JPH0925384A - Polymer gel electrolyte having ionic conductivity and secondary battery containing the electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polymer gel electrolyte excellent in ionic conductivity and uniformity and having a solid strength sufficient for an electrochemical element, particularly for the use as a solid electrolyte for a battery. SOLUTION: This electrolyte is obtained by polymerizing an acrylate monomer having a molecular weight of at most 1,000 in the presence of an electrolyte salt and a nonaqueous solvent and contains an electrolyte salt represented by the formula, LiX(R1 SO2 )n [wherein X is N, C, B, O or C(R2 )m (wherein R2 is H or a 1-12C alkyl group; and m is 1 or 2); R1 is a 1-12C haloalkyl group; and n is an integer of 1 to 3].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel ion conductive polymer gel electrolyte and a secondary battery using the electrolyte.

[0002]

2. Description of the Related Art Conventionally, a secondary battery uses an electrolytic solution and has problems such as leakage of the electrolytic solution and volatilization of the solvent. To solve these problems, a solid electrolyte has been used. However, since the solid polymer electrolyte containing an electrolyte salt is a completely solid, it has low ionic conductivity and cannot be put to practical use.
As the polymer solid electrolyte, for example, siloxane (US 5,
112,512), phosphazene (US 4,840,8)
56) was used to improve the ionic conductivity, but the ionic conductivity was still unsatisfactory and it was difficult to secure battery performance. Further, in recent years, gels composed of a polymer matrix, a solvent, and an electrolyte salt, which have been attracting attention in recent years, include a gel composed of a thermoplastic polymer matrix and a gel composed of a crosslinkable polymer matrix, which can ensure battery performance. However, as a battery, the solid strength is sufficient, but the ionic conductivity is not yet sufficient, or the ionic conductivity is high but the solid strength is not sufficient. is there. 1. <JP-A-2-37673> This is a patent for a battery using a polymer electrolyte containing an imide salt in a polymer matrix containing a hetero atom. The electrolyte of the present invention is a polymer electrolyte containing an electrolyte salt by positively removing or melting a solvent, does not contain a solvent, and is not a gel. In the examples, it is described that 100 μA / cm ² connection discharge is possible, but there is no notation such as cycle characteristics. Also, although there is a description of ionic conductivity, there is no description of elastic modulus. 2. <JP-A-7-235327 Fuji Electric Chemistry> The composition of the electrolyte is electrolyte salt: imide salt, LiBF ₄ / solvent: EC /
Although PC / DMC is used, there is no description of solidification, solid electrolyte, polymer solid electrolyte, gel, etc. in the specification, and the patent is limited to the electrolyte solution. 3. <JP-A-7-6787> A gel electrolyte formed by mixing a trifunctional compound, a solvent and an electrolyte salt and crosslinking the mixture.
The trifunctional acryloyl-modified alkylene oxide is a polymer compound requiring a chain length of 35 or more (molecular weight 15
00 or more). In addition, in the examples, there is no description of ionic conductivity and elastic modulus, and there is no description of cycle improvement.

[0003]

[Object] The present invention solves the above problems found in conventional polymer-based solid electrolytes, has excellent ionic conductivity and uniformity, and is used as a solid electrolyte for electrochemical devices, particularly for batteries. An object of the present invention is to provide an ion conductive polymer gel electrolyte having a solid strength sufficient for use, and an electrochemical device using the electrolyte, particularly a battery.

[0004]

[Structure] One of the features of the present invention is, in order to solve the above-mentioned problems, the molecular weight of 1,0
The ion conductive polymer gel electrolyte obtained by polymerizing an acrylate monomer of 00 or less has the following formula (A):

Embedded image LiX (R ₁ SO ₂ ) n (A) [In the above formula, X is N, C, B, O or C (R ₂ ) m (R ₂
Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms), and R
₁ is a halogenated alkyl group having 1 to 12 carbon atoms, m is 1 or 2, and n is an integer of 1 to 3. ] It is the point which provided the ion conductive polymer gel electrolyte characterized by containing electrolyte salt which is. That is, in the present invention,
The matrix obtained by polymerizing an acrylate monomer having a molecular weight of 1,000 or less, preferably 500 or less contains an electrolyte salt represented by the above formula (A) so that the ionic conductivity can be reduced without deteriorating the elastic modulus. An ion-conductive polymer gel electrolyte having improved properties was obtained. The ionic conductivity of the gel electrolyte of the present invention by the AC impedance method at 25 ° C. and the conductivity of the non-aqueous electrolytic solution which is a constituent of the electrolyte are greatly affected, and the gel conductivity of the non-aqueous electrolyte is not exceeded. There is almost no decrease in conductivity, and the conductivity is usually 10 ⁻³ S / cm or more. Dynamic viscoelasticity tester for gel electrolyte of the present invention [RHEO
METRIC, INC RDS-7700] has an elastic modulus of preferably 10 ² dyne / cm ² or more and Tg.
Is an ion-conducting polymer gel that is -30 ° C or less and does not dissolve even at 100 ° C, and has an elongation of 20%.
As described above, it has a resilience to stretching deformation without breaking up to about 400%. Even if it is bent 180 degrees, it does not break.

The gel electrolyte of the present invention is a creep meter [Yamaden Co., Ltd. RE-3305, plunger cross section 2c].
When the time variation of the strain amount was measured using m ² , load of 30 g], the strain amount does not change with time and has a low creep characteristic. Load 25g / c using creep meter
Even if the gel electrolyte is compressed with m ² , the electrolytic solution contained therein does not flow out. Further, the viscoelastic body exhibits high adhesiveness, and after the viscoelastic bodies are bonded to each other, even if the viscoelastic bodies are to be separated, the material is destroyed and does not peel off from the bonding surface. The gel electrolyte of the present invention can be formed by dissolving a polymerizable compound in a non-aqueous electrolytic solution to cause a polymerization reaction. In this case, the polymerizable compound is polymerizable by actinic rays such as light, ultraviolet rays, electron beams, γ rays, and X rays, in addition to thermopolymerizability. The second feature of the present invention is to provide a battery using the ion conductive polymer gel electrolyte. Hereinafter, the configuration of the present invention will be described in detail.

