JP6178041B2 - Method for producing diffusion layer for fuel cell - Google Patents

Description

  The present invention relates to a method for producing a fuel cell diffusion layer and a fuel cell diffusion layer.

  In a fuel cell, for example, a polymer electrolyte fuel cell, a reaction gas (a fuel gas and an oxidizing gas) is formed on a membrane electrode assembly formed by sandwiching an electrolyte membrane between a pair of electrodes (anode and cathode) via a gas diffusion layer. The chemical energy of a substance is directly converted into electrical energy by causing the electrochemical reaction.

  The gas diffusion layer of the fuel cell is made of, for example, carbon cloth or carbon paper. When the fluff of the fiber of the gas diffusion layer damages the electrolyte membrane, the deterioration of the electrolyte membrane starting from the damaged portion can be promoted. A short circuit may reduce the performance of the fuel cell. In order to suppress such a decrease in the performance of the fuel cell, there is known a method for manufacturing a gas diffusion layer in which part or all of the fluff of the fiber is cut or broken (see, for example, Patent Document 1). .

JP 2007-149613 A JP 2008-34295 A JP 2009-190951 A

  In the method for producing the gas diffusion layer, the fluff is not sufficiently removed, and there is a possibility that the performance of the fuel cell is deteriorated by damaging the electrolyte membrane. Further, there is a possibility that the base material of the diffusion layer may be damaged by a physical force associated with the fluff cutting or breaking process.

In order to solve at least a part of the problems described above, the present invention can take the following forms or application examples. One aspect of the present invention is a method for producing a diffusion layer for a fuel cell formed of a material comprising carbon paper or carbon cloth; the amount of impregnation per unit volume of the binder in the diffusion layer for a fuel cell is as follows: A first step of impregnating a base material of the fuel cell diffusion layer with the binder so as to form a gradient along a perpendicular direction perpendicular to a lamination surface on which the members of the fuel cell diffusion layer are laminated; After the first step, the base material is compressed in the direction perpendicular to the surface, and the carbon that protrudes from the first surface of the base material having the larger amount of the binder without damaging the base material. A second step of deforming or breaking paper or carbon cloth fibers; a third step of firing the substrate after the second step; and a first surface after the third step. While sucking the first surface while blowing gas to the front, A fourth step of sucking carbon paper or carbon cloth fibers separated from the base material in the second or third step; and after the fourth step, compressing the base material in the direction perpendicular to the surface. The length of the carbon paper or carbon cloth fibers protruding from the first surface without damaging the base material along the direction perpendicular to the surface is defined between the electrolyte membrane and the fuel cell diffusion layer. And a fifth step of making the thickness smaller than the thickness D of the cathode and the cathode-side water-repellent layer or the anode and the anode-side water-repellent layer. With such a configuration, the fibers protruding from the first surface in the base material of the fuel cell diffusion layer are reduced, and the fibers protruding from the first surface do not enter the electrolyte membrane and damage the electrolyte membrane. Therefore, it is possible to manufacture a diffusion layer for a fuel cell that prevents a decrease in the performance of the fuel cell. Further, since the amount of the binder impregnated per unit volume on the first opposite surface of the base material of the fuel cell diffusion layer is small, a fuel cell diffusion layer having good gas diffusibility can be produced.

  In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples.

Application Example 1 A method for manufacturing a diffusion layer for a fuel cell,
The base material of the diffusion layer so that the impregnation amount per unit volume of the binder in the diffusion layer can be inclined along a direction perpendicular to the plane substantially perpendicular to the lamination surface on which the members for the fuel cell are laminated. A first step of impregnating the binder with the binder;
A second step of firing the substrate after the first step;
After the second step, a third step of sucking the first surface while blowing a gas to the first surface of the base material having the larger amount of the binder impregnated;
After the said 2nd process, the manufacturing method of the diffusion layer for fuel cells provided with the 4th process of compressing the said base material in the said surface normal direction.

  In this diffusion layer manufacturing method, in the first step, the base material of the diffusion layer is impregnated with a binder, and the base material is along a surface perpendicular direction substantially perpendicular to the lamination surface on which the members for the fuel cell are laminated. A gradient is formed so that the amount of impregnation per unit volume of the binder monotonously decreases. In the subsequent second step, the substrate is fired. In the subsequent third step, the first surface is sucked while blowing gas onto the first surface with the larger amount of binder impregnated in the substrate. Further, in the fourth step after the second step, the base material is compressed in the perpendicular direction. Therefore, while reducing the fibers protruding from the first surface in the base material of the diffusion layer, the fibers protruding from the first surface do not enter the electrolyte membrane and do not damage the electrolyte membrane, thereby reducing the performance of the fuel cell. A prevented diffusion layer can be produced. Further, in this diffusion layer manufacturing method, since the amount of the binder impregnated per unit volume is small on the first opposite surface of the base material of the diffusion layer, a diffusion layer ensuring good gas diffusibility is manufactured. be able to.

[Application Example 2] A method of manufacturing a diffusion layer for a fuel cell according to Application Example 1,
The method for producing a diffusion layer for a fuel cell, wherein the first step is a step of impregnating the binder from the first surface of the substrate.

  In this diffusion layer manufacturing method, since the binder is impregnated from the first surface of the substrate in the first step, the unit volume of the binder in the substrate easily along the perpendicular direction from the first surface. It is possible to manufacture a diffusion layer in which a gradient is formed so that the amount of impregnation per unit decreases monotonously.

[Application Example 3] A method of manufacturing a diffusion layer for a fuel cell according to Application Example 1 or Application Example 2,
The base material is formed of a material composed of a plurality of fibers,
In the third and fourth steps, the maximum protruding amount of fibers from the first surface of the base material is in the direction perpendicular to the surface of the intermediate layer to be disposed between the electrolyte membrane and the diffusion layer. The manufacturing method of the diffusion layer for fuel cells which is a process performed so that it may become below thickness D along.

  In this diffusion layer manufacturing method, the substrate is formed of a material composed of a plurality of fibers, and after the third and fourth steps, the first surface of the fiber that protrudes most from the first surface of the substrate. Is a value equal to or less than the thickness D of the intermediate layer to be disposed between the electrolyte membrane along the perpendicular direction and the diffusion layer. Therefore, even after the third and fourth steps, all the fibers protruding from the first surface do not enter the electrolyte membrane even if the length along the direction perpendicular to the surface protruding from the first surface of the fiber is increased. Therefore, it is possible to manufacture a diffusion layer that does not damage the electrolyte membrane and prevents a decrease in the performance of the fuel cell.

