JP4742571B2 - Manufacturing method of fuel cell - Google Patents

Description

  The present invention relates to a method of manufacturing a fuel cell, and more specifically, a fuel cell in which a surface layer for improving cell performance is provided on the surface of a separator, and the separator and a component adjacent to the separator are bonded with the surface layer interposed therebetween. It relates to the manufacturing method.

A fuel cell has a structure in which a pair of electrodes are disposed with an electrolyte membrane interposed therebetween, and both sides thereof are sandwiched between separators. The electricity generated by the supply of the reaction gas to each electrode is taken out from the electrode through the separator. In order to increase the power generation efficiency of the fuel cell, it is important to reduce the contact resistance between the separator and the electrode. Conventionally, various techniques for reducing the contact resistance of the separator have been proposed. For example, Patent Document 1 discloses a technique for reducing contact resistance by performing gold plating on the surface of a separator. Patent Documents 2 and 3 disclose a technique in which contact resistance can be reduced with a small amount of noble metal used by disposing a noble metal such as gold in an island shape on the surface of a separator.
JP-A-10-228914 JP 2000-323151 A Special Table 2002-54058

  In general, an adhesive is used for joining the separator and the electrode. The separator and the electrode are joined by applying an adhesive to the frame of the separator and bonding an electrode (or membrane electrode assembly) thereto. However, when a noble metal layer is provided on the surface of the separator as in the prior art described in each of the above-mentioned patent documents, there is a problem in that the surface of the noble metal is inactive, so that it is difficult to attach an adhesive. Each of the above patent documents does not disclose a method for bonding the separator and the electrode. However, if a conventional general bonding method is applied, the part to which the adhesive of the separator is applied is a jig or a mask material. In this state, the noble metal is coated by sputtering or the like. According to this, since there is no noble metal layer in the masked portion and the surface of the separator is exposed, it is easy to attach an adhesive, and the adhesion between the separator and the electrode can be ensured.

  However, the conventional bonding method described above requires a masking process. Further, when masking with a mask material, a process of peeling the mask material is also required. In order to reduce the manufacturing cost of the fuel cell, it is desirable to reduce the number of processes as much as possible. Further, in the method of masking with a mask material, there is a possibility that adhesion failure may occur due to the mask material remaining on the surface of the separator.

  The present invention has been made to solve the above-described problems, and relates to a method for manufacturing a fuel cell, and by improving the battery performance by providing a surface layer formed of a low-adhesive substance on the surface of the separator, It aims at making the adhesiveness of a separator and the structural member adjacent to a separator compatible.

In order to achieve the above object, according to a first aspect of the present invention, a surface layer formed of a low-adhesive substance having lower adhesiveness than the material of the separator is provided on the surface of the separator, and the separator is sandwiched between the surface layers. And a component adjacent to the separator is a method for producing a fuel cell, which is bonded with an adhesive,
A first step of disposing and disposing the low-adhesion substance in an island shape as the surface layer on the surface of the separator including a portion to which the constituent member is bonded;
A second step of bonding the constituent member with the adhesive to the surface of the separator in which the low adhesion substance is dispersed and arranged in an island shape;
It is characterized by including.

  A second invention is characterized in that, in the first invention, the low adhesion substance is a highly conductive substance.

  According to a third invention, in the second invention, the highly conductive material is a noble metal.

  According to a fourth aspect of the present invention, in the second or third aspect, in the first step, the surface coverage with which the highly conductive material covers the surface of the separator and the surface coated with the highly conductive material Based on the relationship between the adhesiveness and the electrical conductivity, the highly conductive substance is dispersedly arranged on the surface of the separator so as to have a preset surface coverage.

  The fifth invention is characterized in that, in the first invention, the low adhesion substance is a hydrophilic substance.

A sixth invention is characterized in that, in the fifth invention, the hydrophilic substance is TiO ₂ .

  According to a seventh invention, in the fifth or sixth invention, in the first step, the hydrophilic substance covers the surface of the separator and the adhesion of the surface coated with the hydrophilic substance. The hydrophilic substance is dispersedly arranged on the surface of the separator so as to have a preset surface coverage based on the relationship between the hydrophilicity and the hydrophilicity.

  According to the first invention, since the low adhesive substance forming the surface layer is dispersed and arranged in the form of islands on the separator surface, the low adhesive substance dispersed and arranged in the form of islands on the part to which the constituent members are adhered. The surface of the separator is exposed from between, and the adhesive is attached to the exposed separator surface, so that the adhesion between the separator and the structural member adjacent to the separator is ensured. Therefore, according to 1st invention, the improvement of the battery performance by providing a surface layer on the surface of a separator and the adhesiveness of a separator and an adjacent structural member can be made compatible. This eliminates the need for masking the bonding portion on the separator surface, thereby reducing the number of steps in manufacturing the fuel cell and preventing adhesion failure due to the remaining mask material.

