Nickel Metal Hydride No. 5 battery

Analysis of Nickel Metal Hydride No. 5 battery Coating Technology

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

The coating method has developed from the original dip coating and extrusion to the most advanced double-sided simultaneous coating, all of which are to improve the coating quality and performance of the electrode sheet. Some domestic units with strong economic strength have spent a lot of money to introduce expensive foreign electrode sheet coating machines in order to manufacture reliable lithium-ion batteries.

General process flow of coating: The coated substrate (metal foil) is unwound by the unwinding device and fed into the coating machine. After the head and tail of the substrate are connected into a continuous belt at the splicing table, they are sent to the tension adjustment device and the automatic deviation correction device by the pulling device, and enter the coating device after adjusting the sheet path tension and sheet path position. The electrode slurry is coated in sections according to the predetermined coating amount and blank length in the coating device. When double-sided coating is applied, the front coating and blank length are automatically tracked for coating. The wet electrode after coating is sent to the drying channel for drying, and the drying temperature is set according to the coating speed and coating thickness. The dried electrode is rolled up after tension adjustment and automatic deviation correction for processing in the next step.

The electrode slurry coating is relatively thick, the coating amount is large, and the drying load is large. At present, hot air impact drying technology is commonly used. The positive electrode substrate is aluminum foil, which has a very active chemical property and is 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, high temperature and high humidity can destroy this oxide film and accelerate the oxidation reaction. At present, most of them adopt single-sided coating. When the first side is coated, the other side is completely exposed to hot air. The hot air for coating (oil system) drying should be around 130℃. If the moisture content in the hot air is not effectively controlled, the oxidation of the aluminum foil will be intensified, affecting the adhesion between the positive electrode material and the aluminum foil, and even causing it to fall off.

In view of the energy efficiency of single-layer coating machines and the oxidation of aluminum foil, coating machine manufacturers in the United States and Japan have developed double-sided simultaneous coating technology, which completely solves the oxidation problem of aluminum foil during coating. However, the sky-high price of double-sided simultaneous coating machines is not affordable for general battery manufacturers.

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