Sulfur infiltration and allotrope formation in porous cathode hosts for lithium-sulfur batteries

We investigate sulfur infiltration and formation of lower order allotropes in heated porous hosts during fabrication of lithium-sulfur (Li-S) battery cathodes. Sulfur existence in cathode ultramicropores has been an important question for Li-S batteries, as ultramicropores reduce the polysulfides shuttle effect but also delay sulfur dissolution and Li+ ion diffusion in the trapped solid sulfur. A novel continuum-level model is presented including heat transfer and sulfur infiltration, either from the top of a porous host or from the porous host particle surface, and taking into account the pore size distribution. A novel decay factor in modeling sulfur infiltration incorporates the pore wall repulsion energy and allotrope formation energy (predicted by density functional theory [DFT] simulations). Simulations are performed for a microporous carbon fabric host and an activated carbon powder host with bimodal micropore and macropore size distribution, with Raman and X-ray photoemission spectroscopy (XPS) spectroscopy confirming the predicted existence of linear S-6 and S-4 in ultramicropores.

Automated summary

The study investigates sulfur infiltration and formation of lower order allotropes in heated porous hosts during fabrication of lithium-sulfur (Li-S) battery cathodes. A novel continuum-level model is presented, incorporating heat transfer and sulfur infiltration, while considering the pore size distribution. Simulations confirm the existence of linear S-6 and S-4 in ultramicropores.