Sn-Doped V2O5 Film with Enhanced Lithium-Ion Storage Performance

Homogeneous Sn-doped V2O5 sol was prepared by the sol–gel method with H2O2, V2O5, and SnCl4·5H2O as precursors, and the films were fabricated by drop-casting, drying at ambient, and then annealing at 450 °C in air for 2 h. X-ray photoelectron spectroscopy (XPS) reveals that the Sn-doped V2O5 film contains 10% V4+ likely compensates with the accommodation of Sn4+ ions. Electrochemical and lithium-ion intercalation properties of both the pure and Sn-doped V2O5 films are systematically studied by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry (CP) tests. The Sn-doped V2O5 film shows much enhanced lithium-ion storage capacity, faster kinetics, and improved cyclic stability in comparison with pure V2O5 film. For example, after 50 cycles, the specific capacity of the Sn-doped V2O5 film retains 334 mAh g–1 with a current density of 500 mA g–1, much higher than 157 mAh g–1 of the pure V2O5 film. Sn-doping is found to reduce the electrochemical reaction resistance, increase the electrochemical reaction reversibility, and enhance the lithium-ion diffusivity. The possible explanation for such significant enhancement in lithium-ion intercalation capacity and cyclic stability of the Sn-doped V2O5 film is discussed.