JP2009094062A - Fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery properly carrying out heat management of heat dissipation and heat insulation, etc., and maintaining a stable output. <P>SOLUTION: The fuel battery 1 is provided with: a fuel battery cell 10 with an anode (fuel electrode) 13, a cathode (air electrode) 16, and an electrolyte film 17 held therebetween; a fuel supplying mechanism 40 arranged on the anode (fuel electrode) side of the same fuel battery cell 10 for supplying the fuel to the anode (fuel electrode) 13; and heat accumulating members 60 and 80 for accumulating the heat generated in the fuel battery cell 10 as latent heat. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell using a liquid fuel that can be arranged in a plane effective for the operation of a portable device, for example.

  In recent years, advances in electronic technology have led to downsizing, higher performance, and portability of electronic devices. In portable electronic devices, there is an increasing demand for higher energy density of batteries used. For this reason, there is a demand for a secondary battery having a high capacity while being lightweight and small.

  In response to the demand for such secondary batteries, for example, lithium ion secondary batteries have been developed. In addition, the operation time of portable electronic devices tends to increase further, and in lithium ion secondary batteries, the improvement in energy density is almost limited from the viewpoints of materials and structure, which is further demanded. It is becoming impossible to respond.

  Under such circumstances, small fuel cells are attracting attention instead of lithium ion secondary batteries. In particular, direct methanol fuel cells (DMFC) using methanol as fuel require more difficult handling of hydrogen gas and devices that produce hydrogen by reforming organic fuel, compared to fuel cells using hydrogen gas. It is excellent in miniaturization.

  In DMFC, methanol is oxidatively decomposed at the fuel electrode to generate carbon dioxide, protons and electrons. On the other hand, in the air electrode, water is generated by oxygen obtained from air, protons supplied from the fuel electrode through the electrolyte membrane, and electrons supplied from the fuel electrode through an external circuit. In addition, power is supplied by electrons passing through the external circuit.

  In the DMFC, in order to advance power generation with such a configuration, a pump for supplying methanol and a blower for feeding air are provided as auxiliary devices, and a DMFC having a complicated form as a system has been developed. Therefore, it is difficult to reduce the size of the DMFC having this structure.

On the other hand, instead of supplying methanol with a pump, a membrane for passing methanol molecules is provided between the methanol storage chamber and the power generation element, and instead of allowing methanol to permeate, the methanol storage chamber is brought close to the vicinity of the power generation element. As a result, miniaturization was promoted. For intake of air, a small DMFC was constructed by installing an intake port directly attached to the power generation element without using a blower (see, for example, Patent Document 1). However, it is difficult for such a small DMFC to send a certain amount of methanol to the power generation element when it is affected by external environmental factors such as temperature instead of the mechanism being simplified. For this reason, it has been difficult to achieve stable and high output. Therefore, in order to control the supply amount of methanol, a technique is disclosed in which a porous body is installed between the fuel storage chamber portion and the negative electrode to reduce the supply amount of methanol (see, for example, Patent Document 2). .
WO2005 / 112172 publication JP 2004-171844 A

  However, in the above-described conventional DMFC, a membrane electrode assembly (MEA) generates heat during power generation due to an exothermic reaction on the cathode (air electrode) side, and the temperature of the entire fuel cell rises. The user who possesses the sensation sometimes feels hot and feels uncomfortable. Furthermore, when the temperature of the entire fuel cell rises to 50 to 60 ° C. or higher, the user may not be able to hold it or may be burned. On the other hand, since the power generation reaction at the anode (fuel electrode) is an endothermic reaction, it is desirable to suppress the release of heat to the outside by maintaining the temperature.

  Thus, in a fuel cell that requires heat dissipation in one part and heat retention is desired in the other part, the shape of the fuel cell is reduced in size for mounting on a portable device, and if the thickness is reduced, it is difficult to control the temperature of the fuel cell itself. It becomes. Further, it is desirable that heat is uniformly dissipated at a site where heat dissipation is required, and it is desirable that heat is uniformly maintained at a site where heat insulation is desired.

  Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell capable of accurately managing heat such as heat dissipation and heat retention and maintaining stable output. And

  According to one aspect of the present invention, a membrane electrode assembly having a fuel electrode, an air electrode, and an electrolyte membrane sandwiched between the fuel electrode and the air electrode, and the fuel electrode side of the membrane electrode assembly Provided with a fuel supply mechanism for supplying fuel to the fuel electrode, and a heat storage member for storing heat generated in the membrane electrode assembly as latent heat. .

  According to the fuel cell of the present invention, heat management such as heat dissipation and heat retention can be accurately performed, and a stable output can be maintained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a configuration of a fuel cell 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the fuel cell 1 when the pump 90 is provided in the fuel cell according to the embodiment of the present invention.

