In the field of battery technology, the lithium-sulfur battery has been widely pursued due to high energy density and high theoretical capacity that can satisfy viability thresholds for electric vehicles. However, this elusive technology remains in the research sector due to a wealth of engineering challenges resulting from the complex chalcogenide electrochemistry. The most infamous challenge remains the polysulfide shuttle effect, in which lithium polysulfide intermediates are produced as elemental sulfur (S₈) is reduced to lithium sulfide (Li₂S) during the discharge cycle. Since the higher order polysulfides are soluble in organic electrolyte, battery cycling can result in dissolution of the cathode, dendrite formation upon a lithium metal anode, and introduce impedance via electrode passivation. This can ultimately cause rapid capacity fade and unstable Coulombic efficiency.

This work presents a novel carbon-sulfur composite, utilizing a cost-effective, bimodal-porosity carbon substrate and a sonochemical sulfur loading technique to improve mono-dispersity in sulfur distribution. The cavity-rich carbon substrate, appropriately named carbon compartments, is synthesized through a single step heating process of commercial wheat flour. The surface area and bi-modal porosity of the carbon compartments enable high sulfur loading (ca. 70 %-wt.). Optimization of a novel fluorinated-electrolyte demonstrates radical improvement in columbic efficiency and cycling stability of the carbon-sulfur composite. The demonstrated Li-S cathode has shown stable half-cell performance (ca. 750 mAh g^-1) and columbic efficiency (> 96 %) for all cycles at a current density of 28 mA g^-1.

Further analysis using in-depth multi-scale modeling describes the electrochemical performance of the composite. Density functional theory and ab initio molecular dynamics characterize the development and behavior of sulfur-containing compounds at the electrolyte-composite surface. Stochastic modeling of the composite microstructure describes electrochemical and physical consequences of polysulfide precipitation. This multi-scale model provides fundamental insight into the mechanisms concerning the role of carbon morphology in the polysulfide shuttle phenomenon.