Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
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0013-4651/2001/149共1兲/D1/6/$7.00 © The Electrochemical Society, Inc.
A Highly Conductive Room Temperature Molten Fluoride:
EMIF"2.3HF
Rika Hagiwara,*,z Takayuki Hirashige, Tetsuya Tsuda, and Yasuhiko Ito**
Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University,
Kyoto 606-8501, Japan
Reaction of 1-ethyl-3-methylimidazolium chloride 共EMICl兲 and anhydrous hydrogen fluoride gives a nonvolatile, room temperature molten salt, EMIF•2.3HF. The elemental analysis, vibrational, and nuclear magnetic resonance spectroscopy suggests the
presence of oligomeric anions, (HF) n F⫺ in the salt. The liquid is stable in air and able to be handled in a Pyrex glass vessel. The
specific conductivity is 100 mS cm⫺1 at 298 K, which is extremely high compared with other salts of this kind. The high
conductivity is realized by its low viscosity 共4.85 cP at 298 K兲. The liquid temperature ranges from 180 to 350 K, and electrochemical window is about 3.2 V when a vitreous carbon is used for the electrode material.
© 2001 The Electrochemical Society. 关DOI: 10.1149/1.1421606兴 All rights reserved.
Manuscript submitted March 6, 2001; revised manuscript received August 28, 2001. Available electronically November 29, 2001.
In 1992, Wilkes et al. reported moisture-stable room temperature molten salt 共RTMS兲, 1-ethyl-3-methylimidazolium
tetrafluoroborate.1 Today, a number of RTMS synthesized by the
combinations of alkylimidazolium cations and inorganic and organic
fluoroanions are known, some of which are summarized elsewhere.2
Especially, studies on the 1-ethyl-3-methylimidazolium tetrafluoroborate have been the most extensively reported to date.1,3-16 Reports of the alkylimidazolium RTMS containing remarkably stable
bis关共trifluoromethyl兲sulfonyl兴 amide anion have been increasing in
the last 5 years.10,17-25 These salts are single salt containing only one
kind of cation and anion, respectively. The order of conductivity
ranges 10⫺1 -101 mS cm⫺1. 2
The authors have recently reported a new RTMS, EMIF•2.3HF,
synthesized by a reaction of 1-ethyl-3-methylimidazolium chloride
共EMICl兲 and anhydrous hydrogen fluoride.26 It has been found in
our preliminary work that this compound possesses an extremely
high electrical conductivity of the order of 102 mS cm⫺1. In this
paper, physical properties of EMIF•2.3HF such as density, viscosity,
and conductivity are reported as well as the electrochemical
behavior.
Experimental
Reagents.—Purification of 1-ethyl-3-methylimidazolium chloride 共EMICl兲, C6H11N2Cl 共Sanko Chemical Industry, Co., Ltd.,
solid, Mw 146.5, purity 98.5%, water content 1.4%兲 was made by
dissolving the salt in acetonitrile dried over molecular sieves. The
salt was then precipitated from the solution by adding ethyl acetate.
DF was prepared by the reaction of D2SO4 共Aldrich Chemical Co.
Inc., purity, 98.5%兲 with CaF2 共Nacarai Tesque, reagent grade兲, in a
nickel reactor at around 200°C. DF evolved from the reactor was
trapped in a fluoroethylene-propylene copolymer 共FEP兲 tube cooled
by ice water. AlCl3 共Fluka, purity ⬎99%兲 was purified by a literature method.27 NaBF4 共Aldrich Chemical Industries Ltd., purity
98%兲 and Fe共C5H5兲2 共Aldrich Chemical Co., Inc., 98%兲 were used
as supplied.
Synthesis of molten salt.—EMICl was weighed and charged in a
reaction vessel 共FEP or perfluoroalkoxide polymer 共PFA兲 was used
in the present study although polyethylene would be enough for this
reaction兲 and interacted with a large excess HF at 273-298 K. Volatile gases were eliminated by purging nitrogen gas for several hours.
