High‐Voltage Asymmetric Supercapacitors based on Carbon and Manganese Oxide/Oxidized Carbon Nanofiber Composite Electrodes

Abstract

Abstract Asymmetric supercapacitors with high operating voltages have been successfully developed, using manganese oxide/oxidized carbon nanofibers (MnO 2 /CNFox) composites as the positive electrode and activated carbon (AC) as the negative electrode, in a neutral aqueous 0.5 mol L −1 K 2 SO 4 solution. The assembled MnO 2 /CNFox//AC supercapacitor can operate reversibly in a wide voltage range up to 2.3 V, showing an excellent stability with only a 7.6 % loss of its initial capacitance after 5000 cycles at 1 A g −1 . A high energy density of 24.8 Wh kg −1 at a power density of 100 W kg −1 is achieved. This unique electrochemical performance is attributed to the presence of CNFox with hydrophilic surface properties in the MnO 2 ‐based electrode, which ensures a perfect dispersion of nanofibers in the bulk MnO 2 and a very good adhesion between the components of the MnO 2 /CNFox composite. The obtained results show great potential in developing asymmetric supercapacitors with high energy and power densities working in neutral aqueous media.