[Application Example 4] A method of manufacturing a diffusion layer for a fuel cell according to Application Example 3,
In the third and fourth steps, for each fiber, the length L of the portion protruding from the first surface of the substrate and the angle θ formed by the first surface and the protruding fiber And the manufacturing method of the diffusion layer for fuel cells which is a process performed so that the relationship with the said thickness D may satisfy | fill the conditions represented by Lxsin (theta) <= D.

  In this diffusion layer manufacturing method, for each fiber of the base material, the length L protruding from the first surface, the angle θ between the first surface and the fiber, the electrolyte membrane and the diffusion layer The relationship between the thickness D of the intermediate layer along the stacking direction disposed therebetween is L × sin θ ≦ D. That is, the length along the perpendicular direction protruding from the first surface of each fiber in the substrate is a value smaller than the thickness D of the intermediate layer. Therefore, in this method of manufacturing the diffusion layer 120, the fibers protruding from the first surface do not enter the electrolyte membrane, so that it is possible to manufacture a diffusion layer that does not damage the electrolyte membrane and prevents deterioration of the performance of the fuel cell. .

[Application Example 5] A method for producing a diffusion layer for a fuel cell according to Application Example 4,
The thickness D is a method of manufacturing a diffusion layer for a fuel cell, which is a thickness after creep deformation of the intermediate layer along the perpendicular direction.

  In this diffusion layer manufacturing method, the thickness D of the intermediate layer after creep deformation of the fuel cell is a value obtained by subtracting the amount of creep deformation of the intermediate layer along the perpendicular direction from the initial thickness before creep deformation. Therefore, even after creep deformation of the fuel cell, it is possible to manufacture a diffusion layer that does not damage the electrolyte membrane and prevents deterioration of the fuel cell performance.

[Application Example 6] A method for manufacturing a diffusion layer for a fuel cell according to any one of Application Examples 1 to 5,
The method for producing a fuel cell diffusion layer, wherein the compression pressure value in the fourth step is 1 MPa or more and 5 MPa or less.

  In this diffusion layer manufacturing method, since the pressure value for compressing the substrate in the fourth step is 1 MPa or more and 5 MPa or less, the fluff treatment on the first surface is performed without damaging the substrate, and the electrolyte membrane Thus, a diffusion layer that prevents deterioration of the performance of the fuel cell can be produced. The pressure value is more preferably 1 MPa or more and 3 MPa or less.

Application Example 7 A fuel cell diffusion layer,
The diffusion layer is formed of a material composed of a plurality of fibers,
The amount of impregnation of the binder in the diffusion layer per unit volume forms a gradient along a surface perpendicular direction substantially perpendicular to the stack surface on which the fuel cell members are stacked,
For each fiber, the length L of the portion protruding from the first surface of the diffusion layer where the amount of the binder impregnated is large, and the angle θ formed by the first surface and the protruding fiber A fuel cell diffusion layer, wherein the relationship between the thickness D along the perpendicular direction of the intermediate layer to be disposed between the electrolyte membrane and the diffusion layer is L × sin θ ≦ D.

  The diffusion layer of the fuel cell is formed of a material composed of a plurality of fibers, and the plurality of fibers are bonded by a binder, and the bonding in the diffusion layer is performed from the first surface in the diffusion layer along the stacking direction. The impregnation amount per unit volume of the agent forms a gradient that monotonously decreases. Further, the length L of each fiber protruding from the first surface where the amount of binder impregnated in the diffusion layer is large, the angle θ between the first surface and the fiber, the electrolyte membrane and the diffusion layer The relationship between the thickness D of the intermediate layer along the stacking direction disposed therebetween is L × sin θ ≦ D. Therefore, in the diffusion layer of this fuel cell, the fibers protruding from the first surface are reduced on the first surface side of the diffusion layer, and the fibers protruding from the first surface do not enter the electrolyte membrane, so that the electrolyte membrane is damaged. Without degrading the performance of the fuel cell. Further, in the diffusion layer of this fuel cell, good gas diffusibility can be ensured in a portion where the amount of the binder impregnated per unit volume is small.

  The present invention can be realized in various modes, and includes, for example, a fuel cell, a fuel cell inspection method and manufacturing method, a fuel cell stack, a fuel cell stack inspection method and manufacturing method, and a fuel cell. The present invention can be realized in a manner such as a method for inspecting and manufacturing a moving body provided with a moving body and a fuel cell.

It is explanatory drawing which shows roughly the structure of the fuel cell 100 in the Example of this invention. It is explanatory drawing which expands and shows typically the cross-sectional structure of the fuel cell 100 in the Example of this invention. It is explanatory drawing which shows the impregnation amount per unit volume of the binder of the cathode side diffusion layer 122 in the Example of this invention. It is a flowchart which shows the flow of the manufacturing method of the diffused layer 120 in the Example of this invention. It is explanatory drawing which shows roughly the process of impregnating the base material 126 in the Example of this invention with a binder. It is explanatory drawing which shows an example of the state of the base material 126 after the baking process in the Example of this invention. It is explanatory drawing which shows roughly the state of the base material 126 of the dust suction process in the Example of this invention. It is explanatory drawing which shows an example of the state of the base material 126 after the 2nd press process in the Example of this invention. It is explanatory drawing which shows an example of the state of the carbon fiber Cfn of the base material 126 after the dust suction process of the Example of this invention. It is explanatory drawing which shows roughly the creep deformation | transformation of the fuel cell 100 in the Example of this invention. It is explanatory drawing which shows the relationship between the carbon fiber Cfn protruded from the 1st surface 127 of the diffusion layer 120 in the Example of this invention, and the thickness D of an intermediate | middle layer. It is explanatory drawing which shows the amount of impregnations per unit volume of the binder of the cathode side diffusion layer 122 in a comparative example. It is explanatory drawing which shows the state of the base material 126 after the 2nd press process in a modification.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Example:
A-1. Fuel cell configuration:
A-2. Manufacturing method of diffusion layer:
A-3. Performance evaluation:
A-4. About the thickness of the intermediate layer:
B. Variations:

A. Example:
A-1. Fuel cell configuration:
FIG. 1 is an explanatory diagram schematically showing the configuration of a fuel cell 100 in an embodiment of the present invention. The fuel cell 100 of the present embodiment is a solid polymer fuel cell that is relatively small and excellent in power generation efficiency. The fuel cell 100 includes a separator 140, a cathode side gas flow path layer 132, a cathode side diffusion layer 122, a cathode side water repellent layer 152, a membrane electrode assembly (hereinafter also referred to as “MEA (Membrane Electrode Assembly)”) 110, and an anode side. A plurality of water-repellent layers 154, anode-side diffusion layers 124, and anode-side gas flow path layers 134 are stacked and fastened.

