碎形幾何應用於超級電容電極設計

Fractal Geometry Design for Supercapacitor Electrodes

林正得(Cheng-Te Lin)

指導教授 ： 楊燿州

國立臺灣大學/工學院/機械工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602242

摘要

本研究中，利用微影製程技術優勢，在尼龍濾膜上製作出以SU-8負光阻模具，加入碎形幾何的概念，定義出四種不同外型之指叉電極形狀；以真空過濾法過濾奈米碳管水溶液，製作成巴克紙，作為超級電容元件的電極，並探討元件特性與碎形幾何之電極的對於元件性能的影響。
本研究以聚乙烯醇與氫氧化鉀調配之固態電解液進行元件組裝，此類型電解液同時具有封裝的優勢。本研究針對不同設計之指叉電極元件儲存電能的效果進行比較。以電化學分析技術進行各式設計的儲存電量以及特性之量測。利用循環伏安法，量測得到在最低的掃描速率，20mV/s之下，三層碎形指叉之設計擁有最高比電容，比起單純指叉電極之設計(32.43 mF/cm2)多出約16%之比電容，約為37.63 mF/cm2。以恆電流充放電量進行測，三種電流密度下所測得之比電容，隨著指叉碎形層數增加，比電容值皆越來越高。以最低電流密度(1 mA/cm2)量測，三層碎形指叉之設計(17.25 mF/cm2)比起單純指叉之設計(13 mF/cm2)，多出約33%之比電容。後續以交流阻抗量測分析元件特性，四種設計皆符合理想超級電容元件表現。最後將恆電流充放電測得之數據進行計算，以Ragone plot表示功率密度與能量密度之關係圖。計算結果得知，本研究製作之元件具有高功率密度(~0.2 W/cm3) ，為超級電容快速充放電之特性。在相同的功率密度之下，隨著碎形分層數增加，能量密度也提升。證明本研究探討電極碎形分層之設計，能夠有效增加平面指叉式超級電容儲存的電量。

關鍵字

超級電容 ； 碎形幾何 ； 微影製程 ； 巴克紙 ； 固態電解液

並列摘要

In this work, we fabricate a series of in-plane interdigital Bucky-paper electrodes, which are based on the concept of fractal geometry, on a nylon membrane filter. The electrodes are manufactured by a novel lithography technique with vacuum filtration. The electrolyte is composed of polyvinyl alcohol (PVA) and KOH. The differences of capacitances of four different electrode designs were studied. By measuring the cyclic voltammetry at the scan rate of 20 mV/s, the device with electrodes which shape is the third level of fractal design has the highest specific capacitance (37.63 mF/cm2). The measuring result of galvanostatic charge-discharge also reveals that as the level of fractal design increases, the measured specific capacitance increases as well. The specific capacitance of the third level of fractal design (17.25 mF/cm2) is 33% more than the standard design (13 mF/cm2) with an applied current density of 1 mA/cm2. The electrochemical impedance spectroscopy (EIS) measurement results were also reported. In Ragone plot, the proposed devices have the power density of about 0.2 W/cm3. The energy densities also increase as the level of fractal increases at the same power density. The measuring results confirm that the fractal designs of interdigital electrodes improve the energy storage performance of in-plane supercapacitors.

並列關鍵字

supercapacitor ； fractal geometry ； lithography ； Bucky paper ； solid-state electrolyte

參考文獻

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