Why does the lithium battery catch fire

The principle of a fire in a lithium battery is that the internal heat is not released according to the design intent, and the ignition point of the internal and external combustion materials is exceeded. The main causes are external short circuit, external high temperature and internal short circuit.

　　1, internal short circuit

Unreasonable use of the battery, such as overcharging and overdischarging, produces crystals that pierce the diaphragm and produce micro-short circuits. The release of electrical energy and the release of electricity leads to an increase in temperature. The increase in temperature aggravates the chemical reaction of internal materials and forms a more serious Large short-circuit currents, such mutually accumulating and mutually reinforcing destruction, lead to thermal runaway.

　　2, external short circuit

　　Take electric cars as an example. The probability of a vehicle being dangerous during 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. The weak point of the connection in the circuit will burn out in a long-term external short circuit. Only in extreme cases, the short circuit point crosses the vehicle fuse and the BMS fails, which will cause the battery to suffer thermal runaway. Now, more PACK companies have adopted the method of adding fuses in the loop, which can better avoid the hazards of external short circuits.

　　3, external high temperature

　　 Due to the structural characteristics of lithium batteries, SEI membranes, electrolytes, ECs, etc. will undergo decomposition reactions at high temperatures, and the decomposition products will also react with the positive and negative electrodes, and the battery separator will melt and decompose. Various reactions lead to a large amount of heat generation. The melting of the diaphragm causes an internal short circuit, and the release of electricity increases the heat production. The consequence of this vicious circle is that the explosion-proof membrane of the battery cell ruptures, the electrolyte is sprayed out, and combustion occurs.

　　 We know the cause of the fire of the lithium battery. The fire of the lithium battery is extremely difficult to control. Therefore, once you find signs of smoke or fire in the use of electric vehicles, you must escape as soon as possible!