Stability and Transport Properties of Ultrahigh Charge Density Hydrocarbon Membranes for Vanadium Redox Flow Batteries

About This Grant

Wind and solar power are well-known to suffer from intermittency, i.e. periods when little or no power is generated. This project seeks to improve redox flow batteries (RFBs), a scalable and durable energy storage technology that can strengthen the electric grid and support U.S. energy independence. Reliable large-scale storage is critical for managing fluctuations in energy supply and demand, particularly as the power grid incorporates a broader mix of energy sources. Vanadium redox flow batteries (VRFBs) are promising for grid applications due to their long service life, safety, and flexible design, but further improvements in cost and performance are needed for widespread deployment. The research will investigate a new class of positively charged membranes with exceptionally high charge densities for application in VRFBs. These membranes have the potential to reduce system costs and increase the efficiency and durability of VRFBs. By identifying key relationships between membrane structure and performance, the project will generate fundamental knowledge that supports domestic innovation in electrochemical technologies. The knowledge generated in this project could also advance membranes used in water treatment, resource recovery, and energy generation. The project will train undergraduate and graduate students in advanced materials research, helping develop a skilled technical workforce. It will also include outreach activities to engage K–12 students and broaden participation in science and engineering. The proposed research investigates the transport properties and stability of ultrahigh charge density (UHCD) hydrocarbon-based anion exchange membranes (AEMs) in concentrated sulfuric acid and vanadium electrolyte solutions typical of VRFB operation. These UHCD AEMs, synthesized via copolymerization of custom charged cross-linkers and monomers, exhibit among the highest ionic conductivities and charge densities of reported AEMs. The study is organized into three tasks: (1) quantifying rates and mechanisms of hydrolytic and oxidative degradation of AEMs using Raman spectroscopy, XPS, FTIR, and chemometric analysis; (2) determining ion partitioning and speciation within AEMs under varying states of hydration using Raman, UV-Vis, and X-ray absorption spectroscopy; and (3) measuring both concentration- and electric field-driven transport of vanadium and charge-balancing ions through AEMs under simulated VRFB conditions. These efforts aim to establish structure-property relationships governing stability and selective ion transport in UHCD AEMs and to provide fundamental design principles for membranes used in VRFBs and other electrochemical systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.