JP2003197262A - Polyelectrolyte and battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyelectrolyte wherein battery performance can be maintained at a sufficient level even in a large current discharging and stable battery performance can be obtained with a long life. <P>SOLUTION: This polyelectrolyte is made by gelating by heat- or photo-polymerization a polymerizable resin composition composed of (A) acryl polymer(s) whose weight average molecular weight is 1,000 to 100,000 containing 35 to 89 wt.% of a structural unit derived from (metha)acrylate shown in a formula (1) and 11 to 65 wt.% of a structural unit having polymerizable functional group shown in a formula (2), (B) heat- or photo-polymerization initiator and (C) a nonaqueous electrolytic solution containing alkaline metal salt(s). In the formula, R expresses a hydrogen or methyl group, R<SP>1</SP>expresses a hydrogen, C<SB>1</SB>to C<SB>8</SB>expresses a straight chain alkyl group or an alicyclic alkyl group. X expresses -CH<SB>2</SB>CH<SB>2</SB>-, -(CH<SB>2</SB>CH<SB>2</SB>O)<SB>p</SB>CH<SB>2</SB>CH<SB>2</SB>- (p is an integer of 1 to 500), -R<SP>2</SP>OCONHR<SP>3</SP>- or -R<SP>4</SP>CH(OH)CH<SB>2</SB>-, and R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>respectively express straight chain alkyl groups of C<SB>1</SB>to C<SB>8</SB>or alicyclic alkyl groups independently. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer electrolyte and a battery using the same.

[0002]

2. Description of the Related Art With the progress of electronic technology, the performance of electronic equipment has been improved, and it has become smaller and more portable. Therefore, a battery having a high energy density is desired as a power source. Conventional secondary batteries include lead batteries and nickel-cadmium batteries, but they are still insufficient in terms of obtaining energy density. Therefore, as an alternative to these batteries, a high energy density lithium secondary battery has been developed and rapidly spread.

Lithium secondary batteries generally have a high voltage of 3 V or more, are lightweight and have a high capacity, and are therefore used for various purposes. Many of these lithium secondary batteries used lithium cobalt oxide for the positive electrode and a carbon material for the negative electrode as the active material. Recently, however, active research and development have been actively conducted in order to increase the capacity. ing.
As an electrolyte for a lithium secondary battery, a non-aqueous electrolytic solution in which a lithium salt is dissolved in a carbonate-based aprotic solvent is generally used. However, in a lithium battery using a non-aqueous electrolyte, when the battery temperature rises, the aprotic solvent volatilizes inside the battery,
There are problems that the battery swells, volatile gas diffuses from the leak valve and leaks. Further, a problem often encountered in lithium secondary batteries using a non-aqueous electrolyte is an internal short circuit due to dendrite-like deposition of lithium that grows from the negative electrode to the positive electrode. Accident control is especially difficult. The non-aqueous electrolyte itself is a fluid and cannot essentially suppress the growth of dendrites. Even when a separator is used, the current flowing between the positive and negative electrodes is concentrated in the pores of the separator, which is a limited ionic conduction path, and as a result the growth of lithium dendrites is concentrated in the pores of the separator. To be done.
In order to solve such a problem, a battery system using a polymer electrolyte has been devised, and research and development are being actively conducted at present. This polymer electrolyte is an ionic conductor in which an alkali metal salt is uniformly dissolved in the polymer, and since no solvent is used, there is no fear of volatile gas diffusion or liquid leakage,
Further, it is said that the generation and growth of lithium dendrites can be suppressed because a current flows uniformly over the entire surface of the electrolyte.

In recent years, much research has been conducted on polymer electrolytes having a polyethylene oxide component. For example, a method of crosslinking both ends of a copolymer of ethylene oxide and propylene oxide as described in US Pat. No. 1898067, and a polyethylene glycol component as described in JP-A No. 2-7935. By increasing the molecular weight or three-dimensionally cross-linking a monomer having a urethane group and a monomer having a urethane group, the mechanical strength is improved, and on the other hand, the decrease in ionic conductivity due to crystallization is also prevented, which is practical. I am trying to obtain a certain polymer. However, such a polymer electrolyte has a problem that its ionic conductivity is about 10 ⁻⁵ S / cm at room temperature, which is about two digits lower than that of a non-aqueous electrolyte solution. Therefore, the battery using the polymer electrolyte battery as described above has a large internal resistance value of the battery, and the current output that can be taken out per unit time is significantly inferior to that of the non-aqueous electrolyte secondary battery. As a result, the polymer electrolyte battery has disadvantages such as limited use. For this reason, a polymer electrolyte having an ionic conductivity of 10 ⁻³ S / cm or more, which is considered to be a practical value in industry, has been demanded and actively studied.

As one of the methods for solving the ionic conductivity of the polymer electrolyte, there is a gel polymer electrolyte in which a nonaqueous electrolytic solution is held in a polymer. For example, a gel electrolyte obtained by swelling polyvinylidene fluoride with a non-aqueous electrolyte as described in JP-A-8-507407 has a temperature of 10 ⁻³ S /
It exhibits an ionic conductivity of not less than cm and shows good battery performance. However, polyvinylidene fluoride has a low retention of the non-aqueous electrolyte and cannot improve diffusion and leakage of the volatile gas, which are problems in the non-aqueous electrolyte. On the other hand, in order to improve the retention of the non-aqueous electrolyte solution, gel-type polymer electrolytes using polyethylene oxide-based polymers, which have high affinity with the non-aqueous electrolyte solution, have been widely studied. A lithium battery using a polymer electrolyte has almost reached a practical level. However, the lithium battery using the polyethylene oxide-based polymer as described above shows sufficient battery performance when discharged at a small current, but when discharged at a large current, the interfacial resistance between the electrode and the gel-like polymer electrolyte is big,
There is a problem that it is difficult to maintain the battery performance at a sufficient level.

