Anionic Doping in Layered Transition Metal Chalcogenides for Robust Lithium‐Sulfur Batteries

Lithium-sulfur batteries (LSBs) are among the most promising next-generation energy storage technologies. However, a slow Li-S reaction kinetics at the LSB cathode limit their energy and power densities. To address these challenges, this study introduces an anionic-doped transition metal chalcogenide as an effective catalyst to accelerate the Li-S reaction. Specifically, a tellurium-doped, carbon-supported bismuth selenide with Se vacancies (Te-Bi2Se3-x@C) is prepared and tested as a sulfur host in LSB cathodes. X-ray absorption and in-situ X-ray diffraction analyses reveal that Te doping induces lattice distortions and modulates the local coordination environment and electronic structure of Bi atoms to promote the catalytic activity toward the conversion of polysulfides. Additionally, the generated Se vacancies alter the electronic structure around atomic defect sites, increase the carrier concentration, and activate unpaired cations to effectively trap polysulfides. As a result, LSBs based on Te-Bi2Se3-x@C/S cathodes demonstrate outstanding specific capacities of 1508 mAh·g-1 at 0.1C, excellent rate performance with 655 mAh·g-1 at 5C, and near-integral cycle stability over 1000 cycles. Furthermore, under high sulfur loading of 6.4 mg·cm-2, a cathode capacity exceeding 8 mAh·cm-2 is sustained at 0.1C current rate, with 6.4 mAh·cm-2 retained after 300 cycles under lean electrolyte conditions (6.8 μL·mg-1).