Chemical Evolution of LiCoO2 and NaHSO4•H2O Mixtures with Different Mixing Ratios During Roasting Process

Mixtures of NaHSO4 center dot H2O and LiCoO2 extracted from spent lithium-ion batteries were prepared with molar ratios of 1:1, 1:2 and 1:3. The chemical evolution of the LiCoO2 and NaHSO4 center dot H2O mixtures during the roasting process was investigated by means of thermogravimetric analysis and differential scanning calorimetry (TG-DSC), X-ray diffraction(XRD), scanning electron microscopy(SEM), and X-ray photoelectron spectroscopy (XPS). The results show that the chemical reactions in the LiCoO2 and NaHSO4 center dot H2O mixtures proceed during the roasting process. The Li element in the product of the roasting process is in the form of LiNa(SO4). With the increase of the proportion of NaHSO4 center dot H2O in the mixtures, the Co element evolves as follows: LiCoO2 -> Co3O4 -> Na6Co(SO4)(4)-> Na2Co(SO4)(2). The roasting products exhibit dense structures and irregular shapes, and the bonding energy of Co increases.