Abstract:
Composite members, a fuel cell and manufacturing method, where the composite members are mounted on a base and comprise a first insulator and a second insulator layered on either side of an interconnector, exposed in a chamfered portion on opposite corners. Between a pair of the composite members is formed an electrolyte film. An anode is formed so as to cover the anode surface of the electrolyte film and an anode-side protrusion. The anode formed at the top of anode-side protrusion is stripped, forming a flat exposed surface on the top of the anode-side protrusion. A cathode is formed so as to cover the cathode surface of the electrolyte film and a cathode-side protrusion. The cathode formed on the top of the cathode-side protrusion is stripped using a spatula, a blade, etc., forming a flat exposed surface on the top of the cathode-side protrusion.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to fuel cell. In particular, it relates to a fuel CELL that includes cells in a flat arrangement. 
       BACKGROUND ART 
       [0002]    A fuel CELL is a device configured to generate electrical energy from hydrogen and oxygen and achieves high power generation efficiency. The main features of fuel cell are as follows. Since electricity is directly generated without thermal or kinetic energy processes such as in the case of previous power generation methods, high power generation efficiency can be expected even from a small-scale plant. Moreover, fuel cell are environmentally friendly since they discharge less nitrogen compounds and the like and make less noise and vibration. In sum, fuel cell can effectively use the chemical energy of the fuel and offer environmental advantages. Thus, fuel cell are expected to become an energy supply system for the 21st century and are gathering much attention as a novel, prospective power generating system that can be used in various applications ranging from space use to automobile use and portable device use and from large-scale power generation to small-scale power generation. Technical development toward practical implementation is now in full swing. 
         [0003]    In particular, polymer electrolyte fuel cell have low operating temperature compared to other types of fuel cell and feature high output densities. In recent years, polymer electrolyte fuel cell are expected to be used as power sources for portable devices (such as cellular phones, laptop personal computers, PDAs, MP3 players, digital cameras, electronic dictionaries, and electronic books). One example of polymer electrolyte fuel cell for potable devices is a flat arrangement-type fuel CELL that includes a number of single cells in a flat arrangement. 
         [0004]    As the size of portable devices becomes smaller and the output density increasingly higher, there arises a growing need for high integration of cells of fuel cell for portable devices. In order to achieve higher integration of cells, the number of cells needs to be increased and the miniaturization of the cell structures and other structures such as interconnectors and gaps between the cells is needed. Because the cells are to be highly integrated, it becomes difficult to individually fabricate cells in producing a fuel CELL. Thus, currently, a technique of first forming an anode and a cathode that extend across electrolyte membranes of a plurality of sections and then removing specific regions of the anode and cathode by laser processing to form individual cells is now being implemented. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: International Publication No. 2009/105896 pamphlet 
         PTL 2: Japanese Published Unexamined Patent Application No. 2008-258142 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    According to the cell fabrication technique that uses laser processing, the procedure takes a long time and thus there is a problem in that it takes longer and higher cost to fabricate fuel cell. Another problem is that alignment for laser processing is complicated. To be more specific, since the intervals between the cells are small (for example 0.3 mm), it becomes difficult to adjust the position of laser irradiation. Moreover, if the region to be irradiated with laser has fine irregularities, the laser becomes off-focus and the process accuracy may be degraded. In addition, ash resulting from selective removal of the anode and the cathode by laser irradiation acts as a contaminant and may adversely affect electrolyte membranes and catalyst layers. 
         [0008]    The present invention has been made to address these problems and aims to provide a technique of fabricating integrated cells without using laser processing. 
       Solution to Problem 
       [0009]    An embodiment of the present invention is a fuel CELL. The fuel CELL includes a plurality of membrane electrode assemblies in a flat arrangement, each membrane electrode assembly including an electrolyte membrane, an anode formed on one surface of the electrolyte membrane, and a cathode formed on another surface of the electrolyte membrane; a protruding portion disposed between the membrane electrode assemblies adjacent to each other and having a flat top surface, the protruding portion protruding from a surface of at least one electrode selected from the anode and cathode positioned in regions of main surfaces of the electrolyte membrane where the anode and the cathode are formed; an interconnector formed between the membrane electrode assemblies adjacent to each other so that, at a side surface of the protruding portion on the side of one of the membrane electrode assemblies, the interconnector contacts the electrode of that membrane electrode assembly; and an insulator that forms a part of the top surface and, in the protruding portion, electrically insulates between the interconnector and the electrode on the other membrane electrode assembly-side of the protruding portion. Here, “flat” also refers to a state in which fine irregularities that are visually identifiable are present on a surface. 
         [0010]    In the fuel CELL of the embodiment described above, the interconnector may contact the electrode in a chamfered portion formed at a top of the protruding portion. In this case, the top surface of the protruding portion may be a multilayered surface in which an end surface of the electrode extending from one of the membrane electrode assemblies, an end surface of the interconnector, an end surface of the insulator, and an end surface of the electrode extending from the other membrane electrode assembly are stacked in that order. Furthermore, in a cross-section taken in a direction in which the membrane electrode assemblies are adjacent to each other, the chamfered portion may be receded from a line that connects both ends of the chamfered portion. 
         [0011]    Another embodiment of the present invention is a fuel CELL. The fuel CELL includes a plurality of membrane electrode assemblies in a flat arrangement, each membrane electrode assembly including an electrolyte membrane, an anode formed on one surface of the electrolyte membrane, and a cathode formed on another surface of the electrolyte membrane; a protruding portion disposed between the membrane electrode assemblies adjacent to each other and having a flat top surface, the protruding portion protruding from a surface of at least one electrode selected from the anode and cathode positioned in regions of main surfaces of the electrolyte membrane where the anode and the cathode are formed; an interconnector formed between the membrane electrode assemblies adjacent to each other so that, at a side surface of the protruding portion on the side of one of the membrane electrode assemblies, the interconnector contacts the electrode of that membrane electrode assembly; an insulator that electrically insulates, in the protruding portion, between the interconnector and the electrode on the other membrane electrode assembly-side of the protruding portion; and an insulating coating layer that forms a part of the top surface and covers the interconnector and the insulator. 
