Eco-selective purification to high-capacity LiFePO4: Transforming natural Iron sources via alkali-mediated green synthesis

Lithium iron phosphate (LiFePO₄), renowned for its thermal stability and structural safety, faces cost limitations in conventional synthesis routes. This study presents a transformative approach utilizing natural hematite concentrate through an integrated impurity engineering and structural activation strategy. Thermodynamic analysis guided a two-stage alkaline sintering process that selectively removes detrimental impurities via NaOH-mediated conversion to water-soluble Na₂O·Al₂O₃/Na₂O·SiO₂ complexes, while preserving beneficial Mg dopants for enhanced ionic conductivity. Subsequent rapid quenching induces metastable Fe₂O₃ amorphization (68.79 wt% Fe purity) with fractured nanorod morphologies. The optimized LiFePO₄ cathode exhibits exceptional electrochemical performance, delivering 155.7 mAh g⁻¹ at 0.1C with minimal polarization, and maintains 110.7 mAh g⁻¹ at ultrahigh 15C rates. Long-term cycling reveals 89.9 % capacity retention after 1000 cycles at 1.0C. reducing charge transfer resistance by 59 % versus conventional synthesis. This synergistic impurity removal-amorphization mechanism enables the preparation of LiFePO₄ from low-grade ores, opening up a scalable route for the production of cost-competitive LiFePO₄ anodes and concurrently realizing the value-added utilization of natural mineral resources. This method combines materials engineering with sustainable battery production, greatly reducing the cost of precursors compared to traditional iron sources.