石墨烯基超级电容器电极材料结构调控与性能

发布时间：2018-04-10 20:02

本文选题：超级电容器 + 石墨烯　；参考：《哈尔滨工业大学》2015年博士论文

【摘要】：超级电容器作为一种储能器件,具有高功率、长寿命、高可靠性的特点,被广泛应用于新能源、电子器件、电动车等领域。目前对超级电容器的研究主要集中在保持其高功率特性的前提下,提高其能量密度。由超级电容器能量密度(E)的计算公式E=1/2(CV2)可知,可以通过:(1)开发具有高比容量(C)的新型电极材料;(2)设计具有高工作电压(V)的的电容器体系,来达到提高超级电容器能量密度的目的。本文首先以获得高比容量电极材料为目标,通过利用氧化石墨烯独特的物理化学性质(可还原性、可组装性、可修饰性和阴离子性等),设计制备出氧化石墨烯转化碳球、还原氧化石墨烯/Mn_3O_4复合粉体和氧化石墨烯/聚吡咯复合薄膜三个体系超级电容器电极材料;其次,为获得高的工作电压,分别以MnO_2和水热还原氧化石墨烯为正负极,利用其析氢析氧过电位,设计构建具有高工作电压的非对称水系超级电容器。利用氧化石墨烯的可组装性,通过调控水热环境,实现氧化石墨烯自组装转化形成碳球。发现氧化石墨烯前驱体溶液中引入含氧酸(硫酸、磷酸)或水合肼可促使氧化石墨烯发生结构重构形成碳球。氧化石墨烯转化碳球在电子束辐照下具有独特的刺激响应行为-即球核受热分解发生体积膨胀形成空心化碳球。由于碳球是由石墨烯高度团聚-包覆-脱水重构转化而来,导致电解液难以浸入到碳球内部,即碳球的形成降低了水热还原氧化石墨烯的电化学活性表面。因此碳球的形成不利于获得具有高比容量的水热还原氧化石墨烯材料。通过醋酸锰在还原氧化石墨烯的二甲基甲酰胺/水混合溶剂分散液中水解实现Mn_3O_4纳米颗粒(粒径5nm左右)对还原氧化石墨烯表面的修饰改性。优选的Mn_3O_4修饰量(58 wt.%)既能有效防止还原氧化石墨烯片层在干燥过程中的紧密叠层,而且不发生自身团聚,因此可获得较高的电化学活性表面。还原氧化石墨烯/Mn_3O_4复合粉体在2mA/cm~2的放电电流密度下,比容量达343F/g,且当电流密度增加至50m A/cm~2时,仍能保持215F/g的比容量。利用氧化石墨烯的阴离子性,在吡咯、氧化石墨烯和高氯酸锂前驱体水溶液中通过一步电化学共沉积,获得了厚度达50μm的三维氧化石墨烯/聚吡咯复合薄膜。该薄膜由聚吡咯涂覆的氧化石墨烯片三维交联而形成,因此具有快速的离子扩散孔道。通过控制前驱体溶液中氧化石墨烯浓度可实现对复合薄膜形貌结构的有效控制。活性材料负载量为0.26mg/cm~2的复合薄膜电极质量比容量高达481.1F/g,而负载量为1.02mg/cm~2的复合薄膜电极则表现出最高的面积比容量(387.6m F/cm~2)。氧化石墨烯/聚吡咯复合薄膜电极具有优异的倍率性能,当放电电流密度由0.2增至10m A/cm~2时(50倍),容量保持率均在80%以上。基于氧化石墨烯/聚吡咯复合薄膜电极的水系和固态超级电容器具有优异的电化学电容特性,倍率特性和循环稳定性。其中工作电压0.8V的水系超级电容器在80W/kg的功率密度下,能量密度为16.4Wh/kg,且当功率密度增加至4000W/kg时,能够保持其78%的初始能量密度。利用MnO_2正极和石墨烯负极之间电化学窗口的匹配性,以1mol/L硫酸钠水溶液为电解液,构建了工作电压达2.0V的MnO_2//石墨烯非对称超级电容器。该非对称体系在100W/kg的功率密度下,能量密度可达25.2Wh/kg,优于对称式MnO_2//MnO_2(4.9Wh/kg)和石墨烯//石墨烯电容器(3.6Wh/kg)。循环寿命测试结果表明,MnO_2//石墨烯非对称超级电容器在500次充放电循环之后容量保持为97%。
[Abstract]:The super capacitor as an energy storage device with high power, long life, high reliability, is widely used in the new energy, electronic devices, electric vehicles and other fields. The current research on super capacitors mainly concentrated on the premise of maintaining high power characteristics, improve its energy density by the super capacitor. The energy density (E) of the formula E=1/2 (CV2) that can be adopted: (1) developed with high specific capacity (C) of the new electrode materials; (2) the design of high voltage capacitor (V) system, to improve the super capacitor energy density. Firstly, in order to get high capacity electrode materials as the goal, through the use of graphene oxide to unique physical and chemical properties (reducibility, composability, modification and anionic etc.), designed and prepared graphene oxide into the carbon spheres, graphene oxide /Mn_3O_4 composite powder and reduction Graphene oxide / polypyrrole composite film three system super capacitor electrode material; secondly, in order to obtain high working voltage, respectively by MnO_2 and hydrothermal reduction of graphene oxide as anode and the overpotential of hydrogen, designed with high voltage asymmetric super capacitor. The oxidation of water graphene can be assembled, through the regulation of water and heat environment, realize the graphene oxide self-assembly formation of carbon spheres. Found that the introduction of oxygen acid graphene oxide precursor solution (sulfate, phosphate) or hydrazine hydrate can make graphene oxide structure reconstruction of the formation of carbon spheres. The graphene oxide into the carbon spheres with a response behavior - unique stimulus ball nuclear thermal