JP2010146769A - Membrane-electrode assembly and fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane-electrode assembly 1, which can effectively prevent short-circuit due to piercing of a fibrous material forming a diffusion layer 5 into an electrolyte film 2, and can be manufactured with high productivity. <P>SOLUTION: In the membrane-electrode assembly 1, two opposing sides 5a of a diffusion layer 5 are located outside beyond a catalyst layer 4, and other two opposing sides 5b are located in the inside of side peripheries 4b of the catalyst layer 4. Stiffening members 10 preventing a fibrous material contained in the diffusion layer 5 from penetrating is arranged in a side of the two opposing sides of a side where a region where the diffusion layer 5 is located outside beyond the catalyst layer 4 in the electrolyte film 2 is located. Since the stiffening members 10 exist only in the side of the two opposing sides of the electrolyte film 2, the membrane-electrode assembly 1 can be continuously manufactured by using an electrolyte film of a strip shape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly that forms a power generation unit of a fuel cell, and a fuel cell stack including the membrane electrode assembly, and in particular, a fibrous material constituting a diffusion layer causes a short circuit through an electrolyte membrane. The present invention relates to a membrane electrode assembly and a fuel cell stack having a configuration for preventing the above.

  A polymer electrolyte fuel cell is known as one of the fuel cells, and a main component is a membrane electrode assembly including an electrolyte membrane and an electrode layer in which a catalyst layer and a diffusion layer are laminated in this order on both sides. Element. The diffusion layer has a function of permeating the oxidant gas or fuel gas supplied from the gas flow path of the separator toward the catalyst layer and collecting the generated electricity, and is usually a carbon made of carbon fiber. Made of cloth or carbon paper. The membrane electrode assembly is sandwiched between separators having gas flow paths to form a fuel cell stack.

  In manufacturing the membrane electrode assembly, a catalyst layer is formed on the surface of the electrolyte membrane by coating or transferring, and a diffusion layer is laminated thereon. For the purpose of improving the power generation performance, a diffusion layer having a larger area than the catalyst layer may be laminated on the catalyst layer, and in this case, the periphery of the diffusion layer is in direct contact with the electrolyte membrane. In the case of a membrane electrode assembly having a structure in which the electrolyte membrane and the diffusion layer are in direct contact, carbon fibers constituting the diffusion layer may pierce the electrolyte membrane due to the fastening pressure during stacking. Depending on the mode of piercing, there is a possibility of causing a short circuit during power generation, and it is required to take measures to avoid the short circuit.

  In Patent Document 1, a first membrane reinforcing member is disposed along two opposing sides on one surface of a rectangular electrolyte membrane, and along the other two opposing sides on the other surface. The second membrane reinforcing member is arranged, one catalyst layer is arranged between the first membrane reinforcing members, the other catalyst layer is arranged between the second membrane reinforcing members, and the second membrane reinforcing member is placed on the first membrane reinforcing member. A membrane electrode assembly is described in which a diffusion layer having a thickness and a diffusion layer having a size on a second membrane reinforcing member are laminated on both sides. In this form of membrane electrode assembly, even when a diffusion layer having a larger area than the catalyst layer is laminated on the catalyst layer, the carbon fibers constituting the diffusion layer pass through the electrolyte membrane during stacking. The first film reinforcing member and the second film reinforcing member can be used to prevent the occurrence of a short circuit.

Japanese Patent Laid-Open No. 2007-242637

  In the membrane electrode assembly described in Patent Document 1, the first membrane reinforcing member and the second membrane reinforcing member are arranged in two orthogonal directions on the electrolyte membrane, and a predetermined shape is provided on the belt-shaped electrolyte membrane. Of a membrane electrode assembly in which an electrode layer composed of a catalyst layer and a diffusion layer is continuously arranged at a distance of, and then the electrolyte membrane portion of the joint is cut and separated for each membrane electrode assembly In order to apply to the method, as described in Patent Document 1, the treatment step of arranging the first membrane reinforcing member on the belt-shaped electrolyte membrane and the first step in a direction orthogonal to the first membrane reinforcing member are performed. The treatment process for arranging the two-membrane reinforcing member needs to be performed as a separate process, which is not sufficient from the viewpoint of productivity.

