A New Role of The Oxygen Provider Layer for Boosting SOCs Performance at High-Current Range Operation = 고전류 범위 작동 시 SOC 성능 향상을 위한 산소 공급 계층의 새로운 역할

다국어 초록 (Multilingual Abstract)

Solid oxide electrochemical cells (SOCs) offer high efficiency, fuel flexibility, and compatibility with renewable energy systems; however, their long-term stability under high-current operating conditions remains a critical barrier to commercial deployment. In particular, the cathode/electrolyte interface experiences oxygen starvation in SOFC mode and oxygen overpressure during SOEC operation, leading to nanopore formation, sub-grain reconstruction, and eventual delamination. Conventional gadolinium-doped ceria (GDC) buffer layers partially address interfacial reactions but still suffer from densification challenges, Ce–Zr solid-solution formation, and limited performance at high current.
This dissertation introduces and systematically investigates the concept of an oxygen-provider interlayer, focusing on La-doped ceria (LDC) and its modified compositions as functional interface materials. In Chapter 3, optimized LDC fabricated below 1250 °C demonstrates substantially higher oxygen storage capacitance (OSC) than GDC, achieving a MPD of 2.15 W cm⁻² at 800 °C. Moreover, the high OSC enable to supply oxygen ion continuously under oxygen-starving conditions and obtaining a 59% performance increase in anode-supported cells at 700 °C. Chapter 4 explores Cu- assisted liquid-phase sintering, revealing that 0.25 wt% Cu addition significantly improves LDC densification and OSC, achieving an OSC of ~125 μmol [O₂]/g and a MPD of 2.3 W cm⁻² at 800 °C. In Chapter 5, The grain boundary -engineered segmentation of oxide ion and electronic conduction in LDC that enable triple-charge transport and enhance reversible FC–EC cycling stability. Overall, this work reframes the interlayer from a passive reaction barrier to an active oxygen-management component. By integrating oxygen storage, release, and interfacial stabilization, the oxygen-provider layer represents a promising pathway toward durable, high- performance SOC architectures capable of sustained operation under industrially relevant, high-current conditions.

목차 (Table of Contents)

• Table of Contents i
• List of figures iv
• List of tables x
• Chapter 1. General Introduction 12
• 1.1. Research Background 12
• 1.1.1. Sustainable Environment and Hydrogen Energy 17
• 1.2. Fuel Cells 19
• 1.2.1. Solid Oxide Electrochemical Cells 20
• 1.2.2. Working Principles of SOCs 22
• 1.2.2.1. Nernst Potential and Thermodynamic Efficiency 22
• 1.2.2.2. Oxygen Transport 28
• 1.2.2.3. Electrical Efficiency and Fuel Utilization 28
• 1.2.3. Materials of SOCs 29
• 1.2.3.1. Electrolyte 29
• 1.2.3.2. Fuel Electrode 34
• 1.2.3.3. Oxygen Electrode 35
• 1.3. Advantages and Challenges of SOCs 37
• 1.3.1. Cathode/ Electrolyte Interface Degradation 38
• 1.3.1.1. Mechanical Delamination 38
• 1.3.1.2. Cell Voltage Drop Under Applied Current Conditions 40
• 1.4. Oxygen Provider layer 42
• 1.4.1. Oxygen Storage Capacitance Materials 43
• 1.4.2. Oxygen Ion Flux at the Cathode and Electrolyte 44
• 1.5. Conclusion 45
• Chapter 2. Boosting Electrochemical Performance via Extra‐Role of La‐Doped CeO2‐δ Interlayer for “Oxygen Provider” at High‐Current range SOFC Operation 48
• 2.1. Introduction 48
• 2.2. Experimental Sections 51
• 2.2.1. Preparation of Powder Materials 51
• 2.2.2. Cell Fabrication 51
• 2.2.3. Characterization and their Electrochemical Properties 53
• 2.3. Result and Discussion 54
• 2.3.1. Chemical Compatibility Between Ceria-based Interlayer and YSZ 56
• 2.3.2. Relationship Between Oxygen Partial Pressure and Oxygen ion Capacitance 68
• 2.3.3. Electrochemical Performance at High-current Range 73
• 2.4. Conclusion 81
• Chapter 3. Enhancing Solid Oxide Cells’ Performance under High-Current Operation through Cu Incorporation in “Oxygen Provider” LDC 82
• 3.1. Introduction 82
• 3.2. Experimental Sections 85
• 3.2.1. Cell Preparation 85
• 3.2.2. Characterizations and Electrochemical Measurements 85
• 3.3. Result and Discussion 90
• 3.3.1. Solubility of Metal Additives in LDC 90
• 3.3.2. Effect of Cu Concentration on LDC Structure and Electrochemical Performance of Metal added Interlayer 99
• 3.3.3. Reactivity of YSZ Electrolyte with LDC Interlayer as Function of Cu Content 102
• 3.3.4. Oxygen Storage Capacity 110
• 3.3.5. Electrochemical Performance 114
• 3.3.6. Electrochemical Capacitance Behavior 118
• 3.4. Conclusion 120
• Chapter 4. Investigating the Grain boundary–engineered segmentation of oxygen ion and electronic conduction in LDC for enhanced SOC durability. 122
• 4.1. Introduction 122
• 4.2. Experimental section 124
• 4.2.1. Preparation of the Powder Materials 124
• 4.2.2. Cell Fabrication 126
• 4.2.3. Characterizations 126
• 4.2.4. Electrochemical Measurements 129
• 4.3. Result and Discussion 130
• 4.3.1. Structure and Properties 130
• 4.3.2. Electrochemical Performance and Durability of SOC 138
• 4.4. Conclusion 140
• Chapter 5. Summary 142
• Future Work 144
• ABSTRACT 145
• Acknowledgement 147
• References 148