JP2018133160A - Membrane-electrode assembly, manufacturing method thereof, and fuel cell - Google Patents

Abstract

The present invention provides a membrane electrode assembly having high durability by preventing deterioration of a polymer electrolyte membrane from cracks in a catalyst layer. SOLUTION: A solid polymer electrolyte membrane 1, catalyst layers 2a, 2b arranged adjacent to the solid polymer electrolyte membrane 1, and gas diffusion layers 3a, 3b arranged adjacent to the catalyst layers 2a, 2b are provided. A membrane electrode assembly 20 including a pair of electrode layers 14 a and 14 b disposed on both surfaces of the solid polymer electrolyte membrane 1. The gas diffusion layers 3a and 3b include a porous material, and the catalyst layers 2a and 2b have crack portions 7a and 7b in regions where they contact the solid polymer electrolyte membrane 1, and the crack portions 7a and 7b include the porous material. A membrane electrode assembly 20 filled with a porous material. [Selection] Figure 3

Description

  The present disclosure relates to fuel cells. In particular, the present invention relates to a membrane electrode assembly used in the fuel cell and a manufacturing method thereof.

  One type of fuel cell is a polymer electrolyte fuel cell, in which one surface of a hydrogen ion conductive polymer electrolyte membrane is exposed to a fuel gas such as hydrogen and the other is exposed to oxygen, via the polymer electrolyte membrane. The basic principle is to synthesize water by a chemical reaction and to electrically extract the reaction energy generated thereby.

  A unit cell of a polymer electrolyte fuel cell has a membrane electrode assembly (hereinafter also referred to as “MEA”) and a pair of conductive separators disposed on both sides of the MEA.

  The MEA usually includes a hydrogen ion conductive polymer electrolyte membrane and a pair of electrode layers sandwiching the polymer electrolyte membrane. The pair of electrode layers is formed on the catalyst layer, for example, a catalyst layer mainly composed of a carbon powder supporting a platinum group catalyst and an ion conductive resin, which is disposed so as to contact the polymer electrolyte membrane, And a gas diffusion layer having both current collecting action, gas permeability and water repellency.

  Here, many fine cracks exist in the catalyst layer. The minute cracks in the catalyst layer are generated when the solvent component is removed from the coating film after the catalyst layer forming composition is applied to the polymer electrolyte membrane or the transfer film. The composition for forming a catalyst layer is often a mixture of carbon powder carrying a platinum group catalyst, an ion conductive resin, and a solvent, and volume shrinkage when removing the solvent component causes cracks in the catalyst layer. . That is, minute cracks in the catalyst layer are inevitable in principle.

  On the other hand, when a crack exists in the catalyst layer, mechanical stress is likely to be applied to a region of the polymer electrolyte membrane that contacts the crack of the catalyst layer when the polymer electrolyte membrane swells and shrinks. As a result, there is a problem that the polymer electrolyte membrane is mechanically deteriorated and the durability of the fuel cell is lowered.

  In order to solve the above problem, Patent Document 1 discloses a membrane electrode assembly in which two or more catalyst layers having cracks are laminated. Patent Document 2 discloses a membrane / electrode assembly in which a fibrous substance having a hydrophilic surface is added to a catalyst layer, thereby improving the bonding strength of the catalyst layer and suppressing cracks. Patent Document 3 discloses a method for producing a membrane electrode assembly in which a paste containing an electrolyte membrane component is applied to a cracked catalyst layer.

JP 2007-179893 A JP 2004-247316 A Japanese Patent Laid-Open No. 2006-015211

  However, according to the method of Patent Document 1, since it is necessary to form two or more catalyst layers, it is difficult to form a thin catalyst layer. When the catalyst layer becomes thick, the resistance increases and the gas diffusion decreases, and the battery performance decreases. Further, since cracks remain in the catalyst layer in contact with the polymer electrolyte membrane, mechanical stress accompanying swelling and shrinkage of the polymer electrolyte membrane is inevitable. Further, the catalyst layer is likely to be misaligned, causing problems such as deterioration of the electrode end and an increase in processes.

