18650 lithium battery production process

Preparation of pole pieces

(1) Ingredients

Positive electrode: put a proportion of polyvinylidene fluoride (PVDF) and nitrogen methylpyrrolidone (NMP) into the stir, mix in the mixer and adjust the stirrer speed; then add the positive active material and carbon black, vacuum, adjust the speed of the agitator.

Negative electrode: Mix the latex and water in a blender and mix to adjust the stirrer speed; then add CMS, vacuum and adjust the stirrer speed.

(2) Coating

The aluminum strip (the negative electrode is a copper strip) is placed flat on the coater, and the aluminum strip is not biased, wrinkle-free, smooth belt, no leakage, no slip. Spread the prepared slurry evenly on the machine and set the corresponding parameters.

These include the positive draw speed, the negative draw speed, the oven temperature, and the coating width. In the process of carrying, observe whether the slurry is straight, no inclination, no misalignment, and whether the thickness of the slurry coated on the aluminum strip (copper strip) is uniform, consistent.

(3) Vacuum drying

The coated positive and negative electrodes were placed in a vacuum oven for drying, and the degree of vacuum was -0.09MPa.

(4) Cut large pieces

Cutting the coated positive electrode sheet into a certain length (depending on the specific battery design), the film cutting machine walking speed is 55mm/min, and the incision is required to be free of burrs.

(6) Scraper

The slurry at one end of the positive and negative electrode sheets was scraped off to prepare for ultrasonic spot welding, and the double-sided blade was used.

(7) Rolling

The strip polar sheet is pressed into a polar sheet of a certain thickness for winding. The thickness of the polar sheet is strictly controlled when the sheet is pressed. The head and tail deviation of the polar sheet after rolling shall not be greater than 0.010mm. At the same time keep the tablet press clean, every 2 hours with alcohol to clean the tablet press.

(8) Cut small pieces

Cut the large piece into strips of certain width (according to the specific battery design), and the incisions shall be free from burrs.

1) Welding tab

The positive terminal lug (aluminum strip) and negative terminal lug (nickel strip) were respectively welded to the scraper positions of positive and negative terminal sheets by ultrasonic welding machine. Pay attention to prevent welding deviation, welding dislocation, virtual welding.

(2) Winding

Ion exchange membrane flush on mounting, and out the front roll needle 2-5 mm, pole piece four corners there can be no crease, pole piece don't fall material, adhesive stick oblique, single sided tape dislocation around too long, double-sided tape, tape did not cover defects such as solder joints, the anode materials must hold the shoe anode materials, sheet cannot be partial, pole piece front end must be stuck to.

Check the winding defects: the ion exchange membrane is not uniform, that is, the positive and negative poles beyond the exchange membrane; Slice high slice low; The pole piece is not put in place, the positive end of the outer ring is not locked to the negative end, and the positive and negative end of the inner ring is not coincident with the top of the exchange film, there is still a distance; The exchange membrane holds the negative pole too tight; The positive aluminium strip and the negative nickel strip are longer and shorter. Poor adhesive tape at the end of the cell; The battery cell is not rolled in place: the spacing between positive and negative ears is wide or narrow; The exchange membrane is not flattened and wrinkled; Positive pole curling; The positive plate has no roll Angle and lacks Angle; The exchange membrane does not fully embrace the negative end; The inner and outer polar plates are misaligned.

(3) Bottom welding

First put the insulation gasket into the steel shell, and then put the coiled cell into the steel shell, and use the spot welder to weld the negative pole ear on the bottom of the steel shell. Check the outer surface of the bottom of the steel shell, and pick out the bad appearance such as point yellow, point black, defect and blast, etc., and try to pull out the pole ear, and pick out the batteries that are not firmly spot welded such as blast, false welding and de-welding.

(4) Sealing

Firstly, the battery's steel shell and cover were spot-welded together with a spot welding machine, and then the battery was continuously welded by a laser welding machine. Laser welding shall ensure accurate positioning and clean welding site. It is strictly prohibited to cause battery deformation or damage. After welding, check and repair welding for defective batteries such as welding holes and blowouts.

(5) baking

Under the condition of constant temperature and vacuum degree of -0.09MPa, the main purpose of baking for 12 hours is to dry the moisture of the cell.

(6) Injection

The cell after vacuum baking is injected with electrolyte in the glove box filled with Ar gas. The amount of liquid injection is different according to the battery design. The battery should be weighed before and after liquid injection.

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