What are the problems in the production of lithium-ion battery pole pieces?

The foil substrate is coated with the coating roller and directly fights with the slurry tank. The excess slurry is coated on the foil substrate. When the substrate passes between the coating roller and the doctor blade, the gap between the doctor blade and the substrate determines The thickness of the coating, while scraping the excess slurry back, and thus forming a uniform coating on the surface of the substrate. An example of a scraper is an important comma scraper. The comma blade is one of the key parts in the coating head. Generally, the comma-like blade is formed along the bus bar on the appearance of the round roller. This blade has high strength and hardness, and is easy to control the coating amount and coating accuracy. High solid content and high viscosity slurry. 2. Roller coating transfer type coating rollers move the slurry, adjust the amount of slurry transfer through the comma doctor gap, and operate the back roller and the coating roller to move the slurry to the substrate. The process is shown in Figure 2. Roll coating transfer coating includes two fundamental processes: (1) The coating roller moves the slurry through the metering roller gap to form a slurry layer with a certain thickness; (2) The slurry layer with a certain thickness passes through the coating rollers that are biased and opposed to each other. The back roll moves the slurry to presumably form a coating on the foil. 3. Slit extrusion coating is a compact wet coating technology. The principle is that the coating liquid is extruded and ejected along the deviation 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 even wet thickness. The coating system is closed to prevent the entry of pollutants during the coating process. The slurry operation rate is high, the slurry properties can be kept unchanged, and multi-layer coating can be performed at the same time. And can adapt to the range of different slurry viscosity and solid content, and has stronger adaptability compared with the transfer coating process. In order to form an unchanging and uniform coating, these conditions must be satisfied at the same time during the coating process of the lithium ion battery: (1) The slurry properties are unchanged, no sedimentation, viscosity, solid content and other stable leather. (2) The supply of slurry is unchanged, and a symmetrical and unchanging state of activity is formed inside the die. (3) In the coating window, the coating process forms a constant flow field between the die and the coating roller. (4) The foil travel is unchanged, no belt slippage, severe shaking and wrinkles occur. The coating operation window for lithium-ion batteries is an important process parameter for slit coating. In actual production, when the process parameters exceed the scope of the operation window, coating defects will appear. However, there are many types of defects in the coating film, and the reasons are different. This article mainly focuses on the slit extrusion coating of lithium-ion batteries, clarifies several common defects, and gives corresponding handling methods. Common defects are a little defect, edge effect, sawtooth defect and so on. Point defects 1. The pinhole defects presented by stomata bubbles are relatively easy to understand. The bubbles in the wet film migrate from the inner layer to the outer surface of the film, and split on the outer surface of the film to form pinhole defects. Air bubbles mainly come from mixing, coating liquid transportation and coating process. 2. Various particles of foreign body shrinkage appear. The presence of foreign particles causes the wet film on the appearance of the particles to have areas of low surface tension, and the liquid film migrates to the periphery of the particles, forming shrinkage point defects. 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: What is the important reason for the decay of ternary lithium-ion battery capacity?