Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer – spacer or materials for use therewith
Reexamination Certificate
2001-10-09
2004-05-04
Bell, Bruce F. (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer, spacer or materials for use therewith
C429S247000, C429S231900, C429S231950, C429S304000, C429S309000, C429S306000
Reexamination Certificate
active
06730440
ABSTRACT:
The present invention relates to composites which are suitable for, inter alia, electrochemical cells having electrolytes containing lithium ions; their use as, for example, lithium ion batteries, batteries, sensors, electrochromic windows, displays, capacitors and ion-conducting films comprising such a composite.
BACKGROUND OF THE INVENTION
Electrochemical, in particular rechargeable, cells are generally known, for example from “Ullmann's Encyclopedia of Industrial Chemistry”, 5th Ed., Vol. A3, VCH Verlagsgesellschaft mbH, Weinheim, 1985, pages 343-397.
Among these cells, a special position is occupied by lithium batteries and lithium ion batteries, in particular as secondary cells, owing to their high specific energy storage density.
As described, for example, in the above citation from “Ullmann”, the cathode of such cells comprises lithiated manganese, cobalt, vanadium or nickel mixed oxides which in the stoichiometrically simplest case can be described as LiMn
2
O
4
, LiCoO
2
, LiV
2
O
5
or LiNiO
2
.
These mixed oxides react reversibly with compounds which can incorporate lithium ions into their lattice, for example graphite, with the lithium ions being removed from the crystal lattice and the metal ions such as manganese, cobalt or nickel ions present in the latter being oxidized. This reaction can be utilized in an electrochemical cell for storing electrical energy by separating the compound which takes up lithium ions, i.e. the anode material, and the lithium-containing mixed oxide, i.e. the cathode material, by means of an electrolyte through which the lithium ions migrate from the mixed oxide into the anode material (charging operation).
The compounds suitable for the reversible storage of lithium ions are usually fixed on collector electrodes by means of a binder.
When the cell is charged, electrons flow through an external voltage source and lithium cations flow through the electrolyte to the anode material. When the cell is used, the lithium cations flow through the electrolyte whereas the electrons flow through a load from the anode material to the cathode material.
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 layer can be a solid electrolyte or a conventional separator.
In the production of many electrochemical cells, e.g. a lithium ion battery in the form of a round cell, the necessary battery films, i.e. cathode, anode and separator films, are combined using a rolling apparatus to produce a battery roll. In conventional lithium ion batteries, the cathode and anode film(s) are joined to collector electrodes in the form of, for example, an aluminum or copper foil. Such metal foils ensure sufficient mechanical stability.
In contrast, the separator film has to withstand the mechanical stresses on its own, which presents no problem in the case of conventional separator films based on, for example, polyolefins and having the conventional thickness. To further improve the mechanical stability of such conventional separator films, JP 09-134 730 and JP 09-161 815 propose joining these separator films to the anode and/or cathode film by means of a bonding layer.
In contrast to conventional separator films, the mechanical stability of separator films filled with a solid is generally not sufficient to ensure problem-free rolling of the films.
A composite which is able to withstand the mechanical stresses occurring in the manufacture of, for example, batteries is described in WO 99/19917 by the applicant. The composite claimed there comprises at least one layer which is filled with a solid, e.g. a separator layer, and at least one second layer which can be a cathode layer or an anode layer.
It is an object of the present invention to develop the composite claimed in WO 99/19917 further and to provide a composite which can be used directly as an electrochemical cell, in particular as a lithium ion battery, and can accordingly be introduced directly into an appropriate housing for such a cell or such a battery.
SUMMARY OF THE INVENTION
The present invention accordingly provides, in one embodiment, a composite comprising
Aa) at least one separator layer Aa which comprises a mixture Ia, comprising a mix IIa consisting of
a) from 1 to 95% by weight of a solid III, preferably a basic solid III, having 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 polymerization of
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 able to react with a carboxylic acid or a sulfonic acid or a derivative or a mixture of two or more thereof, and
&bgr;) at least 1 mol per mol of the compound VI of a carboxylic acid or sulfonic acid VII which contains at least one free-radically polymerizable functional group, or a derivative thereof or a mixture of two or more thereof, and
b2) from 0 to 95% by weight, based on the composition IV, of a further compound VIII having a mean molecular weight (number average) of at least 5000 and polyether segments in the main chain or a side chain,
where the proportion by weight of the mix IIa in the mixture Ia is from 1 to 100% by weight,
and the layer is free of an electron-conducting, electrochemically active compound, and
B) at least one cathode layer B which comprises an electron-conducting, electrochemically active compound which is able to release lithium ions on charging,
C) at least one anode layer C which comprises an electron-conducting, electrochemical compound which is able to take up lithium ions on charging.
The separator layer or layers Aa preferably comprise(s) a mixture Ia comprising a mix IIa consisting of
a) from 1 to 95% by weight of a solid III, preferably a basic solid III, having 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 polymerization of
b1) from 5 to 100% by weight, based on the composition IV, of a condensation product V of
&agr;) a polyhydric alcohol VI which has carbon and oxygen atoms in the main chain, and
&bgr;) at least 1 mol per mol of the polyhydric alcohol VI of a &agr;,&bgr;-unsaturated carboxylic acid VII, and
b2) from 0 to 95% by weight, based on the composition IV, of a further compound VIII having a mean molecular weight (number average) of at least 5000 and polyether segments in the main chain or a side chain,
where the proportion by weight of the mix IIa in the mixture Ia is from 1 to 100% by weight.
In a further embodiment, the present invention provides a composite comprising
Ab) at least one first separator layer Ab which comprises a mixture Ib comprising a mix IIb consisting of
a) from 1 to 95% by weight of a solid III, preferably a basic solid, having a primary particle size of from 5 nm to 20 &mgr;m and
b) from 5 to 99% by weight of a polymer IX obtainable by polymerization of
b1) from 5 to 75% by weight, based on the polymer IX, of a free-radically polymerizable compound X which is different from the carboxylic acid or the sulfonic acid VII or a derivative thereof, or a mixture of two or more thereof, and
b2) from 25 to 95% by weight, based on the polymer IX, of a further compound VIII having a mean molecular weight (number average) of at least 5000 and polyether segments in the main chain or a side chain,
where the proportion by weight of the mix IIb in the mixture Ib is from 1 to 100% by weight
and the layer is free of an electron-conducting, electrochemically active compound, and
at least one cathode layer B and at least one anode layer C, each as defined above.
The present invention further provides a composite comprising
at least one separator layer Aa or at least one separator layer Ab or at least one separator layer Aa and at least one separator layer Ab,
at least one cathode layer B,
at least one anode layer C,
each as defined above, and
D) at least one bonding layer D.
The respective layers of the composite
Bauer Stephan
Bronstert Bernd
Möhwald Helmut
BASF - Aktiengesellschaft
Bell Bruce F.
Keil & Weinkauf
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