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 4KO 2, c-axis repeat distance 8.44 Å) and stage 2 (assigned formula C 8KO 2, c-axis repeat distance 11.75 Å) 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.