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研究生: 黃楷斌
Kai-Pin Huang
論文名稱: 低成本之碳熱還原法製備LiFePO4/C鋰離子電池複合陰極材料
A simple, cheap carbonthermal reduction method to synthesize LiFePO4
指導教授: 費定國
George Ting-Kuo Fey
口試委員:
學位類別: 碩士
Master
系所名稱: 工學院 - 化學工程與材料工程學系
Department of Chemical & Materials Engineering
畢業學年度: 97
語文別: 中文
論文頁數: 103
中文關鍵詞: 鋰離子電池磷酸亞鐵鋰碳熱還原法碳塗佈陰極材料
外文關鍵詞: cathode materials, carbon coating, LiFePO4, carbonthermal reduction method, Li-ion battery
相關次數: 點閱:10下載:0
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  • 磷酸亞鐵鋰具有低成本、低汙染、良好熱穩定性與長循環壽命等優點,因此成為近年來熱門研究的鋰離子電池陰極材料。然而,其也有電子導電度低、離子擴散速率低與量產不易等缺點,使其電池性能受到限制。為了克服以上的缺點,許多學者提出各種方法,諸如掺雜金屬、表面塗佈與控制粒徑等,這些方法雖能有效地解決磷酸亞鐵鋰的缺點,卻使生產成本提高,降低其商業價值。為了降低成本,本論文以簡易的碳熱還原法配合工業級碳源合成磷酸亞鐵鋰,起始物全面改用工業級原料,鐵源更使用便宜之氧化鐵。
    從實驗結果得知,球磨液添加量有最小限制量,本製程以煆燒溫度973 K,煆燒時間8小時所合成出的LiFePO4具有優良的導電度 (4.42×10-4 S cm-1),對於磷酸亞鐵鋰/C複合材料,吾人亦利用XRD、SEM、TEM、EDS、DSC、CV與拉曼光譜等鑑定,以進一步了解吾人所製備材料的特性。電池性能方面,吾人所製備的材料於0.2 C充放電率,4.0 V/2.8 V 充放電電壓條件下,初始電容量為150 mAh g-1,經過50次充放電循環後,電池放電電容量幾乎沒有衰退。


    Olivine-structured lithium iron phosphates (LiFePO4) become a promising cathode material because of its low cost, low toxicity, remarkable thermal stability and long operation life. However, it was hard to scale up and reported that this cathode has very low electronic conductivity and diffusion-controlled kinetics. To overcome the problems, various methods have been widely used such as lattice metal doping, surface carbon coating and optimizing the particle size. In order to cut down the synthesis cost, simplify the synthesis technology and enhance the specific capacity of the material, we introduced a carbothermal reduction (CTR) method based on the presence of PEG to synthesize well-carbon-network LiFePO4 by using industrial raw materials and chose ferric oxide as staring material.
    From our results, a required amount of acetone was added to the starting materials for the ball milling process and the precursor was sintered at 700 ℃ for 8 h to form crystalline phase LiFePO4 with greater electronic conductivity (4.42×10-4 S cm-1). The structure and morphology of the carbon coated LiFePO4 samples have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and differential scanning calorimetry (DSC), cyclic voltammetry (CV), and raman spectroscopy, and so on.. Electrochemical measurements show that the LiFePO4/C composite cathode delivered an initial discharge of 150 mAh g-1 at a 0.2 C-rate between 4.0-2.8 V, and almost no capacity loss was observed up to 50 cycles

