Structuring, stochastic behavior, and charge storage capacity of redox-active microemulsions formulated with mixtures of toluene and ionic liquid as oil phase

Santiago-Carboney, Armando; Kolaprath, Mrinalini K. Ayilliath; Imel, Adam; Dadmun, Mark D.; Rodríguez-López, Joaquín

doi:10.1557/s43578-026-01807-8

Title: Structuring, stochastic behavior, and charge storage capacity of redox-active microemulsions formulated with mixtures of toluene and ionic liquid as oil phase

Journal Article · Fri Mar 06 00:00:00 UTC 2026 · Journal of Materials Research

DOI: https://doi.org/10.1557/s43578-026-01807-8 · OSTI ID:3030238

Santiago-Carboney, Armando ^[1]; Kolaprath, Mrinalini K. Ayilliath ^[2]; Imel, Adam ^[3]; Dadmun, Mark D. ^[2];

^[1]

Univ. of Illinois at Urbana-Champaign, IL (United States)
Univ. of Tennessee, Knoxville, TN (United States)
Univ. of Tennessee, Knoxville, TN (United States); UT-Oak Ridge Innovation Institute, Oak Ridge, TN (United States)

Oil/water microemulsions (µEs) are promising electrolytes for redox flow batteries (RFBs) as they simultaneously improve charge capacity and ionic conductivity. Here, we report the successful formulation of bicontinuous µEs where the oil phase is a solution of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid in toluene with redox-active ferrocene. We examined the effect of supporting electrolyte anion (NO₃^–, Cl^–, ClO₄^–) on the structure, reactivity, transport, and electrolytic performance of redox-active µEs. Neutron scattering and nuclear magnetic resonance showed that the domain size increased as Cl^– > NO₃^– > ClO₄^– while the ferrocene diffusion coefficient increased as NO₃^– > Cl^– > ClO₄^–. Scanning electrochemical microscopy indicated anion-dependent current fluctuations during electrolysis, with ClO₄^– exhibiting the least high-frequency oscillations, which correlate to the highest charge and discharge capacity and reversibility. All ionic liquid containing systems improved the performance of toluene-based µEs, highlighting new design principles for these electrolytes.

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Research Organization:: Case Western Reserve Univ., Cleveland, OH (United States); Univ. of Illinois at Urbana-Champaign, IL (United States); Univ. of Tennessee, Knoxville, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: SC0019409

OSTI ID:: 3030238

Journal Information:: Journal of Materials Research, Journal Name: Journal of Materials Research; ISSN 0884-2914; ISSN 2044-5326

Publisher:: Springer NatureCopyright Statement

Country of Publication:: United States

Language:: English

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