Introduction to the thermal runaway process of lithium-ion batteries

The thermal runaway of the battery is caused by the heat generation rate of the battery is much higher than the heat dissipation rate, and the heat is accumulated in a large amount but not released in time. In essence, thermal runaway is a positive energy feedback cycle: increased temperature will cause the system to heat up, and the temperature will increase as the system heats up, which in turn will make the system hotter. Without strict division, battery thermal runaway can be divided into three stages: the research on the kinetic mechanism of thermal runaway reaction of different types of lithium-ion batteries. Phase 1: The internal thermal runaway stage of the battery is due to internal short circuit, external heating, or the battery itself is charged with high current. Self-heating during discharging causes the internal temperature of the battery to rise to about 90°C to 100°C, and the lithium salt LiPF6 begins to decompose; the chemical activity of the carbon negative electrode in the charged state is very high, close to the metal lithium, and the SEI film on the surface is decomposed and embedded at high temperature. The lithium ion of graphite reacts with the electrolyte and the binder, further pushing the battery temperature to 150°C. At this temperature, a new violent exothermic reaction occurs. For example, a large amount of electrolyte decomposes to generate PF5, which further catalyzes organic solvents. Decomposition reaction, etc. occur. The second stage: when the battery temperature reaches 200℃ or higher, the positive electrode material decomposes, releasing a lot of heat and gas, and the temperature continues to rise. The negative electrode in the lithium-intercalated state at 250-350°C begins to react with the electrolyte. The third stage: the battery is out of thermal control, and the explosion failure stage. During the reaction, the charged cathode material begins to undergo a violent decomposition reaction, and the electrolyte undergoes a violent oxidation reaction, releasing a lot of heat, high temperature and a large amount of gas, and the battery burns explosion. 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 article: What exactly limits the energy density of lithium batteries?