Effect of Impurities (Oxides, Hydroxides) in Molten Salt Electrolytes on the Thermal Stability of FeS2 Cathode Material for Thermal Batteries

Abstract

The thermal decomposition of pyrite FeS2 used as cathode material in thermal batteries was investigated under helium and in molten salts (eutectic compositions: LiCl-KCl and LiF-LiCl-LiI), in presence of hydroxides and oxides. This work shows the pyrite decomposes into pyrrhotite and forms a porous structure. It has been shown that the presence of a molten phase increases pyrites thermal stability as it acts as a physical barrier. On the other hand, the addition of hydroxide or oxide decreases its thermal stability. At high temperature hydroxides are transformed into oxides. The decomposition temperature of the pyrite in presence of oxides is decreased by nearly 70 to 100°C.