LiPO2F2 improving the storage performance and high temperature of the battery

Lithium difluorophosphate has a molecular formula of LiPO2F2 and a molecular weight of 107.9. It is a white crystalline powder, which is easy to absorb moisture and has good stability. The main function of adding to the electrolyte of the lithium ion battery is to form a dense and thermally stable protective film on the surface of the electrode, thereby inhibiting the electrolyte from decomposing due to contact with the positive electrode active material and the negative electrode active material, thereby improving the storage performance and high temperature of the battery. Cycle performance, etc. Studies have shown that during the first charging process, lithium difluorophosphate can decompose before the carbonate solvent, and participate in the formation of a layer of SEI film with high temperature stability and favorable for Li+ insertion and deintercalation. The battery with 1% lithium difluorophosphate was stored at a high temperature of 60 ° C for 14 days, the capacity retention rate was increased by 6.05%, and the capacity recovery rate was increased by 6.1%, especially for the high-temperature gas production of the battery, and the thickness expansion ratio was reduced by 20%. 36%, improved battery high temperature storage performance. By comparing the electrochemical performance of the electrolyte with and without the addition of lithium difluorophosphate, it was found that the electrolyte resistance (Photo 2) with 0.5% lithium difluorophosphate added was much smaller than that without the addition, thereby effectively reducing the lithium battery. The heat generation during the charging and discharging process improves the safety performance of the lithium ion battery. Charging and discharging the button battery with a current of 2 A/g (Photo1) found that the discharge gram capacity of adding lithium difluorophosphate was significantly higher than that of the unfilled, and the battery cycle of adding lithium difluorophosphate was increased as the number of cycles increased. The rate is very high, and the drop without the addition of lithium difluorophosphate is relatively obvious. Therefore, lithium difluorophosphate as an electrolyte additive for lithium ion batteries can effectively reduce impedance, increase capacity, and improve cycle performance. In the practical application, the battery system after adding lithium difluorophosphate is mainly characterized by (1) an increase in energy density, an increase in cruising range of more than 10%; (2) an increase in cycle performance and an increase in service life; (3) a small internal resistance. Battery safety performance has been greatly improved.