Fluorine-Doped Antiperovskite Electrolyte for All-Solid-State Lithium-Ion Batteries

A fluorine‐doped antiperovskite Li‐ion conductor Li2(OH)X (X=Cl, Br) is shown to be a promising candidate for a solid electrolyte in an all‐solid‐state Li‐ion rechargeable battery. Substitution of F− for OH− transforms orthorhombic Li2OHCl to a room‐temperature cubic phase, which shows electrochemical stability to 9 V versus Li+/Li and two orders of magnitude higher Li‐ion conductivity than that of orthorhombic Li2OHCl. An all‐solid‐state Li/LiFePO4 with F‐doped Li2OHCl as the solid electrolyte showed good cyclability and a high coulombic efficiency over 40 charge/discharge cycles. Higher conductivity: A fluorine‐doped antiperovskite Li‐ion conductor Li2(OH)0.9F0.1Cl shows electrochemical stability up to 9 V versus Li+/Li and two orders of magnitude higher Li‐ion conductivity than that of orthorhombic Li2OHCl.