Enhanced lithium storage performance of V₂O₅ with oxygen vacancy

Orthorhombic phase V₂O₅ nanosheets with a high V⁴⁺ content (V-V₂O₅) have been fabricated via a facile sol-gel method and freeze-drying technology followed with a vacuum annealing process. XPS tests demonstrated that the content of V⁴⁺ in the as-prepared V-V₂O₅ sample was 7.4%, much higher than that (4.7%) in the V₂O₅ sample annealed in air. Compared with the V₂O₅ annealed in air, the V-V₂O₅ sample exhibited better cycling stability, higher lithium storage activity, and smaller electrochemical reaction resistance when evaluated as a cathode active material for lithium ion batteries. For example, the specific capacity of the V-V₂O₅ and V₂O₅ electrodes after 100 cycles at 200 mA g^-1 are 224.7 and 199.2 mA h g^-1, respectively; after 200 cycles at 3 A g^-1 are 150 and 136.7 mA h g^-1, respectively.