         [0012]    In the fuel CELL of this embodiment, the top surface of the protruding portion may be a multilayered surface in which an end surface of the electrode extending from one of the membrane electrode assemblies, the coating layer, and an end surface of the electrode extending from the other membrane electrode assembly are stacked in that order. 
         [0013]    Yet another embodiment of the present invention is a method for producing a fuel CELL. The method for producing fuel CELL includes a step of preparing a composite material in which insulators are respectively stacked on both sides of an interconnector and the interconnector is exposed in a stacking direction in corner portions of a multilayered surface; a step of placing the composite material between electrolyte membranes of membrane electrode assemblies adjacent to each other so that the stacking direction intersects a surface direction of the electrolyte membranes and a protruding portion that protrudes from an electrode surface of the electrolyte membrane is formed; a step of forming an electrode on the protruding portion and the electrolyte membranes sandwiching the protruding portion; and a step of removing the electrode that covers a top of the protruding portion. 
         [0014]    According to the method for producing a fuel CELL of the above-described embodiment, a composite film for a fuel CELL in which cells are integrated can be easily fabricated without using laser processing to form individual cells. Since laser processing is not employed to form individual cells, generation of ash resulting from laser irradiation is avoided. Accordingly, the electrolyte membranes and catalyst layers can be kept clean. 
         [0015]    In the step of preparing the composite material of the method for producing a fuel CELL according to the above-described embodiment, after the insulators are stacked on both sides of the interconnector, the corner portions of the multilayered surface may be chamfered in a direction intersecting the multilayered surface. The composite material may include a coating layer that covers an end surface in a direction intersecting the stacking direction, and, in the step of removing the electrode, the electrode covering the top of the protruding portion and at least part of the coating layer may be removed. 
       Advantageous Effects of Invention 
       [0016]    According to the present invention, integrated cells can be fabricated without using laser processing. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is an exploded perspective view showing a structure of a fuel CELL according to Embodiment 1. 
           [0018]      FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 . 
           [0019]      FIG. 3  is an enlarged view of a relevant part showing the structures of an anode-side protruding portion and a cathode-side protruding portion in Embodiment 1. 
           [0020]      FIG. 4  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 1. 
           [0021]      FIG. 5  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 1. 
           [0022]      FIG. 6  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 2. 
           [0023]      FIG. 7  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 2. 
           [0024]      FIG. 8  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 2. 
           [0025]      FIG. 9  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 3. 
           [0026]      FIG. 10  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 3. 
           [0027]      FIG. 11  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 3. 
           [0028]      FIG. 12  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 4. 
           [0029]      FIG. 13  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 4. 
           [0030]      FIG. 14  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 4. 
           [0031]      FIG. 15  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 5. 
           [0032]      FIG. 16  is an enlarged view of a relevant part showing the structures of an anode-side protruding portion and a cathode-side protruding portion in Embodiment 5. 
           [0033]      FIG. 17  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 5. 
           [0034]      FIG. 18  includes step diagrams illustrating a method for producing a composite film used in the fuel CELL of Embodiment 5. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0035]    The embodiments of the present invention will now be described with reference to the drawings. In all drawings, identical or similar constitutional components are represented by the same reference characters and the descriptions therefor are omitted to avoid redundancy. 
       Embodiment 1 
       [0036]      FIG. 1  is an exploded perspective view showing a schematic structure of a fuel CELL according to Embodiment 1.  FIG. 2  is a cross-sectional view taken along line A-A′ in  FIG. 1 . 
         [0037]    As shown in  FIGS. 1 and 2 , a fuel CELL  10  includes a composite film  100 , a cathode housing  50 , and an anode housing  52 . 
         [0038]    The composite film  100  includes a plurality of membrane electrode assemblies  20  in a flat arrangement. Each membrane electrode assembly  20  includes an electrolyte membrane  22 , and a cathode  24  on a surface of the electrolyte membrane  22  and an anode  26 . A rim of the composite film  100  is formed of the electrolyte membrane  22 . The membrane electrode assemblies  20  are formed in a region on the inner side of the rim. 
         [0039]    The electrolyte membrane  22  preferably exhibits good ion conductivity in a wet state or a humidified state and functions as an ion exchange membrane through which protons migrate between the cathode  24  and the anode  26 . The electrolyte membrane  22  is formed of a solid polymer material such as a fluorine-containing polymer or a fluorine-free polymer. For example, a sulfonic acid-type perfluorocarbon polymer, a polysulfone resin, a perfluorocarbon polymer having a phosphonic acid group or a carboxylic acid group, or the like can be used. An example of the sulfonic acid-type perfluorocarbon polymer is Nafion (registered trademark, produced by DuPont) ionomer solution. Examples of the fluorine-free polymer include sulfonated aromatic polyether ether ketone and polysulfone. The thickness of the electrolyte membrane  22  is, for example, within the range of about 10 μm to about 200 μm. 
         [0040]    The cathodes  24  are formed to be spaced from each other on one surface of the electrolyte membrane  22 . Air that serves as an oxidizer may be supplied to the cathodes  24 . The anodes  26  are formed to be spaced from each other on the other surface of the electrolyte membrane  22 . Hydrogen that serves as a fuel gas may be supplied to the anodes  26 . In this embodiment, hydrogen is used as a fuel gas. For example, any other suitable fuel, such as methanol, formic acid, butane, and other hydrogen carriers, can be used. A single cell is constituted by a cathode  24 /anode  26  pair and the electrolyte membrane  22  sandwiched between the cathode  24  and the anode  26 . Each single cell generates electric power through an electrochemical reaction between oxygen in air and a fuel (for example, hydrogen). 
