Potassium-Oxygen Graphite Intercalation Compounds.

Abstract Intercalation of potassium superoxide KO 2 into graphite in the presence of potassium metal was studied. Graphite intercalation compounds of stage 1 (assigned formula C 4 KO 2 , c -axis repeat distance 8.44 A) and stage 2 (assigned formula C 8 KO 2 , c -axis repeat distance 11.75 A) were synthesized and isolated for the first time. A quadruple intercalate layer KOOK is supposed. In-plane structure of the intercalate layer is discussed mostly on the basis of X-ray diffraction intensity analysis and transmission electron microscopy electron diffraction. A metal-like temperature dependence of c -axis resistivity was obtained in the 1.5–300 K temperature range where the resistivity values at room temperature are 0.07 and 0.81 Ω cm for stage-1 and stage-2 compounds, respectively. The results of magnetic susceptibility measurements suggest that the oxygen species are in nonmagnetic states.