Why self-discharge is important

At present, lithium batteries are more and more widely used in various digital devices such as notebooks, digital cameras, and digital video cameras. In addition, they also have broad prospects in automobiles, mobile base stations, and energy storage power stations. In this case, the use of batteries no longer appears alone as in mobile phones, but more in the form of series or parallel battery packs. The capacity and life of a battery pack are not only related to every single battery but also related to the consistency between each battery. Poor consistency will greatly affect the performance of the battery pack. The consistency of self-discharge is an important part of the influencing factors. A battery with inconsistent self-discharge will have a large difference in SOC after a period of storage, which will greatly affect its capacity and safety. Research on it will help improve the overall level of our battery packs, obtain a higher lifespan, and reduce the defective rate of products. Self-discharge mechanism The reaction of lithium cobalt graphite battery electrode is as follows: When the battery is open, the above reaction will not occur, but the power will still decrease, which is mainly caused by the self-discharge of the battery. The main reasons for self-discharge are: a. Internal electron leakage caused by local electronic conduction of electrolyte or other internal short circuits. b. External electron leakage caused by poor insulation of battery sealing ring or gasket or insufficient resistance between external lead shells (external conductor, humidity). c. Electrode/electrolyte reaction, such as corrosion of anode or reduction of cathode due to electrolyte and impurities. d. The electrode active material decomposes locally. e. The electrode is passivated due to decomposition products (insoluble matter and adsorbed gas). f. The electrode is mechanically worn or the resistance between the electrode and the current collector becomes larger. Influence of self-discharge 1. Self-discharge causes a decrease in capacity during storage Several typical problems caused by excessive self-discharge: 1. The car cannot be started after parking for too long; 2. Before the battery is put into storage, everything is normal, and low voltage or zero voltage is found when it is shipped; 3. In the summer, when I put the GPS on the vehicle, I feel that the battery is insufficient or the time is obviously insufficient after a period of use, and even the battery bulges. 2. The self-discharge of metal impurities causes the diaphragm aperture to be blocked, and even pierces the diaphragm to cause a local short circuit, endangering the safety of the battery