  As shown in FIG. 1, the fuel cell 1 includes a fuel cell 10 constituting an electromotive unit, and anode conductivity provided on the anode (fuel electrode) side and the cathode (air electrode) side of the fuel cell 10. A layer 18, a cathode conductive layer 19, a fuel distribution layer 30 having a plurality of openings 31 provided to face the anode conductive layer 18, and a side of the fuel distribution layer 30 different from the fuel cell 10 side. The fuel supply mechanism 40 that is disposed and supplies the liquid fuel F to the fuel distribution layer 30, the moisturizing layer 50 stacked on the cathode conductive layer 19, the heat storage member 60 stacked on the moisturizing layer 50, and the heat storage member 60 And a surface cover 70 having a plurality of air inlets 71 stacked on each other. Further, the fuel cell 1 includes a heat storage member 80 so as to cover the periphery of the fuel supply unit main body 42 constituting the fuel supply mechanism 40.

  Here, in the fuel cell 1 shown in FIG. 1, an example in which the heat storage member 60 is disposed between the moisture retention layer 50 and the surface cover 70 is shown, but the configuration is not limited to this, and the cathode (air electrode It suffices that the heat generated on the side is arranged so as to be able to store heat. For example, the heat storage member 60 may be laminated on the surface cover 70. The heat storage member 60 is configured to allow air supplied to the cathode (air electrode) 16 and water (water vapor) generated at the cathode (air electrode) 16 to pass therethrough. Further, in the fuel cell 1 shown in FIG. 1, a configuration in which the heat storage member 60 and the heat storage member 80 are provided on the cathode (air electrode) side and the anode (fuel electrode) side, respectively, is shown. It is good also as a structure provided only with either one.

  The fuel cell 10 is a so-called membrane electrode assembly (MEA), and includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode catalyst layer 14, and a cathode gas diffusion. A cathode (air electrode) 16 having a layer 15 and an electrolyte membrane 17 having proton (hydrogen ion) conductivity 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 a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, and an alloy containing the platinum group element. As the anode catalyst layer 11, for example, Pt—Ru, Pt—Mo, or the like having strong resistance to methanol, carbon monoxide, or the like is preferably used. As the cathode catalyst layer 14, for example, Pt, Pt—Ni, Pt—Co or the like is preferably used. 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 support such as a carbon material or an unsupported catalyst.

  Examples of proton conductive materials constituting the electrolyte membrane 17 include organic materials such as fluorine resins such as perfluorosulfonic acid polymers having sulfonic acid groups, hydrocarbon resins having sulfonic acid groups, or tungstic acid. And inorganic materials such as phosphotungstic acid. Specifically, the electrolyte membrane 17 includes Nafion (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass Co., Ltd.), Aciplex (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.), and the like. The proton-conducting electrolyte membrane 17 is not limited to these. For example, a copolymer membrane of a trifluorostyrene derivative, a polybenzimidazole membrane impregnated with phosphoric acid, an aromatic polyether ketone sulfonic acid membrane, Alternatively, it can be composed of an electrolyte membrane capable of transporting protons such as aliphatic hydrocarbon resin soot.

  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 also serves as a current collector for 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 also serves as a current collector for the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are porous bodies or meshes made of a porous carbonaceous material such as carbon paper, carbon cloth, or carbon silk, or a metal material such as titanium, titanium alloy, stainless steel, or gold. Etc.

  The anode conductive layer 18 laminated on the surface of the anode gas diffusion layer 12 and the cathode conductive layer 19 laminated on the surface of the cathode gas diffusion layer 15 are, for example, conductive having excellent electrical characteristics and chemical stability such as Au. It is composed of a mesh made of a metal material, a porous film, or the like. Among these, the anode conductive layer 18 and the cathode conductive layer 19 are preferably formed of a thin film having a plurality of openings opened corresponding to the fuel cell 10, and the fuel cell is formed through the openings. The fuel from the opening 31 of the fuel distribution layer 30 provided facing the cell 10 is guided to the fuel cell 10. The anode conductive layer 18 and the cathode conductive layer 19 are configured so that fuel and oxidant do not leak from their peripheral edges. Also, rubber O-rings 20 are interposed between the electrolyte membrane 17 and the anode conductive layer 18 and the cathode conductive layer 19, respectively, thereby preventing fuel leakage and oxidant leakage from the fuel cell 10. is doing. Here, the fuel cell 2 including the anode conductive layer 18 and the cathode conductive layer 19 is shown, but the anode gas diffusion layer 12 and the anode conductive layer 18 and the cathode conductive layer 19 are not provided as described above. The cathode gas diffusion layer 15 may function as a diffusion layer and may function as a conductive layer.

  The moisturizing layer 50 is impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 14. The moisturizing layer 50 is composed of a flat plate made of, for example, a polyethylene porous film.

