Construction of hierarchical ZnCo₂O₄@Ni_xCo_2x(OH)_6x core/shell nanowire arrays for high-performance supercapacitors

Rational design and synthesis of core/shell nanostructures as binder-free electrodes has been believed to be an effective strategy to improve the electrochemical performance of supercapacitors. In this work, hierarchical ZnCo₂O₄@Ni_xCo_2x(OH)_6x core/shell nanowire arrays (NWAs) have been successfully constructed by electrodepositing Ni_xCo_2x(OH)_6x nanosheets onto hydrothermally grown ZnCo₂O₄ nanowires and investigated as a battery-type electrode for hybrid supercapacitors. Taking advantage of the hierarchical core/shell structures and the synergetic effect between ZnCo₂O₄ nanowires and Ni_xCo_2x(OH)_6x nanosheets, the optimised core/shell electrode exhibits remarkable electrochemical performance with a high areal capacity (419.1 μA h cm⁻²), good rate capability and cycling stability. Moreover, the assembled ZnCo₂O₄@Ni_xCo_2x(OH)_6x//activated carbon (AC) hybrid device can be reversibly cycled in a large potential range of 0–1.7 V and deliver a maximum energy density of 26.2 W h kg⁻¹ at 511.8 W kg⁻¹. Our findings indicate that the hierarchical ZnCo₂O₄@Ni_xCo_2x(OH)_6x core/shell NWAs have great potential for applications in energy storage devices.