Investigation on Carbonsphere@Nickel Cobalt Sulfide Core-shell Nanocomposite for Asymmetric Supercapacitor Application

The carbon sphere (CS)@nickel cobalt sulfide core-shell nanocomposite at five different mole ratios have been synthesized by a facile low-temperature water-bath method without any thermal treatment. The XRD results on CS, NiCo2S4 and its ternary complexation confirms nanocomposite formation which matches with the cubic structure. The FTIR confirms the complexation of CS and metal-sulfide core-shell. TEM morphology shows CS at NiCo2S4 forming a core-shell which appears as interlinked bunch of grapes. The BET surface analysis observes the high surface area for the core-shell. The XPS studies confirm the elemental presence and valence states of metal composition of the core-shell. Electrochemical studies on the pure NiCo2S4 and CS@NiCo2S4 have shown that CS@NiCo2S4 in 1:1 ratio (scn2) only exhibits higher specific capacitance of 838 F g−1 at 1 A g−1 with capacity retention of 89 % for 5000 cycles than other mole ratios. Using this scn2, asymmetric supercapacitor (ASC) device fabrication has been studied. The electrochemical studies on ASC reveal high energy density of 101 Wh kg−1 with the power density of 6.3 k W kg−1, and having good cycling stability with 92 % of capacitance retention even after 3000 cycles at 20 A g−1.