The molten salt thus obtained still contained trace amount of free
HF at room temperature that was eliminated by evacuation of the
container by a vacuum pump through a cold trap for 3 to 4 days. The
* Electrochemical Society Active Member.
** Electrochemical Society Fellow.
z
E-mail: [email protected]
composition, EMIF•2.3HF, was determined by elemental analysis
and gravimetry. EMIF•2.3DF was obtained in the same manner using DF. EMIBF4 was prepared by the reaction of EMICl and NaBF4
in anhydrous ethanol. NaCl precipitated in the solution was separated by filtration and the filtrate was dried under vacuum to recover
EMIBF4.
Analysis.—Raman spectra of the samples were obtained by a
BIO-RAD FTS-175C spectrometer using Nd-YAG laser 共1200
mW兲. Pyrex nuclear magnetic resonance 共NMR兲 test tubes were
used for the measurement. IR spectra of the samples were obtained
by a BIO-RAD FTS-155 spectrometer. A finely ground powder of a
solid or liquid sample was sandwiched between two AgCl crystal
windows in an airtight cell. A gaseous sample was introduced in a
gas cell with AgCl crystal windows. 1H-NMR measurements of the
sample dissolved in deuterated methanol were performed using
Varian Unity Plus-500 NMR spectrometer 共500 MHz兲 and are referenced to tetramethylsilane 共TMS兲 as an internal standard.
D共2H兲-NMR measurements of the sample prepared from DF dissolved in methanol and were performed using Varian Gemini-2000
NMR spectrometer 共46 MHz兲 and are referenced to a trace signal of
the deuterated solvent. 19F-NMR measurements of the neat sample
were performed at 235-298 K using Varian Gemini-300 NMR spectrometer 共282 MHz兲. Trichloromethane sealed in a Pyrex capillary
was used as an external standard. The spectra are referenced to
共trifluoromethyl兲benzene. All the data were recorded as chemical
shifts. Density of the molten salt was measured with a pycnometer
method at 250-363 K. The kinematic viscosity was also measured
with Ubbelohde-type viscometers at 273-363 K. Low temperature
differential scanning calorimetry 共DSC兲 analysis was performed on
the sample sealed in a Pyrex capsule using Seiko Instruments, EXSTAR 6000 and DSC6200. The temperature was scanned between
133 and 298 K with a rate of 5 K min⫺1. Thermogravimetric 共TG兲
and differential thermal analysis 共DTA兲 analyses were made with the
aid of Seiko Instruments, TG/DTA-32 specially assembled for the
use in F2 and/or HF atmosphere. The measurement was performed
in flowing argon gas, elevating the temperature by 5 K min⫺1. Electrochemical measurement was performed with the aid of Hokuto
Denko, HZ-3000 electrochemical measurement system. Vitreous
carbon 共Tokai Carbon Co., Ltd., GC-20SS, geometric surface area,
0.07 cm2兲 was used as a material for the working electrode, combined with a platinum or tungsten counter electrode. Reference
electrode was constructed of aluminum wire immersed in
EMICl•2AlCl3 salt, a liquid junction to EMIF•2.3HF being made
through a Pyrex glass frit. Conductivity of the salt was obtained in
the temperature range from 195 to 383 K by impedance technique
using a calibrated airtight cell with platinum disk electrodes.
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Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
Figure 1. IR spectra of EMICl, EMIF•2.3HF, and EMIF•2.3DF. Peak po⫺
sitions of 共䊊兲 H2F⫺
3 and 共䊐兲 H3F4 found in potassium salts 共Ref. 29-32兲.
Results and Discussion
Preparation.—The reaction of EMICl and HF started during the
temperature elevation after the melting of HF condensed at liquid
nitrogen temperature. Gas evolution was observed and liquid turned
pale yellow. Only hydrogen chloride and fluoride were detected by
IR spectroscopy of the volatile materials which were eliminated by
purging dry nitrogen gas, successively followed by evacuation at
room temperature by a rotary pump until the pressure reached 10 Pa.
