Novel lithium and sodium salts of sulfonamides and bis(sulfonyl)imides: Synthesis and electrical conductivity

Article abstract of DOI:10.1039/c4nj01191k

The preparation of new electrolytes for application in lithium or sodium batteries is described. Different salts of lithium and sodium sulfonamide and bis(sulfonyl)imide were prepared in good yields. Ionic conductivity measurements were performed on these salts and conductivities of 0.20 to 0.51 mS cm^-1, comparable to those of Li-TFSI, were obtained. The best conductivity was reached for the Li⁺ salt of a bis(sulfonyl)imide bearing CF₃ and 4-FC₆H₄ groups. This journal is

Full text of DOI:10.1039/c4nj01191k

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Novel lithium and sodium salts of sulfonamides
and bis(sulfonyl)imides: synthesis and electrical
conductivity†
Cite this: New J. Chem., 2014,
38, 6193
Vincent Morizur,a Sandra Olivero,a Jean Roger Desmurs,b Philippe Knauthc and
Elisabet Dunach*a
˜
Received (in Montpellier, France)
17th July 2014,
Accepted 23rd September 2014
The preparation of new electrolytes for application in lithium or sodium batteries is described. Different
salts of lithium and sodium sulfonamide and bis(sulfonyl)imide were prepared in good yields. Ionic
conductivity measurements were performed on these salts and conductivities of 0.20 to 0.51 mS cmÀ1
comparable to those of Li-TFSI, were obtained. The best conductivity was reached for the Li+ salt of a
,
DOI: 10.1039/c4nj01191k
bis(sulfonyl)imide bearing CF3 and 4-FC6H4 groups.
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window; (iii) chemical stability at temperatures in the battery
under high power; (iv) Li- or Na-ion conductivity s (Li, Na) 4
Introduction
Secondary lithium-ion batteries constitute today the most advanced 10À4 S cmÀ1 at the temperature of battery operation; (v) very low
energy storage technology, ubiquitously used in various micro- electronic conductivity s (e) o 10À10 S cmÀ1; (vi) a transference
electronic and portable devices or in smart grids.1–6 Furthermore, number s (Li, Na)/s total E 1, where s total includes also
electric vehicles based on lithium batteries are in the final stage of partial conductivities by other ions in the electrolyte; (vii)
industrial development. Concerns about a future limitation of the retention of the electrode/electrolyte interface during cycling;
lithium reserves and an important price increase triggered research (viii) safety, i.e. preferably non-flammable and non-explosive
on secondary sodium batteries in recent years.7,8
components; and (ix) low toxicity and low cost.
All these applications need electrolytes with excellent electrical
A major drawback of current lithium and sodium electrolytes is
conductivity, high safety and low cost.9 Currently, polymer gel the fact that the transference number of the anion is generally
electrolytes10 are mostly applied: they are made of a polymeric higher than that of the cation; this leads to polarization phenomena
support (such as poly(vinylidene fluoride), PVdF) gelled with liquid at the electrodes, which are very detrimental to the battery
organic solvents (typically organic carbonates) containing dissolved cycling. Strategies to reduce the anion transference number
lithium salts, such as LiPF6 or Li-bis(trifluoromethanesulfonyl)imide include enhancing the anion molar mass in order to decrease
(Li-TFSI11,12).
its mobility or fixing the anion on a large macromolecule to
Advanced lithium and sodium battery electrolytes must satisfy impede its migration.9,13,14
many requirements,4 which make their development a very
Few attempts at improving the ionic conductivity have been
challenging task, including: (i) a large electrochemical stability realized via the salt approach, because the choice of anions
window between oxidation at high anodic potentials and suitable for lithium battery electrolytes is limited. Lithium
reduction at high cathodic potentials; (ii) chemical stability bis(trifluoromethanesulfonyl)imide15 proved to be safe, thermally
with respect to the electrodes, including the ability to form stable, and highly conducting and was even commercialized in the
rapidly a passivating solid-electrolyte-interface (SEI) layer, when early 1990s. The application of lithium ion cells, however, never
the electrode potential lies outside the electrolyte stability materialized because the Li-TFSI caused severe corrosion of Al
current collectors. Efforts made to reduce the reactivity by structural
modification of the imide anion extending the perfluorinated alkyl
a
´
Institut de Chimie de Nice, Universite de Nice-Sophia Antipolis, CNRS, UMR 7272,
chain were found to be effective, but aromatic groups were not
explored.9
´
Faculte des Sciences, Parc Valrose, 06108 Nice cedex 2, France.
