一维复合纳米结构的可控构筑及其超级电容器电极性能研究

发布时间：2018-01-20 03:17

本文关键词： 超级电容器电极材料一维复合纳米结构静电纺丝导电聚合物金属氧化物碳纳米纤维　出处：《吉林大学》2017年博士论文　论文类型：学位论文

【摘要】：能源危机与环境问题是当前人类社会面临的两大挑战,随着世界人口的增长与全球经济的发展,开发高效、清洁、可持续的新能源以及先进的能量存储与转换器件已经成为当务之急。超级电容器,又称为电化学电容器,具有功率密度大、充放电速度快、循环寿命长、安全性能好、成本低廉以及绿色环保等优点,是一种新型的储能装置。众所周知,电极材料是决定超级电容器性能的一个重要因素,所以开发高性能电极材料已成为近年来的研究热点。一维纳米结构具有较大的长径比,能够增加电极与电解液之间的可接触面积,并缩短电子与离子的传输路径,有利于提高电极的电容性能。超级电容器常用的电极材料包括碳材料、金属氧化物(MOs)、导电聚合物等,然而,单一组分电极材料由于较小的理论比电容(碳材料)、较低的导电性(MOs)、较差的循环稳定性(导电聚合物)以及不理想的表面性质等,已经无法满足应用要求。一般认为,设计和构筑复合纳米结构材料,利用各组分间的协同效应,充分发挥其效能,是增强超级电容器电极性能的一种有效手段。本论文以上述三种常用的电极材料为研究对象,从设计与构筑一维复合纳米结构的角度出发,旨在通过对材料的组成与形貌进行调控,来改善超级电容器电极的性能,进而为一维复合纳米结构材料在能量存储领域的应用奠定一定的科学基础。具体内容如下:1.一维导电聚合物基电极材料:导电聚合物,尤其是聚苯胺(PANi),是一种典型的赝电容材料。以PANi为基底或壳层,利用简单温和的模板法,在体系中引入无机组分,通过改善PANi自身性能或防止MOs溶解,来提高一维复合电极材料在中性电解液中的电容性能。(1)以Bi_2S_3纳米线为牺牲模板和Bi源,HCl为掺杂剂和Cl源,在低温下,“一锅”合成了新颖的PANi刺/Bi OCl片一维多级纳米结构材料(BPB)。相邻PANi刺之间的空隙有利于电解液离子的扩散,同时,Bi OCl对掺杂H+的稳定作用能使BPB在中性条件下保持电化学活性。与HCl掺杂的PANi电极相比,该异质结构电极表现出较高的比电容(169.9 F g-1,0.5 A g-1)与倍率性能(15.6%,4.0 A g-1),其循环稳定性也有所提高。(2)以单晶VO2纳米带为活性模板,利用原位聚合法,将PANi壳层均匀地沉积在VO2表面,得到了VO2@PANi同轴纳米带。该方法不需要表面活性剂的辅助,通过调节反应时间与体系p H,可以扩展到核/卵黄-壳或中空无机/有机功能纳米材料的合成。所制备的VO2@PANi电极具有较高的比电容值,为246.0 F g-1(0.5 A g-1),高于VO2电极的160.9 F g-1与HCl掺杂PANi电极的139.4 F g-1;同时,VO2@PANi电极的倍率性能也有所改善,当电流密度增大10倍时,其比电容保持率能够达到27.3%,而VO2电极仅为11.3%;1000次充放电循环后,VO2@PANi电极的比电容为初始值的28.6%,高于HCl掺杂的PANi电极(2.8%)。2.一维金属氧化物基电极材料:除了导电聚合物,无机MOs是另一种常用的赝电容材料。α-Fe2O3具有较高的理论比电容,且无毒性、耐腐蚀、原料来源丰富,然而,其较差的导电性导致比电容的实验值远低于理论值。为了解决上述问题,我们将α-Fe2O3与其它MOs复合,即以静电纺α-Fe2O3纳米管为主体,通过掺杂V2O5与包覆MnO_2壳层两种方式,对复合材料的结构与组成进行设计调控,来改善其电化学性能。(1)结合静电纺丝与高温烧结技术制备了一系列不同组成的V2O5/α-Fe2O3纳米管。当V2O5/Fe2O3质量比为1.0%时,复合电极材料表现出较高的比电容(183 F g-1,1.0 A g-1)与循环稳定性(81.5%,200次循环),且其倍率性能与α-Fe2O3纳米管电极相当(60%,5.0 A g-1)。(2)以静电纺α-Fe2O3纳米管为核,利用简单的化学浴沉积法,合成了不同MnO_2含量的α-Fe2O3@MnO_2核壳异质结构材料。与基于MnO_2纳米结构的电极相比,该复合材料,尤其是FM10020(MnO_2含量为60.1 wt%),具有较大的比电容值(289.9 F g-1,1.0 A g-1)、较好的倍率性能(40.8%,5.0 A g-1)与较高的循环稳定性(85.3%,1200次循环)。3.改性碳纤维基电极材料:对于两种MOs的复合电极材料,由于存在电化学溶解与导电性差的问题,导致其电容性能在很大程度上并不理想。改善MOs电极材料性能的另一种可行方法是将其与导电基质复合。静电纺碳纳米纤维(CNFs)除了具有碳材料的固有优点外,其可加工性强,孔结构可调,被认为是良好的导电支撑基底。在聚合物纺丝液前驱体中引入金属盐,可以有效提高CNFs基质的石墨化程度,并造成多孔结构,从而得到改性的C-MOx复合纳米纤维。我们主要以C-MOx为支撑基质,通过在其表面修饰含氮碳层或包覆MnO_2壳层,来增强多元复合体系电极材料的电化学性能。(1)采用静电纺丝、化学气相聚合与高温煅烧技术,制备了表面含氮的C-Co Ox-C多孔复合纳米纤维。由于较高的含碳量与较大的Co Ox粒子,C-Co Ox-C电极的比电容并不理想;然而,与C-Co Ox相比,C-Co Ox-C含氮碳层良好的导电性与独特的保护机制使其倍率性能与循环稳定性均较高。(2)以静电纺C-MOx(M=Mn、Cu、Co)复合纳米纤维为基底,在其表面沉积MnO_2层,得到一系列C-MOx@MnO_2一维核壳异质结构。通过提高碳纤维基底的石墨化度或混入金属Cu,有效改善了C-MOx@MnO_2的导电性,同时,C-MOx核不仅可以作为活性材料参与电荷存储过程,还能充当导电基质使壳层MnO_2充分利用,并引入协同效应。与基于CNFs@MnO_2核壳结构的电极相比,C-MOx@MnO_2电极表现出较高的比电容与倍率性能,且循环稳定性良好。这些实验结果将会为进一步增强碳纤维或金属氧化物基电极材料的电容性能提供可选择的途径。
[Abstract]:The energy crisis and environmental problems are the two major challenges facing human society, with the development of the world's population growth and global economic development of efficient, clean, sustainable energy and energy storage converter and advanced parts has become a pressing matter of the moment. The super capacitor, also known as electrochemical capacitor with high power density, charge discharge speed, long cycle life, good safety performance, low cost and green environmental protection and other advantages, is a new energy storage device. As everyone knows, the electrode material is an important factor in determining the performance of the super capacitor, so the development of high performance electrode material has become a research hotspot in recent years. One dimensional nano structure has larger the ratio of length to diameter, can increase the contact area between the electrode and the electrolyte, and shorten the transmission path of electron