Direct Nickel Recovery From Spent NCM Lithium - Ion Batteries Enabled by Hydrophobic Sulfur - Donor Extractants

The increasing demand for lithium-ion batteries (LIBs) attracts sustainable recycling, particularly for high-value metals such as Ni and Co used in high-Ni ternary cathodes. However, current hydrometallurgical processes rely on multistage solvent extractions that exhibit poor Ni selectivity and generate large quantities of Na₂SO₄ waste because of extensive pH adjustment and extractant saponification. Herein, we report an organocatalyst-inspired, sulfur-donor extractants (TPA-H) designed through molecular-level engineering for highly selective direct Ni recovery. These P(V)-based extractants enable direct and efficient Ni extraction under strongly acidic conditions (pH ∼0.5), achieving an exceptional Ni/Co separation factor (β) exceeding 2300. Mechanistic studies revealed that the optimized structure and coordination of the phosphorodithioate framework preferentially stabilize Ni(II) over competing metals. Large-scale extractions using real spent LIB black mass leachates demonstrated >95% Ni extraction efficiency under acidic conditions. Subsequent stripping and recrystallization without an intermediate scrubbing step afforded high-purity NiSO₄·6H₂O (99.7%), while suppressing Na₂SO₄ byproduct generation. The TPA-Hs exhibited excellent recyclability over 10 consecutive cycles, and the recovered Ni was directly crystallized as high-purity NiSO₄·6H₂O. Furthermore, integration of an advanced-flow reactor (AFR)-Zaiput separator platform enabled biphasic mass transfer, thereby overcoming the limitations of mixer-settler systems and facilitating automated continuous extraction-separation processes.