JP2022072699A - Method for manufacturing separator for fuel cell - Google Patents

Abstract

To accurately arrange an expanded graphite sheet on a core material when the expanded graphite sheet is partially arranged so as to suppress adhesive failures of a seal part by the expanded graphite sheet.SOLUTION: A method for manufacturing a separator for a fuel cell of a fuel cell in which a plurality of fuel cells are laminated includes: a first step of mixing a thermosetting resin and a conductive filler, and forming a sheet-like core material; a second step of arranging an expanded graphite sheet so as to cover the surface of the core material; a third step of press molding the core material arranged with the expanded graphite sheet, and manufacturing a pre-treated separator as the origin of the separator for the fuel cell; and a fourth step of removing the expanded graphite sheet positioned in a seal part positioned between a pair of separators for fuel cells facing across membrane electrode joined bodies, a gasket parts positioned between the two separators for fuel cells adjacent to each other in a lamination direction, and parts to which the parts are bonded.SELECTED DRAWING: Figure 2

Description

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

Generally, in a fuel cell, a plurality of fuel cell cells are stacked. The fuel cell has a membrane electrode assembly and fuel cell separators arranged on both sides of the fuel cell assembly. In order to ensure the sealing property in the fuel cell, a sealing portion is formed between the pair of fuel cell separators facing each other with the membrane electrode assembly interposed therebetween. Further, in order to ensure the sealing property between the fuel cell cells to be stacked, a gasket portion is formed between two separators for fuel cells adjacent to each other in the stacking direction. As a method for manufacturing a separator for a fuel cell, a manufacturing method in which expanded graphite sheets are arranged on both sides of a molded product formed from a mixture of a thermosetting resin and graphite has been proposed (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-207103

When the expanded graphite sheet is arranged on the seal portion or the gasket portion in the fuel cell separator, the expanded graphite sheet may cause poor adhesion of the seal portion or the gasket portion. Therefore, Patent Document 1 discloses a technique of arranging an expanded graphite sheet only in a portion forming a gas flow path of a fuel cell separator during press molding. However, when the expanded graphite sheet is partially arranged on the core material as a molded product, it is necessary to arrange the expanded graphite sheet with high accuracy on the core material.

The present disclosure can be realized in the following forms.

According to one embodiment of the present disclosure, there is provided a method for manufacturing a fuel cell separator for a fuel cell in which a plurality of fuel cell cells are laminated. The method for manufacturing the fuel cell separator is a first step of mixing a thermosetting resin and a conductive filler to form a sheet-shaped core material, and arranging an expanded graphite sheet so as to cover the surface of the core material. The second step of the process, the third step of press-molding the core material on which the expanded graphite sheet is arranged to produce the pretreatment separator which is the source of the fuel cell separator, and the film of the pretreatment separator. A portion where a seal portion located between a pair of fuel cell separators facing each other across an electrode assembly and a gasket portion located between two adjacent fuel cell separators in the stacking direction are bonded to each other. Includes a fourth step of removing the expanded graphite sheet located in. According to this form, since the expanded graphite sheet is arranged so as to cover the surface of the core material in the second step, finer alignment is performed as compared with the case of partially arranging the expanded graphite sheet when arranging the expanded graphite sheet on the core material. Is not required, and it is not necessary to accurately arrange the expanded graphite sheet on the core material. Further, in the fourth step, the expanded graphite sheet located at the portion where the seal portion is adhered and the expanded graphite sheet located at the portion where the gasket is adhered are removed, so that the separator for the fuel cell and the seal portion are separated. Poor adhesion and poor adhesion between the fuel cell separator and the gasket portion can be suppressed.
The present disclosure can be realized in various forms, and in addition to the above-mentioned form, it can be realized in the form of a fuel cell separator manufacturing apparatus or the like that realizes the above-mentioned manufacturing method.

It is an exploded perspective view which shows the outline of the structure of a fuel cell. It is a top view of a separator. It is sectional drawing which shows the schematic structure of the fuel cell. It is a process drawing which shows the manufacturing method of a separator. It is a figure which shows typically the manufacturing apparatus for performing a 2nd step.

