U.S. patent application number 10/657009 was filed with the patent office on 2004-03-18 for mixtures suitable as solid electrolyte or separator for electrochemical cells and having specific plasticizers.
Invention is credited to Bauer, Stephan, Bronstert, Bernd, Hesse, Werner, Mohwald, Helmut, Sterzel, Hans-Josef.
Application Number | 20040054057 10/657009 |
Document ID | / |
Family ID | 26040549 |
Filed Date | 2004-03-18 |
United States Patent
Application |
20040054057 |
Kind Code |
A1 |
Bauer, Stephan ; et
al. |
March 18, 2004 |
Mixtures suitable as solid electrolyte or separator for
electrochemical cells and having specific plasticizers
Abstract
A mixture Ia comprises a mix IIa composed of a) from 1 to 95% by
weight of a solid III, preferably a basic solid III, with a primary
particle size of from 5 nm to 20 .mu.m and b) from 5 to 99% by
weight of a polymeric composition IV, obtainable by polymerizing
b1) from 5 to 100% by weight, based on the composition IV, of a
condensation product V of .alpha.) at least one compound VI which
is capable of reacting with a carboxylic acid or with a sulfonic
acid or with a derivative or a mixture of two or more of these, and
.beta.) at least 1 mol per mole of the compound VI of a carboxylic
acid or sulfonic acid VII which has at least one functional group
capable of free-radical polymerization, or of a derivative thereof
or of a mixture of two or more thereof and b2) from 0 to 95% by
weight, based on the composition IV, of another compound VIII with
an average molecular weight (number average) of at least 5000
having polyether segments in its main or side chain and at least
one ester of the formula (E1) to (E5) 1 where each of R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 is identical with or different from
the others and, independently of the others, is linear or
branched-chain C.sub.1-C.sub.4-alkyl
(--CH.sub.2--CH.sub.2--O).sub.n--CH.- sub.3, where n is from 1 to
3, C.sub.3-C.sub.6-cycloalkyl or an aromatic hydrocarbon group
which may in turn be substituted, with the proviso that at least
one of the groups R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is
(--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3, where n is from 1 to
3.
Inventors: |
Bauer, Stephan;
(Hochdorf-Assenheim, DE) ; Bronstert, Bernd;
(Otterstadt, DE) ; Mohwald, Helmut; (Annweiler,
DE) ; Sterzel, Hans-Josef; (Dannstadt-Schauernheim,
DE) ; Hesse, Werner; (Obrigheim, DE) |
Correspondence
Address: |
KEIL & WEINKAUF
1350 CONNECTICUT AVENUE, N.W.
WASHINGTON
DC
20036
US
|
Family ID: |
26040549 |
Appl. No.: |
10/657009 |
Filed: |
September 8, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10657009 |
Sep 8, 2003 |
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09509690 |
Jul 17, 2000 |
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6642294 |
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Current U.S.
Class: |
524/430 ;
252/500 |
Current CPC
Class: |
H01M 50/414 20210101;
C08K 5/0016 20130101; H01M 10/052 20130101; C08K 3/01 20180101;
H01M 10/0565 20130101; C08J 2381/06 20130101; Y02E 60/10 20130101;
H01G 9/02 20130101; H01M 50/411 20210101; C08J 2385/02 20130101;
H01G 9/025 20130101; A01N 59/16 20130101; C08J 5/2256 20130101;
H01M 10/0525 20130101; A01N 59/16 20130101; A01N 2300/00
20130101 |
Class at
Publication: |
524/430 ;
252/500 |
International
Class: |
H01B 001/00; C08K
003/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 1997 |
DE |
19744659.0 |
Oct 2, 1997 |
DE |
19743748.6 |
Claims
We claim:
1. A mixture Ia, comprising a mix IIa composed of a) from 1 to 95%
by weight of a solid III, preferably a basic solid III, with a
primary particle size of from 5 nm to 20 .mu.m and b) from 5 to 99%
by weight of a polymeric composition IV, obtainable by polymerizing
b1) from 5 to 100% by weight, based on the composition IV, of a
condensation product V of .alpha.) at least one compound VI which
is capable of reacting with a carboxylic acid or with a sulfonic
acid or with a derivative or a mixture of two or more of these, and
.beta.) at least 1 mol per mole of the compound VI of a carboxylic
acid or sulfonic acid VII which has at least one functional group
capable of free-radical polymerization, or of a derivative thereof
or of a mixture of two or more thereof and b2) from 0 to 95% by
weight, based on the composition IV, of another compound VIII with
an average molecular weight (number average) of at least 5000
having polyether segments in its main or side chain and at least
one ester of the formula (E1) to (E5) 9where each of R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 is identical with or different from
the others and, independently of the others, is linear or
branched-chain C.sub.1-C.sub.4-alkyl,
(--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3, where n is from 1 to 3,
C.sub.3-C.sub.6-cycloalkyl or an aromatic hydrocarbon group, which
may in turn be substituted, with the proviso that at least one of
the groups R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is
(--CH.sub.2--CH.sub.2--O).sub.n--- CH.sub.3, where n is from 1 to
3.
2. A mixture Ib, comprising a mix IIb composed of a) from 1 to 95%
by weight of a solid III, preferably a basic solid, with a primary
particle size of from 5 nm to 20 .mu.m and b) from 5 to 99% by
weight of a polymer IX, obtainable by polymerizing b1) from 5 to
75% by weight, based on the polymer IX, of a compound X capable of
free-radical polymerization and differing from the carboxylic acid
or the sulfonic acid VII or from a derivative thereof, or of a
mixture of two or more thereof and b2) from 25 to 95% by weight,
based on the polymer IX, of another compound VIII with an average
molecular weight (number average) of at least 5000, having
polyether segments in its main or side chain, and at least one
ester of the formula (E1) to (E5) 10where each of R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 is identical with or different from the others
and, independently of the others, is linear or branched-chain
C.sub.1-C.sub.4-alkyl, (--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3,
where n is from 1 to 3, C.sub.3-C.sub.6-cycloalkyl or an aromatic
hydrocarbon group, which may in turn be substituted, with the
proviso that at least one of the groups R.sup.1, R.sup.2, R.sup.3
or R.sup.4 is (--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3, where n is
from 1 to 3.
3. A mixture as claimed in claim 1 or 2, where in the at least one
ester of the formula (E1) to (E5) R.sup.1, R.sup.2 and, if present,
R.sup.3 and/or R.sup.4 are identical and are
--CH.sub.2--CH.sub.2--O--CH.sub.3 or
(--CH.sub.2--CH.sub.2--O).sub.2--CH.sub.3.
4. A mixture as claimed in any of claims 1 to 3, where the at least
one ester is selected from the class consisting of compounds (E1a)
to (E5a): and 11
5. A mixture as claimed in any of claims 1, 3 or 4, where the mix
IIa is composed of a) from 1 to 95% by weight of a solid III,
preferably a basic solid III, with a primary particle size of from
5 nm to 20 .mu.m and b) from 5 to 99% by weight of a polymeric
composition IV, obtainable by polymerizing b1) from 5 to 100% by
weight, based on the composition IV, of a condensation product V of
.alpha.) a polyhydric alcohol VI containing carbon and oxygen in
its main chain and .beta.) at least 1 mol per mole of the
polyhydric alcohol VI of an .alpha.,.beta.-unsaturated carboxylic
acid VII and b2) from 0 to 95% by weight, based on the composition
IV, of another compound VIII with an average molecular weight
(number average) of at least 5000, having polyether segments in its
main or side chain.
6. A mixture as claimed in any of claims 1 to 5, further containing
at least one conducting salt selected from the class consisting of
LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiC(CF.sub.3SO.sub.2).sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, LiN(SO.sub.2F).sub.2,
LiN(CF.sub.3CF.sub.2SO.sub.2).sub.2, LiAlCl.sub.4, LiSiF.sub.6 and
LiSbF.sub.6.
7. A mixture as claimed in claim 6, containing at least one
compound (E1a) to (E5a) as defined in claim 3 and LiBF.sub.4.
8. A composite encompassing at least one first layer which
comprises an electron-conducting, electrochemically active
compound, and at least one second layer which comprises a mixture
as claimed in any one of claims 1 to 7 and is free from
electron-conducting, electrochemically active compounds.
9. Use of a mixture according to any of claims 1 to 7 or a
composite of claim 8 for the preparation of a solid electrolyte, a
separator, an electrode, in a sensor, an electrochromic window, a
display, a capacitor or an ion-conductive film.
