Associative pyridinium electrolytes for air-tolerant redox flow batteries.

Autor: Carrington ME; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.; Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., Sokołowski K; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.; Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., Jónsson E; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., Zhao EW; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.; Magnetic Resonance Research Center, Institute for Molecules and Materials, Faculty of Science, Radboud University Nijmegen, Nijmegen, The Netherlands., Graf AM; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.; Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., Temprano I; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., McCune JA; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.; Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK., Grey CP; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK. cpg27@cam.ac.uk., Scherman OA; Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK. oas23@cam.ac.uk.; Melville Laboratory for Polymer Synthesis, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK. oas23@cam.ac.uk.
Jazyk: angličtina
Zdroj: Nature [Nature] 2023 Nov; Vol. 623 (7989), pp. 949-955. Date of Electronic Publication: 2023 Nov 29.
DOI: 10.1038/s41586-023-06664-7
Abstrakt: Pyridinium electrolytes are promising candidates for flow-battery-based energy storage 1-4 . However, the mechanisms underlying both their charge-discharge processes and overall cycling stability remain poorly understood. Here we probe the redox behaviour of pyridinium electrolytes under representative flow battery conditions, offering insights into air tolerance of batteries containing these electrolytes while providing a universal physico-chemical descriptor of their reversibility. Leveraging a synthetic library of extended bispyridinium compounds, we track their performance over a wide range of potentials and identify the singlet-triplet free energy gap as a descriptor that successfully predicts the onset of previously unidentified capacity fade mechanisms. Using coupled operando nuclear magnetic resonance and electron paramagnetic resonance spectroscopies 5,6 , we explain the redox behaviour of these electrolytes and determine the presence of two distinct regimes (narrow and wide energy gaps) of electrochemical performance. In both regimes, we tie capacity fade to the formation of free radical species, and further show that π-dimerization plays a decisive role in suppressing reactivity between these radicals and trace impurities such as dissolved oxygen. Our findings stand in direct contrast to prevailing views surrounding the role of π-dimers in redox flow batteries 1,4,7-11 and enable us to efficiently mitigate capacity fade from oxygen even on prolonged (days) exposure to air. These insights pave the way to new electrolyte systems, in which reactivity of reduced species is controlled by their propensity for intra- and intermolecular pairing of free radicals, enabling operation in air.
(© 2023. The Author(s).)
Databáze: MEDLINE
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