  As shown in FIG. 1, the MEA 110 includes an electrolyte membrane 112, an anode 116 disposed on one side of the electrolyte membrane 112, and a cathode 114 disposed on the other side of the electrolyte membrane 112. . The anode 116 is in contact with the anode-side water-repellent layer 154 on the opposite side of the electrolyte membrane 112, and the anode-side water-repellent layer 154 is in contact with the anode-side diffusion layer 124 on the opposite side of the anode 116. Between the anode side diffusion layer 124 and the separator 140, an anode side gas flow path layer 134 is disposed. The cathode 114 is in contact with the cathode-side water-repellent layer 152 on the opposite side to the electrolyte membrane 112, and the cathode-side water-repellent layer 152 is in contact with the cathode-side diffusion layer 122 on the opposite side to the cathode 114. A cathode side gas flow path layer 132 is disposed between the cathode side diffusion layer 122 and the separator 140. In FIG. 1, only one cell corresponding to one MEA 110 is shown and other cells are not shown for easy understanding of the configuration of the fuel cell 100.

  The electrolyte membrane 112 is an ion exchange membrane formed of a fluorine-based resin material or a hydrocarbon-based resin material, and has good proton conductivity in a wet state. The anode 116 and the cathode 114 are layers that provide a catalyst that promotes an electrode reaction, and are formed of, for example, a material containing carbon carrying platinum and an electrolyte. The anode-side diffusion layer 124 and the cathode-side diffusion layer 122 diffuse reaction gases (oxidation gas and fuel gas) used for the electrode reaction in a plane direction (a direction substantially orthogonal to the stacking direction of the fuel cell 100 (see FIG. 1)). For example, carbon cloth or carbon paper. The anode-side water-repellent layer 154 and the cathode-side water-repellent layer 152 are formed as layers having a water-repellent function using, for example, PTFE resin.

  The separator 140 is formed of a dense material that does not transmit gas and has conductivity, such as dense carbon, metal, and conductive resin that are compression-molded. The anode-side gas flow path layer 134 and the cathode-side gas flow path layer 132 are layers that function as reaction gas flow paths for allowing the reaction gas to flow along the surface direction of the fuel cell 100. For example, a metal porous body or a carbon porous layer is used. It is formed of a porous material having conductivity such as a body.

  Although not shown in FIG. 1, each of the fuel cells 100 includes a fuel gas supply manifold that penetrates the fuel cells 100 in the stacking direction, a fuel gas discharge manifold, an oxidizing gas supply manifold, and an oxidizing gas discharge manifold. ,have. The fuel gas supplied to the fuel cell 100 is distributed to the anode side gas flow path layer 134 of each cell via the fuel gas supply manifold, diffused in the anode side diffusion layer 124, and further supplied to the anode side of the MEA 110. And used for the electrochemical reaction in the MEA 110. The fuel gas not used for the reaction is discharged to the outside through the fuel gas discharge manifold. Further, the oxidizing gas supplied to the fuel cell 100 is distributed to the cathode-side gas flow path layer 132 of each cell via the oxidizing gas supply manifold, diffused in the cathode-side diffusion layer 122, and further on the cathode side of the MEA 110. To be used for the electrochemical reaction in the MEA 110. The oxidizing gas that has not been used for the reaction is discharged to the outside through the oxidizing gas discharge manifold. For example, hydrogen gas is used as the fuel gas, and air is used as the oxidizing gas, for example.

  FIG. 2 is an explanatory diagram schematically showing an enlarged cross-sectional configuration of the fuel cell 100 in the embodiment of the present invention. In the fuel cell 100 of the present embodiment, the cathode side diffusion layer 122 is formed of a carbon cloth of a porous material formed of a plurality of carbon fibers Cfn, and the plurality of carbon fibers Cfn are bonded by a binder. . In the present specification, a specific carbon fiber is represented by an arbitrary integer added to “n” of the carbon fiber Cfn, such as the carbon fiber Cf1 and the carbon fiber Cf2.

  As shown in FIG. 2, the cathode side diffusion layer 122 is adjacent to the cathode side water repellent layer 152 via the first surface 127, and via the cathode side gas flow path layer 132 and the second surface 128. Adjacent. Since the cathode side diffusion layer 122 is formed of a plurality of carbon fibers Cfn, some carbon fibers Cfn protrude from the first surface 127 and penetrate into the cathode 114 and the cathode side water repellent layer 152 ( For example, carbon fiber Cf1). Therefore, in the present embodiment, the first surface 127 of the cathode side diffusion layer 122 is a flat first surface 127 that is calculated as an average value. In this embodiment, the cathode side diffusion layer 122 and the anode side diffusion layer 124 are made of the same material. Hereinafter, the cathode side diffusion layer 122 and the anode side diffusion layer 124 are collectively referred to as a diffusion layer 120.

  As shown in FIG. 2, the carbon fiber Cf1 has a length L1 protruding from the surface of the first surface 127 of the cathode side diffusion layer 122, and has an angle formed by the first surface 127 and the carbon fiber Cf1. The angle is an angle θ1. Therefore, the length along the stacking direction protruding from the first surface 127 of the carbon fiber Cf1 is represented by L1 × sin (θ1), and the total thickness along the stacking direction of the cathode 114 and the cathode-side water-repellent layer 152. Is smaller than D. Therefore, since the carbon fiber Cf1 does not enter the electrolyte membrane 112, the electrolyte membrane 112 is not damaged. Note that the cathode 114 and the cathode-side water-repellent layer 152 and the anode 116 and the anode-side water-repellent layer 154 correspond to the intermediate layer of the present invention, and the cathode 114 and the cathode-side water-repellent layer 152 shown in FIG. The thickness along the direction corresponds to the thickness D of the intermediate layer.

