石墨烯基杂化材料可控制备及其在超级电容器中的应用
发布时间：2018-09-11 17:00
【摘要】：可持续能源的生产、存储和消费是当今世界所面临的重大挑战。目前,核心目标不仅是如何构建可再生和可持续的新型能源,更重要的是如何有效地储存和释放能量以满足实际应用中的需求,比如新能源电动汽车、便携式电子产品、太阳能和风力发电储能系统等。超级电容器作为一种介于传统电容器和电池之间的绿色新型储能器件,由于具有高的功率密度、优异的循环稳定性、良好的可靠性和相对低廉的制作成本,已经引起广大科研者的关注和重视。石墨烯是近年来发现的只有一个碳原子厚度的二维材料,因其极大的比表面积、超高的导电性和良好的化学稳定性,在储能材料领域显示出巨大的应用前景。本论文主要以高性能、低成本石墨烯基杂化材料的可控制备和在超级电容器领域中的应用为主题,利用石墨烯为导电网络和机械支撑设计合成了多种无机化合物与石墨烯的高性能杂化电极材料,并探索了杂化材料的形成机理和其微观结构对其电化学性能的影响,有望促进新型高性能超级电容器电极材料的发展。主要研究内容和取得的进展如下:(1)合成了具有独特介晶多孔结构、大比表面积、高导电性的石墨烯/自组装三氧化二铁纳米介晶杂化材料。探索了石墨烯/自组装三氧化二铁纳米介晶杂化材料的生长过程和形成机理并提出了自组装成型机理。研究显示,石墨烯表面棒状α-Fe_2O_3介晶是由初始形成的FeOOH纳米棒通过自组装和同时伴随的相转变而形成的。恒电流充/放电曲线显示出,石墨烯/自组装三氧化二铁纳米介晶杂化材料具有优越的比电容性能,在1MNa_2SO_4中性水溶液中,在3Ag~(-1)电流密度下,其比容量高达306.9Fg~(-1)。即使在10Ag~(-1)的高放电电流密度下,由于该杂化材料增强的离子和电荷传输效率仍然显示了较高的比电容(98.2Fg~(-1))。石墨烯/自组装三氧化二铁纳米介晶杂化材料也展示了优良的循环性能,并优于先前报道的石墨烯/三氧化二铁复合电极材料。(2)虽然多孔三氧化二铁纳米介晶在石墨烯表面已经成功合成,但其孔隙大小和结晶度是不可控的。为了进一步提高其电化学性能,通过水热法和随后的煅烧过程制备了孔隙大小和结晶度均可控的石墨烯/热诱导多孔三氧化二铁杂化材料。在杂化材料中,多孔α-Fe_2O_3的孔径大小和结晶度可以通过改变加热速率进行有效调控。其中,在1°Cmin~(-1)的缓慢升温速率下所获得杂化材料(S-PIGCs),由于优化的结构、窄的孔径分布、合适的微晶尺寸和良好的导电性,作为超级电容器电极材料在3Ag~(-1)的电流密度下,表现出343.7Fg~(-1)的超高比电容,甚至在10Ag~(-1)的高电流密度下,仍保留182.1Fg~(-1)的比电容。另外,S-PIGCs也显示了优越的循环稳定性,在50,000次循环充放电后,原始比容量仍可保留95.8%,同时其库伦效率可达98.6%。(3)石墨烯由于大的比表面积、良好的化学稳定性、高的机械柔韧性和优异的导电性,可作为赝电容材料的良好载体。但是,目前所制备的石墨烯由于表面存在大量的含氧基团,从而表现出较差的导电性和较低的本质电容容量。对石墨烯进行掺氮处理可以有效提高石墨烯的电导率并增加其表面的电化学活性点。利用掺氮这一优势,本文采用原位一步法制备了多种掺氮石墨烯与锰的氧化物杂化材料。首先,采用低温水热法(120℃)利用尿素作为氮源一步合成掺氮石墨烯/超薄二氧化锰片杂化材料(NGMCs)。在水热反应过程中,石墨烯与超薄二氧化锰片的结合和氮原子在石墨烯中的掺杂是同步进行的。研究表明,石墨烯与超薄二氧化锰片结合非常紧密,同时氮原子的掺杂不仅可以提高杂化材料的导电性,而且还可以有效抑制二氧化锰在石墨烯表面的团聚,使得其均匀分布于石墨烯表面。由于高导电掺氮石墨烯与二维超薄二氧化锰片的优化结合,NGMCs电极的电化学性能明显优于石墨烯/超薄二氧化锰片杂化材料(GMCs)电极。当电流密度从0.2Ag~(-1)增加2Ag~(-1)时,NGMCs电极的比电容仍保留初始电容的~74.9%,而GMCs电极仅保留有27%。此外,NGMCs电极也显示了良好的循环稳定性,在2000次循环充放电后,还保留有94.2%的原始比容量。其次,通过一步水热法利用苯胺作为氮源合成褶皱掺氮石墨烯/超细四氧化三锰杂化材料(CNGMNs),并测试了其作为超级电容器电极材料的电化学性能。在CNGMNs制备过程中,由于苯胺的辅助作用,同时实现了超细四氧化三锰纳米颗粒在石墨烯表面生长和氮原子在石墨烯中的掺杂。在所得CNGMNs中,氮原子在石墨烯中的掺杂以及褶皱掺氮石墨烯与超细四氧化三锰纳米颗粒的优化结合,可以有效提高其导电性、比表面积和电化学利用率,进而增加了其电化学性能。CNGMNs电极的比电容大概是其对应纯四氧化三锰颗粒电极的5倍,在1Ag~(-1)的电流密度下,其比电容可达205.5Fg~(-1)。当电流密度高达10Ag~(-1)时,CNGMNs电极仍显示了较高的比容量(110Fg~(-1)),表现出良好的倍率性能;在2000次循环测试后,比容量保持有98.7%,显示了优异的循环稳定性。最后,在甲酰胺的作用下,开发了掺氮石墨烯/羟基氧化锰纳米线杂化材料(MNGHNs),随后将该杂化材料与热处理氧化石墨烯(AGO)的水溶液进行混合,并通过真空过滤获得了AGO夹杂MNGHNs的三明治结构柔性自支撑薄膜(MNGHNs/AGO)。所得柔性薄膜满足了超级电容器电极所需的各种动力学性能需求,如可与电解液充分接触的大量多孔通道,可供电子高速传递的导电网络,可存储更多电容量和更高能量密度的高含量MNGHNs(70wt%)以及可保持长期循环稳定性所需的稳定材料结构和机械强度。由于以上的诸多优点,MNGHNs/AGO柔性自支撑薄膜显示了优异的电化学性能,其面电容在1mAcm~(-2)的电流密度下高达173.2mFcm~(-2)。最后,将该杂化薄膜组装为柔性固态超级电容器,并系统研究了其电化学性能。研究结果显示,MNGHNs/AGO固态超级电容器的体电容在0.1Acm~(-3)下达到了26.3Fcm~(-3),在功率密度为0.04Wcm~(-3)下获得的最大能量密度是2.34mWhcm~(-3);在5Acm~(-3)的电流密度下,200,000次循环充放电后,初始容量仍保持91.5%。
[Abstract]:The production, storage and consumption of sustainable energy is a major challenge facing the world today. At present, the core objective is not only how to build renewable and sustainable new energy, but also how to effectively store and release energy to meet the needs of practical applications, such as new energy electric vehicles, portable electronic products, the sun. As a kind of green energy storage device between traditional capacitors and batteries, supercapacitors have attracted the attention of researchers for their high power density, excellent cycle stability, good reliability and relatively low manufacturing cost. Two-dimensional materials with only one carbon atom thickness have been found to have great potential applications in the field of energy storage materials due to their large specific surface area, ultra-high conductivity and good