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完整後設資料紀錄
DC 欄位 | 值 | 語言 |
---|---|---|
dc.contributor.advisor | 吳乃立(Nae-Lih Wu) | |
dc.contributor.author | Hao-Hsun Chang | en |
dc.contributor.author | 張顥薰 | zh_TW |
dc.date.accessioned | 2021-06-15T00:24:59Z | - |
dc.date.available | 2011-02-10 | |
dc.date.copyright | 2009-02-10 | |
dc.date.issued | 2009 | |
dc.date.submitted | 2009-01-22 | |
dc.identifier.uri | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/41618 | - |
dc.description.abstract | 鋰鐵磷酸鹽為一新一代之鋰離子電池正極材料。它具有環保、高安全性以及低原料成本之優點,更被證實具有高功率充放電的能力。在本論文中,我們首先以非等溫動力學建立起以固相法合成鋰鐵磷酸鹽的方程式,並以此剖析且獲得一套固相快速製程,可在600oC下,兩小時內合成大量產物,且具有140mAh/g之電容量。產物具有高達1.33g/cc之振實密度,與市售粉末相比,本快速製程之產物的體積能量密度提升了至少20%。
其次,本論文利用同步輻射對鋰鐵磷酸鹽在充放電過程中的結構變化進行了臨場X光繞射分析。結果顯示了結構變化延遲的現象,尤其在1C且55oC的條件下,結構變化更延遲至電流停止後才劇烈發生。此延遲現象可在電池連續充放電,中間電流毫不中斷的狀況下消失,顯示充放電策略亦對鋰鐵磷酸鹽之結構變化有所影響。在循環測試中,發生結構延遲且劇烈變化的電池顯示較差之循環壽命。原因為結構連續的劇烈變化產生了晶格缺陷,在缺陷不斷累積的情形下,結構於是崩解。此結果對於鋰鐵磷酸鹽在極高速充放電的應用具有相當程度的衝擊。 另外,鋰鐵磷酸鹽在高溫進行充放電時,會有因由水與電解液反應產生之氫氟酸腐蝕所導致的鐵溶出,此現象不但影響正極本身之循環壽命,也因為鐵離子穿越電解液而在碳負極上沈積,產生了催化電解液分解形成惰性物質批覆在負極上的現象。為了解決此問題,本論文分別以氧化鈦批覆在鋰鐵磷酸鹽顆粒表面,與在碳負極極版上濺鍍一層金屬層的方法來嘗試改善。前者的結果顯示金屬氧化物之批覆的確有效提升正極之循環壽命,但電解液中的氫氟酸轉而腐蝕金屬氧化物層,使鈦同樣沈積在碳負極上。經測試,鈦金屬催化電解液分解之能力更遠勝於鐵金屬。在眾多文獻中,許多團隊嘗試以類似的方法來解決鋰錳氧化物或鋰鈷氧化物的金屬溶出問題,但皆未測試全電池之效能。此實驗結果顯示所有以金屬氧化物批覆為對策之實驗皆應不可忽略在碳負極上所發生之效應。在碳負極極版上濺鍍金屬層的實驗結果中,以金或銅所形成之金屬層證實具有「過濾」由正極溶出之鐵離子的功能。由於鐵金屬被收集在金屬層之上,並未直接沈積於碳顆粒表面,於是阻止了導致電解液大量分解的催化反應。 | zh_TW |
dc.description.abstract | Lithium iron phosphate (LiFePO4) is a new-generation cathode material for lithium ion batteries. It has the characteristics of environmental benignity, high safety, and low cost, and is proven to have the ability for high-power applications. In this dissertation, the analysis based on a non-isothermal methodology was conducted to establish a model for the synthesis of LiFePO4 via solid-state reaction, thus a rapid synthetic route was acquired which was able to produce a batch of powders at 600oC in merely two hours. The product has the capacity of ~140 mAh/g and the tap density of 1.33 g/cc. Compared with the commercial powders, the volumetric energy density of our product is at least 20% higher.
