During the constant-current discharge ( large current =5 mA), the discharge voltage can only maintain 20 mins, then the voltage becomes negative, as shown in the plot, we seperated the cell, the zinc electrode seems no problem. Wonder why the voltage becomes negative
Dear Jian Wang,
It is typicallly for constant charge-discharge cycling. In generally, in a real device that powered by chemical power source all processes stop, when voltage drops down to defined value or zero volts. But in case of discharge by direct current, potentials of electrodes can change polarity - so, you obtain negative voltage. Really, more natural regimes are tests that use discharge on constant resistor. In such case you do not obtain a negative voltage.
Hope that will be useful to you
Hi Wang Jian,
5 mA actually is not a large current. But to be meaningful, you should give current density by mA cm-2. As for negative voltage, it maybe caused by large polarization, especially the cathode side (eg, poor catalytic effect, water flooding). If your cathode is fully flooded, the diffusion of oxygen will be very difficult and may result in a large polarization in the cathode.
Hope it will be useful.
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