Density Functional Theory Calculations of Alkali Metal (Li, Na, and K) Graphite Intercalation Compounds

First-principles calculations were done to examine the energetics of alkali metal intercalation into graphite. Calculations based on the exchange-correlation functionals that include a nonlocal correlation were found to give reasonable agreement with experiments concerning the crystal structure of graphite and LiC 6, binding energy of graphene sheets, and Li intercalation potential. We found that K intercalation from KC 8 to KC 6 cannot be achieved through electrochemical reactions. We also found that the absence of the stage-I structures for Na graphite intercalation compounds such as NaC 6 or NaC 8 is linked to a relatively high redox potential of Na/Na + compared to that of Li/Li + .