Dual Protection of a Li–Ag Alloy Anode for All-Solid-State Lithium Metal Batteries with the Argyrodite Li6PS5Cl Solid Electrolyte

All-solid-state lithium metal batteries (ASSLMBs) are considered promising candidates for next-generation energy storage systems. However, the growth of Li dendrites and interface side reactions hinder the practical application of ASSLMBs. To address these issues, a preformed Li-Ag alloy anode for an ASSLMB with the Li6PS5Cl electrolyte was constructed. The preformed Li-Ag alloy anode contains two distinct alloy layers, i.e., Li3Ag and Li0.98Ag0.02, with the former as a protection layer and the latter as a Li deposition site. Besides, a beneficial stable interlayer (Ag-P-S-Cl compound) produced by the reaction between Ag and Li6PS5Cl could work as a secondary protection layer between the anode and electrolyte. The dual protection (Li3Ag and Ag-P-S-Cl compound) suppresses dendritic growth and other interfacial issues effectively and simultaneously. Consequently, a LiCoO2/Li6PS5Cl/Li-Ag all-solid-state battery exhibits a remarkable specific capacity and excellent cycle stability. The dual-protection effect from the preformed Li-Ag alloy anode and the investigation of its working mechanism may enlighten a simple strategy for promoting the development of ASSLMBs.