We report on a carbon/carbon hybrid electrochemical capacitor (hybrid EC) based on an aqueous redox-active electrolyte, which operates efficiently down to -40 degrees C. The electrolyte comprises choline iodide (ChI; 0.5 mol kg(-1)) as redox active component and choline nitrate (ChNO(3); 5 mol kg(-1)) as supporting salt which enables the liquid state to be extended down to -42 degrees C, as proved by differential scanning calorimetry. Interestingly, the hybrid EC displays a high discharge capacitance of 81 F g(-1) (at 0.1 A g(-1); per total mass of electrodes), which is twice higher than its symmetric counterpart utilizing only an aqueous solution of ChNO(3) (41 F g(-1)). The doubling of cell capacitance results from hybridization of the positive battery-type electrode (harnessing redox reactions of polyiodides trapped in carbon porosity) with the negative electrical double-layer (EDL) capacitive electrode. Even at -40 degrees C, the hybrid EC retains a high capacitance of 50 F g(-1) and shows negligible ohmic drop. As its energy and power performance is in the same range as for EDL capacitors using tetraethylammonium tetrafluoroborate in acetonitrile, this new hybrid EC is a highly cost-effective and green alternative to these traditional systems.