  Further, in the method of Patent Document 2, the bonding strength of the catalyst layer is improved by adding a hydrophilic fibrous substance to the catalyst layer. However, fibrous materials are prone to lumps and are difficult to disperse uniformly. Therefore, a crack is likely to occur from a portion where the concentration of the fibrous substance is low. Moreover, when the addition amount of a fibrous substance is increased, the applicability | paintability of the composition for forming a catalyst layer will worsen, and it will become difficult to form a catalyst layer uniformly.

  On the other hand, in the method of Patent Document 3, since the paste containing the electrolyte membrane component is applied to the crack portion of the catalyst layer, the crack of the catalyst layer is repaired. However, in this method, since the paste containing the electrolyte membrane component is applied and a layer is separately formed, the thickness of the catalyst layer increases. Therefore, the battery performance decreases due to the increase in resistance and the decrease in diffusibility. There is also a problem that the process becomes complicated.

  Therefore, this indication solves the said subject and prevents a polymer electrolyte membrane from deteriorating by the crack of a catalyst layer, and it aims at providing a highly durable membrane electrode assembly.

  As a result of intensive studies by the present inventors in order to achieve the above object, after forming a catalyst layer on the polymer electrolyte membrane, the catalyst layer is coated on the catalyst layer with a material constituting the gas diffusion layer. Without increasing the thickness of the catalyst layer, the crack portion of the catalyst layer can be filled with the material constituting the gas diffusion layer, the deterioration of the polymer electrolyte membrane in contact with the crack portion of the catalyst layer is suppressed, and the durability is high It has been found that a membrane electrode assembly can be obtained.

In order to achieve the above object, the present disclosure provides the following membrane electrode assembly.
Arranged on both sides of the solid polymer electrolyte membrane, comprising a solid polymer electrolyte membrane, a catalyst layer arranged adjacent to the solid polymer electrolyte membrane, and a gas diffusion layer arranged adjacent to the catalyst layer A pair of electrode layers, wherein the gas diffusion layer includes a porous material, the catalyst layer has a crack portion in a region in contact with the solid polymer electrolyte membrane, and the crack portion includes A membrane electrode assembly filled with the porous material.

The present disclosure also provides a method for producing the following membrane electrode assembly.
Applying a catalyst layer-forming composition comprising a carbon material carrying catalyst particles, a polymer electrolyte, and a first solvent on a solid polymer electrolyte membrane to form a catalyst layer; and Coating and drying a gas diffusion layer forming composition containing conductive particles, a polymer resin, and a second solvent so as to cover the film, and forming a gas diffusion layer. Production method.

Furthermore, this indication also provides the manufacturing method of the following membrane electrode assemblies.
Applying a catalyst layer forming composition containing a carbon material carrying catalyst particles, a polymer electrolyte, and a first solvent on a solid polymer electrolyte membrane to form a catalyst layer; and A step of applying a composition for forming a microporous layer containing conductive particles, a polymer resin, and a second solvent so as to cover the layer; and heating the substrate to the coating film of the composition for forming a microporous layer. Forming a gas diffusion layer including a base material and a microporous layer, and manufacturing the membrane electrode assembly.

  According to the present disclosure, the crack portion of the catalyst layer is filled with the material constituting the gas diffusion layer. Therefore, the deterioration of the polymer electrolyte membrane in contact with the crack portion of the catalyst layer is suppressed, and a highly durable membrane electrode assembly can be obtained.

Schematic diagram of polymer electrolyte fuel cell stack according to the first and second embodiments of the present disclosure Sectional drawing of the polymer electrolyte fuel cell of 1st Embodiment of this indication Sectional drawing of MEA of 1st Embodiment of this indication Flowchart of MEA manufacturing method according to first embodiment of the present disclosure Sectional drawing for every process of MEA of 1st Embodiment of this indication. Sectional drawing of MEA of 2nd Embodiment of this indication Flow diagram of MEA manufacturing method according to second embodiment of the present disclosure

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The basic configuration of the fuel cell according to the first embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a schematic view of a polymer electrolyte fuel cell stack according to a first embodiment and a second embodiment described later. The embodiment of the present disclosure is not limited to the polymer electrolyte fuel cell, and can be applied to various fuel cells.

  As shown in FIG. 1, a fuel cell is formed by stacking a plurality of battery cells 10 that are basic units and fastening them with a current collector plate 11, an insulating plate 12, and an end plate 13 from both sides with a predetermined load.

