Facile template-free fabrication of hierarchical V2O5 hollow spheres with excellent charge storage performance for symmetric and hybrid supercapacitor devices

A facile and low-cost synthetic route is of great importance for materials with special structure, and all the more so when the as-prepared product display a high performance. In this work, we developed a synthetic route to synthesize V2O5 hollow spheres with high capacity and rate capability through a template-free method. Diameter of V2O5 hollow spheres ranged from 400 nm to 600 nm, and thickness of V2O5 shells was about 40 nm in average. V2O5 hollow spheres exhibited porosity varying mesoporous to macroporous. Electrochemical properties of V2O5 hollow spheres were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (ESI) in the aqueous electrolyte. V2O5 hollow spheres displayed excellent capacity and rate capability. Specific capacity of V2O5 hollow spheres first improved with increase of temperatures, then it decreased due to the destruction of hollow structures at high temperature. Specific capacities totaled 512, 470, 423, 390, 358 and 324 C g(-1) at current densities of 0.5, 1, 2, 5, 10 and 20 A g(-1) respectively. Specific capacity of asprepared V2O5 hollow spheres reached as high as 512 C g(-1);, suggesting these materials exhibited excellent charge storage performance. A symmetric supercapacitor (SSC) device and a hybrid supercapacitor (HSC) device were fabricated using hierarchical V2O5 hollow spheres, which exhibit an areal capacitance of 333 and 334 mF cm(-2), and the results demonstrated that the electrochemical performance of V2O5//AC HSC device was better than that of V2O5//V2O5 SSC device. (C) 2018 Elsevier B.V. All rights reserved.