JP2017027724A - Coating device, membrane electrode assembly, fuel cell stack, polymer electrolyte fuel cell, and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating device suppressing cracks and pinholes generated during coating without warming a coating stage 7.SOLUTION: A coating device A includes: a container 70 receiving a catalyst ink 60; a heater 80 warming the catalyst ink 60 received in the container 70; and a circulation mechanism 40 to cause the catalyst ink 60 having been warmed by the heater 80 to circulate between the container 70 and a die head 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coating apparatus for forming an electrode catalyst layer of a fuel cell, a membrane electrode assembly, a fuel cell stack, a polymer electrolyte fuel cell, and a coating method.

In recent years, fuel cells have attracted attention. A fuel cell is a cell that oxidizes a fuel such as hydrogen using an oxidant such as oxygen and converts chemical energy associated therewith into electrical energy.
Fuel cells are classified into alkaline fuel cells, phosphoric acid fuel cells, polymer fuel cells, molten carbonate fuel cells, solid oxide fuel cells, etc., depending on the type of electrolyte. Polymer fuel cells (PEFC) operate at low temperatures, have high power density, and can be reduced in size and weight, making them applicable to portable power sources, household power sources, in-vehicle power sources, etc. Expected.
A membrane electrode assembly of a polymer fuel cell (PEFC) has a structure in which a polymer electrolyte membrane is sandwiched between two electrode catalyst layers (an anode electrode and a cathode electrode). Then, by supplying a fuel gas containing hydrogen (fuel) on the anode side and an oxidant gas containing oxygen (oxidant) on the cathode side, the following electrochemical reaction (reaction 1, reaction 2) To generate electricity.

Anode electrode: H ₂ → 2H + + 2e- (Reaction 1)
Cathode electrode: 1 / 2O ₂ + 2H + + 2e- → H ₂ O (Reaction 2)
The fuel gas supplied to the anode electrode (electrode catalyst layer) becomes protons and electrons (reaction 1). Protons move to the cathode electrode through the polymer electrolyte and polymer electrolyte membrane in the anode electrode (electrode catalyst layer). The electrons pass through the external circuit and move to the cathode electrode (electrode catalyst layer). At the cathode (electrode catalyst layer), protons and electrons react with oxidant gas supplied from the outside to generate water (reaction 2). At that time, electricity is generated by electrons passing through an external circuit.

JP2013-73686A

  Here, as a method for producing a membrane electrode assembly, a catalyst ink comprising a catalyst-supported carbon particle, a polymer electrolyte, and a solvent is prepared, and the catalyst ink is used as a polymer electrolyte membrane (in a broad sense, “base film” )), Or a method of applying a catalyst ink to an electrode transfer substrate (broadly defined “substrate film”) and then thermocompression-bonding to a polymer electrolyte membrane. ing. When the catalyst ink is directly applied to the polymer electrolyte membrane, die coating is often used as the coating method, and each of the anode electrode (electrode catalyst layer) and the cathode electrode (electrode catalyst layer) is formed. After the application of the catalyst ink, the solvent in the electrode catalyst layer is sufficiently removed by drying under reduced pressure or baking.

Regardless of which method is employed, defects due to the application of the catalyst ink often affect the power generation performance. For example, pinholes, cracks, aggregates, mixed foreign matters, and the like.
For example, if pinholes or cracks occur in the anode electrode or cathode electrode (electrode catalyst layer), the polymer electrolyte membrane is exposed, which causes a decrease in durability during power generation. In addition, for example, when an aggregate or a mixed foreign matter is generated, a projection in the height direction is generated. Therefore, when the membrane electrode assembly is stacked, the polymer electrolyte membrane is damaged, and the power generation performance itself is reduced.
Among these, aggregates and contaminants can be removed by filtering, but pinholes and cracks can be removed by the film thickness and drying conditions of the anode and cathode (electrode catalyst layer), the catalyst ink Improvement is relatively difficult due to the influence of the composition and the like. In particular, a factor affecting the generation of cracks and pinholes is the film thickness of the electrode catalyst layer. In the case of thick films, it has been reported that cracks and pinholes are likely to occur during drying. In order to improve the power generation performance, it is necessary to carry a large amount of platinum. However, since a large amount of cracks and pinholes are generated by increasing the film thickness, the amount that can be carried may be limited.

