A green and simplified method for selective recovery of lithium from the cathode scraps of spent LiFexMn1−xPO4 batteries

LiFexMn1−xPO4 (LMFP) batteries will be very important lithium resources in the foreseeable future due to the dramatic increases in their sizes. In this study, E-pH diagrams were constructed for the Li-Fe-Mn-P-H2O system at 298 K, which revealed that LMFP powders release lithium ions with higher redox potentials. A novel and simple method was developed for selective extraction of Li from spent LMFP powders via oxidative leaching with Na2S2O8. The effects of the experimental conditions on the efficiencies for leaching metals from the LMFP powders were investigated. The mechanism for selective leaching of Li was characterized with XRD and XPS analyses. The lithium leaching efficiency exceeded 98.84 %, while the efficiencies for Fe and Mn leaching were only 0.01 % and 0.67 %, respectively, under the optimum conditions; these included 2.0 times the theoretical amount of Na2S2O8, a leaching temperature of 85 ℃, a liquid-solid ratio of 5:1, and a leaching time of 240 min. Selective extraction of Li, Fe, and Mn with the oxidative leaching process was primarily influenced by the amount of Na2S2O8 and the liquid-solid ratio rather than by the leaching temperature and time. The orthorhombic crystal structure of the spent LMFP powders was largely preserved during the oxidative leaching process, as seen with charging of LMFP batteries. This efficient and environmentally friendly process shows potential for use in industrial-scale recycling of spent LMFP batteries.