Molten iodide-based salts due to their low melting points were envisaged to improve the performances of thermal batteries. Iodide-based salt drying and the determination of the basic properties (electrochemical window, conductivity, thermal heat capacity, …) of some electrolytes were carried out. The results obtained showed that some of iodide-based electrolytes are suitable for thermal batteries. In addition, the LiF–LiCl–LiI and LiF–LiBr–KBr electrolytes were tested in Li–Si/FeS2 single cells in the temperature of thermal battery operating conditions. The LiF–LiCl–LiI electrolyte could be considered as an interesting alternative for the improvements of thermal battery performances.