Interlaced nickel phosphide nanoflakes wrapped orthorhombic niobium pentoxide nanowires array for sustainable aqueous asymmetric supercapacitor

Abstract

To obtain simple and cost-effective functional energy storage system at a practical level, a novel core-shell porous nanocomposite based on orthorhombic niobium pentoxide (T-Nb2O5) nanowires and metallic phosphides nanoflakes is reasonably designed and synthesized by a highly efficient solvothermal and subsequently moderate phosphorization procedure. The T-Nb2O5 nanowires act as structure-directing agent to directionally grow hierarchical ultrathin porous nickel phosphide (Ni2P) nanoflakes, thus providing high electrical conductivity, large surface area and sufficient redox active sites. Owing to the distinctive nanostructure and synergistic effects of the T-Nb2O5@Ni2P core-shell heterostructure, its electrochemical properties have vastly improved. When the current density is 1 A g−1, a high specific capacity of 105 mAh g−1 can be obtained. In addition, an asymmetric supercapacitor assembled based on the T-Nb2O5@Ni2P composite positive electrode and activated carbon negative electrode exhibits a high energy density of 30.2 Wh kg−1 at a power density of 453 W kg−1 and impressive cycling stability (90%) after 5000 cycles. The well-defined oxide/phosphide core-shell materials can be expected to a new type of electrode materials for the high-performance supercapacitors.