【作者】 李立；

【导师】 秦宗益；

【作者基本信息】 东华大学 ， 材料科学与工程， 2009， 硕士

【摘要】 作为超级电容器电极材料,碳纳米管具有导电性高和循环稳定性好的特点,但比容量偏低;而导电高分子和过渡金属氧化物具有很高的比电容量、但循环稳定性较差。本工作中拟将聚苯胺、二氧化锰和碳纳米管有机复合,通过材料间协同增强作用,制备出电导率高、比电容大和循环稳定好的超级电容复合储能材料。为此我们制备了具有核壳结构的碳纳米管/聚苯胺纳米复合材料,碳纳米管和纳米晶二氧化锰复合材料,和碳纳米管/二氧化锰/聚苯胺三元复合材料,并作为超级电容器电极材料对其结构性能进行了有效表征。本文主要内容如下:1.采用苯胺和表面缺陷较少的多壁碳纳米管,超声辅助原位合成了一系列具有不同壳层厚度的碳纳米管/聚苯胺复合物;采用SEM、TEM、FTIR、Raman、XRD等分析手段研究了材料的形貌与结构,采用电导测量和电化学测试表征了材料的电学性能与电化学性能;提出了在无缺陷碳管表面发生聚苯胺原位聚合、形成具有核壳结构的纳米复合材料的机理;电化学分析表明复合电极材料的电容由双电层电容和赝电容两部分组成,电极的储能机理是复合储能,电极反应可逆性较好;当碳纳米管含量达到33%时,纳米复合材料的比电容最高,可达到560F/g。2.以高锰酸钾为氧化剂,醋酸锰和碳纳米管为还原剂,草酸和盐酸为质子源调节体系得pH值,采用水热反应制备出一系列二氧化锰与碳纳米管的复合材料;通过合成条件的选择,可以有效地控制复合材料的形貌与复合方式。电化学测试表明系列材料中以纳米晶二氧化锰/碳纳米管核壳结构的复合材料性能最佳;体系中被纳米晶二氧化锰包覆碳纳米管充当导电通路,大大降低电极材料的电阻,而碳管表面所包覆的针状二氧化锰极大地增加了材料的比表面积,核壳结构的复合方式增加了体系的稳定性,其比电容也高达到550F/g,并表现出优异的电化学循环的稳定性。3.以碳纳米管/纳米晶二氧化锰为反应性模板,超声辅助原位合成了碳纳米管/二氧化锰/聚苯胺三元纳米复合材料;该体系中二氧化锰和聚苯胺与碳纳米管的复合提供了较高的比表面积和较低的电阻,二氧化锰与聚苯胺为主要的电化学活性物质,而聚苯胺的引入方便电极制作,无需外加粘合剂就可成型。初步电化学测试表明该三元复合材料材料具有良好超电容特性,比电容也可达134F/g。其电化学性能可通过优化复合体系的微结构、实现材料间协同增强作用而得到进一步的改进。更多还原

【Abstract】 Carbon nanotubes with high surface area,high conductivity and good stability are suitable electrode materials for electrochemical double layer supercapacitors,but the double-layer capacitance of carbon materials is relatively low and highly depends on the pore accessibility and pre-treatment;the conjugated polymers and oxidations of transition metal have high specific capacitances,but they are were not stable enough comparing with the carbon nanotubes during cycling.The combined advantages from carbon nanotubes and the conjugated polymers and oxidations of transition metal and the cooperative effect could make such hybrid composites excellent choices for supercapacitive electrode materials.In our work,we fabricated successfully the nano-hybrid composites of polyaniline/carbon nanotubes with core-shell structures,the manganese dioxide microcrystallites/carbon nanotubes,and ternary composites of carbon nanotubes/manganese dioxides/polyaniline.As supercapacitive electrode materials,structures and properties of these nano-hybrid composites were studied.Our main results are listed as following:1.Multi-wall carbon nanotubes/polyaniline composites with core-shell structures were fabricated using the commercial multi-wall carbon nanotubes treated in the condensed hydrochloric acid and the aniline monomer.By changing the carbon nanotubes and aniline monomer ratio,we can easily control the thickness of polyaniline layer.The structures and morphologies of the composites were studied by means of SEM,TEM,FTIR,Raman and XRD,and more attentions were paid to their electrochemical properties as supercapacitive electrode materials.The results showed that the supercapacitive behavior for the nano-hybrid composites included the electrochemical double-layer capacitance type and the pseudocapacitive type,and the composites exhibited good stable electrochemical properties during recycling.The highest specific capacitance to 560 F/g was obtained for 33wt%multi-wall carbon nanotubes in the composites.2.A series of nano-hybrid composites were synthesized by the hydrothermal reaction of manganese dioxides microcrystallites and the multi-wall carbon nanotubes, in which potassium permanganate was used as oxidant,manganese acetate and multi-wall carbon nanotubes as reducing agent.The morphologies and microstructures of manganese dioxides microcrystallites could be controlled in order of increasing acid strength.The results showed that among these composites,the needle-like manganese dioxide microcrystallites coated on multi-wall carbon nanotubes exhibited excellent supercapacitive properties,in which the multi-wall carbon nanotubes acted as an effective electron conductor,and the needle-like manganese dioxide microcrystallites have large surface area.Good cycling stability of nano-hybrid composites benefited from the structural stability due to the formation of the core-shell structures,and the specific capacitance was about 550 F/g.3.A novel ternary hybrid materials composed of multi-wall carbon nanotubes, manganese dioxides microcrystallites and polyaniline was prepared by using the needle-like manganese dioxide microcrystallites coated on multi-wall carbon nanotubes as the reactive template and ultrasonic assisted in-situ polymerization of aniline.These ternary hybrid materials are very interesting since materials have large surface area, good conductive channel and flexible processing.Measurements of the electrochemical properties of these materials show that manganese dioxide and the polyaniline played important roles during electrochemical process,and the specific capacitance to 134 F/g was obtained.This kind of hybrid materials was the more potential candidates for high-performance supercapacitive electrode materials.Ternary hybrid system could be further optimized to bring the cooperative effect into full play.更多还原