JP2011113883A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of stably obtaining a high power. <P>SOLUTION: The fuel cell includes a fuel cell body having a membrane electrode assembly in which an electrolyte membrane is sandwiched between an anode and a cathode, a fuel supply mechanism arranged on the anode side of the membrane electrode assembly and supplying fuel to the anode, and a cover plate having a plurality of openings, arranged on the cathode side of the membrane electrode assembly, and holding the membrane electrode assembly between the fuel supply mechanism and itself; and a radiator having a plurality of through-holes, covering at least a part on the cathode side of the fuel cell body, and separated from the cover plate. <P>COPYRIGHT: (C)2011,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 without being charged for a long time. 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 by replenishing fuel. 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.

  For example, according to Patent Document 1, in a fuel cell that operates in a high temperature range, heat transfer is performed on the outer surface of a heat insulator that covers the fuel cell in order to prevent the casing of a device that houses the fuel cell from becoming hot. Techniques for covering with the body are disclosed.

  Further, according to Patent Document 2, the first heat insulating member that is laminated on at least one of the outer surface and the inner surface of the cover having the oxidant introduction port and has an opening at a position facing the oxidant introduction port is provided. A fuel cell is disclosed. Further, according to Patent Document 2, in addition to the first heat insulating member, a fuel including a second heat insulating member laminated on the cathode current collector and the anode current collector and having a gas permeable hole. A battery is also disclosed.

JP 2006-202611 A International Publication No. 2007/086432 Pamphlet

  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 particularly advantageous for downsizing of the DMFC. The passive DMFC includes, for example, an anode (fuel electrode), a cathode (air electrode), and a membrane electrode assembly (MEA) having an electrolyte membrane.

  By supplying fuel to the anode side of such a membrane electrode assembly and supplying air (particularly oxygen) to the cathode side, a power generation reaction occurs on the anode side and the cathode side. In particular, heat is generated in the reaction on the cathode side. In addition, among the fuel supplied to the anode, a so-called crossover phenomenon occurs in which unreacted components pass through the electrolyte membrane and reach the cathode side, but at least a part of the fuel that has reached the cathode side due to the crossover is, A combustion reaction occurs with air on the cathode side, and heat is also generated by the combustion reaction.

  The heat generated by these reactions is dissipated to the outside air, but if the amount of heat released is less than the amount of heat generated by the reaction, the temperature of the DMFC will continue to rise, and the amount of heat released will be larger than the amount of heat generated by the reaction. If too much, the temperature of DMFC will fall.

  Here, even if the configuration of the DMFC is constant, there is a problem that the amount of heat released from the DMFC to the outside air varies depending on the external conditions such as the temperature of the outside air and the strength (wind speed) of the wind hitting the DMFC. If it is designed to obtain the optimum heat dissipation under conditions where heat dissipation is difficult, such as when the temperature of the outside air is high or when the wind speed is low, the case where the temperature of the outside air is low or the wind speed is high, etc. Under conditions where heat dissipation is likely to occur, the amount of heat dissipation becomes excessive. In that case, fuel corresponding to the amount of heat released will be supplied to the DMFC, but since a large amount of fuel is supplied to the anode side, the amount of fuel that crosses over will also increase, resulting in the output of the DMFC. Will fall.

  On the other hand, when designed to obtain the optimum heat dissipation under conditions where heat dissipation is likely to occur, control is performed so that the amount of heat dissipation is too low and the amount of fuel supplied to the DMFC is reduced under conditions where heat dissipation is difficult. Is done. For this reason, the amount of reaction that occurs on the anode side also decreases, and as a result, the output of the DMFC decreases.

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

According to one aspect of the invention,
A membrane electrode assembly in which an electrolyte membrane is sandwiched between an anode and a cathode, a fuel supply mechanism that is disposed on the anode side of the membrane electrode assembly and supplies fuel toward the anode, and a plurality of openings are formed and A fuel cell body having a cover plate that is disposed on the cathode side of the membrane electrode assembly and holds the membrane electrode assembly between the fuel electrode supply mechanism and the fuel supply mechanism;
A plurality of through-holes, covering at least part of the cathode side of the fuel cell main body and spaced from the cover plate; and
A fuel cell comprising: is provided.

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

FIG. 1 is a plan view showing the appearance of the cathode side of a fuel cell according to an embodiment of the present invention. FIG. 2 is a view schematically showing a cross section of the fuel cell including the fuel cell main body shown in FIG. FIG. 3 is a schematic cross-sectional view of a fuel cell including a fuel cell main body according to another embodiment. FIG. 4 is a diagram illustrating a measurement result of the output density when the performance evaluation is performed.