  As the material of the current collector plate 11, a gas impermeable conductive material is used, for example, copper, brass or the like. The current collecting plate 11 is provided with a current extraction terminal portion, and current is extracted from the current extraction terminal portion during power generation.

As a material of the insulating plate 12, an insulating resin is used, and for example, a fluorine-based resin, a PPS resin, or the like is used.
As the material of the end plate 13, a highly rigid metal material is used, for example, steel or the like. The end plate 13 is a member for fastening and holding a plurality of stacked battery cells 10, the current collecting plate 11, and the insulating plate 12 with a predetermined load by a pressing means (not shown).

  Hereinafter, the battery cell 10 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the battery cell 10 of the present embodiment. The battery cell 10 is configured by sandwiching a membrane electrode assembly (MEA) 20 between an anode side separator 4a and a cathode side separator 4b.

  The anode side separator 4a and the cathode side separator 4b are collectively referred to as the separator 4 hereinafter. Similarly, the other components are abbreviated when a description is given collectively.

  A fluid flow path 5 is formed in the separator 4, and a fluid flow path 5 for flowing fuel gas is formed in the anode side separator 4 a. On the other hand, the cathode-side separator 4b is formed with a fluid flow path 5 for flowing the oxidant gas. As the material of the separator 4, a carbon-based or metal-based material can be used. The fluid flow path 5 is a groove part, and its periphery is a rib part 6.

  The MEA 20 includes a solid polymer electrolyte membrane 1 (hereinafter also simply referred to as “polymer electrolyte membrane”) and a pair of electrode layers 14a and 14b disposed on both sides of the polymer electrolyte membrane 1, respectively. It is. The electrode layer 14 includes the catalyst layer 2 and the gas diffusion layer 3, respectively. That is, in the MEA 20, the anode catalyst layer 2a and the cathode catalyst layer 2b are formed on both surfaces of the polymer electrolyte membrane 1 that selectively transports hydrogen ions, and further, the anode side gas diffusion layer 3a and the cathode are formed outside thereof. A side gas diffusion layer 3b is disposed.

  The MEA 20 of the present embodiment will be described in further detail using FIG. The polymer electrolyte membrane 1 is not particularly limited as long as it is a membrane made of a polymer electrolyte having proton conductivity. For the polymer electrolyte membrane 1, for example, a membrane made of a perfluorocarbon sulfonic acid polymer or the like is used. Examples of the perfluorocarbon sulfonic acid polymer include Nafion (registered trademark).

  The catalyst layer 2 is a layer containing a carbon material supporting a catalyst particle such as a platinum group particle and a polymer electrolyte, and has a cracked part (crack part 7). The crack portion 7 of the catalyst layer 2 is filled with a porous material constituting the gas diffusion layer 3.

  Here, the polymer electrolyte constituting the catalyst layer 2 plays a role of connecting the catalyst particles and the polymer electrolyte membrane 1 and conducting protons therebetween. This polymer electrolyte can be made of a polymer material similar to the polymer material constituting the polymer electrolyte membrane 1. The amount of the polymer electrolyte contained in the catalyst layer 2 is appropriately selected according to the amount of the catalyst, and can usually be about 0.5 to 2 with respect to the mass of the catalyst contained in the catalyst layer 2. When the polymer electrolyte is included in the range, the proton conductivity of the catalyst layer 2 is improved.

In addition, platinum group particles can be used as the catalyst particles constituting the catalyst layer 2, and specifically, Pt, Pt—Ru alloy, Pt—Co alloy, or the like can be used. The anode catalyst layer 2a contains about 0.01 to 3 mg / cm ² of catalyst particles in basis weight. On the other hand, the cathode catalyst layer 2b contains about 0.05 to 0.5 mg / cm ² of catalyst particles in basis weight. When the catalyst particles are included in the range, the power generation performance of the fuel cell is likely to be sufficiently improved.

  As the carbon material for supporting the catalyst particles, acetylene black, ketjen black, furnace black, carbon nanotube, or the like can be used. The amount of the carbon material can be appropriately set according to the amount of the catalyst particles.

