WO2008050611A1

WO2008050611A1 - Membrane for fuel cell, membrane electrode assembly and fuel cell

Info

Publication number: WO2008050611A1
Application number: PCT/JP2007/069793
Authority: WO
Inventors: Mikio Sugiura
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2006-10-23
Filing date: 2007-10-03
Publication date: 2008-05-02
Also published as: JP2008108468A

Abstract

A membrane (1A) for fuel cell includes opposite surfaces, and an identifier (3). The identifier (3) exhibits an identifying property, and is disposed in at least a part of one of the opposite surfaces. The identifier (3) makes it possible to distinguish the front surface and rear surface of the membrane (1A), or the front and rear of an MEA (1) or fuel cell, which includes the membrane (1A).

Description

DESCRIPTION

MEMBRANE FOR FUEL CELL, MEMBRANE ELECTRODE ASSEMBLY

AND

FUEL CELL TECHNICAL FIELD

[OOOl] The present invention relates to a membrane for fuel cell and a membrane electrode assembly, which make a fuel cell, and a fuel cell.

BACKGROUND ART

[0002] Recently, the energy consumption has enlarged drastically as the global economy develops so that the environmental deterioration has been worried about. Under such circumstances, the development of fuel cells has been drawing people' s attention as one of the solutions to environmental issues and energy issues. Fuel cells convert chemical energy into electric energy by means of the electrochemical reactions using an oxidizing-agent gas, such as oxygen and air, and a reducing-agent gas (or a fuel gas) , such as hydrogen and methane, as raw materials.

[0003] Fuel cells are classified according to the type of employed electrolytes. For example, it is possible to name molten carbonate fuel cells, phosphoric acid fuel cells, solid polymer fuel cells (or proton-exchange membrane fuel cells) and solid oxide fuel cells . Among them, proton-exchange membrane fuel cells have been drawing engineers' utmost attention because they have many advantages. Basically, a proton-exchangemembrane fuel cell comprises a polymer electrolyte membrane, catalytic layers, and diffusion layers.

The polymer electrolyte membrane transports hydrogen ions therethrough selectively. The catalytic layers are formed on the opposite surfaces of the polymer electrolyte membrane, and their major component is a carbon powder with a platinum-group metal loaded. The diffusion layers are formed on the outer surface of the catalytic layers, and exhibits both permeability and conductivity. The diffusion layers and catalytic layers are combined to make catalytic electrodes.

[0004] The polymer electrolyte membrane with the catalytic electrodes attached on the opposite surfaces is referred to as amembrane electrode assembly (hereinafter abbreviated toas "MEA") . Moreover, a conductive separator plate is placed on an outer side of the MEA. The separator is for fixing the MEA mechanically, and is for connecting the neighboring MEAs in series electrically to each other. In addition, a gas flow passage is formed at the contact between the separator plate and the MEA. The gas flow passage is for supplying reaction gases onto the electrode surfaces, and is for taking away the generated gases and excessive gases. Note that, although it is possible to dispose the gas flow passage independently of the separator plate, it is a general practice to provide the surface of the separator plate with a groove to make the gas flow passage.

[0005] Moreover, a plurality of MEAs and separator plates are laminated alternately to make a stack of fuel cells. In such a stacked proton-exchange membrane fuel cell, the anode electrode layers and the cathode electrode layers are formed as an identical shape, and are formed as a symmetrical shape with respect to the central axis of the stacked proton-exchange membrane fuel cell. Accordingly, upon assembling such a stacked proton-exchange membrane fuel cell, especially upon assembling MEAs, it might be highly likely that the anode electrode layers and the cathode electrode layers are assembled faultily if the anode electrode layers and cathode electrode layers are formed as the same shape and do not exhibit any orientation. Consequently, there might arise such a problem that anode electrode layers have been combined with each other, or cathode electrode layers have been combined with each other, or an anode electrode layer and a cathode electrode layer have been placed reversely. In addition, even upon assembling a stacked proton-exchange membrane fuel cell, there might arise a fear that an anode electrode layer and a cathode electrode layer have been placed reversely if the resulting MEA do not exhibit any orientation.

[0006] The following patent publications are available as prior art publications, which disclose countermeasures for the above-described problems:

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-331,851;

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2001-253,763;

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2006-179,221;

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 7-183,033;

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-115,319;

Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2004-179,124; and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2002-367,662.

For example, Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-331,851 discloses, in a fuel cell using a solid polymer electrolytic membrane, to subject at least one of the catalytic layers and gas diffusion layers to marking. The marking makes it possible to distinguish between the anode electrode layers and the cathode electrode layers. Specifically, the marking is made by cutting the catalytic layers or gas diffusion layers at one of the corners at least (hereinafter referred to as "C" cutting) , thereby making it possible to turn the shape of the catalytic layers or gas diffusion layers into an asymmetric shape with respect to the central axis.

[0007] As disclosed in Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-331,851, when subjecting a proton-exchange membrane fuel cell's catalytic layers or gas diffusion layers to the "C" cutting, the resulting MEAs are formed as an asymmetric shape with respect to the central axis. However, when laminating such MEAs to make a stacked proton-exchange membrane fuel cell, the resultant stacked proton-exchangemembrane fuel cell is likely to turn into a distorted shape so that it might show poor stability disadvantageously. Moreover, performing the "C" cuttingmight result in such problems that the gas flowpassages, which are formed in the separator plates, might show deteriorated uniformity, and dead spaces are likely to occur. In addition, the difficulty in designing the separator plates might increase.

DISCLOSURE OF THE INVENTION

[0008] The present invention has been developed in view of the aforementioned circumstances. It is therefore an object of the present invention to provide a membrane for fuel cell, a membrane electrode assembly, and a fuel cell, which can identify specific fuel-cell membranes, and which can inhibit membrane electrode assemblies and fuel cells from being assembled faultily.

[0009] A membrane according to the present invention for fuel cell comprises: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces. Note that in the present membrane, the "identifying property" can preferably be at least one property being selected from the group consisting of optical properties, magnetic properties, visual properties and contact properties. The "optical properties" are those identifying properties, which are based on optical absorbability and/or optical reflectivity. The "magnetic properties" are those identifying properties, which result from magnetic poles or magnetic flux densities. The "visual properties" are those identifyingproperties, whichdepend onhuman being's naked eyes. The "contact properties" are those identifying properties, which are superficial states of contact surface resulting in the change of pressure that is applied onto the contact surface. Since the present membrane comprises an identifier, which exhibits an optical property, amagneticproperty, a visual property or a contact property, in at least a part of one of the opposite surfaces, it is possible to distinguish between the front surface and the rear surface. Accordingly, workers or manufacturing apparatuses can make the distinction between the present membrane' s front surface and rear surface . In particular, giving different properties to each of the present membrane' s front surface and rear surface is effective in making the distinction between the present membrane's front surface and rear surface. Note that the present membrane includes not only an electrolyte membrane but also its attachments (i.e., reinforcement membranes, for instance) .

[OOIO] Moreover, the identifier of the present membrane can preferably comprise at least one member selected from the group consisting of letters, numeric characters, symbols, patterns and irregular states. In addition, as for the identifier, it is possible to further exemplify bar codes and QR codes, for instance .

[OOll] In addition, the present membrane can preferably exhibit translucency in a thickness-wise direction thereof, and can preferably further comprise a front surface and a rear surface; the identifier can preferably comprise a first contour, which is viewed on the front-surface side of the membrane, and a second ^■ contour, which is viewed on the rear-surface side of the membrane; and the front contour and the second contour can preferably be formed as asymmetric shapes to each other. Namely, when observing the present membrane, which exhibits translucency in the thickness-wise direction, on the front-surface side or the rear-surface side, it is possible to make the distinction between whether viewing the front surface of the present membrane and whether viewing the rear surface thereof because the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other. In other words, when the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other, it is possible to distinguish between the front surface and rear surface of the present membrane because the first contour of the identifier, which is viewed on the front-surface side, and the second contour thereof, which is viewed on the rear-surface side, do not coincide with each other.

