NMP solvent participates in the coating stage in the lithium battery winding process! | ZOLSEM

The winding process of lithium batteries is as simple as folding a quilt in the army, but it actually involves a lot of processes. Among them, the NMP solvent (N-methylpyrrolidone) produced and supplied by ZESHENG participated in the batching, coating, coating baking and other stages of the lithium battery winding process. What is the specific winding process of lithium batteries? Please see the edited and edited Chinese and English version of the winding process flow chart to give you an in-depth understanding of the lithium battery winding process.

The winding process of lithium batteries generally contains ten important steps, namely:

Stirring→coating→cold pressing→cutting and slitting→welding→winding→top sealing→liquid injection→formation→forming

The last step is to carry out the battery test project.

Since joining the new energy industry, all kinds of professional vocabulary have been coming. For example, the winding of lithium batteries, you know every word, but you don’t know it when you combine it. Some editors explained it this way: Anyone who has experienced military training knows how to fold a tofu block quilt; while winding is similar to a folded quilt, the upper quilt cover and the lower quilt cover will never meet, just like the positive and negative poles in a battery. They will never meet each other (the positive and negative poles will cause leakage when the positive and negative poles touch each other). Did you understand?

【The working principle of lithium battery winding process】

1. Mixing: Mix the positive or negative electrode powder and other ingredients evenly, and prepare it into a slurry.

2. Coating: Coat the slurry intermittently and evenly on the surface of the transmission current collector, dry it, and make the positive and negative pole piece rolls respectively.

3. Cold Lam: compact the coated pole piece to achieve proper density and thickness.

4. Cutting: The cold-pressed pole piece is rolled into large pieces first, and then divided into required small strips of positive and negative pole pieces.

5. Winding: Small strips of positive and negative pole pieces and separators are wound to form a bare cell.

6. Top sealing: wrap the bare cells with aluminum foil, and thermally seal the top and sides.

7. Inject: Add the electrolyte into the battery cell and completely seal the battery cell. (Environmental requirements: water should be removed before the cell is filled with liquid, and the process requires low humidity.)

8. Pre-formation: The positive and negative materials inside are activated by charging, and at the same time, a good SEI film is formed on the surface of the negative electrode.

9. Forming: make the final processing of the shape of the cell.

NMP solvent is used in the stage of lithium battery slurry batching, stirring and coating. Using the wet process, it is necessary to prepare the PVDF glue in advance (solute: PVDF, solution: NMP (N-methylpyrrolidone)). The quality of PVDF glue is very important to the internal resistance and electrical properties of the battery.

The factors that affect the glue are temperature and stirring speed:

• The higher the temperature, the yellowing of the glue will affect the adhesion;
• If the stirring speed is too high, it is easy to break the glue;
• The specific speed depends on the size of the dispersion disc: in general, the linear speed of the dispersion disc is 10-15m/s (highly dependent on equipment).
• At this time, it is required that the mixing tank needs to open the circulating water, and the temperature: ≤30℃.

So don’t look at NMP as just a small auxiliary solvent, but for the battery preparation process that requires precision, one more dust may cause great performance problems. Therefore, the battery preparation process is strict and strict, and the purity requirements for the NMP solvent are even more stringent.

The NMP solvent was produced and supplied by ZESHENG not only meets the national standards, but also has a complete testing certificate and a professional team of engineers; while providing products to prospective customers, it can also customize NMP waste gas recovery solutions. If prospective customers are worried that the purity of the recovered NMP waste liquid cannot be controlled, there is a professional team in the factory and third part certificates for your reference. Please contact us for more cooperation details.