JP2017107755A - Seal member for fuel cell and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit a gas from being leaked outside when a composite material of a fiber sheet and a resin is used as a sealing member for a fuel cell.SOLUTION: The seal member for a fuel cell includes: a fiber sheet having a loop shape; and a resin impregnated in the fiber sheet. The fiber sheet intersects with a first direction extending from the inside to the outside of the loop, and has a plurality of slits for dividing fibers constituting the fiber sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell sealing member formed from a sheet material including a fiber sheet and a resin, and a fuel cell using the same.

  A fuel cell is a high-efficiency and clean power generation device that generates water by an electrochemical reaction between a fuel and an oxidant to generate water. For example, a polymer electrolyte fuel cell having a polymer electrolyte as an electrolyte membrane is excellent in impact resistance, and is expected to be used not only for a stationary type but also for in-vehicle use.

  The polymer electrolyte fuel cell includes a polymer electrolyte membrane that selectively transports hydrogen ions, an anode supplied with hydrogen as a fuel, and a cathode supplied with oxygen or air as an oxidant. The anode and the cathode include a catalyst layer in which an electrochemical reaction proceeds, and the catalyst layer is covered with a gas diffusion layer having both air permeability and conductivity. The joined body of the electrolyte membrane and the catalyst layer is also abbreviated as CCM (Catalyst Coated Membrane).

  In order to prevent leakage of gas supplied to the catalyst layer to the outside and mixing of the fuel and the oxidant, a seal member is disposed around the anode and the cathode with an electrolyte membrane interposed therebetween. A CCM having a peripheral edge sandwiched between sealing members or a joined body obtained by joining a gas diffusion layer to the CCM is also abbreviated as MEA (Membrane Electrode Assembly).

  The MEA is sandwiched between a pair of conductive separators that electrically connect adjacent MEAs in series. The separator also serves as a path for supplying gas to the anode and the cathode and carrying away generated water and surplus gas. The MEA is a minimum unit having a power generation function, and constitutes a unit cell by being sandwiched between a pair of separators. As the separator, a material having excellent corrosion resistance is suitable, for example, stainless steel is used. Patent Document 1 proposes to use a prepreg, which is a composite material of a fiber sheet and a resin, for the separator from the viewpoint of ensuring the mechanical strength of an in-vehicle fuel cell.

JP-A-2005-339954

  A prepreg is obtained by impregnating a fiber sheet with a resin, and forms a member having excellent productivity and impact resistance. However, it is difficult to completely impregnate the resin between the fibers constituting the fiber sheet, and fine voids are easily formed between the fibers. Therefore, when a member that requires gas sealing properties is formed by the prepreg, hydrogen and air may leak to the outside of the fuel cell through the gap.

  An object of the present invention is to suppress gas leakage to the outside of a fuel cell when a composite material of a fiber sheet and a resin is used as a fuel cell sealing member in general fuel cells.

  One aspect of the present invention includes a fiber sheet having a loop shape and a resin impregnated in the fiber sheet, wherein the fiber sheet intersects a first direction from the inside to the outside of the loop, and The present invention relates to a fuel cell sealing member having a plurality of slits for separating fibers constituting a fiber sheet.

  Another aspect of the present invention includes a unit cell and a pair of separators that sandwich the unit cell. The unit cell includes an anode, a cathode, and a center interposed between the anode and the cathode. An electrolyte membrane having a region and a peripheral portion surrounding the central region, an anode side gas diffusion layer for diffusing fuel supplied to the anode, and a cathode side gas diffusion for diffusing an oxidant supplied to the cathode And a pair of seal members that surround the anode side gas diffusion layer and the cathode side gas diffusion layer and sandwich the periphery of the electrolyte membrane, and at least one of the pair of seal members The present invention relates to a fuel cell which is the fuel cell sealing member.

  According to the fuel cell seal member of the present invention, gas leakage from the fuel cell to the outside can be suppressed.

It is a top view which shows the structure of the sealing member which concerns on one Embodiment of this invention. FIG. 2 is an enlarged view of a part of the seal member of FIG. 1. It is arrow sectional drawing in the AA line of the sealing member of FIG. It is a disassembled perspective view which shows the structure of the fuel cell which concerns on one Embodiment of this invention. It is a cross-sectional photograph which shows the fine space | gap formed in the inside of a sealing member.

