In-situ oxidation for selective lithium extraction from spent LiFePO4 cathodes by low acid dosage

Abstract

Recovery of lithium from spent lithium iron phosphate batteries is crucial to alleviating the storage of lithium. This study proposes a method for the selective recovery of lithium from spent lithium iron phosphate battery cathodes using a leaching system of H2SO4 and H2O2. Efficient and selective lithium recovery was achieved through in-situ oxidation of lithium iron phosphate driven by a low acid dosage, and the mechanism of selective lithium recovery was investigated by precipitation experiments of Fe2+ and PO43−. The shrinking core model was used for the kinetic analysis of the leaching process, and the results suggested that the leaching process was controlled by the internal diffusion of the product layer. Moreover, essential leaching parameters such as acid concentration, H2SO4 dosage, H2O2 dosage, leaching time, and leaching temperature were systematically investigated. The results showed that the leaching rate of Li reached 97.95 % along with a selectivity of 99.60 %, which meets the standard of the battery-grade Li2CO3, while the leaching rate of both Fe and P was less than 1 %.