Lithium battery explosion-proof technology -Lithium - Ion Battery Equipment

What explosion-proof technology does lithium battery have? -Lithium - Ion Battery Equipment

When a lithium-ion battery is charged, the lithium atoms in the positive electrode lose electrons and are oxidized into lithium ions. Lithium ions swim to the negative electrode through the electrolyte, enter the storage compartment of the negative electrode, obtain an electron, and are reduced to lithium atoms. When discharging, the entire process is reversed. In order to prevent the positive and negative electrodes of the battery from directly touching each other and causing a short circuit, a separator paper with many pores is added to the battery to prevent short circuits. A good separator paper can also automatically close the pores when the battery temperature is too high, making it impossible for lithium ions to pass through, thereby defeating the purpose and preventing danger.(Lithium - Ion Battery Equipment)


After the lithium-ion battery cell is overcharged to a voltage higher than 4.2V, it will begin to have secondary uses. The higher the overcharge voltage, the higher the risk. After the lithium battery cell voltage is higher than 4.2V, the number of lithium atoms remaining in the positive electrode material is less than half. At this time, the memory cells often collapse, causing a permanent decrease in battery capacity. If charging continues, since the storage compartment of the negative electrode has been filled with lithium atoms, subsequent lithium metal will accumulate on the surface of the negative electrode material. These lithium atoms will grow dendrites from the surface of the negative electrode in the direction of the lithium ions. These lithium metal crystals will pass through the separator paper and short-circuit the positive and negative electrodes. Sometimes the battery explodes before a short circuit occurs. This is because during the overcharge 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 atoms accumulated on the surface of the negative electrode. And then explode. Therefore, when charging a lithium-ion battery, the upper voltage limit must be set so that the battery life, capacity, and safety can be taken into account at the same time. The ideal upper limit of charging voltage is 4.2V. Lithium batteries also need to have a lower voltage limit when discharging. 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 discharged, the lower the voltage will be. Therefore, it is best not to stop discharging at 2.4V. During the period when a lithium-ion battery is discharged 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 voltage limitation, current limitation is also necessary. When the current is too large, lithium ions have no time to enter the storage location and will accumulate on the surface of the material. After these lithium ions obtain electrons, lithium atoms will crystallize on the surface of the material. This is the same as overcharging and will cause danger. If the battery case ruptures, it will explode.

Therefore, the protection of lithium-ion batteries must at least include: upper limit of charging voltage, lower limit of discharge voltage, and upper limit of current. Generally, in a lithium-ion battery pack, in addition to the lithium-ion battery core, there will be a protective plate. This protective plate mainly provides these three protections. However, these three protections of the protective board are obviously not enough, and lithium-ion battery explosion incidents are still frequent around the world. To ensure the safety of the battery system, a more careful analysis must be conducted on the causes of battery explosions.



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