Air Stability of Sulfide Solid Electrolytes: From Theoretical Insights to Practical Solutions

Sulfide solid electrolytes are pivotal for enabling high‐performance all‐solid‐state batteries due to their high ionic conductivity and good processability. However, their poor air stability remains a key bottleneck hindering large‐scale commercialization. This review provides a comprehensive overview of this pressing challenge. First, a brief overview of the development history and major breakthroughs in the field is presented, followed by an in‐depth description of the various theories currently used to explain the poor air stability of sulfide solid electrolytes, including the soft and hard acid–base theories, the irregular network theory, the theory of grain boundary and defect modulation, the thermodynamic analysis, and the kinetics of interfacial reactions. In addition, the mechanisms of action and practical applications of effective strategies to improve the air stability of various sulfide solid electrolytes are summarized in focus, including doping modification, surface engineering, H 2 S absorbers, and synergistic modification design. Finally, we conduct an in‐depth discussion on the core challenges associated with achieving air‐stable sulfide solid electrolytes in practical scenarios and further envision future research directions in this field.