I measured galvanostatic charge/discharge curve of graphene as a negative electrode for supercapacitor in 1M Na2SO4 electrolyte. Graphene was coated on the nickel foil, voltage range was -1 to 0V in three electrode system.
However, the problem is that voltage does not increase and decrease around -0.1 and -0V, respectively, as shown in the attached picture.
What makes this problem? and how can I solve that?
Current density is 1A/g, I think this is not low. But, the loading mass is low. it's just 0.07mg and the applied current is 0.07mA. It could be a reason of this problem?
From the image you shared for CD cycle, we can find that your electrode discharge and then charge. You might be doing a mistake, while selecting 2 segments (charge/discharge), and your electrode was already partially charged, so it discharges during first segment and then it charges to maximum potential and stop there.
You should select 3 segment during setting parameters for CD test, so that electrode get chance to discharge during 3rd segment. You can use data for 2&3rd segments as complete CD cycle.
Also, sometime if current applied is too high or low then such problems also come, but here, i don't think this is mean reason.
Another thing, I suggest you to check the operating potential range of electrode material by trying CV test at different potential window ranges. And then you use the appropriate potential range.
@Muhammad Asif
The electrode is tested for negative electrode. So, I think the first cycle is charging, not discharging. Reason why it starts at middle voltage (about 0.4V) is because CV test ended at that voltage before GCD test.
I guess some side-reaction occurred due to the contaminants which could be in three electrode test kit. Therefore, I will try again after the washing the kit.
Thanks for your reply.
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