JP2003272439A - Complex high-polymer electrolyte, electrochemical device and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complexed high-polymer electrolyte having an excellent rigidity, strength, and heat resistance and capable of suppressing a micro short circuit and gas leak efficiently. <P>SOLUTION: The complex high-polymer electrolyte 10 is equipped with a solid high-polymer electrolyte 12 and a clay mineral 14 dispersed in the electrolyte 12. The clay mineral 14 should preferably be stratified, and such a stratified clay mineral should preferably be dispersed in the solid high-polymer electrolyte 12 so that the layer surfaces are parallel to one another. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composite polymer electrolyte, and an electrochemical device and a fuel cell using the same, more specifically, a fuel cell, a water electrolyzer, a hydrohalic acid electrolyzer, and a salt electrolyzer. The present invention relates to a composite polymer electrolyte suitable as an electrolyte membrane used in various electrochemical devices such as hydrogen and / or oxygen concentrators, humidity sensors, gas sensors, etc., and electrochemical devices and fuel cells using the same.

[0002]

2. Description of the Related Art A solid polymer electrolyte is a solid polymer material having an electrolyte group such as a sulfonic acid group in the polymer chain.
Since it has a property of strongly binding to a specific ion and selectively permeating a cation or anion, it is used for various purposes by molding it into particles, fibers or a film.

For example, a polymer electrolyte fuel cell is a cell that directly takes out chemical energy generated when a continuously supplied fuel is oxidized as electric energy.
A solid polymer electrolyte membrane having proton conductivity is used as the electrolyte membrane.

The SPE electrolysis method is a method for producing hydrogen and oxygen by electrolyzing water, and a solid polymer electrolyte membrane having proton conductivity is used as an electrolyte instead of a conventional alkaline aqueous solution. Has been.

As solid polymer electrolytes used for such applications, for example, non-crosslinked perfluoro electrolytes represented by Nafion (registered trademark, manufactured by DuPont) and various hydrocarbon electrolytes are known. There is. In particular, perfluoro-based electrolytes, which have extremely high chemical stability, have been awarded as electrolyte membranes for various electrochemical devices used under severe conditions such as fuel cells and SPE electrolysis devices. Is.

By the way, electrolytes used in various electrochemical devices are generally required to have high values for a plurality of properties such as rigidity, strength, heat resistance, and electrical conductivity. Further, as the use condition of the electrochemical device becomes more severe, it is required that these plural characteristics are compatible with each other at a higher level. However, there is a limit to simultaneously improving these plural characteristics by improving the solid polymer electrolyte itself. Therefore, in order to solve this problem, various methods of complexing a solid polymer electrolyte with another substance have been proposed.

For example, KA Mauritz et al., Macromolec
In ules 1989, vol.22, 1730-1734, Nafion membrane was dipped in a solution containing tetraethoxysilane (TEOS),
Obtained by causing a sol-gel reaction in the film,
An electrolyte membrane in which silica is composited is disclosed.

Further, in Japanese Patent Publication No. 2000-516014, in order to suppress crossover of methanol in a fuel cell using methanol as a fuel, a polymer having a cation exchange group such as Nafion is added to a polymer such as zirconium phosphate. A membrane having an inorganic filler dispersed therein is disclosed.

Further, in Japanese Patent Laid-Open No. 2001-3509, in order to exhibit proton conductivity even in the absence of water and to improve heat resistance, organic compounds such as triethoxysilyl polytetramethylene oxide having a terminal group are used. A polymer,
Disclosed is an ion conductive film containing an ion transfer material having a relative dielectric constant of 20 or more, such as propylene carbonate, in a film having a three-dimensional crosslinked structure such as 12 tungstophosphoric acid.

[0010]

Conventional perfluoro-based electrolytes represented by Nafion have excellent oxidation resistance, but since they are non-crosslinked, they have low heat resistance and the glass transition temperature is around 130 ° C. It has the property of creeping. Therefore, there is a problem that the conventional perfluoro-based electrolyte cannot be used at a high temperature, which is advantageous in terms of prevention of poisoning of the electrode catalyst by carbon monoxide and efficiency.

On the other hand, silica is used for the solid polymer electrolyte,
When an amorphous inorganic filler such as zirconium phosphate is compounded, rigidity, strength and heat resistance are improved. for that reason,
The electrochemical device using this can have a higher operating temperature than before. However, in order to further improve the characteristics of the electrochemical device, it is desired to further improve the rigidity, strength and heat resistance without sacrificing other characteristics.

Further, in fuel cells, SPE electrolysis devices, etc., the solid polymer electrolyte is formed into an extremely thin film,
It is used as a membrane electrode assembly (MEA) in which electrodes are bonded to both surfaces thereof. MEA is usually prepared by applying a mixture of catalyst-carrying carbon and electrolyte on the surface of a porous diffusion layer made of carbon cloth, carbon paper, etc., and hot pressing this with a solid polymer electrolyte membrane. Being manufactured.

