Estimation of Sodium Sulfur Cell Characteristics Using Computed Tomograms from High Energy X‐Rays

The density distributions in the axial and radial cross sections of two typical sodium sulfur cells were obtained by a high-energy x-ray computed tomography (CT) system with a linear accelerator. The tomograms of the low-resistance cell showed a uniform density distribution of sulfur and sodium pentasulfide in the graphite felt of the sulfur electrode, while those of the high-resistance one were indicative of a nonuniform density distribution. The difference in the cell characteristics between the cells could be accounted for by the difference in the density distribution of the active material in the sulfur electrode. The low discharge voltage of the high-resistance cell, calculated using an internal-parallel-cell model, agreed well with experimental results. The tomograms of cells taken by x-ray CT can be applied to evaluate sodium sulfur cell characteristics.