10. A solid electrolyte, a separator, an electrode, a sensor, an
electrochromic window, a display, a capacitor or an ion-conducting
film, comprising in each case a mixture as claimed in any one of
claims 1 to 7, or a composite according to claim 8.
11. An electrochemical cell encompassing a solid electrolyte or
encompassing a separator or an electrode as claimed in claim 10, or
encompassing a combination of two or more of these.
12. Use of the electrochemical cell as claimed in claim 11 as an
Automobile battery, appliance battery or flat-type battery.
Description
[0001] The present invention relates to mixtures which, inter alia,
are suitable for electrochemical cells with electrolytes containing
lithium ions; the use of these, e.g. in solid electrolytes,
separators and electrodes; solid electrolytes, separators,
electrodes, sensors, electrochromic windows, displays, capacitors
and ion-conducting films which comprise a mixture of this type;
electrochemical cells with such solid electrolytes, separators
and/or electrodes; and also the use in electrochemical cells of the
solids present in the mixtures, for improving cycle stability.
[0002] Electrochemical cells, in particular those which are
rechargeable, are well known, for example from Ullmann's
Encyclopedia of Industrial Chemistry, 5th ed., Vol. A3, VCH
Verlagsgesellschaft mbH, Weinheim, 1985, pages 343-397.
[0003] Due to their high specific energy storage density, lithium
batteries and lithium ion batteries occupy a particular position
among these cells, especially as secondary cells.
[0004] As described, inter alia, in the above extract from
"Ullmann", the cathodes of such cells contain lithiated compound
oxides of manganese, cobalt, vanadium or nickel; these may be
described in the stoichiometrically simplest case as
LiMn.sub.2O.sub.4, LiCoO.sub.2, LiV.sub.2O.sub.5 or
LiNiO.sub.2.
[0005] These compound oxides react reversibly with substances, such
as graphite, which are capable of incorporating lithium ions into
their lattice, the lithium ions being removed from the crystal
lattice and the metal ions within this, such as manganese, cobalt
or nickel ions, being oxidized. In an electrochemical cell this
reaction can be used to store electrical energy by separating the
compound accepting lithium ions, i.e. the anode material, from the
lithium-containing compound oxide, i.e. the cathode material, by
means of an electrolyte through which the lithium ions from the
compound oxide can migrate into the anode material (charging).
[0006] The compounds suitable for reversible storage of lithium
ions are usually secured to collector electrodes by means of a
binder.
[0007] During charging of the cell, electrons flow through an
external voltage source and lithium cations through the electrolyte
toward the anode material. When the cell is used, the lithium
cations flow through the electrolyte, but the electrons flow from
the anode material to the cathode material through a load.
[0008] In order to avoid a short circuit within the electrochemical
cell, a layer which is electrically insulating but permeable to
lithium cations is located between the two electrodes. This may be
what is known as a solid electrolyte or a conventional
separator.
[0009] As is well known, solid electrolytes and separators are
composed of a carrier material, incorporated into which are a
dissociable compound which contains lithium cations and serves to
increase lithium-ion conductivity, and also usually other
additives, such as solvents.
[0010] Solid electrolytes based on polyalkylene oxides are known,
and are described, for example, in EP-A 559 317, EP-A 576 686, EP-A
537 930, EP-A 585 072 and U.S. Pat. No. 5,279,910. The polyethers
described in these references are modified at their end groups or
functional groups, for example by means of (meth)acryloyl groups,
and are crosslinked by introducing energy (heat or light) before
they are used as solid electrolyte. They generally also contain a
conducting salt, e.g. LiPF.sub.6, to improve their conductivity.
The use of a solid to improve the mechanical, thermal and
electrical strength of the solid electrolyte is not described in
these references. Accordingly, and in spite of crosslinking, the
systems described in these references do not always have
satisfactory properties with regard to mechanical strength and the
porosity of the resultant films, and short-circuit protection.
[0011] The solvents used hitherto in Li storage batteries have been
predominantly alkyl ethers, such as dimethyl ether, and alkene
carbonates, such as ethylene carbonate (EC) and propylene carbonate
(PC). Such systems are described, inter alia, in JP 08 273 700 and
JP 09 115 548.
[0012] Electrolyte solutions based on various esters are also
known.
[0013] For example, WO.sub.97/16862 describes an electrolyte
solution which comprises borates of the following formulae (A) to
(D): 2
[0014] where X is halogen, R.sup.1, R.sup.2, R.sup.3 and R.sup.4
are straight-chain or branched-chain aliphatic or aromatic alkyl
which may be substituted with substituents of various
electronegativities, and Z is a straight-chain or branched-chain
aliphatic or aromatic alkyl or siloxane group.
[0015] J. Electrochem. Soc., 143, 1996 pp. 4047-4053 describes an
electrolyte solvent for rechargeable lithium and lithium-ion
batteries based on a borate termed BEG-1 and having the formula (E)
below, combined with EC and/or PC. 3
[0016] EP-B-0 599 534 describes carbonate compounds of the
following formula (F)
R.sup.1--CH.sub.2--O--CO--O--CH.sub.2R.sup.2 (F)
[0017] where R.sup.1 is hydrogen, alkyl or alkyl substituted with
one or more halogen atoms, and R.sup.2 is alkyl with no hydrogen in
the .alpha. position or alkyl with no hydrogen in the .alpha.
position and substituted with one or more halogen atoms, with the
proviso that R.sup.1 is not identical with R.sup.2, excluding the
compound C.sub.2H.sub.5--O--CO--O--CH.sub.2--(CF.sub.2).sub.4--H
and also its use in a non-aqueous electrolyte solution.
[0018] EP-A 0 698 933 relates to a non-aqueous secondary cell which
encompasses a specific eletrolyte solution including, inter alia,
phosphoric triesters of the formula (RO).sub.3P.dbd.O, where each
of the groups R is identical or different and is
C.sub.1-C.sub.6-alkyl or two RO groups may form a ring, together
with the phosphorus atom to which they are bonded. Alkyl phosphates
of this type and their use in non-aqueous electrolyte solutions and
in secondary cells are likewise described in EP-A 0 696 077.
[0019] The use of phosphates of the formula
O.dbd.P(--O--(CH.sub.2CH.sub.2- O).sub.qR.sup.2).sub.3, where n and
q are from 1 to 10 and R.sup.2 is C.sub.1-C.sub.4-alkyl, as
electrolyte in zinc batteries is described in JP 07 161 357.
[0020] Other phosphates having hydrocarbon groups, and also the use
of these as electrolyte in lithium ion batteries, are described in
JP 58 206 078.
[0021] JP 61 256 573 describes an electrolyte based on a polymer of
a phosphate containing at least one polymerizable group.
[0022] It is an object of the present invention to overcome the
disadvantages described and to provide a mixture which is suitable
in particular for producing solid electrolytes and separators, but
can also be used for producing electrodes in electrochemical cells
and for other applications described herein.
[0023] We have found that this object is achieved by means of the
novel mixture in which a solid III as defined below is present; the
use of the novel mixture gives solid electrolytes, separators or
electrodes which, in comparison with the systems known hitherto,
have improved short-circuit protection, increased compressive
strength, in particular at above 120.degree. C., and also greater
porosity, and are moreover capable of sustained suppression of Li
dendrite formation. The presence of the solid also provides
electrochemical cells with improved cycle stability and higher
current capacities. If the preferred basic solids are used, the
acid formed during operation of an electrochemical cell is moreover
scavenged or neutralized.
[0024] By using the esters present in the mixture and having the
formulae (E1) to (E5) as defined herein, the mechanical properties
of the films produced from the mixture and also the ease with which
they can be peeled from temporary carriers are improved.
[0025] At the same time, the esters used also have electrolyte
properties.
[0026] One embodiment of the present invention therefore provides a
mixture Ia, comprising a mix Ia composed of
[0027] a) from 1 to 95% by weight of a solid III, preferably a
basic solid III, with a primary particle size of from 5 nm to 20
.mu.m and
[0028] b) from 5 to 99% by weight of a polymeric composition IV,
obtainable by polymerizing
[0029] b1) from 5 to 100% by weight, based on the composition IV,
of a condensation product V of
[0030] .alpha.) at least one compound VI which is capable of
reacting with a carboxylic acid or with a sulfonic acid or with a
derivative or a mixture of two or more of these, and
[0031] .beta.) at least 1 mol per mole of the compound VI of a
carboxylic acid or sulfonic acid VII which has at least one
functional group capable of free-radical polymerization, or of a
derivative thereof or of a mixture of two or more thereof and
[0032] b2) from 0 to 95% by weight, based on the composition IV, of
another compound VIII with an average molecular weight (number
average) of at least 5000 having polyether segments in its main or
side chain and
[0033] at least one ester of the formula (E1) to (E5) 4
[0034] where each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is
identical with or different from the others and, independently of
the others, is linear or branched-chain C.sub.1-C.sub.4-alkyl,
(--CH.sub.2--CH.sub.2--O)- .sub.n--CH.sub.3, where n is from 1 to
3, C.sub.3-C.sub.6-cycloalkyl or an aromatic hydrocarbon group,
which may in turn be substituted, with the proviso that at least
one of the groups R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is
(--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3, where n is from 1 to
3.
