Title Page
Abstract
Contents
Chapter 1. Introduction 15
1-1. Lithium-ion secondary batteries 15
1-1-1. Composition of lithium-ion batteries 18
1-1-2. Principle of lithium secondary batteries 18
1-2. All-solid-state lithium ion batteries 25
1-2-1. Ceramic solid electrolytes 25
1-2-2. Properties of ceramic solid-state electrolytes 25
1-2-3. Li⁺ diffusion mechanism of ceramic solid electrolyte 26
1-3. Inorganic/ceramic electrolyte 27
1-3-1. Oxide solid electrolyte 27
1-3-2. Sulfide solid electrolyte 35
1-4. Purpose 39
References 40
Chapter 2. General experimental 45
2-1. Physical characterization 45
2-1-1. X-ray diffraction (XRD) 45
2-1-2. Field emission scanning electron microscopy (FE-SEM) and Energy dispersive X-Ray spectroscopy (EDS) 49
2-1-3. Laser-Raman spectroscopy 49
2-1-4. Nuclear Magnetic Resonance (NMR) 50
2-2. Electrochemical analysis 53
2-2-1. Electrochemical impedance spectroscopy (EIS) 53
2-2-2. Cyclic voltammetry (CV) 56
2-2-3. Direct current cycling (DC-cycling) 56
2-2-4. Galvanostatic charge-discharge measurements (CD) 56
2-2-5. Air stability 57
Reference 58
Chapter 3. Synthesis and electrochemical performance of glass-ceramic Li₇₋₂ₓP₂S₈₋ₓOₓI (0 ≤ x ≤ 0.1) solid electrolyte for all-solid-state lithium batteries 59
3-1. Introduction 59
3-2. Experimental 61
3-2-1. Preparation of Li₇₋₂ₓP₂S₈₋ₓOₓI solid electrolyte 61
3-2-2. Characterization and electrochemical measurements 62
3-3. Results and discussion 63
3-3-1. Structural analysis 63
3-3-2. Electrochemical performance 78
3-3-3. Air stability 91
3-4. Conclusion 96
References 97
Chapter 4. Synthesis and electrochemical performance of Argyrodite type Li₆₋₂ₓZnₓPS₅₋ₓOₓCl (0 ≤ x ≤ 0.1) solid electrolyte for all-solid-state lithium batteries 100
4-1. Introduction 100
4-2. Experimental 102
4-2-1. Preparation of Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolyte 102
4-2-2. Characterization and electrochemical measurements 102
4-3. Results and discussion 104
4-3-1. Structural analysis 104
4-3-2. Electrochemical performance 114
4-3-3. Air stability 124
4-4. Conclusion 128
References 129
Chapter 5. Summary 132
Table 1.1. Properties of various cathode materials used in commercial Lithium Ion Batteries. 21
Table 2.1. 7 crystal system and 14 Bravais lattice. 48
Table 3.1. Crystallographic data of Li₇P₂S₈I obtained from Rietveld refinement. The space group is P 42 nmc. 67
Table 3.2. Crystallographic data of Li₇P₂S₈I obtained from Rietveld refinement. The space group is P 4 nmm 68
Table 3.3. Crystallographic data of Li₆.₉Znₒ.ₒ₅P₂S₇.₉₅Oₒ.ₒ₅I obtained from Rietveld refinement. The space group is P 42 nmc. 69
Table 3.4. Crystallographic data of Li₆.₉Znₒ.ₒ₅P₂S₇.₉₅Oₒ.ₒ₅I obtained from Rietveld refinement. The space group is P 4 nmm. 70
Table 3.5. EIS fitting using the equivalent circuit and corresponding value of the fresh cell before the cycle. 90
Table 3.6. EIS fitting using the equivalent circuit and corresponding value of the cell after the cycle process. 90
Table 4.1. Nyquist plot fitting using the equivalent circuit and corresponding value of the fresh cell. 123
Table 4.2. Nyquist plot fitting using the equivalent circuit and corresponding value of the cell after cycling. 123
