JP2009193845A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell with drainage of generated water improved, as well as excellent in power generation performance. <P>SOLUTION: A flow channel forming material 5b at an air electrode side consists of an expanded metal 50 containing a plurality of meshes 51 communicating between a diffusion layer 23b and a separator 6b and wall parts 52 partitioning between adjacent meshes 51. The wall part 52 repeats convexoconcave in its thickness direction, and made by arraying an inclination part 56c regularly with a bottom part 56a at one end and a top part 56b at the other end. The separator 6b includes a top contact part 6c in contact with the top part 56b. From an edge part 23f of a bottom contact part 23c in contact with the bottom part 56a on the diffusion layer 23b to at least a part of a projection area 23g when the inclination part 56c is projected onto the diffusion layer 23b, a water-repellent treatment part 8 is formed. At a part between adjacent bottom contact parts 23c and other than the water-repellent treatment part 8, a non-water-repellent treatment part 9 without water-repellent treatment is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell, and more particularly to a drainage structure for a fuel cell.

  A fuel cell generates power by an electrochemical reaction between hydrogen gas and oxygen, and is a stack of a plurality of battery cells. The battery cell is disposed between a membrane electrode assembly in which a catalyst layer and a diffusion layer are disposed on both surfaces of a solid polymer electrolyte membrane, a separator, and the membrane electrode assembly and the separator. Hydrogen gas, oxygen, And a flow path forming material constituting a flow path of a fluid such as water. Of the catalyst layers formed on both sides of the electrolyte membrane, hydrogen ions and electrons are generated from hydrogen gas in the catalyst layer on the fuel electrode (anode) side, and received through an external circuit in the catalyst layer on the air electrode (cathode) side. Electrons react with hydrogen ions that have passed through the electrolyte membrane and oxygen in the supplied air to generate water. Fuel cells generate electrical energy by the flow of electrons through an external circuit. The produced water is discharged from the catalyst layer on the air electrode side to the outside of the battery cell through the diffusion layer and the flow path forming material.

  While the generated water keeps the solid polymer electrolyte membrane in a wet state, if it is excessively present in the diffusion layer, the gas flow path of the diffusion layer may be blocked, gas diffusibility may be reduced, and power generation efficiency may be reduced. In view of this, attempts have been made to improve the drainage of the diffusion layer.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-327609, specification “0019”), after coating a diffusion layer (carbon layer) with a fluororesin, a fluororesin present on a surface in contact with a catalyst layer or carbon paper is used. It is disclosed to remove. That is, the diffusion layer removes the fluororesin in the portion where electricity flows to exhibit conductivity, and the other portions are covered with the fluororesin to ensure water repellency.

  In Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-93167, specification “0007”), a water repellent material containing a fluorine-containing compound is formed only on a portion of the diffusion layer (gas diffusion electrode base material) to be subjected to water repellent treatment. Is disclosed.

  In Patent Document 3 (Japanese Patent Laid-Open No. 2000-251900, specification “0010”), the diffusion layer on the fuel electrode side includes a water-repellent material, and the diffusion layer in contact with the convex portion of the gas chamber on the fuel electrode side is disclosed. The water repellency of the region is made smaller than the water repellency of the diffusion layer facing the recess of the gas chamber. As a result, even in the region in contact with the convex portion of the gas chamber, the humidified water can permeate the diffusion layer to the same extent as the region facing the concave portion of the gas chamber, so that the wet state of the electrolyte membrane can be ensured. Battery performance can be ensured.

  In Patent Document 4 (Japanese Patent Application Laid-Open No. 6-84529, specification “0015”), a water repellent is attached to the surface portion of the diffusion layer on the air electrode side made of a carbon fiber sintered body, and the ribs of the ribbed separator are adhered to the surface. By removing the water repellent adhering to the abutting rib surface, electrical conductivity between the rib surface and the ribbed separator is ensured.

On the other hand, expanded metal has recently been used as a flow path forming material. For example, as described in Patent Document 5 (Japanese Patent Laid-Open No. 2006-294327, specification “0004”), an expanded metal has a large number of through holes and a large number of concave and convex shapes on the surface thereof. It has. By adjusting the uneven thickness, the contact between the diffusion layer and the expanded metal can be improved, and the power generation efficiency can be improved.
JP 2005-327609 A JP 2005-93167 A JP 2000-251900 A JP-A-6-84529 JP 2006-294327 A

  However, Patent Documents 1 to 4 do not sufficiently examine in which part of the diffusion layer the generated water generated by the electrochemical reaction tends to accumulate. Moreover, in patent document 5, when an expanded metal is used as a flow-path formation material, the effective drainage structure is not examined. Then, when the inventor diligently investigated paying attention to the site | part where the produced | generated water of a diffused layer tends to accumulate, it came to correspond to this invention.

