This paper develops a computational model and applies it to investigate the performance of a rechargeable battery that is comprised of a molten-sodium anode, a NASICON sodium-ion-conducting separator membrane, and a iodine-based cathode. The cathode compartment is comprised of a porous-carbon felt and an aqueous catholyte that supports an iodine redox process. The battery chemistry can be represented globally as 2Na(+) + 2I(-) reversible arrow 2Na + I-2. The ion transport is represented in terms of a Nernst-Planck formulation that includes four mobile species within the catholyte, Na+, I-, I-3(-) and I-2. The charge transfer chemistry is modeled using a Butler-Volmer formulation. The model considers solubility limits and the potential precipitation of NaI and I-2. Parameter studies investigate the influences of charge and discharge rates, total elemental iodine loading, and effective conductivity of the carbon-felt cathode. (C) 2016 Elsevier Ltd. All rights reserved.