[0012] Moreover, the present membrane can preferably exhibit non- translucency or weak translucency in a thickness-wise direction thereof; and the identifier can preferably be disposed on one of the opposite surfaces of the present membrane. That is, when the present membrane exhibits non-translucency in the thickness-wise direction, or when it is difficult to transmit light in the thickness-wise direction of the present membrane, the identifier, which is disposed on one of the opposite surfaces of the present membrane, makes it possible to distinguish between the front surface and rear surface of the present membrane. To put it differently, when determining or knowing the one of the opposite surfaces of the present membrane, on which the identifier is disposed, in advance, it is possible to identify whether it is the front surface of the present membrane or whether it is the rear surface thereof at least from the presence or absence of the identifier thereon.

[0013] In addition, the present membrane can even have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, coincide with each other. Even if the first contour, being viewed on the front side, and the second contour, beingviewed on the rear side, coincide with each other, it is possible to identify whether it is the front surface or rear surface of the present membrane from the presence of the identifier thereon or the shape of the identifier' s contour. Namely, even when it is not possible to make the distinction between the front and rear of the present membrane from the present membrane' s configuration, it is possible to distinguish them with the identifier.

[0014] However, the present membrane can preferably have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, differ to each other. That is, since the first contour of the membrane, beingviewedon the front side, andthe secondcontour of themembrane, being viewed on the rear side, have different shapes to each other, it is possible to identify whether it is the front surface or rear surface of the present membrane from the present membrane's configuration, in addition to the presence of the identifier thereon or the shape of the identifier's contour. Specifically, it is possible to make the identifier from the present membrane' s own configuration, and thereby it is possible to distinguish the front and rear of the present membrane. In addition, even if a plurality of the present membranes are laminated so that the identifiers are superimposed to be unrecognizable, it is possible to distinguish the front and rear of the present membrane or resulting MEA from the present membrane's own configuration.

[0015] Moreover, thepresent membrane' s identifier can preferably have a function of identifying at least one member selected from the group consisting of the present membrane's front and rear, top and bottom and right and left. Thus, in addition to the configuration of the letters, numeric characters, symbols, patterns and irregular states, or in addition to their placement on the present membrane, it is possible not only to make the distinction between the front surface and rear surface of the present membrane but also to make the distinction between the positional relationships of the present membrane such as the present membrane' s top and bottom as well as right and left. That is, the identifier's identifying property makes it possible to display information, such as the present membrane' s front and rear, top and bottom and right and left, depending on the location of the identifier, which is placed on the present membrane, and depending on the identifier's configuration.

[0016] In addition, the present membrane's identifier can be formed by at least one process selected from the group consisting of printing, mechanical embossing, cutting, stamping inks, ink-jet printing, etching, embossing by means of heat , embossing by means of light, pressing, and adhering. Note that, when forming the identifier employing dyes or inks, it is preferable that the dyes or inks can have a composition which is less likely to decompose thermally. It is more preferable to carbonize the present membrane's surface by means of irradiation (or heat) using a high energy-density beam, such as a laser beam, in order to form the identifier. When forming the identifier, it is preferable to employ a formingprocess, like the aforementioned formingprocesses, that generates products, which are less likely to give adverse affects to the present membrane's performance, as it forms the identifier.

[0017] Moreover, the present membrane can preferably comprise an organic polymer membrane. Note however that, not limited to an organic polymer membrane, the present membrane can even comprise an inorganic membrane, that is, any membrane exhibiting ionic conductivity is allowable for making the present membrane satisfactorily.

[0018] An MEA according to the present invention comprises: a membrane for fuel cell, the membrane comprising: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces; an anode electrode layer being laminated on one of the opposite surfaces of the membrane; and a cathode electrode layer being laminated on the other one of the opposite surfaces of the membrane.

The present MEA makes it possible to distinguish between the front surface and rear surface of fuel-cell membrane in manufacturing MEAs. Accordingly, workers or manufacturing apparatuses can make the distinction between the front surface and rear surface of fuel-cell membrane.

[0019] In thepresentMEA, the anode electrode layer canpreferably comprise an anode catalytic layer, and an anode diffusion layer; and the cathode electrode layer can preferably comprise a cathode catalytic layer, and a cathode diffusion layer. Moreover, in the present MEA, the anode electrode layer and the cathode electrode layer can have different compositions to each other, that is, compositions which are not identical with each other . For example, the anode catalytic layer can preferably comprise a carbon (C) support, and an alloy being loaded on the carbon support and being made of platinum (Pt) and rhodium (Rh) ; and the cathode catalytic layer can preferably comprise a carbon (C) support, and Pt being loaded on the carbon support . Therefore, when the anode electrode layer and the cathode electrode layer thus have different compositions to each other, that is, compositions which are not identical with each other, it is needed to assemble an MEA while making the distinction between the anode electrode layer and the cathode electrode layer. On this occasion, since the present MEA comprises the identifier, it is possible to identify the information concerning the front and rear of MEA upon holding an MEA with separators to make a single cell. Accordingly, it is possible to assemble the present MEA while making the distinction between the anode electrode layer and the cathode electrode layer. Consequently, it is possible to preemptively inhibit the problem of faulty products that result from the failure assemblage of the anode electrode layer and cathode electrode layer.

[0020] The "identifyingproperty" of the present MEA' s identifier can preferably be at least one property being selected from the group consisting of optical properties, magnetic properties, visual properties and contact properties. Since the present MEA comprises an identifier, which exhibits one of these properties, in at least a part of the opposite surfaces, it is possible to distinguish between the front surface and rear surface of the present MEA. Accordingly, workers or manufacturing apparatuses can make the distinction between the present MEA' s front surface and rear surface. In other words, giving different properties to each of the present MEA' s front surface and rear surface enables workers or manufacturing apparatuses to assemble a fuel cell while distinguishing the present MEA' s front surface and rear surface. [0021] Moreover, the identifier of the present MEA can preferably comprise at least one member selected from the group consisting of letters, numeric characters, symbols, patterns and irregular states. In addition, as for the identifier, it is possible to further exemplify bar codes and QR codes, for instance.

[0022] In addition, the present MEA' s fuel-cell membrane can preferably exhibit translucency in a thickness-wise direction thereof, and can preferably further comprise a front surface and a rear surface; the identifier can preferably comprise a first contour, which is viewed on the front-surface side of the fuel-cell membrane, and a second contour, which is viewed on the rear-surface side of the fuel-cell membrane; and the front contour and the second contour canpreferablybe formed as asymmetric shapes to each other. Namely, when observing the present MEA' s fuel-cell membrane, which exhibits translucency in the thickness-wise direction, on the front-surface side or the rear-surface side, it is possible to make the distinction between whether viewing the front surface of the fuel-cell membrane and whether viewing the rear surface thereof because the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other. In other words, when the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other, it is possible to distinguish between the front surface and rear surface of the present MEA because the first contour of the identifier, which is viewed on the front-surface side, and the second contour thereof, which is viewed on the rear-surface side, do not coincide with each other.

[0023] Moreover, the present MEA' s fuel-cell membrane can preferably exhibit non-translucency or weak translucency in a thickness-wise direction thereof; and the identifier can preferably be disposed on one of the opposite surfaces of the fuel-cell membrane. That is, when the present MEA' s fuel-cell membrane exhibits non-translucency in the thickness-wise direction, or when it is difficult to transmit light in the thickness-wise direction of the present MEA' s fuel-cell membrane, the identifier, which is disposed on one of the opposite surfaces of the fuel-cell membrane, makes it possible to distinguish between the front surface and rear surface of the present MEA. To put it differently, when determining or knowing the opposite surfaces of the present MEA' s fuel-cell membrane, on which the identifier is disposed, in advance, it is possible to identify whether it is the front surface of the present MEA or whether it is the rear surface thereof at least from the presence or absence of the identifier on one of the opposite surfaces of the present MEA' s fuel-cell membrane.

