Enhancement of Low-Temperature Cycling Performance of Lithium-Ion Batteries by use of Dual Cosolvent

Abstract Lithium-ion batteries (LIBs) based on conventional electrolyte suffer from poor cycling performance at low temperatures due to the reduced ionic conductivity of electrolytes, sluggish charge transfer reaction, and Li plating during the charging process. Herein, we propose a dual cosolvent composed of methyl acetate (MA) and ethyl fluoroacetate (EFA). MA effectively reduced the viscosity of the electrolyte, improving the ionic conductivity at low temperatures. EFA facilitated the de-solvation of Li+ ions and formed an anion-derived solvation structure, enabling the formation of an inorganic-rich solid electrolyte interphase on the graphite anode. Due to the synergistic effect of MA and EFA, the graphite/LiFePO4 cell employing a dual cosolvent exhibited good cycling performance at low temperatures, delivering a discharge capacity of 68.7 mAh g-1 at -20 °C and 0.2 C and showing a capacity retention of 99.7% after 100 cycles at -20 °C and 0.33 C. Additionally, the cell exhibited an initial discharge capacity of 131.2 mAh g-1 at 25 °C and 1.0 C, with a capacity retention of 99.4% after 300 cycles. Our results demonstrate that liquid electrolytes containing dual cosolvent with various beneficial roles can be a promising solution for improving the low-temperature cycling performance of LIBs.