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.