| Lignin is the solid waste, which are abundant in the straws and bagasses. However, most of the lignin were used as low value-added products in the field of fuel, cement and so on, or burnt and discharged casually, resulting in biomass resources waste, and thus a seriously environmental pollution.Carbon nanofibers (CNFs) have been widely used in clean energy fields such as hydrogen storage materials and anode materials for lithium-ion batteries etc., due to their unique pore structure, high specific surface area, high conductivity, good stability and so on. Nowadays, most of CNFs are obtained from PAN via melt spinning or wet spinning processes. However, the disadvantages of these fibers such as large diameter and wide pore size distribution leads to a low energy strorage capability, which limits their extensive application in the energy fields. In this dissertation, Lignosulfuonate (LN) and poly aery lonitrile (PAN) were employed as a composite precursor to fabricate LN/PAN-based carbon fibers and Germanium/mesoporous carbon fibers (Ge/MCF) composite materials with special structures and properties, which were prepared via elecrosp inning followed by pre-oxidation (stabilization) and carbonization. The processes are described as follows.1) LN and PAN were dissolved in DMF to prepare an elecrosp inning solutioa The LN/PAN-based carbon fibers were fabricated from the obtained solution by electrospinning, thermo stabilization and carbonization process. The prepared carbon fibers possess a diameter 240 nm, Sbet 218.9 m2/g and Vtotal (less than 1 nm) 0.0851 cm3/g. Hydrogen adsorption capacity of the LN/PAN-based carbon fibers under 95 bar at 25℃ are determined to be 0.69 wt%, indicating the materials are available for hydrogen storage.2) Besides, Ni and B elements were employed as a composite catalyst for the graphition of LN/PAN carbon fibers. It is clear that both Ni and B can enhance the graph it izat ion of the fibers. Moreover, the two elements show a synergic catalytic function when presence simultaneously. The R (Id/Ig) value of the LN/PAN-based carbon fibers graphitized with 20%Ni-5%B is determined to be 0.55. The hydrogen adsorption capacity of the graphited LN/PAN-based compositecarbon fibers under 95 bar at 25 ℃ is about 0.92 wt%, suggesting that the hydrogen storage capacity of LN/PAN-based composite carbon fibers can be increased by graphitization treatment.3) The electrospun LN/PAN-based fibers were water-etched to obtain porous fibers, and the porous materials were employed as a precursor to fabricate mesoporous carbon fibers (MCF) via pre-oxidation and carbonization/activation processes. Finally, the Ge-MCF composite materials with a ball-chain like structure were prepared by hydrolysis reaction of GeCl4 on MCF and used as anode material in lithium ion batteries for the electric properties tests. The results show that the discharge capacity of the composite material is as high as 1444 mAhg-1 in the initial time, and keep at 700 mAhg-1 after 50 cycles of charge-discharge at a current density of 200 mA g-1. Furthermore, the value is determined to be 389 mAhg-1 after 500 charge-discharge cycles at large current density of 1 A g-1, which is higher than that of the commercial anode material (372 mAhg-1) for Li-ion batteries. The results suggest that the prepared Ge-MCF composite material is a promising anode material which can be applied in Li-ion batteries. |
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