锌铝水滑石纳米复合材料的制备及其在锌镍电池中的应用研究

发布时间：2018-01-07 20:32

本文关键词：锌铝水滑石纳米复合材料的制备及其在锌镍电池中的应用研究　出处：《中南大学》2014年博士论文　论文类型：学位论文

【摘要】：摘要：锌镍电池是一种高能量密度的碱性蓄电池,其电池性能远远高于镉镍和镍氢电池,加上这种电池原材料丰富,电解液和活性物质无毒,电池体系绿色无污染,越来越受到各国研究机构的重视。然而镍锌二次电池中常规负极材料的放电产物易溶于碱性电解液,从而会导致电池循环寿命降低oZnAl-LDH材料由于其新颖的二维纳米结构,在碱性电解液中具有很好的稳定性和电化学活性等优点,被认为最有潜力成为下一代锌镍电池的新型负极材料。然而,单相的ZnAl-LDH材料本身的导电性较差限制了其电化学性能的进一步提升。因此,将ZnAl-LDH材料与导电性较好的碳、金属等复合,通过发挥两种材料各自的优势,改善复合材料的导电性和机械强度,从而极大地提高复合材料的电化学性能。本文围绕新型ZnAl-LDH纳米复合材料的制备和相关电化学性能展开研究,主要内容如下： (1)通过离心分离的方法将ZnAl-LDH固体沉淀和盐溶液分离,再重新分散在超纯水中,使ZnAl-LDH在超纯水环境中水热生长结晶,水热反应24小时后得到了晶形规则、大小均一的二维纳米片材料。相比于常规的水热法和共沉淀法,本方法合成的水滑石结构更加规则,分布更加均匀,没有出现团聚现象,ZnAl-LDH样品呈规则的六边形晶体结构,质量和纯度较高,非常适合应用到锌镍电池负极材料中。 (2)利用正负电荷之间的静电力作用,将表面修饰后的碳纳米管和ZnAl-LDH两种纳米材料结合在一起,生成三维ZnAl-LDH/CNTs复合物。对复合物的结构进行表征后发现,CNTs均匀分布在ZnAl-LDH纳米片表面,形成一种导电网状结构。将其作为负极活性物质应用到锌镍电池中,通过恒流充放电曲线研究、CV曲线测试、电池循环性能实验,证明电池的循环稳定性、充放电性能以及电极的放电比容量均有显著提升。 (3)运用银镜反应技术,在ZnAl-LDH纳米片表面进行纳米银修饰,首次制备出银包覆ZnAl-LDH纳米片材料。通过电池的恒流充放电实验,发现这种银包覆ZnAl-LDH纳米片材料具有更高的放电容量、更为优异的充放电性能和循环稳定性。进一步采用交流阻抗技术对其进行研究,发现这种银包覆ZnAl-LDH纳米片的电荷转移电阻相比于没有包覆之前有明显的下降,证明了银包覆技术可以显著改善电极的导电性,降低电极的电荷转移电阻,使活性物质的电化学性能显著提升。 (4)合成不同银含量的Ag/ZnAl-LDH复合物,研究复合物中银的含量对其电化学性能的影响。通过各种结构表征手段,证明了导电相银包覆在ZnAl-LDH纳米片表面,不同银含量的复合物样品中银包覆层的分布和存在状态不同,当银的含量达到7.49wt.%(AL15)时,形成一层均匀的银包覆层。综合考虑电池的循环稳定性和放电容量,AL15样品的性能最佳,在循环300次以后,AL15的放电容量没有出现明显衰减,在整个300次充放电循环中放电容量始终稳定在-400mAh g-。 (5)采用溶液直接还原法,在不用任何还原剂的情况下,将硝酸银溶液中的银离子直接还原成纳米银颗粒,沉积在ZnAl-LDH纳米片表面。电化学性能测试表明Ag-LDH复合物样品相比于纯的ZnAl-LDH,其电化学性能得到了显著改善。电化学交流阻抗谱分析结果表明,Ag-LDH复合物的电荷转移电阻明显降低。这证明了高导电的纳米银颗粒沉积在ZnAl-LDH纳米片表面,可以通过降低电荷转移电阻的方式,提高电极材料的电荷传输速率和电子导电性,改善电极材料的电化学性能。(6)采用自组装的方法将GO和ZnAl-LDH组装在一起,然后通过水热还原法,将GO还原成石墨烯,得到graphene/ZnAl-LDH复合物。对graphene/ZnAl-LDH复合物样品的结构进行表征,证明了超薄的石墨烯将ZnAl-LDH纳米片包裹在中心,形成新颖的胶囊状结构。由于外层的graphene具有非常好的电子传导特性,可以大大加快电子在活性物质之间以及活性物质与集流体之间的传导过程。由于胶囊状graphene/ZnAl-LDH复合物具有以上优点,在电池的循环性能和放电容量方面均有大幅提升。在1C条件下电池恒流充放电循环1000次以后,电池容量仅衰减3%,稳定在～405mAh g-1,这种优异的循环特性,非常适合作为锌镍电池负极活性材料。
[Abstract]:Abstract: zinc nickel battery is an alkaline battery with high energy density, the battery performance is far higher than that of nickel cadmium and nickel metal hydride batteries, the battery with abundant raw materials, electrolyte and the active material of non-toxic, pollution-free battery system, more and more attention the world research institutions. However, the conventional nickel zinc anode material discharge products two the battery in soluble in alkaline electrolyte, which will cause the battery cycle life to reduce oZnAl-LDH materials due to their novel two-dimensional nanostructures, has good stability and electrochemical activity and in alkaline electrolyte, is considered the most has the potential to become a novel anode material of Zn Ni battery for the next generation. However, further enhance the conductivity poor single-phase ZnAl-LDH material itself limit its electrochemical performance. Therefore, the ZnAl-LDH material with good electrical conductivity of carbon, metal complex, through the play two The advantages of different materials improve the electrical conductivity and mechanical strength of composites, which greatly improve the electrochemical performance of composites. In this paper, the preparation and electrochemical properties of new ZnAl-LDH nanocomposites are studied.
(1) ZnAl-LDH solid and salt solution separated by centrifugal separation method, re dispersed in ultra pure water, the growth of ZnAl-LDH crystal in hydrothermal ultrapure water environment, hydrothermal reaction after 24 hours the regular crystal shape, two-dimensional nano sheet material with uniform size. Compared to the conventional hydrothermal method and co precipitation method, hydrotalcite structure synthesized by this method is more regular, more uniform distribution, no agglomeration, ZnAl-LDH samples with hexagonal crystal structure rules, quality and high purity, very suitable for application to the zinc nickel battery anode material.
