金属氧化物纳米阵列结构的合成及其超电容性能的研究

发布时间：2018-06-05 16:48

本文选题：金属氧化物 + 阵列　；参考：《湖南大学》2015年博士论文

【摘要】：随着日益增长的移动电子设备对能源的需求,作为电化学储能元件,超级电容器因其快速充放电,高功率密度,长循环寿命和较低的成本,受到了广泛的关注。然而较低的能量密度限制了超级电容器在许多重要领域的应用。为了克服这一缺陷,研究者致力于提升超级电容器的能量密度,使其达到电池的水平。一种行之有效的方法是在导电基底上生长金属氧化物纳米阵列结构,直接作为无粘结剂的集成化电极。这样的设计在提高比容量,改善循环性能以及获得良好的倍率性能方面,具有突出的优势。因为阵列电极具有较为独特的几何结构特点。较高的比表面积提供了更多的活性位点,与基底材料保持紧密接触的纳米阵列可为电子的快速传递提供有效的通道,阵列单元之间的空隙有利于电解液离子扩散进入电极内部,复合核壳阵列可以发挥不同组分之间的协同作用。本文的研究目标在于采用简单环保的水热法合理设计不同种类的金属氧化物纳米阵列结构,并系统地研究阵列的生长过程以及不同阵列结构对性能的影响。研究它们在超级电容器应用方面的性能优势。研究内容主要包括以下几点:(1)在本章,我们报道了一种简单的无模板水热法在泡沫镍基底上大面积合成CoMoO_4纳米片阵列,CoMoO_4纳米片阵列的形貌通过扫描电镜和透射电镜来表征,纳米片的晶相结构通过XRD测试确定。通过一系列改变反应时间的实验,研究CoMoO_4纳米片阵列的生长过程,推测其形成机理。将CoMoO_4纳米片阵列直接作为无粘结剂电极应用于超电容的性能测试,CoMoO_4纳米片阵列表现出非常好的电容特性。在4 m A cm~(-2)电流密度下,纳米片阵列的比容量高达1.26 F cm~(-2)。在12 m A cm~(-2)电流密度下,4000次循环保持率为79.5%,其性能远优于CoMoO_4粉体材料。这主要归因于CoMoO_4完全可逆的电化学属性和纳米片阵列低电阻多通道的结构特点。(2)一种简单可行的无模板水热法用于在泡沫镍基底上合成NiMoO_4纳米线阵列,并构建高性能超级电容器。所制备的NiMoO_4纳米线阵列在大电流密度(112m A cm~(-2)即74.7 A g~(-1))下,表现出很高的比容量(1.96 F cm~(-2)即1308 F g~(-1)),并且具有良好的倍率性能和循环稳定性。这样突出的电容性能是因为一维纳米线阵列的电极结构,以及双金属氧化物中Ni与Mo两种元素的协同作用。我们的工作证实了合理设计新颖的先进电极材料的可行性,而且电极合成思路与设计理念,适用于在导电基底上大面积构建其他二元、三元金属氧化物阵列结构,作为高性能超级电容器的电极材料。(3)通过低成本绿色环保的水热法,成功地在柔性碳布基底上生长NiMoO_4纳米线阵列,并直接用于超级电容器性能测试。碳布上的NiMoO_4纳米线阵列在电化学测试中,具有较高的比容量。在电流密度为5 m A cm~(-2)时,比容量为1.27 F cm~(-2)(1587 F g~(-1))。在电流密度提高至30 m A cm~(-2)时,比容量保持在0.76 F cm~(-2)(951 F g~(-1))。而且,它具备良好的循环能力(在4000次充放电循环后,依然保持初始容量的76.9%)。我们将碳布上的NiMoO_4纳米线阵列构建成对称的双电极电容器元件进行测试,最大电压可达到1.7 V,同时获得较高的能量密度(70.7Wh kg~(-1))和功率密度(在14.1 Wh kg~(-1)能量密度下,功率密度为16,000 W kg~(-1))。这些研究结果表明,钼酸镍纳米线阵列具有较大的比表面积,结合柔性碳布基底,为实用型超级电容器提供了广阔的前景。(4)我们通过高锰酸钾与碳的氧化还原反应,在碳布上原位合成了有序的MnO_2纳米片阵列,运用SEM、TEM、XRD、TGA等多种手段表征其微观形貌结构。并通过对水热反应时间的调控,研究MnO_2纳米片阵列在碳布上的生长过程。研究结果表明,反应时间对MnO_2纳米片阵列的形貌有很大的影响。进一步地,我们将该阵列直接应用于超级电容器电极,研究MnO_2纳米片阵列的赝电容性能。该电极表现出较高的比容量(2.16 F cm~(-2),在电流密度为5 m A cm~(-2)下)和较好的倍率性能,这归因于有序的阵列结构和MnO_2纳米片阵列超薄片层与碳布之间的协同作用。3000次充放电循环后,MnO_2纳米片阵列电极的循环保持率为61.4%。具有高比表面积的MnO_2纳米片和高度有序的阵列结构,与柔性碳布基底相结合,为柔性电容器的构建和发展提供了良好的材料基础。(5)通过“两步法”水热反应,一种新颖的核壳复合结构NiMoO_4@MnO_2阵列在碳布上直接合成,并研究其超电容性能。NiMoO_4纳米线阵列和MnO_2薄纳米片的协同作用,大大提高了电容性能。NiMoO_4@MnO_2阵列在电流密度为8 m A cm~(-2)时,比容量为3.90 F cm~(-2)。在电流密度提高至24 m A cm~(-2)时,比容量保持在3.22 F cm~(-2)。同时,它具备理想的循环能力(在4000次充放电循环后,依然保持初始容量的90.5%)。这样的核壳复合纳米阵列结构具有优异的电化学性能,不仅具有高比容量,而且在长期循环稳定性方面也有出色表现。NiMoO_4@MnO_2阵列是一种理想的赝电容材料。
[Abstract]:With the increasing demand for energy for mobile electronic devices, as an electrochemical energy storage element, supercapacitors have received wide attention due to their rapid charging and discharging, high power density, long cycle life and low cost. However, the low energy density limits the application of super electric containers in many important fields. Defects, the researchers are committed to improving the energy density of supercapacitors to reach the level of the battery. One effective method is to grow metal oxide nanowire arrays on the conductive substrate and directly act as an integrated electrode without adhesive. This design improves the specific capacity, improves the cycle performance and obtains good times. The array electrode