JP2007066768A - Electrolyte membrane-electrode assembly and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MEA which is manufactured with a simple work and having good durability when laminating unit cells. <P>SOLUTION: The electrolyte membrane-electrode assembly includes carbon layer base materials 5a, c, intercalated between catalyst layers 3a, c and gas diffusion layers 4a, c, at the site where the catalyst layers are positioned against a thickness direction of an electrolyte membrane 2 located at least at a cathode side or an anode side, adjacent to the electrolyte membrane at the site where the gas diffusion layers are not located, and with end parts nearly matching the end part of the electrolyte membrane against the thickness direction. A carbon material and a water repellant are filled in a site where the catalyst layers of the carbon layer base materials are positioned, and an adhesive is filled at least on a contacting surface side with the electrolyte membrane at a site where the catalyst layers of the carbon layer base materials are not positioned. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane-electrode assembly (MEA), and more particularly to an electrolyte membrane-electrode assembly for a fuel cell and a fuel cell using the same. More specifically, the present invention relates to an improvement for improving workability at the time of manufacturing an MEA and suppressing a decrease in durability at the time of stacking single cells.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as power sources for electric vehicles and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, the polymer electrolyte fuel cell is expected as a power source for electric vehicles because it operates at a relatively low temperature. The polymer electrolyte fuel cell generally has a structure in which an electrolyte membrane-electrode assembly (MEA) is sandwiched between separators. The electrolyte membrane-electrode assembly is formed by sandwiching an electrolyte membrane between a pair of catalyst layers and a pair of gas diffusion layers. Further, in some cases, for the purpose of improving the water repellency of the gas diffusion layer, a carbon layer containing a carbon material and a water repellent may be interposed between the catalyst layer and the gas diffusion layer. In a polymer electrolyte fuel cell, a plurality of single cells having the above-described configuration are generally stacked to form a stack.

In the polymer electrolyte fuel cell having the MEA as described above, the following electrochemical reaction proceeds. First, hydrogen contained in the fuel gas supplied to the anode side is oxidized by the catalyst component to become protons and electrons (2H ₂ → 4H ⁺ + 4e ⁻ ). Next, the produced protons pass through the electrolyte contained in the catalyst layer and the electrolyte membrane in contact with the catalyst layer, and reach the cathode side catalyst layer. In addition, the electrons generated in the anode side catalyst layer are converted into the cathode side catalyst layer through the conductive carrier constituting the catalyst layer, the gas diffusion layer in contact with the side of the catalyst layer different from the electrolyte membrane, the separator and the external circuit. To reach. The protons and electrons that have reached the cathode catalyst layer react with oxygen contained in the oxidant gas supplied to the cathode side to generate water (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O). In the fuel cell, electricity can be taken out through the above-described electrochemical reaction.

  Here, in order to prevent deterioration in battery performance due to gas supply unevenness or gas leakage to the outside of the cell, each of the electrolyte membrane, catalyst layer, gas diffusion layer, separator, etc. constituting the single cell of the fuel cell It is necessary to minimize misalignment when stacking the components.

In order to achieve such an object, conventionally, an electrolyte membrane, each catalyst layer formed smaller than the electrolyte membrane in the center of the electrolyte membrane, each gas diffusion layer, and a protective film surrounding the periphery of the catalyst layer, There is disclosed a solid polymer fuel cell in which the protective film and the gas diffusion layer are bonded via an adhesive layer (see Patent Document 1).
JP 2004-319153 A

  However, in the configuration described in Patent Document 1, the stacking operation of each component at the time of manufacturing the single cell is complicated, and further, the durability of the single cell, in particular, the stress resistance at the interface between the catalyst layer and the protective film is low. This is not always sufficient, and there is a problem that the MEA is easily damaged when the single cells are stacked.

  Therefore, an object of the present invention is to provide an MEA that can be produced by a simpler operation and that is excellent in durability when single cells are stacked.

  As a result of intensive studies to achieve the above object, the present inventors have found that the end portion of the carbon layer substrate, which has been conventionally arranged for the purpose of improving the water repellency of the gas diffusion layer, is replaced with the MEA electrolyte membrane. The above-mentioned problem is caused by stretching the film until it substantially coincides with the end part, and further exhibiting the function of the protective film described in Patent Document 1 in a part other than the part in contact with the catalyst layer (specifically, the peripheral part). It has been found that the problem can be solved, and the present invention has been completed.

