JP7435510B2 - Manufacturing method of fuel cell - Google Patents

Description

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

A fuel cell is a membrane electrode assembly (MEA) consisting of an ion-permeable electrolyte membrane, an anode catalyst layer (electrode layer) and a cathode catalyst layer (electrode layer) that sandwich the electrolyte membrane. Equipped with. Gas diffusion layers (GDL) are formed on both sides of the membrane electrode assembly to provide fuel gas or oxidant gas and to collect electricity generated by an electrochemical reaction. A membrane electrode assembly in which GDLs are arranged on both sides is called a membrane electrode & gas diffusion layer assembly (MEGA). A resin frame (frame body) is arranged around the outer periphery of the MEGA in order to suppress leakage of reaction gas (so-called cross leak) and electrical short circuit between electrodes, and the MEA is held in the resin frame.

Usually, MEGA is sandwiched between a pair of separators together with a resin frame to form a fuel cell. Generally, sealability is ensured by providing an adhesive layer made of a material different from the resin constituting the resin frame at the sealing portion between the resin frame and the separator.

For example, Patent Document 1 discloses a membrane electrode assembly including an anode, a cathode, and a polymer electrolyte membrane having a central region interposed between the anode and the cathode, and a peripheral region surrounding the central region. a pair of separators that sandwich the membrane electrode assembly; an anode-side seal portion surrounding the anode and interposed between the peripheral region and the separator on the anode side; a cathode-side seal part interposed between a peripheral region and the separator on the cathode side, and at least one of the anode-side seal part and the cathode-side seal part includes a frame body and the cathode-side seal part of the frame body. The first adhesive layer includes a first adhesive layer disposed on the peripheral region side and a second adhesive layer disposed on the separator side of the frame, and the first adhesive layer is made of a first thermoplastic resin having a melting point T1. A polymer electrolyte fuel cell is disclosed in which the second adhesive layer includes a second thermoplastic resin having a melting point T2 and satisfies T1>T2.

Japanese Patent Application Publication No. 2017-117759

In the conventional method, the present inventors ensured sealing performance by providing an adhesive layer made of a material different from the resin constituting the resin frame at the sealing part between the resin frame and the separator. It was thought that the cost would increase by providing this.

In addition, when considering the conventional method of providing an adhesive layer, we found that because the bond between the resin frame and the separator is a chemical bond, it is susceptible to the effects of organic substances such as oil and fats and minute inorganic substances that adhere to the separator surface. We thought that it would be easy to use, have low robustness, and complicate process control.

Therefore, an object of the present disclosure is to provide a method for manufacturing a fuel cell that can seal a resin frame and a stainless steel base material commonly used as a separator without providing an adhesive layer.

The present inventors conducted extensive research to solve the above problems and found that by irradiating the portion of the stainless steel base material to be sealed with laser light at a specific irradiation energy density, it could be bonded to the resin frame. We have discovered what we can do and have come to the present disclosure.

Example aspects of this embodiment are described as follows.
(1) A step of irradiating a portion of the stainless steel base material to be sealed with a laser beam, and
Including the process of pressing the resin frame and the part of the stainless steel base material to be sealed after laser light irradiation,
The irradiation energy density of the laser beam is 110 mJ/mm ² or more,
A method for manufacturing a fuel cell, wherein the pressing is performed in a state where the resin is molten at a portion where the resin frame and the portion to be sealed are in contact.
(2) The method for manufacturing a fuel cell according to (1), wherein the resin frame contains at least one resin selected from polyolefin, polyester, and polyamide.
(3) The method for manufacturing a fuel cell according to (1), wherein the resin frame contains at least one resin selected from polypropylene, polyethylene naphthalate, polyphenylene ether, and polyamide 6.
(4) The method for manufacturing a fuel cell according to any one of (1) to (3), wherein the stainless steel base material is a separator.
(5) The pressing step is a step of arranging a resin frame between the stainless steel base materials after laser beam irradiation and heat pressing the stainless steel base materials onto the resin frame, which are arranged so that the parts to be sealed face each other. , the method for manufacturing a fuel cell according to any one of (1) to (4).

According to the present disclosure, it is possible to provide a method for manufacturing a fuel cell that can seal a resin frame and a stainless steel base material without providing an adhesive layer.

FIG. 2 is a schematic diagram showing a stainless steel base material after laser processing in an experimental example. FIG. 2 is a schematic diagram showing a state in which stainless steel substrates subjected to laser processing are faced to each other and a PP film is placed between them in an experimental example. FIG. 2 is a schematic diagram showing a state when hot pressing is performed in an experimental example. FIG. 2 is a schematic diagram showing the structure of a test piece and the tensile direction when determining peel strength in an experimental example. FIG. 3 is a diagram showing the relationship between irradiation energy density and peel strength in experimental examples.

