JP2010199050A - Composite electrolyte membrane for fuel cell and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate weakness of mechanical strength in a fluorine electrolyte membrane simple substance, and also suppress gas permeability low by a hydrocarbon electrolyte membrane. <P>SOLUTION: A composite electrolyte membrane 50 is obtained by leaving a fixed width w of the periphery of the hydrocarbon electrolyte membrane 1 at the periphery of the hydrocarbon electrolyte membrane, providing a through-hole h on the order of millimeter on the hydrocarbon electrolyte membrane 1 so as to be equally dispersed and coating a fluorine electrolyte membrane resin in the hole and on the membrane surface of the porous hydrocarbon electrolyte membrane 1 including this through-hole h. Further, the composite electrolyte membrane 50 is manufactured with the porous hydrocarbon electrolyte membrane 1 intentionally arranged at the center or non center in a total membrane thickness direction and with the porous hydrocarbon electrolyte membrane 1 interposed by a fluorine electrolyte membrane 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a composite electrolyte membrane for a fuel cell formed by combining two types of electrolyte membranes and a method for producing the same. More specifically, the present invention relates to a composite electrolyte membrane for a fuel cell produced by combining a porous hydrocarbon electrolyte membrane and a fluorine electrolyte membrane, and a method for producing the same.

  An electrolyte membrane for a fuel cell is divided into a fluorine-based electrolyte membrane and a hydrocarbon-based electrolyte membrane when classified according to its constituent materials. In general, a fluorine-based electrolyte membrane is superior in electrical characteristics and chemical stability to a hydrocarbon-based electrolyte membrane, but has a characteristic that gas permeability is high (gas can easily pass through) and mechanical strength is low.

By the way, with respect to the demand for improving the power generation performance of a fuel cell including the same for a fluorine-based electrolyte membrane, the proton conductivity is improved by reducing the membrane resistance by reducing the membrane thickness or by reducing the EW (EQUIVALENT WEIGHT). Things have been done.
However, even if the proton conductivity of the fluorine-based electrolyte membrane is improved, this increases the gas permeability of the membrane, thereby accelerating the consumption of hydrogen fuel supplied from the outside to the fuel cell. When the gas permeability increases, hydrogen gas and oxygen gas permeate through the fluorine-based electrolyte membrane, and hydrogen gas crosses over to the oxidant electrode and oxygen gas crosses over to the fuel electrode. Furthermore, under these circumstances, radical species that chemically degrade the electrolyte component of the fluorine-based electrolyte membrane are likely to be generated, and this radical species attacks the fluorine-based electrolyte membrane and causes a problem of decomposing the membrane component. To do.

On the other hand, when a fluorine-based electrolyte membrane is included in a polymer electrolyte fuel cell (hereinafter referred to as “PEFC”), a catalyst layer is formed on the fluorine-based electrolyte membrane to form a membrane-electrode assembly ( MEMBRANE-ELECTRODE ASSEMBLY (hereinafter abbreviated as “MEA”) is produced as an intermediate product, and then joined over the gas diffusion layer (hereinafter abbreviated as “GDL”) to cover further processes. In FIG. 2, a gas seal (gasket) is joined on the MEA so as to surround the catalyst layer.
For this reason, a fixed margin for gas sealing is preliminarily edged at the peripheral edge of the electrolyte membrane.

  However, since the mechanical strength of the fluorine-based electrolyte membrane is low, in the fuel cell (single cell) between the peripheral portion of the membrane and the gas seal that is joined to the peripheral portion in a frame shape and surrounds the catalyst layer When a pressure difference is generated between the fuel gas and the oxidant gas that are present with the fluorine-based electrolyte membrane interposed therebetween, there is a problem that the fluorine-based electrolyte membrane is damaged.

In addition, when a variable element that applies a constant load (for example, a motor) is connected to a fuel cell equipped with an MEA including a fluorine-based electrolyte membrane and there is no load, the fluorine-based electrolyte membrane dries up, causing mechanical stress and heat. Due to the stress, the constituent members of the fuel cell are distorted, and similarly, there is a problem that the fluorine-based electrolyte membrane is damaged.
In addition, carbon fibers or the like from the GDL base material formed so as to cover the MEA pierce the fluorine-based electrolyte membrane, causing a problem that a cross leak occurs between the two electrodes sandwiching the membrane.

As described above, since the fluorine-based electrolyte membrane has low mechanical strength, it is easily damaged by various factors.
Therefore, when means for reinforcing the fluorine-based electrolyte membrane is required, the present inventors paid attention to the above-described hydrocarbon-based electrolyte membrane as the means.
Some hydrocarbon-based electrolyte membranes have excellent heat resistance, oxidation resistance and mechanical strength, and excellent proton conductivity at high temperature and low humidity. In particular, although the hydrocarbon electrolyte membrane is somewhat brittle, it has rigidity and hardness due to its molecular structure.
Focusing on brittleness, the hydrocarbon electrolyte membrane alone is used for electrode joining (integrated structure by joining the hydrocarbon electrolyte membrane and the catalyst layer) or during assembly for stacking single cells to produce a fuel cell. The handling property tends to be inferior to that of a fluorine-based electrolyte membrane. However, the hard but brittle surface of the hydrocarbon electrolyte membrane can be compensated by coating the hydrocarbon electrolyte membrane if it is coated with a fluorine electrolyte membrane as a relatively flexible resin coating. it can.

  Therefore, the inventors use the hydrocarbon-based electrolyte membrane as a base material that reinforces the mechanical strength of the fluorine-based electrolyte membrane, and at the same time, the fluorine-based electrolyte membrane as a resin coating material that covers the entire hydrocarbon-based electrolyte membrane. By using this method, a method for producing a composite electrolyte membrane (hybrid electrolyte membrane) that takes advantage of both electrolyte membranes and complements the disadvantages was examined.

In this case, a conventional technique for compositing two types of films, which was the subject of examination, is shown below.
First, in Patent Document 1, a composite membrane is prepared by preparing a porous membrane having an average pore diameter of 0.1 μm to 10 μm through the membrane, and filling each pore with an electrolyte resin (ion exchange resin) having proton conductivity. Type electrolyte membrane is presented.

  Further, in Patent Document 2, when preparing a porous film by opening a through hole for filling an electrolyte resin in a polymer film such as polyimide or polyamide, a laser using, for example, a carbon dioxide laser, an excimer laser, or the like is used as a means for opening each hole. A composite electrolyte membrane is proposed that uses heat to fill the through hole with an electrolyte resin.

JP 2005-216769 A JP 2005-108661 A

However, the electrolyte membrane composite method according to the prior art picked up above has the following problems.
First, the average pore diameter of the pores of the composite electrolyte membrane disclosed in Patent Document 1 is in the micron order such as 0.05 μm to 1 μm. In order to fill the electrolyte resin in such an extremely fine hole (straight pipe) while reducing the pressure, a pressure reducing device is separately required. As a result, the equipment becomes large, the work becomes complicated, and the cost increases.

  Next, according to the method for producing a through hole shown in Patent Document 2, the polymer film serving as a base material is melted by laser heat even after drilling, and the hole diameter is further expanded. It is necessary to keep a large interval between the through holes in advance so as not to be connected. Therefore, the aperture ratio of the through holes filled with the proton conductive resin opened in the polymer film is set as small as about 10%. As a result, the composite electrolyte membrane disclosed in Patent Document 2 does not have good proton conductivity because the opening made of proton conductive resin is small.

