A one dimensional mathematical model is presented for a high temperature lithium–aluminum, iron disulfide molten salt battery system. Multi-physics transport phenomena in the electrolyte, charge balances in the solid phases and electrolyte, complex multi-step electrochemical and chemical reactions in the electrodes are described in this model. The model includes the effects of precipitation salt on active area in the electrode and the discharge capacity. In addition the model also takes the change in volume of the active material into account during the electrochemical reactions by incorporating the change in porosity of the electrode and the change in dimension of the electrode. The model results are compared to the existing model in literature and available experimental data.