Title Page
ABSTRACT
국문 초록
PREFACE
Contents
NOMENCLATURE 27
CHAPTER 1. INTRODUCTION 30
1.1. Overview 30
1.1.1. Lithium oxygen batteries 30
1.1.2. Cathode electrocatalysts 33
1.1.3. Perovskite oxides 36
1.1.4. Solid-state lithium oxygen batteries 38
1.2. Previous work and research trend 47
1.2.1. Challenges for lithium oxygen batteries 47
1.2.2. Recent research on the oxygen reactions of perovskite 48
1.2.3. Research trend on the solid-state lithium oxygen batteries 52
1.3. Objective of this study 59
CHAPTER 2. PEROVSKITE NANOWIRE-BASED EFFICIENT ELECTROCATALYSTS FOR LITHIUM OXYGEN BATTERIES 63
2.1. Enhanced activity promoted by perovskite La₀.₈Sr₀.₂VO₃ nanowires electrocatalyst for the oxygen reduction reaction 63
2.1.1. Background 63
2.1.2. Experimental methodology 66
2.1.3. Results and discussion 70
2.1.4. Summary 107
2.2. Perovskite La₀.₈Sr₀.₂CrO₃ nanowires as an enhanced electrocatalysts for the oxygen evolution reaction 108
2.2.1. Background 108
2.2.2. Experimental methodology 111
2.2.3. Results and discussion 114
2.2.4. Summary 159
CHAPTER 3. MUTUAL INTERFACE DESIGN FOR SOLID-STATE LITHIUM OXYGEN BATTERIES 160
3.1. High surface oxygen activity of layered perovskite LaSrCrO₄ nanowires for high-rate lithium oxygen batteries 160
3.1.1. Background 160
3.1.2. Experimental methodology 163
3.1.3. Results and discussion 166
3.1.4. Summary 189
3.2. Interface engineering with layered perovskite electrocatalyst for stable solid-state lithium-oxygen batteries 190
3.2.1. Background 190
3.2.2. Experimental methodology 193
3.2.3. Results and discussion 196
3.2.4. Summary 215
CHAPTER 4. CONCLUSION 216
REFERENCES 218
APPENDICES 241
A. List of papers 241
B. Curriculum Vitae 242
C. Papers (SCI) 243
Table 1-1. Performance overview of recent solid-state LOBs. 58
Table 2-1. Measured molar ratio of main elements (La, Sr and V) using SEM–EDS. 75
Table 2-2. Binding energies (eV) and area percentages (%) of the elements Sr and O from XPS spectra of the LV NFs, LSV4 NFs, and LSV3 p-NFs. 86
Table 2-3. Comparison of the electrocatalytic performance of the LSV3 p-NFs electrode with those of perovskite electrocatalysts for Li–O₂. 105
Table 2-4. Binding energies (eV) and area percentages (%) of elemental Cr from the XPS profiles of the LSCr4, LSCr-A, LSCr3 NWs, and LSCr1000. 132
Table 2-5. Binding energies (eV) and area percentages (%) of elemental Sr and O from the XPS profiles of the LSCr4, LSCr-A, LSCr3 NWs, and LSCr1000. 133
Table 2-6. Binding energies (eV) and area percentages (%) of elemental Cr from the XPS profiles of the LSCr3 NWs electrode at different voltages during the charging process. 146
Table 3-1. Binding energies (eV) and area percentages (%) of elemental Sr and O from the XPS profiles of the LP-Cr, LP-V, and P-LSCr NWs. 178
Table 3-2. Binding energies (eV) and area percentages (%) of elemental Cr from the XPS profiles of the LP-Cr and P-LSCr NWs. 179
Table 3-3. Binding energies (eV) and area percentages (%) of elemental V from the XPS profiles of the LP-V NWs. 180
Table 3-4. Comparison of the electrocatalytic performance of the LP-Cr/NF electrodes with A-PA SPE with those of recently reported SSLOBs. 208
