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.