Extended Data Fig. 6: Characterization of electrolyte capacitance.

a, Cyclic voltammetry characteristics of reference devices in which HTFSI electrolyte is in contact with two mm-sized Au electrodes (inset panel b). The different curves (colour coded) were obtained at sweep rates ranging from 1 mV s^−1 (black) to 40 mV s^−1 (dark blue). b, Geometrical capacitance per unit area as a function of sweep rate extracted from the CV curves shown in panel a. Inset, schematic of reference devices used for this experiment. The dimensions of the active area of the electrodes were 4 mm × 4 mm and 0.3 mm × 1 mm.