Strategies Toward Stable Anode Interface for Sulfide-Based All-Solid-State Lithium Metal Batteries.

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.

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

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

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.

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

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.

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.

Sulfide solid electrolytes are promising materials for next-generation all-solid-state lithium batteries due to their high ionic conductivity, mechanical properties, and compatibility with advanced electrodes like lithium metal. Recent advancements have focused on optimizing synthesis techniques, including both solid-phase and liquid-phase methods, alongside strategic doping modifications that enhance ionic conductivity and improve chemical stability. Despite these improvements, challenges remain, particularly in stabilizing interfaces between sulfide solid electrolytes and electrodes, as chemical reactivity leads to resistive layers and reduced battery performance. Efforts to address these challenges involve protective coatings, surface engineering, and advanced structural modifications. Additionally, sulfide solid electrolytes face environmental sensitivity, with exposure to air and moisture leading to degradation. To counter this, strategies such as hybrid electrolyte systems and surface treatments are being investigated to ensure long-term stability under various conditions. This review summarizes recent developments in sulfide solid electrolytes synthesis, doping modification, and interface engineering, while outlining future directions needed for the successful commercialization of all-solid-state lithium batteries, positioning sulfide-based electrolytes as key components for advancing battery safety, efficiency, and energy density.

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.

Owing to the expanding function of Li-ion transmission channels, it is important to explore the doping effects of different compounds into sulfide solid electrolytes to improve their electrochemical performances. However, it is hard to characterize the doping behaviors within sulfide solid electrolytes with low crystallinity and poor stability just by conventional crystallography analytical methods. In this work, the dielectric spectrum testing combined with other analytical methods, such as 7Li solid-state nuclear magnetic resonance, X-ray photoelectron spectroscopy, and the electrochemical method, havebeen applied to investigate the dual-doping behaviors of WS2 and LiBr within Li7P3S11 glass-ceramic electrolytes. This research method can not only evaluate the internal acting effect between the skeleton of sulfide solid electrolytes and the migrating kinetics of Li ions but also explore the capacitance at the interfaces of LiCoO2/sulfide solid electrolytes. The experimental results show that the number of Li ions with fast transport velocity within Li2S-P2S5-based solid electrolytes has been increased. Meanwhile, the interfacial capacitances between Li2S-P2S5-based solid electrolytes and the LiCoO2 cathode have decreased after dual-doping of WS2 and LiBr, indicating a synergetic effect for the doped Li7P3S11 glass-ceramic electrolytes in terms of the ionic conductivities and interfacial compatibilities. This work may provide a novel analytical approach to explore both the diffusion kinetics and interfacial behaviors for the solid electrolytes of lithium batteries.

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

Enhancing the ionic conductivity of sulfide solid electrolytes (SEs) through dual‐doping is a well‐established approach, yet the atomic‐level mechanisms driving these improvements remain elusive. By dual‐doping Ge and Cl into the Li10GeP2S12 (LGPS) framework, we synthesized Ge/Cl‐doped LGPS (Li10+xGe1+2xP2−2xS12−xClx, x = 0.3) with an ionic conductivity of 12.4 mS/cm at 25°C, a value that stands among the highest for LGPS‐type SEs. This achievement emphasizes the pivotal role of dopant selection in modulating Li‐ion transport mechanisms, thereby enhancing SE performance. Our research elucidates the intricate atomic mechanisms responsible for this enhanced ionic conductivity, with a particular focus on the synergistic effects of Ge and Cl dual‐doping. Integrating advanced multianalytical techniques, including experiments and atomistic modeling (machine‐learning‐assisted molecular dynamics simulations and density functional theory calculations), we provide comprehensive insights into the structure–property relationship in Ge/Cl‐doped LGPS SEs. Our findings reveal that Cl doping significantly enhances the paddle‐wheel dynamics, while Ge doping promotes cooperative Li diffusion through the formation of Li interstitials. This dual‐doping approach not only elucidates the structural and functional dynamics of SEs but also paves the way for designing dopants to enhance ionic conductivity. The insights gained from this study offer a strategic direction for developing higher‐performance SEs, highlighting the importance of tailored dopant selection in advancing energy storage technologies.