Moreover, as a method for suppressing the occurrence of cracks and pinholes, for example, a method for heating a coating stage has been reported. This increases the temperature of the substrate film (electrode transfer substrate, polymer electrolyte membrane) by placing the substrate film (eg, electrode transfer substrate, polymer electrolyte membrane) on the heated coating stage. Then, the catalyst ink is applied onto the base film.
However, the method of heating the coating stage is not common as the specification of the coating apparatus. Moreover, since the coating stage expands by heating, there is a possibility that problems such as an influence on the coating gap in die coating and deterioration of the fixed portion of the coating stage may occur.

  The present invention pays attention to the above points, and a coating apparatus, a catalyst layer, a membrane electrode assembly, and a fuel cell that can suppress cracks and pinholes that occur during coating without heating the coating stage. An object is to provide a stack, a polymer electrolyte fuel cell, and a coating method.

  In order to solve the above-described problem, a coating apparatus according to one embodiment of the present invention uses a die head for a catalyst ink including composite particles including conductive particles and electrode catalyst particles, a polymer electrolyte, and a solvent. A coating apparatus for coating the base film, a container for storing the catalyst ink, a heater for heating the catalyst ink stored in the container, the catalyst ink heated by the heater, the container and the die head And a circulation mechanism that circulates between the two.

  According to one aspect of the present invention, since the heated catalyst ink is circulated between the container and the die head, the temperature of the catalyst ink discharged from the die head can be increased more appropriately, for example, the coating stage is heated. Without cracking, cracks and pinholes that occur during coating can be suppressed.

3 is a cross-sectional view illustrating a configuration of a membrane electrode assembly 50. FIG. 5 is an explanatory diagram for explaining a method for producing a membrane electrode assembly 50. FIG. 5 is an explanatory diagram for explaining a method for producing a membrane electrode assembly 50. FIG. It is a figure showing circulation operation of coating device A. It is a figure showing the coating operation of the coating apparatus A. 5 is an explanatory diagram for explaining a coating method of a catalyst ink 60. FIG. 5 is an explanatory diagram for explaining a coating method of a catalyst ink 60. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
(Configuration of membrane electrode assembly 50)
As shown in FIG. 1, a membrane electrode assembly 50 according to this embodiment includes a polymer electrolyte membrane 3 sandwiched between two electrode catalyst layers (hereinafter also referred to as “anode electrode 1” and “cathode electrode 2”). It has a structure. The anode electrode 1 and the cathode electrode 2 are mainly different in film thickness. The membrane electrode assembly 50 according to this embodiment is provided in, for example, a polymer electrolyte fuel cell, a fuel cell stack, and the like.

2 and 3, 4 is an electrode transfer substrate for the anode electrode, and 5 is an electrode transfer substrate for the cathode electrode. As shown in FIGS. 2 and 3, the electrode catalyst layers (anode electrode 1 and cathode electrode 2) are formed on each of the electrode transfer substrates (broadly defined “substrate films”) 4 and 5, and then the electrode catalyst layers formed are formed. Then, the polymer electrolyte membrane 3 is sandwiched and bonded. At the time of bonding, the polymer electrolyte membrane 3 and the electrode catalyst layer (the anode electrode 1 and the cathode electrode 2) are joined by applying temperature and pressure, and then the electrode transfer substrate (substrate film) 4, 5 Is peeled off to form the membrane electrode assembly 50.
In the present embodiment, the electrode transfer bases 4 and 5 are used as base films, and the catalyst ink 60 is applied to the electrode transfer bases 4 and 5. However, other configurations may be used. The electrolyte membrane 3 may be used as a base film, and the catalyst ink 60 may be applied to the polymer electrolyte membrane 3.

