JP2011175838A - Unit cell, compound unit cell and fuel cell stack using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a unit cell having proper rising of an output at startup. <P>SOLUTION: The unit cell includes a cathode collector, a cathode electrode, an electrolyte film, an anode electrode, and an anode collector in that order, and is also provided with a humidity adjustment layer opposite to a side in contact with the cathode electrode of the cathode collector. The humidity adjustment layer includes a humidity-absorbing layer for taking in outside humidity and a water-absorbing layer for absorbing humidity inside the humidity-absorbing layer, and the water-absorbing layer is arranged so as to be in contact with the cathode collector. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a unit cell and a composite unit cell having a humidity control layer, and a fuel cell stack using them.

  In recent years, there is an increasing expectation for a fuel cell as a small power source used in portable electronic devices and the like that support the information society. A fuel cell is a chemical cell that supplies electrons to a portable electronic device or the like, and high power generation efficiency can be obtained with a single power generation device. The fuel cell utilizes an electrochemical reaction in which fuel (for example, hydrogen, methanol, ethanol, hydrazine, formalin, formic acid, etc.) is oxidized at the anode electrode and oxygen in the air is reduced at the cathode electrode.

  Among various fuel cells, a polymer electrolyte fuel cell (PEMFC) using a proton exchange ion exchange membrane as an electrolyte membrane can obtain high power generation efficiency even at low temperature operation of 100 ° C. or less. Therefore, compared to fuel cells that operate at high temperatures such as phosphoric acid fuel cells and solid oxide fuel cells, it is not necessary to apply heat from the outside, and large-scale accessories are not required. There are merits in the point, etc., and it is expected to be put to practical use as a small power source.

  As a fuel used for the PEMFC, in addition to hydrogen gas using a high-pressure gas cylinder, a mixed gas of hydrogen gas and carbon dioxide gas obtained by decomposing an organic liquid fuel with a reformer is generally used.

  On the other hand, a direct methanol fuel cell (DMFC) needs to be equipped with a reformer because it generates power by supplying a methanol aqueous solution to the anode electrode and extracting protons and electrons directly from the methanol aqueous solution. Absent. As a result, the DMFC can be made smaller than the PEMFC, and is therefore said to be the fuel cell that is most expected to be put to practical use. DMFC is attracting attention for its application to small power sources such as portable electronic devices, especially for secondary battery replacement for portable electronic devices.

  In addition, since the DMFC uses a methanol aqueous solution that is liquid at atmospheric pressure as a fuel, a fuel having a high volumetric energy density can be handled in a small simple container. For this reason, the DMFC is superior in terms of safety because it does not require the use of a high-pressure gas cylinder.

  By the way, in DMFC, the following reactions occur at the anode and cathode, respectively.

Anode electrode: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
Cathode: (3/2) O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
Thus, in the DMFC, methanol and water react at the anode electrode to generate carbon dioxide, protons and electrons. On the other hand, oxygen, protons, and electrons react at the cathode electrode to produce water.

  A fuel containing methanol is supplied to the anode electrode. This fuel is roughly divided into a low-concentration aqueous methanol solution in which the molecular weight of water is higher than the molecular weight of methanol, and the molecular weight of methanol over that of water. There is a high concentration methanol aqueous solution mixed in a large proportion. The latter high-concentration aqueous methanol solution has a high energy density per fuel volume. For this reason, it is possible to reduce the size of the power generation or the fuel cartridge for a long time rather than supplying a low concentration aqueous methanol solution.

  In the anode electrode, methanol and water react with each other in equimolar amounts. Therefore, when high-concentration methanol is supplied, water is insufficient with respect to methanol. This shortage of water is caused by the water generated by the reaction at the cathode electrode moving from the cathode electrode to the anode electrode through the electrolyte membrane due to a concentration gradient or pressure gradient (hereinafter also referred to as “reverse diffusion”). Be compensated.

  However, part of the water generated by the reaction at the cathode electrode is evaporated as water vapor and discharged to the outside together with air. If the amount of water discharged to the outside becomes excessive, back diffusion does not occur, the anode electrode becomes insufficient in water, the reaction overvoltage increases, the electrolyte membrane dries and the electrical resistance increases, and the fuel cell There is a problem that the output decreases.

  As an attempt to solve such a problem, Patent Document 1 discloses a gas diffusion layer of a current collector in a fuel cell in which an electrolyte layer, a catalyst layer, a gas diffusion layer, and a current collector are laminated in this order. A technique of providing a humidity control layer capable of absorbing and releasing moisture on the opposite side is disclosed.

JP 2009-081111 A

  However, when starting the fuel cell of Patent Document 1 after leaving it for a long time without using it for a long time, the temperature and humidity inside and outside the fuel cell in the humidity control layer are the same, so that the water vapor generated at the cathode electrode is humidity controlled. The layer will actively take in. For this reason, there has been a problem that the humidity inside the fuel cell is difficult to increase, water shortage at the anode electrode and drying of the electrolyte membrane occur, and the output hardly rises at the start-up.

  The unit cell of the present invention has been made to solve the above-described problems, and its purpose is to suppress the anode water shortage and the electrolyte layer from drying, and thus to increase the output at startup. Is to improve.

  The unit battery of the present invention includes a cathode current collector, a cathode electrode, an electrolyte membrane, an anode electrode, and an anode current collector in this order, and the side in contact with the cathode electrode of the cathode current collector The moisture conditioning layer includes a moisture absorbing layer for taking in external moisture, and a moisture absorbing layer for absorbing moisture in the moisture absorbing layer, the moisture absorbing layer comprising: It is arranged to be in contact with the cathode current collector.

  It is preferable that the humidity control layer further includes a moisture release layer for releasing moisture retained by the water absorption layer on the side in contact with the cathode current collector.

The moisture release layer is preferably made of a material that has a lower hygroscopic property than the material constituting the moisture absorption layer.
The cathode current collector preferably has a first through hole penetrating the front and back surfaces, and the moisture absorption layer preferably has a second through hole penetrating the front and back surfaces. The second through hole is preferably formed at a position on the first through hole. The area Sb of the diameter of the second through hole is preferably equal to or larger than the area Sa of the diameter of the first through hole.

  The water absorption layer has a third through hole penetrating the front and back surfaces, the third through hole is formed on the first through hole, and the area Sc of the diameter of the third through hole is the first through hole. It is preferable that the area Sa of the diameter of one through hole is smaller.

  It is preferable that the water absorption layer has a third through hole penetrating the front and back surfaces, and a moisture-absorbing material for releasing moisture held in the water absorption layer is filled in the third through hole. It is preferable to provide a protective layer on the side of the humidity control layer opposite to the side in contact with the cathode current collector.

  The composite unit cell of the present invention is a composite unit cell including two unit cells and a fuel supply means for supplying fuel to the anode electrode of the two unit cells, and the anode unit of the two unit cells. Each of the electric bodies is disposed so as to face the fuel supply means, and at least one of the two unit cells is the unit cell described above. The fuel supply means is preferably a fuel flow path or a supply layer.

  The fuel cell stack of the present invention is formed by laminating two or more fuel cell layers in which two or more unit cells are arranged with a gap in the same plane. At least one of the unit cells includes a humidity control layer.

  The fuel cell stack according to the present invention is a fuel cell stack formed by laminating two or more fuel cell layers in which two or more unit cells are arranged with a gap in the same plane, and the fuel cell stack includes: The at least one layer is characterized in that two or more composite unit cells using unit cells including a humidity control layer are arranged with a gap in the same plane.

  According to the unit battery of the present invention, the shortage of water in the anode electrode and the drying of the electrolyte layer can be suppressed, thereby improving the rise in output at the time of startup.

