Recovering Fe, Mn and Li from LiMn1-xFexPO4 cathode material of spent lithium-ion battery by gradient precipitation

Lithium manganese iron phosphate (LiMn1-xFexPO4, LMFP) has been applied in electric vehicles due to combining the performance advantages of LiFePO4 (LFP) and LiMnPO4 (LMP). Because of its more complex composition than LFP, the comprehensive recovery of LMFP remains a challenge. In this study, an effective method for recovery of Fe, Mn and Li from spent LMFP cathode material based on simple gradient precipitation was proposed. Firstly, the recovery of valuable metals by gradient precipitation was proved to be feasible by theoretical calculation. Then, 100% Fe, 99.54% Mn, and 100% Li in the spent LMFP cathode material were leached under the conditions of H2SO4 concentration of 1.5 mol·L−1, liquid-solid (L/S) ratio of 6: 1, temperature of 85 °C and reaction time of 60 min. Subsequently, 96.52% Fe, 98.46% Mn and 96.06% Li in the leaching solution were recovered by gradient precipitation in the form of phosphate at pH values of 1, 5.5 and 12, respectively. Moreover, economic analysis was conducted and the whole process had potential for large-scale application with good economic benefits.