Article Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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110th Anniversary: Unleashing the Full Potential of Quinones for High Performance Aqueous Organic Flow Battery Pan Sun,† Yahua Liu,† Yuanyuan Li, Muhammad A. Shehzad, Yazhi Liu, Peipei Zuo, Qianru Chen, Zhengjin Yang,* and Tongwen Xu* iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), School of Chemistry and Material Science, University of Science and Technology of China, Hefei 230026, P. R. China Ind. Eng. Chem. Res. Downloaded from pubs.acs.org by UNIV OF TEXAS AT DALLAS on 03/10/19. For personal use only.
S Supporting Information *
ABSTRACT: Aqueous organic flow batteries (AOFBs) are promising energy storage solutions to counteract the intermittent and fluctuating nature of renewable energy. However, we have limited options of electrolyte chemistry and we discarded many organic compounds because of their sluggish electrochemical kinetics, which would compromise the power capability of an AOFB. Here, exemplified by 2,5-dihydroxy-3,6-dimethyl-1,4-benzoquinone (DMBQ), we present two approaches including engineering the molecular structure and utilizing an inexpensive catalyst to enhance the electrochemical kinetics of benzoquinones with the ultimate purpose of diminishing the electron transfer barrier thereby increasing the power capability of the AOFB. We show that, by exploiting these strategies, the electron transfer resistance could be reduced by 48.1%, or 55.8%, respectively, thereby leading to a 49.4% or 60.7% increase in the peak power density of a flowing cell. We believe our strategy could be extended to the full family of quinones and that it benefits further exploration of quinone-based high performance AOFBs.
1. INTRODUCTION Pollution from the combustion of fossil fuels and the rapid depletion of fossil fuels, drive society to explore and exploit renewable energy resources as alternatives.1 However, the intermittent and fluctuating nature of renewable energy impedes their grid-scale implementation.2 This may be solved by energy storage technologies. Energy storage technologies are also needed to level out the imbalances between energy supply and demand.3 Redox flow batteries, which store energy externally in liquid electrolytes outside an electrochemical cell, are capable of decoupling energy (determined by the electrolyte volume and concentration) and power (determined by the size of the electrochemical cell) and are considered a promising energy storage solution. Particularly, aqueous organic flow batteries (AOFBs), which exploit the reversible oxidation and reduction of organic compounds in aqueous solution, feature low electrolyte cost, high operational safety, and tunable cell potential by employing inexpensive, nonflammable and aqueous-soluble organic electrolytes. That an aqueous-soluble organic electrolyte consists merely of earth-abundant elements, promising low electrolyte cost and that one can capture the desired properties of the organic redox-active electrolytes (such as stability, redox potential, and solubility) by engineering their structures are the most prominent characteristics of an AOFB.4−8 Prescreening experiments of organic electrolyte candidate focused on the redox behavior revealed by cyclic voltammetry © XXXX American Chemical Society
(CV), and almost all reports tended to indicate the most promising organic compounds to be of ideal electrochemical reversibility, dictated by proper peak separation between the oxidation peak and the reduction peak (ΔE), as well as fast kinetics. For a sluggish redox kinetics, the direct consequences include low power density and low energy efficiency. For instance, Schubert et al. assembled a symmetric AOFB by employing a TEMPO/phenazine combi-molecule, whereas the sluggish redox kinetics resulted in very low energy efficiency (98% for the 200 cycles. The energy efficiency of the K4Fe(CN)6/DMBQ cell is at approximately 55%−65% because of the relatively high resistance. Replacing DMBQ with DMOBQ renders the K4Fe(CN)6/DMOBQ cell with a much higher energy efficiency of 75%−80%. This is attributed to the decreased electron transfer resistance caused by structure optimization, as we have learned in EIS studies. Improved energy efficiency could also be achieved by catalyzing the redox reaction of the same DMBQ molecule, as what we did to the K4Fe(CN)6/DMBQ cell with N/S-CMR coated electrodes. The catalytic effect of the N/S-CMR coated electrodes and the improvement in electrode conductivity, combine to contribute an energy efficiency as high as 80% over 200 cycles. However, after 200 cycles, capacity of the K4Fe(CN)6/ DMBQ cell, the K4Fe(CN)6/DMOBQ cell, and the K4Fe(CN)6/DMBQ cell with N/S-CMR coated electrodes dropped to 76%, 62%, and 70% of the initial value, corresponding to capacity loss rates of 0.12%, 0.19%, and 0.15% per cycle, respectively. The loss in capacity is from the negolyte side, as the posolyte is in 1.5 times excess amount. We then carried out additional cycling experiments by cycling the cells for a certain period, stopping the cycling procedure, letting the cells sit still on bench for 12 h, and then continuing cell cycling (Supporting Information Figure S18). We observed an obvious capacity loss when the negolyte is stored in the reservoir and it suggests a capacity loss due to chemical decomposition. Membrane crossover might be another origin because the Coulombic efficiency was not 100%. However, this contributes only a small fraction of the total capacity loss.