A. Embodiment:
FIG. 1 is an exploded perspective view showing an outline of the configuration of the fuel cell 100. FIG. 2 is a plan view of the separator 50. FIG. 3 is a cross-sectional view showing a schematic configuration of the fuel cell 100, and is a cross-sectional view taken along the line III-III of FIG.

The fuel cell is configured by stacking a plurality of fuel cell 100s. As shown in FIG. 1, in the fuel cell 100, a fuel cell separator (hereinafter, abbreviated as a separator) 40 and a separator 50 are arranged on both sides of a cell frame joint 20. The cell frame assembly 20 has a resin frame 25 and a membrane electrode gas diffusion layer assembly (MEGA) 18. The resin frame 25 has a rectangular outer shape, has an opening 25a in the central region, and is formed into a frame shape. The membrane electrode gas diffusion layer junction 18 is arranged in the opening 25a of the resin frame 25.

As shown in FIG. 3, the membrane electrode gas diffusion layer assembly 18 includes a membrane electrode assembly (MEA) 10 and gas diffusion layers 15 and 17. The membrane electrode assembly 10 includes an electrolyte membrane 12, an anode 14 and a cathode 16 which are catalyst electrode layers. The anode 14 and the cathode 16 are arranged on both sides of the electrolyte membrane 12. Gas diffusion layers 15 and 17 are arranged on both sides of the membrane electrode assembly 10.

The electrolyte membrane 12 is a proton-conducting ion exchange membrane formed of a polyelectrolyte material, for example, a fluororesin, and exhibits good proton conductivity in a wet state. The anode 14 and the cathode 16 are porous bodies having pores, and are formed by coating conductive particles such as platinum or carbon particles carrying a catalyst such as a platinum alloy with a polyelectrolyte having proton conductivity. Will be done. The polymer electrolyte included in the anode 14 and the cathode 16 may be a polymer of the same type as the polymer electrolyte constituting the electrolyte film 12, or may be a polymer of a different type. The gas diffusion layers 15 and 17 are composed of members having gas permeability and electron conductivity, and are made of, for example, a metal member such as foamed metal or a metal mesh, or a carbon member such as carbon cloth or carbon paper. Can be formed.

The end of the membrane electrode gas diffusion layer bonding body 18 is bonded to the resin frame 25. The resin frame 25 is formed by using a resin such as a thermoplastic resin, and has a sealing portion 27. The sealing portion 27 is located between a pair of separators 40 and 50 facing each other with the membrane electrode assembly 10 interposed therebetween. Adhesive layers (not shown) that exhibit adhesiveness by heat pressing are provided on both sides of the seal portion 27, and the seal portion 27 and the separators 40 and 50 are adhered to each other by thermocompression bonding. Specifically, the seal portion 27 is adhered to the first portion 45 of the separator 40 and the first portion 55 of the separator 50. The adhesive layer is, for example, a layer containing a silane coupling agent. The method of adhering the resin frame 25 and each of the separators 40 and 50 is not limited to the method of using an adhesive layer. As a material constituting the sealing portion 27, for example, a modified polyolefin such as modified polypropylene to which adhesiveness is imparted by introducing a functional group (for example, Admer manufactured by Mitsui Chemicals, Inc .; Admer is a registered trademark) is used and pressed by heating. It may be bonded.