Further, US Pat. No. 5,603,982 and US Pat.
A gel electrolyte using a three-dimensional cross-linking acrylic polymer as described in 609974 is prepared by dissolving several kinds of acrylic monomers and a bifunctional acrylic monomer, which is a cross-linking agent, in a non-aqueous electrolytic solution, and then by heat or light. A gel-like polymer electrolyte having an ionic conductivity of 10 ⁻³ S / cm or more is prepared by a crosslinking reaction. This method has an advantage that even if the acrylic monomer is dissolved in the non-aqueous electrolyte, the solution viscosity does not become so large and the wettability to the electrode is excellent, so that the interfacial resistance can be reduced to the level of the non-aqueous electrolyte. . However, this method has a problem that the polymerization progresses nonuniformly because two or more kinds of acrylates are used, and the residual double bonds are many due to insufficient polymerization of the acrylic monomer itself, resulting in deterioration of cycle characteristics. was there.

[0007]

The present invention has been earnestly studied in order to solve various problems of the above-mentioned polymer electrolytes, and the object of the present invention is not to require a special manufacturing process. By realizing high ionic conductivity and reduction of interfacial resistance between the electrode and gel electrolyte, it is possible to maintain the battery performance at a sufficient level even when discharged with a large current, and to obtain stable battery performance with long life. Another object of the present invention is to provide a polymer electrolyte that can be used and a battery using the same. In addition to the above, another object of the present invention is to provide a polymer electrolyte that is further excellent in retention of a non-aqueous electrolyte and has low interfacial resistance with an electrode. Another object of the present invention is to provide a polymer lithium secondary battery which is more excellent in cycle characteristics and discharge characteristics at a large current than a lithium secondary battery using a conventional polymer electrolyte.

[0008]

The present invention comprises (A) 35 to 89% by weight of a structural unit derived from a (meth) acrylate represented by the general formula (1) and a polymerizable functional group represented by the general formula (2). Nonaqueous electrolysis containing an acrylic polymer having a weight average molecular weight of 1,000 to 100,000 containing 11 to 65% by weight of a structural unit having a group, (B) a heat or photopolymerization initiator, and (C) an alkali metal salt. The present invention relates to a polymer electrolyte characterized in that a polymerizable resin composition comprising a liquid is gelled by heat or photopolymerization.

[Chemical 4]

[Chemical 5] (In the formula, R represents hydrogen or a methyl group, R ¹ is hydrogen, C
_{1 to} C _{8 represents} a linear alkyl group or an alicyclic alkyl group, X is —CH ₂ CH ₂ —, — (CH ₂ CH ₂ O) _p CH ₂ CH ₂ — {p is 1 to 50
An integer up to 0}, -R ^2- OCONH-R ³ -or -R ^4- CH (OH) CH _2-
And R ² , R ³ and R ⁴ each independently represent a C _{1 to} C ₈ linear alkylene group or an alicyclic alkylene group. The present invention also relates to the polymer electrolyte, wherein the acrylic polymer (A) contains 0.1 to 54% by weight of the structural unit derived from (meth) acrylonitrile represented by the general formula (3).

[Chemical 6] (In the formula, R represents hydrogen or a methyl group.) Further, in the present invention, the composition amount of the component (A) is 1 to 5% by weight based on the total weight of the components (A) and (C). Regarding a molecular electrolyte. The present invention also relates to a battery using the polymer electrolyte.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The method of synthesizing the acrylic polymer of the component (A) used in the present invention is not particularly limited, but it can be obtained, for example, by the following methods 1) to 3). Note that (meth) acrylate means acrylate and methacrylate. 1) (Meth) acrylate for forming the structural unit represented by the general formula (1) (hereinafter referred to as monomer (a))
And a monomer for forming a structural unit having a polymerizable functional group represented by the general formula (2) (hereinafter referred to as monomer (b)) are copolymerized. 2) A polymer with a (meth) acrylate having a hydroxyl group for forming a structural unit represented by the general formula (4) with the monomer (a) (hereinafter referred to as a monomer (c)) and, if necessary, a (meth) acrylonitrile. Build the main skeleton. After that, by reacting with a hydroxyl group residue of the polymer main skeleton with a monomer (c) and a (meth) acrylate having an isocyanate group represented by the general formula (5) in the same number of moles, the polymerizable compound represented by the general formula (2) is used. A structural unit having a functional group is formed.

