JP2006260810A - Polymer electrolyte type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which can be stably operated for a long period of time, since a pressurizing force applied to a membrane electrode assembly of a unit cell is almost uniformly held, and the breakage of an electrolyte membrane caused by a stress concentration is avoided. <P>SOLUTION: In this polymer electrolyte type fuel cell in which the outer surface of the membrane electrode assembly comprising the electrolyte membrane 1 held between protective sheets 4, a diffusion layer 3A, and a catalyst layer 2A is composed of a first plane T2 disposed face to face with a region where the catalyst layer 2A is formed, a second plane T2 lower than the first plane T1, a separator 6A to sandwich the membrane electrode assembly is structured so as to have a third plane S1 making contact with the first plane T1 face to face, and a fourth plane S2 making contact with the second plane T2 face to face while being higher than the third plane S1 in its inner surface. This fuel cell is formed by blasting the surface of a carbon composite material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte layer, and in particular, has a configuration in which electrical loss inside a cell is small and damage to the solid polymer electrolyte membrane due to stress concentration is avoided. The present invention relates to a solid polymer electrolyte fuel cell.

The solid polymer electrolyte fuel cell is a fuel cell using a solid polymer membrane as an electrolyte layer, and has excellent characteristics such as high output density and long battery life. A fuel cell of this type is configured by laminating a plurality of single cells. Normally, each single cell has a solid polymer electrolyte membrane disposed at the center as shown in the schematic cross-sectional view of FIG. A membrane electrode assembly (hereinafter referred to as MEA) is sandwiched between two separators 6 each having a gas flow path. Among these, MEA joins the electrode which formed the catalyst layer 2 in the diffusion layer 3 which performs the function of current collection and gas diffusion on both surfaces of the solid polymer electrolyte membrane 1 supported by the frame-shaped protective sheet 4. In many cases, a perfluorosulfonic acid polymer is used for the solid polymer electrolyte membrane 1 and a general-purpose plastic film such as PET (polyethylene terephthalate) is used for the protective sheet 4.
The separator 6 that separates the fuel gas supplied to the fuel electrode and the oxidant gas supplied to the air electrode has a gas flow path for supplying these gases and a cooling water flow path for supplying cooling water for discharging heat. It is a structural member that is provided and plays a role of transmitting the electrical energy obtained by the fuel cell power generation reaction to the outside, and is generally composed of a carbon composite material. As the carbon powder for forming the carbon composite material, flake graphite powder, artificial graphite, expanded graphite, carbon black, etc. are used, and as the resin, both thermosetting resin and thermoplastic resin are used. Yes, phenolic resin or epoxy resin is used. The separator is produced by the molding method, the injection molding method, etc. using the compound which mixed these carbon powder and resin. The separator thus produced has a feature that the resin component is unevenly distributed on the surface, and a resin layer having a thickness of about 10 to 100 μm is formed depending on the type and mixing ratio of the material. Since this resin layer has a low electrical conductivity, if it is used as it is, the contact resistance with the constituent members becomes excessive and the characteristics are deteriorated. Therefore, it is necessary to remove this resin layer in order to maintain predetermined characteristics, and the resin layer is removed using a surface polishing method, a dry sand blast method, or a wet blast method (for example, see Patent Document 1).

On the other hand, the gas seal of the single cell, that is, the seal of the fuel gas supplied to the fuel gas channel 7 of the separator 6 and the seal of the oxidant gas supplied to the oxidant gas channel 8 are the end portions of the separator 6. And a seal packing 5 provided between the protective sheet 4 and the protective sheet 4. Fluorine rubber, ethylene propylene rubber, silicon rubber or the like is used as the material of the seal packing 5.
Since the generated voltage of this single cell is a low voltage of less than 1 V, a solid polymer electrolyte fuel cell for practical use is formed by stacking a plurality of single cells suitable for the required voltage and electrically connecting them in series. The FIG. 6 is a side view of a conventional solid polymer electrolyte fuel cell configured by stacking single cells having the configuration shown in FIG. A plurality of unit cells 61 are stacked, and current collecting plates 62 for taking out a direct current, an insulating plate 63 for electrically insulating the laminated body from the structure, and a clamping plate 64 for fastening the laminated body at both ends thereof. Are sequentially disposed, and a coil spring 65 is disposed between the inner surface of the end plate 66 supported by the stud 67 and the nut 68 and the outer surface of the clamping plate 64 to pressurize and laminate the laminate. In this way, in the solid polymer electrolyte fuel cell, by pressurizing and tightening, the contact resistance between the separator and MEA inside each single cell, and the contact resistance between laminated members such as between adjacent single cells is reduced, Reduces electrical resistance loss.

