Selective recovery of lithium from spent lithium iron phosphate cathodes via Fenton reaction

Abstract Recycling of spent lithium iron phosphate (LFP) batteries is essential for resource sustainability and environmental protection. However, conventional recycling methods often involve harsh conditions, sacrificial reagents, high energy consumption, and secondary pollution. This study proposes a novel and efficient lithium extraction method based on a photo-fenton process to selectively recover lithium from spent LiFePO₄ cathodes. Under optimized conditions (800 mmol/L H₂O₂, 100 mmol/L FeSO₄, 30°C, 50 g/L solid density, and 30 min reaction time), a lithium leaching efficiency exceeding 99% was achieved with high selectivity. During this process, iron and phosphorus were simultaneously recovered as FePO₄ precipitate, while lithium was subsequently separated as high-purity Li₂CO₃. Mechanistic investigations, supported by XRD, XPS, and SEM-EDS analyses, revealed that hydroxyl radicals (•OH), generated from the Fe²⁺/H₂O₂ Fenton system, attack the olivine structure of LiFePO₄. This oxidizes Fe(II) to Fe(III), forming insoluble FePO₄ and releasing Li⁺ into solution. Notably, ultraviolet irradiation facilitates the regeneration of Fe²⁺ from the reaction products, enabling its reuse and significantly reducing reagent consumption and iron sludge generation. The proposed photo-Fenton method offers an efficient, low-energy, and environmentally benign route for lithium recovery from spent LFP batteries.