Manufacturing apparatus for membrane electrode assemblies

Abstract

Adjusting the thickness of the catalyst layer while minimizing its impact on other layers. [Solution] A manufacturing apparatus for a film electrode assembly comprising a hot press roll, wherein the hot press roll includes at least a first hot press roll for heating and pressurizing a first catalyst layer, and a second hot press roll for transferring the first catalyst layer to a laminate including a gas diffusion layer and a second catalyst layer.

Description

Technical Field

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[0001] The present disclosure relates to the manufacture of a membrane electrode assembly.

Background Art

[0002] Patent Document 1 discloses that a pair of heat press rolls thermocompression-bond a coating layer of cathode catalyst ink and a coating layer of anode catalyst ink onto an electrolyte membrane. Further, Patent Document 2 discloses providing a second heat press portion between a catalyst layer transfer sheet and a first heat press portion and a peeling portion of an electrolyte membrane to more firmly bond them.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology, since the thickness of the catalyst layer cannot be controlled, the output performance may not be fully exhibited when the manufactured membrane electrode assembly is used in a fuel cell. On the other hand, if a large force is applied during transfer in an attempt to adjust the thickness, it may have an adverse effect on other layers.

[0005] Therefore, an object of the present disclosure is to adjust the thickness of the catalyst layer while suppressing the influence on other layers.

Means for Solving the Problems

[0006] The present application discloses a manufacturing apparatus for a film electrode assembly comprising a hot press roll, wherein the hot press roll comprises at least a first hot press roll for heating and pressurizing a first catalyst layer, and a second hot press roll for transferring the first catalyst layer to a laminate including a gas diffusion layer and a second catalyst layer.

[0007] The first heat press roll may be positioned opposite the transfer roll that is opposite the second heat press roll.

[0008] This application discloses a method for manufacturing a film electrode assembly, wherein the thickness of the first catalyst layer is adjusted by heat pressing the first catalyst layer before the first catalyst layer is transferred to a laminate containing the second catalyst layer.

[0009] The laminate containing the second catalyst layer may also include a gas diffusion layer laminated on the second catalyst layer. [Effects of the Invention]

[0010] According to this disclosure, by heat-pressing the catalyst layer to be transferred to a laminate having a gas diffusion layer before transferring the catalyst layer, the thickness of the catalyst layer can be adjusted without worrying about the cushioning properties or buckling failure of the gas diffusion layer, which is expected to improve the output of the fuel cell. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a conceptual diagram illustrating the structure of the membrane electrode assembly 10. [Figure 2] Figure 2 is a conceptual diagram illustrating the manufacturing apparatus 20 according to Form 1. [Figure 3] Figure 3 is a conceptual diagram illustrating the manufacturing apparatus 30 according to form 2. [Modes for carrying out the invention]

[0012] 1.Membrane electrode assembly Figure 1 illustrates a film electrode assembly 10 according to one example manufactured by the manufacturing apparatus and manufacturing method of the present disclosure. Figure 1(a) is a plan view of the strip-shaped film electrode assembly 10 as seen from the cathode side, and Figure 1(b) is a plan view of the film electrode assembly 10 as seen from the anode side. Figure 1(c) is a cross-section AA of Figure 1(a), with the upper side of the paper being the cathode side. In the manufacturing apparatus and manufacturing method of this disclosure, multiple membrane electrode assemblies are manufactured as a continuous strip-shaped membrane electrode assembly 10, and in a subsequent process, they are cut to the required length to become individual membrane electrode assemblies.

[0013] In this embodiment, the membrane electrode assembly 10 comprises an anode catalyst layer 14 laminated on one side (second side 12b) of the electrolyte membrane 12, an anode gas diffusion layer 16 laminated on the side of the anode catalyst layer 14 opposite to the electrolyte membrane 12, and a cathode catalyst layer 18 laminated on the other side (first side 12a) of the electrolyte membrane 12, and is used in a solid polymer fuel cell.

[0014] 1.1. Electrolyte membrane The electrolyte membrane 12 is a solid polymer thin film that exhibits good proton conductivity in a wet state. For example, it is composed of a fluorine-based ion exchange membrane, and a carbon-fluorine polymer can be used, specifically a perfluoroalkylsulfonic acid polymer (Nafion®). The thickness of the electrolyte membrane 12 is not particularly limited, but is 100 μm or less, preferably 50 μm or less, and more preferably 10 μm or less.

