CA2349903C

CA2349903C - Ionic liquids ii

Info

Publication number: CA2349903C
Application number: CA002349903A
Authority: CA
Inventors: Michael Schmidt; Udo Heider; Winfried Geissler; Nikolai Ignatyev; Volker Hilarius
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH; PNC Bank NA
Priority date: 2000-06-09
Filing date: 2001-06-07
Publication date: 2010-02-02
Anticipated expiration: 2021-06-07
Also published as: BR0102318A; CN100413873C; DE50106762D1; KR20020017934A; CN1327986A; US7153974B2; RU2272043C2; KR100781473B1; TWI300780B; JP5236135B2; DE10027995A1; EP1162204A1; US20020015884A1; JP2002025610A; EP1162204B1; CA2349903A1

Abstract

An ionic liquid of the general formula: K+A- (I), in which: K+ is a cation which is: (see formula II), (see formula III), (see formula IV), (see formula V), (see formula VI), (see formula VII), (see formula VIII), (see formula IX), where R1 to R6 are identical or different, are optionally bonded directly to one another by a single or double bond and each, individually or together, have the following meaning: - H, - halogen, a C1 to C8 alkyl radical, which may be partially or fully substituted by F, Cl, N(C n F(2n+1-x)H x)2, O(C n F(2n+1-x)H x), SO2(C n F(2n+1-x)H x) or C n F(2n+1- x)H x, where 1 < n < 6 and 0 < x <= 2n+1; and A- is tris(pentafluoroethyl)trifluorophosphate or tris(nonafluorobutyl)trifluorophosphate.

Description

2001 10OB265doc 1/25 CA 02349903 2001-06-07 Ionic liquids II

The invention relates to ionic liquids for use in electrochemical cells and organic syntheses.

Solvent-free ionic liquids or "salts which are molten at room temperature" were described for the first time in US 2446331. The problem with these strong Lewis acids is the formation of toxic gases on contact with atmospheric moisture.

Compounds involving AIC13 and 1-ethyl-3-methylimidazolium (EMI) chloride have been investigated for a long time. Wilkes and Zaworotko presented novel solvent-free ionic liquids, EMI BF4 and EMI O2CCH3, in 1992 in J. Chem. Soc., Chem. Commun., p. 965.
However, these compounds are unsuitable for use as electrolyte in electrochemical cells since the BF4 and CH3C02 anions are oxidised even at relatively low potentials.

DE 196 41 138 describes a new class of conductive salts, the lithium fluoroalkylphosphates. These salts are distinguished by high electrochemical stability and low tendency towards hydrolysis (M. Schmidt et al. 10th International Meeting on Lithium Batteries, Como 2000). In cycling experiments, these compounds have shown particularly good results and have proven particularly stable.

US 5827602 describes the use of ionic liquids from the group consist-ing of pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazole-ium, pyrazolium, thiazolium, oxazolium and triazolium salts in electro-chemical cells containing imides and methanides as anions. These ionic liquids are particularly suitable for this application owing to good conductivities. The crucial disadvantage consists in the expensive synthesis of the raw materials, in particular the anions.

The object of the present invention is therefore to provide ionic liquids which have a large liquid range, high thermal stability and low corrosivity and anions which are less expensive to synthesise.

-2-The object according to the invention is achieved by ionic liquids of the general formula K+A- (I) in which:

K+ is a cation selected from the group consisting of ::x:: -'~z R6 ~ R2 R6 ::xx::
N 1S ~ R5 R3 R4 R4 R5 RI R5 ,R1 N
N
R4, Y , ~+~

R5 R1 ,R1 N-N

R4 p R2 R4 N R2 where R' to R6 are identical or different, are optionally bonded directly to one another by a single or double bond and each, individually or together, have the following meaning:

- H, - halogen, - an alkyl radical (C, to C8), which may be partially or fully substituted by further groups, preferably F, Cl, N(CnF(2n+1_X)HX)2, O(CnF(2n+1_X)HX), S02(CnF(2n+l_X)Hx) or CnF(2n+1_X)Hx where 1< n< 6 and 0< x<_ 2n+1

-3-and is an anion selected from the group consisting of [PFx(cyF2y+tz11z)x where 1 x < 6 1 <y<8and 0<z <2y+1.

