Synergistic Additives Enabling Stable Cycling of Ether Electrolyte in 4.4 V Ni‐Rich/Li Metal Batteries

Abstract Ether‐based electrolytes have high ionic conductivity and good stability toward the lithium metal anode relative to carbonate‐based electrolytes, but they typically exhibit poor oxidation stability (<4 V vs Li+/Li). Most approaches aimed at enhancing the oxidative stability of ether‐based electrolytes, such as “salt‐in‐solvent” and “weakly solvating” strategies, often sacrifice their inherent advantage of high ionic conductivity. Herein, this article proposes a cost‐effective synergistic additive strategy by co‐adding LiNO3 and vinylene carbonate (VC) to achieve an optimized ether‐based electrolyte (OEE) that simultaneously offers high Li‐ion (Li+) conductivity (11.52 mS cm−1 at 20 °C) and high‐voltage stability (4.4 V). LiNO3 and VC can enter the inner solvation shell of the electrolyte, preferentially participating in the film‐forming progress at the electrode surface, leading to the formation of a unique organic–inorganic bilayer interfacial protective layer. This layer could effectively suppress electrolyte side reactions and enhance electrode stability. As a result, the 4.4 V Li‐LiNi0.8Mn0.1Co0.1O2 (NCM811) full cells assembled with the OEE exhibit stable cycling performance at both room temperature and low temperature. This work provides a new approach to the design of ether‐based electrolytes for high‐voltage lithium metal batteries.