From the weight uptake, the composition of the product was calculated to be C6H11N2F•2.25HF. The elemental analysis gave a composition (C:H:N:F ⫽ 6.0:13.3:2.0:3.3), which results in an empirical formula of C6H11N2F•2.3HF. The reaction is concluded to
proceed as follows, similar to the synthesis of acidic tetraalkylammonium fluorides from their bromides and chlorides28
EMICl ⫹ 共 n ⫹ 1 兲 HF → EMIF•nHF ⫹ HCl↑
关1兴
The residual HF and byproduct HCl are volatile, which is convenient for the separation of the nonvolatile molten salts. The noninteger number of HF, 2.3, in Eq. 1 obtained for the RTMS prepared
by the method described above is very reproducible and is discussed
below. Reduction of the number of HF was not succeeded by the
reaction of stoichiometric amount of EMICl and HF which gave a
mixture of EMICl and EMIF•nHF. At present the best way to reduce the number of HF in EMIF•nHF is evacuation of HF from
EMIF•2.3HF at elevated temperature which is also discussed below.
Vibrational and NMR spectra.—Figure 1 shows the IR spectra of
EMICl 共solid兲 共a兲, the original EMIF•2.3HF 共b兲, and EMIF•2.3DF
共c兲 synthesized by a reaction of EMICl and deuterium fluoride 共DF兲.
The new peaks other than those of EMI⫹ are broad, found at around
490, 1000, 1800, 2000, and 2600 cm⫺1 in the spectrum of
EMIF•2.3HF 共b兲. These peaks are ascribed to anions of the salt.
According to the IR spectra of KF•2HF (KH2F3) 29-31 and KF•2DF
(KD2F3), 29,32 broad peaks of H2F⫺
3 found at 490, 1100, 1800, and
2400 cm⫺1 in the spectrum shift to lower wavenumbers, 450, 800,
Figure 2. Molecular shape of (HF) n F⫺ anions (n ⫽ 2, 3) found in solids.
1400, and 1800 cm⫺1, respectively, in the spectrum of KD2F3. Also,
⫺1
the peaks of H3F⫺
in IR spectrum of
4 found at 900 and 2900 cm
30-32
shift to 700 and 2200 cm⫺1, respectively, in
KF•3HF (KH3F4)
the spectrum of KF•3DF (KD3F4). 32 Similar peak shifts to lower
wavenumbers are observed in the spectrum of EMIF•2.3DF 共c兲. It is
⫺
suggested that at least these oligomeric anions, H2F⫺
3 and H3F4 , are
present in this salt 共Fig. 2兲. These anionic species have been found
and characterized in solid states.33,34 It should be noted that the
anions in EMIF•2.3HF still have some ambiguities in their shapes.
The bent angle of C 2v H2F⫺
3 which is unknown in this liquid varies
in the solid state depending on the compound33,34 and even in
33
KF•2HF, two H2F⫺
3 anions with different bent angles are present.
⫺
Two molecular symmetries, D 3h and C 3v , are known for H3F4 , the
former being found in KF•2HF and the latter in compounds such as
NH4F•3HF, (CH3兲4NF•3HF, and (pyridine)•4HF. Furthermore, a
34
alstructural isomer of H3F⫺
4 (C 2v) is known in the solid state,
though it is expected by ab initio calculation to be thermally less
stable than the D 3h molecule in vacuum.33 It should also be emphasized that the feature of the EMI⫹ peaks in the spectra is unchanged
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Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
D3
Figure 3. Raman spectra of EMICl and EMIF•2.3HF.
by the substitution of DF for HF. D-H exchange of the protons on
the cation does not seem to occur in the ambient condition. This
result coincides with the result of NMR shown below. Figure 3
shows Raman spectra of EMIF•2.3HF compared with the original
EMICl. These two spectra are essentially identical, only indicating
the presence of EMI cations in EMIF•2.3HF. Peaks ascribed to
anions were not detected. We failed to find any literature on the
Raman spectra of the (HF) n F⫺ in the salts of atomic cations reported so far.
