In a typical experiment, cyclic voltammetry (CV) measurements were conducted in a voltage range from -0.7 to +0.7 V using a scan rate of 5 mV s -1 . Galvanostatic charge/discharge (GCD) measurements were executed in the range of -0.7 to 0.7 V using current densities of 0.34 -5 µA cm -2 . Electrochemical impedance spectroscopy (EIS) measurements were carried out in a frequency range from 10 mHz -100 kHz at open circuit voltage (OCV) with a voltage amplitude of 10 mV. For impedance fitting a randomized and simplex fit was used until consistency was reached.