以分子動態模擬預測液態電容器之電容率

Abstract

自從1991年在日本的飯島博士成功發現並製造了奈米碳管[1, 6]以來，其相關的各種性質及應用形成一股新興的研究熱潮[2, 7, 8]。由於碳管以奈米尺寸合成，其表面的性質會因為尺寸微縮而改變有顯著的不同。因此，結構相似於石墨的奈米碳管在機械、導電性質有相當不錯的應用空間。應用奈米碳管的高比表面積，可以提高電容器電極板上的有效利用面積，更可加強在電極表面電荷對電雙層內的溶液的影響。這種應用奈米碳管改良的電容器一般稱作超級電容器[3, 4, 9]，其單位重量的電容率約為目前市面固態電容器的數千倍以上(達102 farads/g)。本研究應用分子動態模擬來模擬出在奈米尺寸下，各種不同參數的奈米碳管對電解質溶液的介電常數的影響，並以獲得的電解質溶液的介電值可以得出其理想電容器的電容值。也希望籍此來深入了解在微小尺寸下電雙層內外的溶液分子的各種表現。

Since Iijima[1] successfully fabricated carbon nanotube (CNT) from graphitic carbon sheets in 1990, all kinds of physical, chemical and mechanical properties are being studied and analyzed[2]. Recently, a new model of electrochemical storage device was introduced. Based on the ordinary electrolytic capacitor, the CNT were bed on the original electrode plate. The so-called supercapacitor[3, 4] (SC) has more than thousand times of capacitance than commercial ones[5]. The enhancement in capacitance was recognized by two major effects: the increase of surface on the electrode and the capture of ionic species by the CNT. In order to gain a molecular level understanding of each of these effects, we have established the micro structure of SC and performed molecular dynamic simulation (MD) for such systems. At the same time, we could study the phenomena in electrical double layer and solvent.