Polymer electrolyte fuel cell and method for manufacturing a polymer electrolyte fuel cell

Abstract

To provide a solid polymer-type fuel battery in which durability is increased while maintaining a proton transport resistance of a polymer electrolyte membrane.SOLUTION: A solid polymer-type fuel battery of an embodiment includes: a proton conductivity polymer electrolyte membrane; a fuel electrode that is arranged so as to be adjacent to one surface of the polymer electrolyte membrane; and an oxidant electrode that is arranged so as to be adjacent to the other surface of the polymer electrolyte membrane. The polymer electrolyte membrane is a composite membrane having a first film containing a first electrolyte material, and a second film containing a second electrolyte material. The second film covers one part of the first film. An oxygen permeation of the second film is smaller than that of the first film. An tension strength of the second film is larger than that of the first film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments according to the present invention relate to a solid polymer fuel cell and a method for manufacturing the same.

Background Art

[0002] A fuel cell introduces a fuel gas containing hydrogen to a fuel electrode and an oxidant gas containing oxygen to an oxidant electrode to obtain electricity and heat through an electrochemical reaction. In a solid polymer electrolyte fuel cell, a polymer membrane is applied as an electrolyte, and electrodes are disposed on both surfaces thereof. The electrode is obtained by coating a catalyst layer on a gas diffusion layer. As the catalyst, a noble metal such as platinum supported on carbon particles is used (see Patent Document 7, etc.).

[0003] As a conventional polymer electrolyte membrane, one formed by casting perfluorosulfonic acid is used, and those having a film thickness of 15 to 100 μm are used (Patent Document 1). Perfluorosulfonic acid has fluorination in both the main chain and the side chain, that is, hydrogen bonded to carbon is substituted with fluorine, so it has the drawback of being chemically stable but expensive. In a solid polymer electrolyte fuel cell, the polymer electrolyte membrane serves as a conductor of protons and at the same time has a sealing function for reaction gases. If the polymer electrolyte membrane is damaged, cross leakage of reaction gases occurs, resulting in inoperability. In order to commercialize a fuel cell system, a highly durable polymer electrolyte membrane capable of withstanding long-term operation is required.

[0004] Unlike perfluorosulfonic acid, hydrocarbon-based membranes that are not fluorinated at all have been developed. To improve chemical stability, compounds containing aromatic compounds in the main chain, such as polyetheretherketones, are commonly used (see Patent Document 2). Patent Document 3 reports a polymer electrolyte membrane made of polyethersulfone copolymer. Because these hydrocarbon-based membranes are not fluorinated, they can be manufactured inexpensively, costing about one-tenth the price of perfluorosulfonic acid membranes. However, they have low resistance to hydrogen peroxide produced during the oxygen reduction reaction, and the polymer membrane can break down and cross-leak after several thousand hours of operation, so improvement is desired.

[0005] Many researchers have studied and reported on the mechanisms by which polymer films degrade. It is mainly believed that chemical degradation due to OH radicals generated during the dissociation of hydrogen peroxide is the cause (see Patent Document 4). Possible mechanisms for hydrogen peroxide generation include its formation from oxygen leaking from the oxidizing electrode to the fuel electrode, and its formation through a two-electron reaction at the oxidizing electrode. These are explained in detail below.

[0006] In a typical fuel cell reaction at the oxidizing electrode, a reaction occurs where protons and oxygen react to produce water, as shown in equation (1). This reaction is called a four-electron reaction because four electrons contribute to it. 4H + +O2+4e - → 2H2O (1)

[0007] Polymer membranes have a gas sealing function, but minute gas leaks exist even when the membrane is sound. This is because reactive gases dissolve in the water contained in the polymer membrane and diffuse. When oxygen leaks from the oxidizer electrode to the fuel electrode, in the presence of the fuel electrode catalyst, the oxygen reacts with hydrogen, and as an elementary step of the reaction in equation (1), hydrogen peroxide is produced by a reaction like that in equation (2). This reaction is called a two-electron reaction because two electrons contribute to it. 2H + +O2+2e - → H2O2(2)

[0008] Among these reactions, one technique to prevent the generation of hydrogen peroxide from cross-leaked oxygen and hydrogen is to attach a reaction gas permeability barrier layer (see Patent Document 5). This works by preventing cross-leaking oxygen and suppressing hydrogen peroxide generation by consuming the cross-leaked oxygen in the catalyst within the reaction gas permeability barrier layer. It has also been found that attaching the reaction gas permeability barrier layer particularly to the fuel electrode side makes it even more effective.