[0015] 1.2. Anode catalyst layer (the second catalyst layer in this embodiment) The anode catalyst layer 14 is a layer containing a catalyst metal in the form of the catalyst metal being supported on a support. Examples of catalyst metals include Pt, Pd, Rh, or alloys containing these. Examples of support materials include carbon supports, more specifically carbon particles made of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite, as well as carbon nanotubes. Furthermore, the anode catalyst layer 14 contains an electrolyte similar to the polymer electrolyte that constitutes the electrolyte membrane 12.

[0016] 1.3. Anode Gas Diffusion Layer The anode gas diffusion layer 16 can be formed of, for example, a porous body having conductivity. More specific examples include carbon porous bodies (carbon paper, carbon cloth, vitreous carbon, etc.), metal porous bodies (metal mesh, foamed metal), and the like.

[0017] 1.4. Cathode Catalyst Layer (the First Catalyst Layer in this Embodiment) The cathode catalyst layer 18 is also a layer containing a catalyst metal in a form in which the catalyst metal is supported on a carrier, similar to the anode catalyst layer 14. Examples of the catalyst metal include Pt, Pd, Rh, or an alloy containing these. Examples of the carrier include carbon carriers, more specifically, carbon particles composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like, as well as carbon nanotubes. In addition, the cathode catalyst layer 18 includes an electrolyte similar to the polymer electrolyte constituting the electrolyte membrane 12.

[0018] As can be seen from FIGS. 1(b) and 1(c), the anode catalyst layer 14 and the anode gas diffusion layer 16 are laminated in a strip shape continuous with the second surface 12b of the electrolyte membrane 10 and overlapping in this order. On the other hand, as can be seen from FIGS. 1(a) and 1(c), the cathode catalyst layer 18 is laminated on the first surface 12a of the electrolyte membrane 12 so as to be arranged at a predetermined interval along the direction in which the strip extends.

[0019] A cathode gas diffusion layer is laminated on the cathode catalyst layer 18 of such a membrane electrode assembly 10, and after being separated individually as described above, it can be made into a fuel cell by being sandwiched between a pair of separators.

[0020] 2. Manufacturing Apparatus 2.1. Embodiment 1 Figure 2 is a schematic diagram illustrating the manufacturing apparatus 20 for the membrane electrode assembly according to Form 1, and in particular shows the part where the ink that will become the cathode catalyst layer 18 is transferred to the second laminate 10b. Other parts of the manufacturing apparatus can be configured as known. The second laminate 10b and the ink that will become the cathode catalyst layer 18 will be explained later.

[0021] The manufacturing apparatus 20 according to Form 1 has a transfer roll 22, a first heat press roll 24, and a second heat press roll 26 in the transfer area. The transfer roll 22 has a portion of its outer surface positioned opposite the outer surfaces of the first heat press roll 24 and the second heat press roll 26, and receives pressing force from the first heat press roll 24 and the second heat press roll 26 to support a strip-shaped laminate that is passed between the transfer roll 22 and the first heat press roll 24, and between the transfer roll 22 and the second heat press roll 26.

[0022] The first heat press roll 24 is configured to allow temperature adjustment and to move toward the transfer roll 22, so that it can sequentially heat and pressurize the strip-shaped laminate passed between the first heat press roll 24 and the transfer roll 22. The second heat press roll 26 is configured to allow temperature adjustment and to move toward the transfer roll 22, so that the strip-shaped laminate passed between the second heat press roll 26 and the transfer roll 22 can be sequentially heated and pressurized. The first heat press roll 24 and the second heat press roll 26 are arranged so as to be aligned in the direction in which the strip-shaped laminate is fed (the strip-shaped laminate flows), with the first heat press roll 24 on the upstream side and the second heat press roll 26 on the downstream side.

[0023] The first hot press roll 24 and the second hot press roll 26 are not particularly limited as long as they can be temperature-controlled and moved toward the transfer roll 22, and known hot press rolls can be used.