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Muhammad A. Shehzad: 0000-0002-7820-9889 Zhengjin Yang: 0000-0002-0722-7908 Tongwen Xu: 0000-0001-6000-1791 Author Contributions †
P.S. and Y. Liu contributed equally.
Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This project has been supported by the National Natural Science Foundation of China (Nos. 21878281, 91534203), International Partnership Program of Chinese Academy of Sciences (No. 21134ky5b20170010), K. C. Wong Education Foundation (2016-11) and Changjiang Scholars Program Funding(2014). The numerical calculations were performed on the supercomputing system in the Supercomputing Center at the University of Science and Technology of China.
3. CONCLUSIONS In summary, we proposed two approaches in improving the redox kinetics of aqueous-soluble benzoquinones, by engineering the structure or by catalyzing the redox reaction with catalyst and found both to be effective. Improved redox kinetics of the benzoquinones resulted in a sharp decrease in electron transfer resistance, by as much as 55.8%. As the outcome, power capability of the cells, dictated by the peak power density, can be raised by 60.7%. Energy efficiency during long-term cell cycling can be increased from 55%−65% to 75%−80%. Our results imply that some previously discarded organic electrolytes could also be potential candidates for AOFBs and this would give us more choices when exploring new redox chemistries. This would benefit and accelerate the massive-scale application of AOFBs as a viable energy storage solution. Further research efforts shall be devoted to investigating the chemical degradation mechanisms of quinones, establishing the relationships among redox kinetics, electrochemical stability, and chemical stability.
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Synthesis of DMBQ, DMOBQ, and N/S-CMRs; description of characterizations, electrochemical studies, and DFT calculations; 1H-NMR, CV, and RDE results of DMBQ based and DMOBQ based electrolytes; TEM and SEM images, XPS spectrum, XRD pattern of N/SCMRs catalyst;. cycling performance of pH 14 K4Fe(CN)6/DMBQ cell, K4Fe(CN)6/DMOBQ cell, and K4Fe(CN)6/DMBQ cell with N/S-CMR coated carbon paper electrodes; cycling experiment with break for K4Fe(CN)6/DMBQ cell and K4Fe(CN)6/DMOBQ cell; voltage over time curves and open-circuit voltages of the assembled cells; comparison of diffusion coefficient (D) and electron-transfer rate constant (k0) of electrolytes (PDF)
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REFERENCES
(1) Armand, M.; Tarascon, J. M. Building better batteries. Nature 2008, 451 (7179), 652−657. (2) Yang, Z.; Zhang, J.; Kintner-Meyer, M. C. W.; Lu, X.; Choi, D.; Lemmon, J. P.; Liu, J. Electrochemical Energy Storage for Green Grid. Chem. Rev. 2011, 111 (5), 3577−3613. (3) Winsberg, J.; Hagemann, T.; Janoschka, T.; Hager, M. D.; Schubert, U. S. Redox-Flow Batteries: From Metals to Organic Redox-Active Materials. Angew. Chem., Int. Ed. 2017, 56 (3), 686− 711. (4) Beh, E. S.; De Porcellinis, D.; Gracia, R. L.; Xia, K. T.; Gordon, R. G.; Aziz, M. J. A Neutral pH Aqueous Organic−Organometallic Redox Flow Battery with Extremely High Capacity Retention. ACS Energy Lett. 2017, 2 (3), 639−644. (5) Yang, Z.; Tong, L.; Tabor, D. P.; Beh, E. S.; Goulet, M.