JP2010097928A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct methanol type fuel cell, which allows stabilization of output and an extended life by promoting heat release. <P>SOLUTION: The fuel cell is provided with: a membrane electrode assembly 2 having an electrolyte membrane 17, a plurality of fuel electrodes 13 which are arranged at intervals on one surface of the electrolyte membrane, and a plurality of air electrodes 16 which are arranged at intervals on the other surface of the electrolyte membrane so as to face each of the fuel electrodes; and a heat conductor 40 which is arranged on at least either of the surface of the plurality of air electrodes 16 of the membrane electrode assembly 2 on the opposite side of the fuel cell to the electrode membrane side 17 and the surface of the plurality of fuel electrodes 13 on the opposite side of the fuel cell to the electrode membrane side 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technology of a fuel cell using a liquid fuel.

  In recent years, attempts have been made to use a fuel cell as a power source for portable electronic devices such as notebook computers and mobile phones so that they can be used for a long time without being charged. A fuel cell is characterized in that it can generate electric power simply by supplying fuel and air, and can generate electric power continuously for a long time if fuel is replenished. For this reason, if the fuel cell can be reduced in size, it can be said that the system is extremely advantageous as a power source for portable electronic devices.

  In a fuel cell that operates at a high temperature, a technique is disclosed in which the outer surface of a heat insulator that covers the fuel cell is covered with a heat transfer body in order to prevent the casing of a device that houses the fuel cell from becoming high temperature ( For example, see Patent Document 1).

  On the other hand, a thermally conductive molded article having high thermal conductivity suitable for uses such as a fuel cell separator has been disclosed (for example, see Patent Document 2). In particular, according to this thermally conductive molded body, it is disclosed that it is useful in a heat dissipation design of a housing when it is used as a housing or member for an electric / electronic device due to anisotropy of thermal conductivity. Yes.

  In a fuel cell formed by laminating a plurality of unit cells to form a laminate, a gas separation plate and a unit cell whose thermal conductivity in the planar direction is larger than the thermal conductivity in the laminating direction for the purpose of uniform temperature distribution Are alternately stacked, and a cooling plate is disposed on the upper and lower ends (for example, see Patent Document 3).

JP 2006-202611 A JP 2006-49878 A JP-A-9-289026

  As a fuel cell, for example, a direct methanol fuel cell (DMFC) using methanol as a fuel can be miniaturized and can be easily handled as a power source for portable electronic devices. Promising.

  As the liquid fuel supply method in the DMFC, there are known an active method such as a gas supply type and a liquid supply type, and a passive method such as an internal vaporization type in which the liquid fuel in the fuel container is vaporized inside the cell and supplied to the fuel electrode. It has been. Among these, a passive system such as an internal vaporization type is advantageous for downsizing of the DMFC. The passive DMFC includes a membrane electrode assembly (MEA) having a fuel electrode, an electrolyte membrane, and an air electrode, for example.

  An unintended temperature variation may occur in the surface of such a membrane electrode assembly. In particular, heat dissipation is relatively promoted in the peripheral part of the membrane electrode assembly, whereas heat is difficult to escape in the central part, and a large temperature difference tends to occur between the peripheral part and the central part. In addition, a saturated water vapor pressure difference also occurs with such a temperature difference, and the transfer of substances necessary for the power generation reaction in the membrane electrode assembly is hindered. As a result, there is a possibility that the output is reduced or unstable.

  An object of the present invention is to provide a fuel cell capable of stably obtaining a high output.

A fuel cell according to an aspect of the present invention includes:
An electrolyte membrane, a plurality of fuel electrodes arranged on one surface of the electrolyte membrane with a space, and a space on the other surface of the electrolyte membrane so as to face each of the fuel electrodes. A membrane electrode assembly having a plurality of air electrodes;
A heat conductor disposed on at least one of a surface side of the plurality of air electrodes opposite to the electrolyte membrane side of the membrane electrode assembly and a surface side of the plurality of fuel electrodes opposite to the electrolyte membrane side; ,
It is characterized by comprising.

  According to the present invention, a fuel cell capable of stably obtaining a high output can be provided.

FIG. 1 is a cross-sectional view schematically showing the structure of a fuel cell according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing a cross section of a part of the structure of the membrane electrode assembly in the fuel cell shown in FIG. FIG. 3 is a plan view of the membrane electrode assembly shown in FIG. FIG. 4 is a cross-sectional view schematically showing structures of a membrane electrode assembly and a heat conductor applicable to the fuel cell shown in FIG. FIG. 5 is a cross-sectional view schematically showing another structure of the membrane electrode assembly and the heat conductor applicable to the fuel cell shown in FIG. 6 is a cross-sectional view schematically showing another structure of the membrane electrode assembly and the heat conductor applicable to the fuel cell shown in FIG. FIG. 7 is a cross-sectional view schematically showing another structure of the membrane electrode assembly and the heat conductor applicable to the fuel cell shown in FIG. FIG. 8 is a diagram for explaining an example of the in-plane temperature distribution in the membrane electrode assembly. FIG. 9 is a diagram showing the results of measuring the in-plane temperature distribution of the membrane electrode assembly relative to the thermal conductivity ratio of the thermal conductor. FIG. 10 is a diagram showing the results of measuring the in-plane temperature distribution of the membrane electrode assembly relative to the thickness of the heat conductor. FIG. 11 is a diagram schematically illustrating the configuration of the fuel cell according to the fifth embodiment. FIG. 12 is a diagram showing measurement results (average output and average temperature) of performance evaluation in Examples 1 to 5 and Comparative Example 1. FIG. 13 is a diagram for explaining variations of the heat conductors combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 14 is a view for explaining variations of the heat conductors combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 15 is a view for explaining a variation of the heat conductor combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 16 is a diagram for explaining a variation of the heat conductor combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 17 is a diagram for explaining a variation of the heat conductor combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 18 is a diagram for explaining a variation of the heat conductor combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 19 is a diagram for explaining a variation of the heat conductor combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 20 is a diagram for explaining variations of the heat conductors combined with the membrane electrode assembly in the fuel cell of the present embodiment. FIG. 21 is a diagram for explaining the relationship between the shape of the membrane electrode assembly and the thermal conductivity of the thermal conductor. FIG. 22 is a diagram showing measurement results (power density and temperature difference) of performance evaluation in Examples 6 to 8 and Comparative Example 2.

  A technique related to a fuel cell according to an embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing the structure of a fuel cell 1 according to this embodiment.

  The fuel cell 1 mainly includes a membrane electrode assembly (MEA) 2 that constitutes an electromotive unit, and a fuel supply mechanism 3 that supplies fuel to the membrane electrode assembly 2.

  That is, in the fuel cell 1, the membrane electrode assembly 2 includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, and a cathode (cathode catalyst layer 14 and cathode gas diffusion layer 15). (Air electrode / oxidant electrode) 16 and a proton (hydrogen ion) conductive electrolyte membrane 17 sandwiched between the anode catalyst layer 11 and the cathode catalyst layer 14.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 include platinum such as platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), osmium (Os), and palladium (Pd). Examples thereof include a group element simple substance and an alloy containing a platinum group element. For the anode catalyst layer 11, it is preferable to use Pt—Ru, Pt—Mo, or the like that has strong resistance to methanol, carbon monoxide, or the like. It is preferable to use Pt, Pt—Ni or the like for the cathode catalyst layer 14. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive carrier such as a carbon material or an unsupported catalyst.

  Examples of the proton conductive material constituting the electrolyte membrane 17 include fluorine-based resins (Nafion (trade name, manufactured by DuPont) and Flemion (trade name, manufactured by Asahi Glass Co., Ltd.) such as a perfluorosulfonic acid polymer having a sulfonic acid group. Etc.), organic materials such as hydrocarbon resins having sulfonic acid groups, or inorganic materials such as tungstic acid and phosphotungstic acid. However, the proton conductive electrolyte membrane 17 is not limited to these.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and has a current collecting function of the anode catalyst layer 11. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 serves to uniformly supply the oxidant to the cathode catalyst layer 14 and has a current collecting function of the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are made of a porous substrate having conductivity, such as carbon paper.

  Such a membrane electrode assembly 2 is sandwiched between current collectors 18. That is, the current collector 18 has an anode current collector 18A disposed on the anode 13 side of the membrane electrode assembly 2 and a cathode current collector 18C disposed on the cathode 16 side of the membrane electrode assembly 2. ing. The anode current collector 18A overlaps the anode gas diffusion layer 12. The cathode current collector 18C overlaps the cathode gas diffusion layer 15. The anode current collector 18A and the cathode current collector 18C have an opening (not shown).

