One-pot synthesis of NiCo₂O₄/rGO/NF hybrid electrode materials realizing ultrahigh capacitance and rapid charge/discharge at large current density

As an energy storage and conversion device, supercapacitor with fast charge/discharge rate needs higher capacitance and simpler preparation method. This work is to prepare a high-performance hybrid electrode material of cobalt acid nickel (NiCo₂O₄) and reduced graphene oxide (rGO) on nickel foam (NF) substrate (named as NiCo₂O₄/rGO/NF) by a simple one-pot hydrothermal method. The hybrid electrode materials without using any binder to avoid “dead surface”, which can exert the synergistic effect of graphene and NiCo₂O₄. The NiCo₂O₄/rGO/NF composite electrode shows ultrahigh specific capacitance of 2682.6 F/g (2.41 F/cm²) at 1 A/g, even at a larger current density of 30 A/g the capacitance retention rate is still up 80%, which shows its outstanding rate capability. Moreover, the cycling stability test exhibits the specific capacitance can retain 75% after 10,000 cycles at 50 A/g. Furthermore, a symmetric supercapacitor device based on NiCo₂O₄/rGO/NF electrode is assembled, delivering a high specific capacitance 291.5 F/g at 0.5 A/g, high energy density (58.3 Wh/kg), high power density (12 kW/kg at 35 Wh/kg), and 180% capacitance retention after 14,000 charge/discharge cycles at 10 A/g. The facile synthesis method and excellent performance of NiCo₂O₄/rGO/NF hybrid electrode provide a broader application prospect in the field of new energy.