[0024] In addition, the present MEA' s fuel-cell membrane can even have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, coincide with each other. Even if the first contour, being viewed on the front side of the present MEA, and the second contour, being viewed on the rear side thereof, coincide with each other, it is possible to identify whether it is the front surface or rear surface of the present MEA from the presence of the identifier on the fuel-cell membrane or the shape of the identifier's contour. Namely, even when it is not possible to make the distinction between the front and rear of the present MEA from the fuel-cell membrane' s configuration, it is possible to distinguish them with the identifier.

[0025] However, the present MEA' s fuel-cell membrane can preferably have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, differ to each other. That is, since the first contour of the fuel-cell membrane, being viewed on the front side of the present MEA, and the second contour of the fuel-cell membrane, being viewed on the rear side thereof, have different shapes to each other, it is possible to identify whether it is the front surface or rear surface of the present MEA from the fuel-cell membrane's configuration, in addition to the presence of the identifier on the fuel-cell membrane or the shape of the identifier's contour. Specifically, it is possible to make the identifier from the present MEA' s own configuration, and thereby it is possible to distinguish the front and rear of the present MEA. In addition, even if a plurality of the fuel-cell membranes are laminated so that the identifiers are superimposed to be unrecognizable, it is possible to distinguish the front and rear of the present MEA or resulting fuel cell from the fuel-cell membrane's own configuration.

[0026] Moreover, the present MEA' s identifier can preferably have a function of identifying at least one member selected from the group consisting of the present MEA' s front and rear, top and bottom and right and left. Further, it is advisable as well that the present MEA' s identifier can have a function of identifying at least onemember selected fromthe group consisting of the present MEA' s or fuel-cell membrane's material quality, manufacturer and manufacturing process. Thus, in addition to the configuration of letters, numeric characters, symbols, patterns and irregular states, or in addition to their placement on the present MEA' s fuel-cell membrane, it is possible not only to make the distinction between the front surface and rear surface of the present MEA but also to make the distinction between the positional relationships of the present MEA' s fuel-cell membrane such as the fuel-cell membrane's top and bottom as well as right and left. That is, the identifier' s identifying property makes it possible to display information, such as the present MEA' s front and rear, top and bottom and right and left, depending on the location of the identifier, which is placed on the present MEA' s fuel-cell membrane, and depending on the identifier's configuration.

[0027] In addition, the present MEA' s identifier can be formed by at least one process selected from the group consisting of printing, mechanical embossing, cutting, stamping inks, ink-jet printing, etching, embossing by means of heat, embossing by means of light, pressing, and adhering. Note that, when forming the identifier employing dyes or inks, it is preferable that the dyes or inks can have a composition which is less likely to decompose thermally. It is more preferable to carbonize the fuel-cell membrane' s surface by means of irradiation (or heat) using a high energy-density beam, such as a laser beam, in order to form the identifier. When forming the identifier, it is preferable to employa formingprocess, like the aforementioned formingprocesses, that generates products, which are less likely to give adverse affects to the performance of the present MEA' s fuel-cell membrane as it forms the identifier. [0028] Moreover, the present MEA' s fuel-cell membrane can preferably comprise an organic polymer membrane. Note however that, not limited to an organic polymer membrane, the fuel-cell membrane can even comprise an inorganic membrane, that is, any membrane exhibiting ionic conductivity is allowable for making the present MEA' s fuel-cell membrane satisfactorily. [0029] A fuel cell according to the present invention comprises: a membrane electrode assembly comprising: a membrane for fuel cell, the membrane comprising: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces; an anode electrode layer being laminated on one of the opposite surfaces of the membrane; and a cathode electrode layer being laminated on the other one of the opposite surfaces of the membrane; a first separator being disposed on an outer side of the anode electrode layer; and a second separator being disposed on an outer side of the cathode electrode layer.

The present fuel cell makes it possible to distinguish between the front surface and rear surface of fuel-cell membrane in manufacturing fuel cells. Accordingly, workers or manufacturing apparatuses can make the distinction between the front surface and rear surface of fuel-cell membrane, andean assemble the present fuel cell correctly.

[0030] In the present fuel cell, the anode electrode layer can preferably comprise an anode catalytic layer, and an anode diffusion layer; and the cathode electrode layer can preferably comprise a cathode catalytic layer, and a cathode diffusion layer. [003l] Moreover, in the present fuel cell, the anode electrode layer and the cathode electrode layer can have different compositions to each other, that is, compositions which are not identical with each other. When the anode electrode layer and the cathode electrode layer thus have different compositions to each other, that is, compositions which are not identical with each other, it is needed to assemble an MEA while making the distinction between the anode electrode layer and the cathode electrode layer. On this occasion, since the present fuel cell comprises the identifier, it is possible to identify the information concerning the front and rear of MEA upon holding an MEA with separators to make a single cell. Accordingly, it is possible to assemble the present fuel cell while making the distinction between the anode electrode layer and the cathode electrode layer. Consequently, it is possible to preemptively inhibit the problem of faulty products that result from the failure assemblage of the anode electrode layer and cathode electrode layer .

[0032] The "identifying property" of the present fuel cell's identifier can preferably be at least one property being selected from the group consisting of optical properties, magnetic properties, visual properties and contact properties. Since the present fuel cell comprises an identifier, which exhibits one of these properties, in at least a part of the MEA' s opposite surfaces, it is possible to distinguish between the front surface and rear surface of the present fuel cell's MEA. Accordingly, workers or manufacturing apparatuses can make the distinction between the front surface and rear surface of the present fuel cell's MEA. In other words, giving different properties to each of the front surface and rear surface present fuel cell's MEA enables workers or manufacturing apparatuses to assemble a fuel cell while distinguishing the front surface and rear surface of the present fuel cell's MEA.

[0033] Moreover, the identifier of the present fuel cell can preferably comprise at least one member selected from the group consisting of letters, numeric characters, symbols, patterns and irregular states. In addition, as for the identifier, it is possible to further exemplify bar codes and QR codes, for instance . [0034] In addition, the present fuel cell' s fuel-cell membrane can preferably exhibit translucency in a thickness-wise direction thereof, and can preferably further comprise a front surface and a rear surface; the identifier can preferably comprise a first contour, which is viewed on the front-surface side of the membrane, and a second contour, which is viewed on the rear-surface side of the membrane; and the front contour and the second contour can preferably be formed as asymmetric shapes to each other. Namely, when observing the fuel-cell membrane of the present fuel cell' s MEA, fuel-cell membrane which exhibits translucency in the thickness-wise direction, on the front-surface side or the rear-surface side, it is possible to make the distinction'between whether viewing the front surface of the fuel-cell membrane and whether viewing the rear surface thereof because the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other. In other words, when the identifier comprises the first contour and second contour which are formed as asymmetric shapes to each other, it is possible to distinguish between the front surface and rear surface of the present fuel cell' s MEAbecause the first contour of the identifier, which -is viewed on the front-surface side, and the second contour thereof, which is viewed on the rear-surface side, do not coincide with each other.

[0035] Moreover, the present fuel cell' s fuel-cell membrane can preferably exhibit non-translucency or weak translucency in a thickness-wise direction thereof; and the identifier can preferably be disposed on one of the opposite surfaces of the fuel-cell membrane. That is, when the present fuel cell's fuel-cell membrane exhibits non-translucency in the thickness-wise direction, or when it is difficult to transmit light in the thickness-wise direction of the present fuel cell's fuel-cell membrane, the identifier, which is disposed on one of the opposite surfaces of the fuel-cell membrane, makes it possible to distinguish between the front surface and rear surface of the present fuel cell's MEA. To put it differently, when determining or knowing the opposite surfaces of the fuel-cell membrane of the present fuel cell's MEA, on which the identifier is disposed, in advance, it is possible to identify whether it is the front surface of the present fuel cell's MEA or whether it is the rear surface thereof at least from the presence or absence of the identifier on one of the opposite surfaces of the fuel-cell membrane of the present fuel cell's MEA.