Figure 1-1. Specific energies of metal-air batteries. 40
Figure 1-2. Schematic representation of cell configurations in LOBs and potential of the O₂/Li₂O₂ versus Li⁺ (2.96 V). 41
Figure 1-3. Oxygen reduction reaction mechanism in nonaqueous LOBs. 42
Figure 1-4. Li₂O₂ oxidation mechanism during the charging process. 43
Figure 1-5. Compositional flexibility of perovskite oxides. The figure below shows the ideal amount (green bar) of perovskite oxide classified by the difference combination of... 44
Figure 1-6. Schematic diagram of perovskite nanowires activation strategy in LOBs. 45
Figure 1-7. Schematic diagram of various advantages of solid-state lithium oxygen batteries. 46
Figure 1-8. Schematic illustration of current challenges for LOBs. 54
Figure 1-9. Effects of A and B sites on oxygen reduction reactions. 55
Figure 1-10. The electronic band structure for the perovskite oxide corresponding to octahedral oxygen coordination around transition metal ions. 56
Figure 1-11. Schematic of the working mechanism for OER catalyst in LOBs. 57
Figure 1-12. Challenges in LOBs for highly efficiency energy storage. 61
Figure 1-13. Strategies for addressing major challenges. 62
Figure 2-1. (a) XRD patterns of the LSV4 NFs and LSV3 p-NFs. Crystal structures of the (b) LSV4 NFs and (c) LSV3 p-NFs. 72
Figure 2-2. Visual crystal structure and phase information of LaVO₄ (JCPDS No. 70-0216) and LaVO₃ (JCPDS No. 81-2436). 73
Figure 2-3. XRD patterns of (a) Sr-doped/undoped monazite LaVO₄ NFs and (b) Sr-doped/undoped perovskite LaVO₃ NFs. 74
Figure 2-4. FESEM images of (a) LSV4 NFs and (d) LSV3 p-NFs. (b,e) Low-magnification and (c,f) high-resolution TEM images of LSV4 NFs and LSV3 p-NFs, respectively.... 77
Figure 2-5. FESEM images of As-spun nanofibers. 78
Figure 2-6. BET nitrogen adsorption/desorption isotherms and pore volume of LSV4 NFs and LSV3 p-NFs. 79
Figure 2-7. (a) XPS survey of LSV4 NFs and LSV3 p-NFs and magnified XPS spectra of (b) Sr 3d and (c) O 1s. (d) EPR spectra of LV NFs and LSV3 p-NFs. (e) PL spectra of... 84
Figure 2-8. Magnified XPS spectra of V 2p of LV NFs and LSV3 p-NFs, and corresponding binding energies (eV) and area percentages of V 2p spectra. 85
Figure 2-9. (a) ORR and (b) OER linear sweep voltammetry of carbon paper-supported LSV4 NFs and LSV3 p-NFs at a scan rate of 5 mV s⁻¹. (c) Chronoamperometry profiles... 89
Figure 2-10. CV profiles of LSV4 NFs and LSV3 p-NFs electrodes at a scan rate of 100 mV s⁻¹. 90
Figure 2-11. (a) The 1st galvanostatic discharge–charge curves of LSV4 NFs and LSV3 p-NFs electrodes at a current rate of 2000 mA g⁻¹. (b) In situ Raman spectra of... 95
Figure 2-12. FESEM images of LSV4 NFs and LSV3 p-NFs electrodes (a,c) after discharge and (b,d) charge process, respectively. 96
Figure 2-13. Magnified XPS spectra of (a) Li 1s and (b) O 1s for LSV4 NFs and LSV3 p-NFs electrodes after discharge. Magnified XPS spectra of (c) Li 1s and (d) O 1s for... 97
Figure 2-14. XRD patterns of LSV3 p-NFs electrode after discharge and charge process. 98
Figure 2-15. Magnified XPS spectra of V 2p and Sr 3d for LSV3 p-NFs electrodes after charge. 99
