Superior Air‐Stable Li4P0.9Sb0.1S4I Solid Electrolyte for All‐Solid‐State Lithium Batteries

Abstract

Sulfide solid electrolytes have received particular attention due to their outstanding ionic conductivity and good mechanical ductility. Nevertheless, their chemical instability toward humid air is a significant challenge that impedes the commercialization of all‐solid‐state batteries. Herein, air‐stable Li4P0.9Sb0.1S4I solid electrolyte is synthesized by doping LiI and partially replacing P with Sb in Li3PS4 electrolyte. The Li4P0.9Sb0.1S4I solid electrolyte shows superior chemical stability under 30% relative humidity air, which is attributed to the generated LiI·H2O protective barrier between electrolyte and H2O molecule. In addition, benefitting from the formation of a Li4PS4I phase with Sb substitution, the Li4P0.9Sb0.1S4I electrolyte possesses high ion conductivity of 1.6 mS cm−1. Moreover, the Li/Li4P0.9Sb0.1S4I/Li battery can stably cycle for 1500 h at 0.1 mA cm−2, showing enhanced stability against lithium. As a result, the LiCoO2/Li4P0.9Sb0.1S4I/Li battery delivers an initial discharge capacity of 109.2 mAh g−1 with a capacity retention of 83.6% after 500 cycles at 1C. These results demonstrate a promising Li4P0.9Sb0.1S4I solid electrolyte with high ionic conductivity, favorable stability against moisture and lithium for all‐solid‐state lithium batteries.