Detailed explanation of lithium ion battery formation-aging process

The concept of pre-formation is to charge and discharge the manufactured lithium-ion battery with a small current. After the production of the lithium-ion battery is completed, the battery must be charged and discharged with a small current. Regarding the purpose of pre-charging, there are two important ones: 1. After the battery is manufactured, the electrode material is not in the best applicable state, or the physical properties are inappropriate (such as too large particles, not close contact, etc.), or the phase itself It is wrong (for example, some metal oxide negative electrodes of alloy mechanism), it needs to be activated for the first time by charging and discharging. 2. During the first charge of the lithium-ion battery, Li+ is removed from the active material of the positive electrode, and after passing through the electrolyte-diaphragm-electrolyte, it is inserted between the layers of the negative electrode graphite material. In this process, electrons migrate from the positive pole to the negative pole along the peripheral circuit. At this time, due to the low potential of lithium ions inserted into the graphite anode, the electrons will first react with the electrolyte to form an SEI film and some gas. For the use and formation mechanism of SEI, see Dry Goods|What is SEI? It has such a big impact on lithium-ion batteries! During this process, some gas will appear and a small amount of electrolyte will be consumed. Some battery manufacturers will perform battery exhaust and refill operations after this process. Especially for LTO batteries, a large amount of gas will appear and cause the battery to bulge. The thickness exceeds 10%. Regarding the graphite negative electrode, the amount of gas produced is small, and it is not necessary to perform the operation of exhausting. This is because the SEI film that appeared during the first charging process hinders the further reaction of electrons with the electrolyte, and no more gas appears. This is the source of the irreversible capacity of the graphite system battery. Although it has caused the irreversible capacity loss, it has also achieved the stability of the battery. 2. Aging generally refers to the placement of the battery after the first charging and forming after the battery is assembled and injected. It can be aging at room temperature or high temperature. The purpose of both is to make the properties and composition of the SEI film formed after the initial charging and forming better. Stable to ensure the stability of the electrochemical performance of the battery. There are three important purposes for aging: 1. After the battery is pre-formed into a process, a certain amount of SEI film will be formed on the graphite negative electrode inside the battery, but this film has a compact structure and small pores. It will help to age the battery at high temperature. The SEI structure is reorganized to form a loose and porous membrane. 2. The voltage of the battery is in an unstable stage after formation, and its voltage is slightly higher than the real voltage. The purpose of aging is to make its voltage more accurate and stable. 3. Putting the battery at high temperature or normal temperature for a period of time can ensure that the electrolyte can fully infiltrate the pole pieces, which is beneficial to the stability of the battery performance. The formation and aging process of the battery is indispensable. In actual production, the battery charging and discharging process is selected according to the material system and structure system of the battery, but the formation of the battery must be charged and discharged under the condition of small current. After these two key processes, the stabilized battery is divided into capacity, and after packaging and other processes, it can be released. 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: Introduction to the advantages and disadvantages of soft pack batteries