| In recent years, the energy crisis and the concomitant environmental problems have attracted more and more attention due to the extensive use of some traditional energy sources such as oil. The rechargeable lithium ion battery has brought the broad space for the development of energy storage owning to its lots of outstanding merits such as small and light, the long life, high voltage and environmental friendly. In lithium ion anode materials, such as Fe3O4, have attracted wide research interests because of high theoretical capacity, natural abundant, low cost, and environmentally friendly. In this graduation thesis, we have conducted the fabrication, characterization and the electrochemical test of Fe3O4/C composites.The main content is concisely described as follows:Firstly, We succeeded in preparation of Fe3O4/C nanotubes by single nozzle electrostatic spinning method based on the phase separation. The Fe(acac)3 and mineral oil uniformly dissolved in the PAN and DMF to obtain stable precursor solution, and then prepare Fe(acac)3/ PAN nanofibers by electrospinning, and Fe3O4/C nanotubes were obtained followed by stabilization in air 250 degree and carbonization in argon 600 degree. And then we have characterized the fabricated Fe3O4/C nanotubes by SEM, TEM, XRD, BET, Raman, and XPS. We find that the obtained Fe3O4 nanoparticles with diameter 10 to 100 nm were uniformly embedded into highly conductive carbon nanotube wall. In the last, we discusses the formation mechanism of the hollow tubes structure and test its electrochemical performance. The results showed that the Fe3O4/C nanotubes have better cycle stability than the Fe3O4/C nanofibers.Secondly, A flexible composite of CNT-encapsulated Fe3O4 spheres(Fe3O4/CNTs) is successfully synthesized by a simple electrostatic attraction self-assembly followed by vacuum filtration. In the first, the Fe3O4 nanospheres(Fe3O4NSs) were synthesized by simple one-pot hydrothermal method. Then Fe3O4 carries a positive charge after surface modification and CNT carries a negative charge after oxidation. In the last, the CNT-encapsulated Fe3O4(Fe3O4/CNTs) were then fabricated by the electrostatic interaction of positively-charged APS-modified Fe3O4 NSs and negatively-charged CNTs. We have studied the morphology and structure of the composite by SEM, XRD and Raman spectroscopy. Finally, we study the electrochemical properties of the Fe3O4/CNT anode. The result shows that theFe3O4/CNT composites exhibit a larger reversible capacity as well as excellent rate capability compared to the Fe3O4 spheres or a mixture of CNT and Fe3O4 sphere when used as anode material for Li-ion batteries. |
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