JP2012238556A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell capable of preventing breakage of an electrolyte membrane in a vicinity of a border with an electrode caused by a force in an in-plane direction acting to a membrane electrode structure.SOLUTION: The fuel cell includes a membrane electrode structure 1, separators 2A, 2C on an anode side and a cathod side, respectively that hold the membrane electrode structure 1, and a gas seal member 3 that closes a space between a peripheral part of the membrane electrode structure 1 and each of the separators 2A, 2C. At least a part of the gas seal member 3 containing a portion contacted with the separators 2A, 2C is configured by elastic sealing members EA, EC that deform following to displacement of the membrane electrode structure 1 in the in-plane direction, so as to eliminate force in the in-plane direction acting to the membrane electrode structure 1 and to prevent the breakage of the electrolyte membrane of the membrane electrode structure.

Description

  The present invention relates to a fuel cell having a structure in which a membrane electrode structure is sandwiched between a pair of separators.

  As a conventional fuel cell, there is one described in Patent Document 1, for example. The fuel cell described in Patent Document 1 includes a membrane electrode structure having a structure in which an electrolyte membrane is sandwiched between electrode catalyst layers on the anode side and the cathode side, and two metal separators sandwiching the membrane electrode structure. Yes. The anode-side electrode catalyst layer is the fuel electrode layer, and the cathode-side electrode catalyst layer is the air electrode layer.

  In the conventional fuel cell, both separators are provided with the first outer peripheral convex portion and the second outer peripheral convex portion facing each other, and the outer peripheral end portion of the electrode catalyst layer is formed by the first and second outer peripheral convex portions. It has a sandwiched configuration. As a result, the fuel cell prevents the electrolyte membrane from being damaged by preventing stress concentration of the electrolyte membrane generated at the outer peripheral end of the electrode catalyst layer due to swelling of the electrolyte membrane during power generation.

JP 2005-235554 A

  However, in the fuel cell as described above, the membrane electrode structure is swollen by the reaction product water generated during power generation, and contracts as it is dried. Therefore, such swelling and contraction are repeated. That is, the in-plane direction (direction parallel to the surface) generated during swelling and the in-plane tensile force generated during contraction are repeatedly applied to the membrane electrode structure.

  For this reason, in the conventional fuel cell, even if the outer peripheral end portion of the electrode catalyst layer is sandwiched by the outer peripheral convex portion of the separator, the force in the in-plane direction acting on the membrane electrode structure causes the contact with the electrode in the electrolyte membrane. There is a problem that stress tends to concentrate near the boundary and damage may occur at the boundary, and it has been a problem to solve such a problem.

  The present invention has been made paying attention to the above-mentioned conventional problems, and by damaging the electrolyte membrane of the membrane electrode structure by releasing the in-plane force acting on the membrane electrode structure. It aims at providing the fuel cell which can prevent reliably.

  The fuel cell of the present invention includes a membrane electrode structure, anode-side and cathode-side separators that sandwich the membrane electrode structure, and a gas seal member that closes between the peripheral edge of the membrane electrode structure and each separator. ing. The membrane electrode structure has a structure in which an electrolyte membrane is sandwiched between a fuel electrode layer (anode) and an air electrode layer (cathode).

  The fuel cell includes the gas seal member joined to the peripheral portion of the membrane electrode structure and each separator, and at least a part of the gas seal member including a portion in contact with the separator is a membrane electrode structure. It is comprised by the seal | sticker elastic part which deform | transforms following the displacement of an in-plane direction, and it is a means for solving the conventional subject with the said structure. In the above configuration, the in-plane direction of the membrane electrode structure is a direction parallel to the surface of the structure.

  According to the fuel cell of the present invention, even if the membrane electrode structure swells and contracts in the in-plane direction, the seal elastic portion deforms following the displacement, so that the in-plane direction acting on the membrane electrode structure The force is eliminated, and damage to the electrolyte membrane of the membrane electrode structure can be surely prevented.

It is sectional drawing (A) of the principal part explaining one Embodiment of the fuel cell of this invention, and sectional drawing (B) which shows the state which the membrane electrode structure contracted. It is a top view of the membrane electrode structure of the fuel cell shown in FIG. It is sectional drawing explaining the determination point of the various dimensions of a seal elastic part. It is sectional drawing (A) of the principal part explaining other embodiment of the fuel cell of this invention, and sectional drawing (B) which shows the state which the membrane electrode structure contracted. It is sectional drawing (A) of the principal part explaining further another embodiment of the fuel cell of this invention, and sectional drawing (B) which shows the state which the membrane electrode structure contracted. It is sectional drawing of the principal part explaining further another embodiment of the fuel cell of this invention. It is sectional drawing of the principal part explaining further another embodiment of the fuel cell of this invention. It is sectional drawing (A) of the principal part explaining further another embodiment of the fuel cell of this invention, and sectional drawing (B) which shows the state which the membrane electrode structure contracted. It is sectional drawing of the principal part explaining further another embodiment of the fuel cell of this invention.