Furthermore, according to Patent Document 2, there is no means for supporting and reinforcing the electrolyte membrane (solid polymer electrolyte membrane) on the peripheral portion of the MEA and the peripheral portion of the gas seal surrounding the peripheral portion in a frame shape. For this reason, when a pressure difference between the fuel gas and the oxidant gas occurs, the fuel gas and the oxidant gas are liable to be broken, and the components of the fuel cell are easily damaged. In addition, when a load such as an electric device or an electronic device is connected to the fuel cell and is operating, the inside of the single cell of the fuel cell is dried up, and the components of the fuel cell are distorted by mechanical stress or thermal stress. As a starting point, there is a problem that the components of the fuel cell are damaged.
As described above, none of the conventional techniques is suitable for combining (hybridizing) the fluorine-based electrolyte membrane and the hydrocarbon-based electrolyte membrane.

  In view of such circumstances, the present invention easily and firmly combines a fluorine-based electrolyte membrane and a hydrocarbon-based electrolyte membrane, complementing the low mechanical strength of the fluorine-based electrolyte membrane alone, and gas Provided is a composite electrolyte membrane (hybrid electrolyte membrane) capable of suppressing permeability.

(Aspect of the Invention)
Hereinafter, embodiments of the invention will be shown and described. The items (1) to (14) correspond to the claims 1 to 14, respectively.
(1) A fluorine-based electrolyte membrane is formed so as to fill the pores of the porous hydrocarbon-based electrolyte membrane and cover the membrane surface, and the pores of the porous hydrocarbon-based electrolyte membrane have a film thickness A composite electrolyte membrane for a fuel cell, characterized in that it is a through-hole with a diameter of millimeter order opened in the direction and scattered on the membrane surface on average (in this specification, “milli-order” Is the order of length over a hole diameter of at least 0.1 mm and at most about 3 mm).

According to this section, a fluorine-based electrolyte membrane component is filled in through-holes having a pore size larger than that of the conventional micron order, such as a milli-order, more preferably on the order of 10 ⁻¹ mm. The fluorine-based electrolyte membrane can also be formed on the surface of the hydrocarbon-based electrolyte membrane so as to be continuous with the fluorine-based electrolyte membrane filled in the through holes. As a result, as can be seen from the cross-sectional portion 30 cut along the film thickness direction of the through hole for one of the through holes indicated by the alternate long and short dash line in FIG. As a result of filling the pores of the hydrocarbon-based electrolyte membrane and forming on the membrane surface of the porous hydrocarbon-based electrolyte membrane, a horizontal H-shaped portion (or eyelet-like portion) is formed, and thus the fluorine-based electrolyte membrane The portion is firmly bonded to the porous hydrocarbon-based electrolyte membrane, so that both electrolyte membranes are integrated and combined.

  In addition, since a large number of such horizontal H-shaped portions are scattered on the membrane surface of the hydrocarbon-based electrolyte membrane on average, the machine of the composite electrolyte membrane comprising the fluorine-based electrolyte membrane and the hydrocarbon-based electrolyte membrane The overall strength is generally higher than that of a conventional product (for example, a film obtained by simply bonding both films together). In addition, the electrical characteristics and chemical stability, which are the advantages of the fluorine-based electrolyte membrane, are uniformly provided throughout the composite electrolyte membrane.

Conventionally, the diameter of the through hole has been in the micron order as described above, but according to the through hole formed in the hydrocarbon-based electrolyte membrane in the composite electrolyte membrane according to the present invention, it is in the order of millimeter, more preferably 10 ^{Since it has a} relatively large pore size such as ⁻¹ mm, there is no need to reduce the pressure as in the prior art. For example, filling a through-hole with a fluorine-based electrolyte membrane component (resin) by coating by a known casting method Work is done easily.

  Thus, in this section, while increasing the mechanical strength of the composite electrolyte membrane by the hydrocarbon electrolyte membrane, the fluorine-based electrolyte membrane component (in the relatively large-diameter pore formed in the hydrocarbon electrolyte membrane ( Resin) and a fluorine electrolyte membrane was formed on the membrane surface of the hydrocarbon electrolyte membrane so as to be continuous with the filled fluorine electrolyte membrane component (resin). That is, in the composite electrolyte membrane according to the present invention, the hydrocarbon-based electrolyte membrane portion plays a role of increasing mechanical strength and reducing gas permeability, while it has electrical characteristics (proton conductivity) and chemical stability. The fluorine-based electrolyte membrane portion plays a role of ensuring the above.

(2) The composite electrolyte membrane for a fuel cell, wherein an average hole diameter of the through holes is 0.1 mm to 0.5 mm.

This section exemplifies a preferable average hole diameter of the through hole. As described above, the conventional technology (see Patent Document 1) has a size of micron order (μm order or sub-μm order). However, the hydrocarbon electrolyte membrane has a high mechanical strength, and is preferably in the order of millimeter. Even if a large number of holes having a size of the order of 10 ⁻¹ mm were provided, there was no problem in terms of mechanical strength. However, if the pore diameter is larger than 0.5 mm, the mechanical strength of the entire hydrocarbon electrolyte membrane is lowered, which is not preferable. On the other hand, if the hole diameter is smaller than 0.1 mm, a decompression device is required to fill the small hole with the fluorine-based electrolyte as in the conventional case, which is not preferable.

(3) The through-hole is opened at a ratio of 10% to 50% with respect to 100% of the entire surface of the porous hydrocarbon electrolyte membrane, described in (1) or (2) A composite electrolyte membrane for fuel cells.

  This section exemplifies a preferable range of the opening ratio of the through hole with respect to the porous hydrocarbon electrolyte membrane. When the reinforcing membrane corresponding to the porous hydrocarbon-based electrolyte membrane is not an electrolyte membrane [for example, a PTFE (polytetrafluoroethylene) resin membrane], in order to improve proton conductivity, for example, the aperture ratio is 80%. It is necessary to set the degree. However, according to this section, since the porous hydrocarbon-based electrolyte membrane itself is also an electrolyte membrane, it itself has proton conductivity. Therefore, as in this section, the aperture ratio can be kept at 50% at most, the gas permeability of the advantage of the hydrocarbon electrolyte membrane can be suppressed low, and the mechanical strength can be improved. On the other hand, if the aperture ratio is less than 10%, the gas permeability can be suppressed to a lower level and the mechanical strength can be further improved. However, in this case, the advantages of the fluorine-based electrolyte membrane are lost. It is not preferable because it is rejected.

(4) A joining margin for joining the gas diffusion layers in which the through holes are not formed is provided on a constant width surface of a peripheral edge portion of the porous hydrocarbon-based electrolyte included in the composite electrolyte membrane for a fuel cell. The composite electrolyte membrane for a fuel cell according to any one of (1) to (3), wherein:

  In this item, the through hole according to any one of (1) to (3) is used for the porous hydrocarbon electrolyte contained in the composite electrolyte membrane for a fuel cell. Exemplifying the formation on the surface excluding the constant width surface of the peripheral edge. The central surface excluding the constant width surface at the peripheral edge of the porous hydrocarbon-based electrolyte is a surface on which a catalyst layer made of conductive metal-supported conductive particles such as platinum-supported carbon particles is formed on the composite electrolyte membrane for fuel cells. Become. Carbon fibers generated from the catalyst layer and the GDL base material covering the peripheral edge of the peripheral edge of the porous hydrocarbon-based electrolyte surrounding the surface so that there are no through holes in the constant-width surface Can be prevented from piercing the fuel cell composite electrolyte membrane. That is, a hard surface without a through hole in the porous hydrocarbon-based electrolyte membrane functions as a shield (defense surface) against carbon fibers generated from the GDL base material.

(5) The porous hydrocarbon electrolyte membrane has a thickness of 1 μm to 10 μm, and the fluorine electrolyte membrane has a thickness of 2 μm to 30 μm. The composite electrolyte membrane for a fuel cell according to any one of the above.

