Key Words:Nickel compounds;Cobalt compounds - Cobalt deposits - Electrochemical electrodes - Foam control - Hydrothermal synthesis - Manganese oxide - Supercapacitor
Abstract:A facile three-step method is designed for large-scale preparation of a NiCo<inf>2</inf>O<inf>4</inf>@MnO<inf>2</inf>/nickel foam/MnO<inf>2</inf> sandwich architecture with robust adhesion as an advanced electrode for high-performance supercapacitors. The synthesis contains the hydrothermal reaction of a cobalt-nickel hydroxide precursor on a nickel foam (NF) support and subsequent thermal conversion into spinel mesoporous NiCo<inf>2</inf>O<inf>4</inf> nanowire arrays, followed by a hydrothermal oxidation reaction to synthesize NiCo<inf>2</inf>O<inf>4</inf>@MnO<inf>2</inf>/nickel foam/MnO<inf>2</inf> sandwiches. Moreover, the tactics reported in this study enable easy control of the growth of NiCo<inf>2</inf>O<inf>4</inf> on one side of the NF and MnO<inf>2</inf> nanosheets on both sides of the NF to obtain novel NiCo<inf>2</inf>O<inf>4</inf>@MnO<inf>2</inf>/nickel foam/MnO<inf>2</inf> sandwiches. Because of the unusual structural and compositional features, the obtained NiCo<inf>2</inf>O<inf>4</inf>@MnO<inf>2</inf>/nickel foam/MnO<inf>2</inf> sandwiches manifest excellent performance with high specific capacitance (1.70 C cm<sup>-2</sup> at 2 mA cm<sup>-2</sup>), exceptional rate capability (78.5% retention at 20 mA cm<sup>-2</sup>) and ultralong cycling stability (91% retention over 30 000 cycles at 20 mA cm<sup>-2</sup>) as a battery-type electrode material for supercapacitors. When further assembled into an aqueous hybrid supercapacitor, it can deliver an energy density of 53.5 W h kg<sup>-1</sup> at a power density of 80 W kg<sup>-1</sup> and 20.7 W h kg<sup>-1</sup> at 8 kW kg<sup>-1</sup>. This novel sandwich electrode provides a new idea for improving the electrochemical performance of hybrid supercapacitors.<br/> © 2019 The Royal Society of Chemistry.
Volume:48
Issue:21
Translation or Not:no
