Combined Effect of Fluoride Enables the Stable Charging–Discharging Cycle of Carbonate-Based Li-Ion Pouch Cells at −30 °C

Abstract

Carbonate-based electrolytes in Li-ion batteries are limited by low-temperature performance due to their slow ion transport kinetics and high interfacial transport energy barriers. Herein, we propose a component modulation strategy from the combined effect of fluor-solvents and fluor-additives, where the noncoordinated 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether was introduced into a 2.0 M lithium bis(trifluoromethanesulfonyl)imide, fluoroethylene carbonate, and ethyl methyl carbonate electrolyte to promote more cation–anion coordination, thus decreasing Li-ion desolvation energy. Subsequently, the additives of lithium difluoro(oxalato)borate, lithium difluorophosphate, and ethylene sulfate were adopted to construct robust interface layers with inorganic components, reducing the interface transport barrier of the Li-ion. As result, the Li||NCM811 cells achieve an average capacity of 132.2 mAh g^–1 at 0.2 C and −30 °C during the 100 charge–discharge cycles. Significantly, the graphite||NCM523 pouch cell delivers a high initial discharge capacity of 0.85 Ah at −30 °C and 88% capacity retention after 200 charge–discharge cycles.