A novel electrochemical method (RPG method) was theoretically and experimentally developed to determine the diffusion coefficient of intercalary species within insertion-host materials on the basis of the spherical diffusion model. Theoretical results showed that the diffusion coefficient D was dependent to the ratio (q) of the potentio-charge capacity to the galvano-charge capacity (abridged to RPG), the radius of insertion-host particle R, and the galvano-charge time tG. The RPG equation obtained was as D = R2/(15.36qtG) (q ≤ 0.5). Using this method, the values of the Li+ diffusion coefficient determined at different galvano-charge currents with 1.5V cut-off voltage were all around the value of 1.060 x 10-10cm2/s. This result indicated that the RPG method has a good reliability for determination of the diffusion coefficient. The Li+ diffusion coefficient in graphite was reduced from 4.292 x 10-10 to 1.219 x 10-11cm2/s among the voltage range of 1.0 to 2.5V (versus Li/Li+), respectively.

Determination of the Li+ Diffusion Coefficient in Graphite by the Method of the Ratio of Potentio-Charge Capacity to Galvano-Charge Capacity. Tang, X.C., He, L.P., Chen, Z.Z., Xia, X.: Acta Physico-Chimica Sinica, 2002, 18[8], 705-9