  As the anode current collector 18A and the cathode current collector 18C, for example, a porous layer (for example, a mesh) or a foil body made of a metal material such as gold (Au) or nickel (Ni), or stainless steel (SUS) or the like is used. A composite material in which a conductive metal material is coated with a good conductive metal such as gold, and a carbonaceous material such as graphite (graphite) can be used.

  The membrane electrode assembly 2 is sealed by a seal member 19 such as a rubber O-ring disposed on the anode side and the cathode side of the electrolyte membrane 17. That is, the seal member 19 is disposed between the electrolyte membrane 17 and the anode current collector 18A and between the electrolyte membrane 17 and the cathode current collector 18C. Fuel leakage and oxidant leakage are prevented. In the membrane electrode assembly 2, one or more electrolyte membranes 17 are not in contact with the anode catalyst layer 11 and the cathode catalyst layer 14 and at positions corresponding to the inside surrounded by the seal member 19. Individual gas discharge holes (not shown) may be provided.

  On the cathode 16 side of the membrane electrode assembly 2, a plate-like body 20 made of a breathable insulating material is disposed between the current collector 18 and the cover plate 21. This plate-like body 20 mainly functions as a moisture retaining layer. That is, the plate-like body 20 is disposed on the cathode current collector 18C, impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress water evaporation, and to the cathode catalyst layer 14 It adjusts the amount of air taken in and promotes uniform air diffusion. The plate-like body 20 is constituted by, for example, a member having a porous structure, and specific constituent materials include polyethylene and polypropylene porous bodies.

  The membrane electrode assembly 2 described above is disposed between the fuel supply mechanism 3 and the cover plate 21. The cover plate 21 is disposed on the plate-like body 20. The cover plate 21 has a substantially rectangular appearance, and is made of, for example, stainless steel (SUS). The cover plate 21 has a plurality of openings (air introduction holes) 21A for taking in air as an oxidant.

  Between the cathode current collector 18C and the plate-like body 20, a heat conductor 40 described later is disposed. Further, as shown in FIG. 1, it is desirable that an insulator 50 be disposed between the heat conductor 40 and the cathode current collector 18C.

  The fuel supply mechanism 3 is configured to supply fuel to the anode 13 of the membrane electrode assembly 2, but is not particularly limited to a specific configuration. Hereinafter, an example of the fuel supply mechanism 3 will be described.

  The fuel supply mechanism 3 includes a container 30 formed in a box shape, for example. The fuel supply mechanism 3 is connected to a fuel storage unit 4 that stores liquid fuel via a flow path 5. The container 30 has a fuel inlet 30A, and the fuel inlet 30A and the flow path 5 are connected. The container 30 is constituted by a resin container, for example. As a material for forming the container 30, a material having resistance to liquid fuel is selected.

  The fuel supply mechanism 3 includes a fuel supply unit 31 that supplies fuel while dispersing and diffusing fuel in the surface direction of the anode 13 of the membrane electrode assembly 2. Here, in particular, the configuration in which the fuel supply unit 31 includes the fuel distribution plate 31A will be described, but the fuel supply unit 31 may have other configurations.

  That is, the fuel distribution plate 31A has one fuel injection port 32 and a plurality of fuel discharge ports 33, and the fuel injection port 32 and the fuel discharge port 33 are connected to each other through a fuel passage such as a narrow tube 34. It is a connected configuration. The fuel passage may be constituted by a fuel flow groove or the like instead of the narrow tube 34 formed in the fuel distribution plate 31A. In this case, the fuel distribution plate 31A can also be configured by covering the flow path plate having the fuel flow grooves with a diffusion plate having a plurality of fuel discharge ports.

  A fuel injection port 32 is provided at one end (starting end) of the thin tube 34. The narrow tube 34 is branched into a plurality of parts along the way, and a fuel discharge port 33 is provided at each terminal portion of the branched narrow tube 34. The fuel inlet 32 communicates with the fuel inlet 30 </ b> A of the container 30. As a result, the fuel inlet 32 of the fuel distribution plate 31 </ b> A is connected to the fuel storage portion 4 via the flow path 5. There are a plurality of, for example, 128 fuel discharge ports 33, which discharge liquid fuel or vaporized components thereof.

  The liquid fuel injected from the fuel injection port 32 is guided to the plurality of fuel discharge ports 33 via the thin tubes 34 branched into a plurality. By using such a fuel distribution plate 31A, the liquid fuel injected from the fuel injection port 32 can be evenly distributed to the plurality of fuel discharge ports 33 regardless of the direction or position. Therefore, the uniformity of the power generation reaction in the surface of the membrane electrode assembly 2 can be further enhanced.

  Further, by connecting the fuel injection port 32 and the plurality of fuel discharge ports 33 with the thin tube 34, it is possible to design such that more fuel is supplied to a specific portion of the fuel cell. This contributes to improvement in the uniformity of the power generation degree of the membrane electrode assembly 2 and the like.

  Such a fuel distribution plate 31A is formed of a material that does not allow vaporized components of liquid fuel or liquid fuel to permeate. Specifically, for example, polyethylene terephthalate (PET) resin, polyethylene naphthalate (PEN) resin, polyimide resin Etc. are formed. In addition, the fuel distribution plate 31A may be configured by, for example, a gas-liquid separation membrane that separates the vaporized component of the liquid fuel from the liquid fuel and transmits the vaporized component to the membrane electrode assembly 2 side. Examples of the gas-liquid separation membrane include silicone rubber, low density polyethylene (LDPE) thin film, polyvinyl chloride (PVC) thin film, polyethylene terephthalate (PET) thin film, fluororesin (for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene). -Perfluoroalkyl vinyl ether copolymer (PFA) etc.) A microporous film etc. are applicable.

  The membrane electrode assembly 2 is arranged so that the anode 13 faces the fuel discharge port 33 of the fuel distribution plate 31A as described above. The cover plate 21 is fixed to the container 30 by a method such as caulking, screwing, or rivet joint while the membrane electrode assembly 2 is held between the cover plate 21 and the fuel supply mechanism 3. Thereby, the power generation unit of the fuel cell (DMFC) 1 is configured.

  The fuel supply unit 31 is preferably configured to form a space functioning as a fuel diffusion chamber 31B between the fuel distribution plate 31A and the membrane electrode assembly 2. The fuel diffusion chamber 31 </ b> B has a function of promoting vaporization and promoting diffusion in the surface direction even when liquid fuel is discharged from the fuel discharge port 33.

  A support member that supports the membrane electrode assembly 2 from the anode 13 side may be disposed between the membrane electrode assembly 2 and the fuel supply unit 31.

  Further, at least one porous body may be disposed between the membrane electrode assembly 2 and the fuel supply unit 31.

  Liquid fuel corresponding to the membrane electrode assembly 2 is stored in the fuel storage portion 4. Examples of the liquid fuel include methanol fuels such as aqueous methanol solutions of various concentrations and pure methanol. The liquid fuel is not necessarily limited to methanol fuel. The liquid fuel may be, for example, an ethanol fuel such as an ethanol aqueous solution or pure ethanol, a propanol fuel such as a propanol aqueous solution or pure propanol, a glycol fuel such as a glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel. In any case, liquid fuel corresponding to the membrane electrode assembly 2 is stored in the fuel storage portion 4.

  The liquid fuel accommodated in the fuel accommodating part 4 can be dropped and fed by the fuel supply part 31 via the flow path 5 using gravity. Alternatively, the flow path 5 may be filled with a porous body or the like, and the liquid fuel stored in the fuel storage unit 4 may be fed to the fuel supply unit 31 by capillary action.

  The flow path 5 is configured by a pipe or the like, but is not limited to a pipe independent of the fuel supply unit 31 and the fuel storage unit 4. For example, when the fuel supply unit 31 and the fuel storage unit 4 are stacked and integrated, the channel 5 may be a liquid fuel fuel channel that connects them. That is, the fuel supply unit 31 only needs to communicate with the fuel storage unit 4 via various types of fuel flow paths and the like.

  Further, a pump 6 may be interposed in the flow path 5. The pump 6 is not a circulation pump that circulates fuel, but is a fuel supply pump that sends liquid fuel from the fuel storage unit 4 to the fuel supply unit 31 to the last. The fuel supplied from the fuel supply unit 31 to the membrane electrode assembly 2 is used for a power generation reaction, and is not circulated thereafter and returned to the fuel storage unit 4.

  The fuel cell 1 of this embodiment is different from the conventional active method because it does not circulate the fuel, and does not impair the downsizing of the device. Further, the pump 6 is used to supply the liquid fuel, which is different from a pure passive system such as a conventional internal vaporization type. The fuel cell 1 shown in FIG. 1 employs a system called a semi-passive type, for example.

  The type of the pump 6 is not particularly limited, but a rotary vane pump, an electroosmotic pump, and a diaphragm pump can be used from the viewpoint that a small amount of liquid fuel can be fed with good controllability and can be reduced in size and weight. It is preferable to use a squeezing pump or the like.

