Electric-field-induced assists in the preferential extraction of lithium from spent LiFePO4

Abstract

Due to the advantages of high energy density, high conversion efficiency, and rapid response speed associated with power lithium batteries, there has been a significant expansion in their use. However, industry forecasts indicate that if large quantities of waste lithium-ion batteries are not managed properly, it could lead to serious environmental pollution issues as these batteries reach the end of their life cycle. Therefore, developing highly efficient and environmentally friendly recycling technologies is urgently needed. This paper proposes a green and efficient selective lithium extraction process integrating leaching technology with electrochemical methods. This approach enables the separation of Li and FePO₄ within an electrolyte through electric field assistance while effectively minimizing waste liquid generation. The effects of various factors on Li and Fe’s leaching rates were investigated using orthogonal and single factor experiments. Under optimal conditions, the leaching rate of Li reached 98.85%, while that for Fe was only 0.22%, resulting in a selectivity ratio (Li/Fe) of 99.78%, which demonstrates successful selective extraction of lithium. Furthermore, we assessed the feasibility of this experiment through potentiometric-pH diagrams. We elucidated its mechanism using XPS, XRD, and SEM. Unlike conventional destructive leaching methods, the Li extraction process facilitated by the electric-field-induced assistance resembles the charging process of LiFePO₄ batteries. Ultimately, Li was recovered as Li₂CO₃, while Fe and P present in the slag were subsequently retrieved as FePO₄ with battery-grade purity through a hydrothermal method. This study presents an environmentally sustainable and economically viable approach for recovering spent LiFePO₄ batteries.