臺灣博碩士論文加值系統

本論文主要是藉由合成條件的改變來製備不同型態的聚二氧乙基?吩-磷酸鋰鐵複合物，並且探討以不同金屬離子合成的聚二氧乙基?吩於鋰離子電池正極材料之研究。首先，使用紫外線自由基聚合法合成的聚二氧乙基?吩。利用氧化還原聚合的方式，透過3,4-乙烯二氧?吩和有機液相中氧化劑(金屬離子)濃度的改變，以製備出不同型態的聚二氧乙基?吩-磷酸鋰鐵複合物。藉由反應前後溶液顏色改變，推測其反應，並利用掃描式電子顯微鏡(SEM)、紫外光/可見光光譜(UV-Vis)、傅??紅外線光譜(FTIR)和X光繞射分析(XRD)、熱重分析儀(TGA)證實聚二氧乙基?吩成功製備。此本論文將其應用於鋰離子電池正極材料的研究，從硬幣型電池充放電測試、循環壽命測試、放電速率測試、交流電阻抗測試探討經修飾磷酸鋰鐵的特性，由實驗結果得知經修飾磷酸鋰鐵可以有效地提升鋰離子電池的電容量，對電池的循環壽命也有不錯的表現。

Lithium iron phosphate (LiFePO4) is material used in lithium ion battery as positive electrode material which has excellent thermal stability, good safety property, and environmentally friendly. In spite of these advantages, LiFePO4 has low conductivity and thereby its electrochemical performance is limited, resulting in poor rate capability. Poly(3,4-ethylenedioxythiophene) (PEDOT) is a conductive polymer which can be synthesized using chemical oxidation. Coating LiFePO4 with PEDOT conducting polymer can enhances the conductivity and rate capability.
PEDOT had been successfully synthesized on the surface of LiFePO4 using UV radical polymerization or using metal ion as an oxidant. EDOT oxidizes to PEDOT while transferring electron reducing metal ion to metal. Metal ions which can oxidize EDOT are auric and ferric ion. Auric ion reduces to gold metal while ferric ion reduces to ferrous ion. When using ferric ion as oxidant, ferrous ion needs to be washed clearly. Ferrous ion could play a catalytic role in the formation and growth of an interfacial film between electrolyte and electrode. The best ferric ion used to oxidize EDOT is iron (III) tosylate (Fe(OT)3) because the resulting PEDOT contains least contaminant. When using auric ion as oxidant, high concentration EDOT (8 mmol) and low concentration HAuCl4 (25 mmol) sample gives the best performance on electrochemical test. Higher concentration of HAuCl4 can enhance the conductivity of LiFePO4 but no enhancement on electrochemical performance because the amount of active material in electrochemical test, which is LiFePO4, was reduced when there is too much gold in the composite. PEDOT synthesized from UV radical polymerization or using metal ion as an oxidant, all can enhance the conductivity, discharge capacity, and cycling ability of LiFePO4.

Abstract i
中文摘要 ii
Acknowledgement iii
Contents iv
List of Figures vii
List of tables x
Chapter 1 Introduction and literature review 1
1-1 Lithium ion battery 1
1-1-1 Basic concepts of electrochemical cell 1
1-1-2 Lithium ion battery history 1
1-1-3 Working principle of lithium ion battery 2
1-1-4 Positive electrode material 3
1-1-5 Development and improvement of LiFePO4 as positive electrode material 5
1-2 Poly(3,4-ethylenedioxythiophene) (PEDOT) 7
1-2-1 History and development of PEDOT 7
1-2-2 Synthesis of PEDOT 8
1-3 Positive electrode materials of lithium ion battery modified by PEDOT 8
1-4 Research motivation 9
Chapter 2 Experimental 13
2-1 Chemicals 13
2-2 Characterization 13
2-2-1 Fourier transform infra red spectroscopy 13
2-2-2 X-Ray Diffraction 14
2-2-3 Ultraviolet-visible 14
2-2-4 Surface morphology and composition characterizations 14
2-2-5 Thermal analysis 14
2-2-6 Four probe conductance meter 14
2-2-7 Electrochemical measurement 15
2-3 Synthesis procedure 15
2-3-1 Synthesis of LiFePO4-Ag-PEDOT 15
2-3-2 Synthesis of LiFePO4-PEDOT by UV radical polymerization 15
2-3-3 Synthesis of Au-PEDOT 16
2-3-4 Synthesis of LiFePO4-Au-PEDOT 16
2-3-5 Synthesis of Fe-PEDOT by template polymerization 16
2-3-6 Synthesis of Fe-PEDOT with no polymerization template 16
2-3-7 Synthesis of LiFePO4-Fe-PEDOT 17
Chapter 3 Results and discussion 18
3-1 Foreword 18
3-2 Synthesis of LiFePO4 – PEDOT with silver ions as oxidant or UV radical polymerization 19
3-2-1 Attachment of silver ions on LiFePO4 surface 19
3-2-2 Structure and morphology analysis of LiFePO4-Ag-PEDOT 20
3-2-3 Structure and morphology analysis of LiFePO4-PEDOT 21
3-2-4 Thermal analysis of LiFePO4-PEDOT 22
3-2-5 Electrochemical performance of LiFePO4-PEDOT 23
3-3 Synthesis of LiFePO4 – PEDOT with auric ions as oxidant 24
3-3-1 Structure of Au-PEDOT 24
3-3-2 XRD analysis of LiFePO4-Au-PEDOT 25
3-3-3 Thermal analysis of LiFePO4-Au-PEDOT 25
3-3-4 Conductivity of LiFePO4-Au-PEDOT 26
3-3-5 Morphology of LiFePO4-Au-PEDOT 26
3-3-6 Electrochemical performance of LiFePO4-Au-PEDOT 26
3-3-7 UV-vis analysis of LiFePO4-Au-PEDOT supernatant 27
3-4 Synthesis of LiFePO4 – PEDOT with ferric ions as oxidant 28
3-5 Conclusion 31
Chapter 4 Summary 53
References 54
Curriculum Vitae 59

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