(P,T) phase boundary in Li-intercalated graphite: Theory and experiment

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

“…Though lattice parameters, a and b, of graphite were well reproduced by both of LDA and GGA, c was not especially by GGA calculation. The calculated formation energies of the equilibrium LiC 6 , LiC 12 and LiC 18 with αA, αAA and αAAA stacking are negative, where one-third of the carbon hexagons have corresponding Li atoms, though they are somewhat overestimated. The formation energies of hypothetical LiC 2 , LiC 4 and LiC 6 where all the C hexagons have corresponding Li atoms and LiC 8 where one-fourth of the carbon hexagon have Li atoms, are positive.…”

“…As for LiC 6 , for example, since the energies of Li and C (graphite) calculated by LDA are −187.991 and −155.521 eV (a quarter of −622.086 eV of the total energy of graphite) as shown in Table 2, respectively, the energy of the reference state (Li + 6C) is Table 3 Observed and geometrically optimized crystallographic parameters of LiC 6 , LiC 12 and LiC 18 with the in-plane structure shown in Fig. 2 Measured values of the enthalpies of formation of LiC 6 and LiC 12 were −13.9 and −24.8 kJ/mol, respectively at 455 K [16].…”

“…Considering these observed facts, we determined the target of the energetic calculations as followings: (1), effect of stacking of graphen layers to form graphite, (2), equilibrium phases of LiC 6 , LiC 12 and LiC 18 with the in-plane structure shown in Fig. 2 (6), equilibrium LiC 18 which has AB stacking of carbon layers.…”

“…5 It should be noted here that the AB stacking of graphene layer is not found in the stage I compounds but is found in the stage higher than or equal to two compounds. One form of LiC 18 , the stage II compounds, is characterized by a c-axis stacking of αABA [12] and the crysyallographic parametrers are described as shown in Table 1(I).…”

Diffusive Motion in Stage-1 and Stage-2 Li-Graphite Intercalation Compounds: Results of ß-NMR and Quasielastic Neutron Scattering

“…It might be related to a sug gested phase transition at about 200 K ( [22] and refer ences therein). In the LiC12 sample the SLR behaviour might be influenced by the known phase transition at T=248 K [23] in the minority LiC16 phase. The rela tively low abundance of the latter, together with a possible translational Li motion during the lifetime of the 8Li probe might effect an averaging over inequiv alent probe surroundings and prevent a nonexponen tial decay of the ^-asymmetry of 8 Li in the stage-2 sample.…”