(Configuration of coating apparatus A)
As shown in FIG. 4, the coating apparatus A includes a coating stage 7 that adsorbs (installs) electrode transfer base materials (base film) 4 and 5, and an electrode transfer base material that is adsorbed on the coating stage 7 ( And a die head 6 for discharging the catalyst ink 60 on the substrate films 4 and 5. The coating stage 7 is formed of a porous material such as ceramics. Thereby, the electrode transfer base materials (base material films) 4 and 5 can be vacuum-adsorbed to the coating stage 7, and the electrode transfer base materials 4 and 5 can be placed flat on the coating stage 7. Further, as the catalyst ink 60, for example, an ink including composite particles including conductive particles and electrode catalyst particles carried thereon, a polymer electrolyte, and a solvent can be employed.

Then, the coating apparatus A uses the die head 6 to apply the catalyst ink 60 to the electrode transfer base materials (base film) 4, 5 or the polymer electrolyte membrane 3 adsorbed (installed) on the coating stage 7. Is applied to form electrode catalyst layers (anode electrode 1 and cathode electrode 2) of the fuel cell.
In addition, the coating apparatus A includes a container 70 that stores the catalyst ink 60, a heater 80 that is disposed on the bottom surface of the container 70, and that heats the catalyst ink 60 stored in the container 70, and the heater 80 is heated. A circulation mechanism 40 that circulates the catalyst ink 60 between the container 70 and the die head 6 is provided. The heater 80 heats the catalyst ink 60 so that the catalyst ink 60 discharged from the nozzles of the die head 6 has a temperature of 25 ° C. or more and 35 ° C. or less. Thereby, generation | occurrence | production of a crack and a pinhole can be suppressed, suppressing volatilization of the solvent contained in the catalyst ink 60. FIG.

  The circulation mechanism 40 is disposed in the supply path 12 for supplying the catalyst ink 60 contained in the container 70 to the die head 6, the return path 11 for returning the catalyst ink 60 supplied to the die head 6 to the container 70, and the supply path 12. And a liquid feed pump 13 for feeding the catalyst ink 60 from the container 70 to the die head 6. A coating valve 8 is provided in the supply path 12. The return path 11 branches into two paths in the middle of the path and is connected to two left and right locations of the die head 6, and head vent valves 9 and 10 are provided in each of the branched paths. In addition, as the liquid feeding pump 13, for example, a diaphragm pump capable of quantitative discharge is preferable.

Then, the heater 80 heats the catalyst ink 60, and the liquid feed pump 13 supplies the heated catalyst ink 60 to the die head 6 via the supply path 12, and then to the die head 6 via the return path 11. The supplied catalyst ink 60 is returned to the container 70. At that time, the application valve 8 and the head vent valves 9 and 10 are opened. Thereby, the circulation mechanism 40 circulates the catalyst ink 60 heated by the heater 80 between the container 70 and the die head 6. Therefore, the supply path 12, the liquid feed pump 13, and the die head 6 can be heated with the heated catalyst ink 60. Therefore, the temperature of the catalyst ink 60 discharged from the die head 6 can be more appropriately increased.
In the present embodiment, the example in which the catalyst ink 60 is circulated using the liquid feed pump 13 is shown, but the present invention is not limited to this. For example, a circulation pump may be prepared separately from the liquid feed pump 13 and the catalyst ink 60 may be circulated using the prepared circulation pump.

Moreover, although the example which arrange | positions the liquid feeding pump 13 in the supply path | route 12 was shown, when using a circulation pump separately, you may employ | adopt another structure. For example, it may be arranged on at least one of the supply path 12 and the return path 11.
The coating apparatus A further includes a seal unit 14 that is in close contact with the nozzles of the die head 6 so that the catalyst ink 60 is not discharged from the nozzles (tips) of the die head 6 when the catalyst ink 60 is circulated. Thereby, it can prevent that the catalyst ink 60 leaks from the nozzle (tip) of the die head 6, and can circulate the catalyst ink 60 more appropriately. The material of the seal unit 14 is preferably a soft material such as rubber so as not to damage the nozzle tip.
As shown in FIG. 5, when the catalyst ink 60 is applied, the coating valve 8 is opened and the head vent valves 9, 10 are closed, so that the nozzle (tip) of the die head 6 can be closed. A fixed amount of the catalyst ink 60 can be discharged. At this time, the circulation of the catalyst ink 60 is continued until just before the coating, whereby the temperature-controlled catalyst ink 60 can be applied.

