Synthesis, Modification And Electrochemical Properties Of Li₃VO₄ As Anode Material For Lithium Ion Batteries

Recently, Li₃VO₄ is attracting more and more attentions as an insertion type anode material for lithium ion batteries. Compared with graphite and Li4Ti5O12, Li₃VO₄ has a suitable voltage plateau?0.5 1.0V vs. Li/Li+?, which can avoid surface lithium dendrite and also has a lower voltage than Li4Ti5O12. Therefore, Li₃VO₄ has been regarded as a promising anode materials for lithium ion batteries. However, the intrinsic insulation of Li₃VO₄ seriously impedes its electrochemical properties. In order to improve its electrochemical performance, we attempt to synthesize and modify Li₃VO₄ by different methods.Firstly, both a solid reaction method and a liquid reaction method have been used to synthesize Li₃VO₄, followed with high energy ball-milling of Li₃VO₄ to reduce the particle size. The particle size of Li₃VO₄ synthesized by solid-method, liquid-method and ball-milling method are about 1 2 ?m, 3 8 ?m and 300 500 nm, respectively. High energy ball-milling can effectively reduce the size of Li₃VO₄, decrease the diffusion distance of lithium ion during charge-discharge and improve its reversible capacity?254 m Ah/g?, cycle and rate performance.Secondly, carbon-coated Li₃VO₄ was obtained through a chemical vapor deposition method with the toluene as organic carbon source. The influence of coating temperature and coating time on the carbon content has been characterized. By reacting at 800 ? for 2.5 h, a uniform nanoscale carbon layer? 5 nm? is fabricated on the surface of nanosized Li₃VO₄ particles. Carbon layer coated on the surface Li₃VO₄ can improve the electronic conductivity, suppress the side reaction during charge-discharge. Therefore, the carbon-coated Li₃VO₄ exhibits better reversible capacity, better rate performance and better initial efficiency.Thirdly, Li₃VO₄/C nanowires are fabricated by electrospinning technique and following annealing process. The influence of vanadium source, annealing procedure and heating rate on the nanowire morphology has been characterized. The first charge and discharge capacity of Li₃VO₄/C nanowires are 451 mAh/g and 548 mAh/g at a current density of 40 mA/g, respectively. After 100 cycles, the capacity still retains 394 mAh/g, suggesting a good cycleability. When the current density increased to 4000 mA/g, Li₃VO₄/C nanowires can still possess a capacity of 102 mAh/g. Compared with carbon-coated nanosized Li₃VO₄, Li₃VO₄/C nanowires have a good structural stability, benign electronic conductivity and excellent lithium ion diffusion rate. Therefore, Li₃VO₄/C nanowires exhibit the best rate and cycle performance.