18650 battery manufacturing front-end process and control points.

18650 battery manufacturing front-end process and control points.

The front-end process of battery manufacturing includes 10 steps: bonding, coating, rolling, slitting, slicing, winding, shell insertion, bottom welding, roller groove, and baking. The core of the front-end process is to make the powdered positive and negative electrode materials into a core roll.

The slurry mixing process refers to the uniform mixing of positive or negative electrode powder, conductive agent, and adhesive agent in a certain proportion to form a suspended slurry, and then coating a layer of uniform thickness on the surface of the current collector through a coating machine, which is the coating process. After coating is completed, the polarizer needs to be adjusted by a roller press to adjust the roller gap, winding position, tension, etc., and a test piece is used for pressure testing to ensure that the thickness of the test piece after pressure testing meets the process parameter requirements. Then use a slitting machine to cut into the width required for a single battery cell. Finally, weld the electrode ears on the wafer and apply insulation glue to cover the exposed current collector and electrode ears at the electrode ear position. At this point, the production of the positive and negative electrode pieces is completed.

The main process control point of the bonding process lies in the humidity control of the environment, because moisture is a key indicator that needs to be strictly controlled in the production process of lithium-ion batteries. Factors such as high environmental humidity and the use of water-based adhesives can lead to an increase in moisture content during the electrode preparation process; The slitting process needs to focus on controlling the size of burrs on the edge of the polarizer, and there should be no obvious material dropping, otherwise the polarizer may puncture the diaphragm due to material dropping or burrs being too large, causing a short circuit; The production process should prevent virtual soldering, off soldering, leakage soldering, or electrode chip dropping, as well as insulation glue off soldering or leakage soldering; The winding process is an important process for forming cylindrical lithium batteries. The strip shaped positive and negative electrode pieces and separator are wound into a cylindrical core by a winding machine. The key control point of this process is that the negative electrode piece must completely cover the positive electrode piece, and the separator must completely cover the negative electrode piece, which requires very high process accuracy. If the negative electrode is not fully wrapped around the positive electrode, lithium deposition may occur on the separator during the charging process. As the degree of lithium deposition increases, it can cause a short circuit between the positive and negative electrodes. Internal short circuit accidents caused by lithium dendrites are an important form of battery failure and may lead to accidents such as fire and explosion. If the diaphragm does not cover the negative electrode, it will directly cause contact between the positive and negative electrodes, resulting in a short circuit of the battery cell and causing serious safety accidents.

After the core is completed, it needs to be placed in the steel shell and connected to the negative electrode ear through bottom welding. At this point, the entire steel shell is the negative electrode of the battery, and the core inside the steel shell is fixed by the roller groove. The process of entering the shell and roller groove cannot damage the core, and the height of the roller groove must be strictly controlled. If it is too low, the core will be damaged; When it is too high, the core is prone to loosening. Finally, place the core that has been put into the shell in a baking oven until the moisture content of the core reaches the standard before proceeding to the next process. Baking is a crucial step to strictly control the moisture content of the core.