An ionic aqueous pseudocapacitor system: electroactive ions in both a salt electrode and redox electrolyte

We designed a new type of ionic pseudocapacitor system with excellent contributions from ionic-state redox mediators, including a redox couple [Fe(CN)(6)](3-) /[Fe(CN)(6)](4-) in the electrolyte and redox cations in highly electroactive colloid electrodes. The highest pseudocapacitance value of 12 658 mF cm(-2) was obtained, which is a 7-fold increase in the specific capacitance of the CoCl2 electrode for K3Fe(CN)(6) in a KOH alkaline electrolyte at a current density of 20 mA cm 2 and at a potential interval of 0.55 V. The currently designed supercapacitor systems show a versatile strategy to design highperformance supercapacitors with CoCl2, CuCl2, NiCl2, and FeCl3 electrodes.