Reduced graphene oxide (rGO) supported highly porous polycrystalline V(2)O(5) spheres (V(2)O(5)/rGO) were prepared by using a solvothermal approach followed by an annealing process. Initially, reduced vanadium oxide (rVO) nanoparticles with sizes in the range of 10-50 nm were formed through heterogeneous nucleation on rGO sheets during the solvothermal process. These rVO nanoparticles were oxidized to V(2)O(5) after the annealing process in air at 350 °C and assembled into polycrystalline porous spheres with sizes of 200-800 nm. The weight ratio between the rGO and V(2)O(5) is tunable by changing the weight ratio of the precursors, which in turn affects the morphology of V(2)O(5)/rGO composites. The V(2)O(5)/rGO composites display superior cathode performances with highly reversible specific capacities, good cycling stabilities and excellent rate capabilities (e.g. 102 mA h g(-1) at 19 C).