The goal of the work presented here was to develop a simulation approach for studying the effects of materials and geometry on the performance of Li-ion Solid State Batteries (SSB). Simulation provides the opportunity to explore, with ease, different material properties and cell geometries to optimize a Li-ion SSB's performance. Simulations shown in this paper are time-dependent and consider electrochemical reaction, heat transfer, the diffusion of Li-ions and electrons in the electrolyte, and solid Li diffusion in the positive electrode. A 2D model was simulated and the results shown. The simulations were able to show discharge curves, heat flux, the concentration of Li-ions, electrons, and solid Li at any time in the discharge cycle. Copyright (c) 2015 John Wiley & Sons, Ltd.