Shandong Zhongdao Fire Protection specializes in designing and producing special fire extinguishing devices, with a wide sales area and a large service area. This article introduces the characteristics of lithium battery fires:

Lithium battery fire extinguishing is mainly caused by thermal runaway. If you need to extinguish a fire, you must first understand the real cause of thermal runaway.

The factors that cause thermal runaway of lithium batteries are mainly external short circuit, external high temperature and internal short circuit.

◎Internal short circuit: Due to battery abuse, such as branched crystals caused by overcharge and overdischarge, magazines and dust in the battery production process, etc., it will deteriorate and pierce the diaphragm, resulting in micro short circuits. The release of electrical energy leads to temperature rise, and the chemical reaction of the material brought about by the temperature rise expands the short circuit path, forming a larger short circuit current. This mutually accumulated and mutually enhanced destruction leads to thermal runaway. The following takes lithium cobalt oxide batteries as an example to briefly describe a typical thermal runaway process.

A: In the preparation stage, the battery is fully charged;

B: When an internal short circuit occurs, a large current passes through the short circuit point to generate heat, which is then diffused through LiC6 to reach the decomposition temperature of the SEI film. The SEI film begins to decompose, releasing a small amount of CO2 and C2H4, and the shell swells slightly. As the short circuit position continues to discharge, the battery temperature continues to rise, the chain solvent in the electrolyte begins to disperse, and LiC6 and the electrolyte also begin to react and release heat, accompanied by the generation of C2H5FC3H6C3H8, but the reaction is slow and the heat release is small;

C: As the discharge progresses, the temperature of the short circuit position continues to rise, the diaphragm partially shrinks and melts, the short circuit position expands, and the temperature rises further. When the internal temperature When the decomposition temperature of Li0.5Co02 is reached, the positive electrode decomposes instantly and releases O2, which reacts instantly with the electrolyte to release a large amount of heat and CO2 gas, causing the internal pressure of the battery to increase. If the pressure is large enough, it will break through the battery shell and cause the battery to explode;

D: If the shell explodes and the pole pieces scatter, the temperature will not continue to rise and the reaction will terminate; but if the shell only cracks and the pole pieces do not scatter, LiC6 will continue to react with the electrolyte, and the temperature will continue to rise, but the heating rate will decrease. Since the reaction rate is slow, it can be maintained for a long time;

E: When the heat generation rate of the internal reaction of the battery is less than the heat dissipation rate, the battery begins to cool down until the internal reaction is completed;