Bipolar CoSe2 nanocrystals embedded in porous carbon nanocages as an efficient electrocatalyst for Li-S batteries

The confinement and catalysis properties of orthorhombic CoSe2 as a host material for Li-S battery are studied by theoretical and experimental methods. First-principles calculations show that the (111) surface of CoSe2 possesses adjacent nucleophilic and electrophilic centers. This bi-polar surface can easily bond the polysulfide molecules and catalyze their conversion reactions. As a result, the decomposition energy barriers of polysulfides are greatly decreased from ~3.0 eV to 0.2-0.4 eV. Following theoretical prediction, CoSe2 nanocrystals with specific (111) surface are prepared and embedded in porous carbon nanocages using ZIF-67 metal organic framework as a template. Benefited from the advantages of porous C and CoSe2 (111) surface, the shuttling of polysulfides is suppressed and their conversion kinetics is facilitated. The Li-S cell using this host material exhibits high capacity and remarkable cycle stability, showing a discharge capacity of 1199 mA center dot h center dot gxe213; 1 at 0.2C and 400 stable cycles at 1.0C.

Automated summary

The confinement and catalysis properties of orthorhombic CoSe2 as a host material for Li-S battery were studied. It was found that the (111) surface of CoSe2 possesses nucleophilic and electrophilic centers, which can easily bond and catalyze the conversion reactions of polysulfide molecules. CoSe2 nanocrystals with specific (111) surface were prepared and embedded in porous carbon nanocages, which effectively suppressed the shuttling of polysulfides and facilitated their conversion kinetics. The Li-S cell using this host material exhibited high capacity and remarkable cycle stability.