Thin-film Solid-State Batteries (TFSSB) is one of most promising and quickly developing fields in modem electrochemical energy storage. Modeling these devices is interesting from theoretical and practical point of view. This paper represents a simulation approach for TFSSB which overcome a major drawback of available mathematical models, Le. decline in accuracy of the models at high current rates. A one-dimensional electrochemical model, including charge transfer kinetics on the electrolyte-electrode interface, diffusion and migration in electrolyte as well as diffusion in intercalation electrode has been developed and the simulation results are compared to experimental voltage-capacity measurements. A new definition of diffusion coefficient as a function of concentration, based on the experimental measurements, is used to improve the performance of the model. The simulation results fit the available experimental data at low and high discharge currents up to 5 mA cm(-2). The models show that the cathode diffusion constant is a prime factor limiting the rate capability for TFSSB in particular for ultrafast charging applications.