Facile Preparation and Electrochemical Properties of V2O5-Graphene Composite Films as Free-Standing Cathodes for Rechargeable Lithium Batteries

Free-standing, flexible V2O5-graphene composite films were prepared by simple filtration of aqueous dispersions of V2O5 nanowires and graphene sheets. V2O5 nanowires were preferentially oriented along the plane of the film as they were sandwiched between stacked graphene sheets in the composite film. The V2O5 content in the composites was adjusted simply by varying the relative amount of the dispersions. Thermal annealing at 300 degrees C increased the conductivity of the composite films. Due to their integrated structure and high flexibility, the composite films were directly usable as flexible electrodes. In binder-free, sandwich-type lithium battery cells, a composite film containing 75.8 wt% V2O5 delivered discharge capacities of 283 mAh g(-1) and 252 mAh g(-1) at a current density of 50 mA g(-1) during the first and 50th cycles, respectively. Owing to its higher conductivity, a composite film containing 42.8 wt% V2O5 delivered a discharge capacity of 189 mAh g(-1) at 750 mA g(-1). The good performance resulted from the integrated structure of the V2O5 network embedded in stratified graphene nanosheets, with V2O5 as the Li+ host and graphene nanosheets providing the electron pathway. These composite films are promising candidates for electrical energy storage applications that require flexible electrodes. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.004208jes] All rights reserved.