Focus on the safety of lithium battery packs

Concerned about the safety of lithium batteries, lithium electric heating control? At the my country Electric Vehicle Hundred People Forum (2019) Power Lithium Ion Battery Skills Summit held from January 11th to 13th, experts and scholars did not share various lithium battery foresights as they did in the past Skills, but just focus on the safety of lithium batteries. The safety of lithium battery packs is due to the fact that the battery is out of control. In addition to the normal charge and discharge reactions, lithium batteries also have potential side reactions. When the battery is overheated or the charging voltage is too high, these secondary uses will be triggered and release a lot of heat. If the heat is not discharged in time, the temperature and pressure of the battery will rise sharply, forming a vicious circle, which will eventually cause the heat to run out of control and form a safety accident. Unfortunately, from the lithium battery response mechanism, the hidden dangers of thermal runaway of single cells cannot be erased. Only through thermal control and other skills in the electrode (PTC) electrode, ceramic coating appearance, charging protection additives, voltage sensitive diaphragm and comprehensive applications Techniques such as flame-retardant electrolyte to improve the safety of single cells are unlimited, but they cannot be eliminated. Regarding the safety of lithium batteries, professor ai of Wuhan University did a very comprehensive analysis. From the process of thermal runaway, the earliest thermal runaway reaction was the emergence of -SEI differentiation, because of different negative components and additives. The degree of differentiation of SEI is about 120-140℃. The differentiation will occur in the future. The cathode in the electrolyte will be bald, and the violent recovery and differentiation will release a large amount of combustible gas and heat, which will further increase the battery temperature until the anode. The beginning of the process. When the positive electrode differentiates, the temperature is around 180-200°C, and the side reactions of the cells are difficult to control. Because the positive electrode is differentiated, not only a large amount of heat is released, but also highly reactive oxygen atoms are generated, leading to direct oxidation and differentiation of the electrolyte, which will form a large amount of heat to accumulate in the battery in a short period of time. It is worth mentioning that the relationship between temperature and side-use is positively correlated, that is, the higher the temperature, the stronger the side-use; the more violent the side-reaction, the higher the temperature. This vicious circle eventually causes the battery to enter an uncontrollable self-heating state, the so-called thermal runaway. The lithium iron phosphate industry often says that safety is good, because it can be used as an anode at 200-400 ℃ without major differentiation, but the replacement of the positive electrode heat is part of the side reaction, and the oxidation and differentiation of the negative electrode and the electrolyte still exist, so phosphoric acid The safety of ferrous lithium is slightly safer than ternad. With the different components, the differential temperature is also different. The higher the nickel content, the lower the thermal differentiation temperature. For example, when the nickel content reaches 0.8, the thermal differentiation starts at about 120 degrees, even earlier than the negative SEI film, which poses a great challenge to the temperature control of the battery. The battery heats out of control, causing an internal short circuit or overcharge. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.