JPH10154415A - Polymer solid-state electrolyte, lithium secondary battery using it, and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer solid-state electrolyte having small internal resistance and a good preservation characteristic by using a gel electrolyte having good adhesiveness with respect to a current collector or an electrode. SOLUTION: The polymer contains a vinylidene fluoride copolymer as a principal chain and polyvinylidene fluoride as a side chain, the principal chain is made of rubber, the side chain is made of a crystal resin, and this polymer has resilience and a proper crystal property. When a gel electrolyte is formed with this polymer, electrolyte salt, and a solvent, a large quantity of the electrolyte salt and solvent can be contained in an amorphous portion, and high conductivity is obtained. The strong gel electrolyte is obtained due to a proper crystal portion. The gel electrolyte can be used in a wide temperature range, from a low temperature to a high temperature because it has good chemical resistance and a high melting point. Since this gel electrolyte has resilience, it is superior in adhesiveness to an electrode or a current collector, and its boundary resistance is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid polymer electrolyte and an electrode used in a lithium secondary battery and an electric double layer capacitor, and a lithium secondary battery and an electric double layer capacitor using the polymer solid electrolyte and the electrode. , EL elements.

[0002]

2. Description of the Related Art Secondary batteries used in notebook personal computers, video cameras, mobile phones and the like are required to have a large capacity and a good charge / discharge cycle life. Conventional secondary batteries include lead-acid batteries, nickel-cadmium batteries,
Nickel-metal hydride batteries have been used, but lithium secondary batteries have been put to practical use as smaller and higher capacity batteries.

For example, Japanese Patent Application Laid-Open No. 63-121260 describes a secondary battery using a non-aqueous electrolyte, LiCoO 2 and / or LiNiO 2 as a positive electrode, and carbon as a negative electrode. In this secondary battery, for example, in the case of a negative electrode, lithium ions penetrate between the layers of the carbon hexagonal mesh surface to receive electrons during charging, and lithium ions between the carbon layers release electrons during discharging to ionize again. Such a lithium secondary battery is called a lithium ion secondary battery, which is small in size, has a large capacity, and is safe because there is no need to use highly reactive metallic lithium. Is big.

[0004] An electrode used in a lithium secondary battery is manufactured by fixing an active material such as a carbon material powder or a lithium composite oxide powder to the surface of a current collector made of copper foil, aluminum foil, or the like. Specifically, an active material powder or the like is dispersed in a binder solution and applied to the current collector surface. The binder is required to have the following characteristics.

In the battery assembling process, the coating of the active material does not detach from the current collector and has an adhesive strength that does not cause cracking. The coating does not dissolve in the electrolytic solution. Without detaching from
It has adhesive strength that does not cause cracks, etc.It shows sufficient adhesive strength with a small amount of addition.It is not oxidized and reduced within the operating voltage range.It does not dissolve in the organic solvent used for the electrolytic solution, and it goes to the surface of the current collector. Dissolve in the solvent used when applying

In JP-A-63-121260, polyvinylidene fluoride (PVDF) is used as a binder.
Is used. However, in order to increase the adhesive strength, it is necessary to add a large amount of polyvinylidene fluoride. However, since the binder does not contribute to the battery capacity, the battery capacity tends to be insufficient. In addition, since polyvinylidene fluoride is dissolved in the non-aqueous solvent of the electrolytic solution, there is a problem that even if it is added in a large amount, repeated charge / discharge causes peeling or cracking of the coating film, thereby reducing the battery capacity.

Further, since PVDF is a crystalline resin, various problems occur in the actual battery manufacturing process. For example, P
There is a step of applying a coating solution in which an active material is dispersed in a VDF solution to a current collector (for example, a copper foil) and drying the same to manufacture an electrode. In this step, if the drying speed or the like is inappropriate, P
Since the contraction rate of the VDF is significantly different from the contraction rate of the current collector, the electrode mixture layer is separated from the current collector. Problems such as curling of the electrodes occur even if they do not separate. In addition, even if there is no problem immediately after coating and drying, the electrode mixture layer may gradually peel off from the current collector with the lapse of time due to internal stress remaining in the electrode. Furthermore, Japanese Patent Publication No. 8-4007 proposes a fluoropolymer copolymer containing PVDF, but also has the same problem as PVDF.

Various other binders have been used so far. Among them, a preferable example is a crosslinkable polymer. In particular, those crosslinked using a polyamine, a polyol or a peroxide as a crosslinking agent, for example, vinylidene fluoride-6-fluoropropylene copolymer, vinylidene fluoride-6-fluoropropylene-4fluoroethylene copolymer, Tetrafluoroethylene-
Propylene copolymer, tetrafluoroethylene-propylene-
There are those obtained by crosslinking at least one kind of fluorine rubber such as a vinylidene fluoride copolymer and a perfluoro fluorine rubber with the crosslinking agent. The amount of the crosslinking agent added is usually 0.5 to 10 parts by weight, based on 100 parts by weight of the compound to be crosslinked.
Preferably it is about 1 to 5 parts by weight.

A fluorine-containing compound,
Crosslinked by radiation such as β-rays or γ-rays, for example,
There is also one obtained by crosslinking at least one kind of polyvinylidene fluoride, a vinylidene fluoride-6-propylene copolymer, and a fluorine-containing thermoplastic rubber by radiation. These are described in, for example, the Chemical Society of Japan No. 4, P686,1976 and IN
DUSTRIAL AND ENGINEERING CHEMISTRY, VOL.49, No.10, P1
687, 1957 and the like.

There is also a proposal that polyvinylidene fluoride grafted with a silane compound is crosslinked with water and used. The silane-crosslinked polyvinylidene fluoride is described, for example, in JP-A-2-115234.

It is stated that the crosslinked polymer may be used as a mixture of two or more kinds. Also, in addition to the crosslinked polymer, polymethyl methacrylate (PM
MA) or other high molecular compounds such as polycarbonate (PC) may be contained, but these may be included in the entire binder.
The content is about 5% by volume or less.

