Abstract:
According to one embodiment, a fuel cell includes a plurality of planar membrane electrode assemblies each produced by integrating a fuel electrode, an oxidizer electrode and an electrolyte membrane sandwiched between the fuel electrode and the oxidizer electrode, and a polyhedral package frame having plural planes which are disposed in a non-planar arrangement and support the plurality of membrane electrode assemblies so as to surround these membrane electrode assemblies.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a Continuation Application of PCT Application No. PCT/JP2008/070515, filed Nov. 11, 2008, which was published under PCT Article 21(2) in Japanese. 
     
    
       [0002]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-300782, filed Nov. 20, 2007; the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0003]    Embodiments described herein relate generally to a direct methanol fuel cell effective for the operation of portable electronic devices. 
       BACKGROUND 
       [0004]    Various miniaturized electronic devices such as personal computers and portable telephones have been recently developed along with the development of semiconductor technologies and an attempt is currently made to use fuel cells as the power sources of these miniaturized devices. The fuel cell has the advantages that it can generate electricity only by supplying fuel and an oxidizer and can also generate electricity continuously by replenishing and exchanging only fuel. For this reason, the fuel cell is a very advantageous system for the operation of portable electronic devices if it can be miniaturized. Particularly, a direct methanol fuel cell (DMFC) can be miniaturized because it uses methanol having a high energy density as the fuel and current can be drawn directly from methanol on the electrode catalyst. Also, because the fuel can be handled more easily than hydrogen gas fuel, the direct methanol fuel cell is regarded as a promising power source for miniature electronic devices and expected to be put to practical use as the most suitable power source for codeless portable electronic devices such as portable telephones, portable audios, portable game machines and notebook personal computers. 
         [0005]    In the meantime, the direct methanol fuel cell is reduced in the potential of a unit cell generated between a pair of anode and cathode in the generation of electricity, causing a lack of the power voltage required for operating devices. It is therefore necessary to adopt the so-called multi-electrode structure in which plural pairs of anodes/cathodes are connected in series to compensate for the lack of the power voltage. However, the area occupied by these plural pairs of anodes/cathodes is increased, resulting in the production of a large-sized battery, if these cathodes/anodes are arranged on one plane to connect these cathodes/anodes in series. 
         [0006]    JP-A 1997-129258 (KOKAI) and JP-A 2005-353571 (KOKAI) respectively propose a multi-electrode fuel cell in which a membrane-electrode assembly (MEA) containing plural pairs of anodes/cathodes is disposed in a ring form to miniaturize a fuel cell to be used as a portable device power source. 
         [0007]    However, because these conventional fuel cells are made to have a ring form as a whole and therefore tend to roll, they lack in a sense of stability. Also, because in the ring fuel cell, the both ends thereof are opened as the opening of a fuel supply passage, this part cannot be utilized for the generation of electricity and it is difficult to increase the power per unit volume. There is an idea in regard to a ring cell extended in the direction of the major axis to increase the output. However, if the length of the cell becomes large, not only is this contrary to the intention to miniaturize the cell, but also the cell tends to roll more easily, leading to a lack in a sense of stability. 
         [0008]    Embodiments have been made to solve the above problem and it is an object of the embodiments to provide a small-sized fuel cell which exhibits a high power and is superior in long-term stability. 
         [0009]    A fuel cell comprising: a plurality of planar membrane electrode assemblies each comprising a fuel electrode, an oxidizer electrode and an electrolyte membrane sandwiched between the fuel electrode and the oxidizer electrode; and a polyhedral package frame having plural planes which are disposed in a non-planar arrangement and support said plurality of membrane electrode assemblies so as to surround these membrane electrode assemblies. 
         [0010]    The fuel cell according to the embodiment, wherein ventilation holes which supply an oxidizer to the oxidizer electrode are opened at each of surfaces of the package frame that face the membrane electrode assemblies. 
         [0011]    In addition, the ventilation holes are preferably opened at surfaces of the package frame except for a bottom surface thereof. This is because the bottom surface of the package frame is in contact with, for example, a floor so that the bottom surfaces of many cells substantially fail or are limited in the supply of an oxidizer (air), which prevents or suppresses the progress of a cathode reaction on the oxidizer electrode side. As mentioned above, the structure in which only one surface (bottom surface) is made to be a blind patch having no ventilation hole has the advantage that the upper and lower sides of a cell are easily distinguished. However, because this is a structural problem concerning only a difference in setting method (handling on the user side), ventilation holes may be formed on the entire surface before use in the case of a shape, such as a regular polygonal form, having an indistinctive bottom. 
