JP2002324556A - Solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer fuel cell and a solid polymer fuel stack which is superior m generating properties. SOLUTION: A solid polymer fuel cell, which supports a film-electrode joint arranging electrodes on both sides of a solid polymer electrolyte film and gas seal laminated and arranged on the film around the electrodes with a separator from both sides, is provided in the invention. The solid polymer fuel cell is accomplished by the solid polymer fuel cell comprising a thickness of the gas seal made thinner than that of the electrodes before it is supported with the separator from both sides to improve adhesion of the separator and the electrodes and by the solid polymer fuel stack laminating these solid polymer fuel cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polymer electrolyte fuel cell having improved adhesion between a separator and an electrode.

[0002]

2. Description of the Related Art Conventionally, a polymer electrolyte fuel cell shown in FIG. 1 is known. The solid polymer electrolyte membrane 1 in the figure has proton conductivity. On both sides thereof, a gas diffusion electrode 4 on which a catalyst layer 2 having an oxidizing ability for a fuel (hydrogen, methanol, etc.) or a catalyst layer 3 having a reducing ability for an oxidizing agent (oxygen, air, etc.) is disposed, The membrane-electrode assembly 5 is joined. An end of the polymer electrolyte membrane 1 protrudes outward from an end of the gas diffusion electrode 4, and a gas seal (for example, rubber packing) for suppressing leakage of fuel and oxidant is provided on both sides of the protruding portion. And a sealing agent) 6 are provided. These membrane-electrode assembly 5 and gas seal 6
Are sandwiched by separators 9 each having a fuel supply path 7 or an oxidant supply path 8 formed therein, and a polymer electrolyte fuel cell 10 is configured.

Heretofore, individual materials constituting the polymer electrolyte fuel cell 10 have been studied in detail. For example, Japanese Patent Application Laid-Open No. 2000-100456 discloses a method of manufacturing a membrane-electrode assembly in which the thickness of a solid polymer electrolyte at an electrode bonding portion, which is a power generation region, is made smaller than the thickness of a portion protruding from an electrode periphery. A method has been proposed. It is said that a high-performance polymer electrolyte fuel cell capable of reducing the resistance in the power generation region and preventing the membrane from being damaged in the non-power generation region can be obtained. JP 11
JP-A-345620 points out that when a hard gas seal such as a fluororesin is used, it is necessary to precisely adjust the thickness of the electrode and the gas seal in advance. Also, Japanese Patent Application Laid-Open No. 11-219714 points out a problem of deterioration in which a siloxane bond is broken when silicon rubber is used for a gas seal.

That is, if the thickness and the material of the gas seal are not carefully selected, a gap is formed between the separator and the gas seal, and the fuel or oxidant gas leaks and the performance is reduced, and the adhesion between the separator and the electrode is insufficient. In some cases, the desired power generation characteristics could not be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and has been developed in consideration of a membrane-electrode assembly in which electrodes are arranged on both sides of a solid polymer electrolyte membrane, and an electrode peripheral portion. A polymer electrolyte fuel cell in which a gas seal laminated on a membrane is sandwiched between separators, and the thickness of the gas seal before sandwiching the separator is made smaller than the thickness of the electrode, so that the separator and the electrode adhere to each other. By improving the gender,
It is an object of the present invention to provide a polymer electrolyte fuel cell capable of exhibiting excellent power generation characteristics.

[0006]

That is, the present invention provides a membrane-electrode assembly in which electrodes are arranged on both sides of a solid polymer electrolyte membrane,
A gas seal laminated on the membrane of the electrode peripheral portion, a polymer electrolyte fuel cell unit sandwiched by a separator,
A polymer electrolyte fuel cell, wherein the thickness of the gas seal before being held by the separator is smaller than the thickness of the electrode. In the polymer electrolyte fuel cell of the present invention, the thickness of the electrode (d ₁ ) and the thickness of the gas seal (d ₂ ) are 0.3 × d ₁ <d ₂ <0.9 × d ₁ . It is preferable to satisfy the relational expression.