  Each of the plurality of carbon fibers Cfn protruding from the first surface 127 of the cathode side diffusion layer 122 has a length protruding from the first surface 127 as Ln, and an angle formed by the first surface 127 and the plurality of carbon fibers Cfn. In the fuel cell 100 in the present embodiment, the relationship of Ln × sin (θn) ≦ D is satisfied. That is, none of the carbon fibers Cfn protruding from the first surface 127 of the cathode-side diffusion layer 122 penetrates the electrolyte membrane 112, so that the electrolyte membrane 112 is not damaged.

  FIG. 3 is an explanatory diagram showing the impregnation amount per unit volume of the binder in the cathode side diffusion layer 122 in the example of the present invention. As shown in FIG. 3, a portion of the cathode side diffusion layer 122 close to the cathode side water repellent layer 152 has a large amount of binder per unit volume (indicated by deep hatching), and the cathode side gas flow path layer 132 has In the vicinity, the amount of impregnation per unit volume of the binder is small (indicated by thin hatching). That is, along the stacking direction from the cathode-side water repellent layer 152 side to the cathode-side gas flow path layer 132 side, the amount of binder impregnated per unit volume in the cathode-side diffusion layer 122 has a gradient that monotonously decreases. Forming. Note that the monotonically decreasing gradient in the present invention is not limited to the one in which the distance from the cathode-side water-repellent layer 152 in the cathode-side diffusion layer 122 is proportional to the amount of impregnation per unit volume. For example, a gradient in which the relationship between the distance and the amount of impregnation per unit volume changes stepwise, or a combination of gradients with different slopes, or a gradient with different slopes and a gradient with different slopes may be used. Or a gradient combining the above.

  As described above, the diffusion layer 120 of the fuel cell 100 in this embodiment is formed of a porous carbon cloth formed of carbon fibers Cfn, and a plurality of carbon fibers Cfn are bonded by a binder. Yes. Further, a gradient is formed so that the amount of the binder impregnated per unit volume in the diffusion layer 120 monotonously decreases along the stacking direction from the first surface 127 to the second surface 128 in the diffusion layer 120. Yes. Further, the length Ln of each of the carbon fibers Cfn protruding from the first surface 127 where the binder layer impregnation amount of the diffusion layer 120 is large, the angles θn of the angles formed by the first surface 127 and the carbon fibers Cfn, The relationship between the thickness D of the intermediate layer along the stacking direction disposed between the electrolyte membrane 112 and the diffusion layer 120 is Ln × sin (θn) ≦ D (n is an arbitrary integer). Therefore, in the diffusion layer 120 of the fuel cell 100 in the present embodiment, the carbon fibers Cfn protruding from the first surface 127 on the first surface 127 side of the diffusion layer 120 are reduced, while the carbon protruding from the first surface 127 is reduced. Since the fibers Cfn do not enter the electrolyte membrane 112, the electrolyte membrane 112 is not damaged, and a decrease in the performance of the fuel cell 100 can be prevented. In addition, in the diffusion layer 120 of the fuel cell 100 in the present embodiment, since the amount of the binder impregnated per unit volume on the second surface 128 side of the diffusion layer 120 is small, good gas diffusibility can be ensured.

A-2. Manufacturing method of diffusion layer:
FIG. 4 is a flowchart showing a flow of a manufacturing method of the diffusion layer 120 in the embodiment of the present invention. First, in the paper making process, the base material 126 of the diffusion layer 120 is produced (step S210 in FIG. 4). The carbon short fiber is continuously made with a paper making medium, and a binder such as polyvinyl alcohol is added to produce a carbon fiber paper base 126. In addition, a binder is not restricted to the thing of a present Example.

  Next, in the impregnation step, after the base material 126 is impregnated with the binder resin 160, the base material 126 is dried (step S220). FIG. 5 is an explanatory view schematically showing a step of impregnating the base material 126 with a binder in the embodiment of the present invention. As shown in FIG. 5, the binder resin 160 pumped out by the first roller 304 from the first surface 127 adjacent to the cathode-side water-repellent layer 152 when the base material 126 is molded as the diffusion layer 120. The substrate 126 is impregnated with the first roller 304 and the second roller 306. Thereafter, the base material 126 impregnated with the binder resin 160 conveyed by the roller is passed through a drying furnace for a predetermined time to dry the base material 126. By impregnating the base material 126 with the binder resin 160 and drying, the thickness of the base material 126 is reduced. Further, by impregnating the binder resin 160 from the first surface 127 of the base material 126, the amount of impregnation per unit volume of the binder resin 160 in the portion in the vicinity of the first surface 127 of the base material 126 is large. The amount of impregnation per unit volume of the binder resin 160 in the portion near the second surface 128 opposite to the surface 127 is reduced. That is, a gradient is formed so that the amount of impregnation per unit volume of the binder resin 160 in the substrate 126 monotonously decreases along the direction from the first surface 127 to the second surface 128. In this embodiment, a mixed liquid of phenol resin and methanol is used as the binder resin 160, but the binder is not limited to that of this embodiment.

  Next, in the first pressing step, the base material 126 is pressed (step S230). By pressing the base material 126, the thickness of the base material 126 is greatly reduced, and the carbon fiber Cfn protruding from the first surface 127 of the base material 126 is bent and restrained and fixed to the base material 126. Note that some protruding carbon fibers Cfn are deformed or broken by pressing.

