隨著小型電子化商品的演進，高能量密度的電池勢必成為下一個研究發展的目標。在眾多可充放電池中，鋰電池的能量密度在不論是每個重量單位上或是每個體積單位上都佔有優勢。然而，目前商業上使用的碳負極材料，它所能產生的比電容值已經遠遠不足。同時，經過熱力學理論計算發現矽負極材料所能儲存的鋰離子遠比碳負極來得多，每公克的矽所能提供的比電容約為9~10倍的每公克的碳的產出。儘管矽擁有如此優異的表現，至今它卻難以商業化。這可歸因於以下幾個重要的原因：
(1) 劇烈體積膨脹：矽在和鋰合金化後，劇烈的體積膨脹會使得應力集中，促使材料容易從電極上剝落，而減短了使命壽命。
(2) 固態電解質介面不穩定的生成：當電池在放電程序時，電解液傾向分解且形成固態電解質介面於負極材料上，由於此反應會消耗電池內的鋰含量以及增加鋰離子傳導時的阻抗，因此，往往會造成鋰電池的比電容降低。
(3) 低導電性：低電荷轉移效率會使得鋰和矽的反應緩慢且不完全，使得材料實際反應後的比電容低。
本研究以斜角蒸鍍儀製備具有次序性排列的高比表面積螺旋柱體，在固定矽的蒸鍍量和鍍率下，藉由改變載台旋轉角度，可以製造出不同旋轉圈數的螺旋柱體，而不同結構的柱體比表面積以及每個柱體間的間距皆不同。利用此特性來分析增加鋰和矽之間的反應位置和釋放體積膨脹後所帶來的額外應力所帶來的影響。在旋轉3轉至48轉的矽螺旋柱體間，48轉的柱體擁有最大的比表面積以及最疏鬆結構。因此，經過100次的充放電測試後，48轉的柱體僅衰減了第一圈比電容的29%。
雖然本質矽的理論電容比碳材要來得大很多，但其低弱的導電性造成材料無法發揮應有的優勢。在鋰矽合金化的過程中，若導電性好則電荷轉移速率快，也連帶地幫助鋰加速和矽合金化，這將有助於讓反應完全。根據文獻記載，Cu3Si相的銅矽化合物有助於導電性的提高。因此，在後續研究中，利用XRD和I-V圖來鑑定400 °C至800 °C的後退火程序所生成銅矽化合物的相與導電性關係。EIS量測更進一步地說明銅矽化合物作為電池負極材料與本質矽的阻抗比較。CV圖則清楚的說明導電性對於鋰和矽結合反應能力有很大的提升。最後，在0.25 C的高充放效率下，即使經過100次充放，此研究仍能得到1706.68 mAh/cm3的高比體積電容。

The increasing demand for advanced electronic devices and energy storage have stimulated significant interests in lithium ion battery development. Li based batteries are one of the most promising energy storage systems which as they are light-weight and energy-delivery efficient. Compared to the common graphite-anode system, Si is known to have highest theoretical specific capacitance making Si the most promising candidate for the next-generation anode materials for lithium batteries. However, large volume expansion and serious material pulverization after cycling lead to poor life times, and is the main stumbling block toward their commercialization.
In this research, glancing angle deposition (GLAD) technique is utilized to deposit uniform and aligned helix Si nanostructures. By varying the rotation angle during GLAD, various helix Si nanostructures with differing porosities were deposited. With increasing numbers of rotation (3 to 48) the double layer capacitance, related to the surface area, increased to from 0.112 to 0.208 F/cm3. Additionally, the areal spacing also increases and results in occupation of Si nanostructure decreased from 77.5% to 73.77%. As a result, 48 cycle helix Si anode shows the best electrochemical performance with a volumetric specific capacity 846.55 mAh/cm3. Following a 100 cycle test, the anode is able to maintain 70% of its original volumetric specific capacity.
However, the low conductivity of intrinsic silicon makes charge transfer of the electrons slow and also gives rise to incomplete alloying reactions with Li ions. To overcome this we annealed our anode with the aim of forming copper silicide, utilising the underlying copper substrate as a source. In doing so, the volumetric specific capacity was increased to 1706.68 mAh/cm3, using a 100 cycle test at charge/discharge rates as high as 0.25 C.