  The rotary vane pump feeds liquid by rotating wings with a motor. The electroosmotic flow pump uses a sintered porous body such as silica that causes an electroosmotic flow phenomenon. A diaphragm pump drives a diaphragm with an electromagnet or piezoelectric ceramics to send liquid. The squeezing pump presses a part of a flexible fuel flow path and squeezes the fuel. Among these, it is more preferable to use an electroosmotic pump or a diaphragm pump having piezoelectric ceramics from the viewpoint of driving power, size, and the like.

  A reservoir may be provided between the pump 6 and the fuel supply unit 31.

  Further, in order to improve the stability and reliability of the fuel cell 1, a fuel cutoff valve may be arranged in series with the pump 6. As the fuel cutoff valve, an electrically driven valve capable of controlling an opening / closing operation with an electric signal using an electromagnet, a motor, a shape memory alloy, piezoelectric ceramics, bimetal, or the like as an actuator is applied. The fuel cutoff valve is preferably a latch type valve having a state maintaining function.

  Further, a balance valve that balances the pressure in the fuel storage unit 4 with the outside air may be attached to the fuel storage unit 4 and the flow path 5. When fuel is supplied from the fuel storage unit 4 to the membrane electrode assembly 2 by the fuel supply mechanism 3, it is possible to adopt a configuration in which only the fuel cutoff valve is arranged instead of the pump 6. The fuel cutoff valve at this time is provided for controlling the supply of liquid fuel through the flow path 5.

  In the fuel cell 1 of this embodiment, liquid fuel is intermittently sent from the fuel storage unit 4 to the fuel supply unit 31 using the pump 6. The liquid fuel fed by the pump 6 is uniformly supplied to the entire surface of the anode 13 of the membrane electrode assembly 2 through the fuel supply unit 31.

  That is, the fuel is uniformly supplied to the planar direction of each anode 13 of the plurality of single cells C, thereby generating a power generation reaction. The operation of the fuel supply (liquid feeding) pump 6 is preferably controlled based on the output of the fuel cell 1, temperature information, operation information of an electronic device that is a power supply destination, and the like.

  In the fuel cell 1 described above, the liquid fuel introduced into the fuel supply unit 31 from the fuel storage unit 4 via the flow path 5 remains as a liquid fuel or a mixture of vaporized components obtained by vaporizing the liquid fuel and the liquid fuel. In this state, the fuel is supplied from the fuel discharge port 33 of the fuel supply unit 31 to the anode 13 of the membrane electrode assembly 2 through the anode current collector 18A of the current collector 18.

  The fuel supplied to the anode 13 diffuses through the anode gas diffusion layer 12 and is supplied to the anode catalyst layer 11. When methanol fuel is used as the liquid fuel, an internal reforming reaction of methanol shown in the following formula (1) occurs in the anode catalyst layer 11. When pure methanol is used as the methanol fuel, the water generated in the cathode catalyst layer 14 or the water in the electrolyte membrane 17 is reacted with methanol to cause the internal reforming reaction of the formula (1), or The internal reforming reaction is caused by another reaction mechanism that does not require water.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
The electrons (e ⁻ ) generated by this reaction are guided to the outside via the current collector 18, and after operating a portable electronic device or the like as so-called electricity, the electrons (e ⁻ ) are passed to the cathode 16 via the current collector 18. Led. Proton (H ⁺ ) generated by the internal reforming reaction of the formula (1) is guided to the cathode 16 through the electrolyte membrane 17. Air is supplied to the cathode 16 as an oxidant. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 react with oxygen in the air in the cathode catalyst layer 14 according to the following formula (2), and water is generated with this reaction.

6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)
In the power generation reaction of the fuel cell 1 described above, in order to increase the power to be generated, the catalytic reaction is smoothly performed, and the fuel is uniformly supplied to the entire electrode of the membrane electrode assembly 2 so that the entire electrode becomes more effective. It is important to contribute to power generation.

  By the way, in this embodiment, as shown in FIGS. 2 and 3, the membrane electrode assembly 2 includes a plurality of anodes 13 arranged at intervals on one surface 17 </ b> A of a single electrolyte membrane 17. And a plurality of cathodes 16 arranged at intervals so as to face each of the anodes 13 on the other surface 17C of the electrolyte membrane 17. Here, a case where there are four anodes 13 and four cathodes 16 is shown.

  Each combination of the anode 13 and the cathode 16 sandwiches the electrolyte membrane 17 to form a single cell C. The plurality of single cells C have substantially the same size and substantially the same shape. That is, each of the anodes 13 constituting the single cell C is also substantially the same size and substantially the same shape, and each of the cathodes 16 constituting the single cell C is also substantially the same size and substantially the same. Shape. Here, the single cells C are arranged side by side in the direction perpendicular to the longitudinal direction on the same plane. The structure of the membrane electrode assembly 2 is not limited to the example shown here, and may be another structure.

  Each single cell C shown here is formed in a substantially rectangular shape having a long side parallel to the first direction X and a short side parallel to the second direction Y orthogonal to the first direction X. That is, the longitudinal direction of the single cell C corresponds to the first direction X. Further, the anode 13 and the cathode 16 constituting each single cell C are also formed in a substantially rectangular shape having a long side parallel to the first direction X and a short side parallel to the second direction Y.

  The arrangement direction of the plurality of unit cells C is parallel to the longitudinal direction of each unit cell C, that is, the second direction Y orthogonal to the first direction X. That is, the arrangement direction of the plurality of anodes 13 is the second direction Y, and the arrangement direction of the plurality of cathodes 16 is the second direction Y.

  About the external shape of the membrane electrode assembly 2, it may be formed in the substantially rectangular shape, and may be formed in the substantially square shape.

  In the membrane electrode assembly 2 having a plurality of single cells C as shown in FIGS. 2 and 3, each single cell C is electrically connected in series by a current collector (not shown). That is, in order to correspond to the membrane electrode assembly 2 shown in FIG. 2 and the like, each current collector has four anode current collectors and cathode current collectors. Each of the anode current collectors is stacked on the anode gas diffusion layer 12 in each single cell C. Each of the cathode current collectors is stacked on the cathode gas diffusion layer 15 in each single cell C.

  Next, the heat conductor 40 will be described in more detail.

  FIG. 4 is a cross-sectional view schematically showing structures of the membrane electrode assembly 2 and the heat conductor 40. In FIG. 4, only the main part necessary for the description is schematically shown, and the insulator 50 between the heat conductor 40 and the cathode current collector 18C is omitted.

  More specifically, the heat conductor 40 is formed to be equivalent to the size of the membrane electrode assembly 2 (for example, corresponding to the outer dimensions of the electrolyte membrane 17), and is disposed so as to face the cathode 16 of each single cell C. Has been. That is, the single heat conductor 40 is located directly above the space SP between the adjacent cathodes 16 while facing the respective cathodes 16. In other words, the heat conductor 40 is disposed across a plurality of adjacent cathodes 16.

  A cathode current collector 18C is disposed between the heat conductor 40 and the membrane electrode assembly 2, more specifically, between the heat conductor 40 and the cathode gas diffusion layer 15 of the cathode 16. ing. In other words, the heat conductor 40 shown here is disposed between the cathode current collector 18C and the cover plate 21 (not shown).

  Such a heat conductor 40 and cathode current collector 18C are arranged on the cathode side with respect to the membrane electrode assembly 2, but since these have air permeability, each cathode 16 necessary for the power generation reaction. It does not hinder the introduction of air or oxygen into the gas, and the discharge of gas such as water vapor from each cathode 16 to the outside.

  The heat conductor 40 having such a configuration functions as a bypass that enables heat transfer. For this reason, the heat conductor 40 can promote the movement of heat from the high temperature portion to the low temperature portion on the cathode 16 side of the membrane electrode assembly 2. That is, the heat of the high temperature part of the cathode 16 constituting one single cell C can be transferred to the low temperature part of the cathode 16 in the same single cell C via the heat conductor 40 and the other adjacent ones. It becomes possible to move to the relatively low temperature cathode 16 constituting the single cell C. As a matter of course, the heat of the space part SP having a relatively high temperature can be transferred to the low temperature part via the heat conductor 40.

  Therefore, the temperature difference in the surface of the membrane electrode assembly 2 can be reduced, and the temperature distribution can be made uniform. Moreover, even if the space between the single cells C arranged in parallel at intervals (more specifically, between the adjacent cathodes 16) is electrically insulated by air or the like and thermally insulated, The temperature difference in the surface of the membrane electrode assembly 2 can be reduced by the heat transfer promoting action by the heat conductor 40 disposed across the plurality of single cells C.

  In the example shown in FIGS. 1 and 4, the case where the thermal conductor 40 is disposed on the cathode 16 side of the membrane electrode assembly 2 has been described. However, the thermal conductor 40 is not the anode 13 of the membrane electrode assembly 2. It may be arranged on the side.

