Nanoleaf-on-sheet CuO/graphene composites: Microwave-assisted assemble and excellent electrochemical performances for lithium ion batteries

• CuO nanoleaves on graphene composite was synthesized by a microwave-assisted method.
• This method was demonstrated to be rapid, time saving and environmentally friendly.
• The capacity of the composites retains 600 mAh g−1 after 50 cycles at 100 mA g−1.
• Conductive graphene prevents aggregation and pulverization of CuO nanoleaves.

CuO nanoleaves on graphene sheets (CuO/GNS) composite was successfully synthesized by a facile microwave-assisted method using Cu(NO3)2·3H2O, NaOH and ammonia as raw materials and absolute ethanol as solvent. The structure and morphology were characterized by XRD, SEM, TEM, HRTEM. The electrochemical performance was measured by cyclic voltammetry (CV), galvanostatic charge and discharge measurements and AC impedance test. The results revealed that the leaf-shaped rhombic CuO were uniformly dispersed on GNS with a width of 40 nm in the middle and a length of 100-140 nm. As an anode material for Li-ion battery, the CuO/GNS composites showed enhanced electrochemical performance with high lithium storage capacity, satisfactory cyclic durability and rate capacity than pristine CuO. The reversible capacity of the CuO/GNS composites retained 600 mAh g−1 after 50 cycles at 100 mA g−1. Even when cycled at various rates for 50 cycles, the capacity could recover to 600 mAh g−1 at the current of 100 mA g−1. The excellent electrochemical performance was ascribed to the synergy effect of the uniformly distributed CuO nanoleaves and graphene sheets. The CuO nanoleaves between the graphene sheets effectively kept the neighboring graphene sheets separated, and graphene effectively prevented aggregation and pulverization of CuO nanoleaves. The overall electrode was highly conductive, and the stability of the structure was maintained.

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