Vacancy-Defect Topological Insulators Bi₂Te_3−x Embedded in N and B Co-Doped 1D Carbon Nanorods Using Ionic Liquid Dopants for Kinetics-Enhanced Li–S Batteries

Lithium–sulfur (Li–S) batteries are hindered by the shuttle effect and the sluggish redox kinetics of polysulfides. In this study, topological insulators (TIs) Bi₂Te_3−x with abundant Te vacancies embedded in N and B co-doped carbon nanorods (Bi₂Te_3−x@NBCNs) are synthesized and used as sulfur host composites for high-performance Li–S batteries. Bi₂Te_3−x@NBCNs effectively enhance the intrinsic conductivity, strengthened the chemical affinity, and accelerated the redox kinetics of polysulfides. 1D carbon nanorods with N and B co-doped heteroatoms endowed with abundant polar sites improve the chemical affinity of polysulfides, while the embedded Bi₂Te_3−x nanoparticles further promote the nucleation and electrodeposition of Li₂S₂/Li₂S. In situ Raman spectroscopy confirms that Bi₂Te_3−x@NBCNs effectively reduced cathode-side accumulation of polysulfides and suppressed the shuttle effect. Owing to the extraordinary synergistic effects of rich heteroatom polar sites and conductive topological surface states, Bi₂Te_3−x@NBCN-based cells exhibit a high initial specific capacity of 1264 mAh g⁻¹ at 0.2 C and ultra-long lifetime (>1000 cycles, with a degradation rate of 0.02% per cycle at 1.0 C). The fundamental insights offered by this work are likely to enable improvement of the electrochemical performance of Li–S batteries based on TI materials.