Selective oxidative leaching and restoration of FePO4 from spent LiFePO4 powder for regeneration into LiFePO4 cathode

Abstract

With the large-scale commercial use of LiFePO4(LFP), the resource regeneration of retired LFP is one of the crucial issues in the EV industry. More attention is being paid to efficient recovery of Fe and P resources and the high quality of FePO4 precursor through process flows for developing recycling methods. The selective extraction process of lithium from spent LFP powder in H3PO4 system was studied, and the distribution and migration behavior of each element during the leaching process were analyzed. Under the optimized leaching conditions, the leaching rates of each element in spent LFP powder are Li: 96.1 %, Fe: 0.28 % and Al: 23.3 %, respectively, showing high efficiency of Li extraction. At the same time, the leaching kinetics of the oxidation leaching process was studied, and the apparent activation energy was calculated to be 53.45 kJ mol−1, indicating that the oxidation leaching process is controlled by chemical reaction. The FePO4 precursor was directly reconstructed from iron-phosphorus slag using a short H3PO4 purification process. The capacity retention of the regenerated LFP using the H3PO4-purified FePO4 precursor is 99.6 % after 300 cycles at 1C, and its specific capacity for reversible discharge at a high rate of 5C is 140.2 mAh g−1, demonstrating excellent electrochemical performance. The selective leaching in H3PO4 system shows that the regeneration route of FePO4 precursors is promising for scalable fabrication.