Tailoring Organic Molecules for Symmetric Redox Flow Battery Applications and More

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Redox flow batteries (RFBs), where energy is stored in the form of dissolved chemical species that can reversibly gain or lose electrons (reduction and oxidation, respectively), are a leading technology for large scale energy storage to enable integration of renewable energy with the grid and reduce our dependence on fossil fuels. Vanadium RFBs are the most commercially advanced systems, but the high cost of vanadium and sustainability concerns have resulted in the need for alternatives. Within this area of research, the use of organic materials as tunable and sustainable energy storage materials has gained increasing interest in recent years. The proposed research program aims to advance organic RFB technology by developing unique organic energy storage materials that can be both reduced and oxidized. This allows for a simple "symmetric" design, where one molecule acts as both positive and negative electrode active species, which eliminates irreversible capacity fade that plagues asymmetric designs, and can also lead to lower costs systems since expensive ion-exchange membranes are not needed. Moreover, the particular materials chosen here are targeted for their ability to undergo two-electron reduction and two-electron oxidation, which effectively doubles the energy storage capacity of the RFB. The long-term goal of this work is to take advantage of our unique molecular designs to enable commercially viable and sustainable energy storage materials for RFBs. A second aspect of the research program builds on our previously funded Discovery Grant research, and targets more fundamental issues. We have previously developed some of the most highly reducing organic molecules known, and demonstrated their application as homogeneous organic reducing agents in synthesis. In preparing these molecules, we have recently acquired spectroscopic evidence for the involvement of a unique pyridinium ylide intermediate, which we aim to characterize fully, including theoretical modelling to uncover nuances related to its stability, and trapping reactions to prove its involvement. Moreover, we will study biphasic, ionic liquid/organic solvent systems that should enable catalytic processes involving the highly reducing organic molecules that we have developed. Such an advance would greatly increase the possibilities for these reagents, which offer exciting complementarity to more traditional metallic reductants. This program will also provide engaging training opportunities for students to develop general problem solving and critical thinking skills, in addition to specific skills related to chemical synthesis, materials characterization, as well as exposure to cutting edge energy storage research.