FIG. 2 is a schematic cross-sectional view and a top view of the unit battery according to the first embodiment. It is the graph which showed the moisture absorption amount of each layer which comprises a humidity control layer. FIG. 4 is a schematic cross-sectional view and a top view of a unit battery according to a second embodiment. It is the graph which showed the moisture absorption amount of the water absorption layer and the moisture release layer. FIG. 6 is a schematic cross-sectional view and a top view of a unit battery according to a third embodiment. (A) is a top view of a cathode current collector, (b) is a top view of a moisture absorption layer, and (c) is a (b) moisture absorption layer on the cathode current collector (a). It is a top view of what was piled up. FIG. 6 is a schematic cross-sectional view and a top view of a unit battery according to a fourth embodiment. FIG. 6 is a schematic cross-sectional view and a top view of a unit battery according to a fifth embodiment. 7 is an exploded perspective view of a composite unit battery according to Embodiment 6. FIG. FIG. 10 is a schematic perspective view of a composite unit battery according to a sixth embodiment. It is an exploded perspective view formed by laminating two composite unit batteries with a spacer interposed therebetween. (A) is a perspective view showing a preferred example of the fuel cell stack of Embodiment 7, (B) is a top view showing a preferred example of the fuel cell stack of Embodiment 7, (C) FIG. 10 is a side view showing a preferable example of the fuel cell stack according to the seventh embodiment.

  Hereinafter, embodiments of the unit battery of the present invention will be described. In the following description of the embodiments, the description is made with reference to the drawings. In the drawings of the present application, the same reference numerals denote the same or corresponding parts. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description. In the drawings of the present application, dimensional relationships such as length, width, and thickness are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<< Unit battery >>
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view and a top view of a unit battery according to the present embodiment. As shown in FIG. 1, unit cell 100 of the present embodiment includes cathode current collector 105, cathode electrode 103, electrolyte membrane 101, anode electrode 102, and anode current collector 104 in this order. The humidity control layer 120 is provided on the side of the cathode current collector 105 opposite to the side in contact with the cathode electrode 103. The humidity control layer 120 includes a moisture absorption layer 121 for taking in external moisture, and the moisture absorption layer 120. A water absorption layer 122 for absorbing moisture in the layer 121, and the water absorption layer 122 is disposed so as to be in contact with the cathode current collector 105. Below, each part which comprises the unit battery 100 of this Embodiment is demonstrated.

<Humidity control layer>
In the present invention, the humidity adjustment layer 120 includes a moisture absorption layer 121 for taking in external moisture, and a water absorption layer 122 for absorbing moisture in the moisture absorption layer 121. It is preferable that such a humidity control layer 120 has a property of absorbing moisture when the humidity is higher than a predetermined humidity, and releasing moisture when the humidity is lower than the predetermined humidity.

  Thus, by providing the humidity control layer 120 having the two-layer structure of the moisture absorption layer 121 and the water absorption layer 122 in contact with the cathode current collector 105, the humidity control layer 120 does not take in moisture in the fuel cell, and externally. Only moisture can be taken in. As a result, the shortage of water necessary for the anode electrode 102 can be suppressed, the electrolyte membrane 101 can be prevented from drying, and the output rise can be improved when a fuel cell that has not been used for a long time is started.

  For the moisture absorbing layer 121 and the water absorbing layer 122, it is necessary to select a material whose moisture absorption amount increases as the external relative humidity increases. When the external relative humidity is high, it is preferable that the moisture absorption layer 121 actively absorbs external moisture, and the moisture absorption layer 121 has a larger amount of moisture absorption than the water absorption layer 122. On the other hand, when the external relative humidity is low, it is preferable that the water absorption layer 122 positively absorbs the moisture of the moisture absorption layer 121, and the water absorption layer 122 has a larger amount of moisture absorption than the moisture absorption layer 121. Hereinafter, the water absorption amount of the moisture absorption layer 121 and the water absorption layer 122 will be specifically described with reference to FIG.

  FIG. 2 is a graph showing the moisture absorption amount of the moisture absorption layer and the water absorption layer. The vertical axis in FIG. 2 shows the amount of moisture absorption (g / g) per 1 g of the material constituting the moisture absorption layer and the water absorption layer, and the horizontal axis is the external relative humidity (% RH). The solid line indicates the moisture absorption amount, and the dotted line indicates the moisture absorption amount when the moisture is released. A1 represents a moisture absorption layer, and A2 represents a water absorption layer.

  For example, when the relative humidity is 80% RH, the moisture absorption layer (A1) actively absorbs at least 0.2 g of moisture per 1 g of the material constituting the layer, and absorbs up to 0.6 g. If it exceeds 0.6 g, the corresponding moisture is released to the outside (for example, the water absorption layer). On the other hand, when the relative humidity is 80% RH, the water absorption layer (A2) absorbs about 0.43 g per gram of the material constituting the water absorption layer, and when the relative humidity exceeds 0.43 g, the corresponding moisture becomes the cathode current collector. Released to the side of the body.

  Therefore, when the humidity control layer 120 is disposed at a relative humidity of 80% RH, the moisture absorption layer 121 starts to take in moisture from the outside air. At the same time, the water absorption layer 122 starts to take in moisture from the moisture absorption layer 121, and the water absorption layer Moisture is taken in until 122 absorbs 0.43 g / g. Although the moisture absorption layer 121 takes moisture into the water absorption layer 122, the moisture of the taken-in amount is supplemented with external moisture, and the moisture absorption amount is kept at 0.2 g / g. In this way, the humidity control layer 120 takes in external moisture, so that the drying of the electrolyte membrane 101 and the anode electrode 102 can be suppressed, and the rise of output at the time of startup can be improved.

<Hygroscopic layer>
In the present invention, the moisture absorption layer 121 is provided so as to be in contact with the water absorption layer 122 in order to take in external moisture. By providing the moisture absorption layer 121 without contacting the cathode current collector 105 in this manner, it is possible to absorb only the external moisture without absorbing moisture from the cathode current collector 105. This prevents drying of the electrolyte membrane 101 and contributes to prevention of water shortage of the anode electrode 102.

  Examples of the material used for the hygroscopic layer 121 include sepiolite, zeolite, silica gel, and the like, and deliquescent substances such as sodium hydroxide, magnesium chloride, and calcium chloride. By forming such a material in layers on the water absorption layer 122, the moisture absorption layer 121 can be formed.

  Among the materials constituting the hygroscopic layer 121, it is preferable to use sepiolite, zeolite, or the like from the viewpoint of increasing the strength against external impact. Note that a protective layer (not shown) may be further provided on the moisture absorption layer 121 to increase the strength against external impact. The protective layer will be described later.

  Further, the moisture absorbing layer 121 may be formed by incorporating a deliquescent material on the surface of the water absorbing layer 122 opposite to the side in contact with the cathode current collector 105. When the moisture absorbing layer 121 is formed in this way, the interface between the moisture absorbing layer 121 and the water absorbing layer 122 may not be clearly formed as shown in FIG. The part including the deliquescent material is regarded as the moisture absorption layer 121.

<Water absorption layer>
In the present invention, the water absorption layer 122 is provided between the moisture absorption layer 121 and the cathode current collector 105. The water absorbing layer 122 is made of a material that absorbs only the moisture of the moisture absorbing layer 121 but hardly absorbs moisture on the cathode current collector 105 side. For this reason, even when a fuel cell that has not been used for a long time is started, the electrolyte membrane 101 is difficult to dry and water shortage of the anode electrode 102 does not easily occur.

  As a material used for such a water absorption layer 122, any material can be used without particular limitation as long as it is not soluble in water, but a porous body made of an organic substance such as a polymer material is used. It is preferable. Examples of such a porous body include cotton, foam, fiber bundle, woven fiber, non-woven fiber, porous sintered body, or a combination of these materials.

  Examples of the organic substance such as the polymer material include one or two selected from natural fibers, polyester, polyethylene, polypropylene, polyurethane, acrylic, polyamide, polyolefin, polyacetal, polyvinyl, polycarbonate, polyether, polyphenylene, and the like. It is more preferable to use a combination of species or more.