E-mail: dunach@unice.fr
b
c
´
CDP Innovation, G2C Business Center, 63 Rue Andre Bollier, 69307 Lyon, France
In this work, we present a new synthetic strategy for the
preparation of lithium and sodium salts containing sulfonamide
and bis(sulfonyl)imide anions, in particular, with substituted phenyl
groups. We also report their ionic conductivity determined by
impedance spectroscopy. The high ionization degree of superacidic
´
Aix Marseille Universite, CNRS, Madirel (UMR 7246), 13397, Marseille Cedex 20,
France
† Electronic supplementary information (ESI) available: Procedure and analysis
for the preparation of compounds 2a–2b, 4a–4d, 5a–5d, 6a–6d, 9a–9b, 9e–9f and
10a–10f. See DOI: 10.1039/c4nj01191k
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bis(sulfonyl)imides12 together with the high anion mass and
the excellent redox stability of the aromatic groups are promising
properties for battery electrolyte applications.
Table 1 Preparation of sulfonamides 4
Entry
Amines 3
Sulfonamides 4
Yield of 4 (%)
1
98
Results and discussion
Preparation of Li+ and Na+ salts of sulfonamides and
bis(sulfonyl)imides
With the aim of evaluating the effect of several functional groups
and establishing structure–property relationships in the field of
electrical conductivity, a series of differently substituted lithium
and sodium sulfonamide and bis(sulfonyl)imide salts were prepared
in anhydrous form. The different salts were synthesized according to
two different procedures.
2
3
96
50
For lithium and sodium sulfonamides, the starting materials are
the aromatic compounds 1a and 2b, bearing electron-withdrawing
substituents, such as nitro or fluorine groups, respectively.
A chlorosulfonation reaction was carried out, adapting the reported
literature procedures.16,17 The chlorosulfonation, as presented
in Scheme 1, proceeded through the reaction of 1a–1b with
chlorosulfonic acid, followed by treatment with sulfonyl chloride.
The derivatives 2a, 2b, with the chlorosulfonyl group at the 3- or
4-position, respectively, were obtained in almost quantitative yields
after purification by column chromatography. These compounds
could be prepared at a 10 g-scale.
4
80
The reaction of 2 with different aromatic amines 3 led to the
formation of sulfonamides 4a–4d. The reactions were carried
out in acetonitrile, with two equivalents of amine, in order to
trap the evolving HCl. Ammonium chloride being insoluble in the
medium, the sulfonamides could be purified by filtration. Good
yields for compounds 4 were generally obtained as presented in
Table 1.
The preparation of lithium salts of sulfonamides is described
in the literature by the use of LiOH.18,19 However, this procedure
does not allow getting the desired sulfonamides as anhydrous
salts. We prepared the corresponding lithium salts by the direct
reaction of 4 with lithium metal in THF. The procedure afforded
the Li+ derivatives 5a–5d in quantitative yields, as illustrated in
Scheme 2 and in Table 2.
By the reaction of sulfonamides 4 with sodium metal in THF,
the corresponding Na+ salts, 6, could be obtained in anhydrous
form and in quantitative yields (Scheme 2 and Table 2).
For bis(sulfonyl)imide salts, the preparation involved the
reaction of aryl chlorosulfonyl derivatives 2 with several depro-
tonated sulfonamides 7 (Scheme 3). The coupling was carried
out in THF under a room temperature basic medium, either
with NaH or with triethylamine. The coupling reaction could
also be carried out in acetone at room temperature using
triethylamine.
Scheme 2 Synthesis of Li+ and Na+ sulfonamide salts 5 and 6.
