Thermodynamic Properties of the Potassium–Graphite Lamellar Compounds from Solid-State emf Measurements

Thermodynamic properties of the potassium–graphite lamellar compounds have been determined in the temperature range 200°–350°C using a solid-state emf technique. The electrochemical cells were of the type K (liquid) | K-glass | K–graphite where the electrolyte is a glass reversible to potassium ion. Breaks in the emf-vs-temperature plots were observed at compositions between C8K and C24K which indicate that C10K is not stable below 320°C. The thermodynamic data in the potassium–graphite system are compared to the results obtained in the rubidium– and cesium–graphite systems.