Exquisite hybridized electrocatalyst with moderate selenium element integration for reliable lithium-sulfur batteries

Effective immobilization and catalytic conversion of lithium polysulfides (LiPSs) are crucial for enhancing lithium-sulfur (Li-S) battery performance. To this end, a hybrid CoSe₂-Co₃O₄-Se@CNTs electrocatalyst was rationally designed, wherein Co₃O₄ and CoSe₂ synergistically promote LiPS adsorption and catalytic transformation, while CNTs provide a conductive framework to enhance sulfur utilization. Notably, the often-overlooked role of selenium was elucidated via in situ X-ray diffraction pattern revealing its active participation in charge-discharge reactions, which contributes to the stable cycling performance of Li-S batteries. As a result, Li-S cells incorporating a CoSe₂-Co₃O₄-Se@CNTs-modified separator achieve a high discharge capacity of 1,412 mAh g^-1 at 0.1 C with 71 % capacity retention after 400 cycles. At 0.5 C, 76 % of the initial capacity (1,243 mAh g^-1) is retained after 500 cycles, while at 1 C, 70 % of the initial capacity (836 mAh g^-1) is maintained over 550 cycles, corresponding to an exceptionally low decay rate of 0.053 % per cycle. This study highlights the synergistic role of CoSe₂-Co₃O₄-Se@CNTs and Se in LiPS immobilization and catalysis, providing a promising strategy for designing high-performance electrocatalysts to extend the lifespan of Li-S batteries.