[0009] Furthermore, Patent Document 6 introduces a technique for preventing pinhole expansion by laminating multiple polymer electrolyte membranes. Regarding chemical degradation, laminating membranes of the same type can also be expected to improve durability due to the film thickness effect. Patent Document 7 introduces a method for suppressing methanol permeation and improving mechanical strength in a fuel cell using liquid organic fuels such as methanol by laminating polymer electrolyte membranes. In Patent Document 7, a polymer electrolyte membrane made of fluorocarbon resin is laminated with a hydrocarbon polymer membrane such as a polyindole membrane or polyaniline membrane having NH groups, or polystyrene sulfonic acid. The hydrocarbon polymer membrane has the advantage of suppressing oxygen permeation more effectively than the fluorocarbon polymer electrolyte membrane, and combines the advantages of superior mechanical strength compared to the fluorocarbon polymer electrolyte membrane. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 6-342665 [Patent Document 2] Japanese Patent Application Publication No. 6-93114 [Patent Document 3] Japanese Patent Application Publication No. 10-21943 [Patent Document 4] Patent No. 3271801 [Patent Document 5] Japanese Patent Publication No. 2005-149859 [Patent Document 6] Japanese Patent Application Publication No. 6-84528 [Patent Document 7] Japanese Patent Publication No. 2004-335250 [Patent Document 8] Japanese Patent Publication No. 2008-47315 [Overview of the project] [Problems that the invention aims to solve]

[0011] In polymer electrolyte fuel cells, the performance and durability of the polymer electrolyte membrane are challenges. Perfluorosulfonic acid membranes have high proton conductivity and low humidity dependence, but they also have high gas permeability and are prone to chemical degradation due to radical species generated by oxygen cross-leakage. On the other hand, unfluorinated aromatic hydrocarbon membranes can suppress oxygen cross-leakage, which causes the generation of radical species, due to intermolecular interactions by aromatics, but their proton conductivity is highly dependent on humidity, resulting in high proton transport resistance under low humidity conditions. Furthermore, aromatic hydrocarbon membranes lack flexibility, making it difficult to create thin films. In the immersion of polymer electrolyte membranes described in Patent Document 8, a challenge arises in increasing the electrolyte film thickness at the site where the electrode reaction occurs, as a perfluorosulfonic acid film is formed in front of the hydrocarbon-based electrolyte. Specifically, the increase in film thickness due to composite formation increases proton transport resistance, leading to a decrease in battery performance.

[0012] Embodiments of the present invention provide a polymer electrolyte fuel cell that enhances durability while maintaining the proton transport resistance of the polymer electrolyte membrane. [Means for solving the problem]

[0013] The solid polymer fuel cell according to the embodiment has a proton-conductive polymer electrolyte membrane, a fuel electrode disposed adjacent to one surface of the polymer electrolyte membrane, and an oxidant electrode disposed adjacent to the other surface of the polymer electrolyte membrane. The polymer electrolyte membrane is a composite membrane including a first membrane containing a first electrolyte material and a second membrane containing a second electrolyte material. The second membrane covers a part of the first membrane, the oxygen permeability of the second membrane is smaller than the oxygen permeability of the first membrane, and the tensile strength of the second membrane is larger than the tensile strength of the first membrane.

Advantages of the Invention

[0014] According to the embodiment of the present invention, it is possible to provide a solid polymer fuel cell with improved durability while maintaining the proton transport resistance of the polymer electrolyte membrane.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a perspective view showing an example of the solid polymer fuel cell of the embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the polymer electrolyte membrane, fuel electrode, and oxidant electrode in the solid polymer fuel cell of the first embodiment. [Figure 3] FIG. 3 is an exploded perspective view showing the polymer electrolyte membrane and fuel electrode in the solid polymer fuel cell of the second embodiment. [Figure 4] FIG. 4 is an exploded perspective view showing the polymer electrolyte membrane and oxidant electrode in the solid polymer fuel cell of the third embodiment. [Figure 5] FIG. 5 is an exploded perspective view showing the polymer electrolyte membrane, oxidant electrode, and separator in the solid polymer fuel cell of the fourth embodiment. [Figure 6] FIG. 6 is a perspective view for explaining the manufacturing method of the solid polymer fuel cell in the fifth embodiment. FIG. (A) shows a state of pressing the first membrane with a mold, FIG. (B) shows the first membrane having a concave portion formed on one surface, FIG. (C) shows a state of fitting the second membrane to the first membrane, and FIG. (D) shows the polymer electrolyte membrane which is a composite membrane of the first membrane and the second membrane. [Figure 7] Figure 7 is a perspective view illustrating a method for manufacturing a polymer electrolyte fuel cell in the sixth embodiment, where (A) shows a first membrane with a recess formed on one side being covered with a mask material, (B) shows a coating solution being sprayed onto the first membrane partially covered with the mask material, and (C) shows the polymer electrolyte membrane, which is a composite membrane of the first membrane and the second membrane. [Modes for carrying out the invention]

[0016] Various embodiments will be described below with reference to the drawings. Each drawing is a schematic representation of the embodiment to facilitate understanding, and its shape, dimensions, ratios, etc., may differ from the actual product. These can be modified as appropriate in the following description and in reference to known technology.

