What are the difficulties in the production process of 21700 battery pole pieces? Will it become an obstacle to battery technology?

　　What are the problems in the production and manufacturing of 21700 battery pole pieces? As a recognized ideal energy storage component, power lithium batteries have received great attention. The coating machine is a key process equipment for the production of power 21700 battery pole pieces. At present, the main coating process for 21700 battery pole pieces is the scraper type. What are the problems in the production and manufacturing of 21700 battery pole pieces? As a recognized ideal energy storage component, power lithium batteries have received great attention. The coating machine is a key process equipment for the production of power 21700 battery pole pieces. At present, the coating processes for 21700 battery pole pieces mainly include scraper type, roller transfer type and slit extrusion type.

　　Generally, laboratory equipment adopts the scraper type, 3C batteries adopt the roller coating transfer type, and power batteries mostly adopt the slit extrusion type. What problems exist in the production and manufacturing of 21700 battery pole pieces? 1. The blade-coated foil substrate passes through the coating roller and is in direct contact with the slurry trough. Excessive slurry is coated on the foil substrate, and the substrate passes through the coating roller and is in contact with the slurry trough. When the scraper is used, the gap between the scraper and the substrate determines the thickness of the coating. At the same time, the excess slurry is scraped off and reflowed, thereby forming a uniform coating on the surface of the substrate. Scraper type Main comma scraper.

　　The comma scraper is one of the key components of the coating head. It is generally processed into a comma-like cutting edge on the surface of the round roller along the bus line. This scraper has high strength and hardness, and is easy to control the coating amount and coating accuracy. It is suitable for High solid content and high viscosity slurry.

　　2. Roller coating transfer type: The rotation of the coating roller drives the slurry, and the slurry transfer amount is adjusted through the comma scraper gap, and the rotation of the back roller and coating roller is used to transfer the slurry to the substrate. The process is shown in Figure 2.

　　Roller transfer coating consists of two basic processes:

　　(1) The rotation of the coating roller drives the slurry through the gap between the metering rollers to form a slurry layer of a certain thickness;

　　(2) A slurry layer of a certain thickness is transferred to the foil through the rotation of the coating roller and the back roller in opposite directions to form a coating.

　　3. Slit extrusion coating is a precision wet coating technology. The working principle is that the coating liquid is extruded and sprayed along the slit of the coating die under a certain pressure and flow rate 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 to prevent contaminants from entering during the coating process. The slurry utilization rate is high, the properties of the slurry can be kept stable, and multi-layer coating can be performed at the same time. It can adapt to different slurry viscosity and solid content ranges, and has stronger adaptability than the transfer coating process. To form a stable and uniform coating, these conditions need to be met simultaneously during the 21700 battery coating process:

　　(1) The properties of the slurry are stable, no settling occurs, and the viscosity, solid content, etc. do not change.

　　(2) The supply of slurry is stable and a uniform and stable flow state is formed inside the die head.

　　(3) The coating process forms a stable flow field between the die and the coating roller within the coating window.

　　(4) The foil running is stable and does not cause tape slippage, serious jitter and wrinkles. The 21700 battery coating operating window is an important process parameter for slot coating. In actual production, when the process parameters exceed the operating window, coating defects will occur.

　　There are many types of defects in coating films with different causes. This article mainly focuses on 21700 battery slit extrusion coating, analyzes several common defects, and provides corresponding solutions. Common defects include dot defects, edge effects, jagged defects, etc.

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