At this time, since the solid polymer electrolyte membrane is extremely thin, a so-called micro short circuit may occur in which the electrodes contact each other during MEA production or operation. When the number of locations where micro shorts occur increases, the amount of current that directly flows between the electrodes increases, which causes a decrease in the output of the electrochemical device.

On the other hand, if a solid polymer electrolyte membrane is combined with an amorphous inorganic filler such as silica or zirconium phosphate, the rigidity, strength and heat resistance of the membrane are improved. Therefore, when an MEA is manufactured using such a film, micro shorts can be suppressed. However, in order to further improve the performance of the electrochemical device, it is desired to further suppress the generation amount of micro shorts.

Further, in a polymer electrolyte fuel cell using a fuel gas containing hydrogen and an oxidant gas containing oxygen, the reaction gas supplied to one electrode side diffuses to the other electrode side, so-called cross. It is known that an over occurs. When the amount of crossover increases, the amount of fuel that is not consumed in the electrochemical reaction increases, which causes a decrease in fuel utilization rate (fuel consumption) and output. However, it is difficult to efficiently suppress the gas crossover by the method of reinforcing the solid polymer electrolyte with the amorphous inorganic filler.

The problems to be solved by the present invention are rigidity,
It is to provide a composite polymer electrolyte having excellent strength and heat resistance. Another problem to be solved by the present invention is to provide a composite polymer electrolyte capable of reducing micro shorts during MEA production or operation. Further, another problem to be solved by the present invention is to provide a composite polymer electrolyte capable of reducing gas crossover.

[0017]

Means for Solving the Problems To solve the above problems, a composite polymer electrolyte according to the present invention comprises a solid polymer electrolyte and a clay mineral dispersed in the solid polymer electrolyte. Is the gist. In this case, the clay mineral is preferably a layered clay mineral. Further, the layered clay mineral is preferably dispersed in the solid polymer electrolyte so that the layer surfaces thereof are parallel to each other.

In addition, 2 of the composite polymer electrolyte according to the present invention
The second feature is that it is provided with a solid polymer electrolyte and a plate-like powder made of an inorganic insulating material dispersed in the solid polymer electrolyte. Further, the gist of the electrochemical device and the fuel cell according to the present invention is to use the composite polymer electrolyte according to the present invention.

In the composite polymer electrolyte according to the present invention, plate-like powder made of clay mineral or inorganic material is compounded with the solid polymer electrolyte, so that the rigidity, strength and heat resistance are improved. When compounded with a plate-like powder made of a layered clay mineral or an inorganic material, it is possible to efficiently suppress the occurrence of micro shorts during MEA production or during operation, and moreover, due to its physical shielding effect. Therefore, gas crossover can be efficiently suppressed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The composite polymer electrolyte according to the first embodiment of the present invention includes a solid polymer electrolyte and a clay mineral dispersed in the solid polymer electrolyte.

First, the solid polymer electrolyte will be described. The solid polymer electrolyte means one in which an electrolyte group is bound to any of the solid polymer compounds. In the present invention, the type of solid polymer electrolyte is not particularly limited, and solid polymer electrolytes having various compositions, or solid polymer electrolytes having various molecular structures such as linear and branched ones. The present invention can be applied to.

That is, the solid polymer electrolyte is one in which an electrolyte group is bound to any of the solid polymer compounds having a C—F bond in the polymer chain (hereinafter referred to as “fluorine-based electrolyte”). Or a solid polymer compound having only a C—H bond in the polymer chain, to which an electrolyte group is bound (hereinafter, referred to as “hydrocarbon-based electrolyte”). ) Is acceptable.

The fluorine-based electrolyte is C in the polymer chain.
A solid polymer compound having both a —F bond and a C—H bond to which an electrolyte group is bonded (hereinafter, referred to as “fluorine / hydrocarbon-based electrolyte”) may be used, Alternatively, one having an electrolyte group bonded to any of the solid polymer compounds having a C—F bond in the polymer chain and not having a C—H bond (hereinafter, this is referred to as “perfluoro-based electrolyte”). .) In addition to C—F bonds, C—Cl bonds and other bonds (eg, —O—, —S—, —C (═O) —, —
N (R)-, etc.) may be included.

Further, the hydrocarbon electrolyte is one in which an electrolyte group is bound to any of solid polymer compounds having no aromatic ring in the polymer chain (hereinafter, this is referred to as "aliphatic hydrocarbon electrolyte"). Or a solid polymer compound having an aromatic ring in any of its polymer chains, to which an electrolyte group is bonded (hereinafter referred to as "aromatic hydrocarbon electrolyte"). ".).

Further, the aromatic hydrocarbon electrolyte has an alkylene chain (-(CH ₂ ) _n- , n≥
1) or a branched carbon structure (for example, —CHCH ₃ —, —C)
A solid polymer compound containing (CH ₃ ) _2-, etc., to which an electrolyte group is bound (hereinafter, referred to as “partially aromatic hydrocarbon electrolyte”) may be used, or Alternatively, a solid polymer compound having no alkylene chain or branched carbon structure in the bonding chain and having an electrolyte group bonded thereto (hereinafter, referred to as "whole aromatic hydrocarbon electrolyte") may be used. .

