Fabrication of Ni${}_3$S${}_2$-functionalized V${}_2$O${}_3$ nanospheres as promising anode materials for rechargeable batteries and supercapacitors

Supercapacitors (SCs) and lithium-ion batteries (LIBs) are the current representatives for high power applications in the future. In this concern, a simple solvothermal technique was directly implemented to fabricate Ni${}_3$S${}_2$-decorated V${}_2$O${}_3$ nanospheres as a potential anode material for LIB and SC applications. X-ray diffraction analysis (XRD) showed the formation of rhombohedral V${}_2$O${}_3$ structure as major phase, while rhombohedral Ni${}_3$S${}_2$ and tetragonal VO${}_2$ are existed as minor phases. Fourier Transform Infrared Spectrometer (FTIR) inspection revealed the corresponding vibrational modes for V-O-V, V=O, Ni-S and C=S bonds, respectively. Transmission electron microscope (TEM) images of the as-synthesized composite sample exhibited unique strings of nanosized sphere-like morphology. Energy dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED) techniques confirmed the existence of both oxide and sulphide components. Analysis of XPS V2p spectra demonstrated the presence of V${}^{4+}$ and V${}^{3+}$ species, showing a high agreement with the obtained results from X-ray Rietveld analysis. The prepared Ni${}_3$S${}_2$@V${}_2$O${}_3$ composite supercapacitor electrode delivered a high specific capacitance ∼ 1535 F g${}^{-1}$ at 5 mV.s${}^{-1}$ and 295 F g${}^{-1}$ at 50 mV s${}^{-1}$. Meanwhile, the fabricated Ni${}_3$S${}_2$@V${}_2$O${}_3$ battery anode stored about 550 mAh g${}^{-1}$ at 0.1 A g${}^{-1}$. Electrochemical impedance spectroscopy (EIS) results for the assembled lithium batteries revealed a good polarizability and reversibility upon multiple galvanostatic cycling up to 100 cycles.