Title Page

Contents

Abstract 15

Chapter 1. Introduction 17

1. Lithium batteries 17

1.1. Overview of lithium batteries 17

1.2. Operation of lithium batteries 19

2. Materials for lithium batteries 21

3. Solid-state electrolyte membrane 25

3.1. Poly (vinyl alcohol) - based electrolyte membrane 26

3.2. Ionic liquid 28

4. Motivation and outline of this research 30

Chapter 2. Application of nano-conductor imbedded flexible poly(vinyl alcohol)-based hybrid solid electrolyte for high voltage stable solid-state lithium batteries 32

1. Introduction 32

2. Experimental section 37

2.1. Materials 37

2.2. Synthesized process and preparation of HSEs and cathode materials 37

2.3. Materials characterization 38

2.4. Electrochemical property measurements 41

3. Results and Discussion 42

3.1. Morphology of HSE and Li-ion transporting evaluation 42

3.2. Mechanical, adhesive, and thermal properties of HSE 50

3.3. Interfacial resistances and electrochemical window of HSE 55

3.4. Electrochemical investigation of LCO(ALCO)/HSE | HSE | Li cells 59

Chapter 3. Application of multi-functional cathode and flexible poly(vinyl alcohol)-based hybrid solid electrolyte for high performance solid-state lithium-sulfur batteries 62

1. Introduction 62

2. Experimental section 66

2.1. Materials 66

2.2. Synthesis of S@ACNT active material and PDATFSI conductive binder 66

2.3. Synthesis of PVA-g-PCA-80IL-5HTpca HSE 67

2.4. Materials Characterization 67

2.5. Electrochemical measurements 68

3. Results and Discussion 69

3.1. Morphologies and characterizations of S@ACNTs active material and PDATFSI conductive binder 69

3.2. Electrochemical performance of the solid-state lithium-sulfur battery 79

Chapter 4. Application of the force-bearing cathode and multifunctional double-layer hybrid solid electrolyte for high energy and sustainable solid-state lithium-sulfur battery 83

1. Introduction 83

2. Experimental section 86

2.1. Materials 86

2.2. Fabrication of DLHSE 86

2.3. Fabrication of sulfur cathode 87

2.4. Materials Characterization 88

2.5. Electrochemical measurements 89

3. Results and Discussion 90

3.1. Characterization of S@CNT-COOH and PVA-SPALi 90

3.2. Structural characterizations and multifunctional properties of DLHSE 96

3.3. Compatibility of DLHSE with electrode 111

3.4. Electrochemical performance of solid-state LiSB 115

Chapter 5. Future work - applied potential of multifunctional hybrid solid electrolyte in various solid-state metal-sulfur systems 119

1. Introduction 119

2. Experimental section 120

2.1. Materials 120

2.2. Fabrication of DLHSE and sulfur cathode 121

2.3. Electrochemical measurements 121

3. Results and Discussion 122

Chapter 6. Conclusions 127

References 130

논문요약 151

Figure 1-1. (A) Energy density of various secondary batteries[4], (B) applications of LiBs. 18

Figure 1-2. Illustration of (A) configuration[10] and (B) operation of LiBs. 20

Figure 1-3. Representative structures of (A) cathode materials[13, 14] and (B) anode materials. 22

Figure 1-4. Thermal runaway mechanism of liquid electrolyte-based LiBs. 24

Figure 1-5. Hydrogen bonding in PVA and coordination bonding between OH groups and lithium ions. 27

Figure 1-6. Hydrogen bonding in PVA and coordination bonding between OH groups and lithium ions. 29

Figure 2-1. Comparison of (A) cathode | ICE | Li cell, (B) cathode | SPE | Li cell, and (C) cathode/HSE |HSE | Li cell (this work), (D) Li+ conducting mechanism of HTpca-imbedded PVA-g-PCA/IL electrolyte. 36