  The fuel cell sealing member according to the present invention is a frame-like member, and includes a fiber sheet having a loop shape and a resin impregnated in the fiber sheet. The fiber sheet forms a large loop surrounding the anode and the anode side gas diffusion layer, or the cathode and the cathode side gas diffusion layer, and the seal member also forms a loop corresponding to the fiber sheet. The fiber sheet and the seal member may have two or more loops. For example, one or more small loops may be provided at positions corresponding to the manifold of the seal member.

  The fiber sheet has a plurality of slits that intersect the first direction from the inside to the outside of the loop and divide the fiber. There are fine voids between the fibers inside the seal member. Such voids are desirably as small as possible, but it is difficult to completely eliminate voids. The slit for dividing the fiber may penetrate the fiber sheet in the thickness direction.

  FIG. 5 is a cross-sectional photograph showing the inside of the seal member. It can be understood that there are fine voids (spotted areas that appear white) in the fiber bundle extending perpendicular to the paper surface. When such voids continue along the length of the fiber, a gas leak path is formed.

  The seal member has a plurality of slits that intersect with the first direction and divide the fiber in the thickness direction, so that gas leaks along the length direction of the fiber even when there are fine voids between the fibers. The path is divided by slits. The seal member is heated and pressed in the process of assembling the fuel cell. At that time, the resin impregnated in the fiber sheet is softened and enters at least a part of the plurality of slits. Thus, the slit is filled with the resin, and the gas leakage path is blocked by the resin wall filling the slit. Therefore, leakage of gas to the outside is suppressed.

  Here, the first direction from the inside to the outside of the loop is a direction perpendicular to the circumferential direction of the loop, and more specifically, a direction perpendicular to a tangent at an arbitrary point inside the loop. Say. Therefore, the direction (second direction) of the slit that intersects the first direction is typically a direction that is parallel or nearly parallel to the circumferential direction of the loop.

  The plurality of slits are preferably arranged intermittently along the entire circumference of the loop. By disposing the plurality of slits intermittently, the mechanical strength of the seal member can be maintained high. The length per slit is not particularly limited, but by setting it to 10 mm or more, the processing time is reduced and the gas leakage path can be more efficiently divided. Moreover, it becomes easy to maintain the mechanical strength of a sealing member by the length per slit being 20 mm or less. It is sufficient that the width of the slit is small enough that it cannot be visually confirmed. For example, the width is preferably 500 μm or less.

  At least some of the plurality of slits are preferably arranged in a staggered manner so that adjacent slits partially overlap each other in the first direction. According to such an arrangement, even if it is assumed that a gas leakage path in the first direction is formed at any location of the loop, the leakage path is always blocked by the resin wall that fills the slit or the slit. Will be. When a plurality of slits are arranged in a staggered manner, the length of the portion where each slit overlaps with another slit is not particularly limited, but is preferably 10% or more and 30% or less of the entire length of the slit.

  FIG. 1 shows an example of a sealing member having a plurality of slits arranged in a staggered manner. Arrows B1 to B12 all indicate the first direction. The seal member 10A is a frame-like member having a large first loop 11 that encloses the anode and the anode-side gas diffusion layer or the cathode and the cathode-side gas diffusion layer.

  The seal member 10 </ b> A has first manifolds 12 </ b> A and 12 </ b> B for circulating either one of fuel and oxidant inside the first loop 11, and further has another four loops. Of the four loops, two are the second manifolds 13A and 13B, and the other of the fuel and the oxidant flows therethrough. The remaining two are third manifolds 14A and 14B, through which cooling water flows.

  In FIG. 1, many of the plurality of slits 17 arranged in a staggered manner have both ends overlapping with adjacent slits 17 when facing the first direction. A part of FIG. 1 is enlarged and shown in FIG. The length DL in which each slit 17 overlaps with another slit 17 is preferably about 10 to 30% of the total length L of the slit. The distance D1 in the first direction between the adjacent slits 17 is preferably as small as possible from the viewpoint of suppressing gas leakage, and is, for example, 50 μm to 1000 μm.

FIG. 3 conceptually shows a cross-sectional view taken along line AA of the seal member of FIG.
The sealing member 10 </ b> A includes a fiber sheet 15 serving as a core material and a resin 16 impregnated in the fiber sheet 15, but in the illustrated example, both surfaces of the fiber sheet 15 are covered with the resin 16 for convenience. Indicates the state. The fiber sheet 15 is provided with a slit 17 in the second direction perpendicular to the arrow B1 indicating the first direction. When the sealing member 10 </ b> A having such a slit 17 is pressed in the thickness direction, the resin 16 enters the slit 17 and the slit 17 is filled with the resin 16. As a result, the wall 18 of the resin 16 is formed.