[0017] Figure 1 is a perspective view showing an example of a polymer electrolyte fuel cell according to an embodiment. As shown in Figure 1, the polymer electrolyte fuel cell 1 comprises a proton-conducting polymer electrolyte membrane 10, a fuel electrode 20 positioned adjacent to one side of the polymer electrolyte membrane 10, and an oxidizer electrode 30 positioned adjacent to the other side of the polymer electrolyte membrane 10. That is, the fuel electrode 20 and the oxidizer electrode 30 are thermocompressed onto both sides of the polymer electrolyte membrane 10.

[0018] The fuel electrode 20 preferably includes a hydrogen inlet 2A for introducing hydrogen from outside the polymer electrolyte fuel cell 1. The oxidizer electrode 30 preferably includes an air inlet 3 for introducing air from outside the polymer electrolyte fuel cell 1. Such a polymer electrolyte fuel cell 1 is configured to introduce hydrogen and air from the outside and generate electricity using hydrogen and oxygen in the air.

[0019] The fuel electrode 20 and the oxidizer electrode 30 include, for example, a carbon carrier supporting catalyst metal nanoparticles and an ionomer. Platinum and platinum alloys can be used as catalyst metal nanoparticles. More specifically, platinum, platinum-ruthenium alloy, platinum-nickel alloy, platinum-cobalt alloy, etc., can be used.

[0020] Typical examples of ionomers include proton-conducting polymer electrolytes. Particularly preferred examples include Nafion®, Flemion®, and Aciplex®. They can also be composed of proton-transporting electrolytes such as copolymers of trifluorostyrene derivatives, polybenzimidazole impregnated with phosphoric acid, aromatic polyetherketone sulfonic acid, and aliphatic hydrocarbon resins. Among these, Nafion® is particularly preferred.

[0021] The polymer electrolyte membrane 10 is a composite membrane comprising a first membrane 11 and a second membrane 12. The first membrane 11 and the second membrane 12 will be described below.

[0022] The first membrane 11 contains a first electrolyte material. The first electrolyte material is preferably a polymer compound with a fluorocarbon as its main backbone. A specific example of a polymer compound with a fluorocarbon as its main backbone is perfluorosulfonic acid. Perfluorosulfonic acid is a polymer obtained by copolymerization of tetrafluoroethylene and perfluorosulfonylethoxyvinyl ether followed by hydrolysis. Specific examples of perfluorosulfonic acid include Nafion®, Flemion®, and Aciplex®. Among these, Nafion® is preferred. Perfluorosulfonic acid exhibits a high degree of dissociation of the sulfonic acid group due to the high electronegativity of fluorine. Therefore, using perfluorosulfonic acid results in high proton conductivity and low humidity dependence of proton transport resistance. In other words, by using perfluorosulfonic acid in the first film 11, the proton transport resistance in the first film 11 can be kept low, and this low proton transport resistance can be maintained even under low humidity conditions.

[0023] The second membrane 12 contains a second electrolyte material. The second electrolyte material is preferably a polymer compound with an aromatic core. Such a second electrolyte material has the property that oxygen is less likely to permeate between molecules due to intermolecular interactions in the aromatic portion. Therefore, the gas barrier properties of the second membrane 12 are improved, and cross-leakage of oxygen in the second membrane 12 can be suppressed. As a result, the generation of hydrogen peroxide in the fuel electrode 20 can be suppressed. Furthermore, the inclusion of a second electrolyte material in the second membrane 12 increases the tensile strength of the second membrane 12. In other words, the mechanical strength of the polymer electrolyte membrane 10 equipped with the second membrane 12 can be increased.

[0024] Specific examples of polymer compounds with aromatics as the main backbone include sulfonated aromatic polymers and polyether ether ketones. Among these, sulfonated aromatic polymers are preferred. Sulfonated aromatic polymers have higher proton transport capacity compared to non-sulfonated polymer compounds, and can maintain low proton transport resistance in the second membrane 12. Furthermore, membranes of sulfonated aromatic polymers have superior dimensional stability against wet-dry cycles compared to membranes of polymer compounds with fluorocarbons as the main backbone. Therefore, in the polymer electrolyte membrane 10 of the embodiment, because it is a composite membrane of the first membrane 11 and the second membrane 12, mechanical degradation can be suppressed more effectively than when the first membrane 11 is used as the electrolyte membrane alone.

