How does the lithium battery work? What are its potential safety hazards?

The working principle of lithium battery Lithium battery is a kind of secondary battery (rechargeable battery), which mainly depends on the movement of lithium ions between the positive electrode and the negative electrode to work. During charging and discharging, Li+ intercalates and deintercalates back and forth between the two electrodes: during charging, Li+ deintercalates from the positive electrode and inserts into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. Lithium batteries are discharged by chemical oxidation-reduction reactions. When discharging, that is, when we use the battery to consume power, its positive electrode will insert lithium ions, and the negative electrode will drop lithium ions. The opposite is true when charging. The gains and losses of his ions will form a certain voltage, causing the battery to appear power. The charging and discharging process of lithium batteries is the process of intercalation and deintercalation of lithium ions. In the process of intercalation and deintercalation of lithium ions, it is accompanied by the intercalation and deintercalation of electrons equivalent to lithium ions. In the process of charging and discharging, lithium ions are inserted/de-intercalated and inserted/de-intercalated back and forth between the positive and negative electrodes, which is vividly called the rocking chair battery. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon as the negative electrode has a layered structure. It has many micropores. The lithium ions reaching the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions are inserted, the higher the charging capacity. Potential safety hazards of lithium batteries 1. Potential safety hazards of positive electrode materials When lithium batteries are used improperly, the internal temperature of the battery will rise, causing the decomposition of the active material and the oxidation of the electrolyte in the positive electrode material. At the same time, these two reactions can generate a lot of heat, which causes the battery temperature to rise further. Different delithiation states have very different effects on the lattice transformation of the active material, the decomposition temperature and the thermal stability of the battery. 2. Potential safety hazards of negative electrode materials The negative electrode material used in the early days is metal lithium, and the assembled battery is prone to lithium dendrites after repeated charging and discharging, which will pierce the diaphragm, causing the battery to short-circuit, leak and even explode. Lithium intercalation compounds can effectively prevent the appearance of lithium dendrites and greatly improve the safety of lithium batteries. As the temperature increases, the carbon negative electrode in the state of lithium intercalation first reacts exothermically with the electrolyte. Under the same charging and discharging conditions, the heat release rate of the reaction between the electrolyte and the lithium-intercalated artificial graphite is much greater than that of the lithium-intercalated mesophase carbon microspheres, carbon fibers, coke, etc. 3. The safety hazards of diaphragm and electrolyte. The electrolyte of lithium battery is a mixed solution of lithium salt and organic solvent. The commercial lithium salt is lithium hexafluorophosphate. This material is prone to thermal decomposition at high temperatures, and it will be combined with trace amounts of water and organic solvents. The thermochemical reaction between them reduces the thermal stability of the electrolyte. The organic solvents of the electrolyte are carbonates. Such solvents have a low boiling point and flash point. They are easy to react with lithium salts to release PF5 at high temperatures and are easily oxidized. 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 are the common laminated batteries? What are the differences between them?