For Pouch Lithium Battery
The main process that plays the role of battery sealing is the packaging process. The quality of the packaging directly determines the performance of the battery.
Simply, if we want to clear about the main reasons of leakage of pouch lithium batteries, it needs to be analyzed specifically from the type of leakage. Generally speaking, the leakage causes of aluminum-plastic film can be divided into three categories：
For lithium-ion batteries, HF is produced due to the reaction of moisture with the electrolyte. HF is a particularly corrosive acid, which can cause serious damage to aluminum-plastic films, fluid collectors, and cathode materials.
The following are the related chemical reactions:
LiPF6 → LiF + PF5
PF5+H2O → POF3 + 2HF
Pouch lithium battery leakage caused by electrochemical reactions are more difficult to detect. Generally, as the use time becomes longer, the pouch lithium battery leakage will gradually become serious. Due to the long latent time of this failure mode, once it occurs, it can easily cause a crisis of customer trust.
There are generally two conditions under which electrochemical corrosion occurs：
①ion short circuit.
An ion short-circuit channel is formed between the aluminum layer of the aluminum-plastic film and the anode.
②electronic short circuit.
The aluminum layer of the aluminum-plastic film forms an electronic short-circuit channel with the anode.
③Unconsciously contact the negative electrode ear with the aluminum layer externally
After the aluminum layer is corroded, the moisture can be immersed into the inside of the battery unscrupulously, resulting in more intense damage and causing the appearance of the soft-packed battery to leak.
1. overcharge, over discharge, high temperature use
2. Pierce and hit
3. Battery swelling
4. The aging of the sealant causes cracks in the seal
For polymer pouch batteries, you need to confirm the following points:
1.Whether there are burrs in the pole ear, causing damage to the aluminum-plastic film;
2.Whether the width and thickness of the pole ear are appropriate, the pole ear should be heated when charging and discharging;
3.The thermal encapsulation process, that is, whether it is indeed sealed;