The solid polymer electrolyte membrane used in the polymer electrolyte fuel cell of the present invention is a perfluorocarbon sulfonic acid membrane, a polyimide containing a proton conductive substituent or a proton conductive substance, or a proton polymer. It is preferable to use either a conductive substituent or polyphenylene sulfide containing a proton conductive substance.

Further, the polymer electrolyte fuel cell stack of the present invention is preferably a stack of a plurality of the polymer electrolyte fuel cells.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The polymer electrolyte fuel cell of the present invention comprises a membrane-electrode assembly in which electrodes are arranged on both sides of a polymer electrolyte membrane, and a gas seal laminated on the membrane at the periphery of the electrode. Wherein the thickness of the gas seal before sandwiching the separator is made smaller than the thickness of the electrode, thereby improving the adhesion between the separator and the electrode. .

The polymer electrolyte fuel cell shown in FIG.
(Before holding by the separator)
Explain the light. On both sides of the solid polymer electrolyte membrane 1, d₁of
A gas diffusion electrode 4 having a thickness is arranged, and membrane-electrode bonding is performed.
The body 5 is constituted. Further, the end of the electrode 4 at the periphery of the electrode 4
On the more protruding solid polymer electrolyte membrane 1, the thickness d of the electrode
₁Thinner than d_TwoGas seals 6 having
It is. These are held by the separator 9 as shown in FIG.
Thus, the polymer electrolyte fuel cell 10 of the present invention is configured.
It is.

Here, the thickness d ₁ of the electrode 4 is the sum of the thickness of the catalyst layer 2 of the fuel electrode or the catalyst layer 3 of the oxidizer electrode and the thickness of the support such as conductive carbon paper or carbon cloth. Defined. The thickness d _{1 of the} electrode 4 and the thickness d _{2 of the} gas seal are defined by measured values of a general thickness measuring jig such as a micrometer and a dial gauge, respectively.

At this time, the thickness of the portion held by the separator 9 depends on the pressure holding the separator 9, the thickness of each of the solid polymer electrolyte 1, the electrode 4 and the gas seal 6, the compressive deformation strain, the electrode portion and the gas. Although it varies depending on the area ratio of the seal portion, etc., the thickness is generally determined to be slightly smaller than the sum of the thickness of the solid polymer electrolyte membrane and the thickness of the gas seal.

At this time, the thickness of the portion held by the separator 9 depends on the pressure holding the separator 9, the thickness of each of the solid polymer electrolyte 1, the electrode 4 and the gas seal 6, the compressive deformation strain, the electrode portion and the gas. Although it varies depending on the area ratio of the seal portion, etc., the thickness is generally determined to be slightly smaller than the sum of the thickness of the solid polymer electrolyte membrane and the thickness of the gas seal. At this time, the thickness d _{1 of the} electrode 4 and the thickness d _{2 of the} gas seal
Preferably satisfies the relational expression 0.3 × d ₁ <d ₂ <0.9 × d ₁ . Furthermore, 0.4 × d ₁ <d ₂ <0.8 × d
It is more preferable to satisfy the relational expression of ₁ . in this way,
By optimizing the thickness of the electrode and the gas seal, the separator 9 and the gas diffusion electrode 4 are sufficiently adhered to each other, so that the fuel flow path 7 and the oxidant flow path 8 are surely formed. 9 can also be secured. Therefore, the fuel (hydrogen, methanol, etc.)
Is easily and efficiently supplied to the gas diffusion electrode 4. Further, the oxidant (oxygen, air, etc.) is easily and efficiently supplied to the gas diffusion electrode 4 through the oxidant flow path 8. Therefore, it is presumed that an efficient catalytic reaction occurs in the catalyst layers 2 and 3 and that the catalyst layers 2 and 3 exhibit excellent power generation characteristics. In addition, water supplied for humidifying the fuel and the oxidant and water generated at the oxidant electrode can also be efficiently and uniformly diffused in the electrode 4, so that the gas diffusion layer is less likely to be clogged by the water, It is estimated that the power generation characteristics are unlikely to decrease. If the thickness of the gas seal 6 is smaller than these ranges, the adhesion between the gas seal 6 and the separator 9 or the solid polymer electrolyte membrane 1 becomes insufficient, and the periphery of the electrode 4 on which the gas seal 6 is disposed The fuel and the oxidant are likely to leak to the part side, the fuel and the oxidant are not effectively used, and the performance of the cell may be deteriorated, which is not preferable. Gas seal 6
If the thickness is larger than these ranges, the contact between the electrode 4 and the separator 9 becomes insufficient, so that the fuel or the oxidizing agent is not efficiently supplied to the electrode 4 or the conductive property between the separator 9 and the electrode 4 is low. Poor performance may occur and cell performance may be reduced, which is not preferable.

