Controlled phase evolution and pathways to scalable synthesis in iron-oxide-derived LiFePO4 cathodes

Lithium iron phosphate (LiFePO 4 [LFP]) represents a leading cathode material for lithium-ion batteries because of its thermal stability, high performance, and cost-effectiveness. However, conventional manufacturing routes predominantly rely on ferric phosphate (FePO 4 ) and require prolonged high-temperature processing. Here, we systematically investigated iron oxides as naturally abundant and globally distributed raw materials for the synthesis of high-purity LFP cathodes. By decoupling LFP formation from the carbon-coating process, we identified the oxygen chemical potential as the dominant factor governing the formation of LFP and non-conductive secondary phases of Li 4 P 2 O 7 and Fe 2 P 2 O 7 . We could effectively suppress these pyrophosphate byproducts by adjusting the reaction temperatures and reducing the atmosphere. We further demonstrated that the carbon-coating step requires a lower temperature and shorter duration than LFP formation to prevent Fe-P side-phase formation from reactions between LFP and carbon precursors. This fundamental understanding guides the scale-up synthesis of high-quality LFP at a 300 g scale with reduced processing time.