JP2021136205A - Manufacturing method of fuel cell - Google Patents

Abstract

To provide a manufacturing method of a fuel cell in which an adhesion strength of a separator and a seal member is secured.SOLUTION: The present invention relates to a manufacturing method of a fuel cell including: a preparation step of preparing a frame-shaped seal member, a membrane electrode gas diffusion layer assembly which is joined to an inner peripheral edge of the seal member, and first and second separators; and a thermal compression step of thermally compressing the seal member to the first and second separators while holding the seal member and the membrane electrode gas diffusion layer assembly between the first and second separators. The seal member comprises a core layer and first and second adhesive layers which are provided on one side and the other side of the core layer. The first and second adhesive layers have thermal plasticity, have a fusing point lower than that of the core layer and are adhered to the first and second separators in the thermal compression step. At least one of a recess and a projection is provided on at least one of a surface adhered to the first separator by the first adhesive layer and a surface adhered to the second separator by the second adhesive layer, in a region outside of an inner peripheral edge of the core layer.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for manufacturing a fuel cell.

A frame-shaped seal member joined to the outer periphery of the membrane electrode gas diffusion layer joint body and the membrane electrode gas diffusion layer joint body are sandwiched between the two separators, and the seal member is thermally pressure-bonded to the two separators. A method for manufacturing a fuel cell is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-063813

The sealing member has a core layer and an adhesive layer provided on one surface and the other surface of the core layer and adhered to two separators, respectively. Here, at the time of thermocompression bonding, since the sealing member is compressed between the two separators, a part of the adhesive layer flows from between the separator and the core layer to the inner peripheral edge side of the core layer, and the separator and the seal member The adhesive strength with the sealing member may decrease.

Therefore, an object of the present invention is to provide a method for manufacturing a fuel cell in which the adhesive strength between the separator and the sealing member is ensured.

The above object is a preparatory step for preparing a frame-shaped seal member, a film electrode gas diffusion layer bonded body bonded to the inner peripheral edge of the seal member, and first and second separators, and the seal member and the film electrode. The sealing member comprises a thermocompression bonding step of sandwiching the gas diffusion layer bonded body between the first and second separators and thermocompression bonding the sealing member to the first and second separators. And has first and second adhesive layers provided on one surface and the other surface of the core layer, respectively, and the first and second adhesive layers have thermoplasticity and have a melting point higher than that of the core layer. Is low, and is adhered to the first and second separators in the thermocompression bonding step, respectively, and is an area outside the inner peripheral edge of the core layer, and is adhered to the first separator by the first adhesive layer. This can be achieved by a method for manufacturing a fuel cell, in which at least one of a surface and a surface adhered to the second separator by the second adhesive layer is provided with at least one of a concave portion and a convex portion.

It is possible to provide a method for manufacturing a fuel cell in which the adhesive strength between the separator and the sealing member is ensured.

FIG. 1 is an exploded perspective view of a single cell constituting a fuel cell. FIG. 2 is a partial cross-sectional view of a fuel cell in which a plurality of single cells are stacked. 3A and 3B are explanatory views of a method for manufacturing a fuel cell of this embodiment. FIG. 4 is a diagram showing a manufacturing method of a comparative example. FIG. 5 is a diagram showing a part of the seal member. 6A and 6B are explanatory views of a modified example. 7A and 7B are explanatory views of a modified example.

FIG. 1 is an exploded perspective view of a single cell 60 constituting a fuel cell. The fuel cell is configured by stacking a plurality of single cells 60. This fuel cell is a polymer electrolyte fuel cell that generates power by receiving a fuel gas (for example, hydrogen) and an oxidizing agent gas (for example, oxygen) as reaction gases. The single cell 60 includes a frame-shaped sealing member 40, a membrane electrode gas diffusion layer assembly 20 (hereinafter referred to as MEGA (Membrane Electrode Gas diffusion layer assembly)) bonded to the inner peripheral edge of the sealing member 40, and a sealing member. The anode-side separator 33a and the cathode-side separator 33c (hereinafter, referred to as a separator) sandwiching the 40 and the MEGA 20 are included. The MEGA 20 has an anode-side gas diffusion layer 22a and a cathode-side gas diffusion layer 22c (hereinafter, referred to as a diffusion layer).

