Enhanced lithium storage performance of V(2)O(5) with oxygen vacancy

Orthorhombic phase V(2)O(5) nanosheets with a high V(4+) content (V-V(2)O(5)) 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 V(4+) in the as-prepared V-V(2)O(5) sample was 7.4%, much higher than that (4.7%) in the V(2)O(5) sample annealed in air. Compared with the V(2)O(5) annealed in air, the V-V(2)O(5) 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-V(2)O(5) and V(2)O(5) 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.