Electrochemical performance of CNTs/RGO/MnO₂ composite material for supercapacitor

Abstract

In this article, the novel carbon materials (carbon nanotubes (CNTs) and graphene) with high-specific area and superior mechanical behavior are employed to strengthen the specific capacitance and cyclical stability of manganese dioxide (MnO2) for supercapacitors. The electrode material, synthesized by the CNTs, reduced graphene oxide (RGO), and MnO2 (CNTs-RGO-MnO2 composite), is characterized by scanning electron microscope, transmission electron microscope, and X-ray powder diffraction. The results indicate that the MnO2 particles are compactly distributed on the surface of the RGO and CNTs. The state of MnO2 in the CNTs/RGO/MnO2 composite is δ-MnO2. The electrochemical test results indicate that the specific electric capacities of the CNTs/RGO/MnO2 composite are 404 F/g, 255 F/g, and 82 F/g, respectively, at 1 A/g, 3 A/g, and 10 A/g ampere densities, which illustrate that the addition of the CNTs and RGO greatly hoists the specific capacitance of the MnO2. Moreover, the long-time charge–discharge test results indicate that the specific capacitance of the CNTs/RGO/MnO2 composite remains 70% after 5000 circles under the big current density of 30 A/g. The electrochemical impedance spectroscopy test results show that the RGO and CNTs can remarkably reduce the electric charge shifting resistance; at the same time, the electrolyte resistance and electric charge shifting resistance after the charge–discharge test are scarcely increasing, showing that the CNTs/RGO/MnO2 composite is a kind of supercapacitor electrode material with stable structure, which has the prospect of industrialization.