Moreover, the structural transformation of LiFePO4 during charge/discharge was monitored by using synchrotron X-ray diffraction. The results revealed serious delay of structural change, especially at 1C at 55oC, the phase changed abruptly when current stopped. The structural transformation became “normal” while no rest period was between every charge and discharge process, indicating the effect of charge/discharge protocols on the structural change. In the prolonged cycle test, the cell experienced abruptly structural change every cycle showed higher fading rate after a certain cycle. The reason was the abruptly structural change inducing the defects which, after accumulation along cycling, caused structural collapse. These results impact the applications of LiFePO4 at very high rates. A vital problem of LiFePO4 cycling at high temperatures is the dissolution of Fe ions which is induced by HF in the electrolyte. The dissolution not only influences the cycle life of positive electrode itself, but also the carbon negative electrode due to the migration of Fe ions through electrolyte and consequently depositing on the surface of carbon particles. The deposited Fe would catalyze the decomposition reaction of electrolyte and cause a thick passivated layer on the carbon electrode, thus reduce the cycle performance of LiFePO4/C full cells. Two methods in this dissertation were proposed to solve this problem. TiO2 coating on LiFePO4 particles was tried to prevent the direct contact between LiFePO4 particles and HF. The results showed that the cycle performance was indeed enhanced in the case of TiO2-LiFePO4/Li half cell, but not of TiO2-LiFePO4/C full cell. It was revealed that the TiO2 layer was alternatively corroded and the dissolved Ti ions also deposited on the carbon electrode. The canalysis ability of Ti was found even stronger than Fe. This problem has never revealed in the literatures trying to coat metal oxides on LiMn2O4 or LiCoO2 for the same reason in that they didn’t look into the performance of full cells. In the other modification, a metal layer was sputtered on the carbon electrode. It was discovered that the Fe ions which diffused from the positive electrode were almost all collected on the top of metal “sieving” layer. The catalytic reaction of the decomposition of electrolyte was prevented because Fe ions were not directly deposited on the surface of carbon particles. | en |
dc.description.provenance | Made available in DSpace on 2021-06-15T00:24:59Z (GMT). No. of bitstreams: 1 ntu-98-D93524001-1.pdf: 9781609 bytes, checksum: 74c91e4e8223fe1e590fad865f319253 (MD5) Previous issue date: 2009 | en |
dc.description.tableofcontents | 摘要……… I
Abstract…… III Table of Contents V List of Figures VIII List of Tables XIX Chapter 1. Introduction and Background 1 Chapter 2 Theory and Literature Review 7 2-1 Introduction to Li-ion Batteries 7 2-2 Introductions to Cathode Materials for Lithium-Ion Batteries 13 2-3 LiFePO4 Cathode Material for Lithium Ion Batteries 19 2-3.1 Basic Features of Lithium Iron Phosphate 19 2-3.2 Synthesis of Lithium Iron Phosphate 23 2-3.3 Modifications of Lithium Iron Phosphate Powders 31 2-3.4 Phase change and Li+ migration of LiFePO4 during cycling 38 2-4 Introduction to Anode Materials for Lithium-Ion Batteries 48 2-5 Surface Modification on Cathode Materials 63 2-6 Experimental Technique: X-ray Absorption Spectroscopy 69 Chapter 3 Experimental 76 3-1 Chemicals 76 3-2 Synthesis of Lithium Iron Phosphate 79 3-2.1 Synthesis of Carbon-Coated Lithium Iron Phosphate 79 3-2.2 TiO2 Coating on Carbon Coated LiFePO4 via Sol-Gel Process 83 3-3 Analyses and Characterizations 85 3-3.1 Phase Identification 85 3-3.2 In-situ X-ray Diffraction 87 3-3.3 Morphology Observation 89 3-3.4 Surface Area Analysis 90 3-3.5 Determination of Carbon Content 91 3-3.6 Surface Analysis 92 3-4 Electrochemical Characterizations 93 3-4.1 Cell-Fabricating Process 93 3-4.2 Metal Thin Film Deposition on Electrodes by Sputtering 96 3-4.3 Charge/Discharge Test, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy 96 Chapter 4. Synthesis and Non-isothermal Kinetic Analysis of LiFePO4 via Solid State Reaction 97 4-1 Introduction 97 4-2 Kinetic Analysis 100 4-3 Gas-phase Diffusion-limitation 110 4-4 LiFePO4 Powder Made by Packed-bed Method 112 4-5 Summary 120 Chapter 5. Structural Transformation during Charge/Discharge of LiFePO4 121 5-1 Introduction 121 5-2 Investigation of Structural Transformation during Charge/Discharge of LiFePO4 by In-situ XRD 123 5-3 The Effects of Protocols on Electrochemical Performance at High Rates at 55oC 133 5-4 Summary 148 Chapter 6. Enhancement of Cycle Life of LiFePO4-based Li-ion Batteries at 55oC 150 6-1 Introduction 150 6-2 Effects of TiO2 Coating on High- Temperature Cycle Performance of LiFePO4-based Lithium-ion Batteries 152 6-3 Enhanced High-Temperature Cycle Performance of LiFePO4/Carbon Batteries by an Ion-Seiving Metal Coating on MCMB Anode 169 6-4 Summary 179 Chapter 7 Conclusions 180 References 183 | |
dc.language.iso | en | |
dc.title | 鋰離子電池鋰鐵磷酸鹽正極之高速充放電研究 | zh_TW |
dc.title | Study on High-rate Charge/Discharge of LiFePO4 Cathode Material for Lithium-Ion Batteries | en |
dc.type | Thesis | |
dc.date.schoolyear | 97-1 | |
dc.description.degree | 博士 | |
dc.contributor.oralexamcommittee | 何國川,徐振哲,楊模樺,吳弘俊,黃炳照,吳溪煌 | |
dc.subject.keyword | 鋰離子電池,鋰鐵磷酸鹽,動力學,結構變化,批覆, | zh_TW |
dc.subject.keyword | Li-ion battery,LiFePO4,Kinetics,Structural transformation,Coating, | en |
dc.relation.page | 213 | |
dc.rights.note | 有償授權 | |
dc.date.accepted | 2009-01-23 | |
dc.contributor.author-college | 工學院 | zh_TW |
dc.contributor.author-dept | 化學工程學研究所 | zh_TW |
顯示於系所單位: | 化學工程學系 |
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