  This section exemplifies a preferable range of the thickness of the porous hydrocarbon-based electrolyte membrane and the thickness of the fluorine-based electrolyte membrane (one layer in two layers). When a hydrocarbon-based electrolyte membrane is used alone as an electrolyte membrane for a fuel cell, the film thickness is generally about 20 μm. In the present invention, the role of the porous hydrocarbon-based electrolyte membrane is fluorine-based. Since the high gas permeability of the electrolyte membrane is lowered and the low mechanical strength is increased, and the film resistance can be lowered by reducing the film thickness as much as possible, the film thickness can be reduced from 1 μm to 10 μm. It is said. If the thickness is less than 1 μm, the reinforcing effect on the fluorine-based electrolyte membrane is reduced, which is not preferable. If the thickness is more than 10 μm, the membrane resistance increases, which is not preferable. For example, it is considered that the thickness of the porous hydrocarbon electrolyte is most preferably about 5 μm.

  On the other hand, the film thickness of the fluorine-based electrolyte membrane is set to 2 μm to 30 μm in order to ensure the advantages of the excellent electrical characteristics and chemical stability of the fluorine-based electrolyte membrane. However, if the fluorine-based electrolyte membrane is thicker than 30 μm, the membrane resistance is unnecessarily increased, which is not preferable because the power generation performance of the fuel cell is deteriorated. A thickness of 2 μm of the fluorine-based electrolyte membrane is considered to be a lower limit value at which the above-described functions of the two fluorine-based electrolyte membranes reinforced with the porous hydrocarbon-based electrolyte membrane can be exhibited.

(6) The composite electrolyte membrane for a fuel cell according to any one of items (1) to (5), wherein the porous hydrocarbon-based electrolyte membrane is formed at the center in the entire film thickness direction. A composite electrolyte membrane for a fuel cell.

  This section includes two-layer fluorine-based electrolyte membranes, which are constituent elements of the composite electrolyte membrane for fuel cells according to any one of items (1) to (5), and these two-layer fluorine-based electrolyte membranes 1 illustrates an example of a positional relationship with one porous hydrocarbon electrolyte membrane sandwiched between two layers. The composite electrolyte membrane for a fuel cell in this section has a single porous hydrocarbon-based electrolyte membrane in the center of the whole, that is, a two-layer fluorine-based electrolyte membrane is a single-layer porous hydrocarbon-based electrolyte membrane. It is characterized by a symmetric structure parallel to the plane and on the center plane of the film. Since it has a symmetrical structure, it can be set on either the anode electrode side or the cathode electrode side of either of the two-layer fluorine-based electrolyte membranes.

(7) When the thickness of the fuel cell composite electrolyte membrane is 1, the thickness of the porous hydrocarbon electrolyte membrane is 0.01 to 0.5. The composite electrolyte membrane for a fuel cell according to (6).

This section exemplifies the ratio of the thickness (film thickness) of one porous hydrocarbon-based electrolyte membrane disposed in the center of the composite electrolyte membrane for a fuel cell according to item (6) to the total thickness. . That is, the thickness (film thickness) of the porous hydrocarbon-based electrolyte membrane can be made thinner or thicker than the total thickness.
For example, according to this section, when the total thickness of the porous hydrocarbon-based electrolyte membrane is 25 μm, it can be thinned to 0.25 μm and can be thickened to 12.5 μm. A composite electrolyte membrane for a fuel cell in which a porous hydrocarbon-based electrolyte membrane is thinned is suitable for a fuel cell for a use that tends to be in a non-humidified or low-humidified state because the ratio of the fluorine-based electrolyte membrane is high.

  On the other hand, a composite electrolyte membrane for a fuel cell in which a porous hydrocarbon-based electrolyte membrane is thickened is suitable for a fuel cell in which emphasis is placed on increasing mechanical strength because the ratio of the porous hydrocarbon-based electrolyte membrane is high. . Thus, in order to complement the disadvantages of both membranes with the advantages, the porous hydrocarbon electrolyte membrane can be suitably produced according to the specifications or requests of the fuel cell from the user.

(8) A composite electrolyte membrane for a fuel cell, wherein the total thickness of the composite electrolyte membrane for a fuel cell according to (6) or (7) is from 5 to 30 μm.

  This section exemplifies a preferable range of the total film thickness of the composite electrolyte membrane for fuel cells. If it is thinner than 5 μm, it is not preferable in that the mechanical strength becomes weak and the handling property deteriorates. On the other hand, if it is thicker than 30 μm, the unit cell has a stack volume that can obtain a desired power, and proton conductivity is low. This is because it is not preferable in terms of deterioration.

(9) The composite electrolyte membrane for a fuel cell according to any one of (1) to (5), wherein the porous hydrocarbon-based electrolyte membrane is formed at a non-center in the entire thickness direction. A composite electrolyte membrane for a fuel cell.

  This section describes the two-layer fluorine-based electrolyte membrane and the two-layer fluorine-based electrolyte membrane, which are the constituent elements of the fuel cell composite electrolyte membrane according to any one of items (1) to (5) The other aspect of the positional relationship with the porous hydrocarbon electrolyte membrane of one layer pinched | interposed is illustrated. The composite electrolyte membrane for a fuel cell in this section has a single porous hydrocarbon-based electrolyte membrane at the non-center of the whole, that is, a two-layer fluorine-based electrolyte membrane is a single-layer porous hydrocarbon-based electrolyte membrane ( In reality, it is characterized by not having a symmetric structure with respect to the central plane of the film parallel to the film surface.

  Because of the asymmetric structure, when any one of the two-layer fluorine-based electrolyte membranes is set on the anode electrode side and the cathode electrode side, Examples 3-1 and 3-2 described later are used depending on the assembly mode. Therefore, it is necessary to pay attention to which side is the anode side or the cathode side when assembling the fuel cell. However, it is possible to prevent, for example, dry-up that occurs on the anode electrode side by suitably using the characteristics. For this purpose, a composite electrolyte membrane for a fuel cell may be produced so as to have an asymmetric structure in which a porous hydrocarbon electrolyte membrane is positioned closer to the cathode side (see the next section).

(10) The composite electrolyte membrane for a fuel cell according to (9), wherein a surface of the fluorine-based electrolyte membrane positioned close to one surface of the porous hydrocarbon-based electrolyte membrane is used for a cathode electrode of a fuel cell. And the surface of the other fluorine-based electrolyte membrane positioned near the back surface of the one surface of the porous hydrocarbon-based electrolyte membrane is used for an anode electrode of a fuel cell. Composite electrolyte membrane.
This section exemplifies a preferred mode (configuration of a preferred three-layer film) of the composite electrolyte membrane for a fuel cell having the non-target structure described in the previous section.

(11) A fuel cell composite electrolyte membrane according to any one of (8) to (10), wherein the fuel cell composite electrolyte membrane has a thickness of 5 μm to 30 μm.
This section has the same purpose as the total film thickness of the fuel cell composite electrolyte membrane exemplified in (6), which has a symmetrical structure, and the total film thickness of the fuel cell composite electrolyte film having an asymmetric structure. The preferable range of is illustrated. The significance of the upper limit and the lower limit of the preferred range has been described in the paragraph (6), and the description thereof is omitted here.

(12) Milli-order by needle punching or laser irradiation while leaving a certain width of the peripheral edge of the hydrocarbon electrolyte membrane as a joining margin for joining the gas diffusion layer to the peripheral edge of the hydrocarbon electrolyte membrane And a fluorine-based electrolyte resin is applied to the hydrocarbon-based electrolyte membrane in which the through-holes are formed by a casting method. And forming a fluorine electrolyte membrane made of the fluorine electrolyte resin on the porous hydrocarbon electrolyte membrane. A method for producing a composite electrolyte membrane for a fuel cell, comprising:

This section exemplifies the method for producing the composite electrolyte membrane for a fuel cell described in the sections (1) to (12).
The porous hydrocarbon electrolyte membrane contained in the fuel cell composite electrolyte membrane according to the present invention has a through-hole diameter larger than that of the prior art, such as on the order of millimeters, more preferably on the order of 10 ⁻¹ mm. . Therefore, it is preferable that this through hole is formed by needle punching or laser irradiation suitable for mass production.

