钴基氧化物电极材料的合成及其电化学电容性能的研究

发布时间：2018-03-18 08:21

本文选题：超级电容器　切入点：钴酸锰　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：超级电容器是一种介于普通电容器和燃料电池之间的新型储能器件,近年来得到了快速的发展,而电极材料是决定超级电容器性能优劣的决定性因素之一,因此,寻找并开发电化学电容性能优异的电极材料对于提高超级电容器性能具有决定性意义。钴基金属氧化物由于具有很高的理论比容量和优异的倍率性能而受到了广泛的关注,本论文以钴酸锰(MnCo_2O_4)和四氧化三钴(Co_3O_4)为研究对象,分别对其电化学电容性能进行了研究。具体内容分为两个部分:(1)层状MnCo_2O_4电极材料的合成及其电化学电容性能的研究以醋酸钴和醋酸锰为前驱体盐,尿素作为络合剂,乙二醇/水作为混合溶剂,采用溶剂热法制备出层状堆叠的MnCo_2O_4材料。研究发现只有在醋酸锰和醋酸钴的摩尔比为0.25 mmol:0.5 mmol,反应温度为150°C,反应时间为5.5 h时,才可以得到层状堆叠的MnCo_2O_4材料,改变条件后,MnCo2O4的形貌发生严重变化。电化学测试结果表明这种层状堆叠结构的MnCo2O4可以表现出相比于其他形貌更加优异的电化学性能,在1 A·g~(-1)的电流密度下的比电容为480.5 F·g~(-1),当电流密度升高至25 A·g~(-1)时,比电容的保持率仍可达75.7%,循环3000圈以后的比电容保持率可达96.6%。进一步探讨其特殊结构的形成机理,发现其层状堆叠的结构来自于Mn元素与Co元素共同作用的结果,在反应过程中,Mn2+和Co2+的反应速率不断发生变化,导致在反应的各个阶段所得到的产物的形貌不同,但是在MnCo_2O_4的整体形貌上,其立方体结构主要来自于Co元素的作用,层状结构来自于Mn元素的作用。(2)泡沫镍负载Co_3O_4电极材料的合成及其电化学电容性能的研究以硝酸钴为前驱体盐,采用水热法直接在泡沫镍表面负载Co_3O_4材料(Co_3O_4/NF)。研究结果表明,电化学性能最佳的Co_3O_4/NF反应条件为:硝酸钴的浓度为0.1 M,反应温度为120°C,反应时间为4 h。XRD结果表明所制备的产物为泡沫镍上负载的Co_3O_4材料,SEM的结果表明产物为均匀的纳米针状结构。在最佳反应条件下所得到的Co_3O_4/NF电极材料在1 m A·cm~(-2)的电流密度下可以表现出751.1 F·g~(-1)的比电容,而电流密度升高至20 mA·cm~(-2)时,比电容可保持81.3%,循环6000圈以后的比电容保持率可达88.6%,说明其具有优异的电化学性能。
[Abstract]:Supercapacitor is a new type of energy storage device between ordinary capacitor and fuel cell. It has been developed rapidly in recent years, and electrode material is one of the decisive factors to determine the performance of supercapacitor. It is very important to find and develop electrode materials with excellent electrochemical capacitive properties to improve the performance of supercapacitors. Cobalt based metal oxides have attracted wide attention due to their high theoretical specific capacity and excellent rate performance. In this paper, MnCo2O4 (Manganese Cobalate) and Co3O _ 4 (Cobalt tetroxide) are the objects of study. The electrochemical capacitance properties of MnCo_2O_4 electrode materials were studied in two parts. The synthesis and electrochemical capacitance properties of layered MnCo_2O_4 electrode materials were studied. Cobalt acetate and manganese acetate were used as precursors, and urea was used as complexing agent. Using ethylene glycol / water as a mixed solvent, layered stacked MnCo_2O_4 materials were prepared by solvothermal method. It was found that only when the molar ratio of manganese acetate and cobalt acetate was 0.25 mmol:0.5 mmol, the reaction temperature was 150 掳C and the reaction time was 5.5 h. The morphology of MNO _ 2O _ 4 is changed seriously after changing the conditions. The electrochemical test results show that the MnCo2O4 with layered stacking structure can exhibit better electrochemical performance than other morphologies. The specific capacitance at current density of 1 A 路g ~ (-1) is 480.5 F 路g ~ (-1). When the current density is increased to 25 A 路g ~ (-1), the specific capacitance retention rate can still reach 75.7% and the specific capacitance retention rate can reach 96.6 when the current density is increased to 25 A 路g ~ (-1). Further study is made on the formation mechanism of its special structure. It is found that the structure of the layered stacking results from the interaction of mn and Co, and the reaction rates of mn _ 2 and Co2 vary continuously during the reaction, which results in different morphologies of the products obtained at each stage of the reaction. However, in the overall morphology of MnCo_2O_4, the cube structure is mainly due to the effect of Co element. Study on Synthesis and Electrochemical Capacitance performance of Nickel foam supported Co_3O_4 electrode Materials using Cobalt nitrate as precursor salt, the layered structure is directly loaded on the surface of nickel foam by hydrothermal method. The optimum Co_3O_4/NF reaction conditions for electrochemical performance are: the concentration of cobalt nitrate is 0.1m, the reaction temperature is 120 掳C, and the reaction time is 4 h. The results show that the prepared product is a Co_3O_4 material loaded on nickel foam. The result shows that the product is uniform. Nanoscale needle-like structure. Under the optimum reaction conditions, the specific capacitance of the Co_3O_4/NF electrode material obtained at the current density of 1 Ma 路cm ~ (-2) can be 751.1 F 路g ~ (-1). When the current density is increased to 20 Ma 路cm ~ (-2), the specific capacitance can be kept at 81.3 and the specific capacitance retention rate after 6000 cycles can reach 88.6, which indicates that it has excellent electrochemical performance.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM53;O646

【参考文献】