  FIG. 5 is a cross-sectional view schematically showing another structure of the membrane electrode assembly and the heat conductor. In FIG. 5, only the main part necessary for the description is schematically shown, and the insulator 50 between the heat conductor 40 and the anode current collector 18A is omitted.

  More specifically, the heat conductor 40 is formed to be equivalent to the size of the membrane electrode assembly 2 (for example, corresponding to the outer dimensions of the electrolyte membrane 17), and is disposed so as to face the anode 13 of each single cell C. Has been. That is, the single heat conductor 40 is located directly above the space SP between the adjacent anodes 13 while facing the respective anodes 13. In other words, the heat conductor 40 is disposed across a plurality of adjacent anodes 13.

  An anode current collector 18A is disposed between the heat conductor 40 and the membrane electrode assembly 2, more specifically, between the heat conductor 40 and the anode gas diffusion layer 12 of the anode 13. ing. In other words, the heat conductor 40 shown here is disposed between the anode current collector 18A and the fuel supply mechanism 3 (not shown). Such a heat conductor 40 and anode current collector 18A are arranged on the anode side with respect to the membrane electrode assembly 2, but since these have air permeability, each anode 13 necessary for the power generation reaction is provided. There is no hindrance to the introduction of fuel gas.

  The heat conductor 40 having such a configuration functions as a bypass that enables heat transfer. For this reason, the heat conductor 40 can promote the movement of heat from the high temperature portion to the low temperature portion on the anode 13 side of the membrane electrode assembly 2. That is, the heat of the high temperature portion of the anode 13 constituting one single cell C can be transferred to the low temperature portion of the anode 13 in the same single cell C via the heat conductor 40 and the other adjacent ones. It becomes possible to move to the relatively low temperature anode 13 constituting the single cell C. As a matter of course, the heat of the space part SP having a relatively high temperature can be transferred to the low temperature part via the heat conductor 40.

  Therefore, the temperature difference in the surface of the membrane electrode assembly 2 can be reduced, and the temperature distribution can be made uniform. Further, even if the space between the single cells C arranged in parallel at intervals (more specifically, between the adjacent anodes 13) is electrically insulated by air or the like and thermally insulated, The temperature difference in the surface of the membrane electrode assembly 2 can be reduced by the heat transfer promoting action by the heat conductor 40 disposed across the plurality of single cells C.

  In the example described above, the thermal conductor 40 is disposed only on the cathode 16 side of the membrane electrode assembly 2 and the thermal conductor 40 is disposed only on the anode 13 side of the membrane electrode assembly 2. However, the heat conductor 40 may be disposed on both the anode 13 side and the cathode 16 side of the membrane electrode assembly 2.

  FIG. 6 is a cross-sectional view schematically showing another structure of the membrane electrode assembly and the heat conductor. In FIG. 6, only the main part necessary for the explanation is schematically shown, and the insulator 50 between the heat conductor 40 and the anode current collector 18A, and the heat conductor 40 and the cathode current collector are shown. The insulator 50 between the electric body 18C is omitted.

  More specifically, the heat conductor 40 is formed to be equivalent to the size of the membrane electrode assembly 2 (for example, corresponding to the outer dimensions of the electrolyte membrane 17), and faces the anode 13 and the cathode 16 of each single cell C, respectively. Are arranged to be. That is, the single heat conductor 40 is located directly above the space SP between the adjacent anodes 13 while facing the respective anodes 13. In addition, the single heat conductor 40 is located directly above the space SP between the cathodes 16 facing each cathode 16 and adjacent to each other.

  In such a configuration, the effects of both the example shown in FIG. 4 and the example shown in FIG. 5 can be obtained simultaneously.

  Thus, the heat conductor 40 is at least one of the surface of the membrane electrode assembly 2 opposite to the electrolyte membrane 17 side of the plurality of cathodes 16 and the surface of the plurality of anodes 13 opposite to the electrolyte membrane 17 side. It only has to be arranged in.

  The heat conductor 40 does not necessarily have to face all the anodes 13 or the cathodes 16. For example, as shown in FIG. 7, the heat conductor 40 may be formed smaller than the size of the membrane electrode assembly 2, and a part of the plurality of anodes 13 and the plurality of cathodes 16 may be exposed. That is, a part of the anode 13 and the cathode 16 constituting the single cell C at both ends is exposed from the heat conductor 40 without facing the heat conductor 40.

  Even in such a case, the power generation unit including all the single cells C formed in the membrane electrode assembly 2 (that is, the region occupied by all the single cells C surrounded by a seal member (not shown) and adjacent single cells C). If an area of 80% or more of the outer dimension D of the region including the space between the cells C is covered by the heat conductor 40, sufficient heat transfer through the heat conductor 40 becomes possible, and the membrane electrode It is possible to make the temperature distribution in the plane of the joined body 2 uniform.

  In the example shown in FIG. 7, the outer dimensions of both the heat conductor 40 facing the anode 13 and the heat conductor 40 facing the cathode 16 have an area of 80% of the outer dimension D of the power generation section. . It is to be noted that the heat conductor 40 faces only the cathode 16 as in the example shown in FIG. 4 or the heat conductor 40 faces only the anode 13 as in the example shown in FIG. However, if the outer dimensions of the respective heat conductors 40 have an area of 80% or more of the outer dimension D of the power generation section in the membrane electrode assembly 2, the effect of uniforming the temperature distribution can be obtained.

  In the surface of the membrane electrode assembly 2 having a plurality of single cells C as in the above-described example, as shown in FIG. 8, the central portion 2C is relatively difficult to dissipate heat and easily becomes high temperature. 2P tends to be low in temperature compared to the central portion. In this case, by disposing the heat conductor 40, heat transfer from the central part 2C of the membrane electrode assembly 2 to the peripheral part 2P is promoted, and the central part 2C and the peripheral part 2P of the membrane electrode assembly 2 are promoted. It becomes possible to reduce the temperature difference. That is, the temperature distribution in the surface of the membrane electrode assembly 2 can be made uniform.

  For this reason, the saturated water vapor pressure difference due to the temperature difference is also reduced, and in the plane of the membrane electrode assembly 2, it is possible to promote the exchange of substances necessary for the power generation reaction in both the central portion 2C and the peripheral portion 2P. It becomes possible. For example, the peripheral part 2P is moderately heated by heat from the high temperature part without becoming extremely low temperature, thereby suppressing the aggregation of water generated by the power generation reaction and eliminating the shortage of air intake, The vaporization of the liquid fuel on the anode side is promoted, and it is possible to stably maintain high power generation efficiency. On the other hand, the central part 2C does not become extremely high temperature, and by appropriately dissipating heat, it is possible to suppress the evaporation of water necessary for the power generation reaction and stably maintain high power generation efficiency. It becomes.

  As a result, a high output can be stably obtained.

  The above-described heat conductor 40 is desirably formed of a material that does not dissolve, corrode, oxidize, or the like due to liquid fuel, water, oxygen, or the like and that has high thermal conductivity. Moreover, the heat conductor 40 needs to ensure air permeability, and has a porous property or a through hole. Among these, as the porous heat conductor 40, a carbon fiber material is suitable. For example, carbon paper (TGP-H series) manufactured by Toray Industries, Inc. or carbon paper (GDL series) manufactured by SGL Carbon Japan Co., Ltd. Etc. are applicable. Moreover, as the heat conductor 40 having a through hole, a through hole was formed in a graphite sheet (for example, a graphite sheet (eGraf series) manufactured by Graphtec Co., Ltd.) obtained by processing a carbonaceous material such as graphite into a sheet shape. In addition, as the heat conductor 40, a through hole is formed in a metal such as gold, aluminum, copper, tungsten, and molybdenum having excellent heat conductivity, or an alloy of these metals such as stainless steel. The formed one is applicable.

  When a metal material is used as the heat conductor 40, oxidation or corrosion may occur due to water generated at the cathode 16, oxygen, water vapor, or the like contained in the atmosphere. In order to prevent this, the heat conductor 40 is made of a material that does not easily corrode such as stainless steel, or the surface of the heat conductor 40 is plated with a metal that is not easily oxidized such as gold, or a carbonaceous material or Alternatively, it may be coated with resin or rubber, or may be applied with a paint that does not dissolve in the liquid fuel vapor.

  The resin or rubber for coating as described above is polyethylene, polypropylene, polystyrene, polyethylene terephthalate, nylon, polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether. Resins such as copolymer (PFA), polyvinyl chloride, polyimide, and silicone resin, and rubbers such as ethylene / propylene rubber (EPDM) and fluororubber can be used. Since these resins and rubbers have lower thermal conductivity than metals, it is desirable to make the resin or rubber to be coated as thin as possible.

