1. The main reason for the bulge of lithium ion battery is that there is gas in the lithium ion battery cell. When almost all lithium ion battery cells are damaged, the first performance is that there is gas in the battery cell; As for the polymer electric core of vacuum flexible packaging, the performance is the electric core bulge, so the electric core bulge is also an early warning of the electric core damage or possible safety problems.

2. The electric core is affected by high temperature. Most of the time, the electric core is stored at a high temperature for a long time, and the temperature will accelerate some chemical reactions inside the electric core to form gas. Especially when the electric core is fully charged or slightly overcharged, the effect of high temperature storage is more obvious. Therefore, the electric core should be prevented from being stored at a high temperature for a long time.

3. Overcharging will cause all the lithium atoms in the positive material to run into the negative material, leading to the deformation and collapse of the original full grid of the positive material, which is also an important reason for the decline of lithium ion battery power. In this process, more and more lithium ions in the negative electrode are accumulated, and excessive accumulation makes lithium atoms grow into stump crystals, which makes the battery bulge.

4. The SEI film can protect the negative electrode material, so that the material structure is not easy to collapse, and the cycle life of the electrode material can be increased. SEI membrane is not unchangeable, and there will be a little change in the charge discharge process. It is important that some organic substances will change reversibly. After excessive discharge of the battery, the SEI film will be reversible broken, and the SEI of the protective negative electrode material will collapse after it is broken, thus forming a bulge phenomenon.

The chemical and electrochemical reactions of lithium-ion batteries at high temperatures are very complex. It is crucial to study the reaction mechanism between the internal components of the battery, inhibit the occurrence of various exothermic reactions, and improve the safety performance under battery abuse conditions. Lithium ion battery is greatly affected by temperature. In the application field of power lithium battery and the application environment with large temperature impact, thermal management of battery is required to improve the service efficiency of battery and prolong the service life of battery system.