JP2010218907A - Fuel cell and membrane electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to suppress deterioration of an electrolyte membrane. <P>SOLUTION: A fuel cell has the electrolyte membrane, an electrode layer arranged on both faces of the electrolyte membrane, a reaction gas flow passage forming part for supplying a reaction gas to the electrode layer, a frame-like member formed in a frame shape so as to cover the peripheral part of the electrolyte membrane, and a water absorbing member which is arranged between an inner frame of the frame-like member and the outer periphery of the reaction gas flow passage forming part, and swollen by water absorption. The water absorbing member is adhered to the electrolyte membrane, and fixed to the frame-like member. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell.

  2. Description of the Related Art Conventionally, there is a fuel cell in which a reaction gas flow channel through which a reaction gas is circulated is laminated on both surfaces of a membrane electrode assembly (MEA) in which electrodes are arranged on both surfaces of an electrolyte membrane. In such a fuel cell, in order to maintain the shape of the electrolyte membrane, the outer periphery of the electrolyte membrane may be supported by a frame that is harder than the electrolyte membrane. For example, such a frame may have a function as a sealing member for suppressing leakage of the reaction gas.

  As described above, when the frame has a function as a sealing member, for example, the frame is made of a resin such as silicone rubber, so that the dimensional variation is relatively large. Therefore, in consideration of the dimensional variation of the frame, the reactive gas flow path is disposed with a gap in the inner frame of the frame described above (see, for example, Patent Documents 1 to 5).

  During operation of the fuel cell, water is generated by an electrochemical reaction or humidified gas is supplied, so that the electrolyte membrane is kept in a wet state. Since the electrolyte membrane has water absorption, it absorbs water and expands during operation of the fuel cell. On the other hand, after stopping the operation of the fuel cell, for example, a purge gas may be flowed to dry the inside of the fuel cell. Therefore, the electrolyte membrane is dried and shrinks. That is, the electrolyte membrane expands and contracts with the operation / stop of the fuel cell.

  As described above, if there is a gap between the frame and the reaction gas flow path, the electrolyte membrane is exposed at the gap. Therefore, the electrolyte membrane easily expands in the film thickness direction, and when the expansion and contraction are repeated, the electrolyte membrane may be cracked and the electrolyte membrane may be deteriorated.

JP 2006-202535 A Japanese Patent Laying-Open No. 2005-285677 JP 2000-340247 A JP 2001-015137 A JP 2000-323159 A

  Such a problem is common when the membrane electrode assembly is exposed in the gap between the frame and the reaction gas flow path, or when the membrane electrode assembly in which the gas diffusion layer is disposed is exposed. .

  Then, an object of this invention is to provide the technique which suppresses deterioration of an electrolyte membrane.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A fuel cell,
An electrolyte membrane;
Electrode layers disposed on both surfaces of the electrolyte membrane;
A reactive gas flow path forming part for supplying a reactive gas to the electrode layer;
A frame-shaped member formed in a frame shape so as to cover the peripheral edge of the electrolyte membrane;
A water-absorbing member that is disposed between the inner frame of the frame-shaped member and the outer periphery of the reactive gas flow path forming portion and expands by absorbing water;
With
The water absorbing member is bonded to the electrolyte membrane and fixed to the frame member.

  In this way, when the electrolyte membrane is in a swollen state during operation of the fuel cell, moisture moves from the electrolyte membrane to the water-absorbing member, so that the expansion of the electrolyte membrane is suppressed. In addition, when the electrolyte membrane is dried when the fuel cell is stopped, moisture moves from the water absorbing member to the electrolyte membrane, so that drying of the electrolyte membrane is suppressed. Therefore, the expansion / contraction of the electrolyte membrane accompanying the operation / stop of the fuel cell is suppressed, and the deterioration of the electrolyte membrane is suppressed.

[Application Example 2] The fuel cell according to Application Example 1,
The water absorbing member is
A fuel cell that expands when absorbed and contracts when dried.

  Since the electrolyte membrane and the water absorbing member are bonded, when the water absorbing member dries and shrinks, the electrolyte membrane is pulled by the water absorbing member, and the shrinkage of the electrolyte membrane is suppressed. As a result, deterioration of the electrolyte membrane is suppressed.

[Application Example 3] The fuel cell according to Application Example 1 or 2,
The surface forming the inner frame of the frame-shaped member is formed to be inclined with respect to the surface in the thickness direction of the reactive gas flow path forming portion, and the surface forming the inner frame of the frame-shaped member and the reaction A fuel cell in which a gap formed by a surface in a thickness direction of a gas flow path forming portion is wider on the electrolyte membrane side and narrows outward.

  If it does in this way, when a water absorption member absorbs water and expand | swells, it expands and suppresses toward an outer side. Therefore, the water-absorbing member expands toward the electrolyte membrane, a force that holds the electrolyte membrane works, and the expansion of the electrolyte membrane is suppressed. As a result, deterioration of the electrolyte membrane is suppressed.

