Note: Descriptions are shown in the official language in which they were submitted.
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Fluorinated sulfonamides as low-flammability solvents
for use in electrochemical cells
The invention relates to fluorinated sulfonamides as
low-flammability solvents for electrolytes for use in
electrochemical cells.
Lithium ion batteries. are amongst the most promising
systems for mobile applications. The areas of applica-
tion extend from high-quality electronic appliances
(e.g. mobile phones, camcorders) to batteries for
electrically driven motor vehicles.
These batteries consist of a cathode, an anode, a
separator and a non-aqueous electrolyte. The cathodes
used are typically Li (MnMeZ) Z04, Li (CoMeZ) O2,
Li(CoNiXMeZ)02 or other lithium intercalation and
insertion compounds. Anodes can consist of lithium
metal, carbon materials, graphite, graphitic carbon
materials or other lithium intercalation and insertion
compounds or alloy compounds. The electrolytes used are
solutions containing lithium salts, such as LiPF6,
LiBFq, LiC104, LiAsF6, LiCF3S03, LiN (CF3S02) Z or
LiC(CF3S02)3 and mixtures thereof, in aprotic solvents.
A great number of additives for use in lithium ion
batteries is mentioned in the literature. For example,
in EP 0759641 and US 5776627, organic aromatic
compounds, such as biphenyl, substituted thiophenes and
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furans, and in EP 0746050 and EP 0851524, substituted
anisole, mesitylene and xylene derivatives, are added
to the electrolyte in order to increase the safety of
the battery in the case of overcharging. For the same
purpose, US 5753389 uses organic carbonates as
additives. In order to improve the cycle stability,
organic boroxines are added in EP 0856901. However, all
these additives have some crucial disadvantages.
Organic substances, as used in the specifications
mentioned here, generally have low flash points and low
explosion limits.
Additive Explosion limit [$] Flash point [C]
Thiophene 1.5-12 -9
Anisole 0.34-6.3 43
Mesitylene 1-6 54
Furan 2.3-14.3 -35
According to the current state of the art, the
electrolyte liquids used are preferably solvent
mixtures comprising at least two components. The
mixture has to include at least one strongly polar
component which, owing to its polarity, has a strong
dissociating effect on salts. Examples of these polar
components are ethylene carbonate or propylene
carbonate. Since these highly polar solvents are
usually highly viscous, low-viscosity solvents are
generally added to the electrolyte as "diluents". The
diluents, typical examples of which are 1,2-
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dimethoxyethane, dimethyl carbonate or diethyl
carbonate, are added in a proportion between 30 and
70%. A serious disadvantage of these low-viscosity
solvents is their low flash point and their high
volatility.
When electrolyte solutions are used electrochemically
and to an even greater extent in the event of faults
(short-circuiting, overcharging), warming always
occurs, increasing the risk of ignition of the
electrolyte.
To increase safety, cathode and anode spaces can be
separated by a microporous separator membrane.
Furthermore, the safety of these cells can be increased
by installing overpressure protection devices which
react to gas evolution on overcharging.
Flame-retardant phosphorus- and halogen-containing
additives are recommended, but these frequently have an
adverse effect on the performance characteristics of
the batteries.
However, all these measures cannot rule out the
possibility that the volatile and flammable "diluent"
nevertheless ignites eventually in the event of
malfunctions. Burning lithium reacts very violently not
only with water but also with carbon dioxide.
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The object of the present invention is therefore to
provide additives which have a low volatility and a
relatively high flash point and are physically and
chemically stable, sufficiently miscible with other
suitable solvents and have a good conductivity
behaviour.
The object according to the invention is achieved by
compounds of the general formula
X- ( CYZ ) m-SOzN ( CR1R2R3 ) 2 ( I )
where
X is H, F, Cl, CnF2n+1i CnF2n-1 Or
(S02) kN (CR1RZR3) 2r
Y is H, F or Cl,
Z is H, F or C1,
R1, R2 and R3 are H and/or alkyl, fluoroalkyl or
cycloalkyl,
m is 0-9 and, if X = H, m ~ 0,
n is 1-9,
k is 0 if m = 0, and k = 1 if m = 1-9.
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The compounds of the formula (I) can be employed in
electrochemical cells such as supercapacitors and
primary or secondary lithium batteries, in particular
as solvents.
