石墨烯基纳米复合材料的制备及锂电性能研究

发布时间：2018-01-27 05:36

本文关键词： 石墨烯纳米复合材料锂离子电池负极能量存储　出处：《东北大学》2014年博士论文　论文类型：学位论文

【摘要】：进入21世纪以后,随着电动汽车、便携式电子设备的广泛应用,更大的存储容量、更好的循环稳定性和更快速的充放电速率的锂离子电池已成为迫切需要。而发展高比容量、稳定锂离子电池的关键则在于制备能够可插入和脱插锂离子的负极材料。目前,商用的负极材料多为石墨,其理论容量值只有372 mAhg-1,无法满足供能需求。在目前研究的锂离子电池负极材料中,主要分为碳材料、硅基材料、过渡金属氧化物和硫化物四类。过渡金属氧化物和硫化物具有高容量、低成本且无毒等优点,但因其在脱插锂离子过程中的体积塌缩效应,导致循环容量损失严重,制约其发展。石墨烯具有单原子层、六方网络结构,具备很高的电子传导能力、大的比表面积、稳定的物理化学性能、良好的机械性能。因此,本文用水热法制备了金属氧化物／石墨烯纳米复合材料(Co304/石墨烯、NiO/石墨烯和CuO/石墨烯)、金属硫化物／石墨烯纳米复合材料(SnS2/石墨烯),并研究其储锂特性。在保证金属氧化物、硫化物较高存储容量的同时,发挥石墨烯的结构特性,从而实现高存储容量和高循环稳定性。结果表明：C0304/石墨烯纳米复合材料具有高的储锂容量和循环性能,在0.1 C下,可逆容量为906.6 mAhg-1;在50次循环后,容量保持在844.6 mAh g-1。NiO/石墨烯纳米复合材料,可逆容量为844.9 mAh g-1；在50次循环后,容量保持在785.1mAhg-1;在5C下,放电容量可达到497.0 mAh g-1。CuO/石墨烯纳米复合材料在50个充放电循环之中,容量始终保持在670-700 mAhg-1,具备极佳的循环稳定性。SnS2/石墨烯纳米复合材料在0.2 C充放电速率下,可逆容量为766.3 mAhg-1;在30次循环后,储锂容量保持在570.0 mAhg-1,非常接近其理论容量。金属氧化物、硫化物／石墨烯纳米复合材料具备较大的锂电容量和更好的循环稳定性。这主要归因于金属氧化物与石墨烯之间的协同效应,石墨烯限制金属氧化物纳米结构的体积变化,并提供较好的电子传导率；金属氧化物纳米结构有效抑制石墨烯纳米片之间的团聚。由于硅具有最高的理论容量(4200mAhg-1),本文运用一种新的化学腐蚀法制备了表面光滑的单晶硅纳米线和硅纳米片。作为锂离子电池的负极材料,结果表明：首次放电容量分别为4311 mAhg-1和4426 mAhg-1;经过10次循环后,放电容量分别为各自可逆容量的66.2%和75.8%。硅纳米片相比于硅纳米线有更大的放电容量和更高的循环稳定性。这是由于二维纳米结构具有有限的侧面面积和增强的边缘效应,使得Li离子更容易的通过活性材料。
[Abstract]:After 21th century, with the wide application of electric vehicles and portable electronic devices, the storage capacity is larger. Better cycle stability and faster charge and discharge rate of lithium-ion batteries have become an urgent need for the development of high specific capacity. The key to stabilize lithium-ion batteries is to prepare cathode materials that can insert and deintercalate lithium ions. At present, most of the commercial anode materials are graphite, whose theoretical capacity is only 372 mAhg-1. In the current study of lithium ion battery anode materials, mainly divided into carbon materials, silicon-based materials, transition metal oxides and sulfides. Transition metal oxides and sulfides have high capacity. The advantages of low cost and non-toxic, but due to the volume collapse effect in the process of deintercalation of lithium ions, the circulation capacity is seriously lost, which restricts its development. Graphene has a monoatomic layer, hexagonal network structure. With high electronic conductivity, large specific surface area, stable physical and chemical properties, good mechanical properties. In this paper, metal oxide / graphene nanocomposites, such as Co304 / graphene / nio / graphene and CuO / graphene, were prepared by hydrothermal method. Metal sulfides / graphene nanocomposites (SNS _ 2 / graphene) were used to study the lithium storage properties of SNS _ 2 / graphene nanocomposites. The structure characteristics of graphene were obtained by ensuring the high storage capacity of metal oxides and sulfides. The results show that the w / C0304 / graphene nanocomposites have high lithium storage capacity and cyclic properties at 0.1 C. The reversible capacity is 906.6 mAhg-1; After 50 cycles, the capacity of nio / graphene nanocomposites remained at 844.6 mAh g-1.NiO / graphene nanocomposites with reversible capacity of 844.9 mAh g-1; After 50 cycles, the capacity remained at 785.1 mAhg-1; At 5C, the discharge capacity can reach 497.0 mAh g-1.CuO / graphene nanocomposites in 50 charge-discharge cycles. The capacity is always between 670-700 mAhg-1, with excellent cyclic stability. SnS2 / graphene nanocomposites at charge-discharge rate of 0.2 C. The reversible capacity is 766.3 mAhg-1; After 30 cycles, the lithium storage capacity is kept at 570.0 mAhg-1, which is very close to its theoretical capacity. The sulphide / graphene nanocomposites have larger lithium capacity and better cycling stability, which is mainly due to the synergistic effect between metal oxides and graphene. Graphene limits the volume change of metal oxide nanostructures and provides better electron conductivity. Metal oxide nanostructures can effectively inhibit the agglomeration between graphene nanoparticles, because silicon has the highest theoretical capacity of 4200mAhg-1). In this paper, monocrystalline silicon nanowires and silicon nanowires with smooth surface were prepared by a new chemical etching method, which were used as anode materials for lithium ion batteries. The results show that the first discharge capacity is 4311 mAhg-1 and 4426 mAhg-1, respectively. After 10 cycles. The discharge capacity is 66.2% and 75.8.The discharge capacity of silicon nanowires is higher than that of silicon nanowires. This is due to the limited properties of two-dimensional nanostructures. Side area and enhanced edge effect. Make it easier for Li ions to pass through active materials.
【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

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