JP7207049B2 - Method for manufacturing fuel cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a fuel cell including a frame-shaped resin frame to which a peripheral portion of a membrane electrode assembly is fixed, and a pair of separators sandwiching the membrane electrode assembly and the resin frame.

A fuel cell has a fuel cell stack in which a plurality of fuel cells are stacked. Each fuel cell includes a membrane electrode assembly (MEA), a frame-shaped resin frame to which the peripheral edge of the membrane electrode assembly is fixed, a pair of separators that sandwich the membrane electrode assembly and the resin frame from both sides, Consists of

A gas flow path is formed in the separator for supplying reaction gas to the membrane electrode assembly. A separator having gas channels is formed by pressing a sheet-like base material using a mold.

By the way, in forming the separator by press working, there is a case where a lubricant is applied to both surfaces of the sheet-like base material in order to improve the releasability of the separator from the mold. In this case, the releasability of the separator is improved, but the lubricant adheres to the surface of the separator.

A method of manufacturing a fuel cell using a lubricant to improve the releasability of the separator from the mold is disclosed in Patent Document 1, for example.

JP 2018-170291 A

However, if the lubricant remains on the surface of the separator, the lubricant present at the interface between the adhesive layer provided on the surface of the resin frame and the separator will interfere with the adhesive layer when the resin frame and the separator are adhered. Inhibits binding with the separator.

For this reason, when the separator is molded using a lubricant, it is necessary to remove the lubricant residue after the separator is molded, so it takes a long time to manufacture the fuel cell. In addition, when inspecting that the lubricant residue has been completely removed, it is necessary to calibrate the lubricant on the order of ng and it takes about one week.

The present invention has been made in view of these points, and manufactures a fuel cell capable of suppressing deterioration in adhesiveness due to lubricant residue without providing a lubricant removal step after separator molding. The object is to provide a method.

In view of these points, the method for manufacturing a fuel cell according to the present invention includes a membrane electrode assembly, a frame-shaped resin frame to which the peripheral edge of the membrane electrode assembly is fixed, and the membrane electrode assembly. and a pair of separators sandwiching the resin frame, wherein a lubricant having a predetermined melting point is supplied to both surfaces of a sheet-like base material that serves as the separator, and the base material forming a separator having a gas flow path for supplying reaction gas to the membrane electrode assembly by press working on the membrane electrode assembly; The lubricant is dispersed in the adhesive layers by hot-pressing the pair of separators at a temperature higher than the melting point of the lubricant in a state in which the resin frame provided with the adhesive layer is sandwiched between the pair of separators. and bonding the separator to the resin frame.

According to the present invention, in a state in which the resin frame provided with adhesive layers on both sides is sandwiched between the pair of separators, the lubricating agent is heated and pressed at a temperature higher than the melting point of the lubricant. An agent is dispersed in the adhesive layer and the separator is adhered to the resin frame. As a result, the lubricant can be dispersed in the adhesive layer during thermocompression bonding, so that there is no lubricant at the interface between the adhesive layer provided on the surface of the resin frame and the separator. Therefore, it is possible to prevent the lubricant from interfering with the bonding between the adhesive layer and the separator, thereby suppressing a decrease in the adhesive strength between the resin frame and the separator.

In addition, since it is not necessary to remove the lubricant after molding the separator, it is possible to reduce the amount of time required to manufacture the fuel cell. Also, there is no need to check that the lubricant residue has been completely removed.

As described above, it is possible to suppress deterioration in adhesiveness due to lubricant residue without providing a lubricant removal step after separator molding.

1 is a cross-sectional view of a main part of a fuel cell manufactured by a manufacturing method according to an embodiment of the present invention; FIG. FIG. 2 is a perspective view showing the structure of a membrane electrode assembly that constitutes the fuel cell shown in FIG. 1; FIG. 3 is a cross-sectional view taken along line AA of FIG. 2; FIG. 2 is a cross-sectional view of a main part of a fuel cell stack obtained by stacking a plurality of fuel cells of FIG. 1; FIG. 3 is a cross-sectional view showing the structure of a mold used for manufacturing the separator; FIG. 4 is a diagram showing a schematic flow of a separator manufacturing process; FIG. 4 is a cross-sectional view showing a state in the middle of manufacturing a separator; FIG. 4 is a cross-sectional view showing a state in the middle of manufacturing a fuel cell; 1 is a diagram showing a schematic flow of a manufacturing process of a fuel cell; FIG. FIG. 4 is an enlarged cross-sectional view showing a state in the middle of manufacturing the fuel cell, and showing a state before the lubricant is dispersed. FIG. 4 is an enlarged cross-sectional view showing a state in the middle of manufacturing the fuel cell, and showing a state after the lubricant has been dispersed.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings. In the following, as an example, a case where the present invention is applied to a fuel cell mounted on a fuel cell vehicle or a fuel cell system including the same will be described, but the scope of application is not limited to such an example. .

