CR2032 button cell

Briefly describe the impact of pole piece manufacturing on the performance consistency of CR2032 button cell

The coating process is divided into three sections: the slurry feeding system, the coating system, and the pole piece drying system. The trinity requires each system to maintain stability to ensure the consistency of the pole piece. This article will discuss its impact on the performance consistency of lithium batteries from the perspective of coating.

The slurry feeding system transfers the slurry after stirring to the storage tank, transfers it to the transition cylinder through a diaphragm pump, and then uses a screw pump to stably output the slurry through the filter device and the iron removal device to the coating equipment for coating. Several points that need to be paid attention to in the automatic slurry feeding system are: prevent the slurry from stratifying in the storage tank, the slurry level in the transition cylinder, the stability of the screw pump, and the blockage of the filter tank should be cleaned in time. The following figure is a schematic diagram of a certain automatic feeding system, see the reference for details.

The main coating methods of lithium battery slurry are comma scraper type, transfer type, and slit extrusion type coating. The three coating methods have their own characteristics. The scraper type is mainly used in laboratory conditions, the transfer type coating is mainly used in the production of 3C batteries, and the slit extrusion coating is mainly used in power batteries. The parameters that characterize the stability of the pole piece are mainly the pole piece surface density, pole piece thickness and adhesion. In the coating system, the factors that affect the consistency of the pole piece mainly include the manufacturing accuracy of the coating head, the stability of the screw pump conveying slurry, the stability of the compressed gas, the speed stability and the control of dynamic tension.

Scraper type

Transfer type

Slit extrusion type

The pole piece drying system is mainly composed of several sections of ovens with different temperature distributions, the purpose is to dry the pole piece. In the drying system, it is necessary to pay attention to the setting of the drying temperature. If the temperature is too high during the coating process, it is easy to cause the pole piece to crack. If the temperature is low, the pole piece cannot be completely dried, which will cause local polarization inconsistency of the battery. In addition, attention should be paid to preventing the adhesive from floating.

The problems that often occur in the coating process are defects such as thick head and thin tail, thick edges on both sides, dot-shaped dark spots, rough surface, and exposed foil. The thickness of the head and tail can be adjusted by the switching time of the coating valve or the intermittent valve. The thick edge problem can be improved by adjusting the slurry properties, coating gap adjustment, slurry flow rate, etc. The rough, uneven and striped surface can be improved by stabilizing the foil, reducing the speed, adjusting the wind knife angle, etc.

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