Collaborative Research: Biphasic Charge Carriers for Flow-Based Electrochemical Energy Storage

Long-duration energy storage (LDES) technologies provide numerous societal benefits, including enhancing grid stability, enabling greater use of renewable energy, and reducing the dependence on fossil fuels. LDES technologies transform intermittent renewable resources, such as solar and wind power, into dispatchable power sources. Among the available options for LDES are redox flow batteries (RFBs), which store energy electrochemically and feature significant operational flexibility, modularity, and cost advantages. Nonetheless, key challenges remain in developing energy carriers for RFBs, including cost and performance barriers stemming from fundamental limitations in their chemical properties. This research will focus on designing new chemical compounds, called biphasic charge carriers, that can store electric power, and link the fundamental chemical properties of these charge carriers to their function in small-scale working batteries. The goal is to develop a clear set of design principles for a new generation of batteries purpose-built for storing solar and wind power. This research project integrates hardware prototypes under active development by a startup company founded out of one of the participating laboratories, enabling further potential for societal impacts through commercialization and entrepreneurship. Additionally, a new training curriculum for undergraduate students will be developed to learn the fundamentals of electrochemistry and battery science. Work will be undertaken to deploy a series of educational outreach activities encompassing the development of low-cost hardware and software tools to support broader dissemination via the delivery of new laboratory courses at the participating universities, education research literature, and digital media. This project will develop design rules for inorganic charge carriers for redox flow batteries. The overarching objective is to overcome hurdles related to energy density and materials availability by developing redox-active molecules that store charge both as soluble units and in the solid phase. This feature opens opportunities to explore new RFB designs, beyond aqueous transition metal complexes, via the development of biphasic charge carriers, wherein soluble forms of a given molecule are used as mediators to shuttle charge to or from the solid form of the same molecule. The project encompasses hypothesis-driven studies directed at controlling molecular solubility across multiple charge states via ligand modification, alongside detailed investigations of charge transfer at interfaces between the electrode and the electrolyte and between the electrolyte and the solid-state charge carrier. Successful completion of this work will yield lab-scale biphasic battery systems with promising functional properties that can be fully rationalized from basic physical properties, entailing extensive opportunities for further development. 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.