It has been found that the compounds of the formula (I)
have a low flammability. This makes it possible to
reduce the risk of ignition in the event of faults.
Surprisingly, it has been found that the compounds of
the formula (I) have a high electrochemical stability.
Experiments have shown that oxidative decomposition of
an electrolyte which comprises a compound of the
formula (I) and commonly used solvents (e. g. EC, DMC)
and a typical conductive salt (e. g. LiPF6) occurs only
once a potential of about 5.5 V against Li/Li+ has been
reached.
It has been found that the compounds of the formula (I)
are miscible with commonly used solvents. Neither phase
separation nor crystallization of the conductive salt
was observed.
The compounds of the formula (I) may also be used in
electrolytes in the form of mixtures, in proportions
between 1 and 100, preferably between 10 and 50~, with
commonly used solvents such as EC, DMC, PC and DEC.
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Electrolytes which can be used are solutions of LiPFs,
LiBFq, LiClOq, LiAsF6, LiCF3S03, LiN (CF3S02) 2 or
LiC(CF3S02)3 and mixtures thereof, in aprotic solvents
such as EC, DMC, PC, DEC, BC, VC, cyclopentanone,
sulfolane, DMS, 3-methyl-1,3-oxazolidin-2-one, y-
butyrolactone, EMC, MPC, BMC, EPC, BEC, DPC, 1,2-
diethoxymethane, THF, 2-methyltetrahydrofuran, 1,3-
dioxolane, methyl acetate, ethyl acetate and mixtures
thereof.
The electrolytes may further comprise organic
isocyanates (DE 199 44 603) to reduce the water
content. Likewise, the electrolytes may comprise
organic alkali metal salts (DE 199 10 968) as
additives. Suitable alkali metal salts are alkali metal
borates of the general formula
Li+B- ( OR1 ) m ( 0R2 ) p
where
m and p are 0, 1, 2, 3 or 4 with m + p = 4 and
R1 and R2 are identical or different,
if desired are joined directly to one another by a
single or double bond,
are, in each case individually or together, an aromatic
or aliphatic carboxylic, dicarboxylic or sulfonic acid
radical, or
CA 02321373 2000-09-27
are, in each case individually or together, an aromatic
ring selected from the group consisting of phenyl,
naphthyl, anthracenyl and phenanthrenyl, which may be
unsubstituted or monosubstituted to tetrasubstituted by
A or Hal, or
are, in each case individually or together, a
heterocyclic aromatic. ring selected from the group
consisting of pyridyl, pyrazyl and bipyridyl, which may
be unsubstituted or monosubstituted to trisubstituted
by A or Hal, or
are, in each case individually or together, an aromatic
hydroxy acid selected from the group consisting of
aromatic hydroxycarboxylic acids and aromatic
hydroxysulfonic acids, which may be unsubstituted or
monosubstituted to tetrasubstituted by A or Hal,
and
Hal is F, C1 or Br
and
A is alkyl having from 1 to 6 carbon atoms, which may
be monohalogenated to trihalogenated. Likewise suitable
are alkali metal alkoxides (DE 9910968) of the general
formula
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Li+OR-
where R
is an aromatic or aliphatic carboxylic, dicarboxylic or
sulfonic acid radical, or
is an aromatic ring selected from the group consisting
of phenyl, naphthyl, anthracenyl and phenanthrenyl,
which may be unsubstituted or monosubstituted to
tetrasubstituted by A or Hal, or
is a heterocyclic aromatic ring selected from the group
consisting of pyridyl, pyrazyl and bipyridyl, which may
be unsubstituted or monosubstituted to trisubstituted
by A or Hal, or
is an aromatic hydroxy acid selected from the group
consisting of aromatic hydroxycarboxylic acids and
aromatic hydroxysulfonic acids, which may be
unsubstituted or monosubstituted to tetrasubstituted by
A or Hal,
and
Hal is F, C1 or Br,
and
A is alkyl having from 1 to 6 carbon atoms, which may
be monohalogenated to trihalogenated.