[Application Example 4] The fuel cell according to any one of Application Examples 1 to 3,
The frame-shaped member includes a protrusion,
The fuel cell, wherein the water absorbing member is fixed to the frame member by being sandwiched between the protrusions.

  Since the water-absorbing member is pressed by the protrusion, expansion toward the outside of the water-absorbing member is suppressed, and a force for pressing the electrolyte membrane works. As a result, the expansion of the electrolyte membrane is suppressed, and the deterioration of the electrolyte membrane is suppressed.

  The present invention is not limited to the above-described fuel cell mode, and can be implemented in various modes such as a vehicle-mounted mode and a membrane electrode assembly mode. .

It is explanatory drawing which shows typically the structure of the single cell of a 1st Example. It is sectional drawing which shows the cross-sectional structure of the single cell of a 1st Example. It is a figure which expands and shows the X1 part in FIG. 6 is a diagram showing a part of a cross-sectional configuration of a single cell of Comparative Example 1. FIG. 10 is a diagram showing a part of a cross-sectional configuration of a single cell of Comparative Example 2. FIG. It is a figure which shows the conditions of a wet / dry cycle test. It is a figure which shows the relationship between the implementation time of a dry / wet cycle test, and a pressure fall rate. It is a figure which shows a part of cross-sectional structure of the single cell of a 2nd Example. It is a figure which shows the structure of the sealing member of a 2nd Example. 10 is a diagram showing a part of a cross-sectional configuration of a single cell of Comparative Example 3. FIG. It is a figure which shows the relationship between the implementation time of a dry / wet cycle test, and a pressure fall rate. It is a figure which shows a part of cross-sectional structure of the single cell of a 3rd Example. It is a figure which shows the modification of the cross-sectional shape of a sealing member.

A. First embodiment:
A1. Configuration of the first embodiment:
The fuel cell according to the first embodiment of the present invention is a solid polymer fuel cell that generates electric power using air as an oxidizing gas and hydrogen as a fuel gas. This fuel cell is configured by laminating a plurality of single cells each having a separator having a reaction gas flow path disposed on both sides of a seal member integrated MEA. FIG. 1 is an explanatory diagram schematically showing the configuration of a single cell.

  The single cell 100 includes a seal member integrated MEA 40, an anode side gas diffusion layer 22, a cathode side gas diffusion layer (not shown), an anode side separator 50, and a cathode side separator 60. In FIG. 1, the cathode side gas diffusion layer is not shown because it is hidden behind the seal member integrated MEA 40.

  The anode-side separator 50 is disposed to face the anode of the seal member integrated MEA 40. A groove-like anode gas flow channel through which hydrogen as an anode gas flows is formed on the surface of the anode separator 50 facing the anode of the seal member integrated MEA 40. On the other hand, the cathode-side separator 60 is disposed to face the cathode of the seal member integrated MEA 40. A groove-like cathode gas flow path through which air as cathode gas flows is formed on the surface of the cathode-side separator 60 facing the cathode of the seal member integrated MEA 40.

  The anode-side separator 50, the cathode-side separator 60, and the seal member integrated MEA 40 are each provided with a through-hole in the peripheral portion. When the seal member-integrated MEA 40, the anode-side separator 50, and the cathode-side separator 60 are stacked, a manifold for circulating an anode gas and a cathode gas (hereinafter also referred to as “reactive gas”) through these through holes. Configure.

  As illustrated, the anode side separator 50 and the cathode side separator 60 are arranged so that the anode gas channel and the cathode gas channel are orthogonal. In this embodiment, the anode-side separator 50 and the cathode-side separator 60 are made of dense carbon, which is a gas-impermeable conductive member, but are made of metal such as stainless steel, titanium, and aluminum. Also good.

  The seal member integrated MEA 40 includes the MEA 10, the seal member 38, and the water absorbing members 32 and 34. In FIG. 1, the water absorbing member 34 is not shown because it is disposed on the back side.

  The MEA 10 is a thin film having a substantially square outer shape, and the seal member 38 is formed in a frame shape on the periphery of the MEA 10 in order to maintain the shape of the MEA 10. The water absorbing member 32 has a frame shape and is arranged so that the outer frame substantially coincides with the inner frame of the seal member 38. In FIG. 1, the water absorbing member 32 is shown with hatching.

  The seal member 38 is formed using silicone rubber. The seal member 38 functions to maintain the shape of the MEA 10 and suppress leakage of the reaction gas from the above-described through hole. In the present embodiment, silicone rubber is used as the seal member 38, but is not limited to this, and other members having gas impermeability, elasticity, and heat resistance may be used.

