Properties of asymmetric benzyl-substituted ammonium ionic liquids and their electrochemical properties

Benzyl-substituted quaternary ammonium ions were used to form room-temperature ionic liquids with chloroaluminate ions. Asymmetric ammonium structures significantly lowered the melting point of the ionic liquid. Asymmetric benzyl-substituted ammonium chlorides were mixed with AlCl3 to form acidic room-temperature ionic liquids. It is shown that the melting point and viscosity are a function of the symmetry of the quaternary ammonium ion and its molecular weight. Asymmetry and low molecular weight favor lower viscosity and melting point, and higher conductivity. These liquids were neutralized with NaCl and tested as electrolytes for sodium batteries. The neutralized ionic liquid of benzyldimethylethylammonium chloride had a low self-discharge current (3.96 muA/cm(2)) at room temperature on a platinum electrode substrate. (C) 2005 The Electrochemical Society.