JPH11149825A - Slid polymer electrolyte and electrochemical device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte superior in ionic conductivity, uniformity, and the adhesive property to a base material, and to provide an electrochemical device satisfactory in durability and preservability by using it. SOLUTION: This solid polymer electrolyte is a gummy copolymer of vinylidene fluoride and hexafluoropropylene, or a rubber-like copolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, comprising a polymer containing 55 mole % or more of the vinylidene fluoride, an electrolytic salt, and an organic solvent. A lithium secondary battery and an electric double layer capacitor are provided by using this electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte which can be suitably used for electrochemical devices such as batteries, capacitors, displays and sensors, and an electrochemical device using the solid polymer electrolyte. is there.

[0002]

2. Description of the Related Art In a conventional electrochemical device, an aqueous solution or a non-aqueous solution (electrolytic solution) using an organic solvent has been often used as an electrolyte, but there are problems in necessity of sealing, securing of safety, and the like. Therefore, the necessity of an ion conductive polymer having flexibility, elasticity, light weight, thin film forming property, transparency and the like is increasing. In particular, for electrochemical devices such as batteries, which are important components of electronic products, due to demands for weight reduction, compactness, shape freedom, and large area, secondary batteries and the like that use ion-conductive polymers as electrolytes are required. The development of electrochemical devices is being actively pursued.

As an example using an ion conductive polymer,
A type (homogeneous or dry type) composed of a polymer such as polyethylene oxide (PEO) or a polyether such as polypropylene oxide (PPO) or a derivative thereof and an electrolyte salt containing Li or the like; There are a type in which the electrochemical characteristics are improved by mixing (hybrid type / gel type), and a type in which a composite salt of the electrolyte is held by a polymer (PIS: Polymer in Salt).

At present, in the development of polymer batteries and the like using solid polymer electrolytes (SPEs), gel-type SPEs are mainly the focus of research due to their high ionic conductivity. ) System, P
It is said that polymers such as VDF (polyvinylidene fluoride) have high utility. Among them, PVDF has been studied as an SPE for a long time because it has excellent heat resistance and chemical resistance and has sufficient mechanical strength. However, since the crystalline portion of the polymer is not considered to contribute to ion conduction, PVDF having high crystallinity
Is disadvantageous as an SPE as it is, and therefore propylene hexafluoride (HFP), trifluoroethylene (TrFE), tetrafluoroethylene (TF
P (VDF-HFP) using E): US Patent No. 39
No. 85574, P (VDF-TFE), P (VD
F-TrFE): Copolymers as disclosed in JP-A-58-75779 have been proposed.

For example, US Pat. No. 5,296,318 discloses a copolymer of vinylidene fluoride (VDF) and 8 to 25 wt% of propylene hexafluoride (HFP) [P (VDF
-HFP)], the solution in which the lithium salt is dissolved is 20 to 7
A gel electrolyte containing 0 wt% is disclosed. The conductivity of this gel electrolyte reaches 10 ⁻³ S · cm ⁻¹ . Originally, polyvinylidene fluoride (PVDF) is a crystalline polymer that is relatively excellent in chemical resistance. That is, P
Although some solvents dissolve VDF well, they did not dissolve in any solvent and were one of the most usable fluororesins. In fact, PVD
F is used as a binder for the positive and negative electrode active materials of the lithium ion secondary battery. 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,
In addition, the precipitation of lithium salt crystals is suppressed, and a gel electrolyte having higher strength can be produced.

[0006] However, the VDF-HFP copolymer has a high conductivity as described above because HFP reduces the crystallinity of PVDF. Inherently, it has a disadvantage that the contained chemical resistance is lowered and the melting point is lowered. For example, the melting point of PVDF (homopolymer, trade name KYNAR700 series) manufactured by Elf Atochem is 170 ° C., whereas the melting point of a VDF-HFP copolymer manufactured by Elf Atochem, for example, KYNAR2801, is 145 ° C. Since the decrease in chemical resistance means that the polymer easily dissolves in the battery electrolyte, such a VDF-HFP copolymer was used for an electrochemical device such as a lithium ion secondary battery or an electric double layer capacitor. In this case, a problem arises in the adhesion to the electrodes and the current collector. For example, the VDF-
When the HFP copolymer is used in a battery, the storage characteristics of the battery deteriorate. Battery at room temperature or high temperature (40 ° C, 60 ° C,
(80 ° C, 100 ° C), storage capacity degradation occurs,
In an extreme case, an 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.

