JP5585427B2 - Membrane electrode assembly and fuel cell using the same - Google Patents

Description

  The present invention relates to a fuel cell.

  As a fuel cell, a fuel cell is known that includes a membrane electrode assembly in which electrode layers are arranged on both sides of an electrolyte membrane having proton conductivity. The electrode layer has a gas diffusion layer for spreading the reaction gas over the entire electrode surface and a catalyst layer on which a catalyst for promoting the fuel cell reaction is supported (Patent Document 1 below).

  Here, the electrolyte membrane may be deformed or deteriorated due to thermal contraction during the manufacture of the membrane electrode assembly or during the operation of the fuel cell. In addition, when the gas diffusion layer is composed of a conductive fiber substrate, the electrolyte membrane is damaged or deteriorated by piercing with fluff that is a fine protrusion existing on the outer surface of the fiber substrate. There is a possibility that.

  Furthermore, in a fuel cell, during power generation, hydrogen or oxygen, which is a reactive gas, permeates the electrolyte membrane and moves to an electrode on the side opposite to the electrode on which it is supplied. May occur. When the cross leak occurs, hydrogen and oxygen exist on the same electrode layer side of the membrane electrode assembly, and the possibility that hydrogen peroxide is generated in the electrode layer increases. It is known that hydrogen peroxide generated in the electrode layer is radicalized and causes deterioration of the electrolyte membrane. Until now, it has been the actual situation that no sufficient contrivance has been made to suppress the deterioration of the electrolyte membrane as described above and to suppress the deterioration of the membrane electrode assembly.

JP 2007-213830 A Japanese Patent Laid-Open No. 6-084528 JP 7-13004 A JP 2006-059756 A

  An object of this invention is to provide the technique which suppresses deterioration of a membrane electrode assembly.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A membrane electrode assembly used in a fuel cell, an electrolyte membrane layer having a multilayer structure including first and second electrolyte membranes, and first and second electrode layers disposed on both sides of the electrolyte membrane layer The first electrolyte membrane is disposed on the first electrode layer side, and the second electrolyte membrane is disposed on the second electrode layer side, Each of the first and second electrode layers includes a catalyst layer disposed in contact with the outer surface of the electrolyte membrane layer, and a gas diffusion layer disposed on the catalyst layer. When the electrode layer of the first electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral edge of the catalyst layer in the first electrode layer is located inside the outer peripheral edge of the electrolyte membrane layer, and The outer peripheral end of the gas diffusion layer in the electrode layer is inside the outer peripheral end of the catalyst layer in the first electrode layer And the second electrode layer has at least the outer peripheral ends of the catalyst layer and the gas diffusion layer in the second electrode layer when viewed in a direction perpendicular to the electrode surface. The first electrode layer is located outside the outer peripheral end of the catalyst layer, and the electrolyte membrane layer has an amount of heat shrinkage in a predetermined direction of the first electrolyte membrane, the predetermined amount of the second electrolyte membrane. A membrane / electrode assembly in which thermal deformation of the second electrolyte membrane is suppressed by being configured to be smaller than the amount of thermal contraction in the direction of.
According to this membrane electrode assembly, the catalyst layer prevents the gas diffusion layer and the electrolyte membrane layer from coming into direct contact with each other on the surface on the first electrode layer side. Therefore, it can suppress that the electrolyte membrane of an electrolyte membrane layer deteriorates with the fluff in the outer surface of a gas diffusion layer, or the hydrogen peroxide radical produced | generated in the gas diffusion layer. Further, in this membrane electrode assembly, a seal region for suppressing cross leak of the reaction gas is formed in a region between the outer peripheral end of the gas diffusion layer and the outer peripheral end of the electrolyte membrane layer in the first electrode layer. can do. Furthermore, in this membrane electrode assembly, in the electrolyte membrane layer, the first electrolyte membrane having a small amount of heat shrinkage is disposed on the first electrode layer side, and the second electrolyte membrane having a large amount of heat shrinkage is the second electrode. By arrange | positioning at the layer side, it is suppressed that the outer peripheral edge part of the electrolyte membrane layer turns up to the 1st electrode layer side by thermal deformation.

[Application Example 2]
It is a membrane electrode assembly of the application example 1, Comprising: A said 1st electrolyte membrane is a membrane electrode assembly comprised with the material whose heat shrinkage rate is smaller than a said 2nd electrolyte membrane.
According to this membrane electrode assembly, the electrolyte membrane layer including the first and second electrolyte membranes can be easily configured using materials having different heat shrinkage rates.

[Application Example 3]
It is a membrane electrode assembly of the application example 2, Comprising: A said 1st electrolyte membrane is a membrane electrode assembly comprised with the material whose EW value is larger than a said 2nd electrolyte membrane.
According to this membrane electrode assembly, the electrolyte membrane layer including the first and second electrolyte membranes can be easily configured using materials having different EW values. Further, in this membrane electrode assembly, the first electrolyte membrane in which thermal deformation is suppressed and the second electrolyte membrane having a small EW value, that is, a high ion conductivity, are combined. The ion conductivity can be ensured while improving the deterioration resistance.

[Application Example 4]
The membrane electrode assembly according to any one of Application Examples 1 to 3, wherein the electrolyte membrane layer is provided with a reinforcing member on the first electrolyte membrane, whereby a predetermined member of the first electrolyte membrane is provided. The membrane electrode assembly in which the amount of heat shrinkage in the direction of is reduced more than the amount of heat shrinkage in the predetermined direction of the second electrolyte membrane.
According to this membrane electrode assembly, thermal deformation of the second electrolyte membrane can be suppressed by suppressing thermal contraction of the first electrolyte membrane using the reinforcing member.

[Application Example 5]
The membrane / electrode assembly according to Application Example 1, wherein an outer periphery of the electrolyte membrane layer has a rectangular shape, and the first and second electrolyte membranes are made of the same material as each other and are predetermined in advance. Is assembled to the electrolyte membrane layer in a state in which a tensile stress is applied thereto, and the electrolyte membrane layer is disposed such that the direction in which the tensile stress is applied is a short side direction. The second electrolyte membrane is disposed such that the direction in which the tensile stress is applied is the long side direction, whereby the amount of thermal contraction in the long side direction of the first electrolyte membrane is the first side. A membrane electrode assembly configured to be smaller than the amount of thermal contraction in the long side direction of the electrolyte membrane of 2.
According to this membrane / electrode assembly, it is possible to easily suppress thermal deformation of the electrolyte membrane layer by applying tensile stress to the first and second electrolyte membranes in advance.