Although the above-mentioned crosslinked polymer is preferable as a binder, a new crosslinking step is required for practical use, which has been a problem in production.

By the way, most of the conventional batteries on the market use a so-called electrolytic solution in which an electrolyte salt is dissolved in a liquid solvent as an electrolyte. Batteries using an electrolytic solution have the advantage of low internal resistance, but, on the other hand, have the problem of liability to leak and ignition. For such problems, studies on electrolytes containing no solvent, that is, solid electrolytes, have been conducted for many years. For example, a system in which an electrolyte salt is dissolved in a polymer is known. However,
Such a solid electrolyte containing no solvent (for example, a solution obtained by dissolving a lithium salt in polyethylene oxide) has a low conductivity (10 ^-4 S · cm ^-1 or less), and has not been put to practical use. On the other hand, a gel polymer solid electrolyte composed of a polymer, an electrolyte salt and a solvent has recently been spotlighted.

Some of such gel-like polymer solid electrolytes (hereinafter referred to as "gel electrolytes") have a conductivity close to that of a liquid and exhibit a value on the order of 10 ^-3 S · cm ^-1 .

For example, US Pat. No. 5,296,318 discloses vinylidene fluoride (VDF) with 8 to 25% by weight of 6%.
Copolymer of propylene fluoride (HFP) [P (VDF-
HFP)], the solution in which the lithium salt is dissolved is 20-70.
A gel electrolyte having a weight percent content is disclosed. The conductivity of this gel electrolyte reaches 10 ⁻³ S · cm ⁻¹ . originally,
Polyvinylidene fluoride (PVDF) is a crystalline polymer and a polymer having relatively excellent chemical resistance. That is, some solvents dissolve PVDF well, but they do not dissolve in any solvent, and it is one of the fluororesins that is easy to use. In fact, PVDF is used as a binder for positive and negative electrode active materials of commercially available lithium ion secondary batteries. PVD described in the above patent
F is a copolymer of VDF and HFP, where HFP is PVD
The crystallinity of F is reduced. Such VDF-H
The FP copolymer can contain a large amount of a solvent, can suppress the precipitation of lithium salt crystals, and can produce a stronger gel electrolyte.

[0016]

SUMMARY OF THE INVENTION However, VDF
In the -HFP copolymer, since HFP lowers the crystallinity of PVDF, it is possible to obtain the above-described high electrical conductivity, but such a polymer structure is essentially included. This has the disadvantage of lowering chemical resistance and lowering the melting point. For example, PVDF manufactured by Elf Atochem (
The melting point of a homopolymer (trade name: KYNAR700 series) is 170 ° C.
The melting point of a DF-HFP copolymer, for example, KYNAR2801, is 145 ° C. Since the decrease in chemical resistance means that the VDF-HFP copolymer is easily dissolved in the battery electrolyte, the storage characteristics of the battery are deteriorated when such a VDF-HFP copolymer is used for the battery. For example, if the battery is at room temperature or
(60 ° C., 60 ° C., 80 ° C., 100 ° C.), capacity deterioration occurs, and in extreme cases, internal short circuit occurs.
In addition, the lowering of the melting point limits the use at high temperatures and deteriorates the high-temperature storage characteristics as described above.

Also, as in US Pat. No. 5,296,318, for example, a battery electrode using a gel electrolyte is formed by using a composition comprising an electrode active material and a gel electrolyte to increase the adhesion between the electrode and the gel electrolyte to increase the interface resistance. Is smaller. However, in the electrode disclosed in this patent, the adhesiveness to the current collector to be applied is low, and the electrode mixture may peel off after the application. This is considered to be because PVDF has a large shrinkage rate when it is applied and dried because it is a crystalline resin, and is detached from the current collector. That is, the conductivity increased, but the adhesion to the current collector was not sufficient. For this reason, when the gel electrolyte disclosed in the patent is used, it is impossible to form electrodes by a simple coating process, and it is difficult to continuously form a coating film. Therefore, the electrode has been configured using a metal mesh as a support. Further, there is an electric double-layer capacitor in which the above-mentioned binder material is used as an electrode material, and when the electric double-layer capacitor is used as a polarizable electrode material, it is desired to improve the properties of the binder material similarly to the lithium secondary battery. It is about to be done. Further, even for electric double layer capacitors, better gel electrolytes are required.

Further, an EL element having a light-emitting layer containing a fluorescent material and a binder is known, and the development of a binder material in this case is also desired.

It is an object of the present invention to improve the adhesiveness to a current collector or an electrode, which is a drawback of the conventional gel electrolyte, to reduce the internal resistance, to achieve good storage properties, and to enable continuous lamination of a coating film. Polymer solid electrolyte and lithium 2 using the same
Another object of the present invention is to provide a secondary battery or an electric double layer capacitor.

In addition, an electrode that does not require a new crosslinking step in the assembling step, prevents the positive electrode material and the negative electrode material from falling off, and has a small capacity reduction when charging and discharging are repeated, a lithium secondary battery using this electrode, It is to provide an electric double layer capacitor.

It is a further object of the present invention to provide an EL device having good adhesion to electrodes, low internal resistance, and good storage stability.

P shown in US Pat. No. 5,296,318
In order to improve the drawbacks of the (VDF-HFP) -based gel electrolyte and the battery using the same, the present inventors studied various polymers, and found that the vinylidene fluoride copolymer shown in the present invention had a main chain. The polymer having polyvinylidene fluoride in the side chain has excellent adhesion, and P (VDF-
(HFP) system.