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

  FIG. 1 is a plan view showing the appearance of the cathode side of a fuel cell (DMFC) main body 0 according to this embodiment.

  The fuel cell main body 0 is formed in a substantially rectangular flat plate shape. In the plan view shown in FIG. 1, the fuel cell main body 0 has a rectangular shape, a pair of long sides L1 and long sides L2 extending along the first direction X, and a second direction orthogonal to the first direction X. It has a pair of short sides S1 and short sides S2 extending along Y.

  The fuel cell main body 0 includes a membrane electrode assembly (MEA) 2 constituting an electromotive unit. The membrane electrode assembly 2 is formed in a substantially rectangular shape. The detailed structure of the membrane electrode assembly 2 will be described later, but here, a plurality of, for example, four single cells CL1 to CL4 are provided. Each of the single cells CL1 to CL4 has a substantially rectangular shape extending along the first direction X on the same plane, and is arranged side by side in the second direction Y.

  A cover plate 21 is disposed on the surface of the fuel cell main body 0 located on the cathode side of the membrane electrode assembly 2. The cover plate 21 has a substantially rectangular appearance, and is made of, for example, stainless steel (SUS). The cover plate 21 is formed with a plurality of openings 21 </ b> H that can mainly take in air as an oxidant, particularly oxygen.

  A fuel supply mechanism (not shown) that supplies fuel to the membrane electrode assembly 2 is disposed on the anode side of the membrane electrode assembly 2. The cover plate 21 is fastened to the fuel supply mechanism at each of the long sides L1 and L2 and the short sides S1 and S2 of the fuel cell 1 with the membrane electrode assembly 2 held between the cover plate 21 and the fuel supply mechanism. Yes.

  FIG. 2 is a view schematically showing a cross section of the fuel cell 1 including the fuel cell main body 0 shown in FIG.

  The fuel cell main body 0 includes a membrane electrode assembly 2. The membrane electrode assembly 2 includes an anode (fuel electrode) 13, a cathode (air electrode or oxidant electrode) 16, a proton (hydrogen ion) conductive electrolyte membrane 17 sandwiched between the anode 13 and the cathode 16, It is configured with. The anode 13 includes an anode catalyst layer 11 and an anode gas diffusion layer 12 laminated on the anode catalyst layer 11. The anode catalyst layer 11 is laminated on one surface 17A of the electrolyte membrane 17. The cathode 16 has a cathode catalyst layer 14 and a cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14. The cathode catalyst layer 14 is laminated on the other surface 17C of the electrolyte membrane 17.

  Each of the single cells CL1 to CL4 shown in FIG. 1 includes an anode 13 and a cathode 16 that face each other with the electrolyte membrane 17 interposed therebetween. That is, in the membrane electrode assembly 2 including the four single cells CL1 to CL4 shown in FIG. 1, the four anodes 13 not described in detail are arranged in the second direction Y on the one surface 17A of the single electrolyte membrane 17. The four cathodes 16 are arranged on the other surface 17C of the electrolyte membrane 17 at intervals in the second direction Y.

  Such a membrane electrode assembly 2 is sandwiched between current collectors 18. The current collector 18 is disposed on the same surface where the base insulating layer BF, the anode current collector 18A disposed on the base insulating layer BF, and the anode current collector 18A of the base insulating layer BF are disposed. It has a cathode current collector 18C.

  The anode current collector 18A and the cathode current collector 18C are made of, for example, a porous layer (for example, a mesh) or a foil body made of a metal material such as gold, copper, or nickel, or a conductive metal material such as stainless steel (SUS). It can be formed by using a composite material coated with a highly conductive metal such as gold, or may be formed by using a carbonaceous material such as graphite (graphite).

  In the example shown in FIG. 2, the anode current collector 18 </ b> A is stacked on the anode gas diffusion layer 12. The anode current collector 18A is formed with an opening 18AH that enables supply of fuel necessary for power generation reaction toward the anode 13. The cathode current collector 18C is stacked on the cathode gas diffusion layer 15. The cathode current collector 18C can supply oxygen necessary for the power generation reaction toward the cathode 16, and can discharge carbon dioxide, excess water vapor, and other gases generated during the power generation reaction to the outside. A possible opening 18CH is formed. The current collector 18 having such a configuration electrically connects a plurality of single cells CL1 to CL4 provided in the membrane electrode assembly 2 as shown in FIG.

  The membrane electrode assembly 2 includes rubber O-rings sandwiched between one surface 17A of the electrolyte membrane 17 and the current collector 18 and between the other surface 17C of the electrolyte membrane 17 and the current collector 18. It is sealed by a sealing member 19 such as. Thereby, fuel leakage and oxidant leakage from the membrane electrode assembly 2 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 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 of air taken in from the opening 21H of the cover plate 21. The amount of air taken in is adjusted and the uniform diffusion of air is promoted. Such a plate-like body 20 is comprised by the flat plate which consists of a polyethylene-made porous film etc., for example.