         [0041]    The cathode  24  and the anode  26  each include an ion exchange material and catalyst particles, and, in some cases, carbon particles. The ion exchange materials in the cathode  24  and the anode  26  may be used to improve the adhesiveness between the catalyst particles and the electrolyte membrane  22  and may play a role of transmitting protons between the two. The ion exchange materials may be formed of the same polymer material as that used in the electrolyte membrane  22 . Examples of the catalyst metal include alloys of and single elements selected from Sc, Y, Ti, Zr, V, Nb, Fe, Co, Ni, Ru, Rh, Pd, Pt, Os, Ir, lanthanoid-series elements, and actinoid-series elements. In the case where the catalyst is to be supported, furnace black, acetylene black, ketjen black, carbon nanotubes, or the like may be used as the carbon particles. The cathode  24  and the anode  26  may each have a thickness of about 10 μm to about 40 μm. The cathode  24  and the anode  26  may each include a conductive layer through which the fuel gas or air can be diffused. In such a case, the cathode  24  and the anode  26  may each have a thickness of, for example, about 50 to about 500 μm. 
         [0042]    As described above, in the fuel CELL  10  of this embodiment, a cathode  24  and an anode  26  that face each other with an electrolyte membrane  22  therebetween form a pair and a plurality of membrane electrode assemblies (single cells)  20  are formed in a flat arrangement. 
         [0043]    An interconnector (conductive member)  30  is formed between adjacent membrane electrode assemblies  20 . Examples of the material that provides the conductivity to the interconnector  30  include gas-impermeable carbon-based materials prepared by impregnating carbon fibers, a graphite sheet, a carbon paper, or carbon powder with resins, and metal materials such as platinum, gold, stainless steel, titanium, and nickel. 
         [0044]    The interconnector  30  forms a part of an anode-side protruding portion  28  protruding from the surface of the anode  26 . In the anode-side protruding portion  28 , a part of the interconnector  30  has a region R 1  exposed toward one membrane electrode assembly  20  (in  FIG. 2 , the membrane electrode assembly  20  on the right-hand side of the interconnector  30 ) of two membrane electrode assemblies  20  on two sides of the anode-side protruding portion  28  (refer to  FIG. 3 ). In this region, the interconnector  30  makes contact with the anode  26  extending from the aforementioned one membrane electrode assembly  20 . In the anode-side protruding portion  28 , a first insulator  110  electrically insulates between the interconnector  30  and the anode  26  extending from the other membrane electrode assembly  20  (in  FIG. 2 , the membrane electrode assembly  20  on the left-hand side of the interconnector  30 ) of the two membrane electrode assemblies on two sides of the anode-side protruding portion  28 . 
         [0045]    The top surface M of the anode-side protruding portion  28  is flat. In this embodiment, the top surface M of the anode-side protruding portion  28  is a multilayered surface in which an end surface of the anode  26  extending from one of the membrane electrode assemblies  20 , an end surface of the interconnector  30 , an end surface of the first insulator  110 , and an end surface of the anode  26  extending from the other membrane electrode assembly  20  are stacked in that order. 
         [0046]    The interconnector  30  also forms a part of an anode-side protruding portion  28  that protrudes from the surface of the cathode  24 . In the cathode-side protruding portion  38 , a part of the interconnector  30  has a region R 2  exposed toward the other membrane electrode assembly  20  of the two membrane electrode assemblies  20  on two sides of the cathode-side protruding portion  38  (refer to  FIG. 3 ). In this region, the interconnector  30  makes contact with the cathode  24  extending from the aforementioned other membrane electrode assembly  20 . In the cathode-side protruding portion  38 , a second insulator  112  electrically insulates between the interconnector  30  and the cathode  24  extending from one of the membrane electrode assemblies  20  on the two sides of the cathode-side protruding portion  38 . 
         [0047]    The first insulator  110  and the second insulator  112  can be obtained by, for example, hot-pressing glass fibers impregnated with an epoxy resin. 
         [0048]    The top surface N of the cathode-side protruding portion  38  is flat. In this embodiment, the top surface N of the cathode-side protruding portion  38  is a multilayered surface in which an end surface of the cathode  24  extending from the other membrane electrode assembly  20 , an end surface of the interconnector  30 , an end surface of the second insulator  112 , and an end surface of the cathode  24  extending from the one membrane electrode assembly  20  are stacked in that order. 
         [0049]    An interconnector  30  provided between membrane electrode assemblies  20  adjacent to each other electrically connects the anode  26  of one of the membrane electrode assemblies  20  that are adjacent to each other to the cathode  24  of the other membrane electrode assembly  20  of the membrane electrode assemblies  20  adjacent to each other. As a result, the membrane electrode assemblies (single cells)  20  adjacent to each other are serially connected and thus a plurality of membrane electrode assemblies  20  in a flat arrangement are serially connected to one another. In another embodiment, the anodes  26  and/or cathodes  24  may be connected to form a plurality of membrane electrode assemblies electrically connected in parallel or a plurality of membrane electrode assemblies in which serial connections and parallel connections are used in combination. 
         [0050]    Referring again to  FIG. 2 , the cathode housing  50  may constitute a part of a casing of the fuel CELL  10  or may be adjacent to the cathodes  24 . The cathode housing  50  may have air intakes  51  for taking in air from outside. An air chamber  60  in which air is distributed may be formed between the cathode housing  50  and the cathodes  24 . The pressure of air in the air chamber  60  is equal to the atmospheric pressure. 
         [0051]    The anode housing  52  may constitute a part of the casing of the fuel CELL  10  or may be adjacent to the anodes  26 . A fuel gas chamber  62  for storing fuel may be formed between the anode housing  52  and the anodes  26 . The anode housing  52  may have a fuel supply port (not shown in the drawing) through which a fuel gas can be replenished as necessary from a fuel cartridge or the like. The pressure of the fuel gas in the fuel gas chamber  62  may be retained at a level higher than the atmospheric pressure. 
