Based on the reaction mechanism in Fig. , this involves reducing the I -concentration by, for example, using additional, electrochemically inert anions like NO3 -, which allow precipitating a larger fraction of the I -without anion starvation. Using aqueous 0.5 M NaI and 0.5 M NaNO3 as electrolyte (red curve, Fig. ), I2 pore filling and discharge capacities improve significantly. This not only demonstrates a practical way towards improved energy densities of carbon-iodine electrodes used in hybrid supercapacitors or batteries, but also independently confirms the reaction mechanism, derived from in situ Raman and SAXS/WAXS.