[Chemical 7] (In the formula, R represents hydrogen or a methyl group, and R ² represents C _{1 to} C ₈
Represents a linear alkylene group or an alicyclic alkylene group. )

[Chemical 8] (In the formula, R represents hydrogen or a methyl group, and R ³ is C _{1 to} C ₈
Represents a linear alkylene group or an alicyclic alkylene group. ) 3) A (meth) acrylate having an epoxy group for forming a structural unit represented by the general formula (6) with the monomer (a) (hereinafter referred to as a monomer (d)) and, if necessary, (meth) acrylonitrile. To build the polymer backbone. Then, it is reacted with the epoxy residue of the polymer main skeleton with the same number of moles of (meth) acrylic acid as the monomer (d) to form a structural unit having a polymerizable functional group represented by the general formula (2).

[Chemical 9] (In the formula, R represents hydrogen or a methyl group, and R ⁴ is C _{1 to} C ₈
Represents a linear alkylene group or an alicyclic alkylene group. )

The monomer (a) used for synthesizing the acrylic polymer (A) used in the present invention is not particularly limited, but includes methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. , (Meth) acrylic acid isobutyl, (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid cyclohexyl etc., or (meth) acrylic acid cycloalkyl ester, methacrylic acid, acrylic acid, etc. Can be mentioned. These monomers are used alone or in combination of two or more.

The monomer (b) used when synthesizing the acrylic polymer (A) by the method 1) is not particularly limited, but ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate,
Examples include di (meth) acrylate compounds such as triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. However, in the method 1), it is difficult to control the reaction and gelation may occur. Therefore, by using the method described in 2) or 3) above, a polymerizable functional group (double bond residue) can be easily formed on the side chain of the acrylic resin.

The monomer (c) used in the synthesis method of 2) is not particularly limited, but 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth).
Examples thereof include acrylate. The (meth) acrylate having an isocyanate group represented by the general formula (5) is not particularly limited, but 2-isocyanatoethyl (meth) acrylate and the like can be mentioned.

The monomer (d) used in the synthesis method of 3) is not particularly limited, but examples thereof include glycidyl (meth) acrylate.

The content of the structural unit represented by the general formula (1) in the present invention is 35 to 89% by weight, and 60 to 85% by weight based on the total amount of the acrylic polymer as the component (A).
It is preferable to be set to 70 weight%, and it is more preferable to set it to 70 to 80 weight%. If this content is less than 35% by weight, the ionic conductivity will decrease, and if it exceeds 89% by weight, the electrolyte retention will decrease. The content of the structural unit represented by the general formula (2) in the present invention is 11 to 65% by weight, and preferably 15 to 40% by weight, based on the total amount of the acrylic polymer as the component (A), 20 It is more preferable to set the content to 30% by weight. If the content is less than 11%, the electrolyte retaining property is lowered, and if it exceeds 65% by weight, the ionic conductivity is lowered, and a film which increases the electrode interface resistance when a battery is manufactured is easily formed, resulting in a large current. Discharge characteristics are deteriorated.

Acrylic polymer (A) in the present invention
By including the structural unit derived from the (meth) acrylonitrile represented by the general formula (3), the ionic conductivity and the electrolyte retention are further improved. The content of the structural unit derived from (meth) acrylonitrile represented by the general formula (3) in the present invention is preferably 0.1 to 54% by weight based on the total amount of the acrylic polymer (A), and 1 to It is more preferably 35% by weight, and 10 to
30% by weight is particularly preferable. If the content is less than 0.1% by weight, the electrolyte retention tends to decrease, and if it exceeds 54% by weight, a film that increases the electrode interfacial resistance tends to be formed when a battery is manufactured, resulting in a large current. Discharge characteristics tend to deteriorate. When the acrylic polymer (A) contains a structural unit derived from (meth) acrylonitrile represented by the general formula (3), the structure represented by the general formula (1) is based on the total amount of the acrylic polymer (A). The content of the unit is preferably 35 to 88.9% by weight, and the content of the structural unit represented by the general formula (2) is preferably 11 to 64.9% by weight.

The acrylic polymer (A) used in the present invention is more preferably a method of the above-mentioned method 2), that is, a solution containing the monomer (a), the monomer (c) and (meth) acrylonitrile. It is obtained by solution polymerization by the radical polymerization method of 1), and then addition-reacting a (meth) acrylate having an isocyanate group to form a double bond residue. In this case, as the organic solvent, for example, methyl ethyl ketone,
Methyl isobutyl ketone, ketone solvents such as cyclohexanone, ester solvents such as ethyl acetate and butyl acetate,
Nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone and N, N-dimethylacetamide can be used. As the polymerization initiator, organic peroxides such as benzoyl peroxide, dicumyl peroxide, dibutyl peroxide, t-butyl peroxybenzoate, etc., azobis compounds such as azobisisobutyronitrile, azobisvaleronitrile, etc. Etc. can be used. The amount of the polymerization initiator used is
0.01 to the total amount of the acrylic polymer as the component (A)
It is preferably 0.1 part by weight.

The weight average molecular weight of the acrylic polymer of the present invention is preferably 1,000 to 100,000, and is preferably 3.0.
00 to 300,000 is more preferable, and 5,000 to 2
10,000 is especially preferred. This weight average molecular weight is 5,
If it is less than 000, the retention of the non-aqueous electrolytic solution tends to decrease, and if it exceeds 100,000, the solubility in the non-aqueous electrolytic solution decreases and the wettability to the electrode tends to deteriorate. The weight average molecular weight is measured by a gel permeation chromatography method (GPC) using a calibration curve based on standard polystyrene.

