过渡金属氧化物复合微纳结构的可控制备及电化学性能研究

发布时间：2018-01-19 15:19

本文关键词： 锂离子电池超级电容器过渡金属氧化物复合材料协同效应　出处：《山东大学》2017年博士论文　论文类型：学位论文

【摘要】：全球变暖和化石燃料的枯竭对人类的可持续发展造成了严重的威胁。为了应对这些挑战,大量的研究致力于开发和利用来自于太阳能、风能等其它可代替能源以及可再生能源的能量。考虑到这些能源的间歇性,需要可靠的能量存储系统以稳定和易控制的方式来存储和传递获得的电力。抽水蓄能、压缩空气储能、飞轮储能和电化学储能系统是众多能量存储系统中关键和主要的成员,已引起越来越多的关注。可充电电池和超级电容器是电化学储能系统的两个重要技术子类,且已经得到了广泛的应用。尽管其它类型的可充电电池,如钠离子电池、镁离子电池和铝离子电池等,也在不断发展,但其广泛商业化受到其安全性差、持续时间不足以及可操作性等问题的严重妨碍,因此,当前的可充电电池的市场仍由锂离子电池统治。锂离子电池和超级电容器工作过程都依赖于其电化学过程,但遵循不同的工作原理,因此表现出不同的储能特点。锂离子电池充放电是基于发生在块体电极材料中的扩散控制的法拉第反应,因此过程是缓慢的。块体储能机制使得锂离子电池具有高能量密度(高达180Whkg—1),但是同时具有有限的功率密度和较短的寿命(通常只有几百个周期)。与锂离子电池不同,超级电容器通过在电极/电解液表面的快速可逆吸附或在表面/靠近表面的快速氧化还原反应存储电能。因此,超级电容器有着更高的功率密度(10kWkg-1)、超长的循环寿命(105个周期)和良好的可靠性等巨大的优势。然而,超级电容器的能量密度比锂离子电池低得多,商业化的超级电容器通常小于10Whkg-1。因此迫切需要改善当前锂离子电池和超级电容器的储电性能来满足未来电子设备日益严格的要求。过渡金属氧化物被认为是最有潜力的用于锂离子电池和超级电容器的电极材料,因为其具有成本低、易于合成和环境友好等优点,然而单一组分的过渡金属氧化物过快的比容量(电容)衰减、差的导电性、明显的体积膨胀和大的电压滞后,使得它们的商业化严重受挫。制备具有两种或多种组分,形貌易控制的过渡金属氧化物的复合材料对提高锂离子电池和超级电容器的储电性能具有非常重要的意义。本论文通过采用不同的策略成功地设计和制备了具有微纳米尺寸、大的比表面积、良好导电性和结构稳定性以及快速的离子和电子传输的复合材料。复合材料的特殊结构使其具有比单一组分优异的电化学性能,如高的比容量(电容),长的循环寿命和高倍率性能,这主要归因于多种组分的协同作用。本论文的研究工作如下。(1)通过结合溶剂热和溶胶-凝胶法成功构建了三维多孔的Co3O4@a-TiO2核壳微/纳米结构,值得一提的是,通过在溶胶-凝胶过程中精确调节乙醇和水的体积比可获得具有可控孔径的壳层a-TiO2。这是首次使用核壳Co3O4@a-TiO2微/纳米结构作为锂离子电池的负极材料。该复合结构的电化学性能与其结构息息相关。这种新颖的复合结构作为先进的锂离子电池负极材料时表现出高的比容量,长的循环寿命和良好的倍率性能,主要归因于壳层a-TiO2优异的稳定性,核层Co3O4的高比容量和复合材料优化的孔径分布。在0.5 Ag-1的电流密度下获得800 mAhg-1的高可逆比容量,在60次充放电循环后依然保持该比容量稳定。(2)过渡金属氧化物分级结构的制备已经得到深入研究,但是合成多组分分级结构的过渡金属氧化物仍然存在巨大挑战。本文中报道了一种通用的方法来制备三组分过渡金属氧化物,即MnO2@NiO/NiMoO4纳米线@纳米片分级多孔复合结构(MnO2@NiO/NiMoO4HPCSs)。通过化学溶液法以及随后的煅烧处理,MnOOH@NiMo前驱体拓扑转化为MnO2@NiO/NiMoO4 HPCSs,并没有发生显著地结构变化,超薄的NiO/NiMoO4纳米片互连成蜂窝状结构并且具有丰富的间隙孔。对比实验结果表明六次甲基四胺和溶液体系在MnOOH@NiMo前驱体的形成过程中起到重要作用。当用作超级电容器电极材料时,单位面积负载量高达5 mg cm2 的 MnO2@NiO/NiMoO4HPCSs 在 1 Ag-1 的电流密度下提供 918 F g-1 的比电容,并且保持良好的循环稳定性,其显示出比单一组分组成的电极材料更好的电化学性能。基于MnO2@NiO/NiMoO4HPCSs(正极)和活性炭(负极)的高电压非对称超级电容器表现出优异的循环稳定性,高的能量密度(26.5 Wh kg-1)和功率密度(401 Wkg-1)。证实了该多组分分级结构作为先进的超级电容器电极材料的优越性。(3)金属有机簇是零维的、独立的、离散的分子,其具有多于一个的金属中心,是通过桥连阴离子和外壳有机配体聚集成的一个整体。到目前为止,还没有以金属有机簇为前驱体来制备微/纳米复合结构的报道,并且其独特的结构带来的优异性能也未被发现的。本文中,通过在氩气氛围中500 ℃下热解混合价的八核Mn簇得到了一种特殊的复合结构,MnO@Mn3O4核壳纳米颗粒嵌入在氮掺杂的多孔碳骨架内,即MnO@Mn3O4/NPCFs,并将其应用于锂离子电池。由于其新颖的结构和组成特点,这些独特的MnO@Mn3O4/NPCFs表现出优异的电化学性能:超高的比容量,超长的循环稳定性和优异的倍率性能,同时解决了电极材料在充放电过程中的粉化、慢的离子/电子动力学、颗粒团聚等问题。这为设计和构造下一代的锂离子电池负极材料开辟了新的途径。(4)通过简易的两步法成功制备了高比容量的MoO2/石墨烯复合材料,即MoO2纳米颗粒均匀地分散在rGO纳米片上。在MoO2NP/rGO二维纳米复合结构中,rGO可以作为负载具有电化学活性的MoO2纳米颗粒的有利支撑,同时,Mo02纳米颗粒的存在有效地防止了 rGO的堆叠,两者的有利结合为储锂提供了更多的电化学活性位点。MoO2NP/rGO纳米复合材料作为锂离子电池负极材料时表现出优异的循环和倍率性能:在0.2 Ag-1的电流密度下循环150圈比容量能够维持在1516.4 mAh g-1,即使在较高的电流密度1.0 Ag-1充放电300个循环后,比容量仍稳定在641 mAh g-1。该合成方法可扩展到制备其它过渡金属氧化物/石墨烯基复合材料进而提高其在锂离子电池中的电化学性能。
[Abstract]:A serious threat to global warming and depletion of fossil fuels for human sustainable development. In order to deal with these challenges, a lot of research dedicated to the development and utilization of wind energy from solar energy, and other alternative energy sources of energy and renewable energy. Considering these energy needs intermittent, energy storage system in a stable and reliable easy to control the way to store and transfer the power. Pumped storage, compressed air energy storage flywheel energy storage and electrochemical energy storage system is the main and key members of the energy storage system, has attracted more and more attention. The rechargeable battery and super capacitor is an electrochemical energy storage system of two important technology sub class, and has been widely used. Although other types of rechargeable batteries, such as sodium ion, magnesium ion battery and aluminum ion batteries, but also in the continuous development, But the widespread