Ultrathin Nanosheet-Assembled Flowerlike NiSe2 Catalyst Boosts Sulfur Redox Reaction Kinetics for Li–S Batteries

Exploring efficient catalytic materials is of huge significance to tackle the sluggish kinetics of sulfur redox reactions (SRRs) in lithium–sulfur (Li–S) batteries. Herein, we demonstrate ultrathin nanosheet-assembled flowerlike NiSe2 architectures as highly efficient catalysts for SRRs. Such unique NiSe2 architectures are fabricated through a simple urea-assisted precipitation combined with a moderate selenylation process and can offer sufficient binding sites to chemically anchor polysulfides. In the meantime, kinetics test results demonstrate that the NiSe2 sample can effectively catalyze the polysulfide conversion and accelerate the Li2S precipitation and decomposition. When used as a separator modification material, the NiSe2 catalysts enable the sulfur cathode to realize a high capacity of 1280.7 mA h g–1, high average Coulombic efficiency (∼98.9%), and good cycle stability. Furthermore, a freestanding carbon paper-supported sulfur cathode with 8.8 mg cm–2 loading exhibits a high areal capacity of 7.8 mA h cm–2 with the electrolyte/sulfur of 6 μL mg–1. This work will inspire the development of high-efficiency catalysts based on structural engineering for high-energy Li–S batteries.