In one aspect of the present invention, there is provided an ionic liquid of the general formula:

K'A (I), in which:

K+ is a cation which is:

Rl R1 ::x::, RS N'N R4 R4 ~ 1 +
R5,~N R3 R5 N R3 'IN. /~'~
R4 y R2 R4 s R2 N-N
+~.
R4 0 R2 or R4 N R2 where R' to R6 are identical or different, are optionally bonded directly to one another by a single or double bond and each, individually or together, have the following meaning:

- 3a -_H, - halogen, - a C, to C8 alkyl radical, which may be partially or fully substituted by F, Cl, N(CnF(2n+t-x)Hx)2, O(CnF(2n+1-x)Hx), SO2(CnF(2nf t-x)Hx) or CnF(2n+1-x)Hx, where 1 <n<6ando<x<_ 2n+1; and A- is tris(pentafluoroethyl)trifluorophosphate or tris(nonafluorobutyl)trifluorophosphate.
These ionic liquids are suitable as solvents in organic synthesis, but also for use in electrochemical cells. In addition, the ionic liquids are suitable for use in the catalysis of chemical reactions. In addition, they can be used as inert solvents for highly reactive chemicals. A
further area is use as hydraulic liquid. Yet another area of use is in supercapacitors.
It has been found that the compounds according to the invention are hydrophobic due to the use of perfluorinated alkyl chains, preference being given to relatively long-chain perfluorinated alkyl chains.
Furthermore, the anhydrous synthesis minimises the undesired introduction of water into the system.

Surprisingly, it has been found that the ionic liquids do not corrode, but instead even passivate the aluminium current collector usually used in electrochemical cells. This enables the cycle stability to be increased. In addition, improved thermal stability of the system through the use of ionic liquids has been observed.

It has been found that the addition, of solvents of low viscosity enables the conductivity to be improved. Low viscosity together with high conductivity is the prerequisite for use in electrochemical cells.
The compounds according to the invention have a large liquid range, making them particularly suitable for these applications.

A prerequisite for use in double layer capacitors is high conductivity.
The compounds according to the invention satisfy this criterion and can therefore be employed alone or in mixtures with other solvents or 2001 100B265.doC 4/25 CA 02349903 2001-06-07

-4-conductive salts. Suitable solvents are those selected from the group consisting of organic carbonates (for example ethylene carbonate, propylene carbonate and derivatives thereof, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.), organic carboxylic acid esters (for example y-butyrolactone, methyl formate, methyl acetate, ethyl acetate, ethyl propionate, methyl propionate, methyl butyrate, ethyl butyrate, etc.), organic carboxylic acid amides (for example dimethylformamide, methylformamide, formamide, etc.), organic ethers (for example 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydrofuran derivatives, 1,3-dioxolane, dioxane, dioxolane derivatives, etc.) or other aprotic solvents (for example acetonitrile, sulfolane, dimethyl sulfoxide, nitromethane, phosphoric acid triesters, trimethoxymethane, 3-methyl-2-oxazolidinone, etc.). It is likewise possible to use solvent mixtures, such as, for example, ethylene carbonate/dimethyl carbon-ate (EC/DMC).

The compounds according to the invention can be used in customary electrolytes with conventional conductive salts. They may be present in mixtures between 1 and 99%. Examples of suitable electrolytes are those with conductive salts selected from the group consisting of LiPF6, LiBF4, LiCIO4, LiAsF6, LiCF3SO3, LiN(CF3SO2)2 and LiC(CF3SO2)3, and mixtures thereof.

The electrolytes may also comprise organic isocyanates ~5 (DE 199 44 603) for reducing the water content.
Complex salts of the general formula (DE 199 51 804) M"+[EZ]~y in which:

x and y are 1, 2 or 3, MX+ is a metal ion E is a Lewis acid selected from the group consisting of 2001 190B265.doc 5/25