Next, the polymer electrolyte fuel cell 1 of the present invention
The constituent material No. 0 will be described. Solid polymer electrolyte membrane 1
Examples thereof include sulfonic acid groups, phosphoric acid groups, carboxylic acid groups, proton conductive substituents such as phenolic hydroxyl groups, 12-tungstophosphoric acid, tungsten peroxo complexes, monododecyl phosphate, and proton conductive substances such as phosphoric acid. Containing polymer membranes can be used. Further, in order to improve the water retention of the polymer membrane, the retention of the proton conductive substance, and the like, a composite of an inorganic substance typified by a silicon-based compound such as silica may be used. Such polymer electrolyte membranes include, for example, perfluorocarbon sulfonic acid membranes represented by Nafion (manufactured by DuPont), Flemion (manufactured by Asahi Glass), Aciplex (manufactured by Asahi Kasei), and sulfonated polyetheretherketone (JP-A-Hei. 6
-93114, etc.), sulfonated polyethersulfone (JP-A-10-45913, etc.), sulfonated polysulfone (JP-A-9-245818, etc.), sulfonated polyphenylene sulfide (Tokuhyohei 11-5)
10198, etc.) and sulfonated polyimide (Table 2000)
JP-A-5510511), sulfonated SEBS (abbreviation of styrene- (ethylene-butylene) -styrene) (JP-A-10-503788), and a composite material of a proton-conductivity imparting agent and an organic polymer compound. A proton conductive membrane (Japanese Patent Application Laid-Open No. 2000-90946, etc.) can be exemplified, but the present invention is not limited to these, and an improved product thereof or a product having another composition can also be used. In the present invention, the characteristics required for a fuel cell membrane (proton conductivity, gas barrier properties, thermal / chemical stability,
Cost, etc.), a perfluorocarbon sulfonic acid membrane, a polyimide containing a proton conductive substituent or a proton conductive substance, polyphenylene sulfide,
It is preferable that it is either.

As the perfluorocarbon sulfonic acid membrane, it is preferable to use commercially available Nafion (manufactured by DuPont), Flemion (manufactured by Asahi Glass), Aciplex (manufactured by Asahi Kasei), Gore Select (manufactured by Gore-Tex), or the like. In addition, fibers reinforced with a fiber such as polytetrafluoroethylene, a porous support, or a nonwoven fabric can also be used.

The polyimide containing a proton conductive substituent or a proton conductive substance is described in JP-A-2000-5.
Patent No. 10511, sulfonated polyimide containing a sulfonic acid group-containing diamine as a copolymer component, and aromatic compounds such as Kapton (manufactured by Dupont), Apical (manufactured by Kaneka Chemical Industry), and Upilex (manufactured by Ube Industries) Polyimide film in which a sulfonic acid group is introduced by bringing a group-based polyimide film into contact with a sulfonating agent (chlorosulfonic acid, sulfur trioxide, fuming sulfuric acid, concentrated sulfuric acid, etc.), polyimide and a proton-conductive substance (phosphoric acid, 12-tungstic acid) Phosphoric acid)
It is preferable to use a compound of the above.

