導電高分子於超高電容器之應用

Abstract

本論文的研究著重於合成新型高性能以導電高分子為基礎的超級電容器。鑑於超級電容器的在電動車輛與再生能源儲存的潛在應用中，此研究很大一部分重點在於探討導電高分子為基礎的超級電容器在室溫以外，廣泛不同溫度範圍下的各項操作性能。首先，摻雜有對甲苯磺酸之聚吡咯（PPy）膜（17.7％重量百分比）的聚吡咯塗層塗佈於活性炭（AC）電極預成型體。雖然比電容的電極增加為兩倍，從176 F/克增至352 F /克，電容10,000次循環後，在40℃時失去了近60％，而相比之下，在25℃下20％的損失。我們發現，通過嵌入導電的碳化鈦（TiC）納米粒子內的聚吡咯層通過共同電鍍，有效緩解在高溫下的加速衰落的問題，並且在動力性能上有顯著（高達70％）的改善。加入1.7％（重量比）TiC的複合電極，在相同的循環條件下（40℃，10,000個週期）電容保留它的初始電容的92％。增強的高溫循環穩定性已部分被歸因TiC奈米粒子有效的減少導電性聚合物層和AC基板之間的熱膨脹係數的不匹配程度。 接著，則是將高導電性的TiC奈米粒子加入PPy/ 聚乙烯醇(PVA)雙聚合物複合而形成的特定的“核 - 殼”奈米結構的TiC＠PPy/PVA複合材料。通過利用界面聚合成殼聚合物於TiC的表面上。這種奈米複合材料在很寬的工作溫度範圍，從-18到60°C，具有高功率性能和長期穩定的循環壽命。該等優異的性能歸因於PVA誘導增強的PP的機械性能，並且利用TiC核心奈米粒子降低複合材料中的阻抗所致。 最後，一新型超級電容器的複合電極含有（81重量％）聚（3,4 - 乙烯二氧噻吩）：聚苯乙烯磺酸（PEDOT-PSS）的導電性聚合物（CP）和氧化石墨（GO，16％（重量比））和碳奈米管（CNT; 3％（重量比））經由溶液鑄成法製備完成。這些碳的添加劑，具有不同的維度，其彼此的堆疊提供了一個獨特的骨骼結構，一方面能有效提升活物與電解液界面接觸面積，進而提升比電容量，並提供了快速離子與電子導電通道，達到高功率性能增強。與純CP電極相比較，該三元電極增加近10倍的能源和動力性能。它具有比電容365的F /克電極與超過2.0 V的操作電位窗口，並在近200千瓦/千克的功率下，顯示出大於100瓦時/千克的比能量。電極具有良好的循環穩定性的電源電極。有鑑於合成方法的簡易性與出色的動力性能，我們認為本發明的PEDOT-PSSCP-C複合活性材料是具有大型超級電容器應用的極具潛力。

This thesis focuses on the synthesis of novel high-performance supercapacitors based on conducting polymer (CP). In view of potential applications of supercapacitors for electric vehicle and stand-alone renewable energy storage under severe temperatures, much attention has been placed on different performance aspects of the CP-based supercapacitors over widely different temperature ranges other than the room temperature. First, Polypyrrole (PPy) film, doped with p-toluenesulfonate, has been coated onto activated carbon (AC) electrode preform. Although the specific capacitance of the electrode is doubled, from 176 F/g to 352 F/g, with coating of 17.7 wt.% PPy, the capacitance lost nearly 60% after 10,000 cycles at 40 oC, in contrast to 20% loss at 25 oC. It is demonstrated that the problem of accelerated fading at high temperature is effectively alleviated, in conjunction with significant (up to 50%) improvement in power performance, by embedding conductive TiC nanoparticles within the PPy layer via co-electroplating. With addition of 1.7 wt.% of TiC in the composite electrode, the capacitance retain 92% of its initial capacitance under the same cycling conditions (40 oC, 10,000 cycles). The enhanced high-temperature cycling stability has in part been attributed to the reduction in the mismatch of thermal expansion coefficient between the conducting polymer layer and the AC substrate. High conductivity inorganic nanoparticle, TiC, is introduced into PPy/polyvinyl alcohol (PVA) bi-polymers composite to form the particular “core−shell” nanostructurized TiC@PPy/PVA composite by utilizing interfacial polymerization of the shell−forming polymers on the surface of TiC. This nanocomposite possesses high rate performance and stable long term cycle life over a wide operating temperature ranges from −18 to 60 °C. This is attributed to PVA induced enhancement of the mechanical properties of PPy and the aligned nanostructure of PPy/PVA bi-polymers on the surfaces of TiC core nanoparticles, resulting in the reduced resistance of PPy/PVA nanocomposites. Finally, supercapacitor composite electrode containing predominantly (81 wt.%) Poly(3,4-ethylene-dioxythiophene):Polystyrenesulfonate (PEDOT-PSS) conducting polymer (CP) and graphite oxide (GO; 16 wt.%) and carbon nanotube (CNT; 3 wt.%) has been prepared by a solution casting method. The stacking between these carbon additives having very different dimensionality provides a unique skeletal structure that allows for enlarged polymer/electrolyte interface for high-capacitance and for enhanced electronic and ionic conductivities needed for high-power performance. The resulting ternary electrode exhibits nearly ten-fold increase in energy and power performance as compared with pure CP electrode. It possesses a specific capacitance of 365 F/g-electrode over an operating potential window of 2.0 V, and exhibits a specific energy greater than 100 Wh/kg-electrode at the power of nearly 200 kW/kg-electrode with good cycle stability. Given the processing simplicity and outstanding power performance, the present PEDOT-PSSCP-C composite active material is considered possessing great potential for large-scale supercapacitor applications.