Preparation And Lithium Storage Properties Of Vanadium Oxide-based Anode Materials

V₂O₃ has attracted considerable attention as an anode material for LIBs because it possesses the advantages of high theoretical specific capacity(1070 m A h g^-1),broad resource of raw material,low cost and toxicity,etc.In this paper,V₂O₃@C composites with different morphologies were prepared by template-free hydrothermal or solvothermal method through changing a variety of reaction parameters.The relationship between the formation of morphology and the reaction parameters was discussed in detail.The optimal synthesis conditions,morphology,structure,formation mechanism and electrochemical performance of flower-like V₂O₃@C composites and self-supported V₂O₃@C composites were studied systematically.The main results are as follows:(1)V₂O₃@C composites with different morphologies were prepared through adjusting the source of vanadium and carbon,hydrogen peroxide content and the type of reaction solvent,such as one-dimensional nanobelts,two-dimensional nanosheets,three-dimensional flower-like structures and hollow spheres.The effect of reaction parameters on the morphology of V₂O₃@C composites was systematically studied.Among them,three-dimensional flower-like V₂O₃@C exhibits the best electrochemical performance.(2)The three-dimensional flower-like V₂O₃@C composite has been synthesized by solvothermal method using VO(acac)₂and urea as raw materials in glycol/water system.The flower-like V₂O₃@C composite is constructed by bicontinuous 3D hierarchical structures:one is made up of interconnected nanoparticles and the other is formed by the interconnected pores.The diameter of the flower-like V₂O₃@C composite is between 0.8?1.5?m.The material exhibits excellent lithium storage performance:after400 cycles at a current density of 0.5 A g^-1,the discharge specific capacity of flower-like V₂O₃@C electrode(474 m A h g^-1)is far more than that of the pure V₂O₃electrode(139 m A h g^-1).Furthermore,after 1000 and 2000 cycles at a high current density of 2 A g^-1,about 94%and 75%of the first-cycle discharge capacity are maintained,which demonstrates the excellent long-term cycling stability of the V₂O₃@C electrode.(3)Self-supporting V₂O₃@C porous nanosheet arrays without binder and conductive additive were synthesized by the solvothermal method using VO(acac)₂and urea as raw materials and nickel foam as collector current in glycol/water system.The nanosheet arrays are made up of interconnected nanoparticles.The material exhibits excellent lithium storage performance:at a current density of 0.1 A g^-1,it can still maintain a specific discharge capacity of 892 m A h g^-1 after 400 cycles,much higher than that of commercial graphite electrodes.