Prevention of lithium battery safety issues

_{Prevention of lithium battery safety issues
Thermal runaway of batteries is caused by the fact that the rate of heat generation is much higher than the rate of heat dissipation, and a large amount of heat accumulates without being dissipated in a timely manner. Essentially, ‘thermal runaway’ is an energy positive feedback loop process: an increased temperature causes the system to heat up, and as the system heats up, the temperature rises, which in turn makes the system even hotter. Without strict classification, battery thermal runaway can be divided into three stages:
Study on the kinetic mechanism of thermal runaway reaction in different types of lithium batteries
Phase 1: Internal thermal runaway stage of the battery. Due to internal short circuits, external heating, or the battery itself generating heat during high current charging and discharging, the internal temperature of the battery rises to around 90 ℃~100 ℃, and lithium salt LiPF6 begins to decompose; For carbon negative electrodes in a charged state, the chemical activity is very high, close to metallic lithium. At high temperatures, the SEI film on the surface decomposes, and the lithium ions embedded in graphite react with the electrolyte and binder, further pushing the battery temperature to 150 ℃. At this temperature, new intense exothermic reactions occur, such as a large amount of electrolyte decomposition, generating PF5, which further catalyzes the decomposition reaction of organic solvents.
Stage 2: Battery Bulging Stage
When the battery temperature reaches above 200 ℃, the positive electrode material decomposes, releasing a large amount of heat and gas, and continues to heat up. At 250-350 ℃, the lithium embedded negative electrode begins to react with the electrolyte.
Stage 3: Battery thermal runaway, explosion failure stage
During the reaction process, the charged positive electrode material begins to undergo a violent decomposition reaction, and the electrolyte undergoes a violent oxidation reaction, releasing a large amount of heat and producing high temperatures and a large amount of gas, causing the battery to burn and explode.}