Co/CoSe dual-phase hybrids on carbon nanotubes as electrocatalysts for high-performance lithium-sulfur batteries.

The practical application of lithium-sulfur (Li-S) batteries is hindered by critical challenges, including polysulfide shuttling and cathode structural instability. To address these issues, controlling migration to effectively trap polysulfides within the cathode is essential. In this study, an all-in-one Co/CoSe@carbon nanotube (CNT) ternary composite was designed as the electrocatalyst for Li-S batteries. Experimental characterization and DFT calculation reveal that the composite integrates the unique advantages of cobalt, cobalt selenide, and CNTs by combining cobalt's catalytic activity, CoSe's polysulfide adsorption capability, and CNTs' conductive network. Electrochemical characterization demonstrates that the sulfur cathode incorporating Co/CoSe@CNT achieves an initial discharge capacity of 1297.5 mAh g-1 at 0.2 C and maintains 82% capacity retention after 500 cycles at 0.2 C. Furthermore, the Co/CoSe@CNT composite exhibits excellent rate performance, delivering a superior specific capacity of 835.1 mAh g-1 at 2 C, outperforming its Co@CNT and CoSe@CNT counterparts. This ternary electrocatalyst addresses the shuttle effect via the combined action of chemisorption, catalytic conversion, and physical confinement, offering a promising strategy for high-performance lithium-sulfur batteries.