The Preparation And Lithium-storage Properties Of Transition Metal Oxide/Nanocarbon Composites

Transition metal oxides have shown desirable properties, such as high theoreticalcapacity, low processing cost and environment friendly, making them promisinganode materials for high performance lithium-ion batteries. However, the practicalapplication of transition metal oxides as an anode materials is seriously hampered bythe low electronic conductivity and drastic volume variation during the process oflithium ion storage, resulting in the rapid capacity fade upon cycling. By means ofsynthesis of nanocomposites, we extended the transition metal oxides of Fe3O4intothe anode materials basing on the conversion reaction and TiO2into the electrodematerials basing on the interaction reaction.(1) A one-pot solvethermal process for fabricating Fe3O4/MWCNTs―core-shell‖hybrids have been realized using benzyl alcohol as the solvent. Fe3+canelectrostatically adsorb on the surface of MWCNTs network based on the π-πinteraction between the benzene ring of benzyl alcohols and aromatic regions ofMWCNTs. The results demonstrate that Fe3O4nanoparticles about10nm weredeposited on the surface of MWCNTs. The Fe3O4/MWCNTs hybrids exhibit highreversible charge capacity of487mAh g-1at the current density of0.1A g-1after100times cycling, the cycling stability of hybrids are much superior to pure Fe3O4electrode materials. Moreover, the reversible capacity of389mAh g-1can be obtainedeven at the rate of2A g-1.(2) Due to the limitations of electron and ion transport in the one dimensionaldirection within MWCNTs, the improvement of the electrochemical performanceabout active substances has certain restriction. I use the composites of graphene andMWCNTs as a three dimensional conductive substrate to improve the electrochemicalproperties of Fe3O4nanoparticles. The results demonstrated that the deposition ofFe3O4on rGO-CNTs surface were about10nm. The cycling stability of the obtainedcomposite was better than that of pure Fe3O4electrode material. At the current densityof0.1A g-1, after100cycles, its reversible discharge capacity still remained about840mAh g-1, and the415mAh g-1reversible discharge capacity can be obtained evenat the current density of2.0A g-1. (3) A one-pot solvethermal process for fabricating TiO2nanoparticles that areuniform anchored on graphene backbone have been realized. In the solvethermalprocess, benzyl alcohol was used as the solvent and reducing agent. The resultsdemonstrate that the reduction of graphene oxide and the deposition of TiO2nanoparticles about6nm on reduced graphene surface were realized simultaneously.The TiO2/r-GO hybrids exhibit high reversible discharge capacity of156mAh g-1,126mAh g-1and95mAh g-1at the discharge/charge rates of1C,5C and20C after200times cycling, and it has an superior rate performance compared with the bareTiO2electrode.