[Application Example 6]
It is a membrane electrode assembly as described in any one of application examples 1-5, Comprising: When the said 2nd electrode layer sees along a direction perpendicular | vertical to an electrode surface, the said catalyst layer and the said gas diffusion A membrane electrode assembly, wherein an outer peripheral end of the layer substantially overlaps with an outer peripheral end of the electrolyte membrane layer, and a seal portion for suppressing fluid leakage is formed at the outer peripheral end of the electrolyte membrane layer.
According to this membrane electrode assembly, the entire one surface of the electrolyte membrane layer is covered with the second electrode layer, so that the electrolyte membrane layer is further protected. In addition, since the seal portion reliably seals the catalyst layer of the first electrode layer and the catalyst layer of the second electrode layer, occurrence of cross leak of the reaction gas is suppressed.

[Application Example 7]
A fuel cell, comprising: the membrane electrode assembly according to any one of application examples 1 to 6; and a separator sandwiching the membrane electrode assembly.
According to this fuel cell, since the deterioration of the membrane electrode assembly is suppressed, a decrease in power generation performance is suppressed.

  The present invention can be realized in various forms. For example, a membrane electrode assembly, a fuel cell including the membrane electrode assembly, a fuel cell system including the fuel cell, and a fuel cell system thereof It can be realized in the form of a vehicle or the like equipped with.

Schematic which shows the structure of a fuel cell. Schematic for demonstrating the structure of a 1st electrode layer. Schematic for demonstrating suppression of the deterioration of the electrolyte membrane layer in a membrane electrode assembly. Schematic which shows the structure of the fuel cell as a reference example. Schematic which shows the structure of the fuel cell as 2nd Example. The schematic diagram which decomposes | disassembles and shows the electrolyte membrane layer of 2nd Example. Schematic which shows the structure of the fuel cell as another structural example of 2nd Example. Schematic which shows the structure of the fuel cell as another structural example of 2nd Example. Schematic which shows the structure of the fuel cell as 3rd Example. The schematic diagram which decomposes | disassembles and shows the 1st and 2nd electrolyte membrane which comprises an electrolyte membrane layer. The schematic diagram for demonstrating MD direction in an electrolyte membrane.

A. First embodiment:
FIG. 1 is a schematic diagram showing the configuration of a fuel cell as an embodiment of the present invention. The fuel cell 100 is a polymer electrolyte fuel cell that generates power by receiving supply of hydrogen and oxygen as reaction gases. The fuel cell 100 has a stack structure in which a plurality of single cells 110 are stacked. The single cell 110 includes a membrane electrode assembly 120 and two separators 60 and 70 that sandwich the membrane electrode assembly 120.

  The membrane electrode assembly 120 is provided with first and second electrode layers 20 and 30 on both sides of an electrolyte membrane layer 10 having a multilayer structure in which first and second electrolyte membranes 11 and 12 are laminated in the thickness direction. Power generator. As the first and second electrolyte membranes 11 and 12 included in the electrolyte membrane layer 10, fluororesin ion exchange membranes exhibiting good proton conductivity in a wet state can be used. The first and second electrolyte membranes 11 and 12 are made of materials having different thermal shrinkage rates, and the reason will be described later. The first and second electrolyte membranes 11 and 12 are joined to each other by hot pressing or the like. In FIG. 1, the fact that the first and second electrolyte membranes 11 and 12 are made of materials different from each other is illustrated by hatching with different concentrations, and their junction interfaces are illustrated by broken lines. is there.

  The first electrode layer 20 includes a catalyst layer 21 provided on the outer surface of the first electrolyte membrane 11 and a gas diffusion layer 22 provided on the catalyst layer 21. Similarly, the second electrode layer 30 includes a catalyst layer 31 provided on the outer surface of the second electrolyte membrane 12 and a gas diffusion layer 32 provided on the catalyst layer 31. In the fuel cell 100 according to the present embodiment, the first electrode layer 20 functions as a cathode and the second electrode layer 30 functions as an anode during the operation.

  Each of the catalyst layers 21 and 31 has gas diffusibility and conductivity, and supports a catalyst (for example, platinum (Pt)) for promoting a fuel cell reaction. Each catalyst layer 21, 31 is a mixed solution in which an electrolyte which is the same kind of compound as the catalyst-supporting carbon and the electrolyte membrane is dispersed in a water-soluble solvent or an organic solvent on the outer surface of the first or second electrolyte membrane 11, 12. It can form by apply | coating and drying the catalyst ink which is. In addition, each catalyst layer 21 and 31 is good also as what is formed by transcribe | transferring the catalyst layer previously formed in the surface of a film base material to the outer surface of the 1st or 2nd electrolyte membrane 11 and 12. FIG.

  The gas diffusion layers 22 and 32 are for spreading the reaction gas over the entire catalyst layers 21 and 31. The gas diffusion layers 22 and 32 are formed by placing a porous fiber base material having conductivity and gas diffusion properties such as carbon fiber and graphite fiber on the catalyst layers 21 and 31 and bonding them by hot press or the like. Can be formed. A water repellent layer such as MPL (Micro Porous Layer) may be provided on the surfaces of the gas diffusion layers 22 and 32 on the catalyst layers 21 and 31 side. Here, in the membrane electrode assembly 120, the first and second electrode layers 20 and 30 have different configurations as described below.

  FIG. 2 is a schematic diagram for explaining the configuration of the first electrode layer 20, when the first electrode layer 20 side of the membrane electrode assembly 120 is viewed along a direction perpendicular to the electrode surface. FIG. In the membrane electrode assembly 120 of the first embodiment, the outer peripheral shape of the electrolyte membrane layer 10 has a substantially rectangular shape. Similarly, the catalyst layer 21 and the gas diffusion layer 22 of the first electrode layer 20 have a substantially rectangular outer peripheral shape. The catalyst layer 21 and the gas diffusion layer 22 are arranged so that their long side directions coincide with the long side direction of the electrolyte membrane layer 10.

