Use of electrochemical cathode-reduction method for leaching of cobalt from spent lithium-ion batteries

The present work is focused on the use of electrochemical cathode-reduction method for leaching LiCoO2 produced by spent lithium-ion batteries. The thermodynamics, kinetics, and electrochemical impedance spectroscopy analyses are used to determine the probable control mechanism involved in the leaching of cobalt from spent LiCoO2. The leaching efficiencies reached about 90% for cobalt and nearly 94% for lithium using 1.25 mol/L of malic acid and a working voltage of 8 V for 180 min at 70 °C. Kinetics analysis indicates that the leaching process of cobalt could be divided into two stages: the first stage is controlled by a surface chemical reaction, and the second stage is controlled by a combination of the surface chemical reaction and diffusion. Electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy analysis show that the combination control at the second stage is related to the form of Co(OH)3 produced during the leaching process of spent LiCoO2. Finally, a novel process for the leaching of cobalt from spent LiCoO2 is proposed.