三维石墨烯复合材料的制备及其储能性能研究

发布时间：2018-06-16 14:58

本文选题：石墨烯 + 气凝胶　；参考：《北京化工大学》2017年博士论文

【摘要】：石墨烯作为一种典型的二维纳米材料,因其高比表面积、优异电导率和热导率、突出力学性能和化学稳定性等,在能源存储领域具有广阔的应用前景。以氧化石墨烯(GO)为前驱体材料,通过化学还原来制备石墨烯是一种有较大发展潜力的技术路线,可以实现石墨烯的宏量制备。然而,这种方法得到的石墨烯片层容易发生团聚,影响了石墨烯性能的充分发挥,限制了其更为广泛的应用。本论文以GO为前驱体制备了三维的石墨烯材料,预先形成三维石墨烯传导网络,保证了石墨烯优异传导性能的充分发挥。主要创新性研究结果如下:1、泡沫镍还原氧化石墨烯用作超级电容器电极材料:针对目前三维石墨烯构筑过程中需要大量还原剂和能源消耗的问题,我们提出了一种简便方法制备可直接用作超级电容器电极材料的三维还原氧化石墨烯/泡沫镍(RGO/Nifoam)复合材料。在pH=2的室温条件下,直接利用泡沫镍对GO进行还原,无需添加其它化学还原剂。得到的RGO在泡沫镍骨架上组装,制得RGO/Nifoam复合材料,直接用作超级电容器电极材料,无需添加高分子粘结剂,表现出优异的电化学性能。通过调节还原时间可调控RGO/Ni foam中的RGO含量,达到调控复合电极材料的单位面积比电容的目的。当还原时间从3天提高到15天,在0.5 mA·Cm-2的电流密度下,其面积比电容从26 mF·Cm-2增加到了 136.8 mF·Cm-2。此外,温度是影响还原速率的重要因素。当提高还原温度至70℃时,反应5小时后得到的5-hour RGO/Ni foam复合材料比室温下反应15天得到的15-day RGO/Ni foam复合材料呈现出更为优异的电化学性能。5-hour RGO/Ni foam复合材料的面积比电容高达206.7 mF·cm-2,并且兼具优异的倍率性能和循环稳定性,充放电循环10000次,容量保留率高达97.4%。在70℃延长反应时间至9小时,得到的9-hour RGO/Ni foam复合材料表现出了更高的面积比电容,达到323 mF·Cm-2,并且仍然兼具突出的倍率性能和优异的循环稳定性。2、多级孔道结构的石墨烯/胞沫镍复合材料用作电极材料:成功制备一个兼具高导电、含大量含氧官能团、以及多孔道结构的三维石墨烯复合材料,并用作高性能超级电容器电极材料。连续高效的三维网络结构为复合材料提供了优异的倍率性能,而三维网络中丰富的含氧官能团则为复合材料提供较高的赝电容。通过将GO/Ni foam复合材料暴露在打火机外焰下,几秒钟内就可得到具有多级孔道结构的RGO/Ni foam复合材料。这是因为泡沫镍中的GO瞬间受热释放出大量的气体导致片层间膨胀与剥离。当用作电化学储能电极时,这种多级孔道可以为离子扩散和电子传输提供快速的通道,而石墨烯片层表面残留的大量含氧官能团可提供大的赝电容。直接用作超级电容器电极时,RGO/Ni foam复合材料在0.5和30 A·g-1的电流密度下,其比电容分别高达407.2和285.5 F·g-1。当组装成两电极的超级电容器体系时,其稳定电压窗口高达1.8 V,可以得到比较可观的能量密度和功率密度。当用作锂离子电池的负极材料时,在100 mA·g-1的电流密度下,RGO/Ni foam复合材料的首圈可逆放电和充电容量分别高达 2194 和 1372 mA·h·g-1。3、室温干燥的石墨烯复合气凝胶用作高导热相变储能复合材料:为了构筑连续的传导网络和三维骨架,解决相变储能材料热导率低和尺寸稳定性差的问题,我们制备了可以室温干燥的三维石墨烯凝胶。GO和高品质石墨烯(GNPs)在水中进行自组装,随后在空气中室温干燥,即获得高导热和高压缩性能的高密度石墨烯(RGO/GNP)复合气凝胶。RGO片层搭接成一个三维骨架,而GNPs作为增强相可以避免室温干燥过程中RGO/GNP水凝胶的体积过度收缩。利用真空浸渍方法将常用的相变储能材料十八醇填充到多孔的RGO/GNP复合气凝胶中,制得具有优异导热性能的十八醇/RGO/GNP(ORG)复合材料。在12 wt%石墨烯添加量下,ORG复合材料热导率高达～5.92 W·m-1·K-1,相比于纯的十八醇提高了 26倍,其相变焓也高达～202.8 J·g-1。即使在～70 ℃施加1 kg载荷,ORG复合材料仍然能保持良好尺寸稳定性,且未见明显的十八醇熔体漏流。4、高品质的石墨烯气凝胶用于相变储能复合材料:以GO为原料制备的三维石墨烯因其片层上含有残留的含氧官能团和缺陷,严重影响了三维网络的传导性,且这种三维石墨烯材料的尺寸及形状高度依赖于反应器的尺寸和形状。我们以GO为前躯体,通过低温浓缩GO水分散液获得具有优秀加工性能的GO组装物;通过冷冻干燥获得形状固定的GO气凝胶;对上述GO气凝胶进行高温石墨化处理,以去除石墨烯片上残留的含氧官能团并修复缺陷,最终制得兼具高效导热网络和质轻特点的高品质石墨烯气凝胶(HGA)。通过简单地真空浸渍,即可将熔融的十八醇填充到HGAs的三维网络中得到十八醇/HGA (OHGA)相变储能复合材料,在较低石墨烯含量下获得高热导率。在石墨烯填充量仅仅为～5.0 wt%时,OHGA复合材料的热导率高达～4.28 W·m-1·K-1,比纯的十八醇提高了 18倍多;其相变熔融焓也高达225.3 J·g-1。
[Abstract]:Graphene is a typical two-dimensional nanomaterial. Because of its high specific surface area, excellent conductivity, thermal conductivity, outstanding mechanical properties and chemical stability, graphene has a broad application prospect in the field of energy storage. Graphene oxide (GO) is a precursor material, and the preparation of graphene by chemical reduction is of great potential. The technical route can be used to make the macro preparation of graphene. However, the graphene lamellae obtained by this method are easy to be reunion, affecting the full play of the properties of graphene and limiting its more extensive application. In this paper, a three-dimensional graphene material was prepared by GO as a precursor, and a three-dimensional graphene conduction network was formed in advance to guarantee the stone. The main innovative research results are as follows: 1, nickel foam is used