has a unique geometric structure, because the array electrode has a more unique geometric structure. The higher specific surface area provides more active sites. The nanoscale array which is closely connected with the substrate can provide an effective channel for the rapid transmission of the electrons. The gap between the array units is beneficial to the electrolyte ion expansion. The aim of this paper is to design different kinds of metal oxide nanowire arrays by simple and environmentally friendly hydrothermal method, and systematically study the growth process of the array and the effect of different array structures on the performance. The performance advantages of supercapacitor applications include the following points: (1) in this chapter, we report a simple template free hydrothermal method for large area synthesis of CoMoO_4 nanoscale arrays on foamed nickel substrates. The morphology of CoMoO_4 nanoscale arrays is characterized by scanning electron microscopy and transmission electron microscopy. The structure is determined by XRD test. Through a series of experiments that change the reaction time, the growth process of the CoMoO_4 nanoscale array is studied and the formation mechanism is speculated. The CoMoO_4 nanoscale array is used directly as a non binder electrode to test the performance of the supercapacitor. The list of CoMoO_4 nanoscale arrays has a very good capacitance characteristic. In the 4 m A cm~ (-2) electricity Under the flow density, the specific capacity of the nanoscale array is up to 1.26 F cm~ (-2). Under the current density of 12 m A cm~ (-2), the 4000 cycle retention rate is 79.5%, and its performance is much better than that of the CoMoO_4 powder material. This is mainly attributed to the completely reversible electrochemical properties of CoMoO_4 and the structure characteristics of the low resistance and multi-channel nanoarray. (2) a simple and feasible no The template water heat method is used to synthesize NiMoO_4 nanowire arrays on the foamed nickel substrate and construct a high-performance supercapacitor. The prepared NiMoO_4 nanowire array shows a high specific capacity (1.96 F cm~ (-2), 1308.) under the large current density (112m A cm~ (-2), 74.7 A g~ (-1)), and has good multiplier performance and cycle stability. The outstanding capacitive performance is due to the electrode structure of the one Wiener line array and the synergistic effect of the two elements of the Ni and Mo in the bimetallic oxide. Our work confirms the feasibility of the rational design of the advanced electrode materials, and the electrode synthesis idea and design concept are suitable for large area structure on the conductive substrate. The other two yuan, three Yuan metal oxide array structure is used as the electrode material for high performance supercapacitors. (3) the NiMoO_4 nanowire array is successfully grown on the flexible carbon substrate through low cost green water heat method and directly used for the performance test of supercapacitor. The NiMoO_4 nanowire array on carbon cloth is used