  A fuel supply mechanism 3 is disposed on the anode 13 side of the membrane electrode assembly 2. That is, the membrane electrode assembly 2 is disposed between the fuel supply mechanism 3 disposed on the anode 13 side and the cover plate 21 disposed on the cathode 16 side. 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. Such a fuel supply mechanism 3 is connected to a fuel storage portion 4 that stores the liquid fuel F via a flow path 5.

  The flow path 5 is comprised by piping etc. The flow path 5 is not limited to piping independent of the fuel supply mechanism 3 and the fuel storage unit 4. For example, when the fuel supply mechanism 3 and the fuel storage unit 4 are laminated and integrated, a flow path of the liquid fuel F that connects them may be used. That is, the fuel supply mechanism 3 only needs to communicate with the fuel storage unit 4 through a flow path or the like.

  The liquid fuel F accommodated in the fuel accommodating portion 4 can be dropped and sent to the fuel supply mechanism 3 through 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 F stored in the fuel storage unit 4 may be fed to the fuel supply mechanism 3 by capillary action. Further, the liquid fuel F stored in the fuel storage unit 4 may be forcibly sent to the fuel supply mechanism 3 by interposing a pump 6 in a part of the flow path 5.

  The applied pump 6 is not a circulation pump that circulates fuel, but is a fuel supply pump that sends liquid fuel F from the fuel storage unit 4 toward the fuel supply mechanism 3 to the last. The fuel supplied from the fuel supply mechanism 3 to the membrane electrode assembly 2 is used for the power generation reaction, and is not circulated thereafter and returned to the fuel storage unit 4. The type of the pump 6 is not particularly limited, but a pump that can feed a small amount of liquid fuel F with good controllability and can be reduced in size and weight is preferable.

  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. 2 employs a system called a semi-passive type, for example.

  In the fuel supply mechanism 3, a fuel cutoff valve may be disposed in series with the pump 6. 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.

  Liquid fuel F corresponding to the membrane electrode assembly 2 is stored in the fuel storage portion 4. Examples of the liquid fuel F include methanol fuels such as methanol aqueous solutions having various concentrations and pure methanol. The liquid fuel F is not necessarily limited to methanol fuel. The liquid fuel F 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 F. Good. In any case, the fuel containing portion 4 contains the liquid fuel F corresponding to the membrane electrode assembly 2.

  Hereinafter, an example of the fuel supply mechanism 3 will be described.

  The fuel supply mechanism 3 disperses and diffuses fuel in the surface direction of the container 30 formed in a box shape and the anode 13 of the membrane electrode assembly 2 (that is, the direction in the XY plane in the drawing). A fuel distribution plate 31 is provided. The container 30 has a fuel inlet (not shown) to which the flow path 5 is connected. Examples of the resin material forming such a container 30 include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), cyclic olefin copolymer, cycloolefin polymer, polymethylpentene, and polyphenyl sulfide (PPS). The container 30 can also be formed using a metal material such as stainless steel (SUS) or a metal clad material instead of the resin material.

  The fuel distribution plate 31 is disposed in a recess formed inside the container 30. The fuel distribution plate 31 is formed in a flat plate shape. The fuel distribution plate 31 has a plurality of fuel discharge ports 33 formed therein. Such a fuel distribution plate 31 discharges the liquid fuel supplied from the fuel introduction port of the container 30 toward the anode 13 from the fuel discharge port 33. Such a fuel distribution plate 31 is formed of a material that does not allow liquid fuel and its vaporized components to permeate. Is formed.

  The fuel distribution plate 31 may be constituted by a gas-liquid separation membrane that separates liquid fuel and its vaporized component and allows the vaporized component to permeate toward the membrane electrode assembly 2. 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), tetrafluoro An ethylene / perfluoroalkyl vinyl ether copolymer (PFA) or the like) microporous film or the like is applicable.

  In the fuel cell main body 0 described above, the liquid fuel F introduced into the fuel distribution plate 31 from the fuel accommodating portion 4 via the flow path 5 remains in the liquid component or in a state where the liquid component and the gas component are mixed. The fuel is discharged from the fuel outlet 33 of the fuel distribution plate 31. The discharged fuel is supplied to the anode 13 of the membrane electrode assembly 2 via the anode current collector 18A of the current collector 18.

  The gaseous component of 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 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 ⁻ ) 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 main body 0 described above, in order to increase the electric power to be generated, the catalyst 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 is more effective. It is important to contribute to power generation.