  As described above, the catalyst layer 2 has crack portions 7 (the anode side catalyst layer crack portion 7a and the cathode side catalyst layer crack portion 7b) when formed. The size of the crack portion 7 is usually about 1 μm to 100 μm, but in this embodiment, the crack portion 7 is filled with a constituent material (porous material) of the gas diffusion layer 3 described later. When the crack part 7 is hollow, when the polymer electrolyte membrane 1 swells with generated water generated during power generation, that is, when the thickness of the polymer electrolyte film 1 increases, it abuts on the edge part of the crack part 7. High stress is applied to the polymer electrolyte membrane 1. Then, when the polymer electrolyte membrane 1 repeats swelling and shrinking, the polymer electrolyte membrane 1 is repeatedly stressed and deteriorates.

  On the other hand, by filling the crack portion 7 generated in the catalyst layer 2 with the porous material constituting the gas diffusion layer 3, even if the polymer electrolyte membrane 1 swells and shrinks, there is no stress concentration. Therefore, the deterioration of the polymer electrolyte membrane 1 is suppressed, and the durability of the MEA 20 and thus the durability of the entire fuel cell can be improved.

  The method for filling the crack portion 7 generated in the catalyst layer 2 with the material (porous material) constituting the gas diffusion layer 3 is not particularly limited, but in order to fill the crack portion 7, a fluid material is used as the catalyst. It is necessary to apply on layer 2. Specifically, it is realizable with the manufacturing method of MEA mentioned later.

  On the other hand, the gas diffusion layer 3 of the present embodiment is made of a porous material, and the porous material mainly contains conductive particles and a polymer resin. In the present specification, “the porous material is mainly composed of conductive particles and a polymer resin” means that the conductive material is conductive even if it does not include a base material (support member) made of carbon fiber or the like. It means that the shape of the porous material is maintained by the particles and the polymer resin (having a so-called self-supporting structure).

  In addition, when forming the gas diffusion layer 3 which consists of porous materials using electroconductive particle and polymer resin, surfactant and the solvent for dispersion | distribution may be used so that it may mention later. During the formation of the gas diffusion layer 3, the surfactant and the dispersion solvent are removed by firing, but these may remain in the gas diffusion layer 3. Therefore, the porous material may contain a certain amount of a surfactant, a dispersion solvent, and the like as long as the shape can be maintained by the conductive particles and the polymer resin. In addition, within the range in which the object of the present embodiment can be achieved, in the porous material, in addition to the conductive particles, the polymer resin, the surfactant, and the dispersion solvent, other materials (for example, carbon fiber) May be included. The porous material preferably contains 70% by mass or more of conductive particles and polymer resin in total.

  As the conductive particles constituting the gas diffusion layer 3, for example, a carbon material such as carbon black, graphite, activated carbon or the like can be used. Among these, it is preferable to use carbon black having high conductivity and a large pore volume. As carbon black, for example, acetylene black, ketjen black, and furnace black can be used. Among these, it is preferable to use acetylene black with a small amount of impurities, or acetylene black containing acetylene black as a main component and containing 5% by mass to 50% by mass of highly conductive ketjen black. The conductive particles are preferably contained in the gas diffusion layer 3 by 60% by mass or more and 95% by mass or less.

  On the other hand, the polymer resin constituting the gas diffusion layer 3 is not particularly limited as long as it has a function as a binder for binding the conductive particles. The polymer resin preferably has water repellency. By using such a polymer resin, it is possible to prevent water from staying in pores inside the gas diffusion layer 3 and inhibiting gas permeation.

  As the polymer resin, for example, a fluorine-based resin can be used. Specifically, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), PVDF (polyvinylidene fluoride), ETFE (tetrafluoroethylene / ethylene copolymer), PCTFE (polyethylene) Chlorotrifluoroethylene), PFA (polyfluoroethylene / perfluoroalkyl vinyl ether copolymer) and the like can be used. Among these, it is preferable to use PTFE as a polymer resin from the viewpoints of heat resistance, water repellency, and chemical resistance. Examples of the raw material form of PTFE include dispersion and powder. Among these, a dispersion is preferable because of its excellent dispersibility.

