沥青基中空碳球的制备、改性及电化学性能研究

发布时间：2018-05-04 01:10

本文选题：沥青 + 中空碳球　；参考：《新疆大学》2015年硕士论文

【摘要】：随着环境污染日益加重和化石能源逐步枯竭,清洁能源得以快速发展而要实现清洁能源的有效利用,关键还是开发电能存储系统。碳材料在能源储存与转化系统中起着非常重要的作用,在众多碳材料中,中空碳球因其独特的形貌、低密度、大的空腔体积、良好的导电性和卓越的热稳定性,被广泛的应用于能源储存领域中。目前制备中空碳球主要采用的是模板法,碳源主要包括气态碳源和固态碳源。石油沥青作为富碳碳源,已经成功制备出碳球、碳纳米管、碳纤维,而制备中空碳球却鲜有报道。本文采用二氧化硅球作为模板,石油沥青为碳源,通过化学气相沉积法成功制备出了中空碳球,并对中空碳球进行了表面修饰,考察了其在锂离子电池和锂硫电池的应用。1、首先成功的制备出了大小均一,单分散的二氧化硅纳米球,并利用十六烷基三甲基溴化铵(CTAB)和正硅酸乙酯(TEOS)对其进行了修饰,从而进一步得到了具有核壳结构的SiO2@m-SiO2/CTAB球(壳由SiO2和CTAB组成)。随后以该核壳结构的二氧化硅纳米球为模板,以石油沥青为碳源,通过气相沉积法制备出中空结构的碳球。同时考察了不同比例的CTAB和TEOS对二氧化硅纳米球修饰的影响,可以改变SiO2@m-SiO2/CTAB球壳的厚度进而实现了对中空碳球壁厚的调控。2、在碳球的成长过程中,引入氮源乙腈,经过沥青和乙腈的共同热解沉积后,得到了一种石墨化碳层包覆无序碳的特殊壳的中空碳球,并利用硝酸蒸气对其表面进一步改性。将其作为锂离子负极材料时,样品在500 mA g-1电流密度下循环250圈后比容量依然保持在616 mAh g-1,表现出了优越的电化学性能。3、锂硫电池作为目前能量密度较高的正极材料体系,因其在充电过程中存在“穿梭效应”而限制了其商业化应用。中空碳球因导电性好、内腔体积大、多孔性等优点是作为限制“聚硫离子”的良好材料。本章通过对实验参数的调控制备出薄壁中空碳球,再经过硝酸处理后,以改善表面的疏水性,增加控硫能力。考察了不同含硫量的电化学行为,含硫量67%的碳硫复合物在0.1C的电流密度下,循环100圈后依然稳定在531 mAh g-1,表现出了其具有控硫能力,但是性能还有待提高。
[Abstract]:With the worsening of environmental pollution and the gradual depletion of fossil energy, clean energy can be rapidly developed. To realize the effective use of clean energy, the key is to develop electric energy storage system. Carbon materials play a very important role in energy storage and conversion systems. Among many carbon materials, hollow carbon spheres are characterized by their unique morphology, low density, large cavity volume, good electrical conductivity and excellent thermal stability. It is widely used in the field of energy storage. At present, template method is used to prepare hollow carbon spheres. Carbon sources mainly include gaseous carbon sources and solid carbon sources. As a carbon-rich carbon source, petroleum asphalt has been successfully prepared carbon ball, carbon nanotubes, carbon fiber, but the preparation of hollow carbon ball is rarely reported. In this paper, the hollow carbon spheres were prepared by chemical vapor deposition with silica ball as template and petroleum asphalt as carbon source, and the surface of hollow carbon spheres was modified. Its applications in lithium-ion batteries and lithium-sulfur batteries were investigated. At first, homogeneous and monodisperse silica nanospheres were successfully prepared and modified by cetyltrimethylammonium bromide (CTAB) and tetraethyl orthosilicate (TEOS). Thus, the SiO2@m-SiO2/CTAB sphere with core-shell structure (the shell is composed of SiO2 and CTAB) is obtained. The hollow carbon spheres were prepared by vapor deposition using silica nanospheres with core-shell structure as template and petroleum asphalt as carbon source. At the same time, the effects of CTAB and TEOS on the modification of silica nanospheres were investigated. The thickness of SiO2@m-SiO2/CTAB spherical shell could be changed and the wall thickness of hollow carbon spheres could be adjusted by .2.The nitrogen source acetonitrile was introduced into the growth process of carbon spheres. After pyrolysis and deposition of bitumen and acetonitrile, a kind of hollow carbon sphere coated with disordered carbon in graphitic carbon layer was obtained, and the surface was further modified by nitric acid vapor. When it is used as the cathode material of lithium ion, the specific capacity of the sample is kept at 616 mAh g-1 at 500mAg-1 current density, showing excellent electrochemical performance. The lithium sulfur battery is used as the cathode material system with high energy density at present, and the specific capacity of the sample remains at 616 mAh g-1 after the cycle at 500mAg-1 current density, and the specific capacity of the sample remains at 616 mAh g-1. Because of its "shuttle effect" in the charging process, its commercial application is limited. Hollow carbon spheres are good materials for limiting "polysulfide ions" because of their good conductivity, large cavity volume and porosity. In this chapter, thin-walled hollow carbon spheres were prepared by adjusting the experimental parameters, and then treated with nitric acid to improve the hydrophobicity of the surface and increase the sulfur control ability. The electrochemical behavior of the composites with different sulphur content was investigated. At the current density of 0.1C, the sulfur content of the carbon-sulfur complex was still stable at 531 mAh g-1 after 100th cycle, which showed that it had the ability to control sulfur, but the performance needed to be improved.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11

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