chemical stability. A variety of inorganic compounds and graphene hybrid electrode materials were designed and synthesized using graphene as conductive network and mechanical support. The formation mechanism of the hybrid materials and the effect of their microstructure on their electrochemical properties were explored. It is expected to promote the development of novel electrode materials for high performance supercapacitors. The results are as follows: (1) Graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials with unique mesomorphic porous structure, large specific surface area and high conductivity were synthesized. The growth process and formation mechanism of graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials were explored and the self-assembled forming mechanism was proposed. It is shown that the rod-like alpha-Fe_2O_3 mesomorphism on the graphene surface is formed by the self-assembly of the initially formed FeOOH nanorods and the accompanying phase transition. The constant current charge/discharge curves show that the graphene/self-assembled ferrous oxide nano-mesomorphism hybrid material has superior specific capacitance properties in 1MNa_2SO_4 neutral aqueous solution and 3Ag~(-1). The specific capacitance of the hybrid material is as high as 306.9Fg~(-1) at current density. Even at the high discharge current density of 10Ag~(-1), the enhanced ion and charge transfer efficiency of the hybrid material still shows a higher specific capacitance (98.2Fg~(-1). Graphene/self-assembled ferrous oxide nano-mesomorphic hybrid material also exhibits excellent cycling performance and is superior to that of 10Ag~(-1). Previous reports on graphene/ferric oxide composite electrode materials. (2) Although porous ferrous oxide nanocrystals have been successfully synthesized on graphene surface, their pore size and crystallinity are uncontrollable. In order to further improve their electrochemical performance, both pore size and crystallinity were prepared by hydrothermal method and subsequent calcination process. Controllable graphene/thermally induced porous ferric oxide hybrids. Pore size and crystallinity of porous alpha-Fe_2O_3 can be effectively controlled by varying heating rates in hybrids. Hybrids (S-PIGCs) obtained at a slow heating rate of 1 Cmin ~(-1) have narrow pore size distribution due to optimized structure and suitable crystallinity. Microcrystalline size and good conductivity, as a supercapacitor electrode material, show 343.7 Fg-1 supercapacitor at current density of 3Ag~(-1), even at high current density of 10Ag~(-1), retain 182.1 Fg~(-1) specific capacitor. In addition, S-PIGCs also show superior cyclic stability, after 50,000 cycles of charging and discharging, the original. Graphene can be used as a good carrier for pseudocapacitor materials because of its large specific surface area, good chemical stability, high mechanical flexibility and excellent conductivity. However, the graphene prepared at present has a large number of oxygen-containing groups on the surface, thus showing good performance. Nitrogen-doped graphene can effectively improve the conductivity of graphene and increase the electrochemical activity of graphene. Using the advantage of nitrogen-doped graphene, a variety of nitrogen-doped graphene and manganese oxide hybrid materials were prepared by in-situ one-step method. Nitrogen-doped graphene/ultrathin manganese dioxide hybrid materials (NGMCs) were synthesized by one-step synthesis using urea as