Quantifying the impact of viscosity on mass-transfer coefficients in redox flow batteries

Barton, John L.; Milshtein, Jarrod D.; Hinricher, Jesse J.; Brushett, Fikile R.

doi:10.1016/j.jpowsour.2018.07.046

Cited by 86 publications

(117 citation statements)

References 65 publications

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“…We note that some prior reports have chosen to describe electrolyte velocity as an average interstitial velocity by accounting for the electrode porosity in the equation above. 37,51 We elect not to do so here due to the uncertainty associated with porosity and its variation under compression for the different electrode materials. 53 Electrode performances are evaluated at four different electrolyte velocities, 0.5, 1.5, 5.0 and 20 cm s −1 , which correspond to a two order of magnitude range of volumetric flow rates, 0.87 mL min −1 to 75.60 mL min −1 .…”

Section: Methodsmentioning

confidence: 99%

Exploring the Role of Electrode Microstructure on the Performance of Non-Aqueous Redox Flow Batteries

Forner‐Cuenca

Penn

Oliveira

et al. 2019

J. Electrochem. Soc.

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138

259

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Redox flow batteries are an emerging technology for long-duration grid energy storage, but further cost reductions are needed to accelerate adoption. Improving electrode performance within the electrochemical stack offers a pathway to reduced system cost through decreased resistance and increased power density. To date, most research efforts have focused on modifying the surface chemistry of carbon electrodes to enhance reaction kinetics, electrochemically active surface area, and wettability. Less attention has been given to electrode microstructure, which has a significant impact on reactant distribution and pressure drop within the flow cell.Here, drawing from commonly used carbon-based diffusion media (paper, felt, cloth), we systematically investigate the influence of electrode microstructure on electrochemical performance. We employ a range of techniques to characterize the microstructure, pressure drop, and electrochemically active surface area in combination with in-operando diagnostics performed in a single electrolyte flow cell using a kinetically facile redox couple dissolved in a non-aqueous electrolyte. Of the materials tested, the cloth electrode shows the best performance; the highest current density at a set overpotential accompanied by the lowest hydraulic resistance. We hypothesize that the bimodal pore size distribution and periodic, well-defined microstructure of the cloth are key to lowering mass transport resistance.

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Section: Methodsmentioning

confidence: 99%

Exploring the Role of Electrode Microstructure on the Performance of Non-Aqueous Redox Flow Batteries

Forner‐Cuenca

Penn

Oliveira

et al. 2019

J. Electrochem. Soc.

Self Cite

138

259

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“…This section describes the components of the model and their integration into the complete flow battery model, including descriptions of the porous electrodes, membrane, and shunt currents. In brief, the porous electrode model extends upon prior work to accommodate asymmetric kinetics and various states-of-charge (SoCs) [72,73]. The membrane polarization adds linearly to the cell polarization with increases in current, and the model includes a simplistic representation of both concentration-and potential-driven active-species crossover.…”

Section: System Modelsmentioning

confidence: 99%

“…The electrode polarization model was adapted from past work, where it was used to estimate mass transfer coefficients as a function of operating conditions and material properties [72,73]. In that work, the systems analyzed employed model iron-based RAEs with moderately fast and near-symmetric kinetics.…”

Section: Electrode Polarizationmentioning

confidence: 99%

“…Arguably the most accredited VRFB models have been developed through the complementary work of Shah et al and You et al [68][69][70][71], which incorporate numerous physical parameters into a 2D model of the vanadium flow cell. These cell-level models include kinetic (Butler-Volmer), conductivity, and mass-transfer losses in a similar manner to the one used here [72,73]. Each of these models leverage some prior developments from Newman and Tiedemann to describe the porous electrode [74,75].…”

Section: Introductionmentioning

confidence: 99%

“…The major modeled components of the single cell include the porous electrodes, the membrane, and the tanks. The porous electrode model estimates cell losses from mass-transfer, kinetics, and distributed conductivity losses within the electrolyte phase using a numerical solution to a previously reported 1D polarization model [72,73]. With the growing interest in the role of mass-transfer in RFBs, we incorporate hydraulic losses through the porous electrode to offset the electrochemical performance benefits of high flow rates [58].…”

Section: Introductionmentioning

confidence: 99%

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A One-Dimensional Stack Model for Redox Flow Battery Analysis and Operation

Barton

Brushett

2019

Batteries

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Current redox flow battery (RFB) stack models are not particularly conducive to accurate yet high-throughput studies of stack operation and design. To facilitate system-level analysis, we have developed a one-dimensional RFB stack model through the combination of a one-dimensional Newman-type cell model and a resistor-network to evaluate contributions from shunt currents within the stack. Inclusion of hydraulic losses and membrane crossover enables constrained optimization of system performance and allows users to make recommendations for operating flow rate, current densities, and cell design given a subset of electrolyte and electrode properties. Over the range of experimental conditions explored, shunt current losses remain small, but mass-transfer losses quickly become prohibitive at high current densities. Attempting to offset mass-transfer losses with high flow rates reduces system efficiency due to the increase in pressure drop through the porous electrode. The development of this stack model application, along with the availability of the source MATLAB code, allows for facile approximation of the upper limits of performance with limited empiricism. This work primarily presents a readily adaptable tool to enable researchers to perform either front-end performance estimates based on fundamental material properties or to benchmark their experimental results.

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