, and tolerance to reversible local disorder are key factors governing the stability of alluaudite-type polyanionic cathodes for sodium-ion batteries.

The electrode potential directly influences metal plating/stripping behavior and the extent of parasitic reactions.^1-5 In this study, we show that tailoring the hard-soft character of the ionic environment around metal ions markedly shifts the Mⁿ⁺/M redox potential, thereby promoting highly reversible metal cycling.

As a model system, a series of aqueous Zn electrolytes containing different anion/cation combinations was examined to clarify how ionic properties regulate the Zn²⁺/Zn redox potential.¹ The results reveal a clear design rule: weakly attracting soft anions combined with strongly repelling hard cations upshift the redox potential, whereas strongly attracting hard anions combined with weakly repelling soft cations downshift it. Surprisingly, these ion effects shift the redox potential by more than 0.6 V, demonstrating remarkably large yet physiochemically rational tunability for a divalent metal redox couple. To quantitatively describe this effect, we applied a liquid Madelung potential framework, which successfully reproduces the experimentally observed potential shifts, including trends not predicted by conventional Debye-Hückel and Pitzer models.^1,3,6 Moreover, electrolytes that substantially upshift the Zn²⁺/Zn redox potential achieved high Zn plating/stripping Coulombic efficiencies above 99.9% by modulating the Zn deposition potential to values more positive than the hydrogen evolution potential, thereby minimizing electrolyte decomposition.

The ion hardness/softness effect on metal redox potentials established in this study provides a practical strategy for regulating metal electrode potentials and offers a general design concept for electrolyte development in aqueous and nonaqueous metal batteries, as well as other electrochemical systems.

Zinc hydroxide sulfate (ZHS, Zn₄SO₄(OH)₆·xH₂O) is a common interfacial byproduct formed on anodes in aqueous zinc metal batteries, typically arising from inevitable side reactions under mildly acidic conditions. ZHS is generally considered to be a detrimental byproduct since it is usually formed both randomly and unevenly; however, its impact strongly depends on its morphology and distribution. [1] Well-structured ZHS layers can function as a protective solid electrolyte interphase (SEI), providing modulation of Zn²⁺ flux while protecting side reactions. This presents an opportunity to improve the anode stability by carefully engineering the morphology of the ZHS structures. [2] In this work, we conducted synchrotron grazing incident wide angle x-ray scattering (GIWAXS) to evaluate the formation of in-situ formed ZHS during the Zn plating/stripping on Copper (Cu) current collectors. Tin oxide (SnOx) nanoparticle arrays deposited on the Cu surface were employed to induce homogeneous Zn plating and to encourage the formation of highly oriented ZHS. The GIWAXS showed that SnOx nanoparticles on the Cu surface induces the formation of highly oriented ZHS during the Zn plating/stripping, whereas bare Cu yields randomly oriented ZHS associated with dendritic growth and side reactions. The oriented ZHS formed as a result of uniform, dense Zn plating and the subsequent suppression of hydrogen evolution induced by SnOx decoration. The SnOx nanoparticle array and oriented ZHS layer improved Coulombic efficiency and extended cycle life under various capacity conditions compared to bare Cu. These results demonstrate that uniformly distributed SnOx nanoparticles can serve as a novel interface-engineering strategy to improve anode lifetime and Coulombic efficiency by promoting homogeneous Zn plating and oriented ZHS formation. We also show that GIWAXS provides a powerful tool for probing ZHS orientation and highlights the importance of Zn plating homogeneity in governing interfacial structures.

Lithium iron phosphate (LiFePO₄, LFP) is an attractive cathode material for lithium-ion batteries because of its high safety, low cost, and structural stability, making it particularly promising for electric vehicles (EVs) and grid-scale energy storage systems (ESS). However, its rate performance remains limited by low electronic conductivity and one-dimensional lithium-ion diffusion. Since the electrochemical performance of LFP is strongly influenced by the properties of its FePO₄·2H₂O precursor, controlling precursor particle size and morphology is an important strategy for improving high-rate performance. In this study, a two-step synthesis route consisting of amorphous co-precipitation followed by recrystallization was employed to control the microstructure of FePO₄·2H₂O precursors. Functional additives were introduced during the co-precipitation step to modify the precursor formation behavior and reduce particle agglomeration. The resulting precursors and LFP samples were characterized by morphological analysis and electrochemical evaluation. The additive-assisted precursor exhibited finer, and better-separated plate-like particles compared with the additive-free sample, indicating effective modulation of precursor growth behavior. These changes in precursor size and morphology were reflected in the electrochemical properties of the corresponding LFP cathodes, which showed more favorable rate capability and reduced polarization in dQ/dV profiles. The results suggest that additive-mediated control of precursor formation can provide a more favorable microstructure for lithium-ion transport. This work demonstrates that controlling the size of FePO₄·2H₂O precursors is an effective approach for improving the rate performance of LFP cathodes. Furthermore, it highlights precursor design as a useful strategy for the development of high-performance LFP materials.

Oxygen redox-based cathode materials offer higher capacity than conventional Na-based layered transition metal oxides in Na-ion batteries (NIBs). Still, their performance is impeded by voltage hysteresis and structural instability. Herein, a novel P2-Na_0.61Ca_0.03[Mg_2/9Cu_1/9Mn_2/3]O₂ cathode material is developed with Li/Co-free composition for cost-effectiveness and environmental friendliness. Cu substitution in transition-metal layers stabilizes O ions during oxygen redox, while Ca doping in alkaline-metal layers acts as structural “pillars” to suppress phase transformation. The charge storage mechanism is analyzed via operando X-ray absorption spectroscopy, operando X-ray diffraction analysis, on-line gas chromatography, and density functional theory computation. Na_0.61Ca_0.03[Mg_2/9Cu_1/9Mn_2/3]O₂ exhibits a high specific capacity (205 mAh g⁻¹ at 0.1 C), good cyclic stability, and impressive rate capability (142 mAh g⁻¹ at 2.5 C). A Na_0.61Ca_0.03[Mg_2/9Cu_1/9Mn_2/3]O₂//hard carbon full cell with a high energy density (250.7 Wh kg⁻¹) is achieved, demonstrating its potential for high-energy NIBs. This work provides new insights into oxygen-redox-dominated cathodes through a facile sol-gel synthesis and advanced characterization techniques.

Lithium-rich Mn-based layered oxides (LRLOs) are promising cathodes for high energy density lithium-ion batteries because of their high capacity and low cost. Nevertheless, the thermal runaway becomes an urgent concern because of the high-voltage operation (up to 4.8V), and the structural evolution mechanism of delithiated LRLOs during heating remains unclear. Here, we combine in situ high-temperature X-ray diffraction (XRD) and X-ray absorption (XAS) spectroscopy to systematically investigate the structural and chemical evolution of Li_1.2Ni_0.2Mn_0.6O₂ (LLNMO) across distinct charge–discharge states. 

