In situ NMR metrology reveals reaction mechanisms in redox flow batteries
Journal article, 2020

Large-scale energy storage is becoming increasingly critical to balancing renewable energy production and consumption1. Organic redox flow batteries, made from inexpensive and sustainable redox-active materials, are promising storage technologies that are cheaper and less environmentally hazardous than vanadium-based batteries, but they have shorter lifetimes and lower energy density2,3. Thus, fundamental insight at the molecular level is required to improve performance4,5. Here we report two in situ nuclear magnetic resonance (NMR) methods of studying redox flow batteries, which are applied to two redox-active electrolytes: 2,6-dihydroxyanthraquinone (DHAQ) and 4,4′-((9,10-anthraquinone-2,6-diyl)dioxy) dibutyrate (DBEAQ). In the first method, we monitor the changes in the 1H NMR shift of the liquid electrolyte as it flows out of the electrochemical cell. In the second method, we observe the changes that occur simultaneously in the positive and negative electrodes in the full electrochemical cell. Using the bulk magnetization changes (observed via the 1H NMR shift of the water resonance) and the line broadening of the 1H shifts of the quinone resonances as a function of the state of charge, we measure the potential differences of the two single-electron couples, identify and quantify the rate of electron transfer between the reduced and oxidized species, and determine the extent of electron delocalization of the unpaired spins over the radical anions. These NMR techniques enable electrolyte decomposition and battery self-discharge to be explored in real time, and show that DHAQ is decomposed electrochemically via a reaction that can be minimized by limiting the voltage used on charging. We foresee applications of these NMR methods in understanding a wide range of redox processes in flow and other electrochemical systems.


Evan Wenbo Zhao

University of Cambridge

Tao Liu

University of Cambridge

Tongji University

Erlendur Jonsson

University of Cambridge

Chalmers, Physics, Materials Physics

Jeongjae Lee

Seoul National University

University of Cambridge

Israel Temprano

University of Cambridge

Rajesh B. Jethwa

University of Cambridge

Anqi Wang

Imperial College London

Holly Smith

University of Cambridge

Javier Carretero-González

Instituto de Ciencia & Tecnologia de Polimeros

Qilei Song

Imperial College London

C. P. Grey

University of Cambridge


0028-0836 (ISSN) 1476-4687 (eISSN)

Vol. 579 7798 224-228

Subject Categories

Inorganic Chemistry

Other Chemical Engineering

Other Chemistry Topics





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