In Situ Formed Li-Ag Alloy Interface Enables Li₁₀GeP₂S₁₂-Based All-Solid-State Lithium Batteries

All-solid-state lithium-metal batteries (ASSLMBs) have received great interest due to their high potential to display both high energy density and safety performance. However, the poor compatibility at the Li/solid electrolyte (SE) interface and penetration of lithium dendrites during cycling strongly impede their successful commercialization. Herein, a thin Ag layer was introduced between Li and Li₁₀GeP₂S₁₂ for the in situ formation of a Li-Ag alloy interface, thus tuning the interfacial chemistry and lithium deposition/dissolution behavior. Superior electrochemical properties and improved interfacial stability were achieved by optimizing the Ag thicknesses. The assembled symmetric cell with Li@Ag 1 μm showed a steady voltage evolution up to 1000 h with an areal capacity of 1 mAh cm^-2. Moreover, a high reversible capacity of 106.5 mAh g^-1 was achieved in an all-solid-state cell after 100 cycles, demonstrating the validity of the Ag layer. This work highlights the importance of the Li/SE interface re-engineering and provides a new strategy for improving the cycle life of ASSLMBs.