[0025] In the polymer electrolyte membrane 10, the second membrane 12 covers a portion of the first membrane 11. As mentioned above, the first electrolyte material contained in the first membrane 11 has high proton conductivity. By having the second membrane 12 cover only a portion of the first membrane 11, the increase in proton transport resistance in the polymer electrolyte membrane 10 can be suppressed compared to the case where the entire surface of the first membrane 11 is covered. That is, the overall proton transport resistance of the polymer electrolyte membrane 10 can be kept low. Furthermore, by having a structure in which the second film 12 covers a part of the first film 11, the thickness of the polymer electrolyte film 10 can be reduced compared to the case in which the second film 12 covers the entire surface of the first film 11. In other words, it becomes possible to make the polymer electrolyte film 10 thinner. The thickness of the polymer electrolyte film 10 is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. On the other hand, from the viewpoint of maintaining the mechanical strength of the polymer electrolyte film 10, the thickness of the polymer electrolyte film 10 is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0026] From the viewpoint of maintaining low proton transport resistance of the polymer electrolyte membrane 10, the thickness of the second membrane 12 is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. Furthermore, from the viewpoint of maintaining the mechanical strength of the polymer electrolyte membrane 10, the thickness of the second membrane 12 is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 5 μm or more.

[0027] From the viewpoint of maintaining a low proton transport resistance of the polymer electrolyte membrane 10, the ratio of the thickness of the second membrane 12 to the thickness of the polymer electrolyte membrane 10 is preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less. Furthermore, from the viewpoint of maintaining the mechanical strength of the polymer electrolyte membrane 10, the ratio of the thickness of the second membrane 12 to the thickness of the polymer electrolyte membrane 10 is preferably 0.1% or more, more preferably 1% or more, and even more preferably 10% or more.

[0028] In the polymer electrolyte membrane 10, the oxygen permeability of the second membrane 12 is lower than that of the first membrane 11. That is, a portion of the first membrane 11 is covered by the second membrane 12, which has lower oxygen permeability. By doing so, the polymer electrolyte membrane 10 can suppress oxygen cross-leakage compared to the case where the first membrane 11 is the electrolyte membrane alone.

[0029] Oxygen permeability can be measured in accordance with the "Test Method for Gas Permeability of Plastic Films and Sheets (JIS K7126-2:2006 Method B (Isobaric Method))" under conditions of 23°C and 60% relative humidity. The measuring instrument used can be an oxygen permeability analyzer (OX-TRAN 2 / 20, manufactured by Modern Control Co., Ltd.).

[0030] In the polymer electrolyte membrane 10, the tensile strength of the second membrane 12 is greater than that of the first membrane 11. That is, a portion of the first membrane 11 is covered by the second membrane 12, which has greater tensile strength. As a result, the polymer electrolyte membrane 10 has superior dimensional stability and can suppress mechanical degradation compared to the case where the first membrane 11 is the electrolyte membrane alone. The details are as follows.

[0031] During the power generation reaction, the polymer electrolyte fuel cell 1 reaches a temperature of 60-80°C and also becomes highly humid due to the water produced. Some of the first electrolyte materials contained in the first membrane 11 have the property of swelling when they absorb moisture. As the first membrane 11 swells, the fuel electrode 20 or oxidizer electrode 30 is pushed outward, and in a polymer electrolyte fuel cell 1, which is constrained externally by a separator 40, stress is generated between the fuel electrode 20 and the separator 40, etc. When the polymer electrolyte fuel cell 1 is repeatedly powered and stopped, and the temperature and humidity change repeatedly, the generation and relaxation of stress occur repeatedly, and mechanical deterioration progresses. Therefore, by covering a portion of the first film 11, which has low tensile strength, with the second film 12, which has high tensile strength, the dimensional stability of the polymer electrolyte film 10 can be improved, and mechanical degradation can be suppressed.

[0032] In this embodiment, the material used for the separator 40 is preferably conductive porous carbon. By using such a material, the cooling water can be circulated inside the separator 40 under negative pressure. This allows the water generated by the power generation reaction to be forcibly drawn into the cooling water flow path 4B, thereby preventing flooding.

[0033] Tensile strength can be measured by performing a tensile test as follows. Cut a 20mm wide strip from the first film 11 to use as a sample. Clamp both ends of the cut sample in the chuck of a Shimadzu Autograph AG 10kNX (manufactured by Shimadzu Corporation). Pull the sample at a tensile speed of 1m / min and define the tensile strength of the first film 11 as the stress value at the maximum value of the stress-strain curve. The tensile strength of the second film 12 can be measured in the same manner as the tensile strength of the first film 11.

