Straightforward synthesis of Sulfur/N,S-codoped carbon cathodes for Lithium-Sulfur batteries

Abstract

An upgrade of the scalable fabrication of high-performance sulfur-carbon cathodes is essential for the widespread commercialization of this technology. Herein we present a simple, cost-effective and scalable approach for the fabrication of cathodes comprising sulfur and high-surface area, n,S-codoped carbons. the method involves the use of a sulfur salt, i.e. sodium thiosulfate, as activating agent, sulfur precursor and S-dopant, and polypyrrole as carbon precursor and n-dopant. in this way, the production of the porous host and the incorporation of sulfur are combined in the same procedure. the porous hosts thus produced have BET surface areas in excess of 2000 m 2 g −1 , a micro-mesoporous structure, as well as sulfur and nitrogen contents of 5-6 wt% and ~2 wt%, respectively. The elemental sulfur content in the composites can be precisely modulated in the range of 24 to ca. 90 wt% by controlling the amount of sodium thiosulfate used. Remarkably, these porous carbons are able to accommodate up to 80 wt% sulfur exclusively within their porosity. When analyzed in lithium-sulfur batteries, these sulfur-carbon composites show high specific capacities of 1100 mAh g −1 at a low Crate of 0.1 C and above 500 mAh g −1 at a high rate of 2 C for sulfur contents in the range of 50-80 wt%. Remarkably, the composites with 51-65 wt% S can still provide above 400 mAh g −1 at an ultra-fast rate of 4 C (where a charge and discharge cycle takes only ten minutes). the good rate capability and sulfur utilization was additionally assessed for cathodes with a high sulfur content (65-74%) and a high sulfur loading (>5 mg cm −2). in addition, cathodes of 4 mg cm −2 successfully cycled for 260 cycles at 0.2 C showed only a low loss of 0.12%/cycle.

More Sustainable Chemical Activation Strategies for the Production of Porous Carbons

“…2500 m 2 g −1 ; see Table 1). [106,107] Moreover, the polysulfides/sulfides generated during the activation step can be used for the in‐situ synthesis of sulfur nanoparticles confined within the porosity of the porous carbon and, in this way, the synthesis of sulfur/carbon composites for Li−S batteries [106–108] …”

Highly Packed Monodisperse Porous Carbon Microspheres for Energy Storage in Supercapacitors and Li−S Batteries

“…Along these lines, we have recently introduced the use of a harmless chemical activating agent, sodium thiosulphate, for the synthesis of highly porous carbon materials with excellent performance in supercapacitive energy storage . This versatile strategy also allowed the in situ incorporation of elemental sulfur within the pores of synthesized carbons yielding sulfur/carbon composites that can be directly used for the fabrication of cathodes for Li−S batteries …”

Cellulose as a Precursor of High‐Performance Energy Storage Materials in Li–S Batteries and Supercapacitors

“…Following this strategy, we have recently reported the synthesis of sulfur/carbon composites from tannic acid [ 30 ] and polypyrrole, [ 31 ] for which the sulfur content is controlled through the modification of the amount of sodium thiosulfate used. Going one step further, this work shows that, even though this synthesis strategy may be a general approach for the in situ synthesis of sulfur/carbon composites, the selection of an appropriate carbon precursor is a key parameter to achieve composites with high sulfur content at reasonable product yield and chemical reagents consumption.…”

“…In this way, the carbon host within the sulfur/carbon composite is highly porous, which favors accommodation of large amounts of sulfur within its pores (up to ≈80%). As carbon precursor, we have analyzed the use of a biomass‐based substance (i.e., tannic acid) [ 30 ] and an N‐rich polymer (polypyrrole), [ 31 ] both of which allow the production of composites with large sulfur contents at a reasonable carbon yield (≈8 wt%). Herein, we further explore this approach for the most abundant biomass product, i.e., cellulose, and its most important derivative, i.e., cellulose acetate.…”