nitrogen source at 120 C. The combination of graphene with ultrathin manganese dioxide sheets and the doping of nitrogen atoms in graphene were carried out synchronously during hydrothermal reaction. Atomic doping can not only improve the conductivity of hybrid materials, but also effectively inhibit the agglomeration of manganese dioxide on graphene surface and make it evenly distributed on graphene surface. When the current density increased from 0.2Ag~(-1) to 2Ag~(-1), the specific capacitance of the NGMCs electrode remained at ~74.9% of the initial capacitance, while that of the GMCs electrode remained at only 27%. Nitrogen-doped graphene/ultrafine manganese tetroxide hybrid materials (CNGMNs) were synthesized by one-step hydrothermal method using aniline as nitrogen source, and their electrochemical properties as electrode materials for supercapacitors were tested. In the obtained CNGMNs, the doping of nitrogen atoms in graphene and the optimum combination of folded nitrogen-doped graphene and ultrafine manganese tetroxide nanoparticles can effectively improve their conductivity, specific surface area and electrochemical utilization rate, thereby increasing their electrochemical performance. At the current density of 1Ag~(-1), the specific capacitance can reach 205.5Fg~(-1). When the current density is as high as 10Ag~(-1), the CNGMNs electrode still shows a high specific capacity (110Fg~(-1)), showing a good rate performance; after 2000 cycles, the specific capacitance maintains 98.7%, showing an excellent performance. Finally, nitrogen-doped graphene/hydroxy manganese oxide nanowire hybrid material (MNGHNs) was developed under the action of formamide. The hybrid material was then mixed with the aqueous solution of heat-treated graphene oxide (AGO), and the sandwich structure flexible self-supporting films (MNGHNs/AG) containing MNGHNs were obtained by vacuum filtration. O. The resulting flexible film meets the various dynamic requirements of the supercapacitor electrodes, such as a large number of porous channels in full contact with the electrolyte, a conducting network for high-speed transmission of electrons, a high content of MNGHNs (70wt%) with more capacitance and higher energy density, and the stability required to maintain long-term cycle stability. MNGHNs/AGO flexible self-supporting thin films exhibit excellent electrochemical properties, and their surface capacitance is as high as 173.2 mFcm~(-2) at the current density of 1 mAcm~(-2). Finally, the hybrid thin films are assembled into flexible solid-state supercapacitors and their electrochemical properties are systematically studied. The results show that the bulk capacitance of MNGHNs/AGO solid-state supercapacitor reaches 26.3 Fcm~(-3) at 0.1Acm~(-3), the maximum energy density at 0.04 Wcm~(-3) is 2.34 mWhcm~(-3), and the initial capacity remains 91.5% after 200,000 cycles of charging and discharging at 5 Acm~(-3).
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM53;TB33
本文编号：2237295
