Energetic evaluation of possible stacking structures of Li-intercalation in graphite using a first-principle pseudopotential calculation

Energetic evaluation of possible stacking structures of Lithium-graphite intercalation compounds (Li-GICs) has been performed using the density-functional theory under the local density approximation with or without the generalized gradient correction. The calculated formation energies of Li-GICs well reproduced the stability of the structures and their lattice parameters. That is, the calculated formation energies (ΔE) are negative for the equilibrium phases of LiC6, LiC12 and LiC18 with αA, αAA and αAAA stacking where one-third of the carbon hexagons have corresponding Li atoms. In contrast to that, ΔE of hypothetical phases of LiC2, LiC4, LiC6 and LiC8 with different in-plane ratios of carbon-hexagon to Li are positive. Hypothetical LiC4 with the Aα′B stacking has also a positive ΔE, but the equilibrium LiC18 with αABA stacking has a negative ΔE. AA stacking of carbon hexagonal monolayer and graphite with AB stacking are also discussed for the reference state of these Li-GICs.