A structural model to calculate the electrochemical interface area for a composite graphite electrode is described. A new equation using the model predicted area to calculated chemical diffusion coefficient (DLi+) eliminates the effects from fabrication such as active mass (m(B)) and geometric area (S-Geo). The chemical diffusion coefficient values calculated for graphite electrodes of different thicknesses and porosities using the new equation are almost the same as expected. The values of DLi+ in the graphite vary between 10(-11.9) and 10(-9.9) cm(2)/s over the course of the lithium deintercalation in the graphite samples. (C) 2004 The Electrochemical Society.