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

Abstract

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 Fe2(SO4)3:LFP molar ratio of 1:6, H2SO4:LFP molar ratio of 0.5:1, and 0.4 ml H2O2/gLFP 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 g·L−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 Fe2(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.