Metal–Organic Framework-Derived NiSe2 Nanoparticles on Graphene for Polysulfide Conversion in Lithium–Sulfur Batteries

The rechargeable lithium–sulfur battery is regarded as one of the most promising secondary batteries because of its superior energy density and cost-effective raw materials. However, it still faces many challenges, the most important of which lies in the notorious polysulfide shuttle effect. Herein, we design and fabricate graphene-supported, metal–organic framework (MOF)-derived NiSe2 nanoparticles (rGO-NiSe2) as separator modifiers. The NiSe2 nanoparticles with high catalytic activity can effectively adsorb polysulfides and accelerate their conversion. A highly conductive graphene as a catalyst substrate can effectively decrease the internal resistance of the battery. In addition, the intercalation growth of octahedral MOF-derived NiSe2 nanoparticles between graphene sheets provides abundant active sites for polysulfides. The battery with a rGO-NiSe2-modified separator provides an initial capacity of 1356.5 mAh g–1 at 0.2 C, and only experiences a low capacity decay rate of 0.079% per cycle during 500 cycles of operation at 1 C. Even under a relatively high loading amount of 5.2 mg cm–2, the battery can still yield a high specific capacity of 774.3 mAh g–1 at 0.5 C and a capacity retention of 84% after 100 cycles.