High-intensity magnetic separation for recovery of LiFePO4 and graphite from spent lithium-ion batteries

Numerous end-of-life LiFePO4 batteries will emerge soon due to their limited lifespan. High reagent cost and environmental pollution of hydrometallurgy are the main factors that prevent the economic recycling of spent LiFePO4. In this paper, an environment-friendly physical method, that is, high-intensity magnetic separation (HIMS), was introduced for the first time to demonstrate its feasibility in preconcentrating the LiFePO4 from spent LiFePO4 batteries. Numerical simulation combined with laboratory experiments of two typical HIMS separators, namely high gradient magnetic separator (HGMS) and induced roll magnetic separator (IRMS), were conducted. Simulation analysis indicated that the separation performance was related to the magnetic field strength. In the HGMS experiments using 0.21 mm electrode powder (after grinding) as feed, the concentrate grade and recovery of LiFePO4 were 74.54% and 96.60%, respectively. By contrast, in the IRMS experiments using electrode pieces (after shredding) as feed, the concentrate grade and recovery of LiFePO4 cathode pieces were 93.30% and 98.69%, respectively. Surface morphological analysis of electrode powder implied that superfine LiFePO4 particles produced by grinding adhered to or were embedded in coarse graphite particles, which seriously deteriorated the separation performance. By contrast, electrode pieces were considerably larger size, and the generation of superfine LiFePO4 particles can thus be avoided.