[0035] The above mixture Ia preferably comprises a mix Ia composed
of
[0036] a) from 1 to 95% by weight of a solid III, preferably a
basic solid III, with a primary particle size of from 5 nm to 20
.mu.m and
[0037] b) from 5 to 99% by weight of a polymeric composition IV,
obtainable by polymerizing
[0038] b1) from 5 to 100% by weight, based on the composition IV,
of a condensation product V of
[0039] .alpha.) a polyhydric alcohol VI containing carbon and
oxygen in its main chain and
[0040] .beta.) at least 1 mol per mole of the polyhydric alcohol VI
of an .alpha.,.beta.-unsaturated carboxylic acid VII and
[0041] b2) from 0 to 95% by weight, based on the composition IV, of
another compound VIII with an average molecular weight (number
average) of at least 5000, having polyether segments in its main or
side chain.
[0042] In another embodiment, the present invention provides a
mixture Ib, comprising a mix Ib composed of
[0043] a) from 1 to 95% by weight of a solid III, preferably a
basic solid, with a primary particle size of from 5 nm to 20 .mu.m
and
[0044] b) from 5 to 99% by weight of a polymer IX, obtainable by
polymerizing
[0045] b1) from 5 to 75% by weight, based on the polymer IX, of a
compound X capable of free-radical polymerization and differing
from the carboxylic acid or the sulfonic acid VII or from a
derivative thereof, or of a mixture of two or more thereof and
[0046] b2) from 25 to 95% by weight, based on the polymer IX, of
another compound VIII with an average molecular weight (number
average) of at least 5000, having polyether segments in its main or
side chain, and
[0047] at least one ester of the formula (E1) to (E5) 5
[0048] where each of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is
identical with or different from the others and, independently of
the others, is linear or branched-chain C.sub.1-C.sub.4-alkyl,
(--CH.sub.2--CH.sub.2--O)- .sub.n--CH.sub.3, where n is from 1 to
3, C.sub.3-C.sub.6-cycloalkyl or an aromatic hydrocarbon group,
which may in turn be substituted, with the proviso that at least
one of the groups R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is
(--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3, where n is from 1 to
3.
[0049] The solids III used are mainly inorganic solids, preferably
inorganic basic solids selected from the class consisting of
oxides, compound oxides, silicates, sulfates, carbonates,
phosphates, nitrides, amides, imides and carbides of the elements
of the 1st, 2nd, 3rd or 4th main group or the 4th subgroup of the
periodic table; a polymer selected from the class consisting of
polyethylene, polypropylene, polystyrene, polytetrafluoroethylene,
polyvinylidene fluoride, polyamides and polyimides; a solid
dispersion comprising a polymer of this type; or a mixture of two
or more of these.
[0050] Particular examples are: oxides, such as silica, calcium
oxide, alumina, magnesium oxide and titanium dioxide, compound
oxides, for example of the elements silicon, calcium, aluminum,
magnesium and titanium; silicates, such as ladder-type silicates,
ino-, phyllo- and tectosilicates, preferably wollastonite, in
particular hydrophobicized wollastonite; sulfates, such as those of
alkali metals and alkaline-earth metals; carbonates, for example
those of alkali metals and alkaline-earth metals, for example
calcium, magnesium, barium, lithium, potassium or sodium carbonate;
phosphates, such as apatites; nitrides; amides; imides; carbides;
polymers, such as polyethylene, polypropylene, polystyrene,
polytetrafluoroethylene and polyvinylidene fluoride; polyamides;
polyimides; and other thermoplastics, thermosets and microgels, and
solid dispersions, in particular those which comprise the polymers
mentioned above, and also mixtures of two or more of the
abovementioned solids.
[0051] According to the invention, the solids III preferably used
are inorganic Li-ion-conducting solids, more preferably an
inorganic basic Li-ion-conducting solid.
[0052] Particular mention may also be made of: lithium borates,
such as Li.sub.4B.sub.6O.sub.11* xH.sub.2O,
Li.sub.3(BO.sub.2).sub.3, Li.sub.2B.sub.4O.sub.7*xH.sub.2O,
LiBO.sub.2, where x can be a number from 0 to 20; lithium
aluminates, such as Li.sub.2O*Al.sub.2O.sub.3*H.sub- .2O,
Li.sub.2Al.sub.2O.sub.4, LiAlO.sub.2; lithium aluminosilicates,
such as lithium-containing zeolites, feldspars, feldspathoids,
phyllo- and inosilicates, and in particular LiAlSi.sub.2O.sub.6
(spodumene), LiAlSi.sub.4O.sub.10 (petullite), LiAlSiO.sub.4
(eucryptite), micas, such as
K[Li,Al].sub.3[AlSi].sub.4O.sub.10(F--OH).sub.2,/K[Li,Al,Fe].sub.3
[AlSi].sub.4O.sub.10(F--OH).sub.2; lithium zeolites, in particular
those whose form is fiber-like, sheet-like or cube-like, in
particular those of the formula
Li.sub.2/zO*Al.sub.2O.sub.3*xSiO.sub.2*yH.sub.2O where z is
valence-related, x is from 1.8 to about 12 and y is from 0 to about
8; lithium carbides, such as Li.sub.2C.sub.2, Li.sub.4C; Li.sub.3N;
lithium oxides and compound lithium oxides, such as LiAlO.sub.2,
Li.sub.2MnO.sub.3, Li.sub.2O, Li.sub.2O.sub.2, Li.sub.2MnO.sub.4,
Li.sub.2TiO.sub.3; Li.sub.2NH; LiNH.sub.2; lithium phosphates, such
as Li.sub.3PO.sub.4, LiPO.sub.3, LiAlFPO.sub.4, LiAl(OH)PO.sub.4,
LiFePO.sub.4, LiMnPO.sub.4; Li.sub.2CO.sub.3; lithium silicates in
the form of ladder-type silicates, ino-, phyllo- and
tectosilicates, such as Li.sub.2SiO.sub.3, Li.sub.2SiO.sub.4 and
Li.sub.6Si.sub.2; lithium sulfates, such as Li.sub.2SO.sub.4,
LiHSO.sub.4, LiKSO.sub.4; the Li compounds mentioned during the
discussion of the cathode compound, the presence of conductive
carbon black being excluded from the mixture when these are used as
solid III; and also mixtures of two or more of the
Li-ion-conducting solids mentioned above.
[0053] Basic solids are particularly suitable here. For the
purposes of the invention, basic solids are those whose mixture
with a liquid, water-containing diluent, which itself has a pH of
not more than 7, has a higher pH than this diluent.
[0054] The solids should advantageously be very substantially
insoluble in the liquid used as electrolyte, and also be
electrochemically inert in the battery medium.
[0055] Particularly suitable solids are those which have a primary
particle size of from 5 nm to 20 .mu.m, preferably from 0.01 to 10
.mu.m and in particular from 0.1 to 5 .mu.m, the particle sizes
given being determined by electron microscopy. The melting point of
the solids is preferably above the usual operating temperature of
the electrochemical cell, and melting points of above 120.degree.
C., in particular above 150.degree. C., have proven particularly
advantageous.
[0056] The solids here may be symmetrical in their external shape,
i.e. have a dimensional ratio of height:width:length (aspect ratio)
of about 1 and be shaped as spheres or pellets, be approximately
round in shape, or else be in the shape of any desired polyhedron,
such as a cuboid, tetrahedron, hexahedron, octahedron or bipyramid,
or may be distorted or asymmetric, i.e. have a dimensional ratio of
height:width:length (aspect ratio) which is not equal to 1 and be,
for example, in the form of needles, asymmetrical tetrahedra,
asymmetrical bipyramids, asymmetrical hexa- or octahedra, lamellae
or plates, or have fiber-like shape. If the solids are asymmetric
particles, the upper limit given above for the primary particle
size refers to the smallest axis in each case.
