Lithium leaching via calcium chloride roasting from simulated pyrometallurgical slag of spent lithium ion battery

Abstract In the present case, insoluble lithium in the simulated slag which is obtained by pyrometallurgical processing of spent lithium ion batteries (LiBs) is leached aqueously through transformation of insoluble lithium into soluble lithium via roasting with calcium chloride (CaCl2). The change of both Gibbs free energy and the logarithm of the equilibrium constant, which are taken as functions of temperature for the chlorination reaction of simulated slag with CaCl2, are predicted through the simulation with an enthalpy, entropy and heat capacity (HSC) programme. The simulation indicates that CaCl2 is a favourable and effective chlorine donor in this chlorination reaction to yield lithium chloride (LiCl) when the temperature is not less than 500 °C. These predicted results are tested and confirmed experimentally. A maximum of 90.58% lithium recovery can be yielded with the optimal roasting conditions of a temperature of 800 °C for 60 min and a molar ratio of Cl/Li of 1.8:1, along with subsequent leaching conditions of 60 °C for 30 min with a water/calcines mass ratio of 30:1. X-ray diffraction (XRD) results suggest that most of LiAl(SiO3)2 in the slag disappears under the best reaction conditions and is transformed into LiCl.