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Researchers:
Dr. Choongho Yu

Background:
The ability to store energy generated from renewable energy sources, such as solar and wind, is essential to the development of clean energy storage technologies. Rechargeable batteries are regarded as the most suitable candidate for clean energy storage; however, current battery systems, such as Li-ion batteries based on lithium ion intercalation chemistry, cannot meet the demand for higher energy density due to the chemistry of these materials. Li-S based conversion chemistry has shown promise for the next generation of rechargeable batteries. Because of the multi-electron redox reactions and light weight of these materials, they can offer a theoretical specific energy of 2500 Wh/kg, which is almost 7 times of state-of-the-art Li-ion batteries. Moreover, the low price and non-toxicity of elemental sulfur makes the Li-S batteries strong candidates for future battery systems. Here we propose a new composite structure for Li-S batteries that combines a 3D conductive framework and a metal organic framework (MOF). Carbon nanotube (CNT) sponges that were developed in Yu’s group will be utilized as the 3D conductive framework, constructed with multi-wall carbon nanotubes, enabling a highly efficient and three-dimensional electron pathway. Yu’s CNT sponge has been used as a catholyte (dissolved sulfur in electrolyte) reservoir at the cathode of Li-S batteries. Since MOFs have an adjustable pore structure, core metal ions, and surface functionality, it is an ideal candidate for the design of an effective polysulfide holder in these batteries.

Research Plan:
The REU students will participate in fabricating Li-S batteries with cathodes made from sulfur-containing CNT sponge/MOF composite. Specific tasks will include: (1) selection of MOF characteristics; (2) synthesis of cathodes with MOF and anodes with porous CNT sponges (Fig. 5); (3) characterization of the electrodes; and (4) battery cycling and performance evaluation. This project will provide hands-on experiences for REU students at multiple skill levels, ranging from rising second-year to more senior students.