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_ g _
The electrolytes may likewise comprise compounds of the
general formula
L ( LR1 (CRZR3) x] iAx) yKt] + -N (CF3) z
where
Kt is N, P, As, Sb, S or Se,
A is N, P, P (0) , 0, S, S (0) , SOz, As, As (0) , Sb or
Sb(0),
R1, Rz and R3
are identical or different
and are each H, halogen, substituted and/or
unsubstituted alkyl CnHzn+i. substituted and/or
unsubstituted alkenyl having 1-18 carbon atoms and
one or more double bonds, substituted and/or
unsubstituted alkynyl having 1-18 carbon atoms and
one or more triple bonds, substituted and/or
unsubstituted cycloalkyl CmHzm_1, mono- or
polysubstituted and/or unsubstituted phenyl,
substituted and/or unsubstituted heteroaryl,
A can be included in R1, Rz and/or R3 in various
positions,
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Kt can be included in a cyclic or heterocyclic
ring,
the groups bonded to Kt may be identical or
different,
where
n is 1-18
m is 3-7
k is 0 or 1-6
1 is 1 or 2 in the case where x = 1 and 1 in the
case where x = 0
x is 0 or 1
y is 1-4
(DE 9941566). The process for preparing the
compounds is characterized in that an alkali metal
salt of the general formula
~+ N (CF3) z
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where D+ is selected from the group consisting of
the alkali metals, is reacted in a polar organic
solvent with a salt of the general formula
~ C ~R1 (CRZR3) xl iAX) yKt] + -E
where
Kt, A, R1, R2, R3, k, 1, x and y are as defined
above and
-E is F-, C1-, Br-, I-, BF4-, C104-, As F6-, SbF6- or
PF6-.
Lithium complex salts of the formula
Re
R5 O~ ~~O
\ S~0
Li ~ ~~OR~
R4 ~ O~g 2
R3 OR
where
R1 and R2 are identical or different, if desired are
joined directly to one another by a single or double
bond, and are, in each case individually or together,
an aromatic ring selected from the group consisting of
phenyl, naphthyl, anthracenyl and phenanthrenyl, which
may be unsubstituted or monosubstituted to
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hexasubstituted by alkyl (C1 to C6), alkoxy groups (C1
to C6) or halogen (F, Cl, Br),
or are, in each case individually or together, an
aromatic heterocyclic ring selected from the group
consisting of pyridyl, pyrazyl and pyrimidyl, which may
be unsubstituted or monosubstituted to tetrasubstituted
by alkyl (C1 to C6) , alkoxy groups (C1 to C6) or halogen
(F, Cl, Br),
or are, in each case individually or together, an
aromatic ring selected from the group consisting of
hydroxybenzenecarboxyl, hydroxynaphthalenecarboxyl,
hydroxybenzenesulfonyl and hydroxynaphthalenesulfonyl,
which may be unsubstituted or monosubstituted to
tetrasubstituted by alkyl (C1 to C6) , alkoxy groups (C1
to C6) or halogen (F, C1, Br) ,
R3-R6 can, in each case individually or in pairs, if
desired joined directly to one another by a single or
double bond, have the following meanings:
1. alkyl (C1 to C6) , alkyloxy (C1 to C6) or halogen (F,
Cl, Br)
2. an aromatic ring selected from the groups
consisting of
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phenyl, naphthyl, anthracenyl and phenanthrenyl, which
may be unsubstituted or monosubstituted to
hexasubstituted by alkyl (C1 to C6), alkoxy groups (C1
to C6) or halogen (F, Cl, Br),
pyridyl, pyrazyl and pyrimidyl, which may be
unsubstituted or monosubstituted to tetrasubstituted by
alkyl (C1 to C6) , alkoxy groups (C1 to C6) or halogen (F,
C1, Br) ,
which are prepared by the following process
(DE 199 32 317)
a) 3-, 4-, 5-, 6-substituted phenol is admixed in a
suitable solvent with chlorosulfonic acid,
b) the intermediate from a) is reacted with
chlorotrimethylsilane, and the product is filtered and
subjected to fractional distillation,
c) the intermediate from b) is reacted with lithium
tetramethoxyborate(1-) in a suitable solvent and the
end product is isolated therefrom,
can also be present in the electrolyte.
Use can also be made of electrolytes comprising complex
salts of the general formula (DE 199 51 804)
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M"+[EZ]v xiv
where:
x, y are 1, 2, 3, 4, 5 or 6,
M"+ is a metal ion,
E is a Lewis acid selected from the group consisting of
BR1RZR3, AlR1R2R3, PR1RZR3R4R5, AsR1R2R3R9R5 and VR1RZR3R9R5.