  In order to form a fluorine-based electrolyte membrane on the through-holes and the membrane surface of the porous hydrocarbon-based electrolyte membrane, first, the porous hydrocarbon-based electrolyte membrane is fixed on the carrier film. Then, from above the porous hydrocarbon-based electrolyte membrane with a carrier film, an electrolyte solution for forming a fluorine-based electrolyte membrane such as Fion DE2020CS (trade name) is once applied to the through holes and the membrane surface by a known casting method. It is applied a plurality of times (until a desired film thickness is obtained). And after peeling the said carrier film, until the desired film thickness is obtained for the electrolyte solution for fluorine-type electrolyte membrane formation similarly with respect to the porous hydrocarbon-type electrolyte membrane with which the fluorine-type electrolyte membrane was filled in each hole Apply.

According to this production method, the electrolyte solution for forming a fluorine-based electrolyte membrane fills the inside of a through hole having a diameter of the order of millimeter, more preferably of the order of 10 ⁻¹ mm, and the electrolyte solution overflowing from the through hole is It spreads uniformly on the membrane surface of the porous hydrocarbon-based electrolyte membrane, and preferably the fluorine-based electrolyte membrane is formed so as to surround the porous hydrocarbon-based electrolyte membrane.

(14) After fixing one surface of the hydrocarbon-based electrolyte membrane to a carrier film on which a fluorine-based electrolyte resin has been applied in advance, the hydrocarbon-based electrolyte membrane in which the through-holes are formed is compared with the fluorine-based electrolyte resin. The method for producing a composite electrolyte membrane for a fuel cell according to the item (13), wherein the coating is applied by a casting method.

  This section exemplifies a manufacturing method for manufacturing a composite electrolyte membrane for a fuel cell having the symmetrical structure of (6) or the asymmetric structure of (9). When manufacturing the asymmetric structure of (9), it is preferable that the fluorine-based electrolyte resin is formed into a thin film when the fluorine-based electrolyte resin is applied in advance to one side of the hydrocarbon-based electrolyte membrane.

(15) A membrane-electrode assembly comprising the composite electrolyte membrane for a fuel cell according to any one of items (1) to (12).

This section exemplifies one in which the composite electrolyte membrane described in the sections (1) to (12) is applied to a membrane-electrode assembly (abbreviated as “MEMBRANE-ELECTRODE ASSEMBLY:“ MEA ”). More specifically, it is produced by forming a catalyst layer on the composite electrolyte membrane described in the items (1) to (12), leaving a gasket forming portion having a constant width.
In particular, in the case of the composite electrolyte membrane according to (10) or (11), the surface on which the fluorine-based electrolyte membrane is thinned is used for the cathode electrode to prevent dry-up on the anode electrode side. It is preferable that the thickened surface of the electrolyte membrane is used for the anode electrode, and an appropriate amount of the catalyst layer is formed on each surface to produce the MEA.

(16) A solid polymer fuel cell or a direct methanol fuel comprising any one of the composite electrolyte membranes of (1) to (12) or the membrane-electrode assembly of (14) battery.

  In this section, any one of the composite electrolyte membranes described in the sections (1) to (12), or the membrane-electrode assembly (MEA) in the section (14), a solid polymer fuel cell or a direct methanol type This is an example of a suitable type of fuel cell applied to a fuel cell.

  According to the present invention, the composite electrolyte membrane obtained by combining the fluorine-based electrolyte membrane and the hydrocarbon-based electrolyte membrane compensates for the weak mechanical strength of the fluorine-based electrolyte membrane alone by the hydrocarbon-based electrolyte membrane, and The gas permeability can be suppressed low.

It is a flow which shows the manufacturing process of the composite type electrolyte membrane for fuel cells. (A) is a perspective view of a porous hydrocarbon-based electrolyte membrane, and (b) is a partially enlarged view of the perspective view of (a). FIG. 2 is a cross-sectional view of a composite electrolyte membrane in which a fluorine electrolyte membrane is filled in pores of a porous hydrocarbon electrolyte membrane and formed on both sides of the porous hydrocarbon electrolyte membrane. (A) And (b) is the top view and partial enlarged view of the porous hydrocarbon-type electrolyte membrane which concern on Example 1, respectively. It is the schematic which shows the measurement system for measuring the gas permeability of an electrolyte membrane. It is sectional drawing for demonstrating the measuring method of the leak current for measuring the reinforcement effect with respect to the carbon fiber etc. which originate in the GDL base material of the frame-shaped peripheral part of a hydrocarbon type electrolyte membrane. It is sectional drawing of the composite type electrolyte membrane which concerns on Example 2-1. It is sectional drawing of the composite type electrolyte membrane which concerns on Example 2-2. (A) is sectional drawing of the composite type electrolyte membrane which concerns on Example 3-1, (b) is sectional drawing of the composite type electrolyte membrane which concerns on Example 3-2.

  Hereinafter, an embodiment of the present invention will be described along a manufacturing flow (S1 to S7) of a composite electrolyte membrane for a fuel cell according to the present invention shown in FIG.

[Hydrocarbon electrolyte membrane preparation process (S1 process)]
First, in step S1, a hydrocarbon electrolyte membrane (plate or sheet) is prepared. The material of the hydrocarbon-based electrolyte membrane must have the properties of high mechanical strength and low gas permeability, and can be obtained by the production method shown in the Examples section described later, sulfonated aroma Group polyether [for example, PEEK (polyether ether ketone), PEEKKK (polyether ether ketone ketone), etc.], sulfonated polyimide, sulfonated polyimide amide, polybenzimidazole electrolyte, trifluorostyrene sulfonate copolymer, etc. A partially fluorinated hydrocarbon electrolyte or the like can be used. The hydrocarbon-based electrolyte membrane is a composite electrolyte membrane according to the present invention, and functions as an auxiliary membrane that compensates for the disadvantages of the fluorine-based electrolyte membrane. The film thickness is preferably 1 μm to 10 μm, and more preferably about 4 μm to 6 μm. If the hydrocarbon electrolyte membrane has a thickness of, for example, about 5 μm in this range, the hydrocarbon electrolyte membrane has sufficient toughness.

[Porous hydrocarbon-based electrolyte membrane production process (S2 process)]
Step S2 is a step of forming a porous hydrocarbon electrolyte membrane by forming a large number of through holes in the hydrocarbon electrolyte membrane prepared in S1 step.
More specifically, along the film thickness direction of, for example, a 5 μm-thick hydrocarbon-based electrolyte membrane prepared in step S1, it is on the order of millimeters, more preferably on the order of 10 ⁻¹ mm, for example, about 0.1 mm to 0.5 mm. The through-holes having a pore diameter of 2 are opened so as to be scattered on the hydrocarbon electrolyte membrane on average. If the diameter of the through hole is less than 0.1 mm, the absolute amount of the fluorine-based electrolyte formed in the film thickness direction decreases, and the advantages of the fluorine-based electrolyte membrane are lost. Further, when the diameter of the through hole is smaller, that is, on the micron order, a pressure reducing device is required to fill the through hole with a resin of a fluorine-based electrolyte as in the prior art (Patent Document 1). On the other hand, when the diameter of the through hole is larger than 0.5 mm, the mechanical strength of the entire hydrocarbon electrolyte membrane is lowered, which is not preferable.

