Analysis of thermal runaway of lithium-ion batteries

How to control the risk of thermal runaway of lithium-ion batteries is a safety design that must be considered when large-scale lithium-ion battery packs. Thermal runaway of lithium-ion batteries is very dangerous. When the chemical substances in lithium-ion batteries are heated to a certain temperature, the thermal accumulation effect will be The battery pack automatically heats up, and finally evolved into an explosion fire accident; 80% of lithium-ion battery accidents are caused by short circuits, and battery fires and explosion accidents caused by short circuits occur frequently, and lithium-ion battery safety issues have been pushed to the forefront of public opinion. More serious short-circuit consequences are related to thermal runaway. The thermal stability of battery materials has always been an important factor affecting the safety of power lithium-ion batteries. Compared with cathode materials, anode materials have lower energy density and power density. The thermal reaction with the electrolyte is also considered to be an important cause of the development of thermal runaway batteries. Therefore, looking for cathode materials with good thermal stability has become the key to the power of lithium-ion batteries. In essence, thermal runaway is a positive feedback loop of energy: an increase in temperature causes the system to heat up, which in turn causes the system to heat up. Thermal accumulation is a common phenomenon and can occur under any circumstances. The reasons for thermal runaway of lithium-ion batteries are as follows: 1. Frequent overload operation. 2. Unauthorized modification of parameters. 3. The ambient temperature exceeds 60C. 4. The tearing of the separator between the positive electrode and the negative electrode of the lithium ion battery can cause a short circuit, which can lead to thermal collapse. The thermal runaway reaction involves a chemical substance called cobalt oxide in lithium-ion batteries. When a chemical substance is heated to a certain temperature, it starts to heat up spontaneously, and then develops into fires and explosions. In some cases, organic electrolytes can release pressure and cause the battery to rupture. It may also burn if exposed to high temperatures or encounter sparks. The possibility of thermal runaway is related to the lithium-ion battery base. The production of lithium-ion batteries in my country, Japan and South Korea is increasing year by year, especially in the field of mobile phones/notebook computers, where battery accidents seem to occur more frequently. From 2006 to 2011, related incidents occurred in a number of large electronics companies. Since 2012, accidents of small electronic products have rarely occurred, but accidents of large-scale applications such as airplanes have occurred frequently. This illustrates the following phenomenon. Thermal runaway and its strength are related to the size, structure and number of lithium-ion batteries. A small lithium-ion battery pack has only a few lithium-ion batteries, so the chance of heat loss from one defective battery to another is relatively low. The 787's giant battery pack is another matter: they are housed in a sealed metal box and will not release excess heat. When one battery is hot enough to ignite the electrolyte, other batteries will quickly follow up. During the charging process of the battery, the surface deposits of metallic lithium tend to aggregate into branched lithium dendrites, which penetrate the separator and cause a direct short circuit between the positive electrode and the negative electrode. In addition, metal lithium is very active, it can directly react with the electrolyte to release heat, and its melting point is very low. Even if the lithium dendrites on the surface do not pierce the membrane, as long as the temperature is slightly higher, the metal lithium will dissolve and cause a short circuit. The higher the redox reaction temperature, the weaker the oxidation ability. The stronger the oxidation ability of the anode material, the more violent the reaction, the greater the possibility of a safety accident. Lithium-ion batteries of all sizes must be regularly maintained to extend their service life, and lithium-ion batteries are generally replaced every 36 months or so. More importantly, you should charge every time the charge drops to 20%. Excessive discharge will damage the lithium-ion battery and increase the possibility of accidents such as thermal runaway. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: What are the advantages of soft-pack lithium-ion batteries