锂硫银锗矿固态电解质研究进展

Recent Progress on Lithium Argyrodite Solid-State Electrolytes

全固态电池因其较高的安全性和能量密度而成为下一代电动汽车和智能电网用储能器件的重点研究方向之一。开发具有高室温锂离子电导率、化学/电化学稳定性优异、对电极材料兼容性优异等特点的固态电解质材料是推动全固态电池发展的重要研究课题之一。硫化物电解质因其相对较高的室温电导率(~10^(-3) S·cm^(-1))、较低的电解质/电极固-固界面阻抗等优点而在众多无机固体电解质材料中成为研究热点。本文基于作者多年研究成果和当前国内外发表的相关工作,从电解质的结构、离子传导、合成、综合性能改善及在全固态电池中的应用等方面系统总结了锂硫银锗矿固态电解质材料研究,并分析了该类电解质面临的问题和挑战,最后探讨了其未来可能的研究方向和发展趋势。

All-solid-state batteries have attracted significant attention as nextgeneration energy-storage devices for electric vehicles and smart grids because of their excellent safety and high energy density.Research on solid electrolytes with high ionic conductivity at room temperature,good chemical/electrochemical stability,and superior electrode compatibility is important for promoting the development of all-solid-state batteries.Sulfide electrolytes have become a hot topic among different inorganic solid electrolytes because of their relatively high Li-ion conductivity(~10-3 Sžcm-1)and low solid-solid interfacial resistance between the solid electrolytes and electrode particles.Among these sulfide electrolytes,lithium argyrodite solid electrolytes have attracted much attention owing to their high Li-ion conductivity at room temperature and relatively low cost.However,many problems still need to be solved before their practical application,such as difficulties in batch preparation,poor air stability,narrow chemical/electrochemical stability window,and poor interface stability towards high-voltage active materials.Extensive research has been conducted by many research groups to solve these problems and significant progress has been achieved.This review summarizes the current research on the structural information,ion conduction behaviors,synthesis routes,modification methods for improving the chemical/electrochemical stability properties,and applications of lithium argyrodite electrolytes combined with various cathode and anode materials in all-solid-state batteries based on our own research and published works of others.Two types of synthesis routes,the solid-state reaction route and the liquid solution route,are used to prepare lithium argyrodite electrolytes.Typically,electrolytes obtained by the former method deliver higher conductivities than those obtained by the latter.Multiple characterization methods,including alternating current(AC)impedance,molecular dynamics(MD)simulations,spin lattice relaxation in 7Li nuclear magnetic resonance(NMR),and 1D/2D Li exchange NMR,have been applied to probe Li-ion diffusion in the bulk of a signal particle across the interface section between two electrolyte particles,across the cathode,and across electrolyte particles.Increasing the number of Li vacancies via halogen substitution and element doping has been widely applied to increase the Li-ion conductivity of argyrodite electrolytes.Improvements in air stability for these argyrodite electrolytes have been achieved using element doping(such as O,Sb,and Sn)based on the hard-soft-acid-base theory and surface coating strategies.Interface contact and stability between the active materials and solid electrolytes play a key role in battery performance.Owing to the poor chemical/electrochemical stability of cathode materials,homogenous surface coatings and lithium halide electrolyte additives have been introduced into the configuration to isolate the direct contact between sulfides and active materials in the cathode mixture.Poor lithium metal compatibility inhibits the application of lithium argyrodite electrolytes in solid-state lithium metal batteries with high energy densities.Elemental doping in lithium argyrodites can form lithium alloys that impede the growth of lithium dendrites,and the surface modification of lithium metal anodes is helpful in constructing solid-state batteries with lithium metal anodes.Furthermore,research on lithium argyrodite electrolyte film preparation has also been conducted to develop a new solid-state battery construction route.In addition,the challenges and problems are analyzed,and possible research directions and development trends of lithium argyrodite solid electrolytes are proposed.