I'm performing EIS in a two electrodes cell configuration of a symmetric super capacitor. Over the same device, I'm obtaining different curves as shown on the graph. The only difference is that I'm opening and close the cell between the measurements, which electrolyte volume and pressure between the electrodes maybe changing. Does anyone could give me a help on the interpretation? Thanks in advance.
Hi Raquel, I hope this message finds you well.
To properly interpret your EIS data, it’s important to analyze it alongside the Bode plot. Since EIS is based on complex plane analysis, the Nyquist plot and Bode plot are usually used together to provide complementary information. It’s also essential to consider OCP and closed system measurements separately. At OCP, you are mainly looking at the electrode/electrolyte interface, focusing on intrinsic properties such as ion adsorption, interfacial behavior, and potential parasitic effects (which looks that happen in your analysis, based on the data you show). This helps with material characterization and understanding the equilibrium state.
In a closed system, where charging/discharging occur, additional processes come into play, such as faradaic reactions, active ion diffusion, and dynamic charge transfer. Also, based on your data, the diffusion effect happen in all tests, which can often be analyzed and quantified using Warburg models. Other consideration based on the shape of the data you shared, it appears that your material is likely a porous electrode, but to confirm this, I recommend comparing your results with similar studies in the literature. Reviewing other works that use similar structures and EIS analyses will help you better understand and discuss the observed behavior.
Unfortunately, with only the Nyquist plot and without details about your material composition and methodology, it’s difficult to provide a precise interpretation. As a reference, I strongly recommend the book Impedance Spectroscopy: Theory, Experiment, and Applications by Evgenij Barsoukov and J. Ross Macdonald, which provides excellent theoretical and practical insights into EIS analysis.
I hope these considerations are helpful, and I wish you the best with your research!
Dear Robson da silva Souto, for the book that you recommend. İt's very interesting
What seems clear is that your overall charge transfer resistance has increased by 70% after adding "more electrolyte" between the two "tool" conditions.
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