         [0012]    The fuel cell according to the embodiment, further comprising: fuel supply passages which supply fuel to the fuel electrodes of said plurality of membrane electrode assemblies; a plurality of connecting members each of which electrically connects the oxidizer electrode in one of two adjacent membrane electrode assemblies and the fuel electrode in another of the two adjacent membrane electrode assemblies; and output leads connected to both ends of a current collecting circuit formed of the connecting members and the electrodes to draw power generated in the membrane electrode assemblies. 
         [0013]    In the embodiment, each of the membrane electrode assemblies preferably has substantially the same area. This is because almost the same power is output from each surface and therefore, not only is the output to the inverter stabilized but also no overload is applied, leading to a reduction in the variation of temperature caused by local heating. As mentioned above, the polyhedrons each having surfaces of the same area include regular polyhedrons. As these regular polyhedrons, for example, a regular tetrahedron, regular hexahedron, regular octahedron, regular dodecahedron, regular icosahedron or stellate regular dodecahedron as shown in  FIGS. 5A ,  5 B,  5 C,  5 E,  5 F and  5 G, respectively, may be used. Moreover, in the present invention, the package frame may be a cubic or polygonal prismatic solid. As the polygonal prismatic solid, for example, a regular hexagonal prismatic solid, regular triangular solid, regular pentagonal prismatic solid or stellate 5/2 prismatic solid as shown in  FIGS. 1 ,  5 D,  5 H and  5 J, respectively, may be used. 
         [0014]    In the present invention, all of these plural membrane electrode assemblies may be connected in series by connecting members as shown in  FIGS. 4 ,  6 ,  7 ,  8 A and  9 . If they are all connected in series, high voltage can be obtained. Also, as shown in  FIG. 8B , the fuel cell of the present invention may comprise a first current collecting circuit in which parts of these plural membrane electrode assemblies are connected in series by connecting members and a second current collecting circuit in which other parts of the membrane electrode assemblies are connected in series by connecting members and which is connected in parallel to the first current collecting circuit. When the power generating part is divided into plural parts and these plural parts are connected in parallel to each other, large current can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a schematic perspective view showing a fuel cell according to an embodiment. 
           [0016]      FIG. 2  is an internal perspective and sectional view schematically showing a fuel supply mechanism used in a fuel cell according to the embodiment. 
           [0017]      FIG. 3  is a structural block diagram schematically showing another fuel supply mechanism. 
           [0018]      FIG. 4  is a development diagram showing a fuel cell according to an embodiment. 
           [0019]      FIG. 5A  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0020]      FIG. 5B  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0021]      FIG. 5C  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0022]      FIG. 5D  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0023]      FIG. 5E  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0024]      FIG. 5F  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0025]      FIG. 5G  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0026]      FIG. 5H  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0027]      FIG. 5J  is an external appearance diagram schematically showing a multi-electrode fuel cell having a non-planar form. 
           [0028]      FIG. 6  is a development diagram showing a fuel cell according to other embodiment. 
           [0029]      FIG. 7  is a development diagram showing a fuel cell according to other embodiment. 
           [0030]      FIG. 8A  is a development diagram showing a fuel cell (seven series) according to other embodiment. 
           [0031]      FIG. 8B  is a development diagram showing a fuel cell (two parallel and three series) according to other embodiment. 
           [0032]      FIG. 9  is a development diagram showing a fuel cell according to other embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    In general, according to one embodiment will be explained with reference to the drawings. 
       First Embodiment 
       [0034]    A fuel cell according to a first embodiment will be explained with reference to  FIGS. 1 to 4 . The outside of a fuel cell  1  in this embodiment is, as shown in  FIGS. 1 and 2 , covered with a package frame  6  having a hexagonal prismatic form and a cell structure which generates and outputs electricity as a direct methanol fuel cell (DMFC) is contained in the package frame  1 . The cell structure is constituted of plural membrane electrode assemblies  5  fabricated into a hexagonal prismatic form and the membrane electrode assemblies  5  adjacent to each other are connected by connecting members  11   c  to  17   c  which will be explained later. A fuel tank  8  is accommodated in the cell structure. The fuel tank  8  serves to receive liquid fuel supplied from a fuel injection port  8   a  and to distribute and supply liquid fuel (methanol solution) to each membrane electrode assembly  5  through branched plural fuel supply passages  9 . The fuel tank  8  may be an exchange type cartridge which can be mounted or dismounted with ease. 
