Lithium Battery Expansion Damage

Enclosure characteristics
Lithium, with an atomic number of 3 and an atomic weight of 6.941, is the lightest alkali metal element. To improve safety and voltage, scientists have invented materials such as graphite and lithium cobalt oxide to store lithium atoms. The molecular structure of these materials forms tiny storage lattices at the nanometer level, which can be used to store lithium atoms. In this way, even if the battery shell ruptures and oxygen enters, the oxygen molecules are too large to enter these small storage cells, preventing lithium atoms from coming into contact with oxygen and preventing explosion.
protective measures
After overcharging the lithium battery cell to a voltage higher than 4.2V, it will begin to have side effects. The higher the overcharge voltage, the higher the risk. When the voltage of a lithium battery cell is higher than 4.2V, the number of lithium atoms remaining in the positive electrode material is less than half. At this time, the storage cell often collapses, causing a permanent loss of capacity in the battery. If you continue to charge, because the storage cell of the negative electrode is already filled with lithium atoms, subsequent lithium metal will accumulate on the surface of the negative electrode material. These lithium atoms will grow dendritic crystals from the negative electrode surface towards the direction of lithium ions. These lithium metal crystals pass through the membrane, shorting the positive and negative electrodes. Sometimes the battery explodes before a short circuit occurs, because during the overcharge process, materials such as electrolyte will decompose to produce gas, causing the battery shell or pressure valve to bulge and rupture, allowing oxygen to enter and react with lithium atoms accumulated on the surface of the negative electrode, leading to an explosion.
Therefore, when charging a lithium battery, it is necessary to set the upper voltage limit to take into account both the battery life, capacity, and safety. The optimal upper charging voltage limit is 4.2V. When discharging lithium batteries, there should also be a lower voltage limit. When the core voltage is lower than 2.4V, some materials will begin to be damaged. Due to the fact that the battery will self discharge and the voltage will decrease as it is discharged for a long time, it is best not to stop discharging until it reaches 2.4V. During the period of discharging from 3.0V to 2.4V, the energy released by a lithium battery only accounts for about 3% of the battery capacity. Therefore, 3.0V is an ideal discharge cutoff voltage. During charging and discharging, in addition to voltage limitation, current limitation is also necessary. When the current is too high, lithium ions do not have time to enter the storage cell, and will gather on the surface of the material.
After these lithium ions gain electrons, they will generate lithium atom crystals on the surface of the material, which, like overcharging, can cause hazards. Should the battery shell break, it would explode. Therefore, the protection of lithium ion batteries should include at least three items: the upper limit of charging voltage, the lower limit of discharge voltage, and the upper limit of current. In general, in addition to the lithium battery cells, there is a protective plate inside a lithium battery pack, which mainly provides these three protections. However, the three protections provided by the protective plate are obviously insufficient, and the global lithium battery explosion incidents are still frequent. To ensure the safety of the battery system, it is necessary to conduct a more careful analysis of the cause of the battery explosion.