in electrochemical testing. It has a higher specific capacity. When the current density is 5 m A cm~ (-2), the specific capacity is 1.27 F cm~ (-2) (1587 F g~ (-1)). When the current density is increased to 30 m A, the specific capacity is maintained at 0.76 (951). Moreover, it has a good cycle capacity (after the 4000 charge discharge cycle, it remains 76.9% of the initial capacity). The NiMoO_4 nanowire array on the carbon cloth is constructed into a symmetrical double electrode capacitor element to be tested. The maximum voltage can reach 1.7 V, and the high energy density (70.7Wh kg~ (-1)) and power density (at the 14.1 Wh kg~ (-1) energy density, the power density is 16000 W kg~ (-1)). These results show that the nanoscale matrix of nickel molybdenum The column has a large specific surface area, combined with flexible carbon substrate, which provides a broad prospect for practical supercapacitors. (4) we synthesized an ordered MnO_2 nanoscale array in situ on carbon cloth through the redox reaction of Potassium Permanganate with carbon, and characterized its microstructure by means of SEM, TEM, XRD, TGA and so on. The growth process of the MnO_2 nanoscale arrays on the carbon cloth was studied by the regulation of the thermal reaction time. The results showed that the reaction time had a great influence on the morphology of the MnO_2 nanoscale array. Further, we applied the array directly to the electrode of the supercapacitor and studied the pseudo capacitance of the MnO_2 nanoscale array. The electrode showed a high performance. The specific capacity (2.16 F cm~ (-2), under the current density of 5 m A cm~ (-2)) and good multiplier performance, which is attributed to the orderly array structure and the co action of the MnO_2 nanoscale array between the ultra-thin layer and the carbon cloth in the.3000 secondary charge discharge cycle, the cycle retention of the MnO_2 nanoscale array is a MnO_2 Na with a high specific surface area. Rice slice and highly ordered array structure, combined with flexible carbon cloth substrate, provide a good material basis for the construction and development of flexible capacitors. (5) a novel nuclear shell composite structure NiMoO_4@MnO_2 array is directly combined on carbon cloth through the "two step" hydrothermal reaction, and its super capacitive.NiMoO_4 nanowire array is studied. With the synergistic effect of MnO_2 thin nanoscale, the capacitance performance.NiMoO_4@MnO_2 array is greatly improved when the current density is 8 m A cm~ (-2), and the specific capacity is 3.90 F cm~ (-2). When the current density is increased to 24 m A cm~, the specific capacity is kept at 3.22. The initial capacity of 90.5%). The nuclear shell composite nanowire arrays have excellent electrochemical properties, not only have high specific capacity, but also have excellent performance in the long-term cycle stability. The.NiMoO_4@MnO_2 array is an ideal pseudosapapac material.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM53;TB383.1

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