  This invention is made | formed in view of this situation, and makes it a subject to provide the fuel cell which was excellent in the power generation performance while improving the drainage property of generated water.

  In order to solve the above problems, the invention according to claim 1 is a membrane electrode assembly in which a catalyst layer and a diffusion layer are disposed on both the fuel electrode side and the air electrode side of an electrolyte membrane, and the membrane electrode assembly. A fuel cell comprising a flow path forming material disposed on both sides of the fuel electrode side and the air electrode side, and a separator disposed on a surface of the flow path forming material, wherein the membrane electrode assembly Of the flow path forming materials disposed on both sides, at least the flow path forming material on the air electrode side is adjacent to a plurality of through holes arranged in a mesh shape communicating between the diffusion layer and the separator. The wall portion is formed of a conductive porous body having a wall partitioning the through holes, and the wall portion has irregularities in the thickness direction, and regularly has an inclined portion having a bottom at one end and a top at the other end. The diffusion layer has a bottom contact portion in contact with the bottom, and the separator is in front From the edge of the bottom contact portion in the diffusion layer to the projection region formed by projecting the inclined portion of the flow path forming material with respect to the diffusion layer. A water repellent portion is formed between the bottom contact portion and the adjacent bottom contact portions, and a portion other than the water repellent portion is not subjected to water repellent treatment. It has a non-water-repellent treatment part.

  According to a second aspect of the present invention, when the inclination angle formed by the diffusion layer and the inclined portion is θ and the length of the inclined portion is L, the water repellent treatment portion is an edge portion of the bottom contact portion. To the longitudinal direction of the projection area, and is formed in a portion having a length of ½ × L × cos θ or more and less than L × cos θ.

  The invention according to claim 3 is characterized in that the conductive porous body is an expanded metal.

  The invention according to claim 4 is characterized in that a cushion material is interposed only between the flow path forming material on the fuel electrode side and the membrane electrode assembly.

  According to the first aspect of the present invention, the surface of the diffusion layer facing the flow path forming material is inclined from the edge of the bottom contact portion where the bottom of the flow path forming material is in contact with the surface of the diffusion layer. A water repellent portion is formed between at least a part of the projection region when the portion is projected onto the diffusion layer. The bottom contact portion of the air electrode side diffusion layer is located in the flow path of electrons taken in through the air electrode side separator and the flow path forming material. For this reason, electrons are supplied from the bottom contact portion to the catalyst layer through the diffusion layer, and the generated water generated by the electrochemical reaction in the catalyst layer follows substantially the same path as the electron is supplied to the surface of the diffusion layer. Spread. For this reason, a lot of generated water tends to circulate around the edge of the bottom contact portion of the diffusion layer. And the projection area | region which projected the inclination part on the diffused layer also in the periphery of the edge part of a bottom part contact part is a site | part with which the flow of generated water tends to be blocked | interrupted by the inclination part.

  Therefore, according to the present invention, the water repellent portion is formed between the edge of the bottom contact portion in the diffusion layer and at least a part of the projection region of the inclined portion. For this reason, generated water can be made water-repellent and efficiently discharged out of the battery system. In addition, a water repellent treatment portion is formed between the edge of the bottom contact portion and at least a part of the projected area of the inclined portion, and the bottom contact portion, which is an electron distribution path, is not repellent. It has a water treatment section. Therefore, the flow of electrons between the flow path forming material and the diffusion layer is not blocked by the water repellent portion. Further, a non-water repellent treatment part is provided between adjacent bottom contact parts in a portion excluding the water repellent treatment part. For this reason, reaction gas and produced water can distribute | circulate between a diffusion layer and a flow-path formation material through the non-water-repellent treatment part between adjacent bottom part contact parts. Therefore, according to the present invention, the power generation performance of the fuel cell is improved.

