Detailed explanation of the structure and principle of lithium battery

The main components of lithium batteries: (1) The positive electrode active material mainly refers to lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium nickelate, lithium nickel cobalt manganate, etc. The conductive current collector generally uses a thickness of 10-20 microns Aluminum foil; (2) Diaphragm A special plastic film that allows lithium ions to pass through, but it is an electronic insulator. At present, there are mainly two types of PE and PP and their combination. There is also a type of inorganic solid diaphragm, such as alumina diaphragm coating is a kind of inorganic solid diaphragm; (3) The negative electrode active material mainly refers to graphite, lithium titanate, or carbon materials similar to graphite structure. The conductive current collector generally uses Copper foil of 7-15 microns; (4) The electrolyte is generally an organic system, such as a carbonate solvent with lithium hexafluorophosphate dissolved, and some polymer batteries use gel electrolyte; (5) The battery shell is mainly divided into hard shells (Steel shell, aluminum shell, nickel-plated iron shell, etc.) and soft package (aluminum plastic film). When the battery is charged, lithium ions are extracted from the positive electrode and inserted in the negative electrode, and vice versa during discharge. This requires an electrode to be inserted in lithium before assembly. Generally, a lithium-inserting transition metal oxide with a potential greater than 3V relative to lithium and stable in the air is selected as the positive electrode, such as LiCoO2, LiNiO2, LiMn2O4. As the material of the negative electrode, choose the intercalable lithium compound whose potential is as close as possible to the lithium potential. For example, various carbon materials include natural graphite, composition graphite, carbon fiber, central phase pellet carbon, etc. and metal oxides, including SnO, SnO2, and SnO2. Tin composite oxide SnBxPyOz (xu003d0.4～0.6, yu003d0.6～0.4, zu003d(2+3x+5y)/2) etc. The electrolyte is a mixed solvent system of LiPF6 ethylene carbonate (EC), propylene carbonate (PC) and low-viscosity diethyl carbonate (DEC) and other alkyl carbonates. The diaphragm chooses polyolefin microporous membranes such as PE, PP or their composite membranes, especially the PP/PE/PP three-layer membrane not only has a low melting point, but also has high puncture resistance, which has a thermal stability effect. The shell is made of steel or aluminum, and the cover assembly has the function of explosion-proof and power-off. Basic operating principle When the battery is charged, lithium ions are extracted from the lithium-containing compound of the positive electrode, and the lithium ions move to the negative electrode through the electrolyte. The carbon material of the negative electrode has a layered structure. It has many micropores. The lithium ions that reach the negative electrode are inserted into the micropores of the carbon layer. The more lithium ions are inserted, the higher the charging capacity. When the battery is discharged (that is, the process of using the battery), the lithium ions embedded in the carbon layer of the negative electrode are released and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity. What we usually call battery capacity refers to the discharge capacity. In the process of charging and discharging lithium batteries, lithium ions are in a movement from positive to negative to positive. This is like a rocking chair. The two ends of the rocking chair are the poles of the battery, and the lithium ion moves back and forth on both ends of the rocking chair. Therefore, lithium batteries are also called rocking chair batteries. The charging process of a lithium battery is divided into two stages: a constant current charging stage and a constant voltage current decreasing charging stage. Excessive charging and discharging of lithium batteries will cause permanent damage to the positive and negative electrodes. Excessive discharge leads to depressions in the negative carbon sheet layer structure, and the depressions will prevent lithium ions from penetrating during the charging process; overcharging causes too much lithium ions to be embedded in the negative carbon structure, and some of the lithium ions can no longer be released. The best charging and discharging method for lithium batteries insists on shallow charging and shallow discharging. Generally, 60% DOD is 2 to 4 times the cycle life under 100% DOD conditions. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.