[Structure of Fuel Cell Equipped with Separator]
FIG. 1 is a sectional view of a main part of a fuel cell 1 (hereinafter referred to as cell 1). As shown in FIG. 1, the cell 1 is a polymer electrolyte fuel cell that generates an electromotive force through an electrochemical reaction between an oxidant gas (eg, air) and a fuel gas (eg, hydrogen). The cell 1 includes a MEGA 2 and a separator (fuel cell separator) 3 in contact with the MEGA 2 so as to partition the MEGA 2 . It should be noted that the MEGA 2 is sandwiched between a pair of separators 3, 3 in this embodiment.

The MEGA 2 is formed by integrating a membrane electrode assembly (MEA) 4 and gas diffusion layers 7, 7 arranged on both sides thereof. The membrane electrode assembly 4 is composed of an electrolyte membrane 5 and a pair of electrodes 6, 6 that are joined to sandwich the electrolyte membrane 5 therebetween. The electrolyte membrane 5 is made of a proton-conducting ion exchange membrane made of solid polymer material, and the electrode 6 is a porous layer in which a catalyst such as platinum is supported and, for example, a carbon material is dispersed. The electrode 6 arranged on one side of the electrolyte membrane 5 becomes an anode, and the electrode 6 on the other side becomes a cathode. The gas diffusion layer 7 is formed of a conductive member having gas permeability, such as a porous carbon material such as carbon paper or carbon cloth, or a porous metal material such as metal mesh or metal foam.

In this embodiment, the MEGA 2 is the power generation part of the cell 1, and the separator 3 is in contact with the gas diffusion layer 7 of the MEGA 2. Further, when the gas diffusion layer 7 is omitted, the membrane electrode assembly 4 is the power generation part, and in this case the separator 3 is in contact with the membrane electrode assembly 4 . Therefore, the power generation part of the cell 1 includes the membrane electrode assembly 4 and contacts the separator 3 .

The separator 3 is a plate-shaped member whose base material is a metal having excellent electrical conductivity and gas impermeability (for example, metal such as SUS, titanium, aluminum, and nickel). It is in contact with layer 7 .

In this embodiment, each separator 3 is formed to have a corrugated or uneven cross-sectional shape. The shape of the separator 3 is such that the shape of the wave is an isosceles trapezoid, the top of the wave is flat, and both ends of the top are angular with equal angles. That is, each separator 3 has substantially the same shape when viewed from the front side and the back side. The top of the separator 3 is in surface contact with one gas diffusion layer 7 of the MEGA 2 , and the top of the separator 3 is in surface contact with the other gas diffusion layer 7 of the MEGA 2 .

The separator 3 is formed by press-molding a sheet-shaped base material 3a made of the above metal (for example, metal such as SUS, titanium, aluminum, nickel, etc.) using a mold so as to have the shape described above. (plastically deformed) (detailed later).

A gas flow path 21 defined between the gas diffusion layer 7 on one electrode (ie, anode) 6 side and the separator 3 is a flow path through which fuel gas flows. A gas channel 22 defined between the gas diffusion layer 7 and the separator 3 is a channel through which the oxidant gas flows. When the fuel gas is supplied to one of the gas flow paths 21 facing each other through the cell 1 and the oxidant gas is supplied to the gas flow path 22, an electrochemical reaction occurs within the cell 1 to generate an electromotive force.

As shown in FIG. 2, the MEGA 2 is formed in a rectangular shape in plan view, and the periphery of the MEGA 2 is adhesively fixed to a frame-shaped resin frame 30 via an adhesive layer 35 (see FIG. 3). . MEGA 2 and resin frame 30 constitute membrane electrode assembly assembly 40 .

The resin frame 30 is a member that seals fuel gas, oxidant gas, and cooling water (to be described later) flowing through the separator 3 . The resin frame 30 is made of thermoplastic resin or thermosetting resin and has flexibility. As shown in FIG. 3, the peripheral portion of the resin frame 30 is provided with an adhesive layer 31 made of a thermoplastic resin sheet for thermocompression bonding to the separator 3 . A cell 1 is configured by adhesively fixing the separator 3 to the resin frame 30 of the membrane electrode assembly 40 . As the resin used for the adhesive layer 31, for example, a polyolefin resin such as polypropylene can be used, but other resins may be used.