  That is, the present invention includes an electrolyte membrane, a cathode catalyst layer located on one side of the electrolyte membrane, an anode catalyst layer located on the other side of the electrolyte membrane, and the electrolyte membrane of the cathode catalyst layer A cathode-side gas diffusion layer located on a surface facing the anode, a anode-side gas diffusion layer located on a surface facing the electrolyte membrane of the anode catalyst layer, and located on at least one of the cathode side or the anode side, In the part where the catalyst layer is located with respect to the thickness direction of the electrolyte membrane, it is interposed between the catalyst layer and the gas diffusion layer, and in the part where the gas diffusion layer is not located, it is adjacent to the electrolyte membrane and ends. Is substantially coincident with the end portion of the electrolyte membrane with respect to the thickness direction, and a carbon material and a water repellent are disposed in a portion of the carbon layer substrate where the catalyst layer is located. Charge Is made, the adhesive is filled in the contact surface of at least the electrolyte membrane of a portion the catalyst layer of the carbon layer substrate is not located, the electrolyte membrane - an electrode assembly.

  In the MEA of the present invention, the end of the base material constituting the conventional carbon layer is stretched until it substantially coincides with the end of the electrolyte membrane, and the conventional carbon layer and the gas seal layer are integrated. Have a configuration. Therefore, the MEA of the present invention can be produced by a simple operation. Furthermore, according to the present invention, an MEA having excellent durability when single cells are stacked can be provided.

  The present invention includes an electrolyte membrane, a cathode catalyst layer located on one side of the electrolyte membrane, an anode catalyst layer located on the other side of the electrolyte membrane, and the electrolyte membrane of the cathode catalyst layer facing the electrolyte membrane A cathode side gas diffusion layer located on the surface of the anode catalyst layer; an anode side gas diffusion layer located on a surface of the anode catalyst layer facing the electrolyte membrane; and the electrolyte located on at least one of the cathode side or the anode side. In the part where the catalyst layer is located with respect to the thickness direction of the film, it is interposed between the catalyst layer and the gas diffusion layer, in the part where the gas diffusion layer is not located, it is adjacent to the electrolyte membrane, and the end is the A carbon layer base material that substantially coincides with the end of the electrolyte membrane with respect to the thickness direction, and a portion of the carbon layer base material where the catalyst layer is located is filled with a carbon material and a water repellent. Tena , The adhesive is filled in the contact surface of at least the electrolyte membrane of a portion the catalyst layer of the carbon layer substrate is not located, the electrolyte membrane - a electrode assembly (MEA).

  Hereinafter, preferred embodiments of the MEA of the present invention will be described with reference to the drawings. However, the drawings are exaggerated for convenience of explanation, and the dimensional ratios in the drawings do not always match the actual dimensional ratios.

  FIG. 1 shows a preferred embodiment of the MEA of the present invention. As shown in FIG. 1, in the MEA 1 of the present embodiment, the anode catalyst layer 3a is located on one surface of the electrolyte membrane 2, and the cathode catalyst layer 3c is located on the other surface. Further, the anode side gas diffusion layer 4a is located on the surface of the anode catalyst layer 3a facing the electrolyte membrane 2, and the cathode side gas diffusion layer 4c is located on the surface of the cathode catalyst layer 3c facing the electrolyte membrane 2. To do.

  In the MEA of the present embodiment, the catalyst layer (3a or 3c) and the gas diffusion layer (where the catalyst layer (3a or 3c) is located in the thickness direction of the electrolyte membrane 2 on both the cathode side and the anode side. 4a or 4c) is adjacent to the electrolyte membrane 2 at a portion where the gas diffusion layer (4a or 4c) is not located with respect to the thickness direction, and an end portion of the electrolyte membrane 2 is located with respect to the thickness direction. It is characterized in that it has a carbon layer substrate (5a, 5c) that substantially coincides with the end. However, the embodiment is not limited to the above-described form in which the carbon layer base material is present on both sides of the cathode side and the anode side, and a form in which the carbon layer base material is present only in any one of the above can also be adopted.

  This carbon layer base material (5a, 5c) is located at a portion where the catalyst layer (3a or 3c) is located in the thickness direction of the electrolyte membrane 2 (so-called “active area”, portion “A” shown in FIG. 1). It functions as a base material for a conventional carbon layer. Therefore, in this active area, the carbon layer base material (5a, 5c) is filled with at least a carbon material and a water repellent. The carbon layer base material in the active area filled with these has a function of further improving the water repellency of the gas diffusion layer, like the conventional carbon layer.

  On the other hand, the end of the carbon layer base material (5a, 5c) substantially coincides with the end of the electrolyte membrane 2 at a site other than the active area. In the present embodiment, a portion other than the active area of the carbon layer base material (5a, 5c) is filled with an adhesive. Thereby, the carbon layer base material (5a, 5c) in a portion other than the active area functions as a gas seal member for preventing gas leakage from the active area to the outside. However, the present invention is not limited to a form in which the entire region other than the active area is filled with the adhesive, and the adhesive only needs to be filled at least on the contact surface side with the electrolyte membrane 2. This is because the adhesion between the portion other than the active area of the carbon layer base material (5a, 5c) and the electrolyte membrane 2 is sufficiently secured.

  In the fuel cell, fuel gas and oxidant gas are supplied from the separators arranged on the catalyst layer sides. In the MEA of the present invention, the gas flows independently and does not leak outside. When the MEA is sandwiched between the separators, the sealing convex portion may be disposed on the separator (not shown) side of the carbon layer base material (5a, 5c).