  As shown in FIG. 2, the fuel cell 1 of the present embodiment includes a radiator 40 that covers at least a part of the fuel cell body 0 on the cathode 16 side. The radiator 40 is located above the cover plate 21 and is separated from the cover plate 21. A plurality of through holes 40H are formed in such a heat radiating body 40. Each of these through holes 40H is located immediately above the opening 21H of the cover plate 21. The number of through holes 40H is the same as the number of openings 21H, but is not limited to this example. By forming the through hole 40H in the heat radiating body 40, oxygen necessary for the power generation reaction can be taken into the cathode 16 side of the fuel cell main body 0.

  The heat radiator 40 described above 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 has high thermal conductivity. Specifically, as the heat radiating body 40, a metal such as copper, aluminum, tungsten, or molybdenum excellent in thermal conductivity, or an alloy of these metals such as stainless steel can be used. Further, as the heat radiating body 40, a carbonaceous material such as graphite can be used.

  As the heat radiating body 40, it is most desirable to apply a metal material from the viewpoint that the thermal conductivity is high and the strength is high even if the wall thickness is thin. In particular, copper (thermal conductivity at 20 ° C., 370 W / mK), aluminum (thermal conductivity at 20 ° C., 204 W / mK), and tungsten (thermal conductivity at 20 ° C., 198 W / mK) are relatively high in thermal conductivity. preferable. In the present embodiment, a material applicable as the heat radiating body 40 is a material having a thermal conductivity of 10 W / mK or more. Preferably, the material has a thermal conductivity of 50 W / mK or more, more preferably 200 W / mK or more. The thermal conductivity described here is measured by the laser flash method.

  More preferably, the surface of the radiator 40 is anodized (anodized). In order to improve the heat dissipation to the outside air, it is particularly preferable that the surface of the heat radiating body 40 be treated with black alumite.

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

  As the resin or rubber for coating as described above, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, nylon, polyetheretherketone (PEEK: trademark of Victorex), polytetrafluoroethylene (PTFE), tetrafluoroethylene -Resin such as perfluoroalkyl vinyl ether copolymer (PFA), polyvinyl chloride, polyimide, silicone resin, rubber such as ethylene / propylene rubber (EPDM), fluorine rubber, etc. can be used. Since these resins and rubbers have a lower thermal conductivity than metal materials, it is desirable to make the resin or rubber to be coated as thin as possible.

  In the example shown in FIG. 2, in order to separate the cover plate 21 and the heat radiating body 40, the surface 21 </ b> A of the cover plate 21 (the surface opposite to the surface in contact with the plate-like body 20) 21 </ b> A and the back surface 40 </ b> A of the heat radiating body 40. A spacer 50 is disposed between the two. Such a spacer 50 is arranged outside the region where the opening 21H of the cover plate 21 is formed or the region where the through hole 40 of the heat radiating body 40 is formed. The spacer 50 is a rectangular frame-shaped plate formed of an insulator such as polytetrafluoroethylene (PTFE).

  Thereby, an air layer 51 is formed between the cover plate 21 and the radiator 40. The thickness of the air layer 51 in the Z direction, that is, the distance between the surface 21A of the cover plate 21 and the back surface 40A of the heat radiating body 40 is substantially the same in any place in the XY plane in the drawing. It is.

  In order to form such an air layer 51, the spacer 50 may be omitted. For example, the radiator 40 is a part of the casing of the fuel cell 1 or is supported by the casing. Or when the heat radiating body 40 is supported by an electronic device on which the fuel cell 1 is mounted, the air layer 51 can be formed between the cover plate 21 and the heat radiating body 40 without the spacer 50 interposed therebetween. is there.

  In the fuel cell 1 having such a configuration, heat conduction from the cover plate 21 to the heat radiating body 40 is mainly performed by convection of a gas such as radiation or air rather than direct heat transfer at a portion where both are in contact. . According to the present embodiment, the cover plate 21 and the radiator 40 are in close contact with each other and conduct heat by direct heat transfer under conditions in which heat radiation is difficult to be performed, such as when the temperature of the outside air is high or when the wind speed is low. Almost the same heat dissipation. Therefore, by providing the heat radiating body 40, the heat radiation from the fuel cell main body 0 is promoted, the heat radiating amount from the heat radiating body 40 to the outside air is increased, and the fuel corresponding to the amount of heat is supplied. Will improve.

