Pollutant reduction and closed-loop process for recovering high value-added products from spent lithium-ion batteries

The conventional hydrometallurgical process for recycling spent ternary lithium-ion batteries has incomplete lithium recovery, excessive chemical consumption, and generation of wastewater and waste residues. Herein, an innovative route is employed to recover valuable metals from spent ternary cathode material. Firstly, LiNixCoyMnzO2 is dissociated and reduced into Li2CO3, elemental Ni and Co, and MnO via self-reduction roasting with graphite and precise control of phase transformation. Second, 92.8% of Li is selectively extracted via carbonation water leaching. Finally, ammonia leaching in the (NH4)2CO3–NH3–O2 system is used for the first time to selectively extract approximately 98% of Ni and Co from the leaching residue. The trace leaching leaching of Mn and impurity elements simplifies the subsequent solution purification and solvent extraction processes, and reduces the generation of waste residues. Because of the valence difference between Ni and Co in the ammonia leachate, they can be deeply separated via a two-stage solvent extraction, followed by ammonia evaporation to obtain cobalt products directly from the raffinate. Leaching agents and mother liquor can be reused, reducing recycling costs and avoiding the generation of high-salt wastewater. Economic and environmental evaluation results show that the proposed process has low energy consumption, low greenhouse gas emissions, and high recycling profit.