Cubic CoSe2@carbon as polysulfides adsorption-catalytic mediator for fast redox kinetics and advanced stability lithium-sulfur batteries

Although lithium-sulfur batteries (LSBs) are an attractive next-generation rechargeable battery with high theoretical energy density (2600 Wh kg −1 ) and specific capacity (1675 mA h g −1 ), the shuttle of soluble lithium polysulfides (LiPSs) is still the protruding obstacle to accelerate the redox reaction of LSBs. Here, cubic cobalt diselenide@carbon (CoSe 2 @C) derived from zeolite imidazole framework-67 (ZIF-67) was employed as the functional coating of polypropylene (PP) separator to efficiently adsorb and catalyze polysulfides, inhibit “shuttle effect” and improve the electrochemical reaction kinetics of LSBs. The CoSe 2 @C offers larger mesopore proportion of 77.19 % and abundant active sites to ensure space as a secondary reaction region, and infiltration of electrolyte and rapid transport of Li + . The involved adsorption and catalysis effect are discussed by static adsorption experiment, XPS, and Li 2 S nucleation kinetics analysis. The results show that CoSe 2 @C exhibits strong adsorption effect and catalytic activity on LiPSs, and CoSe 2 @C/PP cells display fast Li + diffusion and improved redox kinetics (high Li 2 S nucleation peak current of 0.27 mA and deposition capacity of 148.46 mA h g −1 ). Ascribe to these advantages, the CoSe 2 @C/PP cell provides an initial discharge specific capacity of 1335.01 mA h g −1 at 0.1 C and a fine reversible capacity at 5.0 C, and achieves stable and durable lifespan with an average capacity decay rate of 0.12 % over 400 cycles at 0.5 C. This work could promote the practical application of metal selenides in the key components and devices for LSBs.