Table 2 Synthesis of Li+ and Na+ sulfonamide salts 5 and 6
Entry
Sulfonamides
Sulfonamide salts
Yield (%)
1
2
3
4
5
6
7
8
4a
4a
4b
4b
4c
4c
4d
4d
5a
6a
5b
6b
5c
6c
5d
6d
498
98
97
498
98
98
498
97
Scheme 3 Synthesis of ammonium bis(sulfonyl)imide salts 8.
Triethylamine was used as the tertiary amine in order to
obtain a series of ammonium salts 8a–8f, which were purified
by trituration in diethyl ether. The yields of 8 are given in
Table 3. The Li+ salts of the corresponding bis(sulfonyl)imides,
9, were obtained by treatment of salts 8 with lithium metal in
THF. Following the same procedure with sodium metal, the
Scheme 1 Preparation of sulfonamides 4.
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Table 3 Synthesis of Li+ and Na+ bis(sulfonyl)imide salts 9 and 10
Yield
Yield
Entry Ammonium salts 8 of 8 (%) Li+/Na+ salts 9, 10 of 9, 10 (%)
1
2
51
51
98
99
Fig. 1 Concentration dependence of the ionic conductivity of solutions
of salt 6a in DMSO at 25 1C.
3
4
55
55
97
98
A linear relation between conductivity and concentration,
expected for completely dissociated strong electrolytes, was
observed at very low concentrations. At higher concentration, the
increase of conductivity flattens out because the ionic mobility
decreases at large salt concentrations due to the increased inter-
ionic interactions and to a higher solution viscosity.9 This classical
behavior is well documented in the framework of the Debye–Hu¨ckel
theory.23 The conductivity observed at a concentration of 0.1 mol LÀ1
(1.5 mS cmÀ1) can be compared with data reported in the literature
at higher concentration (5.1 mS cmÀ1 in 1.0 mol LÀ1 solution in
propylenecarbonate (PC),9 4–7 mS cmÀ1 in mixtures with ionic
liquids24).
5
6
7
63
59
94
97
96
97
0.01 mol LÀ1 solutions of Li+ and Na+-salts 5, 6, 9 and 10
were prepared in a glove box using dimethylsulfoxide (DMSO)
as the solvent. The solutions were analyzed using a closed 1 cm3
conductivity cell with a 1 cm2 platinum electrode area at 25 1C.
An impedance spectrometer EG&G model 6310 was used; the
amplitude of the ac signal was typically 20 mV at frequencies
between 100 kHz and 1 Hz.
Fig. 2 shows the conductivity of 0.01 molar solutions of the
various Li+ and Na+ salts in DMSO, a high dielectric constant
solvent. The conductivity of Li-TFSI, which is considered here
as a reference, is consistent with literature data (0.32 mS cmÀ1 in
0.01 mol LÀ1 solution in PC–ethylmethylcarbonate mixtures,20,21
2.1 mS cmÀ1 in 1 mol LÀ1 solution in DMSO22). The good ionic
conductivity is supposed to be the result of a compromise
between a high degree of dissociation and a low ionic mobility.9
The conductivity values of the new Li+ and Na+ salts are in the
order of 0.2 to 0.5 mS cmÀ1; the conductivity values are very
competitive with Li-TFSI and, although quite similar, some
observations on substituent effects can be made. The average
conductivity of the sulfonamides (5, 6) is slightly lower than that
of the bis(sulfonyl)imides (9, 10). This fact can be related to a
slightly lower dissociation degree of the sulfonamides.
8
94
98
9
97
97
98
97
10
bis(sulfonyl)imide Na+ salts, 10, were obtained in quantitative
yields (Scheme 4 and Table 3).
Ionic conductivity of the Li+ and Na+ salts of sulfonamides and
bis(sulfonyl)imides
The concentration dependence of the ionic conductivity for the
sodium salt 6a between 0.01 and 0.1 mol LÀ1 is illustrated in
Fig. 1.
The conductivity of salts with a fluorine group at the para-
position on the aromatic ring is superior to that with a nitro
substituent at the meta-position.
The high conductivity of the bis(sulfonyl)imides with a
trifluoromethyl moiety directly attached to a sulfonyl group
(9e, 10e and 9f, 10f) is consistent with the high electron-
withdrawing effect of the CF3 moiety involved and an increase
in the ionization degree. Two of these salts, namely 9e and 9f,
offered a higher conductivity than the reference compound
Scheme 4 Synthesis of Li+ and Na+ bis(sulfonyl)imide salts 9 and 10.