[Configuration of fuel cell stack]
FIG. 4 is a cross-sectional view of a main part of the fuel cell stack (fuel cell) 10. As shown in FIG. As shown in FIG. 4, the fuel cell stack 10 includes a plurality of stacked cells 1, which are basic units. One surface side of the separator 3 of each cell 1 is in contact with the gas diffusion layer 7 of the MEGA 2 as described above, and the other surface side is in contact with the other surface side of another adjacent separator 3 .

A certain cell 1 and another adjacent cell 1 are arranged with an electrode 6 serving as an anode and an electrode 6 serving as a cathode facing each other. In addition, the top of the back side of the separator 3 arranged along the electrode 6 serving as the anode of a certain cell 1 and the top of the back side of the separator 3 arranged along the electrode 6 serving as the cathode of another cell 1 are in face-to-face contact. Water (cooling water) as a coolant for cooling the cells 1 flows through a space 23 defined between the separators 3 , 3 that are in surface contact between two adjacent cells 1 .

[Manufacturing process of separator]
FIG. 5 is a cross-sectional view showing the structure of a mold used for manufacturing the separator, and FIG. 6 is a diagram showing a schematic flow of the manufacturing process of the separator. FIG. 7 is a cross-sectional view showing a state in the middle of manufacturing the separator. 7, the lubricant 60, which will be described later, is omitted.

In this embodiment, as shown in FIG. 5, the separator 3 described above is molded using a mold 50. As shown in FIG. The mold 50 has an uneven surface in which concave surfaces (surfaces recessed upward) 43 and convex surfaces (surfaces bulging downward) 44 extending in a predetermined direction (flow direction of the gas flow path) are alternately provided. and a lower mold 45 having a press surface 46 formed of an uneven surface having a complementary shape to the uneven surface (press surface 42) of the upper mold. The separator 3 is formed by pressing the base material 3a, which is the raw material of the separator 3, with the pressing surface 42 of the upper mold 41 and the pressing surface 46 of the lower mold 45 in the vertical direction using the metal mold 50, thereby forming the corrugated shape or unevenness. formed to have the shape of

Here, in the present embodiment, in order to ensure releasability of the molded separator 3 from the mold 50, a lubricant 60 having a predetermined melting point is applied to both surfaces (upper surface and lower surface in FIG. 3) of the base material 3a. Apply (supply) (see supply step S1 in FIG. 6). As the lubricant 60, acrylic polymer-based resin, for example, can be used. Further, the acrylic polymer resin is, for example, among methyl acrylate, ethyl acrylate, butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-dimethylaminoethyl acrylate, and 2-hydroxyethyl acrylate. It is obtained by polymerizing one or more kinds so that the melting point is a predetermined temperature or lower. The lubricant 60 is supplied to both surfaces (upper surface and lower surface) of the base material 3a by applying (supplying) the lubricant 60 to the press surface 42 of the upper mold 41 and the press surface 46 of the lower mold 45. may

After that, the base material 3a is sandwiched between the upper mold 41 and the lower mold 45 with a predetermined pressure from above and below and press processing is performed (refer to the press step S2 in FIG. 6). As a result, the separator 3 having a corrugated or uneven shape (that is, a structure forming the gas flow paths 21, 22 and the space 23) is formed as shown in FIG.

Then, the mold 50 is opened and the separator 3 is taken out from the mold 50 (see mold release step S3 in FIG. 6). Thus, the separator 3 is manufactured. Note that the lubricant 60 remains on the surface of the separator 3 after molding.

[Manufacturing method of fuel cell]
FIG. 8 is a cross-sectional view showing a state during the manufacture of the cell 1, and FIG. 9 is a diagram showing a schematic flow of the manufacturing process of the cell 1. FIG. 10 is an enlarged cross-sectional view of the adhesive layer 31 and its surroundings during the manufacture of the cell 1 . Note that the lubricant 60 is omitted in FIG.

As shown in FIG. 8, the cell 1 is molded by thermocompression bonding using a mold 70 in a state in which the resin frame 30 is sandwiched between the pair of separators 3 . The mold 70 includes an upper mold 71 having a frame-shaped pressing portion 71a that presses the peripheral portion of the separator 3 from above and a concave portion 71b that avoids the uneven surface of the separator 3, and a frame that presses the peripheral portion of the separator 3 from below. It includes a lower die 72 having a shaped pressing portion 72a and a concave portion 72b that avoids the uneven surface of the separator 3. As shown in FIG. The pressing portions 71 a and 72 a are provided at positions facing the adhesive layer 31 of the resin frame 30 .