         [0035]    The fuel supply system may be either a passive system in which fuel is transported from the fuel tank  8  by only utilizing a capillary phenomenon of the fuel supply passage  9  as shown in  FIG. 2  or a semi-passive system in which an ultra-micro pump  82  is attached to a fuel tank  81  to transport fuel through a major passage  9   a  and a branched passage  9   b  as shown in  FIG. 3 . In the semi-passive system fuel cell, the fuel supplied to each membrane electrode assembly  5  from the fuel tank  81  is used for a power generating reaction, after which the fuel is neither circulated nor returned to the fuel tank  81 . The semi-passive system fuel cell is different from the conventional active system fuel cell because fuel is not circulated. Therefore, the semi-passive system gives no difficulty in the miniaturization of the cell. The pump  82  and the fuel tank  81  may be installed outside though they are preferably built in the system. Although the type of the pump  82  is not particularly limited, an electro-osmosis pump (EO pump), rotary pump (rotary vane pump), diaphragm pump, shear pump or the like is preferably used from the viewpoints of further miniaturization and weight reduction, and capability to feed a small amount of liquid fuel with good controllability. The electro-osmosis pump is produced using a sintered porous body such as silica, giving rise to an electro-osmosis phenomenon. The rotary pump rotates a blade by using a motor to feed a liquid. The diaphragm pump is provided with a diaphragm driven by an electromagnet or piezoelectric ceramics to feed a liquid. The shear pump applies pressure on a part of a flexible fuel passage to feed fuel with shear. Among these pumps, an electro-osmosis pump or a diaphragm pump provided with a piezoelectric ceramics is preferably used from the viewpoint of, for example, driving power and size. 
         [0036]    It is also preferable to apply an electro-osmosis pump or a diaphragm pump as the pump  82  in order to feed a liquid in a stable amount. In this case, it is so designed that the operation of the pump  82  is controlled by a control circuit (not shown). 
         [0037]    The package frame  6  is a member which functions not only as a cover plate used to cover the external surface of the fuel cell body, but also as a structural material which supports and secures the cell structure and fuel tank  8  ( 81 ) contained in the fuel cell. A metal material such as stainless steel is preferably used as the material of the package frame  6  used as a function material like this and also, a polyacetal-based engineering plastic such as a polyoxymethylene is preferably used. Also, a ceramic material excellent in impact resistance may also be used as the package frame  6 . 
         [0038]    The package frame  6  and the membrane electrode assembly  5  are fastened with a screw and/or secured by edge-caulking processing to thereby integrate the cell structure with the package frame  6 . Also, a seal member (for example, an O-ring) (not shown) is installed in an appropriate place inside the cell structure to seal a space between the package frame  6  and the membrane electrode assembly  5  liquid-tightly, so that the liquid fuel contained in the cell is prevented from leaking from the package. 
         [0039]    As shown in  FIGS. 2 and 4 , the fuel cell  1  comprises six membrane electrode assemblies  12  to  17  on its peripheral surface, one membrane electrode assembly  11  on its upper surface and a blind plate on its bottom  18 . These membrane electrode assemblies  11  to  17  are respectively structured such that a cathode  2  (oxidizer electrode)  2  is positioned outside and an anode (fuel electrode)  3  is positioned inside. Plural ventilation holes  7  are opened on each surface of the package frame  6  except for the bottom  18  to introduce an oxidizer (air) from the outside. Air is introduced into the inside through these ventilation holes  7 , transmits through a humidification plate (not shown) optionally arranged and is supplied to the cathode  2  of the membrane electrode assembly  5  ( 11  to  17 ). 
         [0040]    The membrane electrode assembly  5  ( 11  to  17 ) comprises the cathode  2  consisting essentially of a cathode catalyst layer and a cathode gas diffusing layer, the anode  3  consisting essentially of an anode catalyst layer and an anode gas diffusing layer and a proton-conductive electrolyte membrane  4  supported between the cathode  2  and the anode  3 . Examples of the catalyst contained in the cathode catalyst layer and anode catalyst layer may include single metals (for example, Pt, Ru, Rh, Ir, Os and Pd) which are platinum group elements and alloys containing a platinum group element. Pt—Ru highly resistant to methanol and carbon monoxide is preferably used for the anode catalyst and Pt is preferably used for the cathode catalyst, though the catalyst materials are not limited to these materials. Also, either a supported catalyst using a conductive support such as a carbon material or a non-supported catalyst may be used. 
         [0041]    The electrolyte membrane  4  serves to transfer protons generated in the anode catalyst layer of the anode  3  to the cathode catalyst layer and is constituted of a material which has no electronic conductivity and can transfer protons. Examples of the material used for the electrolyte membrane  4  include fluororesins having a sulfonic acid group (for example, a perfluorosulfonic acid polymer), hydrocarbon-based resins having a sulfonic acid group, tungstic acid and tungstophosphoric acid. Specifically, the electrolyte membrane  4  is constituted of, for example, a Nafion (trademark) film manufactured by Du Pont, Flemion (trademark) film manufactured by Asahi Glass Co., Ltd. or Aciplex (trademark) film manufactured by Asahi KASEI Corporation. Other than the polyperfluorosulfonic acid-based resin film, a copolymer of a trifluorostyrene derivative, polybenzimidazole film impregnated with phosphoric acid, aromatic polyether ketone sulfonic acid film or aliphatic hydrocarbon-based resin film, which can transfer protons may be used to constitute the electrolyte membrane  4 . 
