Molten Triazolium Chloride Systems as New Aluminum Battery Electrolytes

The possibility of using molten mixtures of 1,4-dimethyl-1,2,4-triazolium chloride (DMTC) and aluminum chloride (AlCl3) as secondary battery electrolytes was studied, in some cases extended by the copresence of sodium chloride. DMTC-AlCl, mixtures demonstrated high specific conductivity in a wide temperature range. The equimolar system is most conductive and has kappa values between 4.02 x 10(-5) and 7.78 x 10(-2) S cm-1 in the range from -31 to 123-degrees-C, respectively. The electrochemical window of DMTC-containing sodium tetrachloroaluminate melts varied in the region of 2.5 to 2.2 V (150-170-degrees-C) depending on melt acidity and anode material. DMTC, being specifically adsorbed and reduced on the tungsten electrode surface, had an inhibiting effect on the aluminum reduction, but this effect was suppressed on the aluminum substrate. An electrochemical process with high current density (tens of milliamperes per square centimeter) was observed at 0.344 V on the acidic sodium tetrachloroaluminate background, involving a free triazolium radical mechanism. Molten DMTC-AlCl3 electrolytes are acceptable for battery performance and both the aluminum anode and the triazolium electrolyte can be used as active materials in the acidic DMTC-AlCl3 mixtures.