Synthesis of nano-sized ZnCo₂O₄ anchored with graphene nanosheets as an anode material for secondary lithium ion batteries

ZnCo₂O₄/graphene and pure ZnCo₂O₄ nanoparticles were synthesized by simple and low temperature urea-assisted auto-combustion method and annealed at 400 °C for 5 h in air atmosphere. The electron microscopy image of the obtained ZnCo₂O₄/graphene nanocomposite revealed that the ZnCo₂O₄ nanoparticles were randomly distributed and anchored on the surface of reduced graphene nanosheets. The graphene nanosheets significantly reduced the particles size and suppressed the aggregation of ZnCo₂O₄ nanoparticles as well as maintaining the good electrical conductivity of the overall sample. The size of the nanoparticles was in the range of 50–100 nm and the size of nanoparticles in the nanocomposite sample in the range of 25–50 nm. The electrochemical results showed that the ZnCo₂O₄/graphene nanocomposite electrode had greatly improved cycling stability with high reversible capacity of 755.6 mAh g⁻¹ after 70 cycles, and better rate capability of 378.1 mAh g⁻¹ at 4.5 C than pure ZnCo₂O₄ nanoparticles (299.8 mAh g⁻¹ after 70 cycles and 302.4 mAh g⁻¹ at 4.5 C). The enhanced electrochemical performance of the nanocomposite could be ascribed to the positive synergistic effect of the combination of the ZnCo₂O₄ nanoparticles and conducting graphene nanosheets