The winding process of lithium battery generally consists of ten important steps, which are:
Stirring → coating → cold pressing → slitter → welding → winding → top sealing → liquid injection → formation → molding, and finally the battery test project.
【 Working principle of potassium battery winding process 】
1. Mixing: Mix the positive or negative powder and other ingredients evenly and make it into pulp.
2. Coating: the slurry is intermittently and evenly coated on the surface of the transfer fluid collection, dried, and made into positive and negative pole sheets.
3. Cold pressing: the coated polar sheet will be compacted to achieve the appropriate density and thickness.
4. Cutting and dividing: roll the cold pressed pole piece, cut it into large pieces first, and then divide it into small positive and negative pole pieces as needed.
5. Winding: small strips of positive and negative electrode pieces, isolation film winding combination into a bare cell.
6. Top sealing: The bare cell is wrapped with aluminum foil, and the top and sides are thermally sealed.
7. Liquid injection: Add the electrolyte to the cell and seal the cell completely. (Environmental requirements: Water should be removed before the cell injection, and low humidity should be required during the attention process.)
8. Pre-formation: the positive and negative materials inside are activated by charging, and a good SEI film is formed on the surface of the negative electrode.
9. Molding: the final processing of the cell shape.
NMP solvent is used in the stage of mixing, mixing and coating of lithium battery slurry. In the wet process, PVDF gel (solute: PVDF, solution: NMP (N-methylpyrrolidone)) needs to be prepared in advance. The quality of PVDF glue is very important to the internal resistance and electric performance of the battery.
Factors affecting gluing include temperature and stirring speed:
The higher the temperature is, the yellowing will affect the cohesiveness.
Stirring speed is too high, it is easy to break the glue;
The specific speed needs to see the size of the dispersion disk: in general, the dispersion disk line speed in 10-15m/s (high dependence on equipment).
At this time, circulating water should be opened in the mixing tank, and the temperature should be less than or equal to 30℃.
Although NMP is only a small auxiliary solvent, even one more particle of dust can cause significant performance problems for the sophisticated battery preparation process. Therefore, the battery preparation process is strict, and the purity of NMP solvent is even stricter.
We specialized in NMP more than 10 years.
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