The separator 40 is formed with a flow path groove 28 recessed in a direction away from the membrane electrode gas diffusion layer junction 18 and a convex portion 41 protruding in a direction away from the membrane electrode gas diffusion layer junction 18. Similarly, the separator 50 is formed with a flow path groove 29 recessed in a direction away from the membrane electrode gas diffusion layer junction 18 and a convex portion 51 projecting in a direction away from the membrane electrode gas diffusion layer junction 18. There is. The separator 40 is arranged on the anode side, and the fuel gas flows through a region surrounded by the flow path groove 28 and the membrane electrode gas diffusion layer junction 18. The separator 50 is arranged on the cathode side, and the oxidation gas flows through a region surrounded by the flow path groove 29 and the membrane electrode gas diffusion layer junction 18. Cooling water flows through the cooling water flow path 70 surrounded by the separator 40 adjacent to each other in the stacking direction and the separator 50. When the convex portion 41 of the separator 40 and the convex portion 51 of the separator 50 come into contact with each other and the fuel cell 100 is laminated, the strength of the laminated body of the fuel cell 100 is ensured. The portion where the convex portion 41 and the convex portion 51 are in contact with each other is referred to as a contact portion 86.

The separators 40 and 50 have good conductivity and have a laminated structure in which expanded graphite sheets 92 are arranged on both sides of the core material 91. The core material 91 is made of a mixture of a thermosetting resin and a conductive filler. As the thermosetting resin, for example, an epoxy resin, a phenol resin, or the like can be used, and in this embodiment, the epoxy resin is used. As the conductive filler, for example, powdery or fibrous carbon or metal can be used, and in this embodiment, powdery carbon is used. By making the separators 40 and 50 made of resin, the weight of the separators 40 and 50 can be reduced.

The gasket portion 60 is provided to seal the cooling water flow path 70 formed between the two adjacent fuel cell 100s. The gasket portion 60 is located between two separators 40 and 50 adjacent to each other in the stacking direction. The bottom surface of the gasket portion 60 is adhered to the second portion 56 of the surface of the separator 50 facing the separator 40, and the lip at the tip thereof contacts the contact portion 46 of the surface of the separator 40 facing the separator 50. The gasket portion 60 is an elastic body, and for example, rubber or a thermoplastic elastomer can be used. The laminated body of the fuel cell 100 is sandwiched between plates (not shown) on both sides, and is assembled by applying a load in the compression direction. When a load is applied, the lip of the gasket portion 60 comes into contact with the separator 40, and a pressing force is applied to the gasket portion 60 in the stacking direction. Therefore, a reaction force is generated in the gasket portion 60, whereby the cooling water flow path 70 formed between the fuel cell 100 is sealed.

As shown in FIG. 1, the separators 40 and 50 and the resin frame 25 are formed with manifold holes 31 to 36 forming a manifold. The manifold holes 31 and 36 are for oxidizing gas, the manifold holes 33 and 34 are for fuel gas, and the manifold holes 32 and 35 are for cooling water. The separators 40 and 50 are rectangular plate-shaped members. As described above, the flow path groove 28 is formed on the surface of the separator 40 facing the membrane electrode gas diffusion layer junction 18, and the surface of the separator 50 facing the membrane electrode gas diffusion layer junction 18 is formed. , The flow path groove 29 is formed.

The resin frame 25 is formed with a plurality of slits 39 penetrating the resin frame 25 in the vicinity of the manifold holes 31, 33, 34, 36. For example, the slit portion 39 in the vicinity of the manifold hole 31 extends from the vicinity of the outer periphery of the manifold hole 31 toward the vicinity of the outer periphery of the membrane electrode gas diffusion layer joint 18 between the manifold hole 31 and the opening 25a. The slit portion 39 in the vicinity of the manifold hole 31 is formed at a position overlapping both the manifold hole 31 of the separator 50 and the flow path groove 29 formed in the separator 50. As a result, the oxidizing gas flowing through the manifold hole 31 flows into the slit portion 39 from the manifold hole 31 of the separator 50, and flows out from the slit portion 39 to the flow path groove 29. Similarly, the slit portion 39 in the vicinity of the manifold holes 33, 34, 36 communicates any of the manifold holes 33, 34, 36 with the flow path groove 28 or the flow path groove 29.