as a supercapacitor electrode material for the reduction of graphene oxide by nickel foam reduction. In view of the problem that a large number of reducing agents and energy consumption are needed in the construction of three-dimensional graphene, a simple method is proposed to be used directly as a supercapacitor. The three-dimensional reduction of graphene oxide / nickel foam (RGO/Nifoam) composite material in the electrode material. At room temperature of pH=2, the GO is reduced directly with nickel foam, and no other chemical reductants need to be added. The obtained RGO is assembled on the foamed nickel skeleton to produce RGO/Nifoam composites directly as the electrode material of the supercapacitor, without the need to add. The polymer binder shows excellent electrochemical performance. By regulating the reduction time, the RGO content in RGO/Ni foam can be regulated to achieve the purpose of regulating the unit area of the composite electrode material. When the reduction time is increased from 3 days to 15 days, the area is increased to 136.8 from 26 mF Cm-2 under the current density of 0.5 mA. Cm-2. In addition, mF Cm-2., temperature is an important factor affecting the reduction rate. When the reduction temperature is increased to 70, the 5-hour RGO/Ni foam composite obtained after 5 hours reacts more than the room temperature for 15 days, and the 15-day RGO/Ni foam composite presents a more excellent electrochemical performance of the.5-hour RGO/Ni foam composite material. Up to 206.7 mF. Cm-2, with excellent multiplication and cycle stability, charge discharge cycle 10000 times, the capacity retention rate is up to 97.4%. at 70 C to 9 hours. The obtained 9-hour RGO/Ni foam composite shows a higher area specific capacitance, up to 323 mF. Cm-2, and still has outstanding multiplier performance and performance. Excellent cyclic stability.2, multistage channel structure of graphene / foam nickel composite material used as electrode material: a successful preparation of a high conductivity, a large number of oxygen functional groups, and porous structure of the three-dimensional graphene composite material, and used as a high-performance supercapacitor electric pole material. Continuous and efficient three-dimensional network structure composite The material provides excellent multiplier performance, while the rich oxygen functional groups in the three-dimensional network provide high pseudopotential for the composite. By exposing the GO/Ni foam composite to the flame of the lighter, the RGO/Ni foam composite with multistage channel structure can be obtained in a few seconds. This is due to the instant heat of the GO in the foam nickel. The release of a large number of gases leads to interlaminar expansion and stripping. When used as an electrochemical energy storage electrode, this multistage channel can provide a fast channel for ion diffusion and electron transport. A large number of oxygen functional groups remaining on the surface of the graphene layer can provide large pseudo capacitors. The RGO/Ni foam composite is used directly as the electrode of the supercapacitor. Under the current density of 0.5 and 30 A. G-1, when