  The slit 17 is preferably formed so as to form an angle of 80 ° to 110 ° with the first direction. That is, the angle formed by the first direction and the second direction is desirably 80 ° to 110 °. The angle formed between the slit and the first direction may be obtained by measuring the angle formed with the first direction with respect to 10 slits arbitrarily selected from the plurality of slits and calculating an average value thereof. The closer the angle formed by the slit and the first direction is to 90 °, the greater the effect of dividing the gas leakage path.

  The thickness of the sealing member may be appropriately selected according to the design of the fuel cell, and is preferably 60 μm to 300 μm, for example. If the thickness of the sealing member is 60 μm or more, it is easy to ensure the mechanical strength and the handling of the sealing member becomes easy. Moreover, if the thickness of the seal member is 300 μm or less, it becomes easy to obtain a compact fuel cell excellent in space efficiency.

  The fiber sheet may be a woven fabric or a non-woven fabric. Moreover, the material of the fiber which comprises a fiber sheet is not specifically limited. For example, glass fiber, carbon fiber, resin fiber, etc. are mentioned. As the resin constituting the resin fiber, polyamide, polyimide, and the like are preferable from the viewpoint of excellent heat resistance and mechanical strength. The proportion of the fiber sheet in the sealing member is preferably 40 to 80% by mass, and more preferably 45 to 60% by mass.

  The resin impregnated in the fiber sheet may be a thermoplastic resin or a thermosetting resin, but it is desirable to use a thermosetting resin from the viewpoint of obtaining a fuel cell with better heat resistance. The thermosetting resin may be a thermosetting resin composition containing a curing agent, a curing accelerator, a filler, and the like.

  Examples of the thermosetting resin include an epoxy resin, a phenol resin, a melamine resin, an unsaturated polyester resin, and a diallyl phthalate resin. Among these, an epoxy resin is preferable in that the content of ionic impurities is small and the handleability is excellent. Specific examples of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type and bisphenol F type, novolak type epoxy resins such as phenol novolak type and cresol novolak type, and cyclic aliphatic epoxy resins. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The sealing member according to the present invention is manufactured by impregnating a fiber sheet with a resin, preferably a thermosetting resin composition, to form a prepreg sheet, and then punching a frame-shaped member from the prepreg sheet. Can do. The plurality of slits may be formed in the punched frame member using a cutting device such as a cutter. Alternatively, a plurality of slits may be formed in advance on the fiber sheet before impregnating the resin, and then the fiber sheet having the slits may be impregnated with the resin. However, the manufacturing method of a sealing member is not specifically limited. The prepreg refers to a sheet material in which a fiber sheet is impregnated with an uncured or semi-cured thermosetting resin.

  When the fiber sheet is impregnated with the thermosetting resin, the timing for curing the thermosetting resin is not particularly limited, but the thermosetting resin is attached to the peripheral portion of the electrolyte membrane in a state containing at least an uncured component, and thereafter In the process of assembling the MEA or fuel cell, it is desirable to cure the uncured component by applying pressure while heating the seal member. As a result, the adhesion between the members of the fuel cell is enhanced, and the mechanical strength of the fuel cell is enhanced.

Next, the fuel cell will be described.
FIG. 4 is an exploded perspective view showing the structure of the fuel cell according to the embodiment of the present invention.
The fuel cell 100 includes a unit cell 200 and a pair of separators 300A and 300B that sandwich the unit cell 200. The unit cell 200 includes a CCM 30 disposed in the center, and a first gas diffusion layer 40A and a second gas diffusion layer 40B disposed on both sides of the CCM 30 so as to cover the anode or the cathode, respectively. One of the first gas diffusion layer 40A and the second gas diffusion layer 40B is an anode side gas diffusion layer, and the other is a cathode side gas diffusion layer. The CCM 30 includes an electrolyte membrane 31 having a central region 31X and a peripheral edge 31Y surrounding the central region 31X, a first catalyst layer (not shown) bonded to the lower surface of the central region 31X, and the central region 31X. And a second catalyst layer 32B bonded to the upper surface of the first catalyst layer 32B. One of the first catalyst layer and the second catalyst layer 32B functions as an anode, and the other functions as a cathode.