[0023]

That is, the object of the present invention is achieved by the following constitutions (1) to (16). (1) A polymer solid electrolyte containing a polymer having a vinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain, an electrolyte salt and a solvent. (2) The polymer solid electrolyte according to (1), wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. (3) A polymer solid electrolyte containing a polymer alloy of the polymer of the above (1) and polyvinylidene fluoride, an electrolyte salt and a solvent. (4) A lithium secondary battery having a polymer solid electrolyte containing a polymer having a polyvinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain, an electrolyte salt and a solvent. (5) The lithium secondary battery according to (4), wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. (6) The lithium secondary battery according to (4), further comprising a polymer solid electrolyte in which the polymer is contained as a polymer alloy with polyvinylidene fluoride. (7) A lithium secondary battery in which at least one of the electrodes is a composition of a polymer having a vinylidene fluoride copolymer as a main chain, polyvinylidene fluoride in a side chain, and an electrode active material. (8) The lithium secondary battery according to the above (7), comprising a polymer solid electrolyte containing a polymer having polyvinylidene fluoride as a side chain, a polymer having a vinylidene fluoride side chain, an electrolyte salt and a solvent. (9) The lithium secondary battery according to (8), wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride. (10) The above-mentioned (7), wherein a carbon material, a lithium metal, a lithium alloy or a lithium oxide material is used as a negative electrode active material, and a compound or a carbon material capable of intercalating / deintercalating lithium ions is used as a positive electrode active material. Lithium secondary battery.

(11) a polymer having a vinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain;
An electric double layer capacitor having a polymer solid electrolyte containing an electrolyte salt and a solvent. (12) The electric double layer capacitor according to (11), wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride. (13) The electric double layer capacitor according to the above (11), wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride. (14) The electric double-layer capacitor according to (11), wherein at least one of the polarizable electrodes has a main chain of a vinylidene fluoride copolymer and contains a polymer having polyvinylidene fluoride in a side chain. (15) The electric double layer capacitor according to the above (14), wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride. (16) The electric double layer capacitor according to (14), wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride.

A polymer having a vinylidene fluoride copolymer as a main chain and polyvinylidene fluoride as a side chain has elasticity and moderate crystallinity because the main chain is made of rubber and the side chain is made of a crystalline resin. Have sex. When a gel electrolyte is composed of such a polymer, an electrolyte salt and a solvent, a large amount of the electrolyte salt and the solvent can be contained in the amorphous portion, and high conductivity can be obtained. In addition, a moderately crystalline portion provides a strong gel electrolyte. Furthermore, since it has good chemical resistance and high melting point, it becomes a gel electrolyte that can be used in a wide temperature range from low to high temperatures.

Further, since this gel electrolyte has elasticity, it has excellent adhesion to an electrode or a current collector and has a low interface resistance. Further, by using this gel electrolyte for a lithium secondary battery, the battery has a low internal resistance and can be used in a wide temperature range from low to high. Similar effects can be obtained with an electric double layer capacitor.

In order to fix the coatings of the positive and negative electrode active materials of the electrode to the surface of the current collector, the binder containing the polymer whose main chain is a vinylidene fluoride copolymer and whose side chain is polyvinylidene fluoride is used. Used. Such a polymer has a rubber-like main chain and a crystalline side chain, has flexibility in a rubbery state at around normal temperature, and has a side chain of crystalline PVDF, and the main chain is preferably fluorinated. Since it is a copolymer of vinylidene (VDF) and ethylene trifluoride chloride (CTFE), it has excellent chemical resistance. That is, it has an intermediate property between fluororubber and PVDF.

When this polymer material is used as a binder for an electrode, it has the following advantages. When an electrode is manufactured by applying a coating solution in which a battery active material is dispersed in a solution of the polymer material to a current collector and drying the same, the polymer material has low crystallinity, so that the polymer material has a low shrinkage rate, and Good adhesion to the electrode mixture layer. Also, the electrode is flexible, and the electrode mixture layer does not fall off even when bent. Furthermore, since it has excellent chemical resistance as described above, it does not dissolve in the battery electrolyte, so even when used as a binder for electrodes or a matrix material for gel electrolyte, it has excellent charge / discharge cycle life. Batteries can be manufactured.

In addition, since the active materials or the current collector and the active material can be satisfactorily bonded to each other, the contact resistance is reduced,
Even with an electrode having a thick electrode mixture layer, a predetermined potential can be given to the active material. Therefore, a potential required for intercalation and deintercalation can be secured, and a high-performance, high-capacity lithium secondary battery can be obtained.

Also, when applied to the electrodes of an electric double layer capacitor, good characteristics are exhibited.

That is, according to the present invention, a polymer solid electrolyte having a low internal resistance and good storage characteristics by using a gel electrolyte having good adhesion to a current collector and an electrode. A secondary battery and an electric double layer capacitor can be provided.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. The polymer solid electrolyte (sometimes called a gel electrolyte) of the present invention contains a polymer having a polyvinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain, an electrolyte salt, and a solvent. Preferably, the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride (VDF) and ethylene chloride trifluoride (CTFE). Further, since the polymer and PVDF have good compatibility, a polymer alloy of the polymer and PVDF may be used as the polymer of the gel electrolyte. By using such a gel electrolyte for a lithium secondary battery or the like, good storage stability, charge / discharge characteristics, and high temperature resistance can be obtained.

A polymer having such a structure is sold by Central Glass Co., Ltd. as a soft fluororesin, trade name "Sefuralsoft". Cefralsoft has a main chain of vinylidene fluoride (VDF) and ethylene chloride trifluoride (CTFE) copolymer, and a side chain of polyvinylidene fluoride. The proportion of the main chain in the whole is 45 to 85% by weight, more preferably 50 to 80% by weight, especially 55 to 7% by weight.
5% by weight, more preferably about 60 to 70% by weight,
The proportion of the side chains in the whole is 55 to 15% by weight, more preferably 50 to 20% by weight, particularly about 45 to 25% by weight, and further preferably about 40 to 30% by weight. V in the main chain
The proportion of DF is 65 to 95 mol%, more preferably 70 to 95 mol%.
90 mol%, preferably about 75 to 85 mol%,
The proportion of TFE is 35 to 5 mol%, more preferably 30 to 5 mol%.
It is preferably about 10 mol%, particularly about 25 to 15 mol%. Moreover, melting | fusing point is 155-170 degreeC, density is 1.7-1.9.
It is about.