Examples of the polyimide containing a proton conductive substituent or a proton conductive substance include those described in JP-A-11-51.
No. 0198, a solvent-soluble sulfonated polyphenylene sulfide prepared and formed into a film, or a polyphenylene sulfide film such as Torelina (manufactured by Toray Industries, Inc.) and a sulfonating agent (chlorosulfonic acid, sulfur trioxide, fuming) It is preferable to use a polyphenylene sulfide film or the like in which a sulfonic acid group is introduced by contact with sulfuric acid or concentrated sulfuric acid.

The thickness of the solid polymer electrolyte membrane is not particularly limited, but is preferably as thin as possible, as long as it has practical mechanical strength and fuel / oxidant barrier properties, and is preferably in the range of about 5 to 200 μm.

As the gas diffusion electrode 4 used in the present invention, those used in ordinary polymer electrolyte fuel cells can be used. Specifically, a noble metal catalyst such as platinum or platinum / ruthenium, which has the ability to oxidize a fuel (hydrogen, methanol, etc.), is supported on a conductive carbon paper or carbon cloth having fine pores through which gas can pass. The catalyst layers 2 and 3 were respectively formed by one supported on a carrier such as activated carbon and one supported on a carrier such as activated carbon by a noble metal catalyst such as platinum having a reducing ability of an oxidizing agent (oxygen or air). Things are used. On both sides of the solid polymer electrolyte membrane 1,
A membrane-electrode assembly 5 is used in which the catalyst layers 2 and 3 of the gas diffusion electrode 2 are arranged and bonded by an adhesive layer made of a polymer compound having proton conductivity.
As the gas diffusion electrode 4, E-TEK or Electr
Even if a commercially available product from oChem or the like is used,
It is also possible to use a material prepared independently using the above materials.

As the gas seal 6 of the present invention, any gas seal having a property of blocking fuel and oxidant can be used. Generally, a flexible gas seal made of rubber or the like can be used. Materials used for the gas seal 6 include fluoro rubber, silicon rubber, olefin rubber (ethylene-propylene rubber, acrylic rubber, butyl rubber, halogenated butyl rubber, etc.), diene rubber (isoprene rubber, butadiene rubber, nitrile rubber, chloroprene rubber). Rubber, etc.), and a blend of these can be used. The gas seal 6 is provided with a material processed in advance into a predetermined thickness or shape (sheet shape, O-ring shape, or the like), or is applied with a fluid sealing material or the like to a predetermined thickness or shape and cured. Can be used. Further, the separator 9
And those having adhesiveness to the solid polymer electrolyte membrane 1 can also be used.

As the separator 9, a separator having conductivity and mechanically and electrochemically stable can be used. Generally, a material obtained by processing carbon graphite, stainless steel, or the like to form a fuel and oxidant flow path is used.

The polymer electrolyte fuel cell stack of the present invention is constituted by arbitrarily stacking a plurality of the polymer electrolyte fuel cells described above. The specifications such as the cell size and the number of stacked cells may be determined in consideration of the size and output (current / voltage) according to the application. Thereby, a polymer electrolyte fuel cell stack having excellent power generation characteristics can be obtained,
preferable.

The polymer electrolyte fuel cell and the polymer electrolyte fuel cell stack according to the present invention use pure hydrogen,
Oxygen, air, and the like can be used as oxidizing agents, such as methanol, natural gas, gasoline, and other reformed gases, methanol, dimethyl ether, and the like. These are useful as polymer electrolyte fuel cells that can be used as automobiles, home cogeneration systems, consumer portable devices (such as mobile phones), emergency power supplies, and outdoor power supplies for leisure and construction.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples, and can be appropriately modified without departing from the scope of the invention.

A measurement method and the like will be described prior to the embodiment.

(Ion exchange capacity) A test specimen was immersed in a saturated aqueous solution of sodium chloride,
Let react for hours. After cooling to room temperature, the sample is sufficiently washed with ion-exchanged water, and titrated with a 0.01 N aqueous sodium hydroxide solution using a phenolphthalein solution as an indicator to calculate the ion exchange capacity.

