Uniform decoration of vanadium oxide nanocrystals on reduced graphene-oxide balls by an aerosol process for lithium-ion battery cathode material

VO₂-decorated reduced graphene balls were prepared by a one-pot spray-pyrolysis process from a colloidal spray solution of well-dispersed graphene oxide and ammonium vanadate. The graphene-VO₂ composite powders prepared directly by spray pyrolysis had poor electrochemical properties. Therefore, the graphene-VO₂ composite powders were transformed into a reduced graphene ball (RGB)-V₂O₅ (RGB) composite by post-treatment at 300 C in an air atmosphere. The TEM and dot-mapping images showed a uniform distribution of V and C components, originating from V₂O₅ and graphene, consisting the composite. The graphene content of the RGB-V₂O₅ composite, measured by thermogravimetric analysis, was approximately 5wt %. The initial discharge and charge capacities of RGB-V₂O₅ composite were 282 and 280mA h g^-1, respectively, and the corresponding Coulombic efficiency was approximately 100 %. On the other hand, the initial discharge and charge capacities of macroporous V₂O₅ powders were 205 and 221mA h g^-1, respectively, and the corresponding Coulombic efficiency was approximately 93 %. The RGB-V₂O₅ composite showed a better rate performance than the macroporous V₂O₅ powders. Graphene-based ball: V₂O₅-decorated reduced-graphene balls and macroporous V₂O₅ powders were prepared by a spray-pyrolysis process. The V₂O₅-decorated reduced-graphene balls had higher initial charge and discharge capacities and better cycling and rate performances than the macroporous V₂O ₅ powders (see figure).