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 Li₆P_1−xNb_xS_5−2.5xO_2.5xCl (x = 0, 0.025, 0.05, 0.075, and 0.1) solid electrolytes are synthesized by co-doping Nb and O in Li₆PS₅Cl electrolyte, showing simultaneously enhanced ionic conductivity, air stability, and interfacial compatibility with lithium. Benefitting from the substitution of P⁵⁺ with a larger radius Nb⁵⁺, the powder cold-pressed ionic conductivity of Li₆P_0.95Nb_0.05S_4.875O_0.125Cl electrolyte reaches up to 4.19 mS cm⁻¹ at room temperature. Moreover, the amount of H₂S released by Li₆P_0.95Nb_0.05S_4.875O_0.125Cl 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 Li₃OCl between the Li₆P_0.95Nb_0.05S_4.875O_0.125Cl 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 LiCoO₂/Li₆P_0.95Nb_0.05S_4.875O_0.125Cl/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.