  Between the heat conductor 40 and the cathode current collector 18C described above, and between the heat conductor 40 and the anode current collector 18A, the heat conductor 40 and the current collector 18 are connected as necessary. An insulator 50 is disposed to electrically insulate the gap. Further, when the heat conductor 40 formed of a conductive material is disposed in common with respect to the plurality of single cells C, the heat conductor is also used to insulate between the adjacent single cells C. It is desirable to place an insulator 50 between 40 and the current collector 18.

  Moreover, the insulator 50 needs to ensure air permeability like the heat conductor 40, and has a porous property or a through hole. For this reason, when the insulator 50 is disposed on the cathode 16 side of the membrane electrode assembly 2, introduction of air or oxygen necessary for the power generation reaction to each cathode 16, and further from each cathode 16 to the outside It does not hinder the discharge of gas such as water vapor. Similarly, even when the insulator 50 is disposed on the anode 13 side of the membrane electrode assembly 2, introduction of fuel gas necessary for power generation reaction to each anode 13 is not hindered.

  The insulator 50 is formed in a film shape or a plate shape, and the thickness thereof is not particularly limited as long as the insulating property can be ensured, but is 100 μm or less in order to meet the demand for thinning the module. Is desirable, for example, 20 μm.

  As a material constituting the insulator 50, the same materials as those described above, such as resin and rubber, can be used. For example, polytetrafluoroethylene (PTFE) is preferable. Further, the above-described coating or painting for preventing corrosion of the heat conductor 40 may also serve as the insulator 50.

  The thermal conductor 40 described above desirably has a thermal conductivity anisotropy in which the thermal conductivity λpl in the planar direction is larger than the thermal conductivity λt in the thickness direction. That is, the characteristic required for the heat conductor 40 is to make the in-plane heat distribution uniform. When the thermal conductivity λt in the thickness direction is larger, the movement of heat in the thickness direction is promoted and the in-plane heat distribution is increased. That is, there is a possibility that the transfer of heat from the high temperature portion to the low temperature portion of the membrane electrode assembly is hindered.

  In such a thermal conductor 40, the ratio λ = λpl / λt between the thermal conductivity λpl in the plane direction and the thermal conductivity λt in the thickness direction is preferably 10 or more, and more preferably 20 or more. . The thermal conductivities λpl and λt described here are measured by a laser flash method.

  Here, the in-plane temperature distribution of the membrane electrode assembly 2 that varies depending on the thermal conductivity ratio λ was measured. At this time, the temperature (that is, the surface temperature of the membrane electrode assembly) was measured by a thermocouple sandwiched between the cathode gas diffusion layer 15 and the insulator 50 in each single cell C. A plurality of thermocouples were installed at the center in the longitudinal direction of each single cell C. The measurement results are shown in FIG. In FIG. 9, the vertical axis represents the temperature difference ΔT (° C.) with respect to the in-plane maximum temperature.

  As shown in FIG. 9, when the ratio λ = 1, there was no significant difference from the case where the heat conductor 40 was not arranged. On the other hand, when the thermal conductor 40 having thermal conductivity anisotropy (that is, λpl> λt) is applied, the temperature difference between the central portion 2C and the peripheral portion 2P of the membrane electrode assembly 2 is reduced. The tendency to be confirmed was confirmed.

  When the heat conductor 40 with the ratio λ of 10 or more was applied, the temperature difference at the center of all the single cells C could be relaxed to about 3 ° C.

  Furthermore, when the thermal conductor 40 having a ratio λ of 20 or more was applied, the temperature difference could be relaxed within 3 ° C. over the entire area of the membrane electrode assembly 2. At this time, it was confirmed that the in-plane saturated water vapor pressure difference in the cathode gas diffusion layer 15 was ± 10% or less.

  The above-described heat conductor 40 is desirably thick enough to make the temperature distribution in the surface of the membrane electrode assembly 2 uniform, and the thickness is desirably 100 μm or more. A thinner one is desirable to meet the demands of making it easier.

  Here, the in-plane temperature distribution of the membrane electrode assembly 2 that varies depending on the thickness t of the heat conductor 40 was measured. The temperature measurement conditions at this time are as described above. The measurement results are shown in FIG. In FIG. 10, the vertical axis represents the temperature difference ΔT (° C.) with respect to the in-plane maximum temperature.

  As shown in FIG. 10, it was confirmed that as the thickness t of the thermal conductor 40 is thicker, the temperature difference between the central portion 2C and the peripheral portion 2P of the membrane electrode assembly 2 is reduced. When the heat conductor 40 having a thickness t of 100 μm or more was applied, the temperature difference at the center of all the single cells C could be relaxed to about 3 ° C. Furthermore, when the thermal conductor 40 having a thickness t of 250 μm or more was applied, the temperature difference could be relaxed within 3 ° C. over the entire area of the membrane / electrode assembly 2.

  Here, for the thickness t of the thermal conductor 40, it is preferable that λ × t is 1000 or more, for example, in relation to the thermal conductivity λ of the thermal conductor.

  It is desirable that the porosity of the heat conductor 40 be set higher than the porosity of the plate-like body 20. That is, both the heat conductor 40 and the plate-like body 20 disposed on the cathode side of the membrane electrode assembly 2 have air permeability so as not to inhibit the introduction of air into the cathode 16. On the other hand, since the plate-like body 20 has a function as a moisture-retaining layer, the porosity of the plate-like body 20 is about 25% in order to ensure a sufficient moisturizing power. On the other hand, the heat conductor 40 is located on the cathode side of the plate-like body 20 and is set to have a higher porosity than the plate-like body 20 so as not to inhibit the introduction of air into the cathode 16. ing.

  The porosity of the heat conductor 40 is one of the factors that control the heat conductivity. That is, the higher the porosity, the more the inside of the heat conductor 40 is filled with the gas component, leading to a decrease in heat dissipation performance. That is, the higher the porosity, the lower the thermal conductivity. As described above, the thermal conductor 40 is required to ensure air permeability while ensuring thermal conductivity, and considering both, it is desirable that the porosity of the thermal conductor 40 be 50% or more. .

  In many cases, the in-plane temperature distribution of the membrane electrode assembly 2 is high in the central portion 2C and low in the peripheral portion 2P. In order to cope with this, in the heat conductor 40, it is desirable that the porosity at the central portion is smaller than the peripheral portion. That is, in the heat conductor 40, the portion that faces the central portion 2C of the membrane electrode assembly 2 has a relatively high thermal conductivity, promotes heat transfer, and the portion that faces the peripheral portion 2P has a relatively high heat conductivity. On the other hand, the rate is low, but the air permeability is high and the power generation reaction can be promoted.

  At this time, you may comprise the heat conductor 40 so that the porosity may become large continuously toward a peripheral part from a center part. In this case, the thermal conductivity in the plane of the heat conductor 40 is not constant, and continuously increases from the central portion to the peripheral portion.

<< First Example >>
As shown in FIG. 2 and the like, the membrane electrode assembly 2 of the fuel cell according to each example and comparative example described below has a configuration including four single cells C, and each single cell C is a current collector. They are electrically connected in series by the body 18.

Example 1
As shown in FIG. 4 and the like, in the fuel cell according to Example 1, the heat conductor 40 is disposed only on the cathode 16 side of the membrane electrode assembly 2. Carbon paper was applied as the heat conductor 40. That is, the cathode current collector 18 </ b> C of the current collector 18 overlaps the cathode 16 of each single cell C of the membrane electrode assembly 2. A heat conductor 40 is disposed on the cathode current collector 18C via an insulator 50. A cover plate 21 is disposed on the heat conductor 40 via the plate-like body 20. For this reason, the heat generated at the cathode 16 is transferred to the heat conductor 40 via the cathode current collector 18C and diffused in the plane.

(Example 2)
As shown in FIG. 5 and the like, in the fuel cell according to Example 2, the heat conductor 40 is disposed only on the anode 13 side of the membrane electrode assembly 2. Carbon paper was applied as the heat conductor 40. That is, the anode current collector 18 </ b> A of the current collector 18 overlaps the anode 13 of each single cell C of the membrane electrode assembly 2. A heat conductor 40 is disposed on the anode current collector 18 </ b> A via an insulator 50. For this reason, the heat generated in the anode 13 is transmitted to the heat conductor 40 via the anode current collector 18A and diffused in the plane.

(Example 3)
As shown in FIG. 6 and the like, in the fuel cell according to Example 3, the heat conductor 40 is disposed on both the anode 13 side and the cathode 16 side of the membrane electrode assembly 2. Carbon paper was applied as the heat conductor 40. The respective configurations on the anode 13 side and the cathode 16 side are the same as those in the first and second embodiments.