Further, when a cell is composed of a gel electrolyte and an electrode used in a solution system, the internal resistance is high and charging and discharging cannot be performed at all. Therefore, as conventionally performed, in US Pat. No. 5,296,318, matching is achieved using a composition comprising an electrode active material and a gel electrolyte. However, with the composition shown in this patent, the adhesion to the current collector to be applied is low, and the electrode mixture may peel off after the application. This is thought to be due to the fact that the PVDF has a large shrinkage rate when it is applied and dried because it is a crystalline resin, and is thus separated from the current collector. That is, the conductivity was increased, but the adhesion to the current collector was not sufficient. Also, a better gel electrolyte is required for electric double layer capacitors.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polymer solid electrolyte having good ionic conductivity and uniformity, and good adhesion to a substrate, and an electric power having excellent durability and storage stability by using the same. It is to provide a chemical device.

[0009]

In view of the above problems, the present inventors disclosed in Japanese Patent Application No. 8-274103 a polymer having a PVDF copolymer as a main chain / a polymer having PVDF as a side chain. The SPE used was also described in Japanese Patent Application No. 9-21992, VDF and ethylene chloride trifluoride (CTF).
An SPE using the copolymer (E) has been proposed.

The present inventors have conducted further studies on a larger number of fluoropolymers and found that vinylidene fluoride (V
DF) -6-propylene fluoride (HFP) binary copolymer rubbery region and vinylidene fluoride (VDF) -6-propylene fluoride (HFP) -tetrafluoroethylene (TFE)
It has been found that the rubbery region of the terpolymer also has a composition suitable as a polymer for SPE. Conventionally, the relationship between the liquid retention and the composition of the electrolytic solution was not clear in the rubber-like region, but the present inventors have revealed that there is a region in the rubber-like region where the electrolytic solution is well retained.

That is, the above object is achieved by the present invention described below.

(1) A rubbery copolymer of vinylidene fluoride and propylene hexafluoride, wherein the content of the vinylidene fluoride is at least 55 mol%, an electrolyte salt, and an organic solvent And a polymer solid electrolyte comprising: (2) vinylidene fluoride, propylene hexafluoride,
A solid polymer electrolyte comprising a polymer having a vinylidene fluoride content of 55 mol% or more, a rubbery copolymer with ethylene tetrafluoride, an electrolyte salt, and an organic solvent. (3) The content of the vinylidene fluoride in the polymer is 55 mol% or more, the content of the propylene hexafluoride in the polymer is 10 to 45 mol%, and the content of the 4 The polymer solid electrolyte according to the above (1) or (2), wherein the content of ethylene fluoride is 0 to 35 mol%. (4) The polymer solid electrolyte according to any one of (1) to (3), further comprising an inorganic or organic filler. (5) An electrochemical device using the polymer solid electrolyte according to any of (1) to (4). (6) The electrochemical device according to the above (5), which is a lithium secondary battery. (7) The electrochemical device according to (5), which is an electric double-layer capacitor.

[0013]

The vinylidene fluoride (VDF) -6 propylene fluoride (H) used for the solid polymer electrolyte (SPE) of the present invention.
FP) Binary copolymer and vinylidene fluoride (VDF)
The rubbery region of -6 fluorinated propylene (HFP) -tetrafluoroethylene (TFE) terpolymer is approximately VD
50-85 mol% of VDF in F-HFP binary copolymer
This is a composition region in which TFE is further added to the composition of 0 to 35 mol%. In this composition range, since it is a rubber-like, that is, an amorphous polymer, high swelling property is obtained, and unlike the conventional rubber-like copolymer, high electrolyte-retaining property is obtained. Therefore, high conductivity is obtained. Further, the SPE of the present invention has high heat resistance, cold resistance, solvent resistance and the like.

[0014] Sufficient properties can be obtained even with a rubbery VDF-HFP binary copolymer. However, by introducing TFE, an extremely strong CF bond is increased, and other CC bonds and CH bonds are increased. Since the bonding is also strengthened, the heat resistance is improved.
Further, the VDF-HFP-TFE terpolymer is a VDF-HFP-TFE terpolymer.
, The cold resistance is about the same as that of the VDF-HFP binary copolymer. Solvent resistance is superior to VDF-HFP binary copolymers because the relatively large van der Waals radius of the fluorine atom protects the CC bond from chemical attack.

