In this work, a facile, one-pot route has been applied to synthesize nanohybrids based on mixed oxide NiFe2O4 and reduced graphene oxide （rGO）. The hybrid is constructed by nanosized NiFe2O4 crystals confined by few- layered rGO sheets. The formation mechanism and microstructure of the hybrids have been clarified by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical tests show that the performance of NiFe2O4 can be considerably improved by rGO incorporation. The performance improvement can be attributed to the two-dimensional conductive channels and the unique hybrid structure rGO constructed. The easy synthesis and good electrochemical performance of NiFe2O4/rGO hybrid make it a promising anode material for Li-ion batteries.
A SnSb nanocrystal/graphene hybrid nanocomposite was synthesized by a facile one-step solvothermal route using graphite oxide,SnCl_(2).2H_(2)O and SbCl_(3) 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(Sn^(2+) and Sb^(3+))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.
Nano structured LiFexMn1-xPO4 （x=0, 0.2, 0.4） materials were successfully prepared by one-step reflux method in a water/PEG400 mixed solvent, and were coated by carbon using glucose as the precursor. The materials were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）. The electrochemical properties of the materials were investigated by galvanostatic cycling, cyclic voltammetry （CV） and electrochemical impedance spectroscopy （EIS）. It was found that the materials consisted of nanorods with a diameter of 50 nm and a length of 500 nm. Galvanostatic cycling showed that the capacity of LiMnPO4 could be largely increased by Fe2＋ substitution. At a current rate of C/20, the capacity of the three samples （x=0, 0.2, 0.4） were 47, 107 and 150 mA-h.g-1, respectively. CV result showed that the Fe2＋ substitution could decrease the polarization during charging/discharging, ac- celerating the electrochemical process. EIS result showed that the Fe2＋ substitution could decrease the charge transfer resistance between the electrode and electrolyte, as well as increase the Li-ion diffusion coefficient in the bulk material, resulting in an improved electrochemical performance.