  Further, the gas diffusion layer 3 may contain carbon fibers that are not formed as a base material. At this time, the carbon fiber content in the gas diffusion layer 3 is preferably 20% by mass or less. The content of the polymer resin in the gas diffusion layer 3 is preferably 10% by mass or more and 20% by mass or less. When the amount of the carbon fiber or the polymer resin is within the range, the resistance of the gas diffusion layer 3 can be reduced.

  As the carbon fiber, vapor grown carbon fiber, milled fiber, cut fiber, chop fiber, or the like can be used. Among these, vapor grown carbon fiber is preferable because it has a small fiber diameter and does not hinder the binder effect of the polymer resin.

<Manufacturing method of MEA20>
Next, a method for manufacturing the MEA 20 according to the first embodiment of the present invention will be described with reference to FIGS.
The MEA 20 manufacturing method of the present embodiment includes a step of applying the catalyst layer forming composition to the polymer electrolyte membrane 1 (step 1) and a drying treatment to obtain a solvent (first solvent) in the catalyst layer forming composition. In the gas diffusion layer forming composition by the step of removing the step (Step 2), the step of applying the separately prepared gas diffusion layer forming composition so as to cover the catalyst layer 2 and the drying treatment. Removing the solvent (second solvent) (step 4). In the method for manufacturing the MEA 20 of the present embodiment, the cracks described above are generated in the catalyst layer 2 in step 2. In Step 3, the crack portion 7 of the catalyst layer 2 is filled with the gas diffusion layer forming composition.
Through the steps 1 to 4, the membrane electrode assembly 20 according to the first embodiment of the present disclosure can be manufactured.

  In addition, unless the objective of this embodiment is impaired, the manufacturing method of MEA20 of this embodiment may include the other process, for example, the process (sub process) of preparing the composition for gas diffusion layer formation shown below, for example 1-4) may be included. In addition to this, a step of preparing a composition for forming a catalyst layer may be included.

The step of preparing the gas diffusion layer forming composition includes a step of mixing conductive particles, a polymer resin, a surfactant, and a dispersion solvent (sub-step 1), and firing the mixture obtained in sub-step 1. The step of removing the surfactant and the dispersion solvent (sub-step 2), the step of crushing the fired product obtained in sub-step 2 (sub-step 3), the pulverized fired product and the second solvent Mixing (sub-process 4).
Hereinafter, each process of the manufacturing method of MEA20 of this embodiment is demonstrated.

(Process 1)
Step 1 will be described in detail with reference to FIG. FIG. 5 shows the case where the catalyst layer 2a and the gas diffusion layer 3a on the anode side are formed, but the cathode side can be formed in the same manner.

  In step 1, a composition for forming a catalyst layer is applied to the polymer electrolyte membrane 1 to form a coating film 2a 'made of the composition for forming a catalyst layer. The composition for forming a catalyst can be a mixture of a carbon material carrying catalyst particles such as platinum group particles, a polymer electrolyte, and a solvent (first solvent) such as pure water or alcohol. The composition for forming a catalyst layer can be obtained by stirring and dispersing the above components with a stirrer, bead mill, self-revolving mixer, planetary mixer or the like.

  The method for applying the catalyst layer forming composition is not particularly limited, and for example, a method of applying the composition on the polymer electrolyte membrane 1 by a die coating method, a spray coating method, a screen printing, a gravure printing, an ink jet method or the like can be used. .

(Process 2)
Step 2 will be described in detail with reference to FIG.
In step 2, the solvent (first solvent) such as alcohol contained in the coating film 2a ′ of the catalyst layer forming composition formed in step 1 is removed by a drying treatment. As a drying method, a conventionally known method such as a hot air method or an IR method can be used. The drying temperature may be any temperature that does not affect the polymer electrolyte contained in the catalyst layer forming composition, preferably 40 ° C to 100 ° C, and more preferably 60 ° C to 90 ° C.

  When the coating film 2a 'is dried in this step, volume shrinkage occurs, and a crack portion 7a is generated in the resulting catalyst layer 2a.

(Process 3)
Step 3 will be described in detail with reference to FIG.
In step 3, a separately prepared gas diffusion layer forming composition is applied so as to cover the catalyst layer 2a, thereby forming a coating film 3a ′ made of the gas diffusion layer forming composition. At this time, the crack portion 7a of the catalyst layer 2a is filled with a material (porous material) constituting the gas diffusion layer.