  As described above, according to the present invention, the conventional carbon layer in the MEA and the gas seal member are integrated using a single member called a carbon layer base material. As a result, according to the present invention, an MEA that can be manufactured by a simpler method can be provided. Further, according to the present invention, since the active area and other parts are integrated, the stress concentration at the time of single cell stacking is reduced, and the MEA having excellent durability at the time of single cell stacking is provided. Can be provided.

  In the form shown in FIG. 1, on both the anode side and the cathode side, the end portions of the catalyst layers (3a, 3c) and the end portions of the gas diffusion layers (4a, 4c) are substantially in the thickness direction of the MEA. Match. However, the technical scope of the present invention is not limited to such a form. For example, as shown in FIG. 2, a configuration in which the ends of the catalyst layers (3a, 3c) are terminated inside the ends of the gas diffusion layers (4a, 4c) in the thickness direction of the MEA is also adopted. Can be done. In the form shown in FIG. 2, on the anode side, as in FIG. 1, the end of the catalyst layer 3a and the end of the gas diffusion layer 4a are substantially aligned with the thickness direction of the MEA. On the other hand, on the cathode side, the end of the catalyst layer 3c is terminated inside the end of the gas diffusion layer 4c. In such a form, the carbon layer base material 5c on the cathode side is interposed between the catalyst layer 3c and the gas diffusion layer 4c at the portion where the catalyst layer 3c is located with respect to the thickness direction of the electrolyte membrane 2, and the thickness The portion where the gas diffusion layer 4c is not located with respect to the direction is adjacent to the electrolyte membrane 2, and the end portion is substantially coincident with the end portion of the electrolyte membrane 2 with respect to the thickness direction as in the embodiment shown in FIG. is there. However, on the cathode side in the form shown in FIG. 2, the catalyst layer 3c is not located in the thickness direction of the electrolyte membrane 2, and there is a part where the gas diffusion layer 4c is located (part "B" shown in FIG. 2). To do. In such a part, the cathode-side carbon layer base material 5c is interposed between the electrolyte membrane 2 and the gas diffusion layer 4c.

  In the form shown in FIG. 2, there is a portion where the catalyst layer is not located and the gas diffusion layer is located in the thickness direction of the electrolyte membrane 2 only on the cathode side. However, the present invention is not limited to such a form, and a form in which such a part exists on both the cathode side and the anode side as shown in FIG. 3 and a form in which such a part exists only on the anode side are also included. Can be adopted.

  Hereafter, the member which comprises MEA of this embodiment is demonstrated in detail.

[Electrolyte membrane]
The electrolyte membrane used in the MEA of the present invention is not particularly limited. For example, various Nafion (registered trademark of DuPont) manufactured by DuPont and perfluorosulfonic acid membranes represented by Flemion, ion exchange resins manufactured by Dow Chemical Co., ethylene-tetrafluoroethylene copolymer resin membrane, trifluoro Solid polymer electrolyte membranes that are generally commercially available, such as fluorine-based polymer electrolytes such as resin membranes based on styrene and hydrocarbon-based resin membranes having sulfonic acid groups, can be used. Alternatively, a porous thin film formed from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or the like, impregnated with an electrolyte component such as phosphoric acid or ionic liquid may be used.

  The thickness of the electrolyte membrane may be appropriately determined in consideration of the properties of the obtained MEA, but is preferably 5 to 300 μm, more preferably 10 to 200 μm, and particularly preferably 15 to 100 μm. From the viewpoint of strength during film formation and durability during MEA operation, it is preferably 5 μm or more, and from the viewpoint of output characteristics during MEA operation, it is preferably 300 μm or less.

[Catalyst layer]
In the present invention, the components constituting the catalyst layer are not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of fuel cells. That is, the catalyst component used for the cathode catalyst layer may be any catalyst component that has a catalytic action for the oxygen reduction reaction, and the catalyst component used for the anode catalyst layer may be any catalyst having the catalytic action for the hydrogen oxidation reaction. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. Metal components may be included. Of these, the catalyst layer preferably contains at least platinum from the viewpoints of catalyst activity, poisoning resistance to carbon monoxide and the like, and heat resistance. When the catalyst layer contains an alloy, the composition of the alloy depends on the type of metal to be alloyed, but platinum is 30 to 90 atomic%, and the metal to be alloyed is 10 to 70 atomic%. Good. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of component elements that form separate crystals, a component element that completely dissolves into a solid solution, and a component element that is an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. In the following description, unless otherwise specified, the descriptions of the catalyst components of the cathode catalyst layer and the anode catalyst layer have the same definition for both, and are collectively referred to as “catalyst components”. However, the catalyst components contained in the cathode catalyst layer and the anode catalyst layer do not have to be the same, and may be appropriately selected and different so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as those of conventionally known catalyst components can be adopted, but the catalyst component is preferably granular. At this time, the smaller the average particle size of the catalyst particles, the higher the effective electrode area in which the electrochemical reaction proceeds, so that the oxygen reduction activity is preferably high. However, if the average particle size is too small, the oxygen reduction activity is actually rather small. A decreasing phenomenon is observed. The average particle diameter of the catalyst particles is preferably 1 to 30 nm, more preferably 1.5 to 20 nm, still more preferably 2 to 10 nm, and particularly preferably 2 to 5 nm. From the viewpoint of easy loading, it is preferably 1 nm or more, and from the viewpoint of catalyst utilization, it is preferably 30 nm or less. The “average particle diameter of the catalyst particles” in the present invention is the average particle diameter of the catalyst component measured from the crystallite diameter or transmission electron microscope image determined from the half width of the diffraction peak of the catalyst component in X-ray diffraction. It can be calculated from the value.

