There is not enough information to give any advice for interpretation. We need to know the electrochemical system you are investigating. Also a plot of your spectra would be helpful (Nyquist and/or Bode).
Kind Regards
Peter
Hi Vivek,
You've got more than 2 semi-circles there. Depending on the quality of the measurement (assuming that the data is real, stable and causal and the system you are using to measure is capable of making accurate measurements of these impedances) there are at least 4 processes/aspects that can be resolved there. I'm guessing what you would indicate as the first semi-circle is actually two that overlap a fair amount. The second has some lead in which may be something like a porous bound diffustion but could be...more complex. The third is the long tail which also looks like it may have two parts, but that could easily be due to something like drift or some other non-[linear, stable, causal] behavior.
But, so far as analysis, there still isn't enough information to go on here. Is this 2-electrode or 3-electrode? If the former you should run a 3 electrode measurement if possible. In either case the structure of the working electrode the nature of transport to the surface, whether there are other structures, or layers or membranes....for species to move through, would need to be known to start. Then to isolate between different processes you would need to run different experiments with variations in the components to see what is what.
On the other hand, if this is more QC then maybe you can get away with making a rough model that mostly fits the data, and then looking at "good" and "bad" cells to see if there is some way to distinguish?
In either case, you will likely run into a common issue with EIS analysis: the only person that can really tell you what is happening in your case is someone who has done the same research and figured it out already.
In your case, semi-circle arises at both high (1st semi-circle) and low (2nd semi-circle) frequency region. The first semi-cirlce includes the internal resistance related to electrolyte resistance and the surface film impedance. the second semicircle at lower frequency describes the lithium-intercalation process.
The attached paper definitely clear your confusion and you can have a clear idea.
wishes,
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