Construction of Hierarchical NiCo2S4@Ni(OH)2 Core-Shell Hybrid Nanosheet Arrays on Ni Foam for High-Performance Aqueous Hybrid Supercapacitors

• NiCo2S4@Ni(OH)2 core-shell hybrid nanosheet arrays were grown on Ni foam.
• The 3D Hierarchical nanostructure was revealed by SEM, TEM and STEM.
• The hybrid nanosheets exhibited high capacity and excellent rate performance.
• The hybrid supercapacitor device showed enhanced electrochemical properties.

In this work, we report a novel battery-type electrode of three-dimensional (3D) hierarchical NiCo2S4@Ni(OH)2 core-shell hybrid nanosheet arrays on Ni foam for supercapacitors. The highly interconnected NiCo2S4 nanosheets are utilized as ideal conductive scaffolds, while ultrathin and mesoporous Ni(OH)2 shell nanosheets are controllably deposited on them via a facile electrodeposition method. The optimized NiCo2S4@Ni(OH)2 hybrid electrode demonstrates a high areal capacity of 680 μAh/cm2 (240.3 mAh/g in specific capacity) at 5 mA/cm2, with excellent rate performance (94.9% with current density increased to 100 mA/cm2) and cycling stability (81.4% over 2000 cycles at 40 mA/cm2). Moreover, an aqueous hybrid supercapacitor (HSC) device has been successfully assembled with the NiCo2S4@Ni(OH)2 hybrid nanosheets and activated carbon (AC) as the positive and negative electrodes, respectively. The HSC device exhibits high energy density (53.3 Wh/kg at 290 W/kg), high power density (6420 W/kg at 32.1 Wh/kg), as well as excellent cycling stability (98.8% over 2000 cycles at 20 mA/cm2), suggesting the great potential of this hybrid nanostructure as promising electrode materials for high-performance supercapacitors.

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