The type of electrolyte group provided in the solid polymer electrolyte is also not particularly limited. Suitable examples of the electrolyte group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group.

The solid polymer electrolyte may contain only one kind of these electrolyte groups, or may contain two or more kinds. Furthermore, the position where the electrolyte group is bonded is not particularly limited. That is, the electrolyte group may be directly bonded to the linear solid polymer compound, or
It may be bonded to either the main chain or the side chain of the branched solid polymer compound.

Specific examples of the perfluoro-based electrolyte include Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Co., Ltd., Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., and the like. A preferable example thereof is a derivative of.

As the fluorine / hydrocarbon-based electrolyte, specifically, a polystyrene-graft-ethylenetetrafluoroethylene copolymer (hereinafter referred to as a copolymer having an electrolyte group such as a sulfonic acid group introduced into one of the polymer chains) , This is referred to as "PS-g-ETFE"), polystyrene-graft-polytetrafluoroethylene, and the like, and derivatives thereof.

Further, as the aliphatic hydrocarbon electrolyte,
Specifically, polyamide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, and the like in which an electrolyte group such as a sulfonic acid group is introduced into any of the polymer chains, and derivatives thereof are preferable. As an example.

Specific examples of the partially aromatic hydrocarbon-based electrolyte include polystyrene in which an electrolyte group such as a sulfonic acid group is introduced into one of polymer chains, polyamide having an aromatic ring, polyamide imide, and polyimide. , Polyesters, polysulfones, polyetherimides, polyether sulfones, polycarbonates and the like, and derivatives thereof are mentioned as suitable examples.

As the wholly aromatic hydrocarbon-based electrolyte, specifically, polyether ether ketone in which an electrolyte group such as a sulfonic acid group is introduced into any of polymer chains,
Suitable examples include polyetherketone, polysulfone, polyethersulfone, polyimide, polyetherimide, polyphenylene, polyphenylene ether, polycarbonate, polyamide, polyamideimide, polyester, polyphenylene sulfide, and derivatives thereof.

Of these, fluorine-based electrolytes, especially perfluoro-based electrolytes, have C—F bonds in the polymer chain. Therefore, if the present invention is applied to these, heat resistance and oxidation resistance are improved. A composite polymer electrolyte having excellent properties is obtained. In addition, since aromatic hydrocarbon-based electrolytes, particularly wholly aromatic hydrocarbon-based electrolytes, are relatively easy to introduce acid groups, the application of the present invention to them makes it possible to obtain a composite electrolyte having high electrical conductivity. A molecular electrolyte is obtained.

Next, the clay mineral will be described. Clay minerals are fine minerals that exhibit tackiness and plasticity when appropriate water is added, depending on their composition and crystal structure, etc.
It takes various particle forms such as a layer, a cylinder, and a particle. In the present invention, clay minerals having any particle morphology can be used. Among them, clay minerals having a layered particle form (hereinafter referred to as “layered clay minerals”) are excellent in gas shielding effect and micro-short suppressing effect, so that they can be used in solid polymer electrolytes. It is particularly suitable as a clay mineral for dispersion.

Most of the clay minerals are tetrahedral sheets in which Si—O tetrahedra are two-dimensionally connected by sharing bottom surface oxygen, and medium-sized cations such as Al ³⁺ , Mg ²⁺ , Fe ^2+. The octahedron sheet in which the octahedron surrounded by 6 OH ⁻ or O ²⁻ is shared two-dimensionally by sharing a ridge is a layered silicate stacked in various cycles. Layered silicates are also called phyllosilicates. Bottom spacing of layered silicate (cycle in the direction perpendicular to the layer surface)
Is usually 7 to 12Å.

As will be described later, the layered silicate is easily swollen by a predetermined solvent such as water and dispersed in the form of a layered particle in which ten to several tens of unit layers each consisting of a tetrahedral sheet and an octahedral sheet are laminated. Easy to let. Therefore, the layered silicate is particularly suitable as a clay mineral to be dispersed in the solid polymer electrolyte.

Specific examples of the layered silicate include smectite type layered silicates such as montmorillonite, saponite, hectorite, beidellite, stevensite and nontronite, and vermiculite, halloysite, talc and swollen mica. It is mentioned as a suitable example. In addition, these may be either natural ones or synthetic ones.

Further, the layered silicate may have a negative layer charge by replacing the cation in the layer with another cation having a different charge. In this case, L
The charge balance is maintained by the entry of alkali metal ions such as i, Na, and K, and alkaline earth metal ions such as Ca. In the present invention, it is preferable to use a layered silicate in which the area occupied by the layer surface per negative layer charge is 25 Å ² or more and 200 Å ² or less.

