CAS: Sextuple Multiredox Organic Compounds for Redox Flow Batteries

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Xiaoliang Wei of the Department of Mechanical and Energy Engineering at Indiana University-Purdue University Indianapolis is investigating a new family of soluble, stable multi-redox macrocyclic organic (M2O) molecules that undergo reversible six electron electrochemical reactions. Despite the great progress so far, redox flow batteries are still facing critical technical hurdles including low energy density and/or short cycle life. Dr. Wei aims to address these challenges by developing highly soluble M2O molecules capable of six electron transfer with high stability via extended charge delocalization. The goal of this research is to use these molecules to achieve energy-dense, long-life redox flow batteries. Success of this project will increase the deployment capacity of renewable energies and improve the reliability and efficiency of our power grid. This project is highly interdisciplinary combining organic chemistry, electrochemistry, materials science and computational chemistry, and in this way, provides a well-suited platform for scientific training at all levels. Given the nature of the science, this project is expected to engage students considering careers in STEM (science, technology, engineering and medicine) that can benefit society. This project will explore novel multi-redox macrocyclic organic (M2O) molecules for use in aqueous redox flow batteries to achieve high energy density and long cycle life. The molecular design includes fused heteroaromatic structures with solvatable substituents to provide multi-redox activity, conjugative stabilization, and solubility. The relevant physicochemical and electrochemical properties of synthetic M2O compounds will be correlated with their molecular architectures to unravel the fundamental interplays. The objective of this project is to rationalize the design principles for the development of promising M2O candidates through answering the following questions: (1) What are the mechanisms for establishment of solubility limits and how do the substituents on M2O scaffolds affect the solvation structure and solubility? (2) What are the redox mechanisms of M2O molecules and how do the electrode microstructure affect their redox kinetics? (3) What are the decomposition pathways for unstable M2O molecules and what are the stability-controlling factors? 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.