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Fabrication of All-Solid-State Li-Battery using superionic Li ion conducting LiTa2PO8 Electrolyte

초록/요약

The development of high-performance all-solid-state batteries (ASSLBs) is crucial for advancing energy storage technologies. Among various solid electrolytes, the oxide-type LiTa2PO8 has recently attracted considerable attention due to its excellent air stability and high lithium-ion conductivity, reaching up to 10-4 Scm-1 at room temperature (25°C). These characteristics make LiTa2PO8 a strong candidate for application in ASSLB systems. Nonetheless, practical implementation is still limited by issues such as high interfacial resistance and chemical instability with lithium metal anodes. This thesis investigates the polymorphism, enhancement strategies, and practical application of LiTa2PO8 solid electrolytes for ASSLBs. Initially, the bond valence summation method is employed to predict new solid electrolytes, leading to the selection of LiTa2PO8. To enhance its ionic conductivity, LiPO3 is introduced as a sintering additive. The critical current density necessary for electrochemical testing is then determined. Finally, the optimized solid electrolyte, a combination of LiTa2PO₈ and LiPO3, is utilized in the fabrication of an all-solid-state battery system with an NCM811 cathode material. The performance of this system is evaluated, revealing significant improvements and providing a strong foundation for future research. Keywords: All-solid-state battery, Oxide-type solid electrolyte, Li-ion conductor, LiTa2PO8, Sintering additive

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목차

ABSTRACT i
LIST OF FIGURES vii
LIST OF TABLES xi
Chapter 1. General introduction. 1
1.1. Context and Motivation: Global energy transition, Electric Mobility, and the imperative
for advances Batteries. 1
1.2. Limitations of Conventional Lithium-Ion Technology and the Advent of Solid-State
Systems 2
1.3. Ideal Properties and Leading Candidates for Solid Electrolytes in EVs Applications 4
1.4. Key Impediments to the Commercialization of All-Solid-State Batteries 6
1.5. Introduction to LiTa2PO8 (LTPO): A novel Promising Solid Electrolyte. 7
1.6. Problem Statement and Research Gap 8
1.7. Research scope and objectives 9
1.8. Scope and Significance of the Research. 10
1.9. Dissertation outline 10
1.10. References 13
Chapter 2. Significance, Challenges, and Probing Strategies of All-Solid-State
Batteries. 15
2.1. Introduction 15
2.2. LiTa₂PO₈ (LTPO): A novel Li+ ionic conductor. 17
2.2.1. Discovery and Classification 17
2.2.2. Crystal Structure of LiTa2PO 817
2.2.3. Intrinsic Physicochemical Properties 21
2.3. Significance of LiTa2PO8 in the Context of Solid Electrolytes 23
2.4. Key Challenges in the Development and Application of LiTa2PO8 24
2.4.1. Synthesis, Processing, and Microstructural Control 24
2.4.2. Limitations in Achievable Ionic Conductivity 25
2.4.3. Interfacial Challenges with Electrodes (Especially Lithium Metal Anode) 25
2.4.4. Mechanical Properties and Processability into Thin, Defect-Free Films 26
2.5. Understanding Ion Transport in Solid Electrolytes: The Bond Valence Energy Landscape
(BVEL) Approach and its Application to 3D Framework Conductors 26
2.5.1. Rationale: Predicting and Understanding Ion Mobility in selected solid electrolyte 26
2.5.2. Basic Principles of Bond Valence Energy Landscape (BVEL) Calculation 27
2.5.3. Comparative BVEL Analysis of Known Li-ion Conductors (with 3D framework) 27
2.5.4. Classification of Ionic Conductors 39
2.5.5. Application and Potential of BVEL for LiTa2PO8 41
2.6. Approaches for Studying Non-Lithium Polymorphs 42
2.7. Summary, Identified Research Gaps, and Transition to Current Dissertation Work. 43
2.8. References. 46
Chapter 3. Ion-exchange reactions on LiTa2PO8 to synthesis of new compounds,
HTa2PO8 and NaTa2PO8. 49
3.1. Introduction 49
3.1.1. Benefits of Polymorphs 50
3.1.2. Proton Polymorphs. 51
3.1.3. Sodium Polymorphs 52
3.2. Experimental section 54
3.2.1. Preliminary test for the stability of LiTa2PO8 in acidic aqueous solutions 54
3.2.2. Synthesis of HTa2PO8/DTa2PO8, and TG, and elemental analysis: 55
3.2.3. Synthesis of NaTa2PO8 55
3.2.4. Characterizations 56
3.2.5. Diffraction data collection and structure determination 56
3.2.6. Solid-state 1H NMR 57
3.2.7. Conductivity measurements 57
3.3. Results and discussions 58
3.3.1. Structure of H(D)Ta2PO8 and NaTa2PO8 58
3.3.2. Thermal stability and ion conductivity of HTa2PO 864
3.3.3. Chemical/Thermal stabilities and ion conductivity of LT-NaTa2PO8 68
3.4. Conclusion 79
3.5. References. 81
Chapter 4. Enhancing the ionic conductivity of LiTa2PO8 (LTPO) using sintering
additive of LiPO3. 85
4.1. Introduction 85
4.2. Strategies for Enhancing Solid Electrolyte Performance 86
4.3. Literature Review on LTPO ionic conductivity and densification Optimization 87
4.3.1. Additive Strategy in LTPO 89
4.3.2. Doping Strategy (Aliovalent Substitution) in LTPO. 89
4.3.3. Precursor Strategy in LTPO. 90
4.3.4. Sintering Method Strategy in LTPO. 90
4.4. Rationale and Objectives 91
4.5. Experimental section 93
4.5.1. Synthesis 93
4.5.2. X-ray diffraction 95
4.5.3. Relative density calculation 96
4.5.4. Pellets preparation 96
4.5.5. Scanning electron microscopy (SEM) 96
4.5.6. Spectroscopy impedance 96
4.6. Results and discussions 97
4.6.1. Sintering additive ratio optimization 97
4.6.2. Sintering Temperature optimization 100
4.7. Conclusion 105
4.8. References 107
Chapter 5. Investigation of the critical current density (CCD) for the solid electrolyte
LiTa2PO8. 109
5.1. Introduction. 109
5.2. Objective. 112
5.3. Experimental section. 112
5.3.1. Synthesis. 112
5.3.2. Characterization 113
5.4. Results and discussions 117
5.4.1. Materials characterization 117
5.5. Conclusion 126
5.6. References 128
Chapter 6. Fabrication of All-Solid-State Lithium-ion Batteries with LiTa2PO 8
electrolyte and high-voltage NCM811 Cathode. 131
6.1. Introduction. 131
6.2. Literatures Reviews. 132
6.3. Objectives and Rational 135
6.4. Experimental section. 136
6.4.1. Materials Synthesis and Preparation. 136
6.4.2. Materials Characterization 139
6.4.3. Electrochemical Characterization 141
6.5. Results and discussions. 143
6.5.1. Materials Characterization. 143
6.5.2. Electrochemical Characterization 146
6.6. Conclusion 153
6.7. References 155
Chapter 7. Conclusion and Future Research Directions. 157
7.1. Conclusion 157
7.2 Future Research Directions 159
국문초록 163

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