Recent advances in sulfide electrolytes toward high specific energy solid-state lithium batteries

All-solid-state batteries (ASSBs) have gained extensive attention due to their improved safety and high specific energy density compared with conventional liquid lithium-ion batteries. As the key component of ASSBs, several kinds of solid electrolytes have been developed to meet the complicated requirements. Among such solid electrolytes, sulfide electrolytes are considered to be the most promising candidates because of their high ionic conductivity and suitable mechanical properties. However, there are still several unresolved obstacles restricting the development of sulfide-based ASSBs, such as limited ionic conductivity and intrinsic and interfacial instability. As for these issues, herein, recent research advances are reviewed from two typical approaches: element doping and interface modification. The experiment details and gained achievements are introduced. Furthermore, several modalities of sulfide electrolyte layers oriented towards commercialization of ASSBs and their merits and demerits are discussed.