Density, Viscosity, and Conductivity of Triethylamine Hydrochloride-Aluminum Chloride Ionic Liquid

Abstract—The development of a fast-charged safe battery with the ability of rapid charging without loss of stability at cyclic charge–discharge modes, which is capable of functioning at ambient temperatures, is a challenging problem for scientists. Aluminum-ion battery (AIB) is an energy storage system with the abovementioned properties. The use of an available ionic liquid (IL) of the composition triethylamine hydrochloride (Et₃NHCl)—aluminum chloride as an AIB electrolyte can favor an increase in the power characteristics and a decrease in the cost of AIB. It is necessary to know the influence of the IL composition on the density, viscosity and conductivity of the electrolyte to find the optimum electrolyte composition. Therefore, these physicochemical properties of aluminum chloride IL based on Et₃NHCl are studied in this work in the range of molar ratios of AlCl₃ to Et₃NHCl (N) from 1.3 to 1.95 at a temperature of 303 K. Raman spectroscopy shows that the \({\text{A}}{{{\text{l}}}_{{\text{2}}}}{\text{Cl}}_{7}^{ - }\) concentration increases and the \({\text{AlCl}}_{4}^{ - }\) concentration decreases as N increases. The IL density increases monotonically from 1.236 to 1.311 g/cm³, and its dynamic viscosity and conductivity decrease monotonically as N increases from 22.76 to 18.35 mPa s and from 12.626 to 10.097 mS cm^–1, respectively. According to our studies, the optimum electrolyte for AIB is IL with a molar ratio of AlCl₃ to Et₃NHCl of 1.3.