JP2004247294A - Power generation element for fuel cell, its manufacturing method, and fuel cell using power generation element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power generation element for a fuel cell which enables compatibility of thickening of an electrode layer, a porous structure of the electrode layer, and structural integrity. <P>SOLUTION: This is the power generation element for the fuel cell which is provided with a positive electrode to reduce oxygen, a negative electrode to oxidize the fuel, and a solid electrolyte installed between the positive electrode and the negative electrode, and at least one of the positive electrode and the negative electrode is provided with a laminate in which two or more of the electrode layers containing a catalyst are laminated, and the thickness of respective electrode layers are respectively 50 μm or less, and an adhesive layer is arranged between respective electrode layers. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a power generation element for a fuel cell using a liquid fuel such as methanol, a method for manufacturing the same, and a fuel cell using the power generation element.

  2. Description of the Related Art In recent years, with the spread of cordless devices such as personal computers and mobile phones, there is a demand for smaller and higher capacity secondary batteries as power sources. At present, lithium ion secondary batteries have been put to practical use as secondary batteries having a high energy density and can be reduced in size and weight, and demand for portable power sources is increasing. However, depending on the type of cordless device used, this lithium secondary battery has not yet reached a level where sufficient continuous use time is guaranteed.

Under these circumstances, a solid polymer fuel cell that uses a solid polymer electrolyte as the electrolyte, oxygen in the air as the positive electrode active material, hydrogen, and methanol as the negative electrode active material as a battery that can meet the above demands is described. As a system that can be expected to have a higher energy density than a lithium ion secondary battery, it has been drawing attention. Above all, a direct methanol fuel cell that uses methanol, which is a liquid fuel, directly in the reaction of the cell does not require a blower that supplies air to the cell body or a pump that supplies fuel, and can be downsized. It is promising as a future portable power supply (for example, see Patent Documents 1 to 5).
JP 2000-268836 A JP 2002-184415 A JP-A-10-189004 JP-A-11-288727 JP-A-2002-15743

  However, in a direct methanol fuel cell, the rate of methanol oxidation reaction at the negative electrode is extremely slow, and to compensate for this, the amount of catalyst at the negative electrode must be increased and the reaction surface area must be increased. When a proton-conductive solid polymer membrane or the like is used as the solid polymer electrolyte, a crossover phenomenon occurs in which liquid fuel such as methanol permeates through the electrolyte membrane to the positive electrode side. When this phenomenon occurs, methanol and oxygen directly react (combust) on the catalyst of the positive electrode, and the surface area of the catalyst used in the reduction reaction of oxygen at the positive electrode, which is the original battery reaction, decreases.

If the crossover problem does not occur, the amount of catalyst of the positive electrode can be made smaller than that of the negative electrode. However, in general, the required amount of platinum catalyst for both the positive electrode and the negative electrode is 5 to 15 mg / cm ² per unit area of the electrode. Yes, more catalyst is required than when hydrogen is used as fuel (required amount of catalyst: about 0.3 to 0.5 mg / cm ² ).

  Here, in order to increase the amount of catalyst in the electrode layer, it is essential to increase the thickness of the electrode layer. In the electrode layer of the fuel cell, what is more important than the thickness increase is that fuel and oxygen can be well distributed and move through the electrode layer. For this purpose, it is necessary that the electrode layer has a relatively uniform porous structure and that the electrode layer is structurally free from defects such as cracks, that is, structural integrity.

  However, when the thickness of the electrode layer is increased by applying the electrode layer to the substrate in order to increase the amount of the catalyst, the drying of the surface of the applied electrode layer proceeds faster than the drying of the inside, so that a large crack is formed on the surface of the electrode layer. This may easily occur, and the electrode layer may be peeled off from the electrode substrate or fall off. These phenomena impair the porous structure and structural integrity required of the electrode layer, and as a result, adversely affect battery characteristics. As one of the solutions to this problem, as described in Patent Document 2, a method of suppressing the occurrence of cracks by speeding up the drying process using a porous electrode substrate has been proposed. However, it is difficult to cope with an increase in the thickness of the electrode layer exceeding 50 μm required for a direct methanol fuel cell.

  Accordingly, the present invention provides a power generating element for a fuel cell, which can achieve both a thicker electrode layer and a porous structure and structural integrity of the electrode layer.

The present invention is a fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode has a laminate in which two or more electrode layers containing a catalyst are laminated,
A power generation element for a fuel cell, wherein the thickness of the electrode layer is 50 μm or less, and an adhesive layer is disposed between the electrode layers.

Further, the present invention is a fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode has a laminate formed by laminating two or more electrode layers containing a catalyst and a polymer material having proton conductivity,
The electrode layer has a thickness of 50 μm or less;
There is provided a fuel cell power generating element, wherein the polymer material is present more in the interface than in the electrode layer.

Furthermore, the present invention is a fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode is an electrode having a total thickness of 60 to 300 μm and a mass of a catalyst contained per unit area of 0.3 to 3 mg / cm ^2. Provided is a power generation element for a battery.

