The formation of a stage-one intercalate, LiC6, increased the interlayer distance from 0.335 to 0.371nm. Although the diffusion of Li into graphite preceded intercalate formation, no data existed for Li transport at low Li concentrations. Here, the release kinetics of Li from highly oriented pyrolytic graphite were measured for Li contents of between 1 and 10ppm, and at temperatures ranging from 1000 to 1300K. In this way, the diffusion coefficients for 7Li and 6Li were determined. It was found that the Li transport in this material was strongly anisotropic, and that a negligible contribution (to the total release) arose from diffusion perpendicular to the graphite planes. The diffusion of Li parallel to the graphite planes was described by:

D (cm2/s) = 3000 exp[-1.83(eV)/kT]

The diffusivity at 1070K was 7.6 x 10-6cm2/s).

B.Jungblut, E.Hoinkis: Physical Review B, 1989, 40[16], 10810-5