-5-BR'R2R3, AIR'R2R3, PR'R2R3R4R5, AsR'R2R3R4R5 and VR' R2R3R4R5, R' to R5 are identical or different, are optionally bonded directly to one another by a single or double bond, and each, individually or together, are a halogen (F, Cl or Br), an alkyl or alkoxy radical (Cl to C8), which may be partially or fully substituted by F, Cl or Br, an aromatic ring, optionally bonded via oxygen, from the group consisting of phenyl, naphthyl, anthracenyl and phenanthrenyl, which may be unsubstituted or mono- to polysubstituted by alkyl (Cl to C8) or F, Cl or Br, an aromatic heterocyclic ring, optionally bonded via oxygen, from the group consisting of pyridyl, pyrazyl and pyrimidyl, which may be unsubstituted or mono- to polysubstituted by alkyl (Cl to C8) or F, CI
or Br, and Z is OR6, NR6R', CR6R'R8, OS02R6, N(S02R6)(S02R7), C(S02R6)-(S02R7)(SO2R$) or OCOR6, where R6 to R8 are identical or different, are optionally bonded directly to _ 5 one another by a single or double bond and are each, individually or together, hydrogen or as defined for R' to R5, prepared by reacting a corresponding boron or phosphorus Lewis acid/solvent adduct with a lithium or tetraalkylammonium imide, methanide or triflate, may also be present.

Borate salts (DE 199 59 722) of the general formula y R4 R' MX+ B

"/Y

2001 IQOf3265.doe 6/25 CA 02349903 2001-06-07

-6-in which:

M is a metal ion or tetraalkylammonium ion, x and y are 1, 2 or 3, R' to R4 are identical or different and are alkoxy or carboxyl radicals (Cl-C8), which are optionally bonded directly to one another by a single or double bond, may also be present. These borate salts are prepared by reacting lithium tetraalkoxyborate or a 1:1 mixture of lithium alkoxide with a borate with a suitable hydroxyl or carboxyl compound in a ratio of 2:1 or 4:1 in an aprotic solvent.

It is also possible for additives to be present, such as silane compounds of the general formula SiR'R2R3R4 where R' to R4 are H
CyF2y+1-zHz OCyF2y+,-zHZ
OC(O)CyF2y+,-ZHZ
OSO2CyF2y+l-ZHZ
and 1 <_x<6 1 <_y<_8and 0_z<_2y+1 and R' - R4 are identical or different and are an aromatic ring from the group consisting of phenyl and naphthyl, which may be unsubstituted or monosubstituted or polysubstituted by F, CyF2y+l-ZHZ, OCyF2y+,-ZHZ, OC(O)CyF2y+,-ZHZ, OSO2CyF2y+l-ZHZ or N(CnF2n+1-zHz)2, or a heterocyclic aromatic ring from the group consisting of pyridyl, pyrazyl or pyrimidyl, each of which may be monosubstituted or 2001' 1008265.doc 7/25 CA 02349903 2001-06-07

-7-polysubstituted by F, CYF2Y+1-zHzi OCyF2y+1-zHz, OC(O)CyF2y+1-zHz, OS02CyF2y+1-zHzi N(CnF2n+1_zHz)2 (DE 100 276 26).

The compounds according to the invention may also be employed in electrolytes comprising lithium fluoroalkylphosphates of the following formula Li+[PFx(CyF2Y+1-zHz)6-J
in which 1<_x<_5 3<_y<_8 0<_z<_2y+1 and the ligands (CyF2y+1-zHz) may be identical or different, with the exception of the compounds of the general formula Li+[PFa(CHbFc(CF3)d)el in which a is an integer from 2 to 5, b = 0 or 1, c = 0 or 1, d = 2 and e is an integer from 1 to 4, with the provisos that b and c are not simultaneously each = 0, and the sum a+ e is equal to 6, and the ligands (CHbFc(CF3)d) may be identical or different (DE 100 089 55).
The process for the preparation of lithium fluoroalkylphosphates is characterised in that at least one compound of the general formula HmP(CnH2n+1)3-m, OP(CnH2n+1)3, CImP(CnH2n+1)3-m, FmP(CnH2n+1)3-m+
CIoP(CnH2n+1)5-o, FoP(CnH2n+1)5-o, 200: 100B265.doc 8/25

-8-in each of which 0<m <2, 1 < n < 8 and 0 < o < 4, is fluorinated by electrolysis in hydrogen fluoride, the resultant mixture of fluorination products is separated by extraction, phase separation and/or distillation, and the resultant fluorinated alkyl-phosphorane is reacted with lithium fluoride in an aprotic solvent mixture with exclusion of moisture, and the resultant salt is purified and isolated by conventional methods.