  In the present invention, the catalyst component described above is contained in the catalyst layer as an electrode catalyst supported on a conductive carrier.

  The conductive carrier is not particularly limited as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electron conductivity as a current collector. The component is preferably carbon. Specific examples of the conductive carrier include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

Although the BET specific surface area of the said electroconductive support | carrier should just be a specific surface area sufficient to carry | support a catalyst component highly dispersed, Preferably it is 20-1600m < ² > / g, More preferably, it is 80-1200m < ² > / g. If the specific surface area is 20 m ² / g or more, sufficient power generation performance can be obtained without lowering the dispersibility of the catalyst component and the electrolyte component described later in the conductive support, and if it is 1600 m ² / g or less, the catalyst A decrease in the effective utilization rate of components and electrolyte components is avoided.

  Further, the size of the conductive carrier is not particularly limited, but from the viewpoint that the loading, catalyst utilization, and electrode catalyst layer thickness can be easily controlled within an appropriate range, the average particle size of the conductive carrier. The diameter is 5 to 200 nm, preferably about 10 to 100 nm.

  In the electrode catalyst in which the catalyst component is supported on the conductive support, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. Good. If the loading amount is 80% by mass or less, the degree of dispersion of the catalyst component on the conductive carrier does not decrease, and if the loading amount increases, the power generation performance is greatly improved and the economic advantage does not decrease. . Further, if the supported amount is 10% by mass or more, the catalytic activity per unit mass does not decrease, and desired power generation performance can be obtained by using a small amount of electrode catalyst. The supported amount of the catalyst component can be measured by inductively coupled plasma emission spectroscopy (ICP).

  The catalyst component can be supported on the conductive carrier by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used. Alternatively, a commercially available electrode catalyst may be used.

  The catalyst layer of the present invention can contain an electrolyte component in addition to the electrode catalyst. The electrolyte component is not particularly limited, and conventionally known knowledge can be appropriately referred to. For example, the same electrolyte component as that constituting the above-described electrolyte membrane can be similarly employed.

  In the MEA of the present invention, as shown in FIGS. 2 and 3, each catalyst layer (3a, 3c) is formed so that the area of the anode catalyst layer 3a is larger than the area of the cathode catalyst layer 3c. 3c) is preferably located on each surface of the electrolyte membrane 2. At this time, the positional relationship between the anode catalyst layer 3a and the cathode catalyst layer 3c is not particularly limited, but as shown in FIG. 4A, the cathode catalyst layer is disposed in the anode catalyst layer 3a with respect to the MEA thickness direction. In the case where 3c is completely included; as shown in FIG. 4B, any of the case where the cathode catalyst layer 3c is partially included in the anode catalyst layer 3a in the thickness direction of the MEA may be used. More preferably, the cathode catalyst layer 3c is completely contained in the anode catalyst layer 3a. With such a configuration, the area of the cathode catalyst layer region facing the air existing portion downstream of the anode can be reduced, that is, a portion where the difference between the cathode potential and the electrolyte potential is large can be significantly reduced. Carbon corrosion can be effectively suppressed. Further, according to such a configuration, there is little or no surrounding portion where only the cathode catalyst layer 3c exists in the thickness direction of the MEA, and oxygen from the cathode to the anode at the end of the cathode catalyst layer 3c is present. Cross leakage is minimized, and deterioration of the electrolyte membrane, which has been a serious problem in the past, can also be effectively prevented. Therefore, in a fuel cell using an MEA having such a configuration, high performance can be maintained over a long period of time both during start / stop / continuous operation and when OCV is maintained, and fuel consumption can be improved.

[Gas diffusion layer]
In the MEA of the present invention, the specific form of the gas diffusion layers (4a, 4c) is not particularly limited, and conventionally known knowledge can be appropriately referred to. Examples of the gas diffusion layer to be used include those based on a sheet-like material having conductivity and porosity such as a carbon woven fabric, a papermaking body, and a nonwoven fabric. The thickness of the substrate can be appropriately determined in consideration of the characteristics of the gas diffusion layer to be obtained, but is preferably 30 to 500 μm in consideration of mechanical strength, permeability of gas or water, etc. More preferably, it is 50-300 micrometers.