Example 4
As shown in FIG. 7 and the like, in the fuel cell according to Example 4, the heat conductor 40 is arranged on both the anode 13 side and the cathode 16 side of the membrane electrode assembly 2 in the same manner as in Example 3. ing. Carbon paper was applied as the heat conductor 40. In the first to third embodiments, the heat conductor 40 is disposed so as to face the entire surface of all the anodes 13 or all the cathodes 16. However, in the fourth embodiment, the heat conductor 40 has an outer dimension D. And part of the anodes 13 and part of the cathodes are not opposed to each other.

(Example 5)
In the fuel cell according to Example 5, the heat conductor 40 is disposed on both the anode 13 side and the cathode 16 side of the membrane electrode assembly 2 in the same manner as in Example 3. In particular, in the fifth embodiment, the heat conductor 40 is made of gold (Au) instead of carbon paper.

  More specifically, as shown in FIG. 11, the cathode current collector 18 </ b> C of the current collector 18 overlaps the cathode 16 of each single cell C of the membrane electrode assembly 2. In this case, the cathode current collector 18 </ b> C is formed in a lattice shape and is in contact with the peripheral portion of the cathode 16. A heat conductor 40 is disposed on the cathode current collector 18C via an insulator formed of PTFE (not shown). The heat conductor 40 has the same shape as the cathode current collector 18C, and has a through hole 40A. On the heat conductor 40, the cover plate 21 is arrange | positioned through the plate-shaped body which is not shown in figure.

  With such a configuration, air introduced from the opening 21A passes through the through hole 40A of the heat conductor 40, is taken into the cathode 16 via the cathode current collector 18C, and is used for a power generation reaction.

  On the other hand, the anode current collector 18 </ b> A of the current collector 18 overlaps the anode 13 of each single cell C of the membrane electrode assembly 2. In this case, the anode current collector 18A is formed in a lattice shape similar to the cathode current collector 18C, and is in contact with the peripheral edge of the anode 13 and the like. A heat conductor 40 is disposed on the anode current collector 18A via an insulator formed of PTFE (not shown). The thermal conductor 40 is also formed with a through hole 40A as in the example shown in FIG.

  With such a configuration, the fuel gas supplied from the fuel supply mechanism 3 passes through the through hole 40A of the heat conductor 40, is taken into the anode 13 via the anode current collector 18A, and is used for the power generation reaction.

(Comparative Example 1)
The fuel cell according to the comparative example does not include a heat conductor.

<Performance evaluation>
Performance evaluation was performed about the fuel cell mentioned above. This performance evaluation was performed in an environment at a temperature of 25 ° C. and a relative humidity of 50%. Pure methanol was injected into the fuel container, and power was generated at a constant voltage, and the output voltage and the surface temperature on the cathode side during power generation were measured. For output, the average output over 10 hours was calculated. Moreover, about surface temperature, as shown in FIG. 11, it measured at three places, respectively a center part, an intermediate part, and an edge part, and computed the average temperature in 10 hours.

  The results are shown in FIG. That is, when the average output of Comparative Example 1 was set to 100, it was confirmed that in any Example, an output higher than that of Comparative Example 1 was obtained. Further, when the average temperature in the central part of Comparative Example 1 is 100, in Comparative Example 1, a large temperature difference (15%) occurs from the central part to the end part, whereas in any Example, Also, the temperature difference between the central portion and the end portion was 10% or less, and it was confirmed that the in-plane temperature distribution was more uniform than in Comparative Example 1.

  Next, the variation of the heat conductor 40 combined with the membrane electrode assembly 2 is demonstrated.

  As shown in FIG. 13, the membrane electrode assembly 2 is formed in a substantially rectangular shape, has a long side 2 </ b> L parallel to the first direction X, and a short side 2 </ b> S parallel to the second direction Y. The membrane electrode assembly 2 includes four single cells C. Each single cell C is formed in a substantially rectangular shape, has a long side CL parallel to the first direction X, and a short side CS parallel to the second direction Y.

  The heat conductor 40 is disposed on at least one of the anode 13 side and the cathode 16 side of the membrane electrode assembly 2. In FIG. 13, a state in which the heat conductor 40 overlaps the membrane electrode assembly 2 is illustrated. That is, the heat conductor 40 is formed in a single flat plate shape and has four openings 41. Each opening 41 is formed so as to expose a part of each single cell C. That is, each opening 41 is formed in a substantially rectangular shape smaller than the outer dimension of the single cell C, and has a long side 41L shorter than the long side CL of the single cell C while being parallel to the long side CL of the single cell C. And a short side 41S shorter than the short side CS of the single cell C while being parallel to the short side CS of the single cell C.

  Such a heat conductor 40 is formed in a frame shape along the periphery of each single cell C. That is, the heat conductor 40 is formed in a frame shape along at least one of the peripheral edge of each of the anodes 13 and the peripheral edge of each of the cathodes 16 constituting the single cell C.

  In the thermal conductor 40, a slit 42 is formed immediately above the adjacent single cells C. That is, in the heat conductor 40, the slit 42 is formed immediately above at least one of the adjacent anodes 13 and the adjacent cathodes 16. For this reason, the heat conductor 40 does not straddle the plurality of single cells C, and is disposed independently in each single cell C. However, they are connected at the periphery of the heat conductor 40 and constitute a single heat conductor 40.

  The thermal conductor 40 in the example shown in FIG. 14 is further linear in the first direction X parallel to the long side CL of each unit cell C, compared to the thermal conductor 40 shown in FIG. The difference is that one formed first extending portion 43 is added. The first extending portion 43 is disposed on each single cell C. In other words, the opening 41 on each single cell C is composed of two segments divided by one first extending portion 43. Two or more first extending portions 43 may be arranged on each single cell C.

  The thermal conductor 40 of the example shown in FIG. 15 is further linear in the second direction Y parallel to the short side CS of each unit cell C, as compared with the thermal conductor 40 shown in FIG. The difference is that three formed second extending portions 44 are added. These second extending portions 44 are arranged on each unit cell C at substantially equal intervals. In other words, the opening 41 on each unit cell C includes eight segments divided by one first extending portion 43 and three second extending portions 44. That is, the heat conductor 40 is formed in a lattice shape intersecting the first direction X and the second direction Y on each unit cell C. One or two second extending portions 44 may be disposed on each single cell C, or four or more second extending portions 44 may be disposed.

  The heat conductor 40 in the example shown in FIG. 16 is different from the heat conductor 40 shown in FIG. 15 in that more second extending portions 44 are added. Here, fifteen second extending portions 44 are arranged on each unit cell C at substantially equal intervals. In other words, the opening 41 on each unit cell C is composed of 32 segments each having a substantially square shape divided by one first extending portion 43 and 15 second extending portions 44. That is, the heat conductor 40 is formed in a lattice shape intersecting the first direction X and the second direction Y on each unit cell C.

  The membrane electrode assembly 2 of the example shown in FIG. 17 is formed in a substantially square shape, and the length of each side parallel to the first direction X and the second direction Y is substantially equal. The membrane electrode assembly 2 includes four single cells C. These four single cells C are arranged in a 2 × 2 matrix in which two each are arranged in the first direction X and the second direction Y. That is, the anode 13 and the cathode 16 constituting the single cell C are arranged in a 2 × 2 matrix.

  The heat conductor 40 applied to such a membrane electrode assembly 2 is formed in a substantially square shape, and is disposed on at least one of the anode 13 side and the cathode 16 side of the membrane electrode assembly 2. FIG. 17 illustrates a state in which the heat conductor 40 overlaps the membrane electrode assembly 2. That is, the heat conductor 40 is formed in a single flat plate shape and has an opening 41 that exposes a part of each single cell C. The opening 41 on each single cell C is composed of a plurality of substantially square segments. That is, the heat conductor 40 is formed in a lattice shape on each single cell C.

  Note that the heat conductor 40 as shown in FIGS. 16 and 17 is a membrane electrode assembly 2 including single cells C arranged in a matrix of m × n where m and n are integers of 1 or more. Is applicable.

  The heat conductor 40 in the example shown in FIG. 18 is different from the heat conductor 40 shown in FIG. 17 in that the heat conductor 40 is formed radially from the central portion toward the peripheral portion. That is, the heat conductor 40 has openings 41 that are radially formed while exposing a part of each unit cell C.

  In addition, the heat conductor 40 as shown in FIG. 18 is compared with the membrane electrode assembly 2 including the single cells C arranged in a matrix of m × n where m and n are integers of 1 or more. Applicable.

  The membrane electrode assembly 2 in the example shown in FIG. 19 is formed in a substantially circular shape. The membrane electrode assembly 2 includes four single cells C. These four single cells C are arranged radially from the center of the membrane electrode assembly 2 toward the circumference. That is, each single cell C or the anode 13 and the cathode 16 constituting the single cell C are formed in a fan shape.

