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Redox Flow Batteries: Developments and Applications

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Electrochemistry".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 37024

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Dr. Joanna Krakowiak

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Guest Editor

Faculty of Chemistry, Physical Chemistry Deparment, Gdańsk University of Technology, Gdansk, Poland
Interests: volumetric and acoustic features of liquids; the interactions in aqueous solutions of osmolytes with particular emphasis on their impact on the stability of protein structures (including amyloid formation); the chemistry of the redox flow batteries

Dr. Petr Mazur

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Co-Guest Editor

University of Chemistry and Technology Prague, Department of Chemical Engineering, Technicka 5, 166 28 Prague, Czech Republic
Interests: energy storage; electrochemical energy conversion; flow battery; fuel cell; carbon-based electrodes; ion-exchange membranes; organic redox couples

Dr. Peter Fischer

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Co-Guest Editor

Fraunhofer Institute for Chemical Technology ICT, Pfinztal, Germany
Interests: material characterization; energy storage; materials chemistry; electrochemistry

Special Issue Information

Dear Colleagues,

Storing and releasing electricity is becoming a growing need of civilization at present. Electrical energy storage technologies are required to solve the problems associated to inconsistency between energy production and consumption. Among other energy storage technologies, redox flow batteries (RFBs) have shown huge promise for large amounts of electrical energy stored for several applications (e.g., intermittent renewable, smart-grid), because of their unique features, i.e., decoupled power and energy, simplified heat removal, and non-flammability (for most of the aqueous systems). In spite of these outstanding merits, however, this technology currently displays some drawbacks, such as low energy density and high cost, in comparison with conventional batteries. While current RFB technologies use metal-redox species (all-vanadium, iron, copper, zinc–air, among others), next-generation RFBs are being developed in the form of, for example, organic redox flow batteries or semi-solid flow slurries.

Due to the interdisciplinary character of this research topic, this Special Issue invites papers on (but not limited to): electrochemistry of battery; material science, including active and passive components; membrane physicochemistry; state of charge diagnostics; transport phenomena; safety and reliability of the operation; lifetime and degradation; thermal management; battery performance, testing and monitoring; stack technology; hybrid battery systems; applications in real environments; costs and market; modeling and simulation.

Dr. Joanna Krakowiak
Dr. Petr Mazur
Dr. Peter Fischer
Guest Editors

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Keywords

Energy storage
Redox flow battery
Renewable energy
Ion-exchange membrane
Electrocatalysis
Hybrid system
State of charge

Published Papers (10 papers)

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Research

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20 pages, 2116 KiB

Open AccessArticle

Pristine and Modified Porous Membranes for Zinc Slurry–Air Flow Battery

by Misgina Tilahun Tsehaye, Getachew Teklay Gebreslassie, Nak Heon Choi, Diego Milian, Vincent Martin, Peter Fischer, Jens Tübke, Nadia El Kissi, Mateusz L. Donten, Fannie Alloin and Cristina Iojoiu

Molecules 2021, 26(13), 4062; https://doi.org/10.3390/molecules26134062 - 02 Jul 2021

Cited by 13 | Viewed by 3657

Abstract

The membrane is a crucial component of Zn slurry–air flow battery since it provides ionic conductivity between the electrodes while avoiding the mixing of the two compartments. Herein, six commercial membranes (Cellophane™ 350PØØ, Zirfon^®, Fumatech^® PBI, Celgard^® 3501, 3401 and 5550) were first characterized in terms of electrolyte uptake, ion conductivity and zincate ion crossover, and tested in Zn slurry–air flow battery. The peak power density of the battery employing the membranes was found to depend on the in-situ cell resistance. Among them, the cell using Celgard^® 3501 membrane, with in-situ area resistance of 2 Ω cm² at room temperature displayed the highest peak power density (90 mW cm⁻²). However, due to the porous nature of most of these membranes, a significant crossover of zincate ions was observed. To address this issue, an ion-selective ionomer containing modified poly(phenylene oxide) (PPO) and N-spirocyclic quaternary ammonium monomer was coated on a Celgard^® 3501 membrane and crosslinked via UV irradiation (PPO-3.45 + 3501). Moreover, commercial FAA-3 solutions (FAA, Fumatech) were coated for comparison purpose. The successful impregnation of the membrane with the anion-exchange polymers was confirmed by SEM, FTIR and Hg porosimetry. The PPO-3.45 + 3501 membrane exhibited 18 times lower zincate ions crossover compared to that of the pristine membrane (5.2 × 10⁻¹³ vs. 9.2 × 10⁻¹² m² s⁻¹). With low zincate ions crossover and a peak power density of 66 mW cm⁻², the prepared membrane is a suitable candidate for rechargeable Zn slurry–air flow batteries. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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18 pages, 3678 KiB

