Super-complete summary of knowledge points about self-discharge of lithium-ion battery!

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. A battery with a certain amount of power will lose part of its capacity after being stored for a period of time at a certain temperature, which is self-discharge. Simply understand, self-discharge is the capacity loss of the battery when it is not in use. For example, the power of the negative electrode returns to the positive electrode by itself or the power of the battery is reacted by a side reaction. Importance of self-discharge Currently, lithium batteries are used more and more widely 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 the battery pack are not only related to each individual 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 Li-ion cobalt-graphite battery electrode reactions are as follows: when the battery is open, the above reactions 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 the electrolyte or other internal short circuits. b. External electron leakage caused by poor insulation of battery sealing rings or gaskets or insufficient resistance between external lead shells (external conductors, humidity). c. Electrode/electrolyte reaction, such as corrosion of the anode or reduction of the cathode due to electrolyte and impurities. d. The electrode active material is partially decomposed. 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. The influence of self-discharge 1. Self-discharge causes the capacity to drop during storage. Several typical problems caused by excessive self-discharge: 1. The car has been parked for too long and cannot be started; 2. Before the battery is put into storage, everything is normal, waiting to be shipped Sometimes I find low voltage or even zero voltage; 3. In summer, when I put the car GPS on the car, I feel that the battery is not enough or the use time is obviously insufficient after a period of time, and even the battery swells. 2. The self-discharge of metal impurities causes the diaphragm pore size to be blocked, and even pierces the diaphragm to cause a partial short circuit, which endangers the safety of the battery. 3. The self-discharge causes the SOC difference between the batteries to increase, and the battery pack capacity decreases. After the battery is stored, there is a difference in SOC, and the performance of the battery decreases. Customers can often find performance degradation problems after getting battery packs that have been stored for a period of time. When the SOC difference reaches about 20%, the combined battery capacity is only 60% to 70% remaining. 4. Large differences in SOC can easily lead to overcharge and overdischarge of batteries. 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 principles and precautions of lithium-ion battery formation?