Experimental Protocols for Studying Organic Non-aqueous Redox Flow Batteries

Li, Min; Odom, Susan A.; Pancoast, Adam R.; Robertson, Lily A.; Vaid, Thomas P.; Agarwal, Garvit; Doan, Hieu A.; Wang, Yilin; Suduwella, T. Malsha; Bheemireddy, Sambasiva R.; Ewoldt, Randy H.; Assary, Rajeev S.; Zhang, Lu; Sigman, Matthew S.

doi:10.1021/acsenergylett.1c01675

Cited by 43 publications

(95 citation statements)

References 76 publications

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“…To evaluate whether the decrease in capacity observed in the first 50 cycles could be the result of volume and/or concentration imbalances between the two electrolytes, we inverted the polarity of the battery at that point and ran another 50 charge/discharge cycles. As shown in Figure , this indeed results in capacity recovery (to 99.5% of the initial capacity utilization at cycle 75) and demonstrates that polarity inversion in these bipolar systems can be used to rebalance the cell in a greatly simplified manner in comparison to physical rebalancing methods that require battery disassembly. , It should be noted that, in contrast to “compositionally symmetrical cells” prepared by premixing of (different) posolyte and anolyte materials, the use of intrinsically bipolar materials such as 3a allows the utilization of all electroactive material in solution. Potentiostatic electrochemical impedance spectroscopy (PEIS) measurements of the flow cell before and after cycling did not indicate a significant increase in resistance.…”

Section: Results and Discussionmentioning

confidence: 99%

Blatter Radicals as Bipolar Materials for Symmetrical Redox-Flow Batteries

et al. 2022

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Redox-active organic molecules are promising charge-storage materials for redox-flow batteries (RFBs), but material crossover between the posolyte and negolyte and chemical degradation are limiting factors in the performance of all-organic RFBs. We demonstrate that the bipolar electrochemistry of 1,2,4-benzotriazin-4-yl (Blatter) radicals allows the construction of batteries with symmetrical electrolyte composition. Cyclic voltammetry shows that these radicals also retain reversible bipolar electrochemistry in the presence of water. The redox potentials of derivatives with a C(3)-CF 3 substituent are the least affected by water, and moreover, these compounds show >90% capacity retention after charge/discharge cycling in a static H-cell for 7 days (ca. 100 cycles). Testing these materials in a flow regime at a 0.1 M concentration of the active material confirmed the high cycling stability under conditions relevant for RFB operation and demonstrated that polarity inversion in a symmetrical flow battery may be used to rebalance the cell. Chemical synthesis provides insight in the nature of the charged species by spectroscopy and (for the oxidized state) X-ray crystallography. The stability of these compounds in all three states of charge highlights their potential for application in symmetrical organic redox-flow batteries.

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Section: Results and Discussionmentioning

confidence: 99%

Blatter Radicals as Bipolar Materials for Symmetrical Redox-Flow Batteries

et al. 2022

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“…1). 44 When analyzing radical cations, excess sodium thiosulfate (Na 2 S 2 O 3 ) was added to the DMSO solution to reduce the species. The quenching of radical cations can be recognized through the color change of the solution.…”

Section: Methodsmentioning

confidence: 99%

“…The solubility was calculated by integrating the solute and the standard peaks in the 1 H NMR spectrum and obtaining their ratios (Figure S2, see example with 2-CF3EPT shown in Figure 1). 45 When analyzing radical cations, aqueous sodium thiosulfate (Na2S2O3) was added to the DMSO solution to reduce the species. The quenching of radical cations can be recognized through the color change of the solution.…”

Section: Solubility Determination Using 1 H Nmr Spectroscopy 24mentioning

confidence: 99%

Large variability and complexity of isothermal solubility for a series of redox-active phenothiazines

et al. 2022

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“…One such technique is electron paramagnetic resonance (EPR) spectroscopy, which is used to study unpaired electron spins. EPR has so far been used in studying operando electrolyte phenomena in redox flow batteries 1 , 2 , 3 or fuel cell membranes, 4 , 5 but its utility in studying conductive solid-state materials such as electrocatalysts remains limited.…”

Section: Introductionmentioning

confidence: 99%