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Graduate School of Ajou University Department of Energy Systems 3. Theses(Master)

Synthesis and Characterization of Nanocrystalline Olivine-Structured LiFePO4 and LiMnPO4 Cathodes for Lithium Ion Batteries

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dc.contributor.advisor모선일-
dc.contributor.authorDINH HUNG CUONG-
dc.date.accessioned2018-11-08T08:21:20Z-
dc.date.available2018-11-08T08:21:20Z-
dc.date.issued2014-02-
dc.identifier.other16315-
dc.identifier.urihttps://dspace.ajou.ac.kr/handle/2018.oak/12983-
dc.description학위논문(박사)--아주대학교 일반대학원 :에너지시스템학과,2014. 2-
dc.description.tableofcontentsAcknowlegements i Abstract iii Contents vi List of Figures x Chapter 1 Introduction 1.1 Back ground 1 1.1.1. Li-ion Batteries (LIBs) 1 1.1.2. Working principles of LIBs 7 1.1.3 Type of Cathodes Material 12 1.1.3.1 Layered compounds 14 1.1.3.2 Spinel compounds 17 1.1.3.3 Borate compounds 18 1.1.3.4 Tavorite compounds 21 1.1.3.5 Silicate compounds 21 1.1.3.6 Olivine compounds 24 1.2 Olivine Cathode 26 1.2.1 Structure and Li+ ion migration 26 1.2.2 Advance of Olivine Family 30 1.3 Different synthesis route prepare Olivine compounds 33 1.3.1 Sol-gel method 33 1.3.2 Solid State reaction 36 1.3.3 Hydrothermal method 37 1.4 Influent of additive on direction growth 38 1.4.1 Nonionic surfactant P123 40 1.4.2 Cationic surfactant CTAB 40 1.4.3 Anionic surfactant DBSA 41 1.4.4 Organic additive CA (Citric Acid) 41 1.5 Conductive materials coating on surface of olivine compounds 42 1.5.1 Conducting polymers 42 1.5.2 Carbon 45 1.6 Motivation and goals for this study 46 Chapter 2 Synthesis and Characterization of Nanocrystalline Oilivine-Structure LiFePO4 52 2.1 Introduction 52 2.2 Experimental 55 2.2.1 Synthesis of various morphologies LiFePO4 55 2.2.2 Measurement 57 2.3 Results and Discussion 61 2.3.1 Structure and morphology 61 2.3.1.1 Individual nano-sized and hierarchical architectures via a self-assembly process LiFePO4 62 2.3.1.2 Individual LiFePO4 plate shape grow via [010] direction in the plate plane 67 2.3.2 Characteristic of conductive materials (Polymers or carbon) coating on LiFePO4 surface 73 2.3.2.1 SEM and TEM analysis 73 2.3.2.2 XRD analysis 75 2.3.2.3 FTIR analysis 75 2.3.3 Electrochemical properties of LiFePO4 79 2.3.3.1 CV test 79 2.3.3.2 Performance of various morphologies LiFePO4 81 2.3.3.3 Performance of LiFePO4 plate in [010] direction 89 2.3.3.4 Impedance and Li+ diffusion of LiFePO4 91 2.4 Enhance of this study for application 100 2.5 Conclusion 107 Chapter 3 Synthesis and Characterization of Nanocrystalline Olivine-Structure LiMnPO4 110 3.1 Introduction 110 3.2 Experimental 113 3.2.1 Synthesis of various morphologies LiMnPO4 113 3.2.2 Measurement 116 3.3 Results and Discussion 118 3.3.1 The structure and morphology 118 3.3.1.1 Various morphologies of LiMnPO4 using surfactants 118 3.3.1.2 Individual LiMnPO4 plate shape grow via [010] and [100] direction in the plate plane 127 3.3.2 LiMnPO4-C coated analysis 131 3.3.2.1 SEM images analysis 131 3.3.2.2 XRD analysis 131 3.3.2.3 TGA analysis 134 3.3.2.4 Raman analysis 134 3.3.2 Electrochemical properties of LiMnPO4 137 3.3.3.1 Battery performance of LiMnPO4 coated with different carbon amount as cathode material 137 3.3.3.2 Battery performance of various morphologies LiMnPO4 138 3.3.3.3 CV test 142 3.3.3.3.1 CV test of various morphologies LiMnPO4 142 3.3.3.3.2 CV test of LiMnPO4-C 10% at 25oC and 55oC 144 3.3.3.4 Battery performance of nano-sized LiMnPO4 plate along {010} and {100} facets 144 3.3.3.5 Battery performance of nano-sized crystalline LiMnPO4 particles 147 3.3.3.6 Impedance and Li+ diffusion of nano-sized crystalline LiMnPO4 particles 153 3.4 Enhance of our LiMnPO4 for application 160 3.5 Conclusion 164 Chapter 4 Conclusions 167 References 173 Curriculum vitae 185-