The VDF-TFE binary copolymer has high crystallinity and is disadvantageous as an SPE.

VDF-HFP binary copolymer, VDF-H
The FP-TFE terpolymer changes the rubber heat resistance, cold resistance, solvent resistance, etc. by changing the composition of the two or three components.

VDF-HFP binary copolymer and VDF
In the -HFP-TFE terpolymer, the glass transition point tends to increase and the cold resistance tends to decrease by increasing the fluorine content (relatively reducing VDF), but the solvent resistance is good. Becomes When VDF is reduced, the liquid retention and swelling properties of various electrolytes used in electrochemical devices also tend to decrease.

Since the polymer of the present invention is rubbery, it does not contain any crystal components, and the VDF-HFP terpolymer and VDF-HFP-TFE terpolymer have the same properties.
By setting the ratio of DF to 55 mol% or more, acetone,
In addition to ensuring solubility in some solvents such as methyl ethyl ketone (MEK), dimethylformamide (DMF), and N-methylpyrrolidone (NMP), high liquid retention and swelling of the electrolytic solution are obtained. Thereby, the ionic conductivity of the SPE shows a stable high value.

Further, since the SPE of the present invention has a rubbery base polymer, the adhesion to the electrodes of batteries and capacitors is extremely good, and the formation of an electrochemical interface is easy. By using this SPE 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. The same effect can be obtained by using the same for an electric double layer capacitor.

In Japanese Patent Publication No. 84007, the same VDF-HFP-TFE terpolymer as in the present invention is disclosed as a binder for a non-aqueous battery electrode.
However, the characteristics required for the polymer solid electrolyte and the characteristics required for the binder are essentially different, and do not suggest the use as a polymer solid electrolyte.

Also, as described above, US Pat.
No. 318 discloses a polymer solid electrolyte using a VDF-HFP binary copolymer as in the present invention. However, its composition is VDF 92-75 wt% (about 9%).
6.4 to 87.5 mol%) and HFP 8 to 25 wt% (about 3.6 to 12.5 mol%), which is not a rubbery copolymer unlike the present invention. Therefore, it is more disadvantageous as an SPE than that of the present invention in terms of adhesion to electrodes and the like. The composition of the VDF-HFP binary copolymer used in the present invention is VDF
85 to 50 mol% (about 70 to 30 wt%), HFP 15 to
50 mol% (about 30-70 wt%). In the present invention,
In the rubber-like region, it was found that there was a region where the electrolyte was well retained, and excellent characteristics were realized by using a polymer having that composition for the SPE.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The solid polymer electrolyte of the present invention (SP)
E) is a polymer composed of a rubbery copolymer of vinylidene fluoride (VDF) -6 propylene fluoride (HFP) or vinylidene fluoride (VDF) -6 propylene fluoride (H
FP) -polymer comprising a rubbery copolymer of tetrafluoroethylene (TFE), an electrolyte salt, and an organic solvent. In addition, by adding various inorganic or organic fillers (fillers), the physical properties of SPE
Productivity and the like can be controlled.

<Binary copolymer, ternary copolymer> The rubbery copolymer region of the present invention refers to a VDF-HFP binary copolymer and a VDF-HFP-TFE ternary copolymer. This is the area where the rubber state can be obtained. As described above, the composition range of the rubbery region of the VDF-HFP binary copolymer and the VDF-HFP-TFE terpolymer has a VDF ratio in the VDF-HFP binary copolymer of approximately 50 to 50%.
This is a composition region in which TFE is further added to 0 to 35 mol% to a composition of 85 mol%.

The rubbery copolymer is defined as a glass transition point (Tg)
Is a normal polymer (about 25 ° C.) or lower and is a polymer exhibiting rubber elasticity. Since a rubber-like copolymer does not have a definite melting point (Tm), whether it is rubber-like can be determined by the thermal behavior of the copolymer, for example, by the absence of a definite Tm by differential thermal analysis. .