  Here, in the membrane electrode assembly 120, the first electrode layer 20 includes all the outer peripheral ends of the catalyst layer 21 located inside the outer peripheral end of the electrolyte membrane layer 10 and all the outer peripheral ends of the gas diffusion layer 22. Is configured to be located inside the outer peripheral end of the catalyst layer 21. On the other hand, the second electrode layer 30 is configured such that all the outer peripheral ends of the catalyst layer 31 and the gas diffusion layer 32 substantially overlap with the outer peripheral end of the electrolyte membrane layer 10. Thus, the first and second electrode layers 20 and 30 are formed asymmetrically with respect to the electrolyte membrane layer 10. The reason why the first and second electrode layers 20 and 30 are configured in this manner will be described later.

  When the membrane electrode assembly 120 is assembled as the single cell 110, the seal portion 40 is formed on the outer periphery thereof (FIG. 1). In addition, a cathode separator 60 and an anode separator 70 are disposed on the outer sides of the first and second electrode layers 20 and 30 of the membrane electrode assembly 120 so as to press and hold the seal portion 40 therebetween. A gas flow path member 50 is disposed between each separator 60, 70 and the electrode surface of the membrane electrode assembly 120.

  The seal portion 40 is provided by injection molding of a resin material so as to cover the electrolyte membrane layer 10 of the membrane electrode assembly 120 and the outer peripheral ends of the first and second electrode layers 20 and 30. Ribs (not shown) are formed on the outer surface of the seal portion 40 so that a seal line is formed between the separators 60 and 70 when sandwiched between the separators 60 and 70. . In the fuel cell 100, this seal line suppresses leakage of the reaction gas to the outside of the fuel cell 100.

  Each of the separators 60 and 70 is configured by a gas-impermeable plate member (for example, a metal plate) having conductivity, and functions as a conductive path and a flow path for a reaction gas in the fuel cell 100. A channel groove 61 for oxygen is formed on the surface of the cathode separator 60 on the membrane electrode assembly 120 side, and a channel groove 71 for hydrogen is formed on the surface of the anode separator 70 on the membrane electrode assembly 120 side. Is formed. Each flow channel 61, 71 is formed over the entire region surrounded by the seal portion 40.

  One or both of the channel grooves 61 and 71 may be omitted. Further, the separators 60 and 70 may further be provided with a channel groove for the refrigerant and a manifold for the reaction gas and the refrigerant.

  The two gas flow path members 50 function as gas flow paths between the flow path grooves 61 and 71 of the separators 60 and 70 and the first and second electrode layers 20 and 30 and also as conductive paths. . The gas flow path member 50 can be composed of a member obtained by processing a metal plate such as so-called expanded metal or punching metal into a porous material, or a porous member having conductivity such as a carbon sintered body. Note that one or both of the two gas flow path members 50 may be omitted.

  FIG. 3 is a schematic diagram for explaining suppression of deterioration of the electrolyte membrane layer 10 in the membrane electrode assembly 120 of the present example. FIG. 3 schematically shows only the outer peripheral edge of the membrane electrode assembly 120. As described above, the gas diffusion layers 22 and 32 are made of a fiber base material such as carbon paper or graphite fiber. Usually, fluff is present on the outer surface of the fiber substrate. In particular, there are many fluffs protruding in the thickness direction at the outer peripheral edge. Minute fluff FL is also present on the outer surface of gas diffusion layers 22 and 32 and on the outer peripheral edge thereof. In FIG. 3, for convenience, only the fluff FL protruding toward the catalyst layers 21 and 31 of the gas diffusion layers 22 and 32 is schematically illustrated, and the fluff FL in other portions is not illustrated. is there.

  Here, when the gas diffusion layers 22 and 32 and the electrolyte membrane layer 10 are in direct contact with each other or extremely close to each other, the fluff FL of the gas diffusion layers 22 and 32 pierces the electrolyte membrane layer 10 and the electrolyte. The film layer 10 is damaged / deteriorated. When microholes due to fluff are generated in the electrolyte membrane layer 10, there is a high possibility that reactive gas cross-leakage or short-circuit between electrodes occurs during operation of the fuel cell 100.

  However, in the membrane electrode assembly 120 of the present example, the outer peripheral end of the gas diffusion layer 22 is positioned inside the outer peripheral end of the catalyst layer 21 in the first electrode layer 20. Therefore, direct contact between the gas diffusion layer 22 and the first electrolyte membrane 11 of the electrolyte membrane layer 10 is avoided, and the electrolyte membrane due to the fluff FL of the gas diffusion layer 22 sticking into the electrolyte membrane layer 10 is avoided. Damage and deterioration of the layer 10 are suppressed. That is, in the first electrode layer 20, the catalyst layer 21 functions as a protective layer that separates the gas diffusion layer 22 and the electrolyte membrane layer 10 and protects the electrolyte membrane layer 10 from piercing by the fluff FL.

  Further, in the membrane electrode assembly 120 of the present example, in the second electrode layer 30, the outer peripheral end faces of the catalyst layer 31 and the gas diffusion layer 32 are substantially aligned with the outer peripheral end face of the electrolyte membrane layer 10, and the gas diffusion The outer peripheral end of the layer 32 does not protrude from the outer peripheral end of the catalyst layer 31. Therefore, also in the second electrode layer 30, the catalyst layer 31 suppresses the direct contact between the gas diffusion layer 32 and the second electrolyte membrane 12 of the electrolyte membrane layer 10, and the gas diffusion layer 32. The electrolyte membrane layer 10 is protected from piercing by the fluff FL.

By the way, in the fuel cell, during the power generation, the reaction gas may move through the electrolyte membrane to the electrode opposite to the supplied electrode. If hydrogen and oxygen exist on the same electrode side due to the permeation and transfer of the reaction gas, hydrogen and oxygen may react with each other to generate hydrogen peroxide (H ₂ O ₂ ). is there. Hydrogen peroxide generated in the membrane electrode assembly is radicalized to deteriorate the electrolyte membrane.