  For the anode side gas diffusion layer 22 and the cathode side gas diffusion layer (not shown), a carbon cloth having a substantially square shape with an outer periphery smaller than the inner frame of the seal member 38 is used. When the anode side gas diffusion layer 22 and the cathode side gas diffusion layer are laminated on the MEA 10, a gap is generated between the anode side gas diffusion layer 22 and the cathode side gas diffusion layer and the inner frame of the seal member 38. Carbon paper, carbon felt, a carbon porous body, a metal porous body, or the like may be used as the anode side gas diffusion layer 22 and the cathode side gas diffusion layer.

  FIG. 2 is a cross-sectional view showing a cross-sectional configuration of a single cell. In FIG. 2, the cut surface which cut | disconnected the single cell 100 is shown by A surface shown with a dashed-dotted line in FIG.

  The MEA 10 has a configuration in which the anode 14 is disposed on one surface of the electrolyte membrane 12 and the cathode 16 is disposed on the other surface. In this embodiment, the electrolyte membrane 12 is a polymer electrolyte membrane formed of a fluorine-based resin, and the anode 14 and the cathode 16 are electrodes formed of carbon cloth carrying platinum and a platinum alloy as a catalyst. Each was used. Note that a polymer electrolyte membrane formed of a carbon-based resin may be used as the electrolyte membrane. The electrode may be formed of carbon paper or carbon felt made of carbon fiber.

  In the MEA 10, the outer peripheral shape of the electrolyte membrane 12 is formed larger than that of the anode 14 and the cathode 16, and the peripheral portion of the electrolyte membrane 12 is disposed so as to be exposed from the anode 14 and the cathode 16. Further, the diffusion layer is formed in the same planar shape as the anode 14 and the cathode 16, and is arranged so that the outer periphery of the anode 14 and the cathode 16 and the outer periphery of the diffusion layer substantially coincide with each other.

  The water absorbing members 32 and 34 are respectively laminated on both surfaces of the electrolyte membrane 12. The inner frame of the water absorbing member 32 having a frame shape substantially coincides with the outer periphery of the anode 14. Similarly, the inner frame of the water absorbing member 34 substantially coincides with the outer periphery of the cathode 16. The water-absorbing members 32 and 34 are made of the same fluorine-based resin as the electrolyte membrane 12 and have a property of expanding when absorbing water and contracting when dried. Further, the water absorbing members 32 and 34 have a hardness equal to or higher than that of the electrolyte membrane 12 when dried. As shown in the drawing, the water absorbing members 32 and 34 are partially covered with a seal member 38.

  The cathode-side separator 60 is disposed so that the two sides at both ends of the protrusion forming the groove of the cathode gas flow channel 62 substantially coincide with the two opposite sides of the diffusion layer. When the cathode-side separator 60 is thus arranged, a gap is formed between the seal member 38 and the outer periphery of the cathode gas flow channel 62. As described above, this gap is provided to absorb the dimensional variation because the seal member 38 is made of silicone rubber and tends to cause dimensional variation.

  FIG. 3 is an enlarged view showing a portion X1 in FIG. The water absorbing members 32 and 34 are bonded to the electrolyte membrane 12 via the adhesive layers 36 and 37, respectively. The adhesive layers 36 and 37 are made of a fluorine-based resin, like the electrolyte membrane 12 and the water absorbing members 32 and 34. Adhesive layers 36 and 37 are sandwiched between water-absorbing members 32 and 34 and electrolyte membrane 12, respectively, and heated and pressurized so that water-absorbing members 32 and 34 are interposed via adhesive layers 36 and 37. Are bonded to the electrolyte membrane 12, respectively.

  In the present embodiment, the electrolyte membrane 12, the water absorbing member 32, the water absorbing member 34, the adhesive layer 36, and the adhesive layer 37 are formed of the same fluororesin. However, the EW (Equivalent Weight) value of the electrolyte membrane 12 is 1200 to 1300, the EW value of the water absorbing members 32 and 34 is 800 to 1000, and the EW value of the adhesive layers 36 and 37 is 1050 to 1150. The water absorption (expansion coefficient) is water absorption members 32 and 34> adhesive layers 36 and 37> electrolyte membrane 12.

  The seal member 38 is formed by adhering two plate-shaped plates (an anode side seal member 38a and a cathode side seal member 38c). The MEA 10 to which the water absorbing members 32 and 34 are bonded is sandwiched between the anode side sealing member 38a and the cathode side sealing member 38c, and the electrolyte membrane 12, the anode side sealing member 38a, and the cathode side sealing member 38c are bonded. It is manufactured by bonding with the agent 42. The water absorbing members 32 and 34 are fixed to the seal member 38 by being sandwiched between the anode side seal member 38a and the cathode side seal member 38c.

  Note that a gap is provided between the seal member 38 and the water absorbing member 32 inside the seal member 38. This gap is determined based on the expansion rate of the water absorbing member 32 in consideration of the fact that the water absorbing member 32 expands in the surface direction when the water absorbing member 32 absorbs water. A gap is similarly provided between the seal member 38 and the water absorbing member 34.