The thermal evolution and charge compensation mechanism of LLNMO at different charge/discharge states are illustrated in Figure 1. The pristine material gradually transforms from layered phase to spinel phase during heating. In contrast, electrochemically conditioned LLNMO electrodes directly convert into a Li-containing rock-salt structure. The onset temperature of phase transition decreases with increasing delithiation and partially recovers upon subsequent lithiation.  In situ XAS reveals that Ni is the first element to undergo thermally induced reduction in the charged state of LLNMO. With further increasing the temperature, Mn reduction sets in, coinciding with extensive lattice oxygen loss and phase transition. More intriguingly, after the initial electrochemical cycle, LLNMO exhibits negative thermal expansion at low temperatures below 200 °C, which are attributed to the cycling-induced microstrain accumulation and long-range structural ordering. These findings provide a mechanistic insight into the state-of-charge-dependent thermal behavior of Li-rich layered materials and offer guidelines for designing safer, high-capacity battery materials. The present abstract summarizes our recent published work on the thermal instability and phase evolution of LLNMO ^[1].

Ni-rich layered oxide cathodes are regarded as key candidates for next-generation lithium-ion batteries (LIBs) because of their high energy density, but their practical application remains limited by severe structural degradation, intergranular cracking, and insufficient cycling stability. Although cobalt (Co) is known to enhance structural robustness, its high cost and limited availability necessitate approaches that maximize its functionality at low concentrations. Here, we present a simple coprecipitation strategy for preparing Ni_0.9Co_0.05Mn_0.05 precursors coated with a Co(OH)₂ nanoshell. Upon calcination, the Co-rich shell selectively diffuses along grain boundaries, suppressing excessive sintering and inducing the formation of radially oriented, rod-shaped primary particles. [1]

This unique microstructure promotes the development of nanoscale spinel-like domains, which provide efficient three-dimensional Li⁺ diffusion pathways and help relieve internal stress during repeated charge-discharge cycles. As a result, the Co-nanoshell-engineered cathode exhibits markedly improved rate performance and long-term cycling durability relative to conventional Ni-rich cathodes. In full-cell testing, the modified cathode retains 87.1% of its initial capacity after 1500 cycles, whereas the baseline NCM90 shows much faster capacity fading. These results demonstrate that nanoshell engineering is an effective way to localize Co in structurally critical regions and thereby achieve both economic and performance benefits in high-energy cathode materials.[2]

To improve the energy density of lithium-ion batteries, lithium-rich layered oxides have been considered promising candidates for next-generation cathode materials. Nevertheless, their practical deployment is impeded by several structural and electrochemical issues, including progressive voltage decay, oxygen release, and limited lithium-ion diffusion. In particular, the sluggish diffusion of lithium-ions primarily arises from the asymmetric migration of transition metals (TMs) during electrochemical cycling, which significantly obstructs lithium transport, especially in the lithiation process.[1] To overcome these limitations, O2-type configurations have been explored, emphasizing the critical role of regulating local TM migration in enhancing lithium transport kinetics and cycling durability.[2] In this work, we introduce a more straightforward and direct strategy to alleviate asymmetric TM migration through cation disorder engineering. A lithium-rich Ni–Mn based disordered rock-salt (DRX) compound, Li_1.2Ni_0.4Mn_0.4O₂ (D-LNM244), was prepared via a precursor-structure-controlled high-energy ball milling method. The effect of structural disorder on TM migration suppression and lithium-ion diffusion was systematically examined by benchmarking D-LNM244 against its layered analogue (L-LNM244). Consequently, D-LNM244 delivered a markedly higher discharge capacity, more symmetric charge/discharge kinetics, improved voltage retention, and accelerated lithium ion diffusion at room temperature. Moreover, the DRX framework was found to inhibit TM migration pathways while accommodating lithium storage through isotropic lattice variation. The enhanced kinetic behavior is attributed to intrinsic structural characteristics of the DRX lattice, where a reduced number of migration active tetrahedral sites and a lowered tetrahedral height collectively raise the TM migration barrier relative to the layered structure. Overall, these results demonstrate that cation disorder engineering offers a viable and efficient approach to simultaneously reinforce the structural robustness and electrochemical performance of lithium rich transition metal oxides.

We conducted a comprehensive literature review for LiFePO₄ (LFP) and LiMn_xFe_1-xPO₄ (x=0.1 to 1) (LMFP)-based lithium-ion batteries (LIBs), focusing primarily on electric vehicles (EVs), which account for approximately 90% of LIB consumption. Although numerous individual research studies exist, a unified and coordinated review that covers the subject from mine to chassis is notably absent. Accordingly, our review encompasses the entire LIB development process, starting with I) initial resources, including lithium (Li), iron (Fe), manganese (Mn), and phosphorous (P), their global reserves, mining procedures, and their demand in LIB production. Then, we examined II) the main Fe- and Mn-containing precursors of Fe⁰, Fe_xO_y, FePO₄, FeSO₄, and MnSO₄, focusing on their preparation methods, employment in LIBs, and their effect on the electrochemical performance (EP) of the final active cathode materials (ACMs). These two steps are followed by III) utilizing these precursors in synthesizing ACMs. Specific attention is paid to the pioneering synthesis methods in olivine production lines, particularly hydrothermal liquid-state synthesis (LSS), molten-state synthesis (MSS), and solid-state synthesis (SSS). Afterward, we described IV) electrode engineering and design and optimization of electrolytes and V) the production of cells, modules, and packs. Finally, (VI) our review underscored the challenges associated with the widespread utilization of olivines in LIBs, emphasizing safety, cost, energy efficiency, and carbon emission. In conclusion, our review offers a comprehensive overview of the entire trajectory involved in the fabrication of LFP/LMFP-based LIBs, spanning from the initial elements in the mine to the assembly of final packs that power EVs. 

Lithium-ion cathode materials are extensively utilized in battery technology. This research examines LFP cathode systems because they possess favorable attributes compared to olivine cathode materials, such as exceptional stability and durability. The Graph Neural Network (GNN) module was utilized to predict the electrochemical properties of LFP-based cathode materials, namely binary and high-entropy (HE) doped LFP cathodes. The GNN achieved a coefficient of determination (R²) of 0.996 and a mean absolute error (MAE) of 0.038 eV/atom in predicting thermodynamic stability (formation energy). The analyzed binary- and HE-doped LFP compositions produced favorable outcomes, as these materials displayed a high average voltage of approximately 4.21 V, a high capacity of about 180 mAh/g, and a reduced negative formation energy of about -2.65 eV/atom, thereby indicating their thermodynamic stability and enhanced average voltage and capacity relative to pure LFP. The DFT+U calculation was utilized within the VASP quantum mechanics framework. The mean voltage and formation energy of the 10 chosen binary cathodes were computed. The DFT+U results closely correspond with those generated by the GNN model, demonstrating mean relative absolute errors of 4.1% for average voltage and 3.7% for formation energy, respectively. The utilization of AI in the GNN module proved to be a successful method for discovering advanced new cathode materials with advantageous electrochemical properties. It also lowered the duration and expenses related to simulations intended to guide experimental research on high-entropy doped LFP-based cathode materials.