  However, there is a high possibility that hydrogen peroxide radicals obtained by radicalizing hydrogen peroxide are converted into water and oxygen by the action of the catalyst in the catalyst layer and disappear. In the membrane electrode assembly 120 of this example, as described above, in the first and second electrode layers 20 and 30, the catalyst layers 21 and 31 are disposed between the gas diffusion layers 22 and 32 and the electrolyte membrane layer 10. Direct contact is avoided. Therefore, even when hydrogen peroxide is generated in the gas diffusion layers 22 and 32, the hydrogen peroxide radicals can be extinguished in the catalyst layers 21 and 31 before reaching the electrolyte membrane layer 10. .

  Furthermore, in the membrane electrode assembly 120 of the present example, a protruding portion 11e (shown by a one-dot chain line) in which the first electrolyte membrane 11 protrudes from the catalyst layer 21 is formed on the surface on the first electrode layer 20 side. Yes. As described with reference to FIG. 1, in the single cell 110, the seal portion 40 is formed so as to cover the outer peripheral end portion of the membrane electrode assembly 120. That is, when the membrane electrode assembly 120 is assembled to the single cell 110, the protruding portion 11e of the first electrolyte membrane 11 is covered with the seal portion 40, and the protruding portion 11e is covered with the first and second electrode layers 20. , 30 functions as a seal region that blocks the movement of gas.

  FIG. 4 is a schematic diagram showing a configuration of a fuel cell 100a as a reference example of the present invention. FIG. 4 shows that the electrolyte membrane layer 10 having a single layer structure is provided in place of the electrolyte membrane layer 10 having a multilayer structure, and that a part of the outer peripheral end of the membrane electrode assembly 120 is deformed to form the seal portion 40. 1 is substantially the same as FIG. 1 except that a state in which a defect has occurred is schematically illustrated.

  In the fuel cell 100a of the reference example, the membrane electrode assembly 120a has the first and second electrode layers 20 and 30 having the same configuration as in the present embodiment. Therefore, also in the fuel cell 100a of the reference example, the electrolyte membrane 10a of the membrane electrode assembly 120a is protected from deterioration due to the fluff FL and hydrogen peroxide radicals of the gas diffusion layers 22 and 32. However, the following problems may occur in the membrane electrode assembly 120a of the reference example.

  Here, in general, the electrolyte membrane constituting the membrane electrode assembly is likely to be deformed due to thermal contraction at a high temperature (for example, 100 ° C.). Therefore, deformation of the electrolyte membrane due to thermal contraction occurs in processes where the electrolyte membrane is heated to a high temperature, such as a joining process between members in a fuel cell manufacturing process or an injection molding process for forming a seal portion. There is a possibility that. Therefore, it is preferable that the entire surface of the electrolyte membrane is securely held in such a heating step.

  However, in this reference example, the entire surface of the electrolyte membrane 10a on the second electrode layer 30 side is covered and held by the second electrode layer 30, whereas the surface on the first electrode layer 20 side is The outer peripheral edge of the electrolyte membrane 10a protrudes from the catalyst layer 21 and is not held. Therefore, the electrolyte membrane 10a is likely to be thermally deformed such as being turned up to the first electrode layer 20 side by heating in the bonding process of the gas diffusion layers 22 and 32 and the injection molding process of the seal portion 40.

  In particular, in the injection molding process of the seal portion 40, heating is performed with the catalyst layers 21 and 31 formed on both surfaces of the electrolyte membrane 10a. Generally, the constituent member of the electrolyte membrane has a higher heat shrinkage rate than the constituent member of the catalyst layer. Therefore, in the injection molding process of the seal portion 40, the thermal contraction on the second electrode layer 30 side is suppressed from the first electrode layer 20 side by the catalyst layer 31 at the outer peripheral end portion of the electrolyte membrane 10a. Internal stresses that antagonize each other are generated between the electrode layer 20 side and the second electrode layer 30 side. Therefore, the outer peripheral end of the electrolyte membrane 10 a may be separated from the gas diffusion layer 32 together with the catalyst layer 31 and turn up. As described above, when thermal deformation occurs at the outer peripheral end of the membrane electrode assembly 120 due to the difference in thermal shrinkage between the electrolyte membrane 10a and the catalyst layer 31 on the second electrode layer 30 side, as shown in FIG. There is a possibility of causing molding failure of the seal portion 40.

  Therefore, in the membrane electrode assembly 120 (FIG. 1) of the present embodiment, the first electrolyte membrane 11 is made of a material having a smaller thermal contraction rate than the second electrolyte membrane 12. That is, in the electrolyte membrane layer 10, the amount of heat shrinkage in the long side direction and the short side direction of the first electrolyte membrane 11 is less than the amount of heat shrinkage in the long side direction and short side direction of the second electrolyte membrane 12. ing. Therefore, in the heating process such as the injection molding process of the seal portion 40, the second electrolyte membrane 12 that is in contact with the catalyst layer 31 is moved to the first electrode layer 20 side like the electrolyte membrane 10a of the reference example. Thermal deformation is suppressed by the first electrolyte membrane 11 having a small amount of heat shrinkage. That is, in the membrane electrode assembly 120 of this example, in the electrolyte membrane layer 10 having a multilayer structure, the first electrolyte membrane 11 having a small amount of thermal shrinkage is in contact with the catalyst layer 31. It functions as a support part that suppresses thermal deformation.

  By the way, the thermal contraction rate of the solid electrolyte has a correlation with its EW value (Equivalent Weight). Here, the EW value is a value corresponding to the inverse of the ion exchange capacity (that is, the number of ion exchange groups per unit amount of the solid electrolyte). Usually, the solid electrolyte has a lower rigidity as the number of ion exchange groups is larger, and therefore the thermal contraction rate tends to be higher. That is, the heat shrinkage rate becomes lower as the solid electrolyte has a higher EW value. Therefore, the electrolyte membrane layer 10 may be configured such that the first electrolyte membrane 11 is made of a solid electrolyte material having an EW value larger than that of the second electrolyte membrane 12. The EW value of the solid electrolyte can be measured by a so-called neutralization titration method.