  On the other hand, under conditions where heat is easily radiated such as when the temperature of the outside air is low or when the wind speed is high, the amount of heat released from the radiator 40 to the outside air increases, but the amount of heat conduction from the cover plate 21 to the radiator 40 is increased. Does not increase as much as the amount of heat released from the radiator 40 to the outside air. For this reason, although the surface temperature of the heat radiating body 40 is lowered, it is possible to prevent the heat radiation amount from the fuel cell main body 0 from being excessive, and the fuel cell of the fuel cell accompanying an increase in crossover caused by an excessive increase in the fuel supply amount, etc. It is possible to suppress a decrease in output.

  When the difference between the surface temperature of the cover plate 21 and the surface temperature of the radiator 40 when the difference between the surface temperature of the cover plate 21 and the outside air temperature is A (° C.) is B (° C.). In addition, it is desirable that 0.05 <B / A <0.3. That is, when B / A ≦ 0.05, it indicates that the heat conduction from the cover plate 21 to the heat radiating body 40 is performed to the same extent as the direct heat transfer, and under the condition that the heat is easily radiated. Then, it becomes difficult to suppress a decrease in the output of the fuel cell caused by an excessive increase in the fuel supply amount. Further, when B / A ≧ 0.3, it indicates that the heat conduction from the cover plate 21 to the heat radiating body 40 is not performed so much, and the fuel generated by the decrease in the heat radiation amount under the condition that the heat radiation is difficult to be performed. It becomes difficult to suppress a decrease in battery output.

  Furthermore, when the distance between the surface 21A of the cover plate 21 and the outer surface 40B of the radiator 40 is C (mm), it is desirable that B / C> 2 (° C./mm). At least a part of the water vapor generated by the reaction in the cathode catalyst layer 14 passes through the opening 21 provided in the cover plate 21 and reaches the through hole 40H provided in the radiator 40, but B / C> 2 ( (° C./mm) indicates that a large temperature gradient is generated between the cover plate 21 and the radiator 40, and the gradient of the water vapor partial pressure between the cover plate 21 and the radiator 40 also increases. The amount of water vapor diffused to the outside air through the through hole 40H provided in the heat radiating body 40 is reduced. That is, the amount of water contained in the membrane electrode assembly 2 increases, and the water contained in the membrane electrode assembly 2 functions to suppress an increase in crossover, thereby reducing the output of the fuel cell main body 0. It becomes possible to suppress.

  As described above, according to the present embodiment, a high output can be stably obtained.

  Next, variations of the fuel cell 1 that can be employed in the present embodiment will be described. Note that the same components as those in the example shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 3 is a schematic cross-sectional view of a fuel cell 1 including a fuel cell main body 0 according to another embodiment.

  In the example shown here, compared with the example shown in FIG. 2, in order to separate the cover plate 21 and the radiator 40 from each other, a heat insulating body 60 having air permeability is provided between the cover plate 21 and the radiator 40. It is different in the arrangement. The heat insulator 60 is in contact with the front surface 21 </ b> A of the cover plate 21 and is also in contact with the back surface 40 </ b> A of the heat radiator 40. Such a heat insulator 60 overlaps the opening 21H of the cover plate 21 and the through hole 40 of the heat radiating body 40. However, since it has air permeability, the outside air necessary for the power generation reaction to the fuel cell main body 0 is obtained. (Especially oxygen) uptake is not inhibited.

  The heat insulator 60 is formed of an insulator such as a porous polyethylene film. Further, the thickness of the heat insulator 60 along the Z direction is substantially the same at any location in the XY plane in the drawing. In the present embodiment, a material applicable as the heat insulator 60 is a material having a thermal conductivity of 2 W / mK or less. More preferably, the material has a thermal conductivity of 0.5 W / mK or less.

  In the example shown in FIG. 3, the same effect as the example shown in FIG. 2 can be obtained.

  In the present embodiment, the distance between the surface 21A of the cover plate 21 and the back surface 40A of the heat radiating body 40 is preferably 0.1 mm or more and 3.0 mm or less. It is difficult to form a fixed interval of less than 0.1 mm between the cover plate 21 and the heat radiating body 40, and if the variation of the interval occurs, the variation of the heat dissipation is generated, which is not desirable. When the distance between the cover plate 21 and the radiator 40 exceeds 3.0 mm, the thermal conductivity from the fuel cell main body 0 to the radiator 40 is lowered, resulting in variation in heat dissipation, which is not desirable.

<Performance evaluation>
Example 1
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 (55.5 mm × 8.7 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 carrying the cathode catalyst particles (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 carrying the cathode catalyst particles. 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. , Manufactured by DuPont), the four anode gas diffusion layers 12 and the four cathode gas diffusion layers 15 are arranged side by side so that the longitudinal directions thereof 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. Further, 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. The anode current collector 18A has an opening at a position corresponding to the fuel discharge port 33 of the fuel distribution plate 31. The cathode current collector 18C has an opening at a position corresponding to the opening 21H of the cover plate 21.

