锰氧化物电极材料的制备及其在碱性介质中的电容特性研究

发布时间：2018-02-05 19:36

本文关键词： 超级电容器氧化锰氧化态掺杂介晶碱性电解液　出处：《燕山大学》2015年博士论文　论文类型：学位论文

【摘要】：锰氧化物比容量高、环境友好、原料来源丰富,成为近年来超级电容器电极材料领域的研究热点。由于锰氧化物的导电率低,机械稳定性差,使其实际容量远低于理论容量。本实验通过调控制备工艺获得不同晶体结构和不同形貌的锰氧化物,利用元素掺杂、碳包覆等方法对所制备的锰氧化物进行改性,提高了材料的电化学性能,并研究其微观结构变化及其在碱性电解液中的电化学性能改善的机制。通过液相沉淀法制备了水钠锰矿的二氧化锰纳米颗粒。并通过掺杂钴,铝等离子提高了其电化学性能。红外以及XPS结果显示,Al的加入增强了Mn-O键之间的键合,从而提高了电化学循环过程中的稳定性。根据原位的pH检测显示杂质离子的加入,降低了液相反应的反应速率,从而降低了产物的团聚程度,最终使得产物具有更规则的形貌。通过水热法制备了铈掺杂的多孔δ-MnO2纳米花球。研究显示,铈的加入并未改变二氧化锰的结构,仅仅改变了其表面形貌。铈的加入改善了材料的电化学循环性能及可逆性能。并且当铈掺杂量为1.5%时,材料具有最优的电化学性能,在1 A g-1的电流密度下比容量可达382.4 F g-1,远远高于未掺杂的290 F g-1。这种优异的电化学性能来源于电极/电解液界面的低的电化学阻抗以及颗粒减小和多孔性所带来的快的离子传输速度。采用溶剂热结合热分解的方法制备了Mn2O3介晶。并通过改变葡萄糖的含量以及通过调节溶剂中乙醇的比例来控制所合成介晶的形貌。结果发现溶剂中加入乙醇之后形貌由梭形变为哑铃形,比表面积以及电化学性能也得到了一定的提高。研究发现与纳米Mn2O3相比,介晶Mn2O3更适合作为超级电容器电极材料,并且发现介晶Mn2O3材料比纳米材料具有对赝电容更高的贡献率。通过水热结合高温热解的方法制备了多孔纳米晶Mn3O4六角形片,通过调整KOH以及葡萄糖的含量可以精确控制六角形片的形貌尺寸以及结构。在生成产物的过程中KOH控制着孔的形成以及六角形片的形状,葡萄糖能选择性的吸附在(001)晶面,控制(001)晶面的生长从而控制着六角形片的厚度;所制备的六角形片状结构Mn3O4材料具有优良的电化学特性。这与材料独特的片状结构以及多级孔道分布有着很大的关系;并且以Mn3O4电极为正极,多孔碳电极为负极制备了不对称超级电容器。电压窗口可达1.5 V。结果显示在功率密度为207.3 W kg-1时,能量密度可达17.276 Wh kg-1。采用高温固相结合恒电流充放电的方法制备了一种多级分布的锰氧化物/碳多孔花球,并展现出了良好的电化学特性。这种优良的电化学特性与以下几个方面有关:多孔状结构使得电解液与内部材料之间的接触更加容易;高石墨相的碳带穿插其中形成了碳导电网络,提高了材料的导电性;碳带的穿插使得材料的机械性能得到了提高;锰氧化物与碳材料之间的高相界面结合加速了低价锰的转变,并且能够使得一些惰性物质重新变为活性物质,从而提高了电化学稳定性。同时也深入分析了碳在材料的转化过程中对材料形貌以及结构转化中起的重要作用。由于碳的加入,使得材料转化过程中活性位点增多,这就加速了材料的活化,外延生长的过程更加迅速,生成的片层结构更加弯曲,减弱了体积膨胀。
[Abstract]:Manganese oxides with high specific capacity, environmental friendly, rich sources of raw materials, has become a hot research field of super capacitor electrode material in recent years. Due to the conductivity of manganese oxide is low, the poor mechanical stability, so that the actual capacity is far lower than the theoretical capacity. In this experiment, control of preparation processes of different crystal structures and morphologies of the manganese oxide transfer, using element doping, modification of manganese oxide prepared by carbon coating method, improve the electrochemical performance of the material, and to study the microstructure changes and mechanism of electrochemical properties in alkaline electrolyte. The improvement of MnO2 birnessite nanoparticles were prepared by liquid phase precipitation and through. Doped cobalt, aluminum plasma to improve its electrochemical performance. The IR and XPS results showed that the addition of Al enhances the Mn-O bond between the bond, thereby improving the electrochemical cycle stability According to the qualitative. In situ pH detection shows that the addition of impurity ions, reduced the reaction rate of liquid phase reaction, thereby reducing the agglomeration degree of products, makes the final product with more regular morphology. By hydrothermal method to prepare porous -MnO2 nano cerium doped 8 ball. Studies have shown that cerium addition did not change the structure of manganese dioxide the only change of the surface morphology. Cerium improves the electrochemical performance and reversible properties of materials. And when the Ce content is 1.5%, the electrochemical performance of the material has the best, at a current density of 1 A g-1 than the capacity of up to 382.4 F g-1 ion transmission speed is much higher than that of undoped 290 F g-1. the excellent electrochemical properties from the electrode / electrolyte interface electrochemical impedance and low particle size and porous brought. By solvothermal method combined with thermal decomposition preparation Mn2O3. And to control the mesomorphic mesogens were synthesized by changing the content of glucose and ethanol in the solvent by adjusting the proportion of the morphology. The results showed that after adding ethanol solvent in morphology from spindle into a dumbbell shape, surface area and electrochemical properties have been improved. The study found that compared with nano Mn2O3 mesomorphous Mn2O3 is more suitable to be used as supercapacitor electrode materials, and found that the mesocrystal Mn2O3 material has a higher contribution rate than on pseudocapacitive nano materials by hydrothermal method. Combined with the high temperature pyrolysis of porous nanocrystalline Mn3O4 film prepared by precise control of hexagonal, hexagonal sheet can be adjusted by KOH and glucose content in morphology and size in the process of production and structure. The KOH controls the pore formation and shape of hexagonal tablets, glucose can selectively adsorb on the crystal face (001), (001) the crystal control Long to control the thickness of the hexagonal sheet; hexagonal structure of Mn3O4 composites has excellent electrochemical characteristics. This has a great relationship with the lamellar structure material unique and multi pore distribution; and with Mn3O4 electrode as anode, porous carbon electrode was prepared by asymmetric super capacitor anode voltage up to the window. 1.5 the results of V. showed that the power density is 207.3 W kg-1, the energy density can reach 17.276 Wh kg-1. by the high temperature solid state manganese oxide / a multilevel distributed carbon porous curd was synthesized by the method of constant current charge discharge system, and show good electrochemical properties. The electrochemical properties of the excellent and the following several aspects: a porous structure between the electrolyte and the internal material contact more easily; high ribbon of graphite phase interspersed among the formation of carbon conductive network, improve the conductive material The ribbon; with the mechanical performance of materials has been improved; the high phase interface between manganese oxide and carbon materials with low manganese accelerated transformation, and can make some inert material to become active substances, so as to improve the electrochemical stability. Also analyzes the important role of carbon material morphology and structure transformation in the transformation process. In the material due to the addition of carbon, active site conversion process makes the material increase, which accelerates the process of material activation, epitaxial growth more rapidly, the lamellar structure generated more bending, weakening the volume expansion.

【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ137.12;O646

【相似文献】