Why are the lithium-ion battery packs of electric vehicles bulging?

When a lithium ion battery is charged, the lead sulfate on the positive and negative plates and the water in the electrolyte are chemically reacted, so that the positive plate is reduced to lead oxide, and the negative plate is reduced to pure lead. The temperature of the lithium-ion battery pack will increase. At the same time, if a large amount of gas is released, there will be insufficient space inside the battery to store these gases, which will cause the battery to swell. Reason 2: The internal resistance of the lithium-ion battery is too high. When the internal resistance of a battery is too high, when the current is constant, the voltage will be very high (voltageu003dcurrent*resistance). What we can see is that the battery is very hot before the red light jumps during normal charging, that is, the battery has not reached the charging voltage, and the gas is gassed in advance! Reason three: the electric vehicle charger does not meet the requirements. When the parameters of the electric vehicle charger we use are higher than the rated voltage and current of our battery, it is possible to charge the lithium-ion battery pack! Intimate tips: 1. Use an electric vehicle charger that meets the requirements. Go to the lithium-ion battery repair point for a special charger test. Many places are now tested for free. Two: Check the battery regularly and do maintenance for the lithium-ion battery pack, which can extend the service life of the battery and increase the service life of the electric vehicle. Three: It is not suitable to overcharge for a long time. There are two phenomena of bulging of lithium-ion battery packs in the process of charging and discharging: 1. The bulging caused by overcharging will cause all the lithium atoms in the positive electrode material to run into the negative electrode material, causing the original full grid of the positive electrode to occur. Deformation and collapse, which is also an important reason for the decline in the power of the lithium-ion battery pack. In this process, there are more and more lithium ions in the negative electrode, and the excessive accumulation makes the lithium atoms grow out of the tree stump crystals, causing the battery to swell. 2. Lithium-ion battery bulging caused by over-discharge During the first charge and discharge of liquid lithium-ion battery, the electrode material and electrolyte react at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. The formed passivation layer film can effectively prevent the passage of electrolyte molecules, but Li+ can be freely inserted and extracted through the passivation layer. It has the characteristics of a solid electrolyte. The SEI film is not static, and there will be a little bit during the charge and discharge process. The important thing is that some organic matter will undergo reversible changes. After the battery is over-discharged, the SEI film is reversibly broken, and the SEI that protects the negative electrode material collapses after the destruction of the negative electrode material, thereby forming the bulging phenomenon of the lithium ion battery pack. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Introduction to the internal structure and characteristics of the 18650 cylindrical lithium battery