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Importance of liquid fragility for energy applications of ionic liquids.

Sippel P, Lunkenheimer P, Krohns S, Thoms E, Loidl A - Sci Rep (2015)

Bottom Line: Their possible applications are numerous, e.g., as solvents for green chemistry, in various electrochemical devices, and even for such "exotic" purposes as spinning-liquid mirrors for lunar telescopes.Here we concentrate on their use for new advancements in energy-storage and -conversion devices: Batteries, supercapacitors or fuel cells using ILs as electrolytes could be important building blocks for the sustainable energy supply of tomorrow.Interestingly, ILs show glassy freezing and the universal, but until now only poorly understood dynamic properties of glassy matter, dominate many of their physical properties.

View Article: PubMed Central - PubMed

Affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.

ABSTRACT
Ionic liquids (ILs) are salts that are liquid close to room temperature. Their possible applications are numerous, e.g., as solvents for green chemistry, in various electrochemical devices, and even for such "exotic" purposes as spinning-liquid mirrors for lunar telescopes. Here we concentrate on their use for new advancements in energy-storage and -conversion devices: Batteries, supercapacitors or fuel cells using ILs as electrolytes could be important building blocks for the sustainable energy supply of tomorrow. Interestingly, ILs show glassy freezing and the universal, but until now only poorly understood dynamic properties of glassy matter, dominate many of their physical properties. We show that the conductivity of ILs, an essential figure of merit for any electrochemical application, depends in a systematic way not only on their glass temperature but also on the so-called fragility, characterizing the non-canonical super-Arrhenius temperature dependence of their ionic mobility.

No MeSH data available.


Related in: MedlinePlus

Dielectric spectra of Omim PF6.Spectra are included for a variety of temperatures. The shown quantities are: Dielectric constant (a), dielectric loss (b), conductivity (c) and the imaginary part of the dielectric modulus (d). The lines in (a,b) are fits assuming a distributed RC circuit to model the blocking electrodes25, dc conductivity and three relaxational processes described by the Cole-Davidson or Cole-Cole functions. ε′(ν) and ε″(ν) were simultaneously fitted. The lines in (c,d) were calculated from the fits to ε′ and ε″.
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f2: Dielectric spectra of Omim PF6.Spectra are included for a variety of temperatures. The shown quantities are: Dielectric constant (a), dielectric loss (b), conductivity (c) and the imaginary part of the dielectric modulus (d). The lines in (a,b) are fits assuming a distributed RC circuit to model the blocking electrodes25, dc conductivity and three relaxational processes described by the Cole-Davidson or Cole-Cole functions. ε′(ν) and ε″(ν) were simultaneously fitted. The lines in (c,d) were calculated from the fits to ε′ and ε″.

Mentions: We have measured the dielectric response of 13 ILs. Covering frequencies from about 10−1 to 109 Hz and a wide temperature range, extending deep into the liquid regime and approaching Tg at low temperatures, enables a thorough analysis of the dc conductivity and the fragility. As a typical example, Fig. 2 shows spectra of the real and imaginary part of the dielectric permittivity (ε′ and ε″, respectively), the conductivity (σ′) and the imaginary part of the dielectric modulus24 (M″) of Omim PF6 (for a definition of the sample abbreviations, see Table 1) for selected temperatures. It should be noted, that partly the information contained in these plots is redundant (e.g., σ′ ∝ ε″ ν). However, the various dielectrically active processes of ILs are differently emphasized in these plots, making their separate discussion helpful.


Importance of liquid fragility for energy applications of ionic liquids.

Sippel P, Lunkenheimer P, Krohns S, Thoms E, Loidl A - Sci Rep (2015)

Dielectric spectra of Omim PF6.Spectra are included for a variety of temperatures. The shown quantities are: Dielectric constant (a), dielectric loss (b), conductivity (c) and the imaginary part of the dielectric modulus (d). The lines in (a,b) are fits assuming a distributed RC circuit to model the blocking electrodes25, dc conductivity and three relaxational processes described by the Cole-Davidson or Cole-Cole functions. ε′(ν) and ε″(ν) were simultaneously fitted. The lines in (c,d) were calculated from the fits to ε′ and ε″.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4564824&req=5

f2: Dielectric spectra of Omim PF6.Spectra are included for a variety of temperatures. The shown quantities are: Dielectric constant (a), dielectric loss (b), conductivity (c) and the imaginary part of the dielectric modulus (d). The lines in (a,b) are fits assuming a distributed RC circuit to model the blocking electrodes25, dc conductivity and three relaxational processes described by the Cole-Davidson or Cole-Cole functions. ε′(ν) and ε″(ν) were simultaneously fitted. The lines in (c,d) were calculated from the fits to ε′ and ε″.
Mentions: We have measured the dielectric response of 13 ILs. Covering frequencies from about 10−1 to 109 Hz and a wide temperature range, extending deep into the liquid regime and approaching Tg at low temperatures, enables a thorough analysis of the dc conductivity and the fragility. As a typical example, Fig. 2 shows spectra of the real and imaginary part of the dielectric permittivity (ε′ and ε″, respectively), the conductivity (σ′) and the imaginary part of the dielectric modulus24 (M″) of Omim PF6 (for a definition of the sample abbreviations, see Table 1) for selected temperatures. It should be noted, that partly the information contained in these plots is redundant (e.g., σ′ ∝ ε″ ν). However, the various dielectrically active processes of ILs are differently emphasized in these plots, making their separate discussion helpful.

Bottom Line: Their possible applications are numerous, e.g., as solvents for green chemistry, in various electrochemical devices, and even for such "exotic" purposes as spinning-liquid mirrors for lunar telescopes.Here we concentrate on their use for new advancements in energy-storage and -conversion devices: Batteries, supercapacitors or fuel cells using ILs as electrolytes could be important building blocks for the sustainable energy supply of tomorrow.Interestingly, ILs show glassy freezing and the universal, but until now only poorly understood dynamic properties of glassy matter, dominate many of their physical properties.

View Article: PubMed Central - PubMed

Affiliation: Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.

ABSTRACT
Ionic liquids (ILs) are salts that are liquid close to room temperature. Their possible applications are numerous, e.g., as solvents for green chemistry, in various electrochemical devices, and even for such "exotic" purposes as spinning-liquid mirrors for lunar telescopes. Here we concentrate on their use for new advancements in energy-storage and -conversion devices: Batteries, supercapacitors or fuel cells using ILs as electrolytes could be important building blocks for the sustainable energy supply of tomorrow. Interestingly, ILs show glassy freezing and the universal, but until now only poorly understood dynamic properties of glassy matter, dominate many of their physical properties. We show that the conductivity of ILs, an essential figure of merit for any electrochemical application, depends in a systematic way not only on their glass temperature but also on the so-called fragility, characterizing the non-canonical super-Arrhenius temperature dependence of their ionic mobility.

No MeSH data available.


Related in: MedlinePlus