The urgent need for high-performance, cost-effective, and sustainable energy storage has highlighted the limitations of current lithium-ion batteries (LIBs). Overcoming these challenges requires coordinated advancements across all battery components—cathodes, anodes, electrolytes, and interphases—rather than incremental improvements in individual parts.^1,2 To address this, the National Research Council of Canada (NRC) in Mississauga is developing a self-driving laboratory (SDL) under the Battery Materials Acceleration Platform (BattMAP), within its Critical Battery Materials Initiative (CBMI). BattMAP integrates automated synthesis, high-throughput characterization, and machine learning (ML) in a data-driven, closed-loop system to accelerate the discovery and optimization of next-generation cathode materials for LIBs.³

Building on previous advances, this work focuses on accelerating the optimization of novel high nickel layered cathodes, while also addressing the roles of electrolytes and anodes in full-cell performance. Through a Canadian–German collaboration, two SDLs operate in coordination to systematically map and quantify each battery component’s contribution. By combining complementary expertise, high-throughput experimentation, and ML-driven methods, the partnership moves from component-level optimization to full-system design, accelerating the development of next-generation LIBs.

NRC’s SDL function as fully integrated, low-intervention platform that enable continuous experimentation, rapid testing, and data-driven decision-making. Deep learning algorithms and large language models (LLMs) extract chemical and structural features, linking phase composition to performance while identifying promising candidates from the literature. Cathode materials are synthesized and characterized both structurally and morphologically, followed by rapid, high-throughput electrochemical evaluation through two complementary pathways: a quick-response, rapid materials down-selection method, and standard coin cell testing for longevity measurements. Together, these approaches identify the most promising candidates for full-cell testing using specially tailored electrolytes provided by the German partner, developed in parallel with cathode optimization.

Advanced nuclear magnetic resonance (NMR) spectroscopy further characterizes cathodes, anodes, and electrolytes, at the molecular level. This approach provides detailed insight into local structure and helps reveal how external factors, such as charge rate and temperature, influence battery behavior and performance. ML integrates these datasets to guide iterative optimization, creating a closed-loop platform that accelerates cathode discovery, enables precise performance evaluation, and supports the design of high-efficiency, well-balanced energy storage systems.

Lithium-ion batteries have received considerable investment in the automotive industry over recent decades.  Since cathode has a huge share in this investment and the cost part in battery, it is essential to understand the non-expensive alternatives of lithium iron (manganese) phosphate and their supply chain from mining to battery-grade precursors. This knowledge assures sustainable, particularly regarding geopolitical supply risks. This review investigates current methods of mining, beneficiation, and purification of iron, and manganese resources, toward highly purified iron and manganese concentrates (mostly in oxide forms). Then, we discussed the possible pathways to convert these purified concentrates into battery-grade raw materials, such as metallic iron (≥99.9 wt% Fe) or iron phosphate (FePO₄), iron sulfate (FeSO₄), and iron oxalate, as well as manganese phosphate (MnPO₄) and manganese sulfate (MnSO₄). The synthesis routes, containing solid-state, hydrothermal, and molten-state processes, which directly affect phase purity, particle size, morphology, and electrochemical performance, were discussed in detail. Techno-economic aspects, and potential strategies are introduced to support the sustainable development of phosphate-based cathode materials for next-generation lithium-ion batteries.

Understanding and employing anion redox mechanisms effectively and reversibly is at the current forefront of lithium-ion battery research and is a key method to obtaining the next generation of lithium-ion cathode materials delivering high energy density.^1,2 Oxygen redox processes generally inhibit cycle life and stability of the electrode material. This is often associated with other unfavorable processes including loss of molecular oxygen, transition metal migration and voltage hysteresis.^3–7 Whilst it is understood that oxidation on the oxygen species, ultimately from O^2- to O₂ takes place, mechanistic details of oxygen redox mechanisms are generally still poorly understood. Using a model system to probe the oxygen-redox mechanisms allows for an understanding without the competing interference of transition-metal redox processes occurring simultaneously.

Here we present investigations in to lithium molybdate (Li₂MoO₄) which we have recently shown to achieve a capacity of 100 mAhg^-1.⁸ Molybdenum is present in a Mo (VI) (d⁰) state meaning that the available capacity seen can be accounted for purely by oxygen redox processes. Upon synthesis, Li₂MoO₄ forms a phenacite phase (RH) however on mechanochemical treatment using a vibratory milling scheme the structure is transformed into a spinel phase (Fdm). The phenacite phase has both metals in tetrahedral coordination whereas in the spinel phase the lithium has transitioned to octahedral coordination; this system, therefore offers a unique opportunity to probe the role of local environment on oxygen redox. The lack of d-electrons offers another unique ability to study oxygen redox processes isolated from traditional transition-metal mechanisms allowing for ¹⁷O solid-state NMR (SSNMR) without interfering paramagnetic broadening of which pristine ¹⁷O SSNMR signals have been collected. This study will present insights into the oxygen redox mechanisms of lithium molybdate using local structural characterisation techniques including RIXS, ¹⁷O SSNMR, X-ray and Neutron PDF in both pristine phenacite and spinel forms. ¹⁷O and ⁷Li solid-state NMR and X-ray PDF show significant difference in the local structure of the two materials. Meanwhile, RIXS mapping shows additional environments on charge. The implications of these mechanistic insights on design of high energy density anionic redox materials for lithium-ion cathodes will be discussed.

Mn-enriched surface covering Ni-rich core architecture has been widely employed to improve interfacial stability by reducing direct contact between highly active Ni⁴⁺ and non-aqueous electrolyte in Lithium-ion battery cathode. However, in this study, a parastic chemical instability of Mn-rich coordination environment stemming from precursor processing has been revealed for the first time. The Mn with Mn⁴⁺ (d³ configuration) chemical state has been extensively utilized in stable cathode materials, which is attributed to electrochemical inactivity and strong covalency character with O^2- ligand. In this study, we observed a spontaneous formation of Jahn-Teller distorted (JTD) Mn^4−x−O coordination near the Mn-rich surface via a novel crystal phase evolution during synthesis, followed by oxidizing of hydroxide precursor to oxyhydroxide under oxygen-rich atmosphere exposure. Because of JTD Mn-O coordination environment on the particle surface, the original role of thermodynamically stable Mn has completely disappeared, and instead, it has been revealed that it promotes further interfacial chemical degradation. Due to a electron occupation in anti-bonding orbital, the nucleophilicity of an anion ligand significantly increased and it catalyzed lattice-electrolyte chemical reaction in various ways. The electronic properties change in different Mn coordination system was supported by electron spin quantum state analysis, which was hypothesized based on the Goodenough-Kanamori rule. In addition, we could deconvolute the electronically driven chemical side reaction into two pathways of indirect and direct degradation via electrode-electrolyte calendering procedure. Using our specific aging test protocol, we could investigate that this JTD surface Mn coordination further accelerated solvent molecule decomposition and H₂O release, which were supported by FTIR and NMR analysis. And the more Mn dissolution via proton-induced disproportionation mechanism, transferring electrons along the Ni-O-Mn bonding environment, was also observed during 70 °C temperature aging procedure. These results implicate that the failure of surface Mn to provide chemical stability caused by simple oxidation of precursor surface. Furthermore, we propose that these deterimental surface states can be suppressed by modulating excess Li content, higlighting the important role of controlling the Li stoichiometry in Mn-based oxide structures.

