Hierarchical design of core-shell structured Ni3S2/CoAl-LDH composites on rGO/Ni foam with enhanced electrochemical properties for asymmetric supercapacitor

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Three-dimensional hierarchical hybrid composites incorporating both CoAl-layered double hydroxide and Ni3S2 grown onto the framework of reduced graphene oxide (rGO) on Ni foam were successfully fabricated by hydrothermal procedure combined with electrodeposition method (Ni3S2/CoAl-LDH/rGO). The Ni3S2 nanoplates was anchored on the surface of the CoAl-LDH/rGO nanosheets, forming a cross linked core-shell structure. Electrochemical measurements demonstrate that the outer Ni3S2 layer can significantly influence the morphology and electrochemical properties of the hybrid electrodes. Benefiting from its attractive structural feature and strong synergy of multiple components, excellent results were obtained in the composite with the optimal mass loading of Ni3S2 layer, which exhibited an excellent specific capacitance of 2457.5 F g−1 at 1 A g−1 and a desirable cycling behavior of 90.0% retention over 5000 cycles. The assembled asymmetric supercapacitor using Ni3S2/CoAl-LDH/rGO as positive electrode and active carbon as negative electrode delivers a high energy density of 59.8 W h kg−1 at a power density of 402.8 W kg−1 and a good cycling property (91% capacitance retention after 8000 cycles). These encouraging results demonstrate that such hybrid nanostructure provides great potential as electrode material for the energy storage devices.