  The gas diffusion layer forming composition can be a mixture of a carbon material as conductive particles, a polymer resin, and a solvent (second solvent) such as pure water or low-boiling alcohol. A general gas diffusion layer forming composition contains a surfactant in order to enhance the binding property between the conductive particles and the polymer resin. And in order to remove surfactant after application | coating of the composition for gas diffusion layer formation, it is necessary to bake a coating film at the temperature of 200 degreeC or more. On the other hand, when the composition for forming a gas diffusion layer is prepared through a method (substeps 1 to 4) described later, the conductive particles and the polymer resin are already bound, so the composition for forming the gas diffusion layer There is no need to include a surfactant in the product. That is, it is not necessary to bake the coating film of the gas forming composition at a high temperature in Step 4 described later. Therefore, excessive heat is not applied to the catalyst layer 2a, and deterioration or the like hardly occurs in the polymer electrolyte contained in the catalyst layer 2a. In addition, it is preferable that the 2nd solvent contained in the composition for gas diffusion layer formation has a low boiling point from a viewpoint of suppressing deterioration of the polymer electrolyte in the catalyst layer 2a, and the boiling point of a solvent is specifically, It is preferable that it is 50-150 degreeC or less, and it is more preferable that it is 70-130 degreeC. When the boiling point of the solvent is lower than 50 ° C., the viscosity of the gas diffusion layer forming composition tends to increase due to volatilization of the solvent during application of the gas diffusion layer forming composition, and it becomes difficult to form the gas diffusion layer uniformly. On the other hand, when the boiling point of the solvent is higher than 150 ° C., the solvent needs to be heated to a high temperature in order to dry. As the low boiling point solvent, a mixed solvent of alcohols such as ethanol and isopropyl alcohol (IPA) and pure water, or the like can be used. A method for producing the gas diffusion layer ink will be described later.

  As a method for applying the gas diffusion layer forming composition, a screen printing method, a die coating method, a roll rolling method, or the like is used. According to such a method, the gas diffusion layer forming composition easily enters the crack portion 7a of the catalyst layer 2a.

(Process 4)
Step 4 will be described in detail with reference to FIG.
In Step 4, a solvent such as alcohol (second solvent) contained in the coating film 3a ′ of the gas diffusion layer forming composition formed in Step 3 is removed by a drying process to obtain the gas diffusion layer 3a. For drying, a generally known method such as a hot air method or an IR method can be used. The drying temperature should just be the temperature which does not affect the polymer electrolyte contained in the catalyst layer 2, It is preferable that it is 40 to 160 degreeC, and it is more preferable that it is 60 to 130 degreeC.

(Sub process 1)
In sub-step 1, the conductive particles, the polymer resin, the surfactant, and the dispersion solvent are mixed. Specifically, a carbon material as a conductive particle, a surfactant, and a dispersion solvent are added, and stirred and mixed. After the above materials are uniformly dispersed, a polymer resin is added and again uniformly dispersed to obtain a mixture.

(Sub process 2)
In sub-step 2, the mixture obtained in sub-step 1 is baked to remove the surfactant and the dispersing solvent. The mixture is preferably baked after being cut to about 10 mm before firing. Thereby, the surfactant and the dispersing solvent can be removed in a short time.

(Sub process 3)
In sub-step 3, the fired product from which the surfactant and the dispersion solvent obtained in sub-step 2 have been removed is pulverized. For the pulverization, a cutter mill or a roll crusher can be used. The particle diameter after pulverization is preferably 100 μm to 3 mm, and more preferably 500 μm to 1 mm.

(Sub process 4)
In sub-step 4, the fired product after pulverization and the second solvent are kneaded to obtain a gas diffusion layer forming composition. As described above, the second solvent preferably has a low boiling point so that the polymer electrolyte contained in the catalyst layer 2a is not deteriorated in Step 4 described above. As described above, as the second solvent, a mixed solvent of alcohols such as ethanol and isopropyl alcohol (IPA) and pure water can be used.

  The amount of the second solvent added varies depending on the method of applying the gas diffusion layer forming composition, but for example, when applied by a roll rolling method, it is preferable to adjust the solid content concentration to 40 to 70% by mass. .

