Polarity-Coded Fullerene-like Molecular Cages for Lithium–Sulfur Redox Regulation

Fullerene-like molecular cages offer atomically precise curved scaffolds for examining how local interfacial polarity regulates lithium–sulfur redox chemistry. Here, C 60 and B 30 N 30 are compared as fullerene-like molecular cages with comparable curved topologies but distinct surface polarity, allowing us to examine how nonpolar π-carbon curvature and heteropolar B/N-coded curvature regulate Li–S interfacial chemistry. Density functional theory shows that B 30 N 30 lowers the critical Li 2 S 4 → Li 2 S 2 thermodynamic penalty from 0.74 eV on C 60 to 0.49 eV, while maintaining a substantially larger frontier-orbital gap and avoiding the pronounced electronic softening observed for C 60 . Hirshfeld contact analysis and Mayer bond-order decomposition reveal that C 60 interacts with Li–S intermediates mainly through diffuse Li···C and S···C contacts, whereas B 30 N 30 establishes bifunctional Li/S anchoring through Li–N coordination and S–B sulfur capture. CDA-derived orbital interaction diagrams further indicate earlier and stronger host–polysulfide orbital communication on B 30 N 30, particularly across the Li 2 S 4 /Li 2 S 2 transition. Classical molecular dynamics simulations in composition-matched DOL/DME/LiTFSI/LiNO 3 /Li 2 S 4 electrolytes demonstrate that this polarity effect persists under explicit solvation, with B 30 N 30 producing markedly enhanced Li + and polysulfide-S interfacial enrichment relative to C 60 . These results identify polarity chemically encoded on curved molecular cages as a design principle for sulfur hosts, linking local Lewis acid/base complementarity, orbital coupling, and electrolyte-scale preorganization in Li–S redox regulation.