JP5217533B2 - Current collector and fuel cell - Google Patents

Description

  The present invention relates to a current collector and a fuel cell in which a metal bipolar body in contact with a membrane-electrode assembly and a carbon bipolar plate having ribs in contact with the metal porous body are integrated. The present invention relates to a current collector and a fuel cell coated with a material having a low expansion coefficient.

  Since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put to practical use as industrial power generators, home power generators, satellite power sources, and spacecraft power sources. In recent years, development of fuel cells as power sources for vehicles such as passenger cars, buses, trucks and the like has been progressing. The fuel cell may be of an alkaline aqueous solution type, phosphoric acid type, molten carbonate type, solid oxide type, direct type methanol, etc., but it has a low reaction temperature and is advantageous for miniaturization. A fuel cell is common.

  In a polymer electrolyte fuel cell, an MEA (Membrane Electrode Assembly) in which a solid polymer electrolyte layer is sandwiched between two gas diffusion electrodes and joined together is used. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as a fuel is supplied to the surface of the gas diffusion electrode, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Move through layers. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  The polymer electrolyte fuel cell has a laminated structure in which a separator for forming a reaction gas supply passage such as hydrogen gas as a fuel gas or an oxidant gas such as oxygen is provided outside the MEA. The separator prevents current gas from passing through the MEAs adjacent to each other in the stacking direction, and collects current to extract the generated current to the outside. As described above, a fuel cell stack is configured by laminating a large number of unit cells including MEAs and separators.

In the conventional fuel cell system, a temperature distribution may occur in the stacking direction of the unit cells, and the electrode temperature may increase. In this case, the amount of moisture dissipated to the outside of the MEA through the electrode is excessively increased, and the humidity inside the MEA is lowered, so that the power generation efficiency in each unit cell is lowered. Therefore, a separator unit current collector sandwiched between fuel cells in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode, and cuts off the gas supplied to the fuel electrode and the gas supplied to the oxygen electrode A separator abutting part that abuts on the separator body, an electrode abutting part that abuts on the fuel electrode or the oxygen electrode, and a rib part that connects the separator abutting part and the electrode abutting part, As the contact portion, a current collector made of a member having an opening ratio larger than those of the separator contact portion and the rib portion has been studied (for example, see Patent Document 1).
By the way, the collector which consists of bipolar plates from the composition which contains resin and electroconductive carbon and is cheap and has high moldability has been examined (for example, refer patent document 2).
JP 2007-35527 A JP 2005-129534 A

However, in the invention described in Patent Document 1, it is necessary to coat the surface with a noble metal so that the metal that is the material of the current collector does not corrode. In addition, the invention described in Patent Document 2 has high corrosion resistance and is processed. Because of their excellent properties, it is preferable to employ both of them as a material constituting the current collector of the fuel cell, taking advantage of both characteristics. However, since the difference between the expansion coefficient of the resin and the expansion coefficient of the metal is large, internal stress due to temperature change is likely to occur. In particular, it is used as a component of a fuel cell having a large temperature difference between when it is driven and stopped, and there is a problem that peeling occurs between a metal component and a resin component due to internal stress. There is a fear.
Then, this invention is providing the collector which has the metal and resin as a constituent material, and the distortion between the members by a temperature change was suppressed. Another object of the present invention is to provide a fuel cell in which the current collector is incorporated.

The above object is achieved by the present invention described below.
(1) An electrolyte layer is disposed on both sides of a membrane-electrode assembly sandwiched between a fuel electrode and an oxygen electrode, and a gas flow path for supplying fuel gas to the fuel electrode and oxidizing gas to the oxygen electrode is formed. And a current collector for taking out a current generated by the reaction between the fuel gas and the oxidizing gas,
A metal porous body in contact with the membrane-electrode assembly;
Made of a thermoplastic resin composition containing a thermoplastic resin and conductive carbon, and carbon bipolar plate having ribs for supporting the metal porous body, has been integrated by thermocompression bonding,
The metal porous body, the current collector, characterized in that it is coated with a conductive coating material which have a linear expansion coefficient smaller than the linear expansion coefficient of the carbon bipolar plates.

  (2) The current collector according to (1), wherein the covering material is diamond-like carbon in which a conductive material having corrosion resistance is mixed.

(3) In a fuel cell in which a plurality of membrane-electrode assemblies in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode are stacked with a current collector sandwiched therebetween,
The current collector is made of a thermoplastic resin composition containing a thermoplastic resin and conductive carbon, and a carbon bipolar plate having ribs that form gas flow paths;
One of the fuel electrode and the oxidation electrode of the membrane-electrode assembly supported by a rib of the carbon bipolar plate and coated with a conductive coating material having a linear expansion coefficient smaller than that of the carbon bipolar plate. A fuel cell formed by thermocompression bonding and a metal porous body in contact with the fuel cell.

