What are the effects of aging of lithium-ion batteries

There are several important purposes of aging: one is to make the electrolyte infiltration better, which is conducive to the stability of battery performance; the other is that the active materials in the positive and negative materials can accelerate the progress of some side-uses after aging, such as gas production, Electrolyte decomposition, etc., make the electrochemical performance of lithium-ion batteries quickly stabilized; the third is to screen the consistency of lithium-ion batteries after a period of aging. After formation, the voltage of the battery cell is unstable, and its measured value will deviate from the actual value. The voltage and internal resistance of the battery cell after aging are more stable, which is convenient for screening batteries with high consistency. The aging system has two important factors affecting the performance of lithium-ion batteries, namely, aging temperature and aging time. In addition, it is also important whether the battery is sealed or opened during aging. Regarding the opening formation, if the humidity of the plant can be controlled well, it can be sealed after aging. If high temperature aging is used, it is better to age after sealing. Regarding different battery systems, ternary positive/graphite negative lithium-ion batteries, lithium iron phosphate positive/graphite negative lithium-ion batteries, or lithium titanate negative batteries, targeted tests should be carried out according to the characteristics of the materials and lithium-ion batteries. In the experimental design, the best aging system can be determined through the difference in capacity, internal resistance, and pressure drop characteristics of lithium-ion batteries. 1. Ternary or lithium iron phosphate lithium ion positive electrode/graphite negative electrode lithium ion battery Regarding the lithium ion battery with ternary element as the positive electrode material and graphite as the negative electrode material, the pre-charge formation stage of the lithium ion battery will form a surface of the graphite negative electrode. Layered solid electrolyte membrane (SEI), the formation potential of this kind of membrane is about 0.8V. SEI allows ions to penetrate but not electrons, so that after a certain thickness is formed, it will inhibit the further decomposition of the electrolyte, which can prevent Degradation of battery performance caused by electrolyte decomposition. However, the SEI film formed after chemical conversion has a compact structure and small pores. Re-aging the battery will help the SEI structure to reorganize and form a loose and porous film, thereby improving the performance of the lithium-ion battery. The aging of the ternary/graphite lithium-ion battery generally chooses room temperature aging for 7 days to 28 days, but some factories use high temperature aging system, the aging time is 1-3 days, the so-called high temperature is generally between 38°C and 50°C. High-temperature aging is just to shorten the entire processing cycle. Its purpose is the same as room-temperature aging. It is to allow the positive and negative electrodes, diaphragm, electrolyte, etc. to fully carry out chemical reactions to achieve equilibrium, so that the lithium-ion battery can reach a more stable state. 2. Lithium titanate negative electrode Lithium ion battery, commonly known as lithium titanate battery, is a battery that uses lithium titanate as the negative electrode. The main material for the positive electrode is ternary, lithium cobaltate and other materials. The difference between lithium titanate battery and graphite anode battery is that the lithium ion potential of lithium titanate ion is 1.55V (related to lithium ion metal), which is higher than 0.8V formed by SEI, so it will not be formed during charging and discharging. The solid electrolyte membrane (SEI) also does not form dendritic lithium ions, so it has higher safety. This means that during the charging process of lithium titanate, electrons constantly react with the electrolyte to generate by-products and the appearance of hydrogen, CO, CH4, C2H4 and other gases, which will cause the battery to bulge. The bulging problem of lithium titanate ions is important to be alleviated by the change of material properties, such as material surface coating, changing the particle size distribution, and finding a suitable electrolyte. In addition, the bulging phenomenon of lithium titanate ions can be appropriately reduced by optimizing the pre-charge, chemical conversion, and aging system. The high temperature aging system is generally preferred for the aging system of lithium titanate batteries. The aging temperature is 40℃-55℃, and the aging time is generally 1-3 days. After aging, negative pressure exhaust is required. Carry out multiple high-temperature aging to fully react the moisture inside the battery. After the gas is discharged, the flatulence problem of the lithium titanate battery can be effectively suppressed, and its cycle life can be improved. 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: Do you know the characteristics of lithium-ion batteries?