LAUSR

Abstract The use of sodium-sulfur batteries at the grid level requires high current density operation that can cause cell deterioration, leading to lower sulfur utilization and lower energy efficiency. In addition, it can result in undesired thermal runaway leading to potentially hazardous situations. A rigorous, dynamic model of a sodium-sulfur battery can be used to study these phenomena, design the battery for optimal transient performance, and develop mitigation strategies. With this motivation, a first-principles, fully coupled thermal-electrochemical dynamic model of the entire sodium-sulfur cell has been developed. The thermal model considers heat generation due to Ohmic loss, Peltier heat, and heat due to entropy change. Species conservation equations are written in the sulfur electrode by considering the phase transition and change in the composition depending on the SOD. Species conservation equations are written in the beta”-alumina electrolyte for the ionic species by considering the change in composition due to diffusion and migration. In addition, the potential distribution, and cell resistance for this spatially distributed system has been modeled. Furthermore, temperature-dependent correlations for the physicochemical properties are developed. The model is used to study both charging and discharging characteristics of the cell at varying current densities.