  The heat storage members 60 and 80 are latent heat storage members that store heat as latent heat, and repeat gelation and liquefaction with the phase change temperature as a boundary. Since this latent heat storage member has the effect | action which keeps temperature uniform, it is a preferable material also from a viewpoint of managing temperature. For example, as in the fuel cell 1 shown in FIG. 1, between the moisturizing layer 50 on the cathode (air electrode) side and the surface cover 70, and around the fuel supply body 42 on the anode (fuel electrode) side. When the heat storage member 60 and the heat storage member 80 are provided, the phase change temperatures in the heat storage members 60 and 80 may be different, and the cooling portion and the heat retaining portion may be separately temperature controlled. Here, the cathode (air electrode) side where the heat storage member 60 is installed means the outside of the cathode (air electrode) 16 constituting the fuel cell 10, that is, the surface cover 70 side, and the heat storage member 80 is installed. The anode (fuel electrode) side means the outside of the anode (fuel electrode) 13 constituting the fuel cell 10, that is, the fuel supply unit main body 42 side. For example, each latent heat storage member is set so that the phase change temperature in the heat storage member 60 provided on the cathode (air electrode) side is lower than the phase change temperature in the heat storage member 80 provided on the anode (fuel electrode) side. May be. With this setting, the reaction at the cathode (air electrode) 16 that is an exothermic reaction is promoted by the heat storage member 60 absorbing heat, and the reaction at the anode (fuel electrode) 13 that is an endothermic reaction is heat storage. The member 80 is promoted by the heat kept warm. The heat generated in the cathode (air electrode) 16 is stored in the heat storage member 60, and the anode (via a fixing member for fixing the fuel cell 10, the battery case, and the fuel cell in a stacked state). It is transmitted to the heat storage member 80 of the fuel electrode 13.

  As shown in FIG. 1, the position where the heat storage member is provided is not limited to between the moisturizing layer 50 and the surface cover 70 and around the fuel supply unit main body 42, and the constituent members and parts of the fuel cell 1 It can be changed appropriately depending on the function. For example, the heat storage member 80 may be provided on the anode (fuel electrode) side, between the anode conductive layer 18 and the fuel distribution layer 30, or between the fuel distribution layer 30 and the fuel supply unit main body 42, or the like. For example, when the fuel cell 1 is fixed to a housing such as a battery case, the heat storage member 60 may be laminated on the front cover 70 as described above. Thereby, since the heat storage member 60 absorbs the heat generated on the cathode (air electrode) side, it is possible to prevent the heat generated on the cathode (air electrode) side from being directly transmitted to the casing. Further, the temperature rises uniformly in the casing of the part that contacts the heat storage member 60. In addition, the fuel cell 1 is less susceptible to temperature changes in the external environment. When the heat storage member 60 is disposed on the surface cover 70, the heat storage member 60 may be disposed over the entire surface of the surface cover 70 even if the heat storage member 60 is disposed over the entire surface of the surface cover 70. It may be arranged in a stacked manner only.

  Further, the phase change temperatures in the plural heat storage members can be appropriately changed depending on the constituent members and component functions of the fuel cell 1. Further, as described above, when the heat storage member 60 is disposed, for example, between the moisturizing layer 50 on the cathode (air electrode) side and the surface cover 70 or over the entire surface of the surface cover 70, The heat storage member 60 is configured to allow air supplied to the cathode (air electrode) 16 and water (water vapor) generated by the cathode (air electrode) 16 to pass therethrough. Specifically, for example, a through-hole corresponding to the air introduction port 71 of the surface cover 70 is formed in the heat storage member 60. In addition, air and water (water vapor) can pass through a configuration in which a plurality of heat storage members are arranged at intervals.

  Specifically, the heat storage members 60 and 80 are, for example, an inorganic solution made of an aqueous solution or hydrate of sodium acetate, calcium chloride, sodium carbonate, potassium hydrogen carbonate, potassium chloride, ammonium chloride, sodium chloride, or a mixture thereof. Consists of salts, hydrates and aqueous solutions. Further, the heat storage members 60 and 80 may be made of an organic substance, and specifically, are made of a normal paraffin such as pentadecane, hexadecane, or heptadecane, an emulsion thereof, or a polymer material such as polyethylene glycol. In addition, the heat storage members 60 and 80 are materials in which these materials are microencapsulated, members and powders formed by dispersing the microcapsules in a resin, paints in which these materials are mixed with other resins in a paste, and the like It may be constituted by. Furthermore, the heat storage members 60 and 80 may be configured by filling the above-described material into a bag-shaped pack.

  The front cover 70 adjusts the amount of air taken in, and the adjustment is performed by changing the number and size of the air inlets 71. For example, the front cover 70 can be made of a metal such as SUS304, but is not limited thereto.

  The fuel supply mechanism 40 mainly includes a fuel storage part 41, a fuel supply part main body 42, and a flow path 44.

