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LEV Battery overcharge mechanism and measures to prevent overcharge

LEV Battery overcharge mechanism and measures to prevent overcharge

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Welcome to buy the cheapest and best quality LEV Battery products by Manufacturers china.

Overcharging is one of the most difficult items to pass in the current LEV Battery safety test. Therefore, it is necessary to understand the LEV Battery overcharging mechanism and current measures to prevent overcharging.

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NCM+LMO/Gr system battery voltage and temperature curve when overcharged. The voltage reaches its maximum at 5.4V, and then the voltage drops, eventually causing thermal runaway. The voltage and temperature curve of overcharged ternary battery is very similar to that of LEV Battery.
When LEV Battery is overcharged, heat and gas are generated. Heat includes ohmic heat and heat generated by side reactions, of which ohmic heat is the main component. The side reaction of the battery caused by overcharge is firstly that excessive lithium is inserted into the negative electrode, and lithium dendrites will grow on the surface of the negative electrode (the N/P ratio will affect the initial SOC of the growth of lithium dendrites). Secondly, excessive lithium is released from the positive electrode, causing the structure of the positive electrode to collapse, releasing heat and releasing oxygen. Oxygen will accelerate the decomposition of the electrolyte, the internal pressure of the battery will continue to rise, and the safety valve will open after a certain degree. The contact between the active material and the air will further generate more heat.
Studies have shown that reducing the amount of electrolyte will significantly reduce heat and gas production during overcharging. In addition, it has been studied that when the battery is overcharged without a splint or the safety valve cannot be opened normally, the LEV Battery is prone to explosion.
Slightly overcharging will not cause thermal runaway, but will cause capacity degradation. The study found that when the battery with the NCM/LMO mixed material as the positive electrode is overcharged, the capacity of the SOC is lower than 120%, and the capacity will be significantly attenuated when the SOC is higher than 130%.
There are roughly the following methods to solve the overcharge problem:
1) The protection voltage is set in the BMS, usually the protection voltage is lower than the peak voltage during overcharge;
2) Improve the resistance to overcharge of LEV Battery through material modification (such as material coating);
3) Add anti-overcharge additives, such as redox couples, to the electrolyte;
4) The use of voltage sensitive film, when the LEV Battery is overcharged, the film resistance is significantly reduced, which plays a role of shunting;
5) OSD and CID designs are used in square aluminum shell batteries, which are currently the universal anti-overcharge design. The soft pack battery cannot achieve a similar design.