(a) (b) Symmetric cells with identical NCA electrodes at various SOCs were prepared and characterized by ORP-EIS . Notably, ORP-EIS can simultaneously evaluate the non-stationarity and non-linearity during EIS measurements, thereby assessing the validity of the EIS spectra. Therefore, the Kramers-Kronig test is no longer necessary. The same set of data has been discussed in our previous work , in which EECM with GFLW was applied for the analysis. However, the discussion of the parameters derived from the GFLW was preliminary, owing to the limited physical insights given by the model. In this study, we employ a similar EECM approach but use PDW instead of GFLW for the analysis. The EECM is shown in Figure . A constant phase element (CPE) is used to model the dispersive double-layer capacitance due to the porous structure. The impedance of a CPE is given by: