Direct ECM fit Considering the DRT in Figure , the ECM shown in Figure (b) consisting of three ZARC elements, which cover features at frequencies above about 1 Hz, in series with a Warburg element for low-frequency features, appears a suitable model for the investigated Li-ion button cell. Nonetheless, at least one of the modes modeled by a ZARC element is showing an asymmetric shape, which either indicates a more complicated ECM with overlapping features, or a distribution of parameters that is not accurately represented by a ZARC element.