The polymer lithium-ion battery cell adopts the packaging technology of aluminum-plastic composite film. 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 (there are two kinds of slight bulging and severe bulging). situation), and regardless of the appearance, the performance of the battery cell (Capacity, Cyclelife, C-rate, etc.) will fail seriously, resulting in the battery cell being unusable.

Flatulence can occur during production and in the hands of customers and even end users. Of course, the battery cell will normally generate a certain amount (usually very little) of gas during the process of forming and starting or Baking, which varies according to the raw materials used, and this gas will be pumped out in the Degassing process.

At present, some Models (one-time packaging and molding battery cells) add V18 solvent to eliminate the gas generated when the SEI layer is formed and the phase interface is stable. However, the gas generated due to abnormal process is very obvious on the surface before Degassing or after Degassing can no longer be eliminated or V18 can not be eliminated. Here is a brief introduction to the causes of abnormal gas production in the process:

1. Poor packaging: The proportion of flat battery cells caused by poor packaging has been greatly reduced. The reasons for the poor sealing of Topsealing, Sidesealing and Degassing have been described above. Poor sealing on either side will lead to battery cells. Topsealing and Degassing are the most common. Topsealing is mainly caused by poor sealing of the Tab position, and Degassing is mainly caused by delamination (including electrolysis. Liquid and gel effects lead to detachment of PP from Al). Poor packaging causes moisture in the air to enter the interior of the battery cell, causing the electrolyte to decompose and generate gas, etc.

2. Damage to the surface of the Pocket: During the flow-pulling process of the battery cell, the Pocket is damaged by abnormal damage or man-made damage (such as pinholes), which allows 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 Al damage (the larger the battery cell, the larger the air bag, the easier it is to break), and the barrier to water will be lost. Wrinkle glue or hot-melt glue can be added to the corners for relief. 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 swing of the battery cell on the aging board.

4. The water content inside the battery core exceeds the standard: We have already introduced that there are certain requirements for the water content in the battery core. Once the water content exceeds the standard, the electrolyte will fail and gas will be generated 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 causes flatulence, a retrospective inspection of the process can be carried out.

5. Abnormal formation process: Wrong formation process will cause flatulence in the battery cell.

6. The SEI film is unstable: 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 the machine or the protection board, the battery cell is overcharged or overdischarged, and the battery cell will be seriously inflated.

8. Short circuit: The contact between the two Tabs of the charged cell is short-circuited due to operational errors, 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 the cathode and anode inside the battery cell causes the cell to rapidly discharge and heat up, and at the same time, it is seriously inflated. There are many reasons for internal short circuits: design problems; isolation diaphragm shrinkage, curling, breakage; Bi-cell dislocation; burr piercing isolation diaphragm; excessive clamp pressure; For example, due to insufficient width, the ironing machine over-extruded the cell body, resulting in short-circuiting of the cathode and anode and flatulence.

10. Corrosion: The battery core is corroded, the aluminum layer is consumed by the reaction, and the barrier effect on water is lost, resulting in flatulence. 11. Abnormal vacuum pumping: The system or machine causes abnormal vacuum degree, and the Degassing pumping is not complete; Not clean.

Can the soft-pack lithium battery still be used for flatulence?

1. If the agitation is obvious, it means that the battery is broken.

2. Under normal circumstances, such a battery will become very insufferable or even uncharged and unusable, and it will cause potential safety hazards.

3. It is recommended that users replace the battery as soon as possible to avoid affecting normal use.

Shenzhen Topband Battery Co., Ltd.，established in 2006, is a wholly-owned subsidiary of Shenzhen Topband Co., Ltd. (002139.SZ). We focus on lithium iron phosphate batteries,with independent research and development in cells and BMS. With the ability to integrate the entire industry chain, we are committed to providing customers with one-stop lithium battery solutions and services. Our quality products are widely used in energy storage and light power.