One aspect of the present embodiment includes a step of irradiating a portion of the stainless steel base material to be sealed with a laser beam, and a step of pressing a resin frame and a portion of the stainless steel base material to be sealed after irradiation with the laser beam. In this method of manufacturing a fuel cell, the irradiation energy density of light is 110 mJ/mm ² or more, and the pressing is performed in a state where the resin is molten at a portion where the resin frame and the portion to be sealed are in contact.

According to this embodiment, it is possible to seal the resin frame and the stainless steel base material without providing an adhesive layer. The present inventors speculated the reason for this as follows. In this embodiment, fine irregularities are formed in the sealing area by irradiating the sealing area of the stainless steel base material with a laser beam having an irradiation energy density of 110 mJ/mm ² or more. The unevenness formed in the area to be sealed is on the order of nanometers, for example, the depth from the protrusion to the depression is 30 to 100 nm. It was assumed that by pressing the molten resin and the area to be sealed, the resin would penetrate into the irregularities, and then be cured by cooling, thereby joining the resin frame and the stainless steel base material.

This embodiment will be described in detail below.

(Stainless steel base material)
The stainless steel base material used in this embodiment constitutes a fuel cell, and is usually a separator.

The stainless steel is not particularly limited, and may be, for example, martensitic, ferritic, austenitic, austenite/ferrite two-phase, precipitation hardening, or the like. As the stainless steel, it is preferable to use at least one of, for example, chromium steel of Fe-Cr alloy and chromium-nickel steel of Fe-Cr-Ni alloy. Specifically, the stainless steel is preferably at least one type of stainless steel selected from SUS201, 202, 301 to 305, 316, 317, 329, 403, 405, 420, and 430.

The thickness of the stainless steel base material may be approximately the same as that of a normal fuel cell separator, for example, 0.1 to 0.5 mm.

The shape of the stainless steel base material is not particularly limited, but may be any shape that is used as a separator for normal fuel cells.

When the stainless steel base material is a separator, it may be a cathode separator or an anode separator. Alternatively, the cathode separator and the anode separator may be integrated into a separator. Note that the cathode separator is a separator placed on the cathode side of MEGA, and the anode separator is a separator placed on the anode side of MEGA. In this embodiment, as described later, a resin frame may be placed between the stainless steel substrates after irradiation with laser light, which are arranged so that the parts to be sealed face each other, and the resin frame is heat pressed. For this purpose, it is preferable to use a cathode separator and an anode separator as stainless steel base materials, and to perform hot pressing with a resin frame sandwiched therebetween.

The separator has a portion to be joined to the resin frame (sealing portion), and may have other structures such as a flow path portion and a through hole. Examples of the flow path portion include a fuel gas flow path through which fuel gas flows in the anode separator, and an oxidant gas flow path through which oxidant gas flows in the cathode separator. Further, the flow path portion may also include a cooling water flow path through which a cooling medium flows. A plurality of through holes may be provided, for example, a part of the anode side inlet manifold which is a fuel gas supply port, a part of an anode side outlet manifold which is a fuel gas discharge port, and a part of the oxidizing gas supply port. A portion of a cathode side inlet manifold, a portion of a cathode side outlet manifold that is an oxidant gas outlet, a portion of a cooling water inlet manifold that is a supply of cooling water for cooling the cell, or a cooling water outlet. The cooling water outlet manifold is provided to act as part of the cooling water outlet manifold.

(resin frame)
The resin frame used in this embodiment constitutes a fuel cell, is a member that is usually also called a frame, and is placed around the outer periphery of the MEGA, and is a member that holds the MEA.

The resin frame is a member having, for example, a rectangular or substantially rectangular outer shape, and is a member whose main component is resin. The resin frame has a frame shape, and usually has a rectangular or substantially rectangular opening in the center. In the fuel cell, the MEGA is disposed in the opening, and the outer peripheral end of the MEA is bonded to the resin frame via, for example, an adhesive layer.

Furthermore, the resin frame may be provided with through holes in addition to the openings. A plurality of through holes may be provided, for example, a part of the anode side inlet manifold which is a fuel gas supply port, a part of an anode side outlet manifold which is a fuel gas discharge port, and a part of the oxidizing gas supply port. A portion of a cathode side inlet manifold, a portion of a cathode side outlet manifold that is an oxidant gas outlet, a portion of a cooling water inlet manifold that is a supply of cooling water for cooling the cell, or a cooling water outlet. The cooling water outlet manifold is provided to act as part of the cooling water outlet manifold.