  The gas diffusion layers (4a, 4c) preferably contain a water repellent in the substrate for the purpose of further improving the water repellency and preventing the flooding phenomenon. Although it does not specifically limit as said water repellent, Fluorine-type, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. Examples thereof include polymer materials, polypropylene, and polyethylene.

  When a water repellent is contained in the gas diffusion layer, a general water repellent treatment method may be used. For example, after immersing the base material used for a gas diffusion layer in the dispersion liquid of a water repellent agent, the method of heat-drying with oven etc. is mentioned.

[Carbon layer substrate]
Hereinafter, the carbon layer base material (5a, 5c) which is a characteristic configuration of the MEA of the present invention will be described in detail.

  The material which comprises a carbon layer base material (5a, 5c) in particular is not restrict | limited, The material used as the base material of the carbon layer in the conventional MEA can be employ | adopted similarly. For example, PTFE, PEN, PET, or the like can be used as a constituent material of the carbon layer base material.

  In addition, as described above, the carbon layer base material (5a, 5a, active area) in which the catalyst layer (the cathode catalyst layer 3c on the cathode side and the anode catalyst layer 3a on the anode side) exists in the thickness direction of the MEA. 5c) is filled with a carbon material and a water repellent so as to exhibit the same function as the conventional carbon layer.

  A carbon material is not specifically limited, The carbon material currently used in the conventional carbon layer can be employ | adopted similarly. For example, carbon black, graphite, expanded graphite and the like are exemplified. Among them, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent electron conductivity and a large specific surface area. The particle diameter of the carbon material is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, it becomes possible to improve contact property with a catalyst layer.

  On the other hand, the water repellent is not particularly limited, and the water repellent used in the conventional carbon layer can be similarly employed. For example, water repellents that can be included in the gas diffusion layers (4a, 4c) described above are exemplified. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction.

  In the active area, the mixing ratio of the carbon material and the water repellent filled in the carbon layer base material may not provide water repellency as expected if there is too much carbon material. There is a possibility that a good electronic conductivity cannot be obtained. Considering these, the mixing ratio of the carbon material and the water repellent in the active area is preferably about 90:10 to 40:60 (carbon material: water repellent) in mass ratio. Note that the thickness of the carbon layer base material (5a, 5c) in the active area may be appropriately determined in consideration of the desired water repellency of the gas diffusion layer (4a, 4c). As an example, the thickness of the carbon layer substrate (5a, 5c) in the active area is preferably 5 to 100 μm, more preferably 10 to 50 μm. In general, if the thickness is 5 μm or more, sufficient mechanical strength can be obtained. On the other hand, if the thickness is 100 μm or less, the permeability of gas or water is not lowered, and sufficient catalytic activity is obtained.

  As a method of filling the carbon layer base material with the carbon material and the water repellent, for example, the carbon material and the water repellent are used as a solvent such as water, alcohol solvents such as perfluorobenzene, dichloropentafluoropropane, methanol, and ethanol. A slurry is prepared by dispersing in, and the slurry is applied on a substrate and dried, or the slurry is dried and pulverized to form a powder, and this is applied onto the gas diffusion layer, etc. May be used. Then, it is preferable to heat-process at about 250-400 degreeC using a muffle furnace or a baking furnace.

  On the other hand, as described above, the carbon layer base material (5a) other than the active area where the catalyst layer (the cathode catalyst layer 3c on the cathode side and the anode catalyst layer 3a on the anode side) does not exist in the thickness direction of the MEA. 5c) At least the contact surface side with the electrolyte membrane 2 is filled with an adhesive. According to the form in which the minimum amount of adhesive necessary for adhesion between the electrolyte membrane and the carbon layer base material is filled, it is economically preferable, and the manufacturing cost of MEA can be reduced.

  The specific form of the adhesive is not particularly limited, and a conventionally known adhesive can be appropriately selected. For example, polyolefin adhesives such as polyethylene and polypropylene, hot melt adhesives such as thermoplastic elastomers, acrylic adhesives, and the like can be used as appropriate. Especially, it is preferable to fill with a hot-melt adhesive from the viewpoint of easy adhesion, accurate bonding position, and long-time adhesion. Hot melt adhesives are preferably used. The melting temperature of the hot-melt adhesive when using the hot-melt adhesive is easy to handle (easiness of impregnation into the electrolyte membrane, easy to form an adhesive member), deterioration temperature of the electrolyte membrane, fuel cell In view of durability at the use temperature, the temperature is preferably 100 to 200 ° C, more preferably 110 to 150 ° C.

  Examples of the technique for filling the adhesive filling portion of the carbon layer base material with an adhesive include a technique such as vacuum filling.