Further, the present invention is a method for producing the fuel cell power generating element,
A first step of disposing an adhesive layer on the release substrate;
A second step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on the adhesive layer;
A third step of bringing the electrode layer into contact with a solid electrolyte;
A fourth step of bonding the electrode layer and the solid electrolyte by applying pressure while heating;
A fifth step of peeling the releasable substrate after bonding the electrode layer and the solid electrolyte to expose the adhesive layer,
A sixth step of disposing another electrode layer containing a catalyst and having a thickness of 50 μm or less on the exposed adhesive layer;
And a seventh step of applying pressure while heating the adhesive layer and the other electrode layer to bond the adhesive layer to the other electrode layer.

Further, the present invention is another method for manufacturing the fuel cell power generating element,
A first step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on a release substrate;
A second step of bringing the electrode layer into contact with a solid electrolyte;
A third step of bonding the electrode layer and the solid electrolyte by applying pressure while heating;
A fourth step of peeling off the release substrate after bonding the electrode layer and the solid electrolyte to expose the electrode layer,
A fifth step of disposing an adhesive layer on the exposed electrode layer;
A sixth step of disposing another electrode layer containing a catalyst and having a thickness of 50 μm or less on the adhesive layer;
And a seventh step of applying pressure while heating the adhesive layer and the other electrode layer to bond the adhesive layer to the other electrode layer.

  Furthermore, the present invention provides a fuel cell using the fuel cell power generating element.

  The present invention achieves high power generation efficiency by making the catalyst in the electrode act efficiently by making the thickness of the electrode of the fuel cell power generation element compatible with the porous structure and structural integrity of the electrode. This is an implementation of the element.

  Hereinafter, embodiments of the present invention will be described.

  First, an embodiment of the fuel cell power generating element of the present invention will be described. The power generating element for a fuel cell according to the present embodiment includes a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode. Further, at least one of the positive electrode and the negative electrode has a laminate in which two or more electrode layers containing a catalyst are laminated, and the thickness of each electrode layer is 50 μm or less, more preferably 45 μm or less, and further more preferably. Is 40 μm or less, and an adhesive layer is disposed between the respective electrode layers. The lower limit of the thickness of each electrode layer is preferably 10 μm or more, more preferably 30 μm or more, so as not to increase the number of electrode layers to be laminated so much.

  In addition, in order to improve the oxidation reaction rate of methanol, it is preferable that at least the negative electrode has the above-described laminate, and from the viewpoint of the crossover phenomenon described above, not only the negative electrode but also the positive electrode has the same laminate as above. It is desirable to have. Further, both the electrode layer and the adhesive layer have proton conductivity and electron conductivity.

  Thereby, since it is possible to laminate while maintaining the thickness of each electrode layer in a range that can maintain the porous structure and the structural integrity, even if the total thickness of the entire electrode is increased and the amount of catalyst is increased, The overall porous structure and structural integrity is not lost. In addition, the thickness of each electrode layer for maintaining the porous structure and structural integrity varies depending on the material included in the electrode layer, etc. Structural integrity can be maintained. Further, the adhesive layer disposed between the electrode layers joins the electrode layers while maintaining proton conductivity and electron conductivity, and the adhesive layer facilitates formation of a laminate.

  The electrodes having a layered structure are described in Patent Document 3, Patent Document 4, Patent Document 5, etc., but none of them intends to increase the thickness of the electrodes, and the method is also repeated. This is the formation of a layer structure, and there is a limit in increasing the thickness of the electrode.

  Next, an embodiment of a method for manufacturing a power generating element for a fuel cell according to the present invention will be described. This embodiment includes a first step of disposing an adhesive layer on a release substrate and a second step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on the adhesive layer. A third step of bringing the electrode layer into contact with the solid electrolyte; a fourth step of applying pressure while heating the electrode layer and the solid electrolyte; and adhering the electrode layer and the solid electrolyte. A fifth step of exfoliating the above-mentioned releasable substrate to expose an adhesive layer, and further forming another electrode layer containing a catalyst and having a thickness of 50 μm or less on the exposed adhesive layer. And a seventh step of bonding the adhesive layer and the other electrode layer by applying pressure while heating.

  Further, in the present embodiment, the second step separately formed in the first step and the second step on the exposed adhesive layer between the fifth step and the sixth step. Is further arranged such that the adhesive layer and the second electrode layer are adhered by applying pressure while heating, and then the adhesive layer is exposed by peeling off the release substrate. In addition, a laminate of three or more layers can be formed.

  Another embodiment of the method for producing a fuel cell power generating element of the present invention includes a first step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on a release substrate. A second step of bringing the electrode layer into contact with the solid electrolyte, a third step of applying pressure while heating the electrode layer and the solid electrolyte, and adhering the electrode layer and the solid electrolyte. A fourth step of exfoliating the release substrate to expose the electrode layer, a fifth step of disposing an adhesive layer on the exposed electrode layer, and a catalyst on the adhesive layer. And a seventh step of arranging another electrode layer having a thickness of 50 μm or less and a step of applying pressure while heating the adhesive layer and the other electrode layer.

