JP2010123342A - Fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery capable of retaining a stable output by performing precise thermal control such as heat radiation or heat retention, and also suppressing an abrupt temperature change to achieve a uniform temperature distribution. <P>SOLUTION: The fuel battery 1 includes: a fuel battery cell 10 having an anode (a fuel electrode) 13, a cathode (an air electrode) 16, and an electrolyte membrane 17 pinched by them; a fuel supplying mechanism 40 arranged on an anode (fuel electrode) side of the fuel battery cell 10 for supplying fuel to the anode (fuel electrode) 13; a heat accumulating member 60 which stores heat generated in the fuel cell 10 as latent heat; and a heat transfer member 65 stacked on the heat accumulating member 60 with a thermal conductivity in a plane direction larger than that of the heat accumulating member 60 in a plane direction. The heat transfer member 65 is composed so that a thermal conductivity in the plane direction is larger than that in a thickness direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell using a liquid fuel 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 of energy density is almost limited from the viewpoint 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, a direct methanol fuel cell (DMFC) using methanol as a fuel is more difficult to handle hydrogen gas than a fuel cell using hydrogen gas, and reforms organic fuel to generate hydrogen. There is no need for a device to create, and 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 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 called an active type 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 a 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). .

In addition, a fuel cell is disclosed that includes heat absorption means having a latent heat storage agent that reversibly absorbs heat generated during power generation (see, for example, Patent Document 3).
WO2005 / 112172 publication JP 2004-171844 A JP 2004-186097 A

  However, in the conventional DMFC described above, 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. When it became 50-60 degreeC or more, the user who possessed it felt hot and there was a possibility of obtaining discomfort. For this reason, it is desirable to suppress the temperature rise by promptly dissipating heat. 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.

  In addition, in a fuel cell having a conventional heat absorbing means for absorbing heat generated during power generation, it is difficult to manage heat so that the surface temperature of the fuel cell becomes uniform, for example.

  Accordingly, the present invention has been made to solve the above-described problems, and appropriately manages heat such as heat dissipation and heat retention, and suppresses sudden temperature fluctuations to achieve uniform temperature distribution. Thus, an object of the present invention is to provide a fuel cell capable of maintaining a stable output.

  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 A fuel supply mechanism for supplying fuel to the fuel electrode, a heat storage member that stores heat generated in the membrane electrode assembly as latent heat, and a stack on the heat storage member. There is provided a fuel cell comprising a heat conduction member having a heat conductivity higher than the heat conductivity in the planar direction of the heat storage member.

  According to the fuel cell of the present invention, heat management such as heat dissipation and heat retention is properly performed, and stable output is maintained by suppressing temperature fluctuations and making temperature distribution uniform. be able to.

  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 heat storage member 80 and the heat conduction member 85 are provided around the pump 90 and the fuel supply unit main body 42 in the fuel cell according to the embodiment of the present invention. It is.

  As shown in FIG. 1, the fuel cell 1 is provided on the fuel cell 10 constituting the electromotive unit, and on the anode (fuel electrode) 13 side and the cathode (air electrode) 16 side of the fuel cell 10. The anode conductive layer 18, the cathode conductive layer 19, and the fuel distribution layer 30 having a plurality of openings 31 provided to face the anode conductive layer 18 are different from the fuel cell 10 side of the fuel distribution layer 30. The fuel supply mechanism 40 that is disposed on the side and supplies the liquid fuel F to the fuel distribution layer 30, the moisturizing layer 50 laminated on the cathode conductive layer 19, the heat storage member 60 laminated on the moisturizing layer 50, and the heat storage A heat conducting member 65 laminated on the member 60 and a surface cover 70 having a plurality of air inlets 71 laminated on the heat conducting member 65 are provided.

  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, a porous layer made of a metal material such as gold or nickel (for example, , Mesh, etc.) or a foil, or a composite material obtained by coating a conductive metal material such as stainless steel (SUS) with a good conductive metal such as gold. 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 member 60 stores heat generated in the fuel cell 10 as latent heat. The heat storage member 60 is disposed on the cathode (air electrode) 16 side. The cathode (air electrode) 16 side on which 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. The heat storage member 60 repeats gelation and liquefaction with the phase change temperature as a boundary. The heat storage member that changes its phase by latent heat has a function of keeping the temperature uniform, and is therefore a preferable material from the viewpoint of managing the temperature. By providing the heat storage member 60 in this way, the reaction at the cathode (air electrode) 16 that is an exothermic reaction is promoted by the heat storage member 60 absorbing heat. Further, the heat generated at the cathode (air electrode) 16 is stored in the heat storage member 60.

