Influences of solution pH and redox potential on the bioleaching of LiCoO2 from spent lithium-ion batteries

The influences of solution pH and redox potential on bioleaching of LiCoO2 from spent lithium-ion batteries using Acidithiobacillus ferrooxidans were investigated. Bioleaching at different initial pH and ferrous ion (Fe2+) concentrations were carried out, and electrochemical behavior of LiCoO2 dissolution was examined to study the effect of solution redox potential on the bioleaching process. The results showed maximum cobalt dissolution at initial pH of 1.5 and initial Fe2+ concentration of 35 g/L, and cobalt dissolution showed only slight relationship with pH of solution. Nonetheless, there was improvement of cobalt dissolution at higher redox potential. The cyclic voltammograms showed that dissolution rates increase when the solution potentials are higher than 0.4 V, and rapid decrease at 1.3 V. The anodic polarization curves indicated that the corrosion, primary passive, and passivation potentials were 0.420, 0.776 and 0.802 V, respectively.