Micropore engineering on hollow nanospheres for ultra-stable sodium-selenium batteries

Attracted by high energy density and considerable conductivity of selenium(Se),Na-Se batteries have been deemed promising energy-storage systems.But,it still suffers from sluggish kinetic behaviors and similar“shuttling effect”to S-electrodes.Herein,utilizing uniform hollow carbon spheres as precursors,Se-material is effectively loaded through vapor-infiltration method.Owing to the distribution of optimized pores,the content of microspores could be up to~60%(<2 nm),serving important roles for the physical confinement effect.Meanwhile,the rich oxygen-containing groups and N-elements could be noted,inducing the evolution of electron-moving behaviors.More significantly,assisted by the interfacial C-Se bonds and tiny Se distributions,Se electrodes are activated during cycling.Used as cathodes for Na-Se systems,the as-resulted samples display a capacity of 593.9 mA h g^(-1)after 100 cycles at the current density of 0.1 C.Even after 6000 cycles,the capacity could be still kept at about 225 mA h g^(-1)at 5.0 C.Supported by the detailed kinetic analysis,the designed microspores size induces the increasing redox reaction of nano Se,whilst the surface traits further render the enhancement of pseudo-capacitive contributions.Moreover,after cycling,the product Sex(x<4)in pores serves as the primary active material.Given this,the work is anticipated to provide an effective strategy for advanced electrodes for Na-Se systems.