By the way, the general thickness of the constituent members of the MEA is 10-50 μm for the electrolyte membrane 1, 10-50 μm for the protective sheet 4, 10-50 μm for the catalyst layer 2A, and 100-400 μm for the diffusion layer 3A. As a result, various MEAs are configured. In the MEA incorporated in the single cell of FIG. 5, since the catalyst layer 2 and the protective sheet 4 are selected to have the same thickness, the outer surface of the diffusion layer 3, and thus the outer surface of the MEA has a substantially constant height and is tightened. In this case, a substantially uniform pressure is applied to the diffusion layer 3 and the catalyst layer 2, but depending on the selection of the thickness of the member, the thickness varies depending on the MEA part, and the pressure is not uniform. There is a possibility.
FIG. 7 is a schematic cross-sectional view showing another conventional example of MEA incorporated in a single cell of a solid polymer electrolyte fuel cell. In this MEA, the catalyst layer 2A thicker than the protective sheet 4 is produced to form the MEA. Therefore, the MEA is thick in the portion including the catalyst layer 2A indicated by the symbol A in the drawing (MEA convex portion). ), The portion where the diffusion layer 3A and the protective sheet 4 indicated by the symbol B in the drawing are in contact has a thin MEA (MEA recess). Since the thickness of the catalyst layer 2A is 50 μm at the maximum and the thickness of the protective sheet 4 is 10 μm at the minimum, the difference in thickness between the MEA protrusion and MEA recess is calculated to be 40 μm or less on one side and 80 μm or less on both sides. The

FIG. 8 is a schematic cross-sectional view showing a third conventional example of MEA incorporated in a single cell of a solid polymer electrolyte fuel cell. In this MEA, the MEA is configured by arranging a catalyst layer 2B produced with a uniform thickness substantially the same as that of the protective sheet 4 so as to partially overlap the protective sheet 4, and is indicated by C in the figure. Further, the MEA is thick at the part where the protective sheet 4 and the catalyst layer 2B overlap (MEA convex part), and is thin at the other part indicated by symbol D in the figure (MEA concave part). Since the maximum value of the thickness of the protective sheet 4 and the catalyst layer 2B is 50 μm, the difference in thickness between the MEA convex part and the MEA concave part of this MEA is calculated to be 50 μm or less on one side and 100 μm or less on both sides. .
As described above, an MEA incorporated in a single cell of a solid polymer electrolyte fuel cell does not necessarily have a constant in-plane thickness, and an MEA having irregularities may be used. When an MEA having a non-uniform thickness is used in this way, if the MEA is sandwiched between separators having a uniform thickness and pressed and sandwiched, the pressure applied to the MEA becomes non-uniform in the plane and concentrates on a part of the surface. Become. When the applied pressure is concentrated on a part in this way, the force applied to the electrolyte membrane 1 constituting the MEA becomes excessive, which may cause creep and reduce the film thickness. When the film thickness decreases, the tensile strength of the film at that portion decreases, the film breaks during operation, and a cross leak in which the fuel gas and the oxidant gas are mixed may occur, making the battery inoperable. On the other hand, when a portion with a small pressing force is generated in the surface, the contact electric resistance between the constituent members increases with a decrease in the pressing force, so that the current flowing between the separator and the MEA decreases, and in the electrode surface The reaction may become non-uniform and the battery characteristics may be degraded.