(Method for producing membrane electrode assembly 50)
In the example of FIG. 6, a transfer method is employed to produce a roll-shaped membrane electrode assembly 50. First, the catalyst ink 60 is applied to the roll-shaped electrode transfer base materials (base film) 4 and 5 by the coating apparatus A. Subsequently, the coated catalyst ink 60 is dried in a baking oven 90 to form electrode catalyst layers (anode electrode 1 and cathode electrode 2). The shape of the electrode catalyst layer (anode electrode 1, cathode electrode 2) is formed in a desired shape using a mask material or the like. Subsequently, the formed electrode catalyst layers (anode electrode 1 and cathode electrode 2) are joined to the polymer electrolyte membrane 3 by the electrode catalyst layer pressure roll 30 and transferred to the roll-shaped polymer electrolyte membrane 3. At that time, in order to join the electrode catalyst layers (the anode electrode 1 and the cathode electrode 2) to the polymer electrolyte membrane 3, pressurization or overheating is required. Therefore, it is desirable that the electrode catalyst layer pressure roll 30 has a heating mechanism.

Subsequently, the electrode transfer base materials (base material films) 4 and 5 are peeled off from the electrode catalyst layers (the anode electrode 1 and the cathode electrode 2) by the transfer base material peeling roll 31, and the membrane electrode assembly 50 is produced. Therefore, the electrode transfer base materials (base film) 4 and 5 are preferably made of a material having high peelability with respect to the electrode catalyst layers (the anode electrode 1 and the cathode electrode 2). Thereafter, the produced membrane electrode assembly 50 is wound up by the electrolyte membrane winding roll 17. And the polymer electrolyte fuel cell and fuel cell stack provided with the membrane electrode assembly 50 are produced by assembling the wound membrane electrode assembly 50.
On the other hand, as shown in the example of FIG. 7, without using a transfer method, the roll-shaped polymer electrolyte membrane 3 is used as a base film, and the catalyst ink 60 is directly applied to the roll-shaped polymer electrolyte membrane 3 by the coating apparatus A. It is good also as a structure which coats and forms an electrode catalyst layer (the anode pole 1 and the cathode pole 2), and produces the membrane electrode assembly 50. In the example of FIG. 7, the catalyst ink 60 is separately applied on both sides of the polymer electrolyte membrane (base film) 3 and dried. In this case, it is preferable because the baking oven 90 can be integrated.

(Effect of this embodiment)
The invention according to this embodiment has the following effects.
(1) In the coating apparatus A according to the present embodiment, a container 70 for storing the catalyst ink 60, a heater 80 for heating the catalyst ink 60 stored in the container 70, and the catalyst ink heated by the heater 80 And a circulation mechanism 40 that circulates 60 between the container 70 and the die head 6.
According to such a configuration, since the heated catalyst ink 60 is circulated between the container 70 and the die head 6, the temperature of the catalyst ink 60 discharged from the die head 6 can be increased more appropriately. Therefore, for example, it is possible to suppress cracks and pinholes that occur during coating without heating the coating stage 7.

(2) In the coating apparatus A according to this embodiment, the circulation mechanism 40 uses the supply path 12 for supplying the catalyst ink 60 contained in the container 70 to the die head 6 and the catalyst ink 60 supplied to the die head 6. A return path 11 returning to the inside of the container 70 and a liquid feed pump 13 arranged in the supply path 12 for feeding the catalyst ink 60 are provided.
According to such a configuration, the catalyst ink 60 can be circulated more appropriately.
(3) In the coating apparatus A according to this embodiment, the liquid feed pump 13 is a diaphragm pump capable of quantitative discharge.
According to such a configuration, the liquid feed pump 13 can also be used as a circulation pump.