To enhance the stability of Ni-rich cathodes, doping has proven to be an effective method for enhancing the performance of cathode materials.[1] Doping is typically carried out using one of two approaches[2]. In this study introduces a wet-doping approach that focuses on the shell region (shell doping) with the objective of maximizing the doping effect and offering benefits in scaling up the cathode material production process in terms of commercialization. In particular, W-shell doped NCM90 cathodes were synthesized by introducing tungsten into the shell region of secondary particles during the co-precipitation synthesis of the [Ni0.90Co0.05Mn0.05](OH)2 precursor. W-shell doped NCM90 cathodes exhibit the formation of fine primary particles that are not observed in conventional NCM90 cathodes. Additionally, a LiM2O4-type spinel-like crystal structure formed on the particle surface, contributing to enhanced cycling stability and rate capability.[3] Moreover, the shell doping method, which facilitates the uniform distribution of dopants throughout the co-precipitation synthesis process, was capable of maintaining the homogeneity of the doping effect even in large-scale cathode material synthesis processes.To enhance the stability of Ni-rich cathodes, doping has proven to be an effective method for enhancing the performance of cathode materials.[1] Doping is typically carried out using one of two approaches[2]. In this study introduces a wet-doping approach that focuses on the shell region (shell doping) with the objective of maximizing the doping effect and offering benefits in scaling up the cathode material production process in terms of commercialization. In particular, W-shell doped NCM90 cathodes were synthesized by introducing tungsten into the shell region of secondary particles during the co-precipitation synthesis of the [Ni0.90Co0.05Mn0.05](OH)2 precursor. W-shell doped NCM90 cathodes exhibit the formation of fine primary particles that are not observed in conventional NCM90 cathodes. Additionally, a LiM2O4-type spinel-like crystal structure formed on the particle surface, contributing to enhanced cycling stability and rate capability.[3] Moreover, the shell doping method, which facilitates the uniform distribution of dopants throughout the co-precipitation synthesis process, was capable of maintaining the homogeneity of the doping effect even in large-scale cathode material synthesis processes. 

Olivine lithium manganese iron phosphate (LMFP) cathodes offer a promising route toward higher energy density than lithium iron phosphate (LFP) by accessing the elevated Mn2+/Mn3+ redox plateau at ~4.1 V vs. Li/Li+, while preserving the intrinsic safety and cost advantages of the olivine framework. In this work, LiMnxFe1−xPO4 (x = 0, 0.3, and 0.6) cathode materials were synthesized via a hydrothermal route. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) revealed a clear compositional dependence of particle morphology, evolving from small particles at low Mn content to compact rod-like particles at higher Mn content, indicative of optimized crystal growth and improved interparticle connectivity. Carbon analysis showed 2.1–3.3% carbon in the final carbon-coated active materials. X-ray diffraction (XRD) confirmed the formation of a single-phase olivine structure for all compositions. The Li-ion transport kinetics of the cathodes were systematically investigated by the galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and time-resolved electrochemical impedance spectroscopy (TR-EIS) coupled with distribution of relaxation times (DRT) analysis. Apparent Li⁺ diffusion coefficients (DLi) extracted from the GITT profiles exhibited two distinct plateaus associated with the Fe2+/Fe3+ (~3.5 V) and Mn2+/Mn3+ (~4.0 V) redox couples during lithiation. With increasing Mn content, LiMnPO4 became the dominant phase in the solid solution, leading to reduced ionic conductivity and a decline in DLi, thereby confirming that an appropriate Mn level is critical for optimal electrochemical performance. In the phase-transition region, the Li⁺ diffusion coefficients derived from GITT were in the range of 10⁻20 to 10⁻19 cm² s⁻¹. The charge-transfer resistance (Rct) exhibited a decreasing trend during charge and an increasing trend during discharge, reflecting dynamic variations in electronic and ionic transport throughout cycling. In addition, Rct increased consistently with Mn content, indicating that excessive Mn incorporation progressively deteriorates both electronic and ionic conductivity in LMFP, in agreement with the trends observed by GITT and CV. Overall, these results demonstrate that the combined TR-EIS/DRT/GITT approach provides a mechanistically informative framework for decoupling interfacial, charge-transfer, and transport limitations in LMFP cathodes and offers practical guidance for composition and electrode design optimization.

As a promising cathode material for high performance lithium-ion batteries, olivine LiMn_xFe_1-xPO₄ (LMFP) combines the high safety of LiFePO₄ and the high energy density of LiMnPO4. However, there are still obstacles to overcome for achieving cycling stability due to its intrinsic lattice distortion caused by Mn³⁺ Jahn-Teller effect, as well as high-rate performance, especially its inherent low electronic conductivity and Li⁺ diffusion coefficient [1]. Element doping is an important method to improve the property of LMFP. Various metal doping at transition metal sites have been comprehensively studied [2]. However, no comparative studies of LMFP with different substitutions have been reported yet. In this work, Hydro-Québec and CNRC have carried out joint research on LMFP with different isovalent and aliovalent doping. The performances were systematically compared and analyzed from the point view of crystal defect, ionic radius and bond energy.

Spinel-type LiNi_0.5Mn_1.5O₄ (LNMO) cathodes offer high energy density and operation near 5 V, making them attractive candidates for lithium-ion batteries for electric vehicles and stationary energy storage systems.¹ However, their practical application is hindered by side reactions associated with electrolyte decomposition, transition-metal dissolution, and gas generation under high-voltage and high-temperature conditions. These reactions increase interfacial resistance and accelerate performance degradation during prolonged voltage holding. 

Previous studies have reported that tantalum (Ta)-based coatings suppress HF-induced corrosion at the LNMO cathode surface.² In addition, phosphate (P)-based surface modifications have been suggested to stabilize cathode interfaces under high-voltage conditions by mitigating transition-metal dissolution.³ The objective of this study is to improve the interfacial stability of LNMO cathodes under practical high-voltage conditions through a dual-element surface coating combining Ta and P. LNMO particles were coated with Ta and P using a water-based coating solution followed by calcination. 

