Catalytic additives for the reversible reduction of sodium in chloroaluminate ionic liquids

The ability of five different compounds to facilitate reduction of sodium from a chloroaluminate IL was investigated. PCl6− and 18-Crown-6 act to disrupt the Na+ and AlCl4− ion pairs producing reducible sodium ions. The addition of the small chlorinated compounds, CH2Cl2, CDCl3 or CCl4, resulted in the efficient reduction and reoxidation of sodium. It is believed that the electronegative chlorine atoms are oriented near the positive sodium cation, weakening its attraction to AlCl4−. For the five compounds tested, the highest coulombic efficiencies were measured after the addition of CDCl3 (90.5%) and CCl4 (88.2%). The addition of CDCl3 was found to substantially increase the conductivity of the IL.