According to the first aspect of the present invention, the bipolar plate formed of a thermoplastic resin composition containing a thermoplastic resin and conductive carbon, which is inexpensive and has high moldability, and the metal porous body are thermocompression bonded and integrated. Therefore, it has a high degree of design freedom. In particular, since the porous metal body is coated with a coating material having a smaller linear expansion coefficient than that of the bipolar plate, there is a difference in linear expansion coefficient between the porous metal body coated with the coating material and the bipolar plate. It becomes small and generation | occurrence | production of the internal stress by the temperature change between both is suppressed.

According to the invention described in claim 2, by making the coating material diamond-like carbon, the linear expansion coefficient of the entire porous metal body coated with the coating material can be made closer to the linear expansion coefficient of the bipolar plate. it can.
According to the invention described in claim 3, since internal stress generated between the bipolar plate constituting the current collector and the metal porous body is suppressed, the fuel cell incorporating the current collector is made of metal Separation between the porous body and the bipolar plate is suppressed, and the life is extended.

  FIG. 1 is a diagram showing an embodiment of a fuel cell system of the present invention. In FIG. 1, 20 is a fuel cell stack, which is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts and luggage carts. Here, the vehicle includes a large number of auxiliary devices that consume electricity, such as a lighting device, a radio, and a power window, which are used even when the vehicle is stopped. Since the required output range is extremely wide, it is desirable to use a fuel cell stack 20 as a power source in combination with a secondary battery as a power storage means (not shown). The fuel cell stack 20 is of an alkaline aqueous solution (AFC), phosphoric acid (PAFC), molten carbonate (MCFC), solid oxide (SOFC), direct methanol (DMFC), etc. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell using hydrogen gas as a fuel and oxygen or air as an oxidant, or a PEM (Proton Exchange Membrane) type fuel cell. Here, the PEM type fuel cell generally includes a plurality of fuel cells in which a catalyst layer, a gas diffusion layer, and a current collector are sequentially laminated on both sides of a solid polymer electrolyte layer that moves ions such as protons. And a stack connected in series.

  FIG. 1 shows an apparatus for supplying hydrogen gas as a fuel gas and air as an oxidant to the fuel cell stack 20. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Thereby, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load of the vehicle and supply a necessary current. .

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the fuel chamber of the fuel cell stack 20 through a second fuel supply line 33 as a fuel supply line connected to the first fuel supply line 21. The first fuel supply line 21 is provided with a fuel storage means on-off valve 24, hydrogen pressure sensors 27 and 28 as pressure sensors for detecting the pressure of hydrogen gas, and a first pressure for adjusting the pressure of supplied hydrogen gas. One hydrogen supply pressure regulating valve 25a, a second hydrogen supply pressure regulating valve 25b, and a fuel supply electromagnetic valve 26 are disposed.

  Here, the fuel storage means 73 has a sufficiently large capacity and is capable of always supplying a sufficiently high pressure of hydrogen gas. In the example shown in FIG. 1, a plurality of, for example, three fuel storage means 73 are provided, and the first fuel supply pipe 21 is connected to each fuel storage means 73 at a portion connected thereto. It is branched and is merged on the way to become one. However, the fuel storage means 73 may be singular or plural.

  The hydrogen gas discharged from the fuel chamber of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected to a fuel discharge line 30 for discharging hydrogen gas separated from water. The fuel discharge line 30 is provided with a suction circulation pump 36 as a fuel forced discharge device. Has been. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas led out of the fuel cell stack 20 can be recovered, supplied to the fuel chamber of the fuel cell stack 20, and reused.

  Further, a fuel discharge line 56 is connected to the water recovery drain tank 60, and a hydrogen exhaust valve 62 is disposed in the fuel discharge line 56, and is discharged from the fuel chamber when the fuel cell stack 20 is started up. The hydrogen gas to be discharged can be discharged into the atmosphere. Note that a hydrogen combustor may be provided in the fuel discharge line 56 as necessary. The hydrogen gas discharged by the hydrogen combustor can be combusted to form water, and then discharged into the atmosphere.