For this reason, in order to avoid these difficulties caused by non-uniformity of the applied pressure in the MEA having unevenness, various measures for making the applied pressure uniform have been studied. Is to make the thickness uniform by attaching spacers to the thin part of the MEA, and to adjust the thickness by adjusting the thickness by providing protrusions on the opposing separator. A measure for equalizing pressure is disclosed.
JP 2003-282084 A JP-A-6-333582

  As described above, in the solid polymer electrolyte fuel cell, the thickness of the MEA incorporated in the single cell is not necessarily constant in the plane. Therefore, when the MEA is sandwiched between the separators and pressed and sandwiched, the MEA is added. There is a problem that the applied pressure is not uniform in the plane. In this way, if the applied pressure is uneven, there is a risk that the electrolyte film will be damaged during operation in the part where the applied pressure is excessive, causing a cross leak and making the battery inoperable. In the portion where the pressure is reduced, the contact electrical resistance between the constituent members is increased, the flowing current is decreased, and the battery characteristics may be deteriorated. For this reason, for example, in Patent Document 2 described above, consideration is given to equalizing the pressure by inserting a spacer in the concave portion of the MEA or by providing a protrusion on the opposing separator. If the spacers and protrusions are arranged in this way, the applied pressure is made uniform and the generation of excessive applied pressure is avoided. However, the portion where the contact resistance is increased due to the displacement from the spacers or protrusions remains. Inevitable. In particular, a separator made of a carbon composite material of carbon powder and resin as in the prior art forms a resin layer with low electrical conductivity on the surface, so that the contact resistance between members is further increased, and the conduction current is reduced. The electrical characteristics are likely to deteriorate.

  The present invention has been made in consideration of such problems of the conventional solid polymer electrolyte fuel cell. The object of the present invention is to laminate a plurality of single cells formed by sandwiching MEAs with separators. However, in a solid polymer electrolyte fuel cell configured by pressurizing and tightening, even if the surface of the MEA is composed of an uneven surface, the pressure applied to each part of the MEA is almost uniform in the surface. A solid polymer electrolyte fuel cell that can be operated without causing cross leak due to damage to the electrolyte membrane, stable operation over a long period of time, and deterioration of electrical characteristics due to contact electric resistance. It is to provide.

In order to achieve the above object, in the present invention,
A single cell comprising a membrane electrode assembly formed by arranging a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane, sandwiched by two separators each having a gas flow path, and In the solid polymer electrolyte fuel cell in which both surfaces of the membrane electrode assembly are each composed of a first plane and a second plane having a height lower than the first plane,
(1) A third surface that is incorporated in contact with the first plane of the membrane electrode assembly on the surface of the separator facing the outer surface of the membrane electrode assembly; A fourth surface having a height higher than that of the third surface, which is opposed to and incorporated in contact with the second plane, for example, facing the formation region of the catalyst layer of the membrane electrode assembly. The third surface or the fourth surface is arranged.

  (2) Further, in the solid polymer electrolyte fuel cell according to (1), the separator is made of a carbon composite material made of carbon powder and resin, and the third surface and the fourth The surface is formed by performing a surface treatment for removing the surface layer, for example, a blast treatment.

In the solid polymer electrolyte fuel cell, the thickness of the MEA incorporated in the single cell is not necessarily constant in the plane, and as shown in FIG. 7 or FIG. 8, there are many cases where the surfaces have different heights. . Therefore, as described in (1) above, two types of surfaces (third surface) having different heights are opposed to the MEA having two types of surfaces (first surface and second plane) having different heights. And a fourth plane) are arranged to pressurize and pinch the MEA. By uniformizing the amount of tightening displacement on each surface, the applied pressure on each surface is uniform. Can be Therefore, MEA breakage due to excessive pressurization and deterioration of characteristics due to insufficient pressurization are effectively avoided.
In addition, as described above, the separator used for the single cell is generally made of a carbon composite material made of carbon powder and resin, but the surface of the separator thus produced has low electrical conductivity. When the resin layer was formed and the contact resistance between the members was increased, there was a difficulty in forming the surface (third surface and fourth plane) of the manufactured separator as described in (2) above. If, for example, surface treatment such as blasting is performed and the surface layer is removed, the surface layer with low electrical conductivity is removed, and the electrical conductivity of the separator surface is improved. Therefore, the contact resistance between the members is reduced, the deterioration of the electrical characteristics due to the contact resistance is avoided, and an efficient solid polymer electrolyte fuel cell can be obtained.

  The best mode of the solid polymer electrolyte fuel cell according to the present invention is a separator having a gas flow passage formed of a membrane electrode assembly formed by arranging a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane. A solid polymer electrolyte fuel cell comprising a single cell sandwiched between the first and second surfaces of the membrane electrode assembly having a height lower than that of the first plane. A third surface which is incorporated in contact with and opposed to the first plane of the membrane electrode assembly on the surface of the separator facing the outer surface of the membrane electrode assembly. And a fourth surface having a height higher than that of the third surface, which is opposed to and is in contact with the second plane of the membrane electrode assembly.

