As a popular new energy battery, lithium iron phosphate batteries have become popular in recent years because of their own problems, such as whether lithium iron phosphate batteries can continue to be used, or how to repair or what is the cause of swelling . Next, we will make a comprehensive understanding of the protruding problem of lithium iron phosphate batteries.

LiFePO4 battery swelling

1. Reasons for the expansion of lithium iron phosphate batteries

(1) Manufacturing level

The bulging of lithium ion batteries may be the manufacturing level of lithium iron phosphate battery packs, the electrode coating is uneven, and the production process is relatively rough.

(2) Bumps caused by overcharging of lithium-ion batteries

Overcharging will cause all the lithium atoms in the positive electrode material to run into the negative electrode material, resulting in the deformation and collapse of the full grid of the original positive electrode, which is also an important reason for the decrease in the battery capacity of the lithium iron phosphate battery. During this process, more and more lithium ions are deposited on the negative electrode, causing the lithium atoms to grow into stumps and crystallize, causing the battery pack to swell.

(3) If the lithium iron phosphate battery is not used for a long time, swelling will also occur, because the air has a certain conductivity. Therefore, if the battery is left for too long, it is equivalent to direct contact between the positive and negative electrodes of the battery, resulting in a chronic short circuit.

(4) Excessive expansion

During the first charge-discharge process of a liquid lithium-ion battery, the electrode material reacts with the electrolyte at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. The formed passivation layer can effectively prevent the passage of electrolyte molecules, while Li+ can be freely embedded and exuded from the passivation layer, which has the characteristics of solid electrolyte. Therefore, this passivation layer is called SEI. SEI films are not set in stone. During the charging and discharging process, there will be some changes, the important ones are the reversible changes of organic matter. After the lithium iron phosphate battery pack is overdischarged, the SEI film will be reversibly damaged. When the SEI protecting the anode material is destroyed, the anode material collapses, resulting in a bulge phenomenon.

(5) The violent reaction of the short circuit will generate a lot of heat, which will decompose and evaporate the electrolyte and cause the battery to expand.

(6) Reasons for the low quality of lithium iron phosphate battery chargers. Chargers are made of low-quality circuit boards, innovative or low-quality components. Due to inaccurate heating and parameter drift, the charging voltage limit is out of control, resulting in kneading and deformation of the gas inside the lithium-ion battery, resulting in cracking or even bursting of the battery casing.

(7) Long-term use of lithium iron phosphate batteries will also cause swelling, because the air has a certain conductivity, so if the battery is placed too long, it is equivalent to direct contact between the positive and negative electrodes of the battery, resulting in a slow short circuit.

2. Repair the swelling of lithium iron phosphate battery

(1) When the battery expands, first seal the battery with plastic wrap and put it in the refrigerator to cool for about half an hour.
(2) Remove the battery after cooling down, and then remove the wrapping paper on the surface of the battery.
(3) Then use a needle to pierce a small hole on the surface of the lithium-ion battery package.
(4) Press with your fingers to discharge the gas in the battery.
(5) Seal the air holes with tape.

3. The expansion of lithium iron phosphate batteries will reduce the capacity

During the expansion process, the capacity of the lithium-ion battery pack is reduced, and the battery life is significantly shortened. In severe cases, battery life can be short or unusable. At this time, the battery is usually replaced, for safety or to buy a new battery.

4. Can the lithium iron phosphate battery still be used after it is fully charged?

It is not recommended to use the lithium iron phosphate battery after it is fully charged. During the charging process, the capacity of the lithium-ion battery pack decreases, and the battery life is significantly shortened. In severe cases, battery life can be short or unusable. At this time, the battery is usually replaced, for safety or to buy a new battery.

When the lithium-ion battery pack has bulging problems, it is best not to continue using the battery in question. Due to the expansion of the battery, when the expansion reaches a certain limit, it may cause an explosion, which is very dangerous. For your own safety, it is best to replace the lithium-ion battery pack as soon as you notice swelling.