<Protective layer>
In the present embodiment, it is preferable that a protective layer (not shown) is further provided on the side of the humidity control layer 120 opposite to the side in contact with the cathode current collector 105. By providing the protective layer in this way, the strength against external impact can be improved. Examples of the material constituting the protective layer include one or more porous polymer membranes selected from the group consisting of polyethylene, polyester, polyvinyl, and polycarbonate. The porous polymer membrane constituting such a protective layer preferably has a high porosity. Thereby, the strength of the unit battery against an external impact can be increased without impairing the performance of the moisture absorption layer 121 to absorb moisture of the outside air.

<Membrane electrode composite>
As shown in FIG. 1, the unit cell 100 of the present invention includes a membrane electrode assembly (MEA) including an anode electrode 102, an electrolyte membrane 101, and a cathode electrode 103 in this order. The unit battery 100 further includes an anode current collector 104 and a cathode current collector 105 in order to efficiently exchange electrons.

  As shown in FIG. 1, the anode current collector 104 is preferably provided with a fuel flow path 106, which is a space for transporting fuel, in contact with the anode 102. As a result, fuel can be efficiently supplied to the anode electrode 102, and electrons generated at the anode electrode 102 can flow to the anode current collector 104.

  As shown in FIG. 1, the present invention is not limited to the case where the fuel flow path 106 is provided. For example, a flow path plate having a fuel flow path is provided on the opposite side of the anode current collector 104 from the side in contact with the anode electrode 102. May be. By disposing such a flow path plate, fuel can be supplied from the fuel flow path to the anode electrode 102 via the anode current collector 104.

Hereinafter, the power generation operation of the membrane electrode assembly will be described. In the unit cell 100 of FIG. 1, when an aqueous methanol solution is used as the fuel, the aqueous methanol solution is supplied to the anode electrode 102 through the fuel flow path 106, and CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ Reacts to generate hydrogen ions and electrons.

Here, the generated hydrogen ions move to the cathode electrode 103 through the electrolyte membrane 101. On the other hand, air is supplied from the atmosphere to the cathode electrode 103 and functions as an oxidant at the cathode electrode 103 and reacts with (3/2) O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O to generate water. The flow until the electrons generated in the anode electrode 102 flow to the cathode electrode 103 is taken out as an electric current through an external circuit. Thereby, electric energy can be obtained from the unit battery 100. Here, a part of the water generated at the cathode electrode 103 is evaporated and released to the outside together with air. On the other hand, the water that has not been evaporated is supplied to the electrolyte membrane 101 and the anode electrode 102 to prevent the electrolyte membrane 101 from being dried and to alleviate water shortage at the anode electrode.

<Fuel>
As the fuel supplied to the unit cell 100 of the present invention, any of gaseous fuel and liquid fuel may be used as long as electric power can be obtained by electrolysis. Examples of the gaseous fuel include hydrogen, DME, methane, butane, and ammonia. Examples of the liquid fuel include alcohols such as methanol and ethanol, acetals such as dimethoxymethane, carboxylic acids such as formic acid, esters such as methyl formate, and hydrazine.

  In addition, although the above-mentioned liquid fuel mentions the liquid fuel at normal temperature, you may vaporize liquid fuel and supply it to a gaseous phase. The gas fuel and liquid fuel described above are not limited to one type, and may be a mixture of two or more types. From the viewpoint of energy density per volume, it is preferable to use methanol.

<Oxidizing agent>
As the oxidant supplied to the unit battery of the present invention, oxygen, hydrogen peroxide, and nitric acid are preferably used. From the viewpoint of the cost of the oxidizing agent, it is more preferable to use oxygen in the air. In the following description of each layer constituting the unit cell 100, for convenience of explanation, the case where methanol is used as the fuel and air is used as the oxidant may be described, but the case is limited to the case where these materials are used. is not.

<Electrolyte membrane>
In the present invention, the electrolyte membrane 101 conducts protons generated at the anode electrode 102 and transmits the protons to the cathode electrode 103. The electrolyte membrane 101 is made of any conventionally known material as long as it is an electrically insulating material. Can also be used. The electrolyte membrane 101 can be formed of, for example, a polymer membrane, an inorganic membrane, or a composite membrane.

  As the polymer membrane used for the electrolyte membrane 101, for example, Nafion (NAFION (registered trademark) manufactured by DuPont) which is a perfluorosulfonic acid electrolyte membrane, Dow membrane (manufactured by Dow Chemical Company), Aciplex (ACIPLEX ( (Registered trademark): manufactured by Asahi Kasei Co., Ltd.) and Flemion (registered trademark): manufactured by Asahi Glass Co., Ltd.), as well as hydrocarbon electrolyte membranes such as polystyrene sulfonate and sulfonated polyether ether ketone.

  Examples of the inorganic film used for the electrolyte membrane 101 include phosphate glass, cesium hydrogen sulfate, polytungstophosphoric acid, ammonium polyphosphate, and the like. An example of the composite film is Gore Select film (Gore Select (registered trademark): manufactured by Japan Gore-Tex Co., Ltd.).

  Moreover, in order that the unit battery can cope with temperatures near 100 ° C. or higher, it is preferable to use a material for the electrolyte membrane 101 having high ionic conductivity even when the water content is low. Examples of the material of the electrolyte membrane 101 include sulfonated polyimide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), sulfonated polybenzimidazole, and phosphonated polybenzimidazole. It is preferable to use cesium hydrogen sulfate, ammonium polyphosphate, ionic liquid (room temperature molten salt) or the like as a film.

Such an electrolyte membrane 101 preferably has a proton conductivity of 10 ⁻⁵ S / cm or more, and has a proton conductivity of 10 like a polymer electrolyte membrane such as a perfluorosulfonic acid polymer or a hydrocarbon polymer. It is more preferable to use a material of ⁻³ S / cm or more.

<Anode electrode>
The anode 102 used in the unit cell 100 of the present invention includes at least an anode catalyst layer (not shown) including an anode catalyst that promotes fuel oxidation. The fuel undergoes an oxidation reaction on the anode catalyst to generate protons and electrons. The anode electrode 102 preferably has a structure in which an anode porous substrate (not shown) is laminated on the anode current collector 104 side (the side opposite to the electrolyte membrane 101) separately from the anode catalyst layer.

  The anode catalyst layer preferably includes at least an anode catalyst that promotes oxidation of the fuel, and further includes an anode support and an anode electrolyte. The thickness of the anode catalyst layer is preferably 0.1 μm or more and 0.2 mm or less. If the thickness of the anode catalyst layer is less than 0.1 μm, there is a possibility that the amount of catalyst sufficient to improve the output of the unit cell cannot be supported on the anode catalyst layer. There is a possibility that the resistance increases or the diffusion resistance of the liquid fuel or the oxidant increases. In (1) to (3) below, what is included in the anode catalyst layer will be described.

(1) Anode catalyst The anode catalyst has a function of accelerating the reaction rate of generating protons and electrons from methanol and water when an aqueous methanol solution is used as the fuel. The anode catalyst is not necessarily limited to one kind of material, and two or more kinds of materials may be used. Examples of such an anode catalyst include noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, and Ir, Ni, V, Ti, Co, Mo, Fe, Cu, Zn, Sn, W, and Zr. Base metals, oxides of these noble metals or base metals, carbides and carbonitrides, or one or a combination of two or more materials selected from the group consisting of carbon can be used as the catalyst.

(2) Anode carrier The anode carrier has a function of conducting electrons generated at the anode electrode 102 to the anode porous substrate. Any material may be used for the anode carrier as long as it has electrical conductivity, but it is preferable to use a carbon-based material with high electrical conductivity, and as a carbon-based material with high electrical conductivity, Examples thereof include acetylene black, ketjen black (registered trademark), amorphous carbon, carbon nanotube, and carbon nanohorn. In addition to these carbon-based materials, noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, Ir, Ni, V, Ti, Co, Mo, Fe, Cu, Zn, Sn, W, Base materials such as Zr, oxides of these noble metals or base metals, carbides, nitrides, and carbon nitrides may be used as the support.

