Near-to-Stoichiometric Acidic Recovery of Spent Lithium-Ion Batteries through Induced Crystallization

High consumption of acids and reductants is usually required when spent lithium-ion batteries are recycled using a hydrometallurgy route. The overstoichiometric chemicals end up as pollutants that have to be further treated. Low chemical and energy consumption have attracted considerable attention to achieve sustainability of a recycling process. In this research, LiFePO4 was used as a reductant and induced crystallization was performed for the removal of Fe and P. More importantly, we demonstrate that it is possible to achieve additional reductant-free and near-to-stoichiometric acidic recovery of spent ternary lithium-ion batteries (NCMs) by introducing FePO4·2H2O seed crystals and using waste LiFePO4. High efficiencies (>96%) of critical metals including Ni, Co, Mn, and Li are achieved, while iron phosphate remains as a solid product. Then, the leaching solution can be further used for the Ni–Co–Mn hydroxide precursor and lithium carbonate preparation. In addition, the mechanisms were subsequently investigated by combining thermodynamics analysis and systematic characterizations. This entire recycling process can be a highly economic, closed-loop alternative for recovering valuable metals from spent lithium-ion batteries.