Synthesis of urchin-like Ni3Si2O5(OH)4 hierarchical hollow spheres/GO composite with enhanced electrochemical properties for high-performance hybrid supercapacitors.

Designing scientific and reasonable electrode materials is a valid method to enhance the electrochemical properties of supercapacitors. Herein, urchin-like Ni3Si2O5(OH)4 (NiSi) hierarchical hollow spheres were synthesized using SiO2 spheres as a template via hydrothermal reaction, and then NiSi was combined with graphene oxide (GO) sheets to fabricate an NiSi/GO composite via electrostatic attraction. Furthermore, the influence of the quantity of GO on the electrochemical properties of the NiSi/GO materials was investigated in detail. All the results showed that the NiSi/GO composite dramatically enhanced the electrochemical performance of the urchin-like NiSi hollow spheres. When the NiSi/GO composite was evaluated as a single electrode in 3 M KOH aqueous electrolyte, it exhibited a specific capacitance of 165 F g-1 at a current density of 0.5 A g-1 and cyclic retention of 84% after 5000 cycles. The charge storage mechanism of the NiSi/GO composite is attributed to the faradaic battery-type energy-storage mechanism of NiSi and double-layer capacitive behavior of GO. The hybrid supercapacitor (HSC) device assembled using the NiSi/GO composite and activated carbon (AC) exhibited a capacitance of 109 mF cm-2 (18 F g-1) at a scan rate of 1 mA cm-2, cyclic retention of 71% after 5000 cycles and energy density of 0.37 W h m-2 (6 W h kg-1) at a power density of 1.94 W m-2 (31.8 W kg-1). All these findings suggest that the NiSi/GO composite displays a satisfactory charge storage performance and it can be used as a potential electrode material for high-performance supercapacitors.