Recycling process of Li-ion batteries and final electrochemical purification of the Co containing exhausted solutions.

The recycling process studied deals with cobalt electrolytic recovery from Li-ion batteries by means of both galvanostatic and potentiostatic electrowinning followed by an electrochemical purification made on exhausted partially depleted electrolyte. A good Co metal deposit with a purity of 99.95% is produced by working at 250 A/m2 current density and 50 °C temperature , while working in potentiostatic conditions (-0.9V SCE cathodic potential) a partial cobalt depletion of the electrolyte is provided. This last operation is very interesting because the produced Co powder is transformed at 300 °C in Co3O4 precursor with Li2CO3 for the Lithium Cobalt Oxide cathode material. In this case we have not only a Co recovery but also a true recycle of the cathode active paste. An electrochemical filter has been also designed and studied to complete the recycling process. The electrochemical filter, constituted by a reticulated vitreous carbon (RVC) as cathode and a Ti grid covered by Pt as anode, is able to treat the diluted Co electrolyte coming from potentiostatic electrolysis. The electrolysis tests were performed potentiostatically (-1.3 V vs.SCE), maintaining a solution pH equal to 6.5. Obviously the studied cell could be utilized to deplete any other heavy metal containing solution. Process yield depends on cobalt concentration of solution: starting from a solution containing about 200 ppm Co the initial current efficiency is 35-40%, then reaching a value of 20% when 80% of Co has been deposited. The best yield is obtained by using a RVC covered by Co.