  Further, in the present embodiment, a second electrode layer separately formed in the first step is disposed on the adhesive layer between the fifth step and the sixth step, and the adhesive layer And the second electrode layer are heated and pressurized and bonded, and then the release substrate is peeled off to expose the second electrode layer, and the second electrode layer is bonded on the exposed second electrode layer. By further including one or more steps of further arranging layers, a laminate of three or more layers can be formed.

  According to the above manufacturing method, since it is possible to stack while maintaining the thickness of each electrode layer in a range that can maintain the porous structure and structural integrity, the total thickness of the entire electrode is increased to increase the amount of catalyst. In addition, a fuel cell power generation element can be manufactured without losing the porous structure and structural integrity of the entire electrode. That is, in the present production method, an electrode laminate can be formed by a simple method of sequentially transferring an electrode layer having a porous structure and structural integrity to a solid electrolyte.

  Next, the fuel cell power generating element of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the fuel cell power generating element of the present invention. In FIG. 1, this fuel cell power generating element includes a positive electrode 1 for reducing oxygen, a negative electrode 3 for oxidizing fuel, and a solid polymer electrolyte membrane 2 provided between the positive electrode 1 and the negative electrode 3. I have. The positive electrode 1 is formed by laminating a positive electrode layer 1a, an adhesive layer 4, and a positive electrode layer 1b in this order. Further, similarly to the positive electrode 1, the negative electrode 3 is formed by laminating the negative electrode layer 3a, the adhesive layer 4, and the negative electrode layer 3b in this order.

  FIG. 2 is a schematic sectional view showing another example of the fuel cell power generating element of the present invention. In FIG. 2, this fuel cell power generating element includes a positive electrode 1 for reducing oxygen, a negative electrode 3 for oxidizing fuel, and a solid polymer electrolyte membrane 2 provided between the positive electrode 1 and the negative electrode 3. I have. The positive electrode 1 is formed by laminating a positive electrode layer 1a, an adhesive layer 4, a positive electrode layer 1b, an adhesive layer 4, and a positive electrode layer 1c in this order. Similarly to the positive electrode 1, the negative electrode 3 is formed by laminating a negative electrode layer 3a, an adhesive layer 4, a negative electrode layer 3b, an adhesive layer 4, and a negative electrode layer 3c in this order. .

  The adhesive layer 4 can be made of an adhesive material having only proton conductivity or an adhesive material having both proton conductivity and electron conductivity. When an adhesive material having only proton conductivity is used as the adhesive layer, another method such as diffusing a conductive material contained in the electrode layer described later into the adhesive layer is also applied to the adhesive layer. Finally, it is necessary to impart electronic conductivity.

  As the adhesive material having only proton conductivity, a polymer material having proton conductivity, a mixed material of a polymer material having high adhesiveness and a polymer material having proton conductivity, or the like can be used. Examples of the proton conductive polymer material include polyperfluorosulfonic acid resin, sulfonated polyethersulfonic acid resin, sulfonated polyimide resin, and styrene-divinylbenzenesulfonic acid resin. Examples of the high-adhesive polymer material used by mixing with the proton-conductive polymer material include polystyrene, polyacrylonitrile, polyethylene terephthalate (PET), and polyvinyl acetate.

  Further, as the adhesive material having both proton conductivity and electron conductivity, a polymer material having proton conductivity and electron conductivity, or a polymer material having electron conductivity and the above-mentioned proton conductive polymer material A mixed material or the like can be used. As the polymer material having proton conductivity and electron conductivity, for example, (alkyl) sulfonated polyaniline, (alkyl) sulfonated polypyrrole, (alkyl) sulfonated polythiophene, (alkyl) sulfonated poly p-phenylene, ( (Alkyl) sulfonated polyfuran and the like. Examples of the electron conductive polymer material include polyaniline, alkyl polyaniline, alkyl polypyrrole, alkyl polythiophene, alkyl poly p-phenylene, and alkyl polyfuran.

  The negative electrode layers 3a to 3c can be made of a catalyst, a conductive material, a polymer material, or the like. As the catalyst contained in the negative electrode layer, those having a function of generating protons from the fuel, that is, those having a function of electrochemically oxidizing the fuel can be used.For example, platinum fine particles alone, platinum and ruthenium, indium, Alloy fine particles of iridium, tin, iron, titanium, gold, silver, chromium, silicon, zinc, manganese, molybdenum, tungsten, rhenium, aluminum, lead, palladium, osmium, and the like are used. As the conductive material, a carbon material is mainly used, and for example, carbon black, activated carbon, carbon nanotube, carbon nanohorn and the like are used. Generally, it is used in a state of catalyst-supporting carbon in which the above-mentioned catalyst is dispersed and supported on the surface of a conductive material.

