| Recently, with the rapid development of the portable electronic and communication devices, such as mobile telephone, notebook, digital camera, especially for hybrid electric or all electric vehicles (HEVs or EVs), people need the lithium ion batteries with higher energy density, better cycliability and reliability. The breakthrough in the electrode materials is the key point for exploit the next generation of the lithium ion batteries. At present, a lot of research work focus on two sides:on the one hand, to ensure the lithium ion battery has good cycle stability, the point that designing the electrode materials with reasonable structure to relieve the volume expansion in the charge-discharge process was adopted; on the other hand, standpoint that preparing composite to realize the maximization of the lithium ion battery capacity was accepted. Among the various electrode materials, one-dimensional (1D) nanostructure composite, because of its unique morphology and structure, is thought as a distinguished anode material.1D nanostructure composite is able to provide a direct pathway with less crystal boundaries for the rapid electron transport, which is expectable for the higher reversible capacity. Besides,1D nanostructure composite with higher specific surface can provide more shorter pathway of extraction and insertion lithium ion, which can exhibit little polarization, better reversibility and cycliability. Meanwhile, one-dimensional(1D) nanostructure composite achieve the complex of many ingredients to overcome the shortcoming of unsatisfied capacity of a single component.In this paper, we systematically investigate the preparation and performance of one-dimensional (1D) metal oxide/carbon nanocomposites as anodes of lithium ion battery. Three kinds of electrode materials were successfully prepared by electrospinning, solvothermal and direct redox methods integrated with calcination, respectively. The synthesized samples were well characterized and their electrochemical performances were studied. The e main achievements can be summarized as follows:1. The spinnable solution were prepared by dissolving PVP and Co(NO3)2 into ethanol/water mixed solvent, PVP-Co(NO3)2 composite nanofibers were fabricated by electrospinning technique. One dimensional carbon nanofiber (CNF)/CoOx (0<x<1.33) nanocomposites with different struture prepared from the PVP-Co(NO3)2 composite nanofibers which were sintered at 550℃ for 90,120 and 150 min in argon atmosphere. There are three valence states, such as Co3+, Co2+ and Co0 in CoOx. Also The calcinated time have a important effect on the morphologies of samples. When calcinated for 90 min, CoOx nanoparticles were mainly distributed in interior of CNF while inserted on or in the exterior of CNF at the annealed time of 120 min and 150 min respective. The results demonstrat that compsosite nanofibers sintered for 120 min as anode material possess the most excellent electrochemical performance, which exhibit a reversible capacity of 689.3 mAh/g at the current density of 100 mA/g for 50 cycles.2. Natural jute was simply treated by a controllable hydro thermal process performed in alkaline solutions, wherein abundant natural cellulose fibers in jute in situ get separated and dispersed spontaneously. After carbonization, cellulose fibers were transformed to hollow carbon fibers with roughness surface. Potassium permanganate was employed as the oxidant for pyrrole in the presence of carbon fibers. The carbon fiber/MnO/C was first prepared by solvothermal method followed by calcination in nitrogen, MnO/C distributes on the surface of carbon fiber. The MnO nanoparticles with the size of 50-150nm were wrapped in the carbon which came from the polypyrrole. A high reversible capacity of about 400 mAh/g is maintained without obvious decay up to 50 cycles at the current density of 100mA/g. Meanwhile, the composite also exhibits well rate performance. Our strategy presents a very promising way to massively fabricated anodes for lithium ion batteries.3. The CNT-SnCl2 precursor was prepared by filling SnCl2 in the channel of carbon nanotube (CNT) because of capillary forces and ultrasound, then SnO2@CNT nanocomposite anode materials are fabricated from the CNT-SnCl2 precursor by calcination in nitrogen, which the SnCl22 nanoparticles were wrapped in the channel of CNT. Then, KMnO4 as the oxidant for SnO2@CNT, SnO2@CNT@MnO ternary nanocomposites were prepared by in situ redox reaction between KMnO4 and CNT. The prepared SnO2@CNT@MnO presents an improvement in the capacity and cycling performance, which is ascribe to the synergistic effect of different components, shorter pathway of extract-insert lithium ion in charge-discharge process and more effective electronic transmission channel. As anode materials, the as-obtained SnO2@CNT@MnO shows a reversible capacity as high as 461.2 mAh/g after 40 cycle at the current density of 100mA/g, which is potential for practical application in lithium-ion batteries. Besides, SnO2@CNT@MnO also exhibits high rate performance. |
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