  It is an object of the present invention to provide a membrane electrode assembly that solves the above-mentioned problems, and more specifically, it is effective to cause a fibrous material forming a diffusion layer to pierce an electrolyte membrane and cause a short circuit. It is an object of the present invention to provide a membrane / electrode assembly that can be manufactured with high productivity.

The membrane electrode assembly according to the present invention is a membrane electrode assembly in which a catalyst layer and a diffusion layer are laminated in this order on both surfaces of an electrolyte membrane, and the diffusion layer includes a fibrous substance, and the diffusion layer is opposed to the membrane electrode assembly. Two sides are located outside the catalyst layer, the other two opposite sides are located inward from the side edge of the catalyst layer, and the diffusion layer in the electrolyte membrane is the catalyst layer. A reinforcing material capable of preventing the fibrous substance contained in the diffusion layer from passing through is disposed on the two opposite sides on the side where the region located outside is located. To do.
The present invention also discloses a fuel cell stack including the membrane electrode assembly.

  In the membrane electrode assembly according to the present invention, the fibrous material contained in the diffusion layer passes only on the two opposite sides of the electrolyte membrane on the side where the diffusion layer is located outside the catalyst layer. The reinforcing material which can prevent this is disposed, and the reinforcing material is not disposed on the other two opposite sides of the electrolyte membrane. Then, on the other two opposite sides of the electrolyte membrane, the side edge of the diffusion layer is located on the inner side from the side edge of the catalyst layer.

  On the side of the membrane electrode assembly where the reinforcing material is disposed, the reinforcing material can prevent the fibrous material of the diffusion layer from penetrating the electrolyte membrane. In addition, on the other side of the membrane electrode assembly, the catalyst layer is positioned under the diffusion layer, whereby the fibrous material in the diffusion layer can be prevented from reaching the electrolyte membrane by the catalyst layer. For this reason, it is possible to effectively prevent the fibrous material forming the diffusion layer from being stuck into the electrolyte membrane and causing a short circuit. Thereby, the fuel cell stack including the membrane electrode assembly according to the present invention has high power generation performance and a long life.

  Further, as described above, the reinforcing material is disposed only on the two opposing sides of the electrolyte membrane, and a step of arranging the reinforcing material in the orthogonal direction is not required, so a strip-shaped electrolyte membrane is used. Even when the membrane electrode assembly is continuously manufactured, the membrane electrode assembly can be manufactured without interrupting the manufacturing process, and high productivity can be ensured.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a schematic view of an embodiment of a membrane electrode assembly according to the present invention, and FIG. 2 is a schematic view of another embodiment. 3-5 is a schematic diagram explaining one form when manufacturing the membrane electrode assembly by this invention in order of a work process.

  In FIG. 1, a membrane electrode assembly 1 has a rectangular shape as a whole, and has an electrolyte membrane 2 having proton conductivity having, for example, a sulfonic acid group as a proton exchange group, and an electrode layer 3 laminated on both surfaces (in FIG. 1). Only one of them is shown). The electrode layer 3 includes a catalyst layer 4 facing the electrolyte membrane 2 and a diffusion layer 5 laminated on the outside thereof. A water repellent layer may be formed in a region of the diffusion layer 5 facing the catalyst layer 4.

  The electrode layer 3 is sized to enter the electrolyte membrane 2 as a whole, and a portion extending from the periphery of the electrode layer 3 of the electrolyte membrane 2 is not shown in FIG. A resin material is filled as a gasket (seal member) between the overhanging portion and a separator (not shown), and integration and a sealing process are performed.

  As shown in the figure, the diffusion layer 5 in the electrode layer 3 is positioned outside the catalyst layer 4 with its two opposing sides 5a and 5a passing over the two opposing side edges 4a and 4a of the catalyst layer 4. I am letting. On the other hand, the other two opposite side edges 5b, 5b of the diffusion layer 5 are positioned inside the other two opposite side edges 4b, 4b of the catalyst layer 4.