Figure 2-2. Sample preparation process for adhesion test. 40

Figure 2-3. (A) 1H NMR spectra of PVA-g-PCA, (B) XRD pattern and (C) FT-IR spectra of HTpca nano-conductors, (D) HR-TEM images of HTpca nano-conductors in various magnifications, and (E) surface and... 45

Figure 2-4. (A) The Li+ conductivity of PVA-g-PCA with different feeding ratios of PCA component, Nyquist plots of (B) PVA-g-PCA(10%), (C) PVA-g-PCA(20%), (D) PVA-g-PCA(30 %) with various... 46

Figure 2-5. IL concentration effect of PVA-g-PCA/IL and 5 wt% HTpca-imbedded PVA-g-PCA/IL systems on (a) Li+ conductivity and (b) Li+ transference number at 25 oC, and (c) Li+ conducting mechanisms of... 47

Figure 2-6. (A) DSC curves of PVA, PVA-g-PCA-60IL and PVA-g-PCA-80IL, (B) XRD patterns of PVA-g-PCA with various concentrations of IL. 48

Figure 2-7. Arrhenius plots of temperature dependence of ionic conductivity for PVA-g-PCA-80IL SPE and PVA-g-PCA-80IL-5HTpca HSE. 49

Figure 2-8. (A) The stress-strain curves of PVA-g-PCA/IL SPEs and HTpca-imbedded PVA-g-PCA/IL HSEs, (B) the adhesive strength of cathode systems prepared using PVA-g-PCA/IL and HTpca-imbedded... 53

Figure 2-9. (A) TGA curves of pure PVA, PYR14-TFSI 0.5M LiTFSI IL, PVA-g-PCA-80IL-5HTpca HSE, and PVA-g-PCA-60IL-5HTpca binder, (B) thermal shrinkage of HTpca-doping PVA-g-PCA/IL electrolytes,... 54

Figure 2-10. Interfacial resistance of ALCO | HSE | Li cells prepared using PVDF and PVA-g-PCA-60IL-5HTpca binder (A-1) before activation, (A-2) after 30 days of aging process, voltage profiles of PVA-g-... 58

Figure 2-11. (A) Charge/discharge curves and (B) cycling performance and (C) impedance spectra of LCO| HSE | Li cells at 25 ℃ (0.2 C) and different voltage ranges, (D) charge/discharge profiles of ALCO | HSE... 61

Figure 3-1. Schematic illustration of the designed LiSB combined by multi-functional cathode and flexible HSE. 65

Figure 3-2. (A) SEM images of CNTs, ACNTs, and S@ACNTs, (B) EDS mapping images of ACNTs, (C) TGA curve and EDS mapping images of S@ACNTs. 74

Figure 3-3. (A) ¹H NMR spectra of PDATFSI polymer, (B) FT-IR spectra of PDATFSI material and PDACl precursor. 75

Figure 3-4. (A) Effect of IL concentration on Li+ conductivity of PDATFSI,(B) adhesive strength of cathode material using S@ACNTs and PDATSI binder for aluminum current collector, (C) SEM images, EDS... 76

Figure 3-5. Photos of Li₂S₆ solution (A) before and (B) after 10 min of adsorption test, (C) UV-vis spectrum of (1) 0.05M Li₂S₆ solution, (2) 0.05M Li₂S₆ solution with S@ACNTs/PDATFSI adsorbent, (3) 0.05M Li₂S₆... 77

Figure 3-6. S 2p XPS spectra of S@ANCTs/PVDF cathode material (A) before and (B) after adsorption test. 78

Figure 3-7. (A) Charge/discharge curves, (B) rate capacity, (C) cycling performance of S@CNTs/PVDF | HSE | Li cell and S@ACNTs/PDATFSI-60IL | HSE | Li cell, and (D) impedance spectra of S@CNTs/PVDF... 81