[Polymerizable Compound] The polymerizable compound used in the present invention will be specifically described below. The type of the acrylate monomer used in the present invention is not particularly limited, and includes those that undergo a polymerization reaction such as thermal polymerization and actinic ray polymerization to obtain a polymer, but can form a crosslinked polymer matrix. A combination of monofunctional and polyfunctional monomers is preferred. In particular, as the polyfunctional monomer,
When the trifunctional monomer is used, a crosslinked polymer matrix having higher ionic conductivity and having sufficient strength and viscoelasticity as a gel electrolyte for batteries can be obtained. When the monofunctional acrylate monomer is used in combination with the polyfunctional acrylate monomer, the addition amount of the polyfunctional acrylate is 4% by weight or less, preferably 0.05 to 2 with respect to the non-aqueous electrolyte.
% By weight. Particularly when a trifunctional acrylate is used in combination, a gel electrolyte excellent in ionic conductivity and strength can be obtained with a small addition amount of 2% by weight or less, preferably 0.05 to 0.5% by weight. . As described above, in the present invention, by using the polyfunctional acrylate in combination, it is possible to obtain an ion conductive polymer gel electrolyte which is more excellent in ionic conductivity and strength. In addition, the acrylate monomer in this specification means an acrylate monomer or a methacrylate monomer, and the (meth) acrylate means an acrylate or a methacrylate. The acrylate monomers that can be used in the present invention are shown below.

(Monofunctional Monomer) Monofunctional acrylates include alkyl (meth) acrylates [methyl (meth) acrylate, butyl (meth) acrylate, trifluoroethyl (meth) acrylate, etc.], alicyclic (meth) acrylates, Hydroxyalkyl (meth) acrylate [hydroxyethyl acrylate, hydroxypropyl acrylate, etc.], hydroxypolyoxyalkylene (the number of carbon atoms in the oxyalkylene group is preferably 1 to
4) (meth) acrylate [hydroxypolyoxyethylene (meth) acrylate, hydroxypolyoxypropylene (meth) acrylate, etc.] and alkoxyalkyl (the carbon number of the alkoxy group is preferably 1 to 4) (meth) acrylate [methoxyethyl acrylate , Ethoxyethyl acrylate, phenoxyethyl acrylate, etc.]. As an example of a trifunctional or more polyfunctional (meth) acrylate, [trimethylolpropane tri (meth) acrylate, pentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc.] is preferable. Specific examples of other (meth) acrylates include, for example, methylethylene glycol (meth) acrylate, ethylethylene glycol (meth) acrylate, propylethylene glycol (meth) acrylate, phenylethylene glycol, ethoxydiethylene glycol acrylate, methoxyethyl acrylate, Alkyl ethylene glycol (meth) such as methoxydiethylene glycol methacrylate, methoxytriethylene glycol acrylate, methoxytriethylene glycol methacrylate, methoxytetraethylene glycol methacrylate
Examples thereof include alkyl propylene glycol (meth) acrylates such as acrylate, ethyl propylene glycol acrylate, butyl propylene glycol acrylate, and methoxydipropylene glycol acrylate.

The (meth) acrylate may contain a heterocyclic group, and the heterocyclic group includes oxygen, nitrogen,
It is a heterocyclic residue containing a hetero atom such as sulfur. The type of the heterocyclic group contained in the (meth) acrylate is not particularly limited. For example, a furfuryl group,
Furfuryl (meth) acrylate and tetrahydrofurfuryl (meth) acrylate having a tetrahydrofurfuryl group or the like are preferred. Other (meth) acrylates having a heterocyclic group include furfurylethylene glycol (meth) acrylate, tetrahydrofurfurylethylene glycol (meth) acrylate, furfurylpropylene glycol (meth) acrylate, and tetrahydrofurfurylpropylene glycol (meth) acrylate And alkylene glycol acrylates having a furfuryl group or a tetrahydrofurfuryl group. The molecular weight of the acrylate and its prepolymer is 1000 or less, preferably 500 or less, more preferably 300 or less. The non-aqueous solvent easily exudes in the gel electrolyte obtained by using an acrylate monomer having a molecular weight of 1000 or more. The acrylate monomer is
They may be used alone, or two or more kinds may be mixed and used. When a monofunctional acrylate monomer is used alone, it is 50% by weight or less, preferably 5 to 40% by weight, more preferably 10% by weight, based on the non-aqueous electrolyte.
３０30% by weight.

[Polyfunctional Monomer] Examples of the polyfunctional acrylate include a monomer or a prepolymer having two or more (meth) acryloyl groups, and particularly a trifunctional acrylate having three (meth) acryloyl groups. Most preferable in terms of giving a gel electrolyte excellent in liquid retention, ionic conductivity and strength. Specific examples of the polyfunctional acrylate include ethylene glycol dimethacrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol diacrylate, and ethylene oxide modified triacrylate. Examples thereof include methylolpropane triacrylate, propylene oxide-modified trimethylolpropane triacrylate, butanediol (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.