  When the entire hydrocarbon-based electrolyte membrane is 100%, the opening ratio of the through holes is preferably 10% to 50%. If the opening ratio of the through-hole is less than 10%, the advantages of the resin of the fluorine-based electrolyte membrane filled in the through-hole are lost, while if it is 50% or more, the hydrocarbon-based electrolyte membrane as the reinforcing membrane This is because the strength is lowered, which is not preferable.

Needle punching is suitable as a mass-produced method for opening the through holes on the hydrocarbon-based electrolyte membrane on average. A number of relatively large diameters [holes on the order of millimeters, more preferably on the order of 10 ⁻¹ mm (for example, hole diameters of about 0.1 mm to 0.5 mm)] can be formed at one time. It is most suitable for rapid and continuous accurate dawn in a mass production system. The through hole may be opened by a laser such as a CO ₂ gas laser or an excimer laser. Even if the through-hole has a relatively large diameter and is slightly melted and expanded later by laser heat, the problem described in the prior art (Patent Document 2) does not occur.

  Further, as shown by the W portion in FIG. 2 (a), the through hole is a hydrocarbon-based as a joining margin for joining GDL to the peripheral portion of the hydrocarbon-based electrolyte membrane with respect to the hydrocarbon-based electrolyte membrane. It is made to be clear, leaving a fixed width (W part) of the peripheral part of the electrolyte membrane. When this constant width W portion is present, a catalyst layer (reference number 10 in FIG. 6) is formed on both sides of the composite electrolyte membrane (reference number 50 in FIG. 3) to produce an MEA (reference number 60 in FIG. 6). Further, it is joined by hot pressing so that the GDL (reference numeral 11 in FIG. 6) covers it, but the carbon fiber generated from the GDL substrate is the composite electrolyte membrane (reference numeral 50 in FIG. 3). The peripheral edge (the reference numeral w in FIG. 3) is not pierced, and cross leakage can be prevented. That is, the hydrocarbon-based electrolyte membrane having high mechanical strength serves as a shield for carbon fibers generated from the GDL base material. For example, in the case of the composite electrolyte membrane 50 having a size of 50 mm × 50 mm, the peripheral edge portion only needs to have a constant width W of about 5 mm.

  Furthermore, the through holes h are preferably formed in a staggered arrangement as shown in the perspective views of FIGS. This is because it is considered to be the most preferable arrangement form in order to disperse the through-holes h on the film surface at high density on average. The shape of the through hole h is not limited to a circle, and may be an elliptical shape, a polygonal shape such as a triangle or a square, or a slit shape.

[Casting process of fluorine electrolyte membrane on carrier film (S3 process)]
An engineering plastic film such as PET (polyethylene terephthalate) is prepared as a carrier film (not shown), and fixed and installed on a base (not shown). And the resin for fluorine-type electrolyte membrane is apply | coated to the carrier film with application | coating methods, such as a spray method, the casting method, and the inkjet method. The film thickness at this time is preferably changed as appropriate depending on whether the composite electrolyte membrane is symmetric or asymmetric with respect to the total film thickness direction, and how much μm the total film thickness is. .

[Jointing Step of Porous Hydrocarbon Electrolyte Membrane 1 and Fluorine Electrolyte Membrane with Carrier Film (Step S4)]
Next, the porous hydrocarbon-based electrolyte membrane 1 shown in FIG. 2 produced in the S1 step is joined to the fluorine-based electrolyte membrane with a carrier film produced in the S3 step by a hot press means such as hot press. At this time, in step S3, the porous hydrocarbon-based electrolyte membrane 1 may be placed on the semi-dry fluorine-based electrolyte membrane to join them together.

[Casting step of resin for fluorine electrolyte membrane to porous hydrocarbon electrolyte membrane 1 (step S5)]
In the hole h of the porous hydrocarbon electrolyte membrane (porous hydrocarbon electrolyte membrane with carrier film) 1 bonded to the carrier film covered with the fluorine electrolyte membrane produced in the step S4 and to the membrane surface Then, a fluorine-based electrolyte membrane resin made of the same material as that used in step S4 is applied by a casting method. A number of holes h formed in the porous hydrocarbon-based electrolyte membrane 1 have a diameter on the order of millimeters, more preferably on the order of 10 ⁻¹ mm, and the fluorine-based electrolyte membrane resin easily flows into the holes h. At the same time, the fluorine-based electrolyte membrane resin is also applied to the membrane surface of the porous hydrocarbon-based electrolyte membrane 1. The film thickness at this time is also preferably 10 μm to 30 μm. The reason is the same as that described in step S4.

[Carrier film, fluorine electrolyte membrane, porous hydrocarbon electrolyte membrane bonding and carrier film peeling step (step S6)]
The fluorine-based electrolyte membrane formed on the carrier film, the porous hydrocarbon-based electrolyte membrane 1 formed on the surface of the fluorine-based electrolyte membrane, and the porous hydrocarbon-based electrolyte membrane 1 produced in step S5 Another carrier film is placed on the fluorine-based electrolyte membrane 2 formed on the pores and the membrane surface, and hot pressing means such as hot pressing is applied from both sides of these membranes under loose conditions (low pressure, low temperature). .
Thereafter (after cooling and drying), the two outermost carrier films are peeled off. As a result, the porous hydrocarbon-based electrolyte membrane 1 shown in the cross-sectional view of FIG. 3 and the fluorine-based electrolyte membrane 2 are formed on both sides of the porous hydrocarbon-based electrolyte membrane 1 that fills the holes h of the membrane 1. Thus, a composite electrolyte membrane 50 having a constant width portion w in which no pores of the porous hydrocarbon-based electrolyte membrane 1 are present is obtained inside the peripheral portion.

[Completion of composite electrolyte membrane for fuel cell (S7)]
The composite electrolyte membrane 50 is a membrane that takes advantage of both the hydrocarbon electrolyte membrane and the fluorine electrolyte membrane and complements the disadvantages. In addition, it is clear that attention is paid to the cross section indicated by reference numeral 30 (the cross section surrounded by the alternate long and short dash line), but the fluorine electrolyte membrane 2 is horizontally H-shaped in the hole h of the porous hydrocarbon electrolyte membrane 1. Since the cross-sections are tightly fitted in the shape (fitting shape) and a large number of such cross-sectional portions exist in the membrane, two types of electrolyte membranes are completely integrated to form one electrolyte membrane. To do. Therefore, the composite electrolyte membrane 50 has a high mechanical strength, and the two types of electrolyte membranes are not separated, so that the composite electrolyte membrane 50 is a robust membrane as a composite membrane.

<Example 1, Examples 2-1 and 2-2, Examples 3-1 and 3-2, Comparative Example 1>
The composite electrolyte membrane according to Example 1, Example 2-1, Example 2-2, Example 3-1, and Example 3-2 according to the above-described embodiment will be described, and the electrolyte according to Comparative Example 1 will be described. Each composite electrolyte membrane is evaluated while contrasting with a membrane [a single-layer membrane made of Nafion (trade name)].

  The composite electrolyte membranes according to Example 1, Example 2-1, and Example 2-2 are thicker in order when the central hydrocarbon electrolyte membrane is 5 μm (the membrane is 10 μm thick). ), Having a film thickness thinner than that of Example 1 (the film is 2.5 μm thick). The total thickness of the composite electrolyte membrane was 25 μm.

In the composite electrolyte membranes according to Example 3-1 and Example 3-2, the thickness of the hydrocarbon-based electrolyte membrane is 5 μm, and the hydrocarbon-based electrolyte membrane is close to the anode electrode side in the composite-type electrolyte membrane. And those located near the cathode side in the composite electrolyte membrane. Similarly, the total thickness of the composite electrolyte membrane was set to 25 μm.
Hereinafter, although each Example and Comparative Example 1 are demonstrated, the description is abbreviate | omitted suitably about a common content.

