Regulating Ion Diffusion and Stability in Amorphous Thiosilicate-Based Solid Electrolytes Through Edge-Sharing Local Structures

Amorphous solid-state electrolytes (SSEs) play a pivotal role as fundamental components within all-solid-state lithium batteries, yet their understanding lags behind that of crystalline materials. In this work, a novel amorphous SSE 5Li2S-3SiS2 (mol %) with a high ionic conductivity of 1.2 mS cm−1 is first reported. The silicon and sulfur atoms in the edge-sharing Si2S64− are less attracted to lithium compared to the SiS44− anion, which is expected to facilitate the lithium ions conduction in SSEs. More importantly, the relationship between the material properties and local structure in the amorphous thiosilicate SSEs is revealed, particularly highlighting the desirable edge-sharing local structure. The Si2S64− presents better stability with Li metal. This work offers an important guideline in the development of anion frameworks in amorphous sulfide SSEs for high-performance all-solid-state lithium metal batteries.