The following may be mentioned as examples of the polymerization initiator. [Photopolymerization Initiator] The following substances can be exemplified as the polymerization reaction initiator by the actinic ray, but when the actinic ray is used, the polymerization reaction initiator is not always necessary. Examples of the polymerization initiator using actinic rays include carbonyl compounds {benzoins [benzoin, benzoin methyl ether,
Benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl ether, α-methylbenzoin, α-phenylbenzoin, etc.], anthraquinones (anthraquinone, methylanthraquinone, chloranthraquinone, etc.), other compounds (benzyl, diacetyl, acetophenone, benzophenone, methyl) Benzoyl formate, etc.], sulfur compounds [diphenyl sulfide, dithiocarbamate, etc.], polycondensed ring hydrocarbon halides [α-chloromethylnaphthalene, etc.], dyes [acrylic flavin, fluorescein, etc.], metal salts [chloride Iron, silver chloride, etc.], onium salts [P-methoxybenzenediazonium, hexafluorophosphate,
Diphenyl iodonium, triphenyl sulfonium, etc.]. These can be used alone or as a mixture of two or more kinds.
Preferred photopolymerization initiators are carbonyl compounds, sulfur compounds and onium salts.

[Thermopolymerization Initiator] As the thermal polymerization initiator,
Azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, ethyl methyl ketone peroxide, bis- (4-t-butylcyclohexyl)
Examples thereof include peroxydicarbonates such as peroxydicarbonate and diisopropyl peroxydicarbonate. Further, a polymerization initiator such as dimethylaniline, cobalt naphthenate, sulfinic acid, and mercaptan can be used in combination. Further, a sensitizer and a storage stabilizer can be used in combination if necessary. Further, the above photopolymerization initiator, thermal polymerization initiator and the like can be used in combination.

[Photothermal polymerization initiator] The above photopolymerization initiator,
A polymer gel electrolyte having a higher elastic modulus can be obtained by using together with a thermal polymerization initiator and the like.
The photopolymerization initiator and the thermal polymerization initiator are not particularly limited, but it is preferable to use the photopolymerization initiator benzoin isopropyl ether and the thermal polymerization initiator bis (4-t-butylcyclohexyl) peroxydicarbonate together. . Further, the heat generated by light irradiation also contributes to the polymerization, so that the efficiency of the polymerization can be improved.

[Ion-Conducting Polymer Gel Electrolyte] The gelation of the electrolyte according to the present invention may be carried out by injecting a non-aqueous electrolytic solution comprising a polymerizable compound composition containing an acrylate monomer into a sealed container or by supporting a support (for example, a film). , Metal, glass) and then polymerized with heat or actinic rays. As actinic rays,
Light, ultraviolet rays, electron beams and X-rays can be used. Of these, actinic rays having a main wavelength of 100 to 800 nm are preferable. The obtained ion conductive polymer gel electrolyte is a viscoelastic body by itself, and when the battery is formed, the ion conductivity is kept at 10 ^-3 S / cm or more,
It is a polymer gel electrolyte having an elastic modulus of 10 ² dyne / cm ² or more. It can also work effectively as a polymer electrolyte layer of a battery. The gelled electrolyte can be made into a product in the form of a film or sheet, or in the form of being pre-composited with a part of the constituent elements of the battery.

(Electrolyte Salt) Examples of the electrolyte salt represented by the above formula (A) include LiCF ₃ SO ₃ and LiO (CF ₃ S).
_{O 2), LiN (CF 3} SO 2) 2, LiC (CF 3 SO 2)
₃ , LiCH (CF ₃ SO ₂ ) ₂ , LiC (CH ₃ ) (CF ₃
SO ₂ ) ₂ , LiCH ₂ (CF ₃ SO ₂ ), LiB (CF ₃ S
O ₂ ) _{2 and the} like. However, the electrolyte salt electrolyte (A) is corrosive, and is particularly prominent with respect to the positive electrode current collector metal. In order to suppress this corrosiveness, it is preferable to add an inhibitor. An inorganic electrolyte salt is effective as the inhibitor. As the inorganic electrolyte salt, L
Although iPF _6, LiBF _4, etc. are also effective, in particular, the corrosiveness is suppressed by adding at least one tetrafluoroborate salt selected from the group consisting of the above formulas (B) and (C). You can The concentration of the electrolyte salt in the non-aqueous electrolytic solution is usually 1.0 to 7.0 mol / 1, preferably 1.0 to 5.0 mol / 1 in the non-aqueous solvent. If it is less than 1.0 mol / 1, sufficient solid strength cannot be obtained. Further, if it exceeds 7.0 mol / 1, precipitation of an electrolyte salt occurs, which is not preferable. The inorganic electrolyte salt added as an inhibitor to the electrolyte salt of the formula (A) is preferably in a molar ratio of 1 to 9 with respect to the electrolyte salt of the formula (A). When it is less than 1, it has no effect as an inhibitor, and when it exceeds 9, there is no effect of the electrolyte salt of the above formula (A).

(Non-Aqueous Electrolyte Solution) The amount of the non-aqueous electrolyte solution is usually 200% by weight or more, preferably 400 to 900% by weight, particularly preferably 500 to 800% by weight based on the high molecular weight polymer forming the matrix. . If it is less than 200% by weight, a sufficiently high ionic conductivity cannot be obtained, and if it exceeds 900% by weight, it is difficult to solidify the non-aqueous electrolyte. Examples of the non-aqueous electrolytic solvent include cyclic esters such as propylene carbonate and ethylene carbonate, chain esters such as dimethyl carbonate and diethyl carbonate, 1,2-dimethoxyethane and 1,2-ethoxymethoxyethane, as well as methyl diglyme and methyl. Examples thereof include glymes such as triglyme, methyltetraglyme, ethylglyme, ethyl diglyme, butyl diglyme, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, and γ-butyrolactone. In particular, by containing propylene carbonate, the polymer gel has sufficient solid strength, and the amount used is preferably 5% or more, more preferably 10 to 50.
% By weight. In the present invention, high electrolyte performance can be brought out by using a non-aqueous solvent of a combination of cyclic ester and chain ester among the above solvents. For example, by containing dimethyl carbonate in addition to propylene carbonate, propylene carbonate gives sufficient solid strength, and by increasing ionic conductivity with dimethyl carbonate, one having sufficient solid strength and ionic conductivity is obtained. be able to.