[0057] Compounds which may be used as compound VI, which is capable
of reacting with a carboxylic acid or sulfonic acid VII or with a
derivative or mixture of two or more thereof, are in principle any
of the compounds which fulfill this criterion.
[0058] Compound VI is preferably selected from the class consisting
of: mono- or polyhydric alcohols which have exclusively carbon in
their main chain; mono- or polyhydric alcohols which, in their main
chain, have, besides at least two carbon atoms, at least one atom
selected from the class consisting of oxygen, phosphorus and
nitrogen; silicon-containing compounds; amines having at least one
primary amino group; amines having at least one secondary amino
group; aminoalcohols; mono- or polyfunctional thiols; compounds
having at least one thiol and at least one hydroxyl group; and
mixtures of two or more of these.
[0059] Among these, preference in turn is given to compounds VI
which have two or more functional groups able to react with the
carboxylic acid or sulfonic acid.
[0060] When using compounds VI which contain amino groups as
functional group, it is preferable to use those which have
secondary amino groups, so that after condensation/crosslinking,
mixture Ia contains either no free NH groups at all or only small
amounts of such groups.
[0061] Individual preferred compounds which may be mentioned
are:
[0062] mono- or polyhydric alcohols having exclusively carbon in
their main chain and having from 1 to 20 alcoholic OH groups,
preferably from 2 to 20 alcoholic OH groups and in particular from
2 to 10 alcoholic OH groups, in particular di-, tri- and
tetrahydric alcohols, preferably having from 2 to 20 carbon atoms,
such as ethylene glycol, 1,2-propanediol, 1,3-propanediol,
1,2-butanediol, 1,3-butanediol, 1,4-butenediol, 1,4-butynediol,
1,6-hexanediol, neopentyl glycol, 1,2-dodecanediol, glycerol,
trimethylolpropane, pentaerythritol, sugar alcohols, hydroquinone,
novolak and bisphenol A, but as apparent from the definition above
it is also possible to use monohydric alcohols, such as methanol,
ethanol, propanol, n-butanol, sec-butanol and tert-butanol; it is
moreover also possible to use polyhydroxyolefins, preferably those
having two terminal hydroxyl groups, such as
.alpha.,.omega.-dihydroxybut- adiene;
[0063] polyester polyols, as known, for example, from Ullmann's
Encyclopedia of Industrial Chemistry, 4th ed., Vol. 19, pp. 62-65
and obtained, for example, by reacting dihydric alcohols with
polybasic, preferably dibasic polycarboxylic acids;
[0064] mono- or polyhydric alcohols which in their main chain
contain, besides at least two carbon atoms, at least one oxygen
atom, preferably polyetheralcohols, such as polymerization products
of alkylene epoxides, for example isobutylene oxide, propylene
oxide, ethylene oxide, 1,2-epoxybutane, 1,2-epoxypentane,
1,2-epoxyhexane, tetrahydrofuran and styrene oxide, use of
polyether alcohols modified at the end groups, for example
polyether alcohols modified with NH.sub.2 end groups, also being
possible; these alcohols preferably have a molecular weight (number
average) of from 100 to 5000, more preferably from 200 to 1000, and
in particular from 300 to 800; compounds of this type are known per
se and are commercially available, for example, under the
trademarks Pluriol.RTM. or Pluronic.RTM. (BASF
Aktiengesellschaft);
[0065] alcohols as defined above in which some or all of the carbon
atoms have been replaced by silicon, in particular polysiloxanes or
alkylene oxide/siloxane copolymers or mixtures of polyether
alcohols and polysiloxanes, as described, for example, in EP-B 581
296 and EP-A 525 728, where that which has already been said above
applies to these alcohols, also with respect to their molecular
weight;
[0066] alcohols as defined above, in particular polyether alcohols
in which some or all of the oxygen atoms have been replaced by
sulfur atoms, where that which has been said above applies likewise
to the molecular weight of these alcohols;
[0067] mono- or polyhydric alcohols which contain in their main
chain, besides at least two carbon atoms, at least one phosphorus
atom or at least one nitrogen atom, for example diethanolamine and
triethanolamine;
[0068] lactones which are derived from compounds of the formula
HO--(CH.sub.2).sub.z--COOH, where z is a number from 1 to 20, for
example E-caprolactone, .beta.-propiolactone, .gamma.-butyrolactone
and methyl-.epsilon.-caprolactone;
[0069] silicon-containing compounds, such as di- and
trichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane and
dimethylvinylchlorosila- ne; silanols, such as
trimethylsilanol;
[0070] amines having at least one primary and/or secondary amino
group, for example butylamine, 2-ethylhexylamine, ethylenediamine,
hexamethylenediamine, diethylenetriamine, tetraethylenepentamine,
pentaethylenehexamine, aniline and phenylenediamine;
[0071] polyether diamines, such as 4,7-dioxydecane-1,10-diamine and
4,11-dioxytetradecane-1,14-diamine;
[0072] mono- or polyfunctional thiols, such as aliphatic thiols,
e.g. methanethiol, ethanethiol, cyclohexanethiol and dodecanethiol;
aromatic thiols, e.g. thiophenol, 4-chlorothiophenol and
2-mercaptoaniline;
[0073] compounds having at least one thiol group and at least one
hydroxyl group, such as 4-hydroxythiophenol, and also monothio
derivatives of the polyhydric alcohols defined above;
[0074] aminoalcohols, such as ethanolamine, N-methylethanolamine,
N-ethylethanolamine, N-butylethanolamine, 2-amino-1-propanol,
2-amino-1-phenylethanol, and mono- or polyaminopolyols having more
than two aliphatically bonded hydroxyl groups, such as
tris(hydroxymethyl)-met- hylamine, glucamine and
N,N'-bis(2-hydroxyethyl)ethylenediamine.
[0075] It is also possible to use mixtures of two or more of the
compounds VI defined above.
[0076] According to the invention, the compounds VI mentioned above
are condensed with a carboxylic acid or sulfonic acid VII which has
at least one functional group capable of free-radical
polymerization, or with a derivative thereof or a mixture of two or
more thereof, at least one and preferably all of the groups which
are free and capable of condensation within the compounds VI being
condensed with the compound VII.
[0077] For the purposes of the present invention, the carboxylic
acid or sulfonic acid VII used may in principle be any carboxylic
or sulfonic acid which has at least one functional group capable of
free-radical polymerization, or also derivatives of these. The term
"derivatives" used here encompasses both compounds which are
derived from a carboxylic or sulfonic acid modified at the acid
function, such as esters, acid halides and anhydrides, and also
compounds which are derived from a carboxylic or sulfonic acid
which has been modified on its carbon skeleton, such as
halocarboxylic and halosulfonic acids.
[0078] Compounds VII which may be mentioned here in particular are:
.alpha.,.beta.-unsaturated carboxylic acids and
.beta.,.gamma.-unsaturate- d carboxylic acids.
[0079] Particularly suitable .alpha.,.beta.-unsaturated carboxylic
acids here are those of the formula 6
[0080] where R.sup.1, R.sup.2 and R.sup.3 are hydrogen or
C.sub.1-C.sub.4-alkyl, and where among these preference is in turn
given to acrylic acid and methacrylic acid; successful use may also
be made of cinnamic acid, maleic acid, fumaric acid, itaconic acid
or p-vinylbenzoic acid, and also derivatives of these, such as
anhydrides, e.g. maleic or itaconic anhydride;
[0081] halides, in particular chlorides, such as acryloyl or
methacryloyl chloride;
[0082] esters, such as (cyclo)alkyl (meth)acrylates having up to 20
carbon atoms in the alkyl radical, e.g. methyl, ethyl, propyl,
butyl, hexyl, 2-ethylhexyl, stearyl, lauryl, cyclohexyl, benzyl,
trifluoromethyl, hexafluoropropyl and tetrafluoropropyl
(meth)acrylate, polypropylene glycol mono(meth)acrylates,
polyethylene glycol mono(meth)acrylates, poly(meth)acrylates of
polyhydric alcohols, for example glycerol di(meth)acrylate,
trimethylolpropane di(meth)acrylate, pentaerythritol di- and
tri(meth)acrylate, diethylene glycol bis(mono(2-acryloxy)ethyl)ca-
rbonate, and poly(meth)acrylates of alcohols which themselves in
turn have a group capable of free-radical polymerization, for
example esters of (meth)acrylic acid and vinyl and/or allyl
alcohol;
[0083] vinyl esters of other aliphatic or aromatic carboxylic
acids, e.g. vinyl acetate, vinyl propionate, vinyl butyrate, vinyl
hexanoate, vinyl octanoate, vinyl decanoate, vinyl stearate, vinyl
palmitate, vinyl crotonoate, divinyl adipate, divinyl sebacate,
vinyl 2-ethylhexanoate and vinyl trifluoroacetate;
[0084] allyl esters of other aliphatic or aromatic carboxylic
acids, e.g. allyl acetate, allyl propionate, allyl butyrate, allyl
hexanoate, allyl octanoate, allyl decanoate, allyl stearate, allyl
palmitate, allyl crotonoate, allyl salicylate, allyl lactate,
diallyl oxalate, diallyl malonate, diallyl succinate, diallyl
glutarate, diallyl adipate, diallyl pimelate, diallyl cinnamate,
diallyl maleate, diallyl phthalate, diallyl isophthalate, triallyl
benzene-1,3,5-tricarboxylate, allyl trifluoroacetate, allyl
perfluorobutyrate and allyl perfluorooctanoate;
[0085] .beta.,.gamma.-unsaturated carboxylic acids or derivatives
of these, e g. vinylacetic acid, 2-methylvinylacetic acid, isobutyl
3-butenoate, allyl 3-butenoate, allyl 2-hydroxy-3-butenoate and
diketene;
[0086] sulfonic acids, such as vinylsulfonic acid, allyl- and
methallylsulfonic acid, and also esters and halides of these, vinyl
benzenesulfonates and 4-vinylbenzenesulfonamide.