Figure 4 shows the 1H-NMR spectra of EMIBF4 共a兲,
EMIF•2.3HF 共b兲, D-NMR spectrum of EMIF•2.3DF 共c兲, and
19
F-NMR of EMIF•2.3HF 共d兲. In the spectrum of EMIBF4, all the
peaks are ascribed to protons in EMI cation. A new singlet peak is
found at 5.0 ppm in the spectrum of EMIF•2.3HF. This peak is
⫺
supposed to be assigned to protons in H2F⫺
3 and H3F4 . The protons
⫺
in H2F⫺
and
H
F
are
not
structurally
equivalent,
however,
both are
3 4
3
coordinated by two fluorine atoms facing each other giving a similar
magnetic environment. A rapid exchange of HF between H2F⫺
3 and
H3F⫺
4 compared with the relaxation time of NMR would be a possible explanation for the observation of only a single resonance signal
⫺
H2F⫺
3 ⫹ HF H3F4
关2兴
As shown in Fig. 4共c兲, when the salt was prepared by the reaction
of EMICl and DF, only one signal appeared in D-NMR spectrum at
⫺
the chemical shift very close to that found for H2F⫺
3 and H3F4 in
1
H-NMR spectrum. This suggests that the proton exchange between
the cation and anion, or that between the anion and the solvent does
not occur which coincides with the result obtained from IR spectroscopy. 19F-NMR of the neat EMIF•2.3HF shows only one signal
again. Figure 4d shows the typical spectrum measured at 235 K. The
chemical shift and the linewidth are unchanged in the temperature
range examined in the present study 共235-298 K兲. The spectrum of a
1 M solution of the sample in deuterated methanol is essentially
again the same even at lower temperatures. Thus the fluorine atoms
in the anions are not distinguishable, based on the results of strong
magnetic field measurements. As a conclusion, the most adequate
description of the anionic species in this melt would be a fluoride
ion hydrogen-bonded by two or three HF in average.
Reactivity against moisture and glass.—Neither weight uptake
nor change in IR spectrum of EMIF•2.3HF was observed when
EMIF•2.3HF is left in air for 1 day. EMIF•2.3HF does not etch the
Figure 4. NMR spectra of some EMI salts: 共a兲 1H-NMR spectra of EMIBF4
共at 298 K, dissolved in d-methanol兲; 共b兲 1H-NMR spectra of EMIF•2.3HF 共at
298 K, dissolved in d-methanol兲; 共c兲 D-NMR spectrum of EMIF•2.3DF 共at
298 K, dissolved in methanol兲; and 共d兲 19F-NMR spectrum of EMIF•2.3HF
共at 235 K, neat兲.
borosilicate glasses such as Pyrex, no difference being observed in
IR spectrum before and after interaction. Most of the measurements
were performed using Pyrex glass apparatus in this study. However,
soda-lime glasses are gradually etched by EMIF•2.3HF even in ambient conditions.
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Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
Figure 5. Thermal analysis of EMIF•2.3HF. The rate of temperature elevation, 5 K min⫺1; atmosphere: Ar.
Thermal behavior.—The low temperature DSC measurement of
EMIF•2.3HF shows only a broad anomaly at around 173 K ascribed
to a glass transition. Figure 5 shows TG and DTA of EMIF•2.3HF in
argon atmosphere. The liquid slowly loses the weight from ⬃350 K
and irreversible decomposition occurs at ⬃570 K. The slow weight
decrease lower than 570 K is the reversible elimination of HF from
the (HF) n F⫺ anions. A large endothermic peak is observed at ⬃590
K at which irreversible decomposition takes place to convert the
sample completely to volatile materials. The weight decrease is not
observed at ambient temperature, the dissociation pressure being
negligibly small. This thermal stability contrasts to that found for
⫺
EMICl•nHCl. 35-41 The HCl⫺
2 and H2Cl3 anions in these melts pos42-44
sess weaker bond energies
and dissociation pressure to liberate
HCl at room temperature.45
Density.—Figure 6 shows the temperature dependence of the
density of EMIF•2.3HF. The density at 298 K is 1.135 g cm⫺3,
lower than that found for the other RTMS containing fluoroanions.2
Viscosity.—Viscosity of EMIF•2.3HF is 4.85 cP at ambient temperature, extremely low compared with the other RTMS reported so
far. Figure 7 shows the Arrhenius plots of viscosity for EMIF•2.3HF
compared with EMICl•2AlCl346,47 and EMIBF4. 10,13 An almost linear plot is observed for EMIF•2.3HF in the temperature range examined in this study. From the slope at around 298 K, the activation
energy for viscosity was calculated to be 2.9 kcal mol⫺1 which is
Figure 6. Density of EMIF•2.3HF.
