摘要
以LiFePO4材料作為正極之鋰離子二次電池擁有許多優點：Fe、P來源豐富可使成本降低、結構穩定而有良好熱穩定性及長循環壽命、材料無毒、具環境友善性，使其成為熱門的研究對象。但本質的缺點：導電性差、Li+擴散速率低，成為該材料應用時的首要改進標的。
本實驗室先前已成功製備出形貌特殊的LiFePO4片狀粉末，並改進材料前述缺點，包覆碳以成LiFePO4/C複合物，但為更進一步提升電池表現，本研究仍採球磨法混合前驅物及碳源進行包碳，但藉由燒結溫度的改變及採用不同碳源，期望製備出性能較佳的LiFePO4/C。
本研究第一階段固定使用蔗糖為碳源，於不同溫度550~800oC進行燒結，藉由XRD、SEM、Raman、TEM，及電池測試探討燒結溫度對LiFePO4/C之影響。實驗結果顯示：隨燒結溫度提升，LiFePO4結晶程度越高，碳膜石墨六元環程度增加，電池表現顯著提升，最佳燒結溫度800oC製備的電池，於0.1C放電速率下具最高比電容值160 mAhg-1及最低之極化程度80 mV。
第二階段探討於固定溫度750oC下，添加不同碳源：蔗糖、硬脂酸、檸檬酸、月桂酸對LiFePO4/C之影響。其中以硬脂酸作為碳源之LiFePO4/C具最佳之結晶性、包覆完整性以及次佳的導電性、，因此將其組裝成電池進行測試並與蔗糖碳源結果作一比較。實驗結果顯示：硬脂酸為碳源的電池於0.1C放電速率下擁有接近理論值的168 mAhg-1，且有較佳極化程度110 mV。
實驗結果顯示以硬脂酸為碳源，如再進一步調整燒結溫度，可能製作出表現更優異的電池。

Abstract
LiFePO4 as a positive electrode material in the lithium ion secondary battery possesses many advantages: abundant Fe and P in earth crust, reduced cost, stable structure, good thermal stability, long life cycle, non-toxicity, friendly to the environment. Aforesaid, it becomes a hot research topic. The shortcoming of material properties: poor electrical conductivity and Li+ diffusion rate have limited its’ application and need to be improved firstly. Our laboratory has previously successfully prepared LiFePO4 sheet powders and improved them by coating C to be LiFePO4/C composites. To further improve battery performance, the similar carbon coating scheme: ball milling method was adopted. By changing the sintering temperature and applying different carbon sources, we expect to prepare LiFePO4/C with further improved properties.
Firstly, carbon source at different sintering temperature 550~800oC were tested. We used XRD, SEM, Raman, TEM and battery test to analyze the effect of temperature. Experimental results showed that: both the crystallinity of LiFePO4 and the aromatic graphite percentage increases and so significantly improve battery performance. The battery prepared with LiFePO4/C sintered at 800oC has the highest discharge capacity 160 mAhg-1 and the lowest polarization 80 mV.
Then we tested effects of different carbon sources: sucrose, stearic acid, citric acid and lauric acid at a fixed sintering temperature 750 oC. The LiFePO4/C prepared with stearic acid has the best crystallinity, and coating uniformity and better electrical conductivity, so was applied to make battery for comparison study. Comparing it to the battery made of LiFePO4/C coated with sucrose source, the results showed that: battery with stearic acid as a carbon source has a specific capacity close to the theoretical value 168 mAhg-1, and a better polarization of 110 mV.
The results implied that if applying stearic acid as a carbon source, the battery made of may perform even better than that prepared with LiFePO4/C with sucrose source sintered at 800 oC by further adjusting the sintering temperature.

目錄
第一章 緒論及研究動機................................................1
1.1 前言...................................................................................1
1.2 研究動機與目的...............................................................3
第二章 文獻回顧............................................................5
2.1 鋰離子電池.......................................................................5
2.1.1 發展歷程..................................................................5
2.1.2 工作原理..................................................................7
2.1.3 電池組成..................................................................8
2.2 鋰離子電池正極材料.....................................................10
2.2.1 LiCoO2.....................................................................10
2.2.2 LiNiO2......................................................................11
2.2.3 LiMn2O4...................................................................12
2.3 LiFePO4............................................................................13
2.3.1 起源及比較............................................................13
2.3.2 結構........................................................................15
2.3.3充放電反應機制.....................................................16
2.3.4 製備方法................................................................17
2.3.5電容量衰減.............................................................20
2.3.6缺點及改善方法.....................................................22
2.3.7 燒結溫度影響........................................................29
2.3.8碳膜結構對電性之影響.........................................29
2.4 研究課題.........................................................................30

第三章 實驗方法與步驟..............................................31
3.1實驗流程..........................................................................31
3.2實驗藥品及耗材..............................................................33
3.3實驗儀器..........................................................................34
3.4實驗細節..........................................................................35
3.4.1 Li3PO4合成.............................................................35
3.4.2 Fe3(PO4)2‧8H2O合成...........................................35
3.4.3 LiFePO4/C...............................................................36
3.4.4電池壓制.................................................................36
3.4.5電池測試.................................................................38
3.5粉末物理性質檢測..........................................................38
3.5.1 X-ray繞射分析儀(XRD)........................................38
3.5.2場發射掃描式電子顯微鏡(FESEM)......................39
3.5.3拉曼光譜儀(Raman Spectrometer).........................39
3.5.4 穿透式電子顯微鏡(TEM).....................................39
第四章 結果與討論......................................................40
4.1前驅物粉末分析...............................................................41
4.1.1 Li3PO4 X光繞射結構分析及表面形貌.................41
4.1.2 Fe3(PO4)2‧8H2O X光繞射結構分析及表面形貌..43
4.2不同燒結溫度製備之LiFePO4/C....................................46
4.2.1 X光繞射結構分析..................................................46
4.2.2表面形貌觀察..........................................................48
4.2.3碳膜結構分析..........................................................53
4.2.4碳膜包覆與厚度......................................................56
4.2.5電池性能測試..........................................................58
4.2.6 電池循環測試.......................................................60
4.2.7不同燒結溫度之LiFePO4/C綜合比較.................62
4.3添加不同碳源製備之LiFePO4/C.....................................64
4.3.1 X光繞射結構分析.................................................64
4.3.2表面形貌觀察.........................................................66
4.3.3碳膜結構分析.........................................................70
4.3.4碳膜包覆與厚度.....................................................73
4.3.5電池性能測試.........................................................74
4.3.6 電池循環測試........................................................76
4.3.7不同碳源之LiFePO4/C綜合比較..........................77
第五章 結論..................................................................79
參考文獻..........................................................81

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