JP2020145130A - Manufacturing method of fuel battery cell - Google Patents

Abstract

To provide a manufacturing method of fuel battery cell capable of suppressing deterioration of adhesiveness due to residue of lubrication, without providing a lubrication removal process after separator molding.SOLUTION: A manufacturing method of cell (fuel battery cell) 1 comprising a membrane electrode assembly 4, a resin frame 30 to which the peripheral part of the membrane electrode assembly 4 is fixed, and a pair of separators 3 for sandwiching the membrane electrode assembly 4 and the resin frame 30 includes a process for forming the separators 3 having gas passageways 21, 22 by supplying a lubrication 60 having a prescribed fusion point to both surfaces of a backing material 3a, and applying press working to the backing material 3a at a temperature lower than the fusion point of the lubrication 60, and a process for hot pressing the pair of separators 3 in such a state that the resin frame 30, provided with adhesive layers 31 based on the same thermoplastic resin as the lubrication 60 on both sides, is sandwiched by the pair of separators 3.SELECTED DRAWING: Figure 9

Description

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

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

The separator is formed with a gas flow path for supplying a reaction gas to the membrane electrode assembly. By pressing the sheet-shaped base material using a mold, a separator having a gas flow path is formed.

By the way, in the molding of a separator by press working, a lubricant may be applied to both surfaces of a sheet-shaped base material in order to improve the releasability of the separator with respect to the mold. In this case, the releasability of the separator is improved, but the lubricant adheres to the surface of the separator.

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

JP-A-2018-170291

However, if the lubricant remains on the surface of the separator, when the resin frame and the separator are bonded, the lubricant existing at the interface between the adhesive layer and the separator provided on the surface of the resin frame becomes the adhesive layer. Inhibits binding to the separator.

Therefore, when the separator is molded using the lubricant, it is necessary to remove the lubricant residue after molding the separator, which takes time to manufacture the fuel cell. When inspecting that the lubricant residue has been completely removed, it is necessary to weigh 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 a decrease in adhesiveness due to a lubricant residue without providing a lubricant removing step after separator molding. The challenge 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. A method for manufacturing a fuel cell including a pair of separators sandwiching the resin frame, and supplying a lubricant having a predetermined melting point to both surfaces of a sheet-like base material serving as the separator, and the lubricant. By pressing the base material at a temperature lower than the melting point of the above, a step of forming a separator having a gas flow path for supplying a reaction gas to the membrane electrode assembly and the same heat as the lubricant. At a temperature higher than the melting point of the lubricant and the adhesive layer, the resin frame and the membrane electrode assembly provided on both sides with adhesive layers containing a plastic resin as a main component are sandwiched between the pair of separators. It is characterized by including a step of adhering the separator to the resin frame by hot-pressing the pair of separators.

According to the present invention, the resin frame provided with adhesive layers containing the same resin as the lubricant as a main component on both sides is sandwiched between the pair of separators, and the pair of separators is hot-pressed. The separator is adhered to the resin frame. As a result, at the interface between the lubricant and the adhesive layer, the lubricant and the adhesive layer are mixed to secure a predetermined adhesive strength, and at the interface between the lubricant and the separator, the lubricant adheres to the separator to obtain a predetermined strength. Secured. Therefore, it is possible to prevent the bond between the adhesive layer and the separator from being hindered by the lubricant, so that it is possible to suppress a decrease in the adhesive strength between the resin frame and the separator.

Further, since it is not necessary to remove the lubricant after molding the separator, it is possible to suppress the time required for manufacturing the fuel cell. Nor is it necessary to inspect that the lubricant residue has been completely removed.

As described above, it is possible to suppress the deterioration of the adhesiveness due to the lubricant residue without providing the lubricant removing step after the separator molding.

Further, by pressing the base material at a temperature lower than the melting point of the lubricant, the lubricant does not melt and adhere to the mold, so that the releasability of the separator does not deteriorate.

