A Hybrid Metal Oxide Supercapacitor in Aqueous KOH Electrolyte^†

A novel type of composite electrode based on sheet like cobalt oxide particles has been used in supercapacitors. Cobalt oxide cathodically deposited from Co(NO₃)₂ solution with carbon nanotubes as matrix exhibited large pseudo-capacitance of 322 F·g⁻¹ in 6 mol·L⁻¹ KOH. A sol-gel process for the preparation of ultrafine RuO₂ particles was developed to design electrodes with large surface area. The composite electrodes were developed by the deposition of RuO₂ on the surface of carbon nanotubes. A specific capacitance of 785 F·g⁻¹ can be achieved with the 20% carbon nanotubes loaded. To characterize the metal oxide nanocomposite electrode, a cyclic voltammetry and AC impedance test are executed. This study also reports a hybrid capacitor, which consists of cobalt oxide composite as a cathode and ruthenium oxide composite as an anode. The electrochemical performance of the hybrid capacitor is characterized by a dc charge/discharge test and cyclic voltammograms. The hybrid capacitor shows capacitor behavior with an extended operating voltage of 1.4 V. The maximum energy density and specific power density of the cell reach the value of 23.7 and 8.1 kW·g⁻¹ respectively. The hybrid capacitor exhibits high-energy density and stable power characteristics.