Ultra-small Co3O4 nanoparticles-reduced graphene oxide nanocomposite as superior anodes for lithium-ion batteries.

Reducing the particle size of active component in electrode material could significantly improve the electrochemical performance of lithium-ion batteries. Herein, we report a facile method for preparing cobalt oxide nanoparticles-reduced graphene oxide (Co3O4-RGO) nanocomposite, which was composed of ultra-small Co3O4 nanoparticles (∼12.5 nm in size) anchored on RGO nanosheets, as anode material for lithium-ion batteries. Both of the Co3O4-RGO nanocomposite and Co3O4 nanoparticles showed very high specific surface areas of ∼149.5 m(2) g(-1) and ∼107.4 m(2) g(-1). The Co3O4-RGO nanocomposite showed excellent coulombic efficiency, high lithium storage capacity and good rate capability. With an optimum weight percentage of RGO (∼40 wt%), the nanocomposite displayed a high reversible discharge capacity of 830.7 mA h g(-1) after 75 cycles at 200 mA g(-1), and a reversible capacity of 680.9 mA h g(-1) after 30 cycles at 200 mA g(-1) and 100 consecutive cycles at 500 mA g(-1). After each eight cycles at 50, 100, 200, and 500 mA g(-1), the nanocomposite showed high reversible specific capacities of about 1153.2, 961.0, 851.4 and 736.4 mA h g(-1), respectively. These results show the importance of anchoring ultra-small nanoparticles on graphene nanosheets for maximum utilization of electrochemically active Co3O4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.