Nonflammable Electrolyte Interfacial and Solvation Chemistry for High-Voltage Sodium Metal Batteries

High-voltage sodium metal batteries exhibit excellent advantages in low cost and high energy density. However, the poor compatibility of the traditional electrolyte with sodium (Na) anode and high-voltage cathode leads to interfacial instability and potential flammable risks. In this work, a nonflammable electrolyte is developed to address the cycling stability of 4.7 V sodium metal battery by constructing electrode-electrolyte interphases with sodium perchlorate (NaClO4) additive. The NaClO4 additive not only enables efficient Na plating/stripping with an average Coulombic efficiency of 97.1% in Na||Cu cells, but also enhances the high-voltage stability of Na||Na3V2(PO4)(2)O2F batteries with capacity retention of 97.9% after 200 cycles. The superior performance is attributed to the high ion-conductivity solid/cathode electrolyte interphases, which are tuned by the solvation shell with NaClO4.