Electrodeposition of cobalt from spent Li-ion battery cathodes by the electrochemistry quartz crystal microbalance technique

Information about the cobalt electrodeposition mechanism at different pH values was obtained using an electrochemistry quartz crystal microbalance (EQCM) technique as well as potentiodynamic and potentiostatic techniques. Potentiodynamic and potentiostatic electrodeposition of ionic cobalt at pH 5.40 occurs via a direct reduction mechanism. The mass/charge relation was found to be 33.00 g mol−1. At pH 2.70, electrodeposition under potentiodynamic conditions occurs via a mechanism of cobalt reduction with the formation of adsorbed hydrogen. Potentiostatic analysis verified that cobalt reduction occurs simultaneously via direct reduction and with the formation of adsorbed hydrogen. The ratio mass/charge (M/z) is 13.00 g mol−1 for potentiodynamic conditions and 26.00 g mol−1 for potentiostatic conditions and potentiodynamic conditions. The cobalt electrodissolution occurs directly to Co2+ in pH 2.7 and through of the intermediary Co+ that is oxidized to Co2+ in pH 5.4.