The importance of pore size and surface polarity for polysulfide adsorption in lithium sulfur batteries
Polysulfide shuttling is a crucial factor in lithium sulfur batteries responsible for capacity fading and degradation. Liquid phase adsorption in combination with nuclear magnetic resonance and X-ray photoelectron spectroscopy are used to elucidate and quantify polysulfide retention in typical porous cathode materials used in lithium sulfur batteries without cell assembly to achieve a more fundamental understanding of liquid phase adsorption phenomena as a responsible mechanism for polysulfide retention. The individual impact of each pore size increment is quantified on the polysulfide adsorption (PSA). Ultramicropores show eight times higher PSA (1.48 mmol cm-3) than mesopores. Strong heteroatom-doped ultramicropores show even stronger interactions with polysulfides leading to 25 times higher adsorption compared to hydrophobic mesopores. These findings allow to precisely tailor pore structure and heteroatom distribution of cathode materials for next generation lithium sulfur batteries with prolonged cycle life and reduced capacity fading.