3D hierarchical porous V3O7·H2O nanobelts/CNT/reduced graphene oxide integrated composite with synergistic effect for supercapacitors with high capacitance and long cycling life

Abstract

V3O7·H2O possesses the merit of high specific capacitance, but weakness of cycling stability and low conductivity inhibit its application for energy devices, which requires the addition of carbon materials like carbon nanotubes (CNT) or graphene with properties of high conductivity and brilliant cycling stability to obtain high-performance composites. Since CNT or GO-based binary V3O7·H2O materials have been rarely studied with limited specific capacitance, we developed a novel, highly porous V3O7·H2O nanobelts/CNT/reduced graphene oxide (V3O7·H2O/CNT/rGO) ternary composite with a three-dimensional (3D) hierarchical micro-structure by a single step, facile hydrothermal process and self-assembly method with outstanding electrochemical performances. During the hydrothermal process, CNT-anchored V3O7·H2O nanobelts have been incorporated on the surface of rGO through in situ growth with preferred orientation, forming a 3D hierarchical porous structure composed mostly of mesopores and exhibiting enlarged specific surface area up to 53.7 m2·g−1. The well-designed V3O7·H2O nanobelts also display excellent adhesion with CNT/rGO, which leads to reduced resistance resulted from the synergistic effect of pseudocapacitors (V3O7·H2O nanobelts) and electric double-layer capacitors (EDLCs) (CNT/rGO) and large specific area with sufficient active sites ensure the composite to brilliant capacitive behavior. Applied to SCs, the ternary composite exhibits outstanding electrochemical performance with higher specific capacitance (685 F·g−1 at 0.5 A·g−1), higher energy density (34.3 W·h·kg−1) and extremely prominent cycle stability (99.7% of initial specific capacitance after 10,000 cycles) compared to those of most similar binary materials. Results suggest that the V3O7·H2O/CNT/rGO ternary composite is a promising candidate for electrode materials applying to high-performance supercapacitors.