High-efficiency leaching process for selective leaching of lithium from spent lithium iron phosphate.

ABSTRACT

With the arrival of the scrapping wave of lithium iron phosphate (LiFePO4) batteries, a green and effective solution for recycling these waste batteries is urgently required. Reasonable recycling of spent LiFePO4 (SLFP) batteries is critical for resource recovery and environmental preservation. In this study, mild and efficient, highly selective leaching of lithium from spent lithium iron phosphate was achieved using potassium pyrosulfate (K2S2O7) and hydrogen peroxide (H2O2) as leaching agents. The leaching rates of lithium and iron were 99.83 % and 0.34 %, respectively, at the optimal leaching conditions of 4 vol% 30 wt% H2O2, 0.08 mol/L K2S2O7, 25℃, 5 min, and a solid-liquid ratio of 20 g/L. Meanwhile, the mechanism of the leaching process was explored by thermodynamic, XRD, XPS, FTIR, and SEM analyses. The leaching solution was concentrated and purified, with the addition of potassium carbonate (K2CO3) to convert lithium into lithium carbonate (Li2CO3). A small amount of sulfuric acid (H2SO4) is added to the saline wastewater after precipitation, which can be converted into a leaching agent for recycling after heat treatment. This study provides a sustainable green process for the recovery of lithium iron phosphate and a new idea for resource recovery.