【作者】 原长洲；

【导师】 张校刚；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2009， 博士

【摘要】 超级电容器是一种具有高功率和长寿命的优良储能器件,但其能量密度相对较低。研究如何在保持其高功率优势的同时并获得较高能量密度成为现今研究的热点。具有法拉第准电容特性的电活性物质与具有良好双电层电容特性的碳纳米管的复合有望实现二者优势互补,从而使其在大电流密度下可以获得高的比能量密度。因此,本论文的研究内容主要集中于碳纳米管基复合材料的制备、表征及其在超级电容器中的应用,旨在实现其可以同时获得较高的比能量密度和比功率特性。论文的具体内容介绍如下:1.聚苯乙烯磺酸钠（PSS）对碳纳米管（CNTs）的非共价缠绕修饰及其在超级电容器电极材料中的应用。选用带负电荷的PSS聚电解质对CNTs进行缠绕修饰,不仅使其表面具有丰富的负电荷并作为“锚”便于电活性材料在其表面均匀附着、成核和生长;也可以提高其在水溶液中的分散性。因此,PSS的存在对于均匀分散的碳纳米管基复合材料的制备具有双重作用。本论文采用PSS缠绕修饰的碳纳米管（PSS-CNTs）作为具有氧化还原超电容特性电活性材料的载体,它对于碳纳米管基复合材料结构的设计和有效构筑起到了重要的作用。2.钌基碳纳米管复合材料的制备及其高的电化学利用率。选用荷负电荷的PSS-CNTs为载体,在温和水热条件下实现了弱晶化的水合二氧化钌（RuO₂·nH₂O）纳米点在其表面的均匀分散,在RuO₂·nH₂O高负载的情况下获得了高的电化学利用率。研究表明,水热方法制备的RuO₂·nH₂O /PSS-CNTs复合材料在RuO₂·nH₂O负载量为10 wt.%时,其质量比电容为1474 F g-1,其电化学利用率为71%。当RuO₂·nH₂O的负载量为25 wt.%和45 wt.%时,仍可以保持RuO₂·nH₂O纳米点在PSS-CNTs表面很好的分散性,其质量比电容分别为774和703 F g-1。通过该方法实现了RuO₂·nH₂O纳米点的高负载,高分散和高的电化学利用率。RuO₂·nH₂O纳米点“点饰”碳纳米管的复合材料可以使电解质离子和电子同时接触到更多高电活性的RuO₂·nH₂O纳米点,进行更充分的法拉第氧化还原反应,从而实现较高的电化学储能。二元钌基复合金属氧化物已成为现今一个研究热点,为了在减少钌用量的前提下仍然保持其较高的质量比电容,我们采用水热法合成了具有高分散性的二元钌铟复合金属氧化物(Ru_xIn_1-xOy·nH₂O)/PSS-CNTs复合材料。电化学测试表明,该复合材料具有良好的超电容行为。3.构筑在强酸性电解质中稳定工作的聚苯胺（PANI）/二氧化锰（MnO₂）/PSS-CNTs“三明治”结构复合材料和核壳结构的PANI/PSS-CNTs复合材料。在PSS的协助作用下,使MnO₂均匀负载在碳纳米管表面。进而通过PANI的包覆制备了PANI/MnO₂/PSS-CNTs“三明治”结构复合材料。这样就使在酸性电解质中本来不稳定的MnO₂可以在强酸性电解质中稳定工作,而且其超电容行为取决于酸性电解质中的质子浓度。PANI壳层不仅在强酸性电解质中起到保护MnO₂的作用,也可作为超级电容器电极材料进行更有效的电化学储能。该复合材料在优化的酸性电解质（0.5 M Na₂SO₄ - 0.5 M H₂SO₄）中比电容约为384 F g^-1。其中,MnO₂所贡献的质量比电容约为880 F g^-1。经过1000次连续充放电,其比容量衰减约为初始容量的18%。这说明了MnO₂在强酸性电解质中获得了较高的电化学储能和良好的电化学稳定性。在此基础之上,以制备的MnO₂/PSS-CNTs作为模板和氧化剂,采用“反应模板法”制备了核壳结构的PANI/PSS-CNTs复合材料。研究发现,在2 A g^-1的电流密度下,该复合材料的比电容为296 F g^-1,在5 A g^-1时,其比电容仍可保持为220 F g^-1,这显示出其良好的能量密度和比功率特性。4.具有丰富孔道结构的氧化镍（NiO）/PSS-CNTs复合材料的制备及其超电容行为。采用简单回流和后续热解两步法制备了具有多级孔（中孔和大孔）道结构的NiO球形微纳超结构。该微纳超结构既可充分利用其纳米构筑单元的优良电化学储能能力,又可凭借其微米级的尺寸而便于实际加工并确保其填实密度。研究表明,NiO微纳超结构是由具有丰富中孔结构的NiO纳米片经过取向合并生长和Ostwald熟化生长机理自组装而形成的。其丰富的中孔孔道提供了较高的电活性比表面积。其自组装堆积形成的大孔可以像“蓄水池”一样吸附电解液,满足大电流工作时对电解质离子的大量需求,使其可以在高功率情况下保持其较高的能量密度。为了进一步提高其导电性并获得更好的电化学储能能力,我们制备了具有有序中孔孔道结构的NiO/PSS-CNTs复合材料。碳纳米管交错的三维空间导电网络结构使这种复合材料不仅可以获得高的电活性面积和良好的电子导电性,也可以使其获得丰富的离子通道,从而实现其更有效的电化学储能。电化学测试表明,在6 A g^-1的电流密度下,该复合材料（约48 wt.%的NiO）的比电容约为439 F g^-1,这显示出其良好的功率特性和比能量密度。5.界面（二硫化碳/水）水热法制备了新型的超级电容器电极材料CoSx,并对其在KOH碱性水溶液中真正的电化学储能机理进行了详细探讨。研究表明,在KOH碱性水溶液中,CoSx本身其实并不具有电化学储能能力,而是在KOH水溶液中经过连续多次循环伏安扫描,在其表面电化学诱导形成了真正具有电化学储能能力的新的物相Co（OH）₂,从而达到了电化学储能的效果。为了进一步获得更优的电化学储能能力,我们进而合成了均匀分散的CoSx/PSS-CNTs复合材料。电化学测试表明,碳纳米管的加入使其比功率特性和比能量密度均得到进一步提高。更多还原

【Abstract】 Supercapacitor is a good energy-storage device with high power property and long cycling life, however,its energy density is relatively poor.Thus,it turns out to be a research spot how to further obtain the larger energy density but not sacrifice its immanent higher power density.A hybrid of carbon nanotubes （CNTs） with good electronic double layer capacitance and electroactive materials with good Faradaic pseudocapacitance has been proposed as ideal electrode materials for supercapacitors , because such hybrid can both utilize the fast and reversible Faradaic pseudocapacitance and the indefinitely reversible double-layer capacitance at the electrolyte/CNTs interface so as to obtain large energy density at high rate.Therefore,the thesis is focused upon the preparation and characterization of the CNTs-based composites and their application in electrochemical capacitors （ECs） in order for the simultaneous achievement of large specific energy density and good power property.1.The wrapping modification of CNTs by poly （sodium 4-styrene sulfonate） （PSS） and their use in electrode materials for ECs.PSS was originally applied to solubilize CNTs well into the aqueous solution and noncovalently functionalize CNTs through a polymer-wrapping mechnism.As a consequence,the noncovalent sidewall functionalization of CNTs with negatively charged PSS,as an“anchor”,could create much more electroactive sites facilitating the subsequent nuclearation,growth and good dispersion of electroactive materials onto their surfaces.In addition,the PSS-functionalized CNTs （PSS-CNTs） would be solubilized well in the aqueous solution. The PSS-CNTs were used as a support for the electroactive materials with redox Faradaic psuedocapacitance,which is important in the design and efficient construction of the CNTs-based composites for ECs application.2 . Preparation and investigation of ruthenium oxide-based nanocomposites with high electrochemical utilization for ECs.The RuO₂·nH₂O nanodots,in the case of high loadings,were originally dispersed onto the surface of PSS-CNTs well under the mild hydrothermal treatment.Electrochemical results demonstrated that the synthesized RuO₂·nH₂O nanodots/PSS-CNTs nanocomposite （10 wt.% loading） could deliver a specific capacitance （SC） of 1474 F g^-1 for the Ru species,resulting in an electrochemical utilization of ca. 71%.The composites with even more loadings still maintained the good dispersion of RuO₂·nH₂O nanodots,such as,25 wt.% and 45 wt.%, whose SCs were 774 and 703 F g^-1,respectively,for the Ru species.It indicated that the applied method made the RuO₂·nH₂O nanodots well dispersed and large electrochemical utilization,even in the case of high loadings.Such RuO₂·nH₂O nanodots/PSS-CNTs nanostructures facilitated electrolyte ions and electrons contact much more RuO₂·nH₂O nanodots with high electroactive activity for more efficient Faradaic reactions to realize their high electrochemical energy storage.Binary Ru-based oxides doped with homovalent and/or heterovalent substitution had become the research hot,because they could not only reduce the amount of Ru species but also enhance the utilization of ruthenium oxide . The Ru_1-xIn_xO_y·nH₂O/PSS-CNTs nanocomposite was first synthesized under the mild hydrothermal treatment. Electrochemical data showed a good electrochemical performance for the nanocomposite.3 . Construction and electrochemical performance of the“sandwich-like”polyaniline （PANI）/MnO₂/PSS-CNTs hybrids and core-shell PANI/PSS-CNTs composites for ECs in strong acidic electrolytes.MnO₂ was dispersed uniformly onto the surface of CNTs under the assistance of PSS.The MnO₂/PSS-CNTs composites could operate stably in the strong acidic medium due to the protective modification of PANI coating layer onto their surface.The electrochemical performance of the PANI/MnO₂/PSS-CNTs was greatly dependent upon the concentration of protons in the acidic electrolytes.PANI not only served as a physical barrier to restrain the underlying MnO₂ phase from reductive-dissolution process so as to make the novel ternary hybrid material work in strongly acidic medium to enhance the utilization of MnO₂ as much as possible,but also was another electroactive material for energy