摘要
超級電容器因其高功率密度、快速充放電、長效性等特性，使它在能源儲存相關應用中佔有重要地位。市面上多數的超級電容器使用液態電解液，使得操作溫度受到限制，無法使用於一些高溫和惡劣的環境中，因此本研究著重於如何發展出一耐高溫且高穩定性的超級電容器。本研究利用YSZ為電解液，碳化矽奈米線為電極材料，組成一對稱式超級電容器。YSZ有極佳的熱穩定性，且在高溫時(T≧300 °C)，其離子遷移率會有大幅度的提升，而碳化矽奈米線則具有能提升電容值的高比表面積，且亦在高溫環境下表現出高穩定性，因此這兩者所組成的超級電容器無疑是應用於高溫應用的不二選擇。
本研究利用溶膠凝膠法將YSZ沉積在兩種不同的電極(矽基板與碳化矽奈米線)上，使電極上均勻覆蓋一層YSZ，而所發展出的超級電容器Si/YSZ/Si和SiCNWs/YSZ/SiCNWs均可被用於550 °C的高溫，且在高溫下表現出良好的熱穩定性及電容特性，電容值明顯隨著操作溫度的提升而增加，尤其在溫度大於300 °C時，電容值更是大幅度的提升。Si/YSZ/Si和SiCNWs/YSZ/SiCNWs在以掃速100 mV s-1、電位窗-1至1V下進行循環伏安掃描，可在550 °C的高溫下得到最大電容值，分別為6.9 和240 μF cm-2，由此可見，奈米線的結合可使比電容值增大為單純矽電極的30倍。利用在不同電流密度的充放電測試，經計算可得到其Ragone圖，在高電流密度50 μA cm-2、高溫500 °C下，SiCNWs/YSZ/SiCNWs電容器可產生最大功率密度100 μW cm-2。經過一萬圈、掃速200 mV s-1的循環伏安掃描後，其電容值減少了40%，而CV圖形變得更為方正，顯示此超級電容器有不錯的電化學穩定性。
本研究所製備出之SiCNWs/YSZ/SiCNWs對稱超級電容器，能應用於需要高溫及高穩定性的環境，於450 °C的高溫下，其各項電化學表現仍穩定，是一具有潛力之高溫超級電容器。

Abstract
Supercapacitors play a critical role in energy storage technologies due to its high power density, fast charging/discharging, and long cycle life. Generally, the operating temperatures of current electrochemical energy storage devices are limited because of the use of liquid electrolyte, but some applications need the device to be operated in a harsh environment and at high temperatures. The present thesis develops supercapacitors for such applications. Yttria-stabilized zirconia (YSZ) has excellent thermal stability and its oxygen ion mobility rises drastically at T > 300 °C and silicon carbide nanowires (SiC NWs) have long term stability in high temperature environment and high surface areas, which make them promising candidates for high-T supercapacitor integration.
Here, we develop a symmetric supercapacitor by using YSZ as electrolyte and SiC NWs as electrode, which can be operated at a record high temperature of 550 °C. The fabricated SiC NWs electrodes are successfully coated with completely covered YSZ films via a sol-gel method. In addition, the stacked symmetric supercapacitors Si/YSZ/Si and SiCNWs/YSZ/SiCNWs present excellent thermal stability and good capacitive performances at temperatures above 300 °C. The specific capacitance is distinctly increased with increasing operation temperature, especially at temperatures higher than 300 °C. The maximum specific capacitances obtained for Si/YSZ/Si and SiCNWs/YSZ/SiCNWs are 6.9 and 240 μF cm-2, respectively, at a scan rate of 100 mV s-1 at 550 °C. The specific capacitances at all measurement temperatures increase by 30 times with the integration of NWs. The supercapacitor with SiC NWs electrode is capable of withstanding current density as high as 50 μA cm-2, yielding a highest specific power density of 100 μW cm-2 at 500 °C. A long term stability test over 10,000 CV cycles with a scan rate of 0.2 V s-1 shows excellent stability in capacitance with a specific capacitance retention rate of 60%. Our results indicate that the novel combination of YSZ electrolyte and SiC NWs electrode holds promises for high-T supercapacitor applications.

Contents
Abstract I
摘要 II
Acknowledgement III
Contents IV
Figure Contents VI
Table Contents IX
Chapter 1 Introduction 1
1.1 Fundamentals of Electrochemistry 1
1.1.1 Electrochemical System 1
1.1.2 Factors Affecting Electrochemical System 1
1.1.2.1 Electrode materials 2
1.1.2.2 Electrolyte 3
1.2 Supercapacitors 3
1.2.1 Introduction of supercapacitors 3
1.2.2 Symmetric Capacitors 5
1.2.3 Electric Double Layer Capacitors (EDLC) 5
1.2.4 Pseudocapacitors 7
1.3 Solid state supercapacitors for high temperature applications 7
1.3.1 Silicon Carbide Nanowires (SiC NWs) Electrode 9
1.3.2 Yttrium-Stabilized-Zirconia (YSZ) Electrolyte 9
Chapter 2 Literature Review 11
2.1 Supercapacitors for High Temperature Applications 11
2.2 Silicon Carbide Nanowires as Electrodes for Supercapacitors 21
2.3 Yttria-stabilized-zirconia Thin Film Deposition Techniques and Applications 25
Chapter 3 Experimental Section 31
3.1 Chemicals 31
3.2 Experimental Instruments 34
3.3 Analytical Instruments 35
3.4 Motivation 36
3.5 Methods 38
3.5.1 Clean n-type Si wafer 38
3.5.2 Preparation of SiC NWs 38
3.5.3 Preparation of YSZ Film by Sol-gel Deposition Method 39
3.5.4 Fabrication of a Sandwich Structure Supercapacitor 39
3.5.5 Characteristic Analysis 40
3.5.6 Electrochemical Measurements 40
Chapter 4 Results and Discussions 42
4.1 Characterization of YSZ 42
4.2 Electrochemical Measurements at High Temperatures 46
Chapter 5 Conclusion 62
References 64

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