Structural and chemical analyses revealed the formation of a uniform ~5 nm coating layer on the LNMO surface. After calcination, Ta remained predominantly at the particle surface in a LiTaO₃-like chemical state, while P partially diffused into the subsurface region, forming a bilayer-like structure. Electrochemical performance was evaluated using single-layer laminated full cells with Li[Li_1/3Ti_5/3]O₄ as the negative electrode. Float charging tests at elevated temperature for 144 h showed that the (Ta and P)-coated LNMO cathodes exhibited suppressed gas evolution compared with uncoated and single-element-coated samples. Electrochemical impedance spectroscopy before and after the float tests indicated that the dual-element coating mitigated interfacial resistance growth.⁴ 

The Ta-containing outer layer acts as a physical barrier highly resistant to HF attack and suppress electrolyte decomposition. In contrast, the P-derived region exhibits excellent electrochemical stability under high-voltage conditions, which suppresses transition-metal dissolution. These combined effects lead to improved active material utilization and durability. This study demonstrates that combined Ta and P surface coatings provide a practical and effective strategy for stabilizing high-voltage LNMO cathodes for advanced lithium-ion battery applications.

Cation-disordered rocksalt (DRX) cathodes have emerged as promising candidates for next-generation lithium-ion batteries due to their high energy density and reliance on earth-abundant elements. Among them, Mn-based DRX materials are particularly attractive; however, their practical deployment has been hindered by severe capacity fading during extended cycling. Understanding and mitigating the underlying degradation mechanism is therefore critical for enabling their practical applications.

In this work, we systematically investigate the electrochemical and structural evolution of Mn–Ti oxyfluoride DRX cathodes and identify the fundamental origin of performance decay. We reveal that repeated cycling induces progressive over-reduction of Mn³⁺ to Mn²⁺, driven by irreversible oxygen redox reactions at high voltage. The formation of Mn²⁺, which is highly soluble in conventional electrolytes, leads to substantial Mn dissolution and subsequent structural deterioration of the cathode. This degradation process is accompanied by lattice expansion, a shift in Mn valence state, and continuous loss of active material, collectively resulting in rapid capacity fading.

To address this issue, we propose a valence-engineering strategy that elevates the average Mn oxidation state by partially substituting Ti⁴⁺ with Mn⁴⁺, thereby expanding the Mn³⁺/Mn⁴⁺ redox reservoir. This redox-buffering effect effectively suppresses the over-reduction to Mn²⁺ during discharge and significantly mitigates Mn dissolution. As a result, the modified composition exhibits markedly improved structural stability and enhanced long-term cycling performance compared to the baseline material.

These findings demonstrate that Mn over-reduction is a critical degradation pathway in Mn-based DRX cathodes and highlight the importance of redox-state regulation in compositional design. The proposed strategy provides a general framework for stabilizing high-energy-density cathodes and advancing the development of sustainable lithium-ion battery materials.

The lithium-ion battery industry remains highly dependent on Ni- and Co-rich chemistries, which face increasing challenges in raw material cost and global supply chain stability. As a promising alternative, Mn-rich cathode materials have attracted considerable attention because they offer improved cost effectiveness and resource sustainability for next-generation rechargeable batteries, particularly for electric vehicles and energy storage systems. However, Mn-rich materials often suffer from structural instability, including voltage decay and poor cycle life. Therefore, precise control of precursor properties is essential because these features strongly influence the electrochemical performance of the final cathode materials.

Mn-rich precursors were synthesized by a carbonate-based co-precipitation method in a semi-batch reactor. To understand nucleation and growth behavior during co-precipitation, degree of supersaturation was calculated using thermodynamic variables as the reaction proceeds. For this purpose, the residual metal concentration in solution was modeled by considering ammonia complexation and metal speciation. Based on these calculations, trends in particle size distribution (PSD) and sphericity were predicted under varied co-precipitation conditions. This kinetic analysis was further used to identify a pH window that simultaneously minimizes metal loss and enables uniform co-precipitation. The effectiveness of the methodology was proved by comparing with the experimental PSD and morphology of the synthesized precursors. To investigate electrochemical performances, the corresponding cathode materials were evaluated in coin-type half-cells.

The results showed that higher degree of supersaturation resulted in smaller precursor particles with broader size distributions, whereas lower degree of supersaturation favored the formation of larger, more spherical particles with narrower PSD. The pH window predicted from the kinetic model was in close agreement with the experimental observations. Likewise, the developed kinetic model provided useful guidance for process optimization. Electrochemical evaluation further revealed that cathode materials derived from precursors with appropriate average particle size of approximately 10-15 m and good sphericity exhibited more stable cycling performance.

These results demonstrate that the kinetic model based on thermodynamic data can serve as an effective tool for understanding and controlling the co-precipitation of Mn-rich carbonate precursors. This precursor design strategy provides a practical foundation for developing high-performance, low-cost Mn-rich cathode materials for next-generation rechargeable batteries.

Manganese (Mn) dissolution from Mn-containing cathodes is a well-recognized degradation process in lithium-ion batteries. Dissolved Mn can reduce the amount of active cathode material and migrate to the anode, where it destabilizes interfacial layers and promotes capacity fade. Because these effects are closely linked to long-term cell performance, reliable monitoring of Mn dissolution is important for understanding degradation in Mn-containing cathodes. Conventional techniques such as ICP-MS of electrolyte and elemental mapping of negative electrode provide quantitative information on dissolved Mn, but they are inherently ex situ and usually require cell disassembly. They are therefore limited in their ability to follow dissolution-related behavior in real time during electrochemical cycling. This limitation motivates the development of real-time electrochemical and operando approaches for probing dissolution processes under working conditions. In this work, a custom cell platform with real-time electrochemical sensing elements was used to examine signals potentially associated with dissolved Mn species during cycling of Mn-based cathodes. This study examines whether such responses can be measured reproducibly and interpreted in relation to Mn-dissolution-related behavior. Preliminary measurements showed measurable responses that may include contributions from dissolved Mn species. This is a step-forward to real-time electrochemical monitoring as a promising route for investigating dissolution behaviors. At the same time, we will introduce the challenges and possible approaches in separating Mn-related signals from concurrent electrochemical processes. Overall, this work provides a basis for further operando investigation of Mn-dissolution-related degradation in Mn-containing cathodes for Li-ion rechargeable batteries. 

Lithium- and manganese-rich (LMR) cathode materials have attracted significant attention as promising candidates for next-generation high-energy-density lithium-ion batteries due to their exceptionally high theoretical capacity. Despite this potential, their electrochemical performance is accompanied by complex structural transitions during lithium extraction, arising from the coexistence of multiple phases within the crystal structure. The thermodynamics of the in-situ generated metastable phase remains insufficiently understood. Therefore, gaining insight into the thermodynamic characteristics of these structural changes is essential for designing advanced LMR cathodes. 

Entropymetry determines the reaction entropy as a function of the state of charge by measuring the temperature dependence of the open-circuit potential  This technique provides a non-destructive and electrochemically accessible approach to probe thermodynamic properties, enabling sensitive tracking of structural transitions throughout during the electrochemical cycling. Owing to these advantages, entropymetry is well suited for investigating the complex phase behavior of LMR cathodes. 

