Polymer soft pack battery is called lithium polymer battery, compared with liquid lithium battery, it has high energy density, smaller size, ultra-thin, lightweight, high safety and other obvious advantages. But the shortcomings remain the same, it is prone to bulge. Most lithium polymer battery are soft pack batteries with aluminum plastic film as the outer shell. Polymer soft pack battery can also be thinner, and their low-temperature discharge characteristics are better than lithium polymer battery, and the material energy density is basically the same as that of liquid lithium batteries and ordinary lithium polymer batteries, but because of the use of aluminum-plastic film, they are lighter than the ordinary liquid lithium batteries. In terms of safety, when the liquid is just boiling, the aluminum-plastic film of the soft pack battery will bulge at most, but it will not explode.
The bulge of polymer soft pack lithium battery is related to many factors such as the quality of the lithium battery, the method of use, and the environment.
1. Poor packaging: Moisture from the air enters the inside of the cell during the production process, causing the electrolyte to decompose and produce gas.
2. Water content of cell over standard: In the process, once the water content is over standard, the electrolyte will be invalid and produce gas.
3. Corrosion: The cell of polymer soft pack battery is corroded, the aluminum layer is consumed by the reaction, and loses the barrier effect of water, resulting in a bulge.
4. Surface damage: Damaged and punctured by external force cause moisture to enter the inside of the cell. In addition, the chemical properties of lithium materials are too active, which brings extremely high risks. When lithium metal is exposed to the air, it will produce a violent oxidation reaction with oxygen.
5. Knocking: Aluminum material is easy to deform, just need knock lightly. The larger the battery cell and the larger the airbag, it is easier to get damaged.
6. Short circuit: The contact between the positive and negative electrodes causes a short circuit, and the lithium polymer battery cell generates gas or even smoke.
7. Internal short circuit: Shrinkage, twisting, breakage, and burr piercing the isolating membrane of the soft pack lithium battery will cause an internal short circuit and bulge.
8. Overcharge and over-discharge: The polymer soft pack lithium battery is overcharged or over-discharged, the protection plate is abnormal, and the battery cell will be seriously bulging.