A Perovskite Electrolyte That Is Stable in Moist Air for Lithium-Ion Batteries.

Solid-oxide Li electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H exchanges for the mobile Li of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid-electrolyte separator. We report a new perovskite Li solid electrolyte, Li Sr Ta Hf O F , with a lithium-ion conductivity of σ =4.8×10  S cm at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li -conducting polymer on its surface to prevent reduction of Ta is wet by metallic lithium and provides low-impedance dendrite-free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all-solid-state Li/LiFePO cell, a Li-S cell with a polymer-gel cathode, and a supercapacitor.