  We use first-principles calculation within the density functional theory
(DFT) to explore the electronic properties on stage-1 Li- and
Li+-graphite-intercalation compounds (GIC) for different concentrations,
LiCx/Li+Cx with x= 6,12,18,24,32 and 36. The essential properties, e.g.
geometric structures, band structures and spatial charge distributions are
determined by the hybridization of orbitals, the main focus of our works. The
band structures/density of states/spatial charge distribution display that the
Li-GIC possesses blue shift of fermi energy and just like metals, but the
Li+-GIC still preserves as original graphite or so-call semimetal possessing
the same densities of free electrons and holes. According to these properties,
we find that there exists weak but significant van der Waals interactions
between interlayer of graphite, and 2s-2pz hybridization between Li and C.
There scarcely exists strong interactions between Li+-C. The dominant
interaction between the Li and C is 2s-2pz orbital-orbital couple; the
orbital-orbital couple is not significant in Li+ and C case but the
dipole-diploe couple.