  Here, the heat storage member 60 is specifically 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 inorganic salts / hydrates and aqueous solutions. Further, the heat storage member 60 may be made of an organic substance, and specifically, a normal paraffin such as pentadecane, hexadecane, and heptadecane, an emulsion thereof, and a polymer material such as polyethylene glycol.

  The heat storage member 60 is composed of a material obtained by microencapsulating the above-described material, a member or powder formed by dispersing the microcapsule in a resin, a paint obtained by mixing these materials with other resin in a paste form, or the like. May be. The resin in which the microcapsules are dispersed is preferably a resin having characteristics such as solvent resistance, water resistance, and elasticity, and specifically includes, for example, a silicone resin. Furthermore, the heat storage member 60 may be configured by filling the above-described material into a bag-shaped pack.

  The phase change temperature of the heat storage member is appropriately set depending on the application to be used and the position where it is arranged. Specific examples of the heat storage member include thermo memory (Mitsubishi Paper Co., Ltd.), Passamo (Tamai Kasei Co., Ltd.), latent heat storage material MHS (Mitsubishi Cable Industries Co., Ltd.), and the like.

  In addition, when examining the phase change temperature of a thermal storage member, the temperature of a thermal storage member can be measured as follows.

  For example, the heat storage member to be measured is arranged in a constant temperature bath at room temperature, and the constant temperature bath is set on the high temperature side (for example, 75 ° C.) in a state where the temperature of the heat storage member can be measured. While the temperature in the thermostatic chamber rises and the temperature of the heat storage member also rises, the temperature of the heat storage member becomes constant at the temperature of the phase change temperature (for example, 50 ° C.), and the temperature in the thermostatic bath rises further. It becomes constant at a set temperature (for example, 75 ° C.). Since the temperature of the heat storage member is kept constant (for example, 50 ° C.) until the phase change of the heat storage member is completed, the temperature kept constant can be confirmed as the phase change temperature of the heat storage member. Moreover, in the sheet-like heat storage member, it can be measured by measuring the temperature of the surface of the heat storage member (on the side opposite to the heater) while winding around the heater and raising the heater temperature. If the phase change temperature is 50 ° C., the temperature of the heat storage member becomes constant at 50 ° C., and only the temperature of the heater rises. When the phase change of the heat storage member ends, the temperature of the surface of the heat storage member also exceeds 50 ° C. and starts to rise. The temperature kept constant can be confirmed as the phase change temperature of the heat storage member.

  The heat conducting member 65 is laminated on the heat storage member 60 so that the heat storage member 60 is on the fuel cell 10 side. The thermal conductivity in the planar direction of the heat conducting member 65 is configured to be higher than the thermal conductivity in the planar direction of the heat storage member 60. Specifically, it is preferable to set the thermal conductivity in the planar direction of the heat conducting member 65 to about 100 to 500 times the thermal conductivity in the planar direction of the heat storage member 60 under the same temperature. This range is preferable because it is necessary to accelerate soaking in the plane direction. Here, the plane direction is a direction perpendicular to the thickness direction of the flat plate-like heat conducting member 65.

  The heat conducting member 65 is configured such that the thermal conductivity in the planar direction is higher than the thermal conductivity in the thickness direction. Specifically, the ratio between the thermal conductivity in the plane direction and the thermal conductivity in the thickness direction (thermal conductivity in the thickness direction / thermal conductivity in the plane direction) is about 1/120 to 1/10. It is preferable. This range is preferable because it is necessary to equalize the plane direction before the heat is dissipated in the thickness direction. A more preferable thermal conductivity ratio (thickness direction thermal conductivity / planar direction thermal conductivity) is 1/120 to 1/40. The heat conducting member 65 is made of, for example, a graphite sheet obtained by processing graphite into a sheet shape. Examples of the graphite sheet include 705AP (thermal conductivity ratio is 1/40) manufactured by Graphtec, SS400 (thermal conductivity ratio is 1/114), and the like. In addition, a graphite sheet will not be specifically limited if the conditions as the above-mentioned heat conductive member 65 are satisfy | filled.

  Here, the thermal conductivity is measured using, for example, a thermal resistance measurement device, a thermal conductivity measurement device, a thermal diffusion measurement device, or the like. For example, the Angstrom method is preferably used for the thermal conductivity in the plane direction, and the steady method is preferably used for the thermal conductivity in the thickness direction.