Since the layered silicate having an appropriate layer charge (ie, occupied area) easily swells in a predetermined solvent such as water, it is finely and uniformly dispersed in the solid polymer electrolyte in the form of layered particles. Can be made. On the other hand, when the layer charge is excessive (ie, the occupied area is 25Å ²
In either case, or when the layer charge is too small (that is, when the occupied area exceeds 200Å ² ), the layered silicate is less likely to swell with a predetermined solvent such as water, and the solid high It becomes difficult to disperse uniformly and finely inside the molecular electrolyte. Occupied area is more preferably, 25 Å ² or more 180 Å ² or less, still more preferably 50 Å ² or more 180 Å ² or less.

The average particle size of the clay mineral dispersed in the solid polymer electrolyte is preferably 10 μm or less. By uniformly dispersing the fine clay mineral inside the solid polymer electrolyte, a composite polymer electrolyte excellent in rigidity, strength and heat resistance can be obtained without sacrificing the electric conductivity. The average particle size of the clay mineral is more preferably 5 μm.
It is the following.

When the clay mineral is a layered clay mineral, its average particle diameter (= average value of maximum dimensions) is preferably 5 μm or less, more preferably 1 μm or less.
Also, the average aspect ratio of layered clay minerals (= maximum dimension /
The average value of the minimum dimension) is preferably 10 or more, more preferably 20 or more, and further preferably 40 or more. The average aspect ratio of the layered clay mineral is better if it can maintain its crystal structure.

Further, when the clay mineral is a layered clay mineral, the layer surface of each layered clay mineral (the surface occupying the largest area)
Are preferably dispersed in the solid polymer electrolyte so that the particles are parallel to each other. When the composite polymer electrolyte according to the present embodiment is formed into a film, it is preferable to disperse the layered clay mineral so that the layer surface of the layered clay mineral is parallel to the film surface. When the layered clay mineral is dispersed so that the layer surface is parallel to the membrane surface of the electrolyte membrane, gas crossover and micro short circuit can be efficiently suppressed.

In the present invention, "the layered clay minerals are dispersed in parallel to each other" is not limited to the case where all the layered clay minerals are arranged completely parallel in the solid polymer electrolyte, It also includes the case where all or part of the layered clay mineral is dispersed with a slight inclination.

The content of the clay mineral contained in the composite polymer electrolyte is 0.1 w based on the total weight of the composite polymer electrolyte.
It is preferably t% or more and 30 wt% or less. If the content of the clay mineral is less than 0.1 wt%, a composite polymer electrolyte excellent in rigidity, strength, heat resistance, gas shielding property and micro short resistance cannot be obtained. On the other hand, the content of clay mineral is 30w
When it exceeds t%, the gas shielding property and the micro short-circuit resistance of the composite polymer electrolyte are improved, but the composite polymer electrolyte becomes brittle and the electric conductivity is deteriorated, which is not preferable.
The content of the clay mineral is more preferably 1 wt% or more and 30 wt% or less, and further preferably 1 wt% or more 15
It is less than wt%.

Next, the function of the composite polymer electrolyte according to this embodiment will be described. When a predetermined amount of clay mineral is dispersed in the solid polymer electrolyte, rigidity, strength, and heat resistance can be improved without significantly reducing electric conductivity. Therefore, if various electrochemical devices are produced using this, the operating temperature can be increased,
The efficiency can be improved.

In general, when gas is supplied to one surface of the solid polymer electrolyte, part of the gas dissolves in the solid polymer electrolyte. The dissolved gas diffuses in the solid polymer electrolyte and is discharged into the atmosphere from the other surface. For example, when such a gas crossover occurs in the fuel cell, it causes the output of the fuel cell and the fuel consumption to decrease.

On the other hand, when a predetermined amount of clay mineral is finely dispersed in the solid polymer electrolyte, the clay mineral serves as a physical obstacle and gas crossover is suppressed. Also,
When the layered clay mineral is finely dispersed, the dissolved gas diffuses in the solid polymer electrolyte while largely circumventing the layered clay mineral, so that gas crossover is efficiently suppressed.

In particular, as shown in FIG. 1, the layered clay mineral 1 is applied to the membrane surface of the solid polymer electrolyte 12 formed into a membrane.
In the case of the composite polymer electrolyte 10 in which the layered clay mineral 14 is finely dispersed so that the layer surfaces of 4 are parallel, the physical shielding effect of the layered clay mineral 14 is further increased, and the gas crossover is further increased. Efficiently suppressed.

If a mixture of carbon and an electrolyte carrying a catalyst is applied to the surface of the diffusion layer during the production of the MEA, micro unevenness is generated on the surface of the diffusion layer.
When such a diffusion layer is arranged on both sides of a very thin solid polymer electrolyte membrane and hot pressing is performed, the convex portion on the surface of the diffusion layer deeply digs into the solid polymer electrolyte membrane. As a result, a micro short circuit occurs in a portion where the height of the convex portion is particularly high, which causes a decrease in output of the electrochemical device.

