The composition of the electrolyte not only determines the ion conductivity of the electrolyte, but also affects the formation of the SEI membrane. The properties of SEI membranes, such as pore stability, electronic and ionic conductivity, have a significant impact on the irreversible capacity, low-temperature performance, cycling performance, and safety performance of batteries. A good SE1 film should have organic solvent insolubility, allowing for relatively free entry and exit of the electrode while solvent molecules cannot penetrate, thereby preventing the co insertion of solvent molecules from damaging the electrode and improving its cycling life. Smart et al. found through their study of the impedance of Li/graphite half cells that the SEI film resistance is much greater than the electrolyte resistance, and when the temperature is below -20 ℃, the SEI film resistance increases sharply with the decrease of temperature, corresponding to the rapid deterioration of battery performance. Wang et al. investigated the low-temperature performance of graphite electrodes in a quaternary electrolyte system of 1.0mol/LLIPF/(EC: PC: DMC: EMC) (volume ratio 4:1:3:2) 1 using constant current intermittent titration and electrochemical impedance spectroscopy. The study showed that at -30 ℃, a larger SEI film resistance led to greater battery polarization, resulting in shorter platform voltages for lithium rich phases such as Li. C, LiC, and LiC, without complete phase transitions, and only limited lithium was embedded in the graphite negative electrode, resulting in poor low-temperature performance of the graphite electrode. Therefore, adding an appropriate amount of film-forming additives to the electrolyte of lithium-ion batteries can reduce the SEI film resistance and improve the low-temperature performance of the battery.

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