storage in the acidic mixed electrolytes.It was due to the existence of PNAI layer that an even larger SC of 384 F g^-1 and a much better SC degradation of ca. 18% over 1000 continuous charge/discharge cycles were delivered by the hybrid in the optimum 0.5 M Na₂SO_4-0.5 M H2SO4 mixed electrolyte.Particularly,a SC contributed by the MnO₂ reached about 880 F g^-1 . Furthermore , the core-shell PANI/PSS-CNTs nanocomposite was synthesized by the reacting-template method based on the MnO₂/PSS-CNTs as a template and an oxidant.A SC of 296 F g^-1 could be obtained at 2 A g^-1 and even 220 F g^-1 at 5 A g^-1 for the nanocomposite,revealing that it owned large energy density and good power property.4. Synthesis and electrochemical performance of porous nickel oxide/PSS-CNTs composites for ECs application.First,a facile and efficiency route was described to synthesize NiO microspheres with hierarchical （meso- and macro-） porosity by following thermal decomposition of the precursor obtained via simply refluxing process.Such superstructure could not only make full use of the favorable kinetics and high capacities of the nanosized building blocks but also guarantee its good stability,easiness to fabrication and tap density.The formation mechanism of such superstructure was proposed attentively that the hierarchical structured NiO microspheres were obtained by the self-assembly of two-dimensional and mesoporous NiO petal building blocks based on the coalescence and Ostwald-ripening mechanisms.Such macroporous structure,due to its great role of“ion-buffering reservoirs”,could maintain the sustentation of OH- ions and make sure that the enough Faradaic reactions could take place at high current densities for larger energy storage.To further enhance its conductivity and obtain even better electrochemical behavior,PSS-CNTs were added during the synthetic process.The ordered mesoporous NiO/PSS-CNTs composites were unexpectedly formed.PSS-CNTs,as a good three-dimensional conducting network,not only enhanced the conductivity of the composite,but facilitated electrolyte soaking into particles,maintained the sustentation of it,and created much more porous channel for electrolyte ions to transport and electrochemically access even more electroactive sites of the ordered mesoporous NiO for energy storage at larger current densities.Electrochemical data demonstrated that the unique composite （ca. 48 wt.% NiO） could deliver large energy density and high power property,and a SC of 439 F g^-1 could be delivered at 6 A g^-1.5.Interface hydrothermal synthesis of the CoSx/PSS-CNTs nanocomposites for ECs and minute investigation of their real energy-storage mechanisms in alkaline KOH solution . Novel CoSx/PSS-CNTs composites were first synthesized in the unique H2O/CS2 interface under mild hydrothermal treatment.Electrochemical data demonstrated that the CoSx itself did not own energy-storage ability in the alkaline electrolyte,but the new phase Co（OH）2 formed during the continuous CV scanning in the KOH solution should be responsible for its good energy-storage property in the KOH solution.To obtain much better electrochemical performance, a good dispersed CoSx/PSS-CNTs composite was further obtained. And the CoSx/PSS-CNTs composite delivered even higher energy density and better power properties after the addition of PSS-CNTs.更多还原