What are the reasons for thermal runaway of lithium batteries?

Why do lithium battery safety issues occur frequently? Qiu Xinping told 'Product Safety and Recall' that this is determined by the characteristics of the lithium battery itself. Compared with batteries of other systems, such as lead-acid batteries, nickel-aluminum batteries, etc., lithium batteries have innovatively adopted some new reaction methods. The important manifestations are in the following two aspects: First, the positive and negative electrodes of lithium batteries adopt the intercalation reaction method, which is different from common chemical reactions such as the reaction of lead to lead sulfate in lead-acid batteries. The surface of the material during the intercalation reaction is also the interface. The structure is relatively stable, so the long life system of the lithium battery is guaranteed. Secondly, lithium batteries have the characteristics of high energy density. High energy density is mainly due to two aspects: one is the use of high-capacity electrode materials; the other is the use of electrolytes with a wide electrochemical window (the important thing here is the non-aqueous system electrolyte Or solid electrolyte), which greatly increases the voltage of the battery. There are two reasons for thermal runaway that the heat produced by the battery is an inevitable product in the battery working process. If the heat release of the battery, that is, the thermal diffusion rate is faster than the heat generation rate, the battery temperature will not rise and the thermal runaway temperature will not be reached. But sometimes, the heat dissipation of the battery is not very good. Qiu Xinping divided the causes of thermal runaway into two categories. The first category is the external factors of the battery. If the ambient temperature of the battery is too high, the battery heat dissipation is not good, or the internal winding is not good, resulting in poor heat dissipation of the battery. In addition, there is another situation that the company should pay special attention to, that is, the battery spine can sometimes introduce heat. The metal spine of the battery has copper and aluminum, and the thermal conductivity is relatively good. There are some components with high heat sources in the circuit. , Be sure to stay away from the battery spine to let the heat fully play. Qiu Xinping added. The second category is the internal factors of the battery. One is micro short circuit. There are two cases of micro short circuit. One is short circuit in battery technology, including burrs; the other is short circuit during use. These will cause micro short circuit and cause the local temperature of the battery to be higher than the thermal runaway temperature. As a result, thermal runaway occurs. The second is that the battery is overcharged, which will reduce the thermal runaway temperature of the material after overcharge. For example, the capacity of the battery has decayed in the middle and late stages of use. At this time, the battery itself is already in an overcharged state, and the thermal runaway temperature will naturally drop. Qiu Xinping pointed out. The third is the amount of electrolyte. If the amount is too much, the explosion will be very harmful, and the flame will spray very high and far, so the amount of electrolyte must be strictly controlled. 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 post: What are the differences between 26650 lithium battery and 18650 lithium battery?