Article
and thus to the development of longer-lasting devices with higher
energy densities for large-scale energy storage.
Data availability
The data that support the findings of this study are available from
https://doi.org/10.17863/CAM.46274 and the corresponding author
upon reasonable request.
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Acknowledgements E.W.Z. and C.P.G. acknowledge support from Centre of Advanced
Materials for Integrated Energy Systems (CAM-IES), via EPSRC grant number EP/P007767/1.
E.W.Z., R.J. and C.P.G. acknowledge support from Shell. E.W.Z. acknowledges support from the
Manifest exchange programme via EPSRC grant number EP/N032888/1. T.L. acknowledges
support from the Schlumberger Fellowship, Darwin College. E.J. acknowledges support from
the Swedish Research Council. We thank A. Brookfield for assistance with the EPR
measurement; P. A. A. Klusener from Shell, H. Bronstein, I. Fleming, D. S. Wright, K. Märker,
C. Xu, P. C. M. M. Magusin from the University of Cambridge and E. Castillo-Martínez from
Universidad Complutense de Madrid for discussions; R. Tan from Imperial College London and
D. Lyu, Y. Kim, Y. Jin, and J. Lu from the University of Cambridge for assistance setting up the
redox flow battery. A.W. and Q.S. acknowledge Imperial College start-up funding and CAM-IES
seed funding. J.C.G. acknowledges support from the Spanish Ministry of Science, Innovation
and Universities through a Ramon y Cajal Fellowship (RYC-2015-17722) and the Retos Project
(MAT2017-86796-R).Author contributions C.P.G. supervised the project. E.W.Z and C.P.G. conceived the idea. E.W.Z.
designed the in situ setups and performed the NMR and EPR experiments and analysis. T.L. and
E.W.Z. performed the infrared experiments. E.J. performed the calculations of reaction
equilibrium, CV fittings and NMR chemical shift. J.L. performed the DFT calculations of the
radical species and their proton hyperfine couplings. I.T. and E.W.Z. designed and performed
the in situ mass spectrometry with assistance from T.L. R.J. performed the CV experiments.
A.W. synthesized DBEAQ under the supervision of Q.S. H.S. and J.C.G. assisted in performing
the in situ NMR experiments. All authors contributed to the discussion of the project. E.W.Z.
and C.P.G. wrote the manuscript with input from all co-authors.Competing interests The authors declare no competing interests.
Additional information
Supplementary information is available for this paper at https://doi.org/10.1038/s41586-020-
2081-7.
Correspondence and requests for materials should be addressed to C.P.G.
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