  According to the second aspect of the present invention, the water repellent treatment part has a length of ½ × L × cos θ or more and less than L × cos θ from the edge of the bottom contact part toward the longitudinal direction of the projection region. It is formed in the part. Here, the “longitudinal direction of the projection region” refers to a direction from the bottom contact portion in contact with the bottom of the inclined portion toward the portion projected on the diffusion layer at the top of the inclined portion. The generated water tends to accumulate in a portion near the bottom contact portion in the projection region of the inclined portion, that is, a portion between ½ × cos θ from the edge of the bottom contact portion in the longitudinal direction of the projection region. This part is close to the bottom contact part, which is an electron flow path, and is a part where water is easily generated actively, and is a narrow space behind the inclined part, particularly where water is easily collected. . Therefore, the generated water can be effectively drained by forming the water-repellent treatment portion in the portion. Further, the water repellent treatment part is formed in a portion less than L × cos θ from the edge of the bottom contact part in the longitudinal direction of the projection region. For this reason, the part in which the water-repellent treatment part is not formed remains on the surface of the diffusion layer, and the flow path of the reaction gas is secured. Therefore, the drainage can be effectively enhanced without hindering the flow of the reaction gas.

  According to the third aspect of the present invention, the flow path forming material is constituted by the expanded metal. The expanded metal is formed by regularly and continuously forming mesh-like through holes by processing staggered cuts on a flat thin metal plate and extending the cuts. For this reason, a yield is good compared with the case where a through-hole is formed by punching, for example. Therefore, the manufacturing cost of the fuel cell can be reduced.

  According to the fourth aspect of the present invention, the cushion material is interposed only between the fuel electrode side flow path forming material and the fuel electrode side membrane electrode assembly, and the air electrode side flow path forming material and air A cushion material is not interposed between the membrane electrode assembly on the pole side. The air-electrode-side flow path forming material is made of a conductive porous body, and a water-repellent treatment portion is formed between the edge of the bottom contact portion of the diffusion layer and at least a part of the projection region. Thereby, a dimensional change such as thermal expansion can be absorbed by the cushioning material on the fuel electrode side without lengthening the drainage path of the flow path forming material on the air electrode side. Therefore, both drainage and dimensional stability of the fuel cell can be improved.

  The fuel cell according to the present invention is a stack of a plurality of battery cells. As shown in FIG. 1, the battery cell 1 is formed on the outside of the membrane electrode assembly 2, the flow path forming materials 5a and 5b disposed outside the membrane electrode assembly 2, and the flow path forming materials 5a and 5b. Separators 6a and 6b.

  The membrane electrode assembly 2 includes an electrolyte membrane 21, catalyst layers 22a and 22b arranged on both the fuel electrode side and the air electrode side of the electrolyte membrane 21, and gas diffusibility arranged outside the catalyst layers 22a and 22b. The diffusion layers 23a and 23b having The electrolyte membrane 21 is made of a material having ion conduction performance, for example, Nafion. The catalyst layers 22a and 22b carry a catalyst that promotes an electrochemical reaction, for example, platinum. Of the catalyst layers 22 a and 22 b formed on both surfaces of the electrolyte membrane 21, hydrogen ions and electrons are generated from hydrogen gas in the catalyst layer 22 a on the fuel electrode side. In the catalyst layer 22b on the air electrode side, electrons received through the external circuit react with hydrogen ions and oxygen that have passed through the electrolyte membrane 21 to generate water.

  The diffusion layers 23a and 23b are porous bodies having pores that allow gas and water to pass in the thickness direction, and are made of, for example, a carbon porous body. The carbon porous body is obtained by carbonizing polyimide, a mixture of carbon black and a fluororesin, or a carbon non-woven fabric coated with fluorine. The diffusion layer 23a on the fuel electrode side diffuses electrons generated by the electrochemical reaction in the fuel gas (hydrogen gas) and the catalyst layer in the thickness direction, and the diffusion layer 23b on the air electrode side contains air (oxygen gas) and Water and electrons generated by the electrochemical reaction in the catalyst layer are diffused in the thickness direction.

  On both surfaces of the membrane electrode assembly 2 on the fuel electrode side and the air electrode side, flow path forming materials 5a and 6b and separators 6a and 6b are laminated. Here, among the flow path forming materials 5a and 5b on the fuel electrode side and the air electrode side, at least the flow path forming material 5b on the air electrode side is the same arranged in a mesh shape communicating between the diffusion layer 23b and the separator 6b. It consists of a conductive porous body having a plurality of shaped meshes 51 and wall portions 52 that partition between adjacent meshes 51. The wall portion 52 has irregularities in the thickness direction and is regularly arranged with inclined portions 56c having a bottom portion 56a at one end and a top portion 56b at the other end. The bottom portion 56a is in contact with the bottom contact portion 23c of the diffusion layer 23b. The top portion 56b is in contact with the top contact portion 6c of the separator 6b. The water repellent treatment is performed between the edge 23f of the bottom contact portion 23c in the diffusion layer 23b and at least a part of the projection region 23g formed by projecting the inclined portion 56c of the flow path forming member 5b onto the diffusion layer 23b. Part 8 is formed.

