Stability of Novel Anolyte and Catholyte Materials for Organic Nonaqueous Redox Flow Batteries

Abstract

In recent years, many improvements have been made in renewable energy technologies, allowing them to outcompete fossil fuels in terms of the cost-efficiency of energy production. However, the biggest challenge in the implementation of renewable energies is matching energy production to energy consumption. In an effort to bridge this gap, there has been significant academic and commercial focus on energy storage technologies, with redox flow batteries being of particular interest.Organic nonaqueous redox flow batteries provide several improvements over traditional flow batteries. These improvements include higher accessible cell voltage, enhanced energy density, wider operating temperature range, and reduced operational costs compared to current flow battery technology. Current redox flow battery chemistries often utilize toxic metals such as vanadium for anolyte and catholyte materials. These metals are expensive, difficult to safely dispose of, and require a highly acidic electrolyte. Organic anolyte and catholyte materials provide a potential solution to these problems but also introduce other challenges, most notably stability of the battery materials in their oxidized and reduced states.In this study a number of organic redox-active molecules been evaluated for their use as anolyte and catholyte materials capable of highly reversible one electron and two electron oxidations and reductions. Cyclic voltammetry and spectroelectrochemistry were utilized to determine oxidation or reduction potentials as well as the electrochemical stability of those materials in their oxidized or reduced states.