  The anode carrier may be a material imparted with proton conductivity. Examples of the material imparted with proton conductivity in this way include sulfated zirconia and zirconium phosphate.

  The surface of the anode carrier is preferably hydrophilic. By making the surface of the anode carrier hydrophilic, the fuel (methanol aqueous solution) can be easily held in the pores of the anode catalyst layer, and the diffusibility of fuel and protons in the anode catalyst layer is improved. Here, examples of the method for hydrophilizing the surface of the anode carrier include a method of modifying the surface of the anode carrier with a hydrophilic functional group such as a carboxyl group or a hydroxyl group.

  Examples of the method for hydrophilizing the surface of the anode support include surface modification by graft polymerization of the carbon surface, surface modification with a silane coupling agent, and the like. In addition, since the anode catalyst has electron conductivity, the anode carrier need not be provided.

(3) Anode Electrolyte The anode electrolyte has a function of conducting protons generated at the anode electrode 102 to the electrolyte membrane 101. The anode electrolyte is not particularly limited as long as it is a material having proton conductivity and electrical insulation, and any material can be used. The anode electrolyte is preferably a solid or gel that is not dissolved by a fuel such as methanol. Such an anode electrolyte is preferably an organic polymer having a strong acid group such as a sulfonic acid or phosphoric acid group or a weak acid group such as a carboxyl group. For example, it contains perfluorocarbon (Nafion (registered trademark) (manufactured by DuPont). )), Carboxyl group-containing perfluorocarbon (Flemion (registered trademark) (manufactured by Asahi Kasei Corporation)), polystyrene sulfonic acid copolymer, polyvinyl sulfonic acid copolymer, ionic liquid (room temperature molten salt), sulfonated imide, AMPS Etc. In addition, when using what has proton conductivity as an anode support body, since it can conduct a proton by these, it is not necessary to provide an anode electrolyte and a cathode electrolyte separately.

<Cathode>
The cathode electrode 103 used in the unit cell 100 of the present invention includes at least a cathode catalyst layer (not shown) including a cathode catalyst that promotes reduction of the oxidant. Then, the oxidant takes in protons and electrons on the cathode catalyst to generate a reduction reaction, thereby generating water. The cathode electrode 103 is preferably laminated with a cathode porous substrate (not shown) on the side opposite to the electrolyte membrane 101 in addition to the cathode catalyst layer.

  The cathode catalyst layer preferably includes at least a cathode catalyst that accelerates a reaction rate for generating water from oxygen, protons, and electrons, and further includes a cathode support and a cathode electrolyte. The thickness of the cathode catalyst layer is preferably 0.1 μm or more and 0.2 mm or less. If the thickness of the cathode catalyst layer is less than 0.1 μm, there is a possibility that a catalyst amount sufficient to improve the output of the unit cell cannot be supported on the cathode catalyst layer. There is a possibility that the resistance increases or the diffusion resistance of the liquid fuel or the oxidant increases. In (1) to (3) below, what is included in the cathode catalyst layer will be described.

(1) Cathode catalyst A cathode catalyst has a function which accelerates | stimulates the reaction rate of the reaction which produces | generates water from oxygen, a proton, and an electron. The cathode catalyst is not limited to one kind, and two or more kinds of materials may be used. Examples of such a cathode catalyst include noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, Ir, Ni, V, Ti, Co, Mo, Fe, Cu, Zn, Sn, W, Zr, and the like. Base metals, oxides of these noble metals or base metals, carbides and carbonitrides, or one or a combination of two or more materials selected from the group consisting of carbon can be used as the catalyst.

(2) Cathode carrier The cathode carrier has a function of conducting electrons from the cathode porous substrate to the cathode catalyst layer. Any material may be used for the cathode carrier as long as it has electrical conductivity, but it is preferable to use a carbon-based material with high electrical conductivity, and as a carbon-based material with high electrical conductivity, Examples thereof include acetylene black, ketjen black (registered trademark), amorphous carbon, carbon nanotube, and carbon nanohorn. In addition to these carbon-based materials, noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, Ir, Ni, V, Ti, Co, Mo, Fe, Cu, Zn, Sn, W, Base materials such as Zr, oxides of these noble metals or base metals, carbides, nitrides, and carbon nitrides may be used as the support. The cathode carrier may be a material imparted with proton conductivity. Examples of the material imparted with proton conductivity in this way include sulfated zirconia and zirconium phosphate.

(3) Cathode electrolyte The cathode electrolyte has a function of conducting protons permeated from the electrolyte membrane 101 to the vicinity of the cathode catalyst layer. The cathode electrolyte is not particularly limited as long as it is a material having proton conductivity and electrical insulation, and any material can be used. The cathode electrolyte is preferably a solid or gel that is not dissolved by a fuel such as methanol. Such a cathode electrolyte is preferably an organic polymer having a strong acid group such as a sulfonic acid or phosphoric acid group or a weak acid group such as a carboxyl group. For example, it contains perfluorocarbon (Nafion (registered trademark) (manufactured by DuPont). )), Carboxyl group-containing perfluorocarbon (Flemion (registered trademark) (manufactured by Asahi Kasei Corporation)), polystyrene sulfonic acid copolymer, polyvinyl sulfonic acid copolymer, ionic liquid (room temperature molten salt), sulfonated imide, AMPS Etc. In addition, when using what has proton conductivity as a cathode support body, since a proton can be conducted by these, it is not necessary to provide a cathode electrolyte separately.

<Anode porous substrate and cathode porous substrate>
The anode porous substrate forms a void that allows methanol and water to be supplied to the anode catalyst layer, and has a function of conducting electrons from the anode carrier to the anode current collector 104. On the other hand, the cathode porous substrate forms a void that allows oxygen in the atmosphere to be supplied to the cathode catalyst layer and allows the generated water to be efficiently discharged to the outside, and from the cathode carrier to external wiring (not shown). ) Has the function of conducting electrons.

  The anode porous substrate and the cathode porous substrate are preferably made of a conductive material. For example, carbon paper, carbon cloth, metal foam, metal sintered body, metal fiber nonwoven fabric, and the like can be used. Here, as a metal used for a metal foam, a metal sintered body, and a nonwoven fabric of metal fiber, noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, Ir, Ni, V, Ti, Co, Examples include base metals such as Mo, Fe, Cu, Zn, Sn, W, and Zr, and materials containing one or more of these noble metals, base metal oxides, carbides, nitrides, and carbonitrides. . The anode porous substrate is preferably disposed on the anode current collector 104 side of the anode electrode 102 (on the side opposite to the electrolyte membrane 101 side). Further, the cathode porous substrate is preferably disposed outside the unit cell in the cathode electrode 103 (on the side opposite to the electrolyte membrane 101 side).

  Note that the anode porous substrate and the cathode porous substrate are not necessarily provided. That is, for example, the anode catalyst layer may be formed directly on the electrolyte membrane 101 so that the anode catalyst layer exchanges electrons with the anode current collector, or the cathode catalyst layer exchanges electrons with the external wiring. In addition, the cathode catalyst layer may be formed directly on the electrolyte membrane 101.

<Cathode current collector>
The cathode current collector 105 has a function of exchanging electrons with the cathode electrode 103, and it is preferable to use a highly conductive material in order to reduce electric resistance. As the cathode current collector 105, a cathode current collector having a porous shape such as a shape obtained by opening a plurality of first through holes 105a in a plate or foil, a mesh shape, or an expanded metal shape can be preferably used. By providing the first through hole 105 a in this way, a large surface area for diffusing air can be secured, and air can be efficiently supplied to the cathode electrode 103.

Such area Sa of the diameter of the first through hole 105a is preferably 0.12 mm ² or more 2.05 mm ² or less. If it is less than 0.12 mm ² , the supply of air to the cathode electrode 103 is hindered, so that the output of the unit cell 100 decreases. On the other hand, if it exceeds 2.05 mm ² , the electrical resistance of the cathode current collector 105 increases to a degree that cannot be ignored, and the output of the unit cell 100 decreases.

