Abstract
Variations in the solubility of redox-active organic molecules (ROM) of interest for nonaqueous redox flow batteries (RFB), especially as the ROM state-of-charge changes during charge-discharge cycling, present significant molecular design challenges. The situation is further complicated as ROM solubility can be regulated by the choice of electrolyte salt and solvent that together with the ROM comprise the catholyte or anolyte (redox electrolyte) formulation, presenting materials design challenges. The ROM N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT) is a viscous liquid at room temperature and is miscible in several organic solvents, including acetonitrile and propylene carbonate. The MEEPT radical cation (MEEPT+•) paired with tetrafluoroborate (BF4-) in acetonitrile presents a 0.5 M solubility, a dramatic decrease when compared to the viscous liquid of neutral MEEPT. Here we present a joint experimental, regression modeling, and molecular dynamics (MD) simulations investigation to explore MEEPT-X (where X represents the counteranion) salt solubility variability as a function of concentration and counteranion chemistry in acetonitrile. We find a strong dependence of the salt solubility on the counteranion and relate these findings to explicit intermolecular interactions between MEEPT+• and the counteranion in the electrolyte solution.
| Original language | English |
|---|---|
| Pages (from-to) | 10649-10658 |
| Number of pages | 10 |
| Journal | Energy and Fuels |
| Volume | 39 |
| Issue number | 22 |
| DOIs | |
| State | Published - Jun 5 2025 |
Bibliographical note
Publisher Copyright:© 2025 American Chemical Society.
Funding
This work would not be possible without the incredible intellect and leadership of Dr. Susan A. Odom\u2500we are forever grateful. Work at the University of Kentucky (U.K.) was generously supported by the National Science Foundation (NSF) under Cooperative Agreement Number 2019574 (aspects of the simulation work) and CHE CSDM-B Award Number 1800482 (portions of the experimental and modeling work). Work at U.K., University of Illinois Urbana-Champaign (UIUC), and Argonne National Laboratory (ANL) was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences. We also acknowledge the University of Kentucky (U.K.) Center for Computational Sciences and Information Technology Services Research Computing for their fantastic support and collaboration, and use of the Lipscomb Compute Cluster and associated research computing resources. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (\u201CArgonne\u201D). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. This work would not be possible without the incredible intellect and leadership of Dr. Susan A. Odom\u2500we are forever grateful. Work at the University of Kentucky (U.K.) was generously supported by the National Science Foundation (NSF) under Cooperative Agreement Number 2019574 (aspects of the simulation work) and CHE CSDM-B Award Number 1800482 (portions of the experimental and modeling work). Work at U.K., University of Illinois Urbana\u2013Champaign (UIUC), and Argonne National Laboratory (ANL) was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences. We also acknowledge the University of Kentucky (U.K.) Center for Computational Sciences and Information Technology Services Research Computing for their fantastic support and collaboration, and use of the Lipscomb Compute Cluster and associated research computing resources. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (\u201CArgonne\u201D). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
| Funders | Funder number |
|---|---|
| University of Illinois, Urbana-Champaign | |
| DOE Basic Energy Sciences | |
| University of Kentucky | |
| Argonne National Laboratory | |
| Joint Center for Energy Storage Research | |
| National Science Foundation Office of International Science and Engineering | |
| U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China | 2019574 |
| CHE CSDM-B | 1800482 |
| U.S. Department of Energy Oak Ridge National Laboratory U.S. Department of Energy National Science Foundation National Energy Research Scientific Computing Center | DE-AC02-06CH11357 |
ASJC Scopus subject areas
- General Chemical Engineering
- Fuel Technology
- Energy Engineering and Power Technology