过渡金属氧化物纳米结构的构筑及其储锂性能研究

发布时间：2018-01-19 06:28

本文关键词： 纳米材料锂离子电池过渡金属氧化物氧化锰氧化铁异质纳米结构复合材料同轴纳米棒多级结构碳包覆　出处：《山东大学》2014年博士论文　论文类型：学位论文

【摘要】：由于日益凸显的能源危机、环境问题,核能、太阳能等产生的电能需得到高效储存的要求,发展高效、廉价和环境友好的储能装置就成为科学界和工业界面对的重要的挑战和机遇。二次锂离子电池相较于传统的铅酸、镍氢电池,具有高能量密度、电压平稳、自放电率小、持久的循环性能以及绿色环保等优点,在我们日常所用的小型移动电子设备中发挥着重要的作用。目前,随着锂离子电池在电动汽车和智能电网等大功率用电器和储能领域的发展,人们对商业化的锂离子电池提出了更高的要求。而高性能锂离子电池的实现依赖于其中电极材料的结构设计和性能提升。过渡金属氧化物负极材料具有高于传统的碳/石墨基负极材料2-3倍的理论比容量,是实现高容量、高功率、长寿命的锂离子电池的潜在电极材料。但是,其较差的电子电导率及循环过程中的体积效应限制了其应用。研究发现,纳米技术在过渡金属氧化物材料中的应用可以有效的缓解以上缺点。因此,发展过渡金属氧化物纳米电极材料来解决上述问题,对提高锂离子电池的整体性能具有重要的实际意义。在本论文中,我们旨在利用简单的方法构筑高性能的锂离子电池纳米电极材料,为锂离子电池负极材料的发展提供有益的探索。本论文的主要内容如下： (1)采用水热反应,首次在β-MnO2纳米棒表面成功外延生长α-FeOOH纳米棒。并通过时间演化,研究了该结构的生长过程。该β-MnO2/a-FeOOH枝状结构呈现出四次对称性的新颖特征,经高分辨透射电镜照片证明,主要是由于FeOOH的(010)晶面与Mn02的(100)晶面的晶格匹配。经过高温煅烧,得到结构保持的β-MnO2/a-Fe2O3枝状纳米棒。并且详细考察了β-MnO2纳米棒、α-Fe2O3多孔纳米棒以及β-MnO2/a-Fe2O3枝状纳米棒的电化学性能。β-Mn02/a-Fe2O3枝状结构具有最优异的电化学性能,在1Ag-1的电流密度下,循环200圈后,还能保持1028mAhg-1的比容量；在4Ag-1的电流密度下,比容量还能达到881mAhg-1。 β-MnO2/a-Fe2O3枝状结构具有的较高的比表面积、丰富的多孔性以及β-MnO2与α-Fe2O3之间的协同作用等对提高电极材料的性能起到至关重要的作用。 (2)采用枝状β-MnO2/a-Fe2O3纳米棒与葡萄糖溶液在190℃下水热反应5小时,制备得到多级核壳α-Fe2O3@C纳米管。该纳米管继承了β-MnO2/a-Fe2O3结构的尺寸、形貌和多级的表面结构。通过调节反应物β-MnO2/a-Fe2O3纳米棒与葡萄糖的比例,得到具有不同碳层厚度的多级核壳a-Fe2O3@C纳米管,并研究了其锂离子电池负极性能。通过锂电测试发现,碳层最薄的样品具有最优的倍率性能和循环稳定性。他们在0.2和1Ag-1电流密度下循环100圈后,还能分别得到1173,1014mAh g-1的比容量。甚至在4Ag-1下循环1000圈,容量还能保持在482mAh g-1.该优异的电化学性能主要得益于多级核壳a-Fe2O3@C纳米管较薄的碳层,可以有效地促进电子、离子传输和抑制充放电过程中的体积效应。 (3)采用MnOOH纳米棒为模版,利用吡咯单体的聚合反应,合成了MnOOH@PPy同轴纳米棒。MnOOH@PPy同轴纳米棒经过高温还原,得到了氮掺杂的碳包覆MnO同轴纳米棒结构(MnO@C-N)。研究了MnO@C-N与MnO的电化学性能,发现MnO@C-N具有明显增大的比容量、倍率性能和循环性能。Li/MnO@C-N电极在500mAg1电流密度下的循环100圈后,比容量达到982mAh g-1,相比于Li/MnO电极的703mAh g-1有了较大的提高。Li/MnO@C-N电极在1000mAg-1的大电流密度下循环900圈,还能保持679mAh g-1的比容量。该优异的电化学性能可以归结于氮掺杂的碳包覆一维结构,其可以有效地促进电荷转移和抑制体积效应。
[Abstract]:Due to increasing energy crisis, environmental issues, nuclear energy, solar generated electricity requirements, can be stored, the development of efficient, inexpensive and environmentally friendly energy storage device becomes a scientific and industrial interface on important challenges and opportunities. Lead acid, two lithium ion battery compared to traditional nickel metal hydride battery with high energy density, stable voltage, low self discharge rate, long cycle performance and green environmental protection and other advantages, plays an important role in the small mobile electronic devices we use every day. At present, with the development of lithium ion battery for electrical appliances and storage in the field of electric vehicles and smart power grid the people put forward higher requirements for commercial lithium-ion battery. And the realization of high performance lithium ion batteries depends on the structure and properties of electrode materials improved. Transition metal oxide anode material The material is higher than the traditional carbon / graphite based anode materials 2-3 times the theoretical capacity is to achieve high capacity, high power, potential electrode material of lithium ion battery life. However, the volume effect of its poor electronic conductivity and circulation in the process of limiting its application. The study found application in nanotechnology transition metal oxide materials can effectively alleviate the above disadvantages. Therefore, the development of transition metal oxide electrode material to solve the above problems, it has important practical significance to improve the overall performance of the lithium ion battery.
