石墨烯基材料的制备及储锂性能研究

发布时间：2019-01-14 08:36

【摘要】：锂离子电池以其高的能量密度、长的循环寿命、环境友好、无记忆效应等诸多优点,被广泛应用于便携式移动电子设备中。而随着电子设备技术的快速发展,人们对锂离子电池性能提出了更高的要求。目前传统商业化的负极材料石墨较低的比容量(372mAh g-1)已经不能满足锂离子电池发展的需求。因此有必要开发新型的负极材料。所以本文针对锂离子电池研究体系,以负极材料为研究对象,合成了铋/氮掺杂石墨烯纳米复合材料,并对其储锂性能进行了系统的研究;在此基础上,针对传统电极材料不能弯曲,不具备柔性的特点,制备出了柔性功能化的三维石墨烯泡沫并将其用于锂离子电池负极材料,研究了其电化学性能。具体研究内容如下:(1)采用气液界面反应和快速热处理的方法合成了铋l氮掺杂石墨烯纳米复合材料,并将其用于锂离子电池的负极材料,研究了其电化学性能。该复合材料具有高达522 mAh g-1的比容量,即使在不同的电流密度下循环50次后,其比容量仍高达386 mAh g-1。在1000 mA g-1的大电流密度下,该复合材料的可逆比容量仍保持在218 mAh g-1。与已报道的铋基复合材料相比,展现了更加优异的电化学性能。其优异的电化学性能主要得益于氮掺杂石墨烯的高的导电性和铋纳米粒子与氮掺杂石墨烯之间的协同效应。(2)采用一种简单、温和的途径合成了具有一体化结构、自支撑的功能化的三维石墨烯泡沫,具体方法是以可再生的生物质资源葡萄糖为碳源,通过模板辅助的水热碳化反应来制备。整个制备过程,绿色环保,简单易行,而且成本低廉。此外,制备的功能化的三维石墨烯泡沫具有优异的柔性,我们将其直接用作柔性电极材料,组装成纽扣型的锂离子电池,通过恒流充放电测试、循环伏安测试等方法初步研究了其电化学性能。研究结果表明,在5 mA g-1的小电流密度下,其比容量为22 mAh g-1。由于材料中含氧官能团的存在致使其导电性不佳和材料本身性能的影响,导致其储锂性能并不理想。尽管其比容量不理想,但该材料具有优异的可折柔性,可以将其发展作为柔性集流体材料。(3)分别采用高温还原、水合肼还原和乙二醇还原的三种还原方式对功能化的三维石墨烯泡沫进行还原,并对还原之后的产物分别进行了 SEM、FITR、Raman的表征分析以及弯曲性能测试。通过对比分析,结果表明,采用水合肼还原方式对功能化的三维石墨烯泡沫进行还原可以得到还原效果较好,适合作为柔性集流体的三维石墨烯泡沫材料。
[Abstract]:Li-ion batteries are widely used in portable mobile electronic devices due to their high energy density, long cycle life, environment-friendly, no memory effect and many other advantages. With the rapid development of electronic equipment technology, the performance of lithium ion batteries has been put forward higher requirements. At present, the low specific capacity of graphite (372mAh g-1), a traditional commercial anode material, can no longer meet the needs of lithium ion battery development. Therefore, it is necessary to develop new negative electrode materials. Therefore, in this paper, bismuth / nitrogen-doped graphene nanocomposites were synthesized and their lithium storage properties were studied systematically, aiming at the lithium ion battery research system, taking the anode material as the research object. On this basis, the flexible functional three-dimensional graphene foam was prepared and used as anode material for lithium ion battery. The electrochemical properties of the three dimensional graphene foam were studied. The main contents are as follows: (1) Bi-1-N-doped graphene nanocomposites were synthesized by gas-liquid interfacial reaction and rapid heat treatment, and were used as anode materials for lithium ion batteries, and their electrochemical properties were studied. The specific capacity of the composite is up to 522 mAh g ~ (-1). Even after 50 cycles at different current density, the specific capacity of the composite is as high as 386 mAh g ~ (-1). At a high current density of 1000 mA g ~ (-1), the reversible specific capacity of the composite remains at 218 mAh g ~ (-1). Compared with the reported bismuth matrix composites, the electrochemical properties of the composites are more excellent. Its excellent electrochemical properties are mainly due to the high conductivity of nitrogen-doped graphene and the synergistic effect between bismuth nanoparticles and nitrogen-doped graphene. Self-supporting functional three-dimensional graphene foam was prepared by template assisted hydrothermal carbonization using renewable biomass resource glucose as carbon source. The whole preparation process is environmental friendly, simple and easy to use, and low in cost. In addition, the functionalized three-dimensional graphene foam has excellent flexibility. It is directly used as a flexible electrode material to assemble a button type lithium ion battery, which is tested by constant current charge and discharge. The electrochemical performance was studied by cyclic voltammetry. The results show that the specific capacity is 22 mAh g ~ (-1) at the low current density of 5 mA g ~ (-1). Due to the existence of oxygen functional groups in the materials, the conductivity of the materials is not good and the properties of the materials themselves are affected, which leads to the poor lithium storage performance of the materials. Although its specific capacity is not ideal, the material has excellent flexural flexibility and can be developed as a flexible fluid collecting material. (3) reduction at high temperature, The three reduction methods of hydrazine hydrate and ethylene glycol were used to reduce the functionalized three dimensional graphene foam. The products after reduction were characterized by SEM,FITR,Raman and the bending properties were tested. The results show that the reduction effect of functional three dimensional graphene foam can be obtained by hydrazine hydrate reduction method, which is suitable for the flexible fluid collection of three dimensional graphene foam material.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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