Abstract: In order to study the influence factors of floating charge performance of lithium ion battery in high-voltage system, the gas-producing composition, structure change of cathode and anode materials, metal dissolution, separator morphology and Gurley value change of floating charge failure battery were deeply analyzed. The results show that:In the process of floating charge at high temperature for a long time, the cathode material will undergo phase transformation, and the metal elements will be dissolved. Meanwhile, O₂ will be released to cause the oxidation and decomposition of the electrolyte. Under the condition of high temperature and high voltage, the SEI film on anode surface will also be destroyed, and continuous reforming and repair reactions will occur. These reaction products are deposited on the surface of anode and in the separator pores, resulting in the blockage and even penetration of separator pores near the anode electrode side. In other words, the cathode and anode micro-short circuit will be caused, and a large amount of gas will be released. By improving structure stability of cathode materials, optimizing electrolyte and increasing the puncture strength of separator, the high-temperature floating charge performance of the battery can be significantly improved.

Key words: lithium ion battery, high voltage, high temperature, float charge, swelling