  Here, the first hydrogen supply pressure regulating valve 25a and the second hydrogen supply pressure regulating valve 25b are a butterfly valve, a regulator valve, a diaphragm valve, a mass flow controller, a sequence valve, and the like. Any type may be used as long as the pressure of the hydrogen gas flowing out from the outlets of the supply pressure regulating valve 25a and the second hydrogen supply pressure regulating valve 25b can be adjusted to a preset pressure. The pressure adjustment may be performed manually, but is preferably performed by an actuator including an electric motor, a pulse motor, an electromagnet, or the like. The fuel supply electromagnetic valve 26 and the hydrogen exhaust valve 62 are so-called on-off types, and are actuated by actuators such as an electric motor, a pulse motor, and an electromagnet. The fuel storage means original opening / closing valve 24 is operated manually or automatically using an electromagnetic valve. Further, the suction circulation pump 36 may be of any kind as long as it is capable of forcibly discharging hydrogen gas and bringing the fuel chamber into a negative pressure state.

  On the other hand, air as an oxidant is supplied from an air supply fan 75 as an oxidant supply source through an oxidant supply pipe 76 to the oxygen chamber of the fuel cell stack 20. As the oxidant supply source, an air cylinder, an air tank, or the like can be used instead of the air supply fan 75. Further, oxygen can be used as the oxidant instead of air. The air discharged from the oxygen chamber is discharged into the atmosphere through the exhaust manifold 77.

  In order to maintain the membrane-electrode assembly in a wet state from the air electrode side as the oxygen electrode of the fuel cell stack 20, water can be sprayed and supplied to the air supplied to the oxygen chamber. In this case, for example, water supplied from a tank for storing water is sprayed into the air through a water supply nozzle disposed in the middle of the oxidant supply pipe 76 or at the inlet of the oxygen chamber of the fuel cell stack 20. It is desirable. Further, it is desirable to arrange a condenser in the middle of the exhaust manifold 77 to collect and reuse water contained in the air discharged from the oxygen chamber.

Incidentally, the air supplied to the oxygen chamber of the fuel cell stack 20 may be in a normal pressure state where the pressure is about atmospheric pressure, or in a state where the pressure is increased so as to be higher than the atmospheric pressure. However, in the present embodiment, the description will be made assuming that the pressure is applied. That is, the fuel cell system in the present embodiment is not a so-called normal pressure system but a pressurization system.
A refrigerant conduit 71 through which the refrigerant heat-exchanged with the fuel cell stack 20 passes is connected to the fuel cell stack 20. A radiator 72 as a cooling device for cooling the refrigerant is disposed in the refrigerant pipe 71.

The hydrogen gas supplied to the fuel chamber of the fuel cell stack 20 and the air supplied to the oxygen chamber have a function of cooling the fuel cell stack 20. Therefore, the apparatus that supplies the fuel cell stack 20 with the hydrogen gas as the fuel gas and the air as the oxidant functions as one of the cooling systems for cooling the fuel cell stack 20. And since hydrogen gas and air are consumed or discharged | emitted outside, it can be said that the apparatus which supplies hydrogen gas and air is an open cooling system. In this case, hydrogen gas and air circulate in the fuel cell stack 20 in contact with members such as a solid polymer electrolyte layer, a catalyst layer, and a gas diffusion layer constituting the membrane-electrode assembly, and the fuel cell stack 20 Cool down. As described above, when water is supplied into the air supplied to the oxygen chamber, the cooling capacity is improved.
The fuel cell stack 20 includes a voltmeter 78 that measures a terminal voltage of an electric terminal (not shown), and an exhaust air thermometer 74 that detects the temperature of air flowing through the fuel cell stack 20 or air discharged from the fuel cell stack 20. Is attached.

  The secondary battery as the power storage means is a so-called battery (storage battery), which is generally a lead storage battery, a nickel cadmium battery, a nickel metal hydride battery, a lithium ion battery, a sodium sulfur battery, or the like. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has a control system as shown in FIG. In FIG. 2, reference numeral 81 denotes a type of computer that includes an arithmetic means such as a CPU and MPU, an input / output interface, and the like, and is a control device that controls the operation of the fuel cell system. The control device 81 is connected to a memory 82 as storage means such as a magnetic disk or a semiconductor memory. The control device 81 includes the voltmeter 78, the water level sensors 52a and 60a, the hydrogen pressure sensors 27 and 28, the exhaust air thermometer 74, and the hydrogen gas concentration discharged from the fuel chamber of the fuel cell stack 20. A hydrogen concentration sensor 83 to be detected is connected, and outputs of these various sensors are input to the control device 81. Further, in the control device 81, the first hydrogen supply pressure regulating valve 25a and the second hydrogen supply pressure regulating valve 25b, the hydrogen exhaust valve 62, the air supply fan 75, and the fuel cell system have a failure or accident. In this case, an alarm 86 is connected as a device for outputting an alarm, and the operation of these devices is controlled by the control device 81.