Throughout this work detailed analysis was carried out, including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), I-V characteristics (I-V) Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV), providing an understanding of our results and possibilities for future work. Furthermore, we believe that the adequate porosity and lower conductivity helps to minimize the enormous stress within the film structure by proving enough space for volume expansion, leading to a longer life time and better charge transfer and electrochemical performance.

摘要 i
Abstract ii
Acknowledgement iii
Table of Contents v
List of Figures vii
List of Tables xi
1. Introduction 1
1.1 Global Warming 1
1.2 Lithium Ion Battery 4
1.2.1 Working Mechanism 4
1.2.2 Anode Material 6
1.2.3 Challenges 7
2. Experimental Section 17
2.1 Experimental Section 17
2.1.1 Glancing Angle Deposition, GLAD 17
2.1.2 Furnace 21
2.1.3 Aligned Helix Si Nanostructure Synthesis Method 22
2.1.4 Coin Cell Fabrication Process 24
2.2 Analysis 26
2.2.1 X-Ray Diffraction, XRD 26
2.2.2 Scanning Electron Microscope, SEM 27
2.2.3 Cyclic Voltammetry, CV 28
2.2.4 Electrochemical Impedance Spectroscopy, EIS 29
3. Result and Discussion 31
3.1 Aligned Helix Si Nanostructure 31
3.2 Performance of Aligned Helix Si Nanostructure 37
3.3 Improvement of Conductivity for Aligned Helix Si nanostructure 39
3.4 Electrochemical Analysis of Room Temperature and Post Annealed Si Nanospiral Anodes 44
3.5 Benchmark 51
4. Conclusion and Outlook 52
4.1 Conclusion 52
4.2 Outlook - Solid State Battery 53
5. Reference 54

[1] R. S. Holli Riebeek. Global Mean Surface Temperature. Available: http://earthobservatory.nasa.gov/Features/GlobalWarming/page2.php
[2] U. N. F. C. o. C. Change. (2014). First steps to a safer future: Introducing The United Nations Framework Convention on Climate Change. Available: http://unfccc.int/2860.php
[3] A smart community. Available: https://www.mhi-global.com/discover/earth/issue/history/future/smartcommunity/future_energy.html
[4] B. Lawson. (2005). Energy Density. Available: http://www.mpoweruk.com/chemistries.htm
[5] P. Verma, P. Maire, and P. Novák, "A review of the features and analyses of the solid electrolyte interphase in Li-ion batteries," Electrochimica Acta, vol. 55, pp. 6332-6341, 2010.
[6] N. Nitta and G. Yushin, "High-Capacity Anode Materials for Lithium-Ion Batteries: Choice of Elements and Structures for Active Particles," Particle & Particle Systems Characterization, vol. 31, pp. 317-336, 2014.
[7] H. Wu and Y. Cui, "Designing nanostructured Si anodes for high energy lithium ion batteries," Nano Today, vol. 7, pp. 414-429, 2012.
[8] L. Y. Beaulieu, K. W. Eberman, R. L. Turner, L. J. Krause, and J. R. Dahn, "Colossal reversible volume changes in lithium alloys," Electrochemical and Solid State Letters, vol. 4, pp. A137-A140, 2001.
[9] T. D. Hatchard and J. R. Dahn, "In situ XRD and electrochemical study of the reaction of lithium with amorphous silicon," Journal of the Electrochemical Society, vol. 151, pp. A838-A842, 2004.
[10] A. Magasinski, P. Dixon, B. Hertzberg, A. Kvit, J. Ayala, and G. Yushin, "High-performance lithium-ion anodes using a hierarchical bottom-up approach," Nature Materials, vol. 9, pp. 353-358, 2010.
[11] W. Wang, Z. Favors, R. Ionescu, R. Ye, H. H. Bay, M. Ozkan, et al., "Monodisperse Porous Silicon Spheres as Anode Materials for Lithium Ion Batteries," Scientific Reports, vol. 5, p. 6, 2015.
[12] N. Liu, H. Wu, M. T. McDowell, Y. Yao, C. M. Wang, and Y. Cui, "A Yolk-Shell Design for Stabilized and Scalable Li-Ion Battery Alloy Anodes," Nano Letters, vol. 12, pp. 3315-3321, 2012.
