A laboratory X-ray CT system, ZEISS Xradia 520 Versa (Carl Zeiss Inc., USA) was used to examine the microstructure of commercial Li-S electrodes (Figure ). The lab-based micro-CT system is equipped with a polychromatic micro-focus source (W target) that was set at 80 kV and a maximum power of 7 W. The sulfur electrode sample with a size of ca. 1×1 mm was cut from the electrode sheet and mounted onto a stainless-steel dowel with epoxy [2,4,6-tris (dimethyl aminomethyl) phenol, Devcon]. The micro-CT scans were performed by taking 1601 projections through 360°. The scintillator was coupled to a 40× objective lens and 2048 × 2048 pixel CCD detector with a voxel binning of 1, resulting in a pixel size of 177.1 nm and field of view of ca. 380 μm. The X-ray exposure was set at 45 s. Tomographic datasets were reconstructed using a scoutand-scan reconstructor (Carl Zeiss Inc., USA) using a filtered back-projection algorithm. The micro-CT dataset was imported into Avizo (Visualization Sciences Group, FEI Company) and a volume of 1250×1150×131 voxels was extracted for further post-processing, segmentation and analysis [Figure ]. An edge-preserving de-noising non-local means filter was applied, followed by a rough grey-scale thresholding approach to generate markers used as seed points for watershed segmentation. The electrode was then segmented using the combination of watershed segmentation and manual segmentation into three distinctive phases; namely, elemental sulfur, carbon-binder-domain, and pores that would fill with electrolyte during cell assembly. The segmented image was further processed using an island removal filter and dilation filter to remove small spots and artefacts incorrectly identified as a particulate phase [(Figure and)]. Standard length, areal and volumetric metrics are extracted from the segmented images using Avizo. These metrics includes the volume fraction, sulfur particle size distribution and the sphericity of sulfur particles. The continuous pore size distribution was obtained from an ImageJ plugin, XLib , whereas the representative elementary volume, tortuosity and diffusivity of the pristine electrode and changes in tortuosity with the sulfur dissolution were obtained from TauFactor . As the aim of this model is to discern the effect of heterogeneities in electrode architecture that effects the battery performance, the volume fraction of sulfur is obtained from the microstructural analysis, whereas the electrolyte is saturated with dissolved sulfur; hence, the concentration of dissolved sulfur in the electrolyte is equal to the solubility limit of the elemental sulfur dissolutionprecipitation equilibrium (19 mol m -3 ). During the cell discharge, the concentration of Li + and sulfide ions increases, leading to the formation of one or more polysulfides, ranging from Li2S8 to Li2S. The reaction events considered in this model are presented in Figure .