Preparation of argyrodite Li6–2xZnxPS5−xOxCl with improved electrochemical performance and air stability for all-solid-state batteries

Abstract

The argyrodite Li6PS5Cl (LPSCl) solid electrolyte applied to all-solid-state batteries is gaining increasing attention as an attractive next-generation material, but in humid conditions it causes degradation of battery performance as a result of instability and poor contact with electrodes. In this experiment, LPSCl solid electrolyte was modified by substituting Zn for Li, and O for S through dry ball milling and heat-treatment processing. As evidence of ZnO substitution, X-ray diffraction, Laser-Raman, field emission scanning electron microscopy, nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy analysis of the synthesized solid electrolyte were performed. The Li5.95Zn0.025PS4.975O0.025Cl (LPSCl-ZnO) solid electrolyte showed a high ionic conductivity at 30 °C. Moreover, it showed a higher critical current density value of 0.55 mA·cm−2 compared to the of 0.3 mA·cm−2 of LPSCl. It also exhibited high compatibility with Li metal as a cathode in cyclic voltammetry and in DC profile. In addition, the H2S gas generated after exposure to 10% humid air was a very low 0.38 cm3·g−1. Notably, an all-solid-state battery assembled with the ZnO-substituted solid electrolyte (x = 0.025) showed a specific capacity of 148.5 mAh·g−1 (0.1 C) and a high capacity retention rate of 99.7%.