the specific capacitance is up to 407.2 and 285.5 F. G-1. respectively, when the supercapacitor system is assembled into two electrodes, the stable voltage window is up to 1.8 V, and a considerable energy density and power density can be obtained. When used as a anode material for lithium ion batteries, the current density at 100 mA. G-1 The first ring reversible discharge and charge capacity of RGO/Ni foam composites are as high as 2194 and 1372 mA. H. G-1.3. The dry graphene composite aerogel at room temperature is used as a high thermal conductivity phase change energy storage composite material. We have prepared a three-dimensional graphene gel.GO and high quality graphene (GNPs), which can be dry at room temperature, and then dry in the air at room temperature. The high density and high density graphene (RGO/GNP) composite aerogel.RGO lamellae of high thermal conductivity and high compressibility are lap into a three-dimensional skeleton, and GNPs can be avoided as an enhanced phase. The volume of RGO/GNP hydrogel is overcontracted during the process of warm drying. Using the vacuum impregnation method, the commonly used phase change energy storage material eighteen alcohol is filled into the porous RGO/GNP composite aerogel. The excellent thermal conductivity of the eighteen alcohol /RGO/GNP (ORG) composite is prepared. The thermal conductivity of the ORG composite is up to 5.92 under the addition of 12 wt% graphene. W. M-1. K-1 is 26 times higher than pure eighteen alcohol, and its phase transition enthalpy is up to 202.8 J. G-1., even at 1 kg loading at 70 C, ORG composites still maintain good dimensional stability, and no obvious eighteen alcohol melt leakage.4 is found. High quality graphene gas condensate is used in phase change energy storage composite material: GO as raw material The three dimensional graphene, which contains residual oxygen functional groups and defects, seriously affects the conductivity of the three-dimensional network, and the size and shape of this three-dimensional graphene material depends highly on the size and shape of the reactor. We use GO as a precursor to obtain excellent processability GO by condensing GO water solution at low temperature. The GO aerogels are obtained by freeze-drying. The above GO aerogels are graphitized at high temperature to remove the residual oxygen functional groups on the graphene sheets and repair the defects. Finally, high quality graphene aerogels (HGA), which have high thermal conductivity network and light quality, can be obtained by simple vacuum impregnation. Eighteen alcohol OHGA (OHGA) phase change energy storage composite was obtained by filling the fused eighteen alcohol into the three-dimensional network of HGAs. The high thermal conductivity was obtained under the lower graphene content. The thermal conductivity of OHGA composites reached to 4.28 W. M-1. K-1 when the filling amount of graphene was only 5 wt%, and the enthalpy of the phase change melting enthalpy was more than that of the pure eighteen alcohol. Also up to 225.3 J. G-1.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB332;TQ127.11

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