  The electrolyte membrane 2 is formed by laminating two electrolyte membranes 2 a and 2 b, between the two electrolyte membranes 2 a and 2 b, and the diffusion layer 5 is one side edge 4 a of the catalyst layer 4. , 4a, reinforcing materials 10 and 10 are arranged in the side region opposite to the region located outside.

  The catalyst layer 4 is formed of a catalyst mixture including an electrolyte resin and a catalyst-carrying conductor. Platinum-based metals are mainly used for the catalyst, and carbon powder is mainly used for the conductor supporting the catalyst. The diffusion layer 5 is made of, for example, carbon cloth or carbon paper containing carbon fibers as a fibrous material.

  The reinforcing material 10 may be any material that can prevent the fibrous substance contained in the diffusion layer 5 from passing through. Examples thereof include polyethylene naphthalate, polytetrafluoroethylene, polyethylene terephthalate, and fluoroethylene-propylene. Copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, polyethylene, polypropylene, polyether amide, polyether imide, polyether ether ketone, polyether sulfone, polyphenylene sulfide, polyarylate, polysulfide, polyimide, and polyimide It is preferably at least one synthetic resin selected from the group consisting of amides.

  The membrane electrode assembly 1 shown in FIG. 1 is stacked with a separator (not shown) to form a fuel cell stack. At the time of stacking, the region where the diffusion layer 5 is located outside the side edges 4a, 4a of the catalyst layer 4 is in direct contact with the electrolyte membrane 2. Then, due to the fastening pressure at the time of stacking, the two are brought into a pressure contact state, and the carbon fibers constituting the diffusion layer 5 may pierce the electrolyte membrane 2. However, since the pierced carbon fiber is prevented from further intrusion by the reinforcing material 10, the carbon fiber does not penetrate the electrolyte membrane 2, and the carbon fibers entering from both sides do not contact each other. . Thereby, short-circuiting of both the anode and cathode electrode layers 3 and 3 is avoided.

  On the other hand, the other two opposite sides 5b and 5b side of the diffusion layer 5 are positioned so that the catalyst layer 4 extends from the two sides 5b and 5b below, thereby forming the diffusion layer 5. The carbon fiber to be pierced into the electrolyte membrane 1 is prevented. As a result, in the membrane / electrode assembly 1 according to the present invention, it is possible to reliably avoid the short-circuit phenomenon that is likely to occur when the fibrous material forming the diffusion layer 5 pierces the electrolyte membrane 2 due to the fastening pressure or the like during stacking. .

  In the membrane / electrode assembly 1a shown in FIG. 2, the reinforcing material 10 is arranged not on the two electrolyte membranes 2a and 2b but on both surfaces of the single electrolyte membrane 2, and the catalyst layer 4 is made of the reinforcing material. The membrane electrode assembly 1 is different from the membrane electrode assembly 1 shown in FIG. The other members are the same as those of the membrane electrode assembly 1 shown in FIG. Also in the case of the membrane electrode assembly 1a having the form shown in FIG. 2, it is not necessary to explain that the fibrous material forming the diffusion layer 5 can be reliably prevented from being stuck into the electrolyte membrane 2 by the fastening pressure at the time of stacking. .

  The above-described membrane electrode assembly 1, 1a can be made by any method. For example, the membrane electrode assembly 1a shown in FIG. 1 can be continuously manufactured by the method shown in FIGS. In FIG. 3, reference numeral 20 denotes a raw roll of the strip-shaped electrolyte membrane 2, and the strip-shaped electrolyte membrane 2 unwound from the roll is wound on a winding roll 21. In that process, the catalyst ink is intermittently applied from the tank 22 onto the strip-shaped electrolyte membrane 2 by a conventionally known method, and an appropriate drying process is performed, so that the catalyst layer 4. It is formed continuously. This treatment is performed in both the anode side catalyst layer and the cathode side catalyst layer.

