(Invited) New Synthesis Strategies to Develop High Performance Sulfur-Carbon Composites Cathodes for Lithium/Sulfur Batteries

Abstract

Lithium/sulfur cells (Li/S) are recognized as a highly promising, inexpensive, and high-specific energy storage system due to the low cost of elemental sulfur and high theoretical specific capacity (1,675 mAh/g) of a sulfur cathode when paired with a lithium anode.1 However, practical applications of Li/S cells have been impeded by challenges related to sulfur cathodes, such as low sulfur conductivity of sulfur, the polysulfides shuttle, and changes in electrode microstructure during cycling.2-4 Sulfur-carbon (S-C) composites have been extensively studied as an effective approach to overcome these issues and improve the electrochemical performance of Li/S cells. Carbon materials, including graphene oxide, carbon nanotubes or nanofibers, and porous carbon, have been used in sulfur cathodes due to their high surface area, excellent electrical conductivity, and sulfur-immobilizing ability from their porous structure or surface functional groups.4 Designing high-performance S-C composites involves carefully considering various factors, such as the type of carbon materials, surface area or pore volume of carbon, sulfur-carbon weight ratio, and synthesis method, to achieve optimal performance. Key design strategies for high-performance S-C composites include: (1) confining nano-sized sulfur in porous carbon, (2) coating nano-sized sulfur onto sulfur-philic functional carbon surface, (3) engineering sulfur structures that form an adequate sulfur-electrolyte interface, and (4) preserving the electronically conductive carbon network in sulfur-carbon composite to minimize the electronic resistance of the sulfur cathode.4 S-C composites consisting of sulfur nanostructures confined in carbon porous structures or coated onto large sulfur-philic surface areas of carbon (e.g., graphene oxide) are promising composite designs as they can promote the kinetics and reversibility of the electrochemical process of the sulfur cathode. In this presentation, important recent findings about how to design and synthesize high performance S-C composite design will be introduced, and their effects on the electrochemical behavior of the sulfur cathode for Li/S cells will be discussed. References Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Tarascon, J.-M., Nat. Mater. 2012, 11, 19–29.Fotouhi, A.; Auger, D.J.; O’Neill, L.; Cleaver, T.; Walus, S., Energies 2017, 10, 1937.Peng, H.-J.; Huang, J.-Q.; Cheng, X.-B.; Zhang, Q., Adv. Energy Mater. 2017, 7, 1700260.Hwa, Y.; Cairn, E. J., ChemElectroChem 2020, 7, 3927-3942.