A crystalline nickel vanadium oxide@amorphous cobalt boride nanocomposites with enhanced specific capacity for hybrid supercapacitors

Abstract

The weak electronic conductivity and severe capacity decay are the major impediments that restrict the battery-type nickel-based electrodes with high theoretical capacity. In this report, active sites-rich nickel vanadium oxide@cobalt boride (Ni3V2O8@Co-B) nanocomposites with a particular heterostructure of crystalline core-amorphous shell are synthesized through a convenient and controlled strategy. In this structure, crystalline Ni3V2O8 mainly provides the capacity and maintains the stability of the structure, while amorphous Co-B facilitates the diffusion of ions and optimizes electronic conductivity, synergistically leading to a specific capacity of 216.1 mAh g−1 (1789 F g−1) at 500 mA g−1, which is 1.5 times of Ni3V2O8 and 3.8 times of Co-B. Also, an asymmetric supercapacitors device is fabricated based on the Ni3V2O8@Co-B and activated carbon. The device displays an ultrahigh energy density of 91.2 Wh kg−1 at 400 W kg−1. These results imply that Ni3V2O8@Co-B nanocomposites show great promise for high-performance energy storage materials, and the unique structure of crystalline/ amorphous heterophase exhibits tremendous potential for electrochemical applications.