[13] Z. D. Lu, N. Liu, H. W. Lee, J. Zhao, W. Y. Li, Y. Z. Li, et al., "Nonfilling Carbon Coating of Porous Silicon Micrometer-Sized Particles for High-Performance Lithium Battery Anodes," Acs Nano, vol. 9, pp. 2540-2547, 2015.
[14] F. F. Cao, J. W. Deng, S. Xin, H. X. Ji, O. G. Schmidt, L. J. Wan, et al., "Cu-Si Nanocable Arrays as High-Rate Anode Materials for Lithium-Ion Batteries," Advanced Materials, vol. 23, pp. 4415, 2011.
[15] J. W. Kim, J. H. Ryu, K. T. Lee, and S. M. Oh, "Improvement of silicon powder negative electrodes by copper electroless deposition for lithium secondary batteries," Journal of Power Sources, vol. 147, pp. 227-233, 2005.
[16] S. Chae, M. Ko, S. Park, N. Kim, J. Ma, and J. Cho, "Micron-sized Fe-Cu-Si ternary composite anodes for high energy Li-ion batteries," Energy & Environmental Science, vol. 9, pp. 1251-1257, 2016.
[17] K. Goldshtein, K. Freedman, D. Schneier, L. Burstein, V. Ezersky, E. Peled, et al., "Advanced Multiphase Silicon-Based Anodes for High-Energy-Density Li-Ion Batteries," Journal of the Electrochemical Society, vol. 162, pp. A1072-A1079, 2015.
[18] M. T. Taschuk, M. M. Hawkeye, and M. J. Brett, "Chapter 13 - Glancing Angle Deposition - Martin, Peter M," in Handbook of Deposition Technologies for Films and Coatings (Third Edition), ed Boston: William Andrew Publishing, pp. 621-678, 2010.
[19] H. Kwon, S. H. Lee, and J. K. Kim, "Three-Dimensional Metal-Oxide Nanohelix Arrays Fabricated by Oblique Angle Deposition: Fabrication, Properties, and Applications," Nanoscale Research Letters, vol. 10, p. 369, 2015.
[20] S. R. Kennedy and M. J. Brett, "Porous broadband antireflection coating by glancing angle deposition," Applied Optics, vol. 42, pp. 4573-4579, 2003.
[21] S. H. Lee, J. Kwon, D. Y. Kim, K. Song, S. H. Oh, J. Cho, et al., "Enhanced power conversion efficiency of dye-sensitized solar cells with multifunctional photoanodes based on a three-dimensional TiO2 nanohelix array," Solar Energy Materials and Solar Cells, vol. 132, pp. 47-55, 2015.
[22] Z. Xie, X. Liu, W. Wang, C. Liu, Z. Li, and Z. Zhang, "Fabrication of TiN nanostructure as a hydrogen peroxide sensor by oblique angle deposition," Nanoscale Research Letters, vol. 9, pp. 1-5, 2014.
[23] I. A. Shkrob, J. F. Wishart, and D. P. Abraham, "What Makes Fluoroethylene Carbonate Different?," The Journal of Physical Chemistry C, vol. 119, pp. 14954-14964, 2015.
[24] G. A. Mabbott, "AN INTRODUCTION TO CYCLIC VOLTAMMETRY," Journal of Chemical Education, vol. 60, pp. 697-702, 1983.
[25] U. Kasavajjula, C. Wang, and A. J. Appleby, "Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells," Journal of Power Sources, vol. 163, pp. 1003-1039, 2007.
[26] P. K. Ng, J. Y. Cheng, B. Fisher, C. M. Lilley, and Ieee, In situ Electrical Resistivity Measurement of Self Assembled Cu3Si Nanowires on Si(111). New York: Ieee, 2013.
[27] S. J. Jung, T. Lutz, A. P. Bell, E. K. McCarthy, and J. J. Boland, "Free-Standing, Single-Crystal Cu3Si Nanowires," Crystal Growth & Design, vol. 12, pp. 3076-3081, 2012.
[28] C. H. Chiu, C. W. Huang, J. Y. Chen, Y. T. Huang, J. C. Hu, L. T. Chen, et al., "Copper silicide/silicon nanowire heterostructures: in situ TEM observation of growth behaviors and electron transport properties," Nanoscale, vol. 5, pp. 5086-5092, 2013.
[29] C. Bo, J. Yan-Hui, L. Gong-Ping, and C. Xi-Meng, "Atomic diffusion in annealed Cu/SiO2/Si (100) system prepared bymagnetron sputtering, 2010.
