Bulletproof‐Type Cathode Electrolyte Interphase Enabled by Additive‐Guided Solvent Coordination for High‐Voltage Sodium Metal Batteries

ABSTRACT Layered oxide cathodes receive extensive attention due to their high energy density, long cycle life, and high safety. However, issues such as irreversible phase transitions, transition metal dissolution, and interfacial instability prevent its application in high‐voltage sodium metal batteries. Herein, a bulletproof‐type cathode electrolyte interphase is constructed by an additive‐guided solvent coordination strategy to enhance the interfacial stability between the layered oxide cathode and electrolyte. The addition of 4‐(trifluoromethyl)phenylacetonitrile effectively promotes the entry of more methyl 2,2,2‐trifluoroethyl carbonate into the solvation structure of Na + and reduces the proportion of PF 6 − anions in the solvation structure. The robust cathode electrolyte interphase derived from such solvation structure shows high strength on the outer layer and flexibility on the inner layer. Therefore, the layered oxide cathode exhibits enhanced cycling stability and rate performance at a cut‐off voltage of 4.2 V and high temperature of 60°C. This work provides new insights into the design of robust cathode electrolyte interphases on the layered oxide cathodes.