It is a cross-sectional view of the main part of the fuel cell manufactured by the manufacturing method which concerns on one Embodiment of this invention. It is a perspective view which shows the structure of the membrane electrode assembly assembly which comprises the fuel cell shown in FIG. It is sectional drawing which follows the AA line of FIG. It is a cross-sectional view of the main part of the fuel cell stack obtained by stacking a plurality of fuel cell cells of FIG. 1. It is sectional drawing which shows the structure of the mold used for manufacturing a separator. It is a figure which showed the schematic flow of the manufacturing process of a separator. It is sectional drawing which shows the state in the process of manufacturing a separator. It is sectional drawing which shows the state in the process of manufacturing a fuel cell. It is a figure which showed the schematic flow of the manufacturing process of a fuel cell. It is an enlarged sectional view around the adhesive layer of a fuel cell.

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 as an example, but the scope of application is not limited to such an example. ..

[Construction of fuel cell with separator]
FIG. 1 is a cross-sectional view of a main part of a fuel cell 1 (hereinafter referred to as a cell 1). As shown in FIG. 1, cell 1 is a polymer electrolyte fuel cell that generates an electromotive force by an electrochemical reaction between an oxidant gas (for example, air) and a fuel gas (for example, hydrogen). The cell 1 includes a MEGA 2 and a separator (fuel cell separator) 3 that contacts the MEGA 2 so as to partition the MEGA 2. In this embodiment, MEGA2 is sandwiched by a pair of separators 3 and 3.

The MEGA 2 is a combination of a membrane electrode assembly (MEA) 4 and gas diffusion layers 7 and 7 arranged on both sides thereof. The membrane electrode assembly 4 is composed of an electrolyte membrane 5 and a pair of electrodes 6 and 6 bonded so as to sandwich the electrolyte membrane 5. The electrolyte membrane 5 is made of a proton-conducting ion exchange membrane formed of a solid polymer material, and the electrode 6 is a porous layer in which, for example, a carbon material carrying a catalyst such as platinum is dispersed. The electrode 6 arranged on one side of the electrolyte membrane 5 serves as an anode, and the electrode 6 on the other side serves as a cathode. The gas diffusion layer 7 is formed of a gas-permeable conductive member such as a carbon porous body such as carbon paper or carbon cloth, or a metal porous body such as a metal mesh or foamed metal.

In the present embodiment, the MEGA 2 is the power generation unit of the cell 1, and the separator 3 is in contact with the gas diffusion layer 7 of the MEGA 2. When the gas diffusion layer 7 is omitted, the membrane electrode assembly 4 is the power generation unit, and in this case, the separator 3 is in contact with the membrane electrode assembly 4. Therefore, the power generation unit of the cell 1 includes the membrane electrode assembly 4 and comes into contact with the separator 3.

The separator 3 is a plate-shaped member whose base material is a metal having excellent conductivity and gas impermeable properties (for example, a metal such as SUS, titanium, aluminum, nickel, etc.), and one side thereof is a gas diffusion of MEGA2. It is in contact with the layer 7.

In the present embodiment, each separator 3 has a wavy 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 at the same angle. 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 MEGA2, and the top of the separator 3 is in surface contact with the other gas diffusion layer 7 of MEGA2.

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

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

As shown in FIG. 2, MEGA2 is formed in a rectangular shape in a plan view, and the peripheral edge portion of MEGA2 is adhesively fixed to a frame-shaped resin frame 30 via an adhesive layer 35 (see FIG. 3). .. The membrane electrode assembly assembly 40 is composed of the MEGA 2 and the resin frame 30.

