Analysis of Lithium Battery Coating Technology

As we all know, the positive substrate of Lithium Iron Phosphate Battery is aluminium foil and the negative substrate is copper foil, which are coated and formed into positive electrode sheet rolls and negative electrode sheet rolls for the next step. The quality of the electrode has basically determined some of the performance of the battery, and the coating of the substrate is a very important part of the entire battery manufacturing process!

Coating method from the original dip coating, extrusion development to the current most advanced double-sided coating, all to improve the coating quality and performance of the pole film, some domestic economic strength of the unit, in order to produce reliable performance of LiFePO4 Battery, chemical costs a lot of money to introduce expensive foreign pole film coating machine.

The general process of coating: the coating substrate (metal foil) is released from the unwinding device to the coater. The end and the beginning of the substrate are joined into a continuous strip by the drawing device into the tension adjustment device and the automatic correction device, and after adjusting the tension and position of the strip into the coating device. The pole sheet is coated in sections in the coater according to the predetermined coating amount and blank length. When coating both sides, the front coating and blank length are automatically tracked for coating. The coated wet pole sheet is sent to the drying channel for drying and the drying temperature is set according to the coating speed and coating thickness. The dried pole sheet is rewound after tension adjustment and automatic correction for the next step.

The polar sheet slurry coating is relatively thick, the amount of coating is large and the drying load is high. At present, hot air impact drying technology is commonly used. The positive substrate is aluminium foil, and the chemical properties of aluminium foil are very active and easily oxidised. In the manufacturing process of aluminium foil will form a dense oxide film, prevent the further oxidation of aluminium foil, because the oxide film is thin and porous, soft, with good adsorption, but high temperature and high humidity can destroy this layer of oxide film, accelerate the oxidation reaction. At present, most of them are single-sided coating, when the first side is coated, the other side is completely exposed to the hot air, and the hot air of the coating (oil system) is dry at about 130 ° C, such as the water content of the hot air is not effectively controlled, which will increase the oxidation of aluminium foil and affect the adhesion of the positive electrode material with the aluminium foil, and even cause falling off.

The United States, Japan coating mechanism manufacturers for single-layer coating performance and aluminium foil oxidation problems, the development of double-sided coating technology, completely solve the problem of aluminium foil oxidation during coating, but the price of double-sided coating machine is not the general battery manufacturers can afford.