Theoretically endured defect-engineered antimony selenide nanocrystals grafted within three-dimensional reduced graphene oxide hollow microspheres with large open cavities as polysulfide barrier for robust sulfur kinetics

Defect engineering techniques have gained significant attention worldwide as a promising strategy to amend the electronic and atomic arrangements of nanomaterials. By introducing defects such as dislocations or vacancies in polar materials, it is possible to create electrophilic adsorption sites that can effectively trap polysulfide species by lowering the energy transfer barrier for electrons. In this study, non-stoichiometric antimony selenide (Sb₂Se_2.2) nanocrystals embedded in a three-dimensional hollow microsphere composed of a reduced graphene oxide (rGO) matrix (H-Sb₂Se_2.2@rGO‒600) were synthesized by precisely controlling the heating conditions. Density functional theory (DFT) calculations revealed that thermally induced anionic Se-defects caused atomic disorder in the crystal structure, altering the electronic structure and in turn enhancing the adsorption strength of polysulfide through improved electrophilic coupling interactions between \(\mathrm{Sb}^{\delta+}-\mathrm S_x^{2-}\) and \(\mathrm{Li}^+-\mathrm{Se}^{\delta-}\). Lithium–sulfur (Li–S) batteries incorporating H-Sb₂Se_2.2@rGO‒600-coated separator and a typical sulfur electrode (≈2.0 mg cm^–2) exhibited excellent high-rate capability, with a discharge rate of up to 4.0 C, and exceptional cycling stability. After 1300 continuous charge‒discharge cycles at 4.0 C, the cell showed a capacity retention of 90.4%, with an average capacity decay rate of only 0.007% per cycle. The impressive performance was maintained under more demanding cell conditions, such as high effective S content (66%), high S loading (6.0 mg cm^–2), and a low electrolyte-to-sulfur ratio (4.3 µL mg^–1). The Li–S cell demonstrates excellent cycling stability (120 cycles at 0.1 C) and maintains feasible rate performance up to 0.3 C.