What causes lithium-ion batteries to swell?
1. Over-discharge and over-charge of lithium-ion batteries;
2. Micro-short circuit, which means that the separator is damaged, causing partial contact between the positive and negative electrodes inside the battery;
3. Continuous float charging of lithium-ion batteries at high temperatures can cause side reactions in the electrolyte, as can high-rate charging and discharging at high temperatures. This problem is generally not encountered in civilian use.
4. Low-temperature charging also results in lithium plating piercing the separator and causing a micro-short circuit;
5. The aluminum-plastic film of the outer packaging was corroded;
6. Incomplete vacuuming or use in high-altitude environments can have a significant impact, especially since mobile phone batteries are typically packaged in soft packaging.
What happens when a lithium-ion battery expands due to heat?
Lithium-ion battery swelling, commonly known as bulging, occurs because various factors such as short circuits, excessive current, or internal punctures cause rapid changes in the internal chemical composition of the positive and negative electrode materials. This leads to the formation of gas due to high temperatures. Since batteries are highly sealed products, this gas cannot escape and bulges out through the outer casing, creating more space for the gas to accumulate. Because the bottom and sides of the battery are thicker and have a smaller surface area than the front and back, bulging usually occurs on the front and back sides.
