Constructing Bimetallic Selenide Catalysts with Dense Heterointerfaces and Vacancies Engineering Enables Efficient Polysulfide Conversion Chemistry

The development of heterostructure catalysts with high chemisorption enables effective immobilization and efficient catalytic conversion of lithium polysulfides (LiPSs), thereby enhancing the performance of lithium–sulfur (Li–S) batteries. Herein, an ultrafine bimetallic selenide electrocatalyst (FeSe2–SnSe2/NC) featuring dense heterointerfaces and selenium vacancies was rationally designed and fabricated via ultrafast (<3 s) in situ growth of interpenetrated gel precursors, which was used to modify the separator of a Li–S battery. FeSe2–SnSe2/NC was demonstrated to have dense heterointerfaces and defects, which synergistically modulate the electronic structure, enhance ionic and electronic conductivity, strengthen LiPSs adsorption, and accelerate sulfur redox reaction kinetics. Simultaneously, FeSe2–SnSe2/NC effectively suppresses the lithium anode dendrite formation. Consequently, the FeSe2–SnSe2/NC–based battery delivers high initial discharge capacity (1552.6 mAh g–1 at 0.1 C), outstanding rate capability, long–term cycling stability (ultralow decay rate of 0.042% per cycle at 0.5 C over 700 cycles), and competitive areal capacity under high sulfur loading. This study offers valuable insights for designing efficient transition metal selenide electrocatalysts via an integrated heterostructure and defect engineering for advanced Li–S batteries.