[30] S. a. database, "Cu-Si phase diagram," ed, 2011.
[31] D. M. Piper, J. J. Travis, M. Young, S. B. Son, S. C. Kim, K. H. Oh, et al., "Reversible High-Capacity Si Nanocomposite Anodes for Lithium-ion Batteries Enabled by Molecular Layer Deposition," Advanced Materials, vol. 26, pp. 1596-1601, 2014.
[32] W. Yuan, M. Y. Wu, H. Zhao, X. Y. Song, and G. Liu, "Baseline Si electrode fabrication and performance for the battery for Advanced Transportation Technologies Program," Journal of Power Sources, vol. 282, pp. 223-227, 2015.
[33] S. Jeong, J. P. Lee, M. Ko, G. Kim, S. Park, and J. Cho, "Etched Graphite with Internally Grown Si Nanowires from Pores as an Anode for High Density Li-Ion Batteries," Nano Letters, vol. 13, pp. 3403-3407, 2013.
[34] Y. H. Xu, Y. J. Zhu, F. D. Han, C. Luo, and C. S. Wang, "3D Si/C Fiber Paper Electrodes Fabricated Using a Combined Electrospray/Electrospinning Technique for Li-Ion Batteries," Advanced Energy Materials, vol. 5, p. 7, 2015.
[35] J. Y. Liu, N. Li, M. D. Goodman, H. G. Zhang, E. S. Epstein, B. Huang, et al., "Mechanically and Chemically Robust Sandwich-Structured C@Si@C Nanotube Array Li-Ion Battery Anodes," Acs Nano, vol. 9, pp. 1985-1994, 2015.
[36] Z. L. Zhang, Y. H. Wang, W. F. Ren, Q. Q. Tan, Y. F. Chen, H. Li, et al., "Scalable Synthesis of Interconnected Porous Silicon/Carbon Composites by the Rochow Reaction as High-Performance Anodes of Lithium Ion Batteries," Angewandte Chemie-International Edition, vol. 53, pp. 5165-5169, 2014.
[37] B. Wang, T. F. Qiu, X. L. Li, B. Luo, L. Hao, Y. B. Zhang, et al., "Synergistically engineered self-standing silicon/carbon composite arrays as high performance lithium battery anodes," Journal of Materials Chemistry A, vol. 3, pp. 494-498, 2015.
[38] Y. Y. Huang, D. Han, Y. B. He, Q. B. Yun, M. Liu, X. Y. Qin, et al., "Si Nanoparticles Intercalated into Interlayers of Slightly Exfoliated Graphite filled by Carbon as Anode with High Volumetric Capacity for Lithium-ion Battery," Electrochimica Acta, vol. 184, pp. 364-370, 2015.
[39] S. Li, X. Qin, H. Zhang, J. Wu, Y.-B. He, B. Li, et al., "Silicon/carbon composite microspheres with hierarchical core–shell structure as anode for lithium ion batteries," Electrochemistry Communications, vol. 49, pp. 98-102, 2014.
[40] T. M. Bandhauer, S. Garimella, and T. F. Fuller, "A Critical Review of Thermal Issues in Lithium-Ion Batteries," Journal of the Electrochemical Society, vol. 158, pp. R1-R25, 2011.
[41] B. Kumar, J. Kumar, R. Leese, J. P. Fellner, S. J. Rodrigues, and K. M. Abraham, "A Solid-State, Rechargeable, Long Cycle Life Lithium-Air Battery," Journal of the Electrochemical Society, vol. 157, pp. A50-A54, 2010.
[42] J. F. M. Oudenhoven, L. Baggetto, and P. H. L. Notten, "All-Solid-State Lithium-Ion Microbatteries: A Review of Various Three-Dimensional Concepts," Advanced Energy Materials, vol. 1, pp. 10-33, 2011.
[43] P. H. L. Notten, F. Roozeboom, R. A. H. Niessen, and L. Baggetto, "3-D integrated all-solid-state rechargeable batteries," Advanced Materials, vol. 19, pp. 4564-4567, 2007.
[44] S. Xu, Y. H. Zhang, J. Cho, J. Lee, X. Huang, L. Jia, et al., "Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems," Nature Communications, vol. 4, p. 8, 2013.