Pauling's Rules Guided Design of High‐Entropy Sulfide Solid‐State Electrolyte with High Ionic Conductivity and Stability

All-solid-state lithium batteries (ASSLBs) represent a promising next-generation energy storage technology. While sulfide-based solid-state electrolytes (SSEs) offer high ionic conductivity, their practical application is hindered by inherent instability issues. To further enhance the performance, Pauling's rules are considered. Verified by theoretical calculations, sulfide SSE Li_3.45(Sn_0.2Si_0.8)_0.45P_0.55S_3.65O_0.35 (LSnSiPSO) is designed through entropy engineering. The highly disordered configuration arising from multi-ion synergy endows LSnSiPSO with an ionic conductivity of 7.14 mS cm^-1. Besides the entropy strategy, the effect of ion radius matching can stabilize the coordination environment and polyhedral connectivity and endow the material with remarkable air stability. Exposed to a simulated dry room environment (-30 °C dew point) for ≈100 h, LSnSiPSO retains 80% of its initial conductivity, significantly outperforming Li₆PS₅Cl (70% reduction) and Li₁₀GeP₂S₁₂ (40% reduction). Even after 1-h air exposure, LSnSiPSO remains an ionic conductivity of 0.15 mS cm^-1. The LSnSiPSO-based ASSLBs exhibit initial specific capacity of 143.8 mAh g^-1 with 80% capacity retention over 100 cycles. This work establishes a high-entropy strategy, guided by fundamental principles, to achieve sulfide SSEs with high ionic conductivity and stability, demonstrating the significant practical potential of LSnSiPSO for sulfide-based all-solid-state lithium batteries.