ZrCl4 도핑 효과가 황화물계 고체전해질의 전기화학적 성능 및 대기안정성에 미치는 영향에 관한 연구 = Effects of ZrCl₄ Doping on Electrochemical Performance and Air Stability in Sulfide-Based Solid Electrolytes.

다국어 초록 (Multilingual Abstract)

Sulfide-based solid electrolytes (SEs), including Li3PS4 (314), Li6PS5Cl (615), and Li7P3S11 (7311), offer high ionic conductivities suitable for all-solid-state batteries (ASSBs), yet suffer from intrinsic moisture sensitivity and interfacial instability with lithium metal. In this study, ZrCl4 doping is explored as a universal strategy to enhance the structural stability, ionic transport, and air tolerance of these three representative sulfide electrolytes. ZrCl4-doped samples are synthesized via high-energy ball milling, and their structural evolution, ionic conductivity, activation energy, and electrochemical performance are systematically evaluated. Across all systems, Zr–Cl co-doping produces chemically homogeneous and densely packed microstructures, as confirmed by SEM–EDS analyses, while maintaining the original crystalline framework. The 314, 615 and 7311 electrolytes show the most pronounced improvements, achieving maximum ionic conductivities of 1.12 mS·cm-1, 7.43 mS·cm-1 and 3.13 mS·cm-1, respectively. Activation energy measurements indicate reduced or marginally altered migration barriers depending on the host structure, reflecting distinct doping sensitivities among the sulfide systems. Air-exposure experiments reveal a substantial reduction in H2S generation-up to 60–70% lower than pristine samples—which is attributed to the formation of strong Zr–S bonds and Li–Cl-rich passivation layers. All-solid-state cells employing the doped electrolytes exhibit enhanced discharge capacity, improved coulombic efficiency, and superior cycling stability compared to undoped counterparts. These results demonstrate that ZrCl4 doping provides a robust and scalable approach for simultaneously improving ionic conduction, moisture resistance, and interfacial electrochemical stability in sulfide solid electrolytes. This work offers practical design guidelines for developing chemically durable and high-performance sulfide-based ASSBs.

목차 (Table of Contents)

• Acknowledgement
• Abstract
• List of Tables
• List of Figures
• Chapter 1. Introduction
• 1-1. Lithium ion secondary batteries 1
• 1-1-1. Composition of lithium ion batteries 3
• 1-1-2. Principle of lithium ion batteries 6
• 1-2. All-solid-state lithium ion batteries 9
• 1-2-1. Oxide solid electrolytes 11
• 1-2-1-1. NASICON 13
• 1-2-1-2. Perovskite 15
• 1-2-1-3. Garnet 17
• 1-2-1-4. LISICON 19
• 1-2-2. Sulfide solid electrolytes 21
• 1-2-2-1. Thio-LISICON 22
• 1-2-2-2. Li2S-P2S5 type glassy sulfide 24
• 1-2-2-3. Argyrodite 25
• 1-2-3. Halide solid electrolytes 27
• References 29
• Chapter 2. General experimental
• 2-1. Characterization
• 2-1-1. X-ray diffraction (XRD) 36
• 2-1-2. Field emission scanning electron microscopy (FE-SEM) & Energy dispersive X-Ray spectroscopy (EDS) 39
• 2-2. Electrochemical performance analysis
• 2-2-1. Electrochemical impedance spectroscopy (EIS) 40
• 2-2-3. Cyclic voltammetry (CV) 43
• 2-2-4. Galvanostatic charge-discharge measurements (GCD) 44
• 2-3. Air stability test 45
• References 46
• Chapter 3. Effects of ZrCl₄ Doping on Electrochemical Performance and Air Stability in Sulfide-Based Solid Electrolytes
• 3-1. Introduction 47
• 3-2. Experimental
• 3-2-1. Sample preparation 49
• 3-2-2. Characterization 50
• 3-2-3. Electrochemical performance evaluation 50
• 3-2-4. Air stability measurements 51
• 3-3. Results and discussion 52
• 3-4. Conclusion 84
• References 85
• Chapter 4. Summary 92