Design of Fire‐Resistant Liquid Electrolyte Formulation for Safe and Long‐Cycled Lithium‐Ion Batteries

Abstract Turning an unsafe material into a safe one without performance loss for Li‐ion battery applications provides opportunities to create a new class of materials. Herein, this strategy is utilized to design a fire‐resistant liquid electrolyte formulation consisting of propylene carbonate and 2,2,2‐trifluoroethyl group‐containing linear ester solvents paired with 1 m LiPF 6 salt and fluoroethylene carbonate additive for a Li–ion battery with improved safety and performance. Traditional carbonate‐based electrolytes offer good performance in mild operating conditions, but are however a flammable fuel causing fire and safety hazards. It is shown that the entire replacement of linear carbonate with fluorinated linear ester yields a fire‐resistant and outperforming electrolyte under the harsh condition of 4.5 V high‐voltage, 45 °C and 2C rate, enabling a higher energy, longer cycle life of 500 cycles, faster charged practical graphite‖NCM622 full‐cell than traditional electrolyte‐based cell. The strong correlation between cathode–electrolyte and anode–electrolyte interfacial stabilization and highly reversible cycling performance is clearly demonstrated. The fire‐resistant electrolyte‐incorporated industrial 730 mAh graphite‖NCM811 Li‐ion pouch battery achieves 82% retention after 400 cycles under 4.3 V charge voltage, 45 °C and 1C, and markedly improved safety on overcharge abuse tests. The design strategy for electrolyte formulation provides a promising path to safe and long‐cycled high‐energy Li‐ion batteries.