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Application of the dianion croconate violet for symmetric organic non-aqueous redox flow battery electrolytes

Research output: Contribution to journalJournal articlepeer-review

Published
Article number227037
<mark>Journal publication date</mark>15/11/2019
<mark>Journal</mark>Journal of Power Sources
Volume440
Number of pages9
Publication StatusPublished
Early online date17/09/19
<mark>Original language</mark>English

Abstract

Redox active organic molecules (ROMs) are promising candidates for redox flow battery (RFB) energy storage due to their high sustainability and low cost. Herein, the pseudooxocarbon derivative croconate violet (Croc2-) is applied as a novel symmetric ROM in acetonitrile electrolyte, whereby Croc2- is used as both the battery posolyte and negolyte, with a 1.82 V cell potential and ≃1 M solubility. Characterisation of the dianion Croc2- is given by way of voltammetry and battery cycling techniques to demonstrate the high number of oxidation states accessible by Croc2-, thus highlighting a high intrinsic capacity for a low molecular weight ROM. The stability of Croc2- and its charged radical states is investigated to assess the viability of the symmetric design, and an undesirable radical disproportionation mechanism of the Croc•3- oxidation state is identified to account for poor capacity retention. Asymmetric battery experiments of a Croc2- posolyte with 2,1,3-benzothiadiazole or tetracyanoquinodimethane negolytes gave improved battery performance, indicating that Croc2- is a promising anionic ROM posolyte.