Coupling Electrochemical Leaching with Solvent Extraction for Recycling Spent Lithium-Ion Batteries

We propose coupling electrochemical leaching with solvent extraction to separate and recover Li and Co from spent lithium-ion batteries (LIBs). Electrochemical leaching occurs in the aqueous electrolyte for converting solid LiCoO₂ into soluble Li⁺ and Co²⁺, in which electrons act as reductants to reduce Co(III) to Co(II). Simultaneously, solvent extraction occurs at the interface of aqueous and organic phases to separate Co²⁺ and Li⁺. By capturing and utilizing the protons from P507, leaching yields for both Co and Li exceed ∼7 times than acid leaching without solvent extraction. The extraction efficiency of Co²⁺ reaches 86% at 60 °C, 3.5 V, while simultaneously retaining the majority of Li⁺ in the H₂SO₄ solution. The total leaching amount was improved because the organic phase provides protons to help the leaching of Co²⁺, and the continuous extraction process of Co(II) maintains the low Co²⁺ concentration in the aqueous solution. The synergistic interaction between electrochemical leaching and solvent extraction processes significantly reduces the consumption of chemicals, enhances the utilization efficiency of protons, and simplifies the recovery process. The leaching kinetics of Li and Co both conforms well to the residue layer diffusion control model and the activation energy (<i>E</i>_a) values of the leaching for Li and Co are 4.03 and 7.80 kJ/mol, respectively. Lastly, the economic and environmental assessment of this process also demonstrates the advantages of this method in reducing inputs, lowering environmental pollution, and enhancing economic benefits.