In order to obtain the ion conductive polymer gel electrolyte of the present invention, it is preferable to define the concentration of the above-mentioned electrolyte salt and the concentration of acrylate monomer in the non-aqueous electrolytic solution within an appropriate range, and between them. Have a close relationship. When the electrolyte salt concentration is around the lower limit of 1.0 mol / 1, the concentration of all acrylate monomers for gelling the electrolyte is preferably about 20 to 50% by weight, and the electrolyte salt concentration is 1.5 mol / 1 or more. At a high concentration of 1, the gel electrolyte having sufficient characteristics can be prepared with an addition amount of the acrylate monomer concentration of about 10 to 20% by weight.

[Use of Ion Conducting Polymer Gel Electrolyte as Battery Electrolyte] The ion conducting polymer gel electrolyte of the present invention is a gel electrolyte in electrochemical elements such as batteries, capacitors, sensors, electrochromic devices and semiconductor devices. It can be used as a layer. Next, the case where the gel electrolyte of the present invention is used as a battery electrolyte will be described in detail. Generally, a battery includes a positive electrode made of a positive electrode active material, a negative electrode made of a negative electrode active material, a diaphragm, and an electrolyte. By using the gel electrolyte of the present invention as the electrolyte in this battery, an unprecedented advantageous battery can be obtained. When the gel electrolyte of the present invention is applied to a battery, the gel electrolyte itself of the present invention can also have a function as a diaphragm, but the electric field between the electrodes is made uniform, the strength is improved, and the reliability of the obtained battery is improved. In order to improve the property, it is preferable to be integrated with the diaphragm, and such consideration is necessary especially in the secondary battery. In the case of the present invention, it is easy to integrate the membrane and the gel electrolyte, and by directly forming the gel electrolyte in the battery container having the membrane, or by impregnating the gel electrolyte-forming composition into the membrane, the polymerization reaction Can be integrated by performing. In addition, by polymerizing the polymerizable compound composition for forming a gel electrolyte containing an inorganic or organic filler such as glass fiber, carbon fiber, or a polymer stretched product, it is not necessary to integrate with a diaphragm, which is more robust. An ion conductive gel electrolyte can be obtained.

[Positive Electrode Active Material] The positive electrode active material used in the battery of the present invention is TiS ₂ , MoS ₂ , FeO ₂ , Co ₂
Transition metal oxides such as S ₅ , V ₂ O ₅ , MnO ₂ and CoO ₂ ,
Transition metal chalcogen compounds and their composites with Li (Li composite oxides; LiMnO ₂ , LiV ₂ O ₅ , LiN
_{iO 2, LiMn 2 O 4,} LiCoO 2 , etc.), a conductive polymer having a fluorinated carbon or 10 ^-2 S / cm or more in electrical conductivity, specifically polyaniline, polypyrrole,
Polymers such as polyazulene, polyphenylene, polyacetylene, polyacene, polyphthalocyanine, poly-3-methylthiophene, polypyridine and polydiphenylbenzidine, and their derivatives are mentioned, but they show high cycle characteristics even at a discharge depth of 100%. It is preferable to use a conductive polymer that is relatively resistant to overdischarge compared to inorganic materials. In addition, since the conductive polymer is a plastic in terms of moldability and processability, it can make use of features that have not existed before. Although the conductive polymer has the above advantages, the secondary battery using the conductive polymer in the positive electrode,
The volume energy density is low due to the low density of the active material, and the electrolyte must have sufficient electrolyte for the electrode reaction, and the change in the electrolyte concentration due to the charge / discharge reaction is large, so the liquid resistance, etc. Is large, and there is a problem that an excessive amount of electrolytic solution is required to carry out a smooth charge / discharge reaction. This is disadvantageous in improving the energy density. Since it is difficult to mold the inorganic active material as it is, pressure molding is generally performed using a tetrafluoroethylene resin powder or the like as a binder. Organic and inorganic composite active materials may be used. In this case, any of the polymer active materials used has high electrical conductivity due to electrochemical doping, and 10
It is required to have an electric conductivity of ^-2 S / cm or more. Also, high ionic conductivity is required in terms of diffusivity of ions. These polymer materials have a high electric conductivity to have a current collecting ability, a binding ability as a polymer, and also function as an active material. In addition, since the conductive polymer is insulated at a low potential, even when the composite positive electrode is in an overdischarged state, the conductive polymer is insulated so that unnecessary lithium ions are contained in the inorganic active material contained therein. It prevents accumulation and prevents destruction of the crystal structure of the inorganic active material. As a result, an electrode that is substantially resistant to overdischarge can be formed. What is a conductive polymer used for composite positive electrodes?
Has the ability as an active material, does not dissolve in the electrolyte,
It is a conductive material having a binding property between polymer materials, and fixes an inorganic active material as a binding material.

