Stabilizing the interface between high-Ni oxide cathode and Li6PS5Cl for all-solid-state batteries via dual-compatible halides

All-solid-state batteries (ASSBs) using sulfide solid electrolytes with high room-temperature ionic conductivity are expected as promising next-generation batteries, which might solve the safety issues and enable the utilization of lithium metal as the anode to further increase the energy density of cells. Most researchers in the academic community currently focus on developing novel sulfide solid electrolytes, clarifying the interface issues between sulfide electrolytes and solid electrodes and mechanism of lithium dendrite growth in ASSB. However, there is a lacking in the technical route analysis about the commercialization of ASSBs based on sulfide solid electrolytes. This review mainly introduces the specific preparation methods of various parts in sulfide-based ASSBs, including the preparation methods of sulfide solid electrolyte particles, sulfide-based composite electrolyte membranes, composite cathodes and anodes, and analyzes the advantages and disadvantages of these methods. In addition, several schemes of ASSB assembly are also introduced. Finally, a perspective of large-scale production of sulfide-based ASSBs is provided, which is expected to accelerate the commercialization of sulfide-based ASSBs.

All-solid-state batteries (ASSBs) working at room and mild temperature have demonstrated inspiring performances over recent years. However, the kinetic attributes of the interface applicable to the subzero temperatures are still unidentified, restricting the low-temperature interface design and operation. Herein, a host of cathode interfaces are constructed and investigated to unlock the critical interface features required for cryogenic temperatures. The unstable interface between LiNi0.90Co0.05Mn0.05O2 (Ni90) and Li6PS5Cl (LPSC) sulfide solid electrolyte (SE) results in unfavorable cathode-electrolyte interphase (CEI) and sluggish lithium-ion transport across the CEI. After inserting a Li2ZrO3 (LZO) coating layer, the activation energy of the Ni90@LZO/sulfide SE interface can be reduced from 60.19 kJ mol-1 to 41.39 kJ mol-1 owing to the suppressed interfacial reactions. Through replacing the LPSC SE and LZO coating layer by the Li3InCl6 (LIC) halide SE, both a highly stable interface and low activation energy (25.79 kJ mol-1) can be achieved, thus realizing an improved capacity retention (26.9%) at -30 °C for the Ni90/LIC/LPSC/Li-In ASSB. Moreover, theoretical evaluation clarifies that cathode/SE interfaces with high ionic conductivity and low energy barrier are favorable to the Li+ conduction through the interphase and the Li+ transfer across the cathode/interphase interface. These critical understandings may provide guidance for low-temperature interface design in ASSBs.

Surface to bulk design empowering Ni-rich layered oxide cathode in sulfide-based All-Solid-State batteries

Sulfide-based all-solid-state batteries (ASSBs) have ushered in a new era of energy storage technology, offering the tantalizing prospect of unprecedented energy density and safety. However, the poor electrode-electrolyte interface between Li anodes and sulfide solid electrolytes has hindered its practical application. In this review, the primary focus lies in the current fundamental understanding, challenges, and optimization strategies regarding the interface chemistries between sulfide solid electrolytes and Li anode. First, an in-depth discussion is conducted and provides a detailed summary of the interfacial challenges that exist between the Li anode and sulfide solid electrolytes. Among these challenges, poor interfacial compatibility and stability stand out as the two crucial issues. Subsequently, effective approaches are systematically explored to surmount these issues. These encompass the component optimization and structural design of the bulk anode, doping and coating strategies of the sulfide solid electrolytes, and interface design between the Li anode and sulfide solid electrolytes. Finally, the insights are present into the limitations of current studies, perspectives, and recommendations for the further development of sulfide-based solid-state batteries, aiming to offer a comprehensive and enlightening overview for interface engineering, which is of great significance for the integration of applicable all-solid-state Li metal batteries (ASSLMBs).

