JP2000100456A - Method for producing joined body of solid polymer electrolyte membrane and electrode and solid polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the battery performance and prevent the breakdown of a solid polymer electrolyte film. SOLUTION: In this manufacturing method of a joint 10 of a solid polymer electrolyte film 1 and electrodes, the solid polymer electrolyte film 1 is pinched by an anode electrode 2 and a cathode electrode 3, and they are jointed under pressure so that the film thickness of the electrode faying portion of the power generation region 6 of the solid polymer electrolyte film 1 is made thinner than the film thickness of the periphery section (seal section 7) of the power generation region 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid polymer electrolyte membrane-electrode assembly, a method for producing the same, and a solid polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art In recent years, solid polymer electrolyte fuel cells operate at low temperatures, have high output densities, are being researched as small and lightweight power sources, and are being applied to automobiles, living, leisure, and other applications. Has reached the practical range, but in general, the structural unit of the battery is composed of a stack of several tens to several hundreds of solid polymer electrolyte membranes, and a uniform power generation within one membrane surface and the solid height. There is a demand for high strength reliability such that even a single molecular electrolyte membrane does not break.

The solid polymer electrolyte membrane serves as an electrolyte for the solid polymer electrolyte fuel cell and also serves as a gas seal for separating a fuel gas on the anode electrode side and an oxidizing gas on the cathode electrode side. .

FIG. 2 is a schematic sectional view of a single cell of a general solid polymer electrolyte fuel cell. In the single cell of the solid polymer electrolyte fuel cell, a solid polymer electrolyte membrane-electrode assembly 20 in which a solid polymer electrolyte membrane 11 is sandwiched between an anode electrode 12 and a cathode electrode 13 by hot pressing or the like is sandwiched between fuel cells. Alternatively, it has a structure in which separators 14a and 14b having a flow groove for an oxidizing gas and having a function of extracting electricity generated by the assembly 20 of the solid polymer electrolyte membrane and the electrode to the outside are provided.

The electrode 12 of the solid polymer electrolyte membrane 11,
The fuel gas and the oxidizing gas are sealed by a seal ring 15 using a peripheral portion 17 of a power generation region 16 which is a joint portion with the fuel gas 13. The solid polymer electrolyte membrane 11 has a constant thickness.

At the anode electrode 12, the following reaction occurs when hydrogen in the fuel gas comes into contact with the catalyst.

2H ₂ → 4H ⁺ + 4e ⁻ H ⁺ moves through the solid polymer electrolyte membrane 11, reaches the catalyst of the cathode electrode 13, reacts with oxygen in the oxidant gas to form water.

[0008] 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O In a solid polymer electrolyte fuel cell, an electromotive force is generated by the above reaction.

When electricity is taken out, the solid polymer electrolyte membrane 11 functions as an internal resistance, and the lower the internal resistance, the better the battery performance. It is desirable that the thickness of the region 16 be thin.

On the other hand, the peripheral portion 17 of the solid polymer electrolyte membrane 11 has a problem that the compressive stress caused by the gas and the pressure of the sealing gas fluctuate and the bending stress acts repeatedly, so that the thin film thickness is damaged. Occurs. When the peripheral portion 17 of the solid polymer electrolyte membrane 11 is damaged, the fuel gas and the oxidizing gas come into direct contact with each other and the amount used in the fuel cell decreases. The output drops.

As a prior art, Japanese Patent Application Laid-Open No. 8-185883
In the publication, the solid polymer electrolyte membrane is placed on the stage of the spin coating apparatus and rotated, the solution of the solid polymer electrolyte membrane is dropped from above the center of rotation, and the solid polymer electrolyte membrane is rotated until the solvent of the solution is evaporated. A method for producing a solid polymer electrolyte membrane is disclosed in which a change in film thickness is created by utilizing the action of centrifugal force, and the thickness of the central portion of the solid polymer electrolyte membrane is made thinner than the peripheral portion. .

More specifically, as described above.

[0013]

However, according to the prior art, if the central portion is made thinner and the peripheral portion is made thicker due to the principle of spin coating, the film thickness is not uniform and the central portion of the solid polymer electrolyte membrane is thinner and circular. It gradually changes thickly in the circumferential direction.

When a solid polymer electrolyte fuel cell is manufactured using the solid polymer electrolyte membrane produced in this manner and power is generated, current concentration occurs in a thinner portion, causing local heat generation such as local heat generation. Occurs.

