Repurposing of spent lithium-ion battery separator as a green reductant for efficiently refining the cathode metals

• Published in: Waste management (Elmsford) 2023-01, Vol.155, p.129-136
• Main Authors: Hou, Wei, Huang, Xuanrui, Tang, Rui, Min, Yulin, Xu, Qunjie, Hu, Zhenhu, Shi, Penghui
• Format: Article
• Language: English
• Subjects: Li+ leaching; Pyrolysis; Reduction roasting; Separator; Spent lithium-ion batteries
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2022.11.002

[Display omitted] •A novel roasting method relying on LIB separator was proposed for cathode refining.•Over 93 % Li+ was leached after 2-h separator mediated roasting at 500 °C.•Spent cathode was in situ converted to the desired products, CoO and Li2CO3.•Separator pyrolysis products, C2H4 and CO, dominated the cathode reduction. Developing green and high-efficient pyrometallurgy processes to recycle precious metals from spent lithium-ion batteries (LIBs) is of great importance for resource sustainability and environmental protection. Herein, a novel reduction roasting approach relying on spent LIB separator to refine the spent cathode is proposed. The efficiency of repurposing separator as a reductant for roasting the spent LiCoO2 cathode and the underlying mechanisms were investigated. After the separator-mediated roasting at 500 °C for 2 h, Li+ leaching efficiency of the cathode reached 93.2 %, >2.6 times higher than those after roasting without reductant (25.2 %) or with benchmark reductant graphite (26.1 %). Under the separator-added roasting condition, the cathode was converted to the desired products, CoO and Li2CO3. Based on the analysis of in-situ reaction using thermogravimetric/differential scanning calorimetry and pyrolysis gas species identification, the separator-mediated reduction roasting of cathode was composed of two stages, i.e., reducing gas generation due to separator pyrolysis, followed by the reducing gas mediated LiCoO2 reduction. During the process, the generated C2H4 and CO dominated the reduction. The use of co-existing separator to recover precious metals from spent LIBs is an effective and sustainable strategy to maximize the utilization of spent LIBs.