Ionic conductivity and thermal stability of lithium salt / potassium bifluoride electrolytes for thermal batteries

摘要

The incorporation of potassium bifluoride (KF-HF) as an additive to the lithium-halide electrolyte for thermal batteries was investigated. Different mixtures of lithium fluoride, lithium chloride and lithium sulfide with KF-HF were studied using electrochemical impedance spectroscopy and differential scanning calorimetry. The results from these tests were combined to obtain a better understanding of the relationship between ionic conductivity, melting point, and electrolyte composition. The results indicated that it is feasible to maintain a relatively high ionic conductivity at temperatures lower (250-300 degrees C) than current thermal battery electrolytes (400-550 degrees C). Mixtures of lithium fluoride and potassium bifluoride provided the best ionic conductivity at 260 degrees C. The effect of mixing these lithium halides on the thermal decomposition of the KF-HF was also investigated. It was observed that it can increase decomposition temperature by up to 15 degrees C while at the same time reduce the melting point of the mixture and increase the ionic conductivity.