Figure 1.1. Different shapes of lithium secondary batteries: (a) cylindrical (b) coin (c) prismatic and (d) pouch. 16
Figure 1.2. Comparison of the different battery technologies in terms of volumetric and gravimetric energy density. 17
Figure 1.3. Crystal structure of the three lithium-insertion compounds in which the Li⁺ ions are mobile through the 2-D (layered), 3-D (spinel) and 1-D (olivine) frameworks. 20
Figure 1.4. Schematic design of charge-discharge mechanism of Li⁺ movement in an electrolyte and insertion/extraction of Li⁺ within electrodes in a lithium... 22
Figure 1.5. Lithium insertion - extraction process on lithium secondary battery system. 23
Figure 1.6. Schematic open-circuit energy diagram of a lithium cell. 24
Figure 1.7. Schematic structure of NASICON-like. 29
Figure 1.8. Schematic structure of perovskite-type LLTO. 31
Figure 1.9. Schematic structure of (a) garnet and (b) garnet-related Li₅La₃M₂O₁₂. 34
Figure 1.10. (a) Structure of LISICON and (b) Li₄GeS₄ of thio-LISICON. 36
Figure 1.11. LISICON and thio-LISICON family map with lithium-ion conduction mechanisms and ionic conductivity values. 37
Figure 2.1. Bragg diffraction at the lattice planes. 47
Figure 2.2. Nuclear Magnetic Resonance (NMR) analysis of the MAS technique. 52
Figure 2.3. (a) The Li⁺ diffusion mechanism of lithium-ion batteries, (b) Nyquist plot of an electrode, and (c) equivalent circuit from the Nyquist plot. 55
Figure 3.1. (a) & (b) The XRD patterns and (c) & (d) Rietveld refinement of Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI (x=0, 0.05, 0.1, 0.15, and 0.2) solid electrolyte. 66
Figure 3.2. Laser-Raman spectra of the prepared Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI (x=0, 0.05, 0.1, 0.15, and 0.2) solid electrolyte. 71
Figure 3.3. (a) ⁷Li MAS NMR, (b) ³¹P MAS NMR and (c) ¹²⁷I MAS NMR analysis of prepared solid electrolyte. 73
Figure 3.4. FE-SEM imagery of (a) & (c) Li₇P₂S₈I (x=0), and (b) & (d) Li₆.₉Znₒ.ₒ₅P₂S₇.₉₅Oₒ.ₒ₅I (x=0.05), solid electrolytes. 75
Figure 3.5. FE-SEM images of (a) & (b) Li₆.₈Zn₀.₁P₂S₇.₉O₀.₁ (x=0.1), (c) & (d) Li₆.₇Zn₀.₁₅P₂S₇.₈₅O₀.₁₅I (x=0.15), (e) & (f) Li₆.₆Zn₀.₂P₂S₇.₈O₀.₂I (x=0.2) solid electrolytes. 76
Figure 3.6. EDS mapping for (a) x=0, (b) x=0.05, (c) x=0.1, (d) x=0.15, and (e) x=0.2 of Li₇₋₂ₓ ZnₓP₂S₈₋ₓOₓI, and (f) argyrodite Li₆PS₅Cl solid electrolyte. 77
Figure 3.7. (a) Nyquist plots, (b) calculated ionic conductivity of the Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI (x=0, 0.05, 0.1, 0.15, and 0.2) solid electrolytes, and (c) & (d) cyclic voltammetry of the Li₇P₂S₈I... 79
Figure 3.8. Arrhenius plots of Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI (x=0, 0.05) solid electrolyte. 80
Figure 3.10. (a) & (b) Galvanostatic discharge/charge voltage profiles, (c) calculated critical current density, and (d) long-term galvanostatic discharge/charge voltage profiles at current... 84
Figure 3.11. Galvanostatic discharge/charge voltage profiles of (a) x=0.1, (b) x=0.15, (c) x=0.2 of Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI solid electrolyte and (d) argyrodite type Li₆PS₅Cl solid electrolytes. 85
