Characteristics and electrochemical performances of supercapacitors using double-walled carbon nanotube/δ-MnO2 hybrid material electrodes

Double-walled carbon nanotubes (DWCNTs)/δ-MnO2 composites were synthesized by a microwave irradiation method. The morphologies and microstructures of the samples were examined by scanning electron microscopy, transition electron microscopy and X-ray diffraction. Electrochemical properties were characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The microstructure observations indicate that the birnessite-type MnO2 mainly deposits inside the tubes at low MnO 4 - content, while on the surfaces of the tubes at high MnO 4 - content. As a result, DWCNTs–85%MnO2 composite exhibits high specific capacitance (240.2 F g−1) and good cycling stability (6.8% capacity loss after 2000 cycles). These results demonstrate that DWCNTs–MnO2 composites as electrode materials have potential application for high-performance supercapacitors.