         [0052]    Examples of the material used in the cathode housing  50  and the anode housing  52  include common plastic resins such as phenolic resins, vinyl resins, polyethylene resins, polypropylene resins, polystyrene resins, urea resins, and fluororesins. 
         [0053]    The cathode housing  50  and the anode housing  52  may be joined to each other through a gasket  70  formed in the peripheral portion of the composite film  100  by using a joining member (not shown in the drawing) such as a bolt, a nut, or the like. As a result, pressure is applied to the gasket  70  and the sealing property is enhanced due to the presence of the gasket  70 . 
       (Method for Producing Fuel CELL According to Embodiment 1) 
       [0054]    Of the method for producing a fuel CELL according to Embodiment 1, a method for fabricating a composite film  100  is described in particular with reference to  FIGS. 4 to 5 . 
         [0055]    First, as shown in  FIG. 4(A) , a laminate  200  in which a first insulator  110  and a second insulator  112  are respectively stacked on two sides of an interconnector  30  is prepared. The first insulator  110  and the second insulator  112  each have a thickness of, for example, 0.1 mm. Then the laminate  200  is cut along cutting lines C that are spaced from one another at predetermined intervals so as to form individual rod-shaped composite materials  210  (see  FIG. 4(B) ). The intervals of the cutting lines C may be any as long as each interval is larger than the total thickness of the electrolyte membrane  22 , the cathode  24 , and the anode  26 , and are, for example, about 50 to about 1400 μm. 
         [0056]    Next, as shown in  FIG. 4(C) , a region that includes one corner portion of the second insulator  112  is chamfered along the longitudinal direction (direction intersecting the multilayered surface) of the rod-shaped composite material  210  so as to expose the interconnector  30 . Similarly, a region that includes an opposite corner portion of the first insulator  110  which is positioned diagonally across the aforementioned corner portion of the second insulator  112  in a cross-section that intersects the longitudinal direction of the composite material  210  is chamfered to expose the interconnector  30 . 
         [0057]    Next, as shown in  FIG. 5(A) , the composite materials  210  are placed on a base  300  such as a glass plate so that the layer stacking direction in the composite material  210  is coincident with the surface direction of the base  300 . Grooves  302  into which a part of the composite material  210  can be fit are formed in the base  300  in advance at particular intervals. Thus, the process for alignment needed in placing the composite materials on the base can be omitted. 
         [0058]    Next, as shown in  FIG. 5(B) , an electrolyte solution  310  that contains an ion exchange material such as Nafion is applied between a pair of the composite materials  210 . 
         [0059]    Then, as shown in  FIG. 5(C) , the electrolyte solution is dried to form an electrolyte membrane  22 . As the solvent is removed, the thickness of the electrolyte membrane  22  becomes smaller than the thickness of the electrolyte solution  310  shown in  FIG. 5(B) . A part of the composite material  210  protruding from a surface (hereinafter this surface is referred to as an anode surface) of the electrolyte membrane  22  forms a part of the anode-side protruding portion  28  described above. A part of the composite material  210  protruding from the other surface (hereinafter this surface is referred to as a cathode surface) of the electrolyte membrane  22  forms a part of the cathode-side protruding portion  38 . 
         [0060]    Next, as shown in  FIG. 5(D) , an anode catalyst slurry is applied to the anode surface of the electrolyte membrane  22  and the anode-side protruding portion  28  by a spray coating method to form an anode  26 . During this process, the interconnector  30  exposed in the chamfered portion of the anode-side protruding portion  28  connects to the anode  26 . A cathode catalyst slurry is applied to the cathode surface of the electrolyte membrane  22  and the cathode-side protruding portion  38  by a spray coating method so as to form a cathode  24 . During this process, the interconnector  30  exposed in the chamfered portion of the cathode-side protruding portion  38  connects to the cathode  24 . 
         [0061]    Next, as shown in  FIG. 5(E) , the anode  26  formed at the top of the anode-side protruding portion  28  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the anode-side protruding portion  28 . In this step, the anodes  26  formed on the tops of a plurality of anode-side protruding portions  28  are removed simultaneously so as to simplify the process. In an exposed surface formed by removal of the anode  26 , an end surface (cut surface) of the first insulator  110  is interposed between an end surface (cut surface) of the anode  26  extending from above the electrolyte membrane  22  on the side opposite to the chamfered side and an end surface (cut surface) of the interconnector  30 . As a result, the interconnector  30  is electrically insulated from the anode  26  extending from above the electrolyte membrane  22  on the side opposite to the chamfered side. 
         [0062]    Similarly, the cathode  24  at the top of the cathode-side protruding portion  38  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the cathode-side protruding portion  38 . In this exposed surface, an end surface (cut surface) of the second insulator  112  is interposed between an end surface (cut surface) of the cathode  24  extending from above the electrolyte membrane  22  on the side opposite to the chamfered side and an end surface (cut surface) of the interconnector  30 . As a result, the interconnector  30  is electrically insulated from the cathode  24  that extends from above the electrolyte membrane  22  on the side opposite to the chamfered side. 
         [0063]    A composite film  100  used in the fuel CELL of Embodiment 1 is fabricated through the above-described steps. 
       Embodiment 2 
       [0064]      FIG. 6  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 2. The basic structure of the fuel CELL  10  of this embodiment is the same as that of Embodiment 1 and descriptions for the features similar to Embodiment 1 are omitted to avoid redundancy. 
         [0065]    In this embodiment, some anode-side protruding portions  28 ′ among the anode-side protruding portions  28  each have a flat top surface that has a multilayered structure in which a coating layer  400  is interposed between an end surface of the anode  26  that extends from above the electrolyte membrane  22  on the chamfered side and an end surface of the anode  26  that extends from above the electrolyte membrane  22  on the side opposite to the chamfered side. Alternatively, all of the anode-side protruding portions may have the structure of the anode-side protruding portion  28 ′. 