In this work, entropymetry is applied to LMR cathodes over the full electrochemical cycling to examine entropy of reaction. Particular attention is given to the significant structural changes that are correlated with entropy features during the electrochemical operation. Through this approach, the study seeks to explore the thermodynamics of electrochemical processes that involve structural changes in LMR cathodes. 

This work presents a systematic approach for analyzing the structural and thermodynamic behavior of LMR cathodes using entropymetry and is expected to contribute to a deeper understanding of LMR electrochemistry. The insights gained from this study may further support the development of design strategies for improving the electrochemical and thermal stability of LMR cathode materials for next-generation lithium-ion batteries.

Li- and Mn-rich layered oxide (LMR) have emerged as the most promising cathode due to their ability to deliver a capacity exceeding 250 mAh g-1. Despite this distinct advantage, the practical deployment of LMR is severely hampered by intrinsic challenges associated with the anionic redox reaction, which exhibits sluggish activation. Herein, we elucidate the critical role of stacking faults (SFs) as activators for anionic redox. The presence of SFs is not merely a crystallographic disorder but a modifier that alters the local coordination geometry of lattice oxygen, particularly the Li-O-Li configurations. We postulate that this local structural distortion lowers the activation energy barrier for anionic redox reaction. To validate this hypothesis, we synthesized a series of single-particle LMR with systematically controlled SF density by precisely tuning the temperature, maintaining the global chemical composition across all samples. We found that LMR with high SF exhibited superior capacity, with reduced polarization and charge transfer resistance. These findings establish defect engineering as a vital pathway for designing high-performance cathode materials by alleviating the kinetic bottlenecks of anionic redox.Li- and Mn-rich layered oxide (LMR) have emerged as the most promising cathode due to their ability to deliver a capacity exceeding 250 mAh g-1. Despite this distinct advantage, the practical deployment of LMR is severely hampered by intrinsic challenges associated with the anionic redox reaction, which exhibits sluggish activation. Herein, we elucidate the critical role of stacking faults (SFs) as activators for anionic redox. The presence of SFs is not merely a crystallographic disorder but a modifier that alters the local coordination geometry of lattice oxygen, particularly the Li-O-Li configurations. We postulate that this local structural distortion lowers the activation energy barrier for anionic redox reaction. To validate this hypothesis, we synthesized a series of single-particle LMR with systematically controlled SF density by precisely tuning the temperature, maintaining the global chemical composition across all samples. We found that LMR with high SF exhibited superior capacity, with reduced polarization and charge transfer resistance. These findings establish defect engineering as a vital pathway for designing high-performance cathode materials by alleviating the kinetic bottlenecks of anionic redox.

The drive toward electrified transport and renewable‑energy storage demands safer, longer‑lived lithium‑ion batteries (LIBs). Ni-rich cathodes cut cobalt content and boost energy density but suffer from cation mixing and unstable surface films, and activated Ni⁴⁺ accelerates electrolyte decomposition. In this context, full concentration gradient (FCG) or core-shell cathodes have been developed to improve the stability and performance of high-nickel cathodes for LIBs. These cathodes exhibit reduced surface reactivity by concentrating reactive nickel at the core, often with additional benefits of enhanced mechanical strength through radially grown microstructures. However, current approaches are inherently constrained by the fixed mixing rates determined by the desired average composition, significantly reducing the degrees of freedom to a single configuration, hindering the potential of FCG strategy toward highly stable and safe LIBs. Herein, we have developed a versatile mathematical framework integrated with an automated reactor system to design and reify highly customizable FCG in Ni-rich cathodes for advanced LIBs. This method provides precise and independent control of the average composition, slope, and curvature of FCGs, enabling the optimization of structural and mechanical properties of the cathode materials. We have showcased this method with Ni_0.8Co_0.1Mn_0.1(OH)₂ precursors of controlled FCGs, which unlocked an optimized cathode with excellent cycling stability without crack formation after repeated cycles. This work opens up new possibilities for the design and manufacturing of advanced cathode materials, enabling safer, high-performance batteries. 

Due to its discharge capacity exceeding 200 mAh/g, high-nickel NMC is a promising cathode material for the development of high-energy-density Li-ion batteries. When used in an all-solid-state battery (ASSB) configuration, conventional polycrystalline NMC suffers from fracturing after prolonged charge/discharge cycles. In contrast, the morphology of monolithic NMC has demonstrated good cyclability due to its more isotropic volume expansion [1]. However, to control the particle size of monolithic NMCs, a large portion of the literature reports synthesis processes using molten salts, which are difficult to scale up due to their high cost [2]. Our laboratory has developed a simple three-step process for producing high-quality “monolithic” NMC811 material. We have demonstrated that an optimized calcination method promotes the growth of primary particles and the fragmentation of secondary particles. This step is followed by low-energy milling and a low-temperature annealing step to refine the particle size distribution (Figure 1a). The D₅₀ particle size is effectively reduced from 14 to 4–5 µm after the milling step (Figure 1b), and its crystalline structure remains constant throughout the process. Electrochemical tests in half-cell configuration with liquid electrolyte show similar galvanostatic profiles for the NMC material at each of the three synthesis stages, with an initial coulombic efficiency (ICE) of approximately 87% and a first discharge capacity of 180, 184, and 190 mAh/g, respectively, for the pristine, milled, and annealed samples (Figure 1c). Regarding cycle life, the annealed sample exhibits better capacity retention, with a discharge capacity of 80% of the first-cycle capacity at C/5 and 1D after 100 cycles (Figure 1d). This highlights the importance of the annealing step, as it can mitigate surface defects caused by the grinding process. The annealed material was tested in an ASSB configuration with Li6PS5Cl as the solid electrolyte and exhibits, during the first cycle, a high ICE of 91% and a discharge capacity of 187 mAh/g at C/30 with a low cycling pressure of 9 MPa (Figure 1e). Over the first few tens of cycles the material remains stable, and at C/10, it maintains excellent electrochemical performance with a discharge capacity of 178 mAh/g after 25 cycles.

Commercialized LIB cathodes most commonly use high specific energy oxides or low-cost phosphates. However, the increasing demand for energy storage necessitates the development of additional materials that are both high specific energy and low cost. Though the development of sulfides has long been overtaken by oxides, lithium-rich transition metal sulfides, like Li₂FeS₂ and Li_2.2Al_0.2Fe_0.6S₂, offer a unique ability to reach high specific energy using low-cost materials. Li_2.2Al_0.2Fe_0.6S₂ can reach a specific energy of > 1000 Wh/kg using only industrial metals Fe and Al. The high energy density is achieved through reversible multielectron redox that leverages stable transition metal and anion redox charge compensation. 

