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Iron-Based Flow Batteries: Improving Lifetime and Performance

selverston, steven
http://rave.ohiolink.edu/etdc/view?acc_num=case1495709157583731

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.
For grid-scale energy storage applications, iron-based hybrid flow batteries have advantages of safety, sustainability and low-cost. Still, several challenges such as device lifetime and efficiency have limited their development. In this work, a new type of hydrogen-ferric ion recombination reactor based on catalyzed, three-dimensional felt is proposed in order to maintain chemical balance in the electrolytes and hence improve the battery stability and lifetime. Cyclic voltammetry (CV) and electrochem- ical impedance spectroscopy (EIS) were used to identify a diffusion-limited hydrogen oxidation current near 0.3 psig of hydrogen partial pressure and show that the perfor- mance can be improved with increasing hydrogen pressure up to about P H 2 = 10 psig. Also, pressure-based measurements showed that high rates of hydrogen recombina- tion (greater than 20 mA cm -2 based on the geometric area and greater than 100 mA cm -2 based on the cross-sectional area) were possible using a floating, membrane-less reactor design. A flow battery model that incorporates the hydrogen evolution side-reactions and chemical rebalancing was developed using a system of differential and algebraic equations (DAE). A good agreement between simulated and measured pressure profiles was obtained for an all-iron flow battery operating at ±100 mA cm -2 . Effects of separator porosity and thickness were simulated, showing how increased thickness and reduced porosity can cause higher pH in the negative electrolyte and hence reduced hydrogen generation. Lastly, a new hybrid flow battery based on mixed, lightly acidic electrolytes was investigated. By using the anomalous codeposition (ACD) phenomenon, it was possible to electrodeposit nearly pure zinc from mixed ZnCl 2 -FeCl 2 electrolytes. The cell was shown to provide 17 % higher voltaic efficiency and 40 % higher power density compared to an all-iron battery operating under the same conditions. A zinc-iron chloride flow battery was tested for 30 days and 175 cycles at i = ± 25 mA cm -2 and 50 mAh cm -2 charge loading (two-hour charges) without the use of dendrite suppres- sion additives, flow-fields or temperature control. The average coulombic, voltaic and energy efficiencies were 87 %, 82 % and 71 %, respectively. Therefore, with further development, zinc-iron chloride flow batteries represent a promising new approach for grid-scale energy storage.
robert savinell (Committee Chair)
jesse wainright (Committee Member)
rohan akolkar (Committee Member)
gary wnek (Committee Member)
163 p.
Chemical Engineering; Chemistry; Energy; Engineering
hybrid flow batteries; all-iron; rebalancing; zinc-iron; zn-fe; anomalous codeposition; ACD; energy storage; aqueous flow batteries; iron flow battery; system model;

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Citations

  • selverston, S. (2017). Iron-Based Flow Batteries: Improving Lifetime and Performance [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1495709157583731

    APA Style (7th edition)

  • selverston, steven. Iron-Based Flow Batteries: Improving Lifetime and Performance. 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1495709157583731.

    MLA Style (8th edition)

  • selverston, steven. "Iron-Based Flow Batteries: Improving Lifetime and Performance." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1495709157583731

    Chicago Manual of Style (17th edition)

case1495709157583731
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© 2017, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.