skip to main content

DOE PAGESDOE PAGES

Title: MetILs 3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids

We present a systematic approach for increasing the concentration of redox-active species in electrolytes for nonaqueous redox flow batteries (RFBs). Starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions are substituted incrementally into the structure. While chemical structures can be drawn for molecules with 10 m redox-active electrons (RAE), practical limitations such as melting point and phase stability constrain the structures to 4.2 m RAE, a 2.3× improvement over the original MetIL. Dubbed “MetILs 3,” these ionic liquids possess redox activity in the cation core, ligands, and anions. Throughout all compositions, infrared spectroscopy shows the ethanolamine-based ligands primarily coordinate to the Fe 2+ core via hydroxyl groups. Calorimetry conveys a profound change in thermophysical properties, not only in melting temperature but also in suppression of a cold crystallization only observed in the original MetIL. Square wave voltammetry reveals redox processes characteristic of each molecular location. Testing a laboratory-scale RFB demonstrates Coulombic efficiencies >95% and increased voltage efficiencies due to more facile redox kinetics, effectively increasing capacity 4×. Application of this strategy to other chemistries, optimizing melting point and conductivity, can yield >10 m RAE, making nonaqueous RFB a viable technology for gridmore » scale storage.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Report Number(s):
SAND-2017-10038J
Journal ID: ISSN 2366-7486; 657059
Grant/Contract Number:
AC04-94AL85000; NA0003525
Type:
Accepted Manuscript
Journal Name:
Advanced Sustainable Systems
Additional Journal Information:
Journal Volume: 1; Journal Issue: 9; Journal ID: ISSN 2366-7486
Publisher:
Wiley
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Electricity Delivery and Energy Reliability (OE)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; 36 MATERIALS SCIENCE; electrochemistry; flow batteries; grid scale storage; ionic liquids; redox
OSTI Identifier:
1398783
Alternate Identifier(s):
OSTI ID: 1378388

Small, Leo J., Pratt, Harry D., Staiger, Chad L., and Anderson, Travis M.. MetILs3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids. United States: N. p., Web. doi:10.1002/adsu.201700066.
Small, Leo J., Pratt, Harry D., Staiger, Chad L., & Anderson, Travis M.. MetILs3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids. United States. doi:10.1002/adsu.201700066.
Small, Leo J., Pratt, Harry D., Staiger, Chad L., and Anderson, Travis M.. 2017. "MetILs3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids". United States. doi:10.1002/adsu.201700066. https://www.osti.gov/servlets/purl/1398783.
@article{osti_1398783,
title = {MetILs3: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids},
author = {Small, Leo J. and Pratt, Harry D. and Staiger, Chad L. and Anderson, Travis M.},
abstractNote = {We present a systematic approach for increasing the concentration of redox-active species in electrolytes for nonaqueous redox flow batteries (RFBs). Starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions are substituted incrementally into the structure. While chemical structures can be drawn for molecules with 10 m redox-active electrons (RAE), practical limitations such as melting point and phase stability constrain the structures to 4.2 m RAE, a 2.3× improvement over the original MetIL. Dubbed “MetILs3,” these ionic liquids possess redox activity in the cation core, ligands, and anions. Throughout all compositions, infrared spectroscopy shows the ethanolamine-based ligands primarily coordinate to the Fe2+ core via hydroxyl groups. Calorimetry conveys a profound change in thermophysical properties, not only in melting temperature but also in suppression of a cold crystallization only observed in the original MetIL. Square wave voltammetry reveals redox processes characteristic of each molecular location. Testing a laboratory-scale RFB demonstrates Coulombic efficiencies >95% and increased voltage efficiencies due to more facile redox kinetics, effectively increasing capacity 4×. Application of this strategy to other chemistries, optimizing melting point and conductivity, can yield >10 m RAE, making nonaqueous RFB a viable technology for grid scale storage.},
doi = {10.1002/adsu.201700066},
journal = {Advanced Sustainable Systems},
number = 9,
volume = 1,
place = {United States},
year = {2017},
month = {7}
}

Works referenced in this record:

Pathways to low-cost electrochemical energy storage: a comparison of aqueous and nonaqueous flow batteries
journal, January 2014
  • Darling, Robert M.; Gallagher, Kevin G.; Kowalski, Jeffrey A.
  • Energy & Environmental Science, Vol. 7, Issue 11, p. 3459-3477
  • DOI: 10.1039/C4EE02158D

Redox flow batteries a review
journal, September 2011
  • Weber, Adam Z.; Mench, Matthew M.; Meyers, Jeremy P.
  • Journal of Applied Electrochemistry, Vol. 41, Issue 10, p. 1137-1164
  • DOI: 10.1007/s10800-011-0348-2

A Stable Vanadium Redox-Flow Battery with High Energy Density for Large-Scale Energy Storage
journal, March 2011
  • Li, Liyu; Kim, Soowhan; Wang, Wei
  • Advanced Energy Materials, Vol. 1, Issue 3, p. 394-400
  • DOI: 10.1002/aenm.201100008