  Here, in the fuel cell 1 shown in FIG. 1, an example in which the heat storage member 60 and the heat conduction member 65 are arranged between the moisture retention layer 50 and the surface cover 70 is shown, but the configuration is not limited to this. The heat generated on the cathode (air electrode) 16 side may be arranged so as to be able to store heat. For example, the heat storage member 60 may be laminated on the surface cover 70. In this case, the heat storage member 60 is disposed so as to face the front cover 70. As a case where the heat storage member 60 and the heat conduction member 65 are laminated on the front cover 70 as described above, for example, the fuel cell 1 may be fixed to a housing such as a battery case. Thereby, since the heat storage member 60 absorbs the heat generated on the cathode (air electrode) 16 side, the heat generated on the cathode (air electrode) 16 side can be prevented from being directly transmitted to the casing. Further, since the temperature is made uniform over the plane by the heat conducting member 65, the temperature rises uniformly and uniformly over the contact surface in the casing in the portion in contact with the heat conducting member 65. In addition, the fuel cell 1 is less susceptible to temperature changes in the external environment. When the heat storage member 60 and the heat conduction member 65 are disposed on the surface cover 70, the heat storage member 60 and the heat conduction member 65 may be disposed over the entire surface of the surface cover 70. You may laminate | stack and arrange | position only on the surface cover 70 corresponding to the part to contact.

  Further, when the heat storage member 60 and the heat conduction member 65 are disposed, for example, between the moisturizing layer 50 on the cathode (air electrode) 16 side and the surface cover 70 or over the entire surface of the surface cover 70. The heat storage member 60 and the heat conducting member 65 are configured such that air supplied to the cathode (air electrode) 16 and water (water vapor) generated at the cathode (air electrode) 16 can pass therethrough. Specifically, for example, through holes are formed at the positions of the heat storage member 60 and the heat conduction member 65 corresponding to the air introduction port 71 of the front cover 70.

  In addition, as shown in FIG. 2, the fuel cell 1 may include a heat storage member 80 and a heat conduction member 85 so as to cover the periphery of the fuel supply unit main body 42 constituting the fuel supply mechanism 40. The heat storage member 80 also stores heat as latent heat. In this case, the heat storage member 80 is disposed so as to face the fuel supply unit main body 42. For example, as in the fuel cell 1 shown in FIG. 2, the fuel supply unit main body 42 between the moisturizing layer 50 on the cathode (air electrode) 16 side and the surface cover 70 and the anode (fuel electrode) 13 side. When the heat storage members 60 and 80 and the heat conduction members 65 and 85 are provided in the surroundings, the phase change temperatures in the heat storage member 60 and the heat storage member 80 are different, and the cooling portion and the heat retaining portion are separately temperature controlled. Good.

  For example, each heat storage member may be set such that the phase change temperature in the heat storage member 60 is lower than the phase change temperature in the heat storage member 80. 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. Further, the heat generated in the cathode (air electrode) 16 is stored in the heat storage member 60 and is also anoded through a fixing member for fixing the fuel cell 10, the battery case, and the fuel cell 1 in a stacked state. (Fuel electrode) 13 is transmitted to the heat storage member 80. Moreover, since the heat from the heat storage member 60 is transmitted through the heat conducting member 65, it is conducted with a uniform temperature distribution.

  As shown in FIG. 2, the position where the heat storage member 80 and the heat conduction member 85 are provided is not limited to the periphery of the fuel supply unit main body 42, and is appropriately changed depending on the constituent members and component functions of the fuel cell 1. Is possible. For example, the heat storage member 80 and the heat conduction member 85 may be provided 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. In these cases, the heat storage member 80 is disposed on the fuel cell 10 side.

  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 in various concentrations with a fuel concentration ranging from 100 wt% to several wt%. Particularly in the case of a methanol aqueous solution, a fuel concentration having a fuel concentration of 60 wt% or more is used. It is 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 is not particularly limited, but a rotary vane pump and an electroosmotic flow pump can be used from the viewpoint that a small amount of liquid fuel F can be fed with good controllability and can be reduced in size and weight. It is preferable to use 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. As shown in FIG. 2, when the heat storage member 80 is provided, the internal reforming reaction of methanol of the formula (1) is promoted by using the heat stored in the heat storage member 80.

Electrons (e ⁻ ) generated by this reaction are guided to the outside through 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. Further, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are 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 ⁺ ) reaching the cathode (air electrode) 16 cause a reaction shown in the following formula (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 Formula (2)

  A part of the heat generated by the reaction shown in the formula (2) is stored in the heat storage member 60. Further, the heat transfer from the heat storage member 60 is performed via the heat conducting member 65. In this heat transfer, a uniform temperature distribution in the plane direction is obtained by the heat conducting member 65. As a result, a large fluctuation in the temperature of the fuel cell 1 and a rapid temperature increase of the fuel cell 1, particularly a rapid temperature increase on the cathode (air electrode) 16 side can be suppressed, and the temperature distribution can be made uniform. be able to. Furthermore, large fluctuations in the output density of the fuel cell 1 are suppressed, and a stable output can be maintained.