As shown in FIG. 2, the seal portion 27 and the gasket portion 60 are formed at a plurality of positions of the separator 50. A contact portion 86, a seal portion 27, and a gasket portion 60 are formed in order from the outside along the outer shape of the separator 50. Specifically, the contact portion 86 is formed so as to draw a rectangle along the outer shape of the separator 50, and the seal portion 27 is formed inside the contact portion 86 so as to draw a rectangle. The gasket portion 60 is formed so as to draw a rectangle on the inside. A contact portion 86, a gasket portion 60, and a seal portion 27 are formed around the manifold holes 31, 33, 34, and 36 for the oxidation gas and the fuel gas in this order from the inside. A contact portion 86 is formed around a region including the manifold holes 32 and 35 for cooling water and the membrane electrode assembly 10. A seal portion 27 is formed around the manifold holes 32 and 35 for cooling water. As described above, the portion of the separator 50 to which the seal portion 27 is adhered is the first portion 55, and the portion of the separator 50 that comes into contact with the gasket portion 60 is the second portion 56. The separator 40 also has a first portion 45 having a similar shape and a contact portion 46. Specifically, the separator 40 has a first portion 45 having the same shape as the seal portion 27 and a contact portion 46 having the same shape as the gasket portion 60.

FIG. 4 is a process diagram showing a method for manufacturing the separators 40 and 50. FIG. 5 is a diagram schematically showing a manufacturing apparatus 200 that performs the second step P20. In the first step P10, the thermosetting resin and the conductive filler are mixed to form a sheet-shaped core material 91. In the present embodiment, the mixing ratio of the thermosetting resin and the conductive filler is 2: 8 by volume. The sheet-shaped core material 91 is heated to a temperature lower than the curing temperature of the thermosetting resin to be in a semi-cured state, and is formed into a sheet-like shape. In the present embodiment, the conductive filler is spheroidal graphite having an average particle size of 8 μm.

In the second step P20, the expanded graphite sheet 92 is arranged so as to cover the surface of the core material 91. According to this, as compared with the case where the expanded graphite sheet 92 is arranged with respect to the core material 91 while avoiding the first portions 45 and 55 and the second portion 56, fine alignment is not required and the productivity is improved. In the present embodiment, the average thickness of the expanded graphite sheet 92 is about 30 μm. As shown in FIG. 5, the manufacturing apparatus 200 includes a core material roll 201, two expanded graphite sheet rolls 202, a take-up roller 204, and two rolling rollers 203. The core material roll 201 is a roll-shaped core material 91, and the expanded graphite sheet roll 202 is a roll-shaped expanded graphite sheet 92. The core material 91 sent out from the core material roll 201 is sandwiched on both sides by the expanded graphite sheet 92 sent out from the expanded graphite sheet roll 202, rolled by two opposing rolling rollers 203, and taken up by the take-up roller 204. Be done. The sheet-shaped expanded graphite sheet 92 is easily bent, broken, torn, etc. due to its own weight. In the present embodiment, by using the expanded graphite sheet 92 in the form of a roll instead of the sheet, tension can be applied to the expanded graphite sheet 92, and the expanded graphite sheet 92 can be formed while suppressing the deformation of the expanded graphite sheet 92. It can be arranged on the core material 91. The core material 91 on which the expanded graphite sheet 92 is arranged is wound up by a take-up roller 204 and supplied in a roll shape to the next third step. In general, the form supplied in the form of a roll does not need to be cut into a sheet, for example, as compared with the form supplied in the form of a sheet, so that the manufacturing cost can be reduced. Further, in general, the form supplied in the form of a roll does not require the trouble of transporting each sheet as compared with the form supplied in the form of a sheet, so that the form can be supplied to the press molding machine faster. Therefore, by supplying the core material 91 on which the expanded graphite sheet 92 is arranged in the form of a roll, the manufacturing cost can be reduced and the working time of the process can be shortened.