Further, in the production method by spin coating, since the solvent in the solution of the solid polymer electrolyte membrane has to evaporate and solidify as the solid polymer electrolyte membrane, the spin coating apparatus must continue to rotate, resulting in poor productivity. There is a problem in that the cost is high, and the quality varies widely.

The present invention has solved the above-mentioned problems, and it is a low-cost assembly of a polymer electrolyte membrane and an electrode capable of preventing breakage of the polymer electrolyte membrane and improving battery performance, a method of manufacturing the same, and a method of manufacturing the same. Provided is a polymer electrolyte fuel cell.

[0017]

Means for Solving the Problems In order to solve the above technical problems, the technical means (hereinafter referred to as first technical means) taken in claim 1 of the present invention is a solid polymer electrolyte. The membrane is sandwiched between the electrodes, and the solid polymer electrolyte membrane is joined by applying pressure so that the film thickness of the electrode bonding portion, which is the power generation region, is smaller than the film thickness of the peripheral portion of the power generation region. A method for producing a joined body of a solid polymer electrolyte membrane and an electrode.

The effects of the first technical means are as follows.

That is, the strength of the peripheral portion of the power generation region, which is the gas seal portion, can be improved, and the internal resistance of the solid polymer electrolyte fuel cell can be reduced. A joined body of a solid polymer electrolyte membrane and an electrode that can prevent the electrolyte membrane from being damaged can be manufactured at a low cost by a simple method.

In order to solve the above technical problem, the technical means (hereinafter referred to as the second technical means) taken in claim 2 of the present invention is that the solid polymer electrolyte membrane is made of perfluorocarbon sulfone. 2. The method for producing a joined body of a solid polymer electrolyte membrane and an electrode according to claim 1, wherein the joined body is an acid-based resin.

The effects of the second technical means are as follows.

That is, the use of the above-mentioned materials has an effect that a high-performance solid polymer electrolyte fuel cell can be obtained.

In order to solve the above technical problem, the technical means (hereinafter referred to as the third technical means) taken in claim 3 of the present invention is that the solid polymer electrolyte membrane is made of a fluorocarbon-based material. The method for producing a solid polymer electrolyte membrane / electrode assembly according to claim 1, wherein the sulfonic acid resin is a copolymer of a vinyl monomer and a hydrocarbon vinyl monomer.

The effects of the third technical means are as follows.

That is, the use of the above-mentioned materials has an effect that a high-performance and low-cost solid polymer electrolyte fuel cell can be obtained.

In order to solve the above technical problem, a technical means (hereinafter referred to as a fourth technical means) taken in claim 4 of the present invention is to sandwich a solid polymer electrolyte membrane between electrodes. Thus, the bonding between the solid polymer electrolyte membrane and the electrode is performed by applying pressure so that the film thickness of the electrode joining portion which is the power generation region of the solid polymer electrolyte membrane is made smaller than the film thickness of the peripheral portion of the power generation region. A solid polymer electrolyte fuel cell characterized in that the body is sandwiched between separators.

The effects of the fourth technical means are as follows.

That is, since the solid polymer electrolyte membrane can be prevented from being damaged and the internal resistance in the power generation region can be reduced, a solid polymer electrolyte fuel cell having high cell performance and high reliability can be reduced in cost. it can.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings.

From the viewpoint of performance, the power generating region of the solid polymer electrolyte membrane desirably has a low resistance, that is, a thin film thickness. On the other hand, the periphery of the solid polymer electrolyte membrane which supports and fixes the solid polymer electrolyte membrane is compressed,
It is desirable to increase the film thickness in view of durability against repeated bending.

According to the present invention, an assembly of a solid polymer electrolyte membrane and an electrode in which the thickness of the power generation region of the solid polymer electrolyte membrane is thinner than the thickness of the periphery of the power generation region is industrially advantageously produced. Things.

The joined body of the solid polymer electrolyte membrane and the electrode of the present invention is produced by sandwiching the solid polymer electrolyte membrane between the electrodes from above and below and pressing it with a press at room temperature or in a heated state. At this time, the solid polymer electrolyte membrane may be in a dry, wet or completely absorbed state.

The portion of the solid polymer electrolyte membrane sandwiched between the electrodes becomes thinner in accordance with the temperature and pressure, and the portion of the solid polymer electrolyte membrane that is gas-sealed around the periphery thereof and is not subjected to a press pressure is not crushed and is not crushed. Is ensured.