  For example, an expanded metal 50 may be used as at least the air electrode side flow path forming material 5b of the air electrode side and fuel electrode side flow path forming materials 5a and 5b. The expanded metal 50 is made of a conductive metal, such as stainless steel, titanium, or a titanium alloy. The flow path forming materials 5a and 5b on the fuel electrode side as well as on the air electrode side can be constituted by the expanded metal 50. As shown in FIGS. 2 to 4, the expanded metal 50 is a conductive porous body including a mesh 51 as a plurality of rhombus or hexagonal through holes and a wall portion 52 surrounding the mesh 51. The wall portion 52 has a strand portion 55 constituting the four sides of the mesh 51 and a bond portion 56 in which adjacent strand portions 55 are connected to each other. When the width H of the bond portion 56 is large, the mesh 51 has a hexagonal shape, and when the width H of the bond portion 56 is narrow, the mesh 51 has a rhombus (rectangle). FIG. 2 illustrates the case where the width H of the bond portion 56 is large and the mesh 51 is hexagonal.

  The expanded metal 50 is formed by cutting a metal plate in a zigzag manner and extending the metal plate in a direction perpendicular to the cut. When extending a metal plate, the bond part which connects a notch inclines in the thickness direction. For this reason, regular irregularities are formed in the expanded metal 50 in the thickness direction. And the bond part 56 consists of the inclination part 56c. One end of the inclined portion 56c has a bottom portion 56a, and the other end of the inclined portion 56c has a top portion 56b. The inclined portion 56c is inclined at a predetermined angle θ between the bottom portion 56a and the top portion 56b. The inclined portions 56c of the bond portion 56 of the expanded metal 50 are all inclined at substantially the same predetermined angle θ. The inclined portion 56 c of the bond portion 56 is preferably an inclined angle θ of 10 to 80 ° from the viewpoint of fluidity of the fluid passing through the space in the expanded metal 50. The strand part 55 which connects adjacent bond parts 56 connects between the bottom part 56a of one bond part 56, and the top part 56b of the other bond part 56, and each of the bottom part 56a and the top part 56b is connected. It forms a wave shape with peaks and valleys.

  As shown in FIG. 5, the diffusion layer 23 b on the air electrode side has a bottom contact portion 23 c that contacts the bottom portion 56 a of the bond portion 56 of the expanded metal 50. The separator 6 b on the air electrode side has a top contact portion 6 c that contacts the top portion 56 b of the bond portion 56. On the surface of the diffusion layer 23b facing the expanded metal 50, a water repellent treatment portion 8 is formed between the edge 23f of the bottom contact portion 23c and at least a part of the projection region 23g. The projection region 23g is a region that is behind the inclined portion 56c when the inclined portion 56c is projected in the vertical direction with respect to the diffusion layer 23b. The water repellent treatment portion 8 is not formed on the bottom contact portion 23c.

  As shown in FIG. 6, the water repellent treatment unit 8 has at least a bottom portion between the edge portion 23f of the bottom contact portion 23c in contact with the bottom portion 56a of the expanded metal 50 in the diffusion layer 23b and a part of the projection region 23g. It is preferably formed over the entire width H of the contact portion 23c. The expanded metal 50 is in contact with the diffusion layer 23b over the entire width H of the bottom portion 56a. For this reason, the generated water tends to accumulate at the periphery of the entire width H of the bottom contact portion 23c in the diffusion layer 23b. Therefore, by forming the water repellent treatment portion 8 over the entire width H of the bottom contact portion 56c, the generated water can be drained effectively.

  As shown in FIG. 5, when the inclination angle formed between the diffusion layer 23b and the inclined portion 56c of the bond portion 56 of the expanded metal 50 is θ and the length of the inclined portion 56c is L, the water repellent treatment portion 8 is From the edge 23f of the bottom contact portion 23c of the diffusion layer 23b, a length of ½ × L × cos θ or more and less than L × cos θ toward the longitudinal direction of the projection region 23g (the arrow Y direction in FIGS. 5 and 6). It is preferable to form in the part which has. That is, the water repellent treatment part 8 is formed toward the longitudinal direction of the projection region 23g with the edge 23f of the bottom contact part 23c as a base point, and the length a of the water repellent treatment part 8 is the length of the inclined part 56c. It is preferable that the projection region 23g has a size of ½ or more and less than 1 with respect to L × cos θ, which is the length in the longitudinal direction Y. In this case, the drainage of the generated water can be effectively improved while ensuring a sufficient opening area for the reaction gas to flow in the diffusion layer 23b.