         [0042]    The cathode catalyst layer is laminated on the cathode gas diffusing layer and the anode catalyst layer is laminated on the anode gas diffusing layer. The cathode gas diffusing layer serves to supply the oxidizer uniformly to the cathode catalyst layer and also doubles as the current collector of the cathode catalyst layer. On the other hand, the anode gas diffusing layer serves to supply the fuel uniformly to the anode catalyst layer and also doubles as the current collector of the anode catalyst layer. 
         [0043]    A vapor-liquid separation film (not shown) optionally disposed serves to transmit only the vaporized component of the liquid fuel (for example, a methanol solution) to be supplied to the membrane electrode assembly from the fuel tank  8  ( 81 ) to supply the fuel to the fuel electrode and is of such a nature that it never transmits liquid fuel itself. As the vapor-liquid separation film, a porous film such as a silicon sheet or PTFE film is used. Here, the vaporized component of the liquid fuel means vaporized methanol in the case of using liquid methanol as the liquid fuel and means mixture gas containing the vaporized component of methanol and vaporized component of water in the case of using an aqueous methanol solution as the liquid fuel. 
         [0044]    Incidentally, the liquid fuel to be used in the fuel cell of the present invention is preferably a highly concentrated aqueous methanol solution having a fuel concentration exceeding 80 mol % or a pure methanol solution. This is because the output tends to drop when the concentration of fuel is 80 mol % or less, leading to an increase in the frequency of the supply of the fuel. 
         [0045]    The liquid fuel is not always limited to the above methanol fuel but may be ethanol fuel such as an aqueous ethanol solution or pure ethanol, propanol fuel such as an aqueous propanol solution or pure propanol, glycol fuel such as an aqueous glycol solution or pure glycol, dimethyl ether, formic acid or other liquid fuels. In any case, liquid fuel according to a fuel cell is used. An aqueous methanol solution having a methanol concentration exceeding 80 mol % or pure methanol solution is particularly preferable. 
         [0046]    With regard to the vapor of the liquid fuel supplied to the membrane electrode assembly  5  ( 11  to  17 ), the present invention can be applied when a part of the liquid fuel is supplied in a liquid form, though all the liquid fuel may be supplied in a vapor form. 
         [0047]    The fuel transported from the fuel tank  8  ( 81 ) is supplied to the anode  3  of the membrane electrode assembly  5  ( 11  to  17 ). In the membrane electrode assembly  5  ( 11  to  17 ), the fuel is diffused in the anode gas diffusing layer and is then supplied to the anode catalyst layer. When methanol fuel is supplied as the liquid fuel, methanol undergoes an internal reforming reaction represented in the following formula (1) in the anode catalyst layer. When pure methanol is used as the methanol fuel, the water produced in the cathode catalyst layer and the water produced in the electrolyte membrane are made to undergo a reaction with methanol, causing the internal reforming reaction of the formula (1). Alternatively, an internal reforming reaction is caused by other reaction mechanism which needs no water. 
         [0000]      CH 3 OH+H 2 →CO 2 +6H + +6 e   −   (1) 
         [0048]    The electrons (e − ) produced in this reaction are led externally through the current collector and then led to the cathode  2  after they act as electricity to drive portable electronic devices and the like. Also, the protons (H + ) produced by the internal reforming reaction of the formula (1) are led to the cathode through the electrolyte membrane. Air is supplied as the oxidizer to the cathode. The electrons (e − ) and protons (H + ) which have reached the cathode react with oxygen of the air in the cathode catalyst layer according to the following formula (2), resulting in the production of water. 
         [0000]      6 e   − +6H + +(3/2)O 2 →3H 2 O  (2) 
         [0049]    In order to increase the power to be generated in the above power generating reaction of the fuel cell, it is important to run the catalytic reaction smoothly and to add the contribution of all the electrodes of the membrane electrode assemblies  5  ( 11  to  17 ) to generation of electricity more efficiently. 
         [0050]    Next, the current collecting circuit in the fuel cell  1  will be explained with reference to  FIG. 4 . 
         [0051]    A positive and negative pair of connecting members  11   a  and  11   b  is attached to the cathode  3  side and anode side of the membrane electrode assembly  11 , respectively. The pair of connecting members  11   a  and  11   b  is connected such that the space between these connecting members forms a passage  11   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  11 . The cathode side connecting member  11   a  is connected to a cathode side output lead  19   a  and further, the output lead  19   a  is connected to an inverter (not shown). On the other hand, the anode side connecting member  11   b  is connected to a cathode side connecting member  12   a  of the membrane electrode assembly  12 . 
