JP2000260470A - Polymer electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-reliability polymer electrolyte battery excellent in a load characteristic and not decomposing the electrolyte due to storage. SOLUTION: This polymer electrolyte battery comprises: plural sheet-like positive electrodes 1 each having positive electrode mix layer 1b at least one surface of an aluminum collector, and containing a polymer electrolyte in the positive electrode mix layer 1b; plural sheet-like negative electrodes 2 each having a negative electrode mix layer 2b at least one surface of a copper collector, and containing a polymer electrolyte in the negative electrode mix layer 2b; and plural polymer electrolyte layers; and they are encapsulated by an outer enclosure. In this case, the concentration of the polymer in the polymer electrolyte in the polymer electrolyte layer and at least either of the positive electrodes 1 and the negative electrodes 2 is maximized at the farthest part from the respective electrodes and minimized at a part abutting on the collector of each of the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte battery, and more particularly, to a polymer electrolyte battery suitable for use as a power source for portable devices such as personal computers and mobile phones.

[0002]

2. Description of the Related Art In a polymer electrolyte battery, the electrolyte can be made into a sheet shape, thereby making it possible to produce a large-area and thin battery such as an A4 size plate or a B5 size plate.
Application to various thin products has become possible, and the range of use of batteries has been greatly expanded. Batteries using this polymer electrolyte have excellent safety and storage properties including leakage resistance because the electrolyte is gelled and contain virtually no free liquid. It has the unique feature of batteries that can be designed to meet the needs of conventional batteries.

[0003] In this polymer electrolyte battery, an electrolyte solution obtained by dissolving an inorganic salt such as a lithium salt in an organic solvent in an electrode or an electrolyte support is usually used as a polymer gelling agent (eg, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride). And a gelling component-containing electrolyte solution prepared by mixing the polymer-based gelling agent, and then heating and dissolving the polymer-based gelling agent. Instead of a polymer gelling agent, after impregnating the electrode and the support with a gelling component-containing electrolytic solution prepared by mixing a polyfunctional monomer such as dipentaerythritol hexaacrylate with the electrolytic solution, the ultraviolet light and the like Thin sheet-like electrodes and sheets composed of polymer electrolytes by irradiating actinic rays to polymerize monomers and gel them By combining the polymer electrolyte layer, by sealing and sheathed with outer package made of a laminate film in which the aluminum film on the core material, and finished into thin battery.

[0004]

In this polymer electrolyte battery, in order to make the electrode thin, a metal foil is usually used as a current collector, an aluminum foil is used as a positive electrode current collector, and a negative electrode is used as a current collector. Copper foil is used for the current collector. A non-woven fabric using polypropylene or polyethylene terephthalate fibers is used as a support for the electrolyte.

[0005] The above-mentioned electrode is prepared by forming an active material, a conduction aid and a binder such as polyvinylidene fluoride into a paste with a solvent such as N-methylpyrrolidone, and applying a paste containing the active material to a metal foil. Although it is manufactured through drying and rolling, it has a relatively high strength, but the polymer electrolyte layer interposed between the electrodes has a lower strength than the electrodes, although the nonwoven fabric is used as a support. Is inferior to electrodes in shape retention and shape retention.

Therefore, it has been proposed to increase the gel strength by increasing the amount of the gelling component. However, when the amount of the gelling component increases, the amount of the electrolyte solution naturally decreases, and the ions move smoothly. No longer. In addition, the gel has an excessively strong force to fix the electrolyte, and as a result, there is a problem that load characteristics and low-temperature characteristics are reduced.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and reduces the amount of the gelling component as much as possible without impairing the retention of the electrolytic solution in the polymer electrolyte layer. It is an object of the present invention to provide a highly reliable polymer electrolyte battery without deteriorating battery characteristics.

[0008]

According to the present invention, the above object is achieved by increasing the polymer concentration in the polymer electrolyte of the polymer electrolyte layer using a non-woven fabric or the like as a support and lowering the polymer concentration in the polymer electrolyte of the electrode. Is solved.

That is, with the above configuration,
The polymer electrolyte layer that requires the most strength maintains the strength and holds the liquid by increasing the polymer concentration,
By utilizing the liquid holding capacity and mechanical strength of the binder and the powder inside the electrode, it is possible to reduce the polymer concentration and suppress a decrease in battery characteristics. As a result, the polymer concentration in the polymer electrolyte can be reduced as a whole, and the battery characteristics can be further improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an aluminum foil, a punched metal, a net, an expanded metal and the like can be used as a current collector of a positive electrode, and an aluminum foil is usually used. The current collector of the positive electrode preferably has a thickness of 20 μm or less in order to reduce the thickness of the positive electrode. However, if it is too thin, wrinkles may occur when the positive electrode mixture-containing paste is applied in producing the positive electrode, or the film may be broken by pulling, so the thickness is 20 μm or less and 10 μm or more as described above. Is preferred.