[0087] It is also possible to use mixtures of two or more of the
carboxylic and/or sulfonic acids described above.
[0088] Mention may be made of the following individual compounds X
capable of free-radical polymerization and of being used to prepare
the polymer IX:
[0089] olefinic hydrocarbons, such as ethylene, propylene,
butylene, isobutene, hexene and higher homologs, and
vinylcyclohexane;
[0090] (meth)acrylonitrile;
[0091] halogen-containing olefinic compounds, such as vinylidene
fluoride, vinylidene chloride, vinyl fluoride, vinyl chloride,
hexafluoropropene, trifluoropropene, 1,2-dichloroethylene,
1,2-difluoroethylene and tetrafluoroethylene;
[0092] vinyl alcohol, vinyl acetate, N-vinylpyrrolidone,
N-vinylimidazole and vinylformamide;
[0093] phosphorus nitrile chlorides, such as phosphonitrile
dichloride and hexachlorotriphosphazene, and also derivatives of
these substituted to some extent or fully by alkoxy, phenoxy, amino
or fluoroalkoxy, i.e. compounds which can be polymerized to give
polyphosphazenes;
[0094] aromatic olefinic compounds, such as styrene and
.alpha.-methylstyrene;
[0095] vinyl ethers, such as methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, hexyl, octyl, decyl, dodecyl, 2-ethylhexyl,
cyclohexyl, benzyl, trifluoromethyl, hexafluoropropyl and
tetrafluoropropyl vinyl ether.
[0096] It is, of course, also possible to use mixtures of the above
compounds X, this then giving rise to copolymers which, depending
on the preparation method, contain the monomers in random
distribution or are formed as block copolymers.
[0097] These compounds X, like the condensation products V, are
polymerized in the conventional way well known to the person
skilled in the art, preferably by free-radical polymerization; in
relation to the molecular weights obtained that which is said in
the text below concerning compound VIII is applicable.
[0098] Compounds VIII are mainly compounds with an average
molecular weight (number average) of at least 5000, preferably from
5000 to 20,000,000, in particular from 100,000 to 6,000,000, and
capable of solvating lithium cations and of functioning as a
binder. Examples of suitable compounds VIII are polyethers and
copolymers which have at least 30% by weight, based on the total
weight of compound VIII, of the following structural unit: 7
[0099] where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are aryl or
alkyl, preferably methyl, or hydrogen, and may be identical or
different, and may contain heteroatoms, such as oxygen, nitrogen,
sulfur or silicon.
[0100] Compounds of this type are described, for example, in: M. B.
Armand et al., Fast Ion Transport in Solids, Elsevier, N.Y., 1979,
pp. 131-136, and in FR-A 7832976.
[0101] Compound VIII may also be composed of mixtures of two or
more compounds of this type.
[0102] The polymer composition IV defined above and/or the polymer
IX may also be a foam, the solid II then being distributed as such
therein.
[0103] According to the invention, the mixes IIa should be composed
of from 1 to 95% by weight, preferably from 25 to 90% by weight and
in particular from 30 to 70% by weight, of a solid III and of from
5 to 99% by weight, preferably from 10 to 75% by weight and in
particular from 30 to 70% by weight, of a polymeric composition IV,
where the compound VIII in the polymeric composition IV should
advantageously have an average molecular weight (number average) of
from 5000 to 100,000,000, preferably from 50,000 to 8,000,000. The
polymeric composition IV may be obtained by reacting from 5 to 100%
by weight, preferably from 30 to 70% by weight, based on the
polymeric composition IV, of a compound V and from 0 to 95% by
weight, in particular from 30 to 70% by weight, based on the
polymeric composition IV, of a compound VIII.
[0104] According to the invention, the mixes IIb should be composed
of from 1 to 95% by weight, preferably from 25 to 90% by weight,
and in particular from 30 to 70% by weight, of a solid III and of
from 5 to 99% by weight, preferably from 10 to 75% by weight and in
particular from 30 to 70% by weight, of a polymer IX, where the
compound VIII in the polymer IX advantageously has an average
molecular weight (number average) of from 5000 to 100,000,000,
preferably from 50,000 to 8,000,000. The polymer IX may be obtained
by reacting from 5 to 75% by weight, preferably from 30 to 70% by
weight, based on the polymer IX, of a compound X and from 25 to 95%
by weight, in particular from 30 to 70% by weight, based on the
polymer IX, of a compound VIII.
[0105] The novel mixture also contains at least one ester of the
formulae (E1) to (E5) as defined at the outset.
[0106] Among the esters mentioned above of the formulae (E1) to
(E5), preference is given to the use of the phosphates of the
formula (E3).
[0107] Examples of groups R.sup.1 and R.sup.2 and, if present,
R.sup.3 and/or R.sup.4 are methyl, ethyl, n-propyl, isopropyl,
n-butyl, tert-butyl, cyclopentyl, cyclohexyl and benzyl, and also
(--CH.sub.2--CH.sub.2--O).sub.n--CH.sub.3 where n is from 1 to 3,
care being taken as mentioned above however that at least one of
the groups R.sup.1, R.sup.2, R.sup.3 or R.sup.4 is
(--CH.sub.2--CH.sub.2--O).sub.n--- CH.sub.3, where n is from 1 to
3, preferably 1 or 2.
[0108] It is also preferable to use esters of the formulae (E1) to
(E5) in which R.sup.1, R.sup.2 and, if present, R.sup.3 and/or
R.sup.4 are identical and are --CH.sub.2--CH.sub.2O--CH.sub.3 or
(--CH.sub.2--CH.sub.2--O).sub.2--CH.sub.3, the corresponding
phosphates being preferred here once again.
[0109] Examples of compounds whose use is particularly preferred
are those of the formulae (E1a) to (E5a): 8
[0110] Because of their properties, the esters used here are
exceptionally suitable as plasticizers in mixtures according to the
invention, and generally have a viscosity at room temperature of
.ltoreq.10 mPas, preferably .ltoreq.5 mPas and in particular
.ltoreq.3 mPas. They generally have boiling points of about
200.degree. C. or above, preferably about 250.degree. C. or above,
and in particular about 300.degree. C. or above, measured in each
case at atmospheric pressure, and have a sufficiently low vapor
pressure of from about 10.sup.-5 to about 10 mbar at the
temperatures of from about -50.degree. C. to about 150.degree. C.
at which they are used. Their high boiling points mean that they
can be distilled and can therefore be prepared with high purity.
These esters are, furthermore, liquid at atmospheric pressure over
a wide temperature range, generally remaining liquid down to about
-30.degree. C., preferably down to about -40.degree. C. The esters
described for this purpose may be used as solvents in electrolyte
systems for Li-ion storage batteries at at least about 80.degree.
C., preferably at at least about 120.degree. C., and more
preferably at at least about 150.degree. C.
[0111] It is, of course, also possible to use the esters used
according to the invention as mixtures with the plasticizers
mentioned below.
[0112] Preference is given to solvent combinations which have
sufficiently low viscosity, are capable of powerful solvation of
the ions of the conducting salts, are liquid over a wide
temperature range and are adequately electrochemically and
chemically stable and resistant to hydrolysis.
