硫化物复合材料的可控合成及其超级电容性能研究

发布时间：2018-05-21 19:18

本文选题：超级电容器 + NiCo_2S_4@Ni_3S_2　；参考：《华侨大学》2017年硕士论文

【摘要】：作为新一代储能装置,超级电容器因为功率密度高、循环寿命长、充电快速等突出优势,引起了社会密切的关注。然而,低比容量和较低能量密度却成为其不容忽视的技术瓶颈,大大限制了在储能领域的应用。由能量密度公式(E=1/2QV)推出,提升超级电容器能量密度的决定因素是比容量和工作电压。因此本文选取具有高比容量和良好导电性的硫化物作为研究对象,成功地合成了不同形貌的硫化物及其复合材料,然后以硫化物及其复合材料、三维石墨烯凝胶分别作为正极和负极材料,设计组装成非对称超级电容器。通过阴离子交换这一温和的方法在泡沫镍上原位合成了独特的NiCo_2S_4纳米管阵列。然后,采用电沉积的方法在NiCo_2S_4骨架上包覆适宜质量的Ni_3S_2纳米片,得到NiCo_2S_4@Ni_3S_2核壳纳米管阵列复合材料。运用扫描电镜(SEM)、X射线衍射(XRD)和透射电镜(TEM)等分析手段对电极材料的形貌和结构进行表征,以及在三电极体系中对NiCo_2S_4和NiCo_2S_4@Ni_3S_2电极进行电化学测试。结果表明,在4 m A cm-2电流密度下,NiCo_2S_4@Ni_3S_2的面积比容量高达4.25 C cm-2,比纯NiCo_2S_4电极(2.62 C cm-2)提升了62.21%。当电流密度达到最大值40m A cm-2,NiCo_2S_4@Ni_3S_2复合材料的面积比容量依然保持在3.12 C cm-2。NiCo_2S_4@Ni_3S_2复合材料杰出的电化学性能归功于以下几点:1、NiCo_2S_4纳米管中空结构和良好导电性的贡献;2、核壳结构有利于提高电极材料的机械稳定性和循环稳定性;3、NiCo_2S_4和Ni_3S_2都是优异的法拉第电极材料,发挥了异质协同作用。以NiCo_2S_4、NiCo_2S_4@Ni_3S_2作为正极材料,同时以三维石墨烯凝胶作为负极材料,构造非对称超级电容器。电化学测试结果显示,NiCo_2S_4@Ni_3S_2//r GO凝胶非对称超级电容器取得了优异的电化学性能:在0.5 A g~(-1)电流密度下比容量达到163.15 C g~(-1);当功率密度在0.36 k W kg~(-1)时,能量密度高达32.75 Wh kg~(-1)。此外,循环寿命测试表明,NiCo_2S_4@Ni_3S_2//r GO凝胶非对称超级电容器具有卓越的循环稳定性能(在2 A g~(-1)电流密度下,经过5000次循环充放电后容量保持率依然为77.50%)。由此可见,NiCo_2S_4@Ni_3S_2//r GO凝胶非对称超级电容器在储能领域具有良好的应用前景。采用一步法溶剂热反应合成了形貌可控、粒径均匀的NiCo_2S_4微球,运用SEM、EDS、XRD对制备材料的形貌和结构进行表征,以及在三电极体系中对NiCo_2S_4电极进行电化学测试。结果显示,在1 A g~(-1)电流密度下,NiCo_2S_4电极质量比容量高达599.4 C g~(-1)。即使在20 A g~(-1)最大的电流密度下,其质量比容量仍然有298 C g~(-1)。NiCo_2S_4微球电极在电化学性能上的优势主要来源于:一方面NiCo_2S_4是具有代表性的法拉第材料,不仅具有丰富可逆的氧化还原反应,而且导电性良好;另一方面NiCo_2S_4微球表面拥有交联的纳米片,大大促进电解质离子的扩散,同时为电荷转移提供有效路径。以NiCo_2S_4微球、三维石墨烯凝胶分别作为非对称超级电容器正负极材料,然后进行组装。测试结果显示,随着电流密度的不断增大,NiCo_2S_4//r GO凝胶非对称超级电容器的质量比容量由171.2 C g~(-1)变化到117.6 C g~(-1)。当功率密度为0.39 k W kg~(-1)时,其能量密度高达36.72 Wh kg~(-1)。即使在3.10 k W kg~(-1)高功率密度时,其能量密度依旧可达25.33 Wh kg~(-1)。此外,循环寿命测试表明,在4 A g~(-1)大电流密度下经过5000次循环充放电后,NiCo_2S_4//r GO凝胶非对称超级电容器容量保持率仍为77.85%,表现出优异的循环寿命。通过简单的溶剂热反应一步合成NiCo_2S_4/r GO复合凝胶,NiCo_2S_4纳米粒子均匀地镶嵌在三维石墨烯片表面。运用XRD、Raman、SEM、TEM等手段对所合成材料的结构和形貌进行表征。通过电化学工作站和LAND电池系统对电极材料进行一系列电化学性能测试。结果显示,在1 A g~(-1)电流密度下,NiCo_2S_4/r GO复合凝胶的超大质量比容量为714 C g~(-1)。即使在最大电流密度20 A g~(-1)时,其比容量仍然保持了81.23%(580 C g~(-1)),比纯的NiCo_2S_4还要高,体现出良好的倍率性能。另外,在10 A g~(-1)的大电流密度下,经过5000次循环充放电,NiCo_2S_4/r GO复合凝胶的比容量仍然高达初始值的90.21%,表现出杰出的循环稳定性能。优异的电化学性能来源于三维多孔结构的r GO大比表面积及高导电性的贡献,不仅增多了NiCo_2S_4活性物质法拉第反应的活性位点,而且提供了快速高效的电荷转移和离子扩散速率。
[Abstract]:As a new generation of energy storage devices, supercapacitors have attracted much attention because of their high power density, long cycle life, fast charging and other outstanding advantages. However, low specific capacity and low energy density have become the technical bottlenecks that can not be ignored, which greatly restrict the application in the field of energy storage. The energy density formula (E=1/2QV) is introduced. The determination of the energy density of the supercapacitor is the specific capacity and the working voltage. Therefore, in this paper, the sulfides and their composites with different morphologies have been successfully synthesized with high specific capacity and good conductivity, and then the sulfides and their composite materials are used as positive poles of the three dimensional graphene gels. And the negative electrode was designed and assembled into an asymmetric supercapacitor. A unique NiCo_2S_4 nanotube array was synthesized in situ on the nickel foam by a mild method of anion exchange. Then, the suitable mass Ni_3S_2 nanoscale was coated on the NiCo_2S_4 framework by electrodeposition, and the NiCo_2S_4@Ni_3S_2 core shell nanotube array complex was obtained. The morphology and structure of the electrode materials were characterized by scanning electron microscopy (SEM), X ray diffraction (XRD) and transmission electron microscopy (TEM), and the electrochemical measurements of NiCo_2S_4 and NiCo_2S_4@Ni_3S_2 electrodes were carried out in the three electrode system. The results showed that the area specific capacity of NiCo_2S_4@Ni_3S_2 was at the cm-2 current density of 4 m A. Up to 4.25 C cm-2, higher than pure NiCo_2S_4 electrode (2.62 C cm-2) increased 62.21%. when the current density reached maximum 40m A cm-2, the area specific capacity of NiCo_2S_4@Ni_3S_2 composite