  As the polymer material contained in the negative electrode layers 3a to 3c, a material having only proton conductivity or a material having both proton conductivity and electron conductivity is used. It is preferable to use the same kind of polymer material. This is because the same type can reduce the contact resistance (interface resistance) between the adhesive layer and the electrode layer.

  Further, the negative electrode layers 3a to 3c may include a binder such as polytetrafluoroethylene (PTFE) resin, polyvinylidene fluoride (PVDF) resin, polyethylene (PE) resin, or the like.

  The positive electrode layers 1a to 1c can also be made of a catalyst, a conductive material, a polymer material, or the like. As the catalyst contained in the positive electrode layer, those having a function of electrochemically reducing oxygen can be used, for example, platinum fine particles, iron, nickel, cobalt, tin, ruthenium or gold and platinum and Alloy fine particles are used. As the conductive material, the polymer material, and the binder, the same materials as those for the negative electrode can be used.

The solid polymer electrolyte membrane 2 disposed between the positive electrode 1 and the negative electrode 3 is made of a material having no proton conductivity and having only proton conductivity. For example, a polyperfluorosulfonic acid resin membrane, specifically, "Nafion" (trade name) manufactured by DuPont, "Flemion" (trade name) manufactured by Asahi Glass Co., Ltd., "Aciplex" (trade name) manufactured by Asahi Kasei Corporation Can be used. Others include a sulfonated polyether sulfonic acid resin film, a sulfonated polyimide resin film, a sulfuric acid-doped polybenzimidazole film, a phosphoric acid-doped SiO ₂ film known as a solid electrolyte, a hybrid film of a polymer and a solid electrolyte, or Examples include a gel electrolyte membrane in which molecules and oxides are impregnated with an acidic solution.

Next, an embodiment of a method for manufacturing a power generating element for a fuel cell according to the present invention will be described.
First, in the first embodiment, first, an electrode paste used for forming an electrode layer is prepared. This electrode paste is prepared by dissolving and dispersing a catalyst, a conductive material, a polymer material, and, if necessary, a binder in a solvent mainly composed of a lower alcohol such as ethanol and propanol, and sufficiently stirring the solution. Prepare.

  Separately, a release substrate having an adhesive layer on the surface is prepared. As the release substrate, for example, a PTFE film, a PET film, a polyimide film, a PTFE-coated polyimide film, a PTFE-coated silicon sheet, a PTFE-coated glass cloth, or the like can be used. The thickness of the adhesive layer provided on the release substrate is preferably in the range of 1 to 5 μm. Within this range, the function as the adhesive layer can be sufficiently exhibited, the lamination transfer of the electrode layer can be performed favorably, and the conductive material contained in the electrode layer described later is easily diffused into the adhesive layer. This is because the resistance does not increase and the diffusion resistance of oxygen and fuel can be reduced.

  Further, as the adhesive material used for the adhesive layer, any of the above-described adhesive materials having only proton conductivity or the adhesive materials having both proton conductivity and electron conductivity can be used.

Next, an electrode layer is formed by applying and drying the above-mentioned electrode paste on the adhesive layer provided on the release substrate. The thickness of the formed electrode layer is set to 10 to 50 μm which does not impair the porous structure and structural integrity of the electrode layer and can ensure a certain amount of catalyst. Further, the amount of catalyst (mass per unit electrode area) contained in the electrode layer is preferably in the range of 0.3 to 3 mg / cm ² . If the amount of the catalyst is within this range, the necessary amount of the catalyst can be ensured without increasing the total number of electrode layers.

  Thereafter, the electrode layer formed on the releasable substrate via the adhesive layer is cut into a predetermined electrode size together with the releasable substrate, and the electrode layer surface is formed on both sides of the solid polymer electrolyte membrane. The electrode layers are transferred and joined to the solid polymer electrolyte membrane by hot pressing or hot roll pressing. Thereafter, the release substrate is peeled off, and a power generation element precursor is obtained by the first transfer.

  Subsequently, the electrode layers produced in the same manner as above are superimposed on the adhesive layers exposed on both surfaces of the power generation element precursor, and a second hot press or hot roll press is performed. Thus, the electrode layer can be transferred and joined to the power generation element precursor in the same manner as described above. In the power-generating element precursor obtained here, at the joint portion between the electrode layer and the adhesive layer, both are united together, and even if a material having only proton conductivity is used for the adhesive layer, the conductive material contained in the electrode layer can be used. Electron conductivity can also be imparted to the adhesive layer by diffusion. Therefore, in the present embodiment, the polymer material used for the adhesive layer only needs to have at least proton conductivity, and is not necessarily required to have electronic conductivity.

  After repeating these operations several times, finally, by transferring and joining only the electrode layer formed on the releasable substrate, the thickness of the electrode can be increased, and the porous structure and structural integrity can be improved. A compatible fuel cell power generation element is manufactured.

