What can improve the low-temperature performance of lithium-ion batteries?

The positive electrode: now it is all nanometer, its particle size, electrical resistance, and the axis length of the AB plane will affect the low temperature characteristics of the entire battery. Lithium iron phosphate ions are prepared through three processes. From the perspective of our overall preparation conditions, different lithium iron phosphate processes are nano-sized and coated. From the perspective of the axis length of the AB surface, the axis length of the AB surface increases The lithium migration channel will become larger, which will help improve the battery rate performance. Different processes have different effects on the positive electrode. The low-temperature discharge characteristics of batteries made of lithium iron phosphate ions with a particle size of 100 to 200 nanometers are better, and 94% can be released at -20 degrees. That is, the nanometer particle size shortens the migration path. , It also improves the performance of low-temperature discharge, because the discharge of lithium iron phosphate is mainly related to the positive electrode. Negative electrode: Considering the charging characteristics, low-temperature charging of lithium-ion batteries is mainly due to the influence of the negative electrode, including the particle size and the change in the spacing of the negative electrode. Three different artificial graphites are selected as the negative electrode to study the effect of different layer spacing and particle size on low temperature. The impact of characteristics. From the perspective of the three materials, in terms of impedance, the bulk resistance and ion migration resistance of granular graphite with a large interlayer spacing are relatively small. In terms of charging, the problem of discharging at low temperature in winter is not big, and the important thing is low temperature charging. Because in terms of the cross-current ratio, the cross-current ratio of 1C or 0.5C is very important. It takes a very long time to reach a constant voltage. By improving the comparison of three different graphites, it is found that one of them has a relatively large improvement in the constant current ratio of -20 degrees. , From 40% to more than 70%, the layer spacing increases, and the particle size decreases. Electrolyte: The electrolyte freezes at -20 degrees and -30 degrees, the viscosity increases, and the formation performance deteriorates. The electrolyte comes from three aspects: solvent, lithium ion salt, and additives. Different lithium ion salts have a certain influence on the charge and discharge characteristics at low temperatures. Based on the fixed solvent system and lithium ion salt, low temperature additives can increase the discharge capacity from 85% to 90%. That is to say, in the entire electrolyte system, solvents, lithium ion salts and additives are all effective for our power lithium batteries. The characteristics have a certain influence, including other material systems are equally applicable. Binder: There are three kinds, two kinds of dots, one kind of linear. In the case of charging and discharging at -20 degrees, after the two dots have been cycled for more than 70 to 80, the entire pole piece has the current status of adhesive failure, and the linear adhesive will not have this problem. In the whole system, from the improvement of the positive electrode, negative electrode, electrolyte to the binder, we have done better results in the monomer of lithium iron phosphate battery. One is the charging characteristics, -20, -30, The 0.5C charging constant current ratio can reach 62.9% at a temperature of -40 degrees, and 94% can be released when discharged at a temperature of -20 degrees. This is some characteristics of the rate and cycle. In order to improve the power and low-temperature performance of lithium-ion batteries, it is necessary to reduce the various impedances of the entire lithium-ion battery discharge process. Some of these impedances are relatively large and some are relatively small, and are affected by various factors such as the composition and temperature of the electrolyte. Recently, Dr. Shi Qiao from Shenzhen Xinzhoubang Technology Co., Ltd. gave a keynote speech on the research and application progress of functional electrolytes to improve the power characteristics and low-temperature performance of light hybrid/micro hybrid 12-48V lithium-ion batteries. He analyzed the electrolyte-related factors that affect various impedances from the aspects of lithium conduction process, solvent, lithium ion salt concentration, and additives. As we all know, in the discharge process of lithium-ion batteries, lithium first enters the SEI after being extracted from the negative electrode, then conducts in the SEI, and then enters the electrolyte to be solvated, and then the solvated lithium is conducted in the electrolyte and reaches the surface of the positive electrode. After that, it is firstly desolvated into CEI, then conducts in CEI, and finally is embedded in the positive electrode. In the process of discharging a lithium ion battery, each step corresponds to an impedance. The magnitude of this impedance is related to many factors. The following will importantly list the factors that may affect each impedance and the electrolyte. In the lithium conduction process, the characteristics of SEI and CEI have a very important influence. Based on the performance requirements of different aspects, there is a certain conflict between the requirements of SEI and CEI. From the perspective of improving power and low temperature characteristics, it is hoped that SEI and CEI should be as thin as possible, not too dense and have good conductivity; but from the perspective of improving the high temperature performance and cycle performance of the battery, it is hoped that CEI and SEI should be thicker or denser and stronger And toughness is better. 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: How to use lithium-ion battery UPS correctly