Poly(boron-dipyrromethene)—A Redox-Active Polymer Class for Polymer Redox-Flow Batteries

Winsberg, Jan; Hagemann, Tino; Muench, Simon; Friebe, Christian; Häupler, Bernhard; Janoschka, Tobias; Morgenstern, Sabine; Hager, Martin D.; Schubert, Ulrich S.

doi:10.1021/acs.chemmater.6b00640

Cited by 107 publications

(105 citation statements)

References 37 publications

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“…A long term cycling study was performed using 100 charge–discharge cycles. As shown in Figure the charging capacity decreases throughout the first 40 cycles, consistent with dynamic capacities previously observed for a polymeric BODIPY study . After an induction phase of 40 cycles, stable battery cycling was observed.…”

Section: Resultssupporting

confidence: 86%

Characterization of a BODIPY Dye as an Active Species for Redox Flow Batteries

2016

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An all-organic redox flow battery (RFB) employing a fluorescent boron-dipyrromethene (BODIPY) dye (PM567) was investigated. In a RFB, the stability of the electrolyte in all charged states is critically linked to coulombic efficiency. To evaluate stability, bulk electrolysis and cyclic voltammetry (CV) experiments were performed. Oxidized and reduced, PM567 does not remain intact; however, the products of bulk electrolysis evolve over time to show stable redox behavior, making the dye a precursor for the active species of an RFB. A theoretical cell potential of 2.32 V was predicted from CV experiments with a working discharge voltage of approximately 1.6 V in a static test cell. Mass spectrometry was used to identify the products of bulk electrolysis. Related experiments were carried out using ferrocene and cobaltocenium hexafluorophosphate as redox-stable benchmarks to further explain the stability results. The coulombic efficiency of a model cell using PM567 as a precursor for charge carriers stabilized around 73 %.

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Section: Resultssupporting

confidence: 86%

Characterization of a BODIPY Dye as an Active Species for Redox Flow Batteries

2016

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“…Identifying thinner or more conductive separators can alleviate ohmic resistances; recent literature on size selective separators for NAqRFBs is providing a pathway toward separators that are sufficiently conductive and selective. [54][55][56][57] Interestingly, the ohmic loss through the porous electrode is negligible compared to the ohmic loss through the separator. Mass transfer losses are the second largest impediment to flow cell performance and can be alleviated by increasing electrolyte flow rate, increasing active species concentration, or decreasing electrolyte viscosity.…”

Section: Discussionmentioning

confidence: 99%

“…The implementation of the MeCN-based electrolyte and Celgard 2500 separator is critical in achieving low ASR, but the Celgard 2500 separator is impractical for a NAqRFB device since it offers no selectivity for small redox active molecules. Implementing Celgard 2500 in full flow cell would require mixed active species electrolytes, 21,23,41,83 which would be cost prohibitive, 7,12,23,41 or emerging large polymeric active species, [55][56][57] which may yield high viscosity electrolytes with poor mass transfer characteristics. 84 Additionally, the highly soluble Fc1N112 +/2+ model active species and low viscosity MeCN-based electrolyte facilitates small mass transfer resistances.…”

