Low-cost and efficient extraction of metals from spent lithium-ion batteries via peroxide-enhanced NaCl-EG deep...

The recovery of critical metals from spent LIBs is essential to establish a sustainable and circular battery supply chain; however, current practices remain largely reliant on acid-based hydrometallurgical processes. We report an eco-friendly, low-cost, and efficient leaching medium composed of sodium chloride (NaCl) and ethylene glycol (EG), used as a deep eutectic solvent (DES), and activated with 12 vol% H₂O₂. The NaCl-EG-based DES exhibits minimal volatility and lower corrosivity than strong mineral acids, featuring a chloride-rich, coordinating environment that stabilizes dissolved transition-metal species. To the best of our knowledge, this is the first report to apply NaCl-EG-based DES for leaching Ni-rich spent NMC811 cathodes with high efficiency under mild conditions. Control tests show that EG and H₂O₂ without NaCl affords <20% extraction, underscoring the indispensable role of chloride complexation. Adding H₂O₂ converts high-valent Ni³⁺/Co³⁺/Mn⁴⁺ to soluble M²⁺ and excess Cl^- in the DES forms stable chloro-complexes, and EG provides strong solvation, suppressing reprecipitation. The simplicity, benign reagents, and strong performance of this NaCl-EG-based DES highlight a practical path toward greener, economically attractive hydrometallurgical recycling of Ni-rich LIB cathodes, with clear advantages over mineral acids and high-cost ionic liquids or specialized DES formulations.