Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-17
2003-11-04
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S401000, C524S404000, C524S414000, C524S415000, C524S428000
Reexamination Certificate
active
06642294
ABSTRACT:
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.
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.
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.
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
2
O
4
, LiCoO
2
, LiV
2
O
5
or LiNiO
2
.
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).
The compounds suitable for reversible storage of lithium ions are usually secured to collector electrodes by means of a binder.
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.
In order to avoid a short circuit within the electrochemical cell, a layer which is electrically insulating but permeable co lithium cations is located between the two electrodes. This may be what is known as a solid electrolyte or a conventional separator.
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.
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
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.
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.
Electrolyte solutions based on various esters are also known.
For example, WO97/16862 describes an electrolyte solution which comprises borates of the following formulae (A) to (D):
where X is halogen, R
1
, R
2
, R
3
and R
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.
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.
EP-B-0 599 534 describes carbonate compounds of the following formula (F)
R
1
—CH
2
—O—CO—O—CH
2
R
2
(F)
where R
1
is hydrogen, alkyl or alkyl substituted with one or more halogen atoms, and R
2
is allkyl with no hydrogen in the &agr; position or alkyl with no hydrogen in the &agr; position and substituted with one or more halogen atoms, with the proviso that R
1
is not identical with R
2
, excluding the compound C
2
H
5
—O—CO—O—CH
2
—(CF
2
)
4
—H and also its use in a non-aqueous electrolyte solution.
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)
3
P═O, where each of the groups R is identical or different and is C
1
-C
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.
The use of phosphates of the formula O═P(—O—(CH
2
CH
2
O)
q
R
2
)
3
, where n and q are from 1 to 10 and R
2
is C
1
-C
4
-alkyl, as electrolyte in zinc batteries is described in JP 07 161 357.
Other phosphates having hydrocarbon groups, and also the use of these as electrolyte in lithium ion batteries, are described in JP 58 206 078.
JP 61 256 573 describes an electrolyte based on a polymer of a phosphate containing at least one polymerizable group.
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.
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° 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.
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.
At the same time, the esters used also have electrolyte properties.
One embodiment of the present invention therefore provides 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 &mgr;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
&agr;) 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
&bg
Bauer Stephan
Bronstert Bernd
Hesse Werner
Möhwald Helmut
Sterzel Hans-Josef
BASF - Aktiengesellschaft
Keil & Weinkauf
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