Hydrometallurgical recovery of EoL LFP batteries using oxalic acid as leaching agent

The extraction of lithium (Li), iron (Fe), aluminum (Al), and copper (Cu) by oxalic acid solution from lithium iron phosphate (LFP) electric vehicle batteries was systematically investigated. Following battery disassembly, a comprehensive pretreatment scheme was employed, comprising shredding, crushing/grinding, sieving, and washing to reduce particle size and recover valuable battery materials in a stream collectively known as black mass. The black mass primarily contains the valuable components of the anode (graphite) and cathode (LiFePO4), as well as impurities such as aluminum and copper foils used as current collectors. Leaching experiments were conducted by varying oxalic acid concentration, temperature, and leaching time. Lithium extraction reached 100% at an oxalic acid concentration of 0.7 M, a leaching temperature of 70 °C, a liquid-to-solid ratio of 10 L/kg, and a leaching time of 30 minutes. Under these conditions, iron from LiFePO4 is initially dissolved but subsequently precipitated as iron oxalate and iron phosphate oxide, thereby limiting its overall extraction to very low levels (<5%). Nearly 100% of aluminum is dissolved, whereas copper dissolution remains relatively low (<2%). At lower oxalic acid concentrations, the extraction efficiencies of lithium and aluminum decrease, while remaining largely unaffected by temperature variations. Overall, the oxalic acid-based process demonstrates high efficiency for lithium extraction, effective separation from the solid matrix, and strong potential for subsequent lithium recovery from the leachate.