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Fig. 2 Ionic conductivity of Li+ and Na+ sulfonamide (5, 6) and bis(sulfonyl)imide (9, 10) salts in 0.01 mol LÀ1 solution in DMSO at 25 1C.
Li-TFSI. These Li+ salts could therefore be candidates for the The mixture was heated at 150 1C for 2 h 30 min. The solution
replacement of Li-TFSI in Li-batteries. The highest conductivity was cooled to room temperature and thionyl chloride was
was measured for salt 9f, which presents a directly linked added (1.42 equiv.) and the mixture was then heated at
trifluoromethyl moiety and a fluorine atom instead of a nitro 150 1C for 3 h. The solution was cooled to room temperature
group on the aromatic ring.
and quenched with 20 mL of water. The aqueous phase was
The conductivity of the Na+ salts was generally lower than extracted with 3 Â 20 mL of ethyl acetate. The combined organic
that measured for the corresponding Li+ salts. This is probably phases were dried with MgSO4, filtered and concentrated under
related to the smaller size of the Li+ ion and its higher mobility. reduced pressure. The residue was purified by chromatography
on silica gel using a mixture of dichloromethane/cyclohexane
(50/50) as the eluent.
Conclusions
Preparation of sulfonamides 4a–4d
New lithium and sodium salts of sulfonamide and bis(sulfonyl)-
In a 50 mL flask, the sulfonyl chloride 2 (2.3 mmol) and the
amine 3 (4.8 mmol) were added to 20 mL acetonitrile. The
solution was stirred at room temperature for 2 h, the mixture
was filtered off and the filtrate was evaporated. The residue was
purified by trituration in diethyl ether (3 Â 20 mL) and dried
under vacuum overnight.
imide were prepared and ionic conductivity measurements were
realized. The results obtained are comparable or even superior to
TFSI-Li, a salt generally used as an electrolyte (0.26 mS cmÀ1).
The best result was obtained with N-(trifluoromethanesulfonyl)-
p-fluorobenzenesulfonamide lithium salt, 9f, presenting an ionic
conductivity of 0.51 mS cmÀ1. The conductivities with sulfonamide
salts were lower as compared to those observed for the salts derived
from bis(sulfonyl)imides. Finally, the obtained ionic conductivities
for the lithium salts were generally superior to those measured for
the corresponding sodium salts. This fact is most probably due to
the higher mobility and the lower size of the Li+ ions as compared
to the Na+ ions.
Preparation of Li+ and Na+ sulfonamide salts 5a–5d and 6a–6d
In a 25 mL flask under nitrogen, the sulfonamide 4 (1 mmol)
was dissolved in 15 mL of THF. Lithium or sodium metal
(1.1 mmol) was added to the solution and after 18 h at room
temperature the mixture was filtered off. The residue obtained
was triturated with 2 Â 10 mL of acetonitrile and then dried
under vacuum overnight.
Experimental (ESI†)
Preparation of Li+ and Na+ bis(sulfonyl)imide salts 9a–9b, 9e–9f
and 10a–10f
Details of the analysis of the different compounds are given in
the ESI.†
In a 50 mL flask are introduced 20 mL of acetone, NaH
(2.8 mmol), triethylamine (2.8 mmol) and the sulfonamide 7
Preparation of benzenesulfonyl chlorides 2a–2b
In a two-necked 25 mL flask fitted with a condenser, the aromatic (2 mmol). After stirring for 15 min at room temperature, the
compound 1 (nitrobenzene or fluorobenzene) (81 mmol) was added, sulfonyl chloride 2 (2 mmol) was added. After stirring for 3 h at
followed by addition of chlorosulfonic acid (106 mmol) via a syringe. room temperature, the precipitate formed was filtered off and
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2 Â 20 mL of Et2O. After filtration, the solid was dissolved in
20 mL of CH2Cl2 and the solution was filtered. The solid
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We thank the Region PACA for a fellowship for V.M.
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