[0034] The proton transport resistance of the polymer electrolyte membrane 10 at low humidity increases as the second film 12 covers the first film 11. Therefore, from the viewpoint of maintaining low proton transport resistance, it is preferable to minimize the area covered by the second film 12 over the first film 11. Specifically, the ratio of the area occupied by the second film 12 to the surface area of ​​the polymer electrolyte membrane 10 is preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less. Furthermore, the second film 12 covering the first film 11 prevents oxygen cross-leakage and improves the dimensional stability of the polymer electrolyte membrane 10. From these perspectives, the area covered by the second film 12 over the first film 11 needs to be of a certain size. Specifically, the ratio of the area occupied by the second film 12 to the surface area of ​​the polymer electrolyte membrane 10 is preferably 0.1% or more, more preferably 1% or more, and even more preferably 5% or more. The surface area of ​​the polymer electrolyte membrane 10 refers to the sum of the area of ​​one side (the side in contact with the fuel electrode 20) and the area of ​​the other side (the side in contact with the oxidizer electrode 30). Similarly, the area occupied by the second membrane 12 refers to the sum of the area occupied by the second membrane 12 on one side (the side in contact with the fuel electrode 20) and the area occupied by the second membrane 12 on the other side (the side in contact with the oxidizer electrode 30).

[0035] Next, each embodiment of the polymer electrolyte membrane 10 will be described.

[0036] [First Embodiment] In the first embodiment, as shown in Figure 2, the second film 12 covers the first film 11 at the periphery of both surfaces of the polymer electrolyte film 10 (the surface adjacent to the fuel electrode 20 and the surface adjacent to the oxidizer electrode 30). That is, the periphery of both surfaces of the polymer electrolyte film 10 is composed of the second film 12. The peripheral edges of both sides of the polymer electrolyte membrane 10 are susceptible to stress due to swelling of the first membrane 11. By covering these peripheral edges with the second membrane 12, which has excellent dimensional stability, swelling of the polymer electrolyte membrane 10 can be suppressed, and mechanical degradation of the polymer electrolyte fuel cell 1 can be effectively prevented.

[0037] Furthermore, although not shown in the figures, a configuration in which the second film 12 covers the first film 11 at the periphery of either one surface of the polymer electrolyte film 10 (either the surface adjacent to the fuel electrode 20 or the surface adjacent to the oxidizer electrode 30) is also preferable. By covering either one surface with the second film 12, mechanical degradation of the polymer electrolyte fuel cell 1 can be similarly prevented.

[0038] [Second Embodiment] In the second embodiment, as shown in Figure 3, a second film 12 is formed on a portion of the surface of the polymer electrolyte membrane 10 adjacent to the fuel electrode 20. Furthermore, the second film 12 and the hydrogen inlet 2A are arranged to overlap in a plan view. That is, the portion of the first film 11 adjacent to the hydrogen inlet 2A is covered by the second film 12. Note that the oxidizer electrode 30 is omitted in Figure 3. Furthermore, in this specification, a plan view means observing any surface of the polymer electrolyte membrane 10 (either the surface adjacent to the fuel electrode 20 or the surface adjacent to the oxidizer electrode 30) from above. In the polymer electrolyte fuel cell 1, if the second membrane 12 is absent, cross-leakage is likely to occur near the hydrogen inlet 2A, and chemical degradation by radical species is also likely to occur. In the second embodiment, by covering the portion of the first membrane 11 that is close to the hydrogen inlet 2A with the second membrane 12, which has low oxygen permeability, cross-leakage in the portion close to the hydrogen inlet 2A can be effectively prevented, and the durability of the polymer electrolyte membrane 10 against chemical degradation can be improved.

[0039] In the second embodiment, as shown in Figure 3, multiple hydrogen flow paths 2B are provided in a straight line, and the multiple hydrogen flow paths 2B are arranged in parallel. Hydrogen enters the fuel electrode 20 from the hydrogen inlet 2A and exits the fuel electrode 20 from the opposite side. The hydrogen returns through a manifold (not shown) installed on the outside and is introduced back into the fuel electrode 20. In this way, hydrogen is repeatedly introduced into and out of the fuel electrode 20, allowing for efficient introduction of hydrogen into the fuel electrode 20.

[0040] Furthermore, although not shown in the diagram, the second film 12 may be present in other parts in addition to the vicinity of the hydrogen inlet 2A. For example, the second film 12 may cover the first film 11 in a part of the surface in contact with the oxidizing electrode 30.

