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Exploring the Landscape of Heterocyclic Quinones for Redox Flow Batteries

Accepted version
Peer-reviewed

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Authors

Hey, Dominic 
Kerber, Rachel N 

Abstract

Redox flow batteries (RFBs) rely on the development of cheap, highly soluble, and high energy-density electrolytes. Several candidate quinones have already been investigated in the literature as two-electron anolytes or catholytes, benefitting from fast kinetics, high tunability and low cost. Here, an investigation of nitrogen-rich fused heteroaromatic quinones was carried out to explore avenues for electrolyte development. These quinones were synthesized and screened using electrochemical techniques. The most promising candidate, 4,8-dioxo-4,8-dihydrobenzo[1,2-d:4,5-d']bis([1,2,3]triazole)-1,5-diide (-0.68 V(SHE)), was tested in both an asymmetric and symmetric full-cell setup resulting in capacity fade rates of 0.35%.cycle-1 and 0.0124%.cycle-1, respectively. In situ UV-Vis, NMR and EPR spectroscopies were used to investigate the electrochemical stability of the charged species during operation. UV-Vis spectroscopy, supported by density functional theory (DFT) modelling, reaffirmed that the two-step charging mechanism observed during battery operation consisted of two, single-electron transfers. The radical concentration during battery operation and the degree of delocalization of the unpaired electron were quantified with NMR and EPR spectroscopy.

Description

Keywords

40 Engineering, 34 Chemical Sciences, 3406 Physical Chemistry, 7 Affordable and Clean Energy

Journal Title

ACS Applied Energy Materials

Conference Name

Journal ISSN

2574-0962
2574-0962

Volume Title

Publisher

American Chemical Society (ACS)
Sponsorship
Engineering and Physical Sciences Research Council (EP/R511870/1)
R. B. J., D. S. W., and C. P. G. acknowledge support from the EPSRC and Shell via iCASE studentship EP/R511870/1. R. B. J. also acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101034413. D. H. acknowledges support from the Sheldrick Scholarship in Chemistry, Jesus College Cambridge, and the EPRSC iCASE PhD Fees Only Studentship. We also thank P. A. A. Klusener from Shell for many fruitful discussions.