Nitrogen doped 2D-3D network structure CMN/NiO composite for high-performance hybrid supercapacitors

In order to reduce the dense stacking of NiO nanosheets to obtain higher capacity and energy density, using CNT@mSiO2@NC (CMN) nanotubes as the substrate and urea as the precipitant, porous NiO nanoflowers and nanosheets were successfully grown between CMN nanotubes (CMN/NiO) by solvothermal method to control the morphology. The N-doped porous CMN/NiO composite obtains a high reversible capacity of 529 F g- 1 in 6 M KOH electrolyte, and the capacity cycling retention rate reach 119.84% after 5000 cycles of 20 A g-1. The characteristic mesh-flake/sheet structure and the synergistic effect between components fully expose the elec-trochemically active sites in CMN/NiO and improve it utilization during charging-discharging, and the N atom doping enhances the electrical conductivity of CMN/NiO. The assembled asymmetric supercapacitor has a voltage window of up to 2.0 V, and an energy density performance of 26.27 Wh kg- 1 at a power density of 800 W kg -1. This special structural design improves the specific capacitance, electrical conductivity, energy density and cycling stability of the electrode material compared to NiO.