  The cathode current collector 105 may be any material as long as it has conductivity. However, it is preferable to use a material having a low electron conduction resistance in order to suppress a voltage drop, and a noble metal such as Au, Pt, or Pd, Ti, Ta, W, Nb, Ni, Al, Cr, Ag, Cu, Zn, Su and other metals, Si, and their nitrides, carbides, carbonitrides, etc., stainless steel, Cu-Cr, Ni-Cr It is more preferable to use an alloy such as Ti—Pt, and more preferably to include one or more elements selected from the group consisting of Pt, Ti, Au, Ag, Cu, Ni, and W. In the case of using a metal that is easily corroded in an acidic atmosphere such as Cu, Ag, Zn, etc. as a material of the cathode current collector 105, a noble metal and metal material having corrosion resistance such as Au, Pt, Pd, etc., conductive By coating the surface with a conductive polymer, conductive nitride, conductive carbide, conductive carbonitride, conductive oxide, etc., corrosion of the surface of the cathode current collector 105 can be prevented.

<Anode current collector>
In the present invention, the unit cell 100 constituting the fuel cell layer includes an anode current collector 104 having a function of transferring electrons generated in the anode electrode 102. Such an anode current collector 104 preferably has a fuel flow path 106 in which one or two or more grooves are formed on the surface in contact with the anode 102 on the front and back. The fuel flow path 106 provided in the anode current collector 104 is not particularly limited, and any shape can be used.

  The shape of the fuel flow path 106 is preferably determined in consideration of the electrical resistance of the anode current collector 104, the contact area between the anode current collector 104 and the anode electrode 102, and the like. For example, as shown in FIG. 1, the fuel channel 106 may have a quadrangular cross-sectional shape with respect to the direction in which the fuel flows in the fuel channel 106.

If section relative to the direction through which fuel flows in the fuel passage 106 is a square shape, it is preferred that the rectangular area is 0.01 mm ² or more 1 mm ² or less. If this area is less than 0.01 mm ² , there is a problem that the pressure loss for flowing the liquid increases, so that the fuel supply device becomes large, and if it exceeds 1 mm ² , there is a problem that the unit cell becomes large.

  Further, assuming that the length of the portion in contact with the anode 102 in the quadrangular shape of the cross section of the fuel flow path is the width of the fuel flow path, the width of the fuel flow path may be 0.1 mm or more and 1 mm or less. preferable. If the width of the fuel flow path 106 is less than 0.1 mm, there is a problem in that the efficiency of supplying fuel from the fuel flow path 106 to the anode electrode 102 decreases. If the width exceeds 1 mm, the anode in contact with the anode electrode 102 Since the edge width of the current collector 104 is shortened, the structural stability is poor.

  Further, it is preferable that 20% or more of the area of the surface in contact with the anode current collector 104 of both the front and back surfaces of the anode electrode 102 is in contact with the anode current collector 104. Even when another layer is interposed between the anode electrode 102 and the anode current collector 104 and the anode electrode 102 and the anode current collector 104 are not in contact with each other, the above-described area relationship is the same. . When this area is less than 20%, the contact area between the anode current collector 104 and the anode electrode 102 is reduced, and there is a problem that ohmic resistance increases.

  Any material may be used for the anode current collector 104 as long as it exhibits conductivity. However, carbon materials, conductive polymers, noble metals such as Au, Pt, and Pd, Ti, Ta , W, Nb, Ni, Al, Cr, Ag, Cu, Zn, Su and other metals, Si, and their nitrides, carbides, carbonitrides, etc., and stainless steel, Cu-Cr, Ni-Cr, Ti- An alloy such as Pt can be used.

  Here, the material used for the anode current collector 104 is preferably a material having a small specific resistance, and at least one element selected from the group consisting of Pt, Ti, Au, Ag, Cu, Ni, and W is used. More preferably. By using such a material for the anode current collector 104, voltage drop due to the resistance of the anode current collector 104 can be reduced, and higher power generation characteristics can be obtained.

  In addition, as a material used for the anode current collector 104, when using a metal that is easily corroded in an acidic atmosphere such as Cu, Ag, Zn, etc., a noble metal and metal material having corrosion resistance such as Au, Pt, Pd, etc. It is preferable to coat the surface with a conductive polymer, a conductive nitride, a conductive carbide, a conductive carbonitride, a conductive oxide, or the like. By coating the surface in this way, corrosion of the surface of the anode current collector 104 can be prevented, and the life of the unit cell and the fuel cell stack using the unit cell can be extended.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view and a top view of the unit battery of the present embodiment. As shown in FIG. 3, the unit cell of the present embodiment is the same as that of the first embodiment except that a moisture release layer 223 is further provided on the side of the humidity control layer 220 in contact with the cathode current collector 105. belongs to. Hereinafter, the moisture release layer 223 will be described.

<Moisture release layer>
In this embodiment, the moisture release layer 223 is provided between the water absorption layer 222 and the cathode current collector 105, and is characterized by being made of a material having higher moisture release properties than the water absorption layer 222. As described above, the humidity control layer 220 has a three-layer structure of the moisture absorption layer 221, the water absorption layer 222, and the moisture release layer 223, so that the moisture absorption layer 221 absorbs external moisture, and the moisture absorption layer 222 absorbs the absorbed moisture. The water absorption layer 223 discharges the absorbed water to the cathode current collector 105 side. Thus, drying of the electrolyte membrane 101 can be suppressed, and water necessary for the reaction at the anode electrode 102 can be supplied.

  Here, the moisture release layer 223 is preferably made of a material having a hygroscopicity lower than that of the material constituting the moisture absorption layer 221. By the moisture release layer 223, the effect of releasing the moisture absorbed by the water absorption layer 222 to the cathode current collector 105 becomes remarkable. On the other hand, when the moisture release layer 223 is made of a material having higher hygroscopicity than the material constituting the moisture absorption layer 221, the moisture contained in the electrolyte membrane 101 or water necessary for the reaction at the anode electrode 102 is removed. Absorbs water and the output of the unit battery decreases.

  As a material used for the moisture release layer 223, a material that is the same material as the water absorption layer 222 and that has a lower surface area than the water absorption layer 222 may be used. Since the surface area is thus low, the water absorption of the moisture release layer 223 is lower than that of the water absorption layer 222, and moisture is easily released to the cathode current collector 105. Demonstrate.

  FIG. 4 is a graph showing the moisture absorption amounts of the water absorption layer and the moisture release layer. The vertical axis of FIG. 4 shows the amount of moisture absorption (g / g) per 1 g of the material constituting the water absorption layer and the moisture release layer, and the horizontal axis is the external relative humidity (% RH). The solid line indicates the moisture absorption amount, and the dotted line indicates the moisture absorption amount when the moisture is released. A2 represents a water absorption layer, and A3 represents a moisture release layer.

  For example, when the relative humidity is 80% RH, the water absorption layer (A2) actively absorbs at least 0.1 g of moisture per 1 g of the constituent material and absorbs up to 0.43 g. If it exceeds 0.43 g, the corresponding moisture is released to the moisture release layer. On the other hand, when the relative humidity is 80% RH, the moisture release layer (A3) absorbs about 0.2 g per gram of the material constituting the moisture release layer, and when the relative humidity exceeds 0.2 g, the corresponding moisture is collected in the cathode. Released to the electrical side.

