Selective lithium extraction from spent LiNi_xCo_yMn_zO₂ LIBs using environmentally friendly oxalic acid: the...

Oxalic acid is a naturally occurring organic acid, commonly employed for metal extraction from spent lithium-ion batteries. However, the leaching efficiency of lithium was relatively low (∼85 %) when oxalic acid was used for the direct extraction of lithium from LiNi_xCo_yMn_zO₂ black mass. Herein, a self-activation roasting technique was proposed to facilitate the recycling of lithium from spent LiNi_xCo_yMn_zO₂ lithium-ion battery through oxalic acid, by regulating the lithium phase in the black mass. Without any additional reagents, the lithium phase was converted from LiNi_xCo_yMn_zO₂ and LiPF₆ into LiF, Li₃PO₄ and Li₂CO₃, all of which were readily soluble in oxalic acid, resulting in a satisfactory selective leaching efficiency of 98.1 % for lithium. The phase conversion mechanism underlying the self-activation roasting and oxalic acid leaching processes was revealed through integrated experimental characterization and theoretical calculation. The proposed self-activation roasting promoted the reduction of oxalic acid consumption by at least 45 % while increased the leaching efficiency of lithium by 38 %, compared with the direct treatment of NCM black mass with oxalic acid. This study presents an environmentally friendly approach for phase deconstruction and selective lithium extraction from LiNi_xCo_yMn_zO₂ black mass contaminated with fluoride and phosphorus impurities.