Li_4.1P_0.9Sn_0.1S₄I Solid Electrolyte with Favorable Air Stability for All-Solid-State Lithium Batteries

Sulfide electrolytes are promising materials for all-solid-state lithium batteries because of their high ionic conductivity and good processability. However, the high reactivity of sulfide electrolytes with moisture leads to the structure decomposition and production of toxic H₂S gas, which hinders their practical application. Herein, based on the Li₃PS₄ solid electrolyte, the Li_4.1P_0.9Sn_0.1S₄I solid electrolyte is synthesized through LiI and Sn codoping, which merely generates 0.098 cm³ g^–1 H₂S gas after air exposure due to air-stable SnS₄^4– groups and the protection of reactant LiI·H₂O. Besides, the Li/Li_4.1P_0.9Sn_0.1S₄I/Li battery exhibits a high critical current density of up to 1.1 mA cm^–2 and an excellent cycling durability of 1500 h at a current density of 0.1 mA cm^–2, suggesting great compatibility of the Li_4.1P_0.9Sn_0.1S₄I solid electrolyte with lithium metal. The Li_4.1P_0.9Sn_0.1S₄I-based all-solid-state lithium battery delivers an initial discharge specific capacity of 104.8 mAh g^–1 and maintains a reversible capacity of 76.9 mAh g^–1 after 1200 cycles at a high current density of 1C, making the Li_4.1P_0.9Sn_0.1S₄I solid electrolyte a promising candidate for all-solid-state lithium batteries.