  Thus, according to the membrane electrode assembly 120 of the present embodiment, in the manufacturing process of the fuel cell 100, the first electrolyte membrane 11 having a small heat shrinkage rate is the outer periphery of the second electrolyte membrane 12 having a low heat shrinkage rate. In order to suppress thermal deformation of the end, deterioration due to thermal deformation of the electrolyte membrane layer 10 is suppressed. In the case of the membrane electrode assembly 120, damage to the electrolyte membrane layer 10 due to the fluff FL of the gas diffusion layers 22 and 32 and deterioration of the electrolyte membrane layer 10 due to hydrogen peroxide radicals are suppressed.

B. Second embodiment:
FIG. 5 is a schematic diagram showing the configuration of a fuel cell 100A as a second embodiment of the present invention. FIG. 5 is substantially the same as FIG. 1 except that a first electrolyte membrane 11A is provided instead of the first electrolyte membrane 11 and a reinforcing member 13 is added. That is, the configuration of the fuel cell 100A of the second embodiment is the same as the configuration of the fuel cell 100 of the first embodiment except that the configuration of the electrolyte membrane layer 10A described below is different.

  FIG. 6 is an exploded schematic view showing the electrolyte membrane layer 10A of the second embodiment. The first electrolyte membrane 11A in the electrolyte membrane layer 10A of the second embodiment is made of the same electrolyte material as that of the second electrolyte membrane 12, and the thermal contraction rate of both is equal. However, in the membrane electrode assembly 120A of the second embodiment, the reinforcing member 13 that is a frame-shaped film member having a shape along the outer peripheral edge of the first electrolyte membrane 11A is provided outside the first electrolyte membrane 11A. Bonded on the surface.

  The reinforcing member 13 can be made of a resin material such as polytetrafluoroethylene (PTFE). In the membrane electrode assembly 120 </ b> A, the catalyst layer 21 of the first electrode layer 20 is formed so as to be accommodated in the frame of the reinforcing member 13.

  By means of this reinforcing member 13, the first electrolyte membrane 11 </ b> A has a heat shrinkage amount in the long side direction and the short side direction that is less than that of the second electrolyte membrane 12. Therefore, in the membrane electrode assembly 120A of the second embodiment, similarly to the membrane electrode assembly 120 of the first embodiment, at the outer peripheral end portion of the electrolyte membrane layer 10A when the membrane electrode assembly 120A is heated. Thermal deformation is suppressed.

  FIG. 7 is a schematic diagram showing a configuration of a fuel cell 100Aa as another configuration example of the second embodiment. FIG. 7 is substantially the same as FIG. 6 except that the arrangement position of the reinforcing member 13 is different. In the electrolyte membrane layer 10Aa of this configuration example, the first and second electrolyte membranes 11A and 12 are joined after the reinforcing member 13 is bonded to the surface of the first electrolyte membrane 11A on the second electrolyte membrane 12 side. It is constituted by doing.

  Even in the membrane electrode assembly 120Aa having the electrolyte membrane layer 10Aa, the amount of thermal contraction in the long side direction and the short side direction of the first electrolyte membrane 11A is similar to the membrane electrode assembly 120A. 13, the second electrolyte membrane 12 is reduced. Therefore, in the manufacturing process of the fuel cell 100, thermal deformation at the outer peripheral end portion of the electrolyte membrane layer 10A when the membrane electrode assembly 120Aa is heated is suppressed.

  FIG. 8 is a schematic diagram showing a configuration of a fuel cell 100Ab as another configuration example of the second embodiment. FIG. 8 is substantially the same as FIG. 7 except that a first electrolyte membrane 11Ab including a reinforcing member 14 is provided instead of the first electrolyte membrane 11A to which the reinforcing member 13 is bonded. The reinforcing member 14 in this configuration example is composed of a porous resin member that can be impregnated with fluid, and has a frame shape similar to that of the reinforcing member 13 in the above configuration example.

  The first electrolyte membrane 11Ab is configured by filling the solid electrolyte in the frame of the reinforcing member 14 and impregnating the solid electrolyte in the pores of the reinforcing member 14 using the reinforcing member 14 as an outer frame base material (matrix). Has been. This solid electrolyte material is the same as the solid electrolyte material constituting the second electrolyte membrane 12.

  Even in such a configuration, in the electrolyte membrane layer 10Ab, since the first electrolyte membrane 11Ab contains the reinforcing member 14 therein, the amount of heat shrinkage in the long side direction and the short side direction is the second amount. It is reduced from the electrolyte membrane 12. Therefore, similarly to the configuration example described with reference to FIG. 7, thermal deformation of the second electrolyte membrane 12 can be suppressed, and deterioration of the electrolyte membrane layer 10 </ b> Ab can be suppressed in the heating process.

C. Third embodiment:
FIG. 9 is a schematic diagram showing the configuration of a fuel cell 100B as a third embodiment of the present invention. FIG. 9 is substantially the same as FIG. 5 except that the reinforcing member 13 is omitted. That is, in the membrane electrode assembly 120B used in the fuel cell 100B of the third embodiment, the first and second electrolyte membranes 11A and 12 constituting the multilayer electrolyte membrane layer 10B are made of the same electrolyte material. They have the same heat shrinkage rate. However, in the electrolyte membrane layer 10B of the membrane electrode assembly 120B, the amount of heat shrinkage in the long side direction of the first electrolyte membrane 11A is reduced as compared with the second electrolyte membrane 12 by the configuration described below. .

  FIG. 10 is an exploded schematic view showing the first and second electrolyte membranes 11A and 12 constituting the electrolyte membrane layer 10B. In FIG. 10, a region where the catalyst layer 21 is formed on the outer surface of the first electrolyte membrane 11 </ b> A is illustrated by a one-dot chain line. Also, in FIG. 10, arrows indicating the MD directions (described later) of the first and second electrolyte membranes 11A and 12 are shown along the short side of the first electrolyte membrane 11A. The electrolyte membrane 12 is illustrated along its long side.