         [0052]    A positive and negative pair of cathode side connecting member  12   a  and anode side connecting member  12   b  is attached to the side and corner part of the membrane electrode assembly  12 , respectively. The pair of connecting members  12   a  and  12   b  is connected such that the space between these connecting members forms a passage  12   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  12 . Further, the anode side connecting member  12   b  is connected to a cathode side connecting member  13   a  of the membrane electrode assembly  13 . 
         [0053]    A positive and negative pair of cathode side connecting member  13   a  and anode side connecting member  13   b  is attached to the opposite corner parts of the membrane electrode assembly  13 , respectively. The pair of connecting members  13   a  and  13   b  is connected such that the space between these connecting members forms a passage  13   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  13 . Further, the anode side connecting member  13   b  is connected to a cathode side connecting member  14   a  of the membrane electrode assembly  14 . 
         [0054]    Similarly, a positive and negative pair of cathode side connecting member  14   a  and anode side connecting member  14   b  is attached to the opposite corner parts of the membrane electrode assembly  14 , respectively. The pair of connecting members  14   a  and  14   b  is connected such that the space between these connecting members forms a passage  14   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  14 . Further, the anode side connecting member  14   b  is connected to a cathode side connecting member  15   a  of the membrane electrode assembly  15 . 
         [0055]    Similarly, a positive and negative pair of cathode side connecting member  15   a  and anode side connecting member  15   b  is attached to the opposite corner parts of the membrane electrode assembly  15 , respectively. The pair of connecting members  15   a  and  15   b  is connected such that the space between these connecting members forms a passage  15   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  15 . Further, the anode side connecting member  15   b  is connected to a cathode side connecting member  16   a  of the membrane electrode assembly  16 . 
         [0056]    Similarly, a positive and negative pair of cathode side connecting member  16   a  and anode side connecting member  16   b  is attached to the opposite corner parts of the membrane electrode assembly  16 , respectively. The pair of connecting members  16   a  and  16   b  is connected such that the space between these connecting members forms a passage  16   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  16 . Further, the anode side connecting member  16   b  is connected to a cathode side connecting member  17   a  of the membrane electrode assembly  17 . 
         [0057]    Similarly, a positive and negative pair of cathode side connecting member  17   a  and anode side connecting member  17   b  is attached to the opposite corner parts of the membrane electrode assembly  17 , respectively. The pair of connecting members  17   a  and  17   b  is connected such that the space between these connecting members forms a passage  17   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  17 . Further, the anode side connecting member  17   b  is connected to an anode side output lead  19   b , which is in turn connected to an inverter (not shown). 
         [0058]    A porous layer (for example, a mesh) or a foil body consisting essentially of a metal material such as gold or nickel which is excellent in electric characteristics and chemical stability, or a composite material produced by coating a conductive metal material such as stainless steel (SUS) with a highly conductive metal such as gold may be used for these connecting members  11   a ,  11   b , . . .  17   a  and  17   b . These connecting members  11   b  and  12   a ,  12   b  and  13   a ,  13   b  and  14   a ,  14   b  and  15   a ,  15   b  and  16   a  and  16   b  and  17   a  may be respectively an integrated one. 
         [0059]    A cathode current collector and an anode current collector may be disposed on the sides opposite to each catalyst layer of the cathode diffusing layer of the cathode and the anode diffusing layer of the anode in the membrane electrode assembly. The same material as the connecting member may be used for these current collectors. 
         [0060]    The fuel cell of the present invention may be designed to be a polygonal prismatic solid other than the above hexagonal prismatic solid, and examples of the polygonal prismatic solid include a regular triangular solid, regular pentagonal prismatic solid and stellate 5/2 prismatic solid as shown in  FIGS. 5D ,  5 H and  5 J, respectively. Also, the fuel cell of the present invention may be designed to be a regular polyhedron, for example, a regular tetrahedron, regular hexahedron, regular octahedron, regular dodecahedron, regular icosahedron or stellate regular dodecahedron as shown in  FIGS. 5A ,  5 B,  5 C,  5 E,  5 F and  5 G, respectively. 
       Second Embodiment 
       [0061]    Next, a fuel cell  1 A according to a second embodiment will be explained with reference to  FIGS. 6 and 5A . In this embodiment, the explanations of the same parts that have been described in the above embodiment will be omitted to avoid unnecessary duplications. 
