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

Abstract

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 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 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.

Review of Carbon Materials for Lithium‐Sulfur Batteries

“… (a) SEM cross sectional view of mesporous carbon, the corresponding principle diagram of such carbon in cycle and durability measurements based on galvanostatic charge discharge at 0.2 C rates over 250 cycles. [85] (b) Schematic of the preparation of OMCNS and OMCNS−S composite …”

“…However, well‐defined ordered mesoporous carbon materials with uniform pore structure have rarely been mentioned up to now. Park and co‐workers reported an ordered mesoporous carbon nanosheets (OMCNS) like honeycomb structure synthesized by etching the self‐assembled iron oxide nanocubes and carbon hybrid nanosheets (IO–CNS). The as‐prepared two‐dimensional (2D) nanosheets have uniform close‐packed cubic mesopores with approximately 20 nm side length, and are combined with sulfur to form OMCNS–S composite as the cathode for LSBs.…”

The State of Research Regarding Ordered Mesoporous Materials in Batteries

“…Compared with mesopores, micropores are relatively long, which is unfavorable to the diffusion of reactants, and further, kinetic reactions . Comparatively speaking, mesopores are more favorable for the transport of reactants or solvents.…”

An Extremely High Surface Area Mesoporous-Microporous-Networked Pillared Carbon for High Stability Li-S and Intermediate Temperature Na-S Batteries

“…Majority of the published works have focused on varied carbon forms as the conducting host for the confinement of sulfur. A few reports also employ composites of carbon with metals oxides (e. g. Al 2 O 3 , SiO 2 ) . However, majority of the reports fail to precisely define the mechanism of sulfur confinement as well quantify the exact spatial distribution of the sulfur with respect to the host.…”

“…Additionally, the carbon host employed often show contradictory morphologies as compared to the proposed one. All these lead to an improper quantification of the specific capacities of the S‐cathode …”