리튬이온전지용 양극활물질(NCA)의 표면생성물과 열안전성
- 주제(키워드) Lithium ion batteries , active materials , NCA , thermal stability
- 발행기관 고려대학교 대학원
- 지도교수 서광석
- 발행년도 2016
- 학위수여년월 2016. 2
- 학위구분 박사
- 학과 대학원 신소재공학과
- 원문페이지 106 p
- 실제URI http://www.dcollection.net/handler/korea/000000065739
- 본문언어 한국어
- 제출원본 000045866725
초록/요약
High Ni NCA active materials for lithium ion batteries were investigated to meet the lower cost and better thermal stability compared to commercial NCA. The second heat treatment was eliminated to lower production costs in this study and only washing and drying process was used after the first heat treatment. Generally washing process in NCA manufacturing technique was used to get rid of residual lithium compound at the surface of NCA such as LiOH and Li2CO3. However it was found that new products were formed at the surface of NCA after washing process and they had a good influence on the thermal stability of lithium ion batteries. NiOOH was found to be formed at the surface of NCA after washing process as a result of XPS and TGA. NiOOH was decomposed to NiO and H2O at the elevated temperature(>150℃). So thermal stability of cells would become deteriorated due to the excessive amount of water inside the cell if surface products were not decomposed sufficiently. The specification of powder moisture could be satisfied when NCA powders were dried at 200 ℃ after washing process. However, the specific capacity of NCA dried at 200 ℃ was decreased by 6 % compared to NCA dried at 150 ℃. The excessive amount of NiO created after drying process made the surface resistance of NCA increase, and consequently the cell capacity decreased. The amount of NiO was related to the amount of NiOOH. Al composition of NCA was increased from 1 mol% to 3 mol% to decrease the Ni composition at the surface of NCA. As a result the increased Al composition was very effective to reduce the amount of NiOOH and to prevent from cell capacity reduction. The NCA active materials which were manufactured by controling both Al composition and drying temperature improved the thermal stability and cyclability of lithium ion batteries. It was very difficult to improve the thermal stability and cyclability simultaneously in case of general NCA manufacturing process. However surface products formed after washing process made it possible to improve the safety and life span of lithium ion batteries simultaneously.
more목차
표 목차 (List of Tables) v
그림 목차 (List of Figures) vi
Abstract viii
1 서론 1
1.1 연구배경 1
1.2 리튬 이온 전지의 열안전성 4
2 High Ni NCA의 합성 7
2.1 High Ni NCA의 1차 소성 조건 7
2.2 1차 소성품의 세정 건조 13
2.3 세정 건조된 활물질의 용량 평가 18
3 18650 전지 평가(I) 23
3.1 활물질 분말 물성 23
3.2 화성 평가 결과 25
3.3 DC-IR 평가 25
3.4 열안전성 평가 28
3.5 고온 저장 평가 28
3.6 ARC 평가 결과 32
4 NCA-W 활물질의 수분 특성 36
4.1 측정 온도에 따른 분말 수분 변화 36
4.2 세정비 변화에 따른 TGA 36
4.3 TGA vs 수분 측정 결과 38
4.4 세정 후 활물질 표면변화 42
4.5 세정 후 표면 생성물의 XRD 분석 42
4.6 세정 후 표면 생성물의 XPS 분석 46
4.7 건조 온도 상승 실험 49
4.8 대기 방치 시간에 따른 분말 수분 변화 58
5 18650 전지 평가(2) 63
5.1 화성 평가 결과 63
5.2 AC-IR & DC-IR평가 63
5.3 수명 평가 66
5.4 열안전성 평가 70
5.5 고온 저장 평가 70
5.6 ARC 평가 74
5.7 일반NCA의 열안전성 개선 방법 78
6 NCA-W의 표면 저항 개선 85
6.1 활물질 조성 변경을 통한 저항 개선 85
7 결론 91
8 References 93