  In addition, like the example shown so far, this indication is not limited to the said 1st Embodiment, It can implement in another various aspect.

(Second Embodiment)
A fuel cell according to a second embodiment of the present disclosure will be described. The fuel cell of this embodiment is the same as the fuel cell according to the first embodiment except for the gas diffusion layer 30 of the MEA 200. In FIG. 6, the cross section of MEA200 of this embodiment is shown. The gas diffusion layer 30 of the second embodiment is different from the gas diffusion layer 3 of the first embodiment in that the gas diffusion layer 30 is composed of the base material 8 and the microporous layer 9 (hereinafter also referred to as “MPL layer”). It is the point comprised by. Since the other points are the same as those in the first embodiment, they are denoted by the same reference numerals and description thereof is omitted.

The gas diffusion layer 30 includes a base material 8 and an MPL layer 9.
The base material 8 is a member that supports the MPL layer 9, and for example, a fiber nonwoven fabric having high corrosion resistance and conductivity, a woven fabric that has been water-repellent treated with a water-repellent resin, and the like can be used. Typical examples of the material of the substrate 8 include carbon paper and carbon felt. The base material 8 is required to have high electron conductivity and high gas diffusibility.

  On the other hand, the MPL layer 9 is a layer containing a porous material and is a layer mainly composed of conductive particles and a polymer resin. The said porous material is the same as the porous material which comprises the gas diffusion layer of 1st Embodiment. The MPL layer 9 retains moisture in the electrolyte membrane 1 and the catalyst layer 2 and has a role of efficiently discharging excess moisture. The MPL layer 9 can be of the same composition as the gas diffusion layer 3 of the first embodiment.

  In the present embodiment, the material constituting the MPL layer 9, that is, the porous material fills the crack portion 7 generated in the catalyst layer 2. Therefore, also in the present embodiment, the polymer electrolyte membrane 1 is not subjected to mechanical stress in the region where the polymer electrolyte membrane 1 contacts the crack portion 7 of the catalyst layer 2, and the deterioration of the polymer electrolyte membrane 1 is suppressed, and the durability of the fuel cell is increased. Improves.

<Method for manufacturing MEA 200>
Next, the manufacturing method of MEA200 concerning 2nd Embodiment of this invention is demonstrated. FIG. 7 shows a process chart of a method for manufacturing the MEA 200 of the present embodiment. The MEA 200 manufacturing method includes a step of applying the catalyst layer forming composition to the polymer electrolyte membrane 1 (step 1), a step of drying the catalyst layer forming composition by a drying process (step 2), and a separate preparation. A step of applying the microporous layer-forming composition so as to cover the catalyst layer 2 (step 3), and a step of thermocompression bonding the substrate 9 to the coating film of the composition for forming the microporous layer (step 4) ,including. In the method for manufacturing the MEA 200 of the present embodiment, the cracks described above are generated in the catalyst layer 2 in step 2. In Step 3, the crack portion 7 of the catalyst layer 2 is filled with the composition for forming the microporous layer. Through the above steps, the membrane electrode assembly 200 according to the second embodiment of the present disclosure can be manufactured.

  Here, Step 1 and Step 2 are the same as Step 1 and Step 2 of the method for manufacturing the MEA 20 according to the first embodiment. Moreover, unless the objective of this embodiment is impaired, the manufacturing method of MEA200 of this embodiment may include the other process, for example, the process of preparing the composition for microporous layer formation (sub process 1-4). ) May be included. In addition to this, a step of preparing a composition for forming a catalyst layer may be included. In addition, the preparatory process (sub process 1-4) of the composition for microporous layer formation can be made to be the same as the preparatory process of the composition for gas diffusion layer formation of 1st Embodiment. Therefore, only step 3 and step 4 will be described below.

(Process 3)
In step 3, a separately prepared composition for forming a microporous layer is applied so as to cover the catalyst layer 2a, and a coating film made of the composition for forming a microporous layer is formed. At this time, the crack portion 7a of the catalyst layer 2a is filled with a material (porous material) constituting the microporous layer. The composition for forming a microporous layer can be the same as the composition for forming a gas diffusion layer of the first embodiment. Also, the coating method can be the same.