Figure 7. Viscosity of some RTMS: 共䊊兲 EMIF•2.3HF, 共䊐兲 EMICl•2AlCl3
共Ref. 46兲, 共䉭兲 EMICl•2AlCl3 共Ref. 47兲, 共䊉兲 EMIBF4 共Ref. 10兲, 共䊏兲 EMIBF4
共Ref. 13兲.
lower than that of the other RTMS.10,13,46,47 A detailed structural
analysis of the liquid is necessary in order to explain the low viscosity of EMIF•2.3HF. A diffraction study of the salt using a synchrotron high energy X-ray is now under way.
Conductivity.—The conductivity of EMIF•2.3HF is 100 mS
cm⫺1 at room temperature, much higher than that of the other
RTMS. Figure 8 shows the Arrhenius plots of conductivity for
EMIF•2.3HF compared with EMICl•2AlCl3 46,47 and EMIBF4. 10,13
In the high-temperature region where the viscosity measurement
was also performed, temperature dependence of the conductivity
shows the Arrhenius relation as in the case of the viscosity. However, a distinct downward trend in the curvature was observed at
lower temperatures. The activation energy for conductivity of 2.4
kcal mol⫺1 at room temperature was calculated from a linear region
in the plot. It is lower than that of the other RTMS and close to that
found for the viscosity.
In general, concentrated solutions that form glass phases like
ionic liquids typically exhibit curved Arrhenius plots for temperature
Figure 8. Conductivity of some RTMS: 共䊊兲 EMIF•2.3HF, 共䊐兲
EMICl•2AlCl3 共Ref. 46兲, 共䊉兲 EMIBF4 共Ref. 10兲, 共䊏兲 EMIBF4 共Ref. 13兲.
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Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
D5
Figure 9. VTF plot of the temperature dependence of the conductivity of
EMIF•2.3HF. T 0 ⫽ 85 K, B ⫽ 841 K⫺1.
dependence of conductivity and lend themselves to the VogelTammen-Fulcher 共VTF兲 interpretation, especially at lower
temperatures48
␴ 共 T 兲 ⫽ A T ⫺1/2 exp关 ⫺B/ 共 T ⫺ T 0 兲兴
关3兴
where A, B, and T 0 are constants to be determined empirically. Figure 9 shows the VTF plot of conductivity for EMIF•2.3HF. A linear
relation is observed between logarithmic value of ␴T 1/2 and B/T
⫺ T 0 . The refined value for T 0 , called the ideal glass transition
temperature, is 85 K which is lower than the observed glass transition temperature from DSC measurements. A similar tendency has
been found for the other RTMS.10,47,49
The remarkably high conductivity is one of the excellent features
of EMIF•2.3HF. This is considered to be given by the low viscosity
of the liquid mentioned above. It has been shown that the viscosity
and conductivity of the RTMS containing fluoroanions generally
obey Walden’s rule50 共molar conductivity is inversely proportional
to the viscosity兲 and EMIF•2.3HF is not the exception.
Figure 10. Cyclic voltammogram of a vitreous carbon disk electrode in
EMIF•2.3HF. Reference electrode: Al in EMICl•2AlCl3, Scan rate: 10 mV
s⫺1, Temperature: 298 K. The end and the direction of the arrow in the figure
denote the OCV and direction of scanning, respectively.
