【作者】 葛军；

【导师】 陈丽娟；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 物理化学， 2009， 博士

【摘要】 超级电容器(又称为电化学超级电容器)根据储能机理的不同可以分为两类:一类是双电层电容器,基于电极与电解液界面双电层的非法拉第过程;另一类是赝电容器,基于电极表面的嵌入、欠电位沉积、氧化还原的法拉第过程。双电层电容器中最常用的电极材料是活性碳材料,因为它们不仅造价低廉,而且拥有多种存在形式。双电层电容器的优劣关键在于双电层的充放电效率,高效率的双电层充放电要求电极材料具有高比表面积、与离子大小相适合的孔径。碳材料主要以粉末、纤维、气凝胶、碳纳米管等形式应用于超级电容器,这些材料的性质已经被详细地研究,并被应用于科研和生产中。随着材料研究的发展,不同结构、形态及性能差异的其它碳材料也在不断出现,因而对这种碳材料也需要进行系统地研究。这些材料的研究和应用对推动和完善超级电容器用碳电极材料领域的发展同样具有重要的意义。本论文重点针对材料,对它们的制备、性质、应用等进行探讨和研究:(1)以明胶为原材料,对明胶的碳化条件、形成微孔的原理、复合物的制备、电化学性质等方面进行了系统的研究;(2)研究了化学气相沉积法制备碳球的工艺条件和所得碳球电化学性质;(3)研究了碳微线圈的制备、生长机理、电化学性质。论文围绕这三大部分展开,主要的研究内容如下:1、明胶为前驱体制备明胶碳球。明胶微球首先要在空气中以250℃进行预处理,然后再高温碳化。戊二醛交联前后,明胶在空气和氮气中的热失重曲线仅在300℃之后有细微的差别,熔化温度Tm为228℃。戊二醛交联前后的明胶微球在空气或氮气中250℃热处理7 h,再经过稀硫酸处理,得到不同结构的明胶基材料:空气中处理的未交联明胶微球可得多孔内核结构,而在氮气中处理的得到实心结构,交联后明胶球无论在空气还是氮气中处理均得到实心结构。核壳式明胶基球碳化后保持了多孔内核/致密外壳的结构,对其电化学性质也进行了初步研究。2、利用CaCO3和明胶制备了多种复合微球及其衍生明胶基活性碳球。当纳米CaCO3和明胶质量比为2时,得到的活化明胶基碳球最适合作为超级电容器的碳电极材料。碳纤维与明胶基碳球复合,可明显提高整体的导电性,但复合材料的比电容仍然偏低。3、以苯和乙炔为碳源,分别用两段炉和一段炉法制备化学气相沉积碳球。两段炉方法中,第一段炉的温度对碳球形貌无明显影响,两种方法的碳化温度都要高于1100℃。碳球直径从前向后逐渐减小、分散性从前向后逐渐提高,影响碳球的粒径的主要因素为混合气体总气流速率,总气流速率越大得到的碳球粒径越小。4、水蒸气活化碳球单电极比电容为131 F/g,电容器等效串联电阻为7.5 ;KOH活化碳球单电极比电容为146.4 F/g,电容器等效串联电阻为7.5。对比两种活化方法得到的碳球,虽然KOH活化碳球的比电容略高,但KOH活化的实验步骤较为繁琐,而水蒸气活化操作简单、原料便宜,两者活化的碳球比电容相差不大,所以水蒸气活化方法更适合本实验室活化碳球的制备。5、碳微线圈有一个共同的碳基底并垂直于基底生长。在710~750℃范围内,随温度升高碳微线圈的内径减小、长度增长。730℃条件下得到的碳微线圈基底厚度和韧性适中、碳微线圈含量最高;经水蒸气活化后BET比表面积为511 m2/g,孔径分布较广,微孔占主要部分,中孔和大孔含量较少;单电极比电容为56.4 F/g。电容器等效串联电阻为12.5。6、碳微线圈碳基底背面有密堆六方和面心立方两种晶格结构的Ni共存;进气口附近,Ni为密堆六方晶格结构,颗粒为近似六边形的扁平晶体;离进气口较远处,催化剂小颗粒聚集成饼状的结构,相互之间没有完全熔合在一起。说明微米级半径碳微线圈的生长机理和纳米级半径碳微线圈的生长机理有所不同。更多还原

