The same battery, why ternary lithium battery can not be fully charged, and lith
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2023/10/12 11:52:27
Ternary lithium battery and lithium iron phosphate battery are the two kinds of lithium batteries widely used in new energy vehicles, of which the user manual of the vehicle using ternary lithium battery will inform the user in daily use if not to run long distances, try not to full the battery, but to charge to 80% is appropriate.
The owner's manual for the lithium iron phosphate model tells the user that it is best to fully charge the battery once a week.
So are lithium batteries, why is there such a big difference in use? Today we're going to talk about that.
Why is ternary lithium not recommended to be filled
This is mainly related to the characteristics of the positive electrode material. Lithium batteries essentially rely on the back and forth movement of lithium ions and electrons to generate current and store electricity. When charging, electrons and lithium ions escape from the positive electrode to the negative electrode. The discharge of lithium ions and electrons from the negative electrode to the positive electrode. If the lithium ions flow to the positive electrode when charging, and the positive electrode still retains the position of lithium ions when discharging, then the capacity of the battery is difficult to decay. If the lithium ions flow to the positive electrode when charging, but its vacancy is occupied by other substances, then a part of the lithium ions in the positive electrode will have nowhere to go when discharging, which will cause the battery capacity to decay.
The cathode material of ternary lithium battery is unstable, the diameter of bivalent nickel ion is close to lithium ion, and the lithium ion runs to the negative electrode when charging. At this time, some nickel ions may occupy the position of lithium ions, resulting in battery power attenuation.
Therefore, when designing batteries, the number of positive electrode materials of ternary lithium batteries will be more than negative electrode materials. Simply put, it provides more lithium ions and storage space for lithium ions to ensure the stability of capacity.
But this presents a new problem, namely that the negative electrode does not have much room to hold all the lithium ions in the battery when it is charged. This requires caution when charging, should be full of lithium ions in the negative electrode to stop charging in time, otherwise lithium ions continue to move to the negative electrode, the negative electrode has no place to accommodate, at this time lithium ions will crystallize, light will affect the life, heavy will Pierce the diaphragm leading to short circuit, causing danger. So try not to full each charge, which helps reduce this risk.
Why should lithium iron phosphate batteries be regularly filled?
Because the battery voltage is an important basis for the battery management system to judge the battery pack power, the operating voltage range of lithium iron phosphate batteries is particularly narrow, and the voltage changes with the capacity in a large range is very small. For example, at 30% and 60% of battery capacity, the voltage may be the same. This feature will make the battery management system crazy, it is impossible to judge the battery level by the voltage. Therefore, the battery management system should be fully charged regularly to allow the battery management system to calibrate the power level.
The molecule arrangement of the cathode material of the lithium iron phosphate battery is very tight, which makes it very stable, but also limits the movement speed of lithium ions, resulting in low energy density. However, due to high stability, there will be no other substances occupying the position of lithium ions after lithium ions flow to the negative electrode when charging, so the service life is longer, and it is not very sensitive to overcharging like ternary lithium batteries.
Therefore, if you buy a new energy vehicle, then be sure to find out what kind of battery cell the vehicle uses when charging. It is best to read the manual carefully and charge the battery according to the prompts to maximize battery life.
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