Comparative study on the leaching behavior of lithium-ion battery black mass using sulfuric and organic acids combined with hydrogen peroxide

The black mass obtained from spent lithium-ion batteries offers a promising opportunity to establish a sustainable supply chain for critical battery materials, such as lithium, cobalt, manganese, and nickel. Battery recycling provides an effective solution for substantially reducing environmental waste. This study examines the physicochemical properties and leaching behavior of lithium-ion battery black mass using various acids (sulfuric, malic, acetic, citric, and butyric acids) in combination with hydrogen peroxide (H₂O₂) as a reductant. Physicochemical analyses using powder X-ray diffraction and inductively coupled plasma-optical emission spectroscopy indicated that the black mass originated primarily from the NMC622-type or nickel-rich cathode materials. Leaching experiments revealed that 1 M sulfuric acid combined with H₂O₂ yielded the highest extraction efficiencies, achieving Li (62.2 %), Cu (53.5 %), Fe (26.9 %), Al (46.5 %), Ni (55.1 %), Co (50.6 %), and Mn (36.7 %). Although organic acids generally exhibit lower extraction efficiencies, citric and malic acids perform better than acetic and butyric acids because of their greater capacity to form stable chelate complexes with metal ions. However, strong chelate formation with citric and malic acids limits selective precipitation during subsequent pH adjustment. In contrast, despite their lower overall leaching efficiencies, the use of acetic and butyric acids provided enhanced selectivity for the precipitation of Co, Cu, and Ni at pH 8 and Mn at pH 9 while significantly reducing lithium co-precipitation. These results highlight that the careful selection of acids combined with the reductive action of H₂O₂ is essential for optimizing the selective recovery of valuable metals from battery black mass.