In the present invention, VD of the rubbery region
VDF-HFP binary copolymer or VDF-HFP-T having an F ratio of 55 mol% or more, preferably 58 mol% or more
An FE terpolymer is used. When the VDF ratio is less than 55 mol%, the liquid retention and swelling properties of the electrolyte are insufficient. HFP is 10 to 45 mol%, particularly 12 to 42 mol%.
Is preferred. TFE is preferably 0 to 35 mol%, particularly preferably 0 to 30 mol%.

VDF-HFP binary copolymer, VDF-H
The FP-TFE terpolymer is usually a random copolymer, but may be a block copolymer.

The molecular weight is such that the weight average molecular weight Mw is about 30,000 or more, preferably 50,000, in view of the strength of the material.
It needs to be about 00 or more. The upper limit of Mw is usually about 5,000,000.

When used as a solid polymer electrolyte, a so-called raw rubber state is also suitable for use in the present invention, but vulcanization may be carried out using a vulcanizing agent such as polyamine, polyol or peroxide. At this time, the swellability of the electrolytic solution changes depending on the degree of vulcanization, and as the degree of vulcanization increases, the swellability decreases.

Such a polymer solid electrolyte is made of lithium 2
When used in electrochemical devices such as secondary batteries and electric double layer capacitors, good durability, heat resistance, storage stability, charge / discharge characteristics and the like can be obtained.

VDF-HFP binary copolymer, VDF-H
Since the FP-TFE terpolymer has a low water absorption of 0.1 wt% or less, it is not always necessary to carry out a drying treatment at the time of use, but it may be subjected to normal pressure or vacuum drying at 100 ° C. or less.

In order to synthesize a VDF-HFP binary copolymer, vinylidene fluoride and propylene hexafluoride may be copolymerized according to a known method using persulfate as an initiator. In order to synthesize a VDF-HFP-TFE terpolymer, vinylidene fluoride, propylene hexafluoride and ethylene tetrafluoride may be copolymerized according to a known method using persulfate as an initiator.

The copolymer does not dissolve in an electrolyte such as ethylene carbonate or diethyl carbonate at room temperature, and the polymer solid electrolyte of such a copolymer is used for lithium secondary batteries, electric double layer capacitors, etc. When used for an electrochemical device, the storage characteristics are good.

<Electrolyte Salt> As an electrolyte, considering application to a lithium battery, it is necessary that the electrolyte salt contains Li, and specifically, LiBF ₄ , LiPF ₆ , LiA
sF ₆ , LiSO ₃ CF ₃ , LiClO ₄ , LiN (S
Lithium salts such as O ₂ CF ₃ ) ₂ can be used. When used for an electric double layer capacitor, a quaternary ammonium salt such as tetraethylammonium perchlorate and tetraethylammonium borofluoride can be used in addition to the alkali metal salt containing the Li salt. In addition, an electrolyte salt compatible with a solvent described below may be appropriately selected depending on an applied electrochemical device. Such an electrolyte salt may be used alone, or a plurality of salts may be mixed at a predetermined ratio.

<Solvent> The solvent of the electrolytic solution is not particularly limited as long as it has good compatibility with the above-mentioned copolymer and electrolyte salt. However, in a lithium battery or the like, decomposition does not occur even at a high operating voltage. Polar organic solvents, for example, carbonates such as ethylene carbonate (abbreviation EC) and propylene carbonate (abbreviation PC), cyclic ethers such as tetrahydrofuran (abbreviation THF), sulfolane, and lactone are preferably used. Also, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 2-methyltetrahydrofuran,
1,3-dioxolan, 4-methyldioxolan, γ-
Butyrolactone, 3-methylsulfolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, ethyldiglyme, or the like may be used. In addition, it may be appropriately selected according to the device to be applied.

When it is considered that the electrolyte is composed of the solvent and the electrolyte salt, the concentration of the electrolyte salt is preferably 0.3 to 5 mol.
l / l. Usually, it exhibits the highest ionic conductivity at around 1 mol / l. When the composition of the SPE is represented by a copolymer / electrolyte solution, the weight ratio of the electrolyte solution is preferably 3/2 to 1/9 from the viewpoint of membrane strength and ionic conductivity.