The acrylic polymer as the component (A) used in the present invention can be used in combination with a polymerizable polyfunctional monomer. The polymerizable polyfunctional monomer is not particularly limited, but vinyl acetate, alkyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, Monofunctional compounds such as phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth)
Acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, bisphenol A EO modified di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth ) Bifunctional compounds such as acrylate, neopentyl glycol di (meth) acrylate, 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane, pentaerythritol tri (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate, trimethylolpropane EO-modified tri (meth) acrylate, trimethylolpropane PO-modified tri (meth) acrylate,
Trifunctional compounds such as isocyanuric acid EO modified tri (meth) acrylate, pentaerythritol tetra (meth)
Examples thereof include tetrafunctional compounds such as acrylates, 5 to 6 functional compounds such as dipentaerythritol penta and hexa (meth) acrylate, and 1 to 6 functional melamine (meth) acrylates. These polymerizable polyfunctional monomer components are used alone or in combination of two or more. When using a polymerizable polyfunctional monomer, the compounding amount is (A)
1 to 100 parts by weight of acrylic polymer consisting of components
-30 parts by weight is preferable, 3-20 parts by weight is more preferable, and 5-15 parts by weight is particularly preferable. If it is less than 1 part by weight, good electrolyte retention tends to be unobtainable.
If it exceeds the weight part, the ionic conductivity tends to decrease.
The amount of the acrylic polymer used as the component (A) in the present invention is preferably 1 to 5% by weight, more preferably 2 to 4.5% by weight based on the total amount of the components (A) and (C). It is particularly preferable that the amount is 3 to 4% by weight.
If the content of the component (A) is less than 1% by weight, gelation tends not to occur, and if it exceeds 5% by weight, the ionic conductivity tends to decrease.

Examples of the thermal polymerization initiator of the component (B) in the present invention include dialkyl (allyl) peroxides such as benzoyl peroxide and its derivatives, hydroperoxide and its derivatives, cumyl peroxide and its derivatives, and diacetylperoxide. Diacyl peroxides such as oxides and their derivatives, organic peroxides such as peroxyketals, peroxyesters, peroxycarbonates, and compounds such as azobisisobutyronitrile and azobisisovaleronitrile. . Examples of the photopolymerization initiator of the component (B) in the present invention include dimethylaminobenzoic acids, benzophenone and its derivatives, benzyl such as benzyldimethylketal and its derivatives,
Acetophenone derivatives such as 2,2-diethoxyacetophenone, benzophenone derivatives, benzoin methyl ether, benzoin derivatives such as benzoin isobutyl ether, butylphenone derivatives such as α-hydroxyisobutylphenone, thioxanthone and its derivatives, compounds having an azide group, coumarin Examples thereof include compounds such as derivatives and phenylketone derivatives. These thermal polymerization initiators or photopolymerization initiators are used alone or in combination of two or more kinds. The blending amount of the heat or photopolymerization initiator of the component (B) in the present invention is preferably 0.005 to 10 parts by weight, and 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer of the component (A). More preferably 0.05 to 3
Part by weight is especially preferred. If the proportion of heat or photopolymerization initiator is less than 0.005 parts by weight or exceeds 10 parts by weight, the mechanical strength tends to decrease.

In the present invention, the blending amount of the non-aqueous electrolyte solution containing the (C) metal salt is 95 to 90% of the total amount of the (A) and (C) components.
It is preferably 99% by weight, more preferably 95.5 to 98% by weight, and particularly preferably 96 to 97% by weight. The alkali metal salt used in the non-aqueous electrolytic solution containing the alkali metal salt (C) in the present invention is not particularly limited, but from the practical viewpoint, for example, L
iClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , Li
_{CF 3 SO 3, LiC 2 F} 9 SO 3, LiN (CF 3 SO 2) 2
Lithium compounds such as These lithium compounds are used alone or in combination of two or more, and particularly preferable salt among these salts is LiCl.
O ₄ , LiBF ₄ , LiPF ₆ , and LiN (CF ₃ S
O ₂ ) ₂ . The blending amount of the alkali metal salt in the present invention is preferably 1 to 40% by weight, more preferably 3 to 30% by weight, and 5 to 20% by weight in the total amount of the components (A) and (C). Is particularly preferable. If this amount is less than 1% by weight or more than 40% by weight,
Ionic conductivity tends to decrease.

The non-aqueous solvent capable of dissolving the alkali metal salt used in the non-aqueous electrolyte containing the alkali metal salt (C) in the present invention is not particularly limited as long as it is chemically stable and non-aqueous. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, carbonate compounds such as methyl ethyl carbonate, tetrahydrofuran, dioxane, dimethoxyethane, ether compounds such as polyethylene oxide,
Examples thereof include lactone compounds such as γ-butyrolactone and propyrolactone. These non-aqueous solvents may be used alone or in 2
Used in combination with more than one type. The amount of the non-aqueous solvent capable of dissolving the alkali metal salt in the present invention is (A)
It is preferably 55 to 98% by weight, more preferably 80 to 97% by weight, and particularly preferably 90 to 95% by weight in the total amount of the component (C). If the proportion of the non-aqueous solvent is less than 55% by weight, the ionic conductivity tends to decrease. Further, if it exceeds 98% by weight, the mechanical strength tends to decrease.

