Battery-like supercapacitors from diamond networks and water-soluble redox electrolytes

Abstract

Enhanced performance of electrochemical capacitors can be achieved by larger capacitances as well as higher power and energy densities. In this work, such battery-like supercapacitors were fabricated using a three-dimensional and conductive diamond network as the capacitor electrode and water-soluble redox couples as the electrolyte. In 0.05 M Fe(CN)₆^3−/4− + 1.0 M Na₂SO₄ aqueous solution, a capacitance of 73.42 mF cm⁻² was obtained at a current density of 1 mA cm⁻². This value is 10 000 times higher than the capacitance of diamond electric double layer capacitors (EDLCs). The energy and power densities of a fabricated diamond network symmetric pseudocapacitor were up to 56.50 W h kg⁻¹ and 13.7 kW kg⁻¹, respectively. Compared with those of diamond EDLCs obtained with the same cell voltage, they are enhanced about 3500 and 1440 fold, respectively. Therefore the combination of diamond networks and water-soluble redox electrolytes is a novel approach to construct electrochemical capacitors and thus bridges the gap between normal dielectric capacitors and rechargeable batteries.