[Abstract]:The production, storage and consumption of sustainable energy is a major challenge facing the world today. At present, the core objective is not only how to build renewable and sustainable new energy, but also how to effectively store and release energy to meet the needs of practical applications, such as new energy electric vehicles, portable electronic products, the sun. As a kind of green energy storage device between traditional capacitors and batteries, supercapacitors have attracted the attention of researchers for their high power density, excellent cycle stability, good reliability and relatively low manufacturing cost. Two-dimensional materials with only one carbon atom thickness have been found to have great potential applications in the field of energy storage materials due to their large specific surface area, ultra-high conductivity and good chemical stability. A variety of inorganic compounds and graphene hybrid electrode materials were designed and synthesized using graphene as conductive network and mechanical support. The formation mechanism of the hybrid materials and the effect of their microstructure on their electrochemical properties were explored. It is expected to promote the development of novel electrode materials for high performance supercapacitors. The results are as follows: (1) Graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials with unique mesomorphic porous structure, large specific surface area and high conductivity were synthesized. The growth process and formation mechanism of graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials were explored and the self-assembled forming mechanism was proposed. It is shown that the rod-like alpha-Fe_2O_3 mesomorphism on the graphene surface is formed by the self-assembly of the initially formed FeOOH nanorods and the accompanying phase transition. The constant current charge/discharge curves show that the graphene/self-assembled ferrous oxide nano-mesomorphism hybrid material has superior specific capacitance properties in 1MNa_2SO_4 neutral aqueous solution and 3Ag~(-1). The specific capacitance of the hybrid material is as high as 306.9Fg~(-1) at current density. Even at the high discharge current density of 10Ag~(-1), the enhanced ion and charge transfer efficiency of the hybrid material still shows a higher specific capacitance (98.2Fg~(-1). Graphene/self-assembled ferrous oxide nano-mesomorphic hybrid material also exhibits excellent cycling performance and is superior to that of 10Ag~(-1). Previous reports on graphene/ferric oxide composite electrode materials. (2) Although porous ferrous oxide nanocrystals have been successfully synthesized on graphene surface, their pore size and crystallinity are uncontrollable. In order to further improve their electrochemical performance, both pore size and crystallinity were prepared by hydrothermal method and subsequent calcination process. Controllable graphene/thermally induced porous ferric oxide hybrids. Pore size and crystallinity of porous alpha-Fe_2O_3 can be effectively controlled by varying heating rates in hybrids. Hybrids (S-PIGCs) obtained at a slow heating rate of 1 Cmin ~(-1) have narrow pore size distribution due to optimized structure and suitable crystallinity. Microcrystalline size and good conductivity, as a supercapacitor electrode material, show 343.7 Fg-1 supercapacitor at current density of 3Ag~(-1), even at high current density of 10Ag~(-1), retain 182.1 Fg~(-1) specific capacitor. In addition, S-PIGCs also show superior cyclic stability, after 50,000 cycles of charging and discharging, the original. Graphene can be used as a good carrier for pseudocapacitor materials because of its large specific surface area, good chemical stability, high mechanical flexibility and excellent conductivity. However, the graphene prepared at present has a large number of oxygen-containing groups on the surface, thus showing good performance. Nitrogen-doped graphene can effectively improve the