On the other hand, when the clay mineral is dispersed in the solid polymer electrolyte, the rigidity of the solid polymer electrolyte membrane increases,
The protrusion of the convex portion into the solid polymer electrolyte membrane is suppressed. Further, when the layered clay mineral is finely dispersed, the ratio of shielding between the opposing electrodes by the layered clay mineral increases, and the micro short circuit is efficiently suppressed.

In particular, as shown in FIG. 2, the layered clay mineral 1 is applied to the membrane surface of the solid polymer electrolyte 12 formed into a membrane shape.
In the case of the composite polymer electrolyte 10 in which the layered clay mineral 14 is finely dispersed so that the layer surfaces of 4 are parallel to each other, the carbons 16a ... 16b ... Applied to the diffusion layer (not shown).
Of the layered clay minerals 14 and 1 arranged in parallel with each other even if the protruding portions of the
Since the space between the carbon 16a and the carbon 16b facing each other is shielded by 4, the micro short circuit can be suppressed more efficiently.

Next, a method for manufacturing the composite polymer electrolyte according to this embodiment will be described. The composite polymer electrolyte according to the present embodiment can be manufactured by various methods. The first method is a method of preparing a solution in which a solid polymer electrolyte or its precursor and a clay mineral are added to a solvent and solidifying the solution.

The precursor of the solid polymer electrolyte means a solid polymer compound which can be a solid polymer electrolyte by hydrolysis, substitution reaction, addition reaction or the like. Further, in the solvent, it is possible to dissolve the solid polymer electrolyte or its precursor,
In addition, a material in which the clay mineral can be finely dispersed, that is, a material having an affinity for both the solid polymer electrolyte or its precursor and the clay mineral is used.

For example, a solid polymer electrolyte having an electrolyte group such as Nafion having a sulfonic acid group is hydrophilic and is soluble in water. On the other hand, the layered silicate having a predetermined occupied area easily swells with water and becomes finely dispersed in water in the form of layered particles. Therefore, when the layered silicate is dispersed in the hydrophilic solid polymer electrolyte, it is preferable to use water as the solvent.

Even if it is other than water, a solvent having a relatively large polarity can dissolve the hydrophilic solid polymer electrolyte and finely disperse the layered silicate.
As such a solvent, specifically, diethylene glycol, ethylene glycol, propylene glycol,
Suitable examples include ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monoacetylate, ethylene glycol diacetylate, polyethylene glycol, polypropylene glycol, methanol, ethanol, propanol and dimethyl sulfoxide. These may be used alone or in combination of two or more.

Further, for example, a precursor of a solid polymer electrolyte having a sulfonyl fluoride group such as Nafion fluoride is hydrophobic and is insoluble in water,
It is soluble in fluorine-based solvents. On the other hand, the layered silicate having a predetermined occupied area is finely dispersed in water, but is not finely dispersed in the fluorine-based solvent.

However, when the interlayer ions of the layered silicate are replaced (organized) with a predetermined organic compound, they become hydrophobic and can be easily finely dispersed in a fluorine-based solvent. Therefore, if the precursor and the organically modified layered silicate are added to this solvent, the organically modified layered silicate can be uniformly and finely dispersed in the hydrophobic precursor in the form of layered particles.

Organized layered silicate (organized clay)
Can be obtained by first dispersing a non-organized layered silicate (non-organized clay) in water and adding an organic compound having an organic cation thereto. Specific examples of suitable organic compounds used for organizing the layered silicate include onium salts such as ammonium salts, pyridinium salts, sulfonium salts, and phosphonium salts. Among these, ammonium salts are suitable as organic compounds for organizing because they are easily exchanged with interlayer ions.

Specifically, octadecyl ammonium salt
ON (CH_Three(CH_Two)₁₇N⁺H_Three), Monomethyloctane
Tadecyl ammonium ion (CH_Three(CH_Two)₁₇N⁺
H_Two(CH_Three)), Dimethyl octadecyl ammonium salt
ON (CH_Three(CH_Two)₁₇N ⁺H (CH_Three)_Two), Dodeci
Lumonium ion (CH_Three(CH_Two)₁₁N
⁺H_Three), 4-amino-n-butyrate ion (H_Three ⁺N (C
H_Two)_ThreeCOOH), 6-amino-n-caproic acid io
(H_Three ⁺N (CH_Two)₅COOH), 8-aminocapri
Lactate ion (H_Three ⁺N (CH_Two)₇COOH), 10-a
Minodecanate ion (H_Three ⁺N (CH_Two)₉COOH),
12-aminododecanoate ion (H_Three ⁺N (CH_Two) ₁₁
COOH), 14-aminotetradecanoate ion (H_Three
⁺N (CH_Two)_ThirteenCOOH), 16-aminohexadeca
Acid ion (H_Three ⁺N (CH_Two)₁₅COOH), 18-
Amino octadecanoate ion (H_Three ⁺N (CH_Two)₁₇C
Ammonium salts with organic cations such as (OOH) are preferred.
It is suitable.