As the positive electrode active material, various materials can be used without any particular limitation. However, a transition metal oxide containing lithium is preferably used because of its high energy density and excellent reversibility. Specifically, for example, LiCo
Lithium cobalt oxides such as O ₂ , lithium manganese oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , mixtures thereof, and LiN
Those obtained by substituting a part of Ni of iO ₂ with Co or Mn are preferably used.

The positive electrode mixture layer is usually made of a positive electrode mixture-containing paste prepared by using the above-mentioned positive electrode active material, for example, a conductive aid such as carbon black or a binder such as polyvinylidene fluoride, and made into a paste with an organic solvent. Formed by applying and drying on at least one surface of At that time, a lithium salt is dissolved in an organic solvent, and a positive electrode mixture layer is formed in a state containing a polymer electrolyte using a polymer gelling agent such as polyvinylidene fluoride as a binder. Can also.

In the present invention, as the current collector of the negative electrode, copper foil, punched metal, net, expanded metal, etc. can be used, but copper foil is usually used. The current collector of the negative electrode has a thickness of 20 μm in order to reduce the thickness of the negative electrode.
The following are preferred. However, if it is too thin, wrinkles may occur when the negative electrode mixture-containing paste is applied in the preparation of the negative electrode, or the film may be broken by pulling, so the thickness is 20 μm as described above.
Below, 5 μm or more is preferable.

The negative electrode active material is not particularly limited as long as it is capable of doping / dedoping lithium ions, and various materials can be used. In particular, carbon-based materials are preferably used. For example, graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, graphite and the like are preferably used.

The negative electrode mixture layer usually comprises the above-mentioned negative electrode active material,
A negative electrode mixture-containing paste made into a paste with an organic solvent containing a conductive aid such as carbon black added as necessary and a binder such as polyvinylidene fluoride is applied to at least one surface of the current collector and dried. It is also formed by At that time, a lithium salt is dissolved in an organic solvent, and a negative electrode mixture layer is formed so as to contain a polymer electrolyte by using a polymer gelling agent such as polyvinylidene fluoride as a binder. Can also.

In the present invention, as a support for the polymer electrolyte layer, for example, a porous sheet such as a nonwoven fabric or a microporous film is used. Examples of the nonwoven fabric include nonwoven fabrics such as polypropylene, polyethylene, polyethylene terephthalate, and polybutylene terephthalate. Examples of the microporous film include microporous films of polypropylene, polyethylene, and ethylene-propylene copolymer.

The polymer electrolyte layer is prepared by impregnating the support with an electrolytic solution containing a gelling component and heating or irradiating with an actinic ray. At that time, it can be produced as a polymer electrolyte layer in a state separated from the electrode such as a positive electrode or a negative electrode, and the electrode and the support are integrated by surrounding the periphery of the electrode with the support, The integrated material of the electrode and the support may be impregnated with the above-mentioned gelling component-containing electrolytic solution and heated or irradiated with actinic rays so that the polymer electrolyte layer is held on the electrode.

The integration of the electrode and the support means that the electrode and the support are brought into close contact with each other without bubbles or foreign matter between the electrode and the support. It does not mean to let them.

In the present invention, the electrolyte may be, for example,
For example, dimethyl carbonate, diethyl carbonate,
Tyl ethyl carbonate, methyl propionate, ethyl
Carbonate, propylene carbonate, butylene carbonate
-Carbonate, gamma-butyrolactone, ethylene glyco
Sulfite, 1,2-dimethoxyethane, 1,3
-Dioxolan, tetrahydrofuran, 2-methyl-te
Organic solvents such as trahydrofuran and diethyl ether
For example, LiClO_Four, LiPF₆, LiBF _Four,
LiAsF₆, LiSbF₆, LiCF_ThreeSO_Three, Li
C_FourF₉SO_Three, LiCF_ThreeCO_Two, Li_TwoC_TwoF
_Four(SO_Three)_Two, LiN (CF_ThreeSO_Two)_Two, LiC
(CF_ThreeSO_Two)_Three, LiC_nF_{2n + 1}SO_Three(N ≧
2), LiN (RfOSO_Two)_Two[Where Rf is
Dissolving inorganic ion salts such as
Therefore, those prepared are used. This inorganic ion salt
The concentration in the electrolyte is 0.5 to 1.5 mol / l,
Particularly, 0.9 to 1.25 mol / l is preferable.