Figure 3.12. (a) Initial charge-discharge curves, (b) cycle stability, Nyquist plot of (c) before, and (d) after cycling of Li/LPSCl/LNO-NCM811 and Li/LPSI-0.05 ZnO/LPSCl/LNO-... 88
Figure 3.13. (a) - (c) Initial and 20th cycle charge-discharge curves and (d) cycle stability of Li/LPSI/LNO-NCM811, Li/LPSI-0.05ZnO/LNO-NCM811, and Li/LPSI-0.05ZnO/LNO-...[이미지참조] 89
Figure 3.14. (a) The amount of H₂S gas generation from Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI (x=0, 0.05, and 0.1) powder upon exposure to humid air. (b) calculated ionic conductivity and retention rate,... 93
Figure 3.15. Nyquist plots of (a) x=0, (b) x=0.05, and (c) x=0.1 of Li₇₋₂ₓZnₓP₂S₈₋ₓOₓI solid electrolyte exposed to dry air with 10 % humidity for 1, 2 h. 94
Figure 3.16. (a) XRD analysis, and (b) Laser-Raman spectra of ZnO co-doped solid electrolyte (x=0.1) exposed to dry air with 10% humidity for 1, 2 h. 95
Figure 4.1. (a, b) XRD patterns, (c) Laser-Raman spectra and (d) solid-state NMR analysis of prepared solid electrolyte (x=0, 0.025, 0.05, 0.075, 0.1). 106
Figure 4.2. XPS spectra of (a) P 2p, (b) S 2p region of Li₆₋₂ₓZnₓPS₅₋ₓOₓCl (x=0, 0.025) solid electrolyte. 108
Figure 4.3. XPS spectra of (a) Li 1s, (b) Cl 2p, (c) Zn 2p region for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl (x=0, 0.025) solid electrolyte. 109
Figure 4.4. FE-SEM images of (a) x=0, (b) x=0.025 for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolyte. 111
Figure 4.5. FE-SEM images of (a) & (b) Li₆.₈Zn₀.₁P₂S₇.₉O₀.₁ (x=0.1), (c) & (d) Li₆.₇Zn₀.₁₅P₂S₇.₈₅O₀.₁₅I (x=0.15), (e) & (f) Li₆.₆Zn₀.₂P₂S₇.₈O₀.₂I (x=0.2) solid electrolytes. 112
Figure 4.6. EDS mapping for (a) x=0, (b) x=0.025, (c) x=0.05, (d) x=0.075, and (e) x=0.1 for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolyte. 113
Figure 4.7. (a) Calculated ionic conductivity, (b) Cyclic voltammetry, (c) DC profile, (d) calculated critical current density and (e) long-term DC profile with a fixed stripping/plating... 116
Figure 4.8. (a) Nyquist plots and (b) activation energy plot of Li₆₋₂ₓZnₓPS₅₋ₓOₓCl (0 ≤ x ≤ 0.1) solid electrolyte. 117
Figure 4.9. Cyclic voltammetry of (a) x=0.05, (b) x=0.075, and (c) x=0.1 for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolyte. 118
Figure 4.10. DC profiles of (a) x=0, (b) x=0.05, (c) x=0.075, (d) x=0.1 and (e) long-term DC profile of x=0 for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolyte at room temperature. 119
Figure 4.11. Long-term DC profiles of (a) x=0 and (b) x=0.025 with a fixed stripping/plating current density of 4 mA·cm⁻² at room temperature for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolytes. 120
Figure 4.12. Long-term DC profiles of (a) x=0 and (b) x=0.025 with a fixed stripping/plating current density of 4 mA·cm⁻² at room temperature for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl solid electrolytes. 122
Figure 4.13. (a) H₂S gas generation, (b) Nyquist plots, (c) calculated ionic conductivity, (d) XRD patterns after expose to humid air for 30 min from the prepared solid electrolyte (0 ≤ x ≤ 0.1). 126
Figure 4.14. XRD patterns after exposure to humid air for Li₆₋₂ₓZnₓPS₅₋ₓOₓCl (x=0.05, 0.075, 0.1) solid electrolyte. 127