  The heat conductor 40 applied to such a membrane electrode assembly 2 is formed in a substantially circular shape, and is disposed on at least one of the anode 13 side and the cathode 16 side of the membrane electrode assembly 2. FIG. 19 illustrates a state in which the heat conductor 40 overlaps the membrane electrode assembly 2. That is, the heat conductor 40 is formed in a single flat plate shape and has an opening 41 that exposes a part of each single cell C. The opening 41 on each single cell C is formed radially. That is, the heat conductor 40 is formed radially on each single cell C.

  Note that the heat conductor 40 as shown in FIG. 19 is different from the membrane electrode assembly 2 including three or less single cells C, the membrane electrode assembly 2 including five or more single cells C, and the like. It is applicable.

  The membrane electrode assembly 2 of the example shown in FIG. 20 is formed in a substantially hexagonal shape. The membrane electrode assembly 2 includes six single cells C. These six single cells C are arranged radially from the central part to the peripheral part of the membrane electrode assembly 2. That is, each single cell C or the anode 13 and the cathode 16 constituting the single cell C are formed in a triangular shape.

  The heat conductor 40 applied to such a membrane electrode assembly 2 is formed in a substantially hexagonal shape, and is disposed on at least one of the anode 13 side and the cathode 16 side of the membrane electrode assembly 2. FIG. 20 illustrates a state in which the heat conductor 40 overlaps the membrane electrode assembly 2. That is, the heat conductor 40 is formed in a single flat plate shape and has an opening 41 that exposes a part of each single cell C. The opening 41 on each single cell C is formed radially. That is, the heat conductor 40 is formed radially on each single cell C.

  Note that the heat conductor 40 as shown in FIG. 20 is not limited to the hexagonal membrane electrode assembly, and is applicable to the N-shaped membrane electrode assembly 2 when N is an integer of 3 or more. Is possible.

  By the way, this embodiment is defined as follows from another viewpoint.

  FIG. 21 schematically shows an exploded view of the membrane electrode assembly 2 and the heat conductor 40 constituting the fuel cell 1.

  When the membrane / electrode assembly 2 is formed in a substantially rectangular shape, the length in the first direction X parallel to the long side 2L of the membrane / electrode assembly 2 is Lx, and parallel to the short side 2S of the membrane / electrode assembly 2. Let the length in the second direction Y be Ly. Here, regardless of the number and arrangement of the single cells C, the length along the first direction X of the power generation unit 2X including all the single cells C formed in the membrane electrode assembly 2 is Lx, and the power generation unit 2X The length along the second direction Y is Ly.

  For the thermal conductor 40 applied to such a membrane electrode assembly 2, the product of the thermal conductivity λx of the thermal conductor 40 in the first direction X and the cross-sectional area Sx of the thermal conductor 40 in the first direction X. (Λx × Sx) is the thermal conductivity Λx, and the product (λy × Sy) of the thermal conductivity λy of the thermal conductor 40 in the second direction Y and the cross-sectional area Sy of the thermal conductor 40 in the second direction Y is the heat. Conductivity Λy.

  In this case, the fuel cell 1 in which the membrane electrode assembly 2 and the heat conductor 40 are combined is configured to satisfy the following relationship.

(Λx × Lx) / (Λy × Ly)> 1
According to the fuel cell 1 that satisfies this relationship, the effects of the present embodiment described above can be obtained.

  Further, this embodiment is defined as follows from another viewpoint.

  The membrane electrode assembly 2 is formed in a substantially square shape or a substantially rectangular shape, and the longitudinal direction of each single cell C formed in the membrane electrode assembly 2, that is, the longitudinal direction of each of the anode 13 and the cathode 16, is the first. When the alignment direction of the plurality of single cells C, that is, the alignment direction of the plurality of anodes 13 and the alignment direction of the plurality of cathodes 16 are parallel to the second direction Y perpendicular to the first direction X, The length of the electrode assembly 2 in the first direction X is Lx, and the length of the membrane electrode assembly 2 in the second direction Y is Ly. Also here, the length along the first direction X of the power generation unit 2X including all the single cells C formed in the membrane electrode assembly 2 is Lx, and the length along the second direction Y of the power generation unit 2X is Ly.

  For the thermal conductor 40 applied to such a membrane electrode assembly 2, the product of the thermal conductivity λx of the thermal conductor 40 in the first direction X and the cross-sectional area Sx of the thermal conductor 40 in the first direction X. (Λx × Sx) is the thermal conductivity Λx, and the product (λy × Sy) of the thermal conductivity λy of the thermal conductor 40 in the second direction Y and the cross-sectional area Sy of the thermal conductor 40 in the second direction Y is the heat. Conductivity Λy.

  In this case, the fuel cell 1 in which the membrane electrode assembly 2 and the heat conductor 40 are combined is configured to satisfy the following relationship.

(Λx × Lx) / (Λy × Ly)> 1
According to the fuel cell 1 that satisfies this relationship, the effects of the present embodiment described above can be obtained.

  The second embodiment will be described below.

<< Second Embodiment >>
(Example 6)
To the carbon black supporting the anode catalyst particles (Pt: Ru = 1: 1), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium were added to support the anode catalyst particles. A paste was prepared by dispersing carbon black. The obtained paste was applied to porous carbon paper (81 mm × 9.7 mm rectangle) as the anode gas diffusion layer 12 to obtain an anode catalyst layer 11 having a thickness of 100 μm.

  To the carbon black supporting the catalyst particles for cathode (Pt), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium are added to disperse the carbon black supporting the catalyst particles for cathode. A paste was prepared. The obtained paste was applied to porous carbon paper as the cathode gas diffusion layer 15 to obtain a cathode catalyst layer 14 having a thickness of 100 μm.

  The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 have the same shape and the same size, the same thickness, and the anode catalyst layer 11 and the cathode catalyst layer 14 applied to each gas diffusion layer have the same shape. And the same size.

  A perfluorocarbon sulfonic acid membrane (trade name: nafion membrane) having a thickness of 30 μm and a water content of 10 to 20% by weight as the electrolyte membrane 17 between the anode catalyst layer 11 and the cathode catalyst layer 14 produced as described above. Four anode gas diffusion layers 12 and four cathode gas diffusion layers 15 are arranged side by side so that their longitudinal directions are substantially parallel and the distance between them is 1.2 mm. Membrane electrode assembly 2 was obtained by performing hot pressing in a state where the positions were adjusted so that layer 11 and cathode catalyst layer 14 face each other.

  The membrane electrode assembly 2 thus prepared is sandwiched by the current collector 18, the anode gas diffusion layer 12 and the anode current collector 18A are opposed to each other, and the cathode gas diffusion layer 15 and the cathode current collector 18C are connected to each other. Opposite. That is, a gold foil was laminated on the cathode gas diffusion layer 15 as the cathode current collector 18C. A gold foil was laminated on the anode gas diffusion layer 12 as the anode current collector 18A. The anode current collector 18A and the cathode current collector 18C are formed so that the four pairs of the anode catalyst layer 11 and the cathode catalyst layer 14 are electrically connected in series.

  Between the electrolyte membrane 17 and the current collector 18 of the membrane electrode assembly 2, a rubber O-ring having a width of 2 mm is sandwiched between the anode side and the cathode side as seal members 19, respectively. gave.

  On the cathode current collector 18C, a microporous film made of polytetrafluoroethylene (PTFE) having a thickness of 20 μm and a porosity of 68% was laminated as the insulator 50. Furthermore, on this insulator 50, as a heat conductor 40, a graphite sheet having a thickness of 50 μm (manufactured by Graphtec; model number SS400-0.05) was cut into a shape as shown in FIG. 13 and laminated. . The graphite sheet as the thermal conductor 40 has a thermal conductivity λpl of 400 W / mK in the plane direction (the first direction X and the second direction Y shown in FIG. 13), and its thickness direction (the first direction in FIG. 13). The thermal conductivity λt in the direction X and the direction Z orthogonal to the second direction Y) is 3.5 W / mK.

  In Example 6, the thermal conductivity Λx in the first direction X and the thermal conductivity Λy in the second direction Y of the thermal conductor 40 shown in FIG. 13 and the length of the membrane electrode assembly 2 in the first direction X are shown. The value of (Λx × Lx) / (Λy × Ly) obtained from the thickness Lx and the length Ly in the second direction Y of the membrane electrode assembly 2 is 4.47.

On the heat conductor 40, the plate-like body 20 has a thickness of 0.75 mm and an air permeability of 3.0 seconds / 100 cm ³ (according to the measurement method specified in JIS P 8117: 2009). A polyethylene porous film having a moisture permeability of 3000 g / (m ² · 24 h) (according to the measurement method defined in JIS L 1099: 2006 A-1) is cut into a rectangle having a length of 85 mm and a width of 46.6 mm, and then laminated. did. Air supplied from the outside air to the cathode 16 passes through the plate-like body 20.