A2. Effects of the first embodiment:
Using the single cell 100 of the first example, the single cell 100A of the comparative example 1, and the single cell 100B of the comparative example 2, a dry / wet cycle test was performed, and the amount of cross leak after the dry / wet cycle test was examined. .

  FIG. 4 is a diagram showing a part of a cross-sectional configuration of the single cell of Comparative Example 1. FIG. 4 shows a portion corresponding to the X1 portion of the unit cell 100 of the first embodiment shown in FIG. FIG. 4A shows an initial state in the single cell 100A, and FIG. 4B shows a state in which wet gas is supplied in a wet / dry cycle described later.

  The single cell 100A of the comparative example 1 is different from the single cell 100 of the first example in that the water absorbing members 32 and 34 are not provided. As a result, the shape of the sealing member 38A is also the same as that of the first example. The shape is different from that of the single cell 100. Also in the single cell 100A of Comparative Example 1, a gap is provided between the seal member 38A and the cathode separator 60. Since the single cell 100A does not include the water absorbing members 32 and 34, the electrolyte membrane 12 is exposed in the gap.

  FIG. 5 is a diagram showing a part of a cross-sectional configuration of the single cell of Comparative Example 2. FIG. 5 shows a portion corresponding to the X1 portion of the single cell 100 of the first embodiment shown in FIG. FIG. 5A shows an initial state in the single cell 100B, and FIG. 5B shows a state in which wet gas is supplied in a wet / dry cycle described later.

  The single cell 100B of the comparative example 2 is different from the single cell 100 of the first embodiment in that the water absorbing members 32B and 34B are not bonded to the electrolyte membrane 12, and the water absorbing members 32B and 34B are fixed to 38B. As a result, the shape of the sealing member 38B is also different from that of the single cell 100 of the first embodiment. Also in the single cell 100B of Comparative Example 2, a gap is provided between the seal member 38B and the cathode-side separator 60. The water absorbing members 32B and 34B are provided in the gap.

  FIG. 6 is a diagram illustrating conditions of the wet and dry cycle test. In the present embodiment, the dry-humidity cycle is performed by supplying a dry gas having a relative humidity of 5% at 80 ° C. for 30 minutes and then supplying a wet gas having a relative humidity of 70% at 80 ° C. for 30 minutes. One cycle is repeated. The dry / wet cycle test is a test in which a gas having a humidity as shown in FIG. 6 is simultaneously supplied to the anode side and the cathode side of the single cell 100. The same gas (for example, nitrogen gas) is supplied to the cathode side and the anode side.

  The amount of cross leak is measured by a general differential pressure method. Specifically, it is measured according to the following procedure.

1. The gas supply port and the discharge port to the single cell 100 are sealed, and it is confirmed that there is no external leakage.
2. Nitrogen gas of 100 kPa is introduced from the gas supply port to the anode side and 50 kPa to the cathode side, and sealed.
3. After holding for 10 minutes in a sealed state, the anode pressure is read.
4). Calculate the pressure drop rate.
Pressure drop rate (%) = (initial anode pressure−anode pressure after 10 minutes) / initial anode pressure × 100

  The amount of cross leak is determined based on the pressure drop rate. That is, it is determined that the higher the pressure drop rate, the greater the cross leak amount. In the present embodiment, it is determined that a cross leak has occurred when the pressure drop rate is 3% or more.

  FIG. 7 is a diagram showing the relationship between the duration of the wet and dry cycle test and the pressure drop rate. In FIG. 7, the first example is shown by a solid line, the comparative example 1 is shown by a one-dot chain line, and the comparative example 2 is shown by a broken line.

  As shown in the figure, in the single cell 100 of the present example, the pressure drop rate is less than 3% even after the dry and wet cycle test is performed for 1000 hours. That is, it is not determined that a cross leak has occurred.

  In contrast, in the single cell 100A of Comparative Example 1, the pressure drop rate gradually increases after about 500 hours, and in the single cell 100B of Comparative Example 2, the pressure drop rate gradually increases after about 700 hours. In both Comparative Examples 1 and 2, the pressure drop rate exceeds 3% after 1000 hours. That is, it is determined that the cross leak occurred in both Comparative Examples 1 and 2. In both Comparative Examples 1 and 2, cracks were observed in the electrolyte membrane after 1000 hours.

  Since the electrolyte membrane 12 has water absorption, when the wet gas is supplied, the electrolyte membrane 12 absorbs water and expands. On the other hand, when dry gas is supplied, the electrolyte membrane 12 dries and shrinks. That is, the electrolyte membrane 12 repeats expansion and contraction during the dry / wet cycle test.

  Since the unit cell 100A of Comparative Example 1 has a portion in which the electrolyte membrane 12 is exposed, the portion expands in the film thickness direction (FIG. 4B). Therefore, it is considered that cracks are likely to occur from the exposed portions of the electrolyte membrane 12 and the cross leak is likely to occur due to repeated expansion and contraction of the electrolyte membrane 12.

