Nitrogen, sulfur-codoped graphene sponge as electroactive carbon interlayer for high-energy and -power lithium-sulfur batteries

Sulfur is an attractive cathode material in energy storage devices since its high theoretical capacity of 1672 mAh g^-1. However, practical application of lithium sulfur (Li-S) batteries can be achieved only when the major barriers, including the insulating nature of element sulfur and shuttling effect of polysulfides (Li₂S_x, x = 3-8), are tackled. Here, nitrogen, sulfur-codoped (N,S-codoped) sponge-like graphene, which presents a high reversible capacity, is used as electroactive interlayer for Li-S batteries to address these issues. An impressive high capacity of 2193.2 mAh g^-1 can be obtained for the sulfur cathodes with such an interlayer at the rate of 0.2C, and it can be stably maintained at 829.4 mAh g^-1 at the rate of 6C, for which the contribution from the electroactive interlayer is ca. 30.0%. High energy density of 418.5 Wh Kg^-1 still can be released at the power density of 4.55 kW kg^-1 (6C) based on the total mass of the sulfur cathode and interlayer for the assembled Li-S batteries.