I always get confused on how they plot the charge-discharge cycle on the same plot. How to recognize which is charge and which is discharge curve (and where their start and end points are)?
For a battery anode: charge is in average at lower voltage, discharge is in average at higher voltage, due to the overpotentials.
So, for istance, in the graphite OCP curve that you have there in the figure, the charge goes from 1V to 0V, and the discharge goes from 0V to 1V.
Vice versa for a battery cathode: charge is in average at higher voltage, discharge is in average at lower voltage.
This holds in a full cell configuration, i.e., when the cathode and anode are coupled together. When a battery is in half cell configuration, i.e., when there is a cathode material or an anode material versus lithium metal (or other metal electrodes), the discharge is always at a lower average potential and the charge is always at a higher average potential. This means that the anode or cathode material in a half cell behave like the cathode in the full cell configuration.
Toma Stankulov Thanks.
How you could interpret that? Could you please elaborate?
Also, there are no arrows marked to show this. Is the discharge curve is lower one or on the top? In 5th cycle curve it is difficult to interpret as both curves are from 0 to 1 volts.
I appreciate efforts to explain the concept Toma Stankulov and Alessandro Innocenti . Thanks.
It depends on your electrode.
If your electrode is anode type, the voltage range is of two types, one from 0.01 to 1.2 and the other from 0.01 to 3.
In the cathode electrode, the voltage range is between 2.5 and 4.2. Of course, if the type of electrolyte is organic.
In general, when the applied current moves from low voltage to high voltage, it is charged and in reverse, it is called discharge.
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