  In forming the water repellent portion, for example, a portion other than the water repellent portion forming portion on the surface of the diffusion layer is masked and a water repellent is applied. Examples of the coating method include spraying, screen printing, applicator, and inkjet. The water repellent is polytetrafluoroethylene (hereinafter referred to as “PTFE”), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluorovinyl ether copolymer (PFA), A fluororesin such as polyvinylidene fluoride (PVdF) can be used.

  In addition, the non-water-repellent treatment portion 9 that is not subjected to the water-repellent treatment portion is provided between the bottom contact portion 23c of the diffusion layer 23b and the adjacent bottom contact portions 23c other than the water-repellent treatment portion 8. ing. Therefore, the non-water-repellent treatment portion 9 and the water-repellent treatment portion 8 are alternately arranged on the surface of the diffusion layer 23b. Here, “adjacent bottom contact portions” means between the bottom contact portions adjacent in one direction (first case) or between the bottom contact portions adjacent in two directions (second case). It means either. In the case of the first case, the non-water-repellent treatment part is disposed between the bottom contact parts adjacent in one direction in the planar direction of the diffusion layer, and is not in contact between the bottom contact parts adjacent in the other direction. No part is arranged, and the water repellent part is partially or entirely continuous in the other direction. In the case of the second case, the non-water-repellent treatment portions are disposed between the bottom contact portions adjacent to each other in two directions, and the water-repellent treatment portions are discontinuously disposed in a lattice shape. . 6 and 7 show specific examples of the second case. In both figures, the water-repellent treatment parts 8 are arranged in a lattice pattern in both the longitudinal direction Y of the projection region 23g and the width direction X orthogonal to the longitudinal direction Y, and the adjacent water-repellent treatment parts 8 are adjacent to each other. A non-water-repellent treatment part 9 is interposed therebetween. In FIG. 6, each water repellent treatment unit 8 is arranged in a non-contact state with another adjacent water repellent treatment unit 8. In FIG. 7, each water repellent treatment unit 8 is arranged in contact with another adjacent water repellent treatment unit 8 at a corner portion 8 c.

  The separators 6a and 6b collect electrons generated by an electrochemical reaction between hydrogen and oxygen and have good conductivity as an electrical connector between adjacent battery cells. Further, the separators 6a and 6b serve to separate the battery cells and separate oxygen and hydrogen when the battery cells are stacked. Separator 6a, 6b consists of a flat plate without an unevenness | corrugation, For example, a dense carbon plate or a metal plate (for example, stainless steel, titanium, titanium alloy etc.) can be used.

  The cushion material 3 is interposed only between the fuel electrode side flow path forming member 5a and the membrane electrode assembly 2, and between the air electrode side flow path forming member 5b and the membrane electrode assembly 2, the cushion material is provided. It is good to set it as the structure by which 3 is not interposed. Thereby, the generated water can be effectively drained on the air electrode side, and the dimensional stability of the fuel cell can be enhanced on the fuel electrode side.

  The cushion material 3 has elasticity in the thickness direction and has a porosity through which reaction gas and water can pass. For example, a conductive fiber woven or non-woven fabric made of metal, carbon, or conductive resin, or aeration For example, a conductive foam sheet having pores communicating to such an extent that it has a property can be used. More preferably, the cushion material 3 is made of carbon cloth or carbon paper. The thickness of the cushion material 3 is preferably 50 to 600 μm, and more preferably 200 to 300 μm. As a result, the dimensional change in the thickness direction of the fuel cell due to thermal expansion or the like is elastically absorbed without increasing the diffusion distance of the reaction gas and water between the membrane electrode assembly 2 and the flow path forming material 5b on the air electrode side. can do.

Example 1
The fuel cell of this example is a stack of a plurality of battery cells. As shown in FIG. 1, the battery cell 1 includes a membrane electrode assembly 2, flow path forming materials 5 a and 5 b and separators 6 a and 6 b arranged on both the air electrode side and the fuel electrode side of the membrane electrode assembly 2. And have. The membrane electrode assembly 2 includes an electrolyte membrane 21, and catalyst layers 22a and 22b and diffusion layers 23a and 23b disposed on both the air electrode side and the fuel electrode side of the electrolyte membrane 21. The cushion material 3 is interposed only between the diffusion layer 23a on the fuel electrode side and the flow path forming material 5a on the fuel electrode side. The air electrode side and fuel electrode side flow path forming members 5 a and 5 b are made of a mesh-like expanded metal 50.