commercialization by its poor security, seriously hamper, duration of insufficient and the operability of the rechargeable battery, the current market is still a lithium ion battery rule. Lithium ion batteries and super capacitors are dependent on the working process of the electrochemical process, but follow the different principle, so the performance of different storage characteristics of lithium ion battery charging and discharging is the Faraday reaction diffusion occurs in the bulk of the electrode materials based on control, so the process is slow. Bulk storage mechanism makes lithium ion battery with high energy density (up to 1 180Whkg), but also has the power density and the Co. short life (usually only a few hundred cycles). Unlike lithium ion battery, super capacitor through the electrode / electrolyte surface rapid reversible adsorption or in rapid oxidation of the surface / near surface reaction To store electrical energy. Therefore, the super capacitor has a higher power density (10kWkg-1), long cycle life (105 cycles) and good reliability of huge advantage. However, the super capacitor energy density is much lower than lithium ion batteries, electric energy storage performance of the super capacitor is usually commercial less than 10Whkg-1. so there is an urgent need to improve the current lithium ion battery and super capacitor to meet the increasingly stringent requirements of electronic equipment in the future. The transition metal oxides are considered to be the most promising electrode materials for lithium ion batteries and super capacitors, because of its low cost, easy synthesis and environmental friendly, however, transition metal oxide single component of the excessive capacity (capacitance) attenuation, low conductivity, voltage apparent volume expansion and large lag, making them the business suffered a serious setback. The preparation of two or more Components, has a very important significance to the charge storage properties of transition metal oxide composite material to improve the morphology control of lithium ion batteries and super capacitors. This paper adopts different strategies successfully designed and prepared with micro or nano size, large surface area, good conductivity and structure stability and the composite ion and fast electron transport. The special structure of composite material which has excellent electrochemical performance than single component, such as high specific capacity (capacitance), long cycle life and high rate performance, which is mainly due to the various components of synergy. The research work of this thesis is as follows. (1) by combining solvothermal and sol-gel method to construct Co3O4@a-TiO2 core-shell porous micro / nano structure, it is worth mentioning that, by precisely adjusting the ethanol and water in the sol gel process volume The ratio of pore size controllable shell obtained a-TiO2. this is the first use of nuclear shell Co3O4@a-TiO2 micro / nano structure as anode materials for lithium ion batteries. The electrochemical performance of the composite structure is closely related to its structure. The composite structure of this novel as the advanced lithium ion battery negative electrode materials exhibit high specific capacity, long cycling life and the good rate performance, mainly due to the excellent stability of a-TiO2 shell, high capacity Co3O4 core and aperture optimization of composite material distribution. To obtain a high reversible 800 mAhg-1 at the current density of 0.5 Ag-1 capacity, after 60 cycles the specific capacity remained stable. (2) transition metal oxides the hierarchical structure of the preparation has