In order to synthesize this polymer, vinylidene fluoride, a fluorinated monomer and an unsaturated peroxide are copolymerized according to a known method, and then the peroxy group in the main chain (backbone) resin is decomposed, The branch resin may be polymerized from the generated radicals, and a homopolymer of vinylidene fluoride may be graft-polymerized.

Here, the unsaturated peroxide is t-
There are unsaturated peroxyesters such as butyl peroxymethacrylate and unsaturated peroxycarbonates such as t-butylperoxyallylcarbonate.

Since the formed resin is a graft copolymer with a crystalline side chain resin, the hard segments of the crystalline resin aggregate to form physical cross-linking points in the rubber molecular chain (main chain). It is considered to have given. For this reason, it is non-oriented like a rubber-based material, and has good adhesion to the current collector and the electrode, so that the contact resistance is reduced, the internal resistance of the battery is reduced,
Good charge / discharge characteristics can be obtained. Furthermore, it does not dissolve in electrolytes such as ethylene carbonate and diethyl carbonate and has good storage characteristics. Furthermore, when used as a binder for an electrode, the adhesive strength to the current collector is strong, and as a result, the contact resistance is reduced, and a predetermined potential can be given to the active material. A necessary potential can be secured.

The gel electrolyte using the above polymer contains a vinylidene fluoride-based polymer, particularly a PVDF homopolymer, and may be a polymer alloy. Thereby, tensile strength and the like are improved. The content of the PVDF homopolymer is preferably the above-mentioned polymer: PVDF homopolymer = 90: 10% by weight to 50: 50% by weight.

Next, a specific method for producing a gel electrolyte will be described. The production is preferably carried out in a dry room or a glove box with low moisture. First, a polymer is dispersed and dissolved in a solvent. The solvent at this time may be appropriately selected from various solvents in which the polymer can be dissolved, and for example, N, N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like are preferably used. , In particular, N
-Methylpyrrolidone, N, N-dimethylformamide are preferred. The concentration of the polymer in the solvent is preferably 10
３０30% by weight.

In order to reduce the viscosity of the polymer solution, it is preferable to add methyl ethyl ketone. The dispersing and dissolving method is preferably 100 ° C or less, more preferably 5 ° C or less.
It is preferable to stir while heating to 0 to 100 ° C.

An electrolyte is added to the polymer solution. The content of the electrolyte is as follows: polymer: electrolyte = 50: 50% by weight to 2
0: 80% by weight is preferred. Examples of the solvent for the electrolyte include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,
Non-aqueous solvents such as 3-dioxolan, 4-methyldioxolan, γ-butyrolactone, sulfolane, 3-methylsulfolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, and ethyldiglyme are used.

As an electrolyte, when used for a lithium secondary battery, LiPF6, LiClO4, LiBF
4, LiCF3 SO3, (CF3 SO2) 2 NLi, L
A solution in which an electrolyte salt such as iAsF6 is dissolved is used.
Two or more of these may be used in combination, and the mixing ratio at that time is arbitrary. The concentration of the electrolyte salt in such a non-aqueous solvent-based electrolyte solution is preferably 0.5 to 3 mol / l.

A mixed solution of a polymer solution and an electrolytic solution (referred to as “gel electrolyte solution”) is applied on a substrate. This substrate may be anything as long as it is smooth. For example, polyester film, glass, polytetrafluoroethylene film, and the like. The means for applying the gel electrolyte solution to the substrate is not particularly limited, and may be appropriately determined according to the material and shape of the substrate. Generally, metal mask printing method,
Electrostatic coating, dip coating, spray coating, roll coating, doctor blade, gravure coating, screen printing, and the like are used. Thereafter, if necessary, a rolling treatment is performed by a flat plate press, a calender roll, or the like.

After coating, the solvent used when the polymer was dissolved (eg, N, N-dimethylformamide, boiling point 153)
(Hereinafter, abbreviated as DMF), a gel electrolyte film is obtained. The temperature at which DMF is evaporated may be room temperature, but may be heated. The resulting gel electrolyte is translucent and elastic.

The electrolytic solution may be mixed at the time of preparing the gel electrolyte solution as described above. Alternatively, the film may be impregnated with the electrolytic solution after preparing a film containing no electrolytic solution in advance. In order to increase the film strength and swelling property,
iO2 or the like can be used as a filler.

Lithium 2 using the gel electrolyte of the present invention
The structure of the secondary battery is not particularly limited, but is applied to a stacked battery, a cylindrical battery, and the like.

The electrode combined with the gel electrolyte is
Preferably, a composition of an electrode active material and a gel electrolyte is used.

The negative electrode is composed of a negative electrode active material such as a carbon material, a lithium metal, a lithium alloy or an oxide material. The positive electrode is formed of an oxide or a carbon material capable of intercalating / deintercalating lithium ions. It consists of such a positive electrode active material. By using such an electrode, a lithium secondary battery having excellent characteristics can be obtained.

The carbon material used as the active material is, for example,
Mesocarbon microbeads (MCMB), natural or artificial graphite, resin fired carbon material, carbon black,
What is necessary is just to select suitably from carbon fibers etc. These are used as powders. Of these, graphite is preferred, and its average particle size is 1 to 30 μm, particularly 5 to 25 μm.
m is preferred.

As the oxide capable of intercalating / deintercalating lithium ions, a composite oxide containing lithium is preferable. For example, LiCoO 2, LiM
n2O4, LiNiO2, LiV2O4 and the like. The average particle size of these oxide powders is 1 to 40 μm
It is preferred that it is about.