         [0066]    In this embodiment, some cathode-side protruding portions  38 ′ among the cathode-side protruding portions  38  each have a flat top surface that has a multilayered structure in which a coating layer  410  is interposed between an end surface of the cathode  24  that extends from above the electrolyte membrane  22  on the chamfered side and an end surface of the cathode  24  that extends from above the electrolyte membrane  22  on the side opposite to the chamfered side. Alternatively, all of the cathode-side protruding portions may have the structure of the cathode-side protruding portion  38 ′. 
         [0067]    The coating layer  400  and the coating layer  410  are formed of an insulating material. The coating layer  400  and the coating layer  410  are preferably softer and more easily removable with a spatula or the like than the interconnector  30 . The coating layer  400  and the coating layer  410  preferably have good adhesiveness to the interconnector  30  and do not adversely affect the electrolyte membrane  22  and the catalyst layers. An example of the material used for forming the coating layer  400  and the coating layer  410  is Nafion. 
       (Method for Producing Fuel CELL According to Embodiment 2) 
       [0068]    Of the method for producing a fuel CELL according to Embodiment 2, a method for fabricating a composite film  100  is described in particular with reference to  FIGS. 7 to 8 . 
         [0069]    As shown in  FIG. 7(A) , a coating layer  400  and a coating layer  410  are respectively formed on two multilayered surfaces of the composite material  210  shown in  FIG. 4(B) . 
         [0070]    Next, as shown in  FIG. 7(B) , a region that includes a corner portion of the second insulator  112  and an end portion of the coating layer  400  near the corner portion is chamfered along the longitudinal direction (direction intersecting the multilayered surface) to expose the interconnector  30 . Similarly, in a cross-section intersecting the longitudinal direction of the composite membrane  210 , a region that includes an opposite corner portion of the first insulator  110  which is positioned diagonally across the aforementioned corner portion of the second insulator  112  and an end portion of the coating layer  410  near the opposite corner portion is chamfered along the longitudinal direction of the composite material  210  to expose the interconnector  30 . 
         [0071]    Next, as shown in  FIG. 8(A) , the composite materials  210  are placed on a base  300  such as a glass plate so that the layer stacking direction in the composite material  210  is coincident with the surface direction of the base  300  while fitting parts of the composite materials  210  in the grooves  302 . 
         [0072]    Next, as shown in  FIG. 8(B) , the electrolyte solution  310  containing an ion exchange material such as Nafion is applied between a pair of the composite materials  210 . 
         [0073]    Next, as shown in  FIG. 8(C) , the electrolyte solution is dried to form an electrolyte membrane  22 . As the solvent is removed, the thickness of the electrolyte membrane  22  becomes smaller than the thickness of the electrolyte solution  310  shown in  FIG. 8(B) . A part of the composite material  210  protruding from the anode surface of the electrolyte membrane  22  forms a part of the anode-side protruding portion  28 . A part of the composite material  210  protruding from the cathode surface of the electrolyte membrane  22  forms a part of the cathode-side protruding portion  38 . 
         [0074]    Next, as shown in  FIG. 8(D) , an anode catalyst slurry is applied to the anode surface of the electrolyte membrane  22 , the anode-side protruding portion  28 , and the coating layer  400  by a spray coating method so as to form the anode  26 . During this process, the interconnector  30  exposed in the chamfered portion of the anode-side protruding portion  28  connects to the anode  26 . A cathode catalyst slurry is applied to the cathode surface of the electrolyte membrane  22 , the coating layer  410 , and the cathode-side protruding portion  38  by a spray coating method so as to form the cathode  24 . During this process, the interconnector  30  exposed in the chamfered portion of the cathode-side protruding portion  38  connects to the cathode  24 . 
         [0075]    Next, as shown in  FIG. 8(E) , the anode  26  and the coating layer  400  formed at the top of the anode-side protruding portion  28  are removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the anode-side protruding portion  28 . If all of the coating layer  400  is removed, an anode-side protruding portion  28  identical to that in Embodiment 1 is formed. If a part of the coating layer  400  is left unremoved, the anode-side protruding portion  28 ′ is formed. 
         [0076]    Similarly, the cathode  24  and the coating layer  410  formed at the top of the cathode-side protruding portion  38  are removed by using a spatula, a blade, or the like to form a flat exposed surface at the top of the cathode-side protruding portion  38 . If all of the coating layer  410  is removed, a cathode-side protruding portion  38  identical to that in Embodiment 1 is formed. If a part of the coating layer  410  is left unremoved, the cathode-side protruding portion  38 ′ is formed. 
         [0077]    A composite film  100  used in the fuel CELL of Embodiment 2 is fabricated through the above-described steps. 
       Embodiment 3 
       [0078]      FIG. 9  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 3. The basic structure of the fuel CELL  10  of this embodiment is the same as that of Embodiment 1 and descriptions for the features similar to Embodiment 1 are omitted to avoid redundancy. 
         [0079]    In this embodiment, the flat top surface of the anode-side protruding portion  28  has a multilayered structure in which an end surface of the interconnector  30  and the first insulator  110  are interposed between an end surface of the anode  26  extending from above the electrolyte membrane  22  on one side of the interconnector  30  and an end surface of the anode  26  extending from above the electrolyte membrane  22  on the other side of the interconnector  30 . 
         [0080]    In the interconnector  30  in the anode-side protruding portion  28 , a side surface on the side of the electrolyte membrane  22  located on one side of the interconnector  30  is not covered with the second insulator  112 . The interconnector  30  is electrically connected to the anode  26  that extends from above the electrolyte membrane  22  located on one side of the interconnector  30 . In the anode-side protruding portion  28 , the interconnector  30  is electrically insulated by the first insulator  110  from the anode  26  that extends from above the electrolyte membrane  22  located on the other side of the interconnector  30 . 
