Scalable Synthesis of Honeycomb-like Ordered Mesoporous Carbon Nanosheets and Their Application in Lithium-Sulfur Batteries.

There is a growing need to improve the electrical conductivity of the cathode and to suppress the rapid capacity decay during cycling in lithium-sulfur (Li-S) batteries. This can be achieved by developing facile methods for the synthesis of novel nanostructured carbon materials that can function as effective cathode hosts. In this Article, we report the scalable synthesis of ordered mesoporous carbon nanosheets (OMCNS) via the etching of self-assembled iron oxide/carbon hybrid nanosheets (IO-C NS), which serve as an advanced sulfur host for Li-S batteries. The obtained two-dimensional (2D) nanosheets have close-packed uniform cubic mesopores of ∼20 nm side length, and the gap between the pores is ∼4 nm, which resembles the honeycomb structure consisting of an ordered array of hexagonal pores. We loaded OMCNS with sulfur by a simple melting infusion process and evaluated the performance of the resulting OMCNS-sulfur composites as the cathode material. As a result, the sulfur-loaded OMCNS hybrid (OMCNS-S) electrode infiltrated with 70 wt % sulfur delivers a high and stable reversible capacity of 505.7 mA h g-1 after 500 cycles at 0.5 C-rate with excellent capacity retention (a decay of 0.081% per cycle) and excellent rate capability (580.6 mA h g-1 at a high current density of 2 C). The improved electrochemical properties could be attributed to the fact that the uniform cubic mesopores offer sufficient space for the volume expansion of sulfur inside them and therefore trap the polysulfides during the charging-discharging process. Therefore, these unique structured carbon nanosheets can be promising candidates for other energy-storage applications.