  The fuel storage unit 41 stores liquid fuel F corresponding to the fuel battery cell 10. 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. Examples of the liquid fuel F include, for example, ethanol aqueous solution, pure ethanol, propanol aqueous solution, formic acid aqueous solution, sodium formate aqueous solution, acetic acid aqueous solution, ethylene glycol aqueous solution, organic aqueous solution containing hydrogen such as dimethyl ether, sodium borohydride aqueous solution, borohydride A potassium aqueous solution, a lithium hydride aqueous solution, or the like may be used. Among these liquid fuels, the aqueous methanol solution has carbon number 1 and carbon dioxide is generated during the reaction, and can generate electricity at a low temperature, and can be produced relatively easily from industrial waste. Can do. Therefore, it is preferable to use a methanol aqueous solution as the liquid fuel. In any case, liquid fuel corresponding to the fuel cell 10 is stored in the fuel storage portion 41.

The liquid fuel F can be used at various concentrations in the range of 100 wt% to several wt%, but in the case of an aqueous methanol solution, the fuel concentration may be 60 wt% or more. desirable. The reason is that power can be generated with a smaller volume of fuel.

  The fuel supply unit main body 42 includes a fuel supply unit 43 including recesses for uniformly dispersing the liquid fuel F in order to uniformly supply the supplied liquid fuel F to the fuel distribution layer 30. The fuel supply unit 43 is connected to the fuel storage unit 41 via a flow path 44 of the liquid fuel F configured by piping or the like. Liquid fuel F is introduced into the fuel supply unit 43 from the fuel storage unit 41 via the flow path 44, and the introduced liquid fuel F and / or vaporized components of the liquid fuel F vaporized are the fuel distribution layer 30 and The fuel cell 10 is supplied via the anode conductive layer 18. The flow path 44 is not limited to piping independent of the fuel supply unit 43 and the fuel storage unit 41. For example, when the fuel supply unit 43 and the fuel storage unit 41 are stacked and integrated, a flow path of the liquid fuel F that connects them may be used. That is, the fuel supply part 43 should just be connected with the fuel accommodating part 41 via the flow path.

  The liquid fuel F stored in the fuel storage part 41 can be dropped and sent to the fuel supply part 43 via the flow path 44 using gravity. Alternatively, the flow path 44 may be filled with a porous body or the like, and the liquid fuel F stored in the fuel storage unit 41 may be fed to the fuel supply unit 43 by capillary action. Further, as shown in FIG. 2, the liquid fuel F stored in the fuel storage unit 41 may be forcibly sent to the fuel supply unit 43 by interposing a pump 90 in a part of the flow path 44. .

  The pump 90 functions as a supply pump that simply supplies the liquid fuel F from the fuel storage unit 41 to the fuel supply unit 43, and is a circulation pump that circulates excess liquid fuel F supplied to the fuel cells 10. It does not have the function as. The fuel cell 1 provided with the pump 90 is called a so-called semi-passive type, which does not circulate fuel, and therefore has a different configuration from the conventional active method and a different configuration from a pure passive method such as a conventional internal vaporization type. Applicable to the method. The type of the pump 90 that functions as the fuel supply means is not particularly limited, but from the viewpoint that a small amount of liquid fuel F can be fed with good controllability, and that further reduction in size and weight can be achieved. It is preferable to use a vane pump, an electroosmotic flow pump, a diaphragm pump, 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. When the pump 90 is provided as described above, the pump 90 is electrically connected to control means (not shown), and the supply amount of the liquid fuel F supplied to the fuel supply unit 43 is controlled by the control means. .

  Here, since the main target object of the fuel cell 1 is a small electronic device, it is preferable that the liquid feeding amount of the pump 90 be in the range of 10 μL / min to 1 mL / min. When the amount of liquid delivery exceeds 1 mL / min, the amount of liquid fuel F that is fed at a time becomes too large, and the stop time of the pump 90 that occupies the entire operation period becomes long. For this reason, the fluctuation of the amount of fuel supplied to the fuel battery cell 10 becomes large, and as a result, the fluctuation of the output becomes large. A reservoir for preventing this may be provided on the downstream side of the pump 90. However, even if such a configuration is applied, fluctuations in the fuel supply amount cannot be sufficiently suppressed, and the size of the apparatus is further increased. Etc. will be invited.

  On the other hand, if the amount of liquid delivered by the pump 90 is less than 10 μL / min, there is a risk of insufficient supply capacity when the amount of fuel consumption increases when the apparatus is started up. As a result, the starting characteristics of the fuel cell 1 are deteriorated. From such a point, it is preferable to use a pump 90 having a liquid feeding capacity in the range of 10 μL / min to 1 mL / min. It is more preferable that the liquid feeding amount of the pump 90 be in the range of 10 to 200 μL / min. In order to stably realize such a liquid feeding amount, it is preferable to apply an electroosmotic flow pump or a diaphragm pump to the pump 90.

