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

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 LiPF₆ 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.