Highly Puffed Co9S8/Carbon Nanofibers: A Functionalized S Carrier for Superior Li–S Batteries

Li–S batteries have triggered global research interest because of their higher theoretical energy density and lower cost than popularized Li-ion cells. However, they still do not have practical implementations because of issues induced by intermediate polysulfide dissolution. To better confine both S and polysulfides in cathode regions and prolong the cyclic lifespan, we purposely design the unique highly puffed Co 9 S 8 /carbon nanofibers (Co 9 S 8 @CNFs) as efficient S carriers. Such fibrous products made of interconnected hollow/porous Co 9 S 8 /C nanopolyhedra can provide ample places to load the large amount of S, convenient pathways for both Li + and electrons transfer, and extra reversible capacity contribution. Particularly, each individual Co 9 S 8 subunit is physically robust, metallic, and polarized, synergistically enabling the spatial confinement and chemical bonding to restrict S volume expansions and anchor the soluble polysulfides during cycling. The as-built highly puffed S⊆Co 9 S 8 @CNFs cathodes can exhibit a large specific capacity of ∼1080 mA h g –1, admirable cyclic stability/lifespan (capacity loss rate: ∼0.03% per cycle), and excellent rate capabilities. Our work may hold a great potential in rational design of superior cathodes for applicable Li–S cell systems.