리튬 이차전지 음극용 Si/Carbon 복합 물질 제조 및 전기화학적 특성 = Electrochemical Characteristics and Fabrication of Si/Carbon composite Anode Materials for Lithium Rechargeable Batteries

다국어 초록 (Multilingual Abstract)

In this study, Nano-Si/graphite composite has been synthesized by ball milling with milling time under different milling atmosphere, and Nano-Si/graphite/carbon coated composite has been synthesized by heat-treatment of nano-Si/graphite composite for carbonization at 900 ℃ and 1000 ℃ under argon flow. Their electrochemical characteristics as anode materials for lithium secondary batteries were investigated. Besides, the cycle performance of a Si-based anode consisting of mixed silicon-graphite composite, slurry-coated onto Cu current collectors with different surface morphology was investigated.
Mechanically induced oxidation on the surface, probably along the edges of the graphene planes, is responsible for suppressing the fracture rate and preserving the crystallinity of natural graphite milled in Air and Oxygen atmosphere. Being compared with initial coulombic efficiency of electrode materials synthesized by ball milling with different atmosphere, the electrode material ball milled in Air atmosphere shows better initial coulombic efficiency than that ball milled in Oxygen and Ar.
Cycle-life and initial coulombic efficiency have significantly been improved by heat-treatment of nano-Si/graphite composite for carbonization at 900 ℃ and 1000 ℃ under argon flow. The crystallinity of natural graphite milled in air and oxygen atmosphere affects to the electrochemical characteristics of nano-Si/graphite/carbon coated composite, as before.
Cycle-life of the mixed silicon/graphite composite electrode, with a specific capacity of about 800 mAh/g, lithium-ion batteries has significantly been improved by using a Cu current collector with a properly modified surface morphology. Especially, it is found that the electrode slurry-coated on a nodule-type foil exhibits a quite good capacity retention. The enhanced cyclability was attributed to the formation of suggested that if further optimized current collector system is used with a high-performance Si-based active material, better cycle performance is expected.

목차 (Table of Contents)

• Ⅰ. 서론 = 1
• Ⅱ. 이론적 배경 = 8
• Ⅱ-1. 리튬이차전지의 작동원리 = 8
• Ⅱ-2. Si 계 음극재료 = 9
• Ⅱ-3. 기계적 합금화법 = 14
• Ⅱ-3-1. 기계적 합금화 및 분쇄 = 14
• Ⅲ. 실험방법 = 19
• Ⅲ-1. Nano-Si/graphite composite 제조 = 19
• Ⅲ-2. Nano-Si/graphite/carbon coated composite 제조 = 20
• Ⅲ-3. 표면형상이 다른 집전체 및 Si/graphite composite 제조 = 20
• Ⅲ-4. 전극 물성 분석 = 21
• Ⅲ-5. 전극 제조 및 전기화학적 특성 평가 = 21
• Ⅳ. 실험 결과 및 고찰 = 26
• Ⅳ-1. Nano-Si/graphite composite = 26
• Ⅳ-1-1. Nano-Si 의 특성 = 27
• Ⅳ-1-2. 구조적 특성 = 29
• Ⅳ-1-3. 전기화학적 특성 = 40
• Ⅳ-1-4. 결언 = 48
• Ⅳ-2. Nano-Si/graphite/carbon coated composite = 50
• Ⅳ-2-1. 구조적 특성 = 50
• Ⅳ-2-2. 전기화학적 특성 = 61
• Ⅳ-2-3. Blade milling 방법으로 제조된 구형화한 전극물질의 특성 변화 = 84
• Ⅳ-2-4. 결언 = 88
• Ⅳ-3. 표면형상을 변형시킨 집전체에 의한 Si/graphite composite 전극의 전극특성 변화 = 90
• Ⅳ-3-1. 서로 다른 표면형상을 가지는 Cu 집전체에 슬러리 코팅시킨 Si/graphite composite 로 구성된 Si- based 음극의 사이클 특성 = 90
• Ⅳ-3-2. 결언 = 102
• Ⅴ. 결론 = 103
• 참고문헌 = 106
• Abstract = 112