[0041] [Third Embodiment] In the third embodiment, as shown in Figure 4, a second film 12 is formed on a portion of the surface of the polymer electrolyte membrane 10 adjacent to the oxidant electrode 30. Furthermore, the second film 12 and the air inlet portion 3A are arranged to overlap in a plan view. That is, the portion of the first film 11 adjacent to the air inlet portion 3A is covered by the second film 12. Note that the fuel electrode 20 is omitted in Figure 3. In the polymer electrolyte fuel cell 1, the oxygen partial pressure is highest at the air inlet 3A, and if the second membrane 12 is not present, chemical degradation due to oxygen is likely to occur near the air inlet 3A. In the third embodiment, by covering the portion of the first membrane 11 that is close to the air inlet 3A with the second membrane 12, the first membrane 11 can be protected from chemical degradation, thereby improving the durability of the polymer electrolyte membrane 10 against chemical degradation. In addition, the second membrane 12 has low oxygen permeability and can prevent cross-leakage in areas with high oxygen partial pressure.

[0042] In the third embodiment, as shown in Figure 4, multiple air passages 3B are provided in a straight line, and the multiple air passages 3B are arranged in parallel. Air enters the oxidizer electrode 30 from the air inlet 3A and exits the oxidizer electrode 30 from the opposite side. Oxygen returns through a manifold (not shown) installed externally and is introduced back into the oxidizer electrode 30. In this way, air is repeatedly brought in and out of the oxidizer electrode 30, allowing for efficient introduction of air into the oxidizer electrode 30.

[0043] Furthermore, although not shown in the diagram, the second film 12 may be present in other parts in addition to the vicinity of the air inlet 3A. For example, the second film 12 may cover the first film 11 in a part of the surface in contact with the fuel electrode 20.

[0044] [Fourth Embodiment] In the fourth embodiment, as shown in Figure 5, the polymer electrolyte membrane 10 has a second membrane 12 formed on a portion of the surface adjacent to the oxidizer electrode 30. The polymer electrolyte fuel cell 1 also includes a separator 40 on the surface of the oxidizer electrode 30 opposite to the polymer electrolyte membrane 10. The separator 40 also includes a cooling water inlet 4A for introducing cooling water from outside the polymer electrolyte fuel cell 1. Furthermore, the second membrane 12 and the cooling water inlet 4A are arranged to overlap in a plan view. That is, the portion of the first membrane 11 adjacent to the cooling water inlet 4A is covered by the second membrane 12. Note that the fuel electrode 20 is omitted in Figure 5. In the polymer electrolyte fuel cell 1, the area near the cooling water inlet 4A is the most easily cooled, and in the absence of the second membrane 12, the polymer electrolyte membrane 10 is prone to mechanical deterioration due to rapid contraction. In the fourth embodiment, the portion of the first membrane 11 adjacent to the cooling water inlet 4A is covered with the second membrane 12, which has excellent dimensional stability, thereby improving the durability of the polymer electrolyte membrane 10 against mechanical deterioration. Furthermore, the cooling water may contain dissolved substances (such as iron ions) that chemically degrade the first film 11. Even in such cases, the second film 12 can suppress the chemical degradation of the first film 11.

[0045] In the fourth embodiment, as shown in Figure 5, the cooling water flow path 4B is arranged to meander inside the separator 40. By making the cooling water meander inside the separator 40, the polymer electrolyte fuel cell 1, which generates heat in conjunction with the power generation reaction, can be efficiently cooled.

[0046] Although not shown in the diagram, cooling water may also be introduced into the interior of a component adjacent to the outside of the fuel electrode 20 (on the side opposite to the side where the fuel electrode 20 is adjacent to the polymer electrolyte membrane 10) in addition to the interior of the separator 40. This allows the polymer electrolyte fuel cell 1 to be cooled even more efficiently.

[0047] Next, we will explain the manufacturing method of polymer electrolyte fuel cells.

[0048] [Fifth Embodiment] The manufacturing method of the fifth embodiment comprises, in this order, a step of applying pressure while heating a part of the surface of the first film to form a recess on the surface of the first film (hereinafter referred to as the "pressurization step"), and a step of heating the first film and the second film with the second film fitted into the recess to form a polymer electrolyte film (hereinafter referred to as the "bonding step"). The fifth embodiment will be described below with reference to Figure 6.

