(1) Baking
Baking for 12 hours under constant temperature and vacuum conditions of -0.09MPa is primarily to dry out the moisture in the battery cells.
(2)Injection
After vacuum baking, the battery cells are injected with electrolyte in a glove box filled with Ar gas. The amount of electrolyte injected varies depending on the design of the lithium-ion battery pack. The battery is weighed before and after the electrolyte injection, and the weight difference is the amount of electrolyte injected, which is used to determine whether the amount of electrolyte injected is appropriate.
(3) Welding the electrode tabs: Weld the positive electrode tab (aluminum strip) and negative electrode tab (nickel strip) to the scraper positions of the positive and negative electrode plates respectively using an ultrasonic welding machine. Take care to prevent welding deviation, welding misalignment, and incomplete welding.
(4) Bottom welding. First, place the insulating pad into the steel shell, then place the wound battery cell into the steel shell, and use a spot welding machine to weld the negative electrode tab to the bottom of the steel shell. Inspect the outer surface of the bottom of the steel shell, and pick out those with poor appearance such as yellow spots, black spots, defects, and sparks. Test pull the electrode tabs and pick out 18650 lithium-ion battery packs with poor spot welding such as sparks, cold welds, and detachment.
(5) Seal
First, spot weld the steel casing and cap of the 18650 lithium-ion battery pack together using a spot welding machine. Then, use a laser welding machine for continuous laser welding. Laser welding should ensure accurate positioning and cleanliness of the welded area, and must not cause battery deformation or damage. After welding, inspect the battery and repair any defective batteries with weld holes, sparks, or other defects.
(6) Winding
Place the ion exchange membrane flat on the winding needle, with the front end extending 2-5mm beyond the needle. There should be no wrinkles at the four corners of the electrode. The electrode should not have any defects such as material loss, skewed tape, single-sided tape that is too long, double-sided tape that is misaligned, or tape that does not cover the solder joint. The positive electrode material must hold the negative electrode material firmly. The electrode should not be rolled off-center, and the front end of the electrode must be inserted to the top.