decomposition volume expansion forming hollow carbon spheres under electron beam irradiation. The ball is made of carbon - coated graphene highly agglomeration dehydration transformation and reconstruction, resulting in electrolytic liquid difficult In order to immersed into carbon spheres, electrochemical active surface of graphene oxide by hydrothermal reduction that reduces the formation of carbon ball. So the ball is not conducive to the formation of carbon reduction of graphene oxide material with high specific capacity. The hot water by manganese acetate in two dimethyl formyl amine / reduced graphene oxide water mixed solvent dispersion the realization of Mn_3O_4 nanoparticles in liquid hydrolysis (diameter about 5nm) modification on the surface modification of graphite oxide. The amount of modified Mn_3O_4 preferred (58 wt.%) can prevent the reduction of graphene oxide layers in the drying process closely stacked, and not their reunion, therefore can obtain the electrochemical active surface high. Reduction of graphene oxide /Mn_3O_4 composite powder in the discharge current density of 2mA/cm~2, the specific capacitance of 343F/g, and when the current density increased to 50m A/cm~2, can still maintain the specific capacity of 215F/g. The use of oxygen fossil Anionic, graphene in pyrrole, by one-step electrochemical deposition of graphene oxide and lithium perchlorate precursor in aqueous solution, three-dimensional graphene oxide / the thickness of 50 m polypyrrole composite film. The film is composed of graphene oxide sheets of polypyrrole coated three-dimensional cross-linked form, so it has fast the ion diffusion channels. By controlling the concentration of graphene oxide in the precursor solution can achieve effective control of the morphology of the composite films. The active material loading of 0.26mg/cm~2 composite film electrode quality than the capacity of up to 481.1F/g, and the capacity for the composite film electrode of 1.02mg/cm~2 showed the highest area ratio (387.6m F/cm~2) capacity. Graphene oxide / polypyrrole composite film electrode has excellent rate performance, when the discharge current density increased from 0.2 to 10m A/cm~2 (50 times), the capacity retention rate was more than 80%. On the basis of oxygen Graphene / polypyrrole composite film electrode system and solid super capacitor with excellent electrochemical properties, rate performance and cycle stability. The working voltage of 0.8V system of super capacitors in 80W/kg power density, energy density is 16.4Wh/kg, and when the power density increases to 4000W/kg, the initial energy density can be maintained 78%. Using the matching between MnO_2 cathode and graphene anode electrochemical window, with 1mol/L sodium sulfate solution as electrolyte, MnO_2// graphene constructs the working voltage of 2.0V asymmetricsupercapacitor. The asymmetric system in 100W/kg power density, energy density of up to 25.2Wh/kg, is better than that of symmetric MnO_2//MnO_2 (4.9Wh/kg) and graphene / graphene capacitors (3.6Wh/kg). The cycle life test results show that the MnO_2// graphene asymmetricsupercapacitor in 500 charge / discharge cycles After the loop capacity is still 97%.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;TM53

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