As the method for producing the polymer electrolyte of the present invention, for example, the acrylic polymer (A) and (B) heat or photopolymerization initiator are dissolved in (C) a non-aqueous electrolyte solution in which an alkali metal salt is dissolved. Then, this solution is applied on a glass substrate provided with a spacer having a desired thickness, and then another glass substrate is covered and completely sealed, and a polymer electrolyte is produced by heat or photoreaction. . The polymer electrolyte of the present invention is produced by providing a light irradiation or heating step. Examples of the actinic ray used in the light irradiation include a carbon arc lamp, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a xenon lamp, and a metal halide. The exposure amount is 5
mJ / cm ² or more, preferably 15 mJ / c
More preferably m ² or more, 25 mJ / cm ²
The above is particularly preferable. Exposure amount is 5 mJ / cm
^When it is less than ² , the photo-curing does not proceed sufficiently and the film strength tends to be lowered. The heating temperature is preferably 20 ° C or higher, more preferably 30 ° C or higher, and 4
It is particularly preferably 0 ° C. or higher. If the heating temperature is lower than 20 ° C, thermosetting and insolubilization due to heat do not proceed sufficiently,
The film strength tends to decrease. The heating time is preferably 5 minutes or more. If the heating time is less than 5 minutes, thermosetting and insolubilization due to heat do not proceed sufficiently, and the film strength tends to decrease. The polymer electrolyte of the present invention is a lithium ion secondary battery using an intercalation compound such as graphite for the negative electrode, a lithium secondary battery using lithium metal for the negative electrode, a lithium primary battery, an electric double layer capacitor, an electrode material for an enzyme sensor. Can be used as an electrolyte in electrochemical devices such as. Particularly, it is preferably used as an electrolyte of a battery. In addition, the battery using the polymer electrolyte of the present invention, a mobile phone,
It can be used as a main power source or backup power source for small electronic devices such as PHS, laptop computers, portable terminals, etc., and is also widely used for stationary load leveling power source, backup power source in case of power failure, electric vehicle battery, etc. Can be used.

One method for obtaining a battery using the polymer electrolyte of the present invention will be illustrated. For example, first, the film-shaped polymer electrolyte of the present invention produced by the above-described production method,
To be sandwiched between a positive electrode sheet with a positive electrode material cast on a positive electrode current collector sheet and a negative electrode sheet with a negative electrode material cast on a negative electrode current collector sheet, and to apply heat or pressure. Thus, the positive electrode sheet, the polymer electrolyte of the present invention, and the negative electrode sheet are brought into close contact with each other to form a portion in which a battery reaction occurs. After that, in order to isolate the obtained cell reaction part from moisture, oxygen, nitrogen, etc. in the atmosphere, it is sealed with an insulated container made of, for example, aluminum.At this time, it is formed on the positive electrode sheet and the negative electrode sheet. The electrode portion is exposed to the outside of the insulated container made of aluminum so that charging and discharging can be performed through the electrode. The battery using the polymer electrolyte of the present invention thus obtained becomes a secondary battery capable of alternating charging and discharging.

As the positive electrode current collector sheet, for example,
Examples of the aluminum foil, nickel foil, gold foil, silver foil, titanium foil and the like are preferred, and the aluminum foil is preferable from the viewpoint of stability against high potential. Examples of the positive electrode material include Li _1-x CoO ₂ , Li _1-x NiO ₂ , Li
_1-x Mn ₂ O ₄ , Li _1-x MO ₂ , (0 <X <1, M is C
o, Ni, Mn, Fe, etc.), Li _2-y Mn ₂ O ₄
(0 <y <2), Li _1-x V ₂ O ₅ (0 <X <1), Li
_{2- y} V ₂ O ₅ (0 <y <2), Li _{1-x ′} Nb ₂ O ₅ (0 <
Oxides such as X ′ <1.2), Li _1-x TiS ₂ , Li _1-x
MoS ₂ , Li _1-x NbSe ₂ , Li _1-Z NbSe ₃ (0 <
Metal chalcogenides such as Z <3), dithiol derivatives,
Examples thereof include organic compounds such as disulfide derivatives. These are used alone or in combination of two or more.

Examples of the negative electrode current collector sheet include:
Copper foil, nickel foil, gold foil, silver foil and the like can be mentioned, and from the viewpoint of good electronic conductivity and low cost, copper foil is preferable. Examples of the negative electrode material include metal lithium, metal lithium such as aluminum-lithium alloy, magnesium-aluminum-lithium alloy, etc., graphite, amorphous carbon, carbon material such as low temperature calcined polymer, AlSb, Mg ₂ G.
e, N-based material, SnM'-based oxide (M 'is Si, Ge,
Pb, etc.), Si _1-y M ″ _y O _Z (M ″ is W, Sn,
Pb, B, etc.), a lithium solid solution of a metal oxide such as titanium oxide or iron oxide, Li ₇ MnN ₄ ,
Li ₃ FeN ₄ , Li _3-x Co _x N, Li _3-x NiN, Li
_{3-x Cu x N, Li} 3 BN 2, Li 3 AlN 2, Li 3 SiN 3
Ceramics such as nitrides. These are used alone or in combination of two or more.

