本研究主要為以三價鐵前驅物水熱法合成鋰鐵磷酸鹽(LiFePO4)，以吡咯(pyrrole)作為有效的還原劑，反應中吡咯可將三價鐵前驅物還原成二價鐵並聚合成聚吡咯，加入不同莫耳比例三價鐵前驅物可控制聚吡咯的聚合量，且聚吡咯可在鍛燒熱處理中提供碳源，藉此控制不同碳含量包覆鋰鐵磷酸鹽。以X光繞射儀、掃描式電子顯微鏡及穿透式電子顯微鏡觀察鋰鐵磷酸鹽粉體結構與表面型態，X光繞射儀及穿透式電子顯微鏡鑑定鋰鐵磷酸鹽的橄欖石斜方晶系結構，空間群為Pnma，掃描式電子顯微鏡和穿透式電子顯微鏡觀察鋰鐵磷酸鹽粉體粒徑約為200 nm及表面碳塗層在鋰鐵磷酸鹽上，並以元素分析儀和感應耦合電漿質譜儀分析材料化學組成，而從拉曼及化學分析能譜分析指出以吡咯作為還原劑能夠有效防止三價鐵不純物產生，且反應後聚吡咯作為碳源。電化學測試中以5 %莫耳比例三價鐵前驅物添加合成之鋰鐵磷酸鹽鍛燒600 ℃樣品在0.2 C放電下擁有160 mAh/g電容量，將近理論電容量170 mAh/g，以10 %莫耳比例三價鐵前驅物添加合成之鋰鐵磷酸鹽鍛燒後樣品在10 C高速放電下仍擁有106 mAh/g電容量。

Lithium iron phosphate (LiFePO4) is prepared by hydrothermal process using Fe(III) as precursor and pyrrole as an efficient reducing agent. The Fe(III) precursor in the system reacts with pyrrole to generate polypyrrole (PPy) and reduce Fe(III) to Fe(II). The different molar ratio Fe(III) polymerize different content of PPy and PPy can also be a carbon source for further calcination. The structural and morphological properties of LiFePO4 powder were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and a transmission electron microscope (TEM). The XRD and TEM results demonstrate that LiFePO4 powder has an orthorhombic olivine-type structure with a space group of Pnma. The SEM and TEM results show that the particle size of LiFePO4 is around 200 nm and a layer of carbon coats on LiFePO4. The chemical composition of the LiFePO4 powder was characterized by elemental analysis (EA) and inductively coupled plasma/mass spectroscopy (ICP/MS). Raman and X-ray photoelectron spectroscopy (XPS) results indicate that pyrrole as a reducing agent reduces and prevents the formation of Fe(III) impurity and the resulting PPy plays a role as carbon source. Among the synthesized cathode materials, LiFePO4 synthesized using 5% molar ratio of Fe(III) and subsequent calcinations of 600 °C shows the best electrochemical property with an discharge capacity of 160 mAhg−1 close to its theoretical capacity 170 mAh g−1 at 0.2 C rate. Using 10% molar ratio of Fe(III), and the discharge capacity of LiFePO4 at 10 C rate reaches 106 mAhg−1.

