In Situ Growth of 3D Hierarchical ZnO@Ni _xCo_1−x(OH) _y Core/Shell Nanowire/Nanosheet Arrays on Ni Foam for High-Performance Aqueous Hybrid Supercapacitors

Abstract

In this study, we designed and synthesized a novel battery-type electrode featuring three-dimensional (3D) hierarchical ZnO@Ni _xCo_1−x(OH) _y core/shell nanowire/nanosheet arrays arranged on Ni foam substrate via a two-step protocol including a wet chemical process followed by electro-deposition. We then characterized its composition, structure and surface morphology by X-ray diffraction, energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy, EDS elemental mapping. Our electrochemical measurements show that the ZnO@Ni_0.67Co_0.33(OH) _y electrode material exhibited a noticeably high specific capacity of as much as 255 (mA·h)/g at 1 A/g. Additionally, it demonstrated a superior rate capability, as well as an excellent cycling stability with 81.6% capacity retention over 2000 cycles at 5 A/g. This sample delivered a high energy density of 64 W·h/kg and a power density of 250 W/kg at a current density of 1 A/g. With such remarkable electrochemical properties, we expect the 3D hierarchical hybrid electrode material presented in this work to have promising applications for the next generation of energy storage systems.

Keywords

ZnO@Ni _xCo_1−x(OH) _y / Core/shell nanowire/nanosheet array / Supercapacitor / Ni foam

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