Robust Li₆PS₅I Interlayer to Stabilize the Tailored Electrolyte Li_9.95SnP₂S_11.95F_0.05/Li Metal Interface

All-solid-state lithium-metal batteries (ASSLMBs) with sulfide electrolytes have attracted attention owing to their superior safety and high energy density. However, interfacial instability of sulfide electrolytes against Li metal still hinders their applications. Herein, F-doping is adopted to optimize the structure of Li10SnP2S12. It is demonstrated that the Li9.95SnP2S11.95F0.05 (LSPSF) electrolyte exhibits a high ionic conductivity of 6.4 mS cm–1 because of F-doping, which can reduce the impurity Li2SnS3 and generate Li+ vacancies. In addition, the Li6PS5I (LPSI) glass–ceramic interlayer is employed to enhance the interfacial stability between the sulfide electrolyte and Li metal by restraining the reduction of Sn4+ cations, as indicated by X-ray photoelectron spectroscopy (XPS). As a result, the assembled ASSLMBs with the LPSI interlayer deliver high initial discharge capacity and remarkable cycling stability. This work provides a new design route for manufacturing high-performance ASSLMBs.