What is the roll method of the lithium battery pole piece? Which is better?

In the process of rolling the lithium battery pole piece, does the rolling temperature affect the performance of the battery pole piece and the battery? This time, I shared a piece of information and extracted some of the effects of the roll temperature of the lithium battery. The pole piece rolling is divided into two types: cold rolling and hot rolling. At present, hot rolling is widely used in foreign countries for pole piece rolling, and domestically, cold rolling is often used. Compared with cold rolling, hot rolling has the following main advantages:

1) can reduce the pole piece rebound by about 50%;

2) The thickness of the pole piece can be compressed to the thickness of the process demand by using a small rolling force, and the rolling force can be reduced by up to 62%;

3) Enhance the bonding force between the coating material and the current collector, reduce the occurrence of powder drop during the charge and discharge cycle of the battery, and improve the cycle life of the battery.

We used LiFePO4 as the positive electrode material and lithium wafer as the negative electrode material to make the button-type lithium ion battery. The three parameters of surface density, compaction density and thickness consistency were used as indicators to investigate the rolling temperature of the positive electrode sheet to the battery pole piece and the impact of battery electrochemical performance.

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Figure 1 Thickness of the pole piece at different rolling temperatures

Figure 1 is a thickness curve of a pole piece coated with a thickness of 100 μm at different rolling temperatures, as shown in the figure, as the rolling temperature is increased from 20 ° C to 90 ° C and then increased to 160 ° C, the thickness of the pole piece The deviation is reduced from ±1.9μm to ±1.3μm and then to ±0.8μm, and the thickness uniformity of the pole piece is gradually increased. This is because as the rolling temperature increases, the deformation resistance of the pole piece coating decreases, and the plasticity becomes better. The surface of the pole piece is more uniform in thickness.

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Figure 2 SEM image of the surface of the pole piece coating material at different rolling temperatures

Figure 2 is the SEM image of the surface of the pole piece coating material at different rolling temperatures. As shown in the figure, when the rolling temperature is 20 °C, the surface of the pole piece coating has a relatively tight particle combination, and some areas are not tight enough. There is a small amount of micropores; when the rolling temperature is 90 °C, the surface of the pole piece coating is tightly bonded, the tight bonding area is increased, and the number of micropores is decreasing; when the rolling temperature is 160 ° C, the pole piece is coated. The degree of tight binding of the surface particles is further increased, the tightly bound region 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 different densities.

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