Analysis of the cause of fire in lithium battery

The essence of causing a fire in a lithium battery is that the heat in the battery fails to be released as designed, causing internal and external combustion materials to ignite after ignition. The cause is mainly an external short circuit, an external high temperature flexible internal short circuit. 1. The internal short circuit due to the abuse of the battery, such as the branch crystal caused by overcharge and overdischarge, the impurity dust in the battery processing, etc., will deteriorate to pierce the diaphragm, cause a micro short circuit, and the release of electric energy will cause temperature rise and temperature rise zone The chemical reaction of the incoming materials enlarges the short-circuit path and forms a larger short-circuit current. This mutually reinforcing and mutually reinforcing destruction leads to thermal runaway. 2. Take electric vehicles as an example for external short circuits. The probability of danger in actual vehicle operation is very low. One is that the vehicle system is equipped with fuses and a battery management system BMS, and the other is that the battery can withstand a short-term high current impact. In extreme cases, the short-circuit point crosses the vehicle fuse and the BMS fails. A long-term external short-circuit will generally cause the weak points in the circuit to be burned, and rarely cause thermal runaway events in the battery. At present, more PACK companies have adopted the method of adding fuses in the loop, which can more effectively guard against the hazards caused by external short circuits. 3. External high temperature Due to the structural characteristics of the lithium battery, analysis reactions will occur in the SEI film, electrolyte, EC, etc. at high temperatures. The analytes in the electrolyte will also react with the positive and negative electrodes, and the cell diaphragm will melt for analysis and various reactions. Cause a lot of heat to appear. The melting of the diaphragm causes an internal short circuit, and the release of electrical energy increases the heat processing. This cumulative and mutually reinforcing destructive use results in the breakdown of the explosion-proof membrane of the cell, the ejection of electrolyte, and the occurrence of combustion and fire. Disclaimer: Some pictures and content of articles published on this site are from the Internet, please contact to delete if there is any infringement. Previous: The working principle of lithium batteries The structure of lithium batteries