The solid polymer electrolyte membrane that can be used in the present invention is a perfluorocarbon sulfonic acid resin centered on Nafion (manufactured by DuPont) already marketed in the field of salt electrolysis, or a fluorocarbon vinyl resin. Any solid polymer electrolyte membrane that can be used for a solid polymer electrolyte fuel cell, such as a sulfonic acid-based resin of a copolymer of a monomer and a hydrocarbon-based vinyl monomer, or a material made of a hydrocarbon-sulfonic acid-based resin can be applied.

Regarding the details of the shape of the electrode, the straight portion and the corner portion of the outermost peripheral portion of the electrode which are in contact with the portion where the film thickness changes are chamfered to avoid stress concentration on the film. Needless to say, this is advantageous for securing the strength of the molecular electrolyte membrane, and the reliability is further improved.

(Embodiment) The solid polymer electrolyte membrane used in this embodiment has a copolymer of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer as a main chain, and a hydrocarbon side chain having a sulfonic acid group. It is a cation exchange membrane consisting of

Specifically, ethylene tetrafluoroethylene was irradiated with γ-rays, styrene was grafted starting from the generated radicals, and then a sulfonic acid group was introduced by a sulfonation reaction to prepare the solid polymer electrolyte membrane. .

The thickness of the solid polymer electrolyte membrane is 100 ° C.
It was 75 μm in a completely dry state, and 90 μm in a water-saturated state at room temperature.

The solid polymer electrolyte membrane having a side of 200 mm square was saturated and hydrated at room temperature, and then one side of a 180 μm thick carbon paper was coated with platinum / carbon paste and dried to obtain a 210 μm square, 185 mm side. The solid polymer electrolyte membrane is sandwiched between the two electrodes so that the outer peripheral portion of the solid polymer electrolyte membrane remains with a width of 7.5 mm, and hot pressing conditions are 160 ° C. and 80 kg / cm ^2.
, Until the total thickness became 460 μm, and this state was maintained for 1 minute.

The finished solid polymer electrolyte membrane of the joined body of the solid polymer electrolyte membrane and the electrode was almost completely dried, and the cross section was observed. The entire thickness of the power generation region where the electrodes were present was 460 μm, and the thickness of the power generation region sandwiched between the electrodes of the solid polymer electrolyte membrane was approximately 40 μm, which was almost uniformly compressed. The thickness of the solid polymer electrolyte membrane at the periphery of the power generation region was 75 μm, which was the initial thickness.

FIG. 1 is a schematic cross-sectional view of a single cell of a solid polymer electrolyte fuel cell used for evaluating a solid polymer electrolyte membrane-electrode assembly according to an embodiment of the present invention.

Reference numeral 10 denotes a joined body of the solid polymer electrolyte membrane and the electrode prepared above. Reference numeral 1 denotes a solid polymer electrolyte membrane. The thickness of the power generation region 6 is uniform and thin, and the thickness of the peripheral portion 7 of the power generation region 6 is large. 2 is the anode electrode, 3
Is a cathode electrode.

In the single cell of the solid polymer electrolyte fuel cell, the assembly 10 of the solid polymer electrolyte membrane and the electrode is provided with a fuel gas or oxidant gas flow groove, and the solid polymer electrolyte membrane is connected to the electrode. It has a structure sandwiched between separators 4a and 4b having a function of extracting electricity generated by the joined body 10 to the outside.

The fuel gas and the oxidizing gas are sealed by a seal ring 5 using a peripheral portion 7 of the power generation region 6.

The separator 4a is provided with a hydrogen supply port 21a, a hydrogen flow groove 22a, and a hydrogen discharge port 23a, and the separator 4b is provided with an air supply port 21b, an air flow groove 22b, and an air discharge port 23b. .

Hydrogen, which is a fuel gas of 2.5 atm, is supplied from the hydrogen supply port 21a to the anode electrode 2 through the hydrogen flow groove 22a, and is supplied from the air supply port 21b through the air flow groove 22b. 2.5a for cathode electrode 3
tm of oxidant gas air was supplied.

Steam was supplied to the air and the hydrogen by a bubbling method to perform humidification. The separator 4
a and the electricity generated from the electrical terminals of the separator 4b were taken out, and the resistance was changed by an external variable resistor 8 to measure and evaluate the current density and the cell voltage.

Cell temperature 80 ° C., utilization rate of hydrogen / air 80
% And 40%, the current density was 1 A /
An output of 630 mV was obtained in cm ² .

