Plating and Stripping of Sodium from a Room Temperature 1,2-Dimethyl-3-propylimidazolium Chloride Melt

Room temperature molten salts consisting of 1,2-dimethyl-3-propylimidazolium chloride and aluminum chloride have been examined as possible electrolytes for a room temperature design of the sodium/iron(II) chloride battery This work examines the conditions which provide the most efficient reduction and oxidation of sodium from a sodium chlo-ride buffered, neutral melt. Most work was performed on a tungsten substrate using cyclic voltammetry. Melts were treat-ed with gaseous HC1 using a closed electrochemical cell which allowed for quantification of the effect of HC1 on the elec-trochemical behavior of sodium in the molten salt. The HCI threshold partial pressure was less than 1 kPa for sodium plating. This result was complicated by the slow equilibrium between gaseous HC1 and that dissolved in the molten salt; the effect of HC1 addition was found to last for months, demonstrating the slow equilibrium. Small amounts of water con-tamination were found to produce a similar effect. At elevated temperatures the melt had higher conductivity, an order of magnitude higher current densities, and higher coulombic efficiency