First, a platinum-ruthenium alloy-supported carbon catalyst in which a platinum-ruthenium alloy (alloy ratio 2: 1) is supported on a carbon support and an electrolyte resin solution (manufactured by DuPont, Nafion solution) are mixed, and a catalyst-dispersed slurry for an anode is prepared. Produced. Subsequently, the slurry was applied to a 105 mm × 105 mm region on a carbon paper base material (TGP60, 120 mm × 120 mm, thickness 190 μm, manufactured by Toray Industries, Inc.) treated with a gas diffusion layer, that is, PTFE (polytetrafluoroethylene). The anode electrode was applied. At this time, the catalyst was applied so that the amount of catalyst was 0.7 mg Pt / cm ^2. The thickness of the obtained catalyst layer was 45 μm, and the anode thickness combined with the diffusion layer was 235 μm. Next, a platinum-supported carbon catalyst in which platinum was supported on a carbon carrier and an electrolyte resin solution (manufactured by DuPont, Nafion solution) were mixed to prepare a catalyst dispersion slurry for the cathode. This slurry was applied to a 105 mm × 105 mm region on a carbon paper substrate (Toray, TGPH60, 120 mm × 120 mm) water-repellently treated with a gas diffusion layer, that is, PTFE (polytetrafluoroethylene) to form a cathode electrode. . At this time, the catalyst was applied so that the amount of the catalyst was 0.7 mg Pt / cm ² , the thickness of the obtained catalyst layer was 45 μm, and the cathode thickness combined with the diffusion layer was 235 μm.

Next, Nafion N-112 (manufactured by DuPont, 160 mm × 160 mm, thickness of about 50 μm) was prepared as an electrolyte membrane and sandwiched between two frame-shaped protective sheets. This protective sheet consists of a PFA (polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) sheet having a thickness of 25 μm, and the outer shape is 160 mm × 160 mm, which is the same as the electrolyte membrane, and 100 mm × 100 mm in the center. The hole is made. Therefore, when the electrolyte membrane is sandwiched between the protective sheets, the electrolyte membrane is exposed at a hole portion of 100 mm × 100 mm.
After placing the anode electrode and the cathode electrode prepared as described above on both sides of the electrolyte membrane sandwiched between the protective sheets so that the catalyst layer faces the electrolyte membrane, respectively, this is set in a hot press device, An MEA was manufactured by hot pressing under conditions of a temperature of 140 ° C., a pressure of 5 MPa, and a pressing time of 5 min. According to the result of measuring the thickness of the manufactured MEA using a micrometer, it is about 490 μm in the 105 mm × 105 mm area where the catalyst layer in the center is applied, and only the diffusion layer without the catalyst layer is applied. In the area, it was about 450 μm. Therefore, there is a step of 40 μm on both sides and 20 μm on one side between the part where the catalyst layer is formed and the part where there is no catalyst layer. Since the porous material of the catalyst layer and the diffusion layer is compressed and deformed by pressing, the thickness of the produced MEA is greatly different from the value calculated from the initial thickness of the constituent members.

  As the separator constituting the single cell in combination with the above MEA, a material made of carbon powder and a resin was molded to form a gas flow path and the like and subjected to a surface treatment. That is, a flake graphite powder was used as the carbon powder and a phenol resin was used as the resin, and a compound obtained by mixing them was molded to form a separator having a gas flow path and the like. Subsequently, after masking the part where the seal packing inserted in order to maintain airtightness when sandwiching the MEA with a masking material, surface treatment is performed by sandblasting, and a 50 μm deep layer is removed from the surface. A first surface was formed. Next, the thick part of the MEA, that is, the other area except the part facing the 105 mm × 105 mm area coated with the catalyst layer is masked, and only the part facing the 105 mm × 105 mm area is further deepened. Surface treatment was performed by sandblasting over 20 μm to form a second surface.