In the present invention, the gelling component refers to a component that gels the electrolytic solution. Examples of such a gelling component include polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, vinylidene fluoride-hexafluoride. A polymer-based gelling agent that dissolves a linear polymer such as a propylene copolymer in an electrolyte by heating and then gels the electrolyte by cooling, or polymerizes with actinic rays or heat And a crosslinkable composition containing a monomer or prepolymer containing two or more natural double bonds per molecule as a main component.

Examples of the monomer capable of being polymerized by actinic light include monomers having two double bonds per molecule (bifunctional crosslinkable monomers) such as 1,3-butanediol diacrylate and 1,4 -Butanediol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate Acrylate, tripropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, novolak diacrylate, propoxylated neopentyl glycol diacrylate Such as difunctional acrylates and the acrylate and similar difunctional methacrylates such as chromatography bets and the like.

Examples of a monomer having three double bonds per molecule which can be polymerized by actinic rays (trifunctional crosslinkable monomer) include, for example, tris (2-hydroxyethyl) isocyanurate triacrylate, trimethylolpropane Trifunctional acrylates such as acrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, caprolactone-modified trimethylolpropane triacrylate, and trifunctional methacrylates similar to the above acrylates And the like.

Examples of the monomer having four or more double bonds per molecule which can be polymerized by actinic light (tetrafunctional or more crosslinkable monomer) include, for example, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated Examples include tetrafunctional or higher acrylates such as pentaerythritol tetraacrylate, dipentaerythritol hydroxypentaacrylate, dipentaerythritol hexaacrylate, and tetrafunctional or higher methacrylates similar to the above acrylates.

Further, two double bonds polymerizable by actinic rays
Examples of the prepolymer having at least 4, preferably at least 4, include prepolymers of urethane acrylate, epoxy acrylate, and polyester acrylate, and can be used in place of the above-mentioned monomers.

In the present invention, the monomer or prepolymer having two or more double bonds polymerizable by actinic light per molecule may be used as a main component, and may be used for adjusting physical properties such as gel hardness. For this purpose, a monofunctional monomer or the like can be used in combination.

In the present invention, the term "crosslinkable composition comprising a monomer or prepolymer having at least two double bonds per molecule which can be polymerized by actinic light" as a main component refers to the above-mentioned crosslinkable composition polymerized by actinic light. Monomers or prepolymers containing only possible monomers or prepolymers having two or more double bonds per molecule, and monomers or prepolymers having two or more double bonds per molecule that can be polymerized with actinic rays with monofunctional monomers In the case where a monomer or a prepolymer having two or more double bonds per molecule capable of being polymerized by actinic rays is used in combination with a monofunctional monomer or the like as in the latter case, the crosslinkable composition Of a monomer or a prepolymer having two or more double bonds per molecule which can be polymerized by actinic light, more than 50% by weight, especially 70% by weight. Or more at a wavelength of 550 nm. Also,
The crosslinkable composition does not have to be all crosslinkable as long as the constituents thereof are not crosslinkable, as long as it is entirely crosslinkable.
Other components can be added as needed.

If necessary, as a polymerization initiator, for example, benzoins, benzoin alkyl ethers, benzophenones, benzoylphenylphosphine oxides, acetophenones, thioxanthones, anthraquinones and the like can be used. . Further, alkylamines, aminoesters and the like can be used as a sensitizer of the polymerization initiator.

In the present invention, for example, ultraviolet rays (UV), electron beams (EB), visible rays, far ultraviolet rays, etc. can be used as the active rays.

Examples of the monomer which can be polymerized by heat include 2-ethoxyethyl acrylate, tri (ethyl glycol) dimethacrylate, and ethylene glycol ethyl carbonate methacrylate.

In the present invention, the concentration of the polymer in the polymer electrolyte of the electrode and the polymer electrolyte layer can be adjusted by appropriately changing the concentration of the gelling component, the density of the electrode, the size of the active material particles, and the like. .

The concentration of the polymer in the polymer electrolyte of the electrode or the polymer electrolyte layer is such that the highest concentration is at the portion farthest from the electrode and the lowest concentration is at the portion in contact with the current collector of the electrode. 9% by weight and a minimum concentration of 3 to 5% by weight are preferable. Needless to say, the highest concentration and the lowest concentration are not the same.

[0032]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited only to those illustrated in the embodiments.

Example 1 In Example 1, a positive electrode and an electrode were prepared by forming a mixture layer without containing a polymer electrolyte and then containing a polymer electrolyte. The preparation of a positive electrode and a negative electrode will be described.

Preparation of positive electrode: LiCoO as positive electrode active material
₂ 90 parts by weight, 5 parts by weight of carbon black is a conductive aid, polyvinylidene fluoride 5 parts by weight of a binder mixture of N- methylpyrrolidone to be uniform as a solvent, to prepare a positive electrode mixture-containing paste.

