PLATING END SHIPPING OF SODIUM FROM A ROOM-TEMPERATURE 1,2-DIMETHYL-3-PROPYLIMIDAZOLIUM CHLORIDE MELT

Room temperature molten salts consisting of 1,2-dimethyl-3-propylimida zolium chloride and aluminum chloride have been examined as possible e lectrolytes for a room temperature design of the sodium/iron(II) chlor ide battery. This work examines the conditions which provide the most efficient reduction and oxidation of sodium from a sodium chloride buf fered, neutral melt. Most work was performed on a tungsten substrate u sing cyclic voltammetry. Melts were treated with gaseous HCl using a c losed electrochemical cell which allowed for quantification of the eff ect of HCl on the electrochemical behavior of sodium in the molten sal t. The HCl threshold partial pressure was less than 1 kPa for sodium p lating. This result was complicated by the slow equilibrium between ga seous HCl and that dissolved in the molten salt; the effect of HCl add ition was found to last for months, demonstrating the slow equilibrium . Small amounts of water contamination 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 eff iciency.