  As shown in FIGS. 2 to 4, the expanded metal 50 includes a plurality of hexagonal meshes 51 arranged in a mesh shape that communicates between the diffusion layers 23 a and 23 b and the separators 6 a and 6 b, and adjacent meshes 51. And a wall portion 52 for partitioning. The wall portion 52 includes a strand portion 55 that forms four sides of the hexagonal mesh 51 and a bond portion 56 that forms two sides of the mesh 51 and connects adjacent strand portions 55 to each other. The wall 52 has regular irregularities by repeating irregularities in the thickness direction. The bond portion 56 includes an inclined portion 56c that is inclined in the thickness direction. One end of the inclined portion 56c has a bottom portion 56a, and the other end of the inclined portion 56c has a top portion 56b. All the inclined portions 56c of the bond portion 56 are inclined at substantially the same angle θ. The strand part 55 which connects adjacent bond parts 56 connects between the bottom part 56a of one bond part 56, and the top part 56b of the other bond part 56, and each of the bottom part 56a and the top part 56b is connected. It forms a wave shape with peaks and valleys. The inclination angle θ formed by the diffusion layer 23b and the inclined portion 56c of the expanded metal 50 is 45 °. The length L of the inclined portion 56c, that is, the length from the bottom portion 56a to the top portion 56b is 2 mm. As shown in FIG. 2, the expanded metal 50 has a plate thickness c of 0.1 mm, a mesh 51 having a width d of 1 mm and a length e of 2 mm.

As shown in FIG. 5, the diffusion layer 23 b on the air electrode side has a bottom contact portion 23 c that contacts the bottom portion 56 a of the bond portion 56 of the expanded metal 50. The separator 6 b on the air electrode side has a top contact portion 6 c that contacts the top portion 56 b of the bond portion 56. On the surface of the diffusion layer 23b facing the expanded metal 50, a water repellent treatment portion 8 is formed between the edge 23f of the bottom contact portion 23c and a part of the projection region 23g. And in the part other than the water-repellent process part 8 between the bottom part contact parts 23c and the adjacent bottom part contact parts 23c, it has the non-water-repellent process part 9 which is not water-repellent-treated. Specifically, the water-repellent treatment portion 8 has a square shape when the inclination angle formed by the diffusion layer 23b and the inclined portion 56c is θ (45 °) and the length of the inclined portion 56c is L (2 mm). From the edge 23f of the bottom contact portion 23c of the diffusion layer 23b toward the longitudinal direction Y of the projection region 23g, a length a of ½ × L × cos θ (a portion 23h having 0.71 mm, ie, the projection region 23 g is formed between the center part of the longitudinal direction Y. Moreover, as shown in FIG. Extending by 5 mm and having a width of 1 mm, the water repellent portion 8 is formed in the same shape in the projection region 23g of all the bond portions 56 in the diffusion layer 23b on the air electrode side, and is regularly arranged in the plane direction. and are. the area of the water-repellent processing unit 8, 0.71 mm In a. The ratio of the total area of the water repellent portion 8 with respect to the entire surface area of the diffusion layer 23b is 22%.

  The non-water-repellent treatment portion 9 has a bottom portion adjacent to the diffusion layer 23b from a portion exceeding the length a of ½ × L × cos θ from the edge portion 23f of the bottom contact portion 23c toward the longitudinal direction of the projection region 23g. It arrange | positions between the contact parts 23c. Further, the non-water-repellent treatment part 9 has a distance of 0.5 mm from the center of the width H in the direction of the width H of the bond part 56, and is 0 from the center of the width H in the direction of the width H of the adjacent bond part 56. It is located in the area up to 5mm away. Accordingly, the non-water-repellent treatment part 9 is located in the vicinity of the opening of the mesh 51.

  The cushion material 3 is made of a carbon cloth having a thickness of 300 μm. Carbon cloth is a woven fabric of carbon fibers. Separator 6a, 6b consists of a stainless steel flat plate without the unevenness | corrugation for flow-path formation.

  A method for manufacturing the fuel cell of this example will be described. First, a catalyst layer on the air electrode side composed of 1 g of carbon fine particles (Ketjen Black International Co., Ltd., Ketjen Black EC) supporting 45% by weight of platinum and 2.2 g of a polymer electrolyte (DuPont SE20092). 22b, a catalyst layer 22a on the fuel electrode side composed of 1 g of carbon fine particles (Nippon Cabot, Vulcan XC-72R) loaded with 30% by mass of platinum and 3.5 g of a polymer electrolyte (DuPont, SE20092) Was hot-pressed onto an electrolyte membrane 21 made of a polymer electrolyte membrane (Nafion 112, manufactured by DuPont). Thus, catalyst layers 22a and 22b were formed on the air electrode side and the fuel electrode side of the electrolyte membrane 21.

