고용량 실리콘 기반 음극에 적합한 바인더에 기반한 리튬 이온 전지의 성능 향상에 관한 연구 = Research on the Performance Improvement of Lithium-Ion Batteries Based on Binders Suitable for High-Capacity Silicon-Based anodes

다국어 초록 (Multilingual Abstract)

Research on the Performance Improvement of Lithium-Ion Batteries Based on Binders Suitable for High-Capacity Silicon-Based anodes Hyeonmo Moon Dept. Chemical & Biological Engineering Graduate School Hanbat National University Advisor : Prof, Myung-Hyun Ryou Silicon (Si) has the advantage of having a theoretical capacity (4,200 mAh g ⁻¹) that is about 10 times higher than graphite. Therefore, silicon is an attractive candidate as a next-generation lithium ion battery (LIB) anode material in that it is rich and low-cost. However, there is a disadvantage that volume expansion and contraction of about 300% of the particles are repeated during charging and discharging. This causes particle damage, electrode separation, and SEI instability, resulting in a rapid decrease in capacity and lifespan. In this study, a composite binder (SBR-PAA) in which styrene-butadiene rubber (SBR) and polyacrylic acid (PAA) are mixed will be applied to overcome the following disadvantages. The SBR binder provides elasticity and flexibility between the Si particles and effectively mitigates the mechanical stress generated by the repeated volume change of Si during lithiation and delithiation, while the PAA binder contains carboxyl (-COOH) groups that form strong hydrogen bonds with the Si surface, resulting in excellent adhesion. The Si electrode to which the SBR-PAA binder was applied showed excellent performance in slurry dispersion stability, adhesive strength, and electrical conductivity. In the centrifugal sedimentation experiment, the instability index was 0.260 µm s, which was the most stable, and the peel strength was 515 ⁻¹, which was higher than PAA (470 ⁻¹) and SBR-CMC (417 ⁻¹). In addition, the sheet resistance was measured to be 1.859 mΩ sq ⁻¹ and the electrical conductivity to be 2.53 S cm ⁻¹, confirming that the electron transfer path was improved. As a result of the electro chemical evaluation, the SBR-PAA electrode showed an initial discharge capacity of 3,184 mAh g ⁻¹ (C.E. = 83.5%), and maintained 1,021 mAh g ⁻¹ even after 250 cycles at 1.2 ⁻ ¹. This shows significantly better cyclestability compared to PAA (808 mAh g ⁻¹) and SBR-CMC (152 mAh g ⁻¹). In addition, as a result of SEManalysis, the SBR-PAA electrode maintained a smooth surface with little crack even after charging and discharging, and formed a dense structure without Si particle agglomeration or non-uniform growth of SEI. It has stability that can maintain electrical contact with electrodes through electro chemical analysis and plays an important role in maintaining the long-term life by stabilizing the lithium ion diffusion path. Therefore, the SBR-PAA composite binder is evaluated as an eco-friendly and economical polymer binder because it has the flexibility of SBRandthe adhesion of PAA at the same time, and can replace the binder of the existing Si electrode because it can be water-soluble and low-cost processes. This study provides design guidelines that are useful for structural stability and high capacity strategies of Si-based anodes.

목차 (Table of Contents)

• List of Figures ⅱ
• ABSTRACT ⅳ
• Chapter 1. Introduction 1
• 1.1. Overview of Composite binder on silicon anodes 2
• 1.2. Reference 5
• Chapter 2. Large-are Analysis of Suitable Binders for Silicon-Based Anodes
• in Lithium-Secondary Batteries 7
• 2.1. Introduction 9
• 2.2. Experimental 13
• 2.2.1. Electrode Preparation 13
• 2.2.2. Preparation of Silicon Anodes 13
• 2.2.3. Characterization 14
• 2.2.4. Preparation of the Cell 14
• 2.2.5. Electrochemical Measurements 15
• 2.3. Results and Discussion 16
• 2.4. Conclusion 28
• 2.5. References 30
• Summary in Korean (국 문 요 약) 35