In the third step P30, the core material 91 on which the expanded graphite sheet 92 is arranged is press-molded to produce pretreatment separators which are the basis of the separators 40 and 50. Specifically, a core material 91 on which the expanded graphite sheet 92, which has been cut according to the press molding die, is arranged is placed in a press forming die heated to about 180 ° C., and press forming is performed. As a result, the thermosetting resin contained in the core material 91, which has been in a semi-cured state, is cured, and pretreatment separators formed into the shapes of the separators 40 and 50 are produced. Since the expanded graphite sheet 92 functions as a solid lubricant during press molding, a mold release agent is not used for press molding. When the core material 91 not covered with the expanded graphite sheet 92 is press-molded, a mold release agent may be used to prevent sticking to the press-molding mold. In this respect, in the present embodiment, since the core material 91 is covered with the expanded graphite sheet 92, it can be press-molded without using a mold release agent.

In the fourth step P40, the expanded graphite sheet 92 of the portion corresponding to the seal portion 27 of the pretreatment separator and the portion corresponding to the gasket portion 60 is removed by using a laser. Specifically, expanded graphite is located in the first portions 45 and 55 where the seal portion 27 of the pre-treatment separator is adhered and the second portion 56 where the gasket portion 60 of the pre-treatment separator is adhered. The sheet 92 is removed. In this embodiment, LP-Z256 manufactured by Panasonic Corporation, which is a solid-state laser irradiator, is used. The output conditions are an output of 20 W, a frequency of 25 kHz, and a scanning speed of 3000 mm / s. By removing the expanded graphite sheet 92 of the portion corresponding to the gasket portion 60 and the seal portion 27, it is possible to suppress poor adhesion between the gasket portion 60 and the seal portion 27 and peeling of the expanded graphite sheet 92. The expansion graphite sheet 92 may be removed until the area ratio of the expanded graphite sheet 92 in the surface layer becomes smaller than 100%, and more preferably 50% or less. The adhesive strength of the gasket portion 60 and the seal portion 27 depends on the adhesive conditions, specifically, the adhesive temperature, the heating time, the seal width, and the like. Even if the expanded graphite sheet 92 is not removed until the area ratio of the expanded graphite sheet 92 on the surface layer becomes 0%, sufficient adhesive strength can be ensured by adjusting the adhesive conditions at about 50% or less. can. The method for removing the expanded graphite sheet 92 is not limited to laser irradiation, and may be, for example, shot blasting, wet blasting, polishing, cutting, or the like. After the completion of the fourth step P40, the separators 40 and 50 are completed.

In the present embodiment, the gasket portion 60 of the separator 40 and the expanded graphite sheet 92 of the sealing portion 27 are removed after press molding. On the other hand, a method of arranging the expanded graphite sheet 92 on the core material 91 while avoiding the gasket portion 60 and the sealing portion 27 in advance is also conceivable. Specifically, the following methods (x1) and (x2) can be considered. The method (x1) is a method of preparing a sheet in which the expanded graphite sheet 92 is arranged on the core material 91 while avoiding the first portions 45 and 55 and the second portion 56 before press molding. The method (x2) is a method of separately arranging the core material 91 and the expanded graphite sheet 92 in the press molding mold, and when arranging the core material 91 in the press molding mold, the first portions 45, 55 and the core material 91 are arranged. This is a method of arranging the expanded graphite sheet 92 while avoiding the second portion 56. However, this method may cause the following problems (a) to (g). Tasks (a) to (e) are tasks common to the methods (x1) and (x2).
(A) It becomes necessary to arrange the expanded graphite sheet 92 with high positional accuracy with respect to the core material 91.
(B) In order to solve the above (a), it is conceivable to increase the distance between the contact portion 86 and the seal portion 27 to reduce the required position accuracy, but in this case, the separators 40 and 50 become large. New challenges can arise.
(C) Since the semi-cured resin contained in the core material 91 contains an unreacted component, the resins tend to adhere to each other. Therefore, when the core material 91 before press molding is stored, it is necessary to sandwich a release film between the sheets in order to prevent the resins from adhering to each other.
(D) The core material 91 easily sticks to the press molding mold with respect to the expanded graphite sheet 92. Therefore, in order to suppress sticking to the press molding die, it is necessary to use a mold release material at the time of press molding.
(E) In the core material 91, the physical characteristics of the material differ between the portion where the expanded graphite sheet 92 is arranged and the portion where the expanded graphite sheet 92 is not arranged, and the thickness becomes non-uniform. It costs money to select.
(F) As a problem in the method (x1), it becomes necessary to arrange the core material 91 on which the expanded graphite sheet 92 is arranged with high position accuracy with respect to the press forming mold.
(G) As a problem in the method (x2), since the expanded graphite sheet 92 has low rigidity and is brittle, it is difficult to arrange the expanded graphite sheet 92 alone in the press molding die.
In the present embodiment, since the core material 91 covered with the expanded graphite sheet 92 is used for substantially the entire area, the above-mentioned problems can be avoided.

