Enhancing Interfacial Stability and Electrochemical Performance for High‐Temperature Operation of Ni‐Rich Layered Oxide Cathode‐Li Batteries via Tailoring Electrolyte Chemistry

Abstract Achieving both interfacial stability and enhanced electrochemical performance in Ni‐rich layered oxide cathode (NCM811)‐Li batteries remains a critical challenge, especially at elevated temperatures. Current approaches, including artificial coatings and fluorinated solvents, have improved stability but frequently fail to sustain long‐term performance due to increased interfacial resistance or degradation over extended cycling. Here, an advanced electrolyte optimization strategy through the incorporation of triethyl phosphate is proposed to simultaneously enhance the stability of the electrode‐electrolyte interface by promoting the formation of robust solid electrolyte interphase and cathode electrolyte interphase layers, thereby preventing side reactions and particle cracking. This results in significantly improved cycle life and thermal stability. The NCM811||Li cells featuring the optimized electrolyte exhibit an impressive initial capacity of 196.8 mAh g −1 and a remarkable Coulombic efficiency of 96.2%, retaining 87.3% after 250 cycles at 1 C and an operating temperature of 60 °C. Even at 10 C, it demonstrates a capacity of 138 mAh g −1 with a retention of 87.9% after 100 cycles, showcasing excellent high‐temperature performance and Coulombic efficiency. These results present a promising strategy for enhancing the durability and efficiency of NCM811‐Li batteries under demanding conditions.