The resin frame 30 is a member that seals the fuel gas, the oxidant gas, and the cooling water described later that flow through the separator 3. The resin frame 30 is made of a thermoplastic resin or a thermosetting resin and has flexibility. As shown in FIG. 3, an adhesive layer 31 made of a thermoplastic resin sheet for thermocompression bonding to the separator 3 is provided on the peripheral edge of the resin frame 30. The cell 1 is formed by adhesively fixing the separator 3 to the resin frame 30 of the membrane electrode assembly 40. Examples of the resin used for the adhesive layer 31 include polyolefin resins such as polypropylene, but other resins may be used. Further, as the polyolefin-based resin used for the adhesive layer 31, a modified polyolefin-based resin may be used.

[Fuel cell stack configuration]
FIG. 4 is a cross-sectional view of a main part of the fuel cell stack (fuel cell) 10. As shown in FIG. 4, a plurality of cells 1, which are basic units, are stacked on the fuel cell stack 10. As described above, one side of the separator 3 of each cell 1 is in contact with the gas diffusion layer 7 of MEGA2, and the other side is in contact with the other side of the adjacent separator 3.

One cell 1 and another cell 1 adjacent thereto are arranged so that the electrode 6 serving as an anode and the electrode 6 serving as a cathode face each other. Further, the top of the back surface of the separator 3 arranged along the electrode 6 serving as the anode of a certain cell 1 and the top of the back surface of the separator 3 arranged along the electrode 6 serving as the cathode of another cell 1. Are in surface contact with each other. Water (cooling water) as a refrigerant for cooling the cell 1 flows through the space 23 defined between the separators 3 and 3 which are in surface contact with each other between the two adjacent cells 1.

[Separator manufacturing process]
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 which the separator is being manufactured. In FIG. 7, the lubricant 60, which will be described later, is omitted.

In the present embodiment, as shown in FIG. 5, the above-mentioned separator 3 is molded by using the mold 50. The mold 50 is an uneven surface in which a concave surface (a surface recessed upward) 43 and a convex surface (a surface bulging downward) 44 extending in a predetermined direction (flow direction of a gas flow path) are alternately provided. It is composed of an upper die 41 having a press surface 42 made of, and a lower die 45 having a press surface 46 made of an uneven surface having a shape complementary to the uneven surface (press surface 42) of the upper die. The separator 3 has a wavy shape or unevenness by pressing the base material 3a, which is the material of the separator 3, in the vertical direction with the press surface 42 of the upper mold 41 and the press surface 46 of the lower mold 45 using the mold 50. It is formed so as to exhibit a shape.

Here, in the present embodiment, in order to ensure the mold releasability of the separator 3 after molding with respect to the mold 50, a lubricant 60 having a predetermined melting point is applied to both surfaces (upper surface and lower surface of FIG. 3) of the base material 3a. Apply (supply) (see supply step S1 in FIG. 6). The lubricant 60 contains the same thermoplastic resin as the adhesive layer 31 as a main component. Here, as the lubricant 60, for example, a polyolefin resin such as polypropylene is used. The lubricant 60 may be 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. Good. In the present specification and claims, the "same thermoplastic resin" does not mean that the two resins are, for example, polyolefin-based resins, but that the two resins are, for example, polypropylene. ing. That is, it can be said that the two resins are resins containing the same polymer compound as a main component.

After that, the base material 3a is sandwiched between the upper die 41 and the lower die 45 at a predetermined pressure from the vertical direction and pressed (see the pressing step S2 in FIG. 6). As a result, as shown in FIG. 7, a separator 3 having a wavy or uneven shape (that is, a structure forming the gas flow paths 21, 22 and the space 23) is formed. In the pressing step S12, the temperature of the die 50 rises due to friction during operation (for example, 100 ° C. or higher), but the melting point of the lubricant 60 is set higher than the temperature of the die 50. A cooling device for cooling the mold 50 may be provided so that the temperature of the mold 50 is lower than the melting point of the lubricant 60.

Then, the mold 50 is opened, and the separator 3 is taken out from the mold 50 (see the mold removing step S3 in FIG. 6). In this way, the separator 3 is manufactured. 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 in which the cell 1 is being manufactured, 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 periphery of the adhesive layer 31 during the production of the cell 1. In FIG. 8, the lubricant 60 is omitted.

