What are the basic rolling processes of lithium battery pole pieces?

1) Reduce the elongation and spread rate of the pole piece during the rolling process, and reduce the damage rate of the pore structure of the pole piece coating material; (2) Improve the thickness uniformity of the pole piece coating to improve the cross section of the pole piece shape. (3) Improve the consistency of the compaction density of the electrode material after the pole piece is rolled; (4) Reduce the rebound of the electrode material on the surface after the pole piece is rolled; The compaction density of the surface coating material of the pole piece is related to the electrochemical performance of the battery. A very important relationship. A reasonable compaction density can effectively increase the electrochemical performance of the battery, reduce the contact resistance and AC impedance of the electrode, and increase the area of u200bu200bthe active material involved in the electrochemical reaction, thereby significantly improving the electrical conductivity of the electrode sheet coating material. Chemical properties. Lithium battery pole piece manufacturing 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 of longitudinal extension and lateral expansion of metal materials. The material density does not occur during the rolling process. Variety. The electrode material on the surface of the battery pole piece is a pore structure. During the rolling process, the electrode material on the positive and negative pole pieces 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 dense. The purpose of pole piece rolling is as follows: 1) to ensure the smooth and flat surface of the pole piece, to prevent the burrs on the coating surface from piercing the diaphragm and cause short circuit; 2) to compact the pole piece coating material to reduce the volume of the pole piece , In order to increase the energy density of the battery; 3) make the active material and conductive agent particles more closely contact, improve the electronic conductivity; 4) enhance the bonding strength of the coating material and the current collector, reduce the battery pole pieces in the cycle of powder loss Occurrence, improve the cycle life and safety performance of the battery. Previously, the basic introduction of lithium battery pole piece rolling technology (click to read) article shared the basic knowledge of rolling. Some people asked about the impact of rolling temperature on battery pole pieces and battery performance. This time I share a piece of information and extract some of the instructions. The influence of the rolling temperature of the pole piece of the lithium battery. Pole piece rolling is divided into cold rolling and hot rolling. At present, 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 by using a smaller rolling force. The maximum force can be reduced by 62%; 3) Strengthen the binding force of the coating material and the current collector, reduce the occurrence of powder falling during the charge and discharge cycle of the battery, and improve the cycle life of the battery. Liu Binbin and others used LiFePO4 as the positive electrode material and lithium sheet as the negative electrode material to make a button-type lithium battery. The three parameters of areal density, compaction density and thickness consistency were used as indicators to investigate the impact of the rolling temperature of the positive electrode sheet on the battery pole sheet. And the influence of the electrochemical performance of the battery. In order to coat the thickness curve of a pole piece with a thickness of 100μm at different rolling temperatures, as shown in the figure, as the rolling temperature is increased from 20°C to 90°C and then to 160°C, the thickness deviation of the pole piece changes from ± 1.9μm is reduced to ±1.3μm and then to ±0.8μm, and the thickness consistency of the pole piece is gradually improved. 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 pole piece The surface thickness is more uniform. It is the SEM image of the surface of the pole piece coating material at different rolling temperatures. When the rolling temperature is 20°C, the particles on the surface of the pole piece coating are tightly bound, and some areas are not tight enough, and there are a few micropores; When the temperature is 90℃, the degree of tight bonding of the particles on the surface of the pole piece coating increases, and the tightly bonded area increases, and the number of micropores is decreasing; when the rolling temperature is 160℃, the degree of tight bonding of the particles on the surface of the pole piece coating further increases. , The tightly bonded area is further enlarged, and the number of micropores is further reduced. The different 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. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous article: Do you know how to detect the thickness of the lithium battery separator?