What are the major causes of flatulence in soft-pack lithium batteries?

At present, some models (one-time packaging and molding battery cells) add V18 solvent to eliminate this kind of gas that occurs in the formation of the SEI layer and the stable and on-time interface of the phase interface. However, the gas that appears due to process abnormalities is very clear on the front surface of Degassing or cannot be eliminated after Degassing, or the addition of V18 cannot be eliminated. Here is a brief analysis of the causes of abnormal gas in the process: 1. Poor packaging: The proportion of bloated battery cells caused by poor packaging has been greatly reduced. The causes of poor packaging on the three sides of Topsealing, Sidesealing and Degassing have already been analyzed. Poor packaging on any side will lead to battery cells. Topsealing and Degassing are the most common. Topsealing is mainly due to poor sealing of the Tab position, and Degassing is mainly due to delamination (including electrolysis). The influence of liquid and gel causes pp to separate from Al). Poor packaging causes moisture in the air to enter the battery core, causing gas to appear in the electrolyte analysis. 2. The surface of the pocket is damaged: the battery cell is abnormally damaged or artificially damaged during the flow process, which causes the pocket to be damaged (such as pinholes) and moisture enters the battery cell. 3. Corner damage: Due to the special deformation of the aluminum at the corners of the flange, the air bag shaking will twist the corner and cause Al damage (the larger the battery cell, the larger the air bag, the easier it is to break) and lose its use as a barrier to water. Wrinkle glue or hot melt glue can be added to the corner to relieve it. In addition, it is forbidden to move the battery cell by air bag in each process after the top seal, and pay more attention to the operation method to guard against the swing of the battery cell on the aging board. 4. The internal water content of the battery core exceeds the standard: We have already analyzed 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 appear after formation or degassing. The main reasons that cause the internal water content of the battery to exceed the standard are: the electrolyte water content exceeds the standard, the water content of the bare cell after Baking exceeds the standard, and the humidity in the drying room exceeds the standard. If it is suspected that excessive water content 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 emits a little flatulence during the capacity detection charging and discharging process. 7. Overcharge and over-discharge: The battery cell will be overcharged or over-discharged due to the abnormality of the process, the machine or the protection board, and the battery cell will be severely out of air. 8. Short circuit: due to operating errors, the two tabs of the charged battery cells are short-circuited, the battery cells will swell and the voltage will drop rapidly, and the tabs will be burnt black. 9. Internal short circuit: The internal short circuit of the anode and cathode of the battery cell causes the battery cell to quickly discharge and generate heat at the same time severely inflated. There are many reasons for the internal short circuit: design problems; shrinkage, curling, and breakage of the isolating film; dislocation of Bi-cell; burrs piercing the isolating film; excessive clamp pressure; excessive squeezing of the edge ironing machine, etc. For example, due to insufficient width, the edge ironing machine excessively squeezed the body of the cell, which caused the cathode and anode to short-circuit and swell. 10. Corrosion: The battery core is corroded, the aluminum layer is consumed by the reaction, and it loses its barrier to water and causes flatulence. 11. Abnormal vacuum pumping: The vacuum degree is abnormal due to the system or machine. Degassing pumping is not complete; the heat radiation area of u200bu200bVacuum Sealing (vacuum sealing) is too large, which causes the Degassing pump bayonet to not effectively pierce the pocket bag and cause pumping. Not clean. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Why did Tesla Motors choose 18650 lithium-ion batteries?