According to the above-described embodiment, the expanded graphite sheet 92 is not partially arranged with respect to the core material 91, avoiding the first portions 45, 55 and the second portion 56, but the surface of the core material 91. Since the expanded graphite sheet 92 is arranged so as to cover the core material 91, it is not necessary to arrange the expanded graphite sheet 92 on the core material 91 with high accuracy. Further, since the expanded graphite sheet 92 of the first portion 45, 55 on which the seal portion 27 is formed and the expanded graphite sheet 92 of the second portion 56 on which the gasket portion 60 is formed are removed, the separators 40 and 50 and the separator 40, 50 are removed. Poor adhesion with the seal portion 27 and poor adhesion between the separators 40 and 50 and the gasket portion 60 can be suppressed.

B. Other embodiments:
In the third step of the above embodiment, the core material 91 on which the expanded graphite sheet 92 is arranged is supplied to the press molding machine in the form of a roll. The supply form is not limited to the roll shape, but may be a sheet shape. Regardless of the supply form, by removing the expanded graphite sheet 92 after press molding, it is possible to suppress poor adhesion between the separators 40 and 50 and each of the sealing portion 27 and the gasket portion 60.

The present disclosure is not limited to the above-described embodiment, and can be realized by various configurations within a range not deviating from the gist thereof. For example, the technical features of the embodiments corresponding to the technical features in each of the embodiments described in the column of the outline of the invention may be used to solve some or all of the above-mentioned problems, or a part of the above-mentioned effects. Or, in order to achieve all of them, it is possible to replace or combine them as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

10 ... Membrane electrode assembly, 12 ... Electrolyte membrane, 14 ... Anode, 15, 17 ... Gas diffusion layer, 16 ... Cathode, 18 ... Membrane electrode gas diffusion layer assembly, 20 ... Cell frame junction, 25 ... Resin frame, 25a ... opening, 27 ... seal, 28, 29 ... flow path groove, 31-36 ... manifold hole, 39 ... slit, 40, 50 ... separator, 41, 51 ... convex, 45, 55 ... first part , 46 ... contact part, 56 ... second part, 60 ... gasket part, 70 ... cooling water flow path, 86 ... contact part, 91 ... core material, 92 ... expanded graphite sheet, 100 ... fuel cell, 200 ... manufacturing equipment, 201 ... Core material roll, 202 ... Expanded graphite sheet roll, 203 ... Rolling roller, 204 ... Winding roller, P10 ... 1st step, P20 ... 2nd step, P30 ... 3rd step, P40 ... 4th step

Claims (1)

A method for manufacturing a fuel cell separator for a fuel cell in which a plurality of fuel cell cells are stacked.
The first step of mixing the thermosetting resin and the conductive filler to form a sheet-shaped core material, and
The second step of arranging the expanded graphite sheet so as to cover the surface of the core material, and
A third step of press-molding the core material on which the expanded graphite sheet is arranged to prepare a pretreatment separator which is a source of the fuel cell separator.
Of the pretreatment separators, a seal portion located between a pair of fuel cell separators facing each other across a membrane electrode assembly and a gasket portion located between two adjacent fuel cell separators in the stacking direction. A method for manufacturing a fuel cell separator, which comprises a fourth step of removing the expanded graphite sheet located at a portion to which each of the above is adhered.

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