A linear carboxylic, ester ethyl propionate (EP), was used as the co-solvent of carbonates, ethylene carbonate (EC), ethyl-methyl carbonate (EMC) and dimethyl carbonate (DMC), and its effect on low-temperature performance of LiFePO4-based Li-ion battery was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge test. The application of EP enhances the ionic conductivity of the electrolyte, improves the compatibility of the electrolyte with both LiFePO4 and graphite materials, and thus improves the low-temperature performance of LiFePO4-based Li-ion battery. The Li-ion battery using the optimized electrolyte of 1 mol·L-1 LiPF6/EC:EMC:DMC:EP (1:1:1:3) shows the capacity retention of 82.9%, 75.6%, 59.0%, 46.4%, and 37.6% of discharge capacity at room temperature when discharged at 10 oC (1C), -10 oC (0.2C), -20 oC (0.2C), -30 oC (0.2C), and -40 oC (0.2C), respectively.
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