Causes of lithium-ion battery explosion and battery protection measures

Causes of lithium-ion battery explosion 1. Large internal polarization; 2. The pole piece absorbs water and reacts with the electrolyte; the gas drum; 3. The quality and performance of the electrolyte itself; 4. The amount of liquid injected cannot reach the process when the liquid is injected Requirements; 5. The laser welding sealing performance in the assembly process is poor, and the air leaks when detecting air leakage; 6. Dust and pole piece dust are likely to cause micro short circuits at first; 7. The positive and negative plates are thicker than the process range, and it is difficult to enter the shell; 8 , The problem of liquid injection sealing, the poor sealing performance of the steel ball leads to air bulging; 9. The shell wall is too thick in the incoming material, and the deformation of the shell affects the thickness; 10. The high temperature of the outside environment is also an important reason for the explosion. Protection measures taken by the battery After the lithium-ion battery cell is overcharged to a voltage higher than 4.2V, side uses will begin to appear. The higher the overcharge voltage, the higher the risk. When the voltage of the lithium ion battery cell is higher than 4.2V, the number of lithium ion atoms remaining in the positive electrode material is less than half. At this time, the storage cell often collapses, causing a permanent decrease in battery capacity. If you continue to charge, since the storage cell of the negative electrode has been filled with lithium ion atoms, the subsequent lithium ion metal will accumulate on the surface of the negative electrode material. These lithium ion atoms will grow dendrites from the surface of the negative electrode to and from the lithium. These lithium ion metal crystals will pass through the separator paper and short-circuit the positive and negative electrodes. Sometimes the battery explodes before the short circuit occurs. This is because during the overcharging process, the electrolyte and other materials will crack and produce gas, causing the battery shell or pressure valve to swell and rupture, allowing oxygen to enter and react with the lithium ion atoms accumulated on the surface of the negative electrode. , And then exploded. Therefore, when charging a lithium-ion battery, the upper limit of the voltage must be set so that the battery's life, capacity, and safety can be taken into account at the same time. The most ideal upper limit of the charging voltage is 4.2V. There is also a lower voltage limit when discharging lithium ion batteries. When the cell voltage is lower than 2.4V, some materials will begin to be destroyed. And because the battery will self-discharge, the longer it is left, the lower the voltage will be. Therefore, it is best not to stop when the battery is discharged to 2.4V. During the period of lithium ion battery discharge from 3.0V to 2.4V, the energy released only accounts for about 3% of the battery capacity. Therefore, 3.0V is an ideal discharge cut-off voltage. When charging and discharging, in addition to the voltage limit, the current limit is also necessary. When the current is too large, lithium will not have time to enter the cell and will accumulate on the surface of the material. After these lithium gain electrons, lithium ion atoms will crystallize on the surface of the material, which is the same as overcharging and can cause danger. If the battery casing ruptures, it will explode. Therefore, the protection of lithium-ion batteries must include at least three items: the upper limit of the charging voltage, the lower limit of the discharge voltage, and the upper limit of the current. Generally, in the lithium-ion battery pack, in addition to the lithium-ion battery core, there will be a protective board. This protective board is important to provide these three protections. 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: What is the difference between an electric vehicle battery and an electric vehicle battery pack