Two-dimensional conjugated aromatic polymer as a promising anchoring material for lithium-sulfur batteries

Lithium-sulfur batteries are being regarded as a kind of promising next-generation rechargeable battery technology for their high energy density as well as high theoretical specific capacity. However, the shuttle effect of soluble polysulfides and the poor electrical conductivity of sulfur cathodes significantly impedes the energy efficiency and cycle performance of this battery system. In this work, the anchoring behavior of polysulfides on a newly synthesized material named two-dimensional conjugated aromatic polymers (2D-CAP) was investigated using density functional theory calculations. The results show that the surface of 2D-CAP can provide moderate adsorption energies towards the soluble polysulfides, which can effectively avoid the dissolution of polysulfides into electrolyte while preserving their structural integrity. In the meantime, the small bandgap of 2D-CAP disappeared after lithium polysulfides adsorption and the nanoporous structure of 2D-CAP can facilitate lithium ion transportation, which can improve the cycling performance of Li-S batteries. Moreover, the 2D-CAP can effectively catalyze the decomposition process of Li₂S. All of these properties suggest that 2D-CAP is a prospective anchoring material for lithium-sulfur batteries which not only mediate the shuttle effect of soluble polysulfides but also promote the charge reaction of sulfur cathode.