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

Further, each of the upper die 71 and the lower die 72 has a built-in heating device (not shown) for joining the resin frame 30 and the separator 3. The heating device may be of any form such as an energization type and a steam type as long as it heats the upper mold 71 and the lower mold 72. The heating device is set to a temperature at which the adhesive layer 31 of the resin frame 30 can be melted via the separator 3.

When manufacturing the cell 1, a membrane electrode assembly 40 in which a resin frame 30 is fixed to the peripheral edge of MEGA 2 and a pair of separators 3 having a wavy 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 a mold 70 (see the pressing step S12 in FIG. 9). At this time, thermocompression bonding is performed at a temperature higher than the melting points of the lubricant 60 and the adhesive layer 31. As a result, as shown in FIG. 10, at the interface between the lubricant 60 containing the same resin as the main component and the adhesive layer 31, the lubricant 60 and the adhesive layer 31 are mixed to ensure a predetermined strength. Further, at the interface between the lubricant 60 and the separator 3, the lubricant 60 adheres to the separator 3 to ensure a predetermined strength. Therefore, the adhesion between the separator 3 and the adhesive layer 31 is not hindered.

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 applying cooling air to the cell 1 (see the cooling step S13 in FIG. 9). In this way, 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 step, pressing step, cooling step), for example, the cell 1 is moved. Each of the heat treatment step (pressing step S12) and the cooling step S13 may be divided into two stations and performed twice. In this case, the processing time (stay time) at each station can be reduced to about half, so that the tact time can be shortened.

In the present embodiment, as described above, the pair of separators 3 are heated with the resin frame 30 provided on both sides of the adhesive layer 31 containing the same resin as the lubricant 60 as the main component sandwiched between the pair of separators 3. By pressing, the separator 3 is adhered to the resin frame 30. As a result, at the interface between the lubricant 60 and the adhesive layer 31, the lubricant 60 and the adhesive layer 31 are mixed to ensure a predetermined adhesive strength, and at the interface between the lubricant 60 and the separator 3, the lubricant 60 is the separator 3 Adhesion with and a predetermined strength is secured. Therefore, since it is possible to suppress the bond between the adhesive layer 31 and the separator 3 from being hindered by the lubricant 60, it is possible to suppress a decrease in the adhesive strength between the resin frame 30 and the separator 3.

Further, since it is not necessary to remove the lubricant 60 after molding the separator 3, it is possible to suppress the time required for manufacturing the cell 1. Nor is it necessary to inspect that the lubricant 60 has been completely removed.

As described above, it is possible to suppress the deterioration of the adhesiveness due to the lubricant residue without providing the lubricant removing step after the separator molding.

Further, by pressing the base material 3a at a temperature lower than the melting point of the lubricant 60, the lubricant 60 does not melt and adhere to the mold 50, so that the releasability of the separator 3 does not deteriorate. ..

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

For example, in the above embodiment, the example in which the polyolefin-based resin is used as the adhesive layer 31 and the lubricant 60 has been shown, but a resin other than the polyolefin-based resin may be used as the adhesive layer 31 and the lubricant 60.

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, which includes 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 that sandwich the membrane electrode assembly and the resin frame. There,
The membrane electrode assembly is formed by supplying a lubricant having a predetermined melting point to both sides of a sheet-shaped base material serving as a separator and pressing the base material at a temperature lower than the melting point of the lubricant. A step of forming a separator having a gas flow path for supplying a reaction gas to the
The lubricant and the adhesive layer are provided with adhesive layers containing the same thermoplastic resin as the lubricant as main components on both sides, with the resin frame and the membrane electrode assembly sandwiched between the pair of separators. The step of adhering the separator to the resin frame by thermally pressing the pair of separators at a temperature higher than the melting point of
A method for manufacturing a fuel cell, which comprises.