  Next, in the firing step, the base material 126 is fired (step S240). By baking, the base material 126 is carbonized and the thickness is slightly reduced. FIG. 6 is an explanatory diagram showing an example of the state of the base material 126 after the firing step in the embodiment of the present invention. As shown in FIG. 6, some of the carbon fibers Cfn (for example, carbon fibers Cf2, Cf3, Cf4, Cf5) constrained by the base material 126 are released from the base material 126 and newly become the first surface 127. The carbon fiber Cfn protruded from the surface. For example, the carbon fiber Cf2 shown in FIG. 6 protrudes from the first surface 127, the length protruding from the first surface 127 is the length L2, and the first surface 127 and the carbon fiber Cf2 form. The angle is the angle θ2. In FIG. 6, the length along the perpendicular direction that protrudes from the first surface 127 of the carbon fiber Cf2 is represented by L2 × sin (θ2), and protrudes from the first surface 127 of the other carbon fiber Cfn. It is longer than the length along the perpendicular direction. As shown in FIG. 6, the length along the perpendicular direction of the carbon fiber Cf2 protruding from the first surface 127 is an intermediate layer (cathode 114 and cathode-side water-repellent layer 152 when laminated as the fuel cell 100). Alternatively, the thickness may be larger than the thickness D of the anode 116 and the cathode-side water repellent layer 152), and L2 × sin (θ2)> D may be satisfied. In this case, when the base material 126 is laminated as the diffusion layer 120 to form the fuel cell 100, the carbon fiber Cf2 may enter the electrolyte membrane 112 and damage the electrolyte membrane 112. The “firing” in the present invention is to sinter the base material 126 with a binder, and the material of the base material 126 is not limited to a carbon-based material.

  Next, in the dust suction step, the first surface 127 is sucked while air is blown onto the first surface 127 of the base material 126 (step S250). FIG. 7 is an explanatory view schematically showing the state of the base material 126 in the dust suction step in the embodiment of the present invention. As shown in FIG. 7, the cleaner 170 includes a blowout port 172, a suction tank 174, and a suction port 176. Air is blown from the air outlet 172 to the first surface 127 of the substrate 126. By operating an operation unit (not shown), the air blown onto the first surface 127, the strength of suction, and the like can be adjusted. The suction tank 174 sucks the carbon fibers Cfn separated from the base material 126 through the suction port 176.

  Next, in the second pressing step, the base material 126 is pressed at room temperature (step S260). FIG. 8 is an explanatory diagram showing an example of the state of the base material 126 after the second pressing step in the embodiment of the present invention. The base material 126 shown in FIG. 8 is the same part as the base material 126 shown in FIG. As shown in FIG. 8, the carbon fiber Cfn (for example, carbon fibers Cf2 ′, Cf3 ′, Cf4 ′, Cf5 ′) protruding from the first surface 127 is deformed by pressing the base material 126 at room temperature. Or break. Through the dust suction step and the second pressing step, the carbon fiber Cf2 ′ and the carbon fiber Cf3 ′ are broken, the carbon fiber Cf4 ′ is bent, and the carbon fiber Cf5 ′ is the first surface 127. To the direction along the second surface 128. Note that the length along the perpendicular direction of the carbon fiber Cfn projecting from the first surface 127 is shortened in most cases by performing the dust suction step and the second pressing step. In the second pressing step, a flat plate press or a roll press can be used. The linear pressure by the roll press machine can be converted into a surface pressure by using “Prescale” (registered trademark) of Fuji Film Co., Ltd. and a prescale pressure image analysis system (FPD-9270).

  The carbon fiber Cf2 ′ shown in FIG. 8 has a length L2 ′ protruding from the first surface 127 as in the case of the carbon fiber Cf2 shown in FIG. 6, and the first surface 127 and the carbon fiber Cf2 The angle formed by 'is the angle θ2'. In FIG. 8, the length along the perpendicular direction protruding from the first surface 127 of the carbon fiber Cf2 ′ is represented by L2 ′ × sin (θ2 ′), and the first surface 127 of the other carbon fiber Cfn. It is longer than the length along the direction perpendicular to the surface protruding from. As shown in FIG. 8, the length along the direction perpendicular to the surface of the carbon fiber Cf2 ′ protruding from the first surface 127 is smaller than the thickness D of the intermediate layer, and L2 ′ × sin (θ2 ′ ) <D. In this case, when the base material 126 is laminated as the diffusion layer 120 to form the fuel cell 100, the carbon fiber Cf2 'does not enter the electrolyte membrane 112, so that the electrolyte membrane 112 is not damaged. Note that, in the second pressing step, in order to perform the processing of the carbon fibers Cfn protruding from the first surface 127 without damaging the base material 126, the pressure value of the press is the optimum 1 MPa or more obtained from the actual measurement value. The value is 5 MPa or less. Further, the pressure value of the press is more preferably a value of 1 MPa or more and 3 MPa or less from an actual measurement value.

  Next, in the cutting process, the base material 126 is cut into a predetermined size for use in the fuel cell 100 (step S270).

A-3. Performance evaluation:
FIG. 9 is an explanatory diagram showing an example of the state of the carbon fibers Cfn of the base material 126 after the dust suction step of the embodiment of the present invention. FIG. 9A shows the relationship between the treatment applied to the sample of the base material 126 and the degree of removal of the carbon fibers Cfn protruding from the first surface 127 in the dust suction step (step S250 in FIG. 4). Yes. FIG. 9B shows the relationship between turbidity and fluff weight, which is one of the indexes representing the degree of removal of the carbon fibers Cfn protruding from the first surface 127.

  In FIG. 9A, in the dust suction process, as the processing to be performed on the sample A and the sample B, when no processing is performed, when dust is sucked by the cleaner 170, air blown by the cleaner 170, The case where the suction force is strengthened and the degree of removal of the carbon fiber Cfn protruding from the first surface 127 are shown. The turbidity is determined by irradiating the water with light when 5 samples of the substrate 126 cut into A4 size are rinsed into a predetermined amount of water after any treatment is performed on the substrate 126. It is calculated from the measured value of the ratio of transmitted light and scattered light. The higher the turbidity value, the more scattered light and the more carbon fibers Cfn are contained in the water, that is, more carbon fibers Cfn protruding from the first surface 127 remain in the substrate 126 immediately before rinsing. It shows that. Moreover, the fluff weight shown in FIG. 9 is an index different from turbidity, and indicates the weight (milligram (mg)) of the carbon fiber Cfn contained in 1 milliliter (mL) of water that has been rinsed through the base material 126. Is. This indicates that the larger the fluff weight value, the more carbon fibers Cfn that protrude from the first surface 127 remain on the substrate 126 immediately before swift.

