I-Rich Thioantimonate Argyrodite Glass-Ceramic Electrolyte with High Air Stability and Compatibility with Lithium

Abstract

The argyrodite solid electrolyte has been actively studied due to its high ionic conductivity and good physical properties. However, it has various problems due to low air stability characteristics and low critical current density. In this study, the air stability and electrochemical performance of the solid electrolyte were improved by introducing a method to improve the performance of the solid electrolyte by adding excess iodine based on a thioantimonate-based argyrodite solid electrolyte with excellent air stability. I-rich glass-ceramic argyrodite Li6–xSbS5–xIx was prepared through high-energy ball milling. The structural properties were confirmed using powder X-ray diffraction (XRD). The synthesized Li5.6SbS4.6I1.4 electrolyte showed a higher ionic conductivity of 0.66 mS/cm and a lower activation energy of 0.32 eV compared to pristine Li6SbS5I (0.17 mS/cm, 0.33 eV) at 25 °C. In addition, the high lithium compatibility of the Li5.6SbS4.6I1.4 solid electrolyte was confirmed through DC cycling and cyclic voltammetry, and it showed a high ion conductivity retention rate of 61% after exposure to the atmosphere for 30 min. Finally, the optimized cell with Li6PS5Cl–Li5.6SbS4.6I1.4 solid electrolyte showed a higher initial discharge capacity of 154 mAh/g and Coulombic efficiency of 70%. In particular, it was confirmed that the performance at a high C rate was greatly improved compared to the cell made with Li6PS5Cl.