The compounds according to the invention can also be employed in electrolytes which comprise salts of the formula Li[P(OR' )a(OR2)b(OR3)c(OR4)dFel in which 0 < a+b+c+d_ 5 and a+b+c+d+e = 6, and R' to R4, independently of one another, are alkyl, aryl or heteroaryl radicals, where at least two of R' to R4 may be bonded directly to one another by a single or double bond (DE 100 16 801). The compounds are prepared by reacting phosphorus(V) compounds of the general formula P(OR' )a(OR2)b(OR3)c(OR4)dFe in which 0 < a+b+c+d <_ 5 and a+b+c+d+e = 5, and R' to R4 are as defined above, with lithium fluoride in the presence of an organic solvent.

It is also possible for ionic liquids of the general formula K+A-in which:

K+ is a cation selected from the group consisting of 2001 IUOB265.doo 9/25 CA 02349903 2001-06-07

-9-RSIN R3 RS N'N

R6 R6 N~ R2 I~+~

N
-'N/+\N~ /\
R4 Y R2 R4 s R2 N-N

R4 p R2 R4 N R2 I

where R' to R5 are identical or different, are optionally bonded directly to one another by a single or double bond, and each, individually or together, have the following meaning:

- H, - halogen, - an alkyl radical (C, to C8), which may be partially or fully substituted by further groups, F, Cl, N(CnF(2n+l-x)Hx)2, O(CnF(2n+1-x)Hx), SO2(CnF(2n+,-x)Hx) or CnF(2n+,-x)Hx, where 1< n< 6 and 0< x<_ 2n+1, and A- is an anion selected from the group consisting of [B(OR1)n(OR2)m(OR3)o(OR4)p]
where 0<_ n, m, o, p<_ 4, and m+n+o+p = 4, 200,1 100B265.doc 10/25 CA 02349903 2001-06-07

-10-where R' to R4 are different or are identical in pairs, are optionally bonded directly to one another by a single or double bond and are each, individually or together, an aromatic ring from the group consisting of phenyl, naphthyl, anthracenyl and phenanthrenyl, which may be unsubstituted or monosubstituted or polysubstituted by CnF(2n+,-x)Hx, where 1< n< 6 and 0< x<_ 13, or halogen (F, Cl or Br), an aromatic heterocyclic ring from the group consisting of pyridyl, pyrazyl and pyrimidyl, which may be unsubstituted or mono-substituted or polysubstituted by CnF(2n+,-x)Hx, where 1< n< 6 and 0< x<_ 13, or halogen (F, Cl or Br), an alkyl radical (C, to CS), which may be partially or fully substituted by further groups, preferably F, Cl, N(CnF(2n+t-x)Hx)2, O(CnF(2n+l-x)Hx), S02(CnF(2n+l-x)Hx) or CnF(2n+l-x)Hx, where 1< n< 6 and 0< x<_ 13, or OR' to OR4 individually or together are an aromatic or aliphatic carboxyl, dicarboxyl, oxysulfonyl or oxycarbonyl radical, which may be partially or fully substituted by further groups, preferably F, Cl, N(CnF(2n+l-x)Hx)2, O(CnF(2n+l-x)Hx), S02(CnF(2n+l-x)Hx) or CnF(2n+l-x)Hx, where 1< n< 6 and 0< x<_ 13 (DE 100 265 65), to be present in the electrolyte.

The compounds according to the invention may also be present in electrolytes comprising compounds of the following formula:

NR' R2R3 in which R' and R2 are H, CyF2y+,-ZHZ or (CnF2n-mHm)X, where X is an aromatic or heterocyclic radical, and R3 iS (CnF2n-mHm)Y, where Y is a heterocyclic radical, or (CoF2o-pHp)Z, where Z is an aromatic radical, 20~J1 4 00k3265.doc 11/25

-11-and where n, m, o, p, y and z satisfy the following conditions:
0<_n<_6, 0<m<_2n, 2<_o<_6, 0_p<2o, 1 _ y<_ 8, and 0<-z<2y+1, for reducing the acid content in aprotic electrolyte systems in electro-chemical cells.

It is also possible to employ fluoroalkyl phosphates of the general formula M"+[PFX(CyF2y+l-zHz)6-Jn in which 1<_x<_6 1 <_y<_8 0_z<_2y+1 1 <_n_3,and Mn+ is a monovalent to trivalent cation, in particular:
NR'RZR3R4, PR' RZR3R4, P(NR'R2)kR3mR44-k-m (where k 1- 4, m = 0 - 3 and k+m <_ 4), C(NR' R2)(NR3R4)(NR5R6), C(aryl)3, Rb or tropylium, 2001 100B265.doc 12/25 CA 02349903 2001-06-07

-12-where R' to R8 are H, alkyl or aryl (Cl-C8), which may be partially substituted by F, Cl or Br, where M" = Li+, Na+, Cs+, K+ and Ag+ are excluded. These fluoroalkyl phosphates are obtainable by reacting phosphoranes with a fluoride or metal fluoroalkyl phosphates with a fluoride or chloride in organic aprotic solvents (DE 100 388 58).