  The total thickness of each of the final positive electrode and negative electrode of the fuel cell power generation element is preferably in the range of 30 to 300 μm. Within this range, a sufficient amount of catalyst for obtaining sufficient battery characteristics can be ensured, and there is no problem in diffusion of oxygen and fuel. When the thickness is 50 μm or less, an electrode can be formed as a single layer without forming a laminated body. However, by forming a laminated body, a more uniform electrode can be easily formed. In the case where an electrode having a thickness of 60 μm or more is formed, the present invention is more effective.

Next, a description will be given of a second embodiment of the method for manufacturing a power generating element for a fuel cell according to the present invention. Also in this embodiment, first, an electrode paste used for forming an electrode layer is prepared in the same manner as described above. Next, an electrode layer is formed by applying and drying only the electrode paste on the same releasable substrate as described above. The thickness of the formed electrode layer is set to 10 to 50 μm which does not impair the porous structure and structural integrity of the electrode layer and can ensure a certain amount of catalyst. Also, the amount of catalyst (mass per unit electrode area) contained in the electrode layer is preferably in the range of 0.3 to 3 mg / cm ² as described above.

  Then, the above-mentioned electrode layer formed on the release substrate is cut into a predetermined electrode size together with the release substrate, and is superposed on both surfaces of the solid polymer electrolyte membrane with the electrode layer surface facing the solid polymer electrolyte membrane. The electrode layer is transferred and joined to the polymer electrolyte membrane by hot pressing or hot roll pressing. Thereafter, the release substrate is peeled off, and a power generation element precursor is obtained by the first transfer.

  Subsequently, the electrode layers prepared in the same manner as above are superimposed on both surfaces of the power generation element precursor, and a second hot press or hot roll press is performed. At this time, a thin film made of an adhesive layer having the same size as the separately prepared electrode is arranged between the power generation element precursor and the electrode layer. Thereby, this thin film functions as an adhesive layer, and the electrode layer can be transferred and joined to the power generation element precursor. In the power generation element precursor obtained here, there is a case where the electrode layer and the adhesive layer are hardly united at the joint portion in some cases. Therefore, in this embodiment, the polymer material used for the adhesive layer is proton conductive and electron conductive. A material having both conductivity is desirable.

  The thickness of the thin film of the adhesive layer is preferably in the range of 1 to 5 μm. Within this range, the function as the adhesive layer can be sufficiently exhibited, the lamination transfer of the electrode layer can be performed well, the electronic resistance does not increase, and the diffusion resistance of oxygen and fuel can be reduced.

  By repeating these operations several times, a fuel cell power generation element having both a thick electrode and a porous structure and structural integrity is produced. The final total thickness of the electrode of the fuel cell power generating element is preferably in the range of 30 to 300 μm as in the above. Further, when an electrode having a thickness of 60 μm or more is formed, the present invention is more effective.

  In the electrode laminate of the negative electrode or the positive electrode manufactured as described above, a structure in which a large amount of a polymer material having proton conductivity can be present at an interface portion of each electrode layer rather than inside the electrode layer, Since the interface portion where the polymer material is concentrated functions as an adhesive layer, each electrode layer can be preferably integrated to form a laminate.

  The configuration of each electrode layer may be different from each other, and the desired electrode characteristics can be exhibited by changing the type and amount of the catalyst for each electrode layer, or by changing the thickness of each electrode layer. You can also.

  The fuel cell power generating element is further provided with a diffusion layer on both sides of the positive electrode and the negative electrode, a current collector is provided on each of the positive electrode and the negative electrode to make an electrical connection, the negative electrode, a liquid fuel containing methanol, the positive electrode By supplying air (oxygen) to the fuel cell, it is possible to function as a fuel cell.

  Hereinafter, the present invention will be described based on examples. Note that the present invention is not limited to the following embodiments.

  A fuel cell power generating element having the same structure as that shown in FIG. 1 was produced by the following procedure.

  For the positive electrode, 1 part by mass of platinum-supported carbon “10E50E” (trade name) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. supporting 50% by mass of platinum as a catalyst was mixed with Aldrich (a 5% by mass solution of polyperfluorosulfonic acid resin). An electrode paste is prepared by adding 12 parts by weight of "Nafion" (trade name, EW = 1000) solution and 1 part by weight of water manufactured by Aldrich Co., Ltd., and sufficiently stirring the mixed solution so as to be uniformly dispersed. did. The above EW represents the equivalent mass of an ion exchange group having proton conductivity (a sulfonic acid group in this example). The equivalent mass is a dry mass of the ion exchange resin per equivalent of the ion exchange group, and is expressed in units of “g / ew”.

Next, a PTFE film is prepared in which the above-mentioned “Nafion” solution is applied on the surface thereof as an adhesive layer so as to have a thickness of 5 μm, and the above-mentioned electrode paste is applied on the adhesive layer, dried, and the catalyst is supported. An electrode layer having an amount of 1.0 mg / cm ² and a thickness of 30 μm was obtained. This electrode layer was cut out to a predetermined size to obtain a positive electrode layer A1.