Example 1
[Preparation of porous hydrocarbon electrolyte membrane]
The reaction of the sulfonating agent and the polyimide amide resin was advanced as shown in [Chemical Formula 1] to obtain a hydrocarbon sulfonated resin.

  This resin material was dried at 110 ° C. under reduced pressure for 5 hours. 5 times of sulfuric acid is added to 1 g of the dried resin raw material, and a sulfonating agent is further added to 1.0 times of the resin raw material. went. While stirring the viscous liquid obtained by sulfonation, the liquid is dropped into about 10 times the volume of this liquid and washed and filtered until the pH of the water reaches 7 (determined by pH test paper). Was performed three times. Thereafter, the obtained solid was dried by vacuum drying at 80 ° C. for 5 hours to obtain a sulfonated resin.

  The ion exchange equivalent weight was measured by precisely weighing the sulfonated polymer to be measured into a sealable glass container (= a gram), adding an excessive amount of calcium chloride aqueous solution thereto, and stirring for 12 hours. Hydrogen chloride generated in the system was titrated (b [ml]) with 0.05 N aqueous sodium hydroxide solution (titer f) using phenolphthalein as an indicator.

From the above measured values, the ion exchange equivalent weight (g / mol) was determined by [Formula 1], and further converted to the ion exchange capacity (meq / g) using [Formula 2].
[Formula 1]
Ion exchange equivalent weight [g / mol] = (1000 / a) / (0.05 × b × f)
[Formula 2]
Ion exchange capacity [meq / g] = 1 / (ion exchange equivalent weight / 1000)

The same amount of chlorosulfuric acid was added to the polyamideimide resin. The ion exchange capacity at this time was 0.9 (meq / g) equivalent to Nafion (registered trademark).
The obtained hydrocarbon-based sulfonic acid resin was dissolved in a solvent of water / ethanol = 50/50 (volume ratio) to obtain a hydrocarbon-based sulfonic acid resin solution having a concentration of 5 wt%.

The hydrocarbon-based sulfonic acid resin solution was repeatedly applied to a smooth PET sheet by an ordinary spray method. After the application, it was dried for 10 minutes using a dryer capable of sending hot air at 80 ° C. The thickness of the obtained hydrocarbon-based electrolyte membrane was 5 μm (the hydrocarbon-based electrolyte membrane obtained by this method and the hydrocarbon-based electrolyte membrane obtained by this method had the following differences except for the difference in film thickness) Applies to all examples, comparative example 1).
As shown in FIG. 4, the obtained film is cut into 50 mm × 50 mm, leaving a width w of 5 mm so as to frame the peripheral edge, and needle punching in other places (inside the peripheral edge), The distance L1 between the centers of the through holes (vertical direction in FIG. 4B) is 0.6 mm, and the distance L3 between the centers of the through holes (horizontal direction in FIG. 4B) is 0.5 mm. Furthermore, a through hole having a diameter D of 0.3 mm was opened so that the distance L2 between the centers of the through holes (lateral direction in FIG. 4B) was 1.0 mm. The opening rate of the through holes at this time was 23.5%.

[Preparation of composite electrolyte membrane for polymer electrolyte fuel cells]
Using a Nafion DE2020CS (trade name) solution, a cast film (fluorine electrolyte film) having a thickness of 10 μm was formed on a PET film (corresponding to a carrier film) having a thickness of 38 μm by a casting method. Thereafter, each PET film was cut into 50 mm × 50 mm, and the previously produced porous (with through-hole) hydrocarbon-based electrolyte membrane was disposed thereon. Further, a fluorine-based electrolyte membrane was produced on the porous hydrocarbon-based electrolyte membrane by casting using Nafion DE2020CS (trade name) solution. The produced membrane is dried at a temperature of 80 ° C. for 30 minutes, the porous hydrocarbon electrolyte membrane is centered, and the two fluorine electrolyte membranes are arranged symmetrically in the whole film thickness direction, so that the total thickness is A composite electrolyte membrane 50 according to Example 1 having a thickness of 25 μm was obtained.

(Example 2-1)
FIG. 7 shows a composite electrolyte membrane 50A according to Example 2-1.
First, in manufacturing the composite electrolyte membrane 50A, a fluorine-based electrolyte membrane was formed by a casting method using a Nafion DE2020CS (trade name) solution in the same manner as the method for manufacturing the composite electrolyte membrane 50 according to Example 1. Then, drying and casting under conditions of 80 ° C. for 30 minutes were repeated to form a 15 μm-thick fluorine-based electrolyte membrane (hereinafter referred to as “first cast membrane”). Separately, a fluorine-based electrolyte membrane (hereinafter referred to as “second cast membrane”) having a thickness of 5 μm was produced on a 38 μm-thick PET film by a casting method using Nafion DE2020C (trade name) solution.

  Next, after the 38 μm-thick PET film is peeled off from the first cast film and the second cast film, the first cast film and the second cast film are disposed so that the porous hydrocarbon-based electrolyte film is disposed at the center. The composite electrolyte membrane 50A having a total film thickness of 25 μm according to Example 2-1 was prepared by superimposing on the porous hydrocarbon electrolyte membrane and performing hot-pressure bonding at 130 ° C. and a pressure of 4 MPa for 10 minutes. . After the composite electrolyte membrane 50B is completed, the cross section is observed with a microscope. The composite electrolyte membrane 50A according to Example 2-1 has two fluorine-based electrolytes with the porous hydrocarbon electrolyte membrane 1A at the center. The membrane 2A is disposed symmetrically in the entire thickness direction, and the ratio of the total thickness of the composite electrolyte membrane 50A to the thickness of the central porous hydrocarbon electrolyte membrane 1A is 1: 0.5. It was confirmed (see FIG. 7).

(Example 2-2)
The composite electrolyte membrane 50B according to Example 2-2 shown in FIG. 8 was produced by the same method as in Example 1-1. However, the porous hydrocarbon-based electrolyte membrane 1B disposed at the center of the composite electrolyte membrane 50B is 0.2 μm thick, and the ratio of the total thickness of the composite-type electrolyte membrane 50B to the central porous hydrocarbon-based electrolyte membrane 1B. However, the total thickness of the composite electrolyte membrane was 25 μm (see FIG. 8). Further, since the porous hydrocarbon electrolyte membrane 1B having a thickness of 0.2 μm is extremely thin, the resin for the porous hydrocarbon electrolyte membrane 1B (sulfonated polyimide amide) is discharged from an inkjet nozzle using an inkjet method. Formed. After the composite electrolyte membrane 50B is completed, the cross section thereof is observed with a microscope. The composite electrolyte membrane 50B according to Example 2-2 has two fluorine-based electrolytes with the porous hydrocarbon electrolyte membrane 1B at the center. It is confirmed that the membrane 2B is symmetrically arranged in the entire thickness direction of the composite electrolyte membrane 50B, and the ratio of the total thickness to the central porous hydrocarbon electrolyte membrane 2B is 1: 0.01. (See FIG. 8).

(Example 3-1)
A composite electrolyte membrane 50C according to Example 3-1 shown in FIG. 9A is obtained by placing a porous hydrocarbon electrolyte membrane 1C having a thickness of 5 μm on a PET film having a thickness of 38 μm, and from above. A cast membrane (fluorine electrolyte membrane) was formed by a casting method using Nafion DE2020CS (trade name) solution. At this time, Nafion DE2020CS (trade name) solution is placed between the PET film and the porous hydrocarbon-based electrolyte membrane 1C from each hole h of the porous hydrocarbon-based electrolyte membrane 1C, and the back surface of the porous hydrocarbon-based electrolyte membrane. to as wrap around, between the PET film and the porous hydrocarbon-based electrolyte membrane 1C, Nafion DE2020CS (trade name) fluorinated electrolyte membrane 2C ₁ side is thin (thickness of several μm order) by liquid so as to form did.