The paste containing the positive electrode mixture was coated with a thickness of 20 μm.
20mg of positive electrode mixture on one side of both sides of aluminum foil
/ Cm ² (however, the amount of the positive electrode mixture after drying) is uniformly applied and dried to form a positive electrode mixture layer, and then the density is adjusted to control the penetration of the gelling component. Perform a calendering process, and set the thickness of the positive electrode mixture layer on one side to 6
It was adjusted to 5 μm. It was cut into a size of 70 mm × 40 mm to obtain a positive electrode. However, in producing the above positive electrode, the positive electrode mixture-containing paste was not applied to part of the aluminum foil, leaving an exposed portion of the aluminum foil, and using the exposed portion as a lead for connection with the positive electrode terminal as an external terminal. Department.

Preparation of negative electrode: 77 parts by weight of graphite as the negative electrode active material, 8 parts by weight of Carbotron P (trade name, low crystalline carbon having an average particle size of 22 μm, manufactured by Kureha Chemical Industry Co., Ltd.), and polyvinylidene fluoride as a binder 15 parts by weight were uniformly mixed using N-methylpyrrolidone as a solvent to prepare a negative electrode mixture-containing paste.

This negative electrode mixture mixture paste is 10 μm thick.
The amount of the negative electrode mixture on one side is 12 mg / cm on both sides of the copper foil
² (However, the amount of the negative electrode mixture after drying) is applied uniformly and dried to form a negative electrode mixture layer, and then calendered to adjust the density and control the penetration of gelled components. The thickness of the negative electrode mixture layer on one side was adjusted to 65 μm. This was cut into a size of 72 mm × 42 mm to obtain a negative electrode. However, in producing the above negative electrode, the negative electrode mixture-containing paste was not applied to part of the copper foil, leaving an exposed portion of the copper foil, and using the exposed portion as a lead for connection with the negative electrode terminal as an external terminal. Department.

Fabrication of the positive electrode unit: A polyimide tape having a thickness of 50 μm and a width of 3 mm is adhered from both sides to a portion near the lead portion of the positive electrode fabricated as described above, thereby preventing short-circuiting and maintaining strength of the portion. Was planned. In addition, the surface of the lead portion, which was to be connected to the positive electrode terminal, was covered with a heat-peeling tape from which the adhesiveness of the adhesive surface was lost by heat. This positive electrode is used as a support for the gel polymer electrolyte. The non-woven fabric is a polybutylene terephthalate non-woven fabric having a thickness of 30 μm and a basis weight of 12 g / m ² [manufactured by NKK, MB1230 (trade name)].
Wrapped in

Fabrication of the negative electrode unit: An imide tape having a thickness of 50 μm and a width of 3 mm was adhered from both sides to a portion near the lead portion of the negative electrode to prevent short-circuit and maintain strength in the portion. In addition, the surface of the lead portion, which is to be connected to the negative electrode terminal, was covered with a heat-peeling tape from which the adhesive surface loses tackiness due to heat. Then, this negative electrode is used as a holding body for the gel polymer electrolyte in a polybutylene terephthalate nonwoven fabric having a thickness of 30 μm and a basis weight of 12 g / m ² [manufactured by NKK, MB
1230 (trade name)].

Preparation of Polymer Electrolyte Layer: LiPF ₆ was dissolved in a mixed solvent of propylene carbonate and ethylene carbonate at a volume ratio of 1: 1 by dissolving 1.22 mol / l of LiPF _6, and 2,4,4 was used as a polymerization initiator.
6-trimethylbenzoyldiphenylphosphine oxide (Lucillin TPO (trade name), manufactured by BSF Japan Co., Ltd.) was previously added and dissolved at 2% by weight based on the monomer component, and dipentaerythritol hexaacrylate was used there. Ten minutes before the start, the mixture was added to a concentration of 7% by weight and mixed to prepare an electrolyte solution containing a gelling component. Hereinafter, the electrolytic solution containing the gelling component is referred to as “gelling component-containing electrolytic solution”.

The gelled component-containing electrolyte was absorbed by the positive electrode unit and the negative electrode unit under reduced pressure, respectively. The positive electrode unit and the negative electrode unit impregnated with the gelled component-containing electrolyte were placed in a polyethylene bag. The bag was sealed.

From both sides of a bag containing a positive electrode unit and a bag containing a negative electrode unit impregnated with the gelling component-containing electrolyte, Fusion UV Systems Japan Co., Ltd.
UV light was applied for 10 seconds at an illuminance of 1 W / cm ² using a UV light irradiator manufactured by KK to produce a gel polymer electrolyte layer having a support built in around the positive and negative electrodes.

