A Core‐Shell Structured Argyrodite‐Type Electrolyte Enabling Elevated Chemical/Electrochemical Stability

Abstract 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 grain boundary 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 versus Li/Li + ) and good match for Li metal. As the electrode/electrolyte interface compatibility is optimized by engineering LiCl layer on SE, LiCoO 2 cathode paired with the modified SE retains a remarkable capacity retention of 95.6% over 500 cycles at 1 C.