三维石墨烯（碳）结构的制备及其在锂电材料中的应用研究

发布时间：2018-03-20 10:17

本文选题：三维结构　切入点：石墨烯　出处：《上海应用技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,锂离子电池得到了广泛的研究和长足的发展,但是在电动交通工具、便携式电子设备、柔性可穿戴电子设备等领域还没有达到人们的期望值。这主要是因为正极材料价格偏高、比容量偏低,并可能产生一定的安全问题;负极材料主要是碳材料,其比容量有限,用量较大,若能提升负极材料的比容量,即可大大提高电池的性能并减轻电池的重量和体积;另外现有的电极技术还不能使锂离子电池很好的应用于柔性器件等领域。因此发展高比容量、高倍率性能的正极材料,开发新型的高性能负极材料,以及发展新型的电池技术是未来锂离子电池发展的重要方向。大量研究表明,将石墨烯(碳)材料与正负极材料复合,构建三维结构复合材料被证实能够有效改善电极材料的电化学性能。因此,开发行之有效的制备方法以实现石墨烯(碳)与正负极材料之间的有机结合,是该领域研究的关键。有鉴于此,本研究设计并制备了三类石墨烯(碳)三维结构,分别实现了其与磷酸铁锂正极材料和红磷负极材料的原位复合,并对合成材料的制备过程、物理性质、电化学性能及部分组分间的协同效应进行了研究和探索。本文中开创了新的磷酸铁锂制备方法,以水热法实现了其与石墨烯的原位复合,得到了三维石墨烯/磷酸铁锂(G/LiFePO4)复合正极材料。0.2 C时放电容量为较高的160 mAh/g,且具有良好的倍率性能(10C时放电比容量达到115mAh/g)和循环稳定性(1 C时100次循环的容量保持率为94.2 %)。通过引入三维CVD石墨烯基底,制备了三维石墨烯/磷酸铁锂/石墨烯(3DG/LFP/G)复合正极材料,进一步提高了材料的电化学性能:0.2 C时容量达到164 mAh/g,10 C时容量达到124 mAh/g,1 C下100次循环的容量保持率为95.7 %。交流阻抗分析证明了 3DG/LFP/G比G/LiFePO4具有更优异的动力学特性(更小的电荷转移阻抗、更高的锂离子扩散系数)。负极方面,以碳化法制备出电化学性能优异的柔性碳布,以此为基底,通过蒸气-冷凝法实现了红磷的负载,制备出柔性的红磷/碳布(P/C)复合负极材料,0.1 C时放电比容量为1063 mAh/g,随后通过氧化石墨烯(GO)包覆处理,得到了具有“三明治”结构的GO/P/C复合材料,容量提高到1100 mAh/g,同时其200次循环的容量保持率提升了 13.1 %,显示出了更好的电化学性能。本研究不仅为新型高倍率动力锂离子电池磷酸盐系正极材料的开发提供了有效的技术途径,同时开发了高性能的负极材料并初步研究了其作为柔性电池材料的可行性,具有重要的实际意义和学术价值。
[Abstract]:In recent years, lithium ion batteries have been widely studied and developed, but in electric vehicles, portable electronic devices, Flexible wearable electronics and other fields have not yet met expectations. This is mainly due to the high price of cathode materials, low specific capacity, and may cause certain safety problems; negative materials are mainly carbon materials, whose specific capacity is limited. If the specific capacity of the anode material can be increased, the performance of the battery can be greatly improved and the weight and volume of the battery can be reduced. In addition, the existing electrode technology can not make lithium ion batteries well used in flexible devices and other fields. Therefore, the development of high specific capacity, high rate performance cathode materials, the development of new high performance anode materials, And the development of new battery technology is an important direction for the development of lithium-ion batteries in the future. A large number of studies show that graphene (carbon) materials are combined with cathode and cathode materials. It has been proved that the electrochemical properties of electrode materials can be improved effectively by constructing three-dimensional structure composites. Therefore, an effective preparation method is developed to realize the organic binding between graphene (carbon) and cathode materials. In view of this, three kinds of graphene (carbon) three-dimensional structures were designed and prepared, and in situ recombination with lithium iron phosphate cathode material and red phosphorus negative electrode material were realized respectively, and the preparation process of the synthesized materials was also studied. The physical properties, electrochemical properties and synergistic effects among some groups have been studied and explored. In this paper, a new preparation method of lithium ferric phosphate has been developed, and in situ recombination with graphene has been realized by hydrothermal method. Three-dimensional graphene / LiFePO4 composite cathode material with high discharge capacity of 160mAh/ g was obtained at 0.2C, and its specific discharge capacity reached 115mAh/ g at 10C with good performance, and the capacity of 100 cycles at 1 C cycle stability was maintained. The holdup is 94. 2%. By introducing three dimensional CVD graphene substrates, Three dimensional graphene / lithium iron phosphate / graphene 3 DG / LFP / G composite cathode materials were prepared. The electrochemical performance of the material was further improved when the capacity of the material reached 164mAh/ g ~ (-1) C at a capacity of 164mAh/ g ~ (-1) C, and the capacity retention rate of 100 cycles at 124mAh/ g ~ (-1) C was 95.7%. Ac impedance analysis proved that 3DG / L _ (FPP) _ G had better kinetic properties than that of G _ (P) LiFePO _ 4. (smaller charge transfer impedance, For a higher diffusion coefficient of lithium ion, a flexible carbon cloth with excellent electrochemical performance was prepared by carbonation method, which was used as the substrate to realize the loading of red phosphorus by vapor-condensation method. A flexible red phosphorus / carbon cloth P / C composite negative electrode material with a specific discharge capacity of 1063 mAh/ g at 0.1 C was prepared, and then coated with graphene oxide (GOO) to obtain a "sandwich" structure GO/P/C composite. At the same time, the capacity retention rate of 200 cycles increased by 13.1%, showing better electrochemical performance. This study not only provides a new type of phosphate cathode materials for high-rate power lithium ion batteries, but also provides a basis for the development of phosphate cathode materials for high-rate power lithium-ion batteries. An effective technical approach, At the same time, the high performance negative electrode material is developed and its feasibility as flexible battery material is preliminarily studied, which has important practical significance and academic value.
【学位授予单位】：上海应用技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TM912

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