High Air Stability and Excellent Li Metal Compatibility of Argyrodite‐Based Electrolyte Enabling Superior All‐Solid‐State Li Metal Batteries

Abstract Sulfide solid electrolytes (SSEs) for all‐solid‐state Li metal batteries (ASSLMBs) are attracting increasing attention due to their ultrahigh ionic conductivity and good machinability. However, current SSEs generally suffer from inferior Li metal compatibility and poor air‐stability, which severely impede their practical applications for ASSLMBs. Herein, novel argyrodite‐based SSEs of Li 6+2 x P 1− x Bi x S 5−1.5 x O 1.5 x Cl are synthesized via the Bi, O co‐doping the Li 6 PS 5 Cl for the first time. By adjusting the concentrations of dopant, the optimized Li 6.04 P 0.98 Bi 0.02 S 4.97 O 0.03 Cl presents an ultrahigh ionic conductivity (3.4 × 10 −3 S cm −1 ). Moreover, such electrolyte displays splendid structural stability after exposure to humid air and chlorobenzene, demonstrating admirable air‐stability and solvent‐stability. The mechanism of the enhanced air‐stability of oxide‐doped SSEs is profoundly understood by conducting first‐principles density functional theory calculations. In addition, the Li 6.04 P 0.98 Bi 0.02 S 4.97 O 0.03 Cl electrolyte triggers the generation of LiBi alloy at the anode interface, which plays a crucial role in reducing Li + diffusion energy barriers and improving interfacial compatibility, leading to an ultrahigh critical current density of 1.1 mA cm −2 and splendid cyclic stability in Li symmetric cell. As a result, ASSLMBs equipped with either pristine or air‐exposed Li 6.04 P 0.98 Bi 0.02 S 4.97 O 0.03 Cl can deliver satisfying discharge specific capacity at room temperature.