Co-Incorporated NiV2O6/Ni(HCO3)2 nanoflake arrays grown on nickel foam as a high-performance supercapacitor electrode

Abstract

Co-Incorporated NiV₂O₆/Ni(HCO₃)₂ arrays with different morphologies can grow on nickel foam (NF) via a mild one-step hydrothermal method. Among them, S-0.5-20 and S-0.25-20 were obtained at a 1 : 1 : 20 molar ratio of Co/V/urea with 0.5 and 0.25 mmol Co(NO₃)₂, respectively. They demonstrate high areal capacities of 0.99 mA h cm⁻² (7.94 F cm⁻²) and 0.56 mA h cm⁻² (4.48 F cm⁻²) at 1 mA cm⁻², respectively, which are superior to that of Co-incorporated Ni(HCO₃)₂/NF synthesized in the absence of Na₃VO₄. S-0.25-20 possesses good rate capability with 82.1% retention when the current density is increased 20-fold, and it shows superior long-term durability with 106.2% retention of the initial capacity after 10 000 charging/discharging cycles at 100 mA cm⁻². These results are associated with the porous and orderly hierarchical Co-incorporated NiV₂O₆/Ni(HCO₃)₂ nanoflake arrays directly grown on the Ni foam. Moreover, due to the synergetic effect of the individual components, electrons can be transferred from V centers to Ni active sites, thus improving the stability of the vanadate. The generation of more active species, such as Co³⁺, during cycling could account for the increased capacity. A S-0.25-10//activated carbon (AC) asymmetrical supercapacitor shows a high energy density of 0.533 mW h cm⁻² at a power density of 0.232 mW cm⁻² (0.415 mW h cm⁻² at 4.983 mW cm⁻²). Furthermore, the formation mechanism of the Co-incorporated NiV₂O₆/Ni(HCO₃)₂ nanoflake arrays is proposed.