A team from the Beijing University of Chemical Technology has used a formic acid–hydrogen peroxide system for the efficient selective leaching of lithium ions from spent lithium iron phophate batteries. A paper on their process is published in thr Journal of Power Sources.

With rapid technology development and the support of national policies, the electric vehicle market has expanded rapidly in recent years. Current automotive applications mainly include lithium cobaltate (LCO), lithium iron phosphate (LFP), and ternary lithium (nickel cobalt manganese (NCM) and nickel cobalt aluminum (NCA) batteries. The LFP battery stands out because of its low cost, good cyclability, high stability, and more environmentally friendly nature.

According to 2021 statistics, LFP batteries accounted for 51.7% of total installed capacity. The service life of LFP batteries is generally 5–8 years, so a large number of used batteries will become available for decommissioning and recycling. It is predicted that the mass of spent batteries will reach 400 kt by 2025.

Lithium resources are scarce due to the rapid growth of the lithium-ion battery market. Since the end-of-life LFP battery is rich in lithium resources, effective recycling of spent LFP battery can not only significantly alleviate the shortage of lithium resources, but also can generate considerable economic benefits.

… In this study, formic acid, an organic acid that is less acidic, green, easily decomposed, and less polluting than inorganic acids, was used as the leaching agent and hydrogen peroxide was used as the oxidizing agent. The proposed recovery technology has the advantages of simple, short process, good performance, high lithium concentration in leaching solution with almost no iron ion, and high purity of lithium carbonate.

—Li et al.

Optimal leaching conditions were 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 were 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 achieved 85.05% and 99.9%, respectively.

Resources

• Yongjian Li, Liping Dong, Pei Shi, Zhongqi Ren, Zhiyong Zhou (2024) “Selective recovery of lithium from lithium iron phosphate,” Journal of Power Sources, Volume 598 doi: 10.1016/j.jpowsour.2024.234158