1. The battery is seriously overcharged. The chemical system of the lithium ion cell determines that when the cell is overcharged, the LiCoO2 inside the cell becomes Co3O4. Co3O4 is a strong oxidant and can react with the electrolyte to produce gas (O2) . Oxygen continues to react with the electrolyte to form water (H2O), which can continue to react with Li and electrolyte. . . , So there will be heat and a lot of gas inside the cell, this reaction will increase with the continuous increase of the voltage, generally speaking, when the cell voltage exceeds 4.2V, that kind of reaction occurs, and the cell voltage reaches When it is close to 5V, as the internal temperature of the cell rises and the gas pressure is used, most of the cells will burn (polymer cells) or explode (liquid hard packaging) due to internal short circuits.
2. The cell is heated by high temperature. When the cell is heated by high temperature, the electrolyte will vaporize and decompose at the same time. The internal pressure of the cell will increase. The isolation film inside the cell may melt and cause the internal short circuit of the cell to cause combustion. When the material is fully charged, at a certain temperature, it will undergo an autocatalytic reaction and burn. The higher the cell voltage, the shorter the resistance to high temperature time. The figure below shows the Joule heating characteristic curve of different materials:
3. The battery core is short-circuited, and the battery core is suddenly short-circuited when it is fully charged. This is very likely to cause a safety accident in the battery core. There are two short-circuit situations:
1) The external short circuit of the battery cell. Regarding the liquid hard package battery cell, due to the increase in the temperature of the battery cell, the internal electrolyte will decompose and vaporize, which may cause the internal pressure of the battery cell to be too high and explode. At the same time, some batteries may explode due to various other reasons. The internal pressure is already very high, and the battery cell may explode under the use of short circuit and high temperature. Regarding the battery core of the flexible package, under the use of external short circuit, it will swell or crack. Generally, there is no burning phenomenon.
2) The internal short circuit of the battery core. When the battery is fully charged, due to various reasons, when the cathode and anode inside the battery are short-circuited, the temperature rises sharply, causing a violent reaction inside the battery. At this time, if it is packaged in a hard shell The battery cell will explode, and the polymer soft package battery will burn.