For the negative electrode, a platinum / ruthenium alloy-supported carbon “61V33” (trade name) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., which supported 33% by mass of an alloy of platinum and ruthenium (alloy mass ratio 1: 1) as a catalyst, was used. An electrode layer having a catalyst carrying amount of 1.0 mg / cm ² and a thickness of 35 μm was obtained in the same manner as in the positive electrode. This electrode layer was cut out to a predetermined size in the same manner as the positive electrode, to obtain a negative electrode layer B1.

  As a solid polymer electrolyte membrane (hereinafter, referred to as an electrolyte membrane), a polyperfluorosulfonic acid resin membrane “Nafion 112” (trade name) manufactured by DuPont was cut into a predetermined size and used.

  The positive electrode layer A1 and the negative electrode layer B1 previously prepared are superposed on both sides of the electrolyte membrane with the electrode surface facing the electrolyte membrane, and hot pressed at a temperature of 160 ° C. and a pressure of 4.4 MPa. And joined them. After that, the PTFE films on both sides were peeled off to obtain a power generation element precursor C1.

  Subsequently, a positive electrode layer A2 and a negative electrode layer B2 produced in the same manner as described above, except that a PTFE film having no adhesive layer applied to the surface thereof were used on both surfaces of the power generation element precursor C1, were used. The same poles were arranged so as to overlap the electrode layer portion with the surface facing the power generation element precursor, and a second hot press was performed at a temperature of 160 ° C. and a pressure of 4.4 MPa to join them. Thereafter, the PTFE films on both sides were peeled off, to obtain a fuel cell power generating element in which the positive electrode and the negative electrode each consisted of two electrode layers.

The electrode thickness of this power generation element was 65 μm for the positive electrode and 75 μm for the negative electrode. The amount of the catalyst was 2.0 mg / cm ² for both the positive and negative electrodes since two electrode layers of 1.0 mg / cm ² were laminated.

  A power generating element for a fuel cell having the same structure as that shown in FIG. 2 was produced by the following procedure.

  First, the positive electrode layer A1 and the negative electrode positive layer B1 described in Example 1 were further overlaid on both surfaces of the power generation element precursor C1 of Example 1 so that the electrode surfaces faced the electrolyte membrane, and the temperature was 160 ° C. Hot pressing was performed under the conditions of ° C. and a pressure of 4.4 MPa, and these were joined. Thereafter, the PTFE films on both sides were peeled off to obtain a power generation element precursor C2.

  Next, the positive electrode layer A2 and the negative electrode layer B2 described in Example 1 are placed on both surfaces of the power generation element precursor C2, and the same electrodes overlap the electrode layer portions with the electrode surfaces facing the power generation element precursor. , And a third hot press was performed under the conditions of a temperature of 160 ° C. and a pressure of 4.4 MPa to join them. Thereafter, the PTFE films on both sides were peeled off, to obtain a fuel cell power generating element in which each of the positive electrode and the negative electrode was composed of three electrode layers.

The electrode thickness of this power generation element was 100 μm for the positive electrode and 115 μm for the negative electrode. The amount of the catalyst was 3.0 mg / cm ² for both positive and negative electrodes because three electrode layers of 1.0 mg / cm ² were laminated.

  A fuel cell power generating element having the same structure as that shown in FIG. 1 was produced by the following procedure.

  The positive electrode layer A2 and the negative electrode layer B2 described in Example 1 were superposed on both surfaces of the electrolyte membrane described in Example 1 with the electrode surface facing the electrolyte membrane, and the temperature was 160 ° C and the pressure was 4 ° C. Hot pressing was performed under the condition of 0.4 MPa, and these were joined. After that, the PTFE films on both sides were peeled off to obtain a power generation element precursor C3.

  Next, a 5 μm-thick thin film made of a mixed resin of polyaniline and polyperfluorosulfonic acid resin was prepared as an adhesive layer, and this was cut into the same size as the electrodes to obtain a solid electrolyte membrane D.

  Subsequently, the solid electrolyte membrane D is superimposed on both electrode surfaces of the power generation element precursor C3, and the positive electrode layer A2 and the negative electrode layer B2 described in Example 1 are further superposed thereon. On the precursor side, the same electrodes were arranged so as to overlap with the electrode layer portion, and a second hot press was performed under the conditions of a temperature of 160 ° C. and a pressure of 4.4 MPa to join them. Thereafter, the PTFE films on both sides were peeled off to obtain a fuel cell power generating element composed of two electrode layers.

The electrode thickness of this power generation element was 65 μm for the positive electrode and 75 μm for the negative electrode. The amount of the catalyst was 2.0 mg / cm ² for both the positive and negative electrodes since two electrode layers of 1.0 mg / cm ² were laminated.

  A power generating element for a fuel cell having the same structure as that shown in FIG. 2 was produced by the following procedure.

