What are the reasons for excessive self-discharge of lithium batteries

There are two reasons for the excessive self-discharge of lithium batteries: physical micro-short circuit and chemical reaction. 1. There are many physical short-circuits caused by physical short-circuits, which are divided into the following categories: a. Dust and burrs. Many manufacturers will find black spots on the diaphragm when self-discharged batteries are disassembled. The middle position is mostly dust. For breakdown, the edge position is mostly the burr, which is easier to distinguish; b. Why do the positive electrode metal impurities fall into this category? In fact, the positive electrode metal impurities will also penetrate the separator after the charging reaction. The formation of black spots on the diaphragm also causes physical micro-short circuits; for example, many positive iron-lithium materials will face the problem of excessive self-discharge, which is caused by excessive iron impurities. c. Metal impurities in the negative electrode due to the formation of the galvanic battery, the metal impurities in the negative electrode will be freed and deposited at the diaphragm to cause the diaphragm to conduct and form a physical micro short circuit. Some low-end negative electrode materials in China often encounter this situation; d. Metal impurities in auxiliary materials: such as adhesive tape 2, chemical reaction a, moisture causes electrolyte analysis, releases a large amount of electrons, and the electrons are then embedded in the positive electrode oxidation structure, which causes the positive electrode potential to drop, resulting in low pressure; in addition, moisture is in the whole There is a catalyst inside the battery, which generates a strong Lewis acid, which continuously corrodes the SEI film, consumes the lithium source and causes low battery voltage. b. Electrolyte solvents Some electrolyte solvents will cause the battery voltage to drop too fast. Possible mechanism: These solvents are not resistant to oxidation, and slow chemical reactions occur during storage, which consumes capacity and causes the voltage to drop. c. The SEI film is not formed well. During the storage process, the warehouse has a certain temperature, which causes the SEI film to fall off and re-react, causing battery flatulence and low pressure. d. Poorly packaged tab position is over-sealed, which may cause tab corrosion and consume the low voltage of the lithium source; other locations may be over-sealed, and the electrolyte may corrode the aluminum foil through the CPP layer, resulting in perforation of the aluminum-plastic film, and moisture ingress causing low-pressure flatulence. In many cases, flatulence and low pressure appear together, and this time is often more serious; the most common low pressure is caused by dust and burrs. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it. Previous: What are the negative materials for general lithium batteries?