The positive electrode and the negative electrode having the gel polymer electrolyte layer formed around them as described above are respectively taken out of the bag, and the lead is blown with hot air at 150 ° C. to peel off the thermal release tape from the lead. Then, five negative electrodes and four positive electrodes were alternately laminated to form a laminated electrode group. A laminate film having a three-layer structure composed of a nylon film, an aluminum film, and a modified polyolefin film was prepared as a package for covering the above-mentioned laminated electrode group.

In the positive electrode and the negative electrode in which the gel-like polymer electrolyte layer is formed on the periphery as described above, when the positive electrode unit is impregnated with the gelling component-containing electrolyte, the gelling component-containing electrolyte is made of a porous nonwoven fabric. And then into the voids inside the positive electrode mixture layer of the positive electrode and the voids inside the negative electrode mixture layer of the negative electrode, where polymerization and gelation take place. Into a gelled polymer electrolyte.

The polymer concentration in the polymer electrolyte of the polymer electrolyte layer formed around the positive electrode as described above and the polymer concentration in the polymer electrolyte of the positive electrode were analyzed by extracting unreacted monomers by a solvent extraction method. The polymer electrolyte layer (that is, the portion of the support impregnated in the nonwoven fabric) had a polymerization rate of 97% and a polymer concentration of 6.8.
% In the polymer electrolyte of the positive electrode.
The polymer concentration on the positive electrode surface was 4.7% by weight, and the polymer concentration near the current collector of the positive electrode was 3.8% by weight. Similarly, the polymer concentration in the polymer electrolyte of the polymer electrolyte layer formed around the negative electrode and the polymer concentration in the polymer electrolyte of the negative electrode were determined in the same manner as in the case of the positive electrode. The non-woven fabric impregnated with the polymer has a polymerization rate of 95%, a polymer concentration of 6.7% by weight, a degree of polymerization of 64% in the polymer electrolyte of the negative electrode, and a polymer concentration of 4.5% by weight on the surface of the negative electrode.
And the polymer concentration in the vicinity of the current collector of the negative electrode was 3.6% by weight.

In the solvent extraction method described above, a polymer electrolyte layer or an electrode is immersed in a mixed solvent of ethylene carbonate and propylene carbonate for 24 hours to extract residual monomers, and the amount thereof is determined by ultraviolet absorbance. This is a method for obtaining the polymer concentration in the polymer electrolyte of the electrode by measuring the concentration by separating the electrode into the surface side and the current collector side. Non-woven fabrics have a high porosity and uniform penetration and polymerization of the gelling component, so there is no substantial difference in polymer concentration between the front and back surfaces.However, the electrode controls the penetration rate of the gelling component in the mixture layer. There is a difference in the degree of UV radiation between the inside and the surface of the electrode that can be controlled by changing the density, and the polymer concentration inside the electrode is slightly inferior to the surface. Is considered to be a different cause.

A laminate of the positive electrode lead portion (a laminate of four lead portions composed of exposed portions of four aluminum foils) in the above-mentioned laminated electrode group was made of aluminum 2 mm thick and 3 mm wide. A nickel ribbon having a thickness of 40 μm is stacked as a positive electrode terminal, a 947M ultrasonic oscillator manufactured by Branson is used as a welding machine, welding time is 1 sec, pressure is 3.2 kg / cm ² , and amplitude is Welding was performed under 85% conditions. The position of the welded portion was made to coincide with the seal portion when the laminated electrode group was packaged with a package. Similarly to the above, a negative electrode lead laminate (a laminate of five lead portions composed of five exposed portions of copper foil) in the laminated electrode group was made of copper having a thickness of 100 μm and a width of 3 mm. , And a nickel ribbon having a thickness of 40 μm is stacked as a negative electrode terminal, using a welding machine similar to the above, for a welding time of 1 sec and a pressure of 4 k.
Welding was performed under the conditions of g / cm ² and 100% amplitude. The position of this welded portion was also set to match the sealed portion when the laminated electrode group was packaged with a package. Thereafter, the laminated electrode group was packaged with a package and sealed, thereby producing a laminated polymer electrolyte battery.

The width of the above welded portion was 2 mm on both the positive electrode side and the negative electrode side, and the width of the sealing portion of the outer package was 4 mm in each case.

Next, the structure of the polymer electrolyte battery will be described with reference to the drawings. In describing the structure, first, a positive electrode having a polymer electrolyte layer formed thereon as described above (hereinafter referred to as " A negative electrode having a polymer electrolyte layer formed thereon (hereinafter referred to as a “polymer electrolyte layer holding negative electrode”) will be described below. As shown in FIG. The positive electrode 10 has a support 3 a around the positive electrode 1.
Is formed by producing a gel-like polymer electrolyte layer 3 containing the following.

As shown in FIG. 2, the negative electrode 20 holding a polymer electrolyte layer is formed by producing a gel-like polymer electrolyte layer 3 having a support 3a built around the negative electrode 2.

