NiO nanoflakes decorated needle-like MnCo₂O₄ hierarchical structure on nickle foam as an additive-free and high performance supercapacitor electrode

Although many researches have been made in the construction and fabrication of electrode materials for supercapacitors, it remains a difficult task to realize the application of the supercapacitor with high energy density. The binary MnCo₂O₄@NiO hierarchical electrode has been successfully fabricated on nickel foam (NF) without any binder or additives by simple hydrothermal methods and corresponding annealing processes. By virtue of constructing hierarchical core–shell structure with different morphologies and forming additive-free electrode, the composite electrode not only possesses abundant surface active sites for electrochemical reaction as well as large buffering space for volume deformation in the charging-discharging processes, but also shows the improved contacting area and electric conductivity between active substance and metal collector. The synthetic MnCo₂O₄@NiO/NF electrode presented higher specific capacitance (1186 F g⁻¹ under 1 A g⁻¹) and long cycle lifespan (maintain 91% of the original capacitance over 5000 cycles) under a high current density of 10 A g⁻¹. Further, the asymmetric supercapacitor with MnCo₂O₄@NiO/NF electrode shows higher energy density of 42.2 Wh kg⁻¹ under a power density of 748.2 W kg⁻¹. These results demonstrate that the binary MnCo₂O₄@NiO hierarchical structure is the hopeful candidate material for high performance supercapacitor electrode.