리튬 금속 배터리에서 전해질 최적화를 통한 계면 설계

다국어 초록 (Multilingual Abstract)

Lithium metal batteries possess great potential for portable electronic devices as a next-generation secondary battery owing to their high specific capacity and energy density. However, their cycling stability is hindered by the unstable electrode electrolyte interfaces that accelerate parasitic reactions, dendritic growth, and capacity decay. This thesis focuses on two approaches for interphase engineering achieved by electrolyte tailoring. First, we formulate a moderately concentrated, weakly solvating ether electrolyte 1.5 M LiFSI in 2-methoxytetrahydropyran (2MeTHP). The compact cyclic backbone and steric hindrance induced by methoxy group attenuate Li⁺ solvent coordination and shift the primary solvation structure toward anion-rich contact ion pairs (CIPs) and aggregates (AGGs). This anion-dominated complexes promotes the formation of thin, inorganic-rich SEI/CEI without the viscosity, transport, and cost penalties. Under electrochemical testing, the electrolyte achieves high Li||Cu coulombic efficiency (CE) (~99.4%), long-life Li||Li cycling (~700 h) with low polarization, with 10 wt% triethyl phosphate (TEP) additive Li‖LFP full cell demonstrates outstanding cycling stability over ~600 cycles with high capacity retention. Second, we introduce phenyl isothiocyanate (PITC) as a multifunctional additive in a carbonate-based system (1 M LiTFSI in propylene carbonate) to stabilize the solid- electrolyte interphase layer on the Li metal anode and cathode. LiF, Li3N, sulfur rich and a π–π-stabilized polymeric layer formed on Li anode and cathode which suppress parasitic reactions and smoothing Li deposition. The modified electrolyte increases Li||Cu efficiency, lowers overpotential in Li||Li symmetric cells. In Li||LFP full cells, the optimized electrolyte demonstrated excellent cycling stability, maintaining a discharge capacity of 150 mAh g-1 1after 650 cycles at a 1C rate. Collectively, these results demonstrate that weak-solvation MCEs and targeted additive addition stabilizes SEI and CEI layer across both electrodes, which enables long cycling, high-rate performance, and safer LMBs without adding ultra-high salt concentration or volatile diluents. The findings provides a practical way to optimize solvation structures to achieved interfacial stability and enables scalable electrolyte designs for next-generation high-energy batteries.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• Ⅱ. Experimental procedure 12
• 2.1 Preparation of Electrolytes 12
• 2.2 Preparation of Electrodes 12
• 2.3 Electrochemical measurement 13
• 2.4 Preparation of Electrodes 17
• Ⅲ. Results and discussions 19
• 3.1 Moderate concentrated 2 methoxytetrahydropyran (2MeTHP) -based electrolyte for table LMBs 19
• 3.1.1 Introduction 19
• 3.1.2 Physcial properties and solvation structures 21
• 3.1.3 Lithium metal anode cycling performance 26
• 3.1.4 SEI layer characterization 32
• 3.1.5 Li
• LFP full cell cycling performance 40
• 3.1.6 Characterization of CEI layer 52
• 3.1.7 C rate performance of Li
• LFP cell 49
• 3.1.8 Conclusion 50
• 3.2 Stabilizing the Solid Electrolyte Interphase with Phenyl Isothiocyanate for Long-Cycle Lithium Metal Batteries 52
• 3.2.1 Introduction 52
• 3.2.2 Selection criteria for additives 54
• 3.2.3 Electrochemical properties of Li
• Cu cells 55
• 3.2.4 Electrochemical properties of Li
• Li cells 60
• 3.2.5 Electrochemical performance of Li
• LFP cells 70
• 3.2.6 Conclusion 74
• Ⅳ. Conclusion 76
• Appendix 84
• References 93
• Acknowledgements 120