Introduction of Lithium Battery Electrode Film Coating Process

Coating technology of lithium battery

The coating process is a process of coating one or more layers of liquid or slurry on a substrate based on the study of the physical properties of the fluid. The substrate is usually a flexible film or backing paper, and then the coated liquid coating is dried in an oven or solidified to form a film layer with special functions. At present, the coating methods of lithium battery electrode mainly include comma roll transfer coating and slit extrusion coating. Acey New Energy supplys electrode coating machine with adjustable scraper and heating function can well meet battery coating requirement.

Several coating methods of lithium battery

① Scraper coating

The foil substrate passes through the coating roller and is directly in contact with the slurry trough. Excess slurry is coated on the foil substrate. When the substrate passes between the coating roller and the scraper, the gap between the scraper and the substrate determines the coating thickness. At the same time, the excess slurry is scraped off and backflow, thus forming a uniform coating on the surface of the substrate. The scraper type is mainly comma scraper.

② Slit extrusion coating

As a precise wet coating technology, the working principle is that the coating liquid is extruded and sprayed along the gap of the coating mold under a certain pressure and flow and transferred to the substrate. Compared with other coating methods, it has many advantages, such as fast coating speed, high precision and uniform wet thickness; The coating system is closed, which can prevent pollutants from entering during the coating process. The slurry utilization rate is high, and the slurry property can be kept stable, and multi-layer coating can be carried out at the same time.

Whether the lithium battery coating process can accurately use the best coating and drying process in the design process, balance the relationship between them, and ultimately affect the comprehensive technical performance of the coating. In the polar coating, the common problems include raw material pollution, unstable coating process, nonstandard operation, incorrect drying procedure setting, etc. These problems will cause more or less defects in the polar coating.

Electrode coating is of great significance for lithium batteries, mainly reflected in the following points:

1. It is of great significance to the capacity of finished lithium battery. During the coating process, if the thickness of the positive and negative electrode slurry coating at the front, middle and rear positions of the electrode sheet is not consistent, it is easy to cause the battery capacity to be too low and too high, and it is easier to form lithium precipitation during the battery cycle, affecting the battery life.

2. It is important for the safety of lithium battery. Before coating, should ensure that no particles, sundries, dust, etc. are mixed into the electrode during coating. If mixed with sundries, it will cause micro-circuit inside the battery, which may cause fire and explosion in serious cases.

3. It is of great significance to the consistency of lithium battery performance. The battery factory taboo is that the capacity difference and cycle life difference of a batch of batteries are large, so the parameters before and after the electrode sheet should be consistent during the coating process.

4. It is important for the life of lithium battery. The large difference before and after the slurry coating, the dust mixed into the electrode, the uneven thickness of the left and right electrode, and so on, all affect the electrochemical performance of the battery.

Extrusion coating has been widely used in the field of power lithium battery due to its advantages of high precision, uniform coating, and suitable for large width coating, and it has gradually replaced the transfer coating machine applicable to the pilot line. In the future, the coating process will be developed in the direction of high equipment performance, high productivity, online thickness measurement control accuracy, and improved drying efficiency.

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