and ion, is conducive to improve the capacitance performance of electrode of super capacitor. Electrode materials commonly used include carbon materials, metal oxide (MOs), conductive polymers, however, the single electrode material due to the smaller capacitance theory (carbon), lower conductivity (MOs), the poor cycle stability (conductive polymer) and poor surface properties, has been unable to to meet the application requirements. Generally, the design and construction of composite nano structured materials, the synergistic effect among the components, give full play to its effectiveness, is an effective means to increase the performance of the super capacitor electrode. The above three kinds of common electrode material as the research object, from the design and fabrication of one dimensional nano composite structure point of view, aimed at controlling through the composition and morphology of the materials, to improve the performance of the super capacitor electrode, and for the application of one-dimensional composite nano structure materials in the field of energy storage provide a branch Basis. Details are as follows: 1. one-dimensional conductive polymer based electrode materials, conductive polymers, especially polyaniline (PANi), is a kind of typical pseudocapacitive materials. With PANi as substrate or shell, using the template method is simple and mild, introduction of inorganic group in the system, to prevent the dissolution of MOs by improving the performance of PANi itself or, to improve the capacitance performance of one-dimensional composite electrode in neutral electrolyte. (1) using Bi_2S_3 nanowires as sacrificial template and Bi source, HCl and Cl as the dopant source, at low temperatures, "one pot" synthesis of a novel PANi /Bi OCl thorn one-dimensional hierarchical nanostructured materials (BPB) space. Between adjacent PANi thorn have spread to the electrolyte ions and stabilization of Bi OCl on H+ doping can maintain BPB electrochemical activity in neutral conditions. Compared with PANi doped HCl electrode, the heterostructure electrode exhibits high specific capacitance (169. 9 F g-1,0.5 A g-1) and ratecapability (15.6%, 4 A g-1), the cycle stability is also improved. (2) crystal VO2 nanobelts as active template by in situ polymerization, PANi shell uniformly deposited on the surface of VO2, the VO2@PANi coaxial nanobelts. The method does not need auxiliary surface the active agent, by adjusting the reaction time and the system can be extended to P H, a nuclear - shell or hollow / yolk synthesis of inorganic / organic functional materials. The specific capacitance of the VO2@PANi electrode prepared with high, 246 F g-1 (0.5 A g-1), higher than that of VO2 electrode in 160.9 F g-1 and HCl the doped PANi electrode in 139.4 F g-1; at the same time, rate performance of VO2@PANi electrode is improved, when the current density increased by 10 times, the specific capacitance retention rate can reach 27.3%, while the VO2 electrode is only 11.3%; after 1000 cycles, the specific capacitance of the VO2@PANi electrode for the initial value of 28.6%, high PANi electrode in HCl doped.2. (2.8%) of one-dimensional metal oxide based electrode materials: in addition to conductive polymer, inorganic MOs is another commonly used pseudocapacitive materials. Alpha -Fe2O3 has a high theoretical specific capacitance, and no toxicity, corrosion resistance, rich source of raw materials, however, its poor conductivity leads to far below the theoretical the value of the specific capacitance of the experimental value. In order to solve the above