Figure 2-16. (a) Rate capability of the LSV3 p-NFs electrode at various current rates. (b) Galvanostatic discharge–charge curves of the LSV3 p-NFs electrodes at the... 102
Figure 2-17. Galvanostatic discharge–charge curves of LV NFs and LSV3 p-NFs electrodes at the current rates of 2000 mA g⁻¹ : (a) 1st cycle and (b) 13th cycle. 103
Figure 2-18. Galvanostatic discharge–charge curves of LSV4 NFs electrode. 104
Figure 2-19. Schematic illustration of reversible formation and decomposition of Li₂O₂ products in LSV3 p-NFs electrocatalytst for rechargeable LOBs. 106
Figure 2-20. Schematic of decomposition process of LSCr3 NWs as OER catalysts for rechargeable Li–O₂ battery. 121
Figure 2-21. FESEM images of (a) LSCr4, (b) LSCr-A, and (c) LSCr3 NWs. (d) XRD patterns of LSCr4, LSCr-A, LSCr3 NWs, and LSCr1000. (e) Crystal structure from LSCr4... 122
Figure 2-22. FESEM image of As-spun nanowires. 123
Figure 2-23. (a) FESEM image and (b) XRD pattern of LSCr1000. 124
Figure 2-24. High-resolution TEM images of (a) LSCr4, (b) LSCr-A, and (c) LSCr3 NWs. 125
Figure 2-25. XRD patterns of Sr-substituted samples. 126
Figure 2-26. STEM image of the LSCr3 NWs and EDS mapping images of the main elements (La, Sr, and Cr). 127
Figure 2-27. Magnified XPS spectra of (a) Cr 2p, (b) Sr 3d, and (c) O 1s of LSCr4 and LSCr3 NWs. Low magnification TEM images of (d) LSCr4, (e) LSCr-A, and (f) LSCr3... 128
Figure 2-28. Magnified La 3d XPS profiles of LSCr4 and LSCr3 NWs. 129
Figure 2-29. Magnified XPS profile of Sr 3d, O 1s, and Cr 2p of LSCr-A NW and LSCr1000. 130
Figure 2-30. Low magnification TEM images and average wire diameters of LSCr4, LSCr-A, and LSCr3 NWs. 131
Figure 2-31. (a) OER-LSV of Li₂O₂ -mixing LSCr4, LSCr-A, LSCr3 NW and LSCr1000 electrode at difference voltages at a scan rate of 1 mV s⁻¹. (b) Cr 2p XPS spectra... 139
Figure 2-32. Magnified Cr 2p XPS profiles of the LSCr3 NWs electrode at different voltages during the charging process. 140
Figure 2-33. Magnified Li 1s and La 3d XPS profiles of the LSCr3 NWs electrode at different voltages during the charging process. 141
Figure 2-34. Contour plots 2D images for in situ Raman spectra of the (a) LSCr3 NWs and (b) LSCr1000 electrodes. 142
Figure 2-35. XRD patterns of the OCV electrode and oxidized electrode for 4 V of (a) LSCr3 NWs and (b) LSCr1000, at a scan rate of 1° per min. (c) Enlarged view of the XRD... 143
Figure 2-36. HR-TEM and corresponding FFT images of the Li₂CrO₄ layer between the Li₂O₂ and LSCr3 NWs. The Li₂O₂ -mixed electrode was charged for the 10 hours. 144
Figure 2-37. FESEM images of the LSCr3 NWs and LSCr1000 electrodes containing Li₂O₂ powder for OCV and after 10 hours of charging. 145
Figure 2-38. (a) Galvanostatic discharge–charge curves of LSCr4, LSCr3 NW, and LSCr1000 electrodes at a current rate of 1000 mA g⁻¹. The overpotentials were determined as... 152
Figure 2-39. Galvanostatic discharge–charge curves of LSCr3 NWs electrodes at different current densities. 153
Figure 2-40. FESEM images of the LSCr4, LSCr3 NWs and LSCr1000 electrodes after 3 cycle discharging and charging. 154
Figure 2-41. HR-TEM image of LSCr3 NWs after 3 cycle discharging. 155
Figure 2-42. Cycle performance of LSCr3/Au electrode at the current rates 1000 mA g⁻¹. 156