Open AccessArticle

Novel, Stable Catholyte for Aqueous Organic Redox Flow Batteries: Symmetric Cell Study of Hydroquinones with High Accessible Capacity

by Xian Yang, Sergio Navarro Garcia, Tobias Janoschka, Dénes Kónya, Martin D. Hager and Ulrich S. Schubert

Molecules 2021, 26(13), 3823; https://doi.org/10.3390/molecules26133823 - 23 Jun 2021

Cited by 16 | Viewed by 3462

Abstract

Owing to their broad range of redox potential, quinones/hydroquinones can be utilized for energy storage in redox flow batteries. In terms of stability, organic catholytes are more challenging than anolytes. The two-electron transfer feature adds value when building all-quinone flow battery systems. However, the dimerization of quinones/hydroquinones usually makes it difficult to achieve a full two-electron transfer in practical redox flow battery applications. In this work, we designed and synthesized four new hydroquinone derivatives bearing morpholinomethylene and/or methyl groups in different positions on the benzene ring to probe molecular stability upon battery cycling. The redox potential of the four molecules were investigated, followed by long-term stability tests using different supporting electrolytes and cell cycling methods in a symmetric flow cell. The derivative with two unoccupied ortho positions was found highly unstable, the cell of which exhibited a capacity decay rate of ~50% per day. Fully substituted hydroquinones turned out to be more stable. In particular, 2,6-dimethyl-3,5-bis(morpholinomethylene)benzene-1,4-diol (asym-O-5) displayed a capacity decay of only 0.45%/day with four-week potentiostatic cycling at 0.1 M in 1 M H₃PO₄. In addition, the three fully substituted hydroquinones displayed good accessible capacity of over 82%, much higher than those of conventional quinone derivatives. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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26 pages, 2482 KiB

Open AccessArticle

Systematic Study of Quaternary Ammonium Cations for Bromine Sequestering Application in High Energy Density Electrolytes for Hydrogen Bromine Redox Flow Batteries

by Michael Küttinger, Paulette A. Loichet Torres, Emeline Meyer, Peter Fischer and Jens Tübke

Molecules 2021, 26(9), 2721; https://doi.org/10.3390/molecules26092721 - 06 May 2021

Cited by 13 | Viewed by 3273

Abstract

Bromine complexing agents (BCAs) are used to reduce the vapor pressure of bromine in the aqueous electrolytes of bromine flow batteries. BCAs bind hazardous, volatile bromine by forming a second, heavy liquid fused salt. The properties of BCAs in a strongly acidic bromine electrolyte are largely unexplored. A total of 38 different quaternary ammonium halides are investigated ex situ regarding their properties and applicability in bromine electrolytes as BCAs. The focus is on the development of safe and performant HBr/Br₂/H₂O electrolytes with a theoretical capacity of 180 Ah L⁻¹ for hydrogen bromine redox flow batteries (H₂/Br₂-RFB). Stable liquid fused salts, moderate bromine complexation, large conductivities and large redox potentials in the aqueous phase of the electrolytes are investigated in order to determine the most applicable BCA for this kind of electrolyte. A detailed study on the properties of BCA cations in these parameters is provided for the first time, as well as for electrolyte mixtures at different states of charge of the electrolyte. 1-ethylpyridin-1-ium bromide [C2Py]Br is selected from 38 BCAs based on its properties as a BCA that should be focused on for application in electrolytes for H₂/Br₂-RFB in the future. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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15 pages, 2716 KiB

Open AccessArticle

Evaluation of Electrochemical Stability of Sulfonated Anthraquinone-Based Acidic Electrolyte for Redox Flow Battery Application

by Petr Mazúr, Jiří Charvát, Jindřich Mrlík, Jaromír Pocedič, Jiří Akrman, Lubomír Kubáč, Barbora Řeháková and Juraj Kosek

Molecules 2021, 26(9), 2484; https://doi.org/10.3390/molecules26092484 - 24 Apr 2021

