Oxygen‐Induced Structural Disruption for Improved Li⁺ Transport and Electrochemical Stability of Li₃PS₄

Abstract The performance of all‐solid‐state batteries (ASSBs) relies on the Li⁺ transport and stability characteristics of solid electrolytes (SEs). Li₃PS₄ is notable for its stability against lithium metal, yet its ionic conductivity remains a limiting factor. This study leverages local structural disorder via O substitution to achieve an ionic conductivity of 1.38 mS cm⁻¹ with an activation energy of 0.34 eV for Li₃PS_4−xO_x (x = 0.31). Optimal O substitution transforms Li⁺ transport from 2D to 3D pathways with increased ion mobility. Li₃PS_3.69O_0.31 exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li₃PS₄. The practical implementation of Li₃PS_3.69O_0.31 in ASSBs half‐cells, particularly when coupled with TiS₂ as the cathode active material, demonstrates substantially enhanced capacity and rate performance. This work elucidates the utility of introducing local structural disorder to ameliorate SE properties and highlights the benefits of strategically combining the inherent strengths of sulfides and oxides via creating oxysulfide SEs.