Leaching of NMC industrial black mass in the presence of LFP

This study focuses on the effect of an emerging source of waste, lithium iron phosphate (LFP) cathode materials, on the hydrometallurgical recycling of the currently dominant industrial battery waste that is rich in transition metals (Ni, Co, Mn, and Li). The effects of the dosage of LFP, initial acidity, and timing of LFP reductant addition were investigated in sulfuric acid (H₂SO₄) leaching (t = 3 h, T = 60 °C, ω = 300 rpm). The results showed that addition of LFP increased both transition metal extraction and acid consumption. Further, the redox potential was lowered due to the increased presence of Fe²⁺. An initial acidity of 2.0 mol/L H₂SO₄ with acid consumption of 1.3 kg H₂SO₄/kg black mass provided optimal conditions for achieving a high leaching yield (Co = 100%, Ni = 87.6%, Mn = 91.1%, Li = 100%) and creating process solutions (Co 8.8 g/L, Ni 13.8 g/L, Li 6.7 g/L, Mn 7.6 g/L, P 12.1 g/L) favorable for subsequent hydrometallurgical processing. Additionally, the overall efficiency of H₂O₂ decreased due to its decomposition by high concentrations of Fe²⁺ and Mn²⁺ when H₂O₂ was added after t = 2 h, leading to only a minor increase in final battery metals extraction levels.