Cross-linked solid polyelectrolyte and use thereof

Details Cross-linked solid polyelectrolyte and use thereof Cross-linked solid polyelectrolyte and use thereof

1998-10-21

2001-05-29

Dawson, Robert (Department: 1712)

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...

C524S413000, C524S408000, C524S157000, C524S255000, C528S418000, C528S403000, C528S027000, C549S555000, C523S440000, C429S199000, C429S199000, C252S062200, C361S525000

Reexamination Certificate

active

06239204

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a crosslinkable polyether copolymer, a crosslinked material of the copolymer, and a crosslinked solid polyelectrolyte. More particularly, the present invention relates to a solid polyelectrolyte which is suitable as a material for an electrochemical device such as a battery, a capacitor and a sensor.
RELATED ART
As an electrolyte constituting an electrochemical device such as a battery, a capacitor and a sensor, those in the form of a solution or a paste have hitherto been used in view of the ionic conductivity. However, the following problems are pointed out. There is a fear of damage of an apparatus arising due to liquid leakage, and subminiaturization and thinning of the device are limited because a separator to be impregnated with an electrolyte solution is required. To the contrary, a solid electrolyte such as an inorganic crystalline substance, inorganic glass, and an organic polymer substance is suggested. The organic polymer substance is generally superior in processability and moldability and the resulting solid electrolyte has good flexibility and bending processability and, furthermore, the design freedom of the device to be applied is high and, therefore, the development thereof is expected. However, the organic polymer substance is inferior in ionic conductivity to other materials at present.
For example, a trial of containing a specific alkaline metal salt in a mixture of an epichlorohydrin rubber and a low-molecular weight polyethylene glycol derivative and applying the resultant to a polymer solid electrolyte is suggested in Japanese Patent Kokai Publication No. 235957/1990 including the present applicant, but a practically sufficient conductivity value is not still obtained.
Furthermore, a polymer solid electrolyte prepared by crosslinking a polymer compound having average molecular weight of from 1,000 to 20,000, described in Japanese Patent Kokai Publication Nos. 47833/1991 and 68064/1992, shows a comparatively good ionic conductivity within the practical temperature range, but those having more excellent mechanical characteristics and ionic conductivity are required.
A polyether copolymer having an oligooxyethylene side chain described in Japanese patent Application No. 109616/1995 of the present applicant shows excellent ionic conductivity at room temperature (e.g. 30° C.). However, because of having no crosslinked structure, when using temperature is high (e.g. 60° C.), inconvenience arises by plastic deformation. For example, when using in a thin type battery, there is a fear of a short circuit between a positive electrode and a negative electrode.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a solid electrolyte, which is superior in ionic conductivity, and which causes no plastic deformation or has no fluidity even under high temperature.
Another object of the present invention is to provide a polymer, which gives the above solid electrolyte.
The present invention provides a polyether copolymer having a number-average molecular weight of 50,000 to 2,000,000, a glass transition temperature measured by a differential scanning calorimeter (DSC) of not more than −60° C. and a fusion heat of not more than 70 J/g, comprising:
(A) 1 to 98% by mol of a repeating unit derived from a monomer represented by the formula (I):
wherein R
1
is a group selected from an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms and a tetrahydropyranyl group and n is preferably from 1 to 12;
(B) 95 to 1% by mol of a repeating unit derived from a monomer represented by the formula (II):
(C) 0.005 to 15% by mol of a repeating unit derived from a monomer having one epoxy group and at least one reactive functional group.
The present invention also provides a crosslinked material obtained by crosslinking the above copolymer.
Furthermore, the present invention provides a solid polyelectrolyte comprising the above crosslinked material and an electrolyte salt compound.
Furthermore, the present invention provides a battery comprising said solid polyelectrolyte.
DETAILED DESCRIPTION OF THE INVENTION
The repeating unit (C) may be derived from a monomer of the formula (III-1) or (III-2):
wherein R
2
and R
3
represent a reactive functional group-containing group.
The polymer of the present invention comprises (A) a repeating unit derived from a monomer of the formula (I):
wherein R
1
is a group selected from an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atoms and a tetrahydropyranyl group and n is preferably from 1 to 12,
(B) a repeating unit derived from a monomer of the formula (II):
&Parenopenst;CH
2
—CH
2
—O&Parenclosest;  (II′)
and
(C) a repeating unit derived from a monomer having one epoxy group and at least one reactive functional group.
The repeating unit (C) derived from a monomer of the formula (III-1) or (III-2) is represented by the formula (III′-1) or (III′-2):
wherein R
2
and R
3
represent a reactive functional group-containing group.
The reactive functional group in the repeating unit (C) is preferably (a) a reactive silicon group, (b) an epoxy group, (c) an ethylenically unsaturated group, or (d) a halogen atom.
The polymerization method of the polyether copolymer having a crosslinkable side chain of the present invention is conducted in the same manner as in Japanese Patent Kokai Publication Nos. 154736/1988 and 169823/1987 of the present applicant.
The polymerization reaction can be conducted as follows. That is, the polyether copolymer can be obtained by reacting the respective monomers at the reaction temperature of 10 to 80° C. under stirring, using a catalyst mainly composed of an organoaluminum, a catalyst mainly composed of an organozinc, an organotin-phosphate ester condensate catalyst and the like as a ring opening polymerization catalyst in the presence or absence of a solvent. The organotin-phosphate ester condensate catalyst is particularly preferable in view of the polymerization degree or properties of the resulting copolymer. In the polymerization reaction, the reaction functional group does not react and a copolymer having the reaction functional group is obtained.
In the polyether copolymer of the present invention, the content of the repeating unit (A) is from 1 to 98% by mol, preferably from 3 to 98% by mol, e.g. from 5 to 90% by mol; the content of the repeating unit (B) is from 95 to 1% by mol, preferably from 95 to 1% by mol, e.g. from 90 to 5% by mol; and the content of the repeating unit (C) is from 0.005 to 10% by mol, preferably from 0.01 to 5% by mol, e.g. from 0.05 to 5% by mol. When the content of the repeating unit (B) exceeds 95% by mol, an increase in glass transition temperature and crystallization of the oxyethylene chain arise, which results in drastic deterioration of the ionic conductivity of the solid electrolyte. It is generally known that the ionic conductivity is improved by the decrease of the crystallizability of polyethylene oxide. It has been found that, in case of the polyether copolymer of the present invention, the effect for improvement of the ionic conductivity is remarkably large. On the other hand, when the molar ratio of the repeating unit (C) is smaller than 0.005% by mol, the copolymer can not be sufficiently crosslinked and, therefore, it is difficult to obtain a solid electrolyte at high temperature range (e.g. 60° C.). When the molar ratio of the repeating unit (C) is larger than 15% by mol, it becomes impossible to form a film.
The glass transition temperature and fusion heat of the polyether copolymer are measured by a differential scanning calorimeter (DSC). In the present invention, the glass transition temperature of the polyether copolymer is not m

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