  As for the thickness of the carbon layer base material (5a, 5c) other than the active area, the catalyst layer (3a) has a thickness in the active area described above for the portion where the gas diffusion layer is located in the thickness direction of the MEA. 3c), the thickness is preferably 5 to 150 μm, and more preferably 15 to 80 μm. Furthermore, as shown in FIG. 1, the thickness of the carbon layer base material (5a, 5c) at the so-called outer peripheral edge where no gas diffusion layer is located with respect to the thickness direction of the MEA, It is preferably a value slightly smaller than “the thickness + the thickness of the carbon layer base material + the thickness of the gas diffusion layer”, specifically, preferably 30 to 600 μm, more preferably 50 to 300 μm. According to such a form, since the adhesiveness of the separator and gas diffusion layer at the time of single cell lamination | stacking is excellent, it is preferable.

[Seal convex]
As described above, the sealing convex portion can be disposed on the separator (not shown) side of the carbon layer base material (5a, 5c). At this time, the portion where the sealing convex portion is formed is not particularly limited as long as the sealability of the MEA can be improved, and may be formed in contact with at least a part of the carbon layer base material. Moreover, the convex part for a seal | sticker may be scattered so that the recessed part of the separator formed by flow paths, such as gas and a cooling medium, may be filled up. In addition, the sealing convex portion formed on the carbon layer base material may be formed so as to be fitted between the sealing convex portions also formed on the separator.

  The material which comprises the convex part for a seal | sticker will not be restrict | limited especially if it is a material which can ensure the sealing performance of a separator and MEA. For example, rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene Preferable examples include fluorine-based polymer materials such as a copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. With these materials, the MEA and the separator can be brought into close contact with each other by elastic deformation, and the gas sealability is improved.

  The shape of the sealing convex portion is not particularly limited as long as the sealability of the MEA can be improved, and the cross-sectional shape is a triangle or more polygon, quadrilateral, rectangle, cylinder, truncated cone, polygonal column. , And a polygonal frustum.

  The method for producing the MEA of the present invention is not particularly limited, and can be produced by appropriately referring to conventionally known knowledge about the method for producing MEA. As an example, an MEA having the form shown in FIG. 1 forms a catalyst layer (3a, 3c) on each side of the electrolyte membrane 2, then arranges carbon layer substrates (5a, 5c), and finally gas. Manufacture is possible by arranging the diffusion layers (4a, 4c) and, if necessary, sealing convex portions.

  In the MEA of the present invention, the carbon layer base material (5a, 5c) has a carbon material and a water repellent in the active area, and an adhesive on at least the contact surface side with the electrolyte membrane 2 in a portion other than the active area. However, when the MEA is manufactured by the above-described method, each of these components may be filled after the carbon layer base material (5a, 5c) is arranged. You may arrange | position the carbon layer base material (5a, 5c) with which it filled. Here, as a method for filling the carbon layer base material (5a, 5c) with the carbon material and the water repellent, for example, a method such as vacuum filling is exemplified. This vacuum filling can also be used as a method of filling the carbon layer base material (5a, 5c) with an adhesive. However, it is not limited only to these methods, and other methods may be adopted if possible.

  FIG. 5 is a diagram showing another preferred embodiment of the MEA of the present invention. In the form shown in FIG. 5, a part of the carbon layer base material (5a, 5c) where the gas diffusion layer (4a, 4c) is not located in the thickness direction of the electrolyte membrane 2 (part “C” shown in FIG. 5; Hereinafter, a gasket layer (6a, 6c) different from the carbon layer base material (5a, 5c) is further positioned on the surface of the “peripheral portion” facing the electrolyte membrane 2.

  According to the embodiment shown in FIG. 5, MEA can be manufactured using a simpler method. Moreover, according to such a form, since a carbon layer base material (5a, 5c) and a gasket layer (6a, 6c) can be used as a gas seal member in an outer peripheral part, selection of the constituent material of a gas seal member is possible. The degree of freedom can be improved. The gasket layers (6a, 6c) can be bonded to the carbon layer base materials (5a, 5c) with an adhesive filled in the carbon layer base materials (5a, 5c) at the outer peripheral portion.

  The material constituting the gasket layer (6a, 6c) is not particularly limited, and examples thereof include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and (polyvinylidene fluoride (PVDF)). It is done.

  The thickness of the gasket layer (6a, 6c) is not particularly limited, but preferably 10 to 450 μm in consideration of setting the upper surface of the gasket layer slightly lower than the upper surface of the gas diffusion layer from the same viewpoint as the above embodiment. More preferably, it is 40-250 micrometers.

  If necessary, an adhesive layer may be further provided between the carbon layer base material (5a, 5c) and the gasket layer (6a, 6c) to further improve the adhesion. Although the specific structure of such an adhesive layer is not particularly limited, examples of the constituent material of the adhesive layer include a hot melt adhesive. The thickness of the adhesive layer is not particularly limited, but may be about 5 to 20 μm.