  In the single cell 100B of Comparative Example 2, the water absorbing members 32B and 34B are laminated in the portion where the electrolyte membrane 12 is exposed in the single cell 100A of Comparative Example 1. When the water absorbing members 32B and 34B are laminated on the electrolyte membrane 12, the wet gas is supplied, and when the electrolyte membrane 12 becomes wet, the moisture in the electrolyte membrane 12 is changed to the water absorbing member 32B, Move to 34B. As a result, the water content of the electrolyte membrane 12 decreases. As described above, since the electrolyte membrane 12 expands by absorbing water, if the water content of the electrolyte membrane 12 is reduced, the expansion of the electrolyte membrane 12 can be suppressed. Compared to the cell 100A, the single cell 100B of Comparative Example 2 is considered to be able to suppress the deterioration of the electrolyte membrane 12.

  In the single cell 100B of Comparative Example 2, since the electrolyte membrane 12 and the water absorbing members 32B and 34B are not bonded, as shown in FIG. 5B, when the wet gas is supplied, the electrolyte membrane 12 In addition, the water absorbing members 32B and 34B also absorb water and expand. In the single cell 100B of Comparative Example 2, since the water absorbing member 34B is not fixed to the seal member 38B, the water absorbing member 34B is pushed up in the film thickness direction of the electrolyte membrane 12 when the electrolyte membrane 12 expands. It is done.

  On the other hand, in the single cell 100 of the present embodiment, the water absorbing members 32 and 34 are bonded to the electrolyte membrane 12, so that the electrolyte membrane 12 and the water absorbing member 32 are compared with the single cell 100B of Comparative Example 2. , 34 has good adhesion. Therefore, in the single cell 100 of the present embodiment, the movement of water from the electrolyte membrane 12 to the water absorbing members 32 and 34 is better than that of the single cell 100B of Comparative Example 2.

  Further, the water absorbing members 32 and 34 are fixed by being sandwiched between the seal members 38. Therefore, when the water absorbing members 32 and 34 absorb water and expand, the electrolyte membrane 12 is pressed down. As a result, it is considered that the expansion of the electrolyte membrane 12 can be further suppressed.

  Further, when the electrolyte membrane 12 is dried, water moves from the water-absorbing members 32 and 34 to the electrolyte membrane 12, so that drying of the electrolyte membrane 12 is suppressed. As a result, it is considered that the shrinkage of the electrolyte membrane 12 can be suppressed. Further, when the electrolyte membrane 12 is dried, the water absorbing members 32 and 34 are also dried. It is considered that when the water absorbing members 32 and 34 are dried and contracted, the electrolyte membrane 12 is pulled toward the water absorbing members 32 and 34 and the contraction of the electrolyte membrane 12 is suppressed. That is, according to the single cell 100 of the present embodiment, it is considered that the deterioration of the electrolyte membrane 12 due to the wet and dry of the electrolyte membrane 12 can be suppressed.

  The dry and wet cycle test described above can be considered as a simulation of the state of a single cell when the fuel cell is operated or stopped. Therefore, according to the single cell 100 (fuel cell) of the present embodiment, it is possible to suppress the deterioration of the electrolyte membrane 12 due to the operation / stop of the fuel cell.

B. Second embodiment:
FIG. 8 is a diagram showing a part of the cross-sectional configuration of the single cell of the second embodiment. FIG. 8 shows a portion corresponding to the X1 portion of the unit cell 100 of the first embodiment shown in FIG. The single cell 100C of the second embodiment differs from the single cell 100 of the first embodiment in the cross-sectional shape of the seal member 38C and the arrangement of the water absorbing members 32 and 34.

  FIG. 9 is a diagram showing the configuration of the seal member of this embodiment. 9A is a perspective view showing the sealing member 38C, and FIG. 9B is a cross-sectional view showing a BB cut surface in FIG. 9A. As shown in FIG. 9B, the seal member 38C is divided into four in the thickness direction of the seal member 38C, and the first seal member 381, the second seal member 382, They are referred to as 3 seal member 383 and 4th seal member 384.

  The surfaces of the first seal member 381 and the fourth seal member 384 that form the inner frame of the first seal member 381 and the fourth seal member 384 are surfaces in the thickness direction of the reaction gas flow paths of the anode side separator 50 and the cathode side separator 60 (see FIG. 9B). The surface parallel to the surface in the thickness direction of the reaction gas channel is indicated by a dotted line). In this embodiment, θ = 40 degrees.

The seal member integrated MEA 40C is manufactured by the following procedure.
1. The second seal member 382 and the third seal member 383 sandwich the electrolyte membrane 12 of the MEA 10, and the end portions of the second seal member 382, the third seal member 383, and the electrolyte membrane 12 are bonded with an adhesive 42.
2. The water-absorbing members 32 and 34 are arranged along the third seal member 383 and the second seal member 382, respectively, and the portions overlapping the electrolyte membrane 12 are bonded by the adhesive layers 36 and 37, respectively.
3. The first seal member 381 and the fourth seal member 384 are put on the water absorbing member 34 and the water absorbing member 32, respectively, and the first seal member 381 and the second seal member 382 are bonded with the adhesive 43 and the third seal. The member 383 and the fourth seal member 384 are bonded with the adhesive 44, respectively.

