Separation of Cu impurity from spent lithium-ion batteries by roasting in air and leaching with (NH4)2CO3 solution of low concentration

Separation of Cu impurities from spent lithium-ion batteries (LIBs) before precipitating other valuable metals is critical to improve the quality of final products. Currently, the main process for separating Cu impurity from spent LIBs by extraction and precipitation has the disadvantage of being high cost and complicated process. In this work, the surface characteristics of spent LIBs materials before and after thermal treatment are explored, and the effects of the concentration of ammonium salts, temperature, and pulp density on the leaching of Cu impurity are investigated. The novel process proposed in this work removes Cu impurities from spent LIBs materials using a solution of (NH4)2CO3 at low concentration. The results suggest that organics on the spent LIBs surface can be effectively removed by heating at a temperature of 505 °C to avoid the influence of organics on the removal of Cu impurities. Furthermore, the results of the leaching experiment demonstrate that (NH4)2CO3 displays an excellent leaching effect on Cu compared to NH4Cl, (NH4)2SO4, and NH4HCO3. The leaching efficiency of Cu at the concentration of 0.25 mol/L (NH4)2CO3, temperature 80 °C and leaching time of 120 min reaches 99.1%. On the contrary, the leaching efficiencies of Ni, Co, and Mn are <4% on average. The thermodynamic analysis proves the potential for removing Cu impurities from spent LIBs materials using a solution of (NH4)2CO3 at low concentration. The process lays the foundation for the subsequent hydrometallurgical process to recover other metals.