A Core‐shell Structured Argyrodite‐type Electrolyte Enabling Elevated Chemical/Electrochemical Stability

Sulfide solid electrolytes hold great promise in all‐solid‐state batteries owing to high ionic conductivity and good formability. However, their poor chemical/electrochemical stability imposes limitations on further large‐scale application. In this study, a versatile solid electrolyte (SE) is finely crafted with the core of Cl‐gradient argyrodite structure and the shell of LiCl layer. Leveraging LiCl shell as a “reservoir”, this argyrodite SE preserves the structure integrity and good Li+ conduction upon air exposure, exhibiting remarkable chemical stability. Moreover, Li+ transport from argyrodite bulk and surface is synergistically enhanced through the specific surface engineering strategy, resulting in an exceptionally high ionic conductivity of 10.62 mS cm‐1. The LiCl shell, characterized by favorable electron shielding and lithiophobicity, enables the core‐shell argyrodite with impressive electrochemical stability over a wide voltage range (0~5 V vs Li/Li+) and good match for Li metal. As the electrode/electrolyte interface compatibility is optimized by engineering LiCl layer on SE, LiCoO2 cathode paired with CS‐LPSC SE retains a remarkable capacity retention of 95.6% over 500 cycles at 1 C.