Enhanced Air Stability and Li Metal Compatibility of Li‐Argyrodite Electrolytes Triggered by In₂O₃ Co‐Doping for All‐Solid‐State Li Metal Batteries

Abstract Sulfide solid electrolytes (SSEs) have become an ideal candidate material for all‐solid‐state Li metal batteries (ASSLMBs) because of their high ionic conductivity. However, the vile Li incompatibility and poor air stability of SSEs barriers their commercial application. Herein, novel Li_6+2xP_1−xIn_xS_5−1.5xO_1.5xCl (0 ≤ x ≤ 0.1) SSEs are synthesized via In and O co‐doped Li₆PS₅Cl. By regulating the substitution concentration, the prepared Li_6.12P_0.92In_0.08S_4.88O_0.12Cl exhibits considerable ionic conductivity (2.67 × 10⁻³ S cm⁻¹) and enhanced air stability. Based on the first‐principles density functional theory (DFT) calculation, it is predicted that In³⁺ replaces P⁵⁺ to form InS₄⁵⁻ tetrahedron and O²⁻ replaces S²⁻ to form PS₃O⁴⁻ group. The mechanism of enhancing air stability by In, O co‐substituting Li₆PS₅Cl is clarified. More remarkably, the formation of Li‐In alloys induced by Li_6.16P_0.92In_0.08S_4.88O_0.12Cl electrolyte at the anode interface is beneficial to reducing the migration barrier of Li‐ions, promoting their remote migration, and enhancing the stability of the Li/SSEs interface. The optimized electrolyte shows superior critical current density (1.4 mA cm⁻²) and satisfactory Li dendrite inhibition (stable cycle at 0.1 mA cm⁻² over 3000 h). The ASSLMBs with Li_6.16P_0.92In_0.08S_4.88O_0.12Cl electrolyte reveal considerable cycle stability. This work emphasizes In, O co‐doping to address redox issues of sulfide electrolytes.