Lithium-ion batteries (LIBs) have played a pivotal role in advancing energy storage technologies, enabling high-demand applications such as electric vehicles and renewable energy storage systems. Despite their widespread use, LIBs face significant challenges in terms of energy density and intrinsic safety issues. These challenges have spurred interest in all-solid-state batteries (ASSBs), which utilize solid electrolytes (SEs) to offer safe alternatives to conventional liquid electrolyte-based LIBs. Among the various types of SEs explored to date, halide SEs exhibit improved compatibility with high-voltage oxide cathodes, as compared with sulfide-based SEs. Thus, halide SEs may be utilized as cathode coating materials for ASSBs using sulfide SEs with high ionic conductivity. However, the specific material properties that determine the chemical/electrochemical characteristics of halide coatings have not been clearly studied yet.In this study, we synthesize lithium yttrium chloride (Li3YCl6, LYC) SEs using different methods (solid-state synthesis and ammonium-assisted liquid-phase synthesis) at various heat-treatment temperatures to control phase compositions and crystal structures. These allow us to systematically explore the phase-structure-property relationship of LYC SEs and their roles as coating materials for LiNi0.90Co0.05Mn0.05O2 (NCM). Our experimental findings reveal that the phase, crystal structure and crystallinity of LYC significantly influence the microstructure, ionic conductivity, interfacial compatibility, and thermal stability of LYC-coated NCM (NCM@LYC). The crystal structure and crystallinity of synthesized LYC SEs are explored by Rietveld refinement of X-ray diffraction patterns. Notably, LYC SEs prepared via wet synthesis under optimal heat-treatment conditions exhibit superior Li-ion transport kinetics due to the enhanced crystallinity of phase-pure LYC. This leads to the improved interfacial resistances of NCM@LYC, as evidenced by impedance analyses of NCM composite electrodes. Therefore, the NCM@LYC composite electrodes with the optimized LYC SE show significant improvement in rate capability and cycle lifetimes. This research elucidates the critical role of the synthesis conditions in controlling the properties of halide coating materials and thus in improving the interfacial kinetics and stability of composite cathodes of ASSBs. The insights gained from the phase-structure-property relationships provide valuable guidelines for the development of highly conductive and stable SEs for next-generation batteries.

Interface compatibility between sulfide solid electrolytes and Ni-rich oxide cathode materials: factors, modification, perspectives

Silicon is widely recognized as a promising anode material for all-solid-state batteries (ASSBs) due to exceptional specific capacity, abundant availability, and environmental sustainability. However, the considerable volume expansion and particle fragmentation of Si during cycling lead to significant performance degradation, limiting its practical application. Herein, the development of a pre-lithiated Si-based composite anode (c-Li1Si) is presented, designed to address the key challenges faced by Si-based anodes, namely severe volume changes and low electrochemical stability. The c-Li1Si anodes are prepared by incorporating Li₁Si powders with Li6PS5Cl (LPSCl) sulfide solid electrolyte (SSE), forming a dense structure that enhances conductivity and mitigates structural degradation. The ASSBs with c-Li1Si-60 anode exhibit outstanding electrochemical performance, including excellent rate capability and capacity retention of 84.4% after 1000 cycles at 1C and exceptional performance even at low anode-to-cathode capacity ratios (N/P ratio) of 1.68. EIS and pressure measurements reveal improved reaction kinetics and reduced volume expansion. X-ray micro-CT and SEM further confirmed the introduction of LPSCl effectively alleviated volume changes and maintained electrode structural integrity, contributing to enhanced electrochemical performance. These results underscore the potential of the c-Li1Si anode to overcome the intrinsic limitations of Si-based anodes, offering a promising pathway toward high-energy-density ASSBs.