Holes a1 to a6 and holes c1 to c6 are formed in the separators 33a and 33c, respectively. The seal member 40 is also provided with holes s1 to s6. The holes a1, s1, and c1 communicate with each other to define the cathode inlet manifold. The holes a2, s2, and c2 communicate with each other to define a cooling water outlet manifold. The holes a3, s3, and c3 communicate with each other to define the anode outlet manifold. The holes a4, s4, and c4 communicate with each other to define the anode inlet manifold. The holes a5, s5, and c5 communicate with each other to define a cooling water inlet manifold. The holes a6, s6, and c6 communicate with each other to define the cathode outlet manifold.

On the surface of the separator 33c facing the MEGA 20, a cathode flow path 34c is formed in which the oxidant gas flows through the cathode inlet manifold and the cathode outlet manifold. An anode flow path 34a is formed on the surface of the separator 33a facing the MEGA 20 so that the anode inlet manifold and the anode outlet manifold communicate with each other and the fuel gas flows. A cooling water flow in which cooling water flows through the cooling water inlet manifold and the cooling water outlet manifold on the surface of the separator 33a opposite to the anode flow path 34a and the surface of the separator 33c opposite to the cathode flow path 34c. Roads 35a and 35c are formed, respectively.

FIG. 2 is a partial cross-sectional view of the fuel cell 1 in which a plurality of single cells 60 are stacked. In FIG. 2, only one single cell 60 is shown, and the other single cells are omitted. The MEGA 20 includes the above-mentioned diffusion layers 22a and 22c and a membrane electrode assembly (hereinafter referred to as MEA) 10. The MEA 10 includes an electrolyte membrane 11 and an anode-side catalyst layer 12a and a cathode-side catalyst layer 12c (hereinafter, referred to as a catalyst layer) formed on one surface and the other surface of the electrolyte membrane 11, respectively. The electrolyte membrane 11 is a solid polymer thin film that exhibits good proton conductivity in a wet state, and is, for example, a fluorine-based ion exchange membrane. The electrolyte membrane 11 has a peripheral region 11e and a central region 11c surrounded by the peripheral region 11e.

The catalyst layer 12a is formed on one surface (lower surface in FIG. 2) of the electrolyte membrane 11 as described above, and is formed so as to be substantially aligned with the end portion of the electrolyte membrane 11. That is, the catalyst layer 12a is formed over substantially the entire surface including the peripheral region 11e and the central region 11c of the electrolyte membrane 11. The catalyst layer 12c is formed on the other surface (upper surface in FIG. 2) of the electrolyte membrane 11 as described above, and is not formed on the peripheral region 11e. The catalyst layers 12a and 12c are formed by applying, for example, a carbon carrier carrying platinum (Pt) or the like and an ionomer having proton conductivity to the electrolyte membrane 11.

The diffusion layers 22a and 22c are bonded to the catalyst layers 12a and 12c, respectively. The diffusion layers 22a and 22c are formed of a gas-permeable and conductive material, for example, a porous fiber base material such as carbon fiber or graphite fiber. The diffusion layer 22c is provided at a position where its end is located slightly inside or substantially aligned with the end of the catalyst layer 12c. Therefore, the diffusion layer 22c is provided so as to overlap the central region 11c of the electrolyte membrane 11 via the catalyst layer 12c but not to the peripheral region 11e. As a result, the diffusion layer 22c is provided so as to expose the peripheral region 11e.

Similarly, the diffusion layer 22a is provided at a position where its end is located slightly inside or substantially aligned with the end of the catalyst layer 12a, but as described above, the catalyst layer 12a is one surface of the electrolyte membrane 11. It is formed over almost the entire surface. Therefore, the diffusion layer 22a is provided so as to overlap not only the central region 11c but also the peripheral region 11e via the catalyst layer 12a. Since the diffusion layer 22a is provided so as to overlap the peripheral region 11e in this way, the MEA 10 is stably supported. Further, both the diffusion layers 22a and 22c are bonded to the catalyst layers 12a and 12c, respectively, and are provided so as not to come into direct contact with the electrolyte membrane 11.

