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leehangyue / EISART

Electrochemical Impedance Spectra Analysis and Refining Tool
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Possibility to include DRT calculation of low-frequency inductive loops? #3

Open jianzuo opened 2 months ago

jianzuo commented 2 months ago

In my case studies, I need to compute the drt on low-frequency inductive loops. Can you please comment on this prospect? I am not sure if it is feasible to modify the current version of EISART.

Thank you very much!

leehangyue commented 2 months ago

Thanks for your question! It should be possible to compute DRT on low-frequency "inductive" loops, by accepting negative values in the DRT function. To avoid misunderstanding, I would state my interpretation of "inductive" loops at low frequencies: at some point in a high-to-low frequency sweep, the real part of impedance goes over its maximum and begins to decrease, while the imaginary part crosses 0 and goes positive (to the lower-right quarter in a -Nyquist plot) as the frequency gets lower, forming an arc-like shape.

Realizing this in EISART is theoretically possible but could be a bit challenging numerically. Simply deactivating the non-negative constraint on the DRT function (gamma) could lead to oscillating DRT in some cases (i.e. single RC impedance). Further development on DRT evaluation is necessary. Maybe dynamically deactivate the non-negative constraint on certain regions of tau in DRT could do the trick, while the region selecting algorithm remains a problem in this case. Maybe the EIS residual could help find the regions.

jianzuo commented 2 months ago

Thanks a lot for the valuable information. I will try to understand and to see the possibilities.