  As shown in FIG. 9A, in the sample A and the sample B, in the dust suction process, the first suction is performed while blowing air with the cleaner 170, rather than performing no treatment on the base material 126. The carbon fiber Cfn protruding from the surface 127 can be further removed. Moreover, the cleaner 170 can remove more carbon fibers Cfn protruding from the first surface 127 when the air blown to the base material 126 and the suction force are strengthened. Therefore, the carbon fiber Cfn protruding from the first surface 127 can be further removed by sucking the first surface 127 while blowing air to the first surface 127 of the base material 126 in the dust suction step. . FIG. 9B shows the relationship between the turbidity and the fluff weight in Sample A and Sample B. If the turbidity of the water rinsed with the base material 126 is high, the fluff weight in the rinsed water is high. The value of also increased, indicating that there is a correlation between turbidity and fluff weight.

A-4. About the thickness of the intermediate layer:
When the fuel cell 100 is used, there is a case where stress continuously acts and deforms due to creep. FIG. 10 is an explanatory view schematically showing creep deformation of the fuel cell 100 in the embodiment of the present invention. FIG. 10 shows an enlarged view of the X1 portion (FIG. 1) of the fuel cell 100 before and after creep deformation. As shown in FIG. 10A, the thickness of the first intermediate layer when the fuel cell 100 is manufactured by laminating each layer such as the diffusion layer 120 is the initial thickness D0. At this time, for example, the carbon fiber Cf6 protruding from the first surface 127 of the diffusion layer 120 shown in FIG. 10A has a length L6 protruding from the first surface 127, and the first surface The angle formed by 127 and the carbon fiber Cf6 is an angle θ6. In FIG. 10, the length along the perpendicular direction that protrudes from the first surface 127 of the carbon fiber C6 is represented by L6 × sin (θ6), and protrudes from the first surface 127 of the other carbon fiber Cfn. It is longer than the length along the perpendicular direction. As shown in FIG. 10, the length along the perpendicular direction protruding from the first surface 127 of the carbon fiber C6 is a value smaller than the initial thickness D0, and L6 × sin (θ6) <D. . In this case, since the carbon fiber Cf6 protruding from the first surface 127 of the diffusion layer 120 does not enter the electrolyte membrane 112, the electrolyte membrane 112 is not damaged.

  As shown in FIG. 10B, the thickness D of the intermediate layer after the fuel cell 100 has undergone creep deformation is a value obtained by subtracting the creep deformation amount ΔD of the intermediate layer along the stacking direction from the initial thickness D0. . After the fuel cell 100 undergoes creep deformation, L6 × sin (θ6)> D, and the carbon fiber Cf6 may enter the electrolyte membrane 112 and damage the electrolyte membrane 112 in some cases.

  FIG. 11 is an explanatory diagram showing the relationship between the carbon fiber Cfn protruding from the first surface 127 of the diffusion layer 120 and the thickness D of the intermediate layer in the embodiment of the present invention. The horizontal axis is the length L of the carbon fiber Cfn of the diffusion layer 120 protruding from the first surface 127, and the vertical axis is the angle formed by the first surface 127 and the carbon fiber Cfn protruding from the first surface 127. Is the angle θ. In the diffusion layer 120 of the present embodiment, the carbon fibers Cfn of the diffusion layer 120 are the first to prevent the carbon fibers Cfn protruding from the diffusion layer 120 from entering the electrolyte membrane 112 even after creep deformation of the fuel cell 100. The length L protruding from the first surface 127, the angle θ formed by the first surface 127 and the carbon fiber Cfn protruding from the first surface 127, and the thickness D of the intermediate layer (initial thickness D0—creep deformation). The relationship with the amount ΔD) satisfies the condition represented by L × sin θ ≦ D.

  As described above, in the method for manufacturing the diffusion layer 120 of the present embodiment, in the impregnation step, the base material 126 of the diffusion layer 120 is impregnated with the binder resin 160 (FIG. 5), and the second surface to the second surface 127. A gradient is formed so that the amount of impregnation per unit volume of the binder resin 160 in the substrate 126 monotonously decreases along the direction of the surface 128. In the subsequent firing step, the substrate 126 is fired. In the subsequent dust suction step, the first surface 127 is sucked while air is blown onto the first surface 127 of the base material 126. In the second pressing step after the firing step, the substrate 126 is pressed. Therefore, as described below, in the method for manufacturing the diffusion layer 120 of this embodiment, the diffusion layer 120 that does not damage the electrolyte membrane 112 and ensures good gas diffusibility can be manufactured.

  FIG. 12 is an explanatory diagram showing the impregnation amount per unit volume of the binder in the cathode side diffusion layer 122 in the comparative example. FIG. 12 shows an enlarged view of a part of the cathode side diffusion layer 122 in the comparative example. The cathode side diffusion layer 122 (diffusion layer 120) and the cathode side diffusion layer 122a (diffusion layer 120a) shown in FIG. The impregnation amount per unit volume of the binder is different. As shown in FIG. 12, the impregnation amount of the binder per unit volume in the cathode side diffusion layer 122a is uniformly formed (indicated by hatching), and like the binder in the cathode side diffusion layer 122 of this embodiment. The amount of impregnation per unit volume does not form a gradient.

  The difference between the manufacturing method of the diffusion layer 120a in the comparative example and the diffusion layer 120 of the present example is that in the comparative example, the content of the impregnation step, the absence of the dust suction step, and the second pressing step for the base material 126 There is no. In the method for manufacturing the diffusion layer 120a in the comparative example, in the impregnation step, the entire surface of the base material 126 of the diffusion layer 120a is immersed in the binder resin 160 and then dried. Therefore, as shown in FIG. 12, in the diffusion layer 120a of the comparative example, the impregnation amount per unit volume of the binder resin 160 in the base material 126 is formed uniformly. Moreover, in the manufacturing method of the diffusion layer 120a in the comparative example, since the dust suction step and the second pressing step for the base material 126 are not performed, the base material 126 is released from the first surface 127 after the firing step. The protruding carbon fiber Cfn is not sufficiently removed.

