Ultra-small Ni-VN nanoparticles co-embedded in N-doped carbons as an effective electrode material for energy storage

As a class of emerging anode material, much attention has been dominated to vanadium nitride (VN) in view of its high specific capacitance, exceptional conductivity and proper operating potential window (OPW). Herein, ultra-small Ni nanoparticles (NPs) and VN NPs have been embedded in N-doped carbons (NCs) nanosheets as an anode material for supercapacitors (SCs), making the good use of the conductivity of Ni NPs and NCs nanosheets, as well as the excellent specific capacitance of VN NPs, the novel 3-Ni/VN/NCs-7 composite electrode exhibits an admirable specific capacitance of 236 F g−1 at 1 A g−1. Furthermore, the (−) 3-Ni/VN/NCs-7//CuCo2O4 (+) asymmetrical supercapacitor (ASC) and 3-Ni/VN/NCs-7 symmetrical supercapacitor (SSC) have been assembled, respectively. The (−) 3-Ni/VN/NCs-7//CuCo2O4 (+) ASC device shows a capacitance of 65 F g−1 at a large OPW of 1.8 V. More importantly, it achieves an energy density of 25 Wh kg−1 at 930 W kg−1 and a superb cycling stability (73.5% retention after 5000 cycles). Strikingly, the 3-Ni/VN/NCs-7 SSC device not only presents surpassing cycling behavior, but also possesses favorable energy density of 13.4 Wh kg−1 at a power density of 600 W kg−1, which is superior to most of the carbon-based materials.