  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 according to the present invention described above, the heat storage members 60 and 80 and the heat storage members 60 and 80 are laminated and disposed, and the thermal conductivity in the plane direction is the heat storage members 60 and 80. By providing the heat conductive members 65 and 85 having a higher thermal conductivity in the plane direction and higher in the plane direction than the thermal conductivity in the thickness direction, heat can be evenly transferred in the plane direction. A uniform temperature distribution in the plane direction can be obtained. As a result, large fluctuations in the temperature of the fuel cell 1 and rapid increase in the temperature of the fuel cell, particularly a rapid increase in temperature on the cathode (air electrode) 16 side, can be suppressed, and the temperature distribution can be made uniform. Can do. Furthermore, large fluctuations in the output density of the fuel cell 1 are suppressed, and a stable output can be maintained. Moreover, the safety | security at the time of use can be improved by managing a heat | fever correctly and suppressing the rapid temperature rise of the fuel cell 1. FIG.

  Further, by providing the heat storage member 80 and the heat conduction member 85 so as to cover the periphery of the fuel supply unit main body 42, the reaction at the anode (fuel electrode) 13 that is an endothermic reaction is promoted by the heat retained by the heat storage member 80. In addition, the temperature distribution can be made uniform. This also makes it possible to maintain a stable power generation reaction.

  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, the heat storage members 60 and 80 and the heat storage members 60 and 80 are stacked and disposed, and the thermal conductivity in the planar direction is the thermal conductivity in the planar direction of the heat storage members 60 and 80. By providing the heat conductive members 65 and 85 having a higher thermal conductivity in the plane direction and higher than the thermal conductivity in the thickness direction, it is possible to appropriately manage heat without providing the fins and heaters described above. It can be performed and a stable output can be maintained.

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

Example 1
The fuel cell used in Example 1 has a configuration in which the heat storage member 80 and the heat conduction member 85 are not provided in the fuel cell 1 shown in FIG. 2, and will be described with reference to FIG.

  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 supporting the catalyst particles for cathode (Pt), a perfluorocarbon sulfonic acid solution as a proton conductive resin and water and methoxypropanol as a dispersion medium are added to disperse the carbon black supporting the catalyst particles for cathode. A paste was prepared. The obtained paste was applied to porous carbon paper as the cathode gas diffusion layer 15 to obtain a cathode catalyst layer 14 having a thickness of 100 μm. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 have the same shape and 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.

  A heat storage sheet (thermomemory; Mitsubishi Paper Industries Co., Ltd.) having a phase change temperature of 58 ° C. and a thickness of 1 mm, in which a microencapsulated organic heat storage material is mixed with a resin as the heat storage member 60 on the moisture retaining layer 50. Made). The thermal conductivity in the planar direction of this heat storage sheet was 0.3 W / m · K.

  On this heat storage member 60, a graphite sheet having a thickness of 0.25 mm having a thermal conductivity of 240 W / m · K in the plane direction and a thermal conductivity of 7 W / m · K in the thickness direction as the heat conducting member 65. (710A; manufactured by Otsuka Electric Co., Ltd.) was installed. The thermal conductivity ratio in this graphite sheet is 7/240.

  Here, the thermal conductivity of the heat storage sheet as the heat storage member 60 and the graphite sheet as the heat conduction member 65 was measured using the Angstrom method in the plane direction and the steady method in the thickness direction.

  Note that air intake ports (a circular shape having a diameter of 3.6 mm and 35 units) were formed in the heat storage sheet as the heat storage member 60 and the graphite sheet as the heat conduction member 65. Further, the heat storage sheet and the graphite sheet were installed such that the heat storage sheet was on the fuel cell 10 side and the graphite sheet was on the surface cover 70 side.

  On the heat conducting member 65, a stainless steel plate (SUS304) having a thickness of 1 mm formed with air inlets 71 (circular with a diameter of 3.6 mm, 35 holes) for air intake is formed as a surface cover 70. installed.

  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. The pump 90 was stopped when the surface temperature of the gold foil constituting the cathode conductive layer 19 was higher than 45 ° C. immediately below the cathode (air electrode) side of the moisture retention layer 50, and the pump 90 was operated when the temperature was 45 ° C. or lower.

  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 conditions described above, the surface of the gold foil constituting the cathode conductive layer 19 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 15 mm in the short side direction. The time change of the temperature at the position of was measured. The temperature was measured by directly attaching a thermocouple to the surface of the gold foil constituting the cathode conductive layer 19.

