I have prepared the Fe2O3@graphene nanocomposites using commercial Fe2O3 (size = 200 nm) and commercial graphene oxide (GO) via HI reduction. Afterward, I have prepared the active electrode film by combining the 8:2 ratio of Fe2O3@graphene: SWCNT via vacuum filtering followed by drying in a vacuum oven at 120 oC for overnight. I am using the HS Flat cell for testing the Li-ion capacitor and preparing each electrode under the glove box. By making the Li-ion capacitor half cell (Anode, Fe2O3@graphene//Li), I am using Cu foil as the current collector, cell guard 3501 as a separator and 1 M LiPF6 in EC:DEC:DMC as electrolyte (about 0.5 mL). I have run the CV in the potential window of 0.05 to 3 V for 10 cycles. I have seen good CVs up to 7 cycles (see Figure 1) and afterward, every time I am seeing the loss of CV features from 8 to 10 cycles (see Figure 2). CV peak jumps up at about 2.5 V in 8th cycles and the 9th cycle is by about 2.3 V and the 10th cycle is by 2.2 V. The peak suddenly jumps after the 8th cycle and in further cycles, the CV jump moving towards the lower potential side. I have also given 1-10 cycles CV (see Figure 3). I am seeing the same situation about 5-6 times and it's repeating every time. Anyone, Can you help me to understand these features?
Thanks in advance.
This could be due to several factors such as active material degradation, particle size, impure binder and/or electrolyte. I will suggest you grind well your material and sieve it before making a slurry. You can also prepare a new binder and electrolyte solutions. Another reason could be contamination, especially on Li metal.
Thank you so much for your reply, Ghulam Ali. I have already tried the changing of Li foil and electrolyte. But, the results were the same. I am also thinking about material degradation, that might be causing this problem.
Your 3 images are not comparable because you don't use the same scale range on the current density axis. Use the zoom function. You may discover that you have similar oxidation/reduction current values also in image (II), maybe also in image (III). Put a lower limit for the high potential vortex/limit after the 7th cycle.
Thank you so much for your reply. I have rearranged the scales and attached the images again.
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