         [0062]    The fuel cell  1 A of this embodiment has a regular tetrahedron form. In the current collecting circuit in the fuel cell  1 A, a positive and negative pair of cathode side connecting member  21   a  and anode side connecting member  21   b  are attached to two corner parts of a membrane electrode assembly  21  having a triangular form, respectively. The pair of connecting members  21   a  and  21   b  is connected such that the space between these connecting members forms a passage  21   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  21 . The cathode side connecting member  21   a  is connected to a positive electrode side output lead  29   a  and further, the output lead  29   a  is connected to an inverter (not shown). On the other hand, the anode side connecting member  21   b  is connected to a cathode side connecting member  22   a  of a membrane electrode assembly  22 . 
         [0063]    A positive and negative pair of cathode side connecting member  22   a  and anode side connecting member  22   b  is attached to two corner parts of the membrane electrode assembly  22 , respectively. The pair of connecting members  22   a  and  22   b  is connected such that the space between these connecting members forms a passage  22   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  22 . Further, the anode side connecting member  22   b  is connected to a cathode side connecting member  23   a  of a membrane electrode assembly  23 . Further, the anode side connecting member  23   b  is connected to an anode side output lead  29   b , which is in turn connected to an inverter (not shown). 
       Third Embodiment 
       [0064]    Next, a fuel cell  1 B according to a third embodiment will be explained with reference to  FIGS. 7 and 5B . In this embodiment, the explanations of the same parts that have been described in the above embodiments will be omitted to avoid unnecessary duplications. 
         [0065]    The fuel cell  1 B of this embodiment has a regular hexahedron form (cubic form). In the current collecting circuit in the fuel cell  1 B, a positive and negative pair of cathode side connecting member  31   a  and anode side connecting member  31   b  is attached to two opposite corner parts of a membrane electrode assembly  31  having a square form, respectively. The pair of connecting members  31   a  and  31   b  is connected such that the space between these connecting members forms a passage  31   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  31 . The cathode side connecting member  31   a  is connected to a cathode side output lead  39   a  and further, the output lead  39   a  is connected to an inverter (not shown). On the other hand, the anode side connecting member  31   b  is connected to a cathode side connecting member  32   a  of a membrane electrode assembly  32 . 
         [0066]    A positive and negative pair of cathode side connecting member  32   a  and anode side connecting member  32   b  is attached to the adjacent two corner parts of the membrane electrode assembly  32 , respectively. The pair of connecting members  32   a  and  32   b  is connected such that the space between these connecting members forms a passage  32   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  32 . Further, the anode side connecting member  32   b  is connected to a cathode side connecting member  33   a  of a membrane electrode assembly  33 . 
         [0067]    A positive and negative pair of cathode side connecting member  33   a  and anode side connecting member  33   b  is attached to the opposite two corner parts of the membrane electrode assembly  33 , respectively. The pair of connecting members  33   a  and  33   b  is connected such that the space between these connecting members forms a passage  33   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  33 . Further, the anode side connecting member  33   b  is connected to a cathode side connecting member  34   a  of a membrane electrode assembly  34 . 
         [0068]    Similarly, a positive and negative pair of cathode side connecting member  34   a  and anode side connecting member  34   b  is attached to the opposite two corner parts of the membrane electrode assembly  34 , respectively. The pair of connecting members  34   a  and  34   b  is connected such that the space between these connecting members forms a passage  34   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  34 . Further, the anode side connecting member  34   b  is connected to a cathode side connecting member  35   a  of a membrane electrode assembly  35 . 
         [0069]    Similarly, a positive and negative pair of cathode side connecting member  35   a  and anode side connecting member  35   b  is attached to the adjacent two corner parts of the membrane electrode assembly  35 , respectively. The pair of connecting members  35   a  and  35   b  is connected such that the space between these connecting members forms a passage  35   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  35 . Further, the anode side connecting member  35   b  is connected to an anode side output lead  39   b , which is in turn connected to an inverter (not shown). 
       Fourth Embodiment 
       [0070]    Next, a fuel cell  1 C 1  according to a fourth embodiment will be explained with reference to  FIGS. 8A and 5C . In this embodiment, the explanations of the same parts that have been described in the above embodiments will be omitted to avoid unnecessary duplications. 
         [0071]    The fuel cell  1 C 1  of this embodiment has a regular octahedron form. In the current collecting circuit in the fuel cell  1 C 1 , a positive and negative pair of cathode side connecting member  41   a  and anode side connecting member  41   b  is attached to the corner part and the center of the side of a membrane electrode assembly having a triangular form, respectively. The pair of connecting members  41   a  and  41   b  is connected such that the space between these connecting members forms a passage  41   c  as shown schematically by the internal connecting condition between the cathode and anode of a membrane electrode assembly  41 . The cathode side connecting member  41   a  is connected to a cathode side output lead  49   a  and further, the output lead  49   a  is connected to an inverter (not shown). On the other hand, the anode side connecting member  41   b  is connected to a cathode side connecting member  42   a  of a membrane electrode assembly  42 . 