  According to 2nd invention and 3rd invention, the contact resistance between a separator and an adjacent structural member is reduced by disperse | distributing and arrange | positioning highly conductive substances, such as a noble metal, in the shape of an island on the separator surface.

  According to the fourth aspect of the invention, since the highly conductive material is dispersed and arranged so as to have a surface coverage set in advance based on the relationship between the surface coverage and the adhesion and conductivity, the adhesion and conductivity It is possible to ensure both.

According to the fifth and sixth inventions, in the gas flow path formed between the separator and the adjacent structural member, hydrophilic substances such as TiO ₂ are dispersed and arranged in an island shape on the separator surface. Water flows along the wall surface without being repelled, and gas flow resistance is reduced.

  According to the seventh aspect, since the hydrophilic substance is dispersed and arranged so as to have a surface coverage set in advance based on the relationship between the surface coverage and the adhesiveness and hydrophilicity, Can be reliably achieved.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. In addition, this invention is applicable to manufacture of various fuel cells including a solid polymer type fuel cell.

  FIG. 1 is an explanatory diagram for explaining a method for manufacturing a fuel cell according to a first embodiment of the present invention. In FIG. 1, four states (a), (b), (c), and (d) in the manufacturing process of the fuel cell are shown in cross-sectional views for the conductive portion and the adhesive portion, respectively. In FIG. 1, a state (a) in which a surface layer and an adhesive described later are not provided on the surface of the separator 2 is an initial state. As the material of the separator 2, a metal, particularly a metal having an active surface such as SUS or Ti is used.

  In the first step A shown in FIG. 1, the noble metal 4 is dispersed and arranged in an island shape on the entire surface of the separator 2. The noble metal 4 distributed in an island shape forms a surface layer that sparsely covers the surface of the separator 2. FIG. 2 is an enlarged plan view showing the surface of the separator 2 in which the precious metal 4 is dispersedly arranged, and the state (b) in FIG. 1 corresponds to a cross-sectional view showing the AA cross section of FIG. . As the noble metal 4, Au, Pt, Ru, Pd or the like is used.

  In this step A, the formation of the surface layer by the noble metal 4 is controlled so that the surface coverage with which the noble metal 4 covers the surface of the separator 2 becomes a predetermined target coverage. The film forming method for forming the surface layer with the noble metal 4 is not limited, and a wet method such as plating may be used, or a dry method such as sputtering, vacuum deposition, or CVD may be used. For example, when the surface layer of the noble metal 4 is formed by sputtering, particles of the noble metal 4 are grown from the surface of the separator 2 in an island shape, and the sputtering is terminated when the surface coverage reaches the target coverage. Good.

  The target coverage may be determined based on the relationship between the surface coverage as shown in FIG. 4 and the adhesion and conductivity. As shown in this figure, the precious metal is superior in conductivity compared to the material of the separator 2 but inferior in adhesion. As shown in this figure, the surface conductivity increases as the surface coverage increases, and conversely the adhesion decreases. To do. Therefore, as shown in the figure, an allowable range is defined for each of conductivity and adhesiveness, and the range of surface coverage where both conductivity and adhesiveness are compatible is set as the allowable coverage. What is necessary is just to set a target coverage in the range. As the surface coverage increases, the noble metal 4 island grows and the height increases. Here, the allowable coverage is 40 to 65%, and the height of the island of the noble metal 4 at that time is about 5 to 20 nm. However, these numerical values are an example under a certain condition, and the allowable coverage and the height of the island at that time depend on the type of the precious metal 4 used and the film forming method.

  In the next step B, the adhesive 6 is applied to the bonding portion on the separator 2. In the process A, since the islands of the noble metal 4 are dispersedly arranged over the entire surface of the separator 2, the islands of the noble metal 4 are also arranged at the bonding portion. The adhesive 6 is applied from above the islands of the noble metal 4 as shown in the state (c) in FIG. FIG. 3 is a plan view of the separator 2 to which the adhesive 6 is applied, and the state (c) in FIG. 1 corresponds to an enlarged cross-sectional view of a portion B in FIG. Since the island of the noble metal 4 existing on the surface of the separator 2 is formed by a thin film forming method such as sputtering, unlike the mask material used in the conventional masking process, it is compared with the film thickness of the adhesive 6. Very thin. Therefore, the presence of the island of the noble metal 4 in the bonded portion is not an obstacle to bonding with the adhesive 6 unlike the mask material remaining in the bonded portion.