The electrode composition is such that the positive electrode has an active material: a conductive auxiliary agent:
Gel electrolyte = 30 to 90: 3 to 10:10 to 70% by weight
In the negative electrode, the range of active material: conductive auxiliary agent: gel electrolyte = 30 to 90: 0 to 10:10 to 70% by weight is preferable.

In the present invention, the above-described negative electrode active material and / or positive electrode active material, preferably both active materials, are preferably mixed in the above-mentioned gel electrolyte and adhered to the surface of the current collector.

The production of the electrode may be carried out in accordance with the production of the above-mentioned gel electrolyte. First, the active material and, if necessary, the conductive auxiliary are dispersed in the above-mentioned polymer binder solution to prepare a coating solution. The solvent used for the coating solution may be appropriately selected from the various solvents in which the binder can be dissolved. The concentration and viscosity of the coating liquid may be determined as appropriate according to the coating means.

The means for applying the coating liquid to the current collector is not particularly limited, and may be appropriately determined according to the material and shape of the current collector. Generally, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, and the like are used. Thereafter, if necessary, a rolling treatment is performed by a flat plate press, a calender roll, or the like.

The current collector may be appropriately selected from ordinary current collectors according to the shape of the device to be used, such as a battery and an electric double layer capacitor, and the method of disposing the current collector in the case. Generally, aluminum or the like is used for the positive electrode, copper or the like is used for the negative electrode.
Nickel or the like is used.

An electrode coating solution in which a conductive auxiliary agent, an active material, and the like are mixed is applied on a current collector such as a copper foil, a nickel foil, and an aluminum foil, and the solvent is evaporated to produce an electrode. The coating thickness is 50
It is preferable to set it to about 400 μm. Note that a metal foil, a metal mesh, or the like is usually used as the current collector. Although the metal mesh has a smaller contact resistance with the electrode than the metal foil, in the case of the gel electrolyte of the present invention, the metal foil has a sufficiently small contact resistance.

As described above, when the electrode contains the same gel electrolyte as the gel electrolyte, the adhesion to the gel electrolyte is improved, and the internal resistance is reduced. When lithium metal or a lithium alloy is used as the negative electrode active material, the composition of the negative electrode active material and the gel electrolyte may not be used.

When the electrode of the present invention is used for a battery using a solution-based electrolyte, the electrolyte is prepared by dissolving the electrolyte in a non-aqueous solvent. As the electrolyte, those described above may be used. As the non-aqueous solvent, for example, ethers, ketones, carbonates, and the like can be selected from organic solvents exemplified in JP-A-63-121260, and in the present invention, carbonates are particularly used. Is preferred.

Solution-based lithium 2 using electrode of the present invention
The structure of the secondary battery is not particularly limited, but is applied to a stacked battery or a cylindrical battery.

Further, the electrode of the present invention is also effective for an electric double layer capacitor.

The current collector used for the polarizable electrode may be a conductive rubber such as a conductive butyl rubber or the like, or may be formed by spraying a metal such as aluminum or nickel. A metal mesh may be provided.

An electric double layer capacitor is obtained by combining such a polarizable electrode with the above-mentioned gel electrolyte.

As the electrolyte salt, (C2H5) 4NBF4
, (C2H5) 3MeNBF4, (C2H5) 4PBF4 and the like.

The non-aqueous solvent used for the electrolytic solution may be various known ones, and propylene carbonate, ethylene carbonate, γ-
Butyrolactone, acetonitrile, dimethylformamide, 1,2-dimethoxyethane, sulfolane alone or in mixtures are preferred.

The concentration of the electrolyte in such a non-aqueous solvent-based electrolyte solution may be 0.1 to 3 mol / l.

As the insulating gasket, an insulator such as polypropylene or butyl rubber may be used.

The structure of the electric double-layer capacitor in which the gel electrolyte of the present invention is used is not particularly limited, but usually, a pair of polarizable electrodes are arranged via the gel electrolyte, and the polarizable electrode and the periphery of the gel electrolyte are usually arranged. An insulating gasket is arranged in the part. Such an electric double layer capacitor may be any type called a coin type, a paper type, a laminated type, or the like.

In the above example, the case where the electrode of the present invention is used for a lithium secondary battery or an electric double layer capacitor has been described. However, the application is limited to the electrode of such a secondary battery or electric double layer capacitor. Is not
Various changes and improvements are possible. For example, a change to an EL (electroluminescence) element is conceivable. That is, by using a polymer resin having a main chain of the above-described vinylidene fluoride copolymer and a side chain of polyvinylidene fluoride as a binder for the rare-earth fluorescent material of the dispersion type EL, the electrode surface (hole injection) can be obtained. Transport layer and electron injection / transport layer), and the production cost can be reduced.

[0068]

The present invention will be described more specifically with reference to the following examples. [Example 1] All operations were performed in an argon glove box. In a homogenizer container, N, N-dimethylformamide (DM
32.4 g of F) were added. In addition to this, a polymer, Cefralsoft G180F100 [manufactured by Central Glass Co., Ltd .: main chain is vinylidene fluoride (VDF) and ethylene chloride trifluoride (CT)
FE) Copolymer and the side chain is made of polyvinylidene fluoride. 65% by weight of main chain
And the ratio of side chains to the whole is 35% by weight. The ratio of VDF in the main chain was 80 mol%, and the ratio of CTFE was 20 mol%.
Mol%. The melting point of this polymer is 167 ° C. ]
10.8 g, and warm to 80 ° C. and 10,000 r
Dispersed and dissolved at pm for 30 minutes. Add DM to this solution
27.6 g of F was added and dispersed and dissolved at 80 ° C. and 10,000 rpm for 30 minutes. After standing to cool, 1
19.2 g of M LiPF6 / EC + PC was added. The 1M LiPF6 / EC + PC is obtained by dissolving 1M of LiPF6 as an electrolyte salt in a mixed solvent of EC (ethylene carbonate) and PC (propylene carbonate) at a volume ratio of 1: 1. This solution was stirred at 5000 rpm for 15 minutes to obtain a gel electrolyte solution. This gel electrolyte solution was applied to a polyethylene terephthalate (PET) film to a width of 50 mm with an applicator having a gap of 0.8 mm.
The mixture was left standing for 24 hours to evaporate DMF to obtain a translucent gel electrolyte composed of Sefralsoft G180F100 / LiPF6 / EC + PC.