-A.; De Porcellinis, D.; Aspuru-Guzik, A.; Gordon, R. G.; Aziz, M. J. Alkaline Benzoquinone Aqueous Flow Battery for Large-Scale Storage of Electrical Energy. Adv. Energy Mater. 2018, 8 (8), 1702056. (6) Luo, J.; Hu, B.; Debruler, C.; Liu, T. L. A pi-Conjugation Extended Viologen as a Two-Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries. Angew. Chem., Int. Ed. 2018, 57 (1), 231−235. (7) Zhao, Q.; Zhu, Z.; Chen, J. Molecular Engineering with Organic Carbonyl Electrode Materials for Advanced Stationary and Redox Flow Rechargeable Batteries. Adv. Mater. 2017, 29 (48), 1607007.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.8b06391. E
DOI: 10.1021/acs.iecr.8b06391 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research (8) Winsberg, J.; Janoschka, T.; Morgenstern, S.; Hagemann, T.; Muench, S.; Hauffman, G.; Gohy, J.-F.; Hager, M. D.; Schubert, U. S. Poly(TEMPO)/Zinc Hybrid-Flow Battery: A Novel, ″Green,″ High Voltage, and Safe Energy Storage System. Adv. Mater. 2016, 28 (11), 2238−2243. (9) Winsberg, J.; Stolze, C.; Muench, S.; Liedl, F.; Hager, M. D.; Schubert, U. S. TEMPO/Phenazine Combi-Molecule: A RedoxActive Material for Symmetric Aqueous Redox-Flow Batteries. ACS Energy Lett. 2016, 1 (5), 976−980. (10) Orita, A.; Verde, M. G.; Sakai, M.; Meng, Y. S. A biomimetic redox flow battery based on flavin mononucleotide. Nat. Commun. 2016, 7, 13230. (11) Ding, Y.; Li, Y.; Yu, G. Exploring Bio-inspired Quinone-Based Organic Redox Flow Batteries: A Combined Experimental and Computational Study. Chem. 2016, 1 (5), 790−801. (12) Tsuji, Y.; Hoffmann, R. Frontier Orbital Control of Molecular Conductance and its Switching. Angew. Chem., Int. Ed. 2014, 53 (16), 4093−4097. (13) Huskinson, B.; Marshak, M. P.; Suh, C.; Er, S.; Gerhardt, M. R.; Galvin, C. J.; Chen, X.; Aspuru-Guzik, A.; Gordon, R. G.; Aziz, M. J. A metal-free organic-inorganic aqueous flow battery. Nature 2014, 505 (7482), 195−8. (14) Lin, K.; Chen, Q.; Gerhardt, M. R.; Tong, L.; Kim, S. B.; Eisenach, L.; Valle, A. W.; Hardee, D.; Gordon, R. G.; Aziz, M. J.; Marshak, M. P. Alkaline quinone flow battery. Science 2015, 349 (6255), 1529−32. (15) Sanchez-Lengeling, B.; Aspuru-Guzik, A. Inverse molecular design using machine learning: Generative models for matter engineering. Science 2018, 361 (6400), 360−365. (16) Wang, S.; Zhao, X.; Cochell, T.; Manthiram, A. NitrogenDoped Carbon Nanotube/Graphite Felts as Advanced Electrode Materials for Vanadium Redox Flow Batteries. J. Phys. Chem. Lett. 2012, 3 (16), 2164−7. (17) Lin, K.; Gomez-Bombarelli, R.; Beh, E. S.; Tong, L.; Chen, Q.; Valle, A.; Aspuru-Guzik, A.; Aziz, M. J.; Gordon, R. G. A redox-flow battery with an alloxazine-based organic electrolyte. Nat. Energy 2016, 1, 16102. (18) Sum, E.; Rychcik, M.; Skyllas-Kazacos, M. Investigation of the V (V)/V (IV) system for use in the positive half-cell of a redox battery. J. Power Sources 1985, 16, 85−95. (19) Sum, E.; Skyllas-Kazacos, M. A study of the V (II)/V (III) redox couple for redox flow cell applications. J. Power Sources 1985, 15 (2−3), 179−190.
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DOI: 10.1021/acs.iecr.8b06391 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
