Collaborative Research: Molecular Structures and Electrochemical Activity of Supersaturated Electrolytes for High-Energy-Density Redox Flow Batteries

Renewable electricity sources provide many benefits to society, including ensuring sustainability, enhancing energy independence, and reducing pollution. Effective scale-up of renewable electricity sources, such as wind and solar, to meet the growing societal demand requires developing low-cost energy storage technologies. Redox flow batteries are a promising technology for large-scale and long-duration storage. However, the energy storage capacity per volume of a battery is limited by the chemical properties of the substances responsible for energy storage and transfer. This project will investigate the chemical substances used to store energy, their various molecular forms, their ability to convert between these molecular forms, and how increasing their quantity can reduce energy storage costs and integrate renewable electricity into the grid. The project will provide research and educational opportunities for graduate, and undergraduate researchers. As part of the program, the investigators at the University of Kansas and University of Michigan will give demonstrations involving energy conversion and storage at elementary and middle schools and public venues, such as the Kansas's School of Engineering’s annual exposition. This project aims to advance the understanding of supersaturated, or especially highly concentrated electrolytes, for high energy density flow batteries. The objective is to understand the structure and activity of vanadium and iron metal ions in concentrated and supersaturated metal ion aqueous solutions through three tasks. Task 1 will identify the structure of different vanadium complexes in supersaturated solutions through combined experimental and computational spectroscopy (e.g., UV-Vis and X-ray absorption) of vanadium ions, and the role of supporting electrolyte and preparation conditions on their structure. This task aims to improve the understanding of metal ion structure at concentrated and supersaturated conditions where the local structures are currently unknown. Task 2 is focused on identifying structure-activity relations. In this task electrochemical activity will be measured by determining which ionic structures from Task 1 are capable of electrochemical reactions and evaluating different electrolytes for their performance in redox flow batteries. Task 3 will determine the conversion of electrochemically inactive species to electrochemically active species and identify methods that facilitate this interconversion. The findings of this project will be used to understand ion chemical and electrochemical kinetics and evaluate the feasibility of supersaturated electrolytes in high-energy-density energy storage systems. The gained understanding of the molecular structure and functionality will be used to identify electrolyte compositions and preparation methods that result in supersaturated electrolytes with longer stability and higher chemical and electrochemical activities than what is currently known. The project will create future opportunities to study supersaturated and extreme structures in condensed phases and to explore the feasibility of supersaturated electrolytes in high-energy-density energy storage 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.