多层次结构金属氧化物纳米材料的溶剂热合成及在锂离子电池中的应用

发布时间：2018-01-03 10:21

本文关键词：多层次结构金属氧化物纳米材料的溶剂热合成及在锂离子电池中的应用　出处：《宁波大学》2015年硕士论文　论文类型：学位论文

【摘要】：锂离子电池因为比容量高、工作电压高、能量密度大、污染小等优点已经被广泛应用在可携带式电子设备、混合动力汽车、以及电动汽车等领域。目前商用的锂离子电池主要采用石墨作为负极材料。但石墨由于嵌锂电位较低,容易产生锂枝晶而存在较大的安全隐患;同时石墨电极的比容量较低而无法满足产业发展要求。因此,寻找可替代石墨,具有更高比容量和能量密度、并且循环稳定、安全性好的新一代负极材料已经成为目前锂离子电池领域的研究热点之一。与石墨材料相比,二氧化钛因嵌锂电位相对较高而具有优越的安全稳定性,同时因二氧化钛价格低廉、来源广泛、结构稳定性好、体积应变小等特点,具有成为下一代锂离子电池负极材料的潜力。但是,由于二氧化钛自身导电性较差、锂离子传输性能不佳,致使充放电过程中难以实现其理论比容量而限制其在负极材料上的应用。目前,主要通过将二氧化钛纳米化或与石墨等导电材料复合的方法来改善材料的导电性。设计二氧化钛/碳纳米多层次复合材料一方面能通过将材料纳米化而缩短锂离子传输路径,提升传导能力,另一方面碳能够提供导电基质,达到改善二氧化钛自身导电性不足的目的。在此思路下,本论文的主要研究内容包括:1.采用N,N?-二甲基甲酰胺为溶剂,聚苯乙烯为反应模板和碳源,以四异丙醇钛为二氧化钛前驱体,在浓盐酸作用下,聚苯乙烯发生相分离原位形成聚苯乙烯胶体粒子,并在溶剂热的辅助下形成二氧化钛/聚苯乙烯复合微球,通过氩气气氛煅烧,制备得到形貌均一、可控,多层次结构的二氧化钛/碳复合微球。研究发现,多层次的二氧化钛/碳复合微球具有很高的振实密度,同时,与纯的二氧化钛微球相比,二氧化钛/碳复合微球的质量比容量、循环稳定性、倍率性能都有很大的提高。此外,惰性气氛煅烧下所制备的二氧化钛/碳复合微球可以通过进一步空气气氛退火处理调控其碳含量,从而得到具有不同碳含量的二氧化钛/碳复合微球。本文对二氧化钛/碳复合微球的形成机理、形貌结构、以及锂电性能进行了深入系统的研究。此外,作为拓展性研究工作,还进一步研究了二氧化钛/碳复合微球光照催化产氢性能。2.采用1,4-二氧六环作溶剂,四异丙醇钛作为二氧化钛前驱体,通过改变体系中的浓盐酸的浓度,在溶剂热条件下,通过无模板法合成纳米颗粒构成的微球,纳米棒和纳米颗粒构成的复合微球,纳米棒构成的微球,纳米棒构成的簇等四种微纳结构。通过空气气氛煅烧,可得到相应形貌的结晶二氧化钛微纳结构。本论文对无模板法条件下二氧化钛多层次结构形貌演变机理进行了深入探讨;在此基础上,研究了不同形貌的二氧化钛多层次结构的锂电性能和光照催化产氢性能;并对结构-性能关联性进行了初步讨论。
[Abstract]:Lithium ion battery has been widely used in portable electronic equipment and hybrid electric vehicle because of its high specific capacity, high working voltage, high energy density, low pollution and so on. At present, the commercial lithium ion battery mainly uses graphite as the negative electrode material, but the graphite is easy to produce lithium dendrite because of the low lithium intercalation potential. At the same time, the specific capacity of graphite electrode is low and can not meet the requirements of industrial development. Therefore, the search for alternative graphite, with higher specific capacity and energy density, and cycle stability. The new generation of negative electrode materials with good safety have become one of the research hotspots in the field of lithium-ion batteries. Compared with graphite materials, titanium dioxide has superior safety and stability because of the relatively high lithium intercalation potential. At the same time, titanium dioxide has the potential to become the next generation cathode material for lithium ion batteries because of its low price, wide source, good structural stability and small volume strain. However, the conductivity of titanium dioxide itself is poor. Because of the poor transport performance of lithium ion, it is difficult to realize its theoretical specific capacity in charge and discharge process, which limits its application in negative electrode materials. The conductivity of titanium dioxide / carbon nanocomposites can be improved by nanocrystalline TIO _ 2 or composite with conductive materials such as graphite. On the one hand, the lithium separation can be shortened by nanocrystalline TIO _ 2 / carbon nanocomposites. Subtransmission path. On the other hand, carbon can provide conductive matrix to improve the conductivity of titanium dioxide. In this way, the main contents of this paper include: 1. Polystyrene colloid particles were formed by using dimethylformamide as solvent, polystyrene as reaction template and carbon source, tetraisopropanol titanium as TIO _ 2 precursor and concentrated hydrochloric acid. Titanium dioxide / polystyrene composite microspheres were prepared with the help of solvothermal method. Titanium dioxide / carbon composite microspheres with uniform morphology, controllable structure and multi-level structure were prepared by calcination in argon atmosphere. The multilevel TIO _ 2 / carbon composite microspheres have a high vibrational density. At the same time, compared with pure titanium dioxide microspheres, the mass specific capacity and cyclic stability of TIO _ 2 / carbon composite microspheres are higher than those of pure TIO _ 2 / carbon composite microspheres. In addition, titanium dioxide / carbon composite microspheres prepared by inert atmosphere calcination can be controlled by further annealing in air atmosphere. Titanium dioxide / carbon composite microspheres with different carbon content were obtained. In this paper, the formation mechanism, morphology and structure of titanium dioxide / carbon composite microspheres and lithium electrical properties were studied systematically. As an extensive research work, the photocatalytic hydrogen production of titanium dioxide / carbon composite microspheres was further studied. 2. 1 ~ (4) -dioxane was used as solvent, and titanium tetraisopropanol was used as TIO _ 2 precursor. By changing the concentration of concentrated hydrochloric acid in the system, under solvothermal conditions, microspheres composed of nanocrystalline particles, composite microspheres composed of nanorods and nanoparticles, and microspheres formed by nanorods were synthesized by template-free method. Nanorods formed by clusters and other four kinds of micro-and nano-structure. Calcined in air atmosphere. The morphologies of crystalline titanium dioxide microstructures can be obtained. In this paper, the evolution mechanism of multilayer morphology of TIO _ 2 under the condition of no template method is discussed. On this basis, the lithium electrical properties and photocatalytic hydrogen production properties of titanium dioxide with different morphologies were studied. The relationship between structure and performance is also discussed.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TM912

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