         [0081]    The flat top surface of the cathode-side protruding portion  38  has a multilayered structure in which an end surface of the interconnector  30  and the second insulator  112  are sandwiched between an end surface of the cathode  24  extending from above the electrolyte membrane  22  located on the other side of the interconnector  30  and an end surface of the cathode  24  extending from above the electrolyte membrane  22  on one side of the interconnector  30 . 
         [0082]    In the interconnector  30  in the cathode-side protruding portion  38 , a side surface on the side of the electrolyte membrane  22  located on the other side of the interconnector  30  is not covered with the first insulator  110 . The interconnector  30  electrically connects to the cathode  24  extending from above the electrolyte membrane  22  on the other side of the interconnector  30 . In the cathode-side protruding portion  38 , the interconnector  30  is electrically insulated by the second insulator  112  from the cathode  24  extending from above the electrolyte membrane  22  located on one side of the interconnector  30 . Note that in Embodiment 3, the coating layer  400  and the coating layer  410  may be formed as in Embodiment 2. 
       (Method for Producing a Fuel CELL According to Embodiment 3) 
       [0083]    Of the method for producing a fuel CELL according to Embodiment 3, a method for fabricating a composite film  100  is described in particular with reference to  FIGS. 10 to 11 . 
         [0084]    As shown in  FIG. 10(A) , a laminate  200  in which the first insulator  110  and the second insulator  112  sandwiching the interconnector  30  in a region defined by cutting lines C are staggered in the surface direction of the interconnector  30  is prepared. On one side of the interconnector  30  defined by a pair of the cutting lines C, the interconnector  30  is exposed by a particular length from one of the cutting lines C in the direction intersecting this cutting line C. On the other side of the interconnector  30 , the interconnector  30  is exposed by a particular length from the other cutting line C in the direction intersecting this cutting line C. 
         [0085]    The laminate  200  is cut along the cutting lines C to form individual rod-shaped composite materials  210  (refer to  FIG. 10(B) ). 
         [0086]    Next, as shown in  FIG. 11(A) , the composite materials  210  are placed on a based  300  such as a glass plate so that the layer stacking direction in the composite material  210  is coincident with the surface direction of the base  300  and that a part of each composite material  210  is fitted into a groove  302 . 
         [0087]    Then as shown in  FIG. 11(B) , an electrolyte solution  310  containing an ion exchange material such as Nafion is applied between a pair of the composite materials  210 . 
         [0088]    Then as shown in  FIG. 11(C) , the electrolyte solution is dried to form an electrolyte membrane  22 . As the solvent is removed, the thickness of the electrolyte membrane  22  becomes smaller than the thickness of the electrolyte solution  310  shown in  FIG. 11(B) . A part of the composite material  210  protruding from the anode surface of the electrolyte membrane  22  forms a part of the anode-side protruding portion  28 . A part of the composite material  210  protruding from the cathode surface of the electrolyte membrane  22  forms a part of the cathode-side protruding portion  38 . 
         [0089]    Next, as shown in  FIG. 11(D) , an anode catalyst slurry is applied to the anode surface of the electrolyte membrane  22  and the anode-side protruding portion  28  by a spray coating method to form an anode  26 . During this process, the interconnector  30  exposed in one of the side surfaces of the anode-side protruding portion  28  connects to the anode  26 . A cathode catalyst slurry is applied to the cathode surface of the electrolyte membrane  22  and the cathode-side protruding portion  38  by a spray coating method so as to form a cathode  24 . During this process, the interconnector  30  exposed in the other side surface of the cathode-side protruding portion  38  connects to the cathode  24 . 
         [0090]    Next, as shown in  FIG. 11(E) , the anode  26  formed at the top of the anode-side protruding portion  28  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the anode-side protruding portion  28 . Similarly, the cathode  24  at the top of the cathode-side protruding portion  38  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the cathode-side protruding portion  38 . 
         [0091]    A composite film  100  used in the fuel CELL of Embodiment 3 is fabricated through the above-described steps. 
       Embodiment 4 
       [0092]      FIG. 12  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 4. The basic structure of the fuel CELL  10  of this embodiment is the same as that of Embodiment 1 and descriptions for the features similar to Embodiment 1 are omitted to avoid redundancy. 
         [0093]    In this embodiment, some of the anode-side protruding portions  28  are anode-side protruding portions  28 ″ that each have a flat top surface having a multilayered structure in which the first insulator  110  is interposed between an end surface of the anode  26  extending from above the chamfered-side electrolyte membrane  22  and an end surface of the anode  26  extending from above the electrolyte membrane  22  on the side opposite to the chamfered side. Alternatively, all of the anode-side protruding portions may have the structure of the anode-side protruding portion  28 ″. 
         [0094]    In the anode-side protruding portion  28 ′, the first insulator  110  is formed on the flat top surface and a side surface of the interconnector  30  on the side opposite to the chamfered side. The first insulator  110  electrically insulates between the interconnector  30  and the anode  26  on the side opposite to the chamfered side. 
         [0095]    In this embodiment, some of the cathode-side protruding portions  38  are cathode-side protruding portions  38 ″ that each have a flat top surface having a multilayered structure in which the second insulator  112  is interposed between an end surface of the cathode  24  extending from above the chamfered-side electrolyte membrane  22  and an end surface of the cathode  24  extending from above the electrolyte membrane  22  on the side opposite to the chamfered side. Alternatively, all of the cathode-side protruding portions may have the structure of the cathode-side protruding portion  38 ″. 
         [0096]    In the cathode-side protruding portion  38 ′, the second insulator  112  is formed on the flat top surface and a side surface of the interconnector  30  on the side opposite to the chamfered side. The second insulator  112  electrically insulates between the interconnector  30  and the cathode  24  on the side opposite to the chamfered side. 
       (Method for Producing a Fuel CELL According to Embodiment 4) 
       [0097]    Of the method for producing a fuel CELL according to Embodiment 4, a method for fabricating a composite film  100  is described in particular with reference to  FIGS. 13 to 14 . 
