전고체 전지용 황화물계 고체전해질의 ZnO의 도핑 효과에 관한 전기화학적 성능 연구

다국어 초록 (Multilingual Abstract)

All-solid-state batteries remain problems to be overcome due to the high-temperature heat-treatment process, and the compatibility problem with Li metal as an anode. In this work, glass-ceramic Li7P2S8I (LPSI) and argyrodite Li6PS5Cl (LPSCl) solid electrolyte with high ionic conductivity is prepared using a high-energy dry ball milling process with a low-temperature (200 °C) and high temperature (550°C) heat-treatment process. Then, ZnO are doped with LPSI and LPSCl solid electrolyte, particularly Zn at the Li site and O at the S site, by our optimized synthesis process. The ZnO co-doping is confirmed by powder X-ray diffraction (XRD), Laser–Raman, field emission scanning electron microscopy (FE-SEM), and solid-state nuclear magnetic resonance (NMR) spectroscopy analysis. The ionic conductivity value of the prepared solid electrolytes is measured by electrochemical impedance spectroscopy analysis, and the prepared LPSI and Li6.9Zn0.05P2S7.95O0.05I solid electrolytes exhibit an ionic conductivity of (4.4 and 4.2) mS·cm−1, respectively, at room temperature. The prepared Li6PS5Cl and Li5.95Zn0.025PS4.975O0.025Cl solid electrolytes exhibited ionic conductivities of 4.55 and 4.08 mS·cm−1, respectively at 30°C. To evaluate the electrochemical stability of the prepared solid electrolyte, we perform cyclic voltammetry and galvanostatic discharge/charge voltage profiles analysis. In addition, the fabricated all-solid-state battery exhibits a high specific capacity of 165 mAh·g−1 (0.1 C), and a high-capacity retention rate of 95.2 % for LPSI-0.05ZnO. And the initial discharge capacity of the assembled all-solid-state battery showed a specific capacity of 149 mAh g-1 (0.1 C) and a high capacity retention rate of 99.7 % for LPSCl-0.025ZnO. Interestingly, ZnO co-doped LPSI and LPSCl solid electrolyte exhibits longer air-stability than the undoped LPSI and LPSCl solid electrolyte in dry air with 10 % humidity.

목차 (Table of Contents)

• Acknowledgement …………………………………………………………………………4
• Abstract …………………………………………………………………………………….5
• List of tables ……………………………………………………………………….……….9
• List of figures ……………………………………………………………………………...10
• Chapter 1. Introduction
• 1-1. Lithium-ion secondary batteries ……………………………………………………...14
• 1-1-1. Composition of lithium-ion batteries ………………………………….……….17
• 1-1-2. Principle of lithium-ion batteries ……………………………………...……….17
• 1-2. All-solid-state lithium-ion batteries ………………………………………………….24
• 1-2-1. Inorganic/ceramic solid electrolyte ……………………………………………24
• 1-2-2. Properties of inorganic/ceramic solid electrolyte ……………………………...24
• 1-2-3. Li+ diffusion mechanism of inorganic/ceramic solid electrolyte ………………25
• 1-3. Inorganic solid electrolyte ……………………………………………………………26
• 1-3-1. Oxide solid electrolyte …………………………………………………………26
• 1-3-1-1. NASICON ………………………………………………………...……..26
• 1-3-1-2. Perovskite ………………………………………………………...……...29
• 1-3-1-3. LISICON ………………………………………………………...………31
• 1-3-1-4. Garnet ………………………………………………………...………….31
• 1-3-2. Sulfide solid electrolyte ………………………………………………………..34
• 1-3-2-1. Thio-LISICON ………………………………………………………......34
• 1-3-2-2. Li2S-P2S5 …………………………………………………………….......37
• 1-3-2-3. Argyrodite ………………………………………………………………..37
• 1-4. Purpose …………………………………………………………………………….38
• References ………………………………………………………………………………...39
• Chapter 2. General experimental
• 2-1. Physical characterization ……………………………………………………………..44
• 2-1-1. X-ray diffraction (XRD) ………………………………………………...…......44
• 2-1-2. Field emission scanning electron microscopy (FE-SEM) and Energy dispersive
• X-Ray spectroscopy (EDS) …………………………………………...………...48
• 2-1-3. Laser-Raman spectroscopy ……………………………………………….........48
• 2-1-4. Solid-state Nuclear Magnetic Resonance (NMR) ………………………………49
• 2-2. Electrochemical analysis ……………………………………………………………..52
• 2-2-1. Electrochemical impedance spectroscopy (EIS) …………………………….. ..52
• 2-2-2. Cyclic voltammetry (CV) ……………………………………………………...55
• 2-2-3. Direct current cycling (DC-cycling) …………………………………………...55
• 2-2-4. Galvanostatic charge-discharge measurements (CD) ……………………….…55
• 2-2-5. Air stability …………………………………………………………….………56
• References………………………………………………………………………….……...57
• Chapter 3. Synthesis and electrochemical performance of glass-ceramic Li7-2xP2S8-xOxI (0 ≤ x ≤ 0.2) solid electrolyte for all-solid-state lithium batteries
• 3-1. Introduction …………………………………………………………………………..58
• 3-2. Experimental …………………………………………………………………………60
• 3-2-1. Preparation of Li7-2xP2S8-xOxI solid electrolyte ……..………………………….60
• 3-2-2. Characterization and electrochemical measurements ……..…………………...61
• 3-3. Results and discussion ……………………………………………………………….62
• 3-3-1. Structural analysis ……………………………......…………………………….62
• 3-3-2. Electrochemical performance ………………………………………………….77
• 3-3-3. Air stability ……………………………......…………………………………...90
• 3-4. Conclusion…………………………………………………………………………....95
• References………………………………………………………………………………....96
• Chapter 4. Synthesis and electrochemical performance of Argyrodite type Li6-2xZnxPS5-xOxCl (0 ≤ x ≤ 0.1) solid electrolyte for all-solid-state lithium batteries
• 4-1. Introduction …………………………………………………………………………99
• 4-2. Experimental ………………………………………………………………………..101
• 4-2-1. Preparation of Li6-2xZnxPS5-xOxCl solid electrolyte …………………………..101
• 4-2-2. Characterization and electrochemical measurements ……..………………….101
• 4-3. Results and discussion ………………………………………………………...........103
• 4-3-1. Structural analysis ……………………………......…………………………...103
• 4-3-2. Electrochemical performance ………………………………………………...113
• 4-3-3. Air stability ………………………………………………………………...…123
• 4-4. Conclusion…………………………………………………………………………..127
• References………………………………………………………………………………..128
• Chapter 5. Summary ………………………………………………………………131