Alkali metals induced stacking phase transition of graphite

It is well known that alkali metals can intercalate into graphite to form graphite intercalation compounds but the structural change of graphite induced by alkali metals has been paid less attention. Herein, we report that alkali metals (Li, Na, K) induce the phase transition from ABC-stacking (or 3R phase) to AB-stacking (or 2H phase) of graphite. Specifically, for the graphite powder containing ∼45% 3R phase in a mixed phase, the temperature needed to ensure a complete stacking phase transition is 600 °C, 500 °C or 350 °C, for Li, Na or K, respectively, much lower than that needed in bare annealing (1800 °C) while without these alkali metals. Simulations based on density functional theory (DFT) suggest that the charge transfer from alkali metals to graphene distinctly lowers the energy barrier of transition, explaining the different phase transition temperatures for these alkali metals.