  When the anode-side gas diffusion layer 22 and the cathode-side gas diffusion layer 24 are arranged on both surfaces of the seal member-integrated MEA 40C, respectively, and the anode-side separator 50 and the cathode-side separator 60 are arranged on both sides thereof, the single cell 100C Is completed (FIG. 8). As described above, the surfaces of the first seal member 381 and the fourth seal member 384 that form the inner frame of the first seal member 381 and the fourth seal member 384 are in the thickness direction surfaces of the reaction gas flow paths of the anode side separator 50 and the cathode side separator 60. Since it is formed so as to be inclined by the angle θ, there is a gap formed between the surface forming the inner frame of the first seal member 381 and the fourth seal member 384 and the surface in the thickness direction of the reaction gas channel. The electrolyte membrane side is wider and narrows outward (FIG. 8).

  Using the single cell 100C of the second example, the single cell 100 of the first example, the single cell 100A of comparative example 1, the single cell 100B of comparative example 2, and the single cell of comparative example 3, A dry / wet cycle test was conducted, and the amount of cross leak after the dry / wet cycle test was examined. Since the single cell 100A of the comparative example 1 and the single cell 100B of the comparative example 2 are the same single cells as those used in the first embodiment, description of the configuration is omitted.

  FIG. 10 is a diagram illustrating a part of a cross-sectional configuration of the single cell of Comparative Example 3. The portion shown in FIG. 10 corresponds to the portion of the single cell 100C of the second embodiment shown in FIG. The single cell 100G of Comparative Example 3 has a configuration in which the adhesive layers 36 and 37 are not provided in the single cell 100C of the present example. That is, in the single cell 100G of Comparative Example 3, the water absorbing member 32 and the water absorbing member 34 are not bonded to the electrolyte membrane 12.

  FIG. 11 is a diagram showing the relationship between the duration of the wet and dry cycle test and the pressure drop rate. The wet / dry cycle test in this example is the same as the dry / wet cycle test described in the first example. In FIG. 7, the first and second examples are indicated by solid lines, the comparative example 1 is indicated by a one-dot chain line, the comparative example 2 is indicated by a broken line, and the comparative example 3 is indicated by a two-dot chain line. The relationship between the duration of the wet and dry cycle test and the pressure drop rate in the first example, comparative example 1 and comparative example 2 has been described in the first example, and therefore the description thereof is omitted.

  As shown in the figure, in the single cell 100C of the present example, the pressure drop rate is less than 3% even after the dry and wet cycle test is performed for 1000 hours. That is, it is not determined that a cross leak has occurred. Furthermore, the pressure drop rate is lower than that of the single cell 100 of the first embodiment.

  On the other hand, the pressure drop rate of the single cell 100G of Comparative Example 3 is less than 3% even after the wet and dry cycle test is performed for 1000 hours. That is, it is not determined that a cross leak has occurred. However, the pressure drop rate is higher than that of the single cell 100C of the second embodiment.

  In the unit cell 100C of the present embodiment, the water absorbing members 32 and 34 are bonded to the electrolyte membrane 12 through the adhesive layers 36 and 37, respectively, as in the unit cell 100 of the first embodiment. Therefore, similarly to the first embodiment, the movement of water from the electrolyte membrane 12 to the water absorbing members 32 and 34 becomes good, and the expansion / contraction of the electrolyte membrane can be suppressed.

  Further, when the single cell 100C of this example is compared with the single cell 100 of the first example, the entire surface of the water absorbing members 32 and 34 is bonded to the electrolyte membrane 12 in the single cell 100 of the first example. On the other hand, in the single cell 100C of this embodiment, a part of the water absorbing members 32 and 34 is bonded only to a part of the electrolyte membrane 12 which is exposed if the water absorbing members 32 and 34 are not provided. . If it does in this way, the water | moisture content of the part to which the water absorbing member 32 and the water absorbing member 34 are adhere | attached in the electrolyte membrane 12 can be moved to the water absorbing members 32 and 34 mainly. Therefore, it is considered that the expansion / contraction of the electrolyte membrane 12 can be suppressed as compared with the single cell 100 of the first embodiment.

  Further, as described above, the sealing member 38C provided in the single cell 100C of the present embodiment has a surface forming an inner frame thereof in a thickness direction surface of the reaction gas flow path of the anode side separator 50 and the cathode side separator 60. It is formed so as to be inclined with respect to the angle θ. Therefore, the gap formed by the surface forming the inner frame of the first seal member 381 and the fourth seal member 384 and the surface in the thickness direction of the reaction gas channel is wider on the electrolyte membrane 12 side, and the outer side Narrows towards.

