What do you know about the cause of the lithium-ion battery pack catching fire?

The essence of the ignition of a lithium-ion battery pack is that the heat in the battery fails to be released according to the design intent, causing internal and external combustion materials to ignite after ignition. The main causes are external short circuit, external high temperature and internal short circuit. 1. 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 production process, etc., it will deteriorate to pierce the diaphragm and cause a micro short circuit. The release of electric energy will cause temperature rise and temperature rise. The resulting chemical reaction of the material expands the short-circuit path and forms a larger short-circuit current. This mutually accumulating and mutually reinforcing damage leads to thermal runaway. 2. External short circuit: Take electric vehicles as an example. 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. Now, more PACK companies have adopted the method of adding fuses in the loop, which can more effectively prevent the hazards caused by external short circuits. 3. External high temperature: Due to the characteristics of the structure of lithium ion batteries, SEI membranes, electrolytes, ECs, etc. will undergo decomposition reactions at high temperatures. The decomposition products of the electrolytes will also react with the positive and negative electrodes, and the battery diaphragm will melt and decompose. This reaction causes 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 production. This cumulative and mutually reinforcing destructive use results in the explosion of the explosion-proof membrane of the battery cell, the ejection of electrolyte, and the occurrence of combustion and fire. As the energy source of pure electric vehicles, the important reason for the fire of the lithium-ion battery pack is the thermal runaway caused by the overheating of the battery. This overheating is most likely to occur during the charging and discharging of the battery. Because the lithium-ion battery has a certain internal resistance, a certain amount of heat will appear while outputting electric energy to supply power for pure electric power, making its own temperature higher. When its own temperature exceeds its normal operating temperature range, it will damage the entire battery. Longevity and safety. In pure electric vehicles, the power lithium battery system is composed of multiple power lithium battery cells. During the working process, a large amount of heat is collected in the small battery box. If the heat cannot be quickly dissipated in time, the high temperature will Affect the life of the power lithium battery and even cause thermal runaway, causing fire and explosion accidents. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: What are the important differences between lead-acid batteries and lithium-ion batteries?