Even if a solvent other than the fluorine-based solvent has a relatively small polarity, the hydrophobic precursor can be dissolved and the organized clay can be finely dispersed. Specific examples of such a solvent include N, N-dimethylacetamide, tetrahydrofuran, acetonitrile, benzonitrile, and the like. These may be used alone or in combination of two or more.

The order of adding the solid polymer electrolyte or its precursor and the clay mineral to the solvent is not particularly limited. That is, both may be added to the solvent at the same time, or one of them may be added first.
Alternatively, both may be dissolved or dispersed in a solvent separately and then mixed.

The total amount of the solvent added is preferably 0.3 part by weight or more and 1000 parts by weight or less with respect to 1 part by weight of the "solid polymer electrolyte or its precursor + clay mineral". If the amount of the solvent added is less than 0.3 part by weight, the dispersion of the clay mineral in the solution will be insufficient. On the other hand, the amount of solvent added is 1000
When it exceeds the weight part, a large amount of heat is required to evaporate the solvent, resulting in high cost. The total addition amount of the solvent is more preferably 0.5 parts by weight or more and 500 parts by weight or less,
More preferably, it is 0.5 parts by weight or more and 100 parts by weight or less.

The solid polymer electrolyte or its precursor and the clay mineral are weighed so that a composite polymer electrolyte in which a predetermined amount of clay mineral is dispersed can be obtained, and these are added to a predetermined amount of solvent. A homogeneous solution that is dissolved or dispersed is obtained. When this solution is solidified by solidifying means such as casting on the surface of a substrate to remove the solvent, a molded product having a predetermined shape can be obtained. Further, if necessary, the molded body is subjected to treatment such as hydrolysis and washing to obtain a composite polymer electrolyte membrane in which a predetermined amount of clay mineral is uniformly dispersed.

The first method uses a solvent having an affinity for both the solid polyelectrolyte or the precursor thereof and the clay mineral, so that the solid polyelectrolyte or the precursor thereof can be relatively easily prepared. Clay minerals can be dispersed uniformly and finely. When a layered silicate is used as the clay mineral, the clay mineral can be dispersed in the form of layered particles. Further, if the solution is solidified under appropriate conditions, a composite polymer electrolyte in which layered clay minerals are finely dispersed in parallel with each other can be obtained.

The second method is a method of adding a clay mineral to a molten precursor of a solid polymer electrolyte, kneading the mixture, and molding the kneaded product into a predetermined shape. The solid polymer electrolyte is
Generally, it cannot be melted because it has a decomposition temperature below the melting temperature, but the precursor is melted by heating. Therefore, by adding the clay mineral to the molten precursor, the clay mineral can be dispersed in the precursor.

When a layered silicate is used as the clay mineral and the affinity between the molten precursor and the layered silicate is low, the layered silicate is precursor in a layered particle form by simply kneading them. It is difficult to disperse uniformly and finely in the body. In such a case, it is preferable that the layered silicate is organized by the above-mentioned organic compound, and this is added to the precursor and kneaded. This method is effective when the melting temperature of the precursor is lower than the decomposition temperature of the organic compound.

Alternatively, the layered silicate and a solvent capable of swelling the layered silicate may be added to the molten precursor and kneaded. This method is applicable to both organized and non-organized clays, especially when the melting temperature of the precursor is higher than the decomposition temperature of the organic compound used for organizing, i.e. the organized clay. This is an effective method when you cannot use.

In this case, in order to disperse the layered silicate uniformly and finely, the layered silicate may be brought into contact with the molten precursor in a swollen state. Therefore, the solvent may be added at any timing after or before the contact between the precursor in the molten state and the layered silicate. In particular,
It is preferable to melt the precursor and add the layer silicate swollen with the solvent thereto. Alternatively, the precursor and the layered silicate may be mixed in a dry state, and then the precursor may be melted and sufficiently kneaded, and then a solvent may be added thereto. Alternatively, the layered silicate swollen with a solvent and the precursor may be mixed and then heated to a temperature equal to or higher than the melting temperature of the precursor.

When the layered silicate and the molten precursor are brought into contact with each other in the presence of a predetermined solvent, the solvent breaks the weak chemical bond between the layers of the layered silicate. The solvent vapor then escapes from the layers of the layered silicate, and instead the molten precursor is pressed between the layers. In particular, bringing the layered silicate and the molten precursor into contact with each other under a high-pressure atmosphere created by the vapor of the solvent further promotes the press-fitting of the precursor between the layers. Therefore, even if the affinity between the layered silicate and the precursor is low, the layered silicate can be uniformly and finely dispersed in the precursor in the form of layered particles.

The kneaded product obtained by such a method is
By molding using a molding method such as an extrusion molding method or a calendar molding method, a molded product having a predetermined shape can be obtained. If necessary, the molded body is subjected to treatment such as hydrolysis and washing to obtain a composite polymer electrolyte in which a predetermined amount of clay mineral is uniformly dispersed. Further, by optimizing the molding method and molding conditions, a composite polymer electrolyte in which layered clay minerals are dispersed in parallel with each other can be obtained.

