High-surface vanadium oxides with large capacities for lithium-ion batteries: from hydrated aerogel to nanocrystalline VO2(B), V6O13 and V2O5

Vanadium pentoxide aerogels with high surface area (196 m(2) g(-1)) and ultrathin nanofiber (similar to 10 nm) morphology were prepared through a sol-gel method followed by a freeze-drying process. Such amorphous aerogels were used as a versatile precursor to synthesize vanadium oxides with diverse valences and crystallographic phases. By simply controlling the calcination atmosphere and temperature, we can successfully obtain nanocrystalline VO2(B), V6O13 and V2O5 at high vacuum, pure Ar and air atmosphere, respectively. The evolutions in morphology, structure, crystallization, chemical composition and consequent electrochemical performances upon different calcinations were discussed in detail. These derivative vanadium oxides well inherited the unique structural features of their aerogel precursors, e. g., high surface area, mesoporous network, and nanofibrous morphology, and thus delivered enhanced electrochemical performances comparing with their bulk counterparts when used as the electrode materials for lithium-ion batteries. The larger capacities of these vanadium oxides derived from aerogels were attributed to their high surface area and nanofiber structure which promise both high reaction active surface and short Li+ diffusion paths upon Li+ intercalation/de-intercalation.