Insight into the origin of pseudo peaks decoded by the distribution of relaxation times/differential capacity method for electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy (EIS) is a powerful diagnosis tool. However, it is still a challenge to separate the overlapped physicochemical processes. Both distribution of relaxation times (DRT) and distribution of differential capacity (DDC) can be used to solve above question. But, it is still an open question how to identify pseudo peaks decoded by the DRT/DDC method. In this work, a new insight into the origin of pseudo peaks are presented from the viewpoint of the symmetry of the DRT/DDC method, in term of the impedance model, the spectrogram, the decoding algorithm, and the decoded peak. First, pseudo peaks are identified into three sorts, i.e. the one is decoded at a given frequency but really does not exist; the one really exists at a given frequency but is not decoded; the one is decoded but its real position shifts. Secondly, the decoded peaks by the DRT/DDC method are quantitatively evaluated with respect to the penalty factor, the peak intensity, and the impedance model. Thirdly, the solution to pseudo peaks decoded by the DRT/DDC method is validated based on the simulated impedance spectra from integer to fractional-order models. Finally, insight into the origin of pseudo peaks decoded by the DRT/DDC method are concluded and the future work is proposed. The results obtained in this work might improve the reliability of the DRT/DDC method for EIS diagnosis.

Automated summary

EIS is an important diagnostic tool, but identifying pseudo peaks decoded by the DRT/DDC method remains a challenge. This study presents new insights from the perspective of symmetry, categorizing pseudo peaks into three types and quantitatively evaluating the decoded peaks. The solution to pseudo peaks decoded by the DRT/DDC method was validated through simulated impedance spectra.