Cation and Anion Doping in Sulfide Solid Electrolytes for All-Solid-State Lithium Batteries

Compared with traditional liquid lithium-ion batteries, all-solid-state lithium batteries (ASSLBs) show great application potential. They possess better safety performance, higher energy density and adaptability to a wider range of working temperatures. Among multiple types of solid electrolytes, sulfide solid electrolytes have attracted extensive research attention. Their outstanding room-temperature ionic conductivity and great compatibility with battery electrodes make them one of the most competitive candidates. However, several inherent shortcomings still limit the practical use of sulfide solid electrolytes in high-performance batteries. Unstable interfacial chemical properties, a narrow electrochemical window, and structural damage during repeated charging and discharging cycles are the main obstacles. This review mainly focuses on the latest research progress of cation and anion doping modification strategies for sulfide solid electrolytes. By collecting and analyzing recent relevant studies, this paper summarizes the working mechanisms of different cation and anion dopants. It also compares and discusses how these doping methods affect the ionic conductivity, structural stability and interfacial compatibility of sulfide electrolytes. And in summary, the results demonstrate that rational dual doping or single doping can effectively optimize crystal lattice structure, reduce grain boundary resistance, and suppress interfacial side reactions. Appropriate doping modification significantly improves the electrochemical performance and cycling durability of sulfide electrolytes.