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 Li_9.95SnP₂S_11.95F_0.05 (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.