폐 리튬인산철 재활용을 위한 글리신 기반 선택적 리튬 침출 및 침전법 적용 기초 연구 = A Fundamental Study on Selective recovery of lithium from Spent LFP batteries Using Glycine-Based Leaching and Precipitation process

다국어 초록 (Multilingual Abstract)

LFP batteries have been increasingly used in electric vehicles due to their thermal stability, long cycle life, and low cost. Consequently, the generation of spent LFP is expected to increase significantly. Improper disposal of spent LFP can lead to environmental pollution and resource loss, necessitating the development of recycling technologies. Among various recycling methods, hydrometallurgy is widely applied due to its low energy consumption, high metal recovery, and high product purity. In particular, selective leaching has received attention for simplifying the overall process. However, conventional inorganic acid lixiviants may cause environmental concerns, while organic acids often present limitations in economic feasibility due to their high cost. Therefore, this study established a spent LFP recycling process using glycine, an amino-acid-based alternative lixiviant, in which lithium is selectively leached to simplify the conventional hydrometallurgical process.
Application of the glycine–H2O2 system to LFP cathode active material resulted in 99.5% Li and 1.2% Fe leaching efficiencies and 92.9% Li selectivity within 30 min under the conditions of 1.5 M glycine, 1.0 M H2O2, initial pH 6, pulp density of 20 g/L and 25℃, confirming selective leaching of Li. However, when impurities such as Cu2O and Al2O3 were present, selective leaching was hindered. Under the same conditions, the use of an alternative oxidant (0.5 M Na2S2O8) achieved 98.6% Li, 0.9% Fe, 0.0% Al, and 97.6% Cu leaching efficiencies within 60 min, corresponding to 18.5% Li selectivity, confirming that selective Li leaching is difficult under conditions containing impurities, such as LFP BM, due to the leaching of copper.
Copper was precipitated using a NaHS-based sulfide precipitation process. At 25℃, 1 equivalent of NaHS was added, achieving a copper precipitation efficiency of 99.9% within 10 min. After impurity purification, lithium was recovered using carbonate precipitation. At 80℃, 6 equivalents of Na2CO3 were added, achieving a Li2CO3 precipitation efficiency of 74.0% within 10 min.
Based on these results, this study proposed a glycine-based hydrometallurgical process comprising leaching, impurity precipitation, and carbonate precipitation. This process was suggested as an environmentally friendly and economical alternative to conventional leaching methods for Li recovery from spent LFP batteries.

목차 (Table of Contents)

• 1. 서론 1
• 1.1 연구배경 1
• 2. 문헌연구 9
• 2.1 LFP BM 침출 연구 사례 10
• 2.2 무기산 침출제 적용 침출 연구 사례 12
• 2.3 유기산 침출제 적용 침출 연구 사례 14
• 2.4 산화제 단독 적용 침출 연구 사례 16
• 2.5 글리신 적용 침출 연구 사례 18
• 2.6 황화 침전 적용 연구 사례 20
• 3. 연구목적 22
• 4. 실험재료 및 방법 24
• 4.1 실험 재료 24
• 4.2 침출 실험 26
• 4.3 반응 차수 분석 28
• 4.4 침출 동역학 분석 29
• 4.5 불순물 침전 실험 30
• 4.6 탄산염 침전 실험 31
• 4.7 분석 장비 32
• 5. 실험 결과 및 토론 33
• 5.1 LFP 양극활물질 대상 글리신-H2O2 시스템 적용 연구 33
• 5.1.1 글리신 단독 영향 평가 33
• 5.1.2 H2O2 단독 영향 평가 36
• 5.1.3 글리신 농도의 영향 38
• 5.1.4 H2O2 농도의 영향 40
• 5.1.5 초기 pH의 영향 44
• 5.1.6 광액 농도의 영향 46
• 5.1.7 반응 온도와 시간의 영향 48
• 5.1.8 침출 동역학 분석 50
• 5.1.9 침출 잔사 특성화 분석 53
• 5.2 불순물(Cu2O, Al2O3) 첨가 조건에서 글리신 적용 연구 56
• 5.2.1 불순물 첨가의 영향 56
• 5.2.2 초기 pH의 영향 58
• 5.2.3 H2O2 농도의 영향 60
• 5.2.4 산화제 종류의 영향 62
• 5.3 불순물 침전 연구 64
• 5.3.1 시멘테이션 64
• 5.3.2 황화 침전 66
• 5.3.3 황화 침전물 XRD 분석 68
• 5.4 탄산염 침전 연구 70
• 5.4.1 반응 온도의 영향 70
• 5.4.2 Na2CO3 투입 당량의 영향 72
• 5.4.3 탄산염 침전물 XRD 분석 74
• 5.5 폐 LFP로부터 선택적 Li 회수를 위한 공정도 76
• 6. 결론 및 향후 연구 78
• 6.1 결론 78
• 6.2 향후 연구 80
• 6.2.1 침출액 내 P 침전 제거 80
• 6.2.2 용매추출을 통한 Li 회수 및 글리신 재생 81
• 7. 참고 문헌 82