Lithium-ion batteries (LIBs) are widely used in a variety of applications due to their high energy and power densities, and long cycle life. With the expanding use of LIBs in electric vehicles and energy storage systems, there is very active research into all-solid-state batteries (ASSBs), which offer greater energy density than traditional LIBs and eliminate the inherent fire hazards. Since most of the detailed reactions involved in the performance and degradation of a battery are temperature-sensitive, so-called thermal activation processes, it is very important to accurately assess whether a battery can have the high performance and low degradation characteristics required under different climatic conditions. To evaluate the electrochemical properties of electrode materials in LIBs, a half-cell is typically constructed with the electrode of interest as the working electrode (WE) and lithium metal as auxiliary electrode (AE). Here, lithium metal is close to an ideal non-polarizable material, has a large capacity, and maintains a constant potential during charge/discharge, so it is widely used as AE material in LIB research. However, several issues arise when lithium is used as AE in ASSBs: Lithium metal undergoes mechanical deformation due to the relatively high internal pressure required to ensure good contact between lithium and solid electrolyte; When in contact with sulfide-based solid electrolytes, which are currently of interest due to their high ionic conductivity, side reaction products can lead to an increase in interfacial resistance; the growth of lithium dendrites, often observed in conventional LIBs, is still unavoidable. These issues all affect the half-cell signal, potentially causing a distorted evaluation of the WE’s characteristics.Lithium-indium alloy is being utilized as AE for ASSB half-cells to replace lithium metal. It exhibits excellent mechanical ductility and maintains a constant reduction potential over a wide stoichiometric range, ensuring excellent contact property and voltage stability. Moreover, it is very easy to fabricate through simple compression at room temperature. Nevertheless, the limited study on its electrochemical properties leaves uncertainty regarding its full functionality as AE for accurate evaluation of WE, particularly in extreme operational conditions. For instance, lithium-indium alloy are primarily based on alloying/dealloying reactions involving solid-state diffusion of lithium, which is generally considered to be a relatively slow process kinetically, while lithium only involves a kinetically favorable plating/stripping process on the surface. Therefore, a comparative analysis of these different reaction mechanisms in terms of kinetics is necessary. This presentation presents a comparative analysis of the electrochemical properties of lithium metal and lithium-indium alloys used as AEs in ASSB half-cells. In particular, the electrochemical properties of lithium-indium alloys with different reaction mechanisms with lithium are investigated over a range of temperatures and current densities, and these differences are discussed from a kinetic point of view. For this purpose, first, using a three-electrode half-cell with lithium or lithium-indium alloy as AE, we compared the electrochemical properties of these two AEs during half-cell operation by interpreting their potential and over-potential changes, and quantifying their detailed resistances. Then, through dc experiments on lithium and lithium-indium symmetrical cells, we identified differences in overvoltage behavior due to differences in their reaction mechanism. In particular, we noted distinct differences in the overpotential behavior of these two electrodes at low temperatures and high current densities. Furthermore, based on the results of a combined dc/ac electrochemical analysis, we derived the overvoltage that dominates the overall overvoltage at each of the two electrodes. Based on these results, we analyzed how the kinetic differences between the two electrodes affect the cathode half-cell signal, in order to derive key considerations for reliable ASSB half-cell evaluation. In this presentation, the advantages and disadvantages of lithium-indium alloy compared to lithium metal as AE will be discussed from a kinetic perspective, focusing on interfacial and bulk resistance (overpotential). Furthermore, methods for utilizing AE to conduct accurate and reliable half-cell tests will be proposed.

All-solid-state batteries (ASSBs) employing sulfide solid electrolytes (SEs) are widely recognized as promising candidates for future energy storage owing to their excellent ionic conductivity, facile processability, and compatibility with high-energy electrodes. When integrated with Ni-rich layered oxides and Li metal, sulfide SEs enable energy densities and safety margins beyond those of conventional lithium-ion batteries. Yet their practical application is hindered by complex electrochemo-mechanical degradation that originates from intertwined electrochemical reactions and mechanical instability. Electrochemical reactions such as SE oxidation and interfacial decomposition can both induce and be exacerbated by mechanical degradation, e.g., active material cracking and interfacial contact loss. These coupled processes highlight that sustainable interfacial stability is not simply a matter of chemical passivation or mechanical reinforcement, but requires strategies that address both issues simultaneously. In this Feature Article, we review the origins and evolution of electrochemo-mechanical degradation in sulfide-based ASSBs, elucidate its detrimental impact on cell performance, and propose potential strategies for its mitigation. By providing a unified view of electrochemo-mechanical challenges, this work outlines a roadmap toward practical and reliable sulfide-based ASSBs.

