臺灣博碩士論文加值系統

矽是現今發展鋰離子電池最具潛力的負極材料之一，因為矽負極有較商用的石墨負級材料高十倍的理論電容量（3579 mAh / g）。然而矽材料在朝商業化邁進的道路上有兩大主要的問題分別為奈米結構製程複雜導致成本高昂以及壽命不佳。此研究中，我們研究了直接從稻殼回收提純奈米氧化矽多孔顆粒接著以熔融鹽還原法製成矽奈米線的方法，此方法不僅可以製備奈米結構的矽用以改善體積膨脹問題，更可以藉由廢棄農作物回收來降低成本。全球每年廢棄稻殼產量約為1.5億噸，而用途卻不廣泛。經研究發現稻殼中含有很高的矽含量(約含10-40%)，而且稻殼本身具有獨特的奈米多孔結構。我們實驗的第一步，通過稀釋的氯化氫水溶液浸泡除去稻殼中的金屬離子，接著經由攝氏七百度焚燒後可得到具有奈米結構的二氧化矽，此外在真空環境下焚燒可以得到氧化矽以及碳的混合粉末。接著，我們通過電化學還原法將二氧化矽轉化為矽，此製程溫度遠低於現今商用的碳還原法(需2000度高溫)，此外，我們另外將氧化矽以及碳的混合粉末進行還原可以得到矽/碳化矽/碳(部分石墨化)的粉末用以改善純矽粉末的體積膨脹以及導電度問題。此研究不僅具有成本效益，同時又為綠色能源並且在工業上有大規模合成可能性。

Silicon is one of the most promising anode material candidates for lithium ion batteries because of its high specific capacity (3579 mAh/g), which is ten times higher than existing graphite anodes. One of the most important issues toward commercialization is the high cost of nanostructured silicon related to the complex fabrication amd expansive raw materials.
In this work, we demonstrate the recycling of pure silicon nanowires and Si/SiC/C composite from rice husks (RHs) directly, which is an abundant agricultural byproduct (108 tons/year) in worldwide. Besides, the massive amount of RHs has unique nanoporous structure on the RHs to preform the function as protection and ventilation. In the first step of our experiment, the metal ions in the RHs by HCl leaching were removed and then incinerate the leached RHs to produce silica with nanostructure or silica and carbon mixture under vacuum condition. Next step, the two different precursor are converted to silicon nanowires and Si/SiC/C composite by electrochemical reduction method, which is a potential process for large scale reduction in a relative low temperature compared with conventional carbothermal reduction. Owing to the original carbon and silicon mixture source from RHs, these recovered Si/SiC/C composite shows comparable performance as lithium ion battery anodes, with reversible capacity 476 mAh/g after 100 cycles. Recycling RHs as the source of silicon , this work presents a process to produce Si based Li-ion battery with cost effective, energy-efficient, green, and potential of large scale synthesis in industry.

Content I
Figure III
Tables IX
Abstract X
摘要 XII
Acknowledgement XIII
Chapter 1 Introduction 1
1.1 Lithium ion battery 1
1.1.1 lithium ion battery overview 1
1.1.2 Working mechanism of lithium ion battery 2
1.1.3 Developments in anode material for lithium ion battery 3
1.1.4 Silicon as the anode of lithium ion battery 6
1.2 Introduction of RHs 9
1.2.1 The potential application of rice husk 10
1.2.2Developments of RHs as the source of Si anode 13
1.3 Introduction of FFC Cambridge method 19
1.3.1 Working mechanism of FFC Cambridge method 20
1.3.2 Development of FFC Cambridge method in reduction of Si 21
Chapter 2 motivation 26
2.1 The superiority of Si-based anode materials 26
2.2 The potential of recycling rice husk 27
Chapter 3 Material analysis method and technology 28
3.1 Raman Spectroscopy 28
3.2 X-ray Photoelectron Spectroscopy (XPS) 30
3.3 Scanning Electron Spectroscopy (SEM) 31
3.4 Transmission Electron Microscopy (HR-TEM) 31
3.5 Powder X-ray Diffraction (XRD) 33
3.6 Thermal Gravimetric Analysis (TGA) 33
3.7 Bipotentiostat (Model Chi 760e) 34
3.7 Coin cell testing system (LANHE CT2001A) 35
3.8 Electrochemical Impedance Spectroscopy (EIS) 36
Chapter 4 Results and discussion 38
4.1 The extraction of silicon oxide and carbon from rice husks 38
4.1.1 Experimental design 38
4.1.2 Material Characterization 38
4.2 The reduction of silica by FFC Cambridge method 42
4.2.1 Experimental design 42
4.2.2 Material Characterization 44
4.3 The reduction of silica/carbon by FFC Cambridge method 48
4.3.1 Experimental design 48
4.3.2 Material Characterization 49
4.3.3 Battery and electrochemical performance 56
Chapter 5 Conclusion and future works 60
Chapter 6 Reference 61

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