The resin contained in the resin frame may be any resin that satisfies the required properties such as strength, heat resistance, and rigidity required for the resin frame, and there are no particular restrictions on the type of resin, molecular weight, etc. One preferred embodiment of the resin is a thermoplastic resin. Preferably, the resin frame contains at least one resin selected from polyolefin, polyester, and polyamide. It is also a preferred embodiment that the resin frame contains at least one resin selected from polypropylene, polyethylene naphthalate, polyphenylene ether, and polyamide 6.

As for the molecular weight of the resin, it is preferable that the weight average molecular weight (Mw) is, for example, 10,000 to 100,000.

Although the resin frame includes resin as its constituent component, it may be composed only of resin or may be composed of resin and components other than resin. Components other than the resin may include, for example, additives. Examples of additives include heat aging inhibitors, antioxidants, ultraviolet absorbers, lubricants, reinforcing materials (glass fibers, whiskers, organic fibers, carbon fibers, etc.), flame retardants, surfactants, surface modifiers, etc. It will be done. The additive is contained in an amount of 50% by mass or less, preferably 0 to 5% by mass, based on 100% by mass of all materials constituting the resin frame. Further, the resin may be a composite resin of two or more types having, for example, an alloy structure.

(Process of irradiating laser light)
The method for manufacturing a fuel cell according to the present embodiment includes a step of irradiating a portion of the stainless steel base material to be sealed with laser light. This step is also referred to as an irradiation step. The irradiation energy density of the laser beam is 110 mJ/mm ² or more.

In the irradiation step, a portion of the stainless steel base material to be sealed is irradiated with laser light. The portion to be sealed is a portion to be joined to the resin frame. In this embodiment, fine irregularities are formed in the sealing area by irradiating the sealing area with a laser beam. By joining the stainless steel base material and the resin frame at the sealing portion, it becomes possible to seal the resin frame and the stainless steel base material.

The laser (laser light source) used in the irradiation process is not particularly limited, and includes, for example, a fiber laser (Yb fiber laser).

As mentioned above, the irradiation energy density of the laser beam is 110 mJ/mm ² or more. The upper limit of the irradiation energy density is, for example, 300 mJ/mm ² . From the viewpoint of firmly joining the stainless steel base material and the resin frame, the irradiation energy density is preferably 120 mJ/mm ² or more, more preferably 130 mJ/mm ² or more, and 140 mJ/mm ² or more. More preferably, it is 150 mJ/mm 2 or more, particularly preferably 150 mJ/mm ² or more. As the irradiation energy density increases, the cost tends to increase relatively and productivity may deteriorate, so from these points of view, the irradiation energy density is preferably 295 mJ/mm ² or less, It is more preferably 290 mJ/mm ² or less, even more preferably 285 mJ/mm ² or less, and particularly preferably 280 mJ/mm ² or less. The upper and lower limits of these numerical ranges can be arbitrarily combined to define a preferable range.

(pressing process)
The method for manufacturing a fuel cell according to the present embodiment includes a step of pressing a resin frame and a portion of the stainless steel base material to be sealed after being irradiated with laser light. This process is also referred to as a press process.
The pressing is performed in a state where the resin is molten at the portion where the resin frame and the portion to be sealed are in contact. Through the pressing process, the molten resin enters the unevenness formed by the laser beam irradiation in the area to be sealed, and is then cooled to harden the resin, thereby joining the resin frame and the stainless steel base material.

It is preferable that the pressing step is a step of arranging a resin frame between the stainless steel base materials after laser beam irradiation and heat-pressing the stainless steel base materials on the resin frame, which are arranged so that the parts to be sealed face each other. This is one of the aspects.

Furthermore, one preferable aspect is that MEGA is placed in the opening of the resin frame used in the pressing process before the resin frame is used in the pressing process. When such a resin frame is used and a separator is used as the stainless steel base material, the layer structure of the separator/resin frame (MEGA) or the separator/resin can be changed by cooling after the pressing process and solidifying the molten resin. A fuel cell having a frame (MEGA)/separator layer structure can be easily formed.

The pressing step is usually performed under heated conditions to melt the resin. The heating temperature varies depending on the resin, but is usually from -5°C to melting point +40°C, preferably from melting point +10°C to melting point +20°C. When the resin is polypropylene, the temperature is usually 155 to 200°C, preferably 170 to 180°C. The upper and lower limits of these numerical ranges can be arbitrarily combined to define a preferable range.

The press pressure is, for example, 0.1 to 5 MPa, preferably 0.5 to 2 MPa. Further, the pressing time is, for example, 1 to 30 seconds, preferably 1 to 5 seconds. The upper and lower limits of these numerical ranges can be arbitrarily combined to define a preferable range.

(Other processes)
The fuel cell manufacturing method of this embodiment usually includes a cooling step for cooling and solidifying the resin, which is performed after the pressing step, as a step (other steps) other than the irradiation step and the pressing step. The cooling step may be performed by natural cooling or forced cooling, but natural cooling is preferable.

