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Multiscale Design of Na(Li1/3Mn2/3)O2 Cathode Material Operated by Anionic Redox Reactions for Sodium-Ion Batteries : 소듐 이온 전지에서 음이온 산화 환원 반응에 의해 작동되는 Na(Li1/3Mn2/3)O2 양극재의 멀티스케일 설계

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dc.contributor.advisor조맹효-
dc.contributor.author김두호-
dc.date.accessioned2018-05-28T16:08:27Z-
dc.date.available2018-05-28T16:08:27Z-
dc.date.issued2018-02-
dc.identifier.other000000150542-
dc.identifier.urihttps://hdl.handle.net/10371/140565-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 조맹효.-
dc.description.abstractTo discover new high-energy-density cathode materials for sodium-ion batteries (SIBs), multiscale design is highly considered to be an essential manner because cathode materials occur in complicated physical and chemical reactions from atomic scale to macro scale. Considering the intrinsically larger ionic radius of Na+ than that of Li+, cathode materials for SIBs are operated by electrochemical reactions accompanied by severe structural changes and phase transformations in comparison to those for lithium-ion batteries (LIBs) owing to insertion and extraction of Na+, which leads to cyclic degradation during charge/discharge. That is, the Na-migration affect qualitative and quantitative variations of cathode materials in atomic scale, which are the results of electrochemical performance for the overall system. In addition, the intrinsically lower redox window (by ≈0.3 V) of the cathode for SIBs compared to the LIBs result in low-energy-density properties. Therefore, multiscale-based analysis and design approach in light of the two intrinsic features of Na+ are critical for the rational design of cathode materials for SIBs.
Using the multiscale-based framework from first-principles calculations including thermodynamic mixing enthalpies associated with phase stabilities, kinetic properties, mechanical constants, chemomechanical strain, and qualitative and quantitative electronic structures in the perspective of atomic scale not only to phase separation kinetic simulations consisting of homogeneous chemical potentials originating from homogeneous free energy coupled with the thermodynamic values of atomic calculations, but also to chemomechanical stress obtained by the fitted mechanical constants and chemomechanical strain using polynomial functions, we rationally design and experimentally realize Na(Li1/3Mn2/3)O2 as a high-energy-density cathode material (≈4.2 V versus Na/Na+ with a high charge capacity of 190 mAh g-1) operated by the new reaction paradigm (anionic redox: O2-/O-) beyond the conventional reaction mechanism (cationic redox: Mn+/M(n+1)+, M: transition metals) for sodium-ion batteries (SIBs), which is fundamentally inspired by in-depth understandings of Li2MnO3 redox reactions for LIBs. Furthermore, this rationally designed Na(Li1/3Mn2/3)O2 is an example of a new class of promising cathode materials, Na(Li1/3M2/3)O2 (M: transition metals featuring stabilized M4+), for further advances in SIBs.
To overcome the drawbacks of phase change and separation, and structural collapse related to cyclic performance in the newly discovered Na(Li1/3Mn2/3)O2 material, we further design high-energy-density cathode, Na(Li1/3Mn1/2Cr1/6)O2, utilizing the Cr 3d-electron and labile O 2p-electron for electrochemical reactions with reduced phase change, slow phase separation kinetics, and lower chemomechanical strain and stress compared to those of Na(Li1/3Mn2/3)O2. Additionally, to provide rational insights into the use of anionic redox reactions for future sodium-ion batteries, Na(Li1/3Mn1/2Cr1/6)O2 is regarded as an exciting example of superior Na(Li1/3M2/3(1-y)Mcy)O2 analogues (M and Mc: transition metals with stabilized M4+ species and with cationic redox active Mc4+ species) with good cyclic performance.
The rationally designed and experimentally validated cathode materials by the multiscale-based design approach open an exciting direction to break the energy density limit of cathode materials for SIBs. Furthermore, the present multiscale-based design approach could be applied to various energy-related systems such as batteries, capacitors, fuel cells, solar cells, and even catalyst in order to improve their performance and rationally design new materials.
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dc.description.tableofcontentsChapter 1 Introduction 1
1.1 Electrodes for Batteries 1
1.2 Issues and Challenges for Sodium-Ion Batteries 2
1.3 Mutiscale-based Analysis and Design 3
1.4 Objectives and contributions 5