  The fuel distribution layer 30 is configured by, for example, a flat plate in which a plurality of openings 31 are formed, and is sandwiched between the anode gas diffusion layer 12 and the fuel supply unit 43. The fuel distribution layer 30 is made of a material that does not allow the vaporized component of the liquid fuel F or the liquid fuel F to permeate. Specifically, for example, a polyethylene terephthalate (PET) resin, a polyethylene naphthalate (PEN) resin, or a polyimide resin. Etc. Further, the fuel distribution layer 30 may be constituted by, for example, a gas-liquid separation membrane that separates the vaporized component of the liquid fuel F and the liquid fuel F and permeates the vaporized component to the fuel cell unit 10 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), tetrafluoro An ethylene / perfluoroalkyl vinyl ether copolymer (PFA) or the like) microporous film or the like is used. Here, in the fuel cell 1, the liquid fuel introduced into the fuel supply unit 43 is supplied from the plurality of openings 31 of the fuel distribution layer 30 to the entire surface of the anode (fuel electrode) 13. In this way, the fuel distribution layer 30 can make the amount of fuel supplied to the anode (fuel electrode) 13 uniform.

  Next, the operation of the fuel cell 1 described above will be described.

The liquid fuel F supplied to the fuel supply unit 43 from the fuel storage unit 41 via the flow path 44 remains as a liquid fuel, or in a state where liquid fuel and vaporized fuel vaporized from the liquid fuel are mixed. And supplied to the anode gas diffusion layer 12 of the fuel cell 10 through the anode conductive layer 18. The fuel supplied to the anode gas diffusion layer 12 is diffused in the anode gas diffusion layer 12 and supplied to the anode catalyst layer 11. When methanol fuel is used as the liquid fuel, an internal reforming reaction of methanol represented by the following formula (1) occurs in the anode catalyst layer 11.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Formula (1)

  When pure methanol is used as the methanol fuel, is methanol reformed by water generated in the cathode catalyst layer 14 or water in the electrolyte membrane 17 and the internal reforming reaction of the above formula (1)? Or other reaction mechanisms that do not require water. Further, by using the heat stored in the heat storage member 80, the internal reforming reaction of methanol of the formula (1) is promoted.

Electrons (e ⁻ ) generated by this reaction are guided to the outside via a current collector, and are operated to a cathode (air electrode) 16 after operating a portable electronic device or the like as so-called electricity. The proton (H ⁺ ) generated by the internal reforming reaction of the formula (1) is guided to the cathode (air electrode) 16 through the electrolyte membrane 17. Air is supplied to the cathode (air electrode) 16 as an oxidant. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode (air electrode) 16 cause a reaction shown in the following equation (2) with oxygen in the air in the cathode catalyst layer 14, and accompanying this power generation reaction Water is produced.
(3/2) O ₂ + 6e ⁻ + 6H ⁺ → 3H ₂ O (2)

  A part of the heat generated by the reaction shown in the formula (2) is stored in the heat storage member 60, and the rapid temperature rise of the fuel cell 1, particularly, the rapid temperature rise on the cathode (air electrode) side is suppressed. Is done.

  Thus, in the fuel cell 1, the internal reforming reaction described above is performed smoothly, and a high output and a stable output can be obtained.

  According to the fuel cell 1 of the embodiment of the present invention described above, for example, the heat storage member 60 is provided on the cathode (air electrode) side, and the heat generated by the reaction at the cathode (air electrode) 16 is used as the heat storage member 60. The heat storage member 80 is provided on the anode (fuel electrode) side, and the heat stored in the heat storage member 80 can be used to promote the reaction. In this way, stable output can be maintained by appropriately managing heat such as heat dissipation and heat retention. Furthermore, the rapid temperature rise of the fuel cell 1 can be suppressed and the safety during use can be improved.

  For example, in a small fuel cell that is assumed to be built in a portable device, it is difficult to mount fins or fans for cooling. On the other hand, when a heater as a heat source is installed, power is supplied to the heater. Decrease in output due to is a problem. However, in the fuel cell 1 according to the present invention, by providing a plurality of heat storage members having different phase change temperatures, heat management can be performed accurately without providing the above-described fins, heaters, and the like, and stable. Output can be maintained.

  Furthermore, in the present invention, at least one of the members constituting the fuel cell 1 can be integrated and the heat storage member can be arranged. That is, on the cathode (air electrode) 16 and the cathode side outside the cathode, the latent heat storage material (for example, the microencapsulated organic heat storage material) constituting the heat storage member is used as the cathode catalyst layer 14 and / or the moisture retention. It can be made to contain in the layer 50, and these layers themselves can be made into the layer (latent heat storage layer) of a thermal storage member. In addition, on the anode (fuel electrode) 13 and the anode side outside the anode, the anode catalyst layer 11 and / or the fuel distribution layer 30 contain the latent heat storage material described above, and these layers themselves are layers of the heat storage member (latent heat). Heat storage layer).

  Next, as an example of the fuel cell 1 in which the heat storage member is integrally arranged as described above, the fuel cell 1 having a configuration in which the cathode catalyst layer 14 and the anode catalyst layer 11 contain a latent heat storage material is selected, and a method for manufacturing the fuel cell 1 is described. It is shown below.

  An anode catalyst obtained by supporting a platinum group element simple substance or a platinum group element alloy on a conductive carrier such as carbon, and the latent heat storage material (for example, microencapsulated normal paraffin) It is mixed with an electrolyte solution, an alcohol such as methanol, ethanol and propanol, and a dispersion medium such as glycerin and ethylene glycol are added to adjust the viscosity to obtain an anode catalyst slurry.