         [0072]    A positive and negative pair of cathode side connecting member  42   a  and anode side connecting member  42   b  is attached to the adjacent two corner parts of the membrane electrode assembly  42 , respectively. The pair of connecting members  42   a  and  42   b  is connected such that the space between these connecting members forms a passage  42   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  42 . Further, the anode side connecting member  42   b  is connected to a cathode side connecting member  43   a  of a membrane electrode assembly  43 . 
         [0073]    A positive and negative pair of cathode side connecting member  43   a  and anode side connecting member  43   b  is attached to the corner part and center of the side of the membrane electrode assembly  43 , respectively. The pair of connecting members  43   a  and  43   b  is connected such that the space between these connecting members forms a passage  43   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  43 . Further, the anode side connecting member  43   b  is connected to a cathode side connecting member  44   a  of a membrane electrode assembly  44 . 
         [0074]    Similarly, a positive and negative pair of cathode side connecting member  44   a  and anode side connecting member  44   b  is attached to the corner part and center of the side of the membrane electrode assembly  44 , respectively. The pair of connecting members  44   a  and  44   b  is connected such that the space between these connecting members forms a passage  44   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  44 . Further, the anode side connecting member  44   b  is connected to a cathode side connecting member  45   a  of a membrane electrode assembly  45 . 
         [0075]    Similarly, a positive and negative pair of cathode side connecting member  45   a  and anode side connecting member  45   b  is attached to the corner part and center of the side of the membrane electrode assembly  45 , respectively. The pair of connecting members  45   a  and  45   b  is connected such that the space between these connecting members forms a passage  45   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  45 . Further, the anode side connecting member  45   b  is connected to a cathode side connecting member  46   a  of a membrane electrode assembly  46 . 
         [0076]    Similarly, a positive and negative pair of cathode side connecting member  46   a  and anode side connecting member  46   b  is attached to the corner part and center of the side of the membrane electrode assembly  46 , respectively. The pair of connecting members  46   a  and  46   b  is connected such that the space between these connecting members forms a passage  46   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  46 . Further, the anode side connecting member  46   b  is connected to a cathode side connecting member  47   a  of a membrane electrode assembly  47 . 
         [0077]    Similarly, a positive and negative pair of cathode side connecting member  47   a  and anode side connecting member  47   b  is attached to the corner part and center of the side of the membrane electrode assembly  47 , respectively. The pair of connecting members  47   a  and  47   b  is connected such that the space between these connecting members forms a passage  47   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  47 . Further, the anode side connecting member  47   b  is connected to an anode side output lead  49   b , which is in turn connected to an inverter (not shown). 
       Fifth Embodiment 
       [0078]    Next, a fuel cell  1 C 2  according to a fifth embodiment will be explained with reference to  FIGS. 8B and 50 . In this embodiment, the explanations of the same parts that have been described in the above embodiments will be omitted to avoid unnecessary duplications. 
         [0079]    The fuel cell  1 C 2  of this embodiment has a regular octahedron form and is provided with a current collecting circuit constituted of a two parallel circuits each containing three series circuits. In the current collecting circuit in the fuel cell  1 C 2 , a positive electrode cathode side connecting member  51   a  is attached to a corner of a triangle membrane electrode assembly and a negative electrode connecting member  52   b  is attached to a corner of a membrane side electrode assembly  52 . The pair of cathode side connecting member  51   a  and anode connecting member  52   b  is connected such that the space between these connecting members forms a passage  512  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assemblies  51  and  52 . The cathode side connecting member  51   a  is connected to a cathode side output lead  59   a  and further, the output lead  59   a  is connected to an inverter (not shown). 
         [0080]    A cathode side connecting member  53   a  is attached to a corner of a membrane electrode assembly  53  and an anode side connecting member  54   b  is attached to a corner of a membrane electrode assembly  54 . The pair of cathode side connecting member  53   a  and anode side connecting member  54   b  is connected such that the space between these connecting members forms a passage  521  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assemblies  53  and  54 . Moreover, the positive electrode connecting member  53   a  is connected to the aforementioned cathode side connecting member  51   a  through a passage  511  as shown schematically by the internal connecting condition. 