(4) In the coating apparatus A according to this embodiment, the heater 80 heats the catalyst ink 60 so that the catalyst ink 60 discharged from the nozzles of the die head is 25 ° C. or more and 35 ° C. or less.
According to such a configuration, generation of cracks and pinholes can be suppressed while volatilization of the solvent contained in the catalyst ink 60 is suppressed.
(5) The coating apparatus A according to this embodiment further includes a seal unit 14 that is in close contact with the nozzles of the die head 6.
According to such a configuration, the catalyst ink 60 can be prevented from leaking from the nozzles of the die head 6, and the catalyst ink 60 can be circulated more appropriately.

(6) In the coating apparatus A according to this embodiment, the polymer electrolyte membrane 3 is a roll film.
According to such a configuration, the step of installing the base material can be omitted as compared with the single wafer apparatus, and therefore the electrode catalyst layers (the anode electrode 1 and the cathode electrode 2) can be formed efficiently and in a short time.
(7) In the coating apparatus A according to this embodiment, the polymer electrolyte membrane 3 is a polymer electrolyte membrane.
According to such a configuration, the electrode catalyst layer (anode electrode 1 and cathode electrode 2) applied to the electrode transfer substrate 5 is directly applied to the polymer electrolyte membrane 3 as compared with the method of transferring the electrode catalyst layer 3 to the polymer electrolyte membrane 3. The number of processes can be reduced by coating.

(8) In the coating apparatus A according to this embodiment, the coating stage 7 is formed of a porous material.
According to such a configuration, the electrode transfer base materials (base film) 4 and 5 can be vacuum-adsorbed to the coating stage 7, and the electrode transfer base materials 4 and 5 can be placed flat on the coating stage 7.
(9) The membrane electrode assembly 50 according to the present embodiment includes an electrode catalyst layer (anode electrode 1, cathode electrode 2) manufactured by the coating apparatus A according to any one of (1) to (7) above. ).
According to such a configuration, it is possible to provide the membrane electrode assembly 50 having no power generation performance without cracks and pinholes in the electrode catalyst layer (the anode electrode 1 and the cathode electrode 2).

(10) The fuel cell stack according to this embodiment includes the membrane electrode assembly 50 described in (8) above.
According to such a configuration, it is possible to provide a fuel cell stack having good power generation performance without cracks and pinholes in the electrode catalyst layer (the anode electrode 1 and the cathode electrode 2).
(11) The polymer electrolyte fuel cell according to this embodiment includes the membrane electrode assembly 50 described in (8) above.
According to such a configuration, it is possible to provide a polymer electrolyte fuel cell having good power generation performance without cracks and pinholes in the electrode catalyst layer (the anode 1 and the cathode 2).

(12) In the coating method according to this embodiment, the catalyst ink 60 accommodated in the container 70 is heated by the heater 80, and the catalyst ink 60 heated by the heater 80 is circulated between the container 70 and the die head 6. Let
According to such a configuration, since the heated catalyst ink 60 is circulated between the container 70 and the die head 6, the temperature of the catalyst ink 60 discharged from the die head 6 can be increased more appropriately. Therefore, for example, it is possible to suppress cracks and pinholes that occur during coating without heating the coating stage 7.

Hereinafter, examples of the coating apparatus A and the coating method of the catalyst layer for the fuel cell member will be described.
As the electrode transfer base materials (base material films) 4 and 5, 50 um films having a PET surface subjected to a release treatment were used. Moreover, the shape of the electrode transfer base material (base film) 4 and 5 was not a roll shape but a sheet-like sheet shape. Further, as the coating apparatus A, a single wafer coating machine was used. Further, as the coating stage 7, a ceramic porous material is adopted, and a mechanism capable of vacuum-adsorbing the sheet-like sheet-like electrode transfer base materials (base material films) 4 and 5 is adopted.
A heater 80 capable of controlling the temperature was installed under the container 70 to heat the catalyst ink 60. Further, by using a heater with a stirring function as the heater 80, a mechanism for uniformly heating the catalyst ink 60 in the container 70 is adopted. The heating temperature of the catalyst ink 60 was the temperature of the catalyst ink 60 discharged from the nozzles of the die head 6 and was set to 24 ° C., 25 ° C., 30 ° C., and 35 ° C.

