Separation of Li and Co from the active mass of spent Li-ion batteries by selective sulfating roasting with sodium bisulfate and water leaching

This paper presents a novel approach for recovering valuable metal from spent Li-ion batteries by separating Li and Co by using selective sulfating roasting with NaHSO4·H2O. This study focuses on the effects of the additive ratio of NaHSO4·H2O on the roasting mechanism. The occurrence evolution of the Li and Co elements during sulfating roasting and water leaching is studied by thermogravimetry-differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and inductively coupled plasma. The mixtures of spent LiCoO2 and NaHSO4·H2O possesses two obvious weightlessness platforms with corresponding endothermic peaks at 25-600 °C. As the proportion of NaHSO4·H2O in mixtures increases, the occurrence of the Li and Co elements evolves as follows: LiCoO2 → LiNa(SO4) and LiCoO2 → Co3O4. After being washed with deionized water, the concentrations of the Co and Li elements from the washed products in a mass ratio of 1:1.40 are 72.56% and 0.53%, respectively. The different occurrence forms of the Li and Co elements lead to their separation during sulfating roasting.