Controllable Preparation of V₂O₅/Graphene Nanocomposites as Cathode Materials for Lithium-Ion Batteries

Transition metal oxides and graphene composites have been widely reported in energy storage and conversion systems. However, the controllable synthesis of graphene-based nanocomposites with tunable morphologies is far less reported. In this work, we report the fabrication of V₂O₅ and reduced graphene oxide composites with nanosheet or nanoparticle-assembled subunits by adjusting the solvothermal solution. As cathode materials for lithium-ion batteries, the nanosheet-assembled V₂O₅/graphene composite exhibits better rate capability and long-term cycling stability. The V₂O₅/graphene composites can deliver discharge capacities of 133, 131, and 122 mAh g^-1 at 16 C, 32 C, and 64 C, respectively, in the voltage range of 2.5-4.0 V vs. Li/Li⁺. Moreover, the electrodes can retain 85% of their original capacity at 1C rate after 500 cycles. The superior electrochemical performances are attributed to the porous structures created by the connected V₂O₅ nanosheets and the electron conductivity improvement by graphene.