Electric field-assisted leaching of valuable metals from spent lithium-ion batteries in a mixture of acetic acid and ascorbic acid

Abstract

Recovery of valuable metals from spent lithium-ion batteries (LIBs) has great economic and environmental value. In this study, mixtures of acetic acid and ascorbic acid were used to leach valuable metals from the cathode plates of spent LIBs with assistance from an electric field. Thermodynamic analysis showed that the metal oxides of spent LIBs could be dissolved in the form of metal ions by adjusting potential and pH. Leaching conditions, including the concentrations of acetic acid and ascorbic acid, working voltage, reaction temperature, and reaction time, were systematically investigated. Under conditions with acetic acid concentration of 1 mol/L, ascorbic acid concentration of 0.1 mol/L, working voltage of 4 V, reaction temperature 25 °C and reaction time 70 min, the leaching efficiency of Ni, Co, Mn, and Li reached 99.8%, 99.8%, 99.8%, and 99.9%, respectively. A kinetic study revealed that the surface chemical reaction was the rate-controlling step in the leaching process. The infrared spectra indicated that polyhydroxy groups were transformed into carboxyl or aldehyde groups during mixed acid leaching. The complexity of ascorbic acid and low-valent metal ions increased with leaching time in the ultraviolet spectrum. Finally, the leach residue was analysed using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), which indicated that the metal oxides in the cathode plate were efficiently leached.