[Negative Electrode Active Material] As the negative electrode active material, metal negative electrodes such as lithium, lithium aluminum alloys, lithium tin alloys and lithium magnesium alloys, carbon (including graphite type and non-graphite type), carbon boron Substitute (BC
₂ N), intercalating substances capable of occluding lithium ions such as tin oxide, etc. can be exemplified, but this electrolyte is particularly effective in improving the cycle life of batteries using the latter lithium intercalating substance as the negative electrode. There is. Hereinafter, specific examples of carbon will be described. A carbonaceous material is used as the negative electrode material used in the battery of the present invention. Examples of the carbonaceous negative electrode active material include graphite, pitch coke, synthetic polymer, and fired body of natural polymer. In the present invention, synthetic polymer such as phenol and polyimide, and natural polymer are reduced at 400 to 800 ° C. Insulating or semiconducting carbon body, coal, pitch, synthetic polymer, or natural polymer obtained by firing in an atmosphere is 800 to 130.
Conductive carbon body, coke, pitch, synthetic polymer obtained by firing in a reducing atmosphere at 0 ° C., obtained by firing a natural polymer in a reducing atmosphere at a temperature of 2000 ° C. or higher, and natural graphite Graphite-based carbon bodies such as are used. Of these, when using propylene carbonate, the graphite-based negative electrode active material does not work effectively as an electric element, but in the case of this electrolyte, even when the graphite-based negative electrode active material is used, a polymer gel electrolyte containing propylene carbonate is used. When used, it can have preferable characteristics as an electric element.

The gel electrolyte of the present invention is preferably a gel electrolyte itself which is a conductive polymer material or a composite of a gel electrolyte and a conductive polymer material. This is because the monomer solution before polymerization permeates the polymer material to swell the polymer material, penetrates well into the polymer material, and then gels due to the polymerization reaction. Is not formed, and the interface resistance between the two can be reduced. In a gel electrolyte represented by a gel of a conventional polymer matrix containing an ionic dissociation group and an inorganic salt, polarization is likely to occur at the interface between the gel electrolyte and the active material, and has a large interfacial resistance. On the other hand, the gel electrolyte of the present invention is in the form of a gel while having the properties of a solution as described above. It can be said that this is a more preferable combination in which polarization is less likely to occur in the battery used. The method for obtaining a composite of a conductive polymer material and a gel electrolyte of the present invention is generally a method of impregnating a conductive polymer material with a composition for forming a gel electrolyte, and then using a polymerization means as described above to produce a viscoelastic material. And compound.

[Gel Electrolyte] Examples of the conductive polymer material to be composited with the gel electrolyte of the present invention include, for example, a hetero five-membered ring compound polymer containing pyridine, thiophene, etc. as a monomer, benzene, azulene, etc. Of an aromatic hydrocarbon compound polymer having a monomer of aniline, an amine compound polymer having an aniline or diphenylbenzidine monomer, a polyarylene vinylene, an unsaturated hydrocarbon such as ethylene, butadiene or hexatriene An unsaturated aliphatic compound polymer having a halogen-substituted compound as a monomer can be used. As a method for polymerizing these monomers, a chemical polymerization method using an oxidizing agent or an electrolytic polymerization method utilizing electric energy can be used. Examples of the binder used for the negative electrode include polyvinylidene fluoride and modified polyvinyl pyridine.

[Cathode Current Collector] Examples of the cathode current collector used in the present invention include metal sheets such as stainless steel, gold, platinum, nickel, aluminum, molybdenum, and titanium, metal foils, metal nets, punching metals. , Expanded metal, or nets and non-woven fabrics made of metal-plated fibers, metal-deposited wires, metal-containing synthetic fibers, and the like. Above all, it is particularly preferable to use aluminum, stainless steel or titanium in consideration of electrical conductivity, chemical stability, electrochemical stability, economic efficiency, workability and the like. The ion-conductive polymer gel electrolyte of the present invention can be used as it is as a membrane of a battery, but it can also be used by further dispersing a filler or by being combined with a porous membrane (separator).
Examples of the separator include a glass fiber, a filter, a nonwoven fabric filter made of polymer fibers such as polyester, Teflon, polyflon, and polypropylene, and a nonwoven fabric filter made by mixing glass fibers and these polymer fibers.

In the battery of the present invention, a battery element such as an electrode or a diaphragm is impregnated with a composition for forming a gel electrolyte to form a viscoelastic body by a polymerization means such as heating or irradiation with actinic rays.
It is preferable to integrate the gel electrolyte and the battery element. The battery element and the gel electrolyte may be integrated for each battery element, but the combination of the positive electrode and the diaphragm, the combination of the negative electrode and the diaphragm, or the combination of the positive electrode, the diaphragm and the negative electrode may be combined with the gel electrolyte. May be integrated with. In this way, if the battery element and the gel electrolyte are integrated, the electrode reaction on the positive electrode and the negative electrode and the movement of ions can proceed smoothly, and the internal resistance of the battery can be greatly reduced.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
In the following, parts and% mean parts by weight and% by weight, respectively. In addition, the non-aqueous solvent and the electrolyte salt were sufficiently refined to have a water content of 20 ppm or less, and deoxidized and denitrogenated battery grade ones were used. All operations were performed under an inert gas atmosphere. went. The measurement temperature of the ionic conductivity was 25 ° C., and a SUS cylindrical container (inner diameter 20 mm) in which the inner peripheral surface excluding the bottom surface was covered with an insulating tape was used as the counter electrode, and the gel electrolyte was filled in the container. ,
It was performed by pressing a SUS columnar body having a diameter of 18 mm as a working electrode on the surface of the gel electrolyte (cell for measuring ionic conductivity).