The third method is to add water and an oxide (for example, SiO ₂ , Al ₂ O ₃ or the like), which is a raw material of a clay mineral, to a solid polymer electrolyte or its precursor, and add it at a predetermined temperature. And a method of hydrothermally synthesizing clay minerals under pressure.
According to such a method, the clay mineral can be formed in the solid polymer electrolyte or the precursor thereof in that case. Further, if the synthesis conditions are optimized at this time, the particle morphology of the clay mineral can be controlled. Further, if the obtained reaction product is molded under appropriate conditions, a composite polymer electrolyte in which clay minerals are finely dispersed or a layered clay mineral is dispersed in parallel to each other can be obtained.

Next, a composite polymer electrolyte according to the second embodiment of the present invention will be described. The composite polymer electrolyte according to the present embodiment includes a solid polymer electrolyte and a plate-like powder made of an inorganic insulating material dispersed in the solid polymer electrolyte. That is, it differs from the first embodiment in that a plate-like powder made of an inorganic material is used instead of the clay mineral.

Specific examples of suitable inorganic materials include ceramic insulating materials such as alumina and carbon insulating materials obtained by processing C _{60 and the} like. Among these, alumina, fine plate-like powder is obtained,
Moreover, since it is easy to disperse in the solid polymer electrolyte, it is particularly preferable. Since the other points are the same as those of the composite polymer electrolyte according to the first embodiment, description thereof will be omitted.

The composite polymer electrolyte according to this embodiment is
A method of dispersing a plate-like powder in a solution in which a solid polymer electrolyte or a precursor thereof is dissolved and solidifying, a method of forming a kneaded product by kneading by adding a plate-like powder to a molten precursor, or It can be produced by a method of forming a plate-like powder in that case using a hydrothermal method. If the molding method, molding conditions, etc. are optimized at this time, a composite polymer electrolyte in which plate-like powders are dispersed in parallel with each other can be obtained.

The composite polymer electrolyte according to this embodiment is
Since the plate-like powder is uniformly dispersed, rigidity, strength and heat resistance are improved. In addition, since the plate-like powder increases the rigidity, micro shorts are suppressed during MEA production or during operation. Further, the physical shielding effect of the plate-like powder suppresses gas crossover. In particular,
In the case where the composite polymer electrolyte according to the present embodiment is formed into a film, the plate powder is dispersed so that the surface occupying the largest area of the plate powder is parallel to the film surface,
Micro shorts and crossovers can be efficiently suppressed.

[0076]

EXAMPLES Example 1 High-purity Na-montmorillonite (Kunipia (registered trademark) F, manufactured by Kunimine Industries Co., Ltd.) was dispersed in water to prepare a 0.2 wt% dispersion liquid A. Further, a commercially available Nafion solution (manufactured by Aldrich) was diluted with water to prepare a 2 wt% solution B. Next, dispersion A
While stirring 25.6 g, a predetermined amount of the solution B was dropwise mixed to obtain a mixed solution. Using this mixed solution, a film was produced by a casting method.

Next, the obtained film was subjected to vacuum heat treatment at 140 ° C. to remove water. Next, this was washed twice with 15% nitric acid and then twice with distilled water to obtain a Nafion-montmorillonite composite film. Observation of the fracture surface of the composite film obtained in this example with a scanning electron microscope showed that layered clay mineral particles having an average particle size of 1 μm and a thickness of 5 nm were dispersed parallel to the film surface. Was confirmed. Also,
The obtained film had a thickness of 26 μm and a montmorillonite content of 2.5 wt%.

(Example 2) The weight of Dispersion A was 52.6 g.
A Nafion-montmorillonite composite film was obtained by following the same procedure as in Example 1 except for the above. The composite film obtained in this example had a thickness of 25 μm and a montmorillonite content of 5.0 wt%.

(Example 3) The weight of Dispersion A was set to 111.1.
A Nafion-montmorillonite composite film was obtained by following the same procedure as in Example 1 except that g was used. The composite film obtained in this example had a thickness of 26 μm and a montmorillonite content of 10.0 wt%.

(Example 4) The weight of Dispersion A was 428.6.
A Nafion-montmorillonite composite film was obtained by following the same procedure as in Example 1 except that g was used. The composite film obtained in this example had a thickness of 24 μm and a montmorillonite content of 30.0 wt%.

(Comparative Example 1) Nafion 1 having a thickness of 27 μm
Eleven membranes were used directly in the experiment.

Regarding the composite membranes obtained in Examples 1 to 4 and the Nafion 111 membrane obtained in Comparative Example 1, the electric conductivity,
The hydrogen permeability coefficient and the oxygen permeability coefficient were measured. The electrical conductivity was calculated from the film resistance obtained by the alternating current method (measurement frequency 10 kHz) in pure water at 25 ° C. and the film thickness. The hydrogen and oxygen permeation coefficients were measured using a gas permeation apparatus manufactured by Yamato Scientific Co., Ltd. The measurement temperature of the permeation coefficient was 25 ° C., and the gas to be measured was supplied to the apparatus in a state of being humidified to a relative humidity of 40 to 60% using a bubbler.