  Next, embodiments of the current collector of the present invention will be described. FIG. 3 shows a laminated structure of the current collector and the membrane-electrode assembly of the present invention. 4 is a top view of the stacked configuration shown in FIG. The solid polymer electrolyte layer 11a is sandwiched between the oxygen electrode 11b and the fuel electrode 11c, and the membrane-electrode assembly 11 is formed. The ribs 121 of the carbon bipolar plate 12a having the ribs 121 are thermocompression bonded to the metal porous body 12b, and the carbon bipolar plate 12a and the metal porous body 12b are integrated to form the current collector 12. The metal porous body side of the current collector 12 is in contact with the oxygen electrode side and the fuel electrode side of the membrane-electrode assembly 11. Although not shown in the figure, the current collector 12 is formed with a refrigerant flow path leading to the refrigerant pipe 71 described above, and the space partitioned by the ribs 121 is an air flow path 122 or a hydrogen flow path. 123. In FIG. 3, the air in the air flow path 122 flows in the vertical direction, and the hydrogen in the hydrogen flow path 123 flows in a direction perpendicular to the drawing. In FIG. 4, the air in the air flow path partitioned by the ribs flows in the direction perpendicular to the figure, and the hydrogen in the hydrogen flow path (not shown) flows in the left-right direction in the figure. The air in the air channel and the hydrogen in the hydrogen channel pass through the metal porous body 12b and reach the oxygen electrode 11b and the fuel electrode 11c.

3 and 4, the metal porous body 12b is in contact with the oxygen electrode 11b and the fuel electrode 11c, but the metal porous body 12b may be in contact with only one of the oxygen electrode and the fuel electrode.
A specific example of the metal porous body 12b is configured by coating a metal member such as a foam metal, a metal fiber sintered body, a wire mesh, an expanded metal, or a punching metal with a coating material having corrosion resistance and conductivity. Such a metal member is preferably a metal excellent in corrosion resistance such as stainless steel and Ti alloy. Further, the metal member is coated with a coating material having a linear expansion coefficient smaller than that of the carbon bipolar plate 12a.

The covering material needs to have conductivity so as not to impair the properties as a current collector, and further to have corrosion resistance in order to suppress corrosion due to energization. Examples of such a covering material include diamond-like carbon in which materials having corrosion resistance and conductivity are mixed. Examples of the material mixed in the diamond-like carbon include noble metals and carbon. In the present embodiment, graphite is mixed.
By coating a metal member having a linear expansion coefficient sufficiently smaller than that of the carbon bipolar plate 12a with a coating material having a sufficiently small linear expansion coefficient as compared with the linear expansion coefficient of the carbon bipolar plate 12a, The linear expansion coefficient is close to the linear expansion coefficient of the carbon bipolar plate 12a. Thereby, the internal stress which arises between the carbon bipolar plate 12a and the metal porous body 12b by a temperature change can be reduced.

  As a method for forming a nanocomposite film of graphite and diamond-like carbon, a known method can be used. For example, as described in Japanese Patent Application Laid-Open No. 2004-217975, as step 1, an oxide film is removed from the metal member and an electrically conductive layer is formed. By generating methane gas plasma in the vacuum vessel and applying a negative high voltage pulse to the metal member, the oxide film on the surface of the metal member is removed and an electrically conductive layer is formed. In step 2, a diamond-like carbon film is formed. That is, following the step 1, a switch is made to a hydrocarbon gas having a high molecular weight (for example, toluene), the same treatment as in the step 1 is performed, and a diamond-like carbon film is formed. It is an example of the above film-forming method, Comprising: Another method can also be used.

  The carbon bipolar plate 12a is produced by molding a thermoplastic composition containing a thermoplastic resin and conductive carbon. Specific examples of the thermoplastic resin are polyethylene, polypropylene, ABS resin, acrylic resin, polyethylene terephthalate, polyimide, modified polyphenylene ether, polysulfone, polyether ether ketone, polyvinylidene fluoride, and polytetrafluoroethylene. Specific examples of the conductive carbon are conductive carbon black, activated carbon, graphite, carbon nanotube, fullerene, and a mixture thereof.

  FIG. 5 is a diagram showing a manufacturing flow of the current collector of the present invention. First, a thermoplastic resin and conductive carbon are mixed to produce a thermoplastic resin composition. Next, the thermoplastic resin composition is molded to produce the carbon bipolar plate 12a. On the other hand, in parallel to this, for example, a nanocomposite film of graphite and diamond-like carbon is formed on a metal member such as an expanded metal by the known method described above, thereby forming the metal porous body 12b.

