MetILs3: 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 “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.
- Research Organization:
- Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Electricity Delivery and Energy Reliability (OE)
- Grant/Contract Number:
- AC04-94AL85000; NA0003525
- OSTI ID:
- 1398783
- Alternate ID(s):
- OSTI ID: 1378388
- Report Number(s):
- SAND--2017-10038J; 657059
- Journal Information:
- Advanced Sustainable Systems, Journal Name: Advanced Sustainable Systems Journal Issue: 9 Vol. 1; ISSN 2366-7486
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Effects of chain length on the size, stability, and electronic structure of redox-active organic–inorganic hybrid polyoxometalate micelles
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journal | January 2019 |
Synthesis, Crystal Structures, and Thermal Properties of Protic Metal-Containing Ionic Liquids, Diethanolammonium Halometallates: (HOCH2CH2)2NH2FeCl4 and ((HOCH2CH2)2NH2)2CoCl4
|
journal | April 2020 |
Crossover in Membranes for Aqueous Soluble Organic Redox Flow Batteries
|
journal | January 2019 |
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