As described above, these positive electrode 1 and negative electrode 2
In this case, the gelled component-containing electrolyte solution penetrates into the pores inside the mixture layer, where polymerization and gelation are carried out to form a gel-like polymer electrolyte. Are not shown because they are difficult to show.

Then, the polymer electrolyte holding positive electrode 10
Are laminated with five sheets of the polymer electrolyte holding negative electrode 20,
A stacked electrode group is configured as shown in FIG. That is, 1
The fifth sheet of the polymer electrolyte holding negative electrode 20 and the fifth sheet of the polymer electrolyte holding negative electrode 20 are respectively arranged in the outermost layer, and between them, four sheets of the polymer electrolyte holding cathode 10 and three sheets of the polymer electrolyte holding negative electrode 20 are alternately arranged. It is laminated. Then, between the polymer electrolyte holding positive electrode 10 and the polymer electrolyte holding negative electrode 20, as shown in FIG.
The polymer electrolyte layer 3 formed around the positive electrode 1 and the polymer electrolyte layer 3 formed around the negative electrode 2 between the positive electrode 1 and the negative electrode 2 form a polymer electrolyte layer having a sufficient thickness with them. Thereby, the positive electrode 1 and the negative electrode 2 are sufficiently separated.

The battery was constructed by combining the above-described stacked electrode group with the one shown in FIG.
As shown in the figure, the package is formed by sealing with a package 4 made of a laminate film having a three-layer structure of a nylon film-aluminum film-modified polyolefin film. In this battery, the positive terminal 5 and the negative terminal 6 are external terminals.

FIG. 5 schematically shows the connection between the laminate of the aluminum lead portions 1c of the positive electrode 1 of the battery shown in FIG. 3 and the positive electrode terminal 5 and the vicinity thereof. Is performed at the sealing portion 4a. That is, the two exterior bodies 4 are used, and the sealing is performed by heat-sealing the modified polyolefin film of the laminate film used as the exterior body 4. The connection with the terminal 5 is made by reinforcing the laminate of the lead portions 1c with the reinforcing plate 7, and the reinforcing plate 7
(Ie, the connection between the laminate of the lead portion 1c and the positive electrode terminal 5 is made by welding via the reinforcing plate 7), and the welding is performed by the sealing portion of the exterior body 4. 4a, the connection part of which is located in the region of the sealing part 4a of the exterior body 4.

Reference numeral 4b denotes a seal layer formed by melting the innermost modified polyolefin film of the outer package 4 by heating. The seal layer 4b corresponds to the sealing portion 4a of the outer package 4. The airtightness inside the battery is maintained by the layer 4b.

As shown in FIG. 4, the positive electrode 1 is formed by forming a positive electrode mixture layer 1b on both surfaces of a current collector 1a made of aluminum, and a polymer electrolyte layer 3 is formed around the positive electrode 1. I have. The negative electrode 2 is a current collector 2 made of copper foil.
a, a negative electrode mixture layer 2b is formed on both surfaces of the negative electrode 2a.
A polymer electrolyte layer 3 is formed around the. Further, the negative electrode 2 is not shown in FIG. 5, but as in the case of the positive electrode 1, a lead portion 2a is laminated, and a laminate of the lead portion 2a is schematically shown in FIG. The copper reinforcing plate 7 and the nickel negative electrode terminal 6 are welded and connected to each other at the sealing portion 4 a of the exterior body 4. However, the connection with the negative electrode terminal 6 on the negative electrode 2 side does not necessarily need to be made at the sealing portion of the exterior body. In addition, FIGS. 1 to 5 are schematic views, and the dimensional ratios of the respective components are not always accurate. 1 and 2, the illustration of the current collector and the lead portion is omitted.

Example 2 The surroundings of the positive electrode and the negative electrode were not surrounded by a support made of nonwoven fabric.
After impregnating them with a gelling component-containing electrolytic solution having a dipentaerythritol hexaacrylate concentration of 4.5% by weight, the monomers were polymerized by irradiation with ultraviolet rays in the same manner as in Example 1 and gelled. When the polymer concentration in the polymer electrolyte in these electrodes was measured in the same manner as in Example 1, the polymerization rate was 98%, the polymer concentration on the surface of the positive electrode was 4.4% by weight, and the vicinity of the current collector of the positive electrode was The polymer concentration was 4.1% by weight, the polymer concentration on the surface of the negative electrode was 4.3% by weight, and the polymer concentration near the current collector of the negative electrode was 3.9% by weight.

A polybutylene terephthalate nonwoven fabric having a thickness of 60 μm and a basis weight of 25 g / m ² was used as a support and impregnated with a gelling component-containing electrolytic solution having a dipentaerythritol hexaacrylate concentration of 7% by weight. Thereafter, ultraviolet irradiation was performed in the same manner as in Example 1 to produce a polymer electrolyte layer.