[0025]

【Example】

Example 1 1.5 mol / l Li dissolved in ethylene carbonate (EC) / propylene carbonate (EC) (5/5)
Monofunctional monomer was added to 50 parts of N (CF ₃ SO ₂ ) ₂ electrolyte.
As methyl diethylene glycol acrylate 10.
5 parts, ethylene oxide-modified trimethylolpropane triacrylate as a polyfunctional monomer (molecular weight 42
8) 0.5 parts, benzophenone 0.03 as photoinitiator
Parts were added and mixed and dissolved to prepare a photopolymerizable solution. This solution was put in an ion conductivity measuring cell and irradiated with a high pressure mercury lamp equipped with a cold mirror concentrator to solidify the electrolytic solution to obtain an ion conductive polymer gel electrolyte. This ion conductive polymer gel electrolyte had an ionic conductivity of 2.3 × 10 ⁻³ S / cm and an elastic modulus of 3.7 × 10 ³ dyn / cm ² .

Comparative Example 1 An electrolytic solution was solidified in the same manner as in Example 1 except that a 1.5 mol / LiBF ₄ solution was used [EC / PC = 5 /.
5]. The ion conductive polymer gel electrolyte had an ionic conductivity of 4.7 × 10 ⁻⁴ S / cm and an elastic modulus of 1.4 × 10 ⁴ dyn / cm ² .

Example 2 The electrolytic solution was solidified in the same manner as in Example 1 except that only a 2 mol / l LiN (CF ₃ SO ₂ ) ₂ solution was used.
An ion conductive polymer gel electrolyte was obtained. This ion conductive polymer gel electrolyte had an ionic conductivity of 2.4 × 10 ⁻³ S / cm and an elastic modulus of 2.8 × 10 ³ dyn / cm ² .

Comparative Example 2 As Example 2 except that polyethylene glycol dimethacrylate (molecular weight 1166) was used as the polyfunctional monomer and EC / PC / dimethyl carbonate (5/2/3) was used as the non-aqueous solvent. Similarly, the electrolytic solution was solidified. The ion conductive polymer gel electrolyte had an ionic conductivity of 8.2 × 10 ⁻⁴ S / cm and an elastic modulus of 7.3 × 10 ² dyn / cm ² .

Example 3 Propylene carbonate / ethylene carbonate / dimethyl carbonate (2/5/3: volume ratio) 1.8 mol / l LiN (CF ₃ SO ₂ ) ₂ solution dissolved in a non-aqueous solvent and 0.2 mol / l LiBF ₄ solution mixed electrolyte 86
Parts, 13.8 parts of ethoxydiethylene glycol acrylate as a monofunctional monomer, 0.2 parts of trimethylolpropane triacrylate as a polyfunctional monomer,
Benzoin isopropyl ether 0.0 as photoinitiator
56 parts were added and mixed and dissolved to prepare a photopolymerizable solution. This solution was placed in a cell for measuring ionic conductivity and irradiated with a high pressure mercury lamp equipped with a cold mirror condensing device to solidify the electrolytic solution. The ion conductive polymer gel electrolyte had an ionic conductivity of 2.5 × 10 ⁻³ S / cm and an elastic modulus of 3.3 × 10 ³ dyne / cm ² .

Comparative Example 3 An electrolytic solution was solidified in the same manner as in Example 3 except that only a 2 mol / l LiBF4 solution was used. This ion conductive polymer gel electrolyte had an ionic conductivity of 5.0 × 10 ⁻⁴ S / cm and an elastic modulus of 1.3 × 10 ⁴ dyne / cm ² .

Example 4 LiC (CF ₃ SO ₂ ) ₃ was used as an electrolyte salt in an amount of 1.8 mo.
l / l and LiBF ₄ were 0.2 mol / l,
The electrolytic solution was solidified in the same manner as in Example 3. This ion conductive polymer gel electrolyte has an ionic conductivity of 2.0 × 10 ⁻³ S / cm and an elastic modulus of 2.9 × 10 ³ dyne / c.
m ² .

Comparative Example 4 An electrolytic solution was solidified in the same manner as in Example 4 except that polyethylene glycol chol dimethacrylate (molecular weight 1166) was used as the polyfunctional monomer. This ion conductive polymer gel electrolyte has an ionic conductivity of 4.1 × 10 ⁻⁴ S / cm, an elastic modulus of 6.8 × 10 ² dyne / c.
m ² .

Example 5 Propylene carbonate / ethylene carbonate / dimethyl carbonate (2/4/4: weight ratio) 1.7 mol / l LiN (CF ₃ SO ₂ ) ₂ and 0.3 mol / l LiBF dissolved in a non-aqueous solvent. 86 parts of a mixed electrolyte of ₄ , ethoxydiethylene glycol acrylate 13.8 parts as a monofunctional monomer, trimethylolpropane triacrylate 0.2 parts as a polyfunctional monomer, and benzoin isopropyl ether 0.056 parts as a photoinitiator. It was added, mixed and dissolved to prepare a photopolymerizable solution. The electrolytic solution was solidified. The ion conductive polymer gel electrolyte had an ionic conductivity of 2.3 × 10 ⁻³ S / cm and an elastic modulus of 3.5 × 10 ³ dyne / cm ² .

Example 6 The electrolyte solution was solidified in the same manner as in Example 5 except that only 86 parts of ethylene carbonate was used as the solvent.
The ion conductive polymer gel electrolyte had an ionic conductivity of 1.0 × 10 ⁻³ S / cm and an elastic modulus of 3.0 × 10 ³ dyne / cm ² .

Example 7 L in propylene carbonate / ethylene carbonate / dimethyl carbonate (1/5/4: weight ratio) non-aqueous solvent
iN (CF ₃ SO ₂ ) ₂ (1.8 mol / l), LiBF ₄
The electrolytic solution was solidified in the same manner as in Example 1 except that (0.2 mol / l) was added to form the electrolytic solution. The ion conductive polymer gel electrolyte had an ionic conductivity of 2.3 × 10 ⁻³ S / cm and an elastic modulus of 2.8 × 10 ³ dyne / cm ² .