[0026]

The present invention will be described in more detail below with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples. The evaluation method of the polymer electrolyte obtained in this example is shown below. <Retention of Electrolyte Solution> The weight immediately after preparation of the gel electrolyte and the weight of the gel electrolyte left for one day in an argon atmosphere were measured, and the electrolyte retention was calculated from the following formula. Electrolyte retaining property = (weight of gel electrolyte after standing for one day / weight immediately after preparation of gel electrolyte) x 100 <Ion conductivity> The ion conductivity was measured by sandwiching a polymer electrolyte at 25 ° C with stainless steel electrodes. An electrochemical cell was constructed, an alternating current impedance method in which an alternating current was applied between electrodes to measure a resistance component was used, and calculation was performed from a real impedance intercept of a Cole-Cole plot. <Interfacial resistance> Electrode / polymer electrolyte interface resistance is an electrochemical cell constructed by sandwiching a polymer electrolyte between lithium electrodes at 25 ° C. One hour after the electrochemical cell is constructed, an alternating current is applied between the electrodes. It was carried out by using the AC impedance method in which the resistance component was applied and measured, and was calculated from the real impedance intercept of the Cole-Cole plot.

<Production Method of Acrylic Polymers A to D> The compound (I) shown in Table 1 was placed in a reactor equipped with a mixer and a condenser and heated to 90 to 95 ° C. to prepare the compound shown in Table 1. (II) is added and kept warm for 2 to 5 hours. Next, the compound (III) shown in Table 1 is added dropwise over 2 hours, and the mixture is kept warm for 3 to 6 hours. After cooling, methyl ethyl ketone is added to a solid content of about 30% to dissolve the polymer. Compound (IV) shown in Table 1 was added to this polymer solution to obtain 70-
Heat to 75 ° C and keep warm for 6-12 hours. After cooling, methanol is added to precipitate the polymer, and the organic solvent is removed by suction filtration and vacuum drying to obtain acrylic polymers A to D. The weight average molecular weights of the polymers A to D were measured by the method described below.

[Measurement method of weight average molecular weight] The weight average molecular weight is measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene. <GPC conditions> Equipment used: Hitachi 635 type HPLC [Hitachi, Ltd.] Column: Gel pack R440, R450, R400M
[Hitachi Chemical Co., Ltd. product name] Eluent: Tetrahydrofuran Measurement temperature: 40 ° C. Flow rate: 2.0 ml / min. Detector: Differential refractometer measurement results are shown in Table 1. The glass transition temperature is a calculated value. (Reference data: Introduction to synthetic resins for paints: Kyozo Kitaoka)

1. Preparation of Polymer Electrolyte Example 1 100 parts by weight of acrylic polymer A and 0.1 part by weight of benzoyl peroxide as a thermal polymerization initiator were added to 1 mol / l LiBF ₄
Dissolve in 2000 parts by weight of electrolytic solution of ethylene carbonate and dimethyl carbonate (volume ratio: 1/1), pour this solution on a glass substrate provided with a silicone rubber spacer having a thickness of 100 μm, and cover it with another glass substrate. Completely sealed, and thermally reacted at 80 ° C. for 3 hours in an argon atmosphere to obtain a polymer electrolyte according to Example 1 having a thickness of 100 μm. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interface resistance of the obtained polymer electrolyte according to Example 1.

Example 2 100 parts by weight of acrylic polymer A and trimethylolpropane trimethacrylate 5 as a polymerizable polyfunctional monomer
Parts by weight and 1 part by weight of benzophenone as a photopolymerization initiator are dissolved in 2000 parts by weight of 1 mol / l LiBF ₄ ethylene carbonate and diethyl carbonate (volume ratio: 1/1) electrolytic solution, and this solution is used to form a silicone having a thickness of 100 μm. It is poured onto a glass substrate provided with a rubber spacer, covered with another glass substrate and completely sealed, and is irradiated with 1 J / cm ² of ultraviolet rays in an argon atmosphere to have a thickness of 100 μm.
A polymer electrolyte according to Example 2 was obtained. The electrolyte solution retention, ionic conductivity, and
Table 2 shows the results of evaluating the interface resistance.

Example 3 100 parts by weight of acrylic polymer B and 0.1 part by weight of benzoyl peroxide as a thermal polymerization initiator were added to 1 mol / l LiBF ₄
Dissolved in 2000 parts by weight of a mixed electrolyte of ethylene carbonate and methyl ethyl carbonate (volume ratio: 1/1), and this solution was poured onto a glass substrate provided with a silicone rubber spacer having a thickness of 100 μm. Cover with a glass substrate and seal it completely.
A thermal reaction was performed at 0 ° C. for 3 hours to obtain a polymer electrolyte according to Example 3 having a thickness of 100 μm. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interfacial resistance of the obtained polymer electrolyte according to Example 3.

Example 4 100 parts by weight of acrylic polymer C and pentaerythritol tetraacrylate 10 as a polymerizable polyfunctional monomer
0.1 part by weight and benzoyl peroxide as a thermal polymerization initiator
By weight, 1 mol / l LiN (CF ₃ SO ₂ ) ₂ ethylene carbonate and dimethyl carbonate (volume ratio: 1 /
Dissolve it in 2000 parts by weight of the mixed electrolyte solution of 1), pour this solution on a glass substrate provided with a silicone rubber spacer having a thickness of 100 μm, cover it with another glass substrate and completely seal it, and then carry out an argon atmosphere. The mixture was thermally reacted at 80 ° C. for 3 hours to obtain a polymer electrolyte of Example 4 having a thickness of 100 μm. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interfacial resistance of the obtained polymer electrolyte according to Example 4.

