Nb, O Co‐Doped Argyrodite Electrolytes with Enhanced Moisture and Lithium Stability for All‐Solid‐State Lithium Batteries

Abstract Argyrodite electrolytes with high ionic conductivity and excellent processability have garnered significant attention in the field of all‐solid‐state lithium batteries. However, their limited air stability and poor lithium compatibility impede the practical application in all‐solid‐state lithium batteries. Herein, a series of Li ₆ P _{1− x} Nb _x S _{5−2.5 x} O _{2.5 x} Cl ( x = 0, 0.025, 0.05, 0.075, and 0.1) solid electrolytes are synthesized by co‐doping Nb and O in Li ₆ PS ₅ Cl electrolyte, showing simultaneously enhanced ionic conductivity, air stability, and interfacial compatibility with lithium. Benefitting from the substitution of P ⁵⁺ with a larger radius Nb ⁵⁺ , the powder cold‐pressed ionic conductivity of Li ₆ P _0.95 Nb _0.05 S _4.875 O _0.125 Cl electrolyte reaches up to 4.19 mS cm ⁻¹ at room temperature. Moreover, the amount of H ₂ S released by Li ₆ P _0.95 Nb _0.05 S _4.875 O _0.125 Cl electrolyte is only half of the original electrolyte under a moist atmosphere with 30% relative humidity for 30 min, demonstrating improved moisture stability. Meanwhile, due to the formation of ionic conductor Li ₃ OCl between the Li ₆ P _0.95 Nb _0.05 S _4.875 O _0.125 Cl electrolyte and lithium, a critical current density (CCD) of 1.55 mA cm ⁻² and excellent cycling stability of 3600 h at a current density of 0.2 mA cm ⁻² can be realized. The resultant LiCoO ₂ /Li ₆ P _0.95 Nb _0.05 S _4.875 O _0.125 Cl/Li batteries exhibit prominent capacity and cycling stability, with a capacity of 85.9 mAh g ⁻¹ and 83.5% capacity retention after 1000 cycles at 1C.