How can one determine impedances at different characteristic frequency values in an EIS curve?

I have an EIS curve of a Li ion battery and I had characteristic frequency (fmax and fmin) of the curve. How can I calculate or have an idea about the charge-transfer or diffusion impedance (warburg)?

The figure above has one local minima and one local maxima (characteristic frequencies). How can one determine the impedances based on these characteristic frequencies?

Answer 1

[Javier Gazzarri]

Hello Ekagra,

You can use the scripts described here to find ECM parameters based on your spectrum: Estimate Battery Model Parameters from EIS Data

As to your second question, the characteristic frequency depends on the impedance in a very nonlinear way and the correspondence between frequency and impedance parameters is non-unique. For example, for a simple RC pair, w_peak = 1/(R*C). This means that there is an infinite number of R and C that satisfy the relationship. So, in general, you need to fit an equivalent circuit to the entire spectrum (not just the characteristic frequencies) in order to find the impedance values.

Please let me know if this helps.

Best regards,

Javier