A closed-loop coupling process of leaching and solvent extraction for Li₂CO₃ and FePO₄ recovery from spent LiFePO₄

To satisfy the increasing global demand for the strategic metal lithium, recycling of LiFePO4 (LFP) batteries has become an irresistible trend and poses a challenge due to the cost. A low-cost process of recovering Li and FePO4 from simulated spent LFP was investigated through a closed-loop coupling technology of isomorphic substitution leaching and solvent extraction. A total of 99.41% of Li+ can be leached, and 96% of FePO4 can be recovered with an Fe-2(SO4)(3):LFP molar ratio of 1:6, H2SO4:LFP molar ratio of 0.5:1, and 0.4 ml H2O2/g(LFP) for 30 min. An eleven-stage extraction process for Fe3+ removal from lixivium-containing extraction, stripping and regeneration processes was designed and optimized. The total removal efficiency of Fe3+ was 97.22% by the 40 vt% N235 + 15 vt% TBP + kerosene extraction system at a phase ratio O/A of 3.5/1, and the lithium concentration in raffinate was 10.074 gL-1. The closed-coupling process was carried out on the simulated spent LFP with a total Li recovery efficiency of >99%. The low-cost leaching agent Fe-2(SO4)(3) was cyclically utilized. The coupling process can not only serve as a promising efficient recycling method for spent LFP batteries but also supply an inspiring route for other expensive metal recycling.