The polymerization rate of the polymer in the polymer electrolyte in the polymer electrolyte layer was 100%, and the polymer concentration was 7% by weight.

Using the four positive electrodes, five negative electrodes, and seven polymer electrolyte layers, the negative electrode, the positive electrode, the positive electrode,. To form a laminated electrode group, and using the laminated electrode group, a laminated polymer electrolyte battery was produced as shown below.

That is, the laminate of the aluminum lead portions 1c of the positive electrode was reinforced by the aluminum reinforcing plate 7 in the same manner as in the first embodiment, and the aluminum reinforcing plate 7 was made of aluminum and had a thickness of 100 μm. Is connected by welding, the other end of the aluminum lead body is welded and connected as a positive terminal, and a laminate of a negative lead 2c made of copper is the same as in Example 1. Reinforced with a copper reinforcing plate, the copper reinforcing plate and one end of a copper lead body having a thickness of 100 μm are connected by welding, and the other end of the copper lead body is welded to a negative electrode terminal. A laminated polymer electrolyte battery was produced in the same manner as in Example 1, except that the battery was connected by a connection.

The connection between the aluminum lead body of the positive electrode of the battery and the positive electrode terminal by welding is performed at the sealed portion of the exterior body, and the width of the connection portion is 2 mm and the width of the sealed portion is 4 mm. The connection between the copper lead body of the negative electrode and the negative electrode terminal by welding is also performed at the sealed portion of the exterior body, and the width of the connection portion is 2 mm and the width of the sealed portion is 4 mm.

FIG. 6 schematically shows the connection between the aluminum lead and the positive electrode terminal 5 connected to the laminate of the positive electrode lead of the battery of Example 2 and the vicinity thereof. The connection between the lead body 8 and the positive electrode terminal 5 is made at the sealing portion 4 a of the exterior body 4. That is, also in the second embodiment, as in the first embodiment, two exterior bodies 4 are used, and the seal is formed by heat-sealing the modified polyolefin film of the laminated film used as the exterior body 4. The connection between the aluminum lead body 8 connected to the laminate of the lead body 1c of the positive electrode 1 and the positive electrode terminal 5 is performed at the sealing portion 4a of the exterior body 4, and the connection is made by the exterior body. 4 is located in the area of the sealing portion 4a. The difference between the battery of the second embodiment and the battery of the first embodiment is that the connection between the laminate of the lead portions 1c of the positive electrode 1 and the lead body 8 is made on the inner side (from the sealing portion 4a of the exterior body 4). (Internal side of the battery), and the connection between the lead body 8 and the positive electrode terminal 5 is made at the sealing portion 4a of the exterior body 4. That is, on the inner side of the sealing portion 4a of the exterior body 4, the laminated body of the aluminum lead portions 1c of the positive electrode 1 is reinforced by the aluminum reinforcing plate 7, and the reinforcing plate 7 is provided with the aluminum lead body 8. One end is connected by welding, and the other end of the lead body 8 and the positive electrode terminal 5 are connected by welding at the sealed portion of the exterior body 4.

In this manner, the thickness of the sealing portion 4a of the exterior body 4 can be made smaller than in the first embodiment. The width of the connecting portion between the lead body 8 and the positive electrode terminal 5 is 2 mm, and the width of the sealing portion is 4 mm. Although not shown in FIG. 6, on the negative electrode 2 side, similarly to the positive electrode 1 side, the laminate of the lead portions 2 c of the negative electrode 2 is reinforced with a copper reinforcing plate. One end of the copper lead body is connected by welding, and the other end of the copper lead body is connected by welding at the sealing portion 4a of the negative electrode terminal 6 and the exterior body 4, and The width is 2 mm and the width of the sealing part is 4 mm.

The welding conditions for the reinforcing plate 7 for reinforcing the laminate of the lead portion 1c of the positive electrode 1 and the aluminum lead body 8 and the welding conditions for the lead body 8 and the positive electrode terminal 5 are the same as those of the first embodiment. The welding conditions of the reinforcing plate 7 for reinforcing the laminate of the aluminum lead portions 1c and the positive electrode terminal 5 are the same, and the reinforcing plate for reinforcing the laminate of the lead portions 2c of the negative electrode 2 and a copper lead And the welding conditions between the lead body and the negative electrode terminal are the same as the welding conditions between the negative electrode terminal 6 and the reinforcing plate for reinforcing the laminate of the copper lead portions 2c of the first embodiment.

Comparative Example 1 A laminated polymer electrolyte battery was produced in the same manner as in Example 1, except that the polymer concentration in the polymer electrolyte of the positive electrode, the negative electrode and the polymer electrolyte layer was all 7% by weight.

