August 31, 2023
1. Poor packaging
The proportion of bloated battery cells caused by poor packaging has been greatly reduced. We have already introduced the reasons for poor packaging of Topsealing, Sidesealing, and Degassing. Poor packaging on any side will lead to battery cells. Topsealing and Degassing are the most common manifestations. Topsealing is mainly caused by poor sealing of the Tab position. Liquid and gel effects lead to the detachment of PP from Al). Poor packaging causes moisture in the air to enter the interior of the battery core, causing the electrolyte to decompose and produce gas.
2. The surface of the Pocket is damaged
During the flow-drawing process, the battery core is abnormally damaged or artificially broken, causing the Pocket to be damaged (such as pinholes), and moisture enters the inside of the battery core.
3. Corner damage
Due to the special deformation of the aluminum at the folded corners, the shaking of the air bag will distort the corners and cause Al damage (the larger the battery cell, the larger the air bag, and the easier it is to break), losing its use as a barrier to water. It can be relieved by adding wrinkle glue or hot melt glue to the corner. And in each process after top sealing, it is forbidden to use the air bag to move the battery cell, and more attention should be paid to the operation method to prevent the battery cell on the aging board from swinging.
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 appear after formation or Degassing. The main reasons for the excessive water content inside the battery are: the water content of the electrolyte exceeds the standard, the water content of the bare cell after Baking exceeds the standard, and the humidity of the drying room exceeds the standard. If it is suspected that the water content exceeds the standard and cause flatulence, a retrospective inspection of the process can be carried out.
5. Abnormal formation process
An incorrect formation process can lead to flatulence in the battery cell.
6. The SEI film is unstable
During the charge and discharge process of the capacity test, the emission function of the battery cell is slightly flattened.
7. Overcharge and overdischarge
Due to the abnormality of the process or the machine or the protection board, the battery core is overcharged or over-discharged, and the battery core will be severely inflated.
8. Short circuit
Due to misoperation, the contact between the two tabs of the charged battery cells is short-circuited, the battery core will be gassed and the voltage will drop rapidly, and the tabs will be burned black.
9. Internal short circuit
The short circuit of the cathode and anode inside the battery cell causes the battery cell to discharge rapidly and heat up, and at the same time, it is severely gassed. There are many reasons for internal short circuit: design problems; isolation film shrinkage, curling, damage; Bi-cell misalignment; burrs piercing the isolation film; excessive clamp pressure; For example, due to insufficient width, the ironing machine excessively squeezed the battery body, resulting in short-circuiting of the cathode and anode, and flatulence.
The battery core corrodes, the aluminum layer is consumed by the reaction, loses its barrier function to water, and flatulence occurs.
11. Abnormal vacuum pumping
The system or machine causes abnormal vacuum and incomplete degassing; the heat radiation area of VacuumSealing is too large, so that the degassing bayonet cannot effectively pierce the pocket bag, resulting in unclean degassing.
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