[0024] According to Embodiment 1, only one additional roll is needed to form the first hot press roll 24, and a pair of rolls is not required.

[0025] 2.2.Form 2 Figure 3 is a schematic diagram illustrating a manufacturing apparatus 30 for producing a membrane electrode assembly 10 according to form 2, and in particular shows the part where the ink that will become the cathode catalyst layer 18 is transferred to the second laminate 10b. Other parts of the manufacturing apparatus can be configured as known. The second laminate 10b and the ink that will become the cathode catalyst layer 18 will be explained later.

[0026] The manufacturing apparatus 30 according to Form 2 has a transfer roll 32, a first heat press roll 34, and a second heat press roll 36 in the transfer area. The transfer roll 32 has a portion of its outer surface positioned opposite the outer surface of the second heat press roll 36, and receives pressing force from the second heat press roll 36 to support the strip-shaped laminate that is passed between the transfer roll 32 and the second heat press roll 36.

[0027] The first heat press roll 34 is composed of a pair of rolls arranged so that parts of their outer surfaces face each other, and a strip-shaped laminate is passed between the pair of rolls so that the laminate can be pressurized and heated. In other words, the pair of rolls of the first heat press roll 34 can be temperature-controlled and can be moved to adjust the distance between them so that pressure can be applied to the laminate. The second heat press roll 36 is configured to allow temperature adjustment and to move toward the transfer roll 32, so that the strip-shaped laminate passed between the second heat press roll 36 and the transfer roll 32 can be sequentially heated and pressurized. The first heat press roll 34 is positioned upstream of the transfer roll 32 and the second heat press roll 36 in the direction in which the strip-shaped laminate is fed (the strip-shaped laminate flows).

[0028] The first hot press roll 34 and the second hot press roll 36 are not particularly limited in their specific configuration as long as they can heat and pressurize the laminate as described above, and known hot press rolls can be used.

[0029] According to Embodiment 2, when attempting to construct Embodiment 1, if the transfer roll 22 cannot withstand the temperature or load applied by the first heat press roll 24, the first heat press roll can be formed independently of the transfer roll so as not to put a load on it.

[0030] 3.Manufacturing Next, a method for manufacturing the membrane electrode assembly 10 will be described. This section will focus on the transfer process, but as a prerequisite, the following first laminate 10a and second laminate 10b are prepared. The first laminate 10a and second laminate 10b are also shown in Figures 2 and 3. Both laminates consist of multiple layers stacked in a continuous strip shape. The first laminate 10a and second laminate 10b are as follows.

[0031] 3.1. First Laminate The first laminate 10a is formed by laminating a layer of cathode catalyst ink, which forms the cathode catalyst layer 18, onto a transfer sheet. The transfer sheet used should have excellent release properties from the cathode catalyst ink layer and excellent heat resistance. For example, sheets made of olefin resins such as polyethylene (PE) or polypropylene (PP) are used. In addition, sheets made of other materials such as polytetrafluoroethylene (PTFE), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN) can also be used.

[0032] Cathode catalyst ink is prepared by mixing and stirring catalyst-supported carbon, a proton-conducting ionomer, and their dispersion medium (pure water and ethanol) using a homogenizer. In this embodiment, carbon black supported with platinum particles is used as the catalyst-supported carbon. Furthermore, a fluorine-based ionomer such as perfluorosulfonic acid resin can be used as the ionomer.

[0033] The first laminate 10a is formed by coating a transfer sheet with cathode catalyst ink. The method for coating the transfer sheet with catalyst ink is not particularly limited, but coating by die coater is one example.

[0034] 3.2. Second Laminate The second laminate 10b is formed by laminating a layer of anode catalyst ink, which serves as the anode catalyst layer 14, and an anode gas diffusion layer 18 on the second surface 12b of the strip-shaped sheet formed by the electrolyte layer 12. The electrolyte layer 12 and the anode gas diffusion layer 16 are as described above, and the anode catalyst ink can be considered in the same way as the cathode catalyst ink described above. Furthermore, the lamination of each layer onto the electrolyte layer 12 is as known, for example, by coating with a die coater.

[0035] 3.3. Transfer Process In the transfer process, the cathode catalyst ink of the first laminate 10a is transferred to the first surface 12a of the electrolyte layer 12 of the second laminate 10b as described above. More specifically, it is as follows.

