As climate change response policies are strengthened, the importance of ‘Net-zero’ and ‘Sustainable (circular economy) economic growth’ is being emphasized. In addition, since a competition to secure resources is intensifying due to limited resources, recently, the urban mining industry that recovers valuable metals by recycling the waste electrical and electronic equipment (WEEE) has attracted attention [1]. Lithium-ion battery (LIB), one of representative WEEE, is used in almost all electronic devices such as smartphones and laptops, and is also an essential part in the rapidly growing electric vehicle (EV) business. Considering the valuable critical metals such as Nickel (Ni) and Cobalt (Co) in LIB, the research for the recycling waste LIB as well as the recovery such valuable metals by controlling the composition of LIB-treated slag is being mainly conducted [2]. However, in these studies, the gap between the thermodynamic calculation data and the experimental value is raised as an issue. For example, there is a previous study in which the experimentally measured MgO solubility due to a slag-refractory reaction is higher than that of thermodynamic calculations.

Therefore, the goal of this study is to check the influence of slag composition in MgO solubility and understand the thermodynamic behaviour of MgO dissolution in the iron-silicate based slags for the smelting the spent LIB to establish the optimal slag composition. A commercial thermochemical computing software, FactSageTM (ver. 8.2) was used to design the SiO2-FetO-MgO-MnO-Al2O3-Li2O multicomponent slags, and a metal-slag equilibrium experiment was conducted using a high purity fused MgO crucible under the conditions of p(O2)=10-10 atm and 1550oC. The predicted data through the FactSage and the measured values were compared. In this experiment, the FetO/SiO2 ratio, MnO, Li2O, and Al2O3 contents were used as variables, and the effect of temperature on MgO solubility was examined additionally. Consequently, the thermodynamic behaviour of MgO dissolution in the iron-silicate based slags for spent LIB treatment was identified.