摘要................................................................................................................................ i
Abstract ......................................................................................................................... ii
目錄.............................................................................................................................. iii
圖目錄.......................................................................................................................... vii
表目錄........................................................................................................................... ix
第一章 緒論 ................................................................................................................. 1
1.1 前言..................................................................................................................... 1
1.2 研究目的與動機................................................................................................. 2
第二章 文獻回顧 ......................................................................................................... 3
2.1 鋰二次電池簡介................................................................................................. 3
2.2 鋰離子二次電池工作原理................................................................................. 5
2.3 鋰離子二次電池正極材料................................................................................. 7
2.3.1 正極材料LiCoO2 ........................................................................................ 7
2.3.2 正極材料LiNiO2 ......................................................................................... 8
2.3.3 正極材料LiMn2O4 ...................................................................................... 9
2.3.4 正極材料LiFePO4..................................................................................... 10
2.4 LiFePO4合成方法 ............................................................................................. 15
2.4.1 固相化學.................................................................................................... 15
2.4.1-1 固態反應法(Solid state reaction) ....................................................... 15
2.4.1-2 機械化學活化法(Mechanochemical activation) ............................... 16
2.4.1-3 熱碳還原法(Carbothermal reduction) ............................................... 16
2.4.1-4 微波法(Microwave processing)......................................................... 17
2.4.2 液相化學.................................................................................................... 17
2.4.2-1 水熱法(Hydrothermal processing) ..................................................... 17
2.4.2-2 溶膠-凝膠法(Sol-gel processing)....................................................... 18
2.4.2-3 沉澱法(Precipitation method) ............................................................ 18
2.4.2-4 乳化乾燥法(Emulsion-drying method) ............................................. 19
2.4.2-5 噴霧熱解法(Spray pyrolysis)............................................................. 19
2.5 LiFePO4近期發展之改性 ................................................................................. 20
2.5.1 減小粒徑.................................................................................................... 20
2.5.2 表面包覆導電層........................................................................................ 21
2.5.3 金屬摻雜.................................................................................................... 22
2.6 LiFePO4合成限制 ............................................................................................. 23
第三章 實驗方法 ....................................................................................................... 24
3.1 實驗藥品與器材............................................................................................... 24
3.2 實驗步驟........................................................................................................... 26
3.2.1 水熱法不同反應時間................................................................................ 26
3.2.2 水熱法不同Fe(III)添加 ............................................................................ 27
3.2.3 高溫管狀爐燒結處理................................................................................ 28
3.2.4 半電池組裝................................................................................................ 29
3.3 實驗儀器........................................................................................................... 31
3.3.1 粉體鑑定.................................................................................................... 31
3.3.1-1 X光繞射儀 (XRD) ............................................................................ 31
3.3.1-2 掃描式電子顯微鏡 (SEM) ............................................................... 31
3.3.1-3 穿透式電子顯微鏡 (TEM) ............................................................... 32
3.3.1-4 元素分析儀 (EA) .............................................................................. 32
3.3.1-5 化學分析電子光譜儀 (ESCA) ......................................................... 33
3.3.1-6 感應耦合電漿質譜儀 (ICP-MS) ...................................................... 33
3.3.1-7 拉曼光譜儀 (RS) ............................................................................... 34
3.3.1-8 四點探針量測儀 (FPP) ..................................................................... 34
3.3.2 電化學........................................................................................................ 35
3.3.2-1 循環伏安法分析 (CV) ...................................................................... 35
3.3.2-2 交流阻抗電阻分析 (AC-impedance) ............................................... 36
3.3.2-3 充放電性能及倍率效能測試 (Charge-discharge & c-rate performance) .................................................................................................... 36
3.3.2-4 循環性能測試 (Cycle-life performance) .......................................... 37
第四章 實驗結果與討論 ........................................................................................... 38
4.1 不同反應時間合成........................................................................................... 38
4.1.1 粉體鑑定.................................................................................................... 38
4.1.1-1 X光繞射儀分析 ................................................................................. 38
4.1.1-2 掃描式電子顯微鏡 ............................................................................ 41
4.1.2 電化學測試................................................................................................ 44
4.1.2-1 定電流充放電 .................................................................................... 44
4.1.2-2 倍率放電 ............................................................................................ 45
4.1.2-3 循環壽命比較 .................................................................................... 46
4.1.3 綜合討論.................................................................................................... 47
4.2 不同Fe(III)添加合成 ....................................................................................... 48
4.2.1 粉體鑑定.................................................................................................... 49
4.2.1-1 X光繞射儀分析 ................................................................................. 49
4.2.1-2 掃描式電子顯微鏡 ............................................................................ 52
4.2.1-3 穿透式電子顯微鏡 ............................................................................ 55
4.2.1-4 元素分析 ............................................................................................ 58
4.2.1-5 化學分析能譜 .................................................................................... 59
4.2.1-6 感應耦合電漿質譜 ............................................................................ 62
4.2.1-7 拉曼光譜分析 .................................................................................... 63
4.2.1-8 四點探針導電度測量 ........................................................................ 64
4.2.2 電化學測試................................................................................................ 66
4.2.2-1 循環伏安法分析 ................................................................................ 67
4.2.2-2 交流阻抗電阻 .................................................................................... 71
4.2.2-3 定電流充放電 .................................................................................... 75
4.2.2-4 倍率放電 ............................................................................................ 78
4.2.2-5 循環壽命比較 .................................................................................... 81
4.2.3 綜合討論.................................................................................................... 84
第五章 結論 ............................................................................................................... 86
第六章 參考文獻 ....................................................................................................... 87
附錄.............................................................................................................................. 90

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