Mechanism of Lithium and Cobalt Recovery from Spent Lithium-ion Batteries by Sulfation Roasting Process

Abstract

Different from the traditional pyrometallurgical recovery process of Li and Co from spent lithium-ion batteries, a new recovery method for Li and Co was established by converting LiCoO2 into water-soluble metal sulfates by roasting a mixture of LiCoO2 and NaHSO4·H2O. The evolution law of the mixture with increased roasting temperature was investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), in situ X-ray diffraction(XRD), XRD, and X-ray photoelectron spectroscopy(XPS). The results show that the phase transition of LiCoO2 mixed with NaHSO4·H2O with increased temperature proceeded as follows: LiCoO2, NaHSO4H2O→LiCoO2, NaHSO4→Li1−xCoO2, LiNaSO4, Na2S2O7, Na2SO4→Li1−xCoO2, Co3O4, LiNaSO4, Na2SO4→Co3O4, LiNaSO4. The reaction mechanism of this roasting process may be as follows: LiCoO2+NaHSO4·H2O→1/2Li2SO4+ 1/2Na2SO4+1/3Co3O4+1/12O2+3/2H2O, Li2SO4+Na2SO4=2LiNaSO4.