Hui Dang,Benfeng Wang,Zhidong Chang,Xue Wu,Jingge Feng,Hualei Zhou,Wenjun Li,Changyan Sun
When the spent lithium ion battery is processed pyrometallurgically, lithium is generally fixed as slag with a high melting/boiling point which is difficult to be treated further. In this research, an innovative method to recycle lithium from pyro-slag by evaporation during chlorination roasting was proposed. Different chlorine donors, namely NaCl, AlCl3, and CaCl2 were evaluated by HSC software and experiments, among which CaCl2 possessed a stronger ability of chlorine donation in the chlorination roasting process. Experiments proved that 97.45% lithium was evaporated with the Cl/Li molar ratio of 1.8:1 when the mixture of a simulated slag and CaCl2 was roasted at 1000 °C for 90 min. XRD results demonstrated that the majority of LiAl(SiO3)2 in the slag was transformed into LiCl. All results implied that chlorination roasting should be a promising strategy for lithium recovery from the pyrometallurgical slag after pyro-treatment of the spent lithium ion battery.
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 (CaCl 2 ). 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 CaCl 2 , are predicted through the simulation with an enthalpy, entropy and heat capacity (HSC) programme. The simulation indicates that CaCl 2 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(SiO 3 ) 2 in the slag disappears under the best reaction conditions and is transformed into LiCl.
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