  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, as a plate-like body 20, the thickness is 0.75 mm, and the air permeability is 3.0 seconds / 100 cm ³ (according to the measurement method specified in JIS P 8117: 2009). Yes, 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 formed into a rectangle having a length of 59.5 mm and a width of 42.4 mm. Cut and laminated. 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 64.5 mm × 44.5 mm and a thickness of 0.3 mm was laminated as the cover plate 21. The cover plate 21 is uniformly formed with 64 rectangular openings 21H of 5.6 mm × 2.8 mm.

  In this way, the fuel cell main body 0 was formed.

  As the radiator 40, a rectangular aluminum plate having a thickness of 0.5 mm and an outer shape of 100 mm × 56 mm was applied, and the cross section was bent so as to have the shape shown in FIG. The radiator 40 has 64 through holes 40H having the same shape and the same size as the opening 21 formed in the cover plate 21. Such a heat radiating body 40 is disposed such that the through hole 40H is located immediately above the opening 21.

  Between the cover plate 21 and the radiator 40, a polytetrafluoroethylene (PTFE) plate having a thickness of 0.5 mm and having a rectangular frame shape is sandwiched as a spacer 50. It fixed so that a space | interval might be set to 0.5 mm.

  As for the fuel cell 1 formed in this way, as shown in FIG. 2, the thermocouple TM1 for measuring the temperature of the surface 21A at the center of the cover plate 21 and the temperature of the outer surface 40B at the center of the radiator 40 A thermocouple TM2 for measuring the temperature was attached, and the temperature values measured by the thermocouple TM1 and the thermocouple TM2 were recorded by a data logger.

(Example 2)
The same as Example 1 except that the thickness of the spacer 50 arranged between the cover plate 21 and the radiator 40 is 0.1 mm and the distance between the cover plate 21 and the radiator 40 is 0.1 mm. .

(Example 3)
A porous polyethylene film having a thickness of 0.5 mm and a porosity of 26% is inserted as a heat insulator 60 between the cover plate 21 and the heat radiator 40, and the cover plate 21, the heat insulator 60, and the heat insulator 60 are inserted. And the heat radiating body 40 are the same as in the first embodiment except that they are in close contact with each other.

(Comparative Example 1)
The fuel cell 1 described in the first embodiment is the same as the first embodiment except that the radiator 40 is not provided.

(Comparative Example 2)
The fuel cell 1 described in the first embodiment is the same as the first embodiment except that the spacer 50 is not inserted and the radiator 40 is brought into close contact with the cover plate 21.

(Comparative Example 3)
In the fuel cell 1 described in the first embodiment, the thickness of the spacer 50 inserted between the cover plate 21 and the radiator 40 is 3 mm, and the interval between the cover plate 21 and the radiator 40 is 3 mm. The same as in the first embodiment.

  Performance evaluation was performed on each of the fuel cells 1 of Examples 1 to 3 and Comparative Examples 1 to 3 described above.

  First, pure methanol having a purity of 99.9% by weight was supplied to each fuel cell 1 produced as described above in an environment where the temperature was 25 ° C. and the relative humidity was 50%. Here, the supply amount of pure methanol was controlled so that the temperature measured by the thermocouple TM1 attached to the center surface 21A of the cover plate 21 was constant at 45 ° C.

  Then, 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 in the 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 each of the examples and comparative examples described here, the areas of the anode catalyst layer 11 and the cathode catalyst layer 14 are equal and completely opposed to each other, so that the area of the power generation unit is equal to the areas of these catalyst layers.

  Here, the fuel cell 1 is transparent so that the wind speed of the wind hitting the fuel cell 1 (measured continuously for 1 minute or more with a hot-wire anemometer and averaged over the measurement time) is 0.02 m / s or less. The surface 21 </ b> A of the cover plate 21 and the outer surface 40 </ b> B of the heat radiating body 40 are respectively covered with a polyethylene sheet cover and when blown by a wind fan with a wind speed of 0.04 m / s. The temperature and the output density of the fuel cell 1 were measured.

  FIG. 4 summarizes the above measurement results. In addition, the result of measuring the output density of the fuel cell 1 is shown as a relative value with the value of the output density when measured in an environment of Comparative Example 1 having a wind speed of 0.02 m / s or less as 100.

  In Example 1, since the temperature of the outer surface 40B of the radiator 40 was 42 ° C. when the wind speed was 0.02 m / s or less, the temperature difference B1 between the cover plate 21 and the radiator 40 was 3 ° C. Yes, B1 / A = 3/20 = 0.15. The distance C between the surface 21A of the cover plate 21 and the outer surface 40B of the heat radiating body 40 is 1.0 mm, which is the sum of the distance 0.5 mm between them and the thickness of the heat radiating body 40 of 0.5 mm. Therefore, the temperature gradient B1 / C = 3 (° C./mm). At this time, the output density of the fuel cell 1 was 107.

