In situ synthesis of Co<inf>3</inf>O<inf>4</inf>/graphene nanocomposite material for lithium-ion batteries and supercapacitors with high capacity and supercapacitance

Co3O4/graphene nanocomposite material was prepared by an in situ solution-based method under reflux conditions. In this reaction progress, Co2+ salts were converted to Co3O4 nanoparticles which were simultaneously inserted into the graphene layers, upon the reduction of graphite oxide to graphene. The prepared material consists of uniform Co3O4 nanoparticles (15-25 nm), which are well dispersed on the surfaces of graphene nanosheets. This has been confirmed through observations by field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The prepared composite material exhibits an initial reversible lithium storage capacity of 722 mAh g-1 in lithium-ion cells and a specific supercapacitance of 478 F g-1 in 2 M KOH electrolyte for supercapacitors, which were higher than that of the previously reported pure graphene nanosheets and Co 3O4 nanoparticles. Co3O4/graphene nanocomposite material demonstrated an excellent electrochemical performance as an anode material for reversible lithium storage in lithium ion cells and as an electrode material in supercapacitors. © 2011 Elsevier B.V. All Rights Reserved