【作者】 杨艳静；

【导师】 刘恩辉；

【作者基本信息】 湘潭大学 ， 应用化学， 2010， 硕士

【摘要】 超级电容器作为新型储能元件,对其电极活性材料的研究是目前新能源领域研究的热点之一。过渡金属氧化物二氧化锰作为传统的电极材料应用非常广泛。本文以廉价的二氧化锰作为超级电容器的电极材料,采用TG-DTA,XRD,SEM,BET等现代物理测试方法对制备的样品进行表征,通过电化学性能测试研究了二氧化锰材料的制备方法及后处理条件对电容特性的影响。采用水热法、液相氧化还原法分别制备了不同的二氧化锰纳米材料。主要研究内容如下:1.水热法合成,以高锰酸钾为氧化剂,醋酸锰为还原剂,制得α型MnO₂粉体。扫描电子显微镜SEM结果显示产物形貌为典型的纳米棒,且纳米棒分布均匀。研究了反应温度和反应时间对产品结构形貌和电化学性能的影响,得出在反应温度为140℃反应时间为2 h时得到的纳米棒具有最大长径比,直径约为20-40 nm,长度为几百纳米到几微米,且电化学性能最好,比电容量达到145 F/g。随反应时间的增加比电容量由145 F/g减小到40 F/g,电荷传输电阻增加。2.以酸性有机还原剂草酸与高锰酸钾反应制备了二氧化锰材料并研究了其电化学性能。XRD结果显示制得的产物主要晶相为无定形α-MnO₂,SEM结果表明样品为粒径均匀的纳米球体。KMnO₄与H₂C₂O₄的摩尔比为2:3,反应温度为60℃,反应时间为3 h时,制备的样品经循环伏安测试得到较大的比电容量,且CV曲线矩形特征明显,比电容量为158 F/g。将该样品在400℃下灼烧2 h,在1 mol/L的Na-2SO₄电解液、0-1V扫描电位内以2 mV/s的扫速进行测试时,该电极表现出理想的电容特性,比容量达到265 F/g,增加了68%。并研究了电解液对电极电容特性的影响,分别在碱性（6 mol/L的KOH）和中性（1 mol/L的Na₂SO₄）电解液中对样品进行了循环伏安测试。结果表明,二氧化锰作为超级电容器电极材料更适合在中性电解液中工作。3.以碱性有机还原剂三乙醇胺还原高锰酸钾制备了二氧化锰材料。XRD及SEM结果显示合成样品为纳米二氧化锰颗粒,但有团聚现象发生。对样品进行热处理,温度为400℃时,样品晶化程度增强,晶格排列变得规则有序。N₂吸脱附的结果表明,350℃热处理后的样品具有较大的比表面积,而且在介孔范围内具有较宽的孔径分布。循环伏安测试结果也表明350℃热处理得到的样品在1 mol/L的Na₂SO₄电解液中表现出良好的电容性能,在2 mV/s的扫描速度下得到251 F/g的比电容量,相对于未处理的前躯体样品比电容量增加了48.5%。充放电测试结果表明制备的样品具有良好的循环稳定性。更多还原

【Abstract】 Supercapacitors have been extensively studied as the energy storage devices. And the electrode material has been the focus of research and exploitation in the field of supercapacitor. It is the transition metal oxide manganese dioxide that has been applied widely as the electrode material. So we chose inexpensive manganese dioxide as our target product used for the supercapacitor electrode material. And a series of modern physical methods are taken to characterize the properties of the prepared materials. Power X-ray diffraction （XRD）, scanning electron microscope （SEM） and N2 adsorption and desorption measurements are employed to investigate crystalline structure, surface morphology, the specific surface area and the pore size distribution. And it is discussed that how the synthesized conditions and the heat-treatment effect the capacitance of manganese dioxide materials.Different nanostructured manganese dioxide was prepared by hydrothermal and oxidation reduction method. The major research contents are as follows:First.α-MnO₂ powders were prepared by hydrothermal, in which KMnO₄ oxidized the reductant （CH₃COO）₂Mn that leads the formation of MnO₂. The SEM pictures depict the typical nano-rod of morphologies, and the nano-rods show a uniform distribution. The effect on characteristics of materials by reaction time and temperature were studied. The results show that the better capacitance and the large aspect ratio are obtained when the reaction temperature is 140℃and the reaction time is 2 h. The best specific capacitance is 145 F/g. The nanorods have a diameter about 20-40 nm and the lengths up to a region of hundreds of nanometers to several micrometers. The specific capacitance decreased as the reaction time prolonged, and the charge transfer resistance increased.Second. Oxalic acid was used as reductant to prepare MnO₂ powders. And the electrochemical properties were studied. The XRD results indicate that the product is amorphousα-MnO₂. The SEM pictures show that the surface morphologies are consist of nano-spheres. The optimal prepared conditions are as follows: reaction temperature is 60℃, reaction time is 3h and the molar ratio is KMnO₄:H₂C₂O₄=2:3. The specific capacitance of the product is 158 F/g. The specific capacitance increased by 68%, from 158 F/g to 265 F/g, when the product was heat-treated at 400℃for 2h. And the influence of different electrolyte on the capacitance property was studied. The cyclic voltammetry results indicate that neutral electrolyte is more suitable for the MnO₂ electrode working than basic electrolyte.Last. Amorphous manganese dioxide is prepared by reaction of potassium permanganate with an organic reductant triethanolamine for the first time. XRD and SEM results show that the prepared material is nanoscaled MnO₂ powders, but there is some particle agglomeration. The effect of heat-treatment temperature is studied on the characteristics of the materials. It is found that when the heat-treatment temperature rising to 400℃, the crystalline convert toα-MnO₂ from amorphous MnO₂. The electrochemical characteristics of the prepared MnO₂ powder are characterized by means of cyclic voltammetry experiments in 1 mol/L Na₂SO₄ electrolyte. The specific capacitance value is 251 F/g that is obtained from the product annealing at 350℃at a scan rate of 2 mV/s. And charging-discharging measurement reveals the good stability of the prepared material.更多还原