R1 to RS are identical or different, if desired are
joined directly to one another by a single or double
bond, and may be, in each case individually or
together,
a halogen ( F, C1, Br) ,
an alkyl or alkoxy radical (C1 to C$) which may be
partially or fully substituted by F, C1, Br,
an aromatic ring, if desired bonded via oxygen,
selected from the group consisting of phenyl, naphthyl,
anthracenyl and phenanthrenyl, which may be
unsubstituted or monosubstituted to hexasubstituted by
alkyl (C1 to C8) or F, C1, Br,
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an aromatic heterocyclic ring, if desired bonded via
oxygen, selected from the group consisting of pyridyl,
pyrazyl and pyrimidyl, which may be unsubstituted or
monosubstituted to tetrasubstituted by alkyl (G1 to C$)
or F, Cl, Br, and
Z is OR6, NR6R', CR6R'Re, OSOZR6, N ( S02R6 ) ( S02R' ) ,
C ( SOZR6 ) ( SOZR' ) ( SOZR$ ) or OCOR6, where
R6 to R8 are identical or different, if desired are
joined directly to one another by a single or double
bond, and are, in each case individually or together,
a hydrogen or as defined for R1 to R5, prepared by
reacting a corresponding boron or phosphorus Lewis
acid-solvent adduct with a lithium or tetraalkyl-
ammonium imide, methanide or triflate.
Borate salts (DE 199 59 722) of the general formula
Ra R~ Y_
MX+ ~ B
R3 RZ "~Y
where:
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M is a metal ion or tetraalkylammonium ion,
x, y are 1, 2, 3, 4, 5 or 6,
R1 to R4 are identical or different alkoxy or carboxyl
radicals (C1-CB) which may be joined directly to one
another by a single or double bond can also be present.
These borate salts are prepared by reacting lithium
tetraalkoxyborate or a 1:1 mixture of lithium alkoxide
and a boric ester in an aprotic solvent with a suitable
hydroxyl or carboxyl compound in the ratio 2:1 or 4:1.
The novel compounds can also be used in electrolytes
comprising lithium fluoroalkylphosphates of the
following general formula
Li+ [PFx (CyFZy+i-ZHZ) 6-xJ
where
1 <_ x <_ 5
3 <_ y <_ 8
0 <_ z <_ 2y + 1
and the ligands (CyF2y+i-zHZ) can be identical or
different, with the exception of compounds of the
general formula
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Li+ [ PFa (CHbF~ (CF3 ) d) e~
in which a is an integer from 2 to 5, b = 0 or 1, c = 0
or 1, d = 2 and
a is an integer from 1 to 4, with the provisos that b
and c are not simultaneously 0 and the sum of a + a is
6 and the ligands (CHbF~ (CF3) d) can be identical or
different (DE 100 089 55). The process for preparing
lithium fluoroalkylphosphates is characterized in that
at least one compound of the general formula
HmP ( CnH2n+1 ) 3-m ( I I I ) ,
OP (CnH2n+1) 3 ( IV) r
C 1mP ( CnH2n+1 ) 3-m ( V ) r
FmP (CnH2n+1) 3-m (VI) ,
Clop (CnH2n+1) 5-0 (VII ) Or
FoP ( CnH2n+1 ) 5-0 ( VI I I ) ,
where in each case
0 < m < 2, 3 < n < 8 and 0 < o < 4,
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is fluorinated by electrolysis in hydrogen fluoride,
the resulting mixture of fluorination products is
fractionated by extraction, phase separation and/or
distillation, and the resulting fluorinated
alkylphosphorane is reacted with lithium fluoride in an
aprotic solvent or solvent mixture in the absence of
moisture, and the resulting salt is purified and
isolated by customary methods.
