Polyether copolymer and solid polymer electrolyte

Details Polyether copolymer and solid polymer electrolyte Polyether copolymer and solid polymer electrolyte

1998-07-30

2001-01-30

Nuzzolillo, Maria (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Include electrolyte chemically specified and method

C429S309000, C429S313000, C429S316000

Reexamination Certificate

active

06180287

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polyether copolymer and a solid polymer electrolyte. More particularly, it relates to a solid polymer electrolyte 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. That is, 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 inorganic crystalline substance, inorganic glass and 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 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 solid polymer 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 solid polymer electrolyte prepared by crosslinking a polymeric compound which has been 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.
SUMMARY OF THE INVENTION
An object of the present invention provides a solid electrolyte which is superior mechanical properties and ionic conductivity.
The present invention provides a polyether copolymer having a weight-average molecular weight of 10
3
to 10
7
, which is optionally crosslinked, comprising:
(A) 0.5 to 99% by mol of a repeating unit derived from a monomer represented by the formula (I):
 wherein each of R
1
and R
2
represents 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 atom and a tetrahydropyranyl group; and each of m and n represents numeral of 1 to 12;
(B) 99.5 to 1% by mol of a repeating unit derived from a monomer represented by the formula (II):
(C) 0 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 provides a solid polymer electrolyte comprising:
(1) the above polyether copolymer,
(2) an electrolyte salt compound, and,
(3) if necessary, a plasticizer selected from the group consisting of an aprotic organic solvent, and a derivative or metal salt of a linear or branched polyalkylene glycol having a number-average molecular weight of 200 to 5,000 or a metal salt of said derivative.
The present invention also provides a battery comprising the above solid polymer electrolyte.
A crosslinked material of the polyether copolymer is used when the shape stability at high temperature is required.
When the plasticizer is blended with the solid polymer electrolyte, the crystallization of the polymer is inhibited and the glass transition temperature is lowered and a large amount of an amorphous phase is formed even at low temperature and, therefore, the ionic conductivity is improved. It has been also found that, when the solid polymer electrolyte of the present invention is used, a high-performance battery having small internal resistance can be obtained. The solid polymer electrolyte of the present invention may be in the form of a gel. The term “gel” used herein means a polymer swollen with a solvent.
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
3
and R
4
represent a reactive functional group-containing group.
The polyether polymer of the present invention comprises (A) a repeating unit derived from a monomer (I):
wherein each of R
1
and R
2
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 each of m and n is a numeral of 1 to 12, and
(B) a repeating unit derived from a monomer (II):
&Parenopenst;CH
2
—CH
2
—O&Parenclosest;  (II′)
The polyether copolymer optionally comprises (C) a repeating unit derived from a monomer having one epoxy group and at least one reactive functional group. A crosslinked material can be derived from the polyether copolymer having the repeating unit (C) by utilizing the reactivity of the reactive functional group.
The copolymer used in the present invention may be crosslinked or not crosslinked. Examples of a crosslinking agent for crosslinking a binary copolymer having the repeating unit (I′) and the repeating unit (II′) specifically include isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate and hexamethylene diisocyanate.
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
3
and R
4
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, which may have a crosslinkable side chain, of the present invention is the polymerization method wherein a copolymer is obtained by a ring opening reaction of ethylene oxide portion and can be conducted in the same manner as that described in Japanese Patent Kokai Publication Nos. 154736/1988 and 169823/1987 filed by 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 containing an organoaluminum, a catalyst mainly containing 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. Among of them, the organotin-phosphate ester condensate catalyst is particularly preferable in view of the polymerization degree, or properties of the resulting copolymer and the like. In the polymerization reaction, the reactive functional group does not react so that a copolymer having the reaction functional group is obtained. When an oxirane compound having an epoxy group at only the both ends is used, an only epoxy group containing no substituent such as no methyl group is used for polymerization and an epoxy group containing a methyl group remains in the polymer without any reaction.
In the polyether copolymer of the present invention, the content of the repeating unit (A) is from 0.5 to 99% by mol, e.g. from 3 to 99% by mol, particularly from 10 to 95% by mol, and especially from 10 to 80% by mol; the content of the repeating unit (B) is from 99.5 to 1% by mol, e.g. from 95 to 1% by mol, particularly from 90 to 5% by mol, and specifically from 80 to 5% by mol; and the content of the repeating unit (C) is from 0 to 15% by mol, e.g. 0 to 10% by mol, preferably from

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