conductivity of graphene and increase the electrochemical activity of graphene. Using the advantage of nitrogen-doped graphene, a variety of nitrogen-doped graphene and manganese oxide hybrid materials were prepared by in-situ one-step method. Nitrogen-doped graphene/ultrathin manganese dioxide hybrid materials (NGMCs) were synthesized by one-step synthesis using urea as nitrogen source at 120 C. The combination of graphene with ultrathin manganese dioxide sheets and the doping of nitrogen atoms in graphene were carried out synchronously during hydrothermal reaction. Atomic doping can not only improve the conductivity of hybrid materials, but also effectively inhibit the agglomeration of manganese dioxide on graphene surface and make it evenly distributed on graphene surface. When the current density increased from 0.2Ag~(-1) to 2Ag~(-1), the specific capacitance of the NGMCs electrode remained at ~74.9% of the initial capacitance, while that of the GMCs electrode remained at only 27%. Nitrogen-doped graphene/ultrafine manganese tetroxide hybrid materials (CNGMNs) were synthesized by one-step hydrothermal method using aniline as nitrogen source, and their electrochemical properties as electrode materials for supercapacitors were tested. In the obtained CNGMNs, the doping of nitrogen atoms in graphene and the optimum combination of folded nitrogen-doped graphene and ultrafine manganese tetroxide nanoparticles can effectively improve their conductivity, specific surface area and electrochemical utilization rate, thereby increasing their electrochemical performance. At the current density of 1Ag~(-1), the specific capacitance can reach 205.5Fg~(-1). When the current density is as high as 10Ag~(-1), the CNGMNs electrode still shows a high specific capacity (110Fg~(-1)), showing a good rate performance; after 2000 cycles, the specific capacitance maintains 98.7%, showing an excellent performance. Finally, nitrogen-doped graphene/hydroxy manganese oxide nanowire hybrid material (MNGHNs) was developed under the action of formamide. The hybrid material was then mixed with the aqueous solution of heat-treated graphene oxide (AGO), and the sandwich structure flexible self-supporting films (MNGHNs/AG) containing MNGHNs were obtained by vacuum filtration. O. The resulting flexible film meets the various dynamic requirements of the supercapacitor electrodes, such as a large number of porous channels in full contact with the electrolyte, a conducting network for high-speed transmission of electrons, a high content of MNGHNs (70wt%) with more capacitance and higher energy density, and the stability required to maintain long-term cycle stability. MNGHNs/AGO flexible self-supporting thin films exhibit excellent electrochemical properties, and their surface capacitance is as high as 173.2 mFcm~(-2) at the current density of 1 mAcm~(-2). Finally, the hybrid thin films are assembled into flexible solid-state supercapacitors and their electrochemical properties are systematically studied. The results show that the bulk capacitance of MNGHNs/AGO solid-state supercapacitor reaches 26.3 Fcm~(-3) at 0.1Acm~(-3), the maximum energy density at 0.04 Wcm~(-3) is 2.34 mWhcm~(-3), and the initial capacity remains 91.5% after 200,000 cycles of charging and discharging at 5 Acm~(-3).
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM53;TB33
【参考文献】
相关期刊论文 前1条
1 沈宸;陆云;;石墨烯/导电聚合物复合材料在超级电容器电极材料方面的研究进展[J];高分子学报;2014年10期
，本文编号：2237295
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