The novel compounds can also be used in electrolytes
comprising salts of the formula
Li [ P ( OR1 ) a ( ORZ ) b ( OR3 ) c ( ~R4 ) dF'e ~
where 0 < a+b+c+d <_ 5 and a+b+c+d+e=6, and Rl to R4 are
each, independently of one another, alkyl, aryl or
heteroaryl radicals, it being possible for at least two
of R1 to Rq to be j oined directly to one another by a
single or double bond (DE 100 16801). These compounds
are prepared by reacting phosphorus(V) compounds of the
general formula
P ( OR1 ) a ( ~RZ ) b ( ~R3 ) c ( OR9 ) dFe
where 0 < a+b+c+d <_ 5 and a+b+c+d+e=5, and R1 to R4 are
as defined above, with lithium fluoride in the presence
of an organic solvent.
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The novel compounds can be used in electrolytes for
electrochemical cells which comprise anode material
consisting of coated metal cores selected from the
group consisting of Sb, Bi, Cd, In, Pb, Ga and tin or
alloys thereof (DE 100 16 024). The process for
preparing said anode material is characterized in that
a) a suspension or a _sol of the metal core or alloy
core is prepared in urotropine,
b) the suspension is emulsified with C5-C12-hydro-
carbons,
c) the emulsion is precipitated onto the metal cores or
alloy cores, and
d) the metal hydroxides or oxyhydroxides are converted
into the corresponding oxide by heat-treating the
system.
The novel compounds can also be used in electrolytes
for electrochemical cells comprising cathodes
consisting of commonly used lithium intercalation and
insertion compounds or else cathode materials
consisting of lithium mixed oxide particles which are
coated with one or more metal oxides (DE 199 22 522) by
suspending the particles in an organic solvent,
admixing the suspension with a solution of a
hydrolysable metal compound and a hydrolysis solution
and then filtering off, drying and, if desired,
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calcining the coated particles. They can also consist
of lithium mixed oxide particles which are coated with
one or more. polymers (DE 199 46 066) and are obtained
by a process in which the particles are suspended in a
solvent and the coated particles are subsequently
filtered off, dried and, if desired, calcined.
Likewise, the novel compounds can be used in systems
comprising cathodes which consist of lithium mixed
oxide particles, which are singly or multiply coated
with alkali metal compounds and metal oxides
(DE 100 14 884). The process for preparing these
materials is characterized in that the particles are
suspended in an organic solvent, an alkali metal salt
compound suspended in an organic solvent is added,
metal oxides dissolved in an organic solvent are added,
the suspension is admixed with a hydrolysis solution,
and the coated particles are subsequently filtered off,
dried and calcined.
The present invention accordingly provides electrolytes
comprising compounds of the formula (I).
The present invention further provides electrochemical
cells, in particular primary and secondary lithium
batteries and supercapacitors, essentially consisting
of a .corresponding electrolyte and a cathode, an anode
and a separator.
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In mixtures with commonly used conductive salts, the
compounds of the general formula (I) have a good
conductivity.
A general example of the invention is explained in
greater detail below.
Preparation of compounds of the formula (I)
An apparatus equipped with stirrer and cooling means is
charged with dimethylamine in a suitable solvent.
Suitable solvents are organic solvents, for example
diethyl ether or choloroform.
Partially fluorinated or perfluorinated alkylsulfonyl
fluorides are added while stirring and cooling to
temperatures between -30°C and 0°C. The reaction
solution is then warmed to temperatures between room
temperature and 40°C. The solvent is distilled off.
However, it is also possible to react halosulfonamides
with commonly used fluorinating reagents, for example
antimony trifluoride, arsenic trifluoride or potassium
fluoride.
Halosulfonamides in suitable solvents, for example
benzene, are refluxed for 1-4 hours, preferably for 2
hours, while stirring, with a fluorinating reagent in
an apparatus equipped with condenser and stirrer. The
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reaction solution is cooled down to room temperature
and then filtered. The solvent is distilled off and the
residue is distilled under reduced pressure. The
product is redistilled under atmospheric pressure if
necessary.
Flammabilit
The flammability of the compounds of the formula (I)
was investigated. It was attempted to ignite compounds
prepared according to the processes described above by
means of an open flame. These attempts were
unsuccessful.
