Mechanistic insights into NaOH-driven crystal destruction and selective lithium extraction from spent LiFePO4 via mechanochemistry

NaOH enabled solvent-free mechanochemical recycling of spent LiFePO 4 BM. • The process achieved 98.83 % Li leaching with only 0.27 % Fe co-leaching. • NaOH destroyed the LiFePO 4 crystal structure and formed Li 3 PO 4 . • Fe 2+ oxidation was promoted by NaOH and atmospheric O 2 during milling. • The recovered product reached 99.6 % Li 3 PO 4 purity. The rapid increase in spent lithium iron phosphate (LiFePO 4 ) batteries brings significant challenges related to environmental pollution, human health risks, and resource sustainability. Conventional recycling technologies are often hampered by high energy consumption, secondary pollution, and operational hazards. This study proposes a sustainable mechanochemical approach for recycling spent LiFePO 4 black mass, based on the targeted destruction of the stable LiFePO 4 crystal structure. Using sodium hydroxide as an efficient co-grinding agent in a solvent-free system, a superior lithium leaching efficiency of 98.83 % was achieved under optimized conditions, while iron co-leaching was effectively suppressed to 0.27 %. Comprehensive characterizations, including X-ray diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy confirmed the destruction of the LiFePO 4 crystal structure, the formation of Li 3 PO 4 , and the oxidation of Fe 2+ . An economic assessment demonstrates the viability of this procedure, yielding a net profit of $0.9659 per kilogram of LiFePO 4 black mass. This work presents an efficient, economically viable, and environmentally benign mechanochemical strategy for LiFePO 4 battery recycling, offering fundamental insights into crystal structure destruction for sustainable resource recovery.