Cited by 12 | Viewed by 3009

Abstract

Despite intense research in the field of aqueous organic redox flow batteries, low molecular stability of electroactive compounds limits further commercialization. Additionally, currently used methods typically cannot differentiate between individual capacity fade mechanisms, such as degradation of electroactive compound and its cross-over through the membrane. We present a more complex method for in situ evaluation of (electro)chemical stability of electrolytes using a flow electrolyser and a double half-cell including permeation measurements of electrolyte cross-over through a membrane by a UV–VIS spectrometer. The method is employed to study (electro)chemical stability of acidic negolyte based on an anthraquinone sulfonation mixture containing mainly 2,6- and 2,7-anthraquinone disulfonic acid isomers, which can be directly used as an RFB negolyte. The effect of electrolyte state of charge (SoC), current load and operating temperature on electrolyte stability is tested. The results show enhanced capacity decay for fully charged electrolyte (0.9 and 2.45% per day at 20 °C and 40 °C, respectively) while very good stability is observed at 50% SoC and lower, even at 40 °C and under current load (0.02% per day). HPLC analysis conformed deep degradation of AQ derivatives connected with the loss of aromaticity. The developed method can be adopted for stability evaluation of electrolytes of various organic and inorganic RFB chemistries. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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13 pages, 16635 KiB

Open AccessArticle

Electrochemical Characterization of Aromatic Molecules with 1,4-Diaza Groups for Flow Battery Applications

by Alexandros Pasadakis-Kavounis, Vanessa Baj and Johan Hjelm

Molecules 2021, 26(8), 2227; https://doi.org/10.3390/molecules26082227 - 12 Apr 2021

Cited by 9 | Viewed by 3149

Abstract

The aqueous redox flow battery is a promising technology for large-scale low cost energy storage. The rich possibilities for the tailoring of organic molecules and the possibility to discover active materials of lower cost and decreased environmental impact continue to drive research and development of organic compounds suitable for redox flow battery applications. In this work, we focus on the characterization of aromatic molecules with 1,4-diaza groups for flow battery applications. We examine the influence of electron-withdrawing and electron-donating substituents and the effect of the relative position of the substituent(s) on the molecule. We found that electron-withdrawing substituents increased the potential, while electron-donating decreased it, in agreement with expectations. The number of carboxy-groups on the pyrazinic ring was found to have a strong impact on the heterogeneous electron transfer kinetics, with the slowest kinetics observed for pyrazine-2,3,5,6-tetracarboxylic acid. The stability of quinoxaline was investigated by cyclic voltammetry and in a flow cell configuration. Substitution at the 2,3-positions in quinoxaline was found to decrease the capacity fade rate significantly. Furthermore, we demonstrated how molecular aggregation reduces the effective number of electrons involved in the redox process for quinoxalines. This translates to a significant reduction of the achievable volumetric capacity at higher concentrations, yielding values significantly lower than the theoretical capacity. Finally, we demonstrate that such capacity-limiting molecular aggregation may be reduced by introducing flexible side chains with bulky charged groups in order to increase electrostatic repulsion and steric hindrance. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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19 pages, 3686 KiB

Open AccessArticle

Thermodynamics, Charge Transfer and Practical Considerations of Solid Boosters in Redox Flow Batteries

by Mahdi Moghaddam, Silver Sepp, Cedrik Wiberg, Antonio Bertei, Alexis Rucci and Pekka Peljo

Molecules 2021, 26(8), 2111; https://doi.org/10.3390/molecules26082111 - 07 Apr 2021

Cited by 13 | Viewed by 4374

Abstract

Solid boosters are an emerging concept for improving the performance and especially the energy storage density of the redox flow batteries, but thermodynamical and practical considerations of these systems are missing, scarce or scattered in the literature. In this paper we will formulate how these systems work from the point of view of thermodynamics. We describe possible pathways for charge transfer, estimate the overpotentials required for these reactions in realistic conditions, and illustrate the range of energy storage densities achievable considering different redox electrolyte concentrations, solid volume fractions and solid charge storage densities. Approximately 80% of charge storage capacity of the solid can be accessed if redox electrolyte and redox solid have matching redox potentials. 100 times higher active areas are required from the solid boosters in the tank to reach overpotentials of <10 mV. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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15 pages, 6068 KiB

Open AccessArticle

Composite Polybenzimidazole Membrane with High Capacity Retention for Vanadium Redox Flow Batteries

by Jacobus C. Duburg, Kobra Azizi, Søren Primdahl, Hans Aage Hjuler, Elena Zanzola, Thomas J. Schmidt and Lorenz Gubler

Molecules 2021, 26(6), 1679; https://doi.org/10.3390/molecules26061679 - 17 Mar 2021