Conclusions
It has been found that the new RTMS, EMIF•2.3HF, possesses
some interesting properties such as a wide liquid temperature range,
low viscosity, high electrical conductivity, and chemical stability in
Electrochemical behavior.—Figure 10 shows a cyclic voltammogram of EMIF•2.3HF. The electrochemical window is about 3.2 V
when vitreous carbon is employed as an electrode material, similar
to the result obtained with a platinum electrode.26 The width of the
electrochemical window is comparable to that of acidic and basic
EMICl-AlCl3 systems.51 The electrode reaction at the cathode limit
involves the evolution of gas which is probably hydrogen formed by
the reduction of (HF) n F⫺. Although the reaction at the anode limit
has not been identified yet, the evolution of fluorine gas by the
oxidation of anions is ruled out taking account the reactivity of
EMIF•2.3HF against the elemental fluorine.2 When a constantpotential electrolysis was performed at 3.2 V vs. Al/Al共III兲,
EMIF•2.3HF turned brown. The conceivable reaction is oxidation,
probably accompanied by a fluorination of EMI cation.
Figure 11 shows reversible redox waves found in the cyclic voltammograms of a vitreous carbon disk electrode in the solution of
EMIF•2.3HF containing ferrocene. The number of the electrons involved in the reaction is determined to be one according to the
equation for a reversible process
兩 E p ⫺ E p/2兩 ⫽
56.5
2.2RT
⫽
nF
n
关4兴
where E p and E p/2 are the peak and half-peak potential, respectively.
Figure 11. Cyclic voltammograms for a vitreous carbon disk electrode in
ferrocene 共8.2 mmol kg⫺1兲 in EMIF•2.3HF. Reference electrode: Al in
EMICl•2AlCl3, Scan rate: 共a兲 200, 共b兲 50 mV s⫺1, temperature: 298 K. The
end and the direction of the arrow in the figure denote the OCV and direction
of scanning, respectively.
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Journal of The Electrochemical Society, 149 共1兲 D1-D6 共2002兲
D6
air. Taking advantage of these characteristics as well as the electrochemical window of more than 3 V, practical applications as an
electrolyte are envisaged for many fields in electrochemistry.
Acknowledgments
The authors thank Dr. K. Momota of Morita Chemical Industry,
Co., Ltd., for his help and advice mainly concerning the preparation
of EMIF•2.3HF. The authors also thank Professor S. Matsubara of
Kyoto University for the NMR spectroscopy and Professor M.
Takashima of Fukui University for the DTA and TG analyses. Dr. H.
Matsumoto of National Institute of Advanced Industrial Science and
Technology gave us valuable suggestions on the electrochemistry of
RTMS. The EMICl used in this study was provided by Sanko
Chemical Industry, Co., Ltd., which is also acknowledged. This
work was partially supported by Grant in Aid for Scientific Research
by the Ministry of Education, Science, Sports and Culture, and Iketani Science and Technology Foundation.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Kyoto University assisted in meeting the publication costs of this article.
21.
Appendix
Supplementary Materials
22.
23.
24.
Table A-I. Experimental data of EMIF"2.3HF at different temperatures.
25.
Temperature Density Kinematic viscosity Viscosity Conductivity
共K兲
共g cm⫺3兲
共cSt兲
共cP兲
共mS cm⫺3兲
26.
27.
194.7
228.2
250.2
273.2
285.2
298.2
303.2
308.2
323.2
333.2
343.2
353.2
363.2
373.2
383.2
1.1636
1.1519
1.1465
6.72
7.74
2.8
15.2
30.2
57.7
4.29
4.87
100.0
30.
1.1293
1.1270
1.0980
1.0932
28.
29.
2.99
3.34
2.33
2.55
1.96
2.12
137.6
156.1
173.0
186.9
206.5
224.6
246.2
References
1. J. S. Wilkes and M. J. Zaworotko, J. Chem. Soc. Chem. Commun., 1992, 965.
2. R. Hagiwara and Y. Ito, J. Fluorine Chem., 105, 221 共2000兲.
3. R. T. Carlin, H. C. De Long, J. Fuller, and P. C. Trulove, J. Electrochem. Soc., 141,
L73 共1994兲.
4. J. Fuller, R. T. Carlin, H. C. De Long, and D. Haworth, J. Chem. Soc. Chem.
Commun., 1994, 299.