The degree of swelling of the polymer is 1.6 or more, especially 1.8.
The above is preferred. Here, the degree of swelling is defined as the weight ratio before and after the polymer is impregnated with the electrolyte and swelled. That is, a swelling degree of 2 indicates that the weight of the polymer was doubled by the impregnation of the electrolyte, and the total amount of the electrolyte retained by the swelling of the polymer occupied half of the entire SPE. To indicate that The degree of swelling is generally about 5 or less, although there is a balance with strength.

<Preparation of SPE> Next, a specific method for producing a solid polymer electrolyte will be described. Production is 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. For example, it is preferable to use acetone, methyl ethyl ketone, methyl isobutyl ketone, N, N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and the like. . The concentration of the polymer in the solvent is preferably 5 to 30% by weight. The dispersing and dissolving method is to dissolve simply by stirring at room temperature using a magnetic stirrer or the like. Further, in order to dissolve the polymer in a short time, heating may be performed at a temperature lower than the boiling point of the solvent.

Next, this polymer solution is applied on a substrate and cast to form a sheet. The substrate may be any smooth material. For example, polyester film, glass, polytetrafluoroethylene film, and the like. The means for applying the polymer solution to the substrate is not particularly limited, and may be appropriately determined according to the material and shape of the substrate. In general,
Metal mask printing, dip coating, spray coating, roll coating, doctor blade, gravure coating, screen printing, and the like are used. If necessary, a vulcanizing agent is added to form a sheet.

The sheet thus obtained is left or heat-treated to evaporate the solvent used to dissolve the polymer. Then, if this sheet is impregnated with the electrolytic solution, the SPE
Is obtained. As the electrolytic solution, any one may be used as long as it is used for lithium batteries, electric double layer capacitors and the like and has good compatibility with the copolymer. Since the binary copolymer and the ternary copolymer of the present invention have high electrolyte retention and swelling properties, SPE can be obtained in this manner. The resulting SPE is transparent and elastic.

Further, after mixing the electrolyte solution with the polymer solution in advance and applying the mixed solution (hereinafter referred to as “gel electrolyte solution”) on the substrate, the solvent is dried.
PE is obtained. However, this method cannot be applied to vulcanized rubber.

The thickness of the SPE of the present invention is usually 10 to 5
00 μm.

The polymer solid electrolyte of the present invention thus obtained has a conductivity of 0.5 to 10 S · cm at room temperature.
^{At -1} , it is equivalent to a conventional gel electrolyte and close to that of a liquid.

<Filler> If the above raw rubber SPE has disadvantages in strength, rigidity, pressure resistance, adhesiveness, etc., an inorganic or organic filler such as silica or alumina is added to the SPE. They can be improved.
The material, particle size, shape and filling amount of the filler to be added are not particularly limited, but the ionic conductivity of the SPE essentially decreases with the filling amount. It is preferable that the filling amount is 30% by weight or less.

If the SPE is not self-sustaining, a nonwoven fabric or the like may be included in the SPE as a support for the SPE.

<Electrochemical Device> The SPE of the present invention comprises:
It can be used for electrochemical devices such as batteries, capacitors, EC displays, sensors and the like, and can be particularly suitably used for lithium secondary batteries and electric double layer capacitors.

<Lithium Secondary Battery> Although the structure of the lithium secondary battery using the polymer solid electrolyte of the present invention is not particularly limited, it is generally composed of a positive electrode, a negative electrode, and SPE, and is usually a laminated battery or a cylindrical battery. Applied to batteries and the like.

The electrode to be combined with SPE may be appropriately selected from those known as electrodes of a lithium ion secondary battery, and a composition of an electrode active material and SPE may be used.

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

The carbon used as the active material may be appropriately selected from, for example, natural or artificial graphite, resin-fired carbon material, carbon fiber and the like. These are used in powder.
Of these, graphite is preferred, and its average particle size is preferably 1 to 30 μm, particularly preferably 5 to 25 μm. If the average particle size is too small, the charge / discharge cycle life tends to be short and the variation in capacity (individual difference) tends to be large. If the average particle size is too large, the dispersion of the capacity becomes extremely large, and the average capacity becomes small. It is considered that the capacity variation occurs when the average particle size is large because the contact between the graphite and the current collector and the contact between the graphites vary.

