Ternary doping enhances the moisture and electrochemical stability of Li5.5PS4.5Cl1.5 solid-state electrolyte

Abstract

Sulfide-based solid-state electrolytes (SSEs) have great potential for realizing high-energy all-solid-state lithium metal batteries. However, their application is seriously hindered by their moisture sensitivity and lithium incompatibility. Herein, various elements, including Si, O, and Br, were used for doping to modify the lithium argyrodite Li_5.5PS_4.5Cl_1.5 SSE. The Li_5.55Si_0.05P_0.95S_4.4Cl_0.75Br_0.75O_0.1 (LSiPSClBrO) SSE was synthesized via a mechanical milling and annealing method to improve its stability in humid air while retaining a high ionic conductivity of 7.5 mS cm⁻¹. Lithium symmetric cells with the LSiPSClBrO electrolyte exhibited stable lithium plating/stripping over 1000 h at a current density of 0.1 mA cm⁻², along with a high critical current density of 1.65 mA cm⁻². The all-solid-state Li–In/NCM811 cells assembled with the LSiPSClBrO electrolyte also demonstrated excellent cycling stability and rate performance, with a specific capacity of 123.0 mAh g⁻¹ after 70 cycles at a rate of 0.2 C and 93.1 mAh g⁻¹ after 150 cycles at a rate of 1 C. This study highlights the potential of Si, O, and Br co-doping in improving the air stability of sulfide electrolytes while maintaining high ionic conductivity, providing insights and guidance for the design and synthesis of multielement-doped materials.