  On the plate-like body 20, a stainless plate (SUS304) having a rectangular outer shape of 90 mm × 48 mm and a thickness of 0.3 mm was laminated as the cover plate 21. The cover plate 21 has 120 square openings 21A each having a side length of 3.5 mm.

  In an environment where the temperature was 25 ° C. and the relative humidity was 50%, pure methanol having a purity of 99.9% by weight was supplied to the fuel cell 1 produced as described above. In addition, a constant voltage power supply is connected, and the current flowing through the fuel cell 1 is controlled so that the output voltage of the fuel cell 1 is constant at 0.35 V per pair among four pairs of single cells connected in series. At this time, the output density obtained from the fuel cell 1 was measured.

Here, the output density (mW / cm ² ) of the fuel cell 1 refers to the current density flowing through the fuel cell 1 (current value per 1 cm ² area (mA / cm ² ) of the power generation unit) and the output voltage of the fuel cell 1. Multiplied by. Further, the area of the power generation unit is the area of the portion where the anode catalyst layer 11 and the cathode catalyst layer 14 face each other. In this embodiment, since the anode catalyst layer 11 and the cathode catalyst layer 14 have the same area and are completely opposed to each other, the area of the power generation unit is equal to the area of these catalyst layers.

  Moreover, as shown in FIG. 11, the thermocouple was attached to the surface of the center part and end part of the cover plate 21, respectively, and the temperature difference between these two points was measured.

(Example 7)
Example 6 is the same as Example 6 except that the shape of the heat conductor 40 is as shown in FIG. In Example 7, the value of (Λx × Lx) / (Λy × Ly) is 6.21.

(Example 8)
Example 6 is the same as Example 6 except that the shape of the heat conductor 40 is as shown in FIG. In Example 7, the value of (Λx × Lx) / (Λy × Ly) is 1.53.

(Comparative Example 2)
Example 6 is the same as Example 6 except that the heat conductor 40 of any shape is not provided.

  FIG. 22 summarizes the above results. In addition, the result of measuring the output density of the fuel cell 1 and the result of measuring the temperature difference between the center part and the end part on the surface of the cover plate 21 are shown as relative values with the value of Comparative Example 2 being 100, respectively. is there. In any of Examples 6 to 8, it was confirmed that the temperature distribution was made more uniform than in Comparative Example 2, and that a higher power density than in Comparative Example 2 was obtained.

  As described above, according to this embodiment, variation in the temperature distribution in the surface of the membrane electrode assembly is alleviated, and obstructive factors for the exchange of substances necessary for power generation reaction are removed, and stably high. It is possible to provide a fuel cell capable of obtaining an output and prolonging the life, and further providing an application device thereof.

  The fuel cell 1 of each embodiment described above is effective when various liquid fuels are used, and the type and concentration of the liquid fuel are not limited. However, the fuel supply unit 31 that supplies fuel while being dispersed in the plane direction is particularly effective when the fuel concentration is high. For this reason, the fuel cell 1 of each embodiment can exhibit its performance and effects particularly when methanol having a concentration of 80 wt% or more is used as the liquid fuel. Therefore, each embodiment is suitable for the fuel cell 1 using a methanol aqueous solution having a methanol concentration of 80 wt% or more or pure methanol as a liquid fuel.

  Furthermore, although each embodiment mentioned above demonstrated the case where this invention was applied to the semi-passive type fuel cell 1, this invention is not limited to this, It is an internal vaporization type pure passive type fuel cell. It can also be applied to.

  The present invention can be applied to various fuel cells using liquid fuel. In addition, the specific configuration of the fuel cell, the supply state of the fuel, and the like are not particularly limited, and all of the fuel supplied to the MEA is liquid fuel vapor, all is liquid fuel, or part is liquid state. The present invention can be applied to various forms such as a vapor of supplied liquid fuel. In the implementation stage, the constituent elements can be modified and embodied without departing from the technical idea of the present invention. Furthermore, various modifications are possible, such as appropriately combining a plurality of constituent elements shown in the above embodiment, or deleting some constituent elements from all the constituent elements shown in the embodiment. Embodiments of the present invention can be expanded or modified within the scope of the technical idea of the present invention, and these expanded and modified embodiments are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Membrane electrode assembly 3 ... Fuel supply mechanism 11 ... Anode catalyst layer 12 ... Anode gas diffusion layer 13 ... Anode (fuel electrode)
14 ... Cathode catalyst layer 15 ... Cathode gas diffusion layer 16 ... Cathode (air electrode)
17 ... Electrolyte membrane 18 ... Current collector 20 ... Plate-like body (moisturizing layer)
21 ... Cover plate 40 ... Thermal conductor 50 ... Insulator

Claims (19)

An electrolyte membrane, a plurality of fuel electrodes arranged on one surface of the electrolyte membrane with a space, and a space on the other surface of the electrolyte membrane so as to face each of the fuel electrodes. A membrane electrode assembly having a plurality of air electrodes;
A heat conductor disposed on at least one of a surface side of the plurality of air electrodes opposite to the electrolyte membrane side of the membrane electrode assembly and a surface side of the plurality of fuel electrodes opposite to the electrolyte membrane side; ,
A fuel cell comprising:   The fuel cell according to claim 1, further comprising a current collector between the thermal conductor and the membrane electrode assembly.   The fuel cell according to claim 2, further comprising an air-permeable insulator disposed between the heat conductor and the current collector.   The fuel cell according to claim 1, wherein the heat conductor is porous or has a through hole.   2. The fuel cell according to claim 1, wherein the thermal conductor has a thermal conductivity λpl in a planar direction larger than a thermal conductivity λt in a thickness direction.   5. The fuel cell according to claim 4, wherein in the thermal conductor, a ratio λpl / λt of thermal conductivity λpl and thermal conductivity λt is 10 or more.   The fuel cell according to claim 1, wherein the thermal conductor has a porosity of 50% or more.   2. The fuel cell according to claim 1, wherein the thermal conductor has a porosity at a central portion smaller than that of a peripheral portion.   The fuel cell according to claim 1, wherein the heat conductor is disposed across at least one of the adjacent fuel electrode and the adjacent air electrode.   2. The fuel cell according to claim 1, wherein a slit is formed immediately above at least one of the heat conductors between the adjacent fuel electrodes and between the adjacent air electrodes.   2. The fuel cell according to claim 1, wherein the heat conductor is formed in a frame shape along at least one of a peripheral edge of the fuel electrode and a peripheral edge of the air electrode. The fuel electrode and the air electrode are formed in a substantially rectangular shape,
2. The heat conductor according to claim 1, wherein the heat conductor is formed along at least one of a direction parallel to a long side of each of the fuel electrodes and a direction parallel to a long side of each of the air electrodes. Fuel cell.   The fuel cell according to claim 1, wherein the heat conductor is formed in a lattice shape.   The fuel cell according to claim 13, wherein the fuel electrode and the air electrode are arranged in a matrix of m × n where m and n are integers of 1 or more.   The fuel cell according to claim 1, wherein the heat conductor is formed radially from a central portion toward a peripheral portion.   The fuel cell according to claim 15, wherein the fuel electrode and the air electrode are arranged in a radial shape or in an m × n matrix when m and n are integers of 1 or more. The membrane electrode assembly is formed in a substantially rectangular shape, the length in the first direction parallel to the long side of the membrane electrode assembly is Lx, and the length in the second direction parallel to the short side of the membrane electrode assembly Ly, and the product (λx × Sx) of the thermal conductivity λx of the thermal conductor in the first direction and the cross-sectional area Sx of the thermal conductor in the first direction is the thermal conductivity Λx, and the second direction When the product (λy × Sy) of the thermal conductivity λy of the thermal conductor and the cross-sectional area Sy of the thermal conductor in the second direction is the thermal conductivity Λy,
(Λx × Lx) / (Λy × Ly)> 1
The fuel cell according to claim 1, wherein: A longitudinal direction of each of the fuel electrodes and each of the air electrodes is parallel to a first direction, and a second direction in which the arrangement direction of the plurality of fuel electrodes and the arrangement direction of the plurality of air electrodes are orthogonal to the first direction. The membrane electrode assembly that is parallel to is formed in a substantially square shape or a substantially rectangular shape,
The length in the first direction of the membrane electrode assembly is Lx, the length in the second direction of the membrane electrode assembly is Ly, the thermal conductivity λx of the thermal conductor in the first direction and the length in the first direction. The product (λx × Sx) of the cross-sectional area Sx of the thermal conductor is defined as thermal conductivity Λx, and the thermal conductivity λy of the thermal conductor in the second direction and the cross-sectional area of the thermal conductor in the second direction. When the product (λy × Sy) with Sy is the thermal conductivity Λy,
(Λx × Lx) / (Λy × Ly)> 1
The fuel cell according to claim 1, wherein:   The fuel cell according to claim 1, wherein the heat conductor is a graphite sheet.

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