Recovery of metals from spent lithium-ion batteries using ionic liquid [P₈₈₈₈][Oleate]

A separation method to selectively recover valuable metals (Co, Ni, Mn and Li) from synthetic spent lithium-ion battery cathodes leachate using a fatty-acid-based ionic liquid, tetraoctylphosphonium oleate [P₈₈₈₈][oleate] is demonstrated. The investigated parameters for this selective separation and recovery process include extraction pH, contact time and composition of the regeneration solution. The benefit of using this ionic liquid is that >99% of Co and >99% of the Mn can be separated from the Ni and the Li by a two-stage extraction process. A subsequent single regeneration process separates the Co from the Mn. Finally, Ni and Li are completely separated in an additional regeneration process. An economic potential analysis concludes the paper, revealing that given the current cobalt price, the process outlined here shows a positive zero-order Economic Potential (bases on product sales and raw material cost) when using a 4 M HCl leaching solution and for leachates containing at least 4.5 g Co per liter.