(Proton conductivity) A test specimen (10 mm × 40 mm) stored in ion-exchanged water is taken out, and water on the surface of the test specimen is wiped off with a filter paper. A test specimen was mounted between platinum electrodes at a distance between the electrodes of 30 mm, placed in a two-pole non-sealed Teflon (registered trademark) cell, and then subjected to a voltage of 0.2 V at room temperature.
Under the conditions of AC impedance method (frequency: 42 Hz to
5 MHz), the membrane resistance of the specimen was measured, and the proton conductivity was calculated.

(Power generation characteristics) ElectroChem
Solid polymer fuel cell (electrode area: 5 cm) ^Two)
The separately prepared membrane-electrode assembly and gas seal
And installed, Scribner fuel cell evaluation system
Was used to measure power generation characteristics under predetermined conditions.

(Example 1) As a solid polymer electrolyte membrane,
Nafion 115 manufactured by DuPont, which is a perfluorocarbon sulfonic acid membrane, was used. Table 1 shows the ion exchange capacity and proton conductivity.

The gas diffusion electrode (thickness (d ₁ ): 280 μm, electrode area: 5 cm ² , platinum carrying amount: 1 mg / cm ² ) manufactured by ElectroChem, and the basis weight of Nafion was 0.
A 5% by weight Nafion solution (Aldrich reagent) was applied to a concentration of 6 mg / cm ² and dried under reduced pressure at 70 ° C. for 1 hour. Gas diffusion electrodes are arranged on both sides of Nafion 115, press temperature: 140 ° C., press pressure: 5.9 M
Hot pressing was performed under the conditions of Pa and a press time of 90 seconds to obtain a membrane-electrode assembly.

At the periphery of the membrane-electrode assembly, a thickness (d ₂ )
A 254 μm silicon rubber gas seal was stacked and arranged, and installed in a polymer electrolyte fuel cell. The power generation characteristics of this polymer electrolyte fuel cell were evaluated under the following conditions. The results are shown in FIG. (Power generation characteristic evaluation conditions) Cell operating temperature: 60 ° C Fuel: pure hydrogen gas, 44.77 mL / min Oxidant: oxygen gas, 39.18 mL / min Humidifying temperature: 60 ° C Back pressure: 0 MPa.

Example 2 The procedure was the same as in Example 1 except that a gas seal having a thickness (d ₂ ) of 127 μm was used. The results are shown in FIG.

Example 3 As a solid polymer electrolyte membrane,
A sulfonated polyphenylene sulfide was prepared by the following method. As the polyphenylene sulfide film, TORELINA (thickness: 50 μm) manufactured by Toray Industries, Inc. was used. Polyphenylene sun sulfide film 0.88
g was immersed in a mixed solution of 1.90 g of chlorosulfonic acid and 380 g of dichloromethane at room temperature for 20 hours. After a lapse of a predetermined time, the resultant was sufficiently washed with ion-exchanged water to obtain a sulfonated polyphenylene sulfide. Table 1 shows the ion exchange capacity and proton conductivity of this sulfonated polyphenylene sulfide.

[Table 1]

Example 1 was repeated except that this sulfonated polyphenylene sulfide was used as a solid polymer electrolyte. The results are shown in FIG.

Example 4 The procedure was the same as Example 5 except that a gas seal having a thickness (d ₂ ) of 127 μm was used. The results are shown in FIG.

(Example 5) The cell temperature was 80 ° C, the humidification temperature of hydrogen and oxygen was 80 ° C, and the back pressure of hydrogen and oxygen was 0.2MP.
Except having changed into a, it was the same as Example 5. The results are shown in FIG.

Example 6 The procedure was the same as in Example 7 except that a gas seal having a thickness (d ₂ ) of 127 μm was used. The results are shown in FIG.

Comparative Example 1 The procedure was the same as in Example 1 except that a gas seal having a thickness (d ₂ ) of 300 μm was used. The results are shown in FIG.