Lithium (Li) metal is an ideal anode material for rechargeable batteries due to its extremely high theoretical specific capacity (3860 mAh/g), low density (0.59 g/cm3) and the lowest negative electrochemical potential (-3.04 V vs. the standard hydrogen electrode, SHE). Li battery based on Li metal anode is expected to have an order of magnitude higher energy density than today's Li-ion battery. This will enhance energy and power capability of battery devices used in portable electronics, hybrid electric cars, aerospace, telecommunication, military, etc.). The Li metal battery will fulfill the high energy demand that cannot be met through the current Li-ion batteries (e.g. all electric transportation or many other applications which require light weight, high energy density, high power density batteries with small battery footprint and safest). But, to date, uncontrolled dendritic Li growth and limited Coulombic efficiency (CE) during Li deposition/stripping of a bulk Li anode, are the main reason behind low cycle life, which has limited their practical applications. Furthermore, the rate of dendrite growth gets amplified when the cell is cycled at high charge-discharge current density, high charge voltage, and high areal discharge. Increasing anode surface area would reduce the effective charge/discharge current. Additionally, thin films and high surface area Li anodes exhibit high ionic and electronic conductivity contributing to the high efficiency of the current collection required for high capacity battery. Although low CE can be partially compensated by an excess amount of Li (at the expense of lower useable Li energy), fire and other hazards associated with the dendrite growth have limited the development of rechargeable Li metal batteries. Most approaches to dendrite prevention focus on improving the stability and uniformity of the solid-electrolyte interface (SEI) on the bulk Li surface by adjusting electrolyte components and optimizing SEI formation additives. It is very difficult to achieve sufficient passivation on Li electrode due to the thermodynamic instability of Li with electrolytes [1,2]. As an alternative, various mechanical barriers have been proposed to block dendrite penetration [3]. These approaches rely on a strong mechanical barrier provided by an SEI film or a separator to suppress Li dendrite penetration but do not change the fundamental, self-amplifying behavior of the dendrite growth. Also, it is hard to find a mechanical barrier material with required shear modulus (required > 109 Pa) with desired conductivity. In other words, these methods did not prevent Li dendrites from growing during long-term cycling at high charge-discharge current density, high charge voltage, and high areal discharge, or hardly improved the CE and safety in Li deposition/stripping which is not suitable for practical rechargeable Li batteries [1]. We have developed a novel ionic-electronic-mechanical membrane (an artificial SEI), which allows long-term Li cycleability and improved safety by reducing dendrite formation. The new artificial SEI is comprised of three different materials to fulfill the desired SEI criteria such as: (a) facilitate uniform Li ion dispersion and deposition on entire Li surface, (b) desired SEI conductivity (c) mechanical separation of Li and electrolyte and flexibility to contain anode volume change during Li stripping and deposition. The combined effect of the invented SEI result into more than 300% increase in number of cycles and 3-4 times increase in usable Li energy density (i.e. high Coulombic efficiency (CE)) of a wet battery composed of protected Li metal anode, liquid electrolyte (e.g. lithium hexafluoro arsenate, LiAsF6) and Li-ion cathode (e.g. lithium cobalt oxide, LCO) for the advancement of a battery beyond the state-of-the-art Li-ion battery. The added advantage of the invented SEI is improved safety due to suppression of dendrite growth by mechanically strong/flexible SEI and controlled, uniform deposition/stripping of Li from Li anode surface. The protected Li anode may be incorporated into wet cell batteries or solid state batteries having transition metal oxide cathodes (more specifically the state-of-the-art Li-ion cathodes) or Sulfur cathode (Li-S battery) or Oxygen cathode (Li-O2 battery). Moreover, similar methodologies can be applied to other rechargeable metal anodes (Na, Al, Mg, etc.) used in batteries.

High dielectric single-ion conducting interphase enables fast-charging lithium metal batteries

In situ synthesis of gel polymer electrolyte for lithium-metal anodes with a sulfide-enhanced interface via thiol–ene click chemistry