  The solid electrolyte membrane D of Example 3 was overlaid on both sides of the fuel cell power generation element produced in Example 3, and the positive electrode layer A2 and the negative electrode layer B2 described in Example 1 were further superposed thereon. On the power generation element side, the same poles were arranged so as to overlap the electrode layer portion, and a third hot press was performed under the conditions of a temperature of 160 ° C. and a pressure of 4.4 MPa to join them. Thereafter, the PTFE films on both sides were peeled off to obtain a fuel cell power generating element including three electrode layers.

The electrode thickness of this power generation element was 100 μm for the positive electrode and 115 μm for the negative electrode. The amount of the catalyst was 3.0 mg / cm ² for both positive and negative electrodes because three electrode layers of 1.0 mg / cm ² were laminated.
(Comparative Example 1)

  FIG. 3 is a schematic cross-sectional view of a fuel cell power generation element of Comparative Example 1 including a positive electrode 1, a negative electrode 3, and a solid polymer electrolyte membrane 2 each having a one-layer structure. This power generation element for a fuel cell uses the power generation element precursor C3 produced in Example 3 as it is as a power generation element.

The electrode thickness of this power generation element is 30 μm for the positive electrode and 35 μm for the negative electrode. The amount of the catalyst is 1.0 mg / cm ² for both the positive and negative electrodes because of the single layer structure of the electrode layer of 1.0 mg / cm ² .
(Comparative Example 2)

FIG. 4 is a schematic cross-sectional view of a fuel cell power generation element of Comparative Example 2 including a positive electrode 1, a negative electrode 3, and a solid polymer electrolyte membrane 2 each having a one-layer structure. This fuel cell power generating element was a comparative example except that a positive electrode layer having a catalyst loading of 2.0 mg / cm ² and a thickness of 65 μm and a negative electrode layer having a catalyst loading of 2.0 mg / cm ² and a thickness of 75 μm were used. It was produced in the same manner as in Example 1.
(Comparative Example 3)

Comparative Example 3 was the same as Comparative Example 1 except that a positive electrode layer having a catalyst loading of 3.0 mg / cm ² and a thickness of 100 μm, and a negative electrode layer having a catalyst loading of 3.0 mg / cm ² and a thickness of 115 μm were used. To produce a power generation element for a fuel cell, the number of cracks occurred on the surface of the electrode layer during the process of thickening the electrode layer, and the electrode layer was peeled off and dropped off from the PTFE film. Under the manufacturing conditions of the present comparative example, a practical electrode layer could not be manufactured.

  An evaluation test was conducted by incorporating the power generating elements for fuel cells of Examples 1 to 4 and Comparative Examples 1 and 2 into a single cell for fuel cell evaluation together with a gas diffusion layer also serving as a current collector. FIG. 5 is a schematic cross-sectional view showing a state before the components of the single cell for fuel cell evaluation are combined, and a diffusion layer 6 made of carbon cloth is arranged on both sides of the fuel cell power generation element 5. Is provided with a sealing material 7 made of silicone rubber. Further, on both sides thereof, a stainless steel positive electrode current collector plate 8 having an oxygen inlet hole 10 and a stainless steel negative electrode current collector plate 9 having a fuel supply hole 11 are arranged. Is provided with a fuel tank 12 storing a liquid fuel 13.

  In the evaluation test, a single cell for fuel cell evaluation was discharged at a cell temperature of 25 ° C. using oxygen in the atmosphere as an oxidizing agent and a 15% by mass aqueous methanol solution as a liquid fuel, and the maximum output density was measured. Table 1 shows the results.

  As is clear from Table 1, in Examples 1 to 4, the maximum output density is improved in a manner substantially proportional to the increase in the amount of the catalyst, based on Comparative Example 1. This is probably because each electrode layer maintains a porous structure and structural integrity. On the other hand, in Comparative Example 2, the maximum output density was significantly inferior to that in Example 1 in which the amount of the catalyst was the same, and in Comparative Example 3, it was impossible to produce the electrode layer itself as described above. . Therefore, in order to achieve both the thickening of the electrode layer and the porous structure and structural integrity of the electrode layer, the laminated structure and the laminated transfer method according to the present invention are suitable, and the fuel thus produced is It was confirmed that the battery power generation element exhibited good battery characteristics.

  As described above, according to the present invention, it is possible to achieve both high thickness of the electrode layer of the power generation element for a fuel cell and the porous structure and structural integrity of the electrode layer, and to increase the output of the element. Therefore, by using a fuel cell using the fuel cell power generation element as a power source of a portable electronic device, the size and weight of the device can be reduced.