    中文摘要…………………………………………………………………………………I 英文摘要…………………………………………………………………………………II 致謝………………………………………………………………………………………III 目錄………………………………………………………………………………………IV 圖目錄……………………………………………………………………………………VII 表目錄……………………………………………………………………………………XII 第一章緒論………………………………………………………………………………1 1-1前言………………………………………………………………………………… 1 1-2鋰離子電池陰極材料發展與簡介………………………………………………… 2 1-3研究目的及架構…………………………………………………………………… 6 第二章文獻回顧…………………………………………………………………………8 2-1磷酸亞鐵鋰(LiFePO4)應用於鋰離子電池………………………………………8 2-2磷酸亞鐵鋰的結構……………………………………………………………… 9 2-3磷酸亞鐵鋰的充放電模型……………………………………………………… 11 2-4磷酸亞鐵鋰的合成方法………………………………………………………… 14 2-4-1高溫固態法……………………………………………………………………14 2-4-2碳熱還原法……………………………………………………………………14 2-4-3溶膠凝膠法……………………………………………………………………15 2-4-4水熱法…………………………………………………………………………15 2-4-5噴霧熱裂解法…………………………………………………………………16 2-4-6機械合金法……………………………………………………………………16 2-4-7共沉澱法………………………………………………………………………17 2-4-8微波法…………………………………………………………………………17 2-4-9其它方法………………………………………………………………………17 2-5磷酸亞鐵鋰的改質…………………………………………………………………18 2-5-1添加高導電性塗佈層…………………………………………………………18 2-5-2添加焦磷酸鋰塗佈層…………………………………………………………28 2-5-3掺雜不同金屬改質……………………………………………………………31 2-5-4改變LiFePO4粒徑大小……………………………………………………… 35 2-6以高分子化合物改質磷酸亞鐵鋰………………………………………………… 39 第三章實驗方法…………………………………………………………………………51 3-1實驗儀器設備………………………………………………………………………51 3-2實驗藥品……………………………………………………………………………52 3-3實驗步驟……………………………………………………………………………52 3-4材料鑑定分析………………………………………………………………………54 3-4-1X光繞射(X-ray Diffraction, XRD)分析……………………………………… 54 3-4-2動態光散射 (Dynamic Light Scattering, DLS)量測……………………………54 3-4-3掃描式電子顯微鏡 (Scanning Electron Microscope, SEM)觀測…………55 3-4-4高解析穿透式電子顯微鏡……………………………………………………55 3-4-5拉曼光譜(Raman Spectroscopy)鑑定……………………………………55 3-4-6微分掃描熱卡儀(Differential Scanning Calorimeter, DSC)檢測…56 3-4-7總有機碳(Total Organic Carbon, TOC)量測………………………………… 56 3-4-8導電度(Four-Point probe)測試…………………………………………56 3-5材料電化學特性分析………………………………………………………………58 3-5-1電池性能測試…………………………………………………………………58 3-5-2慢速循環伏安分析(Slow scan cyclic voltammetry)……………………61 第四章結果與討論………………………………………………………………………63 4-1製程評估……………………………………………………………………………63 4-1-1以試藥級起始物合成磷酸亞鐵鋰/碳複合材料…………………………….63 4-1-2以工業級起始物合成磷酸亞鐵鋰/碳複合材料可行性評估……………… 65 4-1-3以攪拌取代球磨的方式合成磷酸亞鐵鋰/碳複合陰極材料……………… 68 4-1-4以不同的球磨液合成磷酸亞鐵鋰/碳複合陰極材料……………………… 68 4-1-5以工業級碳源A合成磷酸亞鐵鋰/碳複合陰極材料…………………………71 4-1-6減少球磨液丙酮添加量以合成磷酸亞鐵鋰/碳…………………………… 72 4-1-7球磨時間對磷酸亞鐵鋰/碳之影響………………………………………… 73 4-1-8煆燒溫度對LiFePO4/C 電池性能影響………………………………………74 4-1-9煆燒時間對LiFePO4/C 電池性能影響………………………………………75 4.2 LiFePO4/C鑑定分析……………………………………………………………… 76 4-2-1 X光繞射結構分析……………………………………………………………76 4-2-2掃描電子顯微鏡 (SEM) 與動態光散射 (DLS)鑑定……………………… 79 4-2-3穿透式電子顯微鏡分析………………………………………………………81 4-2-4微分掃描熱卡儀分析…………………………………………………………83 4-2-5慢速循環伏安測試……………………………………………………………85 4-2-6拉曼光譜鑑定…………………………………………………………………86 4-2-7碳含量、導電度測定…………………………………………………………87 4-2-8 電池性能-長循環測試………………………………………………………… 91 4-2-9 電池性能-特徵曲線測試……………………………………………………… 92 4-2-10 LiFePO4/C放大量可行性測試…………………………………………………93 第五章結論………………………………………………………………………………96 第六章參考文獻…………………………………………………………………………97

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