  Therefore, when the humidity control layer 220 is disposed at a relative humidity of 80% RH, the moisture absorption layer 221 starts to take in moisture from the outside air. At the same time, the water absorption layer 222 starts to take in moisture from the moisture absorption layer 221, and further the moisture release layer. 223 starts to take in moisture from the water absorption layer 222 and takes in moisture until the moisture absorption amount of the moisture release layer 223 becomes 0.2 g / g. The water absorption layer 222 takes moisture into the moisture release layer 223, but the moisture of the taken-in amount is supplemented with the moisture of the moisture absorption layer 221, and the moisture absorption amount is kept at 0.43 g / g. Further, the moisture absorption layer 221 takes moisture into the water absorption layer 222, and supplements the moisture thus taken in with external moisture and keeps the moisture absorption amount to be 0.2 g / g. In this way, the humidity control layer 120 takes in external moisture, so that the drying of the electrolyte membrane 101 and the anode electrode 102 can be suppressed, and the rise of output at the time of startup can be improved. It should be noted that the moisture absorption and moisture release values of the water absorption layer in FIG. 2 and the moisture absorption and moisture release values of the water absorption layer in FIG. FIG. 4 is a convenient graph for explaining the relationship between the moisture absorption amount and the moisture release amount of the moisture absorption layer, the water absorption layer, and the moisture release layer, and both are consistent.

(Embodiment 3)
FIG. 5 is a schematic cross-sectional view and a top view of the unit battery of the present embodiment. As shown in FIG. 5, the unit battery of the present embodiment is different from that of the embodiment except that the moisture absorption layer 321 constituting the humidity control layer 320 has a second through hole 321a penetrating the front and back. It is the same as that of Form 1. Below, the 2nd through-hole 321a is demonstrated.

<Second through hole>
In the present embodiment, the second through hole 321a formed in the moisture absorption layer 321 is formed at a position on the first through hole 105a, and the area Sb of the diameter of the second through hole 321a is the first It is characterized in that it is an area Sa or more of the diameter of one through hole 105a. Such a shape of the second through-hole 321a means a hole through which the front and back are linearly penetrating, and does not include a hole penetrating in a curve such as a fibrous gap. .

  6A is a top view of the cathode current collector, FIG. 6B is a top view of the hygroscopic layer, and FIG. 6C is a top view of the cathode current collector of FIG. 6A. FIG. 7 is a top view of the superposed hygroscopic layer of FIG. 6 (b). In FIG. 6C, a water absorbing layer is further formed between the cathode current collector 105 and the moisture absorbing layer 321, but the water absorbing layer is not shown in FIG. 6 for convenience of explanation.

  As shown in FIG. 6C, the moisture absorption layer 321 hardly absorbs moisture from the cathode current collector 105 side by arranging the second through hole 321a so as to overlap the first through hole 105a. Accordingly, drying of the electrolyte membrane 101 and the anode electrode 102 can be suppressed, and the output rise when the unit battery 100 is activated can be improved. In order to satisfy such a positional relationship between the first through hole 105a and the second through hole 321a, the diameter area Sb of the second through hole 321a is equal to or larger than the area Sa of the diameter of the first through hole 105a. Need to be.

Such area Sb of the diameter of the second through-hole 321a is preferably 0.12 mm ² or more 2.05 mm ² or less. When the thickness is less than 0.12 mm ² , the moisture absorption layer 321 also absorbs moisture on the cathode current collector 105 side.

(Embodiment 4)
FIG. 7 is a schematic cross-sectional view and a top view of the unit battery of the present embodiment. As shown in FIG. 7, the unit battery of the present embodiment is the same as that of the third embodiment, except that the water absorption layer 422 has a third through hole 422a penetrating the front and back. is there. Hereinafter, the third through hole 422a will be described.

<Third through hole>
In the present embodiment, the third through hole 422a formed in the water absorption layer 422 is formed between the first through hole 105a and the second through hole 421a, and the third through hole 422a. The area Sc of the diameter is smaller than the area Sa of the diameter of the first through hole 105a. Such a shape of the third through-hole 422a means a hole in which the front and back are linearly penetrated, and does not include a hole that is curvedly penetrated, such as a fibrous gap. .

  Thus, by making the area Sc of the diameter of the third through hole 422a smaller than the area Sa of the diameter of the first through hole 105a, moisture contained in the electrolyte membrane 101 and the anode electrode 102 is evaporated to the outside. In addition, it is possible to improve the moisture release property from the water absorption layer 422 to the cathode current collector 105 side.

Such area Sc of the diameter of the third through hole 422a is preferably 0.12 mm ² or more 2.05 mm ² or less. If it exceeds 2.05 mm ² , the moisture contained in the electrolyte membrane 101 and the anode electrode 102 tends to evaporate to the outside.

(Embodiment 5)
FIG. 8 is a schematic cross-sectional view and a top view of the unit battery of the present embodiment. As shown in FIG. 8, the unit battery of the present embodiment is the same as that of the first embodiment except that the third through-hole formed in the water absorption layer 522 is filled with a moisture release material 525. belongs to. Below, the moisture release material 525 is demonstrated.

<Moisture release material>
In this embodiment, it is preferable to use the same material as the moisture-releasing material 525 of Embodiment 2 as the moisture-releasing material 525 filled in the third through hole. The material used for the moisture-releasing material 525 is a material that is less hygroscopic than the material constituting the moisture-absorbing layer 521 or the same material as the water-absorbing layer 522, and its surface area is lower than that of the water-absorbing layer 522. Materials can be used. By using such a material, the effect of releasing moisture absorbed by the water absorption layer 522 to the cathode current collector 105 becomes significant.

<< Compound unit battery >>
(Embodiment 6)
FIG. 9 is an exploded perspective view of a composite unit cell formed by arranging the anode current collectors of two unit cells so as to face the supply layer.

  As shown in FIG. 9, the composite unit cell of the present embodiment includes two unit cells 610 and a supply layer 607 for supplying fuel to the anode electrodes of the two unit cells 610. Thus, the anode current collectors of the two unit cells 610 are both disposed so as to face the supply layer 607, and the humidity control layer 620 is disposed on the cathode current collector of any of the unit cells. Features. FIG. 9 shows a case where the humidity control layer 620 is provided in any of the two unit batteries 610. However, the present invention is not limited to this, and any one of the two unit batteries 610 is shown. Only the humidity control layer 620 may be provided.

<Supply layer>
In the present invention, the supply layer 607 has a comb shape, and is disposed between the two unit cells 610 so as to mesh with the comb fuel plate. Then, fuel is supplied by capillary action from the portion corresponding to the comb-shaped handle portion toward the tip. Such a supply layer 607 is preferably made of a material that absorbs fuel and has an appropriate diffusivity in terms of its properties. By supplying fuel using such a supply layer 607, liquid leakage of fuel to the outside can be prevented.

  As the material of the supply layer 607, for example, a porous body made of a polymer material such as natural fiber, polyester, polyvinyl, or polyamide, or a porous sintered body made of an inorganic material such as silica, titania, or alumina is used. be able to. In the present embodiment, the fuel is supplied to the anode electrode using the supply layer 607. However, the present invention is not limited to such a fuel supply means. For example, the fuel flow path is provided on the flow path plate. The provided one may be provided between the anode current collectors of the two unit cells, and the fuel may be supplied from the fuel flow path to the anode electrode.

<Vaporization layer>
In this embodiment, a vaporization layer 609 may be provided between the unit battery 610 and the supply layer 607. The vaporization layer 609 is provided to change the state of the liquid fuel supplied from the supply layer 607 to the anode electrode into a gaseous fuel. By providing such a vaporized layer 609, liquid fuel can be supplied in place of gaseous fuel without directly supplying it to the anode electrode.

  FIG. 10 is a perspective view of a composite unit battery formed by assembling the components shown in FIG. When the components shown in FIG. 9 are assembled, a composite unit battery 600 as shown in FIG. 10 is obtained. By soaking the liquid fuel into a portion of the supply layer 607 protruding, the liquid fuel diffuses inside by capillarity and becomes a gaseous fuel via the vaporization layer. Fuel is supplied to the anode electrode.

  FIG. 11 is an exploded perspective view formed by stacking two composite unit batteries with a spacer in between. As shown in FIG. 11, two composite unit cells can be connected by providing composite unit cells 600 on both sides of two spacers 630. By connecting the composite unit batteries in this manner, the output can be improved and power can be supplied for a long time. Note that FIG. 11 shows a case where two composite unit cells are stacked, but it goes without saying that three or more composite unit cells can be stacked by interposing a spacer.

