Three-dimensional heterostructured MnO₂/graphene/carbon nanotube composite on Ni foam for binder-free supercapacitor electrode

In this article, three-dimensional (3D) heterostructured of MnO₂/graphene/carbon nanotube (CNT) composites were synthesized by electrochemical deposition (ELD)-electrophoretic deposition (EPD) and subsequently chemical vapour deposition (CVD) methods. MnO₂/graphene/CNT composites were directly used as binder-free electrodes to investigate the electrochemical performance. To design a novel electrode material with high specific area and excellent electrochemical property, the Ni foam was chosen as the substrate, which could provide a 3D skeleton extremely enhancing the specific surface area and limiting the huge volume change of the active materials. The experimental results indicated that the specific capacitance of MnO₂/graphene/CNT composite was up to 377.1 F g⁻¹ at the scan speed of 200 mV s⁻¹ with a measured energy density of 75.4 Wh kg⁻¹. The 3D hybrid structures also exhibited superior long cycling life with close to 90% specific capacitance retained after 500 cycles.