  The MEA and separator manufactured using the manufacturing method as described above were assembled by inserting seal packing to manufacture a single cell. FIG. 1 is a schematic cross-sectional view showing the structure of a single cell fabricated in this way. As shown in FIG. 1, the MEA sandwiches the electrolyte membrane 1 sandwiched between two frame-shaped protective sheets 4 between an anode electrode and a cathode electrode, which are produced by applying the catalyst layer 2A to the diffusion layer 3A, It has been compression-molded with a hot press. As already mentioned, the total thickness of the 105mm × 105mm area (indicated by T1 in the figure) is about 490 μm, and the catalyst layer is The total thickness of the peripheral region (the portion indicated by T2 in the figure) that has not been applied is formed to be about 450 μm. In the single cell, this MEA is sandwiched between a fuel electrode side separator 6A provided with a fuel gas flow path 7A and an air electrode side separator 6A provided with an oxidant gas flow path 8A, and is hermetically sealed by an inserted seal packing 5. Is held in. As shown in FIG. 1, the surface of the two separators 6A facing the MEA is composed of two surfaces S1 and S2 having different heights, where S1 is the T1 portion of the MEA and S2 is the T2 portion of the MEA. Incorporated relative.

  FIG. 2 is a plan view of a separator 6A on the fuel electrode side constituting the single cell of FIG. As seen in this figure, the gas flow path provided in the separator 6A is disposed on the power generation region coated with the MEA catalyst layer, that is, the surface of S1 facing the 105 mm × 105 mm region in the center. The fuel gas is supplied from a fuel gas inlet manifold 11 disposed at one end of the separator 6A and flows through the meandering fuel gas passage 7A to contribute to the power generation reaction, and then the fuel gas outlet at the other end. It is discharged from the manifold 12 to the outside. Of the two rectangular areas shown by dotted lines in FIG. 2, the inner square area is the area of the surface of S1, and the area located between the outer square and the inner square is the area of the surface of S2. It is an area. Reference numerals 13 and 14 shown in the drawing are an oxidant gas inlet manifold and an oxidant gas outlet manifold used to flow the oxidant gas through the separator 6A on the opposite air electrode side.

In this example, 30 single cells were produced by the above method, and these single cells were stacked and tightened as shown in FIG. 6 to constitute a solid polymer electrolyte fuel cell. The tightening pressure at this time was selected so that the surface pressure of the surface where the separator and the MEA contact each other was 0.6 MPa. The solid polymer electrolyte fuel cell thus configured uses a mixed gas of 80% H ₂ + 20% CO ₂ as a fuel gas and air as an oxidant gas, a stack temperature of 80 ° C., an anode humidification temperature of 70 ° C., A power generation test was conducted under conditions of a cathode humidification temperature of 70 ° C., a current density of 0.4 A / cm ² , and normal pressure. In this power generation test, first, the internal resistance was measured, and then a continuous operation test for evaluating durability was performed.
According to the measurement results of the internal resistance during power generation, the internal resistance of the cell of this example was 0.11 Ωcm ² . This value is clearly lower than the internal resistance of 0.13 Ωcm ² of the conventional cell structure as shown in FIG. 5, and the contact resistance between the members is reduced by removing the surface layer of the separator 6A by performing the surface treatment. It can be seen that the battery characteristics were improved. FIG. 3 is a characteristic diagram showing the change over time of the open circuit voltage in the subsequent continuous operation test (life test) compared with the case of the conventional example. As shown in the figure, in the case of the conventional example, when the operation time exceeded 2000 hr, the open circuit voltage dropped rapidly, and the occurrence of cross leak due to the damage of the electrolyte membrane was observed. With batteries, it is known that the open circuit voltage does not drop sharply even when the operation time exceeds 4000 hr, and the electrolyte membrane is not damaged. In the single cell of the fuel cell of the present embodiment, the surfaces S2 and S1 of the separator 6A are formed corresponding to the two surfaces T1 and T2 in contact with the MEA separator 6A. Therefore, they are stacked and tightened to form a stack. In doing so, pressure is applied equally to each part of the MEA. Therefore, it is understood that the electrolyte membrane is not damaged by stress concentration as in the conventional example, and a stable open circuit voltage is exhibited for a long time.

