Transition metal oxides anchored on graphene/carbon nanotubes conductive network as both the negative and positive electrodes for asymmetric supercapacitor

Transition metal oxides have drawn greatly interest because of the large specific capacitance, low-cost and abundant source. Nevertheless, the low conductivity of transition metal oxides affects the overall electrochemical properties of the materials. In order to ameliorate the problem, Fe2O3 nanoparticles were grown on graphene/carbon nanotubes (G/CNTs) conductive network by hydrothermal method and further heat treatment. The nanosized Fe2O3 is closely combined with conductive G/CNTs network (G/CNTs/Fe2O3-150), which is conducive to the transport of electrons and ions. The obtained G/CNTs/Fe2O3-150 composites display a specific capacitance of 258 F g(-1) at 1 A g(-1) and superior cycling stability. Moreover, MnO2 was also grown on the surface of G/CNTs to form composite material (G/CNTs/MnO2-720). The G/CNTs/MnO2-720 electrode delivers high specific capacitance and good cycling stability. More importantly, asymmetric supercapacitor was constructed with G/CNTs/(FeO3)-O-2-150 composite as the negative electrode and G/CNTs/MnO2-720 composite as the positive electrode. A wide voltage ranging from 0 to 2.0 V was obtained in 1 M Li2SO4 electrolyte. The asymmetric supercapacitor exhibits superior energy density (43.2 Wh kg(-1) at 200 W kg(-1)) and superior cycling stabilization. (C) 2020 Elsevier B.V. All rights reserved.