As the liquid feed pump 13, a fixed discharge pump was adopted and used in combination with a circulation pump. A diaphragm pump was used as the fixed discharge pump. Then, after the catalyst ink 60 heated by the heater 80 is circulated between the container 70 and the die head 6 for about 1 hour, the heated catalyst ink is applied to the electrode transfer substrates (substrate films) 4 and 5. did. The film thickness was 10 um after drying.
The dryer used was a general-purpose hot air circulation oven, dried at 100 ° C. for 10 minutes, and then collected. The collected samples were visually inspected to confirm the level of pinholes and cracks.

  From Table 1 above, it was confirmed that pinholes and cracks occurred at an ink temperature of 24 ° C., but pinholes and cracks did not occur at an ink temperature of 25 ° C. or higher. Therefore, a membrane electrode assembly free from pinholes and cracks is formed by forming an electrode catalyst layer (anode electrode 1 and cathode electrode 2) using the coating apparatus A and the coating method according to one embodiment of the present invention. It was confirmed that 50 could be produced. Therefore, the effect by practical application of the coating apparatus A and the coating method is great.

  One embodiment of the present invention is characterized in that a heated catalyst ink is applied to a base film. Thereby, an electrode catalyst layer without pinholes and cracks can be formed even after coating and drying. Incidentally, if there are pinholes and cracks, the power generation performance is affected and the durability may be reduced. Therefore, the industrial utility value according to one embodiment of the present invention is high.

DESCRIPTION OF SYMBOLS 1 Anode electrode 2 Cathode electrode 3 Polymer electrolyte membrane 6 Die head 7 Coating stage 11 Return path 12 Supply path 13 Liquid feed pump 14 Seal unit 40 Circulation mechanism 50 Membrane electrode assembly 60 Catalyst ink 70 Container 80 Heater A Coating device

Claims (12)

A coating apparatus that coats a base film using a die head with a catalyst ink containing composite particles containing conductive particles and electrode catalyst particles, a polymer electrolyte, and a solvent,
A container containing the catalyst ink;
A heater for heating the catalyst ink contained in the container;
A coating apparatus comprising: a circulation mechanism that circulates the catalyst ink heated by the heater between the container and the die head. The circulation mechanism is
A supply path for supplying the catalyst ink contained in the container to the die head;
A return path for returning the catalyst ink supplied to the die head into the container;
The coating apparatus according to claim 1, further comprising: a liquid feed pump that is disposed in at least one of the supply path and the return path and that feeds the catalyst ink.   The coating apparatus according to claim 2, wherein the liquid feeding pump is a diaphragm pump capable of quantitative discharge.   The said heater heats the said catalyst ink so that the said catalyst ink discharged from the nozzle of the said die head may be 25 degreeC or more and 35 degrees C or less, The any one of Claim 1 to 3 characterized by the above-mentioned. Coating equipment.   The coating apparatus according to any one of claims 1 to 4, further comprising a seal unit that is in close contact with the nozzle of the die head.   The said base film is an electrode transfer base material, The coating apparatus of any one of Claim 1 to 5 characterized by the above-mentioned.   The coating apparatus according to claim 1, wherein the base film is a polymer electrolyte membrane. A coating stage for adsorbing the base film;
The coating apparatus according to claim 1, wherein the coating stage is formed of a porous material.   A membrane / electrode assembly comprising an electrode catalyst layer produced by the coating apparatus according to claim 1.   A fuel cell stack comprising the membrane electrode assembly according to claim 9.   A solid polymer fuel cell comprising the membrane electrode assembly according to claim 9. A coating method in which a composite ink containing conductive particles and electrode catalyst particles, a polymer electrolyte, and a catalyst ink containing a solvent are applied to a base film using a die head,
A coating method comprising heating a catalyst ink contained in a container with a heater and circulating the catalyst ink heated by the heater between the container and the die head.

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