The oxide capable of intercalating / deintercalating lithium ions is preferably a composite oxide containing lithium, for example, LiCoO ₂ , LiM
_{n 2 O 4, LiNiO 2,} LiV 2 O 4 and the like.
The average particle diameter of these oxide powders is preferably about 1 to 40 μm.

A conductive assistant is added to the electrode if necessary. Preferred examples of the conductive auxiliary agent include metals such as graphite, carbon black, carbon fiber, nickel, aluminum, copper, and silver. Particularly, graphite and carbon black are preferable.

The electrode composition is such that when a gel electrolyte is added as a binder, the weight ratio of active material: conduction aid:
The gel electrolyte is preferably in the range of 10 to 50: 0 to 20:30 to 90. In the negative electrode, the active material: the conductive auxiliary agent:
The gel electrolyte is preferably in the range of 10 to 50: 0 to 20:30 to 90. An electrode containing no gel electrolyte is also preferably used. In this case, a fluorine resin, a fluorine rubber, or the like can be used as the binder, and the amount of the binder is 3 to 30 wt.
%.

In the present invention, the above-mentioned negative electrode active material and / or positive electrode active material, preferably both active materials, are preferably mixed in the above-mentioned binder solution and adhered to the surface of the current collector. When a gel electrolyte is used as the binder, one having the same composition as the SPE of the present invention or one having another composition may be used.

In the production of the electrode, first, an active material and, if necessary, a conductive auxiliary are dispersed in a binder solution to prepare a coating solution.

Then, this electrode coating solution is applied to the current collector. The means for applying is not particularly limited, and may be determined as appropriate 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 used by the battery and the method of disposing the current collector in the case. Generally, aluminum or the like is used for the positive electrode, and copper, nickel, or the like is used for the negative electrode.
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, a sufficiently small contact resistance can be obtained with the metal foil.

Then, the solvent is evaporated to form an electrode. The coating thickness is preferably about 50 to 1,000 μm.

<Electric Double Layer Capacitor> The structure of the electric double layer capacitor using the polymer solid electrolyte of the present invention is not particularly limited.
And an insulating gasket is arranged around the polarizable electrode and the SPE. Such an electric double layer capacitor may be any type called a coin type, a paper type, a laminated type, or the like.

As the polarizable electrode, activated carbon, activated carbon fiber, or the like is used as a conductive active material, and a fluororesin, fluororubber, or the like is added as a binder. The composition of the binder may be the same or different from the composition of the polymer used in the SPE of the present invention. Then, it is preferable to use the mixture formed on a sheet-like electrode. The amount of binder is 5-15
It is about wt%. Further, a gel electrolyte may be used as a binder, in which case, the gel electrolyte is the SPE of the present invention.
A composition having the same composition as described above or a composition having another composition may be used.

The current collector used for the polarizable electrode is platinum,
It may be a conductive rubber such as a conductive butyl rubber or the like, may be formed by spraying a metal such as aluminum or nickel, or may be provided with a metal mesh on one surface of the electrode layer.

The electric double layer capacitor is obtained by combining the above-mentioned polarizable electrode and the above-mentioned SPE.

As the electrolyte salt, (C ₂ H ₅ ) ₄ NB
F ₄ , (C ₂ H ₅ ) ₃ CH ₃ NBF ₄ , (C ₂ H ₅ ) ₄ PB
F _4, 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 a mixed solvent is 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.

[0067]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples.

Example 1 VDF: HFP: T was used as a polymer
FE = 60: 15: 25 (mol%), weight average molecular weight M
An SPE was produced using a fluororubber molded article having a w of 700,000. This fluororubber molded product has a glass transition temperature of-
17 ° C., no apparent melting point.

First, a fluororubber molded product was dissolved in methyl ethyl ketone (MEK) to obtain a 10 wt% solution. Further, this solution contains a silica filler (C
ABOT Co., CAB-O-SIL; TS-530) was added and sufficiently dispersed.

The obtained solution is cast on an 80 μm-thick PET film using an applicator, and the solvent is volatilized to obtain a translucent and uniform fluororubber film (thickness: about 200 μm).
I got A small piece of this film is 1 mol / l- (C ₂ H ₅ ) ₄ NBF
_{A 4} / propylene carbonate (abbreviated PC) electrolyte was immersed at room temperature for 2 hours to swell the electrolyte to obtain an SPE film (Sample 1). And the weight change rate (degree of swelling) Sw
And the ionic conductivity σ was measured by the following method.

