Effective and sustainable lithium ion battery recycling strategy for circular economy: Ultrasound assisted direct leaching of black mass containing NMC/LCO/LMO/graphite mixed powders

The lithium-ion battery (LiB) is an indispensable component of contemporary technology, with applications in mobile phones, personal computers, and electric vehicles. The cathode materials LiCoO₂ (LCO), LiNi_xMn_yCo_(1-x-y)O₂ (NMC), and LiMn₂O₄ (LMO) are widely utilized in these applications due to their specific energy values. The recovery of valuable metals (Li, Co, Ni, and Mn) from cathode materials in LiB whose effective lifespan has ended has become a necessity due to economic and environmental factors. In this study, a detailed characterization of the black mass obtained by sieving from the discharged and shredded LiB cells was performed. Subsequently, this study explicitly targeted a low-acid, short-time route, to directly leach mixed black mass, without prior graphite separation, assisted by ultrasonic probe sonication. Furthermore, this study examined the impact of various acids (HCl, H₂SO₄ and HNO₃), leaching times, concentration of acids and ascorbic acid (C₆H₈O₆) as the reducing agent, ultrasonic sound waves, solid/liquid ratios, and temperatures on leaching efficiency. The dissolution efficiencies of 96.8 % Li, 99.2 % Co, 96.4 % Mn, and 93.1 % Ni were achieved with 0.5 M H₂SO₄ concentration, 0.15 M ascorbic acid concentration, 20 g/L solid/liquid ratio, and 1 h of ultrasound-assisted leaching time. Thus, ∼95 % of all cathode metals were recovered at low acid concentration and short residence time without physically separating graphite and the active cathode material prior to leaching, highlighting the process simplicity and scalability.