Recovery of NMC cathode powder using a novel NADES as beta-alanine: Citric acid and electrochemical characterization

Natural deep eutectic solvents (NADES) are promising green alternatives to inorganic solvents in hydrometallurgy. This study explores the recovery of metals from spent cathode active powders (s-CAP) of Li-ion batteries using a novel NADES composed of beta-alanine (BA), citric acid (CA), and water (W). Key leaching parameters-temperature, time, pulp density, and water content-were optimized, along with the effect of ultrasonic (US) power. At 80 degrees C, 375 rpm stirring, and 10 g/L pulp density for 3 h with BA:CA:W (1:1:5), recovery yields of Li, Co, Mn, and Ni were 97.8 %, 95.5 %, 97.9 %, and 96.7 %, respectively. Similar yields were achieved in just 1 h using 400 W US. Kinetic analysis revealed that the process was controlled by the chemical reaction rate at the interface. Metals were co-precipitated using 1 M C2H2O4, and NADES was reused for five cycles without efficiency loss. This led to precipitation yields near 100 %. The recovered powder was analyzed via XRD, SEM/EDS and HR-TEM. Electrochemical tests on coin cells showed discharge capacities of 136.48 mAh/g at 0.5 C and 89.56 mAh/g at 5 C. 91.04 % capacity retention was calculated after 100 cycles at 0.5 C. Electrochemical Impedance Spectroscopy (EIS) confirmed stable cycling behavior, demonstrating the regenerated cathode's performance comparable to commercial materials, supporting its reuse potential.