Example 5 A polymer electrolyte of Example 5 was obtained in the same manner as in Example 1 except that D was used as the acrylic polymer. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interfacial resistance of the obtained polymer electrolyte according to Example 5.

Comparative Example 1 100 parts by weight of polyethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) having an average molecular weight of 1136 and 0.1 part by weight of benzoyl peroxide as a thermal polymerization initiator were used at 1 mol / l.
It is dissolved in 1000 parts by weight of a mixed electrolyte solution of LiBF ₄ ethylene carbonate and dimethyl carbonate (volume ratio: 1/1), and this solution is poured onto a glass substrate provided with a silicone rubber spacer having a thickness of 100 μm, and the solution is separately added thereto. Then, the glass substrate was completely sealed and heat-reacted at 80 ° C. for 3 hours in an argon atmosphere to obtain a polymer electrolyte of Comparative Example 1 having a thickness of 100 μm. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interface resistance of the obtained polymer electrolyte according to Comparative Example 1.

Comparative Example 2 45 parts by weight of methyl methacrylate, acrylonitrile 4
5 parts by weight, triethylene glycol dimethacrylate 1
0 part by weight and 0.1 part by weight of benzoyl peroxide are added to 1 mol / l.
It is dissolved in 1000 parts by weight of a mixed electrolyte solution of LiBF ₄ ethylene carbonate and dimethyl carbonate (volume ratio: 1/1), and this solution is poured onto a glass substrate provided with a silicone rubber spacer having a thickness of 100 μm, and the solution is separately added thereto. Then, the glass substrate was completely sealed, and heat reaction was performed at 80 ° C. for 3 hours in an argon atmosphere to obtain a polymer electrolyte according to Comparative Example 2 having a thickness of 100 μm. Table 2 shows the results of evaluation of the electrolyte retention, ionic conductivity, and interface resistance of the obtained polymer electrolyte according to Comparative Example 2.

Comparative Example 3 1 g of a polyvinylidene fluoride-hexafluoropropylene copolymer (manufactured by Elf Atchem) was dissolved in 5 g of acetone. This solution was applied onto a glass substrate with an applicator and left for 2 hours in an argon atmosphere under normal pressure.
Acetone was removed by drying at 60 ° C. for 12 hours under vacuum to obtain a polymer film having a thickness of 40 μm. The polymer film was swollen with a mixed electrolyte of 1 mol / l LiBF ₄ of ethylene carbonate and dimethyl carbonate (volume ratio: 1/1) to obtain a polymer electrolyte according to Comparative Example 2. Table 2 shows the results of evaluation of the ionic conductivity, breaking strength and tensile modulus of the obtained polymer electrolyte according to Comparative Example 2.

2. Preparation of Battery Example 6 Lithium cobalt oxide (manufactured by Nippon Chemical Industry Co., Ltd.), graphite (manufactured by Nippon Graphite Co., Ltd.) and polyvinylidene fluoride (manufactured by Kureha Chemical Industry Co., Ltd.) were mixed at a ratio of 80:10:10 volume%. , N
-Methyl-2-pyrrolidone was added and mixed to prepare a slurry-like solution. This solution was applied to an aluminum foil having a thickness of 20 μm and dried. Mixture application amount is 289 g / m
^{Was 2} . The mixture was pressed so that the bulk density was 3.6 g / cm ³ and cut into 1 cm × 1 cm to prepare a positive electrode sheet. Metal lithium was used for the negative electrode sheet. The polymer electrolyte produced in Example 2 was sandwiched between the positive electrode sheet and the negative electrode sheet produced as described above under a load of 0.098 MPa to produce a battery having a sealed structure in which air does not enter. 4.2 at a charging current of 0.5 mA at 20 ° C
After constant current charging up to V and the voltage reached 4.2V,
A constant current discharge was performed at a discharge current of 0.5 mA until the discharge end voltage of 3.5 V was reached. Recharge under the above charging conditions,
Constant current discharge was performed at 5.0 mA until the discharge end voltage reached 3.5 V. Here, the capacity when discharged at 0.5 mA was set to 100%, and the capacity when discharged at 5.0 mA was relatively compared, and the large current discharge characteristics were obtained. Table 3 shows the results of evaluating the large-current discharge characteristics of the obtained battery according to Example 6.

Example 7 A battery was produced in the same manner as in Example 6 except that the polymer electrolyte produced in Example 3 was used. Table 3 shows the results of evaluating the large-current discharge characteristics of the obtained battery according to Example 7.