The electrolyte may also comprise a mixture of a) at least one lithium fluoroalkyl phosphate salt of the general formula Li+ [PFX(CyF2y+l-zHz)s-xl in which 1_<x<_5 1 <_ y _ 8, and 0_ z<_2y+1 and the ligands (CyF2y+,-ZHZ) are in each case identical or different, and b) at least one polymer (DE 100 58 264).

The electrolyte may also comprise tetrakisfluoroalkyl borate salts of the general formula M"+ ([BR4] )n in which Mn+ is a monovalent, divalent or trivalent cation, the ligands R are in each case identical and are (CXF2x+1), where 1 <_x_8, 20~1 00[3265.do¾ 13/25 CA 02349903 2001-06-07

-13-and n = 1, 2 or 3 (DE 100 558 11). The process for the preparation of tetrakisfluoroalkyl borate salts is characterised in that at least one compound of the general formula M"+ ([B(CN)4]-)n, in which Mn+ and n are as defined above, is fluorinated by reaction with at least one fluorinating agent in at least one solvent, and the resultant fluorinated compound is purified and isolated by conventional methods.

The electrolyte may also comprise borate salts of the general formula M"+ [BFX(CyFZy+l-zHz)4-dn in which:

1 <x<3, 1 <_y<_8and0<z<_2y+1,and M is a monovalent to trivalent cation (1 _ n _ 3), apart from potassium and barium, in particular:
Li, NR'R2R3Ra PRSRsR'Ra, P(NR5R6)kR'mR8a-k-m (where k = 1- 4, m=0-3andk+m<_4),or C(NR5R6)(NR'R$)(NR9R10), where R' to R4 are CyF2y+l_zHz and R5 to R10 are H or CYF2y+,-zHz, or an aromatic heterocyclic cation, in particular a nitrogen- and/or oxygen- and/or sulfur-containing aromatic heterocyclic cation (DE 101 031 89). The process for the preparation of these compounds is characterised in that a) BF3/solvent complexes are reacted 1:1 with alkyllithium with cooling, the majority of the solvent is removed after slow warming, and the solid is subsequently filtered off and washed with a suitable solvent, or 2001 600f3265.doc 14/25

-14-b) lithium salts in a suitable solvent are reacted 1:1 with B(CF3)F3 salts, the mixture is stirred at elevated temperature, the solvent is removed, aprotic non-aqueous solvents, preferably solvents which are used in electrochemical cells, are added to the reaction mixture, and the mixture is dried, or c) B(CF3)F3 salts are reacted 1:1 to 1:1.5 with lithium salts in water at elevated temperature and heated at the boiling point for from 0.5 to 2 hours, the water is removed, aprotic non-aqueous solvents, prefer-ably solvents which are used in electrochemical cells, are added to the reaction mixture and the mixture is dried.

The electrolyte may also comprise fluoroalkyl phosphate salts of the general formula N1"+ ([PFx(CyF2y+1-zHz)6-J )n in which Mn+ is a monovalent, divalent or trivalent cation, 1 x_<5, 1 y_<8and 0< Z< 2y+l, n = 1, 2 or 3, and the ligands (CYF2y+l-ZHZ) are in each case identical or different, where the fluoroalkyl phosphate salts in which M"+ is a lithium cation and the salts M+([PF4(CF3)2]-) where M+ = Cs+, Ag+ or K+, M+([PF4(C2F5)2] ) where M+ = Cs+, M+([PF3(C2F5)3] ) where M+ = Cs+, K+, Na+ or para-CI(C6H4)N2+, M+([PF3(C3F7)3]-) where M+ = Cs+, K+, Na+, para-CI(C6H4)N2+ or para-02N(C6H4)N2+, are excluded (DE 100 558 12). The process for the preparation of these fluoroalkyl phosphate salts is characterised in that at least one compound of the general formula 200'1 100B265.doo 15/25 CA 02349903 2001-06-07

