High-Throughput Electrochemical Characterization of Aqueous Organic Redox Flow Battery Active Material

Abstract

The development of redox-active organics for flow batteries providing long duration energy storage requires an accurate understanding of molecular lifetimes. Herein we report the development of a high-throughput setup for the cycling of redox flow batteries. Using common negolyte redox-active aqueous organics, we benchmark capacity fade rates and compare variations in measured cycling behavior of identical volumetrically unbalanced compositionally symmetric cells. We propose figures of merit for consideration when cycling sets of identical cells, and compare three common electrochemical cycling protocols typically used in battery cycling: constant current, constant current constant voltage, and constant voltage. Redox-active organics exhibiting either high or low capacity fade rates are employed in the cell cycling protocol comparison, with results shown from over 50 flow cells.

Influence of Crossover on Capacity Fade of Symmetric Redox Flow Cells

“…The diverse time-dependent capacity trajectories simulated in these scenarios compose a cautionary tale against over-interpreting short-duration cycling behavior, especially when the mechanisms governing the cycling species are unknown. 55 However, we underscore that using a membrane-electrolyte system with sufficiently low crossover flux can avoid the complicated interaction of chemical reactions and net crossover. The combination of ex situ permeability and chemical stability tests with zero-dimensional modeling may be useful as a preliminary screening protocol for choosing materials and conditions for experiments in redox flow cells.…”

Azoniafluorenones: A New Family of Two-electron Storage Electrolytes for Sustainable Near-Neutral pH Aqueous Organic Flow Battery

“…During this long cycling, it was also necessary to add water to compensate the amount lost because of evaporation, again evidencing a capacity recovery after each addition. We associate the reported irreversible capacity fade rates with chemical decomposition because crossover effect is eliminated during symmetric cell testing and the capacity lost due to precipitation was already considered [26] .…”