  The anode catalyst slurry thus obtained is applied to a conductive porous substrate such as carbon paper or carbon cloth serving as the anode gas diffusion layer 12 by using a suction filtration method, a spray method, a roll coater method, a bar coater method, or the like. The anode catalyst layer 11 is formed by applying and drying. Thus, the anode 13 is formed by forming the anode catalyst layer 11 on the anode gas diffusion layer 12.

  Also, a cathode catalyst manufactured in the same manner as the anode catalyst and the latent heat storage material (for example, microencapsulated normal paraffin) are mixed with a solution of a proton conductive electrolyte, methanol, ethanol, propanol, etc. The viscosity is adjusted by adding a dispersion medium such as alcohol and glycerin or ethylene glycol to obtain a cathode catalyst slurry.

  Next, the obtained cathode catalyst slurry is subjected to suction filtration, spraying, roll coater, bar coater, etc. on a conductive porous substrate such as carbon paper or carbon cloth that becomes the cathode gas diffusion layer 15. The cathode catalyst layer 14 is formed by coating and drying. Thus, the cathode 16 is formed by forming the cathode catalyst layer 14 on the cathode gas diffusion layer 15.

  Next, a proton conductive electrolyte membrane 17 is sandwiched between the anode catalyst layer 11 of the anode 13 and the cathode catalyst layer 14 of the cathode 16 thus obtained, and then these are thermocompression bonded by a roll or a press. The fuel cell 10 is obtained. Further, an anode conductive layer 18 and a cathode conductive layer 19 are laminated on the fuel cell 10. The fuel distribution layer 30 and the fuel supply mechanism 40 are disposed outside the anode conductive layer 18, and the moisturizing layer 50 and the surface cover 70 are sequentially stacked and integrated on the outside of the cathode conductive layer 19. Can be manufactured.

  Thus, in the configuration in which the heat storage member is arranged as an integral type with other fuel cell constituent members, compared to the configuration in which the heat storage member such as a sheet is separately arranged, no additional process is required during production, Further, there is an advantage that the thickness and volume of the entire fuel cell are not increased.

  Next, it will be described based on Examples 1 to 3 and Comparative Example 1 that the fuel cell according to the present invention has excellent output characteristics and temperature characteristics.

Example 1
The fuel cell used in Example 1 has a configuration in which only the heat storage member 60 is provided in the fuel cell 1 shown in FIG. 2 without providing the heat storage member 80, and therefore will be described with reference to FIG. 2. To do.

  First, a method for producing the fuel battery cell 10 will be described.

  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 (40 mm × 30 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 size, and the anode catalyst layer 11 and the cathode catalyst layer 14 applied to these gas diffusion layers have the same shape and 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. The fuel cell 10 was obtained by performing hot pressing in a state where the anode catalyst layer 11 and the cathode catalyst layer 14 face each other.

  Subsequently, the fuel battery cell 10 was sandwiched between gold foils having a plurality of openings to form an anode conductive layer 18 and a cathode conductive layer 19. A rubber O-ring 20 was sandwiched between the electrolyte membrane 17 and the anode conductive layer 18 and between the electrolyte membrane 17 and the cathode conductive layer 19 for sealing.

Further, as the moisture retaining layer 50, the thickness is 500 μm, the air permeability is 2 seconds / 100 cm ³ (according to the measurement method specified in JIS P-8117), and the moisture permeability is 4000 g / (m ² · 24 h) (JIS L -1099 A-1 polyethylene porous film (by the measurement method specified in A-1) was used.

  On the moisturizing layer 50, a heat storage sheet having a phase change temperature of 40 ° C. and a thickness of 1 mm, in which a microencapsulated organic heat storage material was mixed with a resin, was installed as the heat storage member 60. The heat storage sheet is formed with air inlets (a circular shape having a diameter of 3.6 mm and 35 holes) for taking in air.

  On the heat storage member 60, a stainless steel plate (SUS304) having a thickness of 1 mm in which air inlets 71 (circular with a diameter of 3.6 mm, 35 holes) for air intake are formed is disposed, and the surface cover 70 is arranged. It was.

  The fuel cell 1 was produced using the fuel cell 10 produced as described above. Pure liquid having a purity of 99.9 wt% was used as the liquid fuel F, and pure methanol was supplied to the fuel supply unit 43 by the pump 90. In addition, when the surface temperature of the gold foil serving as the current collector of the cathode (air electrode) 16 is higher than 45 ° C. immediately below the moisturizing layer 50 on the cathode (air electrode) side, the pump 90 is stopped and 45 ° C. or less. Then, the pump 90 was operated.

  The fuel cell 1 was operated so that the output voltage of the fuel cell 1 was constant at 0.3 V under an environment where the temperature was 25 ° C. and the relative humidity was 50%.