-15-HrP(CsH2s+1)3-r, OP(CsH2s+1)3, CIrP(CsH2s+1)3-r, FrP(CsH2s+1)3-r, CItP(CsH2s+1)5-t and/or FtP(CsH2s+1)5-t, in which in each case 0_r<_2 3<_s<_8and 0<_t<_4, is fluorinated by electrolysis in hydrogen fluoride, the resultant mix-ture of fluorination products is separated, and the resultant fluorinated alkylphosphorane is reacted with a compound of the general formula Mn+(F-)n, in which M"+ and n are as defined above, in an aprotic sol-vent or solvent mixture with exclusion of moisture, and the resultant fluoroalkyl phosphate salt is purified and isolated by conventional methods.
The compounds according to the invention may be present in electro-lytes which comprise fluoroalkyl phosphate salts (DE 10109032) of the formula (Ma+)b[(CnF2n+1-mHm)yPF5-y(CR1 R2)xPF5-y(CnF2n+1-mHm)yI (2-) (a*b / 2) in which Ma+ is a monovalent, divalent or trivalent cation, a= 1, 2or3, b=2fora= 1, b=2fora=3, b= 1 fora=2 and in each case 20C1 100B265.doe 16/25 CA 02349903 2001-06-07

- 16-1 <_n<_8, 0<m<_2forn=1 or 2, 0_m<_4for3<n<8, 1_x_12, 0<y<_2, where R, and R2 are in each case identical or different and are selected from the group consisting of fluorine, hydrogen, alkyl, fluoroalkyl and perfiuoroalkyl substituents, and where in each case the substituents (CnF2n+1_mHm) are identical or different. These compounds are prepared by reacting at least one fluoro-a,co-bis(alkylfluorophosphorano)alkane with at least one fluoride salt of the general formula (Ma+) [Fla, in which (Ma+) and a are as defined above, in solution to give a fluoroalkyl phosphate salt, and, if desired, purifying and/or isolating the latter by conventional methods.
The compounds according to the invention can be used in electrolytes for electrochemical cells containing positive-electrode 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 the preparation of this positive-electrode material is characterised in that a) a suspension or sol of the metal or alloy core in urotropin is prepared, b) the suspension is emulsified with C5-C12-hydrocarbons, c) the emulsion is precipitated onto the metal or alloy cores, and d) the metal hydroxides or oxyhydroxides are converted into the corresponding oxide by heating the system.

2001 I'00B265.doc 17/25 CA 02349903 2001-06-07

-17-The compounds according to the invention can also be employed in electrolytes for electrochemical cells having negative electrodes made from customary lithium intercalation and insertion compounds, but also having negative-electrode materials consisting of lithium mixed oxide particles coated with one or more metal oxides (DE 199 22 522). They can also consist of lithium mixed oxide particles coated with one or more polymers (DE 199 46 066). The compounds according to the invention can likewise be employed in systems having negative electrodes consisting of lithium mixed oxide particles having one or more coatings of alkali metal compounds and metal oxides (DE 100 14 884). The process for the preparation of these materials is characterised 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, a hydrolysis solution is added to the suspension, and the coated particles are subsequently filtered off, dried and calcined. The compounds according to the invention can likewise be employed in systems comprising positive-electrode materials with doped tin oxide (DE 100 257 61). This positive-electrode material is prepared by a) adding urea to a tin chloride solution, b) adding urotropin and a suitable doping compound to the solution, c) emulsifying the resultant sol in petroleum ether, d) washing the resultant gel and removing the solvent by suction, and e) drying and heating the gel.

The compounds according to the invention can likewise be employed in systems comprising positive-electrode materials with reduced tin oxide (DE 100 257 62). This positive-electrode material is prepared by a) adding urea to a tin chloride solution, b) adding urotropin to the solution, 2001 H0B265.doc 18/25 CA 02349903 2001-06-07

-18-c) emulsifying the resultant sol in petroleum ether, d) washing the resultant gel and removing the solvent by suction, e) drying and heating the gel, and f) exposing the resultant Sn02 to a reducing gas stream in an aeratable oven.

A general example of the invention is explained in greater detail below.

The anion selected from the group consisting of [PFX(CYF2Y+!ZHZ)6X
where 1 x < 6 1 y<_8and 0<z<_2y+1 is prepared using a known process from DE 196 411 38.

