With an upper limit of 2% THD, the maximum RMS current for fitting the LA-GEIS data is limited to ~ 10 mA cm -2 , which corresponds to a normalized current (𝑖 = 𝐼/2𝐼 0 ) of ~ 1. Generally, the current range of 0.1 < 𝑖 < 1 seems to be ideal for accurate analysis of the LA-GEIS data. Within this current range, the measured Rct decreases by ~ 12%, which is sufficient to fit the experimental data. (Fig. ). The normalized resistance (𝑟 = 𝑅 𝑐𝑡 /𝑅 𝑐𝑡 0 ) versus normalized current data were fitted to Eq. 13 with least squares error minimization to calculate the value of I0, and the value of α was calculated from Eq. 7. Within the optimal RMS current range of < ~ 10 mA cm -2 , the LA-GEIS measurements yield α = 0.431 and I0 = 6.11 mA cm -2 . If the LA-GEIS data at high current density are used to fit the BV model, the value of α is underestimated due to harmonic distortions, however this leads to only a relatively small inaccuracy. For example, α = 0.438 is calculated for data with RMS excitation currents of < ~5 mA cm -2 , while α = 0.409 is calculated for data with RMS excitation currents of < ~25 mA cm -2 . The α value agrees extremely well between S3E-CP and LA-GEIS measurements, and the value of 𝑅 𝑐𝑡 0 agrees perfectly between LA-GEIS and PEIS measurements. However, the values of 𝑅 𝑐𝑡 0 and I0 from PEIS and LA-GEIS both differ by a factor of √2 from those measured with S3E-CP.