The validity of estimating the solid phase diffusion coefficient, Ds, of a lithium intercalation electrode from impedance measurement by a modified electrochemical impedance spectroscopy method was studied. A macroscopic porous electrode model and concentrated electrolyte theory were used to simulate the synthetic impedance data. The modified electrochemical impedance spectroscopy method was applied for estimating Ds. The influence of parameters such as the exchange current density, radius of active material particle, solid phase conductive, porosity, volume fraction of inert material, and thickness of the porous carbon intercalation electrode, the solution phase diffusion coefficient, and transference number, on the validity of Ds estimation, was evaluated. A simple dimensionless group was developed to correlate all the results. It showed that the accurate estimation of Ds requires large particle size, small electrode thickness, large solution diffusion coefficient, and low active material loading. Finally, a "full model" method was developed for the cases where the modified EIS method does not work well.

Estimation of Diffusion Coefficient of Lithium in Carbon Using AC Impedance Technique. Guo, Q., Subramanian, V.R., Weidner, J.W., White, R.E.: Journal of the Electrochemical Society, 2002, 149[3], A307-18