Further, drying and casting were repeated for the cast membrane (fluorine electrolyte membrane) 2C ₂ at 80 ° C. for 30 minutes, so that the total thickness of the composite electrolyte membrane was 25 μm. The fluorine-based electrolyte membranes 2C ₁ (thin film) and 2C ₂ (thick film) on both sides of the porous hydrocarbon-based electrolyte 1C are different from the fluorine-based electrolyte membranes 2A and 2B according to Examples 2-1 and 2-2, It was confirmed by observing the cross-section with a microscope that it was asymmetric (see FIG. 9A).

(Example 3-2)
The composite electrolyte membrane 50C ′ according to Example 3-2 shown in FIG. 9B is manufactured in the same manner as that according to Example 3-1. In Example 3-2, similarly to Example 3-1, the porous hydrocarbon-based electrolyte 1C is formed in a non-center in the film thickness direction of the composite electrolyte membrane 50C ′ and parallel to the membrane surface. The thick film side fluorine-based electrolyte membrane 2C ₂ was used on the anode side of the fuel cell, and the thin film side fluorine-based electrolyte membrane 2C ₁ was used on the cathode side of the fuel cell. (See FIG. 9B).

(Comparative Example 1)
In Comparative Example 1, a Nafion DE2020CS (trade name) solution was used, and a single-layer electrolyte membrane (conventional Nafion single-layer electrolyte membrane) was obtained by a casting method using only a fluorine-based electrolyte membrane having a total thickness of 25 μm.

<Various evaluations>
(Evaluation of gas permeability)
This evaluation of gas permeability tests the ability to prevent cross leak between the anode and cathode sides of the obtained composite electrolyte membrane.
Therefore, using a gas permeability measuring device 40 as shown in FIG. 5, based on JISK7126 A method (differential pressure method), hydrogen gas at a temperature of 80 ° C. and a relative humidity of 50% is measured with a unit partial pressure difference. The volume of gas passing through the unit area per unit time was measured. The measuring device 40 includes a permeation cell 3, a filter paper 4, a cell accumulation variable unit 9, a pressure detector 5, a test gas supply 6, a vacuum pump 7, a test gas 8, and stop valves V1 to V5, and should be measured. The electrolyte membranes of Examples and Comparative Examples 1 were accommodated in the permeation cell 3, and the volume of gas (hydrogen gas) passing through the unit area per unit time was measured according to the differential pressure method defined in the JIS standard.

Table 1 shows the measurement results. According to Table 1, the composite electrolyte membrane according to Example 1 was suppressed to have a lower hydrogen gas permeability than that of Comparative Example 1 (1/6 or more of Comparative Example 1).
Further, according to the table, the composite electrolyte membrane according to Example 2-1 was also suppressed to have a lower hydrogen gas permeability than that of Comparative Example 1 (about 1/24 of Comparative Example 1).
On the other hand, according to the same table, the composite electrolyte membrane according to Example 2-2 was suppressed in hydrogen gas permeability to be lower than that of Comparative Example 1, but the Comparative Example It was about 1/2 of that according to 1 and was inferior to that according to Example 2-1. This is probably because the material according to Example 2-2 was formed in a thinner film than that according to Example 2-1, and thus facilitated the permeation of hydrogen gas.

(Evaluation of leakage current)
This evaluation of the leakage current is to test the ability of the obtained composite electrolyte membrane to protect the carbon fibers of the GDL substrate.
For this purpose, a short circuit of current leakage between the anode side and the cathode side is performed by measuring a leakage current value between both electrodes sandwiching the composite electrolyte membrane 60 in which the catalyst layer 10 shown in FIG. 6 is formed. The degree of leakage (leakage current value) was examined.
First, a 40 mm × 40 m catalyst layer 10 was formed on one surface of the composite electrolyte membrane 60 by a transfer method. Separately, the GDL substrate is cut into 45 mm × 45 m, and the GDL substrate is subjected to hot pressing at 130 ° C. and 4 MPa for 5 minutes on the composite electrolyte membrane 60 on which the catalyst layer 10 is formed. The substrate was bonded to the MEA including the composite electrolyte membrane 60.

  Then, this bonded product 70 (MEMBRANE ELECTRODE GDL ASSEMBLY: abbreviated as “MEGA70”) is allowed to stand in a constant temperature and humidity chamber at 25 ° C. and 50% RH for 1 hour or longer, and the short circuit state due to the GDL substrate is confirmed. Therefore, using two metal blocks, the MEGA 70 is sandwiched from both outer surfaces under a pressure of 2.3 MPa, and a voltage of 0.2 V is applied between the anode side and the cathode side of the MEGA 70 to reduce leakage current. Measurements were made.

Table 2 shows the measurement results. Referring to Table 2, when Example 1 is compared with Comparative Example 1, the leakage current value is suppressed to about 1/40, and the GDL group is reduced by the hydrocarbon electrolyte membrane (peripheral portion W in FIG. 2). It was found that short-circuiting by the material was prevented. This is because the peripheral portion w of the hydrocarbon-based electrolyte membrane 1 is arranged at the central peripheral portion in the entire film thickness direction of the composite electrolyte membrane 60, and serves as a shield against carbon fibers generated from the GDL base material 11. This is probably because the composite electrolyte membrane 60 was not pierced.

  On the other hand, in the electrolyte membrane (not shown) according to Comparative Example 1, the hydrocarbon electrolyte membrane is not interpolated at all, that is, since the membrane is only a fluorine electrolyte membrane, the mechanical strength is weak and the GDL substrate It is considered that carbon fibers or the like generated from 11 pierced the electrolyte membrane and current leaked between both sides of the electrolyte membrane.

(Evaluation as battery performance when a composite electrolyte membrane is assembled in a fuel cell)
In this evaluation, the obtained composite electrolyte membrane is actually incorporated into a fuel cell, and the cell performance of the fuel cell is tested.

First, a method for assembling each composite electrolyte membrane into a fuel cell (referred to as “single cell”, hereinafter the same) will be described below.
First, a mass ratio of a mixture of Nafion (trade name) liquid and platinum particle-supported catalyst powder in which platinum powder composed of platinum metal particles is supported on carbon particles constituting carbon powder by 45 mass%. The mixture was dispersed in a mixed dispersion medium of ethanol and water so that the ratio was 1: 1. The platinum catalyst dispersion liquid having a solid content concentration of 15% by mass thus obtained was applied to a 200 μm thick PTFE (polytetrafluoroethylene) sheet by a bar coating method and dried at 80 ° C. In this way, a catalyst layer material having a platinum catalyst loading of about 0.4 mg / cm ² was produced.

  Next, this catalyst layer material is cut out to a size of 3 cm × 3 cm, and the catalyst layer side surface of the catalyst layer material and both surfaces of each of the composite electrolyte membranes according to Examples 3-1, 3-2 and Comparative Examples are used. They were sandwiched between two opposing molds of a hot press machine back to back and subjected to hot-pressure treatment at a temperature of 130 ° C. and a pressure of 4 MPa. After cooling, the PTFE sheet was peeled off using the hot-press treated surface as an interface to produce a membrane-electrode assembly (MEA). On the other hand, two sheets of about 300 μm thick carbon paper having a 100 μm thick conductive layer made of carbon powder and PTFE dispersion formed on the surface were prepared and used as GDL substrates. Furthermore, both sides of the MEA were sandwiched between two GDL substrates, and the catalyst layer (3 cm × 3 cm) on the MEA was surrounded by a frame-shaped gasket member to prepare fuel cell MEAs.