  The method for manufacturing the MEA having the form shown in FIG. 5 is not particularly limited. For example, in the MEA having the form shown in FIG. 5, the catalyst layers (3a, 3c) are formed on the respective sides of the electrolyte membrane 2, the carbon layer base materials (5a, 5c) are then disposed, and the gas diffusion layers (4a, 4c) and the gasket layer (6a, 6c) can be manufactured either by arranging them first or at the same time, and after placing the gasket layers (6a, 6c), if necessary, by arranging sealing protrusions. At this time, the timing of filling each component into the carbon layer base material (5a, 5c) is as described above.

  In the form shown in FIG. 5, the portion where the catalyst layers (3a, 3c) are not located and the gas diffusion layers (4a, 4c) are located with respect to the thickness direction of the electrolyte membrane 2 (part “B”), and the gas diffusion The thickness of the carbon layer base material (5a, 5c) is substantially the same in the part (outer peripheral part; part "C") where the layer (4a, 4c) is not located. Note that “substantially the same” means that the difference in thickness between the portion “B” and the portion “C” is ± 20 μm. However, as described above, when the gasket layer (6a, 6c) different from the carbon layer base material (5a, 5c) is disposed, as shown in FIG. )) With respect to the thickness of the carbon layer base (5a, 5c) and the portion where the catalyst layers (3a, 3c) are not located and the gas diffusion layers (4a, 4c) are located (portion "B" shown in FIG. 6). It is preferable to make it thinner. According to such a form, compared with the form shown in FIG. 5, the alignment of each member at the time of MEA manufacture becomes easy. That is, when the MEA having the form shown in FIG. 6 is manufactured, the carbon layer base materials (5a, 5c) are arranged after the formation of the catalyst layers (3a, 3c), and then the gasket layers (6a, 6c) are arranged. Later, by arranging the gas diffusion layers (4a, 4c) and sealing protrusions as necessary, the alignment of the gasket layer and the gas diffusion layer can be precisely controlled. In such a form, the difference in thickness between the part “B” and the part “C” is not particularly limited, but the thickness of the carbon layer base material in the part “C” is equal to the carbon layer base material in the part “B”. It is preferable that it is 10 to 90% with respect to the thickness of, and it is more preferable that it is 30 to 70%.

  As described above, in the MEA of the present invention, a part other than the active area of the carbon layer base material (5a, 5c) is filled with an adhesive. For this reason, in some cases, the adhesive filled in the carbon layer base material may move in the carbon layer base material to the active area. When the adhesive moves through the carbon substrate to the active area of the catalyst layer and the gas diffusion layer, gas diffusion is hindered and battery performance may be deteriorated. Therefore, it is preferable to perform a process for suppressing the movement of the adhesive to the active area.

  As such a process, for example, as shown in FIG. 7, the peripheral portions (shaded portions shown in FIG. 7) of the gas diffusion layers (4a, 4c) and / or the carbon layer base materials (5a, 5c) For example, the porosity of the portion adjacent to the peripheral portion (the shaded portion shown in FIG. 7) is reduced (referred to as low porosity portions (7a, 7c)). When providing such a low porosity part (7a, 7c), the specific value of the porosity is not particularly limited. For example, the porosity of the material constituting the general gas diffusion layer is 50 to 90%, but the porosity of the low porosity portion provided in the gas diffusion layer portion is preferably 5 to 50%, more preferably 10%. It may be ˜30%. Further, the porosity of the constituent material of the carbon base material layer is usually 50 to 90%, but the porosity of the low porosity portion provided in the carbon layer base material portion is preferably 5 to 50%, more preferably 10%. It may be ˜30%. In addition, in the form shown in FIG. 5, although the low porosity part (7a, 7c) is provided in the peripheral part of both the gas diffusion layer (4a, 4c) and the carbon layer base material (5a, 5c), It is not restricted only to such a form, The form by which a low porosity part is provided only in any one peripheral part of a gas diffusion layer (4a, 4c) or a carbon layer base material (5a, 5c) is also employ | adopted. Can be done.

  There is no restriction | limiting in particular about the specific method of the porosity reduction process for providing a low porosity part. For example, as a simple method, a method of increasing the content of the water repellent filled in the gas diffusion layer and the carbon base material layer in a portion where the low porosity portion is desired as compared with other portions is exemplified. Is done. At this time, the specific value of the content of the water repellent to be filled and the content ratio compared with other parts are not particularly limited, and are appropriately adjusted so that the preferable value of the porosity described above is achieved. do it.

  As described above, the MEA of the present invention can be produced by a simple operation. Furthermore, according to the present invention, an MEA having excellent durability when single cells are stacked can be provided.

  The type of fuel cell in which the MEA of the present invention is used is not particularly limited. In the above description, the solid polymer fuel cell has been described as an example. In addition to this, the MEA of the present invention is an alkaline fuel cell, an acid electrolyte fuel cell represented by a phosphoric acid fuel cell, a direct fuel cell, and the like. It can also be applied to methanol fuel cells, micro fuel cells, and the like. Among these, the MEA of the present invention is preferably applied to a polymer electrolyte fuel cell from the viewpoint of being small and capable of high density / high output.