  On the other hand, when the wind speed was 0.04 m / s in Example 1, the temperature of the outer surface 40B of the radiator 40 was 40 ° C., so the temperature difference B2 between the cover plate 21 and the radiator 40 was 5 ° C. Yes, B2 / A = 0.25, and B2 / C = 5 (° C./mm). The output density of the fuel cell 1 at this time was 125.

  In Example 2, when the fuel cell 1 was generated under the same conditions as in Example 1, the temperature of the outer surface 40B of the radiator 40 when the wind speed was 0.02 m / s or less was 43 ° C. The difference B1 is 2 ° C., and B1 / A = 0.1. Further, the distance C between the surface 21A of the cover plate 21 and the outer surface 40B of the heat radiating body 40 is 0.6 mm, which is obtained by adding an interval of 0.1 mm between the two and a thickness of the heat radiating body 40 of 0.5 mm. Therefore, the temperature gradient B1 / C = 3.33 (° C./mm). The output density of the fuel cell 1 at this time was 108.

  On the other hand, in Example 2, when the wind speed was 0.04 m / s, the temperature of the outer surface 40B of the radiator 40 was 41 ° C. Therefore, the temperature difference B2 between the cover plate 21 and the radiator 40 was 4 ° C. Yes, B2 / A = 0.2 and B2 / C = 6.67 (° C./mm). The output density of the fuel cell 1 at this time was 123.

  In Example 3, when the fuel cell 1 was generated under the same conditions as in Example 1, the temperature of the outer surface 40B of the radiator 40 when the wind speed was 0.02 m / s or less was 42.5 ° C. The temperature difference B1 is 2.5 ° C., B1 / A = 0.125, and B1 / C = 2.5 (° C./mm). The output density of the fuel cell 1 at this time was 106.

  On the other hand, in Example 3, when the wind speed was 0.04 m / s, the temperature of the outer surface 40B of the radiator 40 was 41.5 ° C. Therefore, the temperature difference B2 between the cover plate 21 and the radiator 40 was 3 0.5 ° C., B2 / A = 0.175, and B2 / C = 3.5 (° C./mm). The output density of the fuel cell 1 at this time was 122.

  On the other hand, in the fuel cell 1 of Comparative Example 1, since the radiator 40 is not present, the temperature difference B can be regarded as 0 regardless of the wind speed, and B / A = 0. However, since the distance C between the surface 21A of the cover plate 21 and the outer surface of the radiator 40 is also regarded as 0, the temperature gradient B / C cannot be calculated. The power density at a wind speed of 0.02 m / s or less is 100, and the power density at a wind speed of 0.04 m / s is 113.

  In Comparative Example 2, when the fuel cell 1 was generated under the same conditions as in Example 1, the temperature of the outer surface 40B of the radiator 40 when the wind speed was 0.02 m / s or less was 44.5 ° C. The temperature difference B1 is 0.5 ° C. and B1 / A = 0.025. Further, since the distance C between the surface 21A of the cover plate 21 and the outer surface 40B of the radiator 40 is equal to the thickness of the radiator 40, the temperature gradient B1 / C = 1 (° C./mm). It is. At this time, the output density of the fuel cell 1 was 110.

  On the other hand, in Comparative Example 2, when the wind speed was 0.04 m / s, the temperature of the outer surface 40B of the radiator 40 was 44 ° C. Therefore, the temperature difference B2 between the cover plate 21 and the radiator 40 was 1 ° C. Yes, B2 / A = 0.05 and B2 / C = 2 (° C./mm). At this time, the output density of the fuel cell 1 was 105.

  In Comparative Example 3, when the fuel cell 1 was generated under the same conditions as in Example 1, the temperature of the outer surface 40B of the radiator 40 when the wind speed was 0.02 m / s or less was 38 ° C. The difference B1 is 7 ° C., and B1 / A = 0.35. The distance C between the surface 21A of the cover plate 21 and the outer surface 40B of the heat radiating body 40 is 3.5 mm, which is the sum of the distance 3 mm between them and the thickness of the heat radiating body 40 of 0.5 mm. Therefore, the temperature gradient B1 / C = 2 (° C./mm). The output density of the fuel cell 1 at this time was 101.

  On the other hand, in Comparative Example 3, when the wind speed was 0.04 m / s, the temperature of the outer surface 40B of the radiator 40 was 34 ° C. Therefore, the temperature difference B2 between the cover plate 21 and the radiator 40 was 11 ° C. B2 / A = 0.55 and B2 / C = 3.14 (° C./mm). At this time, the output density of the fuel cell 1 was 111.