  The fuel cell MEAs according to Example 2-1 and Example 2-2 are configured as unit cells without distinction between the front and back sides, but the fuel according to Example 3-1 and Example 3-2. Since the battery MEA has an asymmetric structure in the entire film thickness direction, the unit cell is configured while paying attention to the set direction.

  That is, for the fuel cell MEA according to Example 3-1, the fluorine-based electrolyte membrane having the porous hydrocarbon-based electrolyte as a thin film is placed on the anode electrode (fuel electrode) side of the fuel cell. In addition, the fluorine-based electrolyte membrane in which the porous hydrocarbon-based electrolyte is a thick film is placed on the cathode electrode (oxygen electrode) side of the fuel cell, on the other hand, according to Example 3-2 For the above, the same fuel cell MEA as in Example 3-1 was used upside down.

The initial voltage (0 CV) was evaluated by setting the operating temperature to 80 ° C., the hydrogen bubbler temperature, and the air bubbler temperature to 50 ° C. Hydrogen was supplied to the anode electrode (fuel electrode) as a fuel gas at a back pressure of about 0.1 MPa and 2.0 times the stoichiometric ratio. The cathode electrode (oxygen electrode) was supplied with air as oxygen gas at a back pressure of about 0.1 MPa and 2.5 times the stoichiometric ratio. About the load with respect to this fuel cell, it discharged as 1.6 A / cm < ² > and the voltage value after 20 minutes was made into the initial voltage. The internal resistance was measured using a 1 kHz AC milliohm meter.

The cell characteristic results of the above fuel cells are summarized in Table 3.

  As can be seen from Table 3, both the cell voltage (mV) and the open circuit voltage (OCV) of the fuel cell including the composite electrolyte membrane of Example 3-1 were higher than those of Example 3-2. A high measurement value was obtained. Regarding the cell voltage (mV), the fuel cell of Example 3-1 was suppressed from drying in the low humidification region than that of Example 3-2, and the open circuit voltage (OCV) was implemented. Since the gas permeation of the fuel cells of Example 3-2 and Example 3-1 is equivalent, it is considered that such a measurement result was obtained.

Of course, the composite electrolyte membrane of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.
For example, as a modification, in the above embodiment, the steps S5 and S6 can be omitted. In the composite electrolyte membrane 50 in such a case, the fluorine-based electrolyte membrane 2 having a certain thickness is formed on one surface of the porous hydrocarbon-based electrolyte membrane 1, but the fluorine-based electrolyte membrane 2 is not formed on the other surface. It is also possible to do so.

  Even in this case, the weight of the characteristic of the fluorine-based electrolyte membrane occurs on the cathode electrode side and the anode electrode side, but both the protons as long as the porous hydrocarbon-based electrolyte membrane 1 and the fluorine-based electrolyte membrane 2 are electrolyte membranes. Needless to say, the composite electrolyte membrane having proton conductivity as a whole is sufficient. Further, when the fluorine-based electrolyte membrane 2 is formed on one surface of the porous hydrocarbon-based electrolyte membrane 1, the resin of the fluorine-based electrolyte membrane 2 that fills the through holes h and protrudes to the back passes around the back surface and wraps around the back surface. As a result of the appearance of “eyelet-like” portions as in the case where the fluorine-based electrolyte membrane 2 is formed on both surfaces, even in this case, both membranes can be firmly joined and combined.

1: porous hydrocarbon-based electrolyte membrane, 2: fluorine-based electrolyte membrane, 50, 50A, 50B, 50C, 50C ′: composite electrolyte membrane for fuel cell, h: hole, w: peripheral portion of hydrocarbon-based electrolyte membrane Constant width of

Claims (14)

  A fluorine-based electrolyte membrane is formed to fill the pores of the porous hydrocarbon-based electrolyte membrane and cover the membrane surface, and the pores of the porous hydrocarbon-based electrolyte membrane are opened in the film thickness direction. A composite electrolyte membrane for a fuel cell, characterized in that the through-hole has a diameter of a millimeter order and is scattered on the membrane surface on average.   The composite electrolyte membrane for a fuel cell, wherein an average hole diameter of the through holes is 0.1 mm to 0.5 mm.   3. The fuel according to claim 1, wherein the through-hole is opened at an opening ratio of 10% to 50% with respect to 100% of the entire surface of the porous hydrocarbon-based electrolyte membrane. Composite electrolyte membrane for batteries.   The joining margin for joining the gas diffusion layer in which the through-hole is not formed is provided on the constant width surface of the peripheral portion of the porous hydrocarbon electrolyte included in the composite electrolyte membrane for fuel cells. The composite electrolyte membrane for a fuel cell according to any one of claims 1 to 3, wherein the composite electrolyte membrane is for a fuel cell.   5. The thickness of the porous hydrocarbon electrolyte membrane is 1 μm to 10 μm, and the thickness of the fluorine electrolyte membrane is 2 μm to 30 μm. 6. A composite electrolyte membrane for a fuel cell according to Item. A composite electrolyte membrane for a fuel cell according to any one of claims 1 to 5,
A composite electrolyte membrane for a fuel cell, wherein the porous hydrocarbon-based electrolyte membrane is formed in the center in the whole film thickness direction and in parallel with the membrane surface.   The thickness of the composite electrolyte membrane for a fuel cell is set to 1, and the thickness of the porous hydrocarbon-based electrolyte membrane is 0.01 to 0.5. A composite electrolyte membrane for a fuel cell according to 1.   8. The fuel cell composite electrolyte membrane according to claim 6 or 7, wherein the fuel cell composite electrolyte membrane has a thickness of 5 to 30 [mu] m.   The composite electrolyte membrane for a fuel cell according to any one of claims 1 to 5, wherein the porous hydrocarbon-based electrolyte membrane is formed in a non-central direction in the entire film thickness direction and parallel to the membrane surface. A composite electrolyte membrane for a fuel cell, characterized in that A composite electrolyte membrane for a fuel cell according to claim 9,
The surface of the fluorine-based electrolyte membrane on the side where the porous hydrocarbon-based electrolyte membrane becomes thin is used for the cathode electrode of a fuel cell, and the surface of the fluorine-based electrolyte membrane on the side where the porous hydrocarbon-based electrolyte membrane becomes thick For a fuel cell anode, a composite electrolyte membrane for a fuel cell.   The composite electrolyte membrane for a fuel cell according to any one of claims 8 to 10, wherein the thickness of the composite electrolyte membrane for a fuel cell is 5 to 30 µm.   An anode catalyst layer is formed on the surface of the fluorine-based electrolyte membrane on the side where the porous hydrocarbon-based electrolyte membrane becomes thinner in the composite electrolyte membrane for a fuel cell according to any one of claims 9 to 11. A membrane-electrode assembly comprising a cathode catalyst layer formed on the surface of the fluorine-based electrolyte membrane on the side where the porous hydrocarbon-based electrolyte membrane is thickened.   Through holes of millimeter order by needle punch processing or laser irradiation processing while leaving a certain width of the peripheral portion of the hydrocarbon-based electrolyte membrane as a joining margin for joining the gas diffusion layer to the peripheral portion of the hydrocarbon-based electrolyte membrane And applying a fluorine-based electrolyte resin to the hydrocarbon-based electrolyte membrane in which the through-holes are formed by a casting method. Forming a fluorine-based electrolyte membrane made of a fluorine-based electrolyte resin on the porous hydrocarbon-based electrolyte membrane.   A method of casting a fluorine-based electrolyte resin on the hydrocarbon-based electrolyte membrane having the through-holes formed after fixing one surface of the hydrocarbon-based electrolyte membrane to a carrier film to which a fluorine-based electrolyte resin has been applied in advance The method for producing a composite electrolyte membrane for a fuel cell according to claim 13, wherein the method is applied.

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