The fuel cell manufacturing method of the present embodiment is particularly applicable except that the joining (sealing) between the stainless steel base material (separator) and the resin frame is performed by the above-mentioned irradiation process, pressing process, and normally performed cooling process. There are no limitations, and other steps can be performed, for example, according to conventional fuel cell manufacturing methods. Further, a method for manufacturing a fuel cell from a fuel cell can also be carried out according to a conventional method for manufacturing a fuel cell.

The fuel cell manufacturing method of this embodiment can seal the resin frame and the stainless steel base material without providing an adhesive layer, and does not require the cost of providing an adhesive layer. In addition, in the fuel cell manufacturing method of this embodiment, it is possible to physically achieve the bonding between the resin frame and the stainless steel base material by the resin entering into the unevenness, so the stainless steel base material (separator ) It is preferable because it is less susceptible to the effects of organic substances such as oils and fats and minute inorganic substances adhering to the surface, has high robustness, and facilitates process control.

Hereinafter, the present embodiment will be described with reference to examples, but the present disclosure is not limited to these examples.

(Base material)
A SUS304 plate material (20 mm x 50 mm x 0.1 mm) was used as the stainless steel base material.

(film)
A polypropylene film (also referred to as PP film) (WH-OP HM-1 manufactured by Mitsui Chemicals Tohcello) (20 mm x 10 mm x 0.25 mm) was used as the film.

(Experiment example)
Using a scanning FAYb laser LP-MA manufactured by Panasonic, a 10 mm edge of the SUS304 plate was irradiated with laser light to perform laser processing (see FIG. 1).

The laser-processed parts of two laser-processed SUS304 plates were placed opposite each other, and a PP film was placed and sandwiched between them (see FIG. 2).

Heat pressing was performed by heating the PP film to 180° C. and applying pressure at 2 MPa using a jig (see FIG. 3). After hot pressing, the PP film was cooled to room temperature to prepare a sample.

The prepared sample SUS304 plate material was bent at 90° 10 mm from the laser-processed end to produce a test piece (see FIG. 4).

The test piece was pulled up and down in 95° C. warm water using an autograph to determine the peel strength (see FIG. 4: the arrow in FIG. 4 indicates the tensile direction).

The irradiation energy density of the laser beam was 287 mJ/mm ² , 177 mJ/mm ² , 142 mJ/mm ² , 110 mJ/mm ² , or 107 mJ/mm ² .

FIG. 5 shows the relationship between irradiation energy density and peel strength. In FIG. 5, the relationship between the irradiation energy density and the peel strength is shown as a relative value when the lower limit of the peel strength that is determined to be bonded with sufficient strength is set to 1. Examples in which the irradiation energy density is 287 mJ/mm ² , 177 mJ/mm ² , 142 mJ/mm ² , or 110 mJ/mm ² correspond to Examples, and examples in which irradiation energy density is 107 mJ/mm ² correspond to Comparative Examples.

From the Examples and Comparative Examples, it was confirmed that peel strength is excellent when the irradiation energy density is 110 mJ/mm ² or more. Furthermore, it was confirmed that when the irradiation energy density is 110 mJ/mm2 or ^more , samples with excellent peel strength can be similarly produced even when the heating temperature of the PP film is changed from 180 °C to 165 °C.

Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope of the gist of the present disclosure, they are included in the present disclosure. It is something.

1... Stainless steel base material (SUS304 plate material)
3... Laser processing section 5... PP film 7... Jig

Claims (5)

A step of irradiating a portion of the stainless steel base material to be sealed with laser light;
Including the process of pressing the resin frame and the part of the stainless steel base material to be sealed after laser light irradiation,
The irradiation energy density of the laser beam is 110 mJ/mm ² or more,
A method for manufacturing a fuel cell, wherein the pressing is performed in a state where the resin is molten at a portion where the resin frame and the portion to be sealed are in contact. The method for manufacturing a fuel cell according to claim 1, wherein the resin frame contains at least one resin selected from polyolefin, polyester, and polyamide. The method for manufacturing a fuel cell according to claim 1, wherein the resin frame contains at least one resin selected from polypropylene, polyethylene naphthalate, polyphenylene ether, and polyamide 6. The method for manufacturing a fuel cell according to any one of claims 1 to 3, wherein the stainless steel base material is a separator. Claim: The pressing step is a step of arranging a resin frame between the stainless steel base materials after irradiation with laser light and heat pressing the stainless steel base materials on the resin frame, which are arranged so that the parts to be sealed face each other. 5. The method for manufacturing a fuel cell according to any one of 1 to 4.

Images