Electrochemical behavior of aluminum in 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid electrolytes for capacitor applications

Abstract

This study compares two series of solvents for application in aluminum electrolytic capacitors: ethylene glycol (EG) and water mixtures, and ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) ionic liquid (IL) mixtures. Electrochemical impedance spectroscopy and cyclic voltammetry were carried out with a previously anodized aluminum disk electrode. Comparative measurements of solution resistance, polarization resistance, AC capacitance, and passive current were made. The results show that EG–IL mixtures with low amounts of IL (10% IL–90% EG v/v) have a low solution resistance. Low values of solution resistance, high values of polarization resistance, small passive current, and uniform capacitance of anodized aluminum in EG–IL mixtures are favorable properties of the BMI.BF4 IL for use as an electrolyte in the construction of electrolytic aluminum capacitors.