The diffusion coefficient of lithium in highly oriented pyrolytic graphite was measured by using electrochemical impedance spectra and potential step methods in 1mol/L LiPF6, V(EC) : V(DMC) = 1:1 solution. It was found that the resistance of SEI film and the polarization resistance decreased with the increase of lithium intercalation degree. An agreement was obtained between the diffusion coefficient values measured from these two methods. The diffusion coefficient of lithium in highly oriented pyrolytic graphite decreased from 10-11 to 10-12cm2/s in the potential region of 0.2 to 0.05V

Diffusion Coefficient of Lithium for Intercalation in Highly Oriented Pyrolytic Graphite. Nu-Li, Y.N., Wan, C.Y., Yan, M.M., Zhuang, J.H., Jiang, Z.Y.: Chemical Journal of Chinese Universities, 2002, 23[7], 1378