The seal member 40 is a member for preventing leakage of reaction gas, cross leakage, and electrical short circuit between catalyst electrodes, and has insulating properties. As shown in FIG. 1, the seal member 40 is sandwiched between a pair of separators 33a and 33c. Further, the inner edge portion of the sealing member 40 located inside the separators 33a and 33c is adhered to the peripheral region 11e of the electrolyte membrane 11 by the adhesive 50. The sealing member 40 includes a resin core layer 41 and adhesive layers 42a and 42c provided on the anode side and cathode side surfaces of the core layer 41, respectively. The core layer 41 is, for example, polyethylene, polypropylene, polyethylene naphthalate, polyethylene terephthalate, or the like. The adhesive layers 42a and 42c are thermoplastic resins, for example, polyester-based or modified olefin-based. The melting points of the adhesive layers 42a and 42c are formed lower than those of the core layer 41. The adhesive 50 is, for example, a thermosetting resin, but may be an ultraviolet curable resin. Convex portions 41a and 41c are formed on the anode side and cathode side surfaces of the core layer 41, respectively, which will be described in detail later. Although FIG. 2 shows the cross-sectional configurations of the holes c1 to c3, s1 to s3, and a1 to a3, the cross-sectional configurations of the holes c4 to c6, s4 to s6, and a4 to a6 are also formed in the same manner. ing.

The separators 33a and 33c sandwich the MEGA 20 and the seal member 40. The separators 33a and 33c are made of a material having gas-blocking property and conductivity, and in this embodiment, they are made of press-molded stainless steel. The separators 33a and 33c may be formed of a thin plate-like member formed of a metal such as titanium or a titanium alloy, or a carbon member such as dense carbon.

Next, a method of manufacturing the fuel cell 1 will be described. 3A and 3B are explanatory views of the manufacturing method of the fuel cell 1 of this embodiment. First, a plurality of pairs of MEGA 20 and a sealing member 40 bonded by an adhesive 50 and separators 33a and 33c are prepared. Next, the separator 33c, the MEGA 20, the seal member 40, the separator 33a, the separator 33c, the MEGA 20, the seal member 40, the separator 33a, and the like are laminated in this order from the top. In FIG. 3A, only the pair of separators 33c, MEGA 20, the seal member 40, and the separator 33a are shown. In this state, the separators 33c and 33a are heat-bonded to the seal member 40 as shown in FIG. 3B. Since the adhesive layers 42a and 42c are thermoplastic resins, they are melted by applying heat, and then cured in a state where the adhesive layers 42a and 42c are adhered to the separators 33a and 33c, respectively, in the process of cooling. The fuel cell 1 is manufactured by stacking the single cells 60 manufactured in this manner.

FIG. 4 is a diagram showing a manufacturing method of a comparative example. In the comparative example shown in FIG. 4, the core layer 41x of the seal member 40x is different from the core layer 41 of the seal member 40 of the present embodiment described above, and the convex portions 41a and 41c are not provided and both sides are flat. Is formed in. Therefore, at the time of thermocompression bonding, as shown in FIG. 4, the adhesive layer 42c melted by heat is pressed by the separator 33c, and a part of the adhesive layer 42c is directed from the region where the separator 33c contacts to the inside of the sealing member 40x which does not contact. There is a risk of leakage. Similarly, with respect to the adhesive layer 42a, a part of the adhesive layer 42a may flow out from the area where the separator 33a contacts toward the inside of the sealing member 40x which does not contact. In particular, the higher the heating temperature, the shorter the time required for thermal pressure bonding, and therefore, such a situation is likely to occur when the heating temperature is raised in order to shorten the manufacturing time. If the adhesive layers 42a and 42c are cured in this state, the adhesive strength between the sealing member 40x and the separators 33a and 33c may be insufficient.

As described above, in this embodiment, as shown in FIGS. 2, 3A, and 3B, the core layer 41 is provided in the region where the convex portions 41a and 41c are in contact with the separators 33a and 33c, respectively. Therefore, even if the adhesive layers 42a and 42c are melted during thermocompression bonding, the outflow of the adhesive layers 42a and 42c is suppressed as described above, and the adhesive force between the sealing member 40 and the separators 33a and 33c is secured. The height of the convex portion 41c protruding from the surface of the core layer 41 is substantially the same as the thickness of the adhesive layer 42c. That is, the tip of the convex portion 41c is exposed from the adhesive layer 42c and is in contact with the separator 33c. The same applies to the convex portion 41a. Therefore, the outflow of the adhesive layers 42a and 42c can be sufficiently suppressed.

