Direct Measurement of Crossover and Interfacial Resistance of Ion-Exchange Membranes in All-Vanadium Redox Flow Batteries

Gandomi, Yasser Ashraf; Aaron, Douglas; Nolan, Zachary B; Ahmadi, Arya; Mench, Matthew M.

doi:10.3390/membranes10060126

Cited by 17 publications

(4 citation statements)

References 32 publications

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“…84 We posit that the resistance of ion-exchange membranes may exhibit qualitatively-similar trends, however, the specific relationship between temperature and conductivity likely requires consideration of additional phenomena such as ion interactions, species partitioning, and swelling. 85,86 While the mass transfer resistance did not decrease as significantly as the ohmic resistance, the transport rate measurably improved. The smaller magnitude of mass transfer improvement may be attributed to the relatively weak relationship between viscosity (μ, Pa s), active species diffusivity (D, m 2 s -1 ), and mass transfer rate (k m , m s -1 ), which can be described by empirical power-law correlations.…”

Section: Flow Cell Testingmentioning

confidence: 96%

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

Quinn,

Ripley,

Matteucci

et al. 2023

J. Electrochem. Soc.

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The impact of cell temperature is a relatively underexplored area within the burgeoning field of nonaqueous redox flow batteries (NAqRFBs). Here, we investigate the effect of elevated temperature on the performance of nonaqueous redox electrolytes and associated flow cells. Using a model compound, N-(2-(2-methoxyethoxy)-ethyl)phenothiazine (MEEPT), in a propylene-carbonate-based electrolyte, we experimentally measure the temperature dependence of relevant physicochemical properties (i.e., electrolyte conductivity, viscosity, diffusivity) and electrochemical characteristics (i.e., chemical and electrochemical reversibility) across a temperature range of 30 °C to 70 °C. We then perform flow cell studies, finding that while ohmic and mass transport resistances decrease significantly with increases in temperature for the MEEPT/MEEPT+· redox couple, accessible electrolyte capacity gradually reduces at temperatures > 50 °C. Ex-situ, post-test characterization using microelectrode voltammetry suggests that this capacity fade is due to instability of the MEEPT radical cation. Finally, using MEEPT as a posolyte and a model viologen negolyte (bis(2-(2-methoxyethoxy)ethyl)viologen), we assemble a full cell and perform polarization analyses, observing a 2× increase in the peak power density when the operating temperature is increased from 30 °C to 70 °C. Broadly, this work highlights opportunities for systematic engineering of nonaqueous electrolytes and flow cells for higher power operation at elevated temperatures.

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Section: Flow Cell Testingmentioning

confidence: 96%

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

Quinn,

Ripley,

Matteucci

et al. 2023

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…79 We posit that the resistance of ion-exchange membranes may exhibit qualitatively-similar trends, however the specific relationship between temperature and conductivity likely requires consideration of additional phenomena such as ion interactions, species partitioning, and swelling. 80,81 While the mass transfer resistance did not decrease as significantly as the ohmic resistance, the transport rate measurably improved, the benefits of which are likely to be amplified at lower flow rates. 46,82 The smaller magnitude of mass transfer improvement may be attributed to the relatively weak relationship between viscosity (μ, Pa s), active species diffusivity (D, m 2 s -1 ), and mass transfer rate (km, m s -1 ), which can be described by empirical power-law correlations.…”

Section: Flow Cell Testingmentioning

confidence: 97%

Elucidating the effects of temperature on nonaqueous redox flow cell cycling performance

Quinn

Ripley

Matteucci

et al. 2023

Preprint

View full text Add to dashboard Cite

The impact of cell temperature is a relatively underexplored area within the burgeoning field of nonaqueous redox flow batteries (NAqRFBs). Here, we investigate the effect of elevated temperature on the performance of nonaqueous redox electrolytes and associated flow cells. Using a model compound, N-(2-(2-methoxyethoxy)-ethyl)phenothiazine (MEEPT), in a propylene-carbonate-based electrolyte, we experimentally measure the temperature dependence of relevant physicochemical properties (i.e., electrolyte conductivity, viscosity, diffusivity) and electrochemical characteristics (i.e., chemical and electrochemical reversibility) from 30 to 70 °C. We then perform symmetric cell studies, finding that while ohmic and mass transport resistances decrease significantly with increases in temperature, for the MEEPT/MEEPT+● redox couple, accessible electrolyte capacity gradually reduces at temperatures >50 °C. Ex-situ, post-test characterization using microelectrode voltammetry suggests that this capacity fade is due to instability of the MEEPT radical cation. Finally, using MEEPT as a posolyte and a model viologen negolyte (bis(2-(2-methoxyethoxy)ethyl)viologen), we assemble a full cell and perform polarization analysis, observing a 2× increase in the peak power density when the operating temperature is increased from 30 to 70 °C. Broadly, this work highlights opportunities for systematic engineering of nonaqueous electrolytes and flow cells for higher power operation at elevated temperatures.

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“…However, we note that consistency between ex situ and in situ methods is not expected for all redox chemistries, as membrane properties may vary with electrolyte SOC and with time. [39][40][41][42] Thus, we emphasize that the transport characteristics measured by CUSCC are potentially more representative of flow cell conditions, and this technique may better capture non-idealities for less well-behaved chemistries. Using the best-fit parameters as inputs, the dashed lines in Fig.…”

Section: Mmentioning

confidence: 99%

A Method for Quantifying Crossover in Redox Flow Cells through Compositionally Unbalanced Symmetric Cell Cycling

Neyhouse

Darling

Saraidaridis

et al. 2023

J. Electrochem. Soc.

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Active species crossover continues to frustrate durational performance for redox flow batteries (RFBs), requiring thorough evaluation of membrane / separator properties. Characterization workflows typically employ a suite of ex situ experimental techniques, but these approaches do not capture the dynamic conditions (e.g., variable concentrations, alternating polarity) encountered in redox flow cells. Here, we report a facile method for assessing crossover directly in redox flow cells—compositionally unbalanced symmetric cell cycling (CUSCC). Based on conventional symmetric cell cycling, CUSCC imposes a concentration gradient between two chemically similar half-cells, inducing species crossover during galvanostatic cycling, which results in a characteristic “capacity gain” over time. We first develop a zero-dimensional model to describe fundamental processes that underpin the technique and examine the dependence of capacity gain on membrane / separator properties and operating conditions. Subsequently, we perform proof-of-principle experiments using FeCl2 / FeCl3 and NafionTM 117 as a representative system and demonstrate results consistent with those predicted from simulations. Finally, we use model fits of the capacity gain data to extract membrane transport parameters, obtaining similar values to those measured from ex situ techniques. Overall, this work describes a promising new approach for characterizing species crossover and expands the RFB testing toolbox.

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Direct Measurement of Crossover and Interfacial Resistance of Ion-Exchange Membranes in All-Vanadium Redox Flow Batteries

Cited by 17 publications

References 32 publications

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

Elucidating the Effects of Temperature on Nonaqueous Redox Flow Cell Cycling Performance

Elucidating the effects of temperature on nonaqueous redox flow cell cycling performance

A Method for Quantifying Crossover in Redox Flow Cells through Compositionally Unbalanced Symmetric Cell Cycling

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