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.

  Moreover, in measuring the above-described temporal change in temperature, the temperature distribution on the surface of the surface cover 70 in a state where the change in temperature was stable was measured. In the measurement of the temperature distribution, nine temperatures on the surface of the surface cover 70 were measured. The temperature was measured by directly attaching a thermocouple to the surface of the front cover 70.

  FIG. 3 is a diagram illustrating measurement results of the temporal change in temperature and output density described above in Example 1. FIG. 4 is a diagram illustrating a measurement result of the temperature distribution on the surface of the front cover 70 in the first embodiment.

(Comparative Example 1)
In Comparative Example 1, the configuration was the same as that of the fuel cell 1 used in Example 1 except that the heat conducting member 65 was not provided.

  Using the fuel cell 1 having this configuration, the temperature and the power density in Example 1 with the same measurement conditions and measurement method as the measurement conditions and the measurement method of the temperature distribution of the surface of the surface cover 70 and the temperature The change in power density with time and the temperature distribution on the surface of the surface cover 70 were measured.

  FIG. 5 is a diagram illustrating measurement results of the temporal change in temperature and output density described above in Comparative Example 1. FIG. 6 is a diagram showing the measurement result of the temperature distribution on the surface of the front cover 70 in the first comparative example.

(Summary of Example 1 and Comparative Example 1)
As shown in FIG. 3 and FIG. 5, the temporal variation of the temperature and the output density of the fuel cell in Example 1 including the heat conducting member 65 does not include the heat conducting member 65. It was found to be smaller than the temporal variation of temperature and power density. From this result, it was found that by providing the heat conducting member 65, the temperature fluctuation and power generation state in the fuel cell are stabilized, and a constant output density can be obtained.

  Further, as shown in FIGS. 4 and 6, the temperature distribution of the surface of the surface cover 70 in Example 1 that includes the heat conducting member 65 is the surface of the surface cover 70 in Comparative Example 1 that does not include the heat conducting member 65. It was found to be smaller than the temperature distribution of From this result, it was found that by providing the heat conducting member 65, the temperature distribution can be made uniform.

  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. All of 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.

Sectional drawing which shows the structure of the fuel cell of one Embodiment which concerns on this invention. The fuel cell of one Embodiment concerning this invention WHEREIN: Sectional drawing which shows the structure of a fuel cell at the time of providing the thermal storage member and the heat conduction member around the pump and the fuel supply part main body. In Example 1, the surface of the gold foil constituting the cathode conductive layer immediately below the cathode (air electrode) side of the moisturizing layer, at a position of 20 mm in the long side direction corresponding to the center of the entire electrode and 15 mm in the short side direction. The figure which shows the measurement result of the time change of temperature, and the time change of the output density of a fuel cell. The figure which shows the measurement result of the temperature distribution of the surface of a surface cover in Example 1. FIG. In Comparative Example 1, directly below the moisturizing layer on the cathode (air electrode) side, the surface of the gold foil constituting the cathode conductive layer, at a position of 20 mm in the long side direction and 15 mm in the short side direction corresponding to the center of the entire electrode. The figure which shows the measurement result of the time change of temperature, and the time change of the output density of a fuel cell. The figure which shows the measurement result of the temperature distribution of the surface of a surface cover in the comparative example 1.

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 unit main body, 43 ... Fuel supply unit, 44 ... Channel, 50 ... Moisturizing layer, 60, 80 ... Heat storage member, 65, 85 ... Heat conduction member, 70 ... Surface cover, 71 ... Air inlet, F ... Liquid fuel.

Claims (7)

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 heat storage member that stores heat generated in the membrane electrode assembly as latent heat; and
A fuel cell comprising: a heat conductive member disposed on the heat storage member and having a thermal conductivity in a planar direction higher than the thermal conductivity in the planar direction of the thermal storage member.   2. The fuel cell according to claim 1, wherein in the heat conducting member, the heat conductivity in the planar direction is higher than the heat conductivity in the thickness direction.   The fuel cell according to claim 1, wherein the heat storage member and the heat conducting member are disposed on the air electrode side.   The fuel cell according to claim 1, wherein the heat storage member and the heat conduction member are disposed on the fuel electrode side.   5. The fuel cell according to claim 3, wherein the heat conducting member is laminated on the heat storage member so that the heat storage member is on the membrane electrode assembly side.   6. The fuel cell according to claim 1, wherein the heat conducting member is a graphite sheet.   The fuel cell according to any one of claims 1 to 6, wherein the fuel concentration in the fuel is 60% by weight or more.

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