This film was elastic and had sufficient strength to handle. The thickness of this film is 0.1
It was 8 mm. The charge composition at this time was G180F10
0: 1M LiPF6 / EC + PC = 36: 64% by weight
Met. FIG. 1 shows the temperature characteristics of the conductivity of the gel electrolyte. The conductivity was measured by an AC impedance measurement method using an LCR meter 428 manufactured by Hewlett-Packard Company.
It measured using 4A. The measurement was performed using a gel electrolyte with a diameter of 15 mm.
Then, the sheet was sandwiched between electrodes made of SUS304 having a diameter of 20 mm, and a resistance value of 10 KHz was measured. As a result, the conductivity at 25 ° C. was as high as 1.6 × 10 ⁻³ S · cm ^−1, and a high conductivity was obtained in a wide temperature range as shown in FIG.

Example 2 The gel electrolyte solution prepared in Example 1 above (Sefuralsoft G180F100 + DMF)
+ 1M LiPF6 / EC + PC), placed in a homogenizer container, placed 10.8 g of lithium cobaltate and acetylene black (HS-1 manufactured by Denki Kagaku Kogyo KK)
1.00 g) and dispersed at 12,000 rpm for 5 minutes at room temperature. Apply this coating solution to aluminum foil (30 mm long, 3 mm wide)
0mm, thickness 30μm) by metal mask printing machine
The sheet was printed in a circular shape of mm and left for 24 hours to evaporate DMF. The thickness of this electrode was 0.15 mm. This electrode was used as a positive electrode, and the polymer solid electrolyte film prepared in Example 1 was cut out to a diameter of 25 mm, and the diameter was 20 m.
m, a lithium foil having a thickness of 0.1 mm and a nickel foil (length 30 mm, width 30 mm, thickness 35 μm) were laminated in this order, and the periphery thereof was sealed with a polyolefin-based hot melt adhesive to produce a lithium secondary battery. The internal resistance of this battery was as small as 50Ω.

[Example 3] The gel electrolyte solution (Sefuralsoft G180F100 + DMF) prepared in Example 1 was used.
+ 1M LiPF6 / EC + PC) in a homogenizer container and graphite (SFG2, trade name, manufactured by Lonza)
5, 90% cumulative particle size 25 μm) and 8.89 g,
Dispersed at 12,000 rpm for 5 minutes at room temperature. This coating solution was printed on a copper foil (30 mm in length, 30 mm in width, 30 μm in thickness) in a circular shape having a diameter of 15 mm with a metal mask printer, and left for 24 hours to evaporate DMF. The thickness of this electrode is 0.15 mm
Met. This electrode was used as a negative electrode, and the polymer solid electrolyte film produced in Example 1 was cut out to a diameter of 25 mm, the positive electrode produced in Example 2 was laminated, and the periphery was sealed with a polyolefin hot melt adhesive. A lithium ion secondary battery was manufactured. The internal resistance of this battery is 20
It was as small as Ω.

[Embodiment 4] In the same manner as in Embodiment 1, G1
80F100: PVDF: 1M LiPF6 / EC + P
A gel electrolyte with C = 18: 18: 64% by weight was prepared. The PVDF used here was a homopolymer (KYNAR741 manufactured by Elf Atochem). 25
The conductivity at ° C. was as high as 3.0 × 10 ⁻³ S · cm ⁻¹ .

[Embodiment 5] In the same manner as in Embodiment 1, G1
80F100: 1M LiPF6 / EC + PC = 30:
A 70% by weight gel electrolyte was prepared. The conductivity at 25 ° C. was as high as 4.0 × 10 ⁻³ S · cm ⁻¹ .

Example 6 The gel electrolyte film prepared in Example 1 was replaced with 1M LiPF6 / EC + PC electrolyte 10
It was immersed in 0 ml, stored at 80 ° C., and examined for weight change. The results are shown in FIG. From FIG. 2, it was found that the gel electrolyte film of this example can hold more electrolyte than the gel electrolyte film of Comparative Example 3 described later.

[Embodiment 7] In the same manner as in Embodiment 1, G1
80F100: 1M (C2H5) 4 NBF4 / PC = 3
A gel electrolyte of 0: 70% by weight was prepared. The conductivity at 25 ° C. was as high as 1.5 × 10 ⁻³ S · cm ⁻¹ . (C2H5) 4 NBF4 is tetraethylammonium tetrafluoroborate.

Example 8 One side of activated carbon fiber cloth (manufactured by Gunei Chemical Industry Co., Ltd., product number ACC507-20) was sprayed with aluminum and cut into 15 mmφ, and this was cut into a 50 ml gel electrolyte solution prepared in Example 7. After immersion for 5 minutes, it was taken out and dried for 24 hours to obtain a polarizable electrode. A coin-shaped cell was produced by cutting a pair of polarizable electrodes and the gel electrolyte film produced in Example 7 into 20 mmΦ.
The cell was charged to 2 V at 1 mA and then discharged to 1 V. The discharge capacity was 1.5F.