  Next, a mixed solution of carbon black and PTFE dispersion (dispersion) was applied onto the carbon cloth, dried, and fired to form diffusion layers 23a and 23b on the surfaces of the catalyst layers 22a and 22b.

  Next, the cushion material 3 made of carbon cloth was disposed on the surface of the diffusion layer 23a on the fuel electrode side.

Next, on the surface on the flow path forming material 5b side of the diffusion layer 23b on the air electrode side, the area of width (b) 1 mm × length (a) 0.71 mm = 0.71 mm ² in the direction of length a A water repellent portion 8 having a pitch P of 2 mm was formed. In the water repellent treatment, after masking the portion of the diffusion layer where the water repellent treatment is not formed, PTFE dispersion (Mitsui / Dupont Fluoro Chemical Co., Ltd. 31-JR) was applied to the opening of the mask by spraying. Thereafter, the water repellent portion 8 was dried and fired. No water repellent portion was formed on the surface of the diffusion layer 23a on the fuel electrode side.

Next, the fuel electrode-side cushion material 3 and the air electrode-side diffusion layer 23b are sandwiched between the flow path forming materials 5a and 5b made of the expanded metal 50, and are sandwiched between the separators 6a and 6b from the outside to produce the battery cell 1. did.
Example 2
A water repellent treatment part was formed on the flow path forming material side of the diffusion layer on the air electrode side by the same production method as in Example 1. FIG. 7 shows the arrangement of the water-repellent treatment unit 8 and the non-water-repellent treatment unit 9 of this example. The water repellent treatment portions 8 are arranged with the non-water repellent treatment portions 9 interposed in both the longitudinal direction Y and the width direction X of the projection region 23g. The water repellent portion 8 has a length a of 1.42 mm and a width b of 1 mm. The length a of the water repellent treatment unit 8 is equal to the length in the longitudinal direction Y of the projection region 23g. The water repellent portion 8 is formed in a portion 23i having a length a (1.42 mm) of L × cos θ from the edge 23f of the bottom contact portion 23c of the diffusion layer 23b toward the longitudinal direction Y of the projection region 23g. ing. The area of the water repellent treatment part 8 is 1.42 mm ² . The ratio of the total area of the water repellent portion 8 to the entire surface area of the diffusion layer 23b is 44%. Others are the same as in the first embodiment.
Example 3
A water repellent treatment part was formed on the flow path forming material side of the diffusion layer on the air electrode side by the same production method as in Example 1. The length a of the water repellent portion was 0.35 mm, and the width b was 1 mm. The water repellent treatment portion 8 is formed on a portion having a length a (0.35 mm) of 1/4 × L × cos θ from the edge portion 23f of the bottom contact portion 23c of the diffusion layer 23b toward the longitudinal direction of the projection region 23g. Is formed. The area of the water repellent treatment part 8 is 0.35 mm ² . The ratio of the combined area of the water repellent portion 8 to the entire surface area of the diffusion layer 23b is 11%. Others are the same as in the first embodiment.
Comparative Example 1
The difference from the first embodiment is that a water repellent portion is not formed on the flow path forming material side of the diffusion layer on the air electrode side. Others are the same as in the first embodiment.
Experimental Example The battery cells produced in Examples 1 to 3 and Comparative Example 1 were discharged under a discharge condition of 0.2 A / cm ² under a cell temperature of 60 ° C. and full humidification (humidity of 100%). The average voltage and voltage deviation at this time are shown in Table 1.

  As is known from the table, in Examples 1 to 3, the average voltage was higher and the voltage deviation was smaller than in Comparative Example 1. This is because the water repellent treatment portion 8 is formed on at least a part of the projection region 23g of the inclined portion 56c from the edge portion 23f of the bottom contact portion 23c of the expanded metal 50 in the diffusion layer 23b on the air electrode side. It is presumed that the water repellency was imparted to the water and the generated water did not accumulate, resulting in improved drainage. In addition, since the non-water-repellent treatment part 9 is arranged in the bottom contact part 23c which is an electron distribution path, the electron distribution is ensured, and the surface of the diffusion layer 23b is in the vicinity immediately below the mesh 51. Since the non-water-repellent treatment part 9 remains, the fact that the reaction gas can be sufficiently circulated through this part is also considered as one of the factors that increase the power generation performance.

