Synthesis and characterization of hollow and core-shell structured V2O5 microspheres and their electrochemical properties

The hierarchical V2O5 hollow and core-shell microspheres are synthesized via solvothermal method with subsequent annealing treatment. The V2O5 hollow microspheres with the mesoporous characteristics are assembled by nanosheets, which provide high specific surface area (136.33 m(2) g(-1)) and sustain good structural integrity. These advantages are conducive to obtain the excellent electrochemical performance. As the cathode materials, the V2O5 hollow microspheres have no capacity fading after 100 cycles at 100 mA g(-1) and deliver a capacity retention of 91.67% after 500 cycles at 500 mA g(-1), a high average capacity of 129.3 mA h g(-1) can be reached even at a high current density of 5000 mA g(-1), which indicates highly reversible capacity, good cycling stability and rate capability. However, due to the agglomeration and the dissolution in the electrolyte of the active materials and the bad electrical contact between the inner and external shell, the electrochemical performance at high current densities of V2O5 core-shell microspheres is disappointing. An extremely low average capacity of 11.5 mA h g(-1) can be delivered at 5000 mA g(-1). Furthermore, the method of preparing core-shell microspheres provides a novel strategy for synthesizing hierarchical microspheres with void space. (C) 2017 Published by Elsevier B.V.