Experimental and Theoretical Insights Into Synergistic Sn‐N Co‐Doping Enhancing Air Stability and Interfacial Compatibility of Li_5.5PS_4.5Cl_1.5 Electrolytes for All‐Solid‐State Lithium Metal Batteries

Abstract Chlorine‐rich argyrodite sulfide solid‐state electrolytes (SSEs) have risen as prime candidates for all‐solid‐state lithium batteries (ASSLBs) owing to their superior ionic conductivity and exceptional ductility. Nevertheless, the vile Li incompatibility and moisture sensitivity restrict their commercial applications. Herein, a novel Li_5.6PSn_0.05S_4.3N_0.2Cl_1.5 electrolyte is synthesized via a hetero‐pretreated Sn/ N co‐doping strategy. The impact of these two elements on the air stability and electrochemical performance is rigorously validated in combination with the first‐principles density functional theory (DFT) calculation and the ab initio molecular dynamics (AIMD) simulations. With optimal elemental substitutions, Li_5.65P_0.95Sn_0.05S_4.5Cl_1.5 achieves a high ionic conductivity of 9.54 mS cm⁻¹ along with remarkable anti‐hydrolysis properties. The generation of a Li–Sn alloy at the Li/SSEs interface significantly reduces the Li⁺ migration barrier and promotes uniform lithium deposition. Moreover, the in situ formation of Li₃N within Li_5.7PS_4.3N_0.2Cl_1.5 effectively facilitates Li⁺ migration. Under the synergistic effect of Sn/N, Li_5.6PSn_0.05S_4.3N_0.2Cl_1.5 endows an admirable critical current density of 1.53 mA cm⁻² and splendid cycling performance (900 h at 0.1 mA cm⁻²) in lithium symmetric cells. Additionally, ASSLBs fabricated with Li_5.6PSn_0.05S_4.3N_0.2Cl_1.5 reveal satisfactory cycling stability both at room temperature and elevated temperature (50 °C). This study paves the way for advancing the development of Li‐compatibility and moisture‐resistant SSEs.