Space Charge Layer Effect in Sulfide Solid Electrolytes in All-Solid-State Batteries: In-situ Characterization and Resolution

All-solid-state lithium batteries (ASSLBs) have advantages of safety and high energy density, and they are expected to become the next generation of energy storage devices. Sulfide-based solid-state electrolytes (SSEs) with high ionic conductivity and low grain boundary resistance exhibit remarkable practical application. However, the space charge layer (SCL) effect and high interfacial resistance caused by a mismatch with the current commercial oxide cathodes restrict the development of sulfide SSEs and ASSLBs. This review summarizes the research progress on the SCL effect of sulfide SSEs and oxide cathodes, including the mechanism and direct evidence from high performance in-situ characterizations, as well as recent progress on the interfacial modification strategies to alleviate the SCL effect. This study provides future direction to stabilize the high performance sulfide-based solid electrolyte/oxide cathode interface for state-of-the-art ASSLBs and future all-SSE storage devices.