Hierarchical nanocomposites of vanadium oxide thin film anchored on graphene as high-performance cathodes in li-ion batteries.

Hierarchical nanocomposites of V2O5 thin film anchored on graphene sheets were prepared by slow hydrolysis of vanadyl triisobutoxide on graphene oxide followed by thermal treatment. The nanocomposite possessed a hierarchical structure of thin V2O5 film uniformly grown on graphene, leading to a high specific surface area and a good electronic/ionic conducting path. When used as the cathode material, the graphene/V2O5 nanosheet nanocomposites exhibit higher specific capacity, better rate performance, and longer cycle life, as compared to the pure V2O5. The nanocomposite cathode was able to deliver a specific capacity of 243 mAh/g, 191 mAh/g, and 86 mAh/g at a current density of 50 mA/g, 500 mA/g, and 15 A/g, respectively. Even after 300 cycles at 500 mA/g, the composite electrode still exhibited a specific capacity of ∼ 122 mAh/g, which corresponds to ∼ 64% of its initial capacity. This enhanced electrochemical performance can be attributed to facile electron transport between graphene and V2O5, fast Li-ion diffusion within the electrode, the high surface area of the composites, and a pore structure that can accommodate the volume change during lithiation/delithiation, which results from the unique hierarchical nanostructure of the V2O5 anchored on graphene.