The cation selected from the group consisting of 200: tJ0B265.doc 19/25 R6 *N' R2 R6 I R2 R6 ~ R6 N\ R2 I ~ \+

~~ N
~N~ i-`N\ t R4 Y R2 R4 s/ R2 N-N
R4 pR2 R4NR2 is prepared using a known process from US 5827602. The starting materials are reacted in an aprotic organic solvent at temperatures in the liquid range of the solvent for from about 0.5 to 12 hours, prefer-ably for 1-4 hours.

In order to remove the by-products, the mixture is cooled to -30 C, for example to from -10 C to -20 C in the case of LiCi as by-product, and the precipitating by-product is filtered off, preferably filtered off by vacuum.

The solvent/product mixture can be employed directly in the electro-lyte. If desired, the solvent can aiso be distilled off and the resultant product dried in order to be employed in the stated applications.

The following examples are intended to explain the invention in greater detail, but without restricting it.

2001 MB265.doc 20/25 CA 02349903 2001-06-07 Examples Example 1 Synthesis of 1 -ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate Lithium tris(pentafluoroethyl)trifluorophosphate is synthesised in accordance with DE 196 411 38. The product is reacted in acetonitrile in accordance with the following reaction equation:

a-H3C~NTN_CZHS + Li[PF3(C2F)31 H3C,N\ ~,N~CZHS ~3(C2FOj _ + L-C!
H ~H"
The reaction mixture is vacuum filtered through a glass frit with cooling in order to remove the LiCI formed as by-product. The solvent is distilled off under reduced pressure, and the resultant 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate is dried under reduced pressure.
Example 2 Synthesis of 1,2-dimethyl-3-propylimidazolium tris(pentafluoroethyl)-trifluorophosphate Lithium tris(pentafluoroethyl)trifluorophosphate is synthesised in accordance with DE 196 411 38. The product is reacted in acetonitrile in accordance with the following reaction equation:
a FF
H3C~N~N,C3HI + lr[PF3(C2Fs~31 H3C~N~N~C3H' [~s(C2Fs~31 -+ LiCI

The reaction mixture is vacuum filtered through a glass frit with cooling in order to remove the LiCI formed as by-product. The solvent is distilled off under reduced pressure, and the resultant 1,2-dimethyl-201 ('00B265.doC 21/25 CA 02349903 2001-06-07 3-propylimidazolium tris(pentafluoroethyl)trifluorophosphate is dried under reduced pressure.

Example 3 Synthesis of 1 -ethyl-3-methylimidazolium tris(nonafluorobutyl)-trifluorophosphate Lithium tris(nonafluorobutyl)trifluorophosphate is synthesised analogously to lithium tris(pentafluoroethyl)trifluorophosphate. The product is reacted in acetonitrile in accordance with the following reaction equation:
n a- n H3C~NT N.C2H5 + Li[PF3(CaF)31 F~C,,N\'rN.C2H5 pF3(C4F~~ -+ LiCI 31- H H

The reaction mixture is vacuum filtered through a glass frit with cooling in order to remove the LiCi formed as by-product. The solvent is distilled off under reduced pressure, and the resultant 1 -ethyl-3-methylimidazolium tris(nonafluorobutyl)trifluorophosphate is dried under reduced pressure.

Claims

CLAIMS:

1. An ionic liquid of the general formula:
K+A- (I), in which:

K+ is a cation which is:

where R1 to R6 are identical or different, are optionally bonded directly to one another by a single or double bond and each, individually or together, have the following meaning:

H, - halogen, - a C1 to C8 alkyl radical, which may be partially or fully substituted by F, Cl, N(C n F(2n+1-x)H x)2, O(C n F(2n+1-x)H x), SO2(C n F(2n+1-x)H x) or C n F(2n+1-x)H x, where 1 < n < 6 and 0 < x <= 2n+1; and A- is tris(pentafluoroethyl)trifiuorophosphate or tris(nonafluorobutyl)trifluorophosphate.

2. Use of an ionic liquid as defined in claim 1 in a mixture with an aprotic solvent.

3. Use of an ionic liquid as defined in claim 1 in a mixture with another conductive salt.

4. Use of an ionic liquid as defined in claim 1 in an electrochemical cell having improved thermal stability, lower corrosivity and a greater liquid range.

5. Use of an ionic liquid as defined in claim 1 in a supercapacitor.

6. Use of an ionic liquid as defined in claim 1 as a solvent and in the catalysis of a chemical reaction.

7. Use of an ionic liquid as defined in claim 1 as a hydraulic liquid.