| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | July 24, 2018 |
| Latest Amendment Date: | July 24, 2018 |
| Award Number: | 1805566 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Carole Read
cread@nsf.gov (703)292-2418 CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | August 1, 2018 |
| End Date: | July 31, 2021 (Estimated) |
| Total Intended Award Amount: | $262,623.00 |
| Total Awarded Amount to Date: | $262,623.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
77 MASSACHUSETTS AVE CAMBRIDGE MA US 02139-4301 (617)253-1000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
77 Massachusetts Ave Cambridge MA US 02139-4307 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EchemS-Electrochemical Systems |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
This project focuses on a type of battery called non-aqueous redox flow batteries (RFBs) that are promising for large-scale, stationary energy storage applications. RFBs have advantages for electrical grid-scale energy storage options that would reduce overall energy consumption when linked with an electrical grid. Non-aqueous RFBs that contain organic electro-active species have the following unique features relative to other RFB designs: higher operating voltages, non-corrosive electrolytes, smaller size, and use of scalable organic active materials (which are more environmentally friendly and potentially lower cost). This collaborative project addresses fundamental research to support the design of electrolytes for non-aqueous RFBs with high energy density, better stability, and acceptable fluid flow properties. This project will not only establish the foundational knowledge necessary to design electrolytes for next-generation grid storage batteries but will also provide fundamental insights into other electrochemical technologies necessary for a sustainable energy economy. The Principal Investigators Brushett and Odom have worked extensively with underrepresented groups in STEM fields and with mentoring undergraduate and graduate students in both research groups. Further, the PIs will establish summer student exchange programs with each other's institutions. At MIT, Dr. Brushett will engage with the THINK program, which seeks to foster exceptional innovation, networking, and knowledge in high school students working on projects that benefit the community. At University of Kentucky (UK), Dr. Odom will focus on Mixing Art & Science, which will introduce non-scientists to concepts and issues in energy collection and storage by attracting them with an accessible activity and will continue to serve as a co-organizer for UK's Expanding Your Horizons Annual Conference.
Fundamental knowledge gaps exist both in (1) the molecular design of stable concentrated redox active solutions and (2) the electrochemical characterization of these concentrated electrolytes. At present, most investigations have focused on molecular discovery and electrochemical characterization under dilute conditions followed by direct integration into an unoptimized laboratory flow cell for preliminary cycling analysis. This approach has led to uneven advances in the field as, to date, most nonaqueous flow cells have shown poor performance and durability. It is unclear whether the observed results are due to fundamental instabilities of the redox organic materials, concentration-dependent changes in the physical and electrochemical properties of redox electrolytes, or failures in cell design and engineering. This collaborative research project focuses on the development of soluble and stable redox active molecules, based on substituted phenothiazines, as a platform chemistry for characterizing physical and electrochemical properties of solutions containing high concentrations of redox active materials and supporting salts in organic electrolytes - referred to as "redox electrolytes" - for use in nonaqueous flow batteries. The major scientific outcome of this research will be fundamental understanding of the role of chemical structure and surrounding electrolytes on the performance and durability of redox active organic materials at high concentrations in aprotic organic electrolytes. Further, new electrochemical methods will be developed to enable unambiguous characterization of concentrated nonaqueous redox electrolytes.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Redox electrolytes, solutions comprising dissolved species capable of transferring electrons, have broad utility in the areas of energy storage and chemical synthesis. In particular, they are the centerpiece of redox flow batteries, which store energy in reservoirs containing liquid electrolytes. Current techno-economic projections suggest that higher species concentrations are necessary to enable sufficiently high energy densities in nonaqueous systems, but these conditions can be difficult to achieve and may adversely impact other performance metrics in practical embodiments. Therefore, our project sought to more clearly understand the design of high concentration, nonaqueous redox electrolytes by developing analytical tools for electrochemical characterization, testing electrolytes in laboratory-scale flow cells, and modeling the performance of candidate systems.
Within the context of analytical tools, we have developed a workflow for automatically identifying redox-active compounds during device testing. Organic molecules present in redox electrolytes typically undergo chemical decomposition reactions, and quantifying these pathways requires expensive and potentially time-consuming spectroscopy methods. Through our approach, we can augment this workflow with electrochemical tools (i.e., voltammetry), streamlining the characterization process to enable new ways to study concentrated redox electrolytes.
Building on existing knowledge that our groups have established around redox electrolytes, we were able to identify and synthesize stable redox-active organic compounds to serve as platform chemistries for probing concentrated electrolyte phenomena. We focused on understanding factors that increase the solubility of organic molecules across all states of charge. We also studied binary and ternary mixtures of candidate materials to enhance solubility beyond that of the pure constituent components. Using these model systems, we investigated their performance in lab-scale testbeds, allowing us to elucidate key performance factors and link fundamental solution properties to system behavior. To characterize electrolytes more thoroughly during device operation, we also designed and integrated operando (i.e., during operation) sensors for quantifying the state-of-charge and state-of-health, which can aid in electrolyte characterization and serve as a practical tool for on-line controls and diagnostics.
Finally, we developed theoretical models to understand the performance of two-electron redox electrolytes. One approach to augment the benefits of high concentration electrolytes is to leverage molecules which are capable of storing multiple electrons, potentially increasing the energy density of the system. However, these materials have potential drawbacks, presenting complex design tradeoffs. Using theoretical models, we explored key properties influencing these performance tradeoffs and presented potential limitations in using such materials in practical embodiments.
The results of this project has advanced foundational understanding in our fields by pushing the bounds of electrolyte concentrations and developing tools, both experimental and computational, to interrogate systems of interest. Our work has been disseminated to the scientific community through 3 original research articles (with 2 more in preparation), 1 perspective article on characterizing high concentration electrolytes, and 13 conference presentations. We also organized and ran symposium on materials and techniques to advance RFBs at the 257th American Chemical Society Meeting (Orlando, FL). Additionally, our research will continue to advance these aims in ongoing collaborative efforts, particularly through the Joint Center for Energy Storage Research, an Energy Innovation Hub supported by the U.S. Department of Energy.
This project has also supported educational efforts for junior scientists. The research supported the growth and development of 3 graduate student researchers and 1 undergraduate student researcher at the Massachusetts Institute of Technology and the University of Kentucky. Further, we extended our knowledge to the Telluride School on Electrochemical Energy Storage, where members of our team gave a lecture and practicum on RFBs, enabling attendees to understand device fundamentals and potentially conduct groundbreaking research in this field.
Last Modified: 06/29/2022
Modified by: Fikile R Brushett
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