In the lithium-ion battery electrode rolling process, does the rolling temperature affect the battery electrode and battery performance? This article shares some information, extracting parts to explain the impact of lithium-ion battery electrode rolling temperature. Electrode rolling is divided into two methods: cold rolling and hot rolling. Currently, hot rolling is widely used abroad for electrode rolling, while cold rolling is still more common in China. Compared with cold rolling, hot rolling has the following main advantages:
1) It can reduce electrode rebound by approximately 50%;
2) The thickness of the electrode sheet can be compressed to the required thickness using a smaller rolling force, with the rolling force reduced by up to 62%;
3) Enhance the bonding force between the coating material and the current collector, reduce the occurrence of powder shedding during battery charge and discharge cycles, and improve the cycle life of the battery.
We used LiFePO4 as the positive electrode material and lithium foil as the negative electrode material to fabricate a coin cell lithium-ion battery. We investigated the effects of the rolling temperature of the positive electrode sheet on the battery electrode sheet and the battery electrochemical performance using three parameters: areal density, compaction density, and thickness uniformity.
Figure 1. Electrode thickness at different rolling temperatures.
Figure 1 shows the thickness curves of an electrode with a coating thickness of 100 μm at different rolling temperatures. As shown in the figure, as the rolling temperature increases from 20°C to 90°C and then to 160°C, the electrode thickness deviation decreases from ±1.9 μm to ±1.3 μm and then to ±0.8 μm. The uniformity of electrode thickness gradually improves. This is because as the rolling temperature increases, the deformation resistance of the electrode coating decreases and the plasticity improves, making the electrode surface thickness more uniform.
Figure 2. SEM images of the electrode coating material surface at different rolling temperatures.
Figure 2 shows SEM images of the electrode coating material surface at different rolling temperatures. As shown in the figure, at a rolling temperature of 20°C, the particles on the electrode coating surface are relatively tightly bonded in some areas, but not so tightly bonded in others, and a small number of micropores exist. At a rolling temperature of 90°C, the degree of particle bonding on the electrode coating surface increases, the tightly bonded area increases, and the number of micropores decreases. At a rolling temperature of 160°C, the degree of particle bonding on the electrode coating surface further increases, the tightly bonded area further increases, and the number of micropores further decreases. Different rolling temperatures alter the deformation resistance of the coating, resulting in different degrees of density on the electrode coating material surface.
