Next, we analyzed the EIS spectrum collected from an electric double-layer supercapacitor with porous carbone electrodes and a tetraethylammonium-in-acetonitrile electrolyte . The EIS spectrum was acquired at frequencies in the 0.1 Hz to 0.1 MHz range with a 5 mV voltage amplitude. Consistent with the electrochemical nature of this system, we observed diffusional features at low frequencies, see Figure (b). We therefore censored frequencies below 6.3 Hz. The parameters values of the 2×ZARC ECM are presented in Table . The experimental EIS spectrum was regressed closely by GPs (Figure (b) and S16). Lastly, we computed 𝑅 p = 3.00 × 10 1 Ω ± 3.01 × 10 -1 Ω, which is consistent with Figure (b) and the ECM value of 2.998 × 10 1 Ω .