A design of the cathode substrate for high-loading polysulfide cathodes in lean-electrolyte lithium-sulfur cells

High-performance sulfur cathodes characterized by high loading and content of active material and stable electrochemical properties with a lean electrolyte hold the key to realizing lithium-sulfur batteries with a high energy density. In this study, we present high-loading polysulfide cathodes using a series of carbon nanofibers that are generated from the carbonized electrospun nanofibers (CENFs). We fabricate the CENFs with similar porous fibrous skeleton decorating with tunable nanoporosity that allows us to explore the effect of nanoporosity on the electrochemical characteristics of the high-loading polysulfide cathodes. The CENF-polysulfide cathode made with non-nanoporous CENFs attains a high sulfur content of 71 wt% and loading of 14.4 mg cm⁻², both of which exceed sulfur cathodes reported in the literature (<60 wt% and <3 mg cm⁻²). The high-loading CENF-polysulfide cathodes attain high reversible discharge capacities of 802 and 670 mA h g⁻¹, high capacity retention rates of 82% after 200 cycles, and a long shelf life of 3 months at C/20 and C/10 rates, respectively. The cells further demonstrate high areal energy density values of 23.6 and 18.6 mW h cm⁻² in a cell with a low electrolyte-to-sulfur ratio of 4 µL mg⁻¹ at C/20 and C/10 rates. Therefore, our results demonstrate that the porous CENFs with limited nanopores prevent the rapid consumption of electrolyte and enable high-loading polysulfide cathodes to maintain high electrochemical efficiency and stability.