Cradle-to-cradle recycling of spent NMC batteries with emphasis on novel Co2+/Ni2+ separation from HCl leached solution and synthesis of new ternary precursor

Herein, a cradle-to-cradle recycling of post-consumer NMC batteries has been demonstrated with a focused separation of cobalt over nickel by applying the ionic liquid, trihexyl(tetradecyl)phosphonium bis-2,4,4-(trimethylpentyl)phosphinate. At the optimized condition of: 0.8 mol.L-1 ionic liquid, 3.0 mol.L-1 Cl- ions, equilibrium pH value similar to 5.0, and organic-to-aqueous ratio 2/3, > 99% cobalt was extracted in the organic phase with a separation factor of 1097. Approximately 99% cobalt from the loaded organic was stripped back in 2.0 mol.L-1 HCl solution, yielding high-pure CoCl2 center dot xH(2)O crystals after crystallizing the stripped solution. Subsequently, similar to 99% of nickel from the Co-depleted raffinate was extracted over lithium using 0.32 mol.L-1 acetophenone at an organic-to-aqueous ratio of 1 and equilibrium pH similar to 5.3. Nickel stripped in 2.0 mol.L-1 H2SO4 was crystallized to yield high-pure NiSO4 center dot 6H(2)O crystals. Further, Li-bearing raffinate was subjected to carbonate precipitation at a higher pH (similar to 12) and CO32-:Li+ ratio of 1.2. All the recycled products were further employed to the stepwise synthesis of a new ternary precursor, exhibiting similar electrochemical behaviour (with 149 mAh.g(-1) capacity) and found compatible with the precursor prepared using virgin materials. The sustainable process index value determined to be 0.0006 cap.t(-1) for the overall recycling process indicated that the process is suitable for sustainable development.

Automated summary

A cradle-to-cradle recycling process for post-consumer NMC batteries was demonstrated, achieving a focused separation of cobalt over nickel using an ionic liquid. The optimized conditions resulted in over 99% cobalt extraction in the organic phase with a separation factor of 1097. The extracted cobalt was stripped and crystallized to obtain high-purity CoCl2•xH2O crystals. Similarly, around 99% nickel was extracted from the Co-depleted solution using acetophenone, and the stripped nickel was crystallized to yield high-purity NiSO4•6H2O crystals. The recycled products were further used to synthesize a new ternary precursor, showing similar electrochemical behavior and compatibility with precursors made from virgin materials. The overall recycling process was determined to be suitable for sustainable development with a sustainable process index value of 0.0006 cap.t-1.