[0036] In addition, the present fuel cell's fuel-cell membrane can even have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, coincide with each other. Even if the first contour, being viewed on the front side of the present fuel cell, and the second contour, being viewed on the rear side thereof, coincide with each other, it is possible to identify whether it is the front surface or rear surface of the present fuel cell from the presence of the identifier on the fuel-cell membrane or the shape of the identifier' s contour. Namely, even when it is not possible to make the distinction between the front and rear of the present fuel cell from the fuel-cell membrane' s configuration, it is possible to distinguish them with the identifier.

[0037] However, the present fuel cell's fuel-cell membrane can preferably have a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, differ to each other. That is, since the first contour of the fuel-cell membrane, being viewed on the front side of the present fuel cell, and the second contour of the fuel-cell membrane, being viewed on the rear side thereof, have different shapes to each other, it is possible to identify whether it is the front surface or rear surface of the present fuel cell from the configuration of present fuel cell's fuel-cell membrane, in addition to the presence of the identifier on the fuel-cell membrane or the shape of the identifier's contour. Specifically, it is possible to make the identifier from the own configuration of the present fuel cell' s MEA, and thereby it is possible to distinguish the front and rear of the present fuel cell. In addition, even if a plurality of the fuel-cell membranes are laminated so that the identifiers are superimposed to be unrecognizable, it is possible to distinguish the front and rear of the present fuel cell or resulting stacked fuel cell from the own configuration of the present fuel cell's fuel-cell membrane.

[0038] Moreover, the present fuel cell's identifier can preferably have a function of identifying at least one member selected from the group consisting of the present fuel cell' s front and rear, top and bottom and right and left. Further, it is advisable as well that the present fuel cell' s identifier can have a function of identifying at least one member selected from the group consisting of the MEA' s or fuel-cell membrane's material quality, manufacturer and manufacturing process. Thus, in addition to the configuration of the letters, numeric characters, symbols, patterns and irregular states, or in addition to their placement on the present fuel cell's fuel-cell membrane, it is possible not only to distinguish the front surface and rear surface of the present fuel cell but also to distinguish the positional relationships of the gas flow passages, which are formed in the present fuel cell's separators, such as the top and bottom relationship of the gas flow passages' upstream and downstream areas as well as their right and left relationship thereof. Therefore, this identifying function of the present fuel cell's identifier is advantageous in view of designing the gas flow passages and in view of controlling the flow of gases.

[0039] In addition, the present fuel cell's identifier can be formed by at least one process selected from the group consisting of printing, mechanical embossing, cutting, stamping inks, ink-jet printing, etching, embossing by means of heat , embossing by means of light, pressing, and adhering. Note that, when forming the identifier employing dyes or inks, it is preferable that the dyes or inks can have a composition which is less likely to decompose thermally. It is more preferable to carbonize the fuel-cell membrane' s surface by means of irradiation (or heat) using a high energy-density beam, such as a laser beam, in order. to form the identifier. When forming the identifier, it is preferable to employ a formingprocess, like the aforementioned formingprocesses, that generates products, which are less likely to give adverse affects to the performance of the present fuel cell's fuel-cell membrane, as it forms the identifier.

[0040] Moreover, the present fuel cell's fuel-cell membrane can preferably comprise an organic polymer membrane. Note however that, not limited to an organic polymer membrane, the present fuel cell' s fuel-cell membrane can even comprise an inorganic membrane, that is, any membrane exhibiting ionic conductivity is allowable for making the present fuel cell's fuel-cell membrane satisfactorily.

[0041] In the present fuel cell, the fuel-cell membrane can preferably have a larger area than those of the anode electrode layer and cathode electrode layer; and can preferably have an outer periphery protruding from an outer peripheral side-end surface of the anode electrode layer and cathode electrode layer; and the identifier can preferably be disposed in a surface of the outer periphery. That is, the anode electrode layer and cathode electrode layer are placed at the central part of the fuel-cell membrane, and the identifier is disposed in a surface of the fuel-cellmembrane' s outerperiphery, whichprotrudes froman outer peripheral side-end surface of the anode electrode and cathode electrode. Since the identifier is disposed in a surface of the fuel-cell membrane' s outer periphery, it is placed away from the anode electrode layer and cathode electrode layer radially in the overall surface of the fuel-cell membrane. Consequently, the identifier' s physical properties are less likely to affect the anode electrode layer and cathode electrode layer.

[0042] Moreover, in the present fuel cell, the respective MEAs can preferably comprise the identifier which is disposed in one of the opposite surfaces of the outer periphery. Disposing the identifier in one of the opposite surfaces of the outer periphery makes it easier to make the distinction between the MEAs' front and rear, top and bottom and right and left in assembling fuel cells, and is advantageous for inhibiting them frombeing assembled faultily.

[0043] In addition, in the present fuel-cell membrane, present MEA and present fuel cell, the fuel-cell membrane can preferably further comprises an electrolytic membrane, a reinforcement membrane, which is disposed on an outer surface of the electrolytic membrane, and the identifier, which is placed at a predetermined position in the outer surface of the reinforcement membrane. In the fuel-cell membrane with the preferable construction, it is possible to maintain the strength of the electrolytic membrane, in which the outer periphery is included, when laminating single fuel cells to make a stacked fuel cell by superimposing them by way of the electrolytic membrane's outer periphery.

[0044] Moreover, the present fuel cell can preferably further comprise a plurality of the membrane electrode assemblies being laminated one after another; and the identifiers can preferably show a specific rule being based on an lamination order of the membrane electrode assemblies . The term, "specific rule, " herein designates rules, which specify orders explicitly or implicitly, that is, numeric sequences or patterns, which satisfy certain rules . For example, it is possible to name the following that exhibit certain rules: a numeric sequence such as 1, 2, 3 ^{• • •} and so on; a numeric sequence such as 1, 3, 5 •^{• •}, and so on; a series of alphabetic characters such as A, B, C ^{• • •} , and so on; and a series of Japanese "HIRAGANA" characters such as h, V\ o ^• • • , and so on. Note that it is possible to make a plurality of the identifiers with an identical identifier. It such is the case, it is possible to use an asymmetric character, such as "#," one of Japanese

"KATAKANA" characters, for instance. [0045] In addition, a process according to the present invention for manufacturing fuel cell comprises the steps of: preparing an MEA, which comprises a fuel-cell membrane, an anode electrode layer being laminated on one of the opposite surfaces of the fuel-cell membrane, and a cathode electrode layer being laminated on the other one of the opposite surfaces of the fuel-cell membrane; forming an identifier, which exhibits an identifying property, in at least a part of one of the opposite surfaces of the resulting MEA' s fuel-cell membrane; disposing a first separator and a second separator so that they held the resulting MEA in the thickness-wise direction between them; and placing a plurality of the resulting MEAs one after another in a predetermined direction based on the identifiers, thereby assembling a cellular structure.

The present fuel-cell manufacturing process enables workers or manufacturing apparatuses to distinguish the front surface and rear surface of the resultant fuel-cell membranes when manufacturing fuel cells, and thereby workers or manufacturing apparatuses can assemble fuel cells correctly.

