The polymer lithium-ion battery cell adopts aluminum  laminated  film composite packaging technology. When gas is generated inside the battery cell due to the occurrence of abnormal chemical reactions, the pocket will be charged and the battery core will swell.The performance of the battery cell (Capacity, Cycle life, C-rate, etc.) will fail seriously, making the battery cell unusable.

1. Poor packaging, Top sealing, Side sealing and Degassing are the reasons for poor three-sided packaging. Poor packaging on either side will cause the battery core to swell, so you need to choose a suitable sealing machine.

2. The surface of the Pocket is damaged, and the battery cell is abnormally damaged or artificially broken during the flow and pulling process, which causes the Pocket to be damaged (such as pinholes) and allow moisture to enter the interior of the battery cell.

3. Corner damage, due to the special deformation of the aluminum at the folded corner, the shaking of the air bag will distort the angle and cause the Al to be damaged (the larger the battery cell, the larger the air bag, the easier it is to break), and the barrier to water will be lost.

4. The water content inside the battery cell exceeds the standard. Once the water content exceeds the standard, the electrolyte will fail and gas will be generated after formation or Degassing.

5. The operation process of the formation cabinet is abnormal, and the wrong formation process will lead to flatulence of the battery cells.

6. The SEI film is unstable, and the battery cell is slightly bloated during the charging and discharging process of the capacity test.

7. Overcharge and overdischarge, due to the abnormality of the process or machine or protection board, the battery cell is overcharged or overdischarged, and the battery cell will be seriously inflated.

8. Short circuit, due to operation errors, the contact between the two tabs of the charged cell will be short-circuited, the battery cell will be gassed and the voltage will drop rapidly, and the tab will be burnt black.

9. Internal short circuit, the short circuit of cathode and anode inside the battery cell causes the cell to rapidly discharge and heat up and at the same time serious gassing.

10. Corrosion, the battery core corrodes, the aluminum layer is consumed by the reaction, loses the barrier effect on water, and flatulence occurs.

11. Abnormal vacuum pumping, abnormal vacuum degree due to system or machine. Degassing pumping is not complete; the heat radiation area of Vacuum Sealing is too large, so that the Degassing pumping bayonet cannot effectively pierce the pocket bag, resulting in unclean pumping.

12. Secondly, the manufacturing process parameters should be strictly controlled to ensure the reliability of packaging and prevent flatulence caused by excessive moisture inside the battery. The control methods are as follows:

(1) After the battery core is wound, it should be fully dried to prevent the moisture content in the diaphragm from exceeding the standard;

(2) Strictly control the time from the cell to the liquid injection and the humidity of the drying room after vacuum baking;

(3) Ensure the tightness of the injection glove box;

(4) Control the moisture and free acid content in the electrolyte;

(5) Standardize the electrolyte storage environment and sealing conditions to prevent the electrolyte from entering excessive moisture during use and storage;

(6) Use closed-mouth pressure formation or external airbag formation and then vacuum and seal the exhaust;

(7) Adopt multi-step formation and high temperature shelving process to ensure complete gas production;