  Therefore, even when the water absorbing members 32, 34 absorb water when the wet gas is supplied and the electrolyte membrane 12 is in a wet state, the water absorbing members 32, 34 have the anode side separator 50 and the cathode side separator 60. Expansion toward the side (outside) is suppressed. Therefore, when the water absorbing members 32 and 34 absorb water and expand, a force that holds the electrolyte membrane 12 works. As a result, it is considered that the expansion of the electrolyte membrane 12 is suppressed, and the deterioration of the electrolyte membrane 12 due to the wetting and drying of the electrolyte membrane 12 is suppressed as compared with the first embodiment.

  The single cell 100G of Comparative Example 3 includes a sealing member 38C similar to the single cell 100C of the second embodiment. Therefore, as described above, when the water absorbing members 32 and 34 absorb water and expand, a force for pressing the electrolyte membrane 12 works. As a result, the expansion of the electrolyte membrane 12 is suppressed, and it is considered that the deterioration of the electrolyte membrane 12 is suppressed as compared with Comparative Examples 1 and 2. In the single cell 100G of Comparative Example 3, since the water absorbing members 32 and 34 and the electrolyte membrane 12 are not bonded, the movement of moisture between the electrolyte membrane 12 and the water absorbing members 32 and 34 is the second. It is considered that the pressure drop rate is higher than that of the single cell 100C of the second embodiment and compared with the single cell 100C of the second embodiment.

  As described above, according to the single cell 100C (fuel cell) of the present embodiment, it is possible to suppress the deterioration of the electrolyte membrane 12 due to the operation / stop of the fuel cell.

C. Third embodiment:
FIG. 12 is a diagram showing a part of a cross-sectional configuration of a single cell according to the third embodiment. The portion shown in FIG. 12 corresponds to the portion of the single cell 100C of the second embodiment shown in FIG. The single cell 100D of the third embodiment is different from the single cell 100C of the second embodiment in the cross-sectional shape of the seal member 38D.

  In the single cell 100D, the first seal member 385 of the seal member 38D includes a protrusion 385a on the surface in contact with the water absorbing member 34. Similarly, the fourth seal member 386 of the seal member 38D includes a protrusion 386a on the surface in contact with the water absorbing member 32.

  Since the water absorbing members 34 and 32 are sandwiched by the protrusions 385a and 386a of the seal member 38D, even if the water absorbing members 32 and 34 try to expand due to water absorption, expansion toward the anode separators 50 and 60 is performed. Is suppressed, and a force for pressing the electrolyte membrane 12 works. Therefore, according to the single cell 100D (fuel cell) of the present embodiment, it is possible to suppress the deterioration of the electrolyte membrane 12 due to the operation / stop of the fuel cell.

D. Variation:
The present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

  (1) The cross-sectional shape of the seal member and the arrangement of the water absorbing members 32 and 34 are not limited to the above-described embodiments. For example, as shown in FIG. 13, the cross-sectional shape of the seal member may be formed. FIG. 13 is a diagram illustrating a modification of the cross-sectional shape of the seal member. FIG. 13 shows a portion corresponding to the X1 portion of the unit cell 100 of the first embodiment shown in FIG. FIG. 13A shows a single cell 100E of Modification 1 of the single cell 100 of the first embodiment. The sealing member 38E in the single cell 100E of the first modification includes a cathode side sealing member 38Ec and an anode side sealing member 38Ea, and the surface forming the inner frame thereof is the reaction gas flow between the anode side separator 50 and the cathode side separator 60. It is formed so as to be inclined with respect to the surface in the thickness direction of the path.

  FIG. 13B shows a single cell 100F of Modification 2 of the single cell 100 of the first embodiment. The sealing member 38F in the single cell 100F of Modification 2 includes a cathode-side sealing member 38Fc and an anode-side sealing member 38Fa, and the surface that forms the inner frame of the reaction gas flow of the anode-side separator 50 and the cathode-side separator 60 It is formed so as to be inclined with respect to the surface in the thickness direction of the path. Furthermore, a protrusion 38a1 is provided on the surface of the cathode side sealing member 38Fc that contacts the water absorbing member 34, and a protrusion 38c1 is provided on the surface of the anode side sealing member 38Fa that contacts the water absorbing member 32. Even if it does in this way, degradation of the electrolyte membrane 12 can be suppressed.

  (2) In the above-described embodiment, the water-absorbing members 32 and 34 and the adhesive layers 36 and 37 are exemplified as those having a water absorption (expansion coefficient) larger than that of the electrolyte membrane 12, but the present invention is not limited to this, and the electrolyte membrane A water-absorbing material similar to 12 may be used. Alternatively, a material having a smaller water absorption than the electrolyte membrane 12 may be used.

  (3) The angle θ of the surface forming the inner frame of the seal member with respect to the surface in the thickness direction of the reaction gas flow path of the anode side separator 50 and the cathode side separator 60 is not limited to the above-described embodiment. It can be arbitrarily set within a range of 90 degrees. However, if the angle θ is set too large, the gap formed between the seal member 38 and the reaction gas flow path becomes large. Therefore, the angle θ is preferably 5 to 40 degrees.