  In addition, the spacer 630 used here is not limited to the form shown in FIG. 11, and may have any shape as long as it forms an interval between two composite unit batteries. However, the spacer 630 needs to be formed of an insulator so that the two composite unit batteries 600 are not electrically connected.

<< Fuel cell stack >>
(Embodiment 7)
FIG. 12 is a perspective view, a top view, and a side view showing a preferred example of the fuel cell stack of the present embodiment, FIG. 12 (A) is its perspective view, and FIG. 12 (B) is its top view. FIG. 12C is a side view thereof.

  As shown in FIG. 12A, the fuel cell stack 1 according to the present embodiment is formed by alternately stacking four fuel cell layers 10 and three spacer layers 20, Each of the fuel cell layers 10 is formed by arranging five unit cells 100 in parallel with a gap 11 in the same plane.

  On the other hand, each of the spacer layers 20 has five spacers 200 arranged in parallel with a gap 21 in the same plane, and each spacer 200 is arranged to be orthogonal to the unit cell 100. Both the gap 11 of the unit cell 100 formed in the fuel cell layer 10 and the gap 21 of the spacer 200 formed in the spacer layer 20 have a rectangular parallelepiped shape.

  By disposing the unit battery 100 and the spacer 200 in this way, the area where the gap 11 of each unit battery 100 and the spacer 200 are in contact with each other is the same area. In addition, since the unit cells 100 have the same height, the plurality of gaps 11 have the same space volume.

  The fuel cell stack of the present invention is not limited to the structure shown in FIG. 12, but includes two or more fuel cell layers, and at least one of the fuel cell layers. However, any structure in which two or more unit cells are arranged with a gap in the same plane is included in the scope of the present invention, and the spacer layer may not be included.

  However, from the viewpoint of stably supplying oxygen to the cathode electrode of the unit cell constituting the fuel cell layer 10, the fuel cell layer 10 and the spacer layer 20 are preferably laminated alternately. It is more preferable that the spacer 200 is configured as described above, and it is more preferable that two or more spacers 200 constituting the spacer layer 20 are arranged in parallel with a gap 21 in the same direction. When the spacer layer 20 is thus included, it is not always necessary to stack the layers in the order shown in FIG. 12, for example, on either one or both of the lowermost layer and the uppermost layer of each layer constituting the fuel cell stack. The spacer layer 20 may be formed.

  In the case where a plurality of fuel cell layers 10 including two or more unit cells 100 are stacked, it is preferable to use a conductive material for the spacer 200 provided between them. As a result, the fuel cell layers 10 can be connected in series, thereby contributing to an improvement in output.

  In the above description, the case where the fuel cell layer 10 has the five unit cells 100 arranged in the same plane has been described, but a composite unit cell may be arranged in the same plane instead of the unit cell. In this case, the spacer 200 constituting the spacer layer needs to be made of an insulating material.

  In this example, a unit cell having the structure shown in FIG. 1 was produced. First, as the electrolyte membrane 101 constituting the unit battery 100, an electrolyte membrane (trade name: Nafion (registered trademark) 117 (manufactured by DuPont)) having a width of 26 mm × a length of 26 mm and a thickness of about 175 μm was prepared.

  Next, catalyst-carrying carbon particles (trade name: TEC66E50 (Tanaka Kikinzoku Kogyo Co., Ltd.) consisting of Pt and Ru particles having a Pt loading amount of 32.5% by mass and a Ru loading amount of 16.9% by mass and carbon particles. Made of PTFE), an alcohol solution containing 20% by mass of Nafion (registered trademark) (Sigma Aldrich Japan Co., Ltd.), ion-exchanged water, isopropanol, and zirconia beads at a predetermined ratio. And mixing for 50 minutes at 50 rpm using a stirring deaerator. And the anode catalyst paste was produced by removing a zirconia bead from the mixture.

  Further, the catalyst support carbon particles (trade name: TEC10E50E (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.)) composed of Pt particles having a Pt support amount of 46.8% by mass and carbon particles were used. Cathode catalyst paste was prepared by material and method.

  Next, the anode catalyst paste produced above was screen-printed and applied to a carbon paper (product name: GDL25BC (manufactured by SGL Carbon Japan Co., Ltd.)) having an outer shape with a width of 23 mm and a length of 23 mm. The anode electrode 102 was formed by drying and removing ion-exchanged water and isopropanol contained in the anode catalyst paste.

Further, after the cathode catalyst paste prepared above was screen-printed onto the same carbon paper as described above, the cathode electrode 103 was formed by drying ion-exchanged water and isopropanol contained in the cathode catalyst paste. As the anode current collector 104, a gold mesh having a width of 23 mm and a length of 40 mm and having a fuel flow path 106 formed thereon was used. On the other hand, as the cathode current collector 105, a gold mesh having a width of 23 mm × a length of 40 mm and having five first through holes having an aperture area of 0.9 mm ² was used.

  Next, a polymer non-woven fiber (trade name: EXEN Plus (registered trademark) (manufactured by Toray Industries, Inc.)) made of polyester and polyurethane was used as the water absorbing layer 122. And the moisture absorption layer 121 was formed by apply | coating the zeolite dispersion liquid wet-ground with the ball mill with respect to this water absorption layer 122 to the water absorption layer 122, and making it dry. In this way, the humidity control layer 120 including the moisture absorption layer 121 and the water absorption layer 122 was produced.

Then, after placing a 400 μm gap gauge around the humidity control layer 120, the anode current collector 104, the anode electrode 102, the electrolyte membrane 101, the cathode electrode 103, and the cathode current collector 105 in this order. It was sandwiched between two stainless plates (width 150 mm × length 150 mm, thickness 3 mm). At this time, the anode electrode 102 and the cathode electrode 103 were arranged so as to be the center of the electrolyte membrane 101, and the anode electrode 102 was arranged so as to coincide with the cathode electrode 103 through the electrolyte membrane 101. The stainless steel plate was heated to 130 ° C. and thermocompression bonded at 10 kgf / cm ² for 2 minutes in the thickness direction of the stainless steel plate to produce a unit cell of this example.

  As shown in FIG. 3, the present embodiment is the same as the first embodiment except that a moisture release layer 223 is further provided on the side of the humidity control layer 220 in contact with the cathode current collector 105. Below, the material of the moisture release layer 223 and its formation method are demonstrated.

That is, the moisture release layer 223 is made of a polymer non-woven fiber (trade name: EXEN Plus (registered trademark) (manufactured by Toray Industries, Inc.)), which is the same material as the water absorption layer of Example 1, and two stainless steel plates (width) 150 mm × length 150 mm, thickness 3 mm) and formed by pressure bonding in the thickness direction at 10 kgf / cm ² for 2 minutes. This pressure bonding was performed by placing a 250 μm gap gauge around the moisture release layer.

In the present embodiment, as shown in FIG. 5, the second embodiment is the same as the first embodiment except that the moisture absorption layer 321 constituting the humidity control layer 320 is formed with a second through hole 321 a penetrating the front and back. belongs to. Here, the area of the diameter of the second through hole 321a was 1.0 mm ² .

In this embodiment, as shown in FIG. 7, the water absorption layer 422 is the same as the embodiment 3 except that a third through hole 422a penetrating the front and back is used. is there. Here, the area of the diameter of the third through hole 422a was 0.13 mm ² .

  In this embodiment, as shown in FIG. 8, the third embodiment is the same as the first embodiment except that the third through hole formed in the water absorption layer 522 is filled with a moisture release material 525. First, the humidity control layer 520 was prepared by the same method as in Example 1. A moisture retention layer 525 made of polyolefin was formed by spray-coating a 10 mass% polyolefin solution on the opposite side of the moisture conditioning layer 520 from the side where the moisture absorption layer 521 is formed, and drying.