dc.language.isokor-
dc.publisherThe Graduate School, Ajou University-
dc.rights아주대학교 논문은 저작권에 의해 보호받습니다.-
dc.titleSynthesis and Characterization of Nanocrystalline Olivine-Structured LiFePO4 and LiMnPO4 Cathodes for Lithium Ion Batteries-
dc.typeThesis-
dc.contributor.affiliation아주대학교 일반대학원-
dc.contributor.department일반대학원 에너지시스템학과-
dc.date.awarded2014. 2-
dc.description.degreeMaster-
dc.identifier.localId609680-
dc.identifier.urlhttp://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000016315-
dc.description.alternativeAbstractLiMPO4 family (M=Fe, Mn, Ni & Co) with an ordered olivine structure is considered as the most promising cathode materials for Li+ ion batteries, due to moderate theoretical capacity (~170mAhg-1), low cost of its raw materials, reversibility, thermal stability, environmental friendliness, and an increased level of safety. The limitation in its conductivity is to be overcome for the practical application of LiMPO4 to high rate Li+ batteries. In order to increase the electronic and ionic conductivity, much effort have been made such as optimizing particle size (nano-scale) as well as coating conductive polymer, carbon, metal, or metal oxide on the surface of LiMPO4 particles or doping supper-valance ions in crystalline lattice. In this study, LiMPO4 (M= Mn, Fe, Ni, Co) crystalline particles were synthesized using a hydrothermal method. The particle morphology can be controlled by a careful choice of surfactant, solvents, and reaction parameters in hydrothermal synthesis. The obtained nanosized powder was coated with conductive materials; polymer or carbon. Highly uniform hierarchical-microstructured LiFePO4 particles with dumbbell- and donut-shape and individual LiFePO4 nanocrystals were prepared by a hydrothermal method utilizing citric acid or a triblock copolymer (Pluronic P123) as a surfactant. The cathode composed of the individual nanocrystalline LiFePO4 particles exhibited higher specific capacity than the cathodes composed of the hierarchically assembled microparticles. Coating a conductive polymer, poly-3,4-ethylenedioxythiophene (PEDOT), on the surface of LiFePO4 particles improved the battery performances such as large specific capacities, high rate capability and an improved cycle stability. The nanocrystalline LiFePO4 particles coated with PEDOT (20wt%) exhibited the highest discharge capacities of 175 and 136mAhg−1 for the first battery cycle and 163 and 128 mAhg−1 after 1000 battery cycles, with a degradation rate of 6–7%, at the rates of 1 and 10 C, respectively. Nanocrystalline LiMnPO4 particles approximately 100 nm in size are synthesized for use as a cathode material using a hydrothermal method. Small charge transfer resistances (Rct) measured using electrochemical impedance spectroscopy (EIS) indicate that the particles are effectively coated with the conductive C layer by pyrolyzing sucrose in an inert atmosphere. The cathode composed of nanocrystalline C-coated LiMnPO4 exhibits the largest specific capacities of 171 mAhg-1 and 153 mAhg-1 for the first cycle and 166 mAhg-1 and 146 mAhg-1 after 110 battery cycles at a rate of 0.05 C at 55oC and 25oC, respectively, with a degradation rate of 4 ±1% after 110 battery cycles. The specific capacities are 165 mAhg-1 and 142 mAhg-1 for the first cycle at 55oC for the nanoparticles with high crystallinity, even at high discharging current of 0.5 C and 5C, respectively. Diffusion coefficients of Li+ in LiMnPO4 (the fully discharged state) and in MnPO4 (the fully charged state) are estimated to be 3.58x10-16 and 4.99x10-17 Cm2s-1, respectively, from EIS in the low frequency region.-
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