Under the above-described conditions, the surface of the gold foil that is the current collector of the cathode (air electrode) 16 immediately below the moisture retention layer 50 on the cathode (air electrode) side, and 20 mm in the long side direction corresponding to the center of the entire electrode, The temporal change in temperature at a position of 15 mm in the short side direction was measured. Furthermore, the temporal change of the output density (mW / cm ² ) of 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.

  FIG. 3 is a surface of a gold foil that serves as a current collector for the cathode (air electrode) 16 immediately under the cathode (air electrode) -side moisturizing layer 50 in Example 1 and Comparative Example 1 described later. It is a figure which shows the measurement result of the time change of the temperature in the position of 20 mm in the long side direction which hits a center part, and the position of 15 mm in a short side direction, and the time change of the output density of the fuel cell.

(Example 2)
In Example 2, in the fuel cell 1 shown in FIG. 2, the fuel cell 1 provided with only the heat storage member 80 without using the heat storage member 60 was used. The fuel cell 1 has the same configuration as that of the fuel cell 1 used in Example 1, except that the heat storage member 60 is not provided and only the heat storage member 80 is provided.

  As shown in FIG. 2, in the fuel cell 1, a heat storage sheet having a phase change temperature of 30 ° C. and a thickness of 1 mm, in which a microencapsulated organic heat storage material is mixed with a resin, It installed so that the circumference | surroundings, ie, a bottom face and a side surface, might be covered. By installing this heat storage sheet, the temperature of the fuel supply unit main body 42 was kept at around 30 ° C.

  The surface of the gold foil that is the current collector of the cathode (air electrode) 16 immediately below the moisturizing layer 50 on the cathode (air electrode) side, 20 mm in the long side direction corresponding to the center of the entire electrode, and in the short side direction The measurement method and measurement conditions for the temporal change in temperature at the position of 15 mm and the temporal change in the output density of the fuel cell 1 are the same as the measurement method and measurement conditions in Example 1.

  FIG. 4 is a surface of a gold foil that serves as a current collector of the cathode (air electrode) 16 immediately below the cathode (air electrode) -side moisturizing layer 50 in Example 2 and Comparative Example 1 described later. It is a figure which shows the measurement result of the time change of the temperature in the position of 20 mm in the long side direction which hits a center part, and the position of 15 mm in a short side direction, and the time change of the output density of the fuel cell.

(Example 3)
In Example 3, the fuel cell 1 having the same configuration as the fuel cell 1 shown in FIG. 2 was used. The fuel cell 1 includes both the heat storage member 60 used in the first embodiment and the heat storage member 80 used in the second embodiment, and other configurations are the same as those of the fuel cell 1 used in the first embodiment. It is.

  Also, a temperature time at a position of 20 mm in the long side direction and 15 mm in the short side direction, which is the surface of the gold foil that is the current collector of the air electrode, directly below the moisture retention layer 50 on the air electrode side. The measurement method and the measurement conditions for the change in time and the change in the output density of the fuel cell 1 over time are the same as the measurement method and the measurement conditions in Example 1.

  FIG. 5 shows the surface of the gold foil that becomes the current collector of the cathode (air electrode) 16 immediately below the moisturizing layer 50 on the cathode (air electrode) side in Example 3 and Comparative Example 1 described later. It is a figure which shows the measurement result of the time change of the temperature in the position of 20 mm in the long side direction which hits a center part, and the position of 15 mm in a short side direction, and the time change of the output density of the fuel cell.

(Comparative Example 1)
The fuel cell 1 used in Comparative Example 1 has the same configuration as the fuel cell 1 used in Example 1, except that the heat storage member 60 in the fuel cell 1 used in Example 1 is not provided.

  The surface of the gold foil that is the current collector of the cathode (air electrode) 16 immediately below the moisturizing layer 50 on the cathode (air electrode) side, 20 mm in the long side direction corresponding to the center of the entire electrode, and in the short side direction The measurement method and measurement conditions for the temporal change in temperature at the position of 15 mm and the temporal change in the output density of the fuel cell 1 are the same as the measurement method and measurement conditions in Example 1.

In addition, it is 20 mm in the long side direction which is the surface of the gold foil used as the electrical power collector of the cathode (air electrode) 16 just under the moisture retention layer 50 by the side of the cathode (air electrode) in the comparative example 1, and corresponds to the center part of the whole electrode, The measurement results of the temporal change in temperature at the position of 15 mm in the short side direction and the temporal change in the output density of the fuel cell 1 are shown in FIGS. 3 to 5 together with the measurement results in the respective embodiments as described above. Yes.