1 to 3 are diagrams illustrating an embodiment of a fuel cell according to the present invention.
A fuel cell (single cell) C shown in FIG. 1A includes a membrane electrode structure 1, anode-side and cathode-side separators 2 A and 2 C that sandwich the membrane electrode structure 1, and the periphery of the membrane electrode structure 1. And a gas seal member 3 that closes between the separators 2A and 2C.

  The membrane electrode structure 1 is generally called MEA (Membrane Electrode Assembly). For example, an electrolyte layer 4 made of a solid polymer is composed of a fuel electrode layer (anode) 5A and an air electrode layer (cathode) 5C. It has a sandwiched structure. The membrane electrode structure 1 in the illustrated example has anode-side and cathode-side gas diffusion layers 6A, 6C on the surfaces of the fuel electrode layer 5A and the air electrode layer 5C, respectively. These gas diffusion layers 6A and 6C are made of carbon paper or a porous material. The gas diffusion layers 6A and 6C may be referred to as a fuel electrode layer and an air electrode layer.

  Further, as shown in FIG. 2, the membrane electrode structure 1 of the illustrated example is integrally provided with a resin frame F around it, and has a rectangular flat plate shape as a whole. The frame F has a manifold hole H1 for supplying a cathode gas, a manifold hole H2 for supplying a coolant, and a manifold hole H3 for discharging an anode gas on one side (upper side in FIG. 2) of opposing short sides. Have. On the other side of the opposing short sides, a manifold hole H4 for supplying an anode gas, a manifold hole H5 for discharging a coolant, and a manifold hole H6 for discharging a cathode gas are provided. In addition, you may provide the rectification | straightening parts D and D between the membrane electrode structure 1 and each manifold hole group.

  Each of the separators 2A and 2C is obtained by press-molding a metal plate such as stainless steel. Each of the separators 2A and 2C has a rectangular flat plate shape corresponding to the overall shape of the membrane electrode structure 1 and the frame F, and a portion corresponding to the membrane electrode structure 1 has a wave in a cross section in the short side direction shown in FIG. It has a shape. This wave shape is continuous in the long side direction, and each convex portion protruding toward the membrane electrode structure 1 is in contact with the structure body 1, and each concave portion is made of anode gas (hydrogen) and cathode gas ( Air) gas flow paths 7A and 7C.

  The fuel cell C gas seals between the peripheral edge of the membrane electrode structure 1 and the frame F and the peripheral edge of each separator 2A, 2C, or the peripheral edge of the selected manifold holes H1 to H6. At this time, the gas seal member 3 described above is provided on the long side portion of the membrane electrode structure 1.

  The gas seal member 3 closes the gap between the peripheral portion of the membrane electrode structure 1 and the separators 2A and 2C as described above. More precisely, the gas seal member 3 includes at least the electrode end face of the membrane electrode structure 1. The gap between the peripheral edge and each separator 2A, 2C is closed. In other words, since the fuel electrode layer 5A and the air electrode layer 5C have gas permeability, at least the end faces (electrode end faces) of these layers need to be closed in order to prevent gas leakage to the outside of the battery. .

  The gas seal member 3 of this embodiment is disposed outside the fuel electrode layer 5A and the air electrode layer 5C, and is disposed on both surfaces of the electrolyte membrane 4 protruding outward from the electrode layers. That is, in this embodiment, the gas seal members 3 and 3 are provided on both the anode side and the cathode side.

  At least a part of the gas seal members 3 and 3 on the anode side and the cathode side, including a portion in contact with the separators 2A and 2C, follows the displacement in the in-plane direction (direction parallel to the surface) of the membrane electrode structure 1. The seal elastic portions EA and EC are deformed. In this embodiment, the gas seal member 3 includes a seal base MA, MC joined to the peripheral portion (peripheral portion including the electrode end surface) of the membrane electrode structure 1, and a seal base MA, MC and each separator 2A, 2C. Each has sealing elastic portions EA and EC interposed therebetween. Each of the seal bases MA and MC is in contact with the electrode end face and the electrolyte membrane 4. The seal bases MA and MC and the seal elastic portions EA and EC are hermetically bonded to each other with an adhesive, and also to each component member such as the electrode end surface, the electrolyte membrane 4, and the separators 2A and 2C. It is hermetically bonded with an adhesive.