Example 9 Sefralsoft G150F1
A gel electrolyte was prepared in the same manner as in Example 1 except that 00 (manufactured by Central Glass Co., Ltd.) was used. G150F100 has a higher melt viscosity than G180F100 used in Example 1. That is, the main chain is a VDF-CTFE copolymer and the side chain is PVDF. The main chain is 70% by weight, the side chain is 30% by weight, and 80% by mole of VDF and 20% by mole of CTFE in the main chain. With a melting point of 165 ° C.
The composition of the gel electrolyte is G150F100: 1M LiPF
6 / EC + PC = 34: 64% by weight. When this gel electrolyte was evaluated in the same manner as in Example 1, the temperature was 25 ° C.
Was as high as 3.0 × 10 ⁻³ S · cm ⁻¹ .
FIG. 1 shows the relationship between the conductivity of the gel electrolyte and the temperature. As is clear from FIG. 1, high conductivity is obtained in a wide temperature range.

Using this Sefralsoft G150F100, the electric double layer capacitor of Example 8 and Example 13
Produced the same result.

Comparative Example 1 A 200 ml Erlenmeyer flask was charged with tetrahydrofuran (T
HF) with 66.67 g and 1M LiPF6 / EC + PC
And stirred for 5 minutes. This mixed solvent was mixed with a VDF-HFP copolymer manufactured by Elf Atochem (trade name K).
11. YNAR2801, HFP content 10% by weight).
Add 15 g at room temperature for 15 minutes while boiling.
After stirring for minutes, a clear gel electrolyte solution was obtained.
This gel electrolyte solution was applied to a PET film in the same manner as in Example 1, dried at room temperature for 1 hour, and THF was evaporated. The charge composition is KYNAR2801: 1M LiPF6 / EC
+ PC = 36: 64% by weight. The resulting gel electrolyte had a mixture of a translucent portion and a white portion where the electrolyte salt was considered to be crystallized. 25 ℃ of this polymer solid electrolyte
Was 1.2 × 10 ⁻³ S · cm ⁻¹ .

Comparative Example 2 The gel electrolyte solution prepared in Comparative Example 1 (KYNAR2801 + THF + 1M LiPF)
6 / EC + PC), 50 g of lithium cobaltate (same as in Example 2) and 1.5 g of acetylene black (same as in Example 2) were placed in a homogenizer container, and dispersed at 12,000 rpm for 5 minutes. Was. The obtained coating solution was applied to an aluminum foil using a metal mask printer in the same manner as in Example 2, and allowed to stand at room temperature for 1 hour to evaporate THF. Thereafter, a lithium secondary battery was produced in the same manner as in Example 2, but the internal resistance was as large as 1000Ω and charge / discharge was impossible. When a load was applied to this cell, the internal resistance decreased, but was still as high as about 100Ω.

[Comparative Example 3] The gel electrolyte film prepared in Comparative Example 1 was replaced with a 1 M LiPF6 / EC + PC electrolytic solution 10
It was immersed in 0 ml, stored at 80 ° C., and examined for weight change. The results are shown in FIG. As shown in FIG. 2, the gel electrolyte film of this comparative example could not retain the electrolytic solution more than the gel electrolyte film of Example 6.

Example 10 D in a homogenizer container
MF 60.00g and Sefralsoft G180F100
20.00 g. While heating this to 60 ° C, 3
The dispersion was dissolved at 500 rpm to 7000 rpm for 40 minutes. 19.01 g of DMF was further added to this solution,
The mixture was dispersed and dissolved at 2500 ° C. for 30 minutes at 2500 rpm. Next, 59.12 g of high-purity natural graphite NG7 (manufactured by Kansai Thermochemical) and a kneader (Labo Plastmill manufactured by Toyo Seiki)
And put the previously prepared cefral soft solution into 18.66.
g and 7 g of DMF were added and kneaded at 100 rpm for 1 hour.
Add 30.00 g of this clay-like kneaded material to a beaker and add DMF
Was added and kneaded with a mixer at 700 rpm for 1.5 hours. The resulting coating solution was applied to a 12 mm square titanium plate (thickness: 1 mm) with a metal mask over an area of 10 mm × 10 mm. The coating solution was applied to a copper foil having a thickness of 15 μm, a width of 45 mm and a length of 150 mm using an applicator having a gap of 0.8 mm. These were vacuum-dried at 150 ° C. for 2 hours to remove the solvent. The composition of this electrode was Sefralsoft: Graphite = 6: 94 (% by weight). A titanium wire was spot-welded to the titanium plate as a lead to form an electrode. At this time, the thickness of the coating film was 0.2 to 0.3 mm.

A charge / discharge test was performed using this electrode as a working electrode. A lithium plate connected to a titanium wire was used for the counter electrode and the reference electrode, and an electrolytic solution obtained by dissolving 1 mol of lithium perchlorate in a mixed solvent of ethylene carbonate: diethyl carbonate (1: 1 by volume) was used. Using. 0 to 3 volts vs. Li / L at a constant current of 0.25 mA
Charge / discharge was performed in the range of i +. FIG. 3 shows a cross-sectional view of a cell for measuring charge / discharge characteristics. 1 is a glass beaker of 100 cm ³ , 2 is a silicon stopper, 3 is a working electrode, 4 is a counter electrode, 5 is a reference electrode, 8 is a Luggin tube, and 9 is an electrolyte.

A so-called cross-cut test was performed as an adhesion test on the material applied to the copper foil. Specifically, a multi-cross cutter (Model 295) manufactured by Eriksen West Germany was used to make 11 vertical and horizontal cut lines in the coating film, and peeling of the coating film in 100 squares formed. The ratio was checked. Table 1 shows the above results.

[0085]

[Table 1]

The result of the charge / discharge test was 2 g / g of graphite.
The charge capacity at the cycle is as large as 363 mAh / g,
The capacity deterioration rate represented by the following equation was as small as 0.5%, indicating good battery characteristics. Formula Capacity deterioration rate = ｛(discharge capacity at the second cycle) − (3
Discharge capacity at the 0th cycle) / (discharge capacity at the 2nd cycle) × 100 [%] Also in the adhesion test, 0 pieces showed good results, with no peeling.

