Theoretical-molar Fe recovering lithium from spent LiFePO batteries: an acid-free, efficient, and selective process.

In spent lithium iron phosphate batteries, lithium has a considerable recovery value but its content is quite low, thus a low-cost and efficient recycling process has become a challenging research topic. In this paper, two methods about using the non-oxidizing inorganic iron salt - Fe(SO) to recover lithium from LiFePO are proposed. The method-1 is theoretical-molar Fe(SO) (Fe(SO) : LiFePO =1:2) dosage is added and more than 97% of lithium can be leached in just 30 min even under a pretty high solid-liquid ratio of 500 g/L. Spectrophotometry provides the evidence of Fe/Fe substitution in the leaching process. In the method-2, the generated Fe originating from LiFePO is fully utilized with the addition of HO, and the dosage of Fe(SO) is decreased by two thirds (Fe(SO) : LiFePO =1:6). Several sulphates (CuSO, NiSO, MgSO) are employed to explore the leaching mechanism. All the results reveal that the reaction of Fe substituting Fe has a powerful driving force. In addition, these two leaching processes simultaneously present superior selectivity for the impurities. The Fe(SO) in two methods does not cause pollution and is easily regenerated by adding HSO. The proposed rapid, efficient and selective leaching thought would be a competitive candidate for recycling spent LiFePO batteries.