Letter | Published:

A metal-free organic–inorganic aqueous flow battery

Nature volume 505, pages 195198 (09 January 2014) | Download Citation



As the fraction of electricity generation from intermittent renewable sources—such as solar or wind—grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output1,2. In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form3,4,5. Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts6,7. Here we describe a class of energy storage materials that exploits the favourable chemical and electrochemical properties of a family of molecules known as quinones. The example we demonstrate is a metal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br2/Br redox couple, yields a peak galvanic power density exceeding 0.6 W cm−2 at 1.3 A cm−2. Cycling of this quinone–bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals8. This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of π-aromatic redox-active organic molecules instead of redox-active metals represents a new and promising direction for realizing massive electrical energy storage at greatly reduced cost.

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This work was partially funded through US Department of Energy ARPA-E Award DE-AR0000348 and partially funded through the Harvard School of Engineering and Applied Sciences. Theoretical work was funded in part through the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number OCI-1053575. B.H. was supported by an NSF Graduate Research Fellowship. S.E. performed work as part of the Fellowships for Young Energy Scientists programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organization for Scientific Research (NWO). We thank T. Betley, L. Hartle, R. Burton and R. Duncan for discussions.

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Author notes

    • Brian Huskinson
    •  & Michael P. Marshak

    These authors contributed equally to this work.


  1. Harvard School of Engineering and Applied Sciences, 29 Oxford Street, Cambridge, Massachusetts 02138, USA

    • Brian Huskinson
    • , Michael P. Marshak
    • , Michael R. Gerhardt
    • , Roy G. Gordon
    •  & Michael J. Aziz
  2. Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA

    • Michael P. Marshak
    • , Changwon Suh
    • , Süleyman Er
    • , Cooper J. Galvin
    • , Xudong Chen
    • , Alán Aspuru-Guzik
    •  & Roy G. Gordon
  3. Molecular Materials and Nanosystems, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands

    • Süleyman Er


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B.H. and M.P.M. contributed equally to this work. B.H. and M.P.M. designed and tested the battery, with direction from M.J.A. Both M.P.M. and M.R.G. conducted electrochemistry experiments, with direction from M.J.A. M.P.M. and C.J.G. synthesized chemicals with direction from R.G.G. Theoretical calculations were done by C.S. and S.E., with input from M.P.M. and R.G.G. and direction from A.A.-G. X.C. contributed NMR results. B.H., M.P.M., C.S., M.R.G., S.E., A.A.G., R.G.G. and M.J.A. all contributed to writing the manuscript.

Competing interests

Harvard University has filed a patent on some of the intellectual property disclosed by this paper.

Corresponding author

Correspondence to Michael J. Aziz.

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