Solvation effect of [BMIM]Cl/AlCl3 ionic liquid electrolyte

Four kinds of solvents, methylene chloride (CH 2 Cl 2 ), toluene (TOL), ethyl acetate (EtoAc), and dimethyl carbonate (DMC), were added into the 1-butyl-3-methylimidazolium chloroaluminate ionic liquid ([BMIM]Cl/AlCl 3 IL) to improve the property of the IL-based electrolyte for aluminum (Al) electrolysis. Solvation effects of these solvents on the physical properties, electrochemical properties, and electroactive ion of the [BMIM]Cl/AlCl 3 IL-based electrolyte were investigated. It was found that the viscosity of the IL electrolyte decreased after adding CH 2 Cl 2 or TOL, and the conductivity increased while the change of the conductivity and the viscosity moved in the opposite direction with the addition of EtoAc or DMC. The UV-Vis spectra showed that the electroactive Al ion continued existence after adding CH 2 Cl 2 or TOL, but there was solvation effect between TOL and BMIM + . On the other hand, both EtoAc and DMC had solvation effects with electroactive Al ion and BMIM + . The results illustrated that solvation effect was the key effect on the reduction of Al on the cathode, and further influenced the morphology of the Al deposits. In addition, the concentration polarization reduced and the efficiency of electrolysis improved after adding CH 2 Cl 2 or TOL. Furthermore, bright Al coatings were obtained finally by adding CH 2 Cl 2 into [BMIM]Cl/AlCl 3 IL electrolyte (when the mole ratio of CH 2 Cl 2 is around 66.7~75%).