What is the relationship between lithium battery voltage and electric quantity?

During discharge, the lithium ion battery voltage gradually decreases with the passage of the charge, and has a considerable slope.Generally speaking, the higher the charge and discharge voltage of lithium battery, the larger its capacity.Different materials of lithium batteries charge and discharge voltage is different.What is the relationship between lithium battery voltage and charge?This article will open the mystery for you.

For the same battery, with the same residual capacity, the voltage varies according to the size of the discharge current. The higher the discharge current is, the lower the voltage is.The influence of ambient temperature on lithium battery voltage, the lower the temperature, the lower the battery voltage of the same capacity;The influence of the cycle on the battery discharge platform. With the progress of the cycle, the discharge platform of lithium battery tends to deteriorate and the discharge platform decreases. Therefore, the capacity represented by the same voltage also changes accordingly.Different manufacturers, different capacity of lithium ion batteries, the discharge platform is slightly different.

The following is a standard lithium battery voltage to the residual capacity of the battery and large current constant discharge is the battery voltage to capacity table.

100%----4.20V100%----4.20V

90%-----4.06V90%-----3.97V

80%-----3.98V80%-----3.87V

70%-----3.92V70%-----3.79V

60%-----3.87V60%-----3.73V

50%-----3.82V50%-----3.68V

40%-----3.79V40%-----3.65V

30%-----3.77V30%-----3.62V

20%-----3.74V20%-----3.58V

10%-----3.68V10%-----3.51V

5%------3.45V5%------3.42V

0%------3.00V0%------3.00V

What is the reason that the lithium battery voltage decreases with the decrease of electric quantity?

In addition to the change of chemical potential at both ends of the battery, the reason why the lithium battery voltage drops with the decrease of electric charge is partly due to the polarization caused by the transfer of ions and charges.The activated polarization caused by the reaction between the electrode and the electrolyte at the initial stage of discharge can be calculated by the Tafel equation, which is related to the REDOX reaction rate and the activity of each reactant.

At the end of the discharge, due to the limitation of ion diffusion rate of the electrode itself, there will be a concentration difference between the surface of the electrode and the inside of the electrode, resulting in so-called concentration polarization.

What is the optimal level of charge for a lithium battery?

Lithium batteries are best kept at 40-60% charge.Generally, the factory capacity of lithium battery is about 50%, which is the best storage capacity verified by experiments.According to the measured data of most battery factories, the shipment with 50% electric quantity can ensure its storage for more than one year, the voltage is still more than 3.2v, and the recovery capacity is more than 98%.

Because the market position of each lithium battery manufacturer is not the same, the technical process means is different, its control of the discharge platform is not the same, the quality is also very different.In addition, the open circuit voltage of lithium battery has a clear and monotonous corresponding relationship with the battery charge. As long as the accurate open circuit voltage is obtained, the battery charge can be calculated.