Fabrication of NiCo2S4 nanoball embedded nitrogen doped mesoporous carbon on nickel foam as an advanced charge storage material

Material properties such as high surface area, pore size distribution, variable oxidation states and good electronic conductivity are the basis for charge storage application of carbons, polymers, metal oxides and sulfides. Recently, transition metal sulfides, NiCo2S4 in particular, are in the forefront as electrode materials for energy storage devices. Here we show that a composite material of NiCo2S4 with nitrogen doped mesoporous carbon (NMC) can improve the capacitance and cyclic stability to a large extent. For this purpose we fabricated NiCo2S4 and NiCo2S4@NMC heterostructures on nickel foam employing hydrothermal method. This method allows us to directly obtain binder free electrodes for electrochemical studies. The composite materials are characterized by XRD, BET, Raman spectroscopy, SEM, HRTEM, and XPS. The electrochemical activity of these materials is investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and impedance spectroscopy (EIS). The NiCo2S4@NMC composite shows unique nanoball architecture with higher surface area (42 m2 g−1) as compared to NiCo2S4 (11 m2 g−1). This composite material shows highest capacitance value of 2017 F g−1 at 3 A g−1 compared to NiCo2S4, and excellent cyclic stability retaining 88% capacitance after 5000 cycles. The performance of NiCo2S4@NMC composite material is attributed to the conductivity of nitrogen doped mesoporous carbon network and the material porosity for easy accessibility of electrolyte ions supported by Ni foam substrate.