Microwave-Assisted Recovery of Co, Ni, Mn and Li from Spent Li-Ion Battery by Dilute Organic Acids and Synthesis of LiNi0.5Co0.2Mn0.3O2 from Recovered Metal Precursors
摘要
Recycling of spent Li-ion batteries (LIBs) is an important step towards environmental sustainability and circular economy goals. Here, we report a novel hydrometallurgical process for recovering Co, Ni, Mn, and Li from the mixed cathodes of spent LIBs by a combination of microwave irradiation, organic acid leaching, and precipitation. Tartaric acid (TA) was chosen as a chelating agent and gallic acid (GA) as a reducing agent. Here, GA liberated 2 e−, which reduced the insoluble metal ions of the cathode into readily soluble form (i.e., Co+4/+3 to Co2+, Mn+4/+3 to Mn2+ and Ni3+ to Ni2+). The optimized conditions for efficient dissolution were found to be 0.1 M TA and 0.02 M GA with a solid-to-liquid ratio of 2 g/L under microwave irradiation for 5 min. Under the given conditions, 97.5% Co, 98.6% Ni, 96.8% Mn, and 99.5% Li leached from the cathode. From the dissolution mixture, Co, Ni, Mn, and Li were selectively precipitated as CoC2O4.2H2O, Ni(DMG)2, Mn–oxine complex, and Li3PO4 using stoichiometrically excess oxalic acid, dimethyl glyoxime, oxine, and sodium phosphate, respectively. These recovered metal precursors were reused for the synthesis of LiNi0.5Co0.2Mn0.3O2 by the solid-state method. The successful transformation of waste to wealth was achieved by eco-friendly reagents.