Each of the upper die 71 and the lower die 72 incorporates a heating device (not shown) for joining the resin frame 30 and the separator 3 together. As long as the heating device heats the upper mold 71 and the lower mold 72, it may be of any form such as an electric current type or a steam type. The heating device is set to a temperature capable of melting the adhesive layer 31 of the resin frame 30 through the separator 3 .

When manufacturing the cell 1, a membrane electrode assembly 40 in which a resin frame 30 is fixed to the periphery of the MEGA 2, and a pair of separators 3 having a corrugated or uneven shape are prepared (see preparation step S11 in FIG. 9). ).

Then, with the membrane electrode assembly 40 sandwiched between the pair of separators 3, the pair of separators 3 are thermocompression bonded to the resin frame 30 using the mold 70 (see the pressing step S12 in FIG. 9). At this time, the thermocompression bonding is performed at a temperature higher than the melting points of the lubricant 60 and the adhesive layer 31 . As a result, the lubricant 60 existing at the interface between the surface of the separator 3 and the adhesive layer 31 as shown in FIG. disperse to Therefore, since the separator 3 and the adhesive layer 31 are in direct contact with each other, the adhesion between the separator 3 and the adhesive layer 31 is not hindered. Note that the melting point of the adhesive layer 31 is lower than the melting point of the lubricant 60 in this embodiment. Therefore, since the adhesive layer 31 melts before the lubricant 60 melts, the lubricant 60 is more easily dispersed in the adhesive layer 31 .

After that, the mold 70 is opened and the cell 1 is taken out from the mold 70 . Then, the cell 1 is cooled to room temperature by blowing cooling air to the cell 1 (see cooling step S13 in FIG. 9). Thus, the cell 1 is manufactured.

In the manufacturing process of the cell 1, when the cell 1 is intermittently moved by a conveyor or the like (not shown) and processed in each process (preparation process, pressing process, cooling process), for example, the cell 1 is Each of the heat treatment step (pressing step S12) and the cooling step S13 may be performed twice in two stations. In this case, the processing time (residence time) at each station can be shortened by about half, so the takt time can be shortened.

In this embodiment, as described above, the resin frame 30 provided with the adhesive layers 31 on both sides is sandwiched between the pair of separators 3, and the pair of separators 3 are thermally compressed at a temperature higher than the melting point of the lubricant 60. do. As a result, the lubricant 60 can be dispersed in the adhesive layer 31 during hot pressing, and the lubricant 60 at the interface between the adhesive layer 31 provided on the surface of the resin frame 30 and the separator 3 is eliminated. Therefore, it is possible to prevent the bonding between the adhesive layer 31 and the separator 3 from being hindered by the lubricant 60 , thereby preventing the adhesion strength between the resin frame 30 and the separator 3 from decreasing.

In addition, since it is not necessary to remove the lubricant 60 after the separator 3 is formed, it is possible to reduce the time required to manufacture the cell 1 . Also, there is no need to check that the lubricant 60 has been completely removed.

As described above, it is possible to suppress deterioration in adhesiveness due to lubricant residue without providing a lubricant removal step after separator molding.

It should be noted that the embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and includes all modifications within the meaning and scope equivalent to the scope of the claims.

For example, in the above embodiment, an example using an acrylic polymer resin as the lubricant 60 was shown, but the present invention is not limited to this. A resin other than an acrylic polymer may be used as long as the resin disperses in the adhesive layer 31 when the temperature is higher than the melting point in the pressing step S12.

1: cell (fuel cell), 2: MEGA (power generation unit), 3: separator, 3a: base material, 4: membrane electrode assembly, 21, 22: gas flow path, 30: resin frame, 31: adhesive layer , 60: lubricant

Claims (1)

A method for manufacturing a fuel cell comprising: a membrane electrode assembly; a frame-shaped resin frame to which a peripheral edge of the membrane electrode assembly is fixed; and a pair of separators sandwiching the membrane electrode assembly and the resin frame. There is
A gas flow for supplying a reaction gas to the membrane electrode assembly by supplying a lubricant having a predetermined melting point to both sides of the sheet-like base material that will be the separator, and pressing the base material. forming a separator having channels;
In a state in which the resin frame to which the membrane electrode assembly is fixed and which is provided with adhesive layers made of a thermoplastic resin on both sides thereof is sandwiched between the pair of separators, the pair of separators is heated to a temperature higher than the melting point of the lubricant. a step of hot-pressing the separator to melt the lubricant, disperse the lubricant in the adhesive layer, and adhere the separator to the resin frame;
A method of manufacturing a fuel cell, comprising:

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