Effect of Nitrile Group Functionalized Organosilicon as Electrolyte Additive on Low. temperature Performance of LiFePO4 Battery

A nitrile group functionalized organosilicon compound, 3-(diethoxy-methyl-silanyl)-propionitrile (DESCN) was synthesized and its chemical structure and electrochemical window were characterized. The effects of DESCN on the low-temperature performance of LiFePO4 cell were investigated by charge-discharge cycling test, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy(EIS) and so on. It is revealed that adding 2% DESCN could improve the low-temperature performance of LiFePO4 cell. At - 20 degrees C, the cell exhibits a high discharge capacity of 73 mA.h/g and are stable after 50 cycles. DESCN involved in the formation of stable solid electrolyte interface(SEI) film to inhibit electrolyte decomposition and decrease the battery resistance, which facilitate Li+ diffusion and electron transportation at electrode/electrolyte interface at low-temperature.