Recovery of Cobalt from Cathode of Lithium-Ion Battery Using Ternary Deep Eutectic Solvent

A new ternary deep eutectic solvents, consisting of choline chloride, ethylene glycol, and benzoic acid, were designed for efficient leaching of valuable metals from lithium oxide of spent lithium-ion batteries. The influence of experiment parameters on the leaching of cobalt was systematically investigated and optimized by response surface methodology. The leaching kinetics were elucidated in detail. The leaching efficiency of cobalt reached almost 100%, when the temperature was 443.15 K, the time of 3 h, and the molar ratio of the choline chloride: ethylene glycol: benzoic acid of 1:1.6:0.4. The kinetics of Co leaching showed good agreement to the shrinking core model, in which the diffusion of solid product layers was the limiting step, and the apparent activation energy was about 77.22 kJ/mol. Infrared spectroscopy indicated that hydrogen donors provided multiple ligands to facilitate the solubilization of cobalt. The SEM analysis of the leachates showed that the edge of particles changed significantly, the particle size decreased, and the dissolution process appeared. The simultaneous realization of high efficiency green process is expected to bring the DES into practical application for recovery of cathode from spent lithium-ion batteries.