[0113] The content of the esters in the novel mixture is generally
from 1 to 200% by weight, preferably from 2 to 100% by weight and
more preferably from 2 to 70% by weight, based in each case on the
mix IIa/IIb.
[0114] The esters used according to the invention are prepared by
conventional processes, as described, for example, by K. Mura Kami
in Chem. High Polymers (Japan), 7, pp. 188-193 (1950) and in H.
Steinberg, Organoboron Chemistry, Chapter 5, J. Wiley & Sons,
N.Y., 1964. The starting materials here are generally the acids,
anhydrides or acid chlorides on which the esters are based, for
example boric acid, C(O)Cl.sub.2, POCl.sub.3, SO.sub.2Cl.sub.2 and
SiCl.sub.4, and these are reacted in a known manner with the
corresponding mono- or polyhydric alcohols or etherols.
[0115] The novel mixtures Ia and Ib and the mixes IIa and IIb are
discussed together below and are termed, respectively, "novel
mixture" and "novel mix".
[0116] The novel mixture comprises the novel mix and the ester in
amounts of from 1 to 100% by weight, preferably from 35 to 100% by
weight, based in each case on the novel mixture. To prepare the
same, use may be made of a mix made from: a solid III, a
condensation product V and, if desired, a compound VIII, or of a
mix made from: a solid III, a compound X, a compound VIII, and at
least one ester of the formula (E1) to (E5), as well as, if
desired, of usual additives, such as other plasticizers, preferably
those comprising polyethylene oxide or polypropylene oxide.
[0117] Other plasticizers used may be aprotic solvents, preferably
those which solvate Li ions, for example dimethyl carbonate,
diethyl carbonate, dipropyl carbonate, diisopropyl carbonate,
dibutyl carbonate, ethylene carbonate and propylene carbonate;
oligoalkylene oxides, such as dibutyl ether, di-tert-butyl ether,
dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether,
dinonyl ether, didecyl ether, didodecyl ether, ethylene glycol
dimethyl ether, ethylene glycol diethyl ether,
1-tert-butoxy-2-methoxyethane, 1-tert-butoxy-2-ethoxyethane,
1,2-dimethoxypropane, 2-methoxyethyl ether, 2-ethoxyethyl ether,
diethylene glycol dibutyl ether, dimethylene glycol tert-butyl
methyl ether, triethylene glycol dimethyl ether, tetraethylene
glycol dimethyl ether, .gamma.-butyrolactone and dimethylformamide;
hydrocarbons of the formula C.sub.nH.sub.2n+2 where 7<n<50;
organic phosphorus compounds, in particular phosphates and
phosphonates, such as trimethyl phosphate, triethyl phosphate,
tripropyl phosphate, tributyl phosphate, triisobutyl phosphate,
tripentyl phosphate, trihexyl phosphate, trioctyl phosphate,
tris(2-ethylhexyl) phosphate, tridecyl phosphate, diethyl n-butyl
phosphate, tris(butoxyethyl) phosphate, tris(2-methoxyethyl)
phosphate, tris(tetrahydrofuryl) phosphate,
tris(1H,1H,5H-octafluoropenty- l) phosphate,
tris(1H,1H-trifluoroethyl) phosphate, tris(2-(diethylamino)ethyl)
phosphate, diethyl ethylphosphonate, dipropyl propylphosphonate,
dibutyl butylphosphonate, dihexyl hexylphosphonate, dioctyl
octylphosphonate, ethyl dimethylphosphonoacetate, methyl
diethylphosphonoacetate, triethyl phosphonoacetate, dimethyl
2-oxopropylphosphonate, diethyl 2-oxopropylphosphonate, dipropyl
2-oxopropylphosphonate, ethyl diethoxyphosphinylformate, trimethyl
phosphonoacetate, triethyl phosphonoacetate, tripropyl
phosphonoacetate and tributyl phosphonoacetate; organic sulfur
compounds, such as sulfates, sulfonates, sulfoxides, sulfones and
sulfites, for example dimethyl sulfite, diethyl sulfite, glycol
sulfite, dimethyl sulfone, diethyl sulfone, diethylpropyl sulfone,
dibutyl sulfone, tetramethylene sulfone, methylsulfolane, dimethyl
sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, dibutyl
sulfoxide, tetramethylene sulfoxide, ethyl methanesulfonate,
1,4-butanediol bis(methanesulfonate), diethyl sulfate, dipropyl
sulfate, dibutyl sulfate, dihexyl sulfate, dioctyl sulfate and
SO.sub.2ClF; and nitriles, such as acrylonitrile;
[0118] dispersants, in particular those with surfactant
structure;
[0119] and mixtures of these.
[0120] The mixtures according to the invention may be dispersed or
dissolved in an inorganic or preferably an organic liquid diluent,
where the mixture according to the invention should have a
viscosity of preferably from 100 to 50,000 mPas, and may then be
applied in a manner known per se, such as spray coating, casting,
dipping, spin coating, roller coating, relief printing, gravure
printing or planography or screen printing onto a carrier material.
Further processing can take place in the usual way, e.g. by
removing the diluent and curing the mixture.
[0121] Suitable organic diluents are aliphatic ethers, in
particular tetrahydrofuran and dioxane, hydrocarbons, in particular
hydrocarbon mixtures such as petroleum spirit, toluene and xylene,
aliphatic esters, in particular ethyl acetate and butyl acetate,
and ketones, in particular acetone, ethyl methyl ketone and
cyclohexanone. It is also possible to use combinations of diluents
of this type.
[0122] Carrier materials which may be used are those usually used
for electrodes, preferably metals, such as aluminum and copper. It
is also possible to use temporary carriers, such as films, in
particular polyester films, such as polyethylene terephthalate
films. Such films may advantageously be provided with a release
layer, preferably of polysiloxanes.
[0123] The solid electrolytes and separators may likewise be
produced thermoplastically from the mixture according to the
invention, for example by injection molding, melt casting,
compression molding, kneading or extrusion, if desired followed by
a calendering step.
[0124] After the mixture according to the invention has formed a
film, volatile components, such as solvents or plasticizers, may be
removed.
[0125] The crosslinking of the mixture according to the invention
may be done in a manner known per se, for example by irradiating
with ionic or ionizing radiation, or an electron beam, preferably
with an acceleration voltage of from 20 to 2000 kV and a radiation
dose of from 5 to 50 Mrad, or UV or visible light, and it is
usually advantageous here to add an initiator, such as benzil
dimethyl ketal or 1,3,5-trimethylbenzoyltriphen- ylphosphine oxide,
in amounts of in particular at most 1% by weight, based on the
polymeric composition IV and the polymer IX, respectively, and the
crosslinking may generally be carried out within from 0.5 to 15
minutes, advantageously under an inert gas, such as nitrogen or
argon; by thermal free-radical polymerization, preferably at
temperatures above 60.degree. C., it being possible and
advantageous to add an initiator, such as azobisisobutyronitrile,
generally in amounts of at most 5% by weight, preferably from 0.05
to 1% by weight, based on the polymeric composition IV and the
polymer IX, respectively; by electrochemically induced
polymerization; or by ionic polymerization, for example by
acid-catalyzed cationic polymerization, possible catalysts being
primarily acids, preferably Lewis acids, such as BF.sub.3 or in
particular LiBF.sub.4 or LiPF.sub.6. Lithium-ion-containing
catalysts, for example LiBF.sub.4 or LiPF.sub.6, here may
advantageously remain as conducting salt in the solid electrolyte
or separator.
[0126] If the mixture according to the invention is to be used as a
solid electrolyte or a separator in an electrochemical cell, a
dissociable compound containing lithium cations, known as a
conducting salt, and other additives if desired, such as in
particular organic solvents, known as an electrolyte, may be
incorporated.
[0127] The addition of these materials to the mixture may take
place to some extent or completely during the production of the
layer, or they may be introduced into the layer after it has been
produced.
[0128] The conducting salts which may be used are those which are
well known and described, for example, in EP-A 0 096 629. It is
preferable according to the invention for the conducting salt used
to be LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiC(CF.sub.3SO.sub.2).sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, Li(C.sub.nF.sub.2n+1)SO.sub.3,
LiC[(C.sub.nF.sub.2n+1)SO.sub.2].sub.3,
LiN(C.sub.nF.sub.2n+1SO.sub.2).sub.2, where n is from 2 to 20,
LiN(SO.sub.2F).sub.2, LiAlCl.sub.4, LiSiF.sub.6, LiSbF.sub.6 or a
mixture of two or more of these, use of LiBF.sub.4 as conducting
salt being preferred. Particular preference is given to the
combination of the esters of the formulae (E1a) to (E5a) with
LiBF.sub.4 as conducting salt, and particular preference is given
to the combination of the ester of the formula (E3a) with
LiBF.sub.4 as conducting salt.