been studied deeply, but the synthesis of transition metal oxide multicomponent hierarchical structure is still a huge challenge. This paper reports a general The method of preparation of three component transition metal oxide, MnO2@NiO/NiMoO4 nanowires @ nano hierarchical porous composite structure (MnO2@NiO/NiMoO4HPCSs). The chemical solution method and subsequent calcination of the precursor of MnOOH@NiMo topology into MnO2@NiO/NiMoO4 HPCSs, there is no structural changes significantly, the ultrathin NiO/NiMoO4 nanosheets interconnect into honeycomb structure and having a clearance hole rich. The experimental results show that the six methyl four amine solution system and plays an important role in the formation process of MnOOH@NiMo precursor. When used as electrode material for super capacitor, unit area load up to 5 mg cm2 MnO2@NiO/NiMoO4HPCSs at the current density of 1 Ag-1 918 F g-1 the specific capacitance, and maintain a good cycle stability, which shows that the electrochemical performance of electrode material is better than the single component of the base. In MnO2@NiO/NiMoO4HPCSs (positive) and activated carbon (negative) high voltage asymmetric supercapacitor exhibits excellent cycling stability, high energy density (26.5 Wh kg-1) and power density (401 Wkg-1). Proved that the multi-component hierarchical structure as an advanced supercapacitor electrode material (superiority. 3) metal organic clusters is zero dimensional, independent, discrete molecules, which has more than one metal center, through bridging anions and organic ligand shell poly a whole integration. So far, not with metal organic clusters as precursor for the preparation of reports of micro / nano composite structure the excellent properties and its unique structure also has not been found. In this paper, by obtaining a compound with special structure of eight nuclear Mn cluster under 500 DEG C for pyrolysis of mixed valence in argon atmosphere, MnO@Mn3O4 core-shell nanoparticles embedded in nitrogen doped The porous carbon skeleton, namely MnO@Mn3O4/NPCFs, and its application in lithium ion battery. Because of its novel structure and composition characteristics, these unique MnO@Mn3O4/NPCFs exhibited excellent electrochemical properties: high specific capacity, long cycling stability and excellent rate can also solve the powder electrode material in charge during the process of discharge, slow ion / electron dynamics, particle aggregation and other issues. It opens up a new way for lithium ion battery anode materials for the design and construction of the next generation. (4) by a simple two step method to fabricate MoO2/ graphene composite materials with high capacity, namely MoO2 nanoparticles uniformly dispersed in rGO nanosheets. In 2D MoO2NP/rGO nano composite structure, rGO can be used as a powerful support, MoO2 nanoparticles loaded with electrochemical activity at the same time, Mo02 nanoparticles are effectively prevented rGO The stack, both favorable combination of lithium storage provides electrochemical active sites of.MoO2NP/rGO nano composite materials more as anode materials for lithium ion batteries exhibit excellent cycle and rate performance: 150 cycles at the current density of 0.2 Ag-1 capacity can maintain at 1516.4 mAh g-1, even at higher current density of 1 Ag-1 300 charge discharge cycles, the capacity ratio remained stable at 641 mAh g-1. this method can be extended to prepare other transition metal oxides / graphene composites and improve its electrochemical performance.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB33;TM53;TM912

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