Example 8 Amorphous carbon having an average particle size of 20 μm (manufactured by Kureha Chemical Industry Co., Ltd.) and polyvinylidene fluoride (manufactured by Kureha Chemical Industry Co., Ltd.) were mixed at 90:
The mixture was mixed at a ratio of 10% by volume, and was added and mixed into N-methyl-2-pyrrolidone to prepare a slurry-like solution. This solution was applied to a copper foil having a thickness of 10 μm and dried. The mixture coating amount was 65 g / m ² . Mixture bulk density is 1.0g
/ Cm ³ Press to 1.2cm × 1.2c
A negative electrode sheet was produced by cutting into m. The polymer electrolyte prepared in Example 3 was sandwiched between the negative electrode sheet and the positive electrode sheet prepared in Example 6 by applying a load of 0.098 MPa to prepare a battery having a sealed structure in which air does not enter. Two
At 0 ° C., constant current charging was performed at a charging current of 0.5 mA up to 4.2 V, switching to constant voltage charging when the voltage reached 4.2 V, and charging was continued until the total charging time reached 10 hours. After that, constant current discharge was performed at a discharge current of 0.5 mA until a discharge end voltage of 2.5 V was reached. Charging / discharging under these conditions was performed for 2 cycles, and for the 3rd cycle, after charging under the above-mentioned charging conditions, constant current discharging was performed at a discharge current of 5.0 mA until a discharge end voltage of 2.5 V was reached. Where 2
100% capacity when discharged at 0.5 mA at cycle
In comparison with the above case, a comparative comparison of the capacities when discharged at 5.0 mA in the third cycle was taken as the large current discharge characteristic. Table 3 shows the results of evaluating the large-current discharge characteristics of the obtained battery according to Example 6.

Example 9 A battery was prepared in the same manner as in Example 8 except that the polymer electrolyte prepared in Example 5 was used. Table 3 shows the results of evaluating the cycle life of the obtained battery according to Example 9.

Comparative Example 4 A battery was prepared in the same manner as in Example 6 except that the polymer electrolyte prepared in Comparative Example 1 was used. Table 3 shows the results of evaluation of the cycle life of the obtained battery according to Comparative Example 4.

Comparative Example 5 A battery was prepared in the same manner as in Example 8 except that the polymer electrolyte prepared in Comparative Example 2 was used. Table 3 shows the results of evaluation of the cycle life of the obtained battery according to Comparative Example 5.

Comparative Example 6 A battery was prepared in the same manner as in Example 8 except that the polymer electrolyte prepared in Comparative Example 3 was used. Table 3 shows the evaluation results of the cycle life of the obtained battery according to Comparative Example 6.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

As shown in Table 2, it can be seen that the polymer electrolytes of Examples 1 to 5 have high electrolyte retention and high ionic conductivity and are excellent in low interface resistance. On the other hand, the polymer electrolyte of Comparative Example 1 has the same electrolytic solution retention property and ionic conductivity as the polymer electrolytes of Examples 1 to 5, but it is found that the interfacial resistance is large. Further, it can be seen that the polymer electrolyte of Comparative Example 2 is equivalent to the polymer electrolytes of Examples 1 to 5 in electrolyte retention, but is inferior in ionic conductivity and large in interfacial resistance. Further, it is understood that the polymer electrolyte of Comparative Example 3 is inferior in electrolyte retention and ionic conductivity and has a large interface resistance as compared with the polymer electrolytes of Examples 1 to 5. In addition, as shown in Table 3, it is understood that the batteries of Examples 6 to 9 using the polymer electrolytes of Examples 2 to 5 are excellent in large current discharge characteristics. On the other hand, Comparative Examples 4 to 6 using the polymer electrolytes of Comparative Examples 1 to 3
It can be seen that the battery of No. 6 is inferior to the large current discharge characteristics as compared with the batteries of Examples 6 to 9.

[0048]

INDUSTRIAL APPLICABILITY The polymer electrolyte of the present invention is excellent in retention of a non-aqueous electrolyte, ionic conductivity, and reduction of interfacial resistance with an electrode. Further, the polymer electrolyte of the present invention has the above-mentioned effects and is further excellent in the retention of the non-aqueous electrolyte, the ionic conductivity, and the reduction of the interfacial resistance with the electrode. The battery of the present invention is excellent in large current discharge characteristics.

Claims (4)

[Claims] 1. (A) (meta) represented by the general formula (1)
Structural unit 1 having 35 to 89% by weight of a structural unit derived from acrylate and a polymerizable functional group represented by the general formula (2)
Weight average molecular weight of 1-65% by weight is 1,000
A polymerizable resin composition comprising a non-aqueous electrolytic solution containing an acrylic polymer of 100 to 100,000 (B) heat or photopolymerization initiator and (C) alkali metal salt is gelated by heat or photopolymerization. A polymer electrolyte characterized by the following. [Chemical 1] [Chemical 2] (In the formula, R represents hydrogen or a methyl group, R ¹ is hydrogen, C
_{1 to} C _{8 represents} a linear alkyl group or an alicyclic alkyl group, X is —CH ₂ CH ₂ —, — (CH ₂ CH ₂ O) _p CH ₂ CH ₂ — {p is 1 to 50
An integer up to 0}, -R ^2- OCONH-R ³ -or -R ^4- CH (OH) CH _2-
And R ² , R ³ and R ⁴ each independently represent a C _{1 to} C ₈ linear alkylene group or an alicyclic alkylene group. ) 2. The polymer electrolyte according to claim 1, wherein the acrylic polymer (A) contains 0.1 to 54% by weight of a structural unit derived from (meth) acrylonitrile represented by the general formula (3). [Chemical 3] (In the formula, R represents hydrogen or a methyl group.) 3. Based on the total weight of the components (A) and (C),
The polymer electrolyte according to claim 1 or 2, wherein the composition amount of the component (A) is 1 to 5% by weight. 4. A battery using the polymer electrolyte according to claim 1.