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

Abstract

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 Co₉S₈/carbon nanofibers (Co₉S₈@CNFs) as efficient S carriers. Such fibrous products made of interconnected hollow/porous Co₉S₈/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 Co₉S₈ 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⊆Co₉S₈@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.