Leaching of Lithium Iron Phosphate in the Presence of Cu and Al in Mild Sulfuric Acid Solutions

Abstract As the first generations of lithium iron phosphate (LFP) EV batteries face their end-of-life, increasing amounts of LFP-containing battery waste will enter the existing and development stages of hydrometallurgical recycling processes. This research investigates the oxidative and mild acid (0.05–0.1 M) leaching behavior of synthetic LFP black mass, i.e., LFP (LiFePO 4 ) powder, in the presence of the typical impurities–Cu and Al–present in battery waste. Dissolved Fe , Dissolved LFP , Dissolved Cu , and Dissolved Al were observed as leaching responses using a Design of Experiments (DoE). Additionally, a Reference experiment at a higher acidity (1 M) was conducted. In the investigated conditions ( T = 25 °C, t = 120 min, O 2 feed), Li leaching resulted in similar final yields ( t = 120 min) in all experiments (70–88 wt.%). Conversely, the leaching behavior of Fe varied substantially between experiments, with yields ranging from 5 to 76 wt.%. It was found that dissolved Fe 2+ started to oxidize to Fe 3+ and precipitate as phosphate almost immediately after dissolution. The presence of Al did not have any significant impact on the system, due to the passivation of the Al surface by Al 2 O 3 , whereas a high amount of Cu in the system was found to have a positive correlation with increased Fe 2+ oxidation to Fe 3+ . This is assumed to be due to the related pH increase favoring Fe 2+ oxidation and hindering Cu dissolution. Based on the results, predictive leaching models were built and an increased concentration of sulfuric acid was found to have a substantial effect, increasing leaching yield in all created models ( Dissolved Fe, LFP, Cu, and Al ). Graphical Abstract