  Each of the seal elastic portions EA, EC is formed of a material that can be deformed following the displacement in the in-plane direction of the membrane electrode structure 1 between the respective seal bases MA, MC and the separators 2A, 2C. . As materials for the seal elastic portions EA and EC, those generally used as elastic adhesives are desirable, and synthetic rubber resins, silicon resins, urethane resins, olefin resins, acrylic resins, and epoxy resins. Any of these may be used as a component.

  The fuel cell C having the above configuration forms a fuel cell stack by stacking a plurality of sheets, and is used as a power source for a vehicle such as an electric vehicle. In each fuel cell C, the anode gas is supplied to the fuel electrode layer 5A through the gas flow paths 7A and 7C, and the cathode gas is supplied to the air electrode layer 5C. Is generated.

  At this time, in the fuel cell C, reaction product water is generated with power generation, and the membrane electrode structure 1 swells. Further, when the reaction product water is removed and dried, the membrane electrode structure 1 contracts. That is, by the operation and stop of the fuel cell C, the in-plane compressive force accompanying swelling and the in-plane tensile force accompanying drying shrinkage alternately act on the membrane electrode structure 1.

  On the other hand, in the fuel cell C, even if the membrane electrode structure 1 swells and contracts in the in-plane direction, the seal elastic portions EA, EC constituting the gas seal member 3 are deformed following the displacement, The structure is such that a force acting in the in-plane direction of the membrane electrode structure 1 is released.

  That is, when the membrane electrode structure 1 is dried and contracts in the in-plane direction from the state shown in FIG. 1A, the seal elastic portions EA and EC are in contact with the membrane as shown in FIG. Following the contraction of the electrode structure 1 in the in-plane direction, the electrode structure 1 is deformed to the inside of the battery. Further, from the state shown in FIG. 1A, when the membrane electrode structure 1 swells in the in-plane direction, the seal elastic portions EA and EC follow the swelling in the in-plane direction of the membrane electrode structure 1. Deforms outside the battery. That is, the seal elastic portions EA and EC are deformed in the in-plane direction so that the deformation of the membrane electrode structure 1 is not constrained.

  In this way, the fuel cell C eliminates the in-plane compressive force and tensile force acting on the membrane electrode structure 1, and breaks the electrolyte membrane 4 of the membrane electrode structure 1, particularly the electrode in the electrolyte membrane 4. Can be reliably prevented from being damaged. As a result, stable power generation performance can be obtained over a long period of time, which can contribute to the realization of a highly reliable fuel cell stack and the improvement of the performance of a vehicle using the fuel cell stack as a power source.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, and is a diagram for explaining how to determine various dimensions of the seal elastic portion.

  If the shear stress applied to the seal elastic portions EA and EC is smaller than the elastic limit of the seal elastic portion or the tensile shear strength at the contact portion, the seal elastic portions EA and EC will not be damaged or peeled off. The shear stress τ applied to the seal elastic portions EA and EC is determined by the shear displacement a caused by the in-plane displacement of the membrane electrode structure 1 and the thickness h of the seal elastic portions EA and EC. The greater the thickness h of the seal elastic portions EA, EC, the smaller the shear stress τ.

  On the other hand, when the thickness h of the seal elastic portions EA and EC is increased, the pitch (thickness) Z of the fuel cell C is increased, which is disadvantageous for miniaturization of the fuel cell stack. Therefore, it is desirable that the seal elastic portions EA and EC have the thickness h equal to or less than the depth of the gas flow path, and are further disposed in the concave portions at the end portions of the separators 2A and 2C as shown in the illustrated example.

The shear displacement a, the shear stress τ, and the shear force F due to swelling and contraction of the membrane electrode structure 1 are obtained by the following equations. x is the width of the membrane electrode structure 1, α is the swelling rate of the membrane electrode structure 1, G is the shear elastic modulus of the seal elastic part, w is the length of the contact part of the seal elastic parts EA and EC with respect to the seal bases MA and MC. That's it.
a = (x / 2) × α
τ = G × a / h
F = τ × w

If the elastic limit σe of the seal elastic portions EA and EC is larger than the shear stress τ, that is, if the following expression is satisfied, the seal elastic portions EA and EC are not destroyed.
σe> τ = G × α × xx × (0.5 / h)
The fatigue limit may be considered instead of the elastic limit σe.

Specifically, for example, when σe = 1.4 MPa, G = 0.3 MPa, and α = 0.01, the result is as follows.
1.4 [Nmm ⁻² ]> 0.3 [Nmm ⁻² ] × 0.01 × xx (0.5 / h)
→ x / h <933
Approximately, the thickness h of the seal elastic portions EA and EC needs to be 1/1000 or more of the width of the membrane electrode structure 1 x. In addition, said value changes with the swelling rate determined by the structure and physical-property value of the membrane electrode structure 1, the physical-property value of seal elastic part EA, EC, etc.