remains in 3.12 C cm-2.NiCo_2S_4@Ni_3S_2 composites outstanding electrochemical performance attributed to the following points: 1, hollow nanotube hollow structure and good 2, the nuclear shell structure is beneficial to improve the mechanical stability and the cyclic stability of the electrode material; 3, NiCo_2S_4 and Ni_3S_2 are excellent Faraday electrode materials, and play the heterogeneous synergism. NiCo_2S_4, NiCo_2S_4@Ni_3S_2 is used as the positive material, and the three dimensional graphene gel is used as the negative material, and the asymmetric super structure is constructed. The electrochemical test results show that the NiCo_2S_4@Ni_3S_2//r GO gel asymmetric supercapacitor has excellent electrochemical performance: the specific capacity reaches 163.15 C g~ (-1) at 0.5 A g~ (-1) current density, and when the power density is 0.36 K W kg~ (-1), the energy density is up to 32.75. The 2S_4@Ni_3S_2//r GO gel unsymmetrical supercapacitor has excellent cyclic stability (at 2 A g~ (-1) current density, after 5000 cycles charge discharge capacity remains 77.50%). Thus, the NiCo_2S_4@Ni_3S_2//r GO gel asymmetric supercapacitor has a good application prospect in the field of energy storage. One step method is adopted. NiCo_2S_4 microspheres with controllable morphology and uniform particle size were synthesized by solvothermal reaction. The morphology and structure of the prepared materials were characterized by SEM, EDS and XRD, and the electrochemical measurement of NiCo_2S_4 electrodes in the three electrode system showed that the mass ratio of the NiCo_2S_4 electrode was up to 599.4 C g~ (-1) under the 1 A g~ (-1) current density. Under the maximum current density of 20 A g~ (-1), its mass ratio capacity still has 298 C g~ (-1).NiCo_2S_4 microsphere electrode in electrochemical performance mainly from: on the one hand NiCo_2S_4 is a representative Faraday material, not only has a rich reversible redox reaction, but also has good electrical conductivity; on the other hand, NiCo_2S_4 microsphere table With NiCo_2S_4 microspheres, three dimensional graphene gel is used as an asymmetric supercapacitor positive and negative electrode, and then assembled. The test results show that the NiCo_2S_4//r GO gel is asymmetric with the increasing of the current density. The mass ratio of the supercapacitor varies from 171.2 C g~ (-1) to 117.6 C g~ (-1). When the power density is 0.39 K W kg~ (-1), the energy density is up to 36.72 Wh kg~. The energy density is still up to 25.33, even at the high power density of 3.10. After 5000 cycles of charging and discharging, the capacity retention of NiCo_2S_4//r GO gel unsymmetrical supercapacitor is still 77.85%, showing excellent cycle life. NiCo_2S_4/r GO composite gel is synthesized by a simple solvent thermal reaction. NiCo_2S_4 nanoparticles are evenly embedded in the surface of three-dimensional graphene sheet. XRD, Raman, SEM, TEM and so on are used. The structure and morphology of the synthesized materials were characterized. A series of electrochemical properties were tested by electrochemical workstation and LAND battery system. The results showed that the super mass specific capacity of NiCo_2S_4/r GO composite gel was 714 C g~ (-1) at 1 A g~ (-1) current density, even at the maximum current density of 20 A g~ (-1). Its specific capacity remains 81.23% (580 C g~ (-1)), which is higher than pure NiCo_2S_4 and shows good multiplier performance. In addition, the specific capacity of NiCo_2S_4/r GO composite gel is still up to 90.21% of the initial value at the large current density of 10 A g~ (-1), and the specific capacity of NiCo_2S_4/r GO composite gel is still high. Excellent electricity is shown. The chemical properties are derived from the large specific surface area and high conductivity of R GO in the three-dimensional porous structure, which not only increase the active site of the Faraday reaction of the NiCo_2S_4 active substance, but also provide a fast and efficient charge transfer and ion diffusion rate.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332;TM53

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