Cited by 16 | Viewed by 3343 | Correction

Abstract

Currently, energy storage technologies are becoming essential in the transition of replacing fossil fuels with more renewable electricity production means. Among storage technologies, redox flow batteries (RFBs) can represent a valid option due to their unique characteristic of decoupling energy storage from power output. To push RFBs further into the market, it is essential to include low-cost materials such as new generation membranes with low ohmic resistance, high transport selectivity, and long durability. This work proposes a composite membrane for vanadium RFBs and a method of preparation. The membrane was prepared starting from two polymers, meta-polybenzimidazole (6 μm) and porous polypropylene (30 μm), through a gluing approach by hot-pressing. In a vanadium RFB, the composite membrane exhibited a high energy efficiency (~84%) and discharge capacity (~90%) with a 99% capacity retention over 90 cycles at 120 mA·cm⁻², exceeding commercial Nafion^® NR212 (~82% efficiency, capacity drop from 90% to 40%) and Fumasep^® FAP-450 (~76% efficiency, capacity drop from 80 to 65%). Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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11 pages, 2387 KiB

Open AccessArticle

Aqueous Solubility of Organic Compounds for Flow Battery Applications: Symmetry and Counter Ion Design to Avoid Low-Solubility Polymorphs

by Sergio Navarro Garcia, Xian Yang, Laura Bereczki and Dénes Kónya

Molecules 2021, 26(5), 1203; https://doi.org/10.3390/molecules26051203 - 24 Feb 2021

Cited by 10 | Viewed by 2966

Abstract

Flow batteries can play an important role as energy storage media in future electricity grids. Organic compounds, based on abundant elements, are appealing alternatives as redox couples for redox flow batteries. The straightforward scalability, the independence of material sources, and the potentially attractive price motivate researchers to investigate this technological area. Four different benzyl-morpholino hydroquinone derivatives were synthesized as potential redox active species. Compounds bearing central symmetry were shown to be about an order of magnitude less soluble in water than isomers without central symmetry. Counter ions also affected solubility. Perchlorate, chlorate, sulfate and phosphate anions were investigated as counter ions. The formations of different polymorphs was observed, showing that their solubility is not a function of their structure. The kinetics of the transformation can give misleading solubility values according to Ostwald’s rule. The unpredictability of both the kinetics and the thermodynamics of the formation of polymorphs is a danger for new organic compounds designed for flow battery applications. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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Review

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39 pages, 4393 KiB

Open AccessReview

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

by Peter Fischer, Petr Mazúr and Joanna Krakowiak

Molecules 2022, 27(2), 560; https://doi.org/10.3390/molecules27020560 - 16 Jan 2022

Cited by 24 | Viewed by 7223

Abstract

Redox flow batteries (RFBs) are an increasingly attractive option for renewable energy storage, thus providing flexibility for the supply of electrical energy. In recent years, research in this type of battery storage has been shifted from metal-ion based electrolytes to soluble organic redox-active compounds. Aqueous-based organic electrolytes are considered as more promising electrolytes to achieve “green”, safe, and low-cost energy storage. Many organic compounds and their derivatives have recently been intensively examined for application to redox flow batteries. This work presents an up-to-date overview of the redox organic compound groups tested for application in aqueous RFB. In the initial part, the most relevant requirements for technical electrolytes are described and discussed. The importance of supporting electrolytes selection, the limits for the aqueous system, and potential synthetic strategies for redox molecules are highlighted. The different organic redox couples described in the literature are grouped in a “family tree” for organic redox couples. This article is designed to be an introduction to the field of organic redox flow batteries and aims to provide an overview of current achievements as well as helping synthetic chemists to understand the basic concepts of the technical requirements for next-generation energy storage materials. Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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4 pages, 199 KiB

Open AccessCorrection

Correction: Duburg et al. Composite Polybenzimidazole Membrane with High Capacity Retention for Vanadium Redox Flow Batteries. Molecules 2021, 26, 1679

by Jacobus C. Duburg, Kobra Azizi, Søren Primdahl, Hans Aage Hjuler, Elena Zanzola, Thomas J. Schmidt and Lorenz Gubler

Molecules 2022, 27(13), 4234; https://doi.org/10.3390/molecules27134234 - 30 Jun 2022

Viewed by 911

Abstract

The authors wish to make the following changes to their paper [...] Full article

(This article belongs to the Special Issue Redox Flow Batteries: Developments and Applications)

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