Reasons for bulging of lithium iron phosphate battery packs
1. Bulging caused by overcharging
Overcharging causes all the lithium atoms in the positive electrode material to migrate into the negative electrode material, leading to the deformation and collapse of the originally full grid in the positive electrode. This is a major reason for the decrease in the capacity of lithium-ion batteries. During this process, the number of lithium ions in the negative electrode increases, and excessive accumulation causes lithium atoms to grow into stumps and crystals, resulting in the swelling of the lithium-ion battery pack.
II. Bulging caused by over-discharge
The SEI film protects the negative electrode material, preventing structural collapse and extending cycle life. However, the SEI film is not static; it undergoes slight changes during charge and discharge, with some organic components experiencing reversible alterations. Over-discharge of lithium iron phosphate batteries causes reversible damage to the SEI film. This damage to the protective SEI leads to the collapse of the negative electrode material, resulting in bulging.
Third, there are issues with the manufacturing level of lithium iron phosphate battery packs, such as uneven electrode coating and relatively rough production processes.
