【作者】 卢向军；

【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， 2011， 博士

【摘要】 由于具有大容量、高功率特性、长寿命和良好安全性等优良特性，超级电容器在现代电源存储系统中发挥着越来越重要的作用。具有高法拉第赝电容特性的导电聚合物是一类重要的超级电容器电极材料，但其相对较低的电化学利用率、脱掺杂态下的低电导性和容量的快速衰减限制了导电聚合物实际应用的进一步发展。高比表面积、良好电子导电特性和卓越机械强度的石墨烯（GN）与导电聚合物电活性物质的复合有望实现二者的优势互补，使电极材料具有良好的电化学性能。本论文的研究内容主要集中在石墨烯基导电聚合物复合材料的制备、表征及其在超级电容器中的应用，旨在获得较高的比能量密度和良好循环寿命的超级电容器电极材料。论文的主要内容介绍如下：1、以功能化离子液体1-甲基咪唑丙磺酸硫酸氢盐（[MIMPS][HSO₄]）为GN分散剂和聚苯胺（PANI）掺杂剂机械球磨合成了GN/PANI复合物。以功能化离子液体1-丁基-3-甲基咪唑四氯化铁（Bmim[FeCl₄]）作为GN分散剂和聚吡咯（PPy）催化剂与掺杂剂机械球磨合成GN/PPy复合物。在聚合过程中，GN作为支撑材料沉积PANI或PPy，而原位合成的PANI或PPy作为隔离器抑制GN的重新堆垛。强机械力使片状复合物任意堆垛，构筑成三维的分级结构，有利于电解液扩散到电极内部发生充分的氧化还原反应。电化学测试表明复合材料中PANI和PPy的电化学活性和循环稳定性得到明显提高。GN/PANI复合物在电流密度0.2Ag^-1时比容量为616Fg^-1，是纯PANI在相同条件下比容量的两倍多，500圈循环测试后比容量衰减为7%。GN/PPy复合物在0.2Ag^-1时比容量为375Fg^-1，1000圈循环测试后比容量衰减为13%。2、以聚苯乙烯磺酸钠（PSS）为GN和碳纳米管（CNT）分散剂，通过原位化学聚合方法制备了一系列GN/PANI/CNT和GN/PPy/CNT三元复合物。负电荷的PSS与苯胺或吡咯单体的静电吸附作用有利于产生均一的聚合物层，然而由于GN比CNT具有更高的理论比表面积和反应活性，导电聚合物优先聚合在GN表面。CNT的引入能有效抑制GN/PANI或GN/PPy复合物的片层堆积，组装成三维松散结构，有利于电解液与电活性物质的接触，同时CNT较高的电导率与GN可以组合形成三维导电网络，有助于电子的传输和电解质离子的快速扩散。电化学测试表明，由于二维GN和一维CNT的协同作用，三元复合物的电化学特性优于纯导电聚合物和导电聚合物与GN或CNT组成的二元复合物。当GN:CNT=5:1时，GN/PANI/CNT在0.2Ag^-1条件下比电容最佳，为909Fg^-1，4Ag^-1条件下连续循环2000圈以后容量衰减7%。GN:CNT=8:1时，GN/PPy/CNT在0.2Ag^-1条件下最佳比电容为361Fg^-1，4Ag^-1条件下循环2000圈以后容量衰减4%。3、真空抽滤氧化石墨（GO）与PANI纳米纤维或PANI/CNT纳米线的混合分散溶液，流动组装得到自支撑GO/PANI或GO/PANI/CNT复合薄膜，再利用气态水合肼还原复合薄膜中GO，最后重新氧化和掺杂还原态PANI，制备了一维PANI纳米纤维或PANI/CNT纳米线均匀插层GN的“三明治”结构的自支撑复合薄膜材料。在复合薄膜中，GN片可作为集流体改善PANI在充放电过程中的电荷传输，也可作为弹性缓冲器适应PANI链的体积改变；纳米尺寸PANI或PANI/CNT能提供高氧化还原感应电容，提高GN片的层间距和改善GN片的溶液浸润性。特别在GN/PANI/CNT三元复合薄膜中，刚性CNT核的引入不仅极大的提高了PANI的电化学活性，而且近一步改善了PANI的机械稳定性。GN/PANI/CNT自支撑薄膜在电流密度为0.1Ag^-1条件下，达到了569Fg^-1的质量比电容和188Fcm^-3的体积比电容，5000圈循环测试后电容仅损失4%。4、以二维GN为柔性基体，利用真空抽滤GN和PPy/CNT混合分散溶液的方法制备了PPy/CNT纳米线均一分散在GN片间的柔性GN/PPy/CNT薄膜。在独特的层状结构当中，PPy/CNT不仅增加了GN片层空间，而且为电极提供氧化还原赝电容。在0.2Ag^-1电流密度下，柔性GN/PPy/CNT的质量比电容和体积比电容(211Fg^-1和122Fcm^-3)高于GN(73Fg^-1和79Fcm^-3)和PPy/CNT(164Fg^-1和67Fcm^-3)。当电流密度增至12Ag^-1时，GN/PPy/CNT的电容保持率达到78%。有重要意义的是，由于柔性GN层和刚性CNT核协同释放PPy链在充放电过程中的内应力，无支撑柔性GN/PPy/CNT薄膜电极在5000圈充放电循环后仅损失5%的容量。更多还原

