Molecular Engineering of Fluorinated Nitriles as Self‐Passivating Electrolyte for High Voltage Lithium Metal Batteries

ABSTRACT Electrolyte engineering is essential for developing high‐voltage lithium metal batteries (HV‐LMBs). Nitrile‐based compounds are one of the most promising electrolyte solvents with high chemical and oxidative stability, but their low stability against lithium metal anode is a notorious problem that hinders its practical applications. Herein, through molecular engineering of modulating the fluorination degree, partially fluorinated nitrile compounds were first reported, enabling self‐passivation toward lithium metal anodes. Both theoretical calculation and experimental results revealed that the mono‐fluorinated nitrile (F1EON) based solvent not only exhibits a horizontal adsorption configuration on the lithium metal surface, resulting in the spontaneous formation of a dense LiF passivation layer, but also forms a unique tridentate solvation structure, thereby inducing a LiF‐rich cathode electrolyte interphase. Consequently, the 4.6 V high‐voltage Li||LiCoO 2 cells with this F1EON‐based electrolyte demonstrates robust cycling performance of 80.5% capacity retention after 350 cycles at 0.5 C and high‐rate performance of 90.5% after 200 cycles at 4 C. This design strategy provides a promising approach for future exploration of advanced electrolytes for HV‐LMBs.