[0046] The present fuel-cell membrane comprises the identifier. The identifier exhibits an identifying property, and is disposed in at least one of the opposite surfaces of the present fuel-cell membrane . The identifier, which is thus placed at a predetermined position in one of the opposite surfaces of the present fuel-cell membrane, makes it possible to distinguish the orientation of the present fuel-cell membrane, such as the present fuel-cell membrane's front and rear, top and bottom and right and left, for instance. Moreover, the identifier makes it possible to distinguish the anode electrode layer and cathode electrode layer of MEAs, which constitute the present fuel cell. Accordingly, the identifier enables workers or manufacturing apparatuses to assemble the present fuel cell correctly. Moreover, since the identifier allows workers or manufacturing apparatuses to distinguish the front and rear, top and bottom and right and left of MEAs, the identifier can inhibit workers or manufacturing apparatuses from getting wrong MEAs mistakingly instead of correct MEAs in the manufacturing process of stacked fuel cells. In addition, since the present fuel-cell membrane can maintain the membrane's own configuration, the present fuel-cell membrane can help solving the structural distortion of staked fuel cells, which occurs resulting from such a cutting process as the "C" cutting. Consequently, the present fuel-cell membrane is advantageous in view of designing separator plates or gas flow passages. Thus, the present invention makes it possible to distinguish the front and rear, top and bottom and right and left of fuel-cell membranes, thereby making it feasible to inhibit fuel cells from being assembled faultily.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] A more complete appreciation of the present invention and many of its advantages will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings and detailed specification, all of which forms a part of the disclosure.

[0048] Fig. 1 is a frontal (or superficial) conceptual diagram for illustrating a fuel-cell membrane according to an example of the present invention.

[ 0049 ] Fig. 2 a cross-sectional conceptual diagram for illustrating the fuel-cell membrane according to the present example .

[0050] Fig. 3 is a rear conceptual diagram for illustrating the fuel-cell membrane according to the present example.

[0051] Fig. 4 is a frontal conceptual diagram for illustrating an MEA according to an example of the present invention, MEA which makes a fuel cell according to the present invention.

[0052] Fig. 5 is a cross-sectional conceptual diagram for illustrating the MEA according to the present example.

[0053] Fig. 6 is a cross-sectional conceptual diagram for illustrating a fuel cell according to an example of the present example .

[0054] Fig.7 is aperspective conceptual diagram for illustrating a step of stacking (or assembling) cells, which are directed to the fuel cell according to the present example.

[0055] Fig. 8 is another perspective conceptual diagram for illustrating a step of stacking (or assembling) cells, which are directed to a fuel cell according to another example of the present invention.

[0056] Fig. 9 is a frontal conceptual diagram for illustrating a modified example of an identifier, which is directed to a fuel cell according to a still another example of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0057] Having generally described the present invention, a further understanding can be obtained by reference to the specific preferred embodiments which are provided herein for the purpose of illustration only and not intended to limit the scope of the appended claims.

[0058] Hereinafter, specific examples according to the present invention will be described with reference to the accompanying drawings.

[0059] (Example No. 1)

[0060] Fig.1 shows a frontal (or superficial) conceptual diagram of a fuel-cell membrane according to Example No. 1 of the present invention. Note that, in Example No. 1, the fuel-cell membrane makes an MEA. Hereinafter, the fuel-cell membrane according to Example No. 1 will be referred to as an electrolytic membrane 1. As illustrated in Fig. 1, the electrolytic membrane 1 comprises electrode layers 2 (or 2A and 2B) , which are disposed in the central section of the electrolytic membrane 1. The electrolytic membrane 1 has a larger area than those of the electrode layers 2A and 2B. Fig. 2 shows a cross-sectional diagram of an MEA. As can be seen from Fig. 2, the electrode layers 2A and 2B are disposed on the opposite surfaces IA and IB of the electrolytic membrane 1, respectively. Moreover, the electrolytic membrane 1 comprises an outer periphery 110, which protrudes from the side-end surface 211 of the electrode layers 2A and 2B. In addition, the electrolytic membrane 1 further comprises an identifier 3, which is disposed on one of the opposite surfaces 111 of the outer periphery 110. Moreover, the electrolytic membrane 1 according to Example No. 1 exhibits a light transmitability . In addition, the electrolytic membrane 1 according to Example No. 1 comprises a polymer ion-exchange membrane.

[006l] The identifier 3 comprises a marking "M," which is made of an inky material. As shown in Fig. 1, it is possible to make the marking "M" out of a printed character, "#," one of Japanese "KATAKANA" characters, for instance. Note that Fig.1 illustrates the front surface IA of the electrolytic membrane 1. On the other hand, Fig. 3 illustrates the rear surface IB of the electrolytic membrane 1. As can be seen from Fig. 3, the identifier 3' s marking "M" appears as the reversed letter "#" as shown in Fig. 3. That is, in the rear surface IB of the electrolytic membrane 1, the identifier 3's marking "M" appears contrary to the marking "M" that appears regularly in the front surface IA of the electrolytic membrane 1 as shown in Fig. 1. Thus, the identifier 3 makes it possible to distinguish the front surface IA and rear surface IB of the electrolytic membrane 1.

[0062] Hereinafter, an MEA according Example No.1 of the present invention, and a fuel-cell manufacturing process according to Example No. 1 will be described concretely. Fig. 4 illustrates a plan-view conceptual diagram for showing the fundamental structure of an MEA according to Example No. 1. Moreover, Fig. 5 illustrates a cross-sectional conceptual diagram of the MEA according to Example No. 1.

[0063] As shown in Fig. 5, the MEA according to Example No. 1 comprises an anode catalytic layer 21A, and a cathode catalytic layer 21B. The anode catalytic layer 21A is disposed in the central section of the electrolytic membrane l's front surface IA. The cathode catalytic layer 21B is disposed in the central section of the electrolytic membrane l's rear surface IB. Moreover, the MEA according to Example No. 1 further comprises reinforcement membranes 4 for maintaining the strength of the electrolytic membrane 1. The reinforcement membranes 4 are disposed on the opposite surfaces 111 of the electrolytic membrane l's outer periphery 110. Specifically, the reinforcement membranes 4 are provided so that they surround the outer periphery 110' s opposite surfaces 111 and slightly overlap the anode catalytic layer 21A and cathode catalytic layer 21B, which are placed on the central sections of the electrolytic membrane 1. In addition, the MEA according to Example No. 1 furthermore comprises porous gas diffusion layers 22A and 22B, which are formed on the outer surface of the anode catalytic layer 21A and cathode catalytic layer 21B, respectively. Note that the anode catalytic layer 21A and gas diffusion layer 22A make an anode electrode layer 2A, and that the cathode catalytic layer 21B and gas diffusion layer 22B make a cathode electrode layer 2B. Moreover, when the MEA according to Example No. 1 comprises such reinforcement membranes 4, the identifier 3 is disposed at a predetermined position in at least one of the outer surfaces 41 of the reinforcement membranes 4. [0064] The gas diffusion layers 22A and 22B were formed in the following manner. First, a commercially available carbon paper was impregnated with a paste. The carbon paper was "TGP-H-60" produced by TORAY Co., Ltd., and had a thickness of 190 μm. The paste was made by kneading 100-g carbon black, 166.7-g polytetrafluoroethylene (or PTFE) dispersion, a dispersant, and pure water . The carbon black was "VXC-72R" produced by CABOT Co . ,

Ltd., and had a specific surface area of 380 m²/g. The PTFE dispersion was "POLYFRON D-I" produced by DAIKIN KOGYO Co. , Ltd. , and the solid content was 60% by weight . Then, the thus impregnated carbon paper was dried preliminarily at 80 °C for 1 hour, and was thereafter calcined at 380 °C for 1 hour to produce the gas diffusion layers 22A and 22B.

