Tailored Sn Nano-Seed Electroplating on Cu Current Collectors for High- Performance Lithium Metal Batteries

다국어 초록 (Multilingual Abstract)

Lithium metal, with its high specific capacity of 3860 mAh g⁻¹ and low reduction potential of −3.04 V versus the standard hydrogen electrode, is regarded as one of the most promising anodes for realizing next-generation high-energy-density batteries. Nevertheless, dendrite-induced short circuits, galvanic corrosion, continuous formation of the solid–electrolyte interphase, and large volume fluctuations during cycling present major obstacles to its practical use. A stable and well-engineered current collector is therefore essential to promote uniform Li nucleation and suppress dendritic growth. In this study, we demonstrate that Li nucleation and growth on Cu can be effectively controlled by adjusting the spatial distribution of Sn nano-seeds produced through ethanol-assisted electrodeposition. By systematically varying the ethanol fraction in the plating bath, prepared with 0, 10, and 20 vol% ethanol, we simultaneously tuned the electrolyte wettability and the solution resistance. These two factors ultimately determine whether Sn deposits as isolated clusters or as a homogeneously dispersed population of nano-seeds. The Cu foil prepared with 10 vol% ethanol exhibited the most uniform nano-seed distribution, resulting in the lowest nucleation overpotential of 84.4 mV and the most homogeneous initial Li nucleation. Ex-situ electron microscopy further revealed that this early-stage nucleation uniformity directly dictates high-capacity Li growth. A uniform distribution of nano- seeds promotes dense and compact Li layers, whereas clustered seeds or an unmodified Cu surface lead to localized Li accumulation and dendritic morphologies. Long-term cycling confirmed these interfacial advantages. The optimized Cu foil formed a much thinner and denser Li/SEI layer, minimized the buildup of electrically isolated dead Li, and maintained a lower charge-transfer resistance throughout operation. As a result, Li/Cu asymmetric cells retained Coulombic efficiencies above 95% for more than 250 cycles, symmetric cells operated for roughly 650 hours without short-circuit failure, and full cells paired with NCM811 cathodes exhibited enhanced capacity retention and reduced polarization. Collectively, these results demonstrate that the spatial distribution of the seed material, rather than merely the presence of the material itself, plays a decisive role in determining Li nucleation pathways, Li-ion flux uniformity, and interfacial stability. The nano-seed engineering strategy presented here provides a practical and scalable route toward designing advanced current collectors for high-performance lithium-metal batteries.

목차 (Table of Contents)

• CHAPTER 1. Introduction 1
• 1.1 Overview of Rechargeable Batteries 1
• 1.2 Lithium-Metal Anodes: Potential and Challenges 3
• 1.3 Interfacial Failure Mechanisms in Lithium-Metal Batteries 7
• 1.4 Limitations of Conventional Stabilization Strategies 8
• 1.5 Current Collector Surface Engineering 9
• 1.6 Tin-Based Lithiophilic Modification and Its Limitations 10
• 1.7 Research Motivation and Approach 12
• CHAPTER 2. Experimental 13
• 2.1 Preparation of SC_EtOH Electrodes 13
• 2.2 Materials Characterization 14
• 2.2.1 Field-Emission Scanning Electrode Microscope (FE-SEM) 14
• 2.2.2 Contact angle meter 14
• 2.2.3 X-Ray Diffractometer (XRD) 14
• 2.2.4 X-Ray photoelectron spectroscopy (XPS) 15
• 2.3 Preparation of Asymmetric cells 15
• 2.3.1 Cell Fabrication 15
• 2.3.2 Electrochemical Measurements 15
• 2.4 Preparation of Symmetric and Full Cells 16
• 2.4.1 Li pre-deposition 16
• 2.4.2 Symmetric Cells 17
• 2.4.3 Full Cells 17
• CHAPTER 3. Results and Discussion 18
• CHAPTER 4. Conclusions 56
• References 57
• 국문초록 61