Example 8 Propylene carbonate / dimethyl carbonate (5 /
5) The electrolytic solution was solidified in the same manner as in Example 3 except that the non-aqueous solvent was used. This ion conductive polymer gel electrolyte has an ionic conductivity of 2.4 × 10 ⁻³ S / cm and an elastic modulus of 2.8 × 10 ³ dyne / c.
m ² .

Example 9 1.0 mol / l LiN (CF ₃ SO ₂ ) ₂ solution and 1.
Solidification of the electrolytic solution was performed in the same manner as in Example 3 except that the mixed solution of the 0 mol / l LiBF ₄ solution was used as the electrolytic solution. This ion conductive polymer gel electrolyte has an ionic conductivity of 1.1 × 10 ⁻³ S / cm and an elastic modulus of 3.8 × 10 ³ dyne / c.
m ² .

Example 10 The electrolytic solution was solidified in the same manner as in Example 3 except that only dimethoxytetraethylene glycol acrylate was used as the monofunctional monomer. This ion conductive polymer gel electrolyte has an ionic conductivity of 2.4 × 10 ⁻³ S / cm and an elastic modulus of 1.6 × 10 ³ dyne / c.
m ² .

Example 11 0.028 parts of benzoin isopropyl ether as a photopolymerization initiator and 0.02 of bis (4-t-butylcyclohexyl) peroxydicarbonate as a thermal polymerization initiator
Solidification was performed by irradiation with a high pressure mercury lamp in the same manner as in Example 3 except that 43 parts were used together. This ion conductive polymer gel electrolyte had an ionic conductivity of 2.3 × 10 ⁻³ S / cm and an elastic modulus of 3.6 × 10 ³ dyn / cm ² .

Example 12 L dissolved in a non-aqueous solvent of ethylene carbonate / propylene carbonate / dimethyl carbonate (5/3/2)
iN (CF ₃ SO ₂ ) ₂ solution (0.4 mol / l) and L
Mixed electrolyte solution 80 of iPF ₆ solution (1.6 mol / l)
Part, methyldiethyleneglycol as a monofunctional monomer
11.0 parts of luacrylate, as a polyfunctional monomer,
0.6 part of PO-modified trimethylolpropane triacrylate (molecular weight 470) and 0.04 part of methylbenzoyl formate as a photoinitiator were added, mixed and dissolved to prepare a photopolymerizable solution. The electrolytic solution was solidified. The ion conductive polymer gel electrolyte had an ionic conductivity of 3.0 × 10 ⁻³ S / cm and an elastic modulus of 3.5 × 10 ³ dyne / cm ² .

Example 13 The same composition as in Example 5 was used except that 0.03 part of bis (4-t-butylcyclohexyl) peroxydicarbonate was used as the thermal polymerization initiator, and the thermal polymerization was carried out at about 80 ° C.
The solidification of this electrolytic solution was performed. The ion conductive polymer gel electrolyte had an ionic conductivity of 2.0 × 10 ⁻³ S / cm and an elastic modulus of 2.9 × 10 ³ dyne / cm ² .

Example 14 Evaluation of characteristics of negative electrode battery Polyvinylidene fluoride (2 parts by weight) was dissolved in N-methylpyrrolidone (58 parts by weight), and 40 parts by weight of calcined product of coke in a reducing atmosphere at 2500 ° C. was added, followed by roll mill method. Then, they were mixed and dispersed in an inert atmosphere to prepare a negative electrode coating material.
20 μm of this in the air using a wire bar
Apply on copper foil and dry at 100 ° C for 15 minutes to give a film thickness of 6
A 0 μm electrode was prepared. This is the negative electrode and the counter electrode is Li
A plate was used, and the photopolymerizable solutions prepared in Examples 1 to 13 and Comparative Examples 1 to 4 were placed in a beaker cell and irradiated with a high pressure mercury lamp to solidify the electrolytic solution, and a charge / discharge test was conducted. For the charge / discharge test, Hokuto Denko HJ-201B charge / discharge measuring device was used to charge the battery with a current of (1/3) CmA until the battery voltage became 0V, and with a current of (1/3) CmA, the battery voltage was changed. After discharging to 0.8 V, this charging / discharging was repeated. The weight energy densities per weight of the electrode active material at the initial stage (30th cycle) and after 300 cycles are shown in Tables 1, 2 and 3 below.

[Table 1]

[Table 2]

[Table 3]

The embodiments of the present invention will be described below. 1. Molecular weight of 1,0 in the presence of electrolyte salt and non-aqueous solvent
The ion conductive polymer gel electrolyte obtained by polymerizing an acrylate monomer of 00 or less has the following formula (A):

Embedded image LiX (R ₁ SO ₂ ) n (A) [wherein, X is N, C, B, O or C (R ₂ ) m (R ₂
Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms), and R
₁ is a halogenated alkyl group having 1 to 12 carbon atoms, m is 1 or 2, and n is an integer of 1 to 3. ] The ion conductive polymer gel electrolyte characterized by containing electrolyte salt which is these. 2. The molecular weight of the acrylate monomer and its prepolymer is usually 1,000 or less, preferably 500 or less,
More preferably, the ion conductive polymer gel electrolyte according to the above 1, which is 300 or less. 3. 2. The ion conductive polymer gel electrolyte according to 1 above, wherein the acrylate monomer is a mixture of a monofunctional monomer and a polyfunctional monomer. 4. Item 3. The ion-conductive polymer gel electrolyte according to items 1 to 3, wherein the monofunctional acrylate monomer and / or the polyfunctional acrylate monomer has a heterocycle containing a hetero atom other than carbon. 5. The ion conductive polymer gel electrolyte according to 1 to 4 above, wherein the acrylate monomer is a trifunctional acrylate having three acryloyl groups. 6. 6. The ion conductive polymer gel electrolyte according to the above 1 to 5, wherein at least one acrylate monomer is modified with alkylene oxide. 7. The ion conductive polymer gel electrolyte according to 4 to 7 above, wherein the amount of the polyfunctional acrylate added is 4% by weight or less, preferably 0.05 to 2% by weight, based on the non-aqueous electrolyte. 8. The ion-conductive polymer gel electrolyte according to 1 to 7 above, wherein the polyfunctional acrylate is a trifunctional acrylate, and the amount of the acrylate added is 2% by weight or less, preferably 0.05 to 0.5% by weight.

