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

Mixtures of NaHSO4·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-H20 mixtures during the roasting process was investigated by means of thermogravimetric analysis and differential scanning calorimetry （TG-DSC）, X-ray diffraction（XRD）, scanning electron （XPS）. The results show that the chemical reactions in microscopy（SEM）, and X-ray photoelectron spectroscopy the LiCoO2 and NaHSO4·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·H2O in the mixtures, the Co element evolves as follows： LiCoO2→Co3O4→Na6Co（SOa）4→Na2Co（SO4）2. The roasting products exhibit dense structures and irregular shapes, and the bonding energy of Co increases.

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

Diflerent from the traditional pyTometallurgical 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 sul-fates by roasting a mixture of LiCoO2 and NaHSO4-H2O.The evolution law of the mixture with increased roasting temperature was investigated by thennogravimetry-diflerential scamiing calorimetry(TG-DSC),in situ X-ray diflrac-tion(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,NaHSO4 H2O→LiCo02,NaHSO4→Lil-xCo02,LiNaSO4,Na2S2O7,Na2SO4→Li1-xCoCO2,Co3O4,LiNaSO4,Na2SO4→Co3O4,LiNaSO4.The reaction mechanism of this roasting process may be as follows:LiCoO2+NaHSO4-H2O→l/2Li2SO4+l/2Na2SO4+l/3Co3O4+l/12O2+3/2H2O,Li2SO4+Na2SO4=2LiNaSO4.