skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Identifying structure-function relationships to modulate crossover in nonaqueous redox flow batteries
Nonaqueous redox flow batteries (NARFBs) offer a promising solution for large-scale storage of renewable energy. However, crossover of redox active molecules between the two sides of the cell is a major factor limiting their development, as most selective separators are designed for deployment in water, rather than organic solvents. This report describes a systematic investigation of the crossover rates of redox active organic molecules through an anion exchange separator under RFB-relevant non-aqueous conditions (in acetonitrile/KPF6) using a combination of experimental and computational methods. A structurally diverse set of neutral and cationic molecules was selected, and their rates of crossover were determined experimentally with the organic solvent-compatible anion exchange separator Fumasep FAP-375-PP. The resulting data were then fit to various descriptors of molecular size, charge, and hydrophobicity (overall charge, solution diffusion coefficient, globularity, dynamic volume, dynamic surface area, clogP). This analysis resulted in multiple statistical models of crossover rates for this separator. These models were then used to predict tether groups that dramatically slow the crossover of small organic molecules in this system.  more » « less
Award ID(s):
2154502
PAR ID:
10539956
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Royal Society of Chemistry
Date Published:
Journal Name:
Journal of Materials Chemistry A
Volume:
11
Issue:
41
ISSN:
2050-7488
Page Range / eLocation ID:
22288 to 22294
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Materials Advances)
    Non-aqueous organic redox flow batteries (NAORFBs) are considered emerging large-scale energy storage systems due to their larger voltage window as compared to aqueous systems and their metal-free nature. However, low solubility, sustainability, and crossover of redox materials remain major challenges for the development of NAORFBs. Here, we report the use of redox active α-helical polypeptides suitable for NAORFBs. The polypeptides exhibit less crossover than small molecule analogs for both Daramic 175 separator and FAPQ 375 PP membrane, with FAPQ 375 PP preventing crossover most effectivley. Polypeptide NAORFBs assembled with a TEMPO-based polypeptide catholyte and viologen-based polypeptide anolyte exhibit low capacity fade ( ca. 0.1% per cycle over 500 cycles) and high coulombic efficiency (>99.5%). The polypeptide NAORFBs exhibit an output voltage of 1.1 V with a maximum capacity of 0.53 A h L −1 (39% of the theoretical capacity). After 500 charge–discharge cycles, 60% of the initial capacity was retained. Post cycling analysis using spectral and electrochemical methods demonstrate that the polypeptide backbone and the ester side chain linkages are stable during electrochemical cycling. Taken together, these polypeptides offer naturally-derived, deconstructable platforms for addressing the needs of metal-free energy storage. 
    more » « less
  2. ; ; ; ; ; ; (, ChemXriv)
    Redox flow batteries (RFBs) have emerged as significant energy storage systems amid the growing adoption of renewable energy. However, the advancement of all-organic RFBs is hindered by material crossover, limited energy density, and the time-consuming selection of suitable electrolyte partners. To address these challenges, bipolar redox-active organic molecules (BRMs) show promise for charge storage in symmetric organic redox flow batteries (SORFBs), although their development can be complex and tedious. In this study, we report an approach aimed at streamlining the identification of suitable compounds through an examination of the organophotocatalyst literature, illustrated through six acridinium compounds exhibiting stable redox states. These compounds were thoroughly characterized in electrochemical cells and subjected to cycling tests in fully symmetric flow batteries. Notably, a trisubstituted electron-rich acridinium compound emerged as a potential candidate, demonstrating over 20 days of cycling stability. Given the extensive library of organic catalysts and the advantages of SORFB designs, this approach will prove to be essential for developing an innovative electrochemical storage system. 
    more » « less
  3. ; (, Science)
    Aqueous redox flow batteries could provide viable grid-scale electrochemical energy storage for renewable energy because of their high-power performance, scalability, and safe operation ( 1 , 2 ). Redox-active organic molecules serve as the energy storage materials ( 2 , 3 ), but only very few organic molecules, such as viologen ( 4 , 5 ) and anthraquinone molecules ( 6 ), have demonstrated promising energy storage performance ( 2 ). Efforts continue to develop other families of organic molecules for flow battery applications that would have dense charge capacities and be chemically robust. On page 836 of this issue, Feng et al. ( 7 ) report a class of ingeniously designed 9-fluorenone (FL) molecules as high-performance, potentially low-cost organic anode electrolytes (anolytes) in aqueous organic redox flow batteries (see the figure, top). These FL anolytes not only display exceptional energy storage performance but also exhibit an unprecedented two-electron storage mechanism. 
    more » « less
  4. ; ; ; ; ; ; ; (, Angewandte Chemie International Edition)
    Abstract Most reported cathodes of nonaqueous dual‐ion batteries (DIBs) host anions via insertion reactions. It is necessary to explore new cathode chemistry to increase the battery energy density. To date, transition metals have yet to be investigated for nonaqueous DIBs, albeit they may offer high capacity in anodic conversion reactions. Here, we report that bulk copper powder exhibits a high reversible capacity of 762 mAh g−1at 3.2 V vs. Li+/Li and relatively stable cycling in common organic electrolytes. The operation of the copper electrode is coupled with the transfer of anion charge carriers. An anion exchange membrane separator is employed to prevent Cu2+from crossing from the catholyte to the anode side. We designed an unbalanced electrolyte with a more concentrated anolyte than a catholyte. This addresses the concentration overpotential ensued during charge and facilitates the high specific capacity and enhanced reversibility. This finding provides a promising direction for high‐energy DIBs. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Advanced Materials)
    Abstract Molecular doping—the use of redox‐active small molecules as dopants for organic semiconductors—has seen a surge in research interest driven by emerging applications in sensing, bioelectronics, and thermoelectrics. However, molecular doping carries with it several intrinsic problems stemming directly from the redox‐active character of these materials. A recent breakthrough was a doping technique based on ion‐exchange, which separates the redox and charge compensation steps of the doping process. Here, the equilibrium and kinetics of ion exchange doping in a model system, poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno(3,2‐b)thiophene) (PBTTT) doped with FeCl3and an ionic liquid, is studied, reaching conductivities in excess of 1000 S cm−1and ion exchange efficiencies above 99%. Several factors that enable such high performance, including the choice of acetonitrile as the doping solvent, which largely eliminates electrolyte association effects and dramatically increases the doping strength of FeCl3, are demonstrated. In this high ion exchange efficiency regime, a simple connection between electrochemical doping and ion exchange is illustrated, and it is shown that the performance and stability of highly doped PBTTT is ultimately limited by intrinsically poor stability at high redox potential. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email