The analytical formulation presented here is for the prediction of the performance of a solid-state lithium anode/lithium-insertion cathode cell that is limited by solid-state diffusion in the cathode active material. Transient, dimensionless solid-state lithium-ion concentration-incorporating group profiles have been computed for a cell whose performance is controlled by lithium-ion diffusion in the cathode active material. The analytical equation for the voltage loss associated with solid-state lithium-ion diffusion and the resultant solid-state lithium-ion concentration profile in the cathode active material has been developed. To provide examples of the application of the developed formulation, generated numerical data are shown in the form of plots. Preliminary determination of the lithium ion diffusion coefficient in a dilithium phthalocyanine cathode active material from cell discharge data, and the determination of the activity coefficient and reversible cell voltage of an aerogel-based LiV2O5 cathode active material as a function of lithium intercalation have been performed.