Brief introduction to the basic structure and principle of lithium ion battery pack

The composition of important materials for lithium-ion batteries: positive electrode material, negative electrode material, electrolyte, separator (separation material). Simple structure of the battery. From the weight of the battery, the positive electrode material accounts for a large proportion (generally 70% to 80%), because The performance of the material directly affects the performance of the lithium-ion battery, and its cost directly determines the cost of the battery. Cathode materials account for 30% to 40% of the cost of lithium-ion batteries, which also directly affect the energy density and performance of lithium-ion battery packs. The negative electrode material is composed of materials with a lower potential related to the positive electrode, and has a high specific capacity and good charge and discharge reversibility, so as to maintain good dimensional and mechanical stability during the process of lithium ion insertion (without serious deformation) ). The negative electrode material significantly affects the efficiency and cycle performance of lithium-ion batteries. The performance of the negative electrode material also directly affects the performance of the lithium-ion battery. The negative electrode material accounts for about 10-20% of the total cost of the lithium-ion battery. The types of anode materials include carbon-based anodes and non-carbon anodes. Electrolyte The electrolyte is used to transport charge between the positive electrode and the negative electrode (similar to the carrier in the radio), and has a high ionic conductivity, which should generally reach 1x10-3~2x10-2S/cm. It affects the energy density, wide temperature application, cycle life, power density, safety performance and other factors of lithium-ion battery packs. Diaphragm The diaphragm has a certain pore size and porosity to ensure low resistance and high ionic conductivity, good permeability to lithium, good wettability to electrolyte and sufficient liquid absorption and moisture retention ability to maintain ion conductivity It also has electrical insulation properties to ensure the mechanical separation of the positive and negative electrodes. In addition, it should have sufficient mechanical properties such as puncture strength and tensile strength, as well as electrolyte corrosion resistance and sufficient electrochemical stability. Power lithium batteries have higher requirements for separators, and composite membranes are usually used. The working principle of lithium ion battery: Lithium ion battery is a kind of rechargeable battery, which mainly depends on the intercalation and deintercalation of lithium between the positive electrode and the negative electrode to achieve energy storage and release. 1. During the charging process, lithium is extracted from the positive electrode lattice under the drive of an electric field, passes through the electrolyte, and is embedded in the negative electrode lattice. If the voltage is lower than 3V, it must be precharged first. The charging current is 1/10 of the set current. After the voltage rises to 3V, it enters the standard charging process. The standard charging process is: constant current charging with the set current, when the battery voltage rises to 4.20V, change to constant voltage charging, and keep the charging voltage at 4.20V. At this time, the charging current gradually decreases, and when the current drops to 1/10 of the set charging current, charging ends. This is a process of general lithium-ion battery charging. If the lithium-ion battery exists in a smart device, its charging mode will be controlled by the smart device software. 2. Discharge process The discharge process is just the opposite of the charging process. Lithium returns to the positive electrode under the use of an electric field, and the electrons reach the positive electrode through the external circuit to recombine with the lithium. When the battery is discharged, the electron e on the negative electrode runs from the external circuit to the positive electrode, and the positive lithium Li+ jumps from the negative electrode into the electrolyte, crawls through the winding hole in the diaphragm, swims to the positive electrode, and ran over long ago. The electrons are combined together. By knowing the charging and discharging process of lithium-ion batteries, we can understand from a microscopic perspective that the capacity of a battery is actually the amount of charge contained in the battery. The greater the current, the faster the discharge rate, and the shorter the battery life. 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: What should I pay attention to when purchasing lithium-ion batteries?