The above operation was performed in a glove box filled with argon gas.

<Ion Conductivity Measurement Method> A test piece of 2 cm ² was cut out from the obtained polymer solid electrolyte membrane, and the AC impedance between the electrodes was measured in a glove box using a conductivity measurement cell using a SUS electrode. Measured (frequency 1
10 ⁶ Hz). Ionic conductivity was determined by complex impedance analysis. The measurement device was SI1255 manufactured by Solartron.
A type impedance analyzer was used.

Table 1 shows the measured swelling degree Sw and ionic conductivity σ of the sample.

[0074]

[Table 1]

Example 2 1 mol / l-LiPF in electrolyte
₆ / PC electrolyte was used in the same manner as in Example 1 except that
A PE film (sample 2) was prepared and evaluated. Table 1 shows the results.

[Comparative Example 1] VDF: HFP: T
FE = 52: 21: 27 (mol%), weight average molecular weight M
An SPE film (sample 3) was prepared and evaluated in the same manner as in Example 1 except that a fluororubber molded article having a w of 60,000 was used. Table 1 shows the results. The glass transition temperature of the polymer used was −12 ° C., and there was no clear melting point.

Comparative Example 2 VDF: HFP = 5 as a polymer
2:48 (mol%), weight average molecular weight Mw 200,00
An SPE film (sample 3) was prepared and evaluated in the same manner as in Example 1 except that the fluororubber molded article of No. 0 was used. Table 1 shows the results. The glass transition temperature of the polymer used is-
2 ° C., no apparent melting point.

The SPE membrane of the present invention showed higher swelling and ionic conductivity than those of the two comparative examples.

Example 3 A lithium ion secondary battery using the SPE film of Example 2 (sample 2) was manufactured as follows.

A predetermined amount of N, N-
While dimethylformamide (DMF) and Cefralsoft G180 manufactured by Central Glass Co., Ltd. (comprising vinylidene fluoride-3fluoroethylene copolymer as the main chain and polyvinylidene fluoride in the side chain) were added thereto, and the mixture was heated. It was dispersed and dissolved at 3500 rpm to 7000 rpm. Further DMF was added to this solution,
Dispersed and dissolved at pm. The concentration of Cefral soft solution is 10
wt%.

40 g of the above cefral soft solution was placed in a container of a homogenizer, and 43 g of lithium cobaltate (manufactured by Seimi Chemical Co., particle size: 2 to 3 μm) and acetylene black (trade name: HS manufactured by Denki Kagaku Kogyo KK) were used as the positive electrode active material.
-100), and dispersed and mixed at 12,000 rpm for 5 minutes at room temperature to obtain a coating solution for the positive electrode.

This coating solution was applied to an aluminum foil (30 mm long, 30 mm wide).
mm, thickness 30μm) with a metal mask printing machine to a diameter of 15mm
, And left for 24 hours to evaporate DMF to obtain a positive electrode. The thickness of this electrode was 0.15 mm.

40 g of the above cefral soft solution was placed in a container of a homogenizer, and 9 g of graphite (manufactured by Lonza, trade name: SFG25, 90% cumulative particle size: 25 μm) was used as a negative electrode active material.
Was added and dispersed and mixed at 12,000 rpm for 5 minutes at room temperature to obtain a coating solution for a negative electrode.

This coating solution was coated with copper foil (length 30 mm, width 30 mm,
A 30 mm thick film was printed in a 15 mm diameter circle using a metal mask printer, and left for 24 hours to evaporate DMF to obtain a negative electrode. The thickness of this electrode was 0.15 mm.

The two metal foils were cut into a circle having a diameter of 15 mm, and the S foil having a diameter of 17 mm prepared in Example 2 was interposed between the coating films.
A coin-type lithium ion secondary battery was manufactured by sandwiching the PE film (sample 2) and sealing the periphery with a polyolefin-based hot melt adhesive.

This lithium ion battery has a capacity of 0.1 mA / cm ²
It was possible to charge and discharge between 2 and 4 V at a current density of, and it was confirmed that the battery was operated normally, and it was found that there was no problem in the adhesion between the SPE and both electrodes.