All-solid-state batteries (ASSBs) are promising candidates for application as next-generation high-power supply and storage devices in electric vehicles. ASSBs offer excellent safety and a high energy density; however, the high interfacial resistance between the positive electrode and solid electrolyte due to solid–solid contact reactions at elevated temperatures limits their applications. To address these issues, the effect of thermal annealing on the interfacial structure between a sodium super ionic conductor (NASICON)-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte and a LiCoO2 (LCO) cathode in an ASSB fabricated by aerosol deposition was investigated experimentally. Specifically, spectrum imaging was conducted by combining scanning transmission electron microscopy and electron energy loss spectroscopy. Metastable degraded low-density transition layers were formed between LATP and LCO in the as-deposited sample. A significant reduction in interfacial resistance was achieved after thermal annealing at 250–300 °C, which was mainly attributed to structural recovery in this temperature range. However, thermal annealing at 400 °C resulted in increased interfacial resistance due to the formation of a Co3O4-like spinel blocking layer at the LATP/LCO interface. These findings provided valuable insights into the electronic properties of the ASSB composite under investigation and were consistent with theoretical predictions of Li and O transfer between the layers due to thermal annealing.

Enhancement of the rate capabilities for all-solid-state batteries through the surface oxidation of sulfide solid electrolytes

All-solid-state batteries (ASSBs) with ceramic-based solid-state electrolytes (SSEs) enable high safety that is inaccessible with conventional lithium-ion batteries. Lithium metal, the ultimate anode with the highest specific capacity, also becomes available with nonflammable SSEs in ASSBs, which offers promising energy density. The rapid development of ASSBs, however, is significantly hampered by the large interfacial resistance as a matched lithium/ceramic interface that is not easy to pursue. Here, a lithium-graphite (Li-C) composite anode is fabricated, which shows a dramatic modification in wettability with garnet SSE. An intimate Li-C/garnet interface is obtained by casting Li-C composite onto garnet-type SSE, delivering an interfacial resistance as low as 11 Ω cm2 . As a comparison, pure Li/garnet interface gives a large resistance of 381 Ω cm2 . Such improvement can be ascribed to the experiment-measured increased viscosity of Li-C composite and simulation-verified limited interfacial reaction. The Li-C/garnet/Li-C symmetric cell exhibits stable plating/striping performance with small voltage hysteresis and endures a critical current density up to 1.0 mA cm-2 . The full cell paired with LiFePO4 shows stable cycle performance, comparable to the cell with liquid electrolyte. The present work demonstrates a promising strategy to develop ceramic-compatible lithium metal-based anodes and hence low-impedance ASSBs.

Innovative Sn-gradient sulfide solid electrolytes with superior air-stability for practical all-solid-state batteries

Evaluation and optimization of Bi 1−xSr xFeO 3−δ perovskites as cathodes of solid oxide fuel cells

All-solid-state batteries (ASSBs) and solid-state electrolytes (SSE) have emerged as promising alternative energy storage devices for traditional lithium-ion batteries, drawing significant attention from researchers. Notably, SSE materials incorporating rare earth elements have demonstrated remarkable advancements in terms of ionic conductivity, electrochemical stability, and cycle-reversible performance. The unique electron layer structures of rare earth elements facilitate diverse energy level transitions. Meanwhile, their relatively large ionic radius contributes to excellent ionic conductivity, mechanical strength, and electrochemical properties in the electrolyte. This paper offers a comprehensive review of rare-earth-based oxide solid electrolytes, rare-earth-based sulfide solid electrolytes, rare-earth-based halide solid electrolytes, and composite polymer electrolytes enriched with rare earth elements. The characteristics, applications, modification methods, and underlying mechanisms of these SSE materials are investigated, offering valuable insights and inspiration for the design of future SSE materials. Additionally, this paper systematically presents solutions for improving the performance of ASSBs and explores the ion transmission in these batteries. Finally, the research direction, optimization methods, and development prospects of rare-earth-based solid electrolytes are analyzed and forecasted.