【Abstract】 Supercapacitors play an increasingly important role in modern power source application due to their high capacitance, high power density, long cycle life and good operational safety. Conducting polymers with high Faradaic pseudo-capacitor are important electrode materials for supercapacitor applications. However, the poor electrochemical utilization, low electronic conductivity in dedoping state and rapid capacity decay limit their further advancements in promising applications. The combination of conducting polymers and graphene (GN) with high specific surface area, good conducting property and exceptional mechanical strength has been proposed as perfect electrode materials with good electrochemical properties for supercapacitors due to the synergistic effect of GN and conducting polymers. Consequently, the thesis is aimed at the preparation and characterization of the GN-based conducting polymer composites and their application in supercapacitors in order for the synchronous realization of large specific energy density and good cycle stability.1. A simple and effective ionic liquid (IL)-assisted mechanochemical route is used to synthesize GN/PANI and GN/PPy composites. Functionalized IL1-(3-sulfonic acid) propyl-3-methylimidazolium hydrogen sulfate ([MIMPS][HSO4]) acts as the dispersant of GN and the dopant of PANI to prepare GN/PANI composite. Functionalized IL1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeCl4]) acts as not only the dispersant of GN, but also the catalyst and dopant in the synthesis of GN/PPy composite. GN serve as a support material for depositing PANI or PPy during polymerization process, while in-situ produced PANI or PPy deposited onto GN can be used as spacer to effectively avoid the restacking of GN. The strong mechanical energy makes the laminated composites random stack and reconstructs hierarchical architecture, which is convenient for diffusion of the electrolyte ions into the inner region of electrodes to take place redox reaction. Electorchemical tests indicate that the electroactive and cycling stability of PANI and PPy have obvious improving. The GN/PANI shows a specific capacitance of616F g-1at0.2A g-1and a capacity loss of7%after500continuous cycles. For GN/PPy composite, a specific capacitance of375F g-1at0.2A g-1and a capacity degradation of13%after1000continuous cycles can be obtained.2. A series of GN/PANI/carbon nanotube (CNT) and GN/PPy/CNT ternary composites have been fabricated via in situ polymerization method using poly(sodium4-styrene sulfonate)(PSS) for dispersing GN and CNT. The electrostatic interaction between negatively charged PSS and pyrrole or aniline monomer facilitates the generation of homogeneous polymer layer. The conducting polymers preferentially deposit on the surface of GN due to the high chemical activity and high theoretical surface area of GN. The introduction of one-dimensional CNT effectively inhibits the stacking of nanosheet-like GN/PANI or GN/PPy to form three-dimensional hierarchical architecture, favoring the contact between the electrolyte ions and electroactive materials. The high conducting of CNT and GN can construct a3-D conductive architecture for electron transfer and fast ions transport. Owing to the synergistic effect between two-dimensional GN and one-dimensional CNT, electrochemical results demonstrate that the electrochemical properties of ternary composites are better than pure conducting polemers and binary composites of conducting polemers with GN or CNT. A specific capacitance of909F g-1at0.2A g-1and a capacity loss of7%at4A g-1after2000continuous cycles can be obtainedand for GN/PANI/CNT composite with GN:CNT=5:1. The GN/PPy/CNT composite with GN:CNT=8:1has a maximum specific capacitance of372F g-1at0.2A g-1and a capacity degradation of4%after2000continuous cycles at4A g-1.3. Freestanding "sandwich-like" films with PANI nanofibres or PANI/CNT nanocables uniformly distributed between GN sheets have been fabricated by reducing a graphite oxide (GO)/PANI or GO/PANI/CNT precursors prepared by flow-directed assembly from a complex dispersion of GO and PANI or PANI/CNT, followed by reoxidation and redoping of the reduced PANI in the composite to restore the conducting PANI structure. In the composite film, the GN sheets can act as the current collector to improve the electronic and ionic transportation during the redox process of PANI, and elastic buffering to accommodate the volumetric change of the PANI chains. The PANI or PANI/CNT provides high faradaic capacitance and increases the basal spacing between GN sheets to enhance the accessibility to the GN surfaces. Especially for ternary GN/PANI/CNT composite film, rigid CNT core can not only effectively enhance the electroactive of PANI, but also further improve the mechanical stability of PANI. The GN/PANI/CNT film shows that the mass and volume specific capacitances of are569F g-1and188F cm-3at a current density of0.2A g-1, and a capacity loss of4%after5000continuous charge/discharge cycles.4. Unique flexible film with PPy/CNT composite homogeneously distributed between GN sheets is successfully prepared by flow-assembly of the mixture dispersion of GN and PPy/CNT. In such layered structure, the coaxial PPy/CNT nanocables can not only enlarge the space between GN sheets but also provide pseudo-capacitance to enhance the total capacitance of electrodes. According to the galvanostatic charge/discharge analysis, the mass and volume specific capacitances of GN/PPy/CNT are211F g-1and122F cm-3at a current density of0.2A g-1, higher than those of the GN film (73F g-1and79F cm-3) and PPy/CNT (164F g-1and67F cm-3). Significantly, the GN/PPy/CNT electrode shows excellent cycling stability (5%capacity loss after5000cycles) due to the flexible GN layer and the rigid CNT core synergistical releasing the intrinsic differential strain of PPy chains during long-term charge/discharge cycles.更多还原