Tuning Nitrogen in Graphitic Carbon Nitride Enabling Enhanced Performance for Polysulfide Confinement in Li-S Batteries

The cycling performance of lithium-sulfur (Li-S) batteries, which is a major parameter determining the practical application of such an advanced high-energy-density battery system (1675 mA h g-1), is strongly affected by the properties of the cathodic sulfur hosts. As a desirable sulfur host, it should possess high surface area, good electronic conductivity, and superior physisorption and chemisorption to polysulfides. Here, by taking advantage of the magnesiothermic denitriding technology, the graphitic carbon nitride (GCN) with a tunable nitrogen content, surface area, and pore volume has been designed as a sulfur host for high-performance Li-S batteries. With a nitrogen content of ∼6%, a surface area of 594 m2 g-1, and a pore volume of about 2 cm3 g-1, the GCN-based host can retain sulfur and allow its reversible convention within cathodic region, thereby delivering a high capacity of 852.2 mA h g-1 at 0.5 C with a low capacity decay of 0.12% per cycle within 300 cycles. This work provides a feasible way to design nitrogen-doped carbon materials with tunable nitrogen content and enlightens the host material design for practical Li-S batteries.