  Thereafter, the carbon bipolar plate 12a and the metal porous body 12b are thermocompression bonded at a temperature equal to or higher than the softening point of the carbon bipolar plate 12a, and the current collector 12 in which the carbon bipolar plate 12a and the metal porous body 12b are integrated is obtained. Produced. Thickness error when the metal porous body 12b is manufactured and thickness error when the carbon bipolar plate 12a is manufactured are compensated at the time of thermocompression bonding. Therefore, the thickness error of the current collector 12 is small. Therefore, since the clearance of the gas seal portion can be accurately defined, the allowable range of the thickness of the seal gasket can be widened, and it is easy to ensure the gas seal performance.

  6a and 6b show the coupling state of the fitting portion between the carbon bipolar plate 12a and the metal porous body 12b. FIG. 6a shows a coupling state of the fitting portion of the carbon bipolar plate 12a and the porous metal body 12b having a curved convex portion such as a wire mesh. FIG. 6B shows a coupling state of the fitting portion of the carbon bipolar plate 12a and the metal porous body 12b having sawtooth-shaped convex portions formed by pressing such as expanded metal and punching metal. The concave portion formed in the rib 121 of the thermoplastic carbon bipolar plate 12a is along the shape of the convex portion of the porous metal body 12b. Therefore, the adhesion between the carbon bipolar plate 12a and the metal porous body 12b is high, and these are handled as one part. Moreover, since the carbon bipolar plate 12a and the metal porous body 12b are configured to reduce the difference in expansion coefficient value by the coating of diamond-like carbon, internal stress generated between the two due to temperature change is suppressed, It has a structure in which peeling due to temperature change does not easily occur. Furthermore, since the contact area of the fitting part of the rib 121 of the carbon bipolar plate 12a and the metal porous body 12b is large, these contact resistances are low.

  Examples of materials having a smaller linear expansion coefficient than the carbon bipolar plate 12a include oxides such as tungsten, tantalum, and titanium, carbides, and nitrides, and ceramic materials. A conductive material (for example, carbon) can be imparted to these materials and used as a coating material in place of the nanocomposite film of graphite and diamond-like carbon.

  The current collector of the present invention includes a hydrogen fuel solid polymer fuel cell, a direct methanol fuel cell, an alkaline aqueous fuel cell, a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, etc. Built into the fuel cell. The fuel cell in which the current collector of the present invention is incorporated is used as an in-vehicle power source, a household power source, and other power sources.

It is a figure which shows a fuel cell system. It is a figure which shows the control system of a fuel cell system. It is a figure which shows the laminated structure of a collector and a membrane-electrode assembly. It is a top view of the laminated structure which consists of a collector and a membrane-electrode assembly. It is a figure which shows the preparation flow of an electrical power collector. It is a figure which shows the combined state of a carbon bipolar plate and a metal porous body.

Explanation of symbols

11a ... Solid polymer electrolyte layer, 11b ... Air electrode, 11c ... Fuel electrode, 12a ... Carbon bipolar plate, 12b ... Metal porous body, 121 ... Rib

Claims (3)

The electrolyte layer is disposed on both sides of the membrane-electrode assembly sandwiched between the fuel electrode and the oxygen electrode, and forms a gas flow path for supplying fuel gas to the fuel electrode and oxidizing gas to the oxygen electrode, A current collector for extracting an electric current generated by a reaction between the fuel gas and the oxidizing gas,
A metal porous body in contact with the membrane-electrode assembly;
Made of a thermoplastic resin composition containing a thermoplastic resin and conductive carbon, and carbon bipolar plate having ribs for supporting the metal porous body, has been integrated by thermocompression bonding,
The metal porous body, the current collector, characterized in that it is coated with a conductive coating material which have a linear expansion coefficient smaller than the linear expansion coefficient of the carbon bipolar plates. The current collector according to claim 1, wherein the covering material is diamond-like carbon in which a conductive material having corrosion resistance is mixed. In a fuel cell in which a plurality of membrane-electrode assemblies in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode are stacked with a current collector interposed therebetween,
The current collector is made of a thermoplastic resin composition containing a thermoplastic resin and conductive carbon, and a carbon bipolar plate having ribs that form gas flow paths;
One of the fuel electrode and the oxidation electrode of the membrane-electrode assembly supported by a rib of the carbon bipolar plate and coated with a conductive coating material having a linear expansion coefficient smaller than that of the carbon bipolar plate. A fuel cell formed by thermocompression bonding and a metal porous body in contact with the fuel cell.

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