The feasibility of Li-rich transition metal sulfides for use in commercial applications is dependent on their ability to be a drop-in technology from a processing point of view. However, sulfides are commonly assumed to react in air. Here, we report the reactivity of the Li-rich sulfides in both humid air and dry room conditions to decouple their reactivity to H₂O and O₂. Indeed, anion redox capacity decreases proportionally with increasing humidity level and exposure time. However, both Li₂FeS₂ and Li_2.2Al_0.2Fe_0.6S₂ are compatible with battery dry room conditions suggesting reactivity with O₂ is minimal. Material exposure to and cell fabrication inside a dry room atmosphere does not negatively impact these multielectron redox cathode materials. This study provides promising results toward developing commercially relevant Li-rich cathode materials composed of earth-abundant, cost-effective elements that support multielectron redox for higher capacity LIBs. 

High-voltage spinel LiNi0.-generation lithium-ion batteries, but its intrinsic crystallographic durability under practical full-cell operation has remained difficult to evaluate because apparent degradation is often masked by interfacial side reactions, gas evolution, and transition-metal-related crosstalk. Here, we use a practical LiNi0.5Mn1.5O4/titanium niobium oxide full-cell platform in which such extrinsic degradation pathways are strongly suppressed, enabling direct assessment of the bulk stability of LiNi0.5Mn1.5O4 during ultra-fast-charge and ultra-long-cycle operation. A 3 V, 1 Ah-class pouch cell achieved 80% state of charge within 5 min at an average charging rate of 20 C, retained 90% of its initial capacity after 10,000 cycles, and showed negligible gas evolution. Synchrotron X-ray diffraction revealed that the spinel structure was preserved after prolonged cycling, with negligible lattice-parameter variation, no detectable phase collapse, and no appreciable peak broadening. Operando Ni and Mn K-edge X-ray absorption spectroscopy further confirmed highly reversible bulk redox behavior and preservation of the local coordination environments throughout cycling. In contrast, surface-sensitive analyses showed that the remaining structural and chemical evolution was confined mainly to the particle surface. O K-edge soft X-ray absorption spectroscopy indicated changes in the electronic structure at the outermost surface, whereas the bulk oxygen states were essentially unchanged. Transmission electron microscopy combined with energy-dispersive X-ray spectroscopy suggested the formation of an ultrathin surface layer enriched in organic interphase components and containing only limited transition-metal- and fluorine-containing species. Importantly, these surface-localized features did not accompany measurable deterioration of the bulk crystal structure or loss of redox reversibility. The combined diffraction, spectroscopy, microscopy, and full-cell data therefore separate intrinsic crystallographic behavior from extrinsic interfacial effects, which are often convoluted in conventional high-voltage full cells. These results demonstrate that, once gas generation and interfacial crosstalk are effectively suppressed, LiNi0.5Mn1.5O4 exhibits exceptional intrinsic bulk crystallographic durability under practical ultra-fast-charge full-cell conditions. The findings clarify the distinction between true bulk degradation and surface-localized interphase evolution, and provide a structural basis for developing durable cobalt-free high-power lithium-ion batteries based on high-voltage spinel cathodes. This platform thus offers a robust benchmark for evaluating high-voltage cathode durability under stringent realistic operating conditions.

Manganese-based disordered rock-salt (Mn-DRX) cathodes are promising next-generation Li-ion battery materials owing to their high energy density, compositional flexibility, and reduced reliance on critical elements such as Ni and Co. However, their broad compositional design space remains difficult to explore because conventional synthesis methods require prolonged high-temperature annealing or multi-day mechanochemical processing. Here, we demonstrate rapid Joule-heating synthesis as a time- and energy-efficient strategy for producing high-performance Mn-DRX cathodes. Using Li_1.2Mn_0.4Ti_0.4O₂ as a model system, we show that electrochemical performance under rapid thermal processing is governed by the coupled evolution of nanoscale short-range ordering and microscale features, including phase purity, cation homogeneity, and impurity formation. By optimizing these multiscale structural factors, Joule-heated Li_1.2Mn_0.4Ti_0.4O₂ synthesized at 1050 °C for only 10 min achieves a near-phase-pure DRX structure with uniform elemental distribution and reduced short-range ordering compared with furnace-synthesized Li_1.2Mn_0.4Ti_0.4O₂ prepared at 950 °C for 12 h. As a result, the Joule-heated sample delivers improved rate capability, retaining 161 mAh g⁻¹ at 1 A g⁻¹ compared with 137 mAh g⁻¹ for the furnace-synthesized counterpart, while maintaining comparable capacity and cycling stability. The versatility of this approach is further validated by synthesizing multiple Mn-DRX compositions, including Li_1.2Mn_0.6Nb_0.2O₂, Li_1.2Mn_0.2Ti_0.2Cr_0.2O₂, and Li_1.2Mn_0.5Ti_0.3O_1.9F_0.1, with electrochemical performance comparable to conventional furnace products. These findings establish Joule heating as a robust rapid-synthesis platform for accelerating high-throughput discovery and structural optimization of Mn-DRX cathode materials.

Lithium sulfide (Li2S)-based sulfur cathodes can be paired with lithium-free anode materials such as graphite, silicon, and tin, positioning them as core component of the realization of lithium-free anode all-solid-state batteries. Nevertheless, an effective compositing strategy with carbonaceous materials is imperative to overcome the inherently low electrical conductivity of Li2S. In this study, Li2S-carbon (Li2S-C) composites were synthesized by uniformly loading Li2S into high-surface-area activated carbon (AC) via a thermal reduction method. Utilizing ACs with various specific surface areas, the impacts of soft nitriding on the evolution of pore structures and the resulting electrochemical properties were systematically investigated. The results demonstrate that the Li2S-C composite with an optimized pore architecture exhibits significantly enhanced reactivity and electrode performance. These findings suggest that the proposed material design could serve as a robust platform technology for advanced cathode engineering in next-generation all-solid-state batteries.

Ni-rich layered oxide cathodes offer high capacity and energy density, but suffer from poor structural and mechanical stability during extended cycling. To address these issues, we introduce a dual doping strategy using Al³⁺ and Nb⁵⁺ in Li[Ni₀.₉₂Co₀.₀₄Mn₀.₀₄]O₂ (NCM92) to enhance both bulk and microstructural stability. Al³⁺ is incorporated into the transition metal layer, reducing cation mixing and suppressing anisotropic volume change, while Nb⁵⁺ localizes at grain boundaries and inhibits abnormal grain growth. As a result, rod-like, radially aligned primary particles with uniform size distribution are formed, which improve mechanical integrity and reduce microcrack formation. The co-doped NCM92 delivers an initial capacity of ~210 mAh·g⁻¹ and achieves 88.3% capacity retention after 1000 cycles. Under fast-charging at 45 °C, it still maintains 75.0% retention, clearly outperforming the undoped counterpart. Overall, the dual doping approach provides an effective pathway to stabilize Ni-rich cathodes, enabling high-performance lithium-ion batteries with enhanced structural resilience and cycling durability.Ni-rich layered oxide cathodes offer high capacity and energy density, but suffer from poor structural and mechanical stability during extended cycling. To address these issues, we introduce a dual doping strategy using Al³⁺ and Nb⁵⁺ in Li[Ni₀.₉₂Co₀.₀₄Mn₀.₀₄]O₂ (NCM92) to enhance both bulk and microstructural stability. Al³⁺ is incorporated into the transition metal layer, reducing cation mixing and suppressing anisotropic volume change, while Nb⁵⁺ localizes at grain boundaries and inhibits abnormal grain growth.

