Recovery Of Rare Metals From Spent Lithium Ion Cells By Hydrothermal Treatment And Its Technology Assessment

A novel cobalt recovering process from a cobalt-based cathode electrode in a lithium secondary cell was developed using a hydrothermal treatment combined with a pyrometallurgical. technique. A cobalt-based cathode electrode was prepared by casting the mixture of LiCoO2, poly(vinylidene fluoride) and conductive carbon black onto an Al foil, and this model electrode was used as a test sample. A hydrothermal treatment of the cathode sample was carried out using pure water as a solvent in the temperature range of 423-473 K for the duration of 0-40 h. The hydrothermal treatment at 473 K for more than 15 h led the cathode sample to the disintegration into powdery particles. By the hydrothermal treatment under the optimum condition at 473 K for 20 h, more than 99.9 mass% of Co and 98 mass% of Al in the cathode sample was reclaimed as a form of spinel type Co(CoxAl2-x)O-4 (0 < x <= 2), and most of Li and F could be dissolved into the solution. Subsequently, metallic cobalt was successfully recovered from the spinel compound and carbon mixture by the pyrometallurgical treatment with additives for slag formation under a reducing condition at 1623 K for 5 h.