Nonaqueous redox flow batteries show promise for grid-scale energy storage due to their wide electrochemical window. However, the discovery of redox active materials with extreme negative potentials, high solubility in all states of charge, and cycling stability has been challenging. Several N-containing heterocycles have been identified as anolytes (negative charge carriers) due to their reversible reductions but the list is not extensive due the rigorous standards they must meet. Symmetric tetrazines have been unexplored in redox flow batteries but their exceptional chemical stability, high solubility, and low molar mass enables them to meet the criteria for their use as anolytes. We substituted the s-tetrazine core with methoxy, thiomethyl, and methyl substituents and evaluated their effects on electrochemical behavior and cycling stability via cyclic voltammetry, spectroelectrochemistry, and bulk electrolysis cycling. We revealed 3,6-dimethoxy-<i>s</i>-tetrazine undergoes a one electron reduction at –1.2 V versus ferrocene/ferrocenium, can withstand 50 charge-discharge cycles (17 h) with 8% loss in<br/>capacity in a redox flow battery, and is soluble in the neutral state up to 0.78 M in 0.78 M tetrabutylammonium hexafluorophosphate in acetonitrile. Given their success as anolytes, amino substituted tetrazines are now being explored for their use as ambipolar materials, which undergo reversible reduction at the tetrazine core and oxidation at the amine substituent. For these reasons, we believe s-tetrazine derivatives deserve further exploration in non-aqueous redox flow batteries.

Symmetric tetrazines as redox active materials in nonaqueous redox flow batteries

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.