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

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.