Porous Carbon-Supported Single Atom Catalysts for Metal-Sulfur Batteries

Project start date Aug. 15, 2024.

Recent research has shown promising avenues in the utilization of graphitic carbon nitride (g-C3N4) in Li-S batteries to confine and sequester polysulfides, enhance sulfur utilization, and improve overall battery performance. Its high surface area and chemical stability make it an ideal candidate to trap polysulfides and alleviate the shuttle effect, thereby contributing to enhanced capacity retention and reaction kinetics in Li-S batteries. Compared to pristine graphitic carbon nitride (pg-C3N4), defect-rich reduced (rg-C3N4) analogs exhibit superior electrocatalytic activity. This may be attributed to the presence of nitrogen vacancies and edge sites, which serve as active sites for catalyzing sulfur redox reactions and adsorbing polysulfides. Furthermore, the introduction of defects in g-C3N4 enables band structure engineering, which further enhances its catalytic activity and enables precise control over the electrochemical behavior of metal-sulfur battery systems.

The use of catalysts has been shown to improve the kinetics of metal-S conversion reactions, of which single-atom catalysts (SACs) are an intriguing option to improve the redox kinetics and device performance of metal-sulfur batteries. Since adsorption and conversion reactions take place on the surface of nanoscale catalysts, overall catalytic activity is strongly governed by particle size. For instance, only ca. 10% of the total atoms are in contact with the electrolyte and may participate in catalytic reactions for a 30-nm nanoparticle, rendering most of the catalyst particle inactive. However, as particle size is reduced to the sub-nanometer regime, an increasing number of coordinately unsaturated metal atoms are generated. Single-atom catalysts )SAC)represent the extreme in catalytic activity with a theoretical atomic utilization of 100%.

The goal of this project is to develop a unique aluminum sulfur chemistry that not only provides high energy density and low cost, but also provides a domestic supply line for cathode materials and cell fabrication. The team will focus on the design, modeling & simulation, fabrication, characterization, and electrochemical testing of SACfunctionalized porous carbon and graphene nanoribbons (GNRs) to suppress the diffusion of polysulfide species and improve the kinetics involved in Al-S conversion reactions. The potential impact of our work is tremendous,as there are very few reports of stable high-energy aqueous Al-ion/Al-S batteries13 and no reports of utilizing SACs in these systems. With our new approaches in materials design, Al-S batteries have the potential to greatly exceed the current ultrahigh energy density goals of >500 Wh/kg.

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