A Study of Purification and Structural Recovery of Spent LIB Hydrometallurgical Leaching Residues via Water Leaching-Alkali Roasting

Gihyun Kim; Nak-Kyoon Ahn; Kyungsoo Park

doi:10.7844/kirr.2025.34.6.38

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2025 Vol.34, Issue 6 Preview Page Next Page

Research Paper

A Study of Purification and Structural Recovery of Spent LIB Hydrometallurgical Leaching Residues via Water Leaching-Alkali Roasting 폐배터리 습식 제련 침출 잔사의 수침출-알칼리 배소 기반 정제 및 구조 회복에 관한 연구

31 December 2025. pp. 38-47

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Abstract

The rapid expansion of electric vehicles (EVs) and energy-storage systems (ESSs) has significantly increased the demand for lithium-ion batteries (LIBs) and has led to a sharp increase in the number of End-of-Life (EoL) batteries consequently. While graphite anode is an essential LIB component, accounting for approximately 12-21% of its weight, it is often consumed as a reductant during smelting or discarded as a leaching residue in current recycling processes, resulting in limited reuse. To address this issue, a two-step purification and regeneration process that combines water leaching and alkali roasting was suggested to recover graphite from the leaching residues in hydrometallurgical process for recycling EoL-LIBs. Sulfates of transition metals, such as Ni, Co, and Mn, were effectively removed through water leaching, while relatively stable Al species were retained. Insoluble impurities, such as Al₂O₃ and SiO₂, were converted into soluble compounds, such as NaAlO₂ and Na₂SiO₃, in the subsequent alkali-roasting step, which led to a reduction in the ash content of up to 44.5%. Some insoluble phases (e.g., NaAlSiO₄) were also generated; hence, additional acid leaching treatment is expected to be beneficial. Moreover, structural analyses revealed that the interlayer spacing (d₀₀₂) decreased from 0.3360 to 0.3346 nm, whereas the Raman D-band-to-G-band ratio (I_D/I_G) decreased from 0.53 to 0.34-0.37 during treatment. In addition, the C 1s XPS spectrum revealed that the relative intensity of the π-π* satellite peak increased from 5.0% to more than 9%, while the C=O peak disappeared, confirming that both graphite crystallinity and sp² bonding domains were significantly restored. Taken together, these findings suggest that the alkali-roasting-based purification approach developed in this study effectively removes impurities while enhancing the structure and surface chemistry of graphite, with the regenerated graphite potentially usable as a LIB anode material.

Keywords

spent graphite recycling

alkali roasting

removing impurities

regenerating

graphite anode

전기차(EV)와 에너지저장장치(ESS)의 보급 확대에 따라 리튬이온전지(LIB)의 수요가 급증히 증가하면서, 이에 따른 폐배터리 발생량 또한 빠르게 늘어나고 있다. LIB의 구성 성분 중 흑연은 약 12-21 wt%를 차지하는 핵심 소재임에도 불구하고, 재활용 공정에서는 대부분 제련 환원제로 사용되거나 침출 잔사 형태로 처리되어 활용도가 낮은 실정이다. 본 연구에서는 이러한 침출 잔사로부터 회수한 폐흑연을 대상으로 수침출과 알칼리 배소를 연계한 2단계 정제 및 재생 공정을 제안하였다. 수침출 단계에서는 전이금속 황산염(Ni, Co, Mn)이 효과적으로 제거된 반면, Al 성분은 상대적으로 안정적으로 잔류하였다. 이어서 수행한 알칼리 배소에서는 불용성 불순물(Al₂O₃, SiO₂ 등)이 NaAlO₂, Na₂SiO₃ 등의 수용성 화합물로 전환되어 회분(ash) 함량이 최대 44.5%까지 감소하였다. 다만, 일부 NaAlSiO₄와 같은 수불용성상이 형성되어 추가적인 산침출 처리가 필요함을 확인하였다. 구조 분석 결과, 층간 간격(d₀₀₂)은 0.3360 nm에서 0.3346 nm로 감소하였으며, Raman 분석에서 I_D/I_G 비가 0.53에서 0.34-0.37로 낮아졌다. 또한 XPS C 1s에서 π-π* 위성 피크가 5.0%에서 9% 이상으로 증가하고, C=O 피크가 소거되어 흑연의 결정성과 sp² 결합 영역이 뚜렷하게 회복된 것을 확인할 수 있었다. 이상의 결과를 종합하면, 본 연구에서 제안한 알칼리 배소 기반 정제 전략은 불순물 제거, 결정성 회복, 표면 화학 제어를 동시에 달성할 수 있음을 입증하였으며, 경제성 있는 재생 흑연의 LIB 음극재 활용 가능성을 제시한다.

키워드

폐흑연 재활용

알칼리 배소

불순물 제거

구조 회복

음극재

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Information

Publisher :The Korean Institute of Resources Recycling
Publisher(Ko) :한국자원리싸이클링학회
Journal Title :Resources Recycling
Journal Title(Ko) :자원리싸이클링
Volume : 34
No :6
Pages :38-47
Received Date : 2025-09-05
Revised Date : 2025-10-02
Accepted Date : 2025-10-20
DOI :https://doi.org/10.7844/kirr.2025.34.6.38

Resources Recycling ISSN:2765-3439(Print) 2765-3447(Online) 자원리싸이클링

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