problems, we will alpha -Fe2O3 and other MOs compound, namely to electrospun alpha -Fe2O3 nanotubes as the main body, by doping V2O5 and coated with MnO_2 shells in two ways, the regulation of the structure of the composite material and design, to improve its electrochemical performance. (1) a series of V2O5/ alpha -Fe2O3 nanotubes was synthesized by electrospinning and high temperature sintering process. When the mass ratio of V2O5/Fe2O3 is 1%, the composite electrode materials exhibit high specific capacitance (183 F g-1,1.0 A g-1) and cycle stability (81.5%, 2 00 cycles), and the rate performance with alpha -Fe2O3 nanotube electrode (60%, 5 A a g-1). (2) by electrospinning of alpha -Fe2O3 nanotubes as the core, using the chemical bath deposition method simple, alpha -Fe2O3@MnO_2 core-shell heterostructure materials with different MnO_2 content were synthesized. Compared with electrode MnO_2 nano structure based on the composite material, especially FM10020 (the content of MnO_2 is 60.1 wt%), with large specific capacitance (289.9 F g-1,1.0 A g-1), better rate performance (40.8% A, 5 g-1) and high cycle stability (85.3%, 1200 cycles) of.3. modified carbon fiber based electrode materials. The composite electrode material two MOs, due to the low conductivity and electrochemical dissolution, the capacitance performance is not ideal to a great extent. Another possible way to improve the performance of MOs electrode material is the composite conductive matrix. Electrospun carbon nanofibers (CNFs) in addition to Has the inherent advantages of carbon material, its machinability, tunable pore structure, is considered to be good. The introduction of conductive supporting substrate metal salt in the polymer precursor spinning solution, can effectively improve the degree of graphitization of the CNFs matrix, and the resulting porous structure, so as to obtain C-MOx composite nano fiber modification. We mainly use C-MOx as a support matrix, by modifying the surface of nitrogen containing carbon or coated with MnO_2 shells, to enhance the electrochemical performance of composite electrode material system. (1) by electrospinning, polymerization and calcination technology of chemical gas phase, C-Co porous Ox-C composite nano fiber surface nitrogen was prepared. The with high carbon content and larger Co Ox C-Co particles, the specific capacitance of the Ox-C electrode is not ideal; however, compared with C-Co Ox, C-Co Ox-C containing nitrogen and carbon layer of good conductivity and special protection mechanism of the rate capability and cycle stability Qualitatively higher. (2) by electrospinning C-MOx (M=Mn, Cu, Co) composite nanofibers as substrate and deposited on the surface of the MnO_2 layer, to obtain a series of one-dimensional C-MOx@MnO_2 core-shell heterostructure. By increasing the degree of graphitization of carbon fiber substrate or mixed metal Cu, effectively improve the electrical conductivity, C-MOx@ and MnO_2 C-MOx, not only can be used as active materials in the nuclear charge storage process, can be used as a conductive matrix to make full use of MnO_2 shell, and the introduction of a synergistic effect. Compared with the electrode of CNFs@MnO_2 core-shell structure based on C-MOx@MnO_2 electrode exhibits high specific capacitance and good cycle stability and rate capability. These results will provide a way to choose to further enhance the capacitance performance of carbon fiber or metal oxide based electrode materials.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM53;O646

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