  In the illustrated example, each of the pair of seal members is composed of two layers of parts. That is, the seal member 60A (60B) includes the outer seal member 10A (10B) and the inner seal member 20A (20B). As described above, when the sealing member is composed of two or more layers, it is not necessary to form all the parts with a material including the fiber sheet and the resin impregnated in the fiber sheet. Moreover, it is not necessary to provide a plurality of slits intersecting the first direction in all parts. However, it is preferable for the convenience of manufacturing that all parts are formed of a material including a fiber sheet and a resin impregnated in the fiber sheet, and it is preferable to provide a plurality of slits crossing the first direction in all parts. This is preferable in that the effect of suppressing the leakage is increased.

  In the seal member 60A, the outer seal member 10A is in contact with or joined to the separator 300A. The inner seal member 20A is disposed so as to face the separator 300A via bridge plates 50A and 50B serving as spacers, and is in contact with or joined to the peripheral edge portion 31Y of the electrolyte membrane 31. Similarly, in the other seal member 60B, the outer seal member 10B is in contact with or joined to the separator 300B, and the inner seal member 20B is disposed so as to face the separator 300B via the bridge plates 50C and 50D. The peripheral edge 31Y of the film 31 is contacted or joined.

  The inner seal members 20A and 20B desirably cover as many surfaces as possible of the peripheral edge portion 31Y of the electrolyte membrane in order to prevent the fuel or the oxidant from cross leaking the electrolyte membrane 31. On the other hand, the outer seal members 10 </ b> A and 10 </ b> B each have a space inside the first loop 11 for accommodating a pair of bridge plates 50 </ b> A and 50 </ b> B or 50 </ b> C and 50 </ b> D.

  The bridge plates are arranged in pairs so that the anode or the cathode is sandwiched from a pair of end portions where the manifold is arranged. Concavities and convexities are formed on the surface of each bridge plate so that gas supplied from a predetermined manifold can reach the gas diffusion layer through a gap formed by the bridge plate and the separator.

  The anode and cathode include fine particles of a catalytic metal and a polymer electrolyte. As the catalyst metal of the anode, a Pt—Ru alloy or the like can be used. As the catalytic metal of the cathode, Pt, Pt—Co alloy or the like can be used. The catalytic metal may be supported on conductive powder. For example, carbon black can be used as the conductive powder.

  A conductive porous substrate can be used for the anode side gas diffusion layer and the cathode side gas diffusion layer. The conductive porous substrate is preferably formed from a carbonaceous material such as carbon black, graphite, or carbon fiber. The gas diffusion layer may be provided with grooves or ribs to form a gas flow path. The shape of the channel is not particularly limited, and may be formed in a parallel type, a serpentine type, or the like.

  The electrolyte membrane may be a polymer electrolyte sheet having hydrogen ion conductivity, but it is desirable that the polymer electrolyte is excellent in heat resistance and chemical stability. Examples of the polymer electrolyte include perfluorocarbon sulfonic acid polymers. Examples of the perfluorocarbon sulfonic acid polymer include Nafion (registered trademark). The above materials can also be used for the polymer electrolyte contained in the anode and the cathode.

  The separator is not particularly limited as long as it has air tightness, electronic conductivity, and electrochemical stability. A gas flow path may be formed on the inner surface of the separator (the surface facing the gas diffusion layer).

  Although the embodiment has been described using a slit that penetrates the fiber sheet in the thickness direction, this is an example, and the slit does not necessarily have to penetrate the fiber sheet. The slit may be formed from one main surface of the fiber sheet, and may be interrupted in the middle of the thickness direction of the fiber sheet without reaching the other main surface.

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples.
Example 1
<Production of sealing member>
As the fiber sheet, a woven fabric of a glass fiber sheet having a thickness of 100 μm was used. Here, a woven fabric of glass fibers having an average fiber diameter of 7 μm was used. A glass fiber sheet was impregnated with a thermosetting resin composition having the following composition to prepare a prepreg having a thickness of 200 μm. The ratio of the glass fiber sheet in the prepreg was 50% by mass. As the thermosetting resin composition, a thermosetting resin composition mainly composed of an epoxy resin was used.

  The obtained prepreg is punched into a predetermined shape, and as shown in FIG. 4, outer seal members 10A and 10B and inner seal members 20A and 20B are produced, and these are used to provide one unit cell. A fuel cell having the structure shown in FIG. 4 was assembled. As the electrolyte membrane, a 15 μm thick Nafion membrane (manufactured by Gore) was used.

  A plurality of staggered slits as shown in FIGS. 1 and 2 were formed in the outer seal members 10A and 10B using a cutter. The length L of each slit was 10 mm, and the length DL in which each slit overlaps with other slits was 10% of the total length of the slit. The distance D1 in the first direction between adjacent slits was 500 μm. Visually, the width of the slit was almost zero. The angle formed by the first direction and the slit (second direction) was 90 °.

