Electrochemical cell. Sandwich-like structure: Conductive FTO electrode 1, Tungsten oxide layer 2, LiClO4 propylene carbonate solution electrolite 3, and FTO counterelectrode 4. Isolated system with no contact with air. Li+ intercalation into Tungsten oxide gives electrochemical reaction on applied direct current.
So the question is: EIS gives such unordinary result (watch Aftermath project below, or xls file). How on Earth could this be? What could explain low frequency small semicircles or inductive loops? What equivalent circuit could you suggest?
P.S. I suppose some of intercalated ions could deintercalate (or vice versa) during one way low frequency AC, otherwise the reaction goes slower. Let me know your suggestion
There's not really enough to go on here, but there are several regions of that Nyquist plot that look bad (i.e. not valid EIS data). Without knowing more I'd suggest testing on a dummy cell (resistors and capacitors) that are in the same order of magnitude as your impedances (doesn't have to be the same overall spectrum, just the same impedance ballpark) to make sure you can get good data at these frequencies/impedances. You can also try reducing the amplitude of your AC signal.
1. Is this result repeatable ?
2. Did you check the linearity of your system?
3. Is your data consistent with the Kramers-Kronig relations?
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