(Comparative Example 1)
The unit cell of Comparative Example 1 in which the anode current collector, anode electrode, electrolyte membrane, cathode electrode, and cathode current collector were superposed in this order without including the humidity control layer in the unit cell of Example 1 It was.

<Output during driving>
The rising voltage (V) and ohmic resistance (Ω) at the start-up of the unit cells of Examples 1 to 4 and Comparative Example 1 were measured. In this measurement, Table 1 shows values when the current density per unit cell area is 100 mA / cm ² . Further, the rising voltage (V) and ohmic resistance (Ω) of the unit batteries of each Example and Comparative Example after 1 hour from the start of the unit battery were measured, and the results are shown in Table 1.

Here, the ohmic resistance is a measurement frequency of 50 mHz to 10 kHz, and an AC impedance measurement is performed under a load condition of a current density of 100 mA / cm ² with an AC amplitude of ± 10 mA / cm ^2. It was determined from the real part of the plot.

  From the results shown in the start-up voltage and ohmic resistance of the unit battery at start-up in Table 1, the unit batteries of Examples 1 to 4 have a higher start-up voltage than the unit battery of Comparative Example 1 (the power generation characteristics are excellent). It is clear that the ohmic resistance is low.

  This is because the unit cell of each embodiment is provided with a humidity control layer on the side opposite to the side of the cathode current collector that is in contact with the cathode electrode, so that the temperature and humidity inside the unit cell at the start-up can be kept moderate. Therefore, it is considered that water shortage at the anode electrode and drying of the electrolyte membrane did not occur.

  Further, from the results shown in the rising voltage and the ohmic resistance of “1 hour after starting” in Table 1, the unit cells of Examples 1 to 4 are higher in the rising voltage and the ohmic resistance than the unit battery of Comparative Example 1. It can be seen that is not reduced. The unit cells of Examples 1 to 4 are considered to be due to the fact that the temperature and humidity inside the unit cells were maintained moderately even when power was generated for a long time, and water shortage at the anode electrode and drying of the electrolyte membrane did not occur. . That is, by providing the humidity control layer on the side opposite to the side in contact with the cathode electrode of the cathode current collector, a stable voltage can be obtained not only at the start but also after a lapse of a certain time from the start.

In this example, the composite unit battery shown in FIG. 10 was produced. FIG. 9 shows each layer constituting the composite unit battery separately. As shown in FIG. 9, the humidity control layer 620, the unit cell 610, the vaporization layer 609, the fuel channel 608 into which the supply layer 607 is inserted, the vaporization layer 609, the unit cell 610, and the humidity control layer 620 are stacked in this order. In addition, a gap gauge of 1.8 mm was disposed around it. Then, the composite unit battery of this example was manufactured by sandwiching between two stainless plates (width 150 mm × length 150 mm, thickness 3 mm) and pressing in the thickness direction of the stainless plate at 10 kgf / cm ² for 2 minutes.

  As in the composite unit battery of this example, the humidity and humidity control layers are included in each layer constituting the composite unit battery, so that the temperature and humidity inside the composite unit battery are kept moderate, and there is insufficient water at the anode electrode and the electrolyte membrane. Drying did not occur. For this reason, the rising voltage when the composite unit battery is started up is high, and a high voltage can be stably obtained even after a certain time has passed since the start-up.

  In this example, a fuel cell stack having the structure shown in FIG. 12 was produced. First, five composite unit cells were arranged in parallel with a 2.8 mm gap on the same plane. Next, five double-sided tapes having a thickness of 400 μm were arranged in parallel on the above composite unit cell so as to be orthogonal to the composite unit cell with a gap of 2.8 mm.

  In this way, a fuel cell stack in which five composite unit cells and five double-sided tapes are alternately stacked, four composite unit cells in four layers, and five double-sided tapes in three layers are alternately stacked. Produced. Such a fuel cell stack is obtained by connecting composite unit cells in 5 parallel × 4 series.

  Like the fuel cell stack of the present embodiment, by including a humidity control layer in a part of each layer constituting the composite unit cell, the temperature and humidity inside the fuel cell stack can be maintained moderately, water shortage at the anode electrode and It was possible to prevent the electrolyte membrane from drying. For this reason, the rising voltage when the fuel cell stack is started up is high, and a high voltage can be stably obtained even after a certain time has elapsed since the start-up.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, a notebook computer, a mobile phone, an electronic notebook, a portable game device, a mobile TV device, a handy terminal, a PDA, a mobile DVD player, a notebook computer, a video device, a camera device, a ubiquitous device, a mobile generator, etc. A fuel cell system for electronic equipment can be provided.

  1 fuel cell stack, 10 fuel cell layer, 11 gap, 20 spacer layer, 21 gap, 100 unit cell, 101 electrolyte membrane, 102 anode electrode, 103 cathode electrode, 104 anode current collector, 105 cathode current collector, 105a 1 through hole, 106 fuel flow path, 120, 220, 320, 620 humidity control layer, 121, 221, 321, 521 moisture absorption layer, 122, 222, 422, 522 water absorption layer, 200 spacer, 223 moisture release layer, 321a , 421a 2nd through-hole, 422a 3rd through-hole, 525 moisture release material, 600 composite unit cell, 607 supply layer, 609 vaporization layer, 610 unit cell, 630 spacer.

Claims (14)

A unit battery including a cathode current collector, a cathode electrode, an electrolyte membrane, an anode electrode, and an anode current collector in this order,
A humidity control layer is provided on the opposite side of the cathode current collector from the side in contact with the cathode electrode,
The humidity control layer includes a moisture absorption layer for taking in external moisture, and a water absorption layer for absorbing moisture in the moisture absorption layer,
The unit cell is arranged such that the water absorption layer is in contact with the cathode current collector.   2. The unit cell according to claim 1, wherein the humidity control layer further includes a moisture release layer for releasing moisture retained by the water absorption layer on a side in contact with the cathode current collector.   The unit battery according to claim 2, wherein the moisture release layer is made of a material having a lower hygroscopic property than a material constituting the moisture absorption layer. The cathode current collector has a first through hole penetrating the front and back thereof,
The unit battery according to claim 1, wherein the moisture absorption layer has a second through hole penetrating the front and back surfaces thereof.   The unit battery according to claim 4, wherein the second through hole is formed at a position on the first through hole.   6. The unit battery according to claim 4, wherein an area Sb of the diameter of the second through hole is equal to or larger than an area Sa of the diameter of the first through hole. The water absorption layer has a third through hole penetrating the front and back surfaces thereof,
The third through hole is formed on the first through hole,
The unit cell according to any one of claims 4 to 6, wherein an area Sc of the diameter of the third through hole is smaller than an area Sa of the diameter of the first through hole. The water absorption layer has a third through hole penetrating the front and back surfaces thereof,
The unit cell according to any one of claims 1 to 6, wherein a moisture-releasing material for releasing moisture held in the water absorption layer is filled in the third through hole.   The unit cell according to any one of claims 1 to 8, further comprising a protective layer on a side of the humidity control layer opposite to a side in contact with the cathode current collector. A composite unit cell comprising two unit cells and a fuel supply means for supplying fuel to the anode electrode of the two unit cells,
Both of the anode current collectors of the two unit cells are arranged so as to face the fuel supply means,
A composite unit battery, wherein at least one of the two unit batteries is the unit battery according to claim 1.   The composite unit cell according to claim 10, wherein the fuel supply means is a fuel flow path.   The composite unit cell according to claim 10, wherein the fuel supply means is a supply layer. A fuel cell stack in which two or more unit cells are stacked with two or more fuel cell layers arranged with a gap in the same plane,
A fuel cell stack, wherein at least one of the two or more unit cells is the unit cell according to claim 1. A fuel cell stack in which two or more unit cells are stacked with two or more fuel cell layers arranged with a gap in the same plane,
At least one of the fuel cell layers is a fuel cell stack in which two or more composite unit cells according to any one of claims 10 to 12 are arranged with a gap in the same plane.

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