Study on metal recovery process and kinetics of oxidative leaching from spent LiFePO4 Li-batteries

Abstract

A green environmental protection and enhanced leaching process was proposed to recover all elements from spent lithium iron phosphate (LiFePO4) lithium batteries. In order to reduce the influence of Al impurity in the recovery process, NaOH was used to remove impurity. After impurity removal, the spent LiFePO4 cathode material was used as raw material under the H2SO4 system, and the pressure oxidation leaching process was adopted to achieve the preferential leaching of lithium. The E-pH diagram of the Fe-P-Al-H2O system can determine the stable region of each element in the recovery process of spent LiFePO4 Li-batteries. Under the optimal conditions (500 r·min–1, 15 h, 363.15 K, 0.4 MPa, the liquid-solid ratio was 4:1 ml·g–1 and the acid-material ratio was 0.29), the leaching rate of Li was 99.24%, Fe, Al and Ti were 0.10%, 2.07% and 0.03%, respectively. The Fe and P were precipitated and recovered as FePO4∙2H2O. The kinetic analysis shows that the process of high-pressure acid leaching of spent LiFePO4 materials depends on the surface chemical reaction. Through the life cycle assessment (LCA) of the spent LiFePO4 whole recovery process, eight midpoint impact categories were selected to assess the impact of recovery process. The results can provide basic environmental information on production process for recycling industry.