2,5-Dimercapto-1,3,4-Thiadiazole (DMCT)-Based Polymers for Rechargeable Metal-Sulfur Batteries

Organosulfur materials are a sustainable alternative to the present-day layered oxide cathodes in lithium-based batteries. One such organosulfur material that was intensely explored from the 1990s to early 2010s is 2,5-dimercapto-1,3,4-thiadiazole (DMCT). However, research interest declined as the electrode reactions with DMCT were assumed to be too sluggish to be practical. Armed with the advances in metal-sulfur batteries, we revisit DMCT-based materials in the form of poly[tetrathio-2,5-(1,3,4-thiadiazole)], referred to as pDMCT-S. With an appropriate choice of electrode design and electrolyte, pDMCT-S cathode paired with a Li-metal anode shows a capacity of 715 mA h g(-1) and a Coulombic efficiency of 97.7% at a C/10 rate, thus quelling the concerns of sluggish reactions. Surprisingly, pDMCT-S shows significantly improved long-term cyclability compared to a sulfur cathode. Investigations into the origin of the stability reveals that the discharge product Li-DMCT in its mesomeric form can strongly bind to polysulfides, preventing their dissolution into the electrolyte and shuttling. This unique mechanism solves a critical problem faced by sulfur cathodes. Encouragingly, this mechanism results in a stable performance of pDMCT-S with Na-metal cells as well. This study opens the potential for exploring other organic materials that have inherent polysulfide sequestering capabilities, enabling long-life metal-sulfur batteries.

Automated summary

Organosulfur materials, such as poly[tetrathio-2,5-(1,3,4-thiadiazole)] (pDMCT-S), have emerged as a sustainable alternative to current layered oxide cathodes in lithium-based batteries. By improving the electrode design and electrolyte, pDMCT-S cathode paired with a Li-metal anode exhibits high capacity and Coulombic efficiency, overcoming the sluggish reactions associated with the organosulfur material 2,5-dimercapto-1,3,4-thiadiazole (DMCT). Moreover, pDMCT-S demonstrates improved long-term cyclability and stability compared to sulfur cathodes, making it a promising candidate for long-life metal-sulfur batteries.