On the other hand, the tensile strength of the peripheral portion 7 of the uncompressed solid polymer electrolyte membrane was measured by the method of JIS K-6251 (No. 6 dumbbell) to be 3.5 kg / cm.
The strength retention rate, which is the tensile strength as compared with the tensile strength of the solid polymer electrolyte membrane before preparing the joined body, is almost 10%.
It was found that it was 0%, and it was confirmed that the strength of the gas seal portion was high.

(Comparative Example) A solid polymer electrolyte membrane having only a different film thickness was produced in the same manner as in the example. The thickness of the solid polymer electrolyte membrane was 40 μm in a 100 ° C. absolute dry state.
After using the solid polymer electrolyte membrane in a dry state, a small amount of an ion exchange solution (manufactured by Wako Pure Chemical Industries, Nafion 5 wt% solution) was applied to the surface of the solid polymer electrolyte membrane, and the same electrode as in the example was used. An assembly of the solid polymer electrolyte membrane and the electrode was produced under the same pressing conditions as in the example.

The entire thickness of the power generation area where the electrodes are present is 460 μm, the thickness of the power generation area sandwiched between the electrodes of the solid polymer electrolyte membrane, and the thickness of the solid polymer electrolyte membrane at the periphery of the power generation area. Was finished to the same thickness of 40 μm.

When the battery performance was evaluated in the same manner as in the example, the current density was 1 A / cm ^{2 at} almost the same level as in the example.
Output of 600 mV.

The tensile strength of the solid polymer electrolyte membrane at the peripheral portion of the power generation region was measured in the same manner as in the embodiment according to JIS K-6251.
(No. 6 type dumbbell) 2.0 kg
/ Cm, which is 57% of the tensile strength of the example. Although the tensile strength is almost proportional to the film thickness, it is important that the tensile strength is large in order to prevent breakage of the solid polymer electrolyte membrane.

As described above, in the embodiment, the thickness of the power generation region sandwiched between the electrodes of the solid polymer electrolyte membrane is uniform and thin, and the tensile strength of the peripheral portion of the electrode other than the power generation region of the solid polymer electrolyte membrane is increased. It has been confirmed that the strength of the gas seal portion can be increased while the battery performance is high, and the breakage of the solid polymer electrolyte membrane can be prevented.

The method for manufacturing a joined body of a solid polymer electrolyte membrane and an electrode according to the embodiment can be manufactured at low cost because there is no need to provide a new step.

[0056]

As described above, according to the present invention, the solid polymer electrolyte membrane is sandwiched between the electrodes, and the film thickness of the electrode junction portion, which is the power generation region of the solid polymer electrolyte membrane, is set at the periphery of the power generation region. Since the manufacturing method and the solid polymer electrolyte fuel cell of the assembly of the solid polymer electrolyte membrane and the electrode characterized by being joined by applying pressure so as to be thinner than the film thickness of the part, the cell performance is high, A solid polymer electrolyte membrane-electrode assembly and a solid polymer electrolyte fuel cell which can prevent the solid polymer electrolyte membrane from being damaged can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a single cell of a solid polymer electrolyte fuel cell used for evaluating a solid polymer electrolyte membrane-electrode assembly according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a single cell of a general solid polymer electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid polymer electrolyte membrane 2 ... Electrode (anode) 3 ... Electrode (cathode) 4a, 4b ... Separator 6 ... Power generation area 7 ... Peripheral part of electrode 10 ... Joint body of solid polymer electrolyte membrane and electrode

Claims (4)

[Claims] 1. A solid polymer electrolyte membrane sandwiched between electrodes,
A solid polymer electrolyte membrane characterized in that the solid polymer electrolyte membrane is joined by applying pressure so that the film thickness of an electrode bonding portion that is a power generation region is smaller than the film thickness of a peripheral portion of the power generation region. A method for manufacturing an electrode assembly. 2. The method according to claim 1, wherein the solid polymer electrolyte membrane is a perfluorocarbon sulfonic acid-based resin. 3. The solid polymer electrolyte membrane according to claim 1, wherein the solid polymer electrolyte membrane is a sulfonic acid resin of a copolymer of a fluorocarbon vinyl monomer and a hydrocarbon vinyl monomer. A method for manufacturing an electrode assembly. 4. A solid polymer electrolyte membrane sandwiched between electrodes,
The joined body of the solid polymer electrolyte membrane and the electrode joined by applying pressure so that the film thickness of the electrode joining portion which is the power generation region of the solid polymer electrolyte membrane is thinner than the film thickness of the peripheral portion of the power generation region. A solid polymer electrolyte fuel cell characterized by being sandwiched between separators.