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.