Comparative Example 4 An electrode was manufactured in the same manner as in Example 10, except that polyvinylidene fluoride (PVDF, KYNAR741, manufactured by Elf Atochem) was used as a binder. As a result, the discharge capacity in the second cycle was 3
At 20 mAh / g, the capacity deterioration rate was as large as 10%. Also in the adhesiveness test, the adhesive strength was low, with 50 peeled out of 100 pieces.

Example 11 An electrode was produced in the same manner as in Example 10 except that the electrode composition was Sefralsoft G180F100: graphite = 10: 90 (% by weight). As a result,
The discharge capacity at the second cycle was as large as 364 mAh / g, and the capacity deterioration rate was as small as 0.4%, indicating good battery characteristics.
Also, in the adhesion test, none was peeled off, indicating good adhesion.

Comparative Example 5 An electrode having the same composition as in Example 11 was produced except that polyvinylidene fluoride (PVDF, KYNAR741, manufactured by Elf Atochem) was used as a binder. As a result, the discharge capacity in the second cycle was 320 mAh / g, and the capacity deterioration rate was as large as 9%.
In the adhesion test, all 100 pieces peeled off.

[Example 12] A positive electrode using lithium cobaltate as a positive electrode active material was manufactured using Sefralsoft G180F100 as a binder. Acetylene black (Denka Black HS100, manufactured by Denki Kagaku Kogyo) was used as a conductive assistant. The composition was lithium cobaltate: cefuralsoft: acetylene black = 82: 9: 9 (% by weight). Except for these points, an electrode was prepared and evaluated in the same manner as in Example 1. Using this electrode as a working electrode, lithium as a counter electrode and a reference electrode, charging and discharging were performed at 0.5 mA at a potential of 3.0 V to 4.2 V.

As a result, the discharge capacity in the second cycle was 15
The battery performance was as large as 0 mAh / g, and the capacity deterioration rate was as small as 0.5%.

[0092] In the same adhesive test as above, no peeling was observed, showing a good result.

Incidentally, the results of Examples 10 to 12 were equally realized with Cefralsoft G150F100.

[Comparative Example 6] PVDF (K
A positive electrode was produced in the same manner as in Example 12, except that YNAR741) was used. As a result, the discharge capacity in the second cycle was 100 mAh / g, and the capacity deterioration rate was as large as 8%.

Example 13 The electrode of Example 12 was replaced with the positive electrode 1
3, the electrode of Example 10 was a negative electrode 12, and the positive electrode 13 and the negative electrode 12 were each provided with a titanium wire 14 as an external terminal.
And a separator 15 made of polyethylene was connected to ethylene carbonate and diethyl carbonate (1: 1 by volume) in which 1 M LiClO4 was dissolved as an electrolyte.
The battery case 1 together with the electrolytic solution 16 using the mixed solvent of 1)
1 and produced a lithium secondary battery as shown in FIG. Again,
The results were the same for Sefralsoft G150F100.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the temperature and the electrical conductivity of the gel electrolyte of the present invention.

FIG. 2 is a graph showing a change in weight when the gel electrolyte of the present invention is immersed in an electrolytic solution.

FIG. 3 is a sectional view of a cell for measuring charge / discharge characteristics.

FIG. 4 is a cross-sectional view of a lithium secondary battery that is an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beaker 2 Silicon stopper 3 Working electrode 4 Counter electrode 5 Reference electrode 8 Luggin tube 9 Electrolyte 11 Battery case 12 Negative electrode 13 Positive electrode 14 Titanium wire (external terminal) 15 Separator 16 Electrolyte

Claims (16)

[Claims] 1. A vinylidene fluoride copolymer having a main chain,
A polymer solid electrolyte containing a polymer having polyvinylidene fluoride in a side chain, an electrolyte salt, and a solvent. 2. The solid polymer electrolyte according to claim 1, wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. 3. A polymer solid electrolyte comprising a polymer alloy of the polymer of claim 1 and polyvinylidene fluoride, an electrolyte salt and a solvent. 4. A vinylidene fluoride copolymer having a main chain,
A lithium secondary battery having a polymer solid electrolyte containing a polymer having polyvinylidene fluoride in a side chain, an electrolyte salt, and a solvent. 5. The lithium secondary battery according to claim 4, wherein said vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. 6. The lithium secondary battery according to claim 4, wherein the polymer has a polymer solid electrolyte contained as a polymer alloy with polyvinylidene fluoride. 7. A lithium secondary battery in which at least one of the electrodes is a composition of a polymer having a vinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain, and an electrode active material. 8. A vinylidene fluoride copolymer having a main chain,
The lithium secondary battery according to claim 7, further comprising a polymer solid electrolyte containing a polymer having polyvinylidene fluoride in a side chain, an electrolyte salt, and a solvent. 9. The lithium ion according to claim 8, wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride.
Next battery. 10. A positive electrode active material comprising a carbon material, a lithium metal, a lithium alloy, or a lithium oxide material as a negative electrode active material, and a compound or a carbon material capable of intercalating / deintercalating lithium ions as a positive electrode active material. Lithium secondary battery. 11. An electric double layer capacitor having a polymer solid electrolyte containing a polymer having polyvinylidene fluoride as a main chain and polyvinylidene fluoride in a side chain, an electrolyte salt and a solvent. 12. The electric double-layer capacitor according to claim 11, wherein the vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. 13. The electric device according to claim 11, wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride.
Multilayer capacitor. 14. The electric double-layer capacitor according to claim 11, wherein at least one of the polarizable electrodes contains a polymer having a vinylidene fluoride copolymer as a main chain and polyvinylidene fluoride in a side chain. 15. The electric double-layer capacitor according to claim 14, wherein said vinylidene fluoride copolymer is a copolymer of vinylidene fluoride and ethylene trifluoride chloride. 16. The electric device according to claim 14, wherein the polymer is contained as a polymer alloy with polyvinylidene fluoride.
Multilayer capacitor.