  FIG. 11 is a schematic diagram for explaining the MD (Machine Direction) direction in the electrolyte membrane. Generally, in the manufacturing process of a membrane electrode assembly, the strip-shaped electrolyte membrane 6 drawn out from the roll 5 is cut out and used. Generally, the direction along the direction in which the strip-shaped electrolyte membrane 6 is drawn out from the roll 5 and is conveyed is called “MD direction”, and the direction orthogonal to the MD direction is called “TD (Transverse Direction) direction”. . In the electrolyte membrane, it can be estimated that the direction in which the tensile strength of the electrolyte membrane is lowest among the directions along the surface is the MD direction.

  The first and second electrolyte membranes 11A and 12 are cut out from the strip-shaped electrolyte membrane 6 drawn out from the roll 5 and assembled to the membrane electrode assembly 120B. At the time of this cutting, the first electrolyte membrane 11A is cut out so that the short side direction thereof coincides with the MD direction of the strip-shaped electrolyte membrane 6. On the other hand, the second electrolyte membrane 12 is cut out so that the long side direction thereof coincides with the MD direction of the strip-shaped electrolyte membrane 6.

  Here, when the belt-shaped electrolyte membrane 6 is unwound from the roll 5, a tensile stress along the MD direction is applied, and this tensile stress is applied to the first and second electrolyte membranes 11A and 12. It remains as residual stress. Due to this residual stress, when the first electrolyte membrane 11A is heated, the amount of heat shrinkage in the short side direction is larger than the amount of heat shrinkage in the long side direction, and in the second electrolyte membrane 12, The amount of heat shrinkage in the long side direction is larger than the amount of heat shrinkage in the short side direction.

  In the membrane / electrode assembly 120B of the third embodiment, the electrolyte membrane layer 10B is formed by joining the first and second electrolyte membranes 11A and 12 so that the long side directions thereof coincide with each other. (FIG. 10). That is, in the electrolyte membrane layer 10 </ b> B, the MD directions of the first and second electrolyte membranes 11 </ b> A and 12 are orthogonal to each other, and the first electrolyte membrane 11 </ b> A is heated more than the second electrolyte membrane 12. The heat shrinkage amount in the long side direction is reduced.

  That is, in the membrane electrode assembly 120B of the third embodiment, thermal deformation at the short side of the second electrolyte membrane 12 is suppressed by the first electrolyte membrane 11A. However, in the configuration of the third embodiment, the long side of the second electrolyte membrane 12 is less effective in suppressing thermal deformation by the first electrolyte membrane 11A than the short side. However, the possibility that thermal deformation of the second electrolyte membrane 12 is high is the long side direction in which the heat shrinkage amount is larger than the short side direction in which the heat shrinkage amount due to heating is small. Therefore, in the membrane electrode assembly 120B, the MD direction of the first and second electrolyte membranes 11A and 12 is configured as shown in FIG. 10, so that the thermal deformation of the electrolyte membrane layer 10B in the membrane electrode assembly 120B is sufficient. To be suppressed.

D. 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.

D1. Modification 1:
In the first embodiment, the electrolyte membrane layer 10 has the first and second electrolyte membranes 11 and 12. However, a plurality of electrolyte membranes may be further laminated on the electrolyte membrane layer 10. Specifically, a third electrolyte membrane may be interposed between the first and second electrolyte membranes 11 and 12, and between the first electrolyte membrane 11 and the first electrode layer 20. A third electrolyte membrane may be inserted. That is, the electrolyte membrane layer 10 has a multilayer structure including the first and second electrolyte membranes 11 and 12, and the first electrolyte membrane 11 is disposed on the first electrode layer 20 side, The second electrolyte membrane 12 may be disposed on the second electrode layer 30 side. Similarly, a plurality of electrolyte membranes may be added to the electrolyte membrane layers 10A, 10Aa, 10Ab, and 10B of other embodiments.

D2. Modification 2:
In the fuel cell of the above embodiment, the first electrode layer 20 functions as a cathode, and the second electrode layer 30 functions as an anode. However, in the fuel cell, the first electrode layer 20 may function as an anode, and the second electrode layer 30 may function as a cathode.

D3. Modification 3:
In the first and second embodiments, the outer peripheries of the electrolyte membrane layers 10, 10A, 10Aa, 10Ab, the catalyst layers 21, 31, and the gas diffusion layers 22, 32 have a substantially rectangular shape. However, the outer peripheral shape of the electrolyte membrane layers 10, 10A, 10Aa, 10Ab, the catalyst layers 21, 31, and the gas diffusion layers 22, 32 may not be substantially rectangular, and may be, for example, substantially square. .

D4. Modification 4:
In the above embodiment, in the second electrode layer 30, the positions of the outer peripheral ends of the catalyst layer 31 and the gas diffusion layer 32 are the electrolyte membrane layers 10, 10A, 10Aa when viewed along the direction perpendicular to the electrode surface. , 10Ab, 10B substantially coincided with the outer peripheral end. However, the positions of the outer peripheral ends of the catalyst layer 31 and the gas diffusion layer 32 may not coincide with the outer peripheral ends of the electrolyte membrane layers 10, 10A, 10Aa, 10Ab, and 10B. The positions of the outer peripheral ends of the catalyst layer 31 and the gas diffusion layer 32 may be positioned outside at least the outer peripheral end of the catalyst layer 21 in the first electrode layer 20 when viewed along the direction perpendicular to the electrode surface. It ’s fine. In this case, it is preferable that the outer peripheral end of the gas diffusion layer 32 is located inside the outer peripheral end of the catalyst layer 31. However, the outer peripheral edge of the electrolyte membrane layers 10, 10A, 10Aa, 10Ab, 10B is protected in the fuel cell manufacturing process when the surface on the second electrode layer 30 side is covered with the catalyst layer 31. Therefore, it is preferable.