Example 4 An electric double-layer capacitor using the SPE film of Example 1 (sample 1) was manufactured as follows.

Cefral soft solution 4 prepared in Example 3
0 g, 20 g of powdered coconut shell activated carbon (average particle size: 10 μm) and 1 g of acetylene black as electrode active materials
Was added and mixed. Then, this paste was applied on a stainless steel foil, and DMF was removed by drying to obtain a polarizable electrode.

This polarizable electrode was formed into a circular shape having a diameter of 15 mm.
An SPE film (sample 1) cut out and cut to a diameter of 20 mm was sandwiched between the pair of electrodes, inserted into an aluminum laminate bag, and a lead extraction portion was heat-sealed to produce an electric double layer capacitor.

This capacitor was confirmed to be charged and discharged between 1-2 V at a current density of 1 mA / cm ² , indicating that there was no problem in the adhesion between the SPE and both electrodes. No deterioration of the characteristics was observed even after 3 days.

Example 5 VDF: HFP = 8 as polymer
5:15 (mol%), weight average molecular weight Mw 120,000
An SPE film (sample 4) was prepared and evaluated in the same manner as in Example 1 except that the fluororubber molded article of No. 0 was used. The fluororubber molded article used had a glass transition temperature of -30 ° C and had no clear melting point.

This SPE film had the same degree of swelling and ionic conductivity as the SPE film of Example 1 (Sample 1).

Example 6 The same VD as in Example 5 was applied to the polymer.
F: HFP = 85: 15 (mol%), weight average molecular weight M
An SPE film (sample 5) was prepared in the same manner as in Example 2 except that a fluororubber molded article having a w of 120,000 was used.
Evaluation was performed in the same manner as in Example 1.

This SPE film had the same degree of swelling and ionic conductivity as the SPE film of Example 2 (sample 2).

Example 7 Using the SPE film of Example 6 (sample 5), a lithium ion secondary battery was fabricated in the same manner as in Example 3, and evaluated.

This lithium ion secondary battery was manufactured in Example 3.
In the same manner as in the above, charging / discharging between ² and 4 V was possible at a current density of 0.1 mA / cm ² , and it was confirmed that the battery was operated normally.

Example 8 Using the SPE film of Example 5 (sample 4), an electric double-layer capacitor was fabricated and evaluated in the same manner as in Example 4.

In the same manner as in Example 4, charge and discharge of this capacitor were confirmed at a current density of 1 mA / cm ² between 1-2 V, and it was found that there was no problem in the adhesion between the SPE and both electrodes. . No deterioration of the characteristics was observed even after 3 days.

The fluorinated binary copolymer and terpolymer of the present invention exhibit a high degree of swelling with respect to other electrolytes used in electrochemical devices and a high ionic conductivity as SPE. It can be applied to various electrochemical devices.

[0100]

As described above, according to the present invention, a uniform solid polymer electrolyte having sufficient strength and ionic conductivity can be obtained, and furthermore, a good electrochemical interface with an electrode can be obtained. Formation is possible. When such a polymer solid electrolyte is used for an electrochemical device such as an electric double layer capacitor or a lithium ion secondary battery, good characteristics can be obtained.

Claims (7)

[Claims] 1. A rubber-like copolymer of vinylidene fluoride and propylene hexafluoride, wherein the content of the vinylidene fluoride is 55 mol% or more, an electrolyte salt, and an organic solvent. A polymer solid electrolyte having: 2. A rubbery copolymer of vinylidene fluoride, propylene hexafluoride and ethylene tetrafluoride,
A polymer solid electrolyte comprising: a polymer having a content of vinylidene fluoride of 55 mol% or more; an electrolyte salt; and an organic solvent. 3. The content of the vinylidene fluoride of the polymer is 55 mol% or more, and the content of the propylene hexafluoride of the polymer is 10 to 10.
45 mol%, and the content of the polymer tetrafluoroethylene is 0 to 35.
3. The polymer solid electrolyte according to claim 1, wherein the amount is mol%. 4. The polymer solid electrolyte according to claim 1, further comprising an inorganic or organic filler. 5. An electrochemical device using the solid polymer electrolyte according to claim 1. 6. The electrochemical device according to claim 5, which is a lithium secondary battery. 7. The electrochemical device according to claim 5, which is an electric double layer capacitor.