Why does the battery bulge in normal use or if it is not used for a long time?

There are two phenomena of bulging in the process of charging and discharging: one. The overcharge caused by overcharge will cause all the lithium ion atoms in the positive electrode material to run into the negative electrode material, causing the original full grid of the positive electrode to deform and collapse, which is also an important reason for the decline in the power of the lithium ion battery. In this process, the negative electrode has more and more lithium, and the excessive accumulation makes the lithium ion atoms grow out of the tree stump crystals, causing the battery to swell. two. The bulging caused by over-discharge During the first charge and discharge process of the liquid lithium ion battery, the electrode material and the electrolyte react at the solid-liquid interface to form a passivation layer covering the surface of the electrode material. The formed passivation film can effectively prevent the passage of electrolyte molecules, but Li+ can be freely inserted and extracted through the passivation layer, which has the characteristics of a solid electrolyte, so this passivation film is called a solid electrolyte interface film (solidelectrolyteinterface), referred to as SEI. The SEI film has a protective effect on the negative electrode material, so that the material structure is not easy to collapse, and the cycle life of the electrode material can be increased. The SEI film is not static, there will be a little change during the charging and discharging process, the important thing is that some organic matter will undergo reversible changes. After the battery is over-discharged, the SEI film will be reversibly broken, and the SEI protecting the negative electrode material will collapse after the destruction of the negative electrode material, thereby forming a bulging phenomenon. 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: Are lithium ion battery packs really environmentally friendly than lead-acid batteries?