  FIG. 4 is a schematic cross-sectional view showing the structure of a single cell used in the second embodiment of the solid polymer electrolyte fuel cell of the present invention. This unit cell is also manufactured by using the material and the manufacturing method used in manufacturing the unit cell of the first embodiment. The difference from the first embodiment is that the anode side electrode and the cathode side electrode of the MEA are both configured by forming a catalyst layer having a thickness of 45 μm in the first embodiment. In the second embodiment, the catalyst layer 2B having the same thickness as the protective sheet 4 and having a thickness of 25 μm is formed. For this reason, the MEA is a portion where the catalyst layer 2B and the protective sheet 4 are overlapped ( The thickness is only thick (indicated by T3 in the figure), and the center part indicated by T4 in the figure and the end part indicated by T5 in the figure are formed in the same thickness which is thinner than T3. . The surface of the MEA side of the separator 6B is processed corresponding to the surface of the MEA formed in this way, and is opposed to the surfaces of T3, T4, and T5 of the MEA so as to be in contact with the surface of the MEA. Thus, S3, S4 and S5 are formed. Therefore, when the MEA is clamped by the separator 6B and tightened, almost uniform pressure is applied to each surface, so there is no risk of stress concentration and the electrolyte membrane 1 is not damaged. Further, when processing the surface of the separator 6B, a layer having poor electrical conductivity can be removed by removing the surface layer by sandblasting, so that the contact electrical resistance between members is reduced and the internal resistance of the fuel cell is reduced. As a result, the electrical characteristics are improved.

  As described above, if the solid polymer electrolyte fuel cell is constituted as in claim 1, further, claim 2 or claim 3, the surface of the MEA has a concave portion and a convex portion. Even if it exists, the applied pressure applied to each part of the MEA is maintained almost uniformly in the plane, the damage of the electrolyte membrane is avoided, and stable operation is possible over a long period of time. Since the contact electrical resistance is reduced and the internal resistance loss is reduced, the deterioration of electrical characteristics is avoided. Therefore, the present invention is effective for various solid polymer electrolyte fuel cells used in various fields. Can be applied.

Sectional schematic diagram showing the structure of a single cell of the first embodiment of the solid polymer electrolyte fuel cell of the present invention The top view which shows the fuel gas flow path of the separator of the single cell used for the 1st Example of the solid polymer electrolyte fuel cell of this invention FIG. 3 is a characteristic diagram showing the change over time of the open circuit voltage in the continuous operation test of the first embodiment of the solid polymer electrolyte fuel cell of the present invention Sectional schematic diagram showing the structure of a single cell of the second embodiment of the solid polymer electrolyte fuel cell of the present invention Cross-sectional schematic diagram showing the structure of a typical single cell of a conventional solid polymer electrolyte fuel cell Side view of a conventional solid polymer electrolyte fuel cell Sectional drawing of other conventional examples of MEAs incorporated in a single cell of a solid polymer electrolyte fuel cell Sectional drawing of the 3rd prior art example of MEA incorporated in the single cell of a polymer electrolyte fuel cell

Explanation of symbols

1 Electrolyte membrane
2A, 2B catalyst layer
3A, 3B diffusion layer
4 protection sheets
5 Seal packing
6A, 6B separator
7A, 7B Fuel gas flow path
8A, 8B Oxidant gas flow path
S1, S2, S3, S4, S5 Separator surface
T1, T2, T3, T4, T5 MEA surface

Claims (5)

A membrane / electrode assembly formed by arranging a catalyst layer and a diffusion layer on both sides of a solid polymer electrolyte membrane is composed of a single cell sandwiched between two separators each having a gas flow path, and the membrane In the solid polymer electrolyte fuel cell in which both surfaces of the electrode assembly are each composed of a first plane and a second plane having a height lower than the first plane,
A third surface that is incorporated in contact with the surface of the separator facing the outer surface of the membrane electrode assembly, facing the first plane of the membrane electrode assembly, and the second surface of the membrane electrode assembly. A solid polymer electrolyte fuel cell comprising: a fourth surface having a height higher than that of the third surface, which is incorporated in contact with a flat surface. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the third surface of the separator is arranged to face a formation region of a catalyst layer of the membrane electrode assembly. 3. Polymer electrolyte fuel cell. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the fourth surface of the separator is disposed to face a formation region of a catalyst layer of the membrane electrode assembly. 3. Polymer electrolyte fuel cell. 4. The solid polymer electrolyte fuel cell according to claim 1, wherein the separator is made of a carbon composite material formed of carbon powder and a resin, and the third surface and the fourth surface are The solid polymer electrolyte fuel cell is characterized by being formed by performing a surface treatment to remove the surface layer. 5. The solid polymer electrolyte fuel cell according to claim 4, wherein the surface treatment for removing the surface layer is a blast treatment.

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