TY - JOUR

T1 - Application of the dianion croconate violet for symmetric organic non-aqueous redox flow battery electrolytes

AU - Armstrong, C.G.

AU - Hogue, R.W.

AU - Toghill, K.E.

PY - 2019/11/15

Y1 - 2019/11/15

N2 - 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.

AB - 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.

KW - Croconate violet

KW - Non-aqueous organic

KW - Redox flow battery

KW - Symmetric electrolyte

U2 - 10.1016/j.jpowsour.2019.227037

DO - 10.1016/j.jpowsour.2019.227037

M3 - Journal article

VL - 440

JO - Journal of Power Sources

JF - Journal of Power Sources

SN - 0378-7753

M1 - 227037

ER -