In-situ synthesis of highly graphitized and Fe/N enriched carbon tubes as catalytic mediums for promoting multi-step conversion of lithium polysulfides

The development of Li–S batteries is severely limited by the poor conductivity and slow reaction kinetics of sulfur cathodes. Herein, we prepare a highly graphitized and Fe/N enriched carbon tube (Fe/N-g-CT) as multifunctional host. It is found that the introduction of Fe can efficaciously promote the transformation from amorphous carbon sheets to graphitized carbon tubes (CT), while the residual Fe species embedded in CT can act as catalytic active sites along with the doped heteroatoms. Specifically, Fe sites can accelerate the inter-conversion of soluble lithium polysulfides, while the doped-N heteroatoms can promote the deposition of Li2S. Consequently, Fe/N-g-CT catalytic mediums synchronously improve the conductivity and reaction kinetics of sulfur electrodes, and Fe/N-g-CT/S cathode exhibits a high initial specific capacity (1500.5 mAh g−1 at 0.1 C) and a low fading rate (0.06% per cycle at 2 C over 500 cycles). Moreover, even with high sulfur loading (4.5 mg cm−2) and lean electrolyte consumption (E/S = 5 μL mg−1), a satisfactory areal capacity of 5.1 mAh cm−2 can also be achieved. This paper raises a good strategy or idea to boost the development and commercialization application of Li–S battery with high performance through reasonably constructing sulfur host with high conductivity and catalysis activity.