In situstudy of staging disorder in cesium-intercalated graphite

Abstract

Staging structure and kinetics in cesium-intercalated graphite were studied in situ using x-ray diffraction. The stage disorder was characterized via detailed Hendricks-Teller model analyses of (00L) profiles corresponding to various stage configurations. Broad distributions of stages were obtained under equilibrium conditions. Both stage purity and phase separation decreased with decreasing concentration; stages 5 and higher were highly miscible, while stages 3 and 2 completely phase separated. The miscibility also varied non-monotonically during a stage-n--to--(n-1) transition, suggesting that the kinetics are island-growth dominated towards the middle of the transition. We propose that the miscibility gap observed in a previous study of potassium graphite is caused by the enhanced development of stage-(n-1) cells with increasing chemical potential (or time), triggered by island growth; as these equilibrate, a discontinuously large stage-(n-1) volume results. Finally, an estimate for the exponent in the power-law repulsion between intercalate layers in alkali-graphite systems is made.