  In the next step C, an electrode (or membrane electrode assembly) 8 that is an adjacent structural member is bonded onto the separator 2 to which the adhesive 6 is applied. Since the noble metal 4 forming the surface layer is dispersed and arranged in an island shape on the surface of the separator 2, the surface of the separator 2 is exposed from between the islands of the noble metal 4 to the bonding portion to which the electrode 8 is bonded. Adhesiveness between the separator 2 and the electrode 8 is ensured by interposing the adhesive 6 between the exposed surface of the separator 2 and the electrode 8. Moreover, in the conductive part to which the adhesive 6 is not applied, each island of the noble metal 4 having excellent conductivity comes into contact with the electrode 8, so that the contact resistance between the separator 2 and the electrode 8 is reduced.

  As described above, according to the manufacturing method of the fuel cell according to the present embodiment, the contact resistance is reduced by providing the surface layer formed of the noble metal 4 on the surface of the separator 2, and the separator 2 and the electrode by the adhesive 6 are used. 8 can be made compatible with adhesiveness. Thereby, it is not necessary to mask the adhesive portion on the surface of the separator 2 as in the conventional case, and the number of steps in manufacturing the fuel cell can be reduced. Further, adhesion failure due to remaining mask material can be prevented.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The present invention can also be applied to the manufacture of various fuel cells including solid polymer fuel cells.

In the first embodiment, the noble metal is dispersed and arranged in the form of islands on the surface of the separator. However, in this embodiment, TiO ₂ that is a hydrophilic material is dispersed and arranged in the form of islands instead of the noble metal. 5A and 5B are cross-sectional views of gas flow paths provided in each cell of the fuel cell. As shown in each drawing, the separator 2 connects an electrode contact surface 2a that contacts the electrode 8, a bottom surface 2c that is parallel to the electrode contact surface 2a and is positioned away from the electrode 8, and an electrode contact surface 2a and the bottom surface 2c. And an elevation surface 2b. A space surrounded by the electrode 8, the bottom surface 2c, and the left and right vertical surfaces 2b and 2b is a gas flow path 10 through which a reactive gas (oxidizing gas or fuel gas) flows. In the gas flow path 10, generated water generated by a reaction during power generation and humidified water for humidifying the electrolyte membrane also flow. 5A and 5B show a state in which these waters 12 are flowing in the gas flow path 10.

FIG. 5A shows the flow of water 12 when a surface layer made of TiO ₂ is not provided on the surface of the separator 2. Usually, a conductive coating 16 having corrosion resistance is applied to the gas flow path surface of the separator 2. Since the conductive coat 16 is generally water-repellent, the water 12 repelled on the gas flow path surface (the bottom surface 2 c and the vertical surface 2 b) of the separator 2 becomes a ball in the gas flow path 10. As a result of the gas channel 10 being blocked by the water 12 that has become a ball, the flow resistance of the gas in the gas channel 10 increases, and the cell performance of the fuel cell decreases.

On the other hand, as shown in FIG. 5B, when the TiO ₂ film 14 is coated on the conductive coating 16, the surface layer formed by the TiO ₂ film 14 is formed on the surface because TiO ₂ is hydrophilic. By being present, the water 12 flows along the gas flow path surface of the separator 2. As a result, the gas flow path 10 is not blocked by the water 12, and the gas flow resistance in the gas flow path 10 is reduced.

However, since TiO ₂ is inferior in adhesiveness, if the entire surface of the separator 2 is covered with the TiO ₂ film 14, the adhesiveness with the adjacent electrode 8 cannot be ensured. As a method of ensuring the adhesiveness, a method of masking the adhesive portion on the surface of the separator 2 and coating the TiO ₂ film 14 thereon can be considered, but this method increases the number of masking steps. Further, the mask material may remain on the surface of the separator 2, which may cause poor adhesion. Therefore, in the present embodiment, the entire surface of the separator 2 is not covered with the TiO ₂ film 14, but the TiO ₂ film 14 is formed in an island shape on the surface of the separator 2 as shown in an enlarged view of a portion C in FIG. 5B. Distributed.

In this embodiment, the fuel cell shown in FIG. 5B is manufactured by the manufacturing method described below. First, in the first step, the TiO ₂ film 14 is dispersed and arranged in an island shape over the entire surface of the separator 2 to which the conductive coating 16 is applied. The TiO ₂ film 14 dispersed and arranged in an island shape forms a surface layer that sparsely covers the surface of the separator 2. In this step, the formation of the surface layer by the TiO ₂ film 14 is controlled so that the surface coverage with which the TiO ₂ film 14 covers the surface of the separator 2 becomes a predetermined target coverage. The film forming method for forming the surface layer by the TiO ₂ film 14 is not limited, and a wet method such as plating or spray coating may be used, or a dry method such as sputtering or CVD may be used.

