Constructing highly active sulfur atoms on MoS₂ surface via p-p orbital covalent coupling matching the liquid-solid transition in lithium-sulfur batteries

Abstract

Herein, we propose a strategy involving Co atoms and Mo vacancies to precisely adjust the orbital orientation of sulfur atoms on MoS₂ surface, accurately modulating their interaction with lithium and sulfur sites in polysulfide species for stronger interactions with short-chain polysulfides, thereby promoting efficient liquid-solid conversion. Through a combination of theoretical modeling and experimental validation, multiple electron-deficient sulfur sites are constructed to demonstrate the p_z orbitals of unsaturated surface sulfur atoms couple strongly with the p orbitals of short-chain polysulfides, facilitating formation of selective S-S bonds via enhanced p-p interactions, thereby accelerating the transition kinetics from Li₂S₄ to Li₂S₂/Li₂S. This selective coupling is driven by sulfur molecular orbital occupation, charge distribution, and lattice matching. Moreover, we construct an electrocatalytic membrane composed of vertically aligned MoS₂ nanosheets and carbon nanotube nanochannels to ensure efficient contact between reactants and catalysts, enabling continuous polysulfide conversion. Consequently, the cell shows ultralow capacity decay (0.022 % per cycle over 1000 cycles at 2 C). This study emphasizes manipulation of the 3p orbital orientation of sulfur atoms to form selective dual-coordination, and provides valuable insights for the rational design of advanced electrocatalysts at the atomic level.