Facile synthesis of hierarchical and porous V₂O₅ microspheres as cathode materials for lithium ion batteries

Hierarchical and porous V₂O₅ microspheres have been fabricated by a refluxing approach followed by annealing in air. The resulting porous V₂O₅ microspheres typically have diameters of 3-6μm and are constructed of intertwined laminar nanocrystals or crosslinked nanobricks. It is found that the vanadyl glycolates rinsed with water have pronounced pore structures than that rinsed with ethanol alone. In addition, the configuration of the vanadyl glycolates microspheres can be tuned during the refluxing along with stirring. The possible formation processes of the vanadyl glycolates and V₂O₅ products have been discussed based on the experimental data. Electrochemical tests indicate that the hierarchical and porous V₂O₅ microspheres exhibit relatively high and stable Li⁺ storage properties. The porous V₂O₅ microspheres assembled by intertwined nanoparticles maintain reversible Li⁺ storage capacities of 102 and 80mAhg^-1, respectively; whilst the porous V₂O₅ microspheres assembled by crosslinked nanobricks maintain reversible Li⁺ storage capacities of 100 and 85mAhg^-1 over 100 cycles at current rates of 0.5 and 1 C, respectively. The superior Li⁺ storage performance of the hierarchical and porous V₂O₅ microspheres could mainly be ascribed to the improved electrode/electrolyte interface, reduced Li⁺ diffusion paths, and relieved volume variation during lithiation and delithiation processes.