Comparative Example 2 The procedure of Example 3 was repeated except that a gas seal having a thickness (d ₂ ) of 300 μm was used. The results are shown in FIG.

Comparative Example 3 The procedure of Example 5 was repeated except that a gas seal having a thickness (d ₂ ) of 300 μm was used. The results are shown in FIG. Comparison between Example 1 of FIG. 3 and Comparative Example 1,
A comparison between Example 3 and Comparative Example 2 in FIG. 4 and a comparison between Example 5 and Comparative Example 3 in FIG. 5 shows that the thickness of the gas seal (d ₂ ) is smaller than that of the electrode (d ₁ ). The polymer electrolyte fuel cell of the present invention exhibits superior power generation characteristics as compared with the comparative example in which the thickness of the gas seal (d ₂ ) is larger than the thickness of the electrode (d ₁ ), and the present invention is effective. Sex was shown.

The comparison between Examples 1 and 2 in FIG. 3, the comparison between Examples 3 and 4 in FIG. 4, and the comparison between Examples 5 and 6 in FIG. 5 shows that the electrode thickness (d ₁ ) and gas Seal thickness (d ₂ )
Is a polymer electrolyte fuel cell (d ₂ = 0.10) configured to satisfy the relational expression of 0.3 × d ₁ <d ₂ <0.9 × d ₁ .
45 × d ₁ ) exhibited even more excellent power generation characteristics, indicating the effectiveness of the present invention.

[0043]

According to the present invention, a membrane-electrode assembly having electrodes disposed on both sides of a solid polymer electrolyte membrane and a gas seal laminated on a film on the periphery of an electrode are sandwiched by a separator. A polymer electrolyte fuel cell, wherein the thickness of the gas seal before sandwiching the separator is made smaller than the thickness of the electrode to improve the adhesion between the separator and the electrode. Exhibits excellent power generation characteristics as compared with conventional ones.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a polymer electrolyte fuel cell (after sandwiching a separator).

FIG. 2 is a cross-sectional view of a main part of a polymer electrolyte fuel cell (before holding a separator).

FIG. 3 shows a relationship between current density and cell voltage of a polymer electrolyte fuel cell (Nafion 115, cell temperature: 60 ° C., back pressure: 0 MPa).

FIG. 4 Relationship between current density and cell voltage of a polymer electrolyte fuel cell (sulfonated polyphenylene sulfide, cell temperature: 60 ° C., back pressure: 0 MPa)

FIG. 5: Relationship between current density and cell voltage of a polymer electrolyte fuel cell (sulfonated polyphenylene sulfide, cell temperature: 80 ° C., back pressure: 0.2 MPa)

[Explanation of symbols]

 1: Solid polymer electrolyte membrane 2: Electrode catalyst layer (fuel electrode) 3: Electrode catalyst layer (oxidant electrode) 4: Gas diffusion electrode 5: Membrane-electrode assembly 6: Gas seal 7: Fuel flow path 8: Oxidation Agent flow path 9: Separator 10: Polymer electrolyte fuel cell

Claims (6)

[Claims] 1. A polymer electrolyte fuel cell comprising a membrane-electrode assembly having electrodes arranged on both sides of a polymer electrolyte membrane, and a gas seal laminated on the membrane at the periphery of the electrodes sandwiched by separators. A polymer electrolyte fuel cell, wherein the thickness of the gas seal before being held by the separator is smaller than the thickness of the electrode. Wherein the thickness of the electrodes (d _1), the gas seal of thickness (d ₂₎ is, according to claim 1 satisfying _{0.3 × d 1 <d 2 <} 0.9 × d 1 of equation The polymer electrolyte fuel cell according to the above. 3. The polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte membrane is a perfluorocarbon sulfonic acid membrane. 4. The polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte membrane is a polyimide containing a proton conductive substituent or a proton conductive substance. 5. The polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte membrane is a polyphenylene sulfide containing a proton conductive substituent or a proton conductive substance. 6. A polymer electrolyte fuel cell stack in which a plurality of the polymer electrolyte fuel cells according to claim 1 are stacked.