What is the effect of the rolling temperature of the lithium ion battery pole piece

The compaction density of the surface coating material of the pole piece has a very important relationship with the electrochemical function of the battery. A reasonable compaction density can effectively increase the electrochemical function of the battery, reduce the contact resistance and communication impedance of the electrode, and add to participate in the electrochemical reaction. The active material area, and then significantly improve the electrochemical function of the pole piece coating material. The manufacture of pole pieces for lithium-ion batteries belongs to the category of high-precision manufacturing. Pole piece rolling is different from plate and strip rolling. Plate and strip rolling is a process in which metal material undergoes longitudinal extension and lateral expansion. The data density in the rolling process is not Changes in seizures. The electrode material on the outer surface of the battery pole piece is a kind of pore structure. During the rolling process, the electrode data on the positive and negative electrodes is compacted and the density changes. The pole piece rolling is a process in which the pore structure is filled and the coating particles are gradually compacted. The purpose of the pole piece rolling is as follows: 1) to ensure the lubrication and smoothness of the pole piece surface, to prevent the burr of the coating surface from piercing the diaphragm and cause a short circuit; 2) to compact the pole piece coating material to reduce the volume of the pole piece , In order to improve the energy density of the battery; 3) make the active material and conductive agent particles more tightly contacted, improve the electronic conductivity; 4) enhance the bonding strength of the coating material and the current collector, reduce the battery pole piece in the cycle process of powder loss The occurrence of battery life, improve the cycle life and safety functions of the battery. Previously, the basic analysis of lithium-ion battery pole piece rolling process (click to read) shared the basic knowledge of rolling. Someone asked about the impact of rolling temperature on battery pole pieces and battery functions. This time I share a piece of information and extract some of them. Explain the influence of the temperature of lithium-ion battery pole piece rolling. Pole piece rolling is divided into two methods: cold rolling and hot rolling. Nowadays, hot rolling has been widely used in foreign countries for pole piece rolling, but cold rolling is still used in China. Compared with cold rolling, hot rolling has the following advantages: 1) It can reduce the rebound of the pole piece by about 50%; 2) The thickness of the pole piece can be reduced to the thickness required by the process with a smaller rolling force. The maximum force can be reduced by 62%; 3) Enhance the binding force of the coating material and the current collector, reduce the occurrence of battery powder falling during the charge and discharge cycle process, and improve the cycle life of the battery. Liu Binbin and others selected LiFePO4 as the positive electrode material and lithium sheet as the negative electrode material to make a button lithium-ion battery. With the three parameters of areal density, compaction density and thickness consistency as the goal, they investigated the impact of the rolling temperature of the positive electrode sheet on the battery electrode. The influence of the electrochemical function of the chip and the battery. The thickness curve of the pole piece with a coating thickness of 100μm at different rolling temperatures, as shown in the figure, as the rolling temperature increases from 20C to 90C and then to 160C, the thickness deviation of the pole piece decreases from ±1.9μm to ±1.3μm Then it drops to ±0.8μm, and the consistency of the pole piece thickness gradually improves. This is because with the increase of the rolling temperature, the deformation resistance of the pole piece coating decreases and the plasticity becomes better, making the surface thickness of the pole piece more uniform. When the rolling temperature is 20C, some areas of the surface of the pole piece coating are tightly bonded, and some areas are not tight enough, and there are a few micropores; when the rolling temperature is 90C, the degree of tight bonding of the particles on the surface of the pole piece coating is added, tightly. When the bonding area is added, the number of micropores is decreasing; when the rolling temperature is 160C, the degree of tight bonding of the surface particles of the pole piece coating is further increased, and the tight bonding area is further increased, and the number of micropores is further reduced. The difference in rolling temperature changes the deformation resistance of the coating, so that the surface of the pole piece coating material has a different degree of density. The Coulomb power of each sample battery, 9#, 8#, and 3# are batteries manufactured by rolling pole pieces under the conditions of 20C, 90C, and 160C, respectively. It can be seen from Figure 3 that when the rolling temperature increases from 20C to 90C and then to 160C, the Coulomb power of the sample also improves. Coulomb power is the ratio of discharge specific capacity to charge specific capacity in the same charge-discharge cycle. When the thickness consistency of the pole piece increases, the resistance will decrease, and the Coulomb power will increase accordingly. The cyclic voltammetric function curve of each sample, 9#, 8#, and 3# are batteries made by rolling pole pieces under the conditions of 20C, 90C, and 160C, respectively. It can be seen from the figure that when the rolling temperature is 160C in the test sample, the upward oxidation peak and the downward recovery peak are more symmetrical, the peak position difference is also the smallest, and the reversibility of charging and discharging is also the best. high. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it. Previous: Do you know what are the functional requirements of echelon lithium iron phosphate batteries?