Exploring small molecule diffusion in Fumasep FAPQ-375-PET for nonaqueous redox flow batteries

John N. Vergados

Massachusetts Institute of Technology

September 9th 5pm EST

Amgen 360 Binney St, Cambridge, MA 02141

‍ ‍Abstract

Nonaqueous redox flow batteries (RFBs) serve as a nascent alternative to existing aqueous RFBs, providing opportunities for devices with elevated energy densities and energy efficiencies. The development and future adoption of these devices relies, in part, on judicious design and improvement of internal material components (e.g., membranes, electrodes). In particular, existing membranes are borrowed from aqueous RFB and fuel cell applications and exhibit significant losses in performance metrics—selectivity and ionic conductivity—when transferred to the nonaqueous RFB electrolyte environment. Consequently, there is a need for new materials and corresponding structure-property-performance relationships in nonaqueous solvents with which to guide materials design. This work aims to investigate local environments and small molecule diffusion within a model anion exchange NAqRFB membrane—Fumasep FAPQ-375- PET—to better understand membrane morphology and small molecule transport under the influence of nonaqueous solvents. Coupling NMR diffusometry and relaxation measurements with macroscopic swelling and ionic conductivity data, the study hypothesizes the presence of two regimes within the membrane: a solvent rich and a polymer rich region. These regions and underlying transport trends are posited to contribute to the membrane’s performance in nonaqueous redox flow batteries; however, it is found that phenomena not captured in this study likely play additional roles in membrane behavior.

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