O/W interface-assisted hydrothermal synthesis of NiCo2S4 hollow spheres for high-performance supercapacitors

Abstract

The NiCo2S4 hollow spheres were prepared by an oil/water (O/W) interface-assisted hydrothermal process using CoCl2 · 6H2O, NiCl2 · 6H2O, ethanediamine, and carbon disulfide (CS2) as raw materials. Powder X-ray diffraction (XRD), UV–Vis absorption spectrum, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy dispersive spectrometry (EDS), N2 adsorption-desorption isotherm, and X-ray photoelectron spectroscopy (XPS) were measured to characterize the morphology and microstructure of the prepared NiCo2S4 hollow spheres. When applied as the electrode material for supercapacitor, the NiCo2S4 hollow spheres show outstanding performances. The specific capacitance of the NiCo2S4 hollow spheres is 1753.2 F/g at a current density of 1 A/g. Of the capacity, 77.8 % were retained when the current density increased from 1 to 10 A/g. At a current density of 3 A/g, the specific capacitance of the NiCo2S4 hollow sphere electrode is about 1350.5 F/g after suffering 1000 continuous cycles. The supercapacitor possesses high energy density of 39.0 Wh/kg at a power density of 200 W/kg. The as-prepared NiCo2S4 hollow sphere electrode exhibits high specific capacitance, rate capacity, energy density, and good cycle stability, making it a promising electrode material for high-performance supercapacitors.