A novel process to recycle spent LiFePO4 for synthesizing LiFePO4/C hierarchical microflowers

Abstract

A novel process has been demonstrated to recycle LiFePO4 from spent lithium-ion batteries. The spent LiFePO4 cathode materials were leached by phosphoric acid (H3PO4) solution and followed by subsequent heat treatment to obtain FePO4·2H2O hierarchical microflowers. Furthermore, new LiFePO4/C sample was prepared via a carbothermal reduction process of calcining the obtained FePO4·2H2O precursor with Li2CO3 and glucose in N2 atmosphere. The re-synthesized LiFePO4/C sample inherits the hierarchical microflower structure of the FePO4·2H2O precursor, with a diameter of 1–2μm. Electrochemical test indicates that the re-synthesized LiFePO4/C shows excellent electrochemical performance as cathode material for lithium ion batteries. The discharge capacity can reach 159.3mAhg−1 at 0.1C rate and 86.3mAhg−1 even at 20C rate, respectively. After 500 cycles at 5C, they still can deliver a discharge capacity of 105mAhg−1 with a high capacity retention rate of 95.4%. Moreover, the lithium element was also recovered in the form of LiH2PO4 from the filtrate after collecting the FePO4·2H2O precipitate. This work provides a promising route for large scale recovery and reuse of spent LiFePO4 cathode materials of lithium-ion batteries.