Electrochemical stabilit
Compounds of the formula (I) are added to an
electrolyte consisting of commonly used conductive
salts such as LiPF6, LiBF4, LiC104, LiAsF6, LiCF3S03,
LiN (CF3SOZ) Z or LiC (CF3SOZ) 3 and mixtures thereof, in
aprotic solvents such as EC, DMC, PC, DEC, BC, VC,
cyclopentanone, sulfolane, DMS, 3-methyl-1,3-
oxazolidin-2-one, 'y-butyrolactone, EMC, MPC, BMC, EPC,
BEC, DPC, 1,2-diethoxymethane, THF, 2-methyltetra-
hydrofuran, 1,3-dioxolane, methyl acetate, ethyl
acetate and mixtures thereof. The proportion of the
compounds of the formula (I) in the solvent mixture is
between 1 and 1000.
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In each case, 3-5 cyclic voltammograms were recorded
successively in a measurement cell containing a
stainless steel, platinum or gold working electrode, a
lithium counterelectrode and a lithium reference
electrode. To this end, starting from the rest
potential, the potential was firstly increased at a
rate of from 1 mV/s to 100 mV/s to voltages above the
respective decomposition potential of the corresponding
additive against Li/Li+, and then moved back to the rest
potential.
The results show that oxidative decomposition of these
electrolytes occurs only once a potential of about 5.0
V against Li/Li+ has been reached. They are therefore
suitable for use in electrochemical cells.
Miscibility with standard solvents and resulting
conductivities
Incrementally increasing amounts of compounds of the
formula (I) were added to a reference electrolyte
consisting of LiPF6, LiBF9, LiC104, LiAsF6, LiCF3S03,
LiN (CF3S02) 2 or LiC (CF3S02) 3 and mixtures thereof, in
aprotic solvents such as EC, DMC, PC, DEC, BC, VC,
cyclopentanone, sulfolane, DMS, 3-methyl-1,3-
oxazolidin-2-one, y-butyrolactone, EMC, MPC, BMC, EPC,
BEC, DPC, 1,2-diethoxymethane, THF, 2-methyltetra-
hydrofuran, 1,3-dioxolane, methyl acetate, ethyl
acetate and mixtures thereof.
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Neither phase separations nor crystallizations of the
conductive salt were observed. The compounds of the
formula (I) are miscible with the reference
electrolytes in any proportion.
Conductivity tests are carried out using a reference
electrolyte at various_temperatures.
The following examples are intended to explain the
invention in more detail without limiting it.
Examples
Example 1
N,N-Dimethyltrifluoromethylsulfonamide
The reaction is carried out in a three-neck flask
equipped with cold trap, stirrer and means for
introducing gaseous reagents. The cold trap is
maintained at a temperature of -78°C. 250 cm3 of diethyl
ether are introduced into the flask and cooled with
ice-water. 138 g (3.07 mol) of gaseous dimethylamine,
obtained from the reaction of 260 g (3.19 mol) of
dimethylamine hydrochloride with 153 g (3.83 mol) of
saturated sodium hydroxide solution and dried over
potassium hydroxide, are condensed in the flask. 202 g
(1.33 mol) of gaseous trifluoromethylsulfonyl fluoride
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are added in the course of 2 hours while stirring.
After addition of all reagents is complete, the
reaction vessel is warmed to 40°C in the course of 2
hours. The reaction mixture is diluted with 0.5 1 of
water and subsequently extracted with diethyl ether.
The extract is washed with water and dried over MgS04.
The diethyl ether is distilled off and the residue is
distilled under atmospheric pressure.
230.4 g of N,N-dimethyltrifluoromethylsulfonamide are
obtained.
Yield: 98%
CF3SOZN(CH3)Z: b.p.. 151-152°C
19F-NMR: -75.1 sep (CF3S02)
1H-NMR : 3 . 0 5 q ( 2 CH3 )
SJH,E ° 1.2 HZ
Example 2
N,N-Dimethylnonafluorobutylsulfonamide
The reaction is carried out in a three-neck flask
equipped with cold trap, stirrer and dropping funnel.
The cold trap is maintained at a temperature of -78°C.
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100 g (0.331 mol) of perfluorobutylsulfonyl fluoride
are slowly added to 43 g (0.95 mol) of liquid
dimethylamine at -30°C while stirring. After addition
is complete, the reaction mixture is warmed to room
temperature and stirred for 3 hours . 0 . 1 1 of water is
added and the resulting mixture is subsequently
extracted with diethyl ether. The extract is washed
with water and dried over Na2S0q. The solvent is
distilled off.
114.5 g of white crystalline N,N-dimethylnonafluoro-
butylsulfonamide are obtained.