[0065] Moreover, the cathode electrode layer 21B was formed as hereinafter described. First, 10-g carbon with Pt loaded was dispersed into a mixture solution of 82.5-g polymer electrolyte solution and 38-g ion exchange water with a ball mill for 1 hour. The carbon with Pt loaded was "TEC10E70TPM" produced by TANAKA KIKINZOKU Co. , Ltd. , and the platinum content was 67% by weight. Thepolymer electrolyte solutionwas "SS-1100/05"producedbyASAHI KASEI Co. , Ltd. , and the ion-exchange-resin content was 5% by weight. The ball mill contained φ2-mm zirconia balls, and was operated at a peripheral speed of 15 m/sec. The resulting dispersion was turned into a paste. In the resultant paste, the weight ratio of the ion exchange resin to the carbon content of the Pt-loaded carbon was 1.25. Then, the thus prepared paste was coated onto the gas diffusion layer 22B by a doctor blade with a gap of 250 μ.m provided therebetween so as to produce the cathode electrode layer 21B which contained platinum in an amount of about 1 mg/cm².

[0066] In addition, the anode electrode layer 21A was formed as follows. First, 10-g carbon with Pt and Ru loaded was dispersed into a mixture solution of 108.5-g polymer electrolyte solution and 38-g ion exchange water with a ball mill for 1 hour. The carbon with Pt and Ru loaded was "TEC62E58" produced by TANAKA KIKINZOKU Co., Ltd., the platinum content was 27.8% by weight , the ruthenium content was 28.8% by weight, and the ratio of Pt to Ru was 1/2 by atomic percentage. The polymer electrolyte solution was "SS-1100/05" produced by ASAHI KASEI Co., Ltd., and the ion-exchange-resin content was 5% by weight. The ball mill contained φ2-mm zirconia balls, and was operated at a peripheral speed of 15 m/sec. The resulting dispersion was turned into a paste . In the resultant paste, the weight ratio of the ion exchange resin to the carbon content of the Pt-Ru-alloy-loaded carbon was 1.25. Then, the thus prepared paste was coated onto the gas diffusion layer 22A by a doctor blade with a gap of 200 μm. provided therebetween so as to produce the anode electrode layer 21A which contained platinum in an amount of about 0.25 mg/cm².

[0067] Moreover, the electrolytic membrane 1 used in the MEA according to Example No. 1 was an ion exchange membrane "GORE30-III-B" produced by JAPAN GORETEX Co., Ltd.

[0068] Note that the MEA according to Example No. 1 had the following specific dimensions. The electrolytic membrane 1 had a thickness of 30 μm. The anode catalytic layer 21A and cathode catalytic layer 21B had a thickness of from 8 to 15 μm. The gas diffusion layer 22A and gas diffusion layer 22B had a thickness of from 210 to 250 μm.

[0069] Then, the thus preparedanode electrode layer 2Aandcathode electrode layer 2B were perforated to exhibit a reactive area of 100 cm². The cut-out anode electrode layer 2Aand cathode electrode layer 2B were disposed on the opposite sides of the electrolytic membrane 1, which had been cut to a 12-cm X 12-cm squared-shape in advance, and were hot pressed at a temperature of 140⁰C under a pressure of 8 MPa for 3 minutes. Thus, the MEA according to Example No. 1 was completed.

[0070] The resulting MEA according to Example No. 1 was held between later-described first and second separators 5A and 5B illustrated in Fig.6 to make a single fuel cell according to Example No 1 of the present invention. In the resultant single fuel cell according to Example No. 1, a reformed gas, which included carbon monoxide (CO) and sulfur, was supplied to the anode catalytic layer 21A by way of the gas diffusion layer 22A. On the other hand, an oxygen gas was supplied to the cathode catalytic layer 21B by way of the gas diffusion layer 22B. Thus, the single fuel cell according to Example No. 1 carried out the electric-power generation reactions.

[ 0071 ] Since carbon monoxide and sulfur exhibit strong adsorbability to platinum electrodes, they adsorb strongly onto platinum electrodes to cover the surface of platinum electrodes so that they inhibit the catalytic activities of platinum. The phenomenon is the so-called poisoning of platinum electrodes by carbon monoxide and sulfur. Compared with the cathode catalytic layer 21B which is made mainly of platinum, the anode catalytic layer 21A which is made mainly of a Pt-Ru alloy exhibits better resistance to the poisoning resulting from carbon monoxide and sulfur. Accordingly, the fuel gas is supplied to the anode catalytic layer 21A, which comprises a Pt-Ru alloy, in order to prevent it frombeing poisoned by carbon monoxide and sulfur. Note however that it is often the case that fuel gases contain carbon monoxide and/or sulfur as aforementioned. Consequently, it is needed to distinguish the anode catalytic layer 21A and the cathode catalytic layer 21B and then assemble an MEA.

[0072] As described above, it is necessary to distinguish the front and rear of an MEA because the cathode electrode layer 2A and anode electrode layer 2B whose properties differ to each other are placed on the opposite front surface IA and rear surface IB of the resulting MEA' s electrolytic membrane 1 respectively. If the anode electrode layer 2A and the cathode electrode layer 2B are assembled onto the electrolytic membrane 1 faultily, the faulty assembly might result in the poisoning of the cathode electrode layer 2B to damage the performance of the resultant fuel cell. [0073] Fig. 6 is a conceptual diagram of a single fuel cell "S," which comprises an MEA and first and second separators 5A and 5B, according to Example No. 1 of the present invention. The first and second separators 5A and 5B are bonded onto the MEA by way of sealants 52 and 52 so that they form gas flow passages 51A and 51B. The fuel gas and oxygen gas are transferred through the gas flow passage 51A and gas flow passage 51B, respectively. Thus, the fuel gas is supplied to the anode electrode layer 2A, and the oxygen gas is supplied to the cathode electrode layer 2B.

[0074] Moreover, the single fuel cell "S" according to Example No. 1 comprises the identifier 3, which is disposed on the electrolytic membrane 1. Note that the identifier 3 is present on an outer side with respect to the sealants 52 and 52. As a result, not only the identifier 3 makes it possible to distinguish the rear and front of the single fuel cell "S" according to Example No. 1, but also the dyeing components, such as inks, which make the identifier 3's marking "M," are less likely to come into the gas flow passages 51A and 51B. Moreover, when stacking the single fuel cells "S" (or making a plurality of the single fuel cells "S" into a cellular structure) , the identifier 3 makes it possible to distinguish the anode electrode layer 2A and the cathode electrode layer 2B. In addition, after building the single fuel cells "S" up (or stacking the single fuel cells "S" up) , the identifier 3' s marking "M" does not adversely affect the appearance of the stacked single fuel cells "S" because the marking "M" comes under the separators 5A and 5B (or inside the sealants 52 between the separators 5A and 5B) . Moreover, Fig.7 illustrates a cellular structure of the single fuel cells "S" that comprise the identifier 3 made of the same marking "M." As shown in Fig. 7, the markings "M" appear at a predetermined position in the electrolytic membrane 1 because the single fuel cells "S" are stacked in a predetermined direction. Note that Fig. 7 shows the stacked single fuel cells "S" in such a state that their first and second separators 5A and 5B are omitted.

[0075] As described above, the fuel cell according to Example No.1 of the present invention comprises a plurality of the stacked single fuel cells "S." The respective single fuel cells "S" comprise the MEA shown in Figs. 4 and 5, the first separator 5A, and the second separator 5B, as illustrated in Fig. 6. Moreover, as shown in Fig. 4, the MEA comprises the electrolytic membrane 1, the anode electrode layer 2A, and the cathode electrode layer 2B. The electrolytic membrane 1 exhibits ionic conductivity, and comprises the identifier 3, which exhibits an identifying property and is disposed in at least a part of one of the electrolytic membrane l's opposite surfaces IA and IB. The anode catalytic layer 2A is laminated on one of the opposite surfaces IA and IB of the electrolytic membrane 1 (that is, on the electrolytic membrane 1' s front surface IA) . The cathode catalytic layer 2B is laminated on the other one of the opposite surfaces IA and IB of the electrolytic membrane 1 (that is, on the electrolytic membrane l's rear surface IB) . The first separator 5A is disposed on the outside of the anode electrode layer 2A. As shown in Fig. 6, the second separator 5B is disposed on the outside of the cathode electrode layer 2B. Thus, when manufacturing the fuel cell according to Example No. 1, the identifier 3 makes it possible to identify the front surface IA and rear surface IB of the electrolytic membrane 1, and thereby enables workers or manufacturing apparatuses to distinguish the front and rear of the electrolytic membrane 1. As a result, it is possible for workers or manufacturing apparatuses to assemble the fuel cell according to Example No. 1 correctly.

