A medium temperature electrolyte with potential for use in high safety thermal batteries: LiF-LiCl-KBr-CsCl

Thermal batteries, as high-temperature primary batteries, typically operate at temperatures of 400 to 550 ℃ due to the high melting point of the electrolytes used. The extensive use of heating powder and the leakage and corrosion of the electrolyte caused by high operating temperatures pose significant safety threats to thermal batteries. To address this, we developed a LiF-LiCl-KBr-CsCl electrolyte with a melting point of 347 ℃, an enthalpy of melting of 103.9 J/g, a saturated vapor pressure of 7.21 Pa, and solid–liquid specific heat capacities of 0.58 J/(K·g) and 0.79 J/(K·g), respectively. Compared with the commercial LiF-LiCl-LiBr, the electrolyte leakage in the single battery was reduced to only 8.39% of that of LiF-LiCl-LiBr. The various physicochemical properties and experimental results of LiF-LiCl-KBr-CsCl indicate that its use in thermal batteries will enhance safety. Additionally, its reliable small-current discharge performance suggests it is a candidate for small-current, long-life thermal battery electrolytes.