Sulfur-Functionalized Mesoporous Carbons as Sulfur Hosts in Li–S Batteries: Increasing the Affinity of Polysulfide Intermediates to Enhance Performance

Abstract

The Li-S system offers a tantalizing battery for electric vehicles and renewable energy storage due to its high theoretical capacity of 1675 mAh g(-1) and its employment of abundant and available materials. One major challenge in this system stems from the formation of soluble polysulfides during the reduction of S8, the active cathode material, during discharge. The ability to deploy this system hinges on the ability to control the behavior of these polysulfides by containing them in the cathode and allowing for further redox. Here, we exploit the high surface areas and good electrical conductivity of mesoporous carbons (MC) to achieve high sulfur utilization while functionalizing the MC with sulfur (S-MC) in order to modify the surface chemistry and attract polysulfides to the carbon material. S-MC materials show enhanced capacity and cyclability trending as a function of sulfur functionality, specifically a 50% enhancement in discharge capacity is observed at high cycles (60-100 cycles). Impedance spectroscopy suggests that the S-MC materials exhibit a lower charge-transfer resistance compared with MC materials which allows for more efficient electrochemistry with species in solution at the cathode. Isothermal titration calorimetry shows that the change in surface chemistry from unfunctionalized to S-functionalized carbons results in an increased affinity of the polysulfide intermediates for the S-MC materials, which is the likely cause for enhanced cyclability.

Catalytic oxidation of Li 2 S on the surface of metal sulfides for Li−S batteries

“…Therefore, the introduction of heteroatoms into carbonaceous materials (such as nitrogen, oxygen, boron, phosphorous, sulfur, or codoping) for the generation of polar functional groups was adopted to enhance the interaction and immobilization of LiPS species in the electrode (15). For instance, nitrogen-or sulfur-doped mesoporous carbons (16,17), boron-doped carbons (18), oxygen-or nitrogenfunctionalized carbon nanotubes and graphenes (19,20), aminofunctionalized reduced graphene oxides (21), and nitrogen/ sulfur-codoped graphene sponges (22) have shown great promise in trapping LiPSs due to the strong anchoring sites induced by heteroatom doping. In addition to carbon, a wide variety of anchoring materials (AM) have been introduced with polysulfide binding and trapping abilities (23)(24)(25).…”

Capacitance behavior of ordered mesoporous carbon/Fe2O3 composites: Comparison between 1D cylindrical, 2D hexagonal, and 3D bicontinuous mesostructures

“…Since the first synthesis in 1999 [1], ordered mesoporous carbons (OMCs) have been widely used as host materials for metal [2,3], metal oxide [4][5][6][7], sulfur [8][9][10], or polymers [11] for electrochemical sensors [11,12], fuel cells [2,3], supercapacitors [4][5][6][7]13,14], lithium ion batteries [15][16][17], Li-O batteries [18], and Li-S batteries [8][9][10] due to their high corrosion resistance, good electrical conductivity, high surface area, large pore volume, and easy handling. In addition, the welldefined porous dimensions were found to enable controlled metal or metal oxide nanoparticles impregnation into the porous scaffold [2], facilitating higher material utilization for catalysis and energy storage.…”

“…Therefore, a systematically comparison of electrochemical behaviors between different structured OMC composites is essential for a better understanding of the effects of pore structures on the performance. However, very few reports deal with non-CMK-3 composites and they all lack detailed investigation of the mesostructure's influence on the application [4,[8][9][10]13,15,16]. Hence it is important to design controlled experiments with various OMCs structures synthesized and tested under similar conditions in order to better understand and optimize OMCs related composites based on their structure stabilities and porosities.…”

Three-dimensionally ordered macro-/mesoporous carbon loading sulfur as high-performance cathodes for lithium/sulfur batteries

“…Various carbon materials, including mesoporous carbon [12], microporous carbon [13], carbon nanotubes [14] and grapheme [15], have been applied to restrain the solubility of lithium polysulfides, maintain good conductivity and improve sulfur utilization.…”