  On the other hand, in the manufacturing method of the diffusion layer 120 in the present embodiment, the carbon fiber Cfn protruding from the first surface 127 on the first surface 127 side of the diffusion layer 120 is reduced, and the carbon fiber Cfn protrudes from the first surface 127. It is possible to manufacture the diffusion layer 120 in which the carbon fiber Cfn does not enter the electrolyte membrane 112 and does not damage the electrolyte membrane 112 and prevents the performance of the fuel cell 100 from being deteriorated. Further, in the method for manufacturing the diffusion layer 120 of the fuel cell 100 in the present example, since the amount of the binder impregnated per unit volume on the second surface 128 side of the diffusion layer 120 is small, good gas diffusibility is ensured. The diffusion layer 120 can be manufactured.

  Further, in the method of manufacturing the diffusion layer 120 in this embodiment, since the binder resin 160 is impregnated from the first surface 127 of the base material 126 in the impregnation step, the first surface 127 to the second surface 128 are easily impregnated. A diffusion layer 120 having a gradient that monotonously decreases the amount of impregnation per unit volume of the binder resin 160 in the substrate 126 along the direction can be manufactured. Therefore, in the method for manufacturing the diffusion layer 120 in the present embodiment, the carbon fiber Cfn protruding from the first surface 127 on the first surface 127 side in the diffusion layer 120 is reduced to prevent a decrease in the performance of the fuel cell 100, The diffusion layer 120 that ensures good gas diffusibility on the second surface 128 side of the diffusion layer 120 can be manufactured.

  Moreover, in the manufacturing method of the diffusion layer 120 in a present Example, each of the length Ln which protruded from the 1st surface 127 of each carbon fiber Cfn in the base material 126, and the angle which the 1st surface 127 and carbon fiber Cfn make | form each And the thickness D of the intermediate layer along the stacking direction disposed between the electrolyte membrane 112 and the diffusion layer 120 is Ln × sin (θn) ≦ D (n is an arbitrary integer) It has become. That is, each length along the direction perpendicular to the surface of the base material 126 protruding from the first surface 127 of the carbon fiber Cfn is smaller than the thickness D of the intermediate layer. Therefore, in the method for manufacturing the diffusion layer 120 in the present embodiment, the carbon fiber Cfn protruding from the first surface 127 does not enter the electrolyte membrane 112, so that the electrolyte membrane 112 is not damaged and the performance of the fuel cell 100 is prevented from being deteriorated. A diffusion layer 120 can be manufactured.

  Further, in the method of manufacturing the diffusion layer 120 in the present embodiment, the thickness D of the intermediate layer after the fuel cell 100 undergoes creep deformation is subtracted from the creep deformation amount ΔD of the intermediate layer along the stacking direction from the initial thickness D0. Value. In this embodiment, the angle θ formed by the length L of the carbon fiber Cfn of the diffusion layer 120 protruding from the first surface 127 and the carbon fiber Cfn protruding from the first surface 127. And the thickness D of the intermediate layer (initial thickness D0−creep deformation ΔD) satisfies the condition represented by L × sin θ ≦ D. Therefore, in the method for manufacturing the diffusion layer 120 in this embodiment, the carbon fiber Cfn protruding from the diffusion layer 120 does not enter the electrolyte membrane 112 even after creep deformation of the fuel cell 100, so that the electrolyte membrane 112 is not damaged and the fuel A diffusion layer 120 that prevents a decrease in the performance of the battery 100 can be manufactured.

  Moreover, in the manufacturing method of the diffusion layer 120 in the present embodiment, in the second pressing step, the pressure value for pressing the base material 126 is 1 MPa or more and 5 MPa or less, so the first surface without damaging the base material 126. The carbon fiber Cfn protruding from 127 can be processed, and the diffusion layer 120 that prevents the deterioration of the performance of the fuel cell 100 without damaging the electrolyte membrane 112 can be manufactured.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
FIG. 13 is an explanatory diagram showing the state of the base material 126 after the second pressing step in the modification. FIG. 13 shows the same portion as the substrate 126 shown in FIG. The base material 126 shown in FIG. 13 is different from the base material 126 shown in FIG. 8 in that the length L4 ′ of the length protruding from the first surface 127 of the carbon fiber Cf4 ′ is arranged along the perpendicular direction. The thickness D of the intermediate layer to be equal is the same value. Since the carbon fiber Cf4 ′ is bent and deformed, the length L4 is a length when the carbon fiber Cf4 ′ is straight. In FIG. 13, the length L4 ′ in which the carbon fiber Cf4 ′ of the base material 126 in the modified example protrudes from the first surface 127 is longer than the length Ln in which the other carbon fiber Cfn protrudes from the first surface 127. . Therefore, the length L4 ′ protruding from the first surface 127 of the carbon fiber Cf4 that protrudes most from the first surface 127 of the base material 126 is equal to or less than the thickness D of the intermediate layer along the perpendicular direction. . Therefore, in the manufacturing method of the diffusion layer 120 in the modification, even if the length along the perpendicular direction protruding from the first surface 127 of the carbon fiber Cfn becomes longer after the dust suction step and the second pressing step. Since all the carbon fibers Cfn protruding from the first surface 127 do not enter the electrolyte membrane 112, the electrolyte membrane 112 is not damaged, and the diffusion layer 120 that prevents the performance of the fuel cell 100 from being deteriorated can be manufactured.

B2. Modification 2:
In the method of manufacturing the diffusion layer 120 of the above embodiment, in the impregnation step, the binder resin 160 is impregnated from the first surface 127 of the substrate 126 by the first roller 304 or the like shown in FIG. Not limited to. For example, only the first surface 127 of the base material 126 is immersed in the binder resin 160 for a predetermined time without using the first roller 304 or the like, so that the impregnation amount per unit volume of the binder resin 160 in the base material 126 is obtained. A gradient can be formed.

  Moreover, in the manufacturing method of the diffusion layer 120 of the said Example, although the pressure value of the press was 1 MPa or more and 5 MPa or less in the 2nd press process, it is not restricted to this value. Even if the pressure value is less than 1 MPa, the fluff treatment of the base material 126 can be performed, and even if the pressure value is greater than 5 MPa, the fluff treatment can be performed without damaging the base material 126.