[0076] Note that, in the fuel cell according to Example No. 1, the anode electrode layer 2A comprises the anode catalytic layer 21A, and the anode diffusion layer 22A; and the cathode electrode layer 2B comprises the cathode catalytic layer 21B, and the cathode diffusion layer 22B; as shown in Figs. 5 and 6.

[0077] Moreover, the fuel cell according to ExampleNo.1 comprises the anode catalytic layer 21A and cathode catalytic layer 21B whose compositions differ to each other (or whose compositions are not identical with each other) . Accordingly, when manufacturing the MEA, it is needed to carry out the assemblage while making the distinction between the anode electrode layer 2A and the cathode electrode layer 2B. Whenmaking the single fuel cell "S" by holding the MEA between the first separator 5A and the second separator 5B, it is possible to read out the information, such as the front and rear of the MEA, because the fuel cell "S" according to Example No. 1 comprises the identifier 3. Consequently, it is possible to make the distinction between the anode electrode layer 2A and the cathode electrode layer 2B and then assemble the MEA. Therefore, it is possible to inhibit the problem of faulty products that result from the failure assemblage of the anode electrode layer 2A and cathode electrode layer 2B.

[0078] In addition, in the fuel cell according to Example No. 1, the electrolytic membrane 1 has a larger area than those of the anode electrode layer 2A and cathode electrode layer 2B as shown in Figs 2 and 5. Moreover, the electrolytic membrane 1 has an outer periphery 110, which protrudes from the outer peripheral side-end surface 211 of the anode electrode layer 2A and cathode electrode layer 2B as shown in Fig.2. In addition, the identifier 3 is disposed in one of the opposite surfaces of the outer periphery 110. That is, the anode' electrode layer 2A and cathode electrode layer 2B are placed in the central section of the electrolytic membrane 1, and the electrolytic membrane 1 is provided with the outer periphery 110, which protrudes from the side-end surface 211 of the anode electrode layer 2A and cathode electrode layer 2B so as to be disposed on an outside with respect to the anode electrode layer 2A and cathode electrode layer 2B. Accordingly, the identifier 3, which is disposed in the electrolytic membrane I's outer periphery 110, is placed away from the anode electrode layer 2Aand cathode electrode layer 2B in the electrolyticmembrane I's surface. Consequently, the identifier 3' s physical property is less likely to adversely affect the anode electrode layer 2A and cathode electrode layer 2B.

[0079] Moreover, the fuel cell according to Example No.1 comprises the identifiers 3, which are disposed in one of the opposite surfaces of the outer periphery 110 of all the MEAs in the stacked fuel cell that are made by laminating the single fuel cells "S." The identifiers 3, which are disposed in one of the opposite surfaces of the outer periphery 110 of the MEAs, make it much easier to make the distinction between the front and rear of the MEAs. In addition, such identifiers 3 are advantageous inpreventingworkers or manufacturing apparatuses from assembling the MEAs faultily. [0080] (Example No. 2)

[0081] A fuel cell according to Example No. 2 of the present invention is an example which does not require to make the identifiers 3 of the identical marking "M." Accordingly, it is possible to make the identifiers 3 of a literal series or numeric series, which shows a specific rule. Namely, as illustrated in Fig. 8, the fuel cell according to Example No. 2 has a cellular structure in which the markings "M, " comprising a numeric series showing a specific rule, make the identifiers 3. Likewise, it is possible to make the identifiers 3 of bar codes or QR codes. The identifiers 3, which are made of the markings "M" comprising a numeric series, make it possible to identify a specific electrolytic membrane 1 out of a plurality of the electrolytic membranes 1. Consequently, such identifiers 3 are effective in inspecting or evaluating fuel cells. Note that Fig. 8 shows the stacked single fuel cells "S" in such a state that their first and second separators 5A and 5B are omitted. [0082] (Example No. 3)

[0083] An electrolytic membrane 1 according to Example No. 3 of the present invention comprises an identifier 3, which is made of a marking "M" and a "C" cutting, as illustrated in Fig. 9. The identifier 3, which uses the marking "M" in combination with the "C" cutting, makes it more readily to make the distinction between the front and rear of the electrolytic membrane 1 according Example No. 3.

[0084] (Example No. 4)

[0085] An electrolytic membrane 1 according to Example No. 4 of the present invention exhibits translucency in the thickness-wise direction, as illustrated in Figs. 1, 2 and 3. Moreover, the electrolytic membrane 1 according to Example No. 4 comprises an identifier 3, which has a first contour, being viewed on the front-surface side of the electrolytic membrane 1 according to Example No. 4, and a second contour, being viewed on the rear-surface side of it. In addition, the first contour and the second contour are formed as asymmetric shapes to each other. The electrolytic membrane 1, which exhibits translucency in the thickness-wise direction, makes it possible to observe the identifier 3, which is disposed in at least a part of one of the opposite surfaces, on the front-surface side or the rear-surface side. Since the identifier 3 has the first contour and second contour, which are formed as asymmetric shapes to each other when being viewed on the front-surface side and rear-surface side of the electrolytic membrane 1 according to Example No. 4, it is possible to tell whether the observing surface is the front surface or rear surface of the electrolytic membrane 1. Namely, the identifier 3 is formed as an asymmetric shape so that the first contour, being viewed on the front-surface side of the electrolytic membrane 1 according to Example No. 4, does not coincide with the second contour, being viewed on the front-surface side of it. As a result, the identifier 3 with such an asymmetric shape enables workers or manufacturing apparatuses to distinguish the front surface and rear surface of an MEA that comprises the electrolytic membrane 1 according to Example No. 4. [0086] (Example No. 5)

[0087] An electrolytic membrane 1 according to Example No. 5 of the present invention exhibits non-translucency or weak translucency in the thickness-wise direction, as illustrated in Figs. 1 and 2. Moreover, an identifier 3 is disposed on one of the opposite surfaces of the electrolytic membrane 1 according to Example No. 5. When the electrolytic membrane 1 according to Example No. 5 exhibits non-translucency in the thickness-wise direction, or when it is difficult to transmit light in the thickness-wise direction of the electrolytic membrane 1 according to Example No. ,5, the identifier 3, which is disposed on one of the opposite surfaces of the electrolytic membrane 1 according to Example No. 5, makes it possible to distinguish between the front surface and rear surface of the electrolytic membrane 1 according to Example No.5. Toput it differently, when determining or knowing the one of the opposite surfaces of the electrolytic membrane 1 according to Example No. 5, on which the identifier

3 is disposed, in advance, at least the presence or absence of the identifier 3 enables workers or manufacturing apparatuses to distinguish the front surface and rear surface of an MEA that comprises the electrolytic membrane 1 according to Example No.

5.