FIG. 2 is a cross-sectional view illustrating an example of a fuel cell power generating element of the present invention. It is sectional drawing which shows another example of the power generation element for fuel cells of this invention. FIG. 3 is a cross-sectional view of a fuel cell power generation element of Comparative Example 1. FIG. 7 is a cross-sectional view of a fuel cell power generation element of Comparative Example 2. It is sectional drawing which shows each component before assembling of the unit cell for fuel cell evaluation.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode layer 1b Positive electrode layer 1c Positive electrode layer 2 Solid polymer electrolyte membrane 3 Negative electrode 3a Negative electrode layer 3b Negative electrode layer 3c Negative electrode layer 4 Adhesive layer 5 Fuel cell power generation element 6 Diffusion layer 7 Sealing material 8 Positive electrode current collector 9 Negative electrode current collector 10 Oxygen inflow hole 11 Fuel supply hole 12 Fuel tank 13 Liquid fuel

Claims (16)

A fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode has a laminate in which two or more electrode layers containing a catalyst are laminated,
The power generation element for a fuel cell, wherein the thickness of the electrode layer is 50 μm or less, and an adhesive layer is disposed between the electrode layers.   The power generation element for a fuel cell according to claim 1, wherein the adhesive layer includes a polymer material having proton conductivity.   The power generation element for a fuel cell according to claim 2, wherein the electrode layer includes a polymer material of the same type as a polymer material included in the adhesive layer. The mass per unit electrode area of the catalyst contained in the electrode layer, the fuel cell power generation device according to any one of claims 1 to 3 is 0.3 to 3 mg / cm ^2.   The power generation element for a fuel cell according to claim 1, wherein a thickness of the adhesive layer is 1 to 5 μm.   The power generation element for a fuel cell according to any one of claims 1 to 5, wherein the total thickness of the laminate is 30 to 300 µm. A fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode has a laminate formed by laminating two or more electrode layers containing a catalyst and a polymer material having proton conductivity,
The electrode layer has a thickness of 50 μm or less;
The power generation element for a fuel cell, wherein the polymer material is present more in the interface than in the electrode layer. Mass per unit electrode area of the catalyst contained in the electrode layer, the power generating element for a fuel cell according to claim 7, which is 0.3 to 3 mg / cm ^2.   The power generation element for a fuel cell according to claim 7 or 8, wherein the total thickness of the laminate is 30 to 300 µm. A fuel cell power generating element including a positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode,
At least one of the positive electrode and the negative electrode is an electrode having a total thickness of 60 to 300 μm and a mass of a catalyst contained per unit area of 0.3 to 3 mg / cm ^2. Power generation element for batteries. A positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode has at least two electrode layers containing a catalyst. A method for producing a power generation element for a fuel cell, comprising a stacked body in which an adhesive layer is disposed between the electrode layers,
A first step of disposing an adhesive layer on the release substrate;
A second step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on the adhesive layer;
A third step of bringing the electrode layer into contact with a solid electrolyte;
A fourth step of bonding the electrode layer and the solid electrolyte by applying pressure while heating;
A fifth step of peeling the releasable substrate after bonding the electrode layer and the solid electrolyte to expose the adhesive layer,
A sixth step of disposing another electrode layer containing a catalyst and having a thickness of 50 μm or less on the exposed adhesive layer;
And a seventh step of applying pressure while heating the adhesive layer and the other electrode layer to bond the adhesive layer to the other electrode layer. Between the fifth step and the sixth step,
A second electrode layer separately formed in the first step and the second step is further disposed on the exposed adhesive layer, and the adhesive layer and the second electrode layer are heated. The method for producing a power generating element for a fuel cell according to claim 11, further comprising at least one step of exfoliating the release substrate and exposing the adhesive layer after applying pressure while bonding. A positive electrode for reducing oxygen, a negative electrode for oxidizing fuel, and a solid electrolyte provided between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode has at least two electrode layers containing a catalyst. A method for manufacturing a fuel cell power generating element, comprising a stacked body including a stacked body in which an adhesive layer is disposed between the electrode layers,
A first step of disposing an electrode layer containing a catalyst and having a thickness of 50 μm or less on a release substrate;
A second step of bringing the electrode layer into contact with a solid electrolyte;
A third step of bonding the electrode layer and the solid electrolyte by applying pressure while heating;
A fourth step of peeling the releasable substrate after bonding the electrode layer and the solid electrolyte to expose the electrode layer,
A fifth step of disposing an adhesive layer on the exposed electrode layer;
A sixth step of disposing another electrode layer containing a catalyst and having a thickness of 50 μm or less on the adhesive layer;
And a seventh step of applying pressure while heating the adhesive layer and the other electrode layer to bond the adhesive layer to the other electrode layer. Between the fifth step and the sixth step,
A second electrode layer separately formed in the first step is arranged on the adhesive layer, and the adhesive layer and the second electrode layer are bonded by applying pressure while heating, and then the mold release is performed. 14. The fuel cell according to claim 13, further comprising one or more steps of exposing the conductive substrate to expose the second electrode layer, and further disposing an adhesive layer on the exposed second electrode layer. Of manufacturing power generation element for industrial use.   A fuel cell, comprising the fuel cell power generation element according to claim 1. A fuel cell, comprising the fuel cell power generation element according to claim 10.

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