[0129] Possible electrolytes, besides the esters present in the
mixture, are the compounds discussed above under "plasticizers",
preference being given to the use of the usual organic
electrolytes, preferably esters, such as ethylene carbonate,
propylene carbonate, dimethyl carbonate and diethyl carbonate or
mixtures of compounds of this type.
[0130] The novel solid electrolytes, separators and/or electrodes
suitable for electrochemical cells should advantageously have a
thickness of from 5 to 500 .mu.m, preferably from 10 to 500 .mu.m,
more preferably from 10 to 200 .mu.m and in particular from 20 to
100 .mu.m.
[0131] If the novel mixture is to be used as, or for preparing, a
cathode, then one of the conventionally used electron-conducting,
electrochemically active compounds (cathode compound) is
incorporated, preferably a lithium compound. Particular examples of
these are:
[0132] LiCoO.sub.2, LiNiO.sub.2, LiNi.sub.xCo.sub.yO.sub.2,
LiNi.sub.xCo.sub.yAl.sub.zO.sub.2, where 0<x,y,z.ltoreq.1,
Li.sub.xMnO.sub.2 (0<x.ltoreq.1), Li.sub.xMn.sub.2O.sub.4
(0<x.ltoreq.2), Li.sub.xMoO.sub.2 (0<x.ltoreq.2),
Li.sub.xMnO.sub.3 (0<x.ltoreq.1), Li.sub.xMnO.sub.2
(0<x.ltoreq.2), Li.sub.xMn.sub.2O.sub.4 (0<x.ltoreq.2),
Li.sub.xV.sub.2O.sub.4 (0<x.ltoreq.2.5), Li.sub.xV.sub.2O.sub.3
(0<x.ltoreq.3.5), Li.sub.xVO.sub.2 (0<x.ltoreq.1),
Li.sub.xWO.sub.2 (0<x.ltoreq.1), Li.sub.xWO.sub.3
(0<x.ltoreq.1), Li.sub.xTiO.sub.2 (0<x.ltoreq.1),
Li.sub.xTi.sub.2O.sub.4 (0<x.ltoreq.2), Li.sub.xRuO.sub.2
(0<x.ltoreq.1), Li.sub.xFe.sub.2O.sub.3 (0<x.ltoreq.2),
Li.sub.xFe.sub.3O.sub.4 (0<x.ltoreq.2), Li.sub.xCr.sub.2O.sub.3
(0<x.ltoreq.3), Li.sub.xCr.sub.3O.sub.4 (0<x.ltoreq.3.8),
Li.sub.xV.sub.3S.sub.5 (0<x.ltoreq.1.8), Li.sub.xTa.sub.2S.sub.2
(0<x.ltoreq.1), Li.sub.xFeS (0<x.ltoreq.1), Li.sub.xFeS.sub.2
(0<x.ltoreq.1), Li.sub.xNbS.sub.2 (0<x.ltoreq.2.4),
Li.sub.xMoS.sub.2 (0<x.ltoreq.3), Li.sub.xTiS.sub.2
(0<x.ltoreq.2), Li.sub.xZrS.sub.2 (0<x.ltoreq.2),
Li.sub.xNbSe.sub.2 (0<x.ltoreq.3), Li.sub.xVSe.sub.2
(0<x.ltoreq.1), Li.sub.xNiPS.sub.2 (0<x.ltoreq.1.5),
Li.sub.xFePS.sub.2 (0<x.ltoreq.1.5).
[0133] For use as an anode, the anode material incorporated is a
conventional electron-conducting, electrochemically active compound
(anode compound) known from the prior art, of which the following
in particular may be mentioned:
[0134] lithium, lithium-containing metallic alloys, micronized
carbon black, natural and synthetic graphite, synthetically
graphitized carbon dust and carbon fibers, oxides, such as titanium
dioxide, zinc oxide, tin oxide, molybdenum oxide and tungsten
oxide, and carbonates, such as titanium carbonate, molybdenum
carbonate and zinc carbonate.
[0135] When the novel mixture is used as, or for producing, an
anode, it contains an addition of up to 20% by weight, based on the
total weight of the mixture, of conductivity black and, if desired,
the usual additives mentioned above. If the mixture is used as, or
for producing, a cathode, it contains, based on its total weight,
from 0.1 to 20% by weight of conductivity black.
[0136] The novel mixtures may be used in electrochemical cells as
sole solid electrolyte and/or separator and/or electrode, or in a
mixture with other solid electrolytes, separators and/or
electrodes.
[0137] The present invention moreover provides a composite which
can be used in particular in electrochemical cells, preferably in
the form of a film, more preferably in the form of a film with an
overall thickness of from 15 to 1500 .mu.m, in particular with an
overall thickness of from 50 to 500 .mu.m, encompassing at least
one first layer which comprises an electron-conducting,
electrochemically active compound, and at least one second layer
which comprises the novel mixture defined above and is free from
electron-conducting, electrochemically active compounds.
[0138] The present invention also describes a process encompassing
the following stages for producing a composite of this type:
[0139] (I) producing at least one first layer, as defined
above;
[0140] (II) producing at least one second layer, as defined above;
and
[0141] (III) then bringing together the at least one first layer
with the at least one second layer by means of a conventional
process for providing layers.
[0142] It is preferable to produce the at least one second layer on
a temporary carrier. According to the invention, use may be made
here of conventionally used temporary carriers, such as a release
film made from a polymer or from a preferably coated paper, e.g. a
siliconized polyester film. It is, however, also possible to
produce this second layer on a permanent carrier, such as a
collector electrode, or else even entirely without a carrier.
[0143] The bringing together and the production of the layers
defined above takes place by means of atmospheric-pressure
processes for providing layers or for the production of films, such
as casting or doctoring, or also by process methods at
superatmospheric pressure, such as extrusion, lamination,
calendering or compression molding. The composite thus produced
may, if desired, be crosslinked and/or hardened by radiation,
electrochemically or thermally.
[0144] Besides the second layer defined above, the first layer
defined above may, of course, also comprise the novel mixture.
[0145] As apparent from the above, this method makes it possible
with ease to provide a composite with the constituents release
film/separator (second layer)/electrode (first layer).
[0146] It is also possible, by double-sided coating, to provide a
composite with the constituents anode/sepa-rator/cathode.
[0147] An example of a procedure for this is:
[0148] Anode materials, e.g. tin oxide, conductivity black, the
novel mixture, a conducting salt and a plasticizer, e.g. propylene
carbonate, are firstly mixed with one another and the resultant
blend is cast onto a collector electrode and then irradiated with
UV light (component 1). A cathode material, e.g. LiMn.sub.2O.sub.4,
is then applied to a collector electrode coated with conductivity
black, and onto this is cast a blend of the novel mixture, a
conducting salt and a plasticizer. This composite, too, is then
UV-irradiated (component 2). Bringing together the two components
described above gives a composite which, combined with any desired
solid and/or liquid electrolyte, can be used as an electrochemical
cell.
[0149] It is also possible to produce an anode/separator/cathode
composite as described above even without using a carrier and/or
the collector electrodes, since the resultant composite composed of
a first and a second layer, as defined above, has sufficient
mechanical stability in its own right for use in electrochemical
cells.
[0150] The filling of composites of this type with an electrolyte
and conducting salt may take place either before the layers are
brought together or else, preferably, after they are brought
together, if desired after contact has been established with
suitable collector electrodes, e.g. with a metal film, and can even
take place after the composite has been introduced into a battery
casing; the specific microporous structure of the layers when the
mixture according to the invention is used, resulting in particular
from the presence of the solid defined above in the separator and,
if present, in the electrodes, makes it possible for the
electrolyte and the conducting salt to be absorbed and the air in
the pores to be displaced. The filling may be carried out at from 0
to about 100.degree. C., depending on the electrolyte used.
[0151] The novel electrochemical cells may be used in particular as
automobile battery, appliance battery, flat-type battery or
all-plastics battery.
[0152] As apparent from the above, the present invention also
provides the use of the novel mixture or of the composite described
above for producing a solid electrolyte, a separator or an
electrode, or in a sensor, in an electrochromic window, in a
display, in a capacitor or in an ion-conducting film; it also
provides a solid electrolyte, a separator, an electrode, a sensor,
an electro-chromic window, a display, a capacitor and an
ion-conducting film, each of which comprise the novel mixture or
the composite described above.