  Further, in the method for manufacturing the diffusion layer 120 of the above embodiment, as shown in FIG. 4, after the firing step, the dust suction step is performed and then the second pressing step is performed on the base material 126. The dust suction step may be performed after the pressing step. For example, after performing the second pressing step and the cutting step after the firing step, the dust suction step may be finally performed. Even in the manufacturing method of the diffusion layer 120 in this case, the diffusion that sufficiently removes the carbon fibers Cfn protruding from the first surface 127 of the base material 126 and prevents deterioration of the performance of the fuel cell without damaging the electrolyte membrane 112. Layer 120 can be manufactured.

  In the manufacturing method of the diffusion layer 120 of the above embodiment, the base material 126 is cut in the cutting step, but the order of the steps is not limited thereto. For example, the cathode-side water-repellent layer 152 or the anode-side water-repellent layer 154 may be applied to the substrate 126 and then cut into a predetermined size used in the fuel cell 100.

B3. Modification 3:
In the manufacturing method of the diffusion layer 120 of the above embodiment, the surface of the first surface 127 of the cathode side diffusion layer 122 (diffusion layer 120) is the flat first surface 127 calculated as an average value. It may not be so. For example, in the X-ray CT image as shown in FIG. 2, a flat first surface 127 may be formed by connecting points on both ends of the obtained enlarged image of the cathode side diffusion layer 122 with a straight line. The straight line connecting the average value of the five arbitrary points acquired in step 1 or the median value and the rightmost point may be used as the flat first surface 127. Further, the calculation method of the first surface 127 may be changed as appropriate depending on the material of the diffusion layer 120.

  Moreover, in the manufacturing method of the diffusion layer 120 of the said Example, although the diffusion layer 120 was formed with carbon cloth or carbon paper, it may not be so. For example, the diffusion layer 120 made of a fibrous metal having conductivity may be used.

B4. Modification 4:
The configuration of the fuel cell 100 in the manufacturing method of the above embodiment is merely an example, and various modifications can be made. For example, although the fuel cell 100 of the above embodiment includes the cathode-side water-repellent layer 152 and the anode-side water-repellent layer 154, these water-repellent layers may not be provided, and the cathode is provided only on the cathode side or the anode side. The side water-repellent layer 152 or the anode side water-repellent layer 154 may be provided.

  In the fuel cell 100 in the manufacturing method of the above embodiment, as shown in FIG. 1, the electrolyte membrane 112, the anode 116, the cathode 114, the cathode-side water-repellent layer 152, and the anode-side water-repellent layer 154 have an area in the plane direction. Are the same but may be different. For example, the area of the anode 116 may be larger or smaller than the area of the electrolyte membrane 112.

  In the fuel cell 100 in the manufacturing method of the above embodiment, a method for manufacturing the diffusion layer 120 of the polymer electrolyte fuel cell has been described. However, the present invention is applicable to other types of fuel cells (for example, direct methanol fuel). The present invention can also be applied to a method for manufacturing a diffusion layer 120 of a battery or a phosphoric acid fuel cell.

  Of the constituent elements in the above-described embodiments, examples, and modifications, elements other than those described in the independent claims are additional elements, and can be omitted or combined as appropriate.

100 ... Fuel cell 110 ... MEA
DESCRIPTION OF SYMBOLS 112 ... Electrolyte membrane 114 ... Cathode 116 ... Anode 120 ... Diffusion layer 120a ... Diffusion layer 122 ... Cathode side diffusion layer 122a ... Cathode side diffusion layer 124 ... Anode side diffusion layer 126 ... Base material 127 ... First surface 128 ... Second Surface 132 ... Cathode side gas flow path layer 134 ... Anode side gas flow path layer 140 ... Separator 152 ... Cathode side water repellent layer 154 ... Anode side water repellent layer 160 ... Binder resin 170 ... Cleaner 172 ... Outlet 174 ... Suction tank 176 ... Suction port 304 ... First roller 306 ... Second roller L ... Length D ... Thickness of intermediate layer Cfn ... Carbon fiber

Claims (5)

A method for producing a diffusion layer for a fuel cell formed of a material comprising carbon paper or carbon cloth,
The amount of impregnation of the binder in the fuel cell diffusion layer per unit volume is such that the fuel cell has a gradient along a perpendicular direction perpendicular to a stacking surface on which the members of the fuel cell diffusion layer are stacked. A first step of impregnating the binder of the battery diffusion layer with the binder;
After the first step, the carbon paper that has been compressed from the first surface of the base material having a larger amount of the binder without compressing the base material in the direction perpendicular to the base and damaging the base material. Or a second step of deforming or breaking the carbon cloth fibers;
A third step of firing the substrate after the second step;
After the third step, the first surface is sucked while gas is blown on the first surface, and the carbon paper or the carbon cloth separated from the base material in the second or third step A fourth step of sucking the fibers;
After the fourth step, the base material is compressed in the direction perpendicular to the surface, and the carbon paper or carbon cloth fibers that are protruded from the first surface without damaging the base material are in the direction perpendicular to the surface. The length along the first electrode is made smaller than the thickness D of the cathode and the cathode-side water-repellent layer or the anode and the anode-side water-repellent layer disposed between the electrolyte membrane and the fuel cell diffusion layer. And a process for producing a diffusion layer for a fuel cell comprising the step of 5. It is a manufacturing method of the diffusion layer for fuel cells according to claim 1,
The method for producing a diffusion layer for a fuel cell, wherein the first step is a step of impregnating the binder from the first surface of the substrate. It is a manufacturing method of the diffusion layer for fuel cells according to claim 2,
The fourth and fifth steps include, for carbon fiber or carbon cloth fibers, the length L of the portion protruding from the first surface of the base material, the first surface and the protruding carbon. A method for producing a diffusion layer for a fuel cell, which is a process performed so that a relationship between an angle θ formed with a fiber of paper or carbon cloth and the thickness D satisfies a condition represented by L × sin θ ≦ D . It is a manufacturing method of the diffusion layer for fuel cells according to claim 3,
The method of manufacturing a diffusion layer for a fuel cell, wherein the thickness D is a thickness after creep deformation of the cathode and the cathode-side water-repellent layer or the anode and the anode-side water-repellent layer along the perpendicular direction. A method for producing a diffusion layer for a fuel cell according to any one of claims 1 to 4,
The method for producing a fuel cell diffusion layer, wherein the compression pressure value in the fifth step is 1 MPa or more and 5 MPa or less.

Images