Understanding the Factors Behind Lithium Iron Phosphate Battery Swelling

Lithium iron phosphate batteries, as the leading power batteries, are widely used in products like electric vehicles, industrial equipment, smart manufacturing, and warehousing. Many of these products use lithium iron phosphate batteries. However, during their usage, it's common to find that these batteries tend to swell, regardless of whether it's winter or summer. Once the battery swells, it affects its performance, which is detrimental to the battery product. So, what exactly causes the swelling of lithium iron phosphate batteries?

Manufacturing Level The swelling of lithium-ion batteries may be due to the manufacturing level of the lithium iron phosphate battery pack. Inconsistencies in electrode coating and a rough production process can be contributing factors.

Swelling Due to Overcharging Overcharging can cause all lithium atoms in the cathode material to move into the anode material. This leads to the original cathode becoming deformed and collapsing. This is also a significant reason for the decline in the battery capacity of lithium iron phosphate batteries. In this process, an increasing number of lithium ions deposit on the anode, causing the lithium atoms to grow into dendrites and crystallize, leading to battery expansion.

Prolonged Storage Lithium iron phosphate batteries can also swell if left unused for an extended period, as air has a certain conductivity. If the battery is left for too long, it's akin to a direct contact between the positive and negative electrodes, leading to a chronic short circuit.

Excessive Expansion During the first charge and discharge process of a liquid lithium-ion battery, the electrode material reacts with the electrolyte at the solid-liquid interface, forming a passivation layer that covers the surface of the electrode material. This formed passivation layer, known as the Solid Electrolyte Interface (SEI), can effectively prevent the passage of electrolyte molecules, while Li+ can freely embed and permeate through the SEI. The SEI is not static. It undergoes changes during the charge-discharge process, mainly reversible changes of organic substances. After over-discharging a lithium iron phosphate battery, the SEI undergoes reversible damage. Once the SEI protecting the anode material is damaged, the anode material collapses, leading to swelling.

Short Circuit The intense reaction from a short circuit can produce a lot of heat, causing the electrolyte to decompose and evaporate, leading to battery expansion.

Low-quality Battery Chargers Chargers made of low-quality circuit boards or inferior components can be problematic. Due to inaccurate heating and parameter drift, the charging voltage limit becomes uncontrolled, leading to the deformation of the internal gas kneading of the lithium-ion battery. This can cause the battery casing to crack or even explode.

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