(Process 4)
In step 4, the substrate 8 is thermocompression bonded to the coating film of the microporous layer forming composition formed in step 3. The thermocompression bonding temperature is preferably 40 ° C to 160 ° C, more preferably 60 ° C to 130 ° C. By thermocompression bonding the base material 8, the solvent (second solvent) in the microporous layer forming composition is removed to form the MLP layer 9, and the base material 8 and the MPL layer 9 can be joined. it can.

  In this embodiment, the crack part of a catalyst layer can be filled with the material which comprises an MPL layer with the said manufacturing method. Therefore, by manufacturing the MEA 200 by this method, the polymer electrolyte membrane 1 is not subjected to mechanical stress at the crack portion of the catalyst layer 2, the deterioration of the polymer electrolyte membrane is suppressed, and the durability of the fuel cell is improved. improves.

  With the membrane electrode assembly of the present disclosure, it is possible to improve the durability of the fuel cell. The membrane electrode assembly and the fuel cell using the membrane electrode assembly can be applied to uses such as a home cogeneration system, an automobile fuel cell, a mobile fuel cell, and a backup fuel cell.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2a Anode catalyst layer 2b Cathode catalyst layer 3a, 30a Anode side gas diffusion layer 3b, 30b Cathode side gas diffusion layer 4a Anode side separator 4b Cathode side separator 5 Fluid flow path 6 Rib part 7a Anode side catalyst layer crack Part 7b Cathode side catalyst layer crack part 8 Base material 9 Microporous layer 10 Battery cell 11 Current collecting plate 12 Insulating plate 13 End plate 14 Electrode layer 20, 200 MEA

Claims (8)

A solid polymer electrolyte membrane;
A pair of electrode layers disposed on both sides of the solid polymer electrolyte membrane, including a catalyst layer disposed adjacent to the solid polymer electrolyte membrane and a gas diffusion layer disposed adjacent to the catalyst layer;
Have
The gas diffusion layer includes a porous material,
The catalyst layer has a crack portion in a region in contact with the solid polymer electrolyte membrane, and the crack portion is filled with the porous material,
Membrane electrode assembly. The porous material is mainly composed of conductive particles and a polymer resin.
The membrane electrode assembly according to claim 1. The gas diffusion layer has a base material, and a microporous layer that is disposed on the base material and includes the porous material.
The membrane electrode assembly according to claim 1 or 2.   The fuel cell containing the membrane electrode assembly of any one of Claims 1-3. Applying a catalyst layer-forming composition comprising a carbon material carrying catalyst particles, a polymer electrolyte, and a first solvent on a solid polymer electrolyte membrane to form a catalyst layer; and
Coating and drying a gas diffusion layer forming composition containing conductive particles, a polymer resin, and a second solvent so as to cover the catalyst layer, and forming a gas diffusion layer;
The manufacturing method of the membrane electrode assembly containing this. Before forming the gas diffusion layer,
Mixing the conductive particles, the polymer resin, a surfactant, and a dispersion solvent to prepare a mixture;
Firing the mixture to obtain a fired product from which the surfactant and the dispersion solvent have been removed;
Crushing the fired product;
Mixing the fired product after pulverization and the second solvent to obtain the gas diffusion layer forming composition;
The manufacturing method of the membrane electrode assembly of Claim 5 containing this. Applying a catalyst layer forming composition comprising a carbon material carrying catalyst particles, a polymer electrolyte, and a first solvent on a solid polymer electrolyte membrane to form a catalyst layer; and
Applying a composition for forming a microporous layer containing conductive particles, a polymer resin, and a second solvent so as to cover the catalyst layer;
A step of thermocompression bonding a base material to the coating film of the microporous layer forming composition to form a gas diffusion layer including the base material and the microporous layer;
The manufacturing method of the membrane electrode assembly containing this. Before applying the composition for forming a microporous layer,
Mixing the conductive particles, the polymer resin, a surfactant, and a dispersion solvent to prepare a mixture;
Firing the mixture, removing the surfactant and the dispersion solvent to obtain a fired product, and grinding the fired product;
Mixing the fired product after pulverization and the second solvent to obtain the microporous layer-forming composition;
The manufacturing method of the membrane electrode assembly of Claim 7 which has these.

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