  (4) In the above-described embodiment, the water-absorbing member is exemplified by a fluorine-based resin that expands when water is absorbed and contracts when dried, but is not limited thereto. For example, a carbon-based resin may be used. Moreover, what is necessary is just a member which expands when it absorbs water.

  (5) In the above-described embodiment, the MEA 10 is configured not to include the anode side gas diffusion layer 22 and the cathode side gas diffusion layer 24. However, the MEA 10 includes the anode side gas diffusion layer 22 and the cathode side gas diffusion layer 24. You may make it the structure provided.

  (6) In the above-described embodiment, the MEA 10 having the structure in which the electrolyte membrane 12 is formed larger than the anode 14 and the cathode 16 and the electrolyte membrane 12 is exposed is illustrated. However, the electrolyte membrane 12, the anode 14, and the cathode 16 are You may make it the structure of the same magnitude | size.

  (7) In the above-described embodiment, the method of fixing the water absorbing members 32 and 34 to the seal member 38 by sandwiching the water absorbing members 32 and 34 with the seal member 38 is exemplified. The method of fixing the to the seal member 38 is not limited to the above-described embodiment. For example, the water-absorbing members 32 and 34 are formed in a shape that fits into the gap between the surface forming the inner frame of the seal member 38 and the surface in the thickness direction of the reaction gas flow path, and the adhesive layer Alternatively, the seal member 38 may be adhered to the surface forming the inner frame. Even if it does in this way, degradation of an electrolyte membrane can be controlled.

  (8) In the above-described embodiment, the groove flow path is exemplified as the reactive gas flow path, but the present invention is not limited to the groove flow path, and various flow paths can be applied. For example, a porous body (a metal porous body, a carbon porous body, etc.) having a plurality of pores communicating with each other may be used as the reaction gas flow path.

10 ... MEA
DESCRIPTION OF SYMBOLS 12 ... Electrolyte membrane 14 ... Anode 16 ... Cathode 22 ... Anode side gas diffusion layer 24 ... Cathode side gas diffusion layer 32, 32B, 34, 34B ... Water absorbing member 36, 37 ... Adhesive layer 38, 38A, 38B, 38C, 38D , 38E, 38F ... Sealing member 38a, 38Ea, 38Fa ... Anode side sealing member 38c, 38Ec, 38Fc ... Cathode side sealing member 38a1, 38c1 ... Projection 38F ... Cathode side sealing member 40, 40C ... Sealing member integrated MEA
42, 43, 44 ... Adhesive 50 ... Anode-side separator 60 ... Cathode-side separator 62 ... Cathode gas channel 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G ... Single cell 381 ... First seal member 382 ... Second seal member 383 ... Third seal member 384 ... Fourth seal member 385 ... First seal member 385a ... Projection 386 ... Fourth seal member 386a ... Projection

Claims (5)

A fuel cell,
An electrolyte membrane;
Electrode layers disposed on both surfaces of the electrolyte membrane;
A reactive gas flow path forming part for supplying a reactive gas to the electrode layer;
A frame-shaped member formed in a frame shape so as to cover the peripheral edge of the electrolyte membrane;
A water-absorbing member that is disposed between the inner frame of the frame-shaped member and the outer periphery of the reactive gas flow path forming portion and expands by absorbing water;
With
The water absorbing member is bonded to the electrolyte membrane and fixed to the frame member. The fuel cell according to claim 1,
The water absorbing member is
A fuel cell that expands when absorbed and contracts when dried. The fuel cell according to claim 1 or 2,
The surface forming the inner frame of the frame-shaped member is formed to be inclined with respect to the surface in the thickness direction of the reactive gas flow path forming portion, and the surface forming the inner frame of the frame-shaped member and the reaction A fuel cell in which a gap formed by a surface in a thickness direction of a gas flow path forming portion is wider on the electrolyte membrane side and narrows outward. A fuel cell according to any one of claims 1 to 3,
The frame-shaped member includes a protrusion,
The fuel cell, wherein the water absorbing member is fixed to the frame member by being sandwiched between the protrusions. A membrane electrode assembly used in a fuel cell,
An electrolyte membrane;
Electrode layers disposed on both surfaces of the electrolyte membrane;
A frame-shaped member formed in a frame shape so as to cover the peripheral edge of the electrolyte membrane;
A water-absorbing member that is bonded to the electrolyte membrane and is fixed to the frame-shaped member, and that expands by absorbing water;
With
The water absorbing member is
When the fuel cell is configured using the membrane electrode assembly, when a reaction gas flow path forming part for supplying a reaction gas to the electrode layer is disposed, an inner frame of the frame member, A membrane electrode assembly formed so as to be disposed between the outer periphery of the reaction gas flow path forming portion.

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