【Abstract】 Supercapacitor ( also called electrochemical supercapacitor )can be classified into two types according to the mechanism of energy storage: electrical double layer capacitor (EDLC), utilizing electrolyte charging at the electric double layer on electrode surface by Non Faradaic process, and pseudocapacitor involving fast Faradaic reactions such as intercalation, underpotential deposition or redox processes occurring at or near a solid–electrode surface at an appropriate potential. Activated carbons are the most often used EDLC electrode material because of their low cost and versatile existing forms. An e?cient charging of the electrical double layer requires materials with a high surface area and pores adapted to the size of ions, which is crucial for EDLC performance.Carbon materials such as powders, ?bers, aerogels and nanotubes are widely used for supercapacitor applications. The performance of these carbon materials have been studied thoroughly and used in industrial applications and scientific researches. However, systematic researches of other carbon materials and discoveries of unknown materials are still needed.In this dissertation, firstly, a systematic study including the carbonization parameters, the formation mechanism of pore structures, preparations of composite materials, electrochemical properties of gelatin, as a carbon precursor, was performed; secondly, the preparation process and electrochemical properties of carbon spheres produced by chemical vapor deposition were studied; finally, the preparation, the formation mechanism and electrochemical properties of carbon microcoils were investigated. The main research work in the present dissertation can be summarized as follows:a) Gelatin based carbon microspheres were produced from gelatin spheres by heat treating at 250℃and carbonization. The empty gelatin microspheres (GMs) and glutaraldehyde crosslinked gelatin microspheres (CGMs) were characterized by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that CGMs had an equal slight weight loss more than GMs from 300℃in air and nitrogen atmosphere respectively. The melting temperature (Tm) of GMs and CGMs were both at 228℃. After being heat treated at 250℃and acid treated in sulfuric acid solution for 7 h, the GMs heat treated in air had a foam like core/solid shell structure and that heat treated in nitrogen had solid cores/shell structure, and CGMs were all solid microspheres with cracks. After carbonization, the foam like core/solid shell structure was maintained, and the properties of the as prepared carbon materials were analysed.b) Several kinds of composite spheres were produced from CaCO3 particles and gelatin. The active carbon spheres produced from the composite spheres, whitch the mass ratio of nano CaCO3 and gelatin was 2, was the most suitable material for supercapacitor compared with other gelatin based carbon spheres. The carbon fibers/carbon spheres composite material had a low specific capacitance because of large percentage of gelatin based carbon spheres and low resistance because of the carbon fibers.c) Benzene and acetylene were used in chemical vapor deposition (CVD) process to produce carbon spheres. A double furnace apparatus and a one furnace apparatus were used for the pyrolysis of precursors. The temperature of the first furnace in the double furnace apparatus had not effect on the diameter of produced carbon spheres, and the pyrolysis temperature should over 1100℃. The diameter and accretion of prepared carbon spheres decreased along the direction of gas flow and with the increasing of gas flow rate.d) The steam activated carbon sphere had a specific capacitance of 131 F/g and the value of equivalent series resistance (ESR) of the supercapacitor was 7.5 ; the KOH activated carbon sphere had a specific capacitance of 131 F/g and the value of ESR of the supercapacitor was 7.5 . Compared these two kinds of activated carbon, the one prepared from KOH activation had higher capacitance, while the steam activation was easy to operate and low cost. So the steam activation was more efficient in our lad.e) The carbon micro coils had a carbon co substrate and were vertical with the co substrate. The coil diameter decreased and length increased with the increasing of pyrolysis temperature from 710 to 750℃. The specimen obtained at 730℃had a substrate of proper thickness and thoughness, highest percentage of coils, and a BET surface area of 511 m2/g after steam activation. The porosity distribution was primarily micro pores, with some meso and micro pores. The value of specific capacitance was 56.4 F/g and the ESR value of the supercapacitor was 12.5 .f) On the back surface of co substrate of carbon micro coils, Ni particles exhibited face centered cubic (fcc) phase and hexagonal close packed (hcp) phase. Only hcp Ni was found in the vicinity of the gas inlet, and Ni monolith shaped as flat hexagonal plates. Far from the gas inlet, Ni grains aggregated into flat plates without total fusion. The evidences above indicated that the mechanism of micro diameter carbon micro coils was different from that of nano diameter carbon micro coils.更多还原