Conduction Through Viscoelastic Phase in a Redox‐Active Ionic Liquid at Reduced Temperatures

Thorsmølle, V. K.; Topgaard, Daniel; Brauer, Jan C.; Zakeeruddin, Shaik M.; Lindman, Björn; Grätzel, Michaël; Moser, Jacques-E.

doi:10.1002/adma.201104230

Cited by 18 publications

(14 citation statements)

References 28 publications

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“…Although some solid-state studies exist, 15,16,24,25,36 most experimental studies that have empirically motivated the iodide Grotthuss exchange mechanism have been based on liquidphase electrolytes. 3,4,8−14,17−19 A central question for the generality of our results to the liquid state concerns the proximity of I 3 − and I − anions in solution, since the EMIM/I 3 crystal structure confines iodide to be no more than 7 Å from the closest triiodide anion.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally even though the PMIM/I/I 3 ionic liquid undergoes a liquid to nematic phase transition upon cooling, 15 the conductivity remains largely unchanged, even though the viscosity increases by ∼6 orders of magnitude! 16 Another example of nonintuitive conductivity/viscosity trends was observed for iodide ionic liquids based on long-chain cations, 1-undecyl-3-methylimidazolium (C 11 MIM) and 1-dodecyl-3methylimidazolium (C 12 MIM). 10,11 C 12 MIM/I/I 3 forms ther-motropic liquid crystals at room temperature whereas C 11 MIM/I/I 3 does not, and surprisingly it was found that the iodide diffusion was faster in the higher viscosity, liquid crystalline C 12 MIM/I/I 3 electrolyte.…”

Section: Introductionmentioning

confidence: 99%

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Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal

McDaniel

Yethiraj

2017

J. Phys. Chem. B

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Highly ionic environments can mediate unusual chemical reactions that would otherwise be considered impossible based on chemical intuition. For example, the formation of a chemical bond between two iodide anions to form a divalent polyiodide anion is seemingly prohibited due to Coulombic repulsion. Using ab initio molecular dynamics simulations, we show that in the 1-ethyl-3-methylimidazolium (EMIM)/I ionic crystal, the reactive formation of divalent and even trivalent polyiodide anions occurs with extremely small energetic barriers, due to the electrostatic field of the ionic lattice. A practical consequence of this anomalous reactivity is that iodide anions are efficiently transported within the crystal through a "Grotthuss-exchange" mechanism involving bond-breaking and forming events. We characterize two distinct transport pathways, involving both I and I intermediates, with fast transport of iodide resulting from the release of an I anion on the opposite side of the intermediate species from the initial bond formation. The ordered cation arrangement in the crystal provides the necessary electrostatic screening for close approach of anions, suggesting a new counterintuitive approach to obtain high ionic conductivity. This new design principle could be used to develop better solid-state electrolytes for batteries, fuel cells, and supercapacitors.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal

McDaniel

Yethiraj

2017

J. Phys. Chem. B

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“…is also a general interest in diaminiumalkane iodide/triiodide systems derived from the knowledge that the choice of the diaminium cation significantly modifies the redox potential in dye-sensitized solar cells (DSSC) [16][17][18][19][20][21]. They play an important role in other electrochemical processes, e.g., lithium iodide batteries [22,23] or hydrogen production as well [24].…”

Section: Open Accessmentioning

confidence: 99%

I62− Anion Composed of Two Asymmetric Triiodide Moieties: A Competition between Halogen and Hydrogen Bond

Megen

Reiß

2013

Inorganics

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The reaction of 1,8-diaminooctane with hydroiodic acid in the presence of iodine gave a new polyiodide-containing salt: 1,8-diaminiumoctane bis(triiodide), (H 3 N-(CH 2) 8-NH 3)[I 3 ] 2. The title compound has been characterized by crystallographic and spectroscopic methods. The polyiodide ion is the first example of a hydrogen bonded I 6 2− dianion consisting of two very asymmetric triiodide components with I−I distances of 2.7739(4) and 3.1778(4) Å interacting by a weak halogen bond (I•••I: 3.5017(2) Å). The structural parameters of the triiodide anions, derived from X-ray crystallographic data, are in good agreement with the Raman and Far-IR spectroscopic results.

