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Why does the battery bulge?
        Polymer lithium ion battery with aluminum film packaging technology, when the battery internal gas due to abnormal chemical reaction, the Pocket will be filled up, ballooning pool core (a slight bulge and severe ballooning two cases), no matter how ballooning situation, battery performance of batteries (Capacity, Cycle life, C - rate, etc.) will be serious failure, lead to the battery can't use.

        1. Battery swelling caused by the use end:
1) Overcharge and overdischarge: These two factors will cause a violent reaction similar to short circuit in the battery during the use of the battery, generating a large amount of heat, which will lead to the decomposition and gasification of the electrolyte and the battery will be inflated.
2) Long-term storage (especially for fully charged bears)
3) Large current charge and discharge.
4) Damaged water enters the battery.

        2. Battery bulge caused by manufacturing design end:
1) Poor packaging, which causes the water in the air fluoride to enter the cell core and the electrolyte decomposition to produce gas, etc.
2) Pocket surface is damaged, and the battery cell is often damaged or artificially damaged in the current drawing process, which causes Pocket damage (such as pinhole) and causes water to enter the cell.
3) Angular position damage. Due to the special deformation of the folded corner aluminum, the air bag shaking will distort the angular position, leading to the damage of the aluminum plastic film (the bigger the cell is, the bigger the fluorine bag is, the more likely it will be damaged), and the blocking effect of water sealing will be lost.Can be added in the Angle pecked grain xing or ripe melt xing to alleviate.It is forbidden to move the cell with air bag in each process after the top sealing, and more attention should be paid to the operation mode to prevent the swing of the cell on the aging board.
4) Abnormal forming process. The wrong forming process leads to gas expansion in the battery cell.
5) Excessive amount of water in the battery. I have introduced earlier that there are certain requirements on water content in the battery cell. Once the water content is exceeding, electrolyte assing will be invalid and gas generation after Degassing.The main reasons for the excessive water content in the battery include: the electrolyte water content exceeds the standard, the water content of bare cell after Baking exceeds the standard, and the humidity in the drying room exceeds the standard.
6) THE SEI film is unstable, and the battery cell slightly bulges during capacity test charging and discharging.
7) Short circuit: Due to the operation error, the contact between two tabs in the live battery cell will be short circuit, and the battery cell will inflate and the voltage will drop rapidly, so the Tab will be burned black.
8) Internal short circuit, cathode short circuit inside the cell leads to rapid discharge and heating of the cell and serious gas swelling.There are many reasons for internal short circuit: design problems;Shrinkage, crimp and damage of the isolation film;Burrs Pierce the isolation membrane.
9) Corrosion occurs in the cell, and the aluminum chips are consumed by the reaction. The water barrier is lost and gas bloating occurs.
10) Abnormal vacuum extraction, which is caused by system or machines and Degassing of vacuum degree is not complete;Vacuum Sealing of ripe radiation area is too large, resulting in Degassing of gas bayonets which cannot punctures Pocket bags effectively and leads to gas pollution.