18650 rechargeable battery lithium 3.7v 3500mah.Lithium battery production link: coating technology analysis

　　As we all know, the positive electrode substrate of a lithium-ion battery is aluminum foil, and the negative electrode substrate is copper foil. After coating, the positive electrode sheet roll and the negative electrode sheet roll are made for the next step of processing. The quality of the pole pieces has basically determined certain performance of the battery, and the coating of the substrate is a very important part of the entire battery manufacturing process!

　　Coating methods have evolved from the original dip coating and extrusion to the most advanced double-sided simultaneous coating, all in order to improve the coating quality and performance of the pole pieces. Some domestic units with strong economic strength, in order to ensure reliable manufacturing performance For lithium-ion batteries, a large amount of money has been spent to introduce expensive pole plate coating machines from abroad.

　　The general process flow of coating: the coated substrate (metal foil) is fed into the coating machine from the unwinding device. The first and last ends of the substrate are connected into a continuous belt on the splicing table and sent to the tension adjustment device and the automatic correction device by the puller device. After adjusting the film path tension and the film path position, they enter the coating device. The pole piece slurry is coated in sections according to the predetermined coating amount and blank length in the coating device. During double-sided coating, the front coating and blank length are automatically tracked for coating. The coated wet electrode sheet is sent to the drying tunnel for drying. The drying temperature is set according to the coating speed and coating thickness. The dried pole pieces are rolled up after tension adjustment and automatic deviation correction for the next step of processing.

　　The pole piece slurry coating is relatively thick, the coating volume is large, and the drying load is large. Currently, hot air impact drying technology is commonly used. The positive electrode substrate is aluminum foil. The chemical properties of aluminum foil are very active and are easily oxidized. During the manufacturing process of aluminum foil, a dense oxide film will be formed to prevent further oxidation of the aluminum foil. Because the oxide film is thin, porous, soft, and has good adsorption properties, high temperature and high humidity can destroy this oxide film. Speed up the oxidation reaction. At present, most of them adopt a single-sided coating method. When the first side is coated, the other side is completely exposed to the hot air. However, the dry hot air for coating (oil system) should be around 130°C, such as in hot air. If the moisture content is not effectively controlled, it will intensify the oxidation of the aluminum foil and affect the adhesion between the positive electrode material and the aluminum foil. In severe cases, it may even cause falling off.

　　Coating machine manufacturers in the United States and Japan developed double-sided simultaneous coating technology to address the energy efficiency of single-layer coating machines and the oxidation of aluminum foil, which completely solved the problem of aluminum foil oxidation during coating. However, the price of double-sided simultaneous coating machines is astronomical It is not something that ordinary battery manufacturers can afford.

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