吳乃立臺灣大學：化學工程學研究所林永茂Lin, Yong-MaoYong-MaoLin2007-11-262018-06-282007-11-262018-06-282004http://ntur.lib.ntu.edu.tw//handle/246246/52319本實驗分別以溶膠凝膠法(sol-gel)和流體化床輔助化學氣相沉積(fluidized-bed chemical vapor deposition)的方式，批覆氧化鋯(ZrO2)於鋰錳氧(LiMn2O4)表面，並且以此材料為鋰離子二次電池的正極材料進行分析。經由X光繞射圖譜顯示出批覆於鋰錳氧表面的氧化鋯是非晶體(amorphous)的結構。掃瞄式電子顯微鏡以及穿透式電子顯微鏡的結果顯示出經由上述方法，氧化鋯均勻的批覆於鋰錳氧的表面。相對於未做任何表面處理的鋰錳氧，以氧化鋯批覆鋰錳氧電極所組成的電池不論在室溫或是高溫(55℃)下的充放電性能皆有明顯的改善。實驗結果顯示批覆於鋰錳氧表面的氧化鋯可以有效的抑制Jahn-Teller distortion，使得鋰錳氧結構在充放電過程中更加穩定，因此可以有效的延長其循環壽命。Two synthetic routes including sol-gel process and fluidized-bed chemical vapor deposition (FBCVD) process were introduced to the preparation of ZrO2-coated LiMn2O4 as cathode materials for lithium ion secondary batteries. X-ray diffraction (XRD) spectra from the ZrO2-coated LiMn2O4 indicated that ZrO2 exist as amorphous phase. The morphology of ZrO2-coated samples were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), which revealed that the zirconium oxide attached smoothly onto the surface of LiMn2O4. The surface-modified LiMn2O4 samples showed much better capacity retention than the unmodified LiMn2O4 cathode at both room temperature and 55℃. The improved cycle life performance could be due to a suppression of the Jahn-Teller distortion which took place at low voltage during cycling.摘要 I Abstract II Table of Contents III List of Figures V Preface 1 Chapter 1. Introduction and Background 3 1.1 Introduction to Lithium Secondary Batteries 3 1.1-1 The Development of Lithium Secondary Batteries 3 1.1-2 Composition and Intercalation Mechanism of Li-ion Batteries 7 1.2 Introduction to Lithium Manganese Spinel: LiMn2O4 11 1.2-1 LiMn2O4 as a Cathode for Li-ion Batteries 11 1.2-2 Capacity Fading Mechanism: Jahn-Teller Distortion 16 1.2-3 Capacity Fading Mechanism: Manganese Dissolution 18 1.3 Surface Modification of Cathode Materials 19 1.4 Sol-Gel Process 21 1.5 Chemical Vapor Deposition (CVD) Process 23 1.6 Electrochemical Impedance Spectroscopy 24 Chapter 2. Experimental 28 2.1 Electrode Preparation 28 2.1-1 Sol-Gel coating of ZrO2 on LiMn2O4 28 2.1-2 Fluidized Bed Chemical Vapor Deposition of ZrO2 on LiMn2O4 31 2.1-3 Cell Fabricating Process 33 2.2 Analysis 35 2.2-1 Structure and morphology Analysis 35 2.2-2 Electrochemical measurements 36 Chapter 3. Result and Discussion 37 3.1 Physical and Structural Characterization 37 3.1-1 Structural Characterization of ZrO2-coated LiMn2O4 37 3.1-2 Surface Morphology of ZrO2-coated LiMn2O4 40 3.2 Electrochemical Performance 45 3.2-1 Cycling Behavior of Uncoated-LiMn2O4 at room temperature 45 3.2-2 Cycling Behavior of ZrO2 coated-LiMn2O4 at room temperature 51 3.2-3 Cycling Behavior of Uncoated-LiMn2O4 at 55℃ 61 3.2-4 Cycling Behavior of ZrO2 coated-LiMn2O4 at 55℃ 64 3.2-5 Cycle test of cells with deep discharging 71 3.2-6 Physical mixing of LiMn2O4 with ZrO2 as cathode material 75 3.2-7 Electrochemical impedance spectroscopic studies 77 Chapter 4. Conclusion 82 References 832308119 bytesapplication/pdfen-US鋰離子二次電池表面改質氧化鋯zirconiaLi-ion batterysurface modificationthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/52319/1/ntu-93-R91524031-1.pdf