D5. Modification 5:
In the said 2nd Example, the reinforcement members 13 and 14 were comprised as a frame-shaped member. However, the reinforcing members 13 and 14 may not be configured as frame members. For example, the film-like reinforcing member 13 may be configured as a mesh-like member in which a plurality of through-holes are bonded to the entire surface of the first electrolyte membrane 11A and arranged over the entire surface. The porous reinforcing member 14 may be included in the entire surface of the first electrolyte membrane 11Ab. Alternatively, in the electrolyte membrane layers 10A, 10Aa, and 10Ab, the long side portion or the short side portion of the reinforcing members 13 and 14 are omitted, and one of the long side direction and the short side direction of the first electrolyte membranes 11A and 11Ab is omitted. It is good also as what is comprised so that the amount of thermal contractions in may be reduced from the 2nd electrolyte membrane 12. FIG.

D6. Modification 6:
In the second and third embodiments, the first and second electrolyte membranes are made of the same solid electrolyte material and have the same heat shrinkage rate. However, in the configurations of the second and third embodiments, the first and second electrolyte membranes may be made of different electrolyte materials and have different heat shrinkage rates. The first and second electrolyte membranes may be configured so that the amount of heat shrinkage in the predetermined direction of the first electrolyte membrane is smaller than the amount of heat shrinkage in the predetermined direction of the second electrolyte membrane. .

D7. Modification 7:
In the third embodiment, the electrolyte membrane layer 10B is configured with the MD direction of the first electrolyte membrane 11A as the short side direction and the MD direction of the second electrolyte membrane 12 as the long side direction. However, the electrolyte membrane layer 10B may be configured such that the MD direction of the first electrolyte membrane 11A is the long side direction and the MD direction of the second electrolyte membrane 12 is the short side direction. With this configuration, thermal deformation on the long side of the second electrolyte membrane 12 can be suppressed. In the third embodiment, a third electrolyte membrane having the MD direction as a long side direction may be added on the first electrolyte membrane 11A of the electrolyte membrane layer 10B. According to this structure, generation | occurrence | production of the thermal deformation in the long side of 1st and 2nd electrolyte membrane 11A, 12 can be suppressed.

D8. Modification 8:
In the said 3rd Example, the arrangement direction of 1st and 2nd electrolyte membrane 11A, 12 was prescribed | regulated by the delivery direction (MD direction) of the strip-shaped electrolyte membrane 6 which is those base materials. However, the arrangement direction of the first and second electrolyte membranes 11A and 12 does not have to be defined by the MD direction, and the first and second electrolyte membranes 11A and 12 are preliminarily attached before being assembled as the electrolyte membrane layer 10B. It may be defined by the direction of the applied tensile stress. That is, the first electrolyte membrane 11A is arranged with the tensile stress applied in the short side direction, and the second electrolyte membrane 12 is arranged with the tensile stress applied in the long side direction. The heat shrinkage amount in the long side direction of the first electrolyte membrane 11A may be configured to be smaller than the heat shrinkage amount in the long side direction of the second electrolyte membrane 12.

D9. Modification 9:
In the fuel cells 100, 100 </ b> A, 100 </ b> Aa, 100 </ b> Ab, and 100 </ b> B of the above embodiments, the seal portion 40 is formed so as to cover the outer peripheral end portions of the first and second electrode layers 20 and 30. However, the seal portion 40 only needs to be provided on the outer periphery of the membrane electrode assembly 120, 120 </ b> A, 120 </ b> Aa, 120 </ b> Ab, 120 </ b> B, and does not cover the outer peripheral end portions of the first and second electrode layers 20, 30. Good. That is, part of the outer surface of the electrolyte membrane layers 10, 10 </ b> A, 10 </ b> Aa, 10 </ b> Ab, and 10 </ b> B on the first electrode layer 20 side may be exposed from the seal portion 40.

  Here, when the fuel cell is operated, the fuel cell is at a high temperature (for example, 80 ° C.). However, in the case of a membrane electrode assembly to which the present invention is applied, a part of the outer surface of the electrolyte membrane layer on the first electrode layer side is not supported by the seal portion during operation of the fuel cell. Even so, thermal deformation of the second electrolyte membrane is suppressed by the first electrolyte membrane.

DESCRIPTION OF SYMBOLS 5 ... Roll 6 ... Electrolyte membrane 10, 10A, 10Aa, 10Ab, 10B ... Electrolyte membrane layer 10a ... Electrolyte membrane 11, 11A, 11Ab ... 1st electrolyte membrane 11e ... Projection part 12 ... 2nd electrolyte membrane 13 ... Reinforcement member DESCRIPTION OF SYMBOLS 14 ... Reinforcement member 20 ... 1st electrode layer 21 ... Catalyst layer 22 ... Gas diffusion layer 30 ... 2nd electrode layer 31 ... Catalyst layer 32 ... Gas diffusion layer 40 ... Seal part 50 ... Gas flow path member 60 ... Cathode separator 61 ... Channel groove 70 ... Anode separator 71 ... Channel groove 100, 100A, 100Aa, 100Ab, 100B, 100a ... Fuel cell 110 ... Single cell 120, 120A, 120Aa, 120Ab, 120B, 120a ... Membrane electrode assembly FL ... Fuzz

Claims (7)