Section: 76mentioning

confidence: 99%

Towards Low Resistance Nonaqueous Redox Flow Batteries

Milshtein

Barton

Carney

et al. 2017

J. Electrochem. Soc.

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Nonaqueous redox flow batteries (NAqRFBs) are a promising, but nascent, concept for cost-effective grid-scale energy storage. While most studies report new active molecules and proof-of-concept prototypes, few discuss cell design. The direct translation of aqueous RFB design principles to nonaqueous systems is hampered by a lack of materials-specific knowledge, especially concerning the increased viscosities and decreased conductivities associated with nonaqueous electrolytes. To guide NAqRFB reactor design, recent techno-economic analyses have established an area specific resistance (ASR) target of <5 cm 2 . Here, we employ a state-of-the-art vanadium flow cell architecture, modified for compatibility with nonaqueous electrolytes, and a model ferrocene-based redox couple to investigate the feasibility of achieving this target ASR. We identify and minimize sources of resistive loss for various active species concentrations, electrolyte compositions, flow rates, separators, and electrode thicknesses via polarization and impedance spectroscopy, culminating in the demonstration of a cell ASR of ca. 1.7 cm 2 . Further, we validate performance scalability using dynamically similar cells with a ten-fold difference in active areas. This work demonstrates that, with appropriate cell engineering, low resistance nonaqueous reactors can be realized, providing promise for the cost-competitiveness of future NAqRFBs. Grid-scale energy storage has emerged as a critical technology for alleviating the intermittency of renewables, 1 improving the efficiency of the existing grid infrastructure, and offering frequency or voltage regulation.2 Redox flow batteries (RFBs) are particularly attractive storage devices for energy-intensive grid applications.2,3 In a typical RFB, charge-storing active species are dissolved in liquid electrolytes, which are housed in large and inexpensive tanks. The electrolytes are pumped through a power-generating electrochemical reactor, where the active species undergo reduction or oxidation on the surfaces of porous electrodes to charge or discharge the battery. [3][4][5][6] This unique architecture offers several advantages over conventional battery systems, including decoupled power and energy scaling, long operational lifetimes, easy maintenance, simplified manufacturing, and high active-to-inactive materials ratio (particularly at long storage durations). Despite many attractive features, state-of-the-art RFBs are currently too expensive for widespread adoption.7 While the majority of RFB electrolytes are aqueous, 6 transitioning to nonaqueous chemistries could enable higher cell potentials via wider electrolyte stability windows, subsequently increasing the electrolyte energy density and reducing chemical costs. 6,[8][9][10][11] Furthermore, the use of nonaqueous solvents enables a broader palette of potentially inexpensive active materials, which could significantly lower RFB costs. 7,12 In contrast to their aqueous counterparts, nonaqueous redox flow batteries (NAqRFBs) are a nascent technology,...

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“…A unique aspect of RFBs is the spatial separation of the electrodes from the reservoirs serving to decouple energy (stored capacity) and power (energy released per unit time). A moderate library of electrolyte materials including complexes, organic compounds, and redox active polymers has been explored as charge‐carriers in RFBs; however, the broad‐scale implementation of these devices is hindered by the lack of suitable charge‐carriers.…”

Section: Introductionmentioning

confidence: 99%

Repurposing the Industrial Dye Methylene Blue as an Active Component for Redox Flow Batteries

Kosswattaarachchi

Cook

2018

ChemElectroChem

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Methylene blue is a common component of industrial wastewater in the textile industry. The redox properties of this environmentally damaging molecule make it suitable for use in the electrolyte solutions of aqueous redox flow batteries. Here, we carry out electrochemical analyses of aqueous methylene blue solutions to establish the dye as a pH tuneable, two‐electron redox transfer agent with fast transfer kinetics. Galvanostatic charge‐discharge experiments demonstrated ∼100 % coulombic efficiency for 50 cycles over seven days. Cycling performance was dependent on the membrane separator used. Cells containing an AMI‐7001 membrane showed a capacity decay with the state‐of‐charge falling to 56 % due to dye adsorption. Nafion NE1035 showed no adsorption nor membrane crossover. The combination of chemical and redox stability, and fast kinetics motivate the recycling of methylene blue wastewater as the basis for flow battery electrolyte solutions.

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Poly(boron-dipyrromethene)—A Redox-Active Polymer Class for Polymer Redox-Flow Batteries

Cited by 107 publications

References 37 publications

Characterization of a BODIPY Dye as an Active Species for Redox Flow Batteries

Characterization of a BODIPY Dye as an Active Species for Redox Flow Batteries

Towards Low Resistance Nonaqueous Redox Flow Batteries

Repurposing the Industrial Dye Methylene Blue as an Active Component for Redox Flow Batteries

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