[0036] As shown in Figures 2 and 3, the first laminate 10a that is sent is heated and pressurized by the first hot press rolls 24 and 34 before it is placed on top of the second laminate 10b and the cathode catalyst ink is transferred. This allows the thickness of the cathode catalyst ink layer to be adjusted so that the final thickness of the cathode catalyst layer is approximately 8 μm to 9 μm. In the first form of Figure 2, the process is carried out by passing the first laminate 10a between the transfer roll 22 and the first heat press roll 24, while in the second form of Figure 3, the process is carried out by passing the first laminate 10a between the pair of rolls of the first heat press roll 34, which consists of a pair of rolls. The degree of heating and pressurizing of the first laminate 10a by the first hot press rolls 24 and 34 is not limited, but can range from room temperature to 250°C and 1 MPa to 5 MPa.

[0037] The first laminate 10a, heated and pressurized by the first hot press rolls 24 and 34, is further fed and placed between the transfer roll 22 and the second hot press roll 26. Meanwhile, the second laminate 10b is placed between the transfer roll 22 and the second hot press roll 26 via a different route than the first laminate 10a. As shown in Figures 2 and 3, the first laminate 10a and the second laminate 10b are then stacked while being heated and pressurized between the transfer roll 22 and the second hot press roll 26, and the cathode catalyst layer of the first laminate 10a is transferred to the second laminate 10b, forming the film electrode assembly 10.

[0038] 4. Effects, etc. As described above, when transferring a catalyst layer (first catalyst layer) to a laminate (second laminate) equipped with a gas diffusion layer while applying pressure, even if one attempts to adjust (reduce) the thickness of the first catalyst layer by applying pressure, the gas diffusion layer acts as a cushion, preventing force from being applied to the first catalyst layer, making it difficult to adjust the thickness. If the pressure is increased too much and applied force is forced, the gas diffusion layer will buckle and break. In contrast, according to this disclosure, the thickness of the first catalyst layer is adjusted in advance by the first hot press roll, so only the force necessary for transfer needs to be applied during the transfer, and the above-mentioned problems can be solved. In this way, by heat-pressing the catalyst layer with another roll before transferring it to the laminate having a gas diffusion layer, the thickness of the catalyst layer can be adjusted without worrying about the cushioning effect or buckling failure of the gas diffusion layer, which is expected to improve the output of the fuel cell.

[0039] In the above description, the cathode catalyst layer was referred to as the first catalyst layer and the anode catalyst layer as the second catalyst layer. However, conversely, the cathode catalyst layer can be referred to as the second catalyst layer and the anode catalyst layer as the first catalyst layer. In this case, the gas diffusion layer is the cathode gas diffusion layer, not the anode gas diffusion layer. [Explanation of symbols]

[0040] 10…Membrane electrode assembly, 12…Electrolyte membrane, 14…Anode catalyst layer (second catalyst layer), 16…Anode gas diffusion layer, 18…Cathode catalyst layer (first catalyst layer), 20…Manufacturing equipment, 22…Transfer roll, 24…First hot press roll, 26…Second hot press roll, 30…Manufacturing equipment, 32…Transfer roll, 34…First hot press roll, 36…Second hot press roll

Claims

1. A manufacturing apparatus for a film electrode assembly equipped with a hot press roll, The aforementioned hot press roll includes a first hot press roll that heats and pressurizes the first catalyst layer, A laminate including a gas diffusion layer and a second catalyst layer, comprising at least a second hot press roll for transferring the first catalyst layer, Manufacturing equipment for membrane electrode assemblies.

2. The apparatus for manufacturing a film electrode assembly according to claim 1, wherein the first hot press roll is provided opposite to a transfer roll that is opposite to the second hot press roll.

3. A method for manufacturing a membrane electrode assembly, Before the first catalyst layer is transferred to a laminate containing the second catalyst layer, the first catalyst layer is heat-pressed to adjust its thickness. A method for manufacturing a film electrode assembly.

4. The method for manufacturing a film electrode assembly according to claim 3, wherein the laminate including the second catalyst layer includes a gas diffusion layer laminated on the second catalyst layer.

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