  From the results shown in FIG. 4, the fuel cells of Examples 1 to 3 satisfying 0.05 <B / A <0.3 and satisfying B / C> 2 (° C./mm) have a wind speed of 0.02 m. It can be seen that a high output density can be obtained under either condition, whether it is less than / s or less, and even if the wind speed is 0.04 m / s.

  In Comparative Example 1 in which the radiator 40 is not provided and in Comparative Example 3 in which a large space is provided between the fuel cell body 0 and the radiator 40, the wind speed is 0.02 m / s or less, and the wind speed is 0.04 m. In either case of / s, the output density is lower than in Examples 1-3. This is because the absolute amount of heat that can be dissipated from the fuel cell is small, and therefore the temperature at the center of the cover plate is maintained at 45 ° C. even with a small amount of fuel supply, so that only a power generation reaction corresponding to the supply amount is performed. .

  On the other hand, in Comparative Example 2 in which the fuel cell and the radiator 40 are in close contact with each other, the output density when the wind speed is 0.02 m / s or less is higher than those in Examples 1 to 3 and Comparative Examples 1 and 3. . However, the output density when the wind speed is 0.04 m / s is lower than those of Examples 1 to 3 and Comparative Examples 1 and 3. This is because the fuel cell main body 0 and the heat radiating body 40 are in close contact with each other, so that heat conduction from the fuel cell main body 0 to the heat radiating body 40 is excessive, and the absolute amount of heat that can be radiated from the fuel cell 1 increases. Because. For this reason, a large amount of fuel is supplied to maintain the temperature at the center of the cover plate at 45 ° C., and a power generation reaction corresponding to the supply amount is performed. However, under the condition where the wind speed is 0.04 m / s, the absolute amount of heat radiated from the fuel cell becomes excessive, so that a large amount of fuel is supplied, so that the anode passes through the electrolyte membrane and crosses over to the cathode. This is probably because the amount of fuel increases.

  As described above, according to this embodiment, it is possible to stably obtain a high output regardless of the ease with which heat is radiated from the fuel cell 1 to the outside air.

  The fuel cell 1 according to the 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 distribution plate 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 the embodiment can exert its performance and effects particularly when methanol having a concentration of 80 wt% or more is used as the liquid fuel. Therefore, the 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 embodiment mentioned above demonstrated the case where this invention was applied to the semi-passive type fuel cell 1, this invention is not restricted to this, It is with respect to an internal vaporization type pure passive type fuel cell. Is applicable.

  The present invention can be applied to various fuel cells using liquid fuel. Further, the specific configuration of the fuel cell, the supply state of the fuel, and the like are not particularly limited, and all the fuel supplied to the membrane electrode assembly is the vapor of the liquid fuel F, all the liquid fuel F, or one The present invention can be applied to various forms such as a vapor of the liquid fuel F supplied in a liquid state. 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 13 ... Anode 16 ... Cathode 17 ... Electrolyte membrane 21 ... Cover plate 21H ... Opening part 3 ... Fuel supply mechanism 40 ... Radiator 40H ... Through-hole 50 ... Spacer 51 ... Air layer 60 ... Insulation

Claims (6)

A membrane electrode assembly in which an electrolyte membrane is sandwiched between an anode and a cathode, a fuel supply mechanism that is disposed on the anode side of the membrane electrode assembly and supplies fuel toward the anode, and a plurality of openings are formed and A fuel cell body having a cover plate that is disposed on the cathode side of the membrane electrode assembly and holds the membrane electrode assembly between the fuel electrode supply mechanism and the fuel supply mechanism;
A plurality of through-holes, covering at least part of the cathode side of the fuel cell main body and spaced from the cover plate; and
A fuel cell comprising:   Furthermore, a heat-insulating body having air permeability disposed between the cover plate and the radiator, or a spacer for forming an air layer between the cover plate and the radiator is provided. The fuel cell according to claim 1.   2. The fuel cell according to claim 1, wherein an interval between the cover plate and the radiator is 0.1 mm or more and 3.0 mm or less.   The fuel cell according to claim 1, wherein the surface of the heat dissipating body is black anodized.   When the temperature difference between the cover plate and the radiator is B (° C.) when the difference between the surface temperature of the cover plate and the outside air temperature is A (° C.), 0.05 <B / The fuel cell according to claim 1, wherein A <0.3.   When the temperature difference between the cover plate and the radiator is B (° C.), and the distance between the cover plate surface and the outer surface of the radiator is C (mm), B / C The fuel cell according to claim 1, wherein> 2 (° C./mm).

Images