A membrane electrode assembly used in a fuel cell,
An electrolyte membrane layer having a multilayer structure including first and second electrolyte membranes;
A first electrode layer disposed on one side of the electrolyte membrane layer;
A second electrode layer disposed on the other side of the electrolyte membrane layer;
With
The first electrolyte membrane is disposed on the first electrode layer side with respect to the second electrolyte membrane, and the second electrolyte membrane is the first electrolyte membrane with respect to the first electrolyte membrane. 2 is disposed on the side of the electrode layer,
Each of the first and second electrode layers has a catalyst layer disposed in contact with the outer surface of the electrolyte membrane layer, and a gas diffusion layer disposed on the catalyst layer,
When the first electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral edge of the catalyst layer in the first electrode layer is located inside the outer peripheral edge of the electrolyte membrane layer, and The outer peripheral edge of the gas diffusion layer in the first electrode layer is located inside the outer peripheral edge of the catalyst layer in the first electrode layer;
When the second electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral ends of the catalyst layer and the gas diffusion layer in the second electrode layer are at least in the first electrode layer. It is located outside the outer peripheral edge of the catalyst layer,
When the electrolyte membrane layer is viewed along a direction perpendicular to the outer surface of the electrolyte membrane layer, the positions of the outer peripheral ends of the first and second electrolyte membranes are aligned,
The electrolyte membrane layer has a length of thermal contraction of the first electrolyte membrane in a predetermined direction along an outer surface of the electrolyte membrane layer, and a length of thermal contraction of the second electrolyte membrane in the predetermined direction. A membrane electrode assembly configured to be smaller than the thickness. A membrane electrode assembly used in a fuel cell,
An electrolyte membrane layer having a multilayer structure including first and second electrolyte membranes;
A first electrode layer disposed on one side of the electrolyte membrane layer;
A second electrode layer disposed on the other side of the electrolyte membrane layer;
With
The first electrolyte membrane is disposed on the first electrode layer side with respect to the second electrolyte membrane, and the second electrolyte membrane is the first electrolyte membrane with respect to the first electrolyte membrane. 2 is disposed on the side of the electrode layer,
Each of the first and second electrode layers has a catalyst layer disposed in contact with the outer surface of the electrolyte membrane layer, and a gas diffusion layer disposed on the catalyst layer,
When the first electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral edge of the catalyst layer in the first electrode layer is located inside the outer peripheral edge of the electrolyte membrane layer, and The outer peripheral edge of the gas diffusion layer in the first electrode layer is located inside the outer peripheral edge of the catalyst layer in the first electrode layer;
When the second electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral ends of the catalyst layer and the gas diffusion layer in the second electrode layer are at least in the first electrode layer. It is located outside the outer peripheral edge of the catalyst layer,
In the electrolyte membrane layer, the first electrolyte membrane is made of a material having a thermal contraction rate smaller than that of the second electrolyte membrane, whereby the first electrolyte membrane layer in a predetermined direction along the outer surface of the electrolyte membrane layer. A membrane electrode assembly, wherein thermal deformation due to thermal contraction of the first electrolyte membrane is suppressed more than thermal deformation due to thermal contraction in the predetermined direction of the second electrolyte membrane. The membrane electrode assembly according to claim 2, wherein
The membrane electrode assembly, wherein the first electrolyte membrane is made of a material having an EW value larger than that of the second electrolyte membrane. A membrane electrode assembly used in a fuel cell,
An electrolyte membrane layer having a multilayer structure including first and second electrolyte membranes;
A first electrode layer disposed on one side of the electrolyte membrane layer;
A second electrode layer disposed on the other side of the electrolyte membrane layer;
With
The first electrolyte membrane is disposed on the first electrode layer side with respect to the second electrolyte membrane, and the second electrolyte membrane is the first electrolyte membrane with respect to the first electrolyte membrane. 2 is disposed on the side of the electrode layer,
Each of the first and second electrode layers has a catalyst layer disposed in contact with the outer surface of the electrolyte membrane layer, and a gas diffusion layer disposed on the catalyst layer,
When the first electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral edge of the catalyst layer in the first electrode layer is located inside the outer peripheral edge of the electrolyte membrane layer, and The outer peripheral edge of the gas diffusion layer in the first electrode layer is located inside the outer peripheral edge of the catalyst layer in the first electrode layer;
When the second electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral ends of the catalyst layer and the gas diffusion layer in the second electrode layer are at least in the first electrode layer. It is located outside the outer peripheral edge of the catalyst layer,
In the electrolyte membrane layer, since the reinforcing member is provided on the first electrolyte membrane, thermal deformation due to thermal contraction of the first electrolyte membrane in a predetermined direction along the outer surface of the electrolyte membrane layer is achieved. The membrane electrode assembly is suppressed from thermal deformation due to thermal contraction in the predetermined direction of the second electrolyte membrane. A membrane electrode assembly used in a fuel cell,
An electrolyte membrane layer having a multilayer structure including first and second electrolyte membranes;
A first electrode layer disposed on one side of the electrolyte membrane layer;
A second electrode layer disposed on the other side of the electrolyte membrane layer;
With
The first electrolyte membrane is disposed on the first electrode layer side with respect to the second electrolyte membrane, and the second electrolyte membrane is the first electrolyte membrane with respect to the first electrolyte membrane. 2 is disposed on the side of the electrode layer,
Each of the first and second electrode layers has a catalyst layer disposed in contact with the outer surface of the electrolyte membrane layer, and a gas diffusion layer disposed on the catalyst layer,
When the first electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral edge of the catalyst layer in the first electrode layer is located inside the outer peripheral edge of the electrolyte membrane layer, and The outer peripheral edge of the gas diffusion layer in the first electrode layer is located inside the outer peripheral edge of the catalyst layer in the first electrode layer;
When the second electrode layer is viewed along a direction perpendicular to the electrode surface, the outer peripheral ends of the catalyst layer and the gas diffusion layer in the second electrode layer are at least in the first electrode layer. It is located outside the outer peripheral edge of the catalyst layer,
The outer peripheral ends of the first and second electrolyte membranes have a rectangular shape,
The first and second electrolyte membranes are made of the same material,
The first electrolyte membrane is assembled to the electrolyte membrane layer in a state in which tensile stress is applied in the short side direction in advance,
The second electrolyte membrane is assembled to the electrolyte membrane layer in a state in which a tensile stress is applied in the long side direction in advance.
In the electrolyte membrane layer, the long side direction of the first electrolyte membrane is aligned with the long side direction of the second electrolyte membrane, and the short side direction of the first electrolyte membrane is short of the second electrolyte membrane. By being aligned in the side direction, thermal deformation due to thermal contraction in the long side direction of the first electrolyte membrane is suppressed more than thermal deformation due to thermal contraction in the long side direction of the second electrolyte membrane. A membrane electrode assembly. A membrane electrode assembly according to any one of claims 1 to 5,
The second electrode layer is configured such that the outer peripheral ends of the catalyst layer and the gas diffusion layer overlap with the outer peripheral end of the electrolyte membrane layer when viewed along a direction perpendicular to the electrode surface. ,
A membrane electrode assembly in which a seal portion for suppressing fluid leakage is formed at an outer peripheral end of the electrolyte membrane layer. A fuel cell,
The membrane electrode assembly according to any one of claims 1 to 6,
A separator for sandwiching the membrane electrode assembly;
A fuel cell comprising:

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