Quaternary ammonium salts have been studied as ionic liquids for electrochemical applications, including sodium batteries. Mixtures of benzyltrialkylammonium chlorides with chloroaluminate formed ionic liquids near room temperature. The maximum coulombic efficiency for the reduction and re-oxidation of sodium ions with benzyltriethylammonium chloride ionic liquid was over 91%. The self-discharge current for a sodium electrode in this ionic liquid was 32.7 and 18 muA/cm(2) by chronopotentiometry at tungsten electrodes at 6.37 and 2.55 mA/cm(2), respectively. These are comparable to values in 1-methyl-3-propylimidazolium chloride melt. Issues with the coulombic efficiencies and the self-discharge currents are discussed. (C) 2004 The Electrochemical Society.