9. 9. The ion-conductive polymer gel electrolyte according to 1 to 8 above, wherein the non-aqueous solvent contains a cyclic carbonate and a chain carbonate. 10. 9. The ion conductive polymer gel electrolyte according to 9 above, wherein the cyclic carbonate is propylene carbonate. 11. 10. The ion conductive polymer gel electrolyte according to 10 above, wherein propylene carbonate is 10 to 50% by volume based on the total volume of the non-aqueous solvent. 12. The ion-conductive polymer gel electrolyte according to 9 to 11 which further contains dimethyl carbonate. 13. 13. The ion conductive polymer gel electrolyte according to claim 1, wherein the non-aqueous solvent further contains an inorganic electrolyte salt other than the above formula (A). 14． 13. The inorganic electrolyte salt other than the above formula (A) contains at least one tetrafluoroborate salt selected from the group consisting of the following formulas (B) and (C):
Ion conductive polymer gel electrolyte.

Embedded image M (BF ₄ ) ... (B) (R ₃ R ₄ R ₅ R ₆ ) NBF ₄ (C) (wherein M is an alkali metal, an alkaline earth metal,
14. R ₃ , R ₄ , R ₅ , and R ₆ are alkyl groups) 15. The ion conductive polymer gel electrolyte according to 13 to 14, wherein the mixing ratio of the electrolyte salt of the formula (A) and the inorganic electrolyte salt other than the formula (A) is 10:90 to 90:10. 16. The ion conductive polymer gel electrolyte according to any one of 1 to 15 above, which is formed by polymerizing a photopolymerization initiator and a thermal polymerization initiator in combination. 17． 16. The ion conductive polymer gel electrolyte according to 16 above, wherein the thermal polymerization initiator is a peroxycarbonate-based polymerization initiator. 18. The ion conductive polymer gel electrolyte according to claim 1, wherein the ion conductive polymer gel electrolyte has a crosslinked polymer matrix containing an inorganic or organic filler. 19. The ion conductive polymer gel electrolyte according to claim 1, which is a viscoelastic body having an elastic modulus of 10 ² to 10 ⁵ dyne / cm ² . 20. The ion conductive polymer gel electrolyte according to 1 to 19 which is a viscoelastic body having a conductivity of 1/10 ⁴ to 1/10 ² S / cm. 21. An electrochemical device comprising the ion conductive polymer gel electrolyte of 1 to 20 as a constituent element. 22. 22. The battery according to 21 above, wherein the ion conductive polymer gel electrolyte is formed integrally with at least one kind of constituent members of the electrochemical device. 23. 23. The battery according to 1 to 22 above, wherein the negative electrode active material is non-graphite.

[0045]

[Effect] By including the electrolyte salt represented by the above formula (A) in a polymer matrix obtained by polymerizing an acrylate monomer having a molecular weight of 1,000 or less, the ionic conductivity is improved without deteriorating the elastic modulus. An ion conductive polymer gel electrolyte was obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01M 10/40 H01M 10/40 Z (72) Inventor Toshiyuki Osawa Nakamagome 1-3, Ota-ku, Tokyo No. 6 in Ricoh Co., Ltd.

Claims (8)

[Claims] 1. An ion-conductive polymer gel electrolyte obtained by polymerizing an acrylate monomer having a molecular weight of 1,000 or less in the presence of an electrolyte salt and a non-aqueous solvent is represented by the following formula (A): LiX ( R ₁ SO ₂ ) n (A) [wherein, X is N, C, B, O or C (R ₂ ) m (R ₂
Is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms), and R
₁ is a halogenated alkyl group having 1 to 12 carbon atoms, m is 1 or 2, and n is an integer of 1 to 3. ] The ion conductive polymer gel electrolyte characterized by containing electrolyte salt which is these. 2. The acrylate monomer has a molecular weight of 1,0.
The ion conductive polymer gel electrolyte according to claim 1, which is a monofunctional monomer or a polyfunctional monomer having a molecular weight of 00 or less. 3. The ion conductive polymer gel electrolyte according to claim 1, wherein at least one acrylate monomer is modified with alkylene oxide. 4. The ion conductive polymer gel electrolyte according to claim 1, wherein the non-aqueous solvent contains a cyclic carbonate and a chain carbonate. 5. The ion conductive polymer gel electrolyte according to claim 4, wherein the cyclic carbonate is propylene carbonate. 6. The ion conductive polymer gel electrolyte according to claim 5, wherein the propylene carbonate is 10 to 50% by volume based on the total volume of the non-aqueous solvent. 7. The non-aqueous solvent, which further contains an inorganic electrolyte salt other than the above formula (A),
The ion-conductive polymer gel electrolyte according to 2, 3, 4, 5 or 6. 8. The method of claim 1, 2, 3, 4, 5, 6, or 7.
A secondary battery containing the ion-conductive polymer gel electrolyte as a constituent element, wherein the negative electrode is capable of forming an intercalation compound with Li.