First, according to Eq. 13, the interfacial impedance should decrease with increasing current excitation amplitude, so the values of α and I0 canin theorybe calculated by simply fitting the Rct versus current data to the reformulated BV equation. However, the non-linear voltage response also generates harmonic distortions of the impedance signal, which overestimate the magnitude of the linear impedance. When this harmonic distortion is significant, typical methods for EIS data analysis which assume the condition of linearity will give inaccurate results . However, linearity of the impedance signal can be maintained if the analysis is limited to the weakly nonlinear region of the kinetics where the harmonic distortion is sufficiently low.