         [0081]    A cathode side connecting member  55   a  is attached to a corner of a membrane electrode assembly  55  and an anode side connecting member  56   b  is attached to a corner of a membrane electrode assembly  56 . The pair of cathode side connecting member  55   a  and anode side connecting member  56   b  is connected such that the space between these connecting members forms a passage  532  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assemblies  55  and  56 . Moreover, the cathode side connecting member  56  is connected to the aforementioned anode side connecting member  56   b  through a passage  522  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assemblies  52  and  55 . Also, the anode side connecting member  56   b  is connected to an anode side output lead  59   b  and further, the output lead  59   b  is connected to an inverter (not shown). 
         [0082]    Ventilation holes  7  are opened at equal intervals on the first to sixth side surfaces  51  to  56 . However, no ventilation hole is opened on the bottom surfaces  57  and  58 . 
         [0083]    In the fuel cell  1 C 2  of this embodiment, a first current collecting circuit in which the first, second and fifth membrane electrode assemblies  51 ,  52  and  55  are connected in series and a second current collecting circuit in which the side surfaces of the third, fourth and sixth membrane electrode assemblies  53 ,  54  and  56  are connected in series are connected in parallel to the output leads  59   a  and  59   b , respectively, so as to draw the output generated from each current collecting circuit. In this case, the membrane electrode assembly  5  is additionally attached to each of the side surface  57  and bottom surface  58 , and current collecting electrodes and connecting terminals are additionally attached to thereby add the bottom surfaces  57  and  58  to the first and second current collecting circuits. In this case, the fuel cell is made to have a structure in which the side surface  57  and the bottom surface  58  are coated with a cover plate  6  having the ventilation holes  7  and a separate stand is used to prevent these ventilation holes from being closed. A two-parallel and four-series structure is thereby obtained, making it possible to raise the voltage to be drawn, resulting in improved generating efficiency. 
       Sixth Embodiment 
       [0084]    Next, a fuel cell  1 D according to a sixth embodiment will be explained with reference to  FIGS. 9 and 5D . In this embodiment, the explanations of the same parts that have been described in the above embodiments will be omitted to avoid unnecessary duplications. 
         [0085]    The fuel cell  1 D of this embodiment has a triangular prism form. In the current collecting circuit in the fuel cell  1 D, a positive and negative pair of cathode side connecting member  61   a  and anode side connecting member  61   b  is attached to the corner part and center of the side, which are to be on the upper surface, of a membrane electrode assembly  61  having a triangular form, respectively. The pair of connecting members  61   a  and  61   b  is connected such that the space between these connecting members forms a passage  61   c  as shown schematically by the internal connecting condition between the cathode and the anode of the membrane electrode assembly  61 . The cathode side connecting member  61   a  is connected to a cathode side output lead  69   a  and further, the output lead  69   a  is connected to an inverter (not shown). On the other hand, the anode side connecting member  61   b  is connected to a cathode side connecting member  62   a , which is to be on the side surface, of the membrane electrode assembly  62 . 
         [0086]    A positive and negative pair of cathode side connecting member  62   a  and anode side connecting member  62   b  is attached to each center of the opposite sides of the membrane electrode assembly  62 , respectively. The pair of connecting members  62   a  and  62   b  is connected such that the space between these connecting members forms a passage  62   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  62 . Further, the anode side connecting member  62   b  is connected to a cathode side connecting member  63   a  of a membrane electrode assembly  63 . 
         [0087]    A positive and negative pair of cathode side connecting member  63   a  and anode side connecting member  63   b  is attached to the opposite two corner parts of the membrane electrode assembly  63 , respectively. The pair of connecting members  63   a  and  63   b  is connected such that the space between these connecting members forms a passage  63   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  63 . Further, the anode side connecting member  63   b  is connected to a cathode side connecting member  64   a  of a membrane electrode assembly  64 . 
         [0088]    A positive and negative pair of cathode side connecting member  64   a  and anode side connecting member  64   b  is attached to the corner part and center of the side of the membrane electrode assembly  64 , respectively. The pair of connecting members  64   a  and  64   b  is connected such that the space between these connecting members forms a passage  64   c  as shown schematically by the internal connecting condition between the cathode and anode of the membrane electrode assembly  64 . Further, the anode side connecting member  64   b  is connected to an anode side output lead  69   b  and further, the output lead  69   b  is connected to an inverter (not shown). 
         [0089]    According to the present invention, stably generated output reduced in variation can be obtained and it is therefore possible to provide excellent miniature power sources for codeless portable electronic devices such as portable telephones, portable audios, portable game machines and notebook personal computers. 
         [0090]    Although the present invention has been described by way of various embodiments, the invention is not limited to the above embodiments and may be embodied by modifying the structural elements without departing from the spirit of the invention. Also, various inventions can be made by proper combinations of plural structural elements disclosed in the above embodiments. For example, several structural elements may be excluded from all structural elements shown in the embodiments. Moreover, the structural elements form different embodiments may be appropriately combined. 
         [0091]    While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.