[0049] In the pressurization step, for example, a heated mold 51 is pressed against the surface of the first film 11 containing the first electrolyte material (Figure 6(A)). At this time, by heating the mold 51 so that its temperature is above the melting point or glass transition point of the first electrolyte material, the first film 11 undergoes plastic deformation, and the film thickness in the pressurized area becomes thinner. As a result, a recess 13 can be formed on the surface of the first film 11 (Figure 6(B)). In this specification, a recess means a part in which the film thickness is thinner than the surrounding area, and includes not only a part in which the film thickness is thinner than the surrounding area near the center of the film, but also a part in which the film thickness is thinner at the periphery of the film. Furthermore, by appropriately changing the shape of the mold 51, a recess 13 of a desired shape can be provided on the surface of the first film 11. A known hot press can be used for the pressurizing process.

[0050] In the bonding process following the pressurization process, for example, a second film 12 cut to fit the shape of a recess 13 is fitted into the recess 13 on the surface of the first film 11 (Figure 6(C)). In this state, the first film 11 and the second film 12 are heated. At this time, by heating to a temperature above the melting point or glass transition point of the first electrolyte material and above the melting point or glass transition point of the second electrolyte material, the first film 11 and the second film 12 are bonded at the interface, forming an integrated composite film (Figure 6(D)). In this way, a polymer electrolyte film 10 can be manufactured in which a portion of one side of the first film 11 is covered with a second film 12 of a desired shape. In the bonding process, the first film 11 and the second film 12 can be bonded together without the use of an adhesive. Therefore, it is possible to prevent a decrease in the proton conductivity of the polymer electrolyte film 10 due to an adhesive between the first film 11 and the second film 12.

[0051] The other side of the first film 11 can be similarly covered with a second film 12 of a desired shape. As a result, a polymer electrolyte film 10 as shown in Figure 2 can be manufactured. Furthermore, by appropriately changing the shape of the mold 16 and the shape of the second membrane 12 from those shown in Figure 6, it is also possible to manufacture the polymer electrolyte membrane 10 as shown in Figures 3 to 5.

[0052] [Sixth Embodiment] The manufacturing method of the sixth embodiment comprises, in this order, a step of applying pressure to a part of the surface of the first film while heating it to form a recess on the surface of the first film (pressurization step), a step of applying a coating solution containing the second electrolyte material to the recess (hereinafter referred to as the "coating step"), and a step of drying the coating solution to form the second film (hereinafter referred to as the "drying step"). The sixth embodiment will be described below with reference to Figure 7. The pressurization process in the sixth embodiment is the same as that in the fifth embodiment, so its explanation will be omitted.

[0053] In the coating process following the pressurization process, for example, the portion of the surface of the first film 11 that was not pressurized in the pressurization process is pre-covered with a mask material 52 of a predetermined shape (Figure 7(A)). In this state, the coating solution containing the second electrolyte material is sprayed from a spray nozzle 53 to perform spray coating (Figure 7(B)). The coating solution can be applied to the recesses 13 by spray coating. At that time, the coating solution is applied to the mask material 52 as well as the recesses 13. Alternatively, the coating may be applied using other wet coating methods instead of spray coating. For example, it may be applied using methods such as spin coating, doctor blade coating, or die coating.

[0054] In the drying step following the coating step, for example, the mask material 52 is removed from the first film 11, and the first film 11 is heated and dried using a heating device. Heat drying removes the solvent from the coating solution applied to the recesses 13, forming a second film 12 made of a second electrolyte material in the recesses 13 (Figure 7(C)). In this way, a polymer electrolyte membrane 10 can be manufactured in which a portion of one side of the first film 11 is covered with a second film 12 of a desired shape. Note that the masking material 52 may be removed after drying, rather than before.

[0055] In the sixth embodiment, the thickness of the formed second film 12 can be adjusted by appropriately controlling the concentration of the second electrolyte material in the coating solution and the application time of the coating solution. From the viewpoint of shortening the drying time in the drying process, the concentration of the secondary electrolyte material in the coating solution is preferably 0.001 g / mL or higher, more preferably 0.005 g / mL or higher, and even more preferably 0.01 g / mL or higher. Furthermore, from the viewpoint of ease of handling of the coating solution, the concentration of the secondary electrolyte material in the coating solution is preferably 0.1 g / mL or lower, more preferably 0.05 g / mL or lower, and even more preferably 0.03 g / mL or lower. From the viewpoint of reliably forming the second film 12, the coating time of the coating solution is preferably 5 seconds or more, more preferably 30 seconds or more, and even more preferably 60 seconds or more. Furthermore, from the viewpoint of shortening the drying time in the drying process, the coating time of the coating solution is preferably 600 seconds or less, more preferably 300 seconds or less, and even more preferably 150 seconds or less.

[0056] When heat drying is performed in the drying process, it is preferable that the heating temperature be below the melting point or glass transition point of the first electrolyte material, from the viewpoint of preventing deformation of the first film 11.

