A Versatile Li 6.5 In 0.25 P 0.75 S 5 I Sulfide Electrolyte Triggered by Ultimate‐Energy Mechanical Alloying for All‐Solid‐State Lithium Metal Batteries

Abstract Sulfide solid electrolytes (SSEs) have captured plentiful interest on account of their high ionic conductivity and appropriate mechanical strength. However, the poor air stability and cost‐intensive preparation process of SSEs limit their applications. Herein, a novel ultimate‐energy mechanical alloying (UEMA) approach is applied to rapidly synthesize the argyrodite‐type electrolytes in a one‐pot process. According to the hard‐soft‐acid‐base theory and the first‐principles density functional theory (DFT) calculation, In‐doping in Li 6 PS 5 I is attempted to enhance air stability and the experimental results demonstrate the success of this approach. The synthesized Li 6.5 In 0.25 P 0.75 S 5 I electrolyte has a high ionic conductivity (1.06 mS cm –1 ), and also presents excellent interfacial stability against Li metal, benefiting from the formation of a LiI‐rich interphase layer. The assembled Li–S battery with Li 6.5 In 0.25 P 0.75 S 5 I as an interlayer delivers a high discharge capacity (954 mAh g –1 ) and presents the capacity retention of 96% after 200 cycles. The In‐doped Li 6 PS 5 I is a novel promising electrolyte with high air stability and ionic conductivity for the application of all‐solid‐state lithium metal batteries.