Chapter 2 Multiscale Design and Realization of Na(Li1/3Mn2/3)O2 9
2.1 Theoretical Design of Na(Li1/3Mn2/3)O2 9
2.2 Experimental Validation 13
2.3 Reaction Mechanism 14
2.4 Establishing New Material Analogues 17
2.5 Challenges of Na(Li1/3Mn2/3)O2 18
2.6 Multiscale Phase Field Simulation: Phase Separation 19

Chapter 3 Multiscale Design and Realization of Na(Li1/3Mn1/2Cr1/6)O2 42
3.1 Theoretical Design of Na(Li1/3Mn1/2Cr1/6)O2 42
3.2 Electrochemical Enhancement 43
3.3 Thermodynamic Enhancement 43
3.4 Multiscale Phase Field Simulation: Phase Separation 45
3.5 Chemomechanical Strain Enhancement 46
3.6 Chemomechanical Stress Enhancement: Volumetric Stress 47
3.7 Multiscale Phase Field Simulation: Phase Separation Coupled Volumetric
Stress 48
3.8 Chemomechanical Stress Enhancement: Normal Stresses 49
3.9 Multiscale Phase Field Simulation: Phase Separation Coupled Normal
Stresses 50
3.10 Atomic Structure Enhancement 51
3.11 Cation-Anion-Coupled Redox Mechanism 52
3.12 Developing the Material Analogues 54

Chapter 4 Methodologies for Multiscale Design 83
4.1 Atomistic Approaches 83
4.1.1 Density Functional Theory 83
4.1.2 Thermodynamics and Kinetics 84
4.1.3 Electrochemistry 110
4.1.4 Crystal and Ligand Field Approaches 87
4.2 Multiscale Approaches 88
4.2.1 Homogeneous Chemomechanical Stress 88
4.2.2 Homogeneous Bulk Free Energy and Chemical Potential 89
4.2.3 Phase Separation Kinetic Simulations 91
4.3 Experimental Details 92
4.3.1 Material Synthesis 92
4.3.2 Material Characterizations 92
4.3.3 Electrochemical Measurements 93

Chapter 5 Conclusions 96

Appendix 100
Appendix A: Design of Nickel-rich Layered Oxides Using d Electronic Donor for Redox Reactions 100

Appendix B: Understanding of Surface Redox Behaviors of Li2MnO3 in Li-Ion Batteries: First-Principles Prediction and Experimental Validation 116

Appendix C: Phase Separation and d Electronic Orbitals on Cyclic Degradation in Li-Mn-O Compounds: First-Principles Multiscale Modeling and Experimental Observations 135

Appendix D: Hexacyanometallates for Sodium-Ion Batteries: Insights into Higher Redox Potentials Using d Electronic Spin Configurations 150
Bibliography 167
국문요약 182
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dc.formatapplication/pdf-
dc.format.extent10143442 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectMultiscale Design-
dc.subjectFirst-principles Calculations-
dc.subjectPhase Separation Kinetics-
dc.subjectSodium-ion Batteries-
dc.subjectChemomechanics-
dc.subject.ddc621-
dc.titleMultiscale Design of Na(Li1/3Mn2/3)O2 Cathode Material Operated by Anionic Redox Reactions for Sodium-Ion Batteries-
dc.title.alternative소듐 이온 전지에서 음이온 산화 환원 반응에 의해 작동되는 Na(Li1/3Mn2/3)O2 양극재의 멀티스케일 설계-
dc.typeThesis-
dc.contributor.AlternativeAuthorDuho Kim-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 기계항공공학부-
dc.date.awarded2018-02-
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