  The configuration of the fuel cell is not particularly limited, and a conventionally known technique may be used as appropriate. Generally, the fuel cell has a structure in which an MEA is sandwiched between separators.

  The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating air and fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  Furthermore, a stack in which a plurality of MEAs are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  The electrolyte membrane-electrode assembly (MEA) of the present invention is applied to a fuel cell and can reduce the number of man-hours required for the work for manufacturing the fuel cell. Moreover, the MEA of the present invention can improve the durability of the fuel cell.

It is a figure which shows preferable one Embodiment of MEA of this invention. It is a figure which shows other preferable embodiment of MEA of this invention. It is a figure which shows other preferable embodiment of MEA of this invention. It is a figure which shows arrangement | positioning of the cathode catalyst layer and anode catalyst layer in MEA of this invention. It is a figure which shows other preferable embodiment of MEA of this invention. It is a figure which shows other preferable embodiment of MEA of this invention. It is a figure which shows other preferable embodiment of MEA of this invention.

Explanation of symbols

1 electrolyte membrane-electrode assembly,
2 electrolyte membrane,
3a anode catalyst layer,
3c cathode catalyst layer,
4a anode side gas diffusion layer,
4c cathode side gas diffusion layer,
5a Anode-side carbon layer substrate,
5c cathode side carbon layer base material,
6a Anode side gasket layer,
6c cathode side gasket layer,
7a Anode-side low porosity part,
7c Cathode side low porosity part.

Claims (11)

An electrolyte membrane;
A cathode catalyst layer located on one side of the electrolyte membrane;
An anode catalyst layer located on the other side of the electrolyte membrane;
A cathode-side gas diffusion layer located on a surface of the cathode catalyst layer facing the electrolyte membrane;
An anode-side gas diffusion layer located on a surface of the anode catalyst layer facing the electrolyte membrane;
At the part where the catalyst layer is located in at least one of the cathode side or the anode side with respect to the thickness direction of the electrolyte membrane, the catalyst layer is interposed between the gas diffusion layer and the gas diffusion layer is located. A carbon layer base material that is adjacent to the electrolyte membrane at a portion that does not, and whose end substantially coincides with the end of the electrolyte membrane in the thickness direction;
A portion of the carbon layer substrate where the catalyst layer is located is filled with a carbon material and a water repellent, and at least the electrolyte membrane of the portion of the carbon layer substrate where the catalyst layer is not located An electrolyte membrane-electrode assembly in which the contact surface side is filled with an adhesive.   The carbon layer base material is interposed between the catalyst layer and the gas diffusion layer at a portion where the catalyst layer is located with respect to the thickness direction of the electrolyte membrane, and the gas diffusion layer is not located. Is located between the electrolyte membrane and the gas diffusion layer at a portion where the gas diffusion layer is located, is adjacent to the electrolyte membrane at a portion where the gas diffusion layer is not located, and an end portion is an end of the electrolyte membrane with respect to the thickness direction. The electrolyte membrane-electrode assembly according to claim 1, which substantially coincides with the portion.   The electrolyte membrane-electrode assembly according to claim 1 or 2, wherein the carbon layer substrate is present on both the cathode side and the anode side.   The gasket layer according to any one of claims 1 to 3, further comprising a gasket layer positioned on a surface facing the electrolyte membrane in a portion where the gas diffusion layer is not positioned with respect to the thickness direction of the carbon layer base material. Electrolyte membrane-electrode assembly.   The thickness of the carbon layer base material is substantially the same in a portion where the catalyst layer is not located and the portion where the gas diffusion layer is located and a portion where the gas diffusion layer is not located in the thickness direction. 2. The electrolyte membrane-electrode assembly according to 1.   The thickness of the carbon layer base material at a portion where the gas diffusion layer is not located with respect to the thickness direction is thinner than a portion where the catalyst layer is not located and the gas diffusion layer is located. Electrolyte membrane-electrode assembly.   The gas diffusion layer has a low porosity part whose porosity is small compared to other parts of the gas diffusion layer in at least a part of the peripheral part, or the carbon layer base material is the peripheral part. The electrolyte membrane according to any one of claims 1 to 6, which has a low porosity part having a porosity lower than that of the other part of the carbon layer base material in at least a part of a part adjacent to the carbon layer base material. Electrode assembly.   The electrolyte membrane-electrode assembly according to claim 7, wherein the content of the water repellent is higher in the low porosity part than in the other part.   The electrolyte membrane-electrode assembly according to claim 1, wherein an area of the anode catalyst layer is larger than an area of the cathode catalyst layer.   The electrolyte membrane-electrode assembly according to claim 1, wherein the adhesive is a hot melt adhesive.   A fuel cell using the electrolyte membrane-electrode assembly according to any one of claims 1 to 10.

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