5. R. T. Carlin and J. Fuller, in Molten Salts X, R. T. Carlin, S. Deki, M. Matsunaga,
D. S. Newman, J. R. Selman, G. R. Stafford, and D. A. Shores, Editors, PV 96-7,
p. 362, The Electrochemical Society Proceedings Series, Pennington, NJ 共1996兲.
6. C. Nanjundiah, F. McDevitt, and V. R. Koch, J. Electrochem. Soc., 144, 3392
共1997兲.
7. J. Fuller, J., R. T. Carlin, and R. A. Osteryoung, J. Electrochem. Soc., 144, 3881
共1997兲.
8. J. Fuller and R. T. Carlin, in Molten Salts XI, P. C. Trulove, H. C. De Long, G. R.
Stafford, and S. Deki, Editors, PV 98-11, p. 227, The Electrochemical Society
Proceedings Series, Pennington, NJ 共1998兲.
9. M. L. Mutch and J. S. Wilkes, in Molten Salts XI, P. C. Trulove, H. C. De Long,
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
G. R. Stafford, and S. Deki, Editors, PV 98-11, p. 254, The Electrochemical Society Proceedings Series, Pennington, NJ 共1998兲.
A. B. McEwen, H. L. Ngo, K. LeCompte, and J. L. Goldman, J. Electrochem. Soc.,
146, 1687 共1999兲.
J. D. Holbrey and K. R. Seddon, J. Chem. Soc. Dalton Trans., 1999, 2133.
P.-Y. Chen and I.-W. Sun, Electrochim. Acta, 45, 441 共1999兲.
A. Noda and M. Watanabe, Electrochim. Acta, 45, 1265 共2000兲.
P.-Y. Chen and I.-W. Sun, Electrochim. Acta, 45, 3163 共2000兲.
Y. Katayama, S. Dan, T. Miura, and T. Kishi, in Molten Salts XII, P. C. Trulove, H.
C. De Long, G. R. Stafford, and S. Deki, Editors, PV 99-41, p. 110, The Electrochemical Society Proceedings Series, Pennington, NJ 共2000兲.
A. J. Carmichael, C. Hardacre, J. D. Holbrey, K. R. Seddon, and M. Nieuwenhuyzen, in Molten Salts XII, P. C. Trulove, H. C. De Long, G. R. Stafford, and S.
Deki, Editors, PV 99-41, p. 209, The Electrochemical Society Proceedings Series,
Pennington, NJ 共2000兲.
P. Bonhôte, A.-P. Dias, M. Armand, N. Papageorgiou, K. Kalyanasundaram, and M.
Grätzel, Inorg. Chem., 35, 1168 共1996兲.
N. Papageorgiou, Y. Athanassov, M. Armand, P. Bonhôte, H. Pettersson, A. Azam,
and M. Grätzel, J. Electrochem. Soc., 143, 3099 共1996兲.
V. R. Koch, C. Nanjundiah, G. B. Appetecchi, and B. Scrosati, J. Electrochem.
Soc., 142, L116 共1995兲.
V. R. Koch, L. A. Dominey, C. Nanjundiah, and M. J. Onderechen, J. Electrochem.
Soc., 143, 798 共1996兲.
J. Golding, D. R. MacFarlane, and M. Forsyth, in Proceedings of Molten Salt
Forum 5-6 (Molten Salt Chemistry and Technology-5), 589 共1998兲.
J. L. Goldman and A. B. McEwen, Electrochem. Solid-State Lett., 2, 501 共1999兲.
D. R. McFarlane, J. Sun, J. Golding, P. Meakin, and M. Forsyth, Electrochim. Acta,
45, 1271 共2000兲.
H. Every, A. G. Bishop, M. Forsyth, and D. R. MacFarlane, Electrochim. Acta, 45,
1279 共2000兲.
R. T. Carlin, T. H. Cho, and J. Fuller, in Molten Salts XII, P. C. Trulove, H. C. De
Long, G. R. Stafford, and S. Deki, Editors, PV 99-41, p. 20, The Electrochemical
Society Proceedings Series, Pennington, NJ 共2000兲.
