臺灣博碩士論文加值系統

本研究目的主要探討藉由表面改質的方法，來改善鋰離子電池負極石墨材料的表面結構，以達到降低不可逆電容量、穩定電容量衰退現象以及提升電容量等電化學性能。本實驗所使用的石墨粉末分別為台灣大學材料研究所以熔解偏析石墨（Dissolution precipitation graphite；DPG）製備的人工石墨以及外購的球形天然石墨，表面氟化是藉由氟氣於不同反應溫度及時間下使 DPG 人工石墨的表面結構形成 CxF，以及表面氧化是利用氧化性溶液對球形天然石墨進行反應，以形成碳氧化物披覆於球狀天然石墨的表面。藉由表面改質的方式可穩定石墨的層間結構，以降低充放電過程中第一次不可逆電容量與電容量衰退的現象。

實驗中利用拉曼光譜儀（Raman spectroscopy）分析石墨表面性質，X光繞射分析儀（XRD）分析石墨整體特性，以及掃描式電子顯微鏡（SEM）觀察表面形態，發現 DPG人工石墨在適當的溫度與時間下與氟氣反應，其第一次不可逆性有降低的現象，由此可見經由表面氟化處理，於表面形成 CxF，有助於第一次不可逆電容量的降低；另外球形天然石墨經過表面氧化處理之後，其電容量的衰退較為穩定，且循環電容量有所提升。

關鍵字：鋰離子電池、石墨、表面改質、表面氟化、表面氧化、氧化性溶液

Abstract
The purpose of this research was to improve electrochemical characteristics and surface structure on graphite negative material of lithium ion secondary battery by surface modification methods that decrease the irreversible capacity, steady and enhance the capacity. In this study, the raw materials were used by DPG (Dissolution precipitation graphite) artificial graphite from NTU material institute and spherical natural graphite. The DPG was heated to form CxF on the DPG surface by fluorine gas. The surface oxidation of natural graphite reacted with oxidative solutions to form dense oxides layer on its surface. Due to the surface modifications, the structure of graphene layer can be steady that to decrease the first irreversible capacity and electrochemical performance.
The analysis on surface properties is investigated by Raman spectroscopy and the bulk is analyzed by X-ray diffraction measurements. The morphology of graphite is obtained by scanning electron microscope (SEM). It was observed that artificial graphite reacted with fluorine by different temperature and time. The CxF of DPG surface shows a lower the first irreversible capacity. Spherical natural graphite with mild oxidation can steady and increase cycle capacity.
Keywords: lithium ion battery; graphite; surface modification; surface fluorination; surface oxidation; oxidative solution

目 次

中文摘要 .............................................................................. i
英文摘要 ............................................................................ ii
目 次 ....................................................................................... iii
表 目 錄 ............................................................................................ vi
圖 目 錄 ........................................................................................... vii
第一章 緒 論 ............................................................................... 1
第二章 文獻回顧 ............................................................................... 4
2-1 鋰離子電池的發展 .................................................................. 4
2-2 鋰離子二次電池的運作原理 .................................................... 6
2-3 鋰離子二次電池的電極材料 ................................................... 10
2-3-1正極材料 ...................................................................... 10
2-3-2負極材料 ...................................................................... 13
2-3-3 電解質造成的電化學現象 .............................................. 15
2-4 石墨材料的簡介與分類 ............................................................ 16
2-5 石墨材料改質的方式........................................................ 22
2-5-1石墨表面之氟化處理 .............................................. 24
2-5-2石墨表面之氧化處理 .............................................. 27

第三章 實驗方法與步驟 ...................................................... 30
3-1 實驗設備 ............................................................................... 30
3-2分析設備 ................................................................ 31
3-3 人工石墨之氟化處理 ................................................. 32
3-4 天然石墨之氧化處理 ............................................................... 35
3-4-1 氧化性溶液之氧化處理 ....................................................... 35
3-4-2 空氣（Air）之氧化處理 ...................................................... 36
3-5電池電極之塗佈與電池組裝.............................................. 38
3-5-1 電極塗佈 ...................................................................... 38
3-5-2 電池組裝 ...................................................................... 39
3-5-3 充放電測試 .................................................................... 41
3-6人工石墨粉末鑑定分析 .............................................................. 42
3-6-1 X光繞射分析儀（XRD）............................................... 42
3-6-2 拉曼光譜分析儀（Raman spectroscopy）........................ 43
3-6-3 掃描式電子顯微鏡（SEM）............................................ 44

第四章 結果與討論 ............................................................................................... 45
4-1 人工石墨氟化處理之分析 ............................................................ 46
4-1-1 人工石墨之氟化處理XRD分析 ....................................... 46
4-1-2人工石墨氟化處理之Raman光譜分析 ............................. 50
4-1-3人工石墨氟化處理之SEM觀察 ....................................... 52
4-1-4人工石墨氟化處理作為鋰電池負極材料之特性 ................. 55
4-2 天然石墨氧化處理之分析 ............................................................. 59
4-2-1天然石墨氧化處理之XRD分析 ....................................... 59
4-2-2 天然石墨之氧化處理Raman光譜分析 ............................. 63
4-2-3天然石墨氧化處理之SEM觀察 ...................................... 65
4-2-4 天然石墨氧化處理作為鋰電池負極材料之特性 ................. 73

第五章 結 論 .............................................................................. 78

參考文獻 ............................................................................................. 80

附錄 ........................................................................................................................... 85
作者簡介 .................................................................................................... 86

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