Figure 3-8. 3D laser confocal investigation and elemental analysis of cathode surface (A) before activation and (B) after 200 cycles, SEM images of the surface of (C) HSE membrane and (D) Li anode at initial state... 82

Figure 4-1. (A) PXRD patterns and (B) FT-IR spectra of CNT and CNT-COOH, (C) SEM images of CNT, (D) EDS mapping images and (E) TGA curve of S@CNT-COOH active material. 94

Figure 4-2. (A) FT-IR spectra of PVA and cross-linking 70IL@PVA-SPALi, (B) XPS spectrum at Li 1s, S2p, and C 1s of 70IL@PVA-SPALi conductive binder, (C) effect of IL concentration on Li⁺ conductivity of... 95

Figure 4-3. (A) Crystal structure of MOF, (B) N₂ sorption isothermal of MOF at 77 K, (C) XRD profiles of MOF, (D) FT-IR spectra of H₂TCCP and MOF nanosheets, (E) TEM images, (F) AFM... 102

Figure 4-4. TGA curve of MOFIL. 103

Figure 4-5. N₂ adsorption/desorption isothermal at 77K of (A) pristine MOF and (B) MOFIL, pore size distribution of (C) pristine MOF and (B) MOFIL. 104

Figure 4-6. (A) synthesis procedure of DLHSE membrane, (B) SEM image of cross-section and EDS mapping images of DLHSE. 105

Figure 4-7. (A) The stress-strain curve of DLHSE membrane, (B) bending images of DLHSE and 70IL@PVA-SPALi membrane, (C) TGA curves of MOFIL, 70IL@PVA-SPALi, and DLHSE membrane,... 106

Figure 4-8. (A) H-type permeation device with DLHSE membrane and PE separator, (B) UV-vis spectrum of solution after permeation test using DLHSE membrane and PE separator, (C) FT-IR spectra of MOFIL... 107

Figure 4-9. (A) Arrhenius plot of the ionic conductivity of DLHSE, (B) Li+ transference number of DLHSE, (C) the mechanism of fast Li+ transport and uniform Li+ flux achieved in DLHSE. 108

Figure 4-10. (A) Li⁺ conductivity of MOFIL with different loading amounts of IL, (B) S 2s spectra, (C) Zn 2p spectra, (D) F 1s spectra and (E) S 2p spectra of MOFIL. 109

Figure 4-11. Current-time plots and impedance spectra before and after polarization of (A) MOFIL, (B) 70IL@PVA-SPALi. 110

Figure 4-12. Interfacial resistance of cathode | DLHSE cells using PVDF and 70IL@PVA-SPALi binder (A-1) before activation and (A-2) after 30 days of the aging process, voltage profile of DLHSE with Li⁺... 113

Figure 4-13. LSV profile of DLHSE membrane. 114

Figure 4-14. (A) Charged/discharged curves, (B) rate capacity, (C) cycling performance of S@CNT-COOH/70IL@PVA-SPALi | DLHSE | Li cell and S@CNT/PVDF | PE(LE) | Li cell, (D) impedance spectra... 117

Figure 4-15. (A) Cycling performance of S@CNT-COOH/70IL@PVA-SPALi | DLHSE | Li cell, S@CNT-COOH/70IL@PVA-SPALi | PE(LE) | Li cell, S@CNT-COOH/PVDF | PE(LE) | Li and S@CNT/PVDF |... 118

Figure 5-1. (A) Zn²⁺ ion conductivity, (B) Zn²⁺ transference number, (C) LSV profile of DLHSE, (D) voltage profile of DLHSE with Zn²⁺ symmetric cells during Zn plating/stripping process at current densities... 125

Figure 5-2. (A) CV profiles, (B) Charged/discharged curves, (C) rate capacity, (D) cycling performance of S@CNT-COOH/70IL@PVA-SPALi | DLHSE | Zn cell and S@CNT/PVDF | PE(1M Zn(TFSI)₂ aq) | Zn cell. 126