Figure 2-43. DC polarization curves of the LSCr4, LSCr-A, LSCr3 NWs, and LSCr1000 electrodes at 0.5 V. 157
Figure 2-44. Nyquist plots of LSCr4, LSCr-A, LSCr3 NWs, and LSCr1000 for ionic/electronic conductivities. 158
Figure 3-1. FESEM image of As-spun nanowires. 170
Figure 3-2. Field emission scanning electron microscopy images of (a) LP-Cr, (b) LP-V and (c) P-LSCr NWs. (d) X-ray diffraction patterns of the LP-Cr, LP-V and P-LSCr... 171
Figure 3-3. Enlarged XRD patterns of layered Cr and V-based perovskite showing the peak at 2θ=~31.5 and 32.7. 172
Figure 3-4. (a) FESEM image and EDS mapping images of the main elements (La, Sr, Cr, and O). (b) Area EDS spectrum and right table for the weight and mol percentage of... 173
Figure 3-5. Low magnification and high-resolution TEM images of LP-Cr, LP-V, and P-LSCr NWs. 174
Figure 3-6. Magnified XPS spectra of (a) Sr 3d, (b) O 1s, and (c) Cr 2p, and (d) V 2p of LP- Cr and LP-V NWs. (e) Relative area of oxidation states of B-site metal of... 175
Figure 3-7. Magnified La 3d XPS profiles of LP-Cr, LP-V, and P-LSCr NWs. 176
Figure 3-8. Magnified XPS spectra of (a) Cr 2p, (b) Sr 3d, and (c) O 1s of P-LSCr NWs. 177
Figure 3-9. (a) ORR and OER linear sweep voltammetry of LP-Cr, LP-V, and P-LSCr NWs electrodes at a scan rate of 0.1 mV s⁻¹. Double-layer capacitance measurements for... 183
Figure 3-10. Nyquist plots of LP-Cr, LP-V, and P-LSCr electrodes for charge transfer. 184
Figure 3-11. Galvanostatic discharge–charge curves for cycles of (a) LP-Cr, (b) LP-V, and (c) P-LSCr NWs electrodes, respectively, at the current rates 500 mA g⁻¹ and a fixed... 187
Figure 3-12. Rate capability of LP-Cr NWs electrode at various current rates. 188
Figure 3-13. (a) Digital image and molecular structure of A-PR SPE. (b) XRD patterns of PR and A-PR SPE. (c) Temperature-dependent ionic conductivity of the SPE at... 199
Figure 3-14. Schematic illustration of crystalline structure of A-PR SPE, and contact angle of the A-PR SPE with water. 200
Figure 3-15. Thermogravimetric analysis (TGA) analysis of A-PR SPE. 201
Figure 3-16. (a) Cycling performance of the symmetric Li cells with A-PR SPE at a current density of 0.2 mA cm⁻². Enlarged profiles corresponding to (b) 75-80 cycles and... 202
Figure 3-17. Field emission scanning electron microscopy images of (a) LP-Cr, (b) LSCr and (c) LSV NWs as electrocatalysts used for solid state LOBs valuation. (d) XRD... 206
Figure 3-18. Galvanostatic discharge–charge curves for cycles of (a) LP-Cr/NF, (b) LSCr/NF, and (c) LSV/NF NWs electrodes with A-PA SPE, respectively, at the current rates... 207
Figure 3-19. (a) Schematic illustration of synthesize of LP-Cr/CF and LP-Cr/CFR electrodes. Field emission scanning electron microscopy images of (b) the forward side of CF,... 211
Figure 3-20. Field emission scanning electron microscopy images of (a) LP-Cr/NF, (b) LP- Cr/CC, and (c) LP-Cr/CF electrodes (d) Comparison of 1st discharge–charge...[이미지참조] 212
Figure 3-21. Comparison of 1st discharge–charge capacities between the LP-Cr/CF and LP- Cr/CFR electrodes with A-PA SPE.[이미지참조] 213
Figure 3-22. Raman spectroscopy of the LP-Cr/CF electrode after discharge and charge process. 214