Detailed analysis of the cause of lithium-ion battery explosion

Lithium ion battery principle Lithium ion battery is mainly composed of positive electrode, negative electrode, separator and electrolyte. The positive and negative electrode layers are tightly rolled together, and the layers are separated by insulators. The positive and negative electrodes are immersed in the electrolyte.. Cylindrical batteries and prismatic batteries are taken as examples. The positive and negative electrodes of lithium-ion batteries are composed of two different lithium-ion intercalation compounds.. The positive electrode materials mainly include transition metal oxides, metal oxides, and metal sulfides.. The cathode materials commonly used in commercial lithium-ion batteries are transition metal oxides. The most widely used anode materials are inorganic non-metallic materials, metal materials, metal-non-metal composite materials, metal oxides, etc.. Lithium iron phosphate anode and cathode materials The material is coated on the conductive material to form the electrode. The electrode material determines the voltage and capacity of the battery. As an important part of the lithium ion battery, the electrolyte plays an important role in the transmission of current during the charge and discharge of the battery. In order to prevent short-circuiting of the positive and negative materials immersed in the electrolyte due to mutual contact, the positive and negative materials are separated by a polyolefin separator. The lithium secondary battery is actually a battery with a poor lithium concentration. When charging, the Li is taken out from the positive electrode and inserted into the negative electrode through the electrolyte. The negative electrode is in a lithium ion-rich state, and the positive electrode is in a lithium ion-poor state. The electronic compensation charge is supplied to the carbon negative electrode by an external circuit to ensure the balance of charge. In relation to discharge, Li is removed from the negative electrode and inserted into the cathode material through the electrolyte. Under normal charging and discharging conditions, lithium is inserted and removed between the layered carbon material and the layered structure oxide, which usually only causes the change of the material layer spacing without destroying their crystal structure. During the charging and discharging process, the chemical structure of the negative electrode material is basically unchanged. The ionic reaction equation is increasingly impossible to add safety measures inside the battery, because it is now pursuing higher capacity to improve battery life. From the commercialization of lithium-ion batteries in 1991 to the present, the power capacity of lithium-ion batteries has increased four or five times the mechanism of lithium-ion battery explosion. So we know how it works, so we can know what causes lithium-ion Batteries explode. The charging and discharging of lithium ion dendritic growth batteries are the transfer of lithium back and forth. During the charging process, lithium is reduced to metallic lithium ions embedded in the negative electrode. Generally speaking, lithium ions are embedded in the interlayer structure. However, due to the uncertainty of growth, lithium ions may grow on the surface of the electrode. The growth layer has a thorn-like structure like branches, which can damage the internal diaphragm of the battery and cause the battery Internal short circuit and battery explosion. If the battery is defective, the metal particles are connected to the positive and negative electrodes through the insulating layer of the battery, changing the direction of the current, and a large amount of heat appears, which degrades the internal materials, makes the chemical reaction out of control, releases more heat, and ignites the battery pack Charging Our current battery has a protection system that feeds back the battery voltage at any time to prevent overcharging, which may cause damage to the battery protection system or battery charger during overcharging. When overcharging occurs, the lithium left in the cathode material continues It is removed and embedded in the negative electrode material. If the maximum lithium ion embedded in the carbon negative electrode is reached, the excess lithium ion will be deposited on the negative electrode material in the form of lithium ion metal, which greatly reduces the stability performance of the battery. Even if the explosion is concerned with lithium-ion batteries, not only the battery capacity is an area to be improved, but also the safety performance cannot be ignored. Now some battery manufacturers have very high safety standards and even have to test batteries. We know that when the nail penetrates the battery, it will directly connect the positive and negative poles, which will cause an internal short circuit. Gel electrolytes and polymer electrolytes are also under further exploration, especially the development of polymer electrolytes. There is no volatilization of liquid organic electrolyte in the battery, which greatly improves the safety of the battery. 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: Which is more harmful to lithium-ion batteries and lead-acid batteries?