Yield: 87.5
C4F9SOZN(CH3)2: m.p.. 32°C
19F-NMR: -81.5 tt (3F, CF3)
-112.2 tm (2F, CFZ)
-121.9 m (2F, CFZ)
-126.4 tm (2F, CFz)
3Je,e = 2.2 Hz
qJF,e = 9.9 Hz
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4JF,F = 13.9 Hz
1H-NMR : 3 . 1 s ( 2CH3 )
Example 3
Bis(N,N-dimethylamidosulfonyl)difluoromethane
The reaction is carried out in a three-neck flask
equipped with cold trap, stirrer and dropping funnel.
The cold trap is maintained at a temperature of -78°C.
99 g (0.458 mol) of di(fluorosulfonyl)difluoromethane
are slowly added to 101 g (2.084 mol) of liquid
dimethylamine in 100 cm3 of chloroform at -30°C while
stirring. After addition is complete, the reaction
mixture is warmed to room temperature and stirred for 3
hours. The solvent is distilled off 0.3 1 of water is
added to the residue and the resulting mixture is
subsequently extracted with diethyl ether. The extract
is washed with water and dried over Na2S0q. About 80~ of
the solvent is distilled off.
91.2 g of white crystalline bis(N,N-dimethylamido-
sulfonyl)difluoromethane are obtained.
Yield: 74.8a
(CH3) ZNSOZCFzSO2N (CH3) 2: m. p. . 71-72 °C
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i9F-NMR: -100.4 m (2F, CFZ)
1H-NMR: 3.06 t (4CH3)
SJH,F = 1.0 Hz
Example 4
N,N-Dimethylamidosulfonyl fluoride
The reaction is carried out in a two-neck flask
equipped with stirrer and cooling means. 80 g
(0.557 mol) of N,N-dimethylamidosulfonyl chloride in
100 crn3 of dry benzene are added to 66 g (0.369 mol) of
antimony trifluoride. 5 cm3 of antimony pentachloride
are added while stirring. The reaction mixture is
refluxed for 2 hours. The solution is cooled to room
temperature and filtered. The benzene is distilled off
and the residue is distilled under reduced pressure.
Redistillation under atmospheric pressure afforded
53.8 g of pure N,N-dimethylamidosulfonyl fluoride
(R. Heap, J. Chem. Soc. 1948, 1313).
Yield: 76%
FSOZN (CH3) 2: b.p. . 149-150°C
i9F-NMR: 33.0 sep
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2.0 HZ
Example 5
Flammability of N,N-dimethyltrifluoromethylsulfonamide
It was attempted to ignite 100 ml of N,N-
dimethyltrifluoromethyl.sulfonamide in air by means of
an open flame. This attempt was unsuccessful.
Example 6
Electrochemical stability of N,N-dimethyltrifluoro-
methvlsulfonamide
5 cyclic voltammograms were recorded successively in a
measurement cell containing a platinum electrode, a
lithium counterelectrode and a lithium reference
electrode. To this end, starting from the rest
potential, the potential was firstly increased at a
rate of 10 mV/s to 6 V against Li/Li+, and then moved
back to the rest potential.
The characteristic profile shown in Fig. 1 is obtained.
Oxidative decomposition of the electrolyte, consisting
of 1 mol/1 of LiPF6 in EC/DMC/N,N-dimethyltrifluoro-
methylsulfonamide (47.5/47.5/5), occurs only once a
potential of about 5.5 V against Li/Li+ has been
reached. The electrolyte is therefore suitable for use
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in lithium ion batteries comprising a transition metal
cathode.
Example 7
Miscibility with standard solvents and resulti
conductivities
Incrementally increasing amounts of N,N-dimethyltri-
fluoromethylsulfonamide are added to a reference
electrolyte (1 mol/1 of LiPF6 in EC/DMC (1:1)). The
fluorinated solvent is miscible with the reference
electrolyte in any proportion. Neither phase separation
nor crystallization of the conductive salt was
observed.
Conductivity data:
Electrolyte: 1 mol/1 of LiPF6 in EC/DMC/N,N-dimethyl-
trifluoromethylsulfonamide (47.5/47.5/5)
Temperature in C 20 -20 -30
Conductivity in mS/cm 8.6 2.9 2.1