<Cathode>
The catalyst layer of the cathode was formed of carbon black carrying Pt fine particles and Nafion (manufactured by Gore) which is a polymer electrolyte.

<Anode>
The anode catalyst layer was also formed of carbon black carrying Pt fine particles and Nafion (manufactured by Gore).

<Gas diffusion layer>
For the cathode side gas diffusion layer and the anode side gas diffusion layer, a conductive composite material containing conductive particles and a binder resin was used. A parallel type gas flow path through which hydrogen gas or air flows was formed on the surface of the gas diffusion layer facing the separator.

<Fabrication of fuel cell>
An inner seal member is placed to surround the anode and cathode, an anode side gas diffusion layer is placed to cover the anode, a cathode side gas diffusion layer is placed to cover the cathode, and a bridge plate is placed near the manifold of the electrolyte membrane Further, an outer seal member was arranged so as to surround the anode side gas diffusion layer, the cathode side gas diffusion layer, and the bridge plate to constitute a unit cell, and the unit cell was sandwiched between a pair of stainless steel separators. Then, from the outside of the separator, the unit cell was heated at 160 ° C. and pressurized at a pressure of 1 MPa for 60 minutes to produce a fuel cell A. The heating conditions are sufficient to cure the thermosetting resin contained in the seal member.

<Evaluation>
A pressurized gas was passed through each gas flow path of the obtained fuel cell A, and the gas flow rate leaking from the fuel cell A was measured. Here, nitrogen gas was circulated through the gas flow path at a gas pressure of 150 kPa. The gas pressure stabilized soon after the start of gas introduction, and no gas leak occurred even after 1 hour.

<< Comparative Example 1 >>
A fuel cell B was prepared in the same manner as in Example 1 except that a plurality of zigzag slits were not formed in the outer seal members 10A and 10B, and was similarly evaluated. It was confirmed that the gas pressure was not stable even after 1 hour from the start of gas introduction, and gas leakage occurred.

  The fuel cell according to the present invention can be suitably used as a stationary power source for a home cogeneration system or a vehicle power source. The present invention is suitable for application to polymer electrolyte fuel cells, but is not limited to this, and can be applied to fuel cells in general.

B1 to B12: first direction, 10A: seal member (outer seal member), 10B: outer seal member, 11: first loop, 12A, 12B: first manifold, 13A, 13B: second manifold, 14A, 14B: Third manifold, 15: fiber sheet, 16: resin, 17: slit, 18: resin wall, 20A, 20B: inner seal member, 30: CCM, 31: electrolyte membrane, 31X: central region, 31Y: peripheral edge, 32B: second catalyst layer, 40A: first gas diffusion layer, 40B: second gas diffusion layer, 50A, 50B, 50C, 50D: bridge plate, 60A, 60B: seal member, 100: fuel cell, 200: unit cell , 300A, 300B: Separator

Claims (7)

A fiber sheet having a loop shape, and a resin impregnated in the fiber sheet,
The fuel cell sealing member, wherein the fiber sheet has a plurality of slits that intersect a first direction from the inner side to the outer side of the loop and divide the fibers constituting the fiber sheet.   The fuel cell sealing member according to claim 1, wherein the plurality of slits penetrate the fiber sheet in a thickness direction.   The fuel cell sealing member according to claim 1, wherein at least a part of the plurality of slits is filled with the resin.   The fuel cell seal member according to any one of claims 1 to 3, wherein the plurality of slits are intermittently disposed along the entire circumference of the loop.   The at least part of the plurality of slits is arranged in a staggered manner such that adjacent slits partially overlap each other facing the first direction. Fuel cell sealing member.   6. The fuel cell seal member according to claim 1, wherein at least a part of the plurality of slits is formed so as to form an angle of 80 ° to 110 ° with the first direction. Comprising a unit cell and a pair of separators sandwiching the unit cell;
The unit cell is
An anode,
A cathode,
An electrolyte membrane having a central region interposed between the anode and the cathode, and a peripheral edge surrounding the central region;
An anode side gas diffusion layer for diffusing fuel supplied to the anode;
A cathode side gas diffusion layer for diffusing an oxidant supplied to the cathode;
A pair of sealing members that surround the anode gas diffusion layer and the cathode gas diffusion layer and sandwich the peripheral edge of the electrolyte membrane,
The fuel cell, wherein at least one of the pair of seal members is the seal member according to claim 1.