Further, a platinum carbon electrode was joined to the obtained membrane to prepare a fuel cell. Next, for each fuel cell, under the conditions shown in Table 1, the open circuit voltage (OCV) and the output voltage when the steady operation (current density 0.5 A / cm ² ) were performed were evaluated. Further, the cell was completely dried and the cell resistance was measured. The results are shown in Table 2.

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[Table 1]

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[Table 2]

The electrical conductivity of the composite film is 30 w of clay.
It was almost the same as the Nafion 111 film (Comparative Example 1) except for Example 4 in which t% was set. The output voltage of the fuel cell produced using the composite membrane was almost the same as that of Comparative Example 1 except for Example 4 in which the membrane was damaged during MEA production. That is, even if the clay mineral is dispersed in the solid polymer electrolyte,
It did not adversely affect the output characteristics.

On the other hand, both the hydrogen and oxygen permeability coefficients became smaller as the amount of clay increased. Also,
The open circuit voltage of the fuel cell increased as the amount of clay increased. The open circuit voltage is an index of gas leak, and the higher the open circuit voltage, the less the gas leak.

Furthermore, the cell resistance during dryness increased as the amount of clay increased. The cell resistance is a measure of the amount of micro shorts, and the higher the cell resistance, the smaller the amount of micro shorts.

From Table 2, it can be seen that by dispersing an appropriate amount of layered clay mineral inside Nafion, hydrogen and oxygen crossovers and micro shorts can be suppressed without sacrificing electrical conductivity and output voltage.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments and various modifications can be made without departing from the gist of the present invention. is there.

For example, in the above-described embodiment, the example in which the plate-like powder made of the clay mineral or the inorganic material is dispersed in the solid polymer electrolyte has been described. Both of the plate-like powders may be dispersed. Alternatively, in the solid polymer electrolyte,
In addition to dispersing the plate-like powder made of clay mineral and / or inorganic material, an amorphous inorganic material such as silica or zirconium phosphate may be further dispersed.

Further, in the above-mentioned embodiment, an example in which the composite polymer electrolyte according to the present invention is applied to a solid polymer fuel cell has been described, but the use of the present invention is not limited to this. The present invention can also be applied to various electrolytic devices, hydrogen and / or oxygen concentrators, various sensors, and the like.

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The composite polymer electrolyte according to the present invention has the effect of improving rigidity, strength and heat resistance because clay mineral is dispersed in the solid polymer electrolyte. In addition, when the layered clay mineral is dispersed, there is an effect that micro shorts and gas leak can be efficiently suppressed during MEA production and during operation. In particular, when the layered clay mineral is dispersed so that its layer surfaces are parallel to each other, there is an effect that the micro short circuit and the gas leak can be more efficiently suppressed by the physical shielding effect.

In addition, 2 of the composite polymer electrolyte according to the present invention
Secondly, since plate-like particles made of an inorganic material are dispersed in the solid polymer electrolyte, there is an effect that rigidity, strength and heat resistance are improved. Further, the physical shielding effect of the plate-like powder has an effect that micro shorts and gas leak can be efficiently suppressed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a composite polymer electrolyte according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an MEA produced using the composite polymer electrolyte shown in FIG.

[Explanation of symbols]

10 Composite polymer electrolyte 12 Solid polymer electrolyte 14 Clay minerals (layered clay minerals)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/10 H01M 8/10 (72) Inventor Usuki Arimitsu Aichi-gun Aichi-gun Nagakute-machi Nagakage-cho Yokozoji 41 Address No. 1 F-term in Toyota Central Research Laboratory Co., Ltd. (reference) 4J002 AA041 BC121 BN201 CE001 CF001 CF141 CG001 CG021 CH071 CH091 CL001 CL071 CM041 CN011 CN031 DA016 DE140 DJ006 DJ036 DJ046 DJ056 FA016 FB086 FD111 GQ02 5G12 CA26 CD01 5H12 CA26 CD01 5H12 CA26 CD01

Claims (6)

[Claims] 1. A composite polymer electrolyte comprising a solid polymer electrolyte and a clay mineral dispersed in the solid polymer electrolyte. 2. The composite polymer electrolyte according to claim 1, wherein the clay mineral is a layered clay mineral. 3. The composite polymer electrolyte according to claim 2, wherein the layered clay mineral is dispersed in the solid polymer electrolyte so that the layer surfaces thereof are parallel to each other. 4. A composite polymer electrolyte comprising a solid polymer electrolyte and a plate-like powder made of an inorganic insulating material dispersed in the solid polymer electrolyte. 5. An electrochemical device using the composite polymer electrolyte according to any one of claims 1 to 4. 6. A fuel cell using the composite polymer electrolyte according to any one of claims 1 to 4.