[0088] (Example No. 6)

[0089] As illustrated in Figs. 1 and 3, an electrolytic membrane 1 according to Example No. 6 of the present invention has a shape whose first contour, being viewed on the front side, and second contour, being viewed on the rear side, coincide with each other. Thus, even if the electrolytic membrane 1 according to Example No. 6 makes an MEA whose first contour, being viewed on the front side, and second contour, being viewed on the rear side, coincide with each other, the identifier 3 makes it possible to make the distinction between the front surface and rear surface of the resulting MEA. Namely, even when it is not possible to make the distinction between the front and rear of an MEA from the MEA' s configuration, the identifier 3 makes it possible to distinguish the front and rear of such an MEA. [0090] (Example No. 7)

[0091] As illustrated in Fig. 9, an electrolytic membrane 1 according to Example No. 7 of the present invention has a shape whose first contour, being viewed on the front side, and second contour, being viewed on the rear side, differ to each other . That is, since the electrolytic membrane 1 according to Example No. 7 makes an MEA, whose first contour, being viewed on the front side, and second contour, being viewed on the rear side, have different shapes to each other, the resultant MEA' s own configuration makes it possible to confirm the front and rear surface of the MEA in addition to the presence of the identifier on the MEA or the shape of the identifier' s contour . Consequently, even if a plurality of the electrolytic membranes 1 according to Example No. 7 are laminated to make a stacked fuel cell so that the identifiers 3, which are disposedon one of the opposite surfaces of the electrolytic membranes 1 according to Example No. 7, are superimposed to be unrecognizable, the configuration of the electrolytic membrane 1 according to Example No .7 enables workers or assembly apparatuses to make the distinction between the front and rear of the resulting MEA or even a fuel-cell structure made of such an MEA. [0092] (Example No. 8)

[0093] An electrolytic membrane 1 according to Example No. 8 of the present invention comprises an identifier 3, which has a function of identifying at least one member selected from the group consisting of the electrolytic membrane l's front and rear, top and bottom and right and left, as illustrated in Figs. 1 and 2. The identifier 3 not only makes it possible to distinguish the front and rear, top and bottom or right and left of an MEA in which the electrolytic membrane 1 according to Example No.8 is assembled, but also makes it possible to distinguish the positional relationships, such as the top and bottom and right and left that relate to the upstream area or downstream area of the gas flow passages, which are formed in first and second separators 5A and 5B for making a fuel cell. Thus, the electrolytic membrane 1 according to Example No. 8 is advantageous in view of designing the gas flow passages and in view of controlling the flow of gases. [0094] (Example No. 9)

[0095] A fuel cell according to Example No. 9 of the present invention comprises an identifier 3, which is formed by printing, as illustrated in Figs. 1 and 2. Note that, when forming the identifier 3 using a dye or ink, it is preferable to employ those which are less likely to be decomposed thermally. [0096] (Example No. 10)

[0097] A fuel cell according to Example No. 10 of the present invention comprises an identifier 3, which is formedby irradiation (or heat) using a high energy-density beam, such as a laser beam, as illustrated in Figs .1 and 2. In this instance, an electrolytic membrane 1 of an MEA, which makes the fuel cell according to Example No. 10, is carbonized, and thereby the identifier 3 is formed. [0098] Like the aforementioned manufacturing method of the fuel cell according to Example No. 10, it is preferable to employ a forming method that produces products, which are less likely to adversely affect the performance of the resulting MEA' s electrolytic membrane 1, as the identifier 3 is formed. [0099] (Example No. 11)

[OIOO] A fuel cell according to Example No. 11 of the present invention comprises reinforcement membranes 4, as illustrated in Figs. 5 and 6, which are disposed on the opposite surfaces 111 of an electrolytic membrane l's outer periphery 110 to reinforce the electrolytic membrane 1. Moreover, the fuel cell "S" according to Example No. 11 comprises an identifier 3, which is placed at a predetermined position in the outer surface of the reinforcement membrane 4. With the reinforcement membranes 4, not only the electrolytic membrane 1 proper but also the outer periphery 110 can maintain the strength even when superimposing the electrolytic membranes l's outer peripheries 110 to laminate the electrolytic membranes 1 one after another to make a stacked fuel cell. [0101] (Example No. 12)

[0102] ExampleNo.12 of the present invention relates to aprocess for manufacturing fuel cell . The fuel-cell manufacturing process according to Example No. 12 comprises the steps of: preparing an MEA; forming an identifier; disposing a first separator and a second separator; and placing a plurality of the resulting MEAs one after another. In the MEA preparation step, an MEA is prepared, MEA which comprises an electrolytic membrane 1 exhibiting ionic conductivity, an anode electrode layer 2A being laminated on the electrolytic membrane l's opposite surface IA, and a cathode electrode layer 2B being laminated on the electrolytic membrane 1' s another opposite surface IB. In the identifier formation step, an identifier 3, which exhibits an identifying property, is formed in at least a part of one of the opposite surfaces IA and IB of the resulting MEA' s electrolytic membrane 1. In the first-separator and second-separator disposition step, a first separator 5A and a second separator 5B are disposed so that they held the resulting MEA in the thickness-wise direction between them. In the MEAs placement step, a plurality of the resulting MEAs are laminated one after another in a predetermined direction based on the identifiers 3, thereby assembling a cellular structure. In the fuel-cell manufacturing process according to Example No. 12, the identifier formation step is incorporated into a usual fuel-cell manufacturing process. As a result, the fuel-cell manufacturing process according to Example No. 12 enables workers or manufacturing apparatuses to distinguish the information on assemblage, such as the orientation of MEA, even at the stage of manufacturing an MEA. Therefore, the fuel-cell manufacturing process according to Example No. 12 makes it possible to preemptively inhibit workers or manufacturing apparatuses from assembling the anode electrode layer 2A and cathode electrode layer 2B faultily upon assembling MEAs, and eventually to prevent them from assembling stacked fuel cells incorrectly. Note that it is advisable as well to carry out the identifier formation step prior to the MEA preparation step.

INDUSTRIAL APPLICABILITY

[0103] The present fuel-cell membrane, MEA and fuel cell can avail themselves of designing, manufacturing and evaluating fuel cells .

Claims

1. A membrane for fuel cell, the membrane comprising: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces.

2. The membrane according to claim 1, wherein the identifier comprises at least one member selected from the group consisting of letters, numeric characters, symbols, patterns and irregular states .

3. The membrane according to claim 1 having a shape whose first contour, being viewed on a front side thereof, and second contour, being viewed on a rear side thereof, differ to each other.

4. A membrane electrode assembly comprising: a membrane for fuel cell, the membrane comprising: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces; an anode electrode layer being laminated on one of the opposite surfaces of the membrane; and a cathode electrode layer being laminated on the other one of the opposite surfaces of the membrane.

5. A fuel cell comprising: a membrane electrode assembly comprising: a membrane for fuel cell, the membrane comprising: opposite surfaces; and an identifier exhibiting an identifying property and being disposed in at least a part of one of the opposite surfaces; an anode electrode layer being laminated on one of the opposite surfaces of the membrane; and a cathode electrode layer being laminated on the other one of the opposite surfaces of the membrane; a first separator being disposed on an outer side of the anode electrode layer; and a second separator being disposed on an outer side of the cathode electrode layer.

6. The fuel cell according to claim 5, wherein: the membrane has a larger area than those of the anode electrode layer and cathode electrode layer; and has an outer periphery protruding from an outer peripheral side-end surface of the anode electrode layer and cathode electrode layer; and the identifier is disposed in a surface of the outer periphery.

7. The fuel cell according to claim 5 further comprising a plurality of the membrane electrode assemblies being laminated one after another; and the identifiers show a specific rule being based on an lamination order of the membrane electrode assemblies.

8. The membrane according to claim 1 further comprising: an electrolytic membrane exhibiting ion conductivity; a reinforcement membrane being disposed on an outer surface of the electrolytic membrane to reinforce the electrolytic membrane; and the identifier being disposed at a predetermined position in an outer surface of the reinforcement membrane.

9. The membrane electrode assembly according to claim 4, wherein: the membrane further comprises: an electrolytic membrane exhibiting ion conductivity; a reinforcement membrane being disposed on an outer surface of the electrolytic membrane to reinforce the electrolytic membrane; and the identifier being disposed at a predetermined position in an outer surface of the reinforcement membrane.

10. The fuel cell according to claim 5, wherein: the membrane further comprises: an electrolytic membrane exhibiting ion conductivity; a reinforcement membrane being disposed on an outer surface of the electrolytic membrane to reinforce the electrolytic membrane; and the identifier being disposed at a predetermined position in an outer surface of the reinforcement membrane.