Heterostructure of metal selenides or metal sulfides: which is a better choice as host of sulfur cathode?

Heterostructures, consisting of metal selenides and metal sulfides, have been extensively reported as hosts for sulfur (S), aiming to address three significant challenges confronted by S cathodes in lithium-sulfur batteries. To answer the key question—whether a heterostructure of metal selenides or metal sulfides is a better choice as the host for an S cathode —two types of zeolitic imidazolate framework (ZIF)-8-derived ZnSe@VSe 2 and ZnS@VS 2 polyhedra are designed and successfully synthesized. Results show that ZnSe@VSe 2 /NC (nitrogen-doped carbon) host possesses stronger anchoring and catalytic conversion abilities (Li 2 S precipitation capacity: 178.97 mAh·g −1 ) to polysulfides than ZnS@VS 2 /NC host (107.79 mAh·g −1 ). Meanwhile, ZnSe@VSe 2 /NC@S cathode presents fast S redox and Li + diffusion kinetics, superior charge-discharge stability, and low electrochemical polarization. As a result, ZnSe@VSe 2 /NC@S cathode exhibits significantly better cycling performance (525 mAh·g −1 at 1C after 300 cycles) and rate capability than ZnS@VS 2 /NC@S cathode (378 mAh·g −1 ). These advantages are primarily attributed to the synergistic effects arising from the built-in electric field at the ZnSe@VSe 2 heterointerface (directed from VSe 2 to ZnSe), the lower electronegativity of Se compared to S, and the higher electrical conductivity of ZnSe/VSe 2 relative to ZnS/VS 2 . Graphical