Minimum Ethylene Carbonate Electrolytes Enabled by Fluorinated Ether Dilution for High‐Voltage Fast‐Charging Lithium‐Ion Batteries

Fast charging at high voltages is critical for improving the energy–power performance of lithium‐ion batteries, yet it is fundamentally constrained by sluggish interfacial Li + desolvation and unstable electrode interphases. Ethylene carbonate (EC)‐rich electrolytes ensure robust interphase formation on graphite but suffer from strong Li + ‐solvent coordination, high viscosity, and poor oxidative stability on high‐voltage cathodes. Simply lowering the EC content reduces viscosity and desolvation energy yet often compromises ionic conductivity and interfacial robustness, while EC‐free formulations further degrade conductivity and interfacial stability. Here, a minimum EC electrolyte is developed that is enabled by a weakly coordinating fluorinated ether, 2‐trifluoromethyl‐3‐methoxyperfluoropentane (TMMP), which partially replaces EC within a minimum EC window while preserving its essential film‐forming role. TMMP weakens Li + –solvent interactions, promotes anion‐enriched solvation, and increases the Li + transference number, thereby enhancing effective Li + conductivity and lowering the desolvation barrier. The optimized minimum EC formulation (1E1T8D) forms ultrathin LiF‐rich interphases on graphite and NCM811, enabling NCM811||graphite cells to retain 80% capacity after 500 cycles under 4C charging and a 4.5 V cutoff.