  In particular, Examples 1 and 2 had a higher average voltage and a smaller voltage deviation than Example 3. In Examples 1 and 2, the portion forming the water repellent treatment portion is ½ × L × cos θ or more from the edge portion 23f of the bottom contact portion 23c toward the longitudinal direction of the projection region 23g of the inclined portion 56c. It is formed in a portion having a length less than L × cos θ. This portion is a portion close to the bottom contact portion 23c, which is an electron flow path, in the projection region 23g of the inclined portion 56c, and is a portion where generated water is actively generated, and is a narrow space behind the inclined portion 56c. It is. Therefore, this portion is a portion where generated water tends to accumulate particularly on the surface of the diffusion layer 23b. In Examples 1 and 2, the water-repellent treatment part 8 is formed in this portion, and the area of the water-repellent treatment part capable of repelling the generated water is larger than that in Example 3, and the water repellency is high. This is thought to be because of

  On the other hand, in Comparative Example 1, the power generation performance was low. This is presumably because the water repellent portion was not formed, and water accumulated on the surface of the diffusion layer 23b, particularly in the vicinity of the bottom contact portion 23c in the projection region 23g of the inclined portion 56c. .

It is sectional explanatory drawing of the battery cell of the fuel cell in Example 1 which concerns on this invention. 2 is a plan view of an expanded metal of Example 1. FIG. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. It is a BB arrow line sectional view of Drawing 2. FIG. 3 is a cross-sectional explanatory view of a flow path forming material on the air electrode side in Example 1. FIG. 3 is a plan view of a diffusion layer showing a positional relationship between a water repellent treatment part and an expanded metal in Example 1. In Example 2, it is a top view of the diffusion layer which shows the arrangement | positioning relationship between the water-repellent process part and an expanded metal.

Explanation of symbols

1: battery cell, 2: membrane electrode assembly, 3: cushion material, 5a: fuel electrode side flow path forming material, 5b: air electrode side flow path forming material, 6a: fuel electrode side separator, 6b: air Electrode side separator, 6c: top contact part, 8: water repellent treatment part, 9: non-water repellent treatment part, 21: electrolyte membrane, 22a: fuel electrode side catalyst layer, 22b: air electrode side catalyst layer, 23a : Diffusion layer on the fuel electrode side, 23b: diffusion layer on the air electrode side, 23c: bottom contact portion, 23f: edge, 23g: projection region, 50: expanded metal, 51: mesh, 52: wall, 55: strand Part, 56: bond part, 56a: bottom part, 56b: top part, 56c: inclined part.

Claims (4)

A membrane electrode assembly in which a catalyst layer and a diffusion layer are disposed on both the fuel electrode side and the air electrode side of the electrolyte membrane, and disposed on both the fuel electrode side and the air electrode side of the membrane electrode assembly. A fuel cell comprising a flow path forming material and a separator disposed on a surface of the flow path forming material,
Among the flow path forming materials provided on both surfaces of the membrane electrode assembly, at least the flow path forming material on the air electrode side is a plurality of meshes arranged in communication with the diffusion layer and the separator. It consists of a conductive porous body having a through hole and a wall part that partitions between the adjacent through holes,
The wall portion is formed by repeating irregularities in the thickness direction and regularly arranging inclined portions having a bottom portion at one end and a top portion at the other end,
The diffusion layer has a bottom contact portion in contact with the bottom portion, and the separator has a top contact portion in contact with the top portion,
Between the edge portion of the bottom contact portion of the diffusion layer and at least a part of the projection region formed by projecting the inclined portion of the flow path forming material onto the diffusion layer, a water repellent treatment portion is provided. Formed,
The non-water-repellent treatment portion that is not subjected to water-repellent treatment is provided between the bottom contact portion and the adjacent bottom contact portions other than the water-repellent treatment portion. Fuel cell. When the inclination angle formed by the diffusion layer and the inclined portion is θ and the length of the inclined portion is L,
The water repellent portion is formed in a portion having a length of ½ × L × cos θ or more and less than L × cos θ from the edge of the bottom contact portion toward the longitudinal direction of the projection region. The fuel cell according to claim 1.   The fuel cell according to claim 1, wherein the conductive porous body is an expanded metal.   The fuel according to any one of claims 1 to 3, wherein a cushion material is interposed only between the flow path forming material on the fuel electrode side and the membrane electrode assembly. battery.

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