As a result, rod-like, radially aligned primary particles with uniform size distribution are formed, which improve mechanical integrity and reduce microcrack formation. The co-doped NCM92 delivers an initial capacity of ~210 mAh·g⁻¹ and achieves 88.3% capacity retention after 1000 cycles. Under fast-charging at 45 °C, it still maintains 75.0% retention, clearly outperforming the undoped counterpart.

Overall, the dual doping approach provides an effective pathway to stabilize Ni-rich cathodes, enabling high-performance lithium-ion batteries with enhanced structural resilience and cycling durability.

Ni-rich layered cathodes are promising for high-energy-density lithium-ion batteries, but their cycling stability is often limited by microstructural degradation. High-temperature calcination improves crystallinity but also induces uncontrolled grain coarsening, resulting in heterogeneous primary particles that compromise the mechanical integrity of secondary particles and promote microcrack formation during cycling. Here, we present a controlled grain-coarsening strategy for Ni-rich Li[Ni_0.94Co_0.04Al_0.02]O₂ (NCA) cathodes by tailoring the primary particle size distribution. The introduction of Nb species at grain boundaries suppresses abnormal grain growth, producing a homogeneous and densely packed primary particle microstructure.^[1] This microstructural control enhances the mechanical strength of the cathode particles and mitigates microcrack propagation driven by lattice volume changes.^[2] As a result, electrolyte infiltration into the particle interior is suppressed, reducing the formation of resistive NiO-like rock-salt layers and maintaining electrical connectivity during extended cycling. The Nb-doped NCA cathode delivers 90.0% capacity retention after 500 cycles in pouch-type full cells. These results demonstrate that regulating grain coarsening during calcination is an effective strategy to enhance the mechanical integrity and cycling durability of Ni-rich cathode materials.

Fast-charging technology for electric vehicles (EVs) is highly desirable because it can reduce charging time to be comparable to that of conventional refueling; however, its practical implementation is hindered by kinetic limitations in lithium-ion batteries (LIBs). In particular, Ni-rich cathodes have attracted significant attention as high energy density electrode materials, making their fast-charging stability a key issue.

In this study, we investigate the mechanism of fast-charging performance degradation in Ni-rich cathodes during extended cycling by comparing materials with different microstructures. The results show that microcrack formation and the associated cathode deterioration severely impair fast-charging capability over extended cycling.[1] Electrolyte penetration through microcracks accelerates the formation of thick rocksalt impurity phases, producing electrochemically inactive regions under high-current conditions.

As a result, these findings indicate that suppressing microcrack formation by tailoring microstructures is essential for maintaining fast-charging stability in Ni-rich cathodes.[2] A profound understanding of the relationship between microcrack evolution and the loss of fast charging capability provides important guidelines for developing durable cathode materials for next-generation EV batteries.

The demand for cost-effective, cobalt-free, and high-performance energy storage continues to drive the development of next-generation battery technologies. Among these, Lithium Nickel Manganese Oxide (LNMO) cathode active material stands out as an attractive candidate owing to its operation at nearly 5V vs. Li/Li+, lower nickel content than conventional NMC-type materials, and inherently higher energy delivered per electron transfer. These advantages translate to a cell-level cost comparable to LFP batteries, while offering significantly higher energy density. TOPSOE's recent progress in LNMO development has been guided by a systematic failure mode analysis approach. This has helped to identify the key degradation mechanisms behind capacity fade and gas evolution at high potentials, including both chemical and non-chemical crosstalk between cathode and anode. Isolating the root causes and developing targeted mitigation strategies, has culminated into TOPSOE’s 3rd generation LNMO material, designed for improved cell-level stability and lifetime performance. This work will show how failure mode-driven development has advanced 5V class LNMO and demonstrate the recent progress towards bringing high voltage lithium-ion batteries closer to commercial viability.The demand for cost-effective, cobalt-free, and high-performance energy storage continues to drive the development of next-generation battery technologies. Among these, Lithium Nickel Manganese Oxide (LNMO) cathode active material stands out as an attractive candidate owing to its operation at nearly 5V vs. Li/Li+, lower nickel content than conventional NMC-type materials, and inherently higher energy delivered per electron transfer. These advantages translate to a cell-level cost comparable to LFP batteries, while offering significantly higher energy density.

TOPSOE's recent progress in LNMO development has been guided by a systematic failure mode analysis approach. This has helped to identify the key degradation mechanisms behind capacity fade and gas evolution at high potentials, including both chemical and non-chemical crosstalk between cathode and anode. Isolating the root causes and developing targeted mitigation strategies, has culminated into TOPSOE’s 3rd generation LNMO material, designed for improved cell-level stability and lifetime performance.

This work will show how failure mode-driven development has advanced 5V class LNMO and demonstrate the recent progress towards bringing high voltage lithium-ion batteries closer to commercial viability.

Application demands for lithium ion batteries continue to evolve demanding new strategies for materials design. A recent approach for active material design is the concept of entropy stabilization where the random arrangement of multiple components increases the configurational entropy (∆Sconfig) to stabilize a single-phase structure. This concept can be applied to the preparation of metal oxides consisting of multiple cations, typically five or more, within a single oxygen lattice framework. These high entropy oxides (HEOs) are an attractive and expansive class of materials due to the broad possible range of cation combinations. 

We have successfully synthesized HEO materials targeting layered and spinel structural forms and compositions including equimolar metals and manganese rich designs. In-situ characterization of the synthesis was done showing the structural evolution as a function of time and temperature. The electrochemical behavior of the materials was probed where voltammetry as well as galvanostatic cycling were utilized. 

Detailed characterization of the materials using multiple approaches reveals their inherent complexity. Synchrotron based operando experiments were conducted where x-ray absorption spectroscopy was used to determine the redox activity of the metal centers revealing that some centers did not electrochemically participate during oxidation or reduction. This work sheds light on the synthetic parameters for high entropy layered oxides where the influence on electrochemical behavior is determined. Characterization shows the presence of defects and disorder in the materials. Operando examination of electrochemical cells reveals the redox active and inactive metal centers. 

This work sheds light on the synthetic parameters for high entropy layered oxides where the influence on electrochemical behavior is determined. Characterization shows the presence of defects and disorder in the materials. Operando examination of electrochemical cells reveals the redox active and inactive metal centers. The results provide foundational information for the design, preparation, and use of high entropy oxides as active battery materials.