I2I Phase I: Optimization of selective lithium recovery from spent lithium iron phosphate batteries with a green and environmentally responsible process

磷酸铁锂(LFP)电池是几乎所有锂离子电池中生产成本最低且性能优异的锂离子电池(LIB)之一。与其他类型的LIB不同，LFP电池制造不需要任何钴、镍或锰，这些都是LIB制造的昂贵成分之一。因此，这些LFP电池的制造成本显著低于其他类型的LIB，通常为50%。LFP电池中含有的金属价值较低，这使得它们的回收在经济上没有吸引力，特别是因为回收过程中使用的试剂的成本超过了从LFP电池中回收的金属(即主要是锂)的价值。该项目进一步开发了一种工艺，该工艺旨在选择性地从粉碎的LFP电池中浸出锂，同时留下铁和磷。换句话说，该工艺旨在仅从LFP电池中回收有价值的金属，即锂，从而将该工艺的能源、水和试剂成本降至最低。粉碎的LFP电池在水-甲酸-过氧化氢体系中浸出，其中甲酸的浓度设计为1M左右，过氧化氢作为氧化剂添加在1-5wt%的范围内。然后，LFP电池中的锂以甲酸锂的形式回收到浸出液中。随后，富锂溶液从固体残留物中分离出来。溶液主要携带锂和少量铁作为杂质，通常在低镁/L铁范围内。经过pH调节除铁后，该工艺水可用于结晶高品位、高质量的磷酸锂晶体，品位在99.5%Li3PO4以上。该工艺开发使用环保试剂，是一个闭路工艺，不产生废水；因此，该工艺可应用于城市附近有废电池可用的地方。

Lithium iron phosphate (LFP) batteries are among the lithium-ion batteries (LIBs) that have the lowest production cost among almost all lithium-ion batteries and have excellent performance. Unlike other types of LIBs, LFP battery manufacturing does not require any cobalt, nickel, or manganese, which are among the expensive ingredients of LIBs manufacturing. Therefore the manufacturing cost of these LFP batteries is significantly, often 50%, less than the other types of LIBs. The lower contained metal value within LFP batteries makes their recycling economically unattractive, particularly because the cost of reagents used in the recycling process exceeds the value of the metals (i.e. mostly lithium) recovered from the LFP batteries.This project further develops a process that has been designed to selectively leach lithium from shredded LFP batteries, while leaving behind iron and phosphorous. In other words, the process is designed to recover only the valuable metal, i.e. lithium, from the LFP batteries, thus minimizing the energy, water, and reagent costs of the process. The shredded LFP batteries are leached in a water-formic acid-hydrogen peroxide system, where the concentration of formic acid is designed to be around 1 M, and hydrogen peroxide is added as an oxidant in the range of 1 to 5 wt%. The lithium from the LFP batteries is then recovered into the leach solution as lithium formate. Subsequently, the lithium-rich solution is separated from the solid residues. The solution carries mostly lithium and an insignificant amount of iron as an impurity, often in the low mg/L Fe range. After a pH adjustment for iron removal, the process water is ready for crystallization of high-grade and high-quality lithium phosphate crystals, with a grade above 99.5% Li3PO4.The process is developed to use environmentally friendly reagents and is a closed-loop process, producing no wastewater; therefore, the process can be applied in the vicinity of cities, where spent batteries are available.