[0057] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0058] 1 Polymer electrolyte fuel cell 2A Hydrogen Inlet 2B Hydrogen flow path 3A Air Inlet 3B Airflow path 4A Cooling water inlet 4B Cooling water flow path 10 Polymer electrolyte membrane 11 First membrane 12 Second membrane 13 recess 20 Fuel electrode 30 Oxidizing electrode 40 Separators 51 molds 52 Masking material 53 Spray nozzle

Claims

1. A polymer electrolyte fuel cell comprising a proton-conducting polymer electrolyte membrane, a fuel electrode disposed adjacent to one side of the polymer electrolyte membrane, and an oxidizer electrode disposed adjacent to the other side of the polymer electrolyte membrane, The polymer electrolyte membrane is a composite membrane comprising a first membrane containing a first electrolyte material and a second membrane containing a second electrolyte material. At the periphery of the polymer electrolyte membrane, the second membrane covers the first membrane. The oxygen permeability of the second membrane is less than that of the first membrane. A polymer electrolyte fuel cell in which the tensile strength of the second membrane is greater than that of the first membrane.

2. A polymer electrolyte fuel cell comprising a proton-conducting polymer electrolyte membrane, a fuel electrode disposed adjacent to one side of the polymer electrolyte membrane, and an oxidizer electrode disposed adjacent to the other side of the polymer electrolyte membrane, The polymer electrolyte membrane is a composite membrane comprising a first membrane containing a first electrolyte material and a second membrane containing a second electrolyte material. The second film covers a portion of the first film. The oxygen permeability of the second membrane is less than that of the first membrane. The tensile strength of the second film is greater than that of the first film. The fuel electrode is equipped with a hydrogen inlet for introducing hydrogen from outside the polymer electrolyte fuel cell, A polymer electrolyte fuel cell in which the second membrane adjacent to the fuel electrode and the hydrogen inlet overlap in a plan view.

3. A polymer electrolyte fuel cell comprising a proton-conducting polymer electrolyte membrane, a fuel electrode disposed adjacent to one side of the polymer electrolyte membrane, and an oxidizer electrode disposed adjacent to the other side of the polymer electrolyte membrane, The polymer electrolyte membrane is a composite membrane comprising a first membrane containing a first electrolyte material and a second membrane containing a second electrolyte material. The second film covers a portion of the first film. The oxygen permeability of the second membrane is less than that of the first membrane. The tensile strength of the second film is greater than that of the first film. The oxidizing electrode is equipped with an air inlet for introducing air from outside the polymer electrolyte fuel cell, A polymer electrolyte fuel cell in which the second membrane adjacent to the oxidizing electrode and the air inlet overlap in a plan view.

4. A polymer electrolyte fuel cell comprising a proton-conducting polymer electrolyte membrane, a fuel electrode disposed adjacent to one side of the polymer electrolyte membrane, and an oxidizer electrode disposed adjacent to the other side of the polymer electrolyte membrane, The polymer electrolyte membrane is a composite membrane comprising a first membrane containing a first electrolyte material and a second membrane containing a second electrolyte material. The second film covers a portion of the first film. The oxygen permeability of the second membrane is less than that of the first membrane. The tensile strength of the second film is greater than that of the first film. The solid polymer fuel cell has a separator positioned on the side of the oxidizing electrode opposite to the polymer electrolyte membrane, The separator includes a cooling water inlet for introducing cooling water from outside the polymer electrolyte fuel cell, A polymer electrolyte fuel cell in which the second membrane adjacent to the oxidizing electrode and the cooling water inlet overlap in a plan view.

5. The polymer electrolyte fuel cell according to any one of claims 1 to 4, wherein the first electrolyte material is a polymer compound having a fluorocarbon as its main backbone.

6. The polymer electrolyte fuel cell according to any one of claims 1 to 4, wherein the second electrolyte material is a hydrocarbon polymer compound having an aromatic core.

7. In a method for manufacturing a polymer electrolyte fuel cell according to any one of claims 1 to 4, A step of applying pressure while heating a part of the surface of the first film to form a recess on the surface of the first film, A step of forming the polymer electrolyte membrane by heating the first membrane and the second membrane with the second membrane fitted into the recess, A method for manufacturing a polymer electrolyte fuel cell, comprising the elements in this order.

8. In a method for manufacturing a polymer electrolyte fuel cell according to any one of claims 1 to 4, A step of applying pressure while heating a part of the surface of the first film to form a recess on the surface of the first film, The steps include applying the coating solution containing the second electrolyte material to the recess, A step of drying the coating solution to form the second film, A method for manufacturing a polymer electrolyte fuel cell, comprising the elements in this order.

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