Sustainable approach to achieve overall leaching of Li and Co in spent lithium-ion batteries without liberation by overall pyrolysis

Abstract

Dissociation is generally considered to be a necessary treatment of the electrode sheets before leaching, and the inadequacy dissociation cause the loss of electrode materials. In the present study, the feasibility of overall leaching of the undissociated electrode sheets to achieve satisfactory leaching was verified, which was believed to avoid complex crushing and sieving processes and reduce metal loss. Hence, the enhancement of the overall pyrolysis on the overall leaching of the electrode sheets was also analyzed. The undissociated electrode sheets were pyrolyzed at 480 °C that could remove the PVDF effectively. It was conducive to the infiltration of leaching solution between particles, the complete removal of PVDF was identified by SEM, EDS and XPS. Whereafter, the leaching kinetic behavior of the Li and Co in the pyrolyzed and unpyrolyzed electrode sheets were analyzed by the Aframi model. The morphology and composition of the leaching residue were analyzed by SEM-EDS to verify the characteristics of overall leaching behavior. Leaching results show that the overall leaching is feasible for the undissociated electrode sheets, the leaching rate of Li and Co of the undissociated and unpyrolyzed electrode sheet reaches 80.51% and 74.42% with 50 min leaching at 70 °C. Further, overall pyrolysis can enhance the leaching of the undissociated electrode sheet, the leaching rates of Li and Co can reach 93.25% and 93.31% only with 30 min leaching after pyrolysis at 70 °C. The kinetic results illustrate that the leaching of Li and Co is surface chemical reaction. The SEM analysis reveals that overall leaching process is gradual leaching, and the pores generated by pyrolysis help to penetrate the leaching solution and strengthen the leaching process.