R. Hagiwara, T. Hirashige, T. Tsuda, and Y. Ito, J. Fluorine Chem., 99, 1 共1999兲.
M. Matsunaga, T. Kitazaki, K. Hosokawa, S. Hirano, and M. Yoshida, in Molten
Salts IX, C. L. Hussey, Y. Ito, G. Mamantov, D. A. Shores, and D. S. Newman,
Editors, PV 94-13, p. 422, The Electrochemical Society Proceedings Series, Pennington, NJ 共1990兲.
I. N. Rozhkov and I. Y. Alyev, Tetrahedron, 31, 977 共1975兲.
A. Azman, A. Ocvirk, D. Hadzi, P. A. Giguère, and M. Schneider, Can. J. Chem.,
45, 1347 共1967兲.
K. Wada, T. Takenaka, S. Hayashi, and S. Takeno, Jpn. J. Appl. Phys., Suppl., 2,
109 共1974兲.
K. M. Harmon and I. J. Gennick, Mol. Str., 38, 97 共1977兲.
H. Omori, Master’s Thesis, Kyoto University 共1996兲.
J. D. Forrester, M. E. Senko, A. Zalkin, and D. H. Templeton, Acta Crystallogr., 16,
58 共1963兲.
D. Mootz and D. Boenigk, J. Am. Chem. Soc., 108, 6634 共1986兲.
T. A. Zawodzinski, Jr. and R. A. Osteryoung, Inorg. Chem., 27, 4383 共1988兲.
G. P. Smith, A. S. Dworkin, R. M. Pagni, and S. P. Zingg, J. Am. Chem. Soc., 111,
525 共1989兲.
G. P. Smith, A. S. Dworkin, R. M. Pagni, and S. P. Zingg, J. Am. Chem. Soc., 111,
5075 共1989兲.
T. L. Riechel and J. S. Wilkes, J. Electrochem. Soc., 139, 977 共1992兲.
P. C. Trulove and R. A. Osteryoung, Inorg. Chem., 31, 3980 共1992兲.
J. L. E. Campbell and K. E. Johnson, Inorg. Chem., 32, 3809 共1993兲.
J. L. E. Campbell and K. E. Johnson, J. Electrochem. Soc., 141, L19 共1994兲.
D. G. Tuck, Prog. Inorg. Chem., 9, 161 共1968兲.
G. C. Pimentel and R. D. Spratley, Chemical Bonding, Holden-Day, Inc., San
Francisco, CA 共1969兲.
J. Emsley, Chem. Soc. Rev., 9, 91 共1980兲.
H. F. Herbrandson, R. T. Dickerson, Jr., and J. Weinstein, J. Am. Chem. Soc., 76,
4046 共1954兲.
M. Matsunaga, Yoyuen oyobi Koon Kagaku, 42, 109 共1999兲.
A. A. Fannin, Jr., D. A. Floreani, L. A. King, J. S. Landers, B. J. Piersma, D. J.
Stech, R. L. Vaughn, J. S. Wilkes, and J. L. Williams, J. Phys. Chem., 88, 2614
共1984兲.
C. A. Anell and C. T. Moynihan, Molten Salts Characterization and Analysis, G.
Mamantov, Editor, p. 315, Marcel Dekker, New York 共1969兲.
P. A. Z. Suarez, S. Einloft, J. E. L. Dullius, R. F. de Souza, and J. Dupont, J. Chim.
Phys., 95, 1626 共1998兲.
H. Matsumoto, M. Yanagida, K. Tanimoto, T. Kojima, Y. Tamiya, and Y. Miyazaki,
in Molten Salts XII, P. C. Trulove, H. C. De Long, G. R. Stafford, and S. Deki,
Editors, PV 99-41, p. 186, The Electrochemical Society Proceedings Series, Pennington, NJ 共2000兲.
C. Scordilis-Kelley, J. Fuller, R. T. Carlin, and J. S. Wilkes, J. Electrochem. Soc.,
139, 694 共1992兲.
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