         [0098]    As shown in  FIG. 13(A) , a composite material  210  that includes a rod-shaped interconnector  30  and an insulator  114  that covers the periphery of the interconnector  30  is prepared. 
         [0099]    Next, as shown in  FIG. 13(B) , a pair of corner portions that are diagonally across from each other in a cross-section intersecting the longitudinal direction of the composite material  210  are chamfered along the longitudinal direction of the composite material  210  so as to expose the interconnector  30 . As a result, a first insulator  110  and a second insulator  112  separated from the first insulator  110  are formed. 
         [0100]    Next, as shown in  FIG. 14(A) , the composite materials  210  are placed on a base  300  by fitting a part of each composite material  210  into a groove  302  so that the direction in which the first insulator  110 , the interconnector  30 , and the second insulator  112  are stacked is coincident with the surface direction of the base  300 . 
         [0101]    Next, as shown in  FIG. 14(B) , an electrolyte solution  310  containing an ion exchange material such as Nafion is applied between a pair of the composite materials  210 . 
         [0102]    Then as shown in  FIG. 14(C) , the electrolyte solution is dried to form an electrolyte membrane  22 . As the solvent is removed, the thickness of the electrolyte membrane  22  becomes smaller than the thickness of the electrolyte solution  310  shown in  FIG. 14(B) . A part of the composite material  210  protruding from the anode surface of the electrolyte membrane  22  forms a part of the anode-side protruding portion  28 . A part of the composite material  210  protruding from the cathode surface of the electrolyte membrane  22  forms a part of the cathode-side protruding portion  38 . 
         [0103]    Next, as shown in  FIG. 14(D) , an anode catalyst slurry is applied to the anode surface of the electrolyte membrane  22  and the anode-side protruding portion  28  by a spray coating method to form an anode  26 . During this process, the interconnector  30  exposed in one of the side surfaces of the anode-side protruding portion  28  connects to the anode  26 . A cathode catalyst slurry is applied to the cathode surface of the electrolyte membrane  22  and the cathode-side protruding portion  38  by a spray coating method so as to form a cathode  24 . During this process, the interconnector  30  exposed in the other side surface of the cathode-side protruding portion  38  connects to the cathode  24 . 
         [0104]    Next, as shown in  FIG. 14(E) , the anode  26  formed at the top of the anode-side protruding portion  28  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the anode-side protruding portion  28 . If all of the first insulator  110  is removed, an anode-side protruding portion  28  identical to that in Embodiment 1 is formed. If a part of the first insulator  110  on the top surface of the anode-side protruding portion  28  is left unremoved, the anode-side protruding portion  28 ″ is formed. 
         [0105]    Similarly, the cathode  24  at the top of the cathode-side protruding portion  38  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the cathode-side protruding portion  38 . If all of the second insulator  112  constituting the top surface of the cathode-side protruding portion  38  is removed, a cathode-side protruding portion  38  identical to that in Embodiment 1 is formed. If a part of the second insulator  112  constituting the top surface of the cathode-side protruding portion  38  is left unremoved, the cathode-side protruding portion  38 ″ is formed. 
         [0106]    A composite film  100  used in the fuel CELL of Embodiment 4 is fabricated through the above-described steps. 
       Embodiment 5 
       [0107]      FIG. 15  is a cross-sectional view showing a structure of a fuel CELL according to Embodiment 5.  FIG. 16  is an enlarged view of a relevant part showing the structures of an anode-side protruding portion and a cathode-side protruding portion of Embodiment 5. The basic structure of the fuel CELL  10  of this embodiment is the same as that of Embodiment 3 and descriptions for the features similar to Embodiment 3 are omitted to avoid redundancy. 
         [0108]    In the anode-side protruding portion  28 , the interconnector  30  has a step surface S 3 , which is the portion not covered with the second insulator  112  and is receded from a side surface of the interconnector  30  covered with the second insulator  112 . In other words, a step not covered with the second insulator  112  is formed in the interconnector  30  in the anode-side protruding portion  28 . A step side surface S 2  of the step and an anode-side protruding portion  28 -side end surface S 1  of the second insulator  112  are flush with each other. 
         [0109]    In the cathode-side protruding portion  38 , the interconnector  30  has a step surface S 6 , which is the portion not covered with the first insulator  110  and is receded from a side surface of the interconnector  30  covered with the first insulator  110 . In other words, a step not covered with the first insulator  110  is formed in the interconnector  30  in the cathode-side protruding portion  38 . A step side surface S 5  of the step and a cathode-side protruding portion  38 -side end surface S 4  of the first insulator  110  are flush with each other. 
         [0110]    This embodiment is one of the embodiments in which, in a cross-section taken along a direction in which the membrane electrode assemblies  20  are adjacent to one another, the chamfered portion of the interconnector  30  and the first insulator  110  and the chamfered portion of the interconnector  30  and the second insulator  111  are receded from a line connecting two ends of each chamfered portion (located on the interconnector  30 -side of the line connecting the two ends of the chamfered portion). In the chamfered portion having such a structure, the chamfered angle (angle A and angle B in  FIG. 3 , 90 degrees in this embodiment) at the two ends of the chamfered portion is preferably 90 degrees or less. In this manner, the interconnector  30  and the second insulator  112  can reliably contact the anode  26 . In Embodiment 5 also, the coating layer  400  and the coating layer  410  can be formed as in Embodiment 2. 
       (Method for Producing Fuel CELL According to Embodiment 5) 
       [0111]    Of the method for producing a fuel CELL according to Embodiment 3, a method for fabricating a composite film  100  is described in particular with reference to  FIGS. 17 to 18 . 
         [0112]    First, as shown in  FIG. 17(A) , a laminate  200  in which the first insulator  110  and the second insulator  112  are respectively stacked on two sides of the interconnector  30  is prepared. The first insulator  110  and the second insulator  112  each have a thickness of 0.1 mm, for example. 