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“…ILs are organic salts composed of only free ions and ion pairs, exhibiting high thermal and chemical stability, broad electrochemical windows and non-ammability; especially room temperature ionic liquids (RTILs), having melting points below 100 C, present attractive physicochemical properties such as negligible vapour pressure. 10 Their eld of use is growing at an extremely high pace due to their promising potential for a great number of diverse applications, including their use in lithium-ion batteries, 11 electrochemical actuators, 12 supercapacitors, 13 reaction media, 14 separation solvents, 15 fuel cells 16 and CO 2 capture. 17 A unique feature of ILs is that simple changes in the cationanion combinations or the nature of the moieties attached to each ion allow their physical properties to be tailored for specic applications.…”

Section: Introductionmentioning

confidence: 99%

Ionic liquid redox electrolytes based on binary mixtures of 1-alkyl-methylimidazolium tricyanomethanide with 1-methyl-3-propylimidazolium iodide and implication in dye-sensitized solar cells

et al. 2013

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Innovative redox electrolytes for dye-sensitized solar cells (DSCs) were prepared using binary mixtures of 1methyl-3-propylimidazolium iodide (MPII) with 1-alkyl-methylimidazolium tricyanomethanide, C n mimTCM (n ¼ 2, 4, 6, 8) ionic liquids (ILs) to lower the high viscosity of MPII. The investigation of the physicochemical properties of the IL blends as a function of temperature has shown that both density and viscosity strongly depend on the kind of the C n mim cation in the mixture. The corresponding Raman spectra were dominated by the vibrational modes of the IL components in an additive way and confirmed the absence of any specific interaction, independent of the C n alkyl chain length. The electrochemical properties (triiodide diffusion coefficients, specific conductivity), determined in symmetrical thin layer cells using polarization and electrochemical impedance spectroscopy (EIS) measurements, have shown that both diffusion and conductivity decreased with increasing viscosity, and further confirmed the electrolytes' compatibility with the cathode. Incorporation of the novel electrolytes in DSC devices revealed a systematic dependence of the cell photovoltaic performance on the alkyl chain length of C n mimTCM; the maximum power conversion efficiency exceeded 5 and 6.5% under 1 and 0.1 sun AM 1.5 G illumination, respectively, for the ionic liquid with the shortest alkyl chain. The solar cells were further characterized by EIS (IMPS) spectroscopy, exploring charge recombination dynamics and identifying conduction band edge shifts. Solidification of the electrolytes with silica nanoparticles, demonstrated that the ionic liquid electrolytes with long chain length (n > 4) not only retain their efficiencies, but also exhibit a 22% efficiency enhancement, which is most pronounced for the electrolytes employing ionic liquids with the longest (hexyl-and octyl-) alkyl chains.

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Conduction Through Viscoelastic Phase in a Redox‐Active Ionic Liquid at Reduced Temperatures

Cited by 18 publications

References 28 publications

Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal

Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal

I62− Anion Composed of Two Asymmetric Triiodide Moieties: A Competition between Halogen and Hydrogen Bond

Ionic liquid redox electrolytes based on binary mixtures of 1-alkyl-methylimidazolium tricyanomethanide with 1-methyl-3-propylimidazolium iodide and implication in dye-sensitized solar cells

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Conduction Through Viscoelastic Phase in a Redox‐Active Ionic Liquid at Reduced Temperatures

Cited by 18 publications

References 28 publications

Grotthuss Transport of Iodide in EMIM/I3 Ionic Crystal

Grotthuss Transport of Iodide in EMIM/I3 Ionic Crystal

I62− Anion Composed of Two Asymmetric Triiodide Moieties: A Competition between Halogen and Hydrogen Bond

Ionic liquid redox electrolytes based on binary mixtures of 1-alkyl-methylimidazolium tricyanomethanide with 1-methyl-3-propylimidazolium iodide and implication in dye-sensitized solar cells

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Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal

Grotthuss Transport of Iodide in EMIM/I₃ Ionic Crystal