(Summary of Examples 1 to 3 and Comparative Example 1)
As shown in FIG. 3, it is the surface of the gold foil used as the current collector of the cathode (air electrode) 16 immediately below the moisturizing layer 50 on the cathode (air electrode) side in Example 1, and the length corresponding to the center of the entire electrode. The change in temperature at a position of 20 mm in the side direction and 15 mm in the short side direction causes the surface temperature to become dull from around 40 ° C., and then maintained at a uniform temperature of about 46 ° C., and the surface of the cathode (air electrode) 16 is excessive. It was found that it can be prevented from being heated. Further, it was found that the output density, like the surface temperature, was very small and stable output was obtained. On the other hand, compared with the measurement result in Example 1, both the surface temperature of the gold foil, which is the current collector of the cathode (air electrode) 16 in Comparative Example 1, and the output density of the fuel cell 1 fluctuate greatly and lack stability. all right. In particular, at the surface temperature of the gold foil that is the current collector of the cathode (air electrode) 16, the temperature may exceed 55 ° C., and it becomes clear that the surface of the cathode (air electrode) 16 is excessively heated. It was.

  As shown in FIG. 4, the surface of the gold foil that is the current collector of the cathode (air electrode) 16 immediately below the moisturizing layer 50 on the cathode (air electrode) side in Example 2, and corresponds to the central portion of the entire electrode. It was found that the temperature at the position of 20 mm in the side direction and 15 mm in the short side direction can suppress an excessive increase compared to the temperature at the same location in Comparative Example 1. Moreover, it turned out that the fall of the output density which arises with progress of time is smaller in Example 2 than in Comparative Example 1. Therefore, after the measurement, when the fuel cell 1 used in Comparative Example 1 was disassembled, about 10 wt% methanol aqueous solution remained in the fuel supply unit 43. On the other hand, when the fuel cell 1 used in Example 2 was disassembled, almost no liquid remained in the fuel supply unit 43.

  As shown in FIG. 5, the surface of the gold foil that is the current collector of the cathode (air electrode) 16 immediately below the moisture retention layer 50 on the cathode (air electrode) side in Example 3, and the length corresponding to the central portion of the entire electrode. It was found that the temperature at the position of 20 mm in the side direction and 15 mm in the short side direction can suppress an excessive increase compared to the temperature at the same location in Comparative Example 1. Further, it was found that the decrease in output density that occurred with the passage of time was smaller in Example 3 than in Comparative Example 1.

  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, etc. are not particularly limited, and all the fuel supplied to the fuel cell is liquid fuel vapor, all is liquid fuel, or part is liquid. The present invention can be applied to various forms such as liquid fuel vapor supplied in a 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 components shown in the above embodiment, or deleting some components from all the components 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.

1 is a cross-sectional view showing a configuration of a fuel cell system according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the structure of the fuel cell system at the time of providing the pump in the fuel cell of one Embodiment which concerns on this invention. In Example 1 and Comparative Example 1 to be described later, the surface of the gold foil that is the current collector of the cathode (air electrode) immediately below the moisturizing layer on the cathode (air electrode) side, and the long side direction corresponding to the center of the entire electrode The figure which shows the measurement result of the time change of the temperature in the position of 15 mm in a short side direction at 20 mm in FIG. In Example 2 and Comparative Example 1 to be described later, the surface of the gold foil that becomes the current collector of the cathode (air electrode) immediately below the moisturizing layer on the cathode (air electrode) side, and the long side direction corresponding to the center of the entire electrode The figure which shows the measurement result of the time change of the temperature in the position of 15 mm in a short side direction at 20 mm in FIG. In Example 3 and Comparative Example 1 to be described later, the surface of the gold foil that becomes the current collector of the cathode (air electrode) immediately below the moisturizing layer on the cathode (air electrode) side, and the long side direction corresponding to the center of the entire electrode The figure which shows the measurement result of the time change of the temperature in the position of 15 mm in a short side direction at 20 mm in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 10 ... Fuel cell, 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 ... anode conductive layer, 19 ... cathode conductive layer, 20 ... O-ring, 30 ... fuel distribution layer, 31 ... opening, 40 ... fuel supply mechanism, 41 ... fuel storage, 42 ... Fuel supply part main body, 43 ... Fuel supply part, 44 ... Flow path, 50 ... Moisturizing layer, 60, 80 ... Heat storage member, 70 ... Surface cover, 71 ... Air inlet.

Claims (5)

A membrane electrode assembly having a fuel electrode, an air electrode, and an electrolyte membrane sandwiched between the fuel electrode and the air electrode;
A fuel supply mechanism disposed on the fuel electrode side of the membrane electrode assembly for supplying fuel to the fuel electrode;
A fuel cell comprising: a heat storage member for storing heat generated in the membrane electrode assembly as latent heat.   The fuel cell according to claim 1, wherein the heat storage member is disposed on the air electrode side.   The fuel cell according to claim 1, wherein the heat storage member is disposed on a fuel electrode side.   The heat storage member includes an air electrode side heat storage member disposed on the air electrode side and a fuel electrode side heat storage member disposed on the fuel electrode side, and the phase change temperature in the air electrode side heat storage member and the fuel electrode side heat storage The fuel cell according to claim 1, wherein a phase change temperature in the member is different.   The fuel cell according to any one of claims 1 to 4, wherein a fuel concentration in the fuel is 60 wt% or more.

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