The target coverage may be determined based on the relationship between the surface coverage, adhesion, and hydrophilicity. TiO ₂ is superior in hydrophilicity to the material of the separator 2 but is inferior in adhesiveness. Therefore, as the surface coverage increases, the hydrophilicity of the surface increases and conversely the adhesiveness decreases. Therefore, an allowable range is set for each of hydrophilicity and adhesiveness, and the surface coverage range where both hydrophilicity and adhesiveness are compatible is set as the allowable coverage, and the target coverage is set within this allowable coverage range. do it.

In the next step, an adhesive is applied to the bonding portion on the separator 2. Since the islands of the TiO ₂ film 14 are dispersed and arranged over the entire surface of the separator 2 as described above, the islands of the TiO ₂ film 14 are also arranged at the bonding portion. The adhesive is applied from above the islands of the TiO ₂ film 14. In the next step, the electrode (or membrane electrode assembly) 8 is bonded onto the separator 2 to which the adhesive is applied. Since the TiO ₂ film 14 forming the surface layer is dispersed and arranged in the form of islands on the surface of the separator 2, the surface of the separator 2 is exposed from between the islands of the TiO ₂ film 14 to the bonding portion to which the electrode 8 is bonded. is doing. Adhesiveness between the separator 2 and the electrode 8 is ensured by interposing an adhesive between the exposed surface of the separator 2 and the electrode 8.

As described above, according to the method for manufacturing a fuel cell according to the present embodiment, the flow resistance in the gas flow path 10 is reduced by providing the surface layer of the TiO ₂ film 14 on the surface of the separator 2, and the adhesive is used. The adhesiveness between the separator 2 and the electrode 8 can be made compatible. As in the first embodiment, this eliminates the need for masking the adhesion portion on the separator surface as in the prior art, reduces the number of steps in manufacturing the fuel cell, and prevents adhesion failure due to remaining mask material. You can also.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In each of the above embodiments, the electrode is bonded to the separator to which the adhesive is applied. However, the adhesive may be applied to the electrode and the separator may be bonded to the electrode.

  In the fuel cell to which the manufacturing method of the present invention is applied, the structural member adjacent to the separator is not limited to the electrode. For example, a resin frame and other separators are also included in the adjacent structural member. Also by applying the present invention to bonding with these, it is possible to achieve both improvement in battery performance by providing a surface layer on the surface of the separator and adhesion between the separator and the adjacent structural member.

In the first embodiment, noble metal is used as the material for forming the surface layer, but other highly conductive materials may be used. Similarly, in Embodiment 2, TiO ₂ is used as the material for forming the surface layer, but other hydrophilic materials may be used.

It is explanatory drawing for demonstrating the manufacturing method of the fuel cell concerning Embodiment 1 of this invention. It is a top view which expands and shows the surface of the separator by which the noble metal was distributedly arranged. It is a top view of the separator with which the adhesive agent was apply | coated. It is a figure which shows about the relationship between the surface coverage which a noble metal coat | covers the surface of a separator, and the adhesiveness of the surface coat | covered with the noble metal, and electroconductivity. It is a sectional view showing a flow of water gas flow path when no surface layer of TiO ₂ is provided on the surface of the separator. It is a sectional view showing a flow of water gas flow path when the surface layer of TiO ₂ on the surface of the separator is provided.

Explanation of symbols

2 Separator 4 Precious metal 6 Adhesive 8 Electrode 10 Gas flow path 12 Water 14 TiO ₂ film 16 Conductive coating

Claims (2)

A method of manufacturing a fuel cell in which a noble metal is disposed on a surface of a separator, and the separator and a component adjacent to the separator are bonded with an adhesive across the noble metal ,
A step of sparsely covering the surface of the separator including the portion to which the constituent member is bonded with the noble metal, and growing the noble metal from the surface of the separator in an island shape using a thin film forming method The first step;
A second step of bonding the constituent member to the surface of the separator sparsely covered with the noble metal grown in an island shape with the adhesive;
A method for producing a fuel cell, comprising: TiO on the separator surface ₂ Is arranged, said TiO ₂ A method of manufacturing a fuel cell in which the separator and a component adjacent to the separator are bonded with an adhesive,
The surface of the separator including the part to which the constituent member is bonded is the TiO. ₂ Sparsely covering the TiO 2 from the surface of the separator using a thin film forming method. ₂ A first step of growing the material into islands;
TiO grown in island shape ₂ A second step of bonding the constituent member to the surface of the separator sparsely covered by the adhesive with the adhesive;
A method for producing a fuel cell, comprising:

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