Wentao Song

Self-assembly of a ZnFe2O4/graphene hybrid and its application as a high-performance anode material for Li-ion batteries

A nanohybrid based on ZnFe2O4 nanospheres and graphene nanosheets (ZnFe2O4/G) has been synthesized by a facile one-pot in situ solvothermal route. The results show that the formation of ZnFe2O4 and the reduction of graphite oxide take place simultaneously during the solvothermal reactions. Spheric ZnFe2O4 nanoparticles with a size of 100–200 nm are confined in between the graphene sheets, forming a unique hybrid nanostructure. The electrochemical measurements have shown that the ZnFe2O4/G hybrid exhibits improved electrochemical Li-storage properties compared with bare ZnFe2O4, due to the combined buffering, confining and conducting effects of the in situ introduced graphene nanosheets.

One-pot synthesis of ultrafine ZnFe2O4 nanocrystals anchored on graphene for high-performance Li and Li-ion batteries

A ZnFe2O4-nanocrystals/graphene-nanosheets (ZnFe2O4/G) nanohybrid has been prepared by a facile in situ hydrothermal route using Zn(NO3)2·6H2O, Fe(NO3)3·6H2O and graphite oxide (GO) as the precursors. Ultrafine ZnFe2O4 nanocrystals (below 10 nm) are confined by the few-layer graphene sheets reduced from GO, forming a unique sheet-like hybrid. In this structure, the direct restacking of the hydrophobic graphene sheets is refrained by loading ZnFe2O4 nanocrystals as the spacers and the aggregation of ZnFe2O4 nanocrystals is inhibited by the dispersing and confining effects of the graphene sheets. ZnFe2O4/G shows excellent rate capability and high-rate cycling stability for lithium storage. It also shows a high capacity when used as an anode for a ZnFe2O4/G–LiFePO4/C full cell.

Preparation and Li-storage properties of SnSb/graphene hybrid nanostructure by a facile one-step solvothermal route

A SnSb nanocrystal/graphene hybrid nanocomposite was synthesized by a facile one-step solvothermal route using graphite oxide, SnCl2.2H2O and SbCl3 as the starting materials, absolute ethanol as the solvent, and NaBH4 as the reductant. The formation of SnSb alloy and the reduction of the graphene oxide occur simultaneously. SnSb nanoparticles with a size of 30–40 nm were uniformly anchored and confined by the graphene sheets, forming a unique SnSb/graphene hybrid nanostructure. The electrostatic attraction between the positively charged ions (Sn2+ and Sb3+) and the negatively charged graphene oxide plays an important role in the uniform distribution of the SnSb particles on the graphene sheets. The electrochemical Li-storage properties of the nanocomposite were investigated as a potential high-capacity anode material for Li-ion batteries. The results show that the nanocomposite exhibits an obvious enhanced Li-storage performance compared with bare SnSb. The improvement of the electrochemical performance could be attributed to the formation of two-dimensional conductive networks, homogeneous dispersion and confinement of SnSb nanoparticles and the enhanced wetting of active material with the electrolyte for increased specific surface area by the introduction of graphene into SnSb nanoparticles. Li-ion chemical diffusion coefficient and ac impedance were measured to understand the underlying mechanism for the improved electrochemical performance.

One-pot synthesis of Sb-Fe-carbon-fiber composites with in situ catalytic growth of carbon fibers

A Sb-Fe-carbon-fiber (CF) composite was prepared by a chemical vapor deposition (CVD) method with in situ growth of CFs using Sb2O3/Fe2O3 as the precursor and acetylene (C2H2) as the carbon source. The Sb-Fe-CF composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), and its electrochemical performance was investigated by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The Sb-Fe-CF composite shows a better cycling stability than the Sb-amorphous-carbon composite prepared by the same CVD method but using Sb2O3 as the precursor. Improvements in cycling stability of the Sb-Fe-CF composite can be attributed to the formation of three-dimensional network structure by CFs, which can connect Sb particles firmly. In addition, the CF layer can buffer the volume change effectively.

RAPID SYNTHESIS OF CoSb3/GRAPHENE NANOCOMPOSITES BY ONE-POT SOLVOTHERMAL ROUTE AND THEIR ELECTROCHEMICAL PROPERTIES

A facile synthetic approach for CoSb3/graphene nanocomposite has been developed in this work. By adjusting Co/Sb molar ratio, reaction temperature, and reaction time, we found that nanocrystalline CoSb3 (5–10 nm) can form at a low temperature of 180°C and a short time of only 1 h via a one-pot solvothermal route. At the same time, graphite oxide can be reduced to graphene with uniformly loaded CoSb3 nanoparticles. The composites have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The nanocomposite shows improved cycling stability compared to bare CoSb3.

Preparation and characterization of LiFePO 4 /graphene-oxide composites

LiFePO 4 /graphene-oxide (GNO) composites were prepared by co-precipitation method. Their structure and morphology were investigated by X-ray diffraction, Fourier transform infrared spectra, field emission scanning electron microscopy, and transmission electron microscopy. A low content of GNO can be uniformly dispersed in the matrix of LiFePO 4 nano particles, while at a higher content, GNO will aggregate severely and has a negative effect on the electrochemical performance of LiFePO 4 . Further heat treatment can improve the crystallinity of LiFePO 4 , and improve the electrochemical performance of LiFePO 4 with a relatively low content of GNO.