Hui Li

Chloride molten salt systems are widely used as electrolytes for molten salt electrolysis because of their relatively low eutectic temperatures and good thermal stability, but there is a serious lack of data on the thermophysical properties of chloride molten salts at elevated temperatures, whereas the nature of the electrolyte is very important for the electrolysis process. In this paper, the variation of the microstructure and thermophysical properties of the binary mixed LiCl–CaCl ₂ molten salt system with temperature and composition is calculated using molecular dynamics (MD) simulations based on the BMH potential. The microscopic conformations observed in LiCl–CaCl ₂ molten salts are mainly irregular, distorted tetrahedra and octahedra, which dynamically coexist, as analyzed by the radial distribution function, coordination number and angular distribution function. In addition, the effects of temperature and composition on the density, ionic self-diffusion coefficient, shear viscosity, and ionic conductivity of the molten salts were investigated, and the relationships of the thermophysical properties of LiCl–CaCl ₂ molten salts with temperature and composition were obtained, which provide fundamental thermophysical data for the molten salt electrolytes.

The presence of calcium-containing molten salts in the electrolysis of oxides for metal production can lead to the formation of CaO and, subsequently, the generation of intermediate products, affecting the reduction of metals. To investigate the impact of CaO on the reduction process, experiments were conducted using a Fe₂O₃-CaO cathode and a graphite anode in a NaCl-CaCl₂ molten salt electrolyte at 800 °C. The electrochemical reduction kinetics of the intermediate product Ca₂Fe₂O₅ were studied using cyclic voltammetry and I-t curve analysis. The phase composition and morphology of the electrolysis products were analyzed using XRD, SEM-EDS, and XPS. The experimental results demonstrate that upon addition of CaO to the Fe₂O₃ cathode, Ca₂Fe₂O₅ is formed instantly in the molten salt upon the application of an electrical current. Research conducted at different voltages, combined with electrochemical analysis, indicates that the reduction steps of Ca₂Fe₂O₅ in the NaCl-CaCl₂ molten salt are as follows: Ca₂Fe₂O₅ ⟶ Fe₃O₄ ⟶ FeO ⟶ Fe. The presence of CaO accelerates the electrochemical reduction rate, promoting the formation of Fe. At 0.6 V and after 600 min of electrolysis, all of the Ca₂Fe₂O₅ is converted into Fe, coexisting with CaCO₃. With an increase in the electrolysis voltage, the electrolysis product Fe particles visibly grow larger, exhibiting pronounced agglomeration effects. Under the conditions of a 1 V voltage, a study was conducted to investigate the influence of time on the reduction process of Ca₂Fe₂O₅. Gradually, it resulted in the formation of CaFe₃O₅, CaFe₅O₇, FeO, and metallic Fe. With an increased driving force, one gram of Fe₂O₃-CaO mixed oxide can completely turn into metal Fe by electrolysis for 300 min.