A mild closed-loop process for lithium–iron separation and cathode materials regeneration from spent LiFePO4 batteries

The recycling and reusing of waste LiFePO4 batteries significantly promote sustainable development and environmental protection. In this study, an innovative process of iron-lithium separation and cathode materials regeneration from used LiFePO4 batteries is proposed. The spent LiFePO4 powder was put into NaH2PO4 and H2O2 combined treatment solution for an oxidation leaching reaction. Under the optimal condition, excellent lithium–iron separation was achieved, with 98.65% leaching of lithium and only 0.028% leaching of iron. The selective separation of lithium ion can be efficiently achieved during the leaching process. Li+ from the leachate was precipitated into Li3PO4 by evaporation crystallization, and the saline solution, after precipitation, was converted into a leaching agent by adding H3PO4 for reusing. The regenerated LiFePO4 from recovered FePO4 displays excellent rate capability and long-term cyclic stability. Through the synergistic effect of NaH2PO4 and H2O2, this work achieves efficient and mild separation of iron-lithium while maintaining the raw material olivine structure, regenerating LiFePO4 cathode material with good electrochemical properties, avoiding the cost of wastewater treatment and forming a stable closed loop.