Hollow nickel-cobalt bimetal phosphides as a confined polysulfide reactor for high-performance lithium-sulfur batteries

Highlights: ¨Hollow NiCoP are fabricated via a facile internal phase transition reaction. ¨The designed NiCoP can be applied as confined reactor for Li-S battery. ¨The NiCoP can provide both chemical adsorption and catalytic capabilities. ¨NiCoP modified separator can effective regulate the electrochemical reaction of Li-S battery. -- Abstract: Lithium-sulfur (Li-S) battery has attracted considerable attention as a promising kind of energy storage device. However, its practical application is always hindered by the "shuttle effect" of lithium polysulfides (LiPSs) and the sluggish sulfur conversion kinetics. Transition metal phosphides can serve as promising mediates to boost the conversion of LiPSs due to their high catalytic activity for sulfur redox reaction. Unfortunately, how to effectively capture LiPSs and realize high sulfur utilization is still the bottleneck of current research. Considering the solubility and liquidity of LiPSs, herein, a hollow nickel-cobalt bimetal phosphides nanocage, which consists of many interconnected nanosheets on the outer and inside shells, is designed and utilized as an interlayer to realize LiPSs's confined reactor. The unique microstructure endows abundant adsorption and electrocatalytic active sites. The hollow confined reactor enhances the capture rate of LiPSs and implements strong LiPSs immobilization, improves the sulfur utilization and achieves rapid and durable sulfur electrochemistry. This rational design of interlayer may provide a new vision for designing effective LiPSs's confined reactor for high-performance Li-S batteries.