Construction of carbon-nickel cobalt sulphide hetero-structured arrays on nickel foam for high performance asymmetric supercapacitors

Abstract NiCo 2 S 4 and carbon-NiCo 2 S 4 hetero-structured nanosheet arrays have been firstly synthesized on nickel foams in a facile hydrothermal and CVD method. The products NiCo 2 S 4 and carbon-NiCo 2 S 4 are obtained in Na 2 S aqueous solution in a hydrothermal reaction from precursor of NiCo x (OH) y and carbon-NiCo 2 O 4 through anion exchange respectively, which are characterized by XRD, TEM, Raman analysis. The obtained binary metal sulphide NiCo 2 S 4 nanosheet delivers better electrochemical activity and higher mass loading compared with NiCo 2 O 4 . In addition, carbon introduced enhances the capacitive behaviours and cycle performance for enhanced electric conductivity and stable architecture. The integrated carbon-NiCo 2 S 4 electrode exhibits high areal capacitance of 8.33 F cm −2 and ultrahigh specific capacitance of 1893.2 F g −1 with a potential window of 0.8 V and high mass loading of 4.4 mg cm −2 and good cycle performance in a three-electrode system. The asymmetric supercapacitor is further assembled using carbon-NiCo 2 S 4 as the positive electrode and activated carbon as the negative electrode. The integrated asymmetric supercapacitor demonstrates a high energy density of 68.82 Wh kg −1 at a power density of 47.83 W kg −1 , which confirms its practical applicability.