A metal-free organic–inorganic aqueous flow battery

Abstract

This paper can be cited as: B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, "A metal-free organicinorganic aqueous flow battery", Nature 505, 195-198 (2014).The formatted version of this manuscript can be found at the following link: http://www.nature.com/nature/journal/v505/n7482/full/nature12909.html A metal-free organic-inorganic aqueous flow batteryBrian Huskinson 1 *, Michael P. Marshak 1,2 *, Changwon Suh 2 , Süleyman Er 2,3 , Michael R. *These authors contributed equally to this work.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 output 1,2 . 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 form 3-5 . 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 electrocatalysts 6,7 . 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 Br 2 /Br  redox couple, yields a peak galvanic power density exceeding 0.6 W cm Solutions of AQDS in sulphuric acid (negative side) and Br 2 in HBr (positive side) were pumped through a flow cell as shown schematically in Fig. 1a. The quinone-bromide flow battery (QBFB) was constructed using a Nafion 212 membrane sandwiched between Toray carbon paper electrodes (six stacked on each side) with no catalysts; it is similar to a cell described elsewhere (see figure 2 in ref. 7). We report the potential-current response (Fig. 1b) and the potential-power relationship ( measured with respect to the quinone side of the cell). As the SOC increased from 10% to 90%, the open-circuit potential increased linearly from 0.69 V to 0.92 V. In the galvanic direction, peak power densities were 0.246 W cm 2 and 0.600 W cm 2 at these same SOCs, respectively ( Fig. 1c). In order to avoid significant water splitting in the electrolytic direction, we used a cutoff voltage of 1.5 V, at which point the current densities observed at 10% and 90% SOCs were −2.25 A cm −2 and −0.95 A cm −2 , respectively, with corresponding power densities of −3.342 W cm −2 and −1.414 W cm −2 .In Fig. 2 we report the results of initial cy...

Direct Solar Charging of an Organic–Inorganic, Stable, and Aqueous Alkaline Redox Flow Battery with a Hematite Photoanode

“…As seen from the CVs in Figure 2 a, the redox couples are electrochemically reversible and the redox potentials are as expected from previous reports 2, 10. The battery charge–discharge cycles were tested in a 25 cm 2 single redox flow cell (RF) and the potential as function of time for ten cycles are shown in Figure 2 b.…”

Redox‐Flow Batteries: From Metals to Organic Redox‐Active Materials

“…The described flow cell revealed a short‐circuit current density above 4000 mA cm −2 at 90 % SOC and a peak galvanic power density of 1 Wcm −2 127. These data represent a significant improvement in reference to the published results of Huskinson et al 78. Furthermore, the achieved peak galvanic power density of 1.0 Wcm −2 is 75 % higher than the maximum values of previously published VRFBs .…”

“…Conversion factors: SHE to AgCl/Ag=+0.197 V, SHE to SCE=+0.241 V, SHE to Fc + /Fc= +0.750 V;130 SHE: standard hydrogen electrode, SCE: standard calomel electrode, Fc: ferrocene 35, 41, 78, 126, 131, 132, 133, 134, 135, 136, 137…”

“…However, ANL‐8 features a diffusion coefficient of the same order of magnitude as vanadium,157, 158 DBBB,159, 160 and several quinone derivatives 78, 161. The battery tests were performed with 1 m m ANL‐8 plus 0.5  m LiBF 4 as a conducting salt, dissolved in propylene carbonate, at a constant charging current of 0.4 mA in a bulk‐electrolysis cell, where an energy density of 0.05 Wh L −1 for the catholyte could be achieved.…”

An Aqueous Ca‐Ion Battery

“…It shows that PNDIE electrode undergoes a reversible discharge and charge process in this electrolyte delivering ≈148 mAh g −1 capacity between −0.9 and 0 V versus Ag/AgCl. The reduction and oxidation processes of the conjugated carbonyl groups processes are accompanied by the coordination of cations to the carbonyl groups 18. To have a better understanding of the redox mechanism, the changes in bonding in the reduced and oxidized states were characterized by Fourier transform infrared (FTIR) analysis.…”