(2) the use of electrostatic interaction between positive and negative electric charges, the surface modification of carbon nanotubes and ZnAl-LDH two nano materials together, 3D ZnAl-LDH/CNTs complexes. The complexes were characterized and found that CNTs distributed evenly on the surface of nano ZnAl-LDH, the formation of a conductive mesh as the structure. The anode active material applied to nickel zinc batteries, by galvanostatic charge discharge curve, CV curve test, cell cycle performance test, cycle stability proof battery, charge and discharge performance and electrode discharge capacity were significantly improved.
(3) the use of silver mirror reaction technology of silver nanoparticles on the surface of ZnAl-LDH nano film, first prepared silver coated ZnAl-LDH nano materials. By galvanostatic charge discharge test battery, found that the silver coated nano ZnAl-LDH materials have higher discharge capacity, more charge discharge performance and cycle stability excellent further. AC impedance technique is used to study, found that compared to uncoated before significantly decreased the silver coated ZnAl-LDH nano sheet charge transfer resistance, proved that the conductivity silver coating technology can significantly improve the electrode, electrode low charge transfer resistance, the electrochemical performance of active material was significantly improved.
(4) Ag/ZnAl-LDH complexes synthesized with different silver content, content of silver complexes influence on its electrochemical properties. Through various structural characterization, proved that the conductive coating on the surface of ZnAl-LDH nano silver, silver with different silver content composite coating sample distribution and existence, when the content of silver reach 7.49wt.% (AL15), to form a uniform layer of silver coating layer. Considering the cell cycle stability and discharge capacity of AL15, the best performance in the sample, after 300 cycles, the discharge capacity of AL15 without significant attenuation, the 300 charge discharge cycles in discharge capacity has stabilized at -400mAh g-.
(5) using the method of direct reduction in the solution without any reducing agent under the condition of silver ions in silver nitrate solution of the direct reduction of silver nanoparticles, nanosheets deposited on ZnAl-LDH surface. The electrochemical performance tests show that the Ag-LDH composite samples compared to the pure ZnAl-LDH, the electrical properties are significantly improved. Electrochemical AC impedance analysis results show that the charge transfer resistance of Ag-LDH composite decreased obviously. This proved that nano silver particles deposited in high conductive nano ZnAl-LDH surface, and can reduce the charge transfer resistance, charge rate and provided transmission of high electronic conductivity of the electrode material, improve the electrochemical performance of electrode materials (6.) by a self-assembly method GO and ZnAl-LDH are assembled together, and then through the hydrothermal reduction method, GO reduced to graphene, graphene/ZnAl-LDH complexes of graphene/ZnAl-LDH complex. The structure of complexes were characterized and proved that graphene thin ZnAl-LDH nano film wrapped in the center, forming a capsule like structure of the novel. Because the outer graphene has very good electronic transmission characteristics, can greatly accelerate the process of electronic conduction between the active substance and active substances and collector. Because the capsule shaped graphene/ZnAl-LDH composite has more advantages, greatly enhance the cell cycle performance and discharge capacity were. Under the condition of 1C battery constant current 1000 charge discharge cycles, battery capacity decay is only 3%, stable in g-1 ~ 405mAh, the excellent cycle characteristics, very suitable as anode active material of nickel zinc battery.

【学位授予单位】：中南大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB332;TM912.2

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