Supercapacitors can provide high rate capability and long-term cycleability, thanks to their simple mechanism based on the adsorption and desorption of ions on the surface of electrodes. Based on the high power characteristics, supercapacitors can augment the batteries or fuel cells for electric vehicles or heavy equipment. So far, most of supercapacitors have symmetric configuration with activated carbon electrodes as the positive and negative electrodes (Fig. 1a). And they follow a Daniell-type mechanism, where the electrolyte is depleted of and replenished with ions upon charging and discharging, respectively (Fig. 1b). In this mechanism, electrolyte serves as an ionic reservoir, from which cations and anions are separated to negative and positive electrodes, respectively. This leads to a limitation in energy density and an increase in the internal resistance as the starvation of the concentration of salts in the electrolyte decreases during operation. Herein, we introduce a hybrid supercapacitor that follows a ‘rocking-chair’ mechanism. This hybrid supercapacitor is composed of metal anodes and activated carbon as the negative and positive electrodes, respectively (Fig. 1c). Metal (M, e.g. Mg or Zn) ions are replenished at the negative electrode while they are adsorbed into the pores of the positive electrode upon the discharging of the cell (Fig. 1d). As a result, only a minimum amount of electrolyte is needed to operate the cell. The use of metal electrodes can increase the energy density of the cell significantly by virtue of the large volumetric capacity. Therefore, ‘rocking-chair’-type metal hybrid supercapacitors can double the energy density of a supercapacitor. Detailed studies on the ‘rocking-chair’-type mechanism will be presented.