  As shown in FIG. 4, the strip-shaped electrolyte membrane 2a formed with the anode-side catalyst layer and the strip-shaped electrolyte membrane 2b formed with the anode-side catalyst layer are separated from the raw rolls 23 and 24 with the catalyst layer 4 outward. It is unwound so as to face each other in the posture. A reinforcing material roll 25 in which the above-described reinforcing material 10 is wound in a roll shape is located between the two raw rolls 23 and 24, and extends from the reinforcing material roll 25 along both sides of the belt-shaped electrolyte membrane. In this manner, the two strip-shaped reinforcing materials 10 and 10 having a width from the side edges of the electrolyte membranes 2a and 2b to the side edges of the catalyst layer 4 are unwound.

  A pair of hot-pressing rolls 26, 26 are positioned downstream of the reinforcing material roll 25, and the two strip-shaped electrolyte membranes 2 a, 2 b are strip-shaped reinforcing materials 10, 10 at positions along both side edges. In a posture in which is positioned, the pressure is integrally pressed by the pair of hot-pressing rolls 26 and 26. The laminate 30 composed of the electrolyte membranes 2 a and 2 b provided with the catalyst layers 4 and 4 on both surfaces which are pressed and integrated and the reinforcing materials 10 and 10 is wound around a roll 27.

  As shown in FIG. 5, the laminate 30 is unwound from a roll 27, and the diffusion layer 5 is laminated on the catalyst layer 4 to form the electrode layer 3, thereby forming the membrane electrode assembly 1. In the present invention, the size of the diffusion layer 5 to be stacked is such that the size of the diffusion layer 5 enters the width of the stack 30 in the feed direction P of the stack 30 in the feed direction P of the stack 30. The width of the catalyst layer 4 is larger than the width of the catalyst layer 4 in the direction perpendicular to the feeding direction P of the laminate 30, and smaller than the width of the electrolyte membranes 2a and 2b in the direction perpendicular to the feeding direction P. Yes.

  In this way, a large number of membrane electrode assemblies 1 are continuously formed using the electrolyte membrane 2 as a connecting material, and the connecting portion of the electrolyte membrane 2 is cut by the cutter 40 in the course of feeding, As a membrane electrode assembly 1.

  As described above, the membrane electrode assembly 1 having the configuration shown in FIG. 1 according to the present invention can be continuously manufactured using the strip-shaped electrolyte membrane. Moreover, both the membrane electrode assembly 1 of the form shown in FIG. 1 and the membrane electrode assembly 1a of the form shown in FIG. 2 are the structures which arrange | position the reinforcement material 10 along only one opposing two sides, 4 Compared with the embodiment in which the reinforcing material is arranged along the side, the manufacturing cost can be reduced.

  Although not shown, a fuel cell stack having high power generation performance can be obtained by sandwiching the membrane electrode assembly with a separator having a gas flow path by a conventionally known technique.

The schematic diagram of one Embodiment of the membrane electrode assembly by this invention. The schematic diagram of other embodiment of the membrane electrode assembly by this invention. The 1st figure explaining the one aspect | mode which manufactures the membrane electrode assembly by this invention. The 2nd figure explaining the one aspect | mode which manufactures the membrane electrode assembly by this invention. The 3rd figure explaining the one aspect | mode which manufactures the membrane electrode assembly by this invention.

Explanation of symbols

1 ... Membrane electrode assembly,
2, 2a, 2b ... electrolyte membrane,
3 ... electrode layer,
4 ... Catalyst layer,
4a ... Two opposite side edges of the catalyst layer,
4b ... the other two opposite side edges of the catalyst layer,
5 ... diffusion layer,
5a ... two opposite sides of the diffusion layer,
5b ... the other two opposite sides 10 of the diffusion layer ... a reinforcing material.

Claims (2)

A catalyst layer and a diffusion layer are laminated in this order on both surfaces of the electrolyte membrane, and the diffusion layer is a membrane electrode assembly including a fibrous substance,
Two opposite sides of the diffusion layer are located outside the catalyst layer, and the other two opposite sides are located on the inner side from the side edge of the catalyst layer. Reinforcing materials capable of preventing the passage of fibrous substances contained in the diffusion layer are disposed on the two opposite sides on the side where the region where the diffusion layer is located outside the catalyst layer is located. A membrane electrode assembly characterized by   A fuel cell stack comprising the membrane electrode assembly according to claim 1.

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