Synthesis of hierarchical three-dimensional vanadium oxide microstructures as high-capacity cathode materials for lithium-ion batteries.

Hierarchical three-dimensional (3D) vanadium oxide microstructures, including urchin-like microflowers, nanohorn-structured microspheres, nanosheet-assembled microflowers, and nanosheets bundles, are successfully synthesized by a versatile template-free solvothermal method. It is found that the concentration of the precursor (VOC(2)O(4)) solution has a significant effect on the morphologies of the products. As an example, the time-dependent phase and morphology evolution for the urchin-like vanadium oxide microflowers has been investigated in detail. Urchin-like VO(2) microflowers can be self-assembled within 2 h without using any surfactants. After calcination, the VO(2) microflowers can be easily transformed to urchin-like V(2)O(5) microstructures. The as-obtained V(2)O(5) microflowers are highly porous with a specific surface area of 33.64 m(2) g(-1). When evaluated as a cathode material for lithium-ion batteries, the V(2)O(5) sample delivers very high specific discharge capacity of 267 mA h g(-1) at a current density of 300 mA g(-1). Further, it also exhibits improved cycling stability. The excellent electrochemical performance is attributed to multiple advantageous structural features, including the nanosized building blocks, high porosity, and the 3D hierarchical microstructures.