Lithium Storage Properties Of Carbon Nanotubes Films And Oxide-carbon Nanotubes Composites

Because of the high specific area,excellent mechanical property and electronic conductivity for its unique structure,carbon nanotubes?CNTs?have great potential in application when used as electrode materials.However,there are still obvious disadvantages compared with silicon based materials and transitional metal oxide,such as low capacity and high irreversible capacity for the first cycle.In this paper,we improved the application performance of CNTs by modifying the morphology of CNTs through nitrogen doping and designing hybrid structural system composed of CNTs and oxide,and investigated lithium ion storage properties of the as-prepared films.Continuous Fe₂O₃/CNTs composite films have been fabricated along the CVD gas flow reaction and subsequent annealing process in the air.Fe₂O₃ nanoparticles are homogeneously bounded with CNT network in Fe₂O₃/CNTs composite films.In addition,the 3D CNT network endow the as-synthesized composite films with increased electrical conductivity and mechanical stability.The flexible composite films can be used as electrode materials with no addition of carbon additive and binder,and deliver an initial reversible capacity of 985.8 mAh g^-1 at current density of 30 mA g^-1,and maintain a high reversible capacity of 392.4 mAh g^-1 even at a current density up to 3 A g^-1.Meanwhile,Fe₂O₃/CNTs films exhibit excellent cycling performance with a reversible capacity of 375.5 mAh g^-1 after 800 cycles at the current density of 3 A g^-1.SiO₂/CNTs composite films were fabricated by CVD using ethyl silicate as silicon precursor,ethanol as carbon precursor and ferrocene as catalyst.Results indicate that wrapping structure is obtained when the mass fraction of ethyl silicate is 8 wt.%,and the as-synthesized SiO₂/CNTs composite films deliver an initial reversible capacity of 2180.8 mAh g^-1 at current density of 30 mA g^-1 with coulombic efficiency of 44.1%,and maintain a high reversible capacity of 397.1 mAh g^-1 even at a current density up to 2 A g^-1.In this paper,we investigated the impact of different nitrogen sources on CNTs morphology.There are a small amount of long and straight carbon nanotubes and a large number of bamboo-like carbon nanotubes in reaction product using ethanol amine as nitrogen sources.As a result,the initial capacity(1642.2 mAh g^-1)and coulombic efficiency?36.9%?for the first cycle are markedly increased.