Comparative Example 2 A laminated polymer electrolyte battery was produced in the same manner as in Example 1, except that the polymer concentration in the polymer electrolyte of the positive electrode, the negative electrode and the polymer electrolyte layer was all 5% by weight.

With respect to the batteries of Examples 1 and 2 and Comparative Examples 1 and 2, load characteristics and electrolyte retention after storage were examined. Table 1 shows the results.

The above load characteristics are as follows: when the battery is charged at a constant current and a constant voltage of 4.2 V and 0.2 C for 8 hours, discharged to 2.75 V at 1 C and 0.2 C, respectively, the discharge capacity is measured, and the battery is discharged at 1 C. Is calculated by dividing the discharge capacity at 0.2 C by the discharge capacity at the time of discharge at 0.2 C [(discharge capacity at 1 C / discharge capacity at 0.2 C) × 100]. The retention of the electrolyte after the storage was performed by disassembling the battery after storing the battery at 60 ° C. for 20 days, visually observing the inside, and examining whether or not the electrolyte was released.

[0070]

[Table 1]

As is evident from the results shown in Table 1, Examples 1 and 2 exhibited excellent load characteristics, and exhibited stable electrolyte retention without liberation of the electrolyte even after storage at 60 ° C. for 20 days. Was.

On the other hand, in Comparative Example 1, the load characteristics were deteriorated because the polymer concentration in the polymer electrolyte was high, although the electrolyte solution had good retention after storage. In Comparative Example 2, the load characteristics were good,
The electrolyte was liberated due to the storage, and there was a problem in the deterioration of the battery characteristics and the resistance to liquid leakage due to the storage.

When the polymer electrolyte is gelled, other than the case described in the above embodiment, for example, a polymer gelled, a radical polymerizable unsaturated polyester, or a radical polymerizable acrylic epoxy may be used. Photocurable resins such as acrylates, urethane acrylates, polyester acrylates, alkyd acrylates, and silicon acrylates may be gelled using ultraviolet rays or electron beams.

[0074]

As described above, according to the present invention, it is possible to provide a highly reliable polymer electrolyte battery having excellent load characteristics and free of electrolyte solution during storage.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a polymer electrolyte holding positive electrode used in a polymer electrolyte battery according to Example 1 of the present invention.

FIG. 2 is a cross-sectional view schematically showing a polymer electrolyte holding negative electrode used in the polymer electrolyte battery of Example 1 of the present invention.

FIG. 3 is a cross-sectional view schematically showing one example of the polymer electrolyte battery of Example 1 of the present invention.

FIG. 4 is an enlarged view of a main part of a stacked electrode group in the battery shown in FIG.

5 is a cross-sectional view schematically showing a connection portion between a laminate of a lead portion of a positive electrode of the battery shown in FIG. 3 and a positive electrode terminal serving as an external terminal and the vicinity thereof.

FIG. 6 is a cross-sectional view schematically showing a connection portion between a lead body connected to a laminate of a lead portion of a positive electrode of a polymer electrolyte battery according to a second embodiment of the present invention and a positive electrode terminal as an external terminal, and the vicinity thereof; .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Aluminum foil 1b Positive electrode mixture layer 1c Lead part 2 Negative electrode 2a Copper foil 2b Negative electrode mixture layer 2c Lead part 3 Polymer electrolyte 4 Outer body 4a Sealing part 5 Positive terminal 6 Negative terminal 7 Reinforcement plate 8 Lead body 10 Polymer electrolyte Retained positive electrode 20 Polymer electrolyte retained negative electrode

Claims (3)

[Claims] At least one of a sheet-like positive electrode and a copper current collector having a positive electrode mixture layer on at least one surface of an aluminum current collector and containing the polymer electrolyte in the positive electrode mixture layer Having a plurality of sheet-shaped negative electrodes and a plurality of sheet-shaped polymer electrolyte layers each having a negative electrode mixture layer on the surface thereof and containing a polymer electrolyte in the negative electrode mixture layer, and covering the same with an outer package. In the battery, the concentration of the polymer in the polymer electrolyte of the at least one electrode of the polymer electrolyte layer and the positive electrode or the negative electrode was set to the highest concentration at the portion farthest from the electrode, and set to the lowest concentration at the portion in contact with the current collector of the electrode. A polymer electrolyte battery, comprising: 2. The polymer electrolyte battery according to claim 1, wherein the maximum concentration of the polymer in the polymer electrolyte is 6 to 9% by weight, and the minimum concentration is 3 to 5% by weight. 3. The method according to claim 1, wherein the concentration of the polymer in the polymer electrolyte outside the electrode is substantially constant, and the concentration of the polymer in the polymer electrolyte inside the electrode changes from the surface toward the current collector. Polymer electrolyte battery.