Title Page
Abstract
Contents
Chapter 1. Introduction 13
1.1. Beyond Li-ion: Lithium metal batteries. 13
1.2. Electrolyte engineering for stabilizing Lithium metal interface 14
Chapter 2. Exploiting the Steric Effect and Low Dielectric Constant of 1,2-Dimethoxypropane for 4.3 V Lithium Metal Batteries 17
2.1. Introduction 17
2.2. Experimental Methods 21
2.3. Results and discussion 28
2.3.1. Molecular design and Li⁺ solvation structure of electrolytes 28
2.3.2. Performance and morphology analyses in various cell configurations 40
2.3.3. Interface characterization 50
2.3.4. Oxidation stability and degradation analysis 55
2.4. Conclusion 61
Chapter 3. Localized high-concentration electrolyte with 1,2-dimethoxypropane for lithium metal batteries 62
3.1. Introduction 62
3.2. Experimetal Methods 66
3.3. Results and discussion 72
3.3.1. Molecular design and Li⁺ solvation structure of electrolytes 72
3.3.2. Performance and Morphology Analyses in Various Cell Configurations. 79
3.4. Conclusion 84
4.1. Bibliography 85
국문초록 98
Figure 1.1. Schematic diagram of the composition of the electrode interface according to the solvation structure of the solvent with Li⁺... 16
Figure 2.1. Schematic illustration of steric hindrance and interaction with Li-ion for (a) DME and (b) DMP. (c) Calculated minimum... 28
Figure 2.2. Natural population analysis (NPA) of (a) DME and (b) DMP calculated using density functional theory (DFT, B3LYP... 29
Figure 2.3. Dipole moment of (a) DME and (b) DMP calculated using density functional theory (DFT). The IUPAC convention was used;... 31
Figure 2.4. (a) ⁷Li NMR spectra of 2 M-LiFSI-in-DME and 2 M-LiFSI-in-DMP. (b) Raman spectra of 2 M-LiFSI-in-DME and 2... 34
Figure 2.5. (a) Radial distribution functions (RDF) of the 2 M-LiFSI-in-DME electrolyte by MD simulation. Li-ODME curve... 37
Figure 2.6. (a) Radial distribution functions (RDF) of the 2 M-LiFSI-in-DMP electrolyte by MD simulation. Li-ODMP curve...[이미지참조] 38
Figure 2.7. Coordination structures between one Li⁺ ion and three (a) DME and (b) DMP molecules calculated using DFT. 39
Figure 2.8. (a) Aurbach measurement of Li metal CEs in Li|Cu cells. CEs of Li|Cu cells cycled at (b) 0.5 mA cm¯² and (c) 3 mA cm¯² .... 40
Figure 2.9. (a) Cycling measurements of Li|Cu cells with different electrolytes at the current density and capacity of 1 mA cm¯² and 1... 43
Figure 2.10. Surface topographies of Li metal after Li|Cu cell cycling. Scanning electron microscopy (SEM) images of Li surface... 44
Figure 2.11. Cyclic voltammetry (CV) data (0 V to 2.0 V) of (a) 2 M-LiFSI-in-DME and (b) 2 M-LiFSI-in-DMP recorded at a scan... 44
Figure 2.12. Cycling performance of (a) Li|LFP full cells at 0.5C and Li|NCM811 full cells at (b) 1C and (c) 2C after 2 formation... 47
Figure 2.13. Electrochemical performance of full cells. Charge-discharge profiles of Li|NCM811 full cells with (a) 2 M-LiFSI-in-... 48
Figure 2.14. (a) Linear sweep voltammetry (LSV) curves of Li|Al cells at a scan rate of 1 mV s¯¹ with different electrolytes. (b)... 48
Figure 2.15. Rate capability of Li|NCM811 coin cells at the same charge-discharge rate. 49
Figure 2.16. Cycling performance of Li|NCM811 full cells at 1C after 2 formation cycles at 0.1C with 2 M-LiFSI-in-DMP. The... 49
Figure 2.17. Ex situ interfacial analysis of Li metal anode surface in Li|NCM811 full cells. X-ray photoelectron spectroscopy (XPS)... 50
Figure 2.18. X-ray photoelectron spectroscopy (XPS) depth profiles of NCM811 cathode surface after disassembly of the Li|NCM... 53
Figure 2.19. X-ray photoelectron spectroscopy (XPS) depth profiles of LFP cathode surface after disassembly of the Li|LFP... 54
Figure 2.20. (a) X-ray diffraction (XRD) patterns of NCM811 from Li|NCM811 full cells after 20 cycles. dQ/dV profiles of Li|NCM811... 55
Figure 2.21. Aluminum corrosion test. Potentiostatic test curves of Li|Al cells with 2 M-LiFSI-in-DME and 2 M-LiFSI-in-DMP at... 59
Figure 2.22. Photographs of Al foil after maintaining Li|Al coin cells with (a) 2 M-LiFSI-in-DME and (b) 2 M-LiFSI-in-DMP at fixed... 59
Figure 2.23. SEM images of Al foil after maintaining Li|Al coin cell with (a) 2 M-LiFSI-in-DME and (b) 2 M-LiFSI-in-DMP at fixed... 60
Figure 2.24. SEM images of bare Al foil. 60
Figure 3.1. (a) Schematic diagram of LHCE strategy based on changes in the amount of diluent used according to the coordinating... 72
Figure 3.2. (a) Linear sweep voltammetry (LSV) curves of Li|Al cells at a scan rate of 1 mV s¯¹ with different electrolytes. (b)... 74
Figure 3.3. Most probable solvation structures of the first Li+ solvation sheath of (a) 2 M LiFSI-in-DME:BTFE (1:1) and (b) 2 M... 76
Figure 3.4. CEs of Li|Cu cells cycled at (a) 1.0 mA cm¯², 1 mAh cm¯², (b) zoom in plot of a. (c) Aurbach measurement of Li metal... 79
Figure 3.5. Scanning electron microscopy (SEM) images of Li surface after exposure to (a,c) 2 M-LiFSI-in-DME:BTFE(1:1)... 81
Figure 3.6. Cycling performance of (a) Li|NCM811 full cells at 1C after 2 formation cycles at 0.1C with 2 M LiFSI-in-... 82