FIG. 5 is a diagram showing a part of the seal member 40. The convex portion 41c is formed between each of the holes s1 to s3 and the MEGA20 side. Further, the convex portion 41c is formed so as to extend so as to be substantially parallel to the lateral direction of the seal member 40 in which the holes s1 to s3 are lined up. The same applies to the convex portion 41a.

In the sealing member 40, for example, adhesive layers are provided on both sides of a plate-shaped core layer by screen printing or transfer, and then these layers are cut into a frame shape by press punching to form holes s1 to s6. Manufactured by Further, the adhesive 50 is applied to the peripheral edge region 11e of the MEGA 20 to adhere the inner peripheral edge of the sealing member 40 to the peripheral edge region 11e. As a result, the seal member 40 and the MEGA 20 are joined.

Next, a plurality of modified examples will be described. 6A to 7B are explanatory views of a modified example. As shown in FIG. 6A, the convex portion 41c1 of the seal member 401 extends in a straight line adjacent to the plurality of holes s1 to s3. The convex portion 41c2 of the seal member 402 of FIG. 6B extends so as to surround each of the holes s1 to s3.

The convex portions 41a3 and 41c3 of the core layer 413 of the seal member 403 of the single cell 603 of the fuel cell 1-3 shown in FIG. 7A are covered with the adhesive layers 42a and 42c, respectively. In other words, the protruding height of the convex portion 41a3 from one surface of the core layer 413 is set lower than the maximum thickness of the adhesive layer 42a, and the protruding height of the convex portion 41c3 from the other surface of the core layer 413 is set. The height is set lower than the maximum thickness of the adhesive layer 42c. This also makes it possible to suppress the outflow of the adhesive layers 42a and 42c during thermocompression bonding.

Recesses 41a4 and 41c4 are formed on one surface and the other surface of the core layer 414 of the seal member 404 of the single cell 604 of the fuel cell 1-4 of FIG. 7B, respectively. This also makes it possible to suppress the outflow of the adhesive layers 42a and 42c during thermocompression bonding.

Both the above-mentioned convex portion 41c or 41c3 and the concave portion 41c4 may be formed on one surface of the core layer of the sealing member. Similarly, both the above-mentioned convex portion 41a or 41a3 and the concave portion 41a4 may be formed on the other surface of the core layer of the seal member. Further, at least one of the above-mentioned convex portion and concave portion may be provided on at least one surface of the core layer of the seal member. Even in this case, at least the outflow of the adhesive layer on that surface can be suppressed.

The above-mentioned protrusions and recesses are not limited to extending linearly, and may be curved, may extend in an arc shape, may meander, or have a plurality of straight lines, for example. The shaped portion may be extended so as to be connected, or the curved portion and the straight portion may be extended so as to be connected.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and modifications are made within the scope of the gist of the present invention described in the claims. It can be changed.

1 Fuel cell 20 Membrane electrode gas diffusion layer junction 33a Anode side separator 33c Cathode side separator 40 Sealing member 41 Core layer 41a, 41c Convex part 42a, 42b Adhesive layer 60 Single cell

Claims (1)

A preparatory step for preparing a frame-shaped seal member, a membrane electrode gas diffusion layer bonded body bonded to the inner peripheral edge of the seal member, and first and second separators.
The seal member and the membrane electrode gas diffusion layer joint body are sandwiched between the first and second separators, and the seal member is heat-bonded to the first and second separators.
The sealing member has a core layer and first and second adhesive layers provided on one surface and the other surface of the core layer, respectively.
The first and second adhesive layers have thermoplasticity and a lower melting point than the core layer, and are adhered to the first and second separators in the thermocompression bonding step, respectively.
A region outside the inner peripheral edge of the core layer, the surface of which is adhered to the first separator by the first adhesive layer and the surface of which is adhered to the second separator by the second adhesive layer. A method for manufacturing a fuel cell, wherein at least one of a concave portion and a convex portion is provided.

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