Selective recovery of lithium from lithium iron phosphate

Lithium-ion batteries are becoming widely used in the electric vehicle industry. Owing to its low cost, good stability, and long cycle life, lithium iron phosphate becomes the most widely used power battery. With widespread use of Li-ion batteries, a large number of spent batteries are generated. Effective recycling of these spent batteries has enormous economic and environmental benefits. The only valuable metal in lithium iron phosphate is lithium, so a selective recovery method is required. A formic acid–hydrogen peroxide system is employed for selective leaching of lithium ions. Optimal leaching conditions are obtained by single-factor optimization: formic acid concentration of 0.8 mol/L, solid–liquid ratio of 50 g/L, initial hydrogen peroxide volume fraction of 8 %, temperature of 60 °C, and a reaction time of 1 h. Under these optimal leaching conditions, the extent of lithium leaching reaches 99.9 %, while that of iron is only 0.05 %. The optimal leaching conditions are verified by multi-factor response surface experiments, and the results obtained by the two methods are very similar. Using sodium carbonate precipitation to recover lithium ions from the leach filtrate, the primary precipitation extent and purity of the lithium product achieve 85.05 % and 99.9 %, respectively.