In this paper, we aim to build high-performance lithium-ion battery nano electrode materials by simple methods, and provide useful exploration for the development of anode materials for lithium ion batteries.
(1) by hydrothermal reaction for the first time, the growth of -FeOOH nanorods in alpha beta -MnO2 nanorods. And through the successful extension of time evolution, to study the growth process of the structure. The beta -MnO2/a-FeOOH dendritic structure presents four novel symmetrical features, proved by high resolution transmission electron microscope photograph, mainly due to FeOOH (010) surface and Mn02 (100) crystal plane lattice matching. After calcination, get beta -MnO2/a-Fe2O3 branched nanorods structure. And keep the detailed examination of the beta -MnO2 nanorods, porous -Fe2O3 nanorods and -MnO2/a-Fe2O3 beta alpha branched nano rod. The electrochemical properties of beta -Mn02/a-Fe2O3 dendritic structure has excellent electrochemical performance and in the current density of 1Ag-1, after 200 cycles, can maintain the specific capacity of 1028mAhg-1; in the current density of 4Ag-1, the specific capacity can reach 881mAhg-1. beta -MnO2/a-Fe2O3 dendritic structure with a The high specific surface area, abundant porosity and synergism between the beta -MnO2 and the alpha -Fe2O3 play an important role in improving the performance of the electrode materials.
(2) using dendritic beta -MnO2/a-Fe2O3 nanorods and glucose solution at 190 DEG C hydrothermal reaction for 5 hours, the prepared multi core shell nanotubes. The alpha -Fe2O3@C beta -MnO2/a-Fe2O3 nanotubes inherited the structure size, morphology and surface structure. By adjusting the multistage reactant beta -MnO2/ a-Fe2O3 nanorods with glucose ratio, by multistage nuclear the shell of a-Fe2O3@C nanotubes with different thickness of carbon layer, and to study the performance of lithium ion battery cathode by lithium. The test found that the rate performance and cycle stability of carbon layer of the thin sample has the best. They in 0.2 and the current density of 1Ag-1 after 100 cycles, but also were 11731014mAh g-1 or even cyclic capacity. The 1000 circle in 4Ag-1, the capacity can still maintain carbon layer on the electrochemical properties of the 482mAh g-1. is mainly due to the excellent multi core shell a-Fe2O3@C nanotube thin, can effectively promote the The volume effect in the electron, ion transmission and inhibition of charge discharge.
(3) using MnOOH nanorods as template, using the polymerization of pyrrole monomer, MnOOH@PPy nanorods and.MnOOH@PPy nanorods through coaxial coaxial reductive synthesis, the nitrogen doped carbon coated MnO coaxial nanorod (MnO@C-N) was studied. The electrochemical performances of MnO@C-N and MnO, found that MnO@C-N has significantly increased the capacity, rate the performance and cycle performance of.Li/MnO@C-N electrode in 500mAg1 current densities after 100 cycles, specific capacity reached 982mAh g-1, compared to the Li/MnO 703mAh g-1 electrode has improved.Li/MnO@C-N electrode larger at high current density of 1000mAg-1 under 900 cycles, 679mAh can maintain the specific capacity of g-1. The excellent electrochemical performance can be attributed to nitrogen doped carbon coated one-dimensional structure, which can effectively promote the charge transfer and inhibit the volume effect.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912;O611.2

【共引文献】