Composite of CoOOH Nanoplates with Multiwalled Carbon Nanotubes as Superior Cathode Material for Supercapacitors

A hydrothermal-oxidation two-step method has been employed to fabricate a composite of CoOOH nanoplates with conducting multiwalled carbon nanotubes (MWCNTs), which present excellent electrochemical performance as a cathode material for a supercapacitor. The conductive nanostructure network of MWCNTs not only provides effective surface area for the contact between the electrode material and the electrolyte but also shortens the diffusion distances for ions and electrons and buffers the volume change, resulting in higher capacitance, faster redox reaction kinetics, and outstanding cycling stability. The maximum specific capacitance of the composite can achieve 270 F g(-1) at a current density of 1 A g(-1) in 0.5 mol L-1 KOH aqueous solution. It also exhibits good rate capability with a capacitance of 169 F g1 even at a high current density of 10 A g(-1) and outstanding long-term cycling stability, almost 100% retention of its initial capacitance after 10 000 full cycles. In contrast, the virginal CoOOH shows a capacitance of only 124 and 100 F g(-1) at 1 and 10 A g(-1), respectively, and its capacitance retention is only 79.4% after 10 000 full cycles. These results, for the first time, indicate that the composite of CoOOH nanoplates with MWCNTs is a promising cathode material for high-performance aqueous supercapacitors.