         [0113]    Next, as shown in  FIG. 17(B) , the second insulator  112  and the second insulator  112 -side interconnector  30  are partly and selectively removed by laser processing. The regions of the second insulator  112  and the interconnector  30  to be removed extend along every other cutting lines C among a plurality of cutting lines C parallel to each other. Each region in which removal is conducted has a width with a cutting line C as the center line. Similarly, the first insulator  110  and the first insulator  110 -side interconnector  30  are partly and selectively removed by laser processing. The regions of the first insulator  110  and the interconnector  30  to be removed extend along every other cutting lines C among a plurality of cutting lines C parallel to each other. Each region in which removal is conducted has a width with a cutting line C as the center line. The regions from which the first insulator  110  is removed and the regions from which the second insulator  112  is removed are formed in a staggered manner with the interconnector  30  interposed therebetween. 
         [0114]    Then the laminate  200  is cut along the cutting lines C to form individual rod-shaped composite materials  210 . 
         [0115]    Next, as shown in  FIG. 18(A) , the composite materials  210  are placed on a base  300  by fitting a part of each composite material  210  into a groove  302  so that the layer stacking direction in the composite material  210  is coincident with the surface direction of the base  300 . 
         [0116]    Next, as shown in  FIG. 18(B) , an electrolyte solution  310  containing an ion exchange material such as Nafion is applied between a pair of the composite materials  210 . During this process, if the electrolyte solution  310  is applied to the end surface S 1  of the second insulator  112  and/or the step side surface S 2  of the interconnector  30 , the undesirable electrolyte solution  310  applied to such surfaces is removed by using a jig such as a knife. 
         [0117]    Next, as shown in  FIG. 18(C) , the electrolyte solution is dried to form the electrolyte membrane  22 . As the solvent is removed, the thickness of the electrolyte membrane  22  becomes smaller than the thickness of the electrolyte solution  310  shown in  FIG. 11(B) . A part of the composite material  210  protruding from the anode surface of the electrolyte membrane  22  forms a part of the anode-side protruding portion  28 . A part of the composite material  210  protruding from the cathode surface of the electrolyte membrane  22  forms a part of the cathode-side protruding portion  38 . 
         [0118]    Next, as shown in  FIG. 18(D) , an anode catalyst slurry is applied to the anode surface of the electrolyte membrane  22  and the anode-side protruding portion  28  by a spray coating method to form an anode  26 . During this process, the interconnector  30  exposed in one of the side surfaces of the anode-side protruding portion  28  connects to the anode  26 . A cathode catalyst slurry is applied to the cathode surface of the electrolyte membrane  22  and the cathode-side protruding portion  38  by a spray coating method so as to form a cathode  24 . During this process, the interconnector  30  exposed in the other side surface of the cathode-side protruding portion  38  connects to the cathode  24 . 
         [0119]    Next, as shown in  FIG. 18(E) , the anode  26  formed at the top of the anode-side protruding portion  28  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the anode-side protruding portion  28 . Similarly, the cathode  24  at the top of the cathode-side protruding portion  38  is removed by using a spatula, a blade, or the like so as to form a flat exposed surface at the top of the cathode-side protruding portion  38 . 
         [0120]    A composite film  100  used in the fuel CELL of Embodiment 5 is fabricated through the above-described steps. 
         [0121]    As shown in  FIG. 16 , in the step of the interconnector  30  in the anode-side protruding portion  28  in the fuel CELL  10  of this embodiment, the step surface S 3  and the step side surface S 2  contact the anode  26 . Accordingly, the area of contact between the interconnector  30  and the anode  26  can be increased compared to Embodiment 3. Moreover, in the step in the interconnector  30  of the cathode-side protruding portion  38 , the step surface S 6  and the step side surface S 5  are in contact with the cathode  24 . Accordingly, the area of contact between the interconnector  30  and the cathode  24  can be increased compared to Embodiment 3. As a result, the resistance between the interconnector  30  and each electrode can be decreased. 
         [0122]    In the step shown in  FIG. 18(B) , the excess electrolyte solution can be easily removed without damaging the electrolyte solution in the needed portion by sliding a jig such as a knife over the step side surface S 2  using the step surface S 3  as a guide. 
         [0123]    According to the methods for producing a fuel CELL of the embodiments described above, a composite film for a fuel CELL in which cells are integrated can be easily fabricated without using laser processing to form individual cells. Since laser processing is not employed to form individual cells, generation of ash resulting from laser irradiation is avoided. Accordingly, the electrolyte membranes and catalyst layers can be kept clean. 
         [0124]    According to a method for producing a fuel CELL of Embodiment 2, presence of the coating layer  400  and the coating layer  410  more reliably electrically insulates between the interconnector  30  and the anode or cathode to which the interconnector  30  should not be connected. 
         [0125]    According to a method for producing a fuel CELL of Embodiment 4, presence of the first insulator  110  and the second insulator  112  more reliably electrically insulates between the interconnector  30  and the anode or cathode to which the interconnector  30  should not be connected. 
         [0126]    Although the protruding portions are formed on both the anode side and the cathode side, a protruding portion may be formed in only one of the anode side and the cathode side. On the side where the protruding portion is not formed, for example, surfaces of the electrolyte membrane, the interconnector, and the insulator that insulates between the electrolyte membrane and the interconnector may be arranged to be substantially flush with each other and then cathodes or anodes may be formed by using a mask so that they are in individual regions corresponding to the cells. 
       REFERENCE SIGNS LIST 
       [0127]      10  fuel CELL,  20  membrane electrode assembly,  22  electrolyte membrane,  24  cathode,  26  anode,  28  anode-side protruding portion,  30  interconnector,  38  cathode-side protruding portion,  50  cathode housing,  52  anode housing,  60  air chamber,  62  fuel gas chamber,  100  composite film 
       INDUSTRIAL APPLICABILITY 
       [0128]    The present invention is applicable to fuel cell.