Three-dimensional NiCo2O4@NiWO4 core–shell nanowire arrays for high performance supercapacitors

Abstract

Hierarchical NiCo₂O₄@NiWO₄ core–shell nanowire arrays supported on nickel foam have been synthesized via a facile hydrothermal route coupled with a post-thermal treatment. The hydrothermally synthesized NiCo₂O₄ nanowire arrays serve as the scaffold for anchoring the NiWO₄ nanosheets. When evaluated as binder-free electrodes for supercapacitors, the optimized NiCo₂O₄@NiWO₄ hybrid electrode demonstrates remarkable electrochemical performance with a high specific capacitance of 1384 F g⁻¹ at a current density of 1 A g⁻¹ and superior cycling stability (87.6% retention over 6000 cycles at a current density of 5 A g⁻¹). In addition, an asymmetric supercapacitor (ASC) based on the optimized NiCo₂O₄@NiWO₄ electrode and activated carbon is assembled with 6 M KOH as the electrolyte. The as-fabricated ASC device can achieve a maximum high energy density of 41.5 W h kg⁻¹ at a power density of 760 W kg⁻¹. The excellent supercapacitive performance could be ascribed to the unique core–shell architecture and the synergistic effect from the NiCo₂O₄ nanowires and the ultrathin NiWO₄ nanosheets.