[0153] The invention further provides an electrochemical cell
encompassing a solid electrolyte, a separator or an electrode, as
defined above, or a combination of two or more of these, and also
the use of the electrochemical cell defined above as an automobile
battery, appliance battery or flat-type battery.
EXAMPLES
[0154] Example of Preparation of an Ester
[0155] To prepare the phosphates of the formula
O.dbd.P(--O--CH.sub.2--CH.- sub.2--OCH.sub.3).sub.3, 274 g (3.6
mol) of methylglycol were placed in a 1000 ml round-bottomed flask
with 2 g of ZnCl.sub.2 and cooled to 5.degree. C. 153.33 g (1 mol)
of POCl.sub.3 were then added dropwise within a period of 50 min,
the temperature being held at from about 5 to 10.degree. C. After
the addition had finished, the solution was clear and was allowed
to warm to room temperature. The resultant product mixture was then
distilled under reduced pressure (from 80 to 90 mbar) at from about
50 to 55.degree. C. in order to remove unreacted starting material
and by-products.
[0156] A further distillation was then carried out at very low
pressure (about 0.02 mbar) at about 170.degree. C., giving the
desired product. The water content of the above phosphate was 20
ppm.
Example 1
[0157] 75 g of a wollastonite (Tremin.RTM. 800 EST, Quarzwerke
Frechen) which had an average particle size of 3 .mu.m and had been
hydrophobicized with epoxysilane and whose aqueous suspension had a
pH of 8.5, was dispersed by a high-speed stirrer in 300 g of
toluene and 5 g of the phosphate of the preparative example. The
following were then added to the mixture: 12.5 g of a polyethylene
oxide having an average molecular weight (number average) of
2,000,000 (Polyox.RTM., Union Carbide), 12.5 g of a dimethacrylate
of a propylene oxide-ethylene oxide block polymer (Pluriol.RTM.
PE600, BASF Aktiengesellschaft) and 0.02 g of a UV photoinitiator
(Lucirin.RTM. BDK, BASF Aktiengesellschaft).
[0158] The mixture was then applied, using a doctor with a coating
gap of 300 .mu.m, to a siliconized release paper at 60.degree. C.,
the diluent was removed within a period of minutes, and peeling off
the dried coating gave a film of about 40 .mu.m thickness which was
photo-crosslinked under an argon atmosphere by irradiation for 10
minutes at a distance of 5 cm in a field of superactinic
fluorescent tubes (TL 09, Philips).
[0159] The flexible film had excellent flexural strength, and
tolerated bending radii down to well below 1 mm without
fracturing.
[0160] The film also showed no spherulite-type polyethylene oxide
crystals after storage for two weeks at room temperature, and had
good resistance to swelling in the organic electrolytes which have
been mentioned and which contain a conducting salt.
[0161] The organic electrolytes containing a conducting salt were
absorbed in sufficient amounts within a few minutes through a
process of spontaneous diffusion into the material, with swelling,
in weight terms, of less than 50% by weight.
[0162] The swollen film had good strength.
Comparative Example 1
[0163] 12.5 g of a polyethylene oxide having an average molecular
weight (number average) of 2,000,000 (Polyox.RTM., Union Carbide),
12.5 g of a dimethacrylate of a propylene oxide-ethylene oxide
block polymer (Pluriol.RTM. PE600, BASF Aktiengesellschaft) and
0.02 g of a UV photoinitiator (Lucirin.RTM. BDK, BASF
Aktiengesellschaft) were dissolved in 200 g of THF.
[0164] The mixture was then applied, using a doctor with a coating
gap of 750 .mu.m, to a siliconized release paper at 60.degree. C.,
the diluent was removed within a period of 5 minutes, and peeling
off the dried coating gave a film of about 40 .mu.m thickness which
was photo-crosslinked under an argon atmosphere by irradiation for
10 minutes at a distance of 5 cm in a field of superactinic
fluorescent tubes (TL 09, Philips).
[0165] The flexible film had excellent flexural strength, and
tolerated bending radii down to well below 1 mm without fracturing.
The film also showed no spherulite-type polyethylene oxide crystals
after storage for two weeks at room temperature, and had
satisfactory resistance to swelling in the organic electrolytes
which have been mentioned and which contain a conducting salt.
[0166] The organic electrolytes containing a conducting salt were
absorbed in sufficient amounts within a few minutes through a
process of spontaneous diffusion into the material, with swelling,
in weight terms, of less than 150% by weight, with considerable
change taking place in the size and thickness of the film.
[0167] Its strength was markedly lower than was the case in Example
1.
[0168] In lithium-ion batteries, the film always caused failure of
the cells as a result of excessive self-discharge rates or micro
short-circuits.
[0169] The results are given in the table.
Comparative Example 2
[0170] 75 g of a wollastonite (Tremin.RTM. 800 EST, Quarzwerke
Frechen) which had an average particle size of 3 .mu.m and had been
hydrophobicized with epoxysilane and whose aqueous suspension had a
pH of 8.5, was dispersed by a high-speed stirrer in 300 g of
toluene. The following were then added to the mixture: 12.5 g of a
polyethylene oxide having an average molecular weight (number
average) of 2,000,000 (Polyox.RTM., Union Carbide), 12.5 g of a
dimethacrylate of a propylene oxide-ethylene oxide block polymer
(Pluriol.RTM. PE600, BASF Aktiengesellschaft) and 0.02 g of a UV
photoinitiator (Lucirin.RTM. BDK, BASF Aktiengesellschaft).
[0171] The mixture was then applied, using a doctor with a coating
gap of 300 .mu.m, to a siliconized release paper at 60.degree. C.,
the diluent was removed within a period of 5 minutes, and peeling
off the dried coating gave a film of about 40 .mu.m thickness.
[0172] The flexible film had excellent flexural strength, and
tolerated bending radii down to well below 1 mm without
fracturing.
[0173] The film also showed no spherulite-type polyethylene oxide
crystals after storage for two weeks at room temperature, and had
insufficient resistance to swelling in the organic electrolytes
which have been mentioned and which contain a conducting salt. Even
after a few minutes of swelling time, fissures appear or the film
sticks to itself, so that the swollen film is no longer
handleable.
[0174] The results are given in the table.
Comparative Example 3
[0175] As in U.S. Pat. No. 5,429,891, Example 1 (F), to a mixture
of 30 g of a vinylidene fluoride hexafluoropropene copolymer
(Kynarflex.RTM. 2822, Elf Atochem), 20 g of a silanized pyrogenic
silica (Aerosil R974, Degussa) whose aqueous suspension has a pH of
7, 50 g of dibutyl phthalate (Palatinol C, BASF Aktiengesellschaft)
and 200 g of acetone were added 5% by weight, based on dibutyl
phthalate, on trimethylolpropane trimethacrylate.
[0176] The mixture was then applied to a glass plate using a doctor
with a coating gap of 750 .mu.m, dried in a stream of air for 15
minutes, and embedded between layers of Mylar.RTM. of thickness
0.075 mm. The film layer of thickness 100 .mu.m was then
crosslinked by irradiation with electrons of an energy level of 4.5
MeV, at a dose of 5 Mrad, a dose of 2.5 Mrad being used for each
pass.
[0177] The flexible film had good flexural strength.
[0178] Before use of the film in lithium-ion batteries, it was
necessary for complicated measures to be taken to remove the
plasticizer by extraction from the film, since otherwise the cycle
stability achieved was inadequate due to poisoning of the
electrodes. To remove the plasticizer, the film was extracted five
times, for 10 minutes on each occasion, with 50 times its own
weight of diethyl ether at room temperature. After the plasticizer
has been removed, the film is unstable and easily fractures on
bending.
[0179] The plasticizer-free film showed good resistance to swelling
in the organic electrolytes which have been mentioned and which
contain a conducting salt.
[0180] The organic electrolytes containing a conducting salt were
absorbed in sufficient amounts within a few minutes by spontaneous
diffusion into the material.
[0181] The swollen film had good strength.
[0182] The results are given in the table below.
1 TABLE Ex. 1 Comp. 1 Comp. 2 Comp. 3 Strength with not not not 2
plasticizer applicable applicable applicable Extraction not not not
required applicable applicable applicable Strength without 2 2 5 5
plasticizer Resistance to 2 3 5 2 swelling Strength after 2 4 6 2
swelling Conductivity 2 2 4 2 Short-circuit 1 4 6 1 protection
Current capacity 1 5 6 4 Cycle stability 1 5 6 2 Grades: 1 very
good 2 good 3 satisfactory 4 unsatisfactory 5 poor 6 so poor that
test could not be carried out
* * * * *