  4-9 is a figure explaining other embodiment of the fuel cell of this invention. In each embodiment shown in FIGS. 4-9, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted.

  In the fuel cell C shown in FIG. 4A, the end portions of the electrolyte membrane 1, the fuel electrode layer 5A, and the air electrode layer 5C are aligned with respect to the previous embodiment in which the end portions of the electrolyte membrane 4 protrude from the electrode layers. ing. For this reason, the gas seal member 3 includes a single seal base M joined to the peripheral edge (end surface) of the membrane electrode structure 1, and the anode side interposed between the seal base M and the separators 2A and 2C. And cathode-side seal elastic portions EA and EC. Each of the seal elastic portions EA and EC can be deformed following the displacement in the in-plane direction of the membrane electrode structure 1.

  Even in the fuel cell C described above, as in the previous embodiment, when the membrane electrode structure 1 is dried and contracted in the in-plane direction from the state shown in FIG. As shown in B), the seal elastic portions EA, EC are deformed inward of the battery following the contraction of the membrane electrode structure 1. When the membrane electrode structure 1 swells in the in-plane direction, the seal elastic portions EA and EC are deformed to the outside of the battery following the swelling of the membrane electrode structure 1.

  In this way, the fuel cell C eliminates the in-plane compressive force and tensile force acting on the membrane electrode structure 1, and breaks the electrolyte membrane 4 of the membrane electrode structure 1, particularly the electrode in the electrolyte membrane 4. Can be reliably prevented from being damaged. Moreover, in this embodiment, since the end surface of the membrane electrode structure 1 is covered with the single seal base M, the gas seal performance can be further enhanced.

  The fuel cell C shown in FIG. 5 (A) has the same basic configuration as that of the embodiment shown in FIG. 1, and the anode-side and cathode-side sealing elastic portions EA, EC include the membrane electrode structure 1 and each separator 2A. , 2C is provided with an extending portion e.

  As in the previous embodiment, the fuel cell C eliminates the in-plane compressive force and tensile force acting on the membrane electrode structure 1 and reliably prevents the vicinity of the electrode in the electrolyte membrane 4 from being damaged. be able to.

  Further, in the fuel cell C, even when a differential pressure (for example, the anode side is large) occurs in the gas flow paths 7A and 7C and a load in the thickness direction is applied to the membrane electrode structure 1, as shown in FIG. Furthermore, the bending moment generated at the contact portion between the end portion of the gas seal member 3 and the electrolyte membrane 4 can be relaxed, and the electrolyte membrane 4 can be prevented from being damaged at the contact portion.

  The fuel cell C shown in FIG. 6 has the same basic configuration as that of the previous embodiment, and the anode-side and cathode-side seal elastic portions EA, EC are both made of the same material and have thickness dimensions h1, h2. And the width dimensions w1 and w2 in the battery inside / outside direction are the same (h1 = h2, w1 = w2).

  The illustrated fuel cell C is stacked to form a fuel cell stack. At this time, a coolant flow path 8 is formed between the adjacent separators 2A and 2C. Even in the fuel cell C of each of the previous embodiments, a similar coolant flow path is formed during stacking.

  As in the previous embodiment, the fuel cell C eliminates the in-plane compressive force and tensile force acting on the membrane electrode structure 1 and reliably prevents the vicinity of the electrode in the electrolyte membrane 4 from being damaged. be able to. Moreover, in the fuel cell C, the strength against breakage or peeling of the seal elastic portions EA and EC, that is, the shear stress (τ) applied to the seal elastic portions EA and EC becomes equal on the anode side and the cathode side, and the minimum necessary The necessary minimum strength can be obtained with the thicknesses h1 and h2.

  The fuel cell C shown in FIG. 7 has the same basic configuration as that of the previous embodiment, and the anode-side and cathode-side seal elastic portions EA, EC are both made of the same material and have thickness dimensions h1, h2. And the ratio of the width dimensions w1 and w2 in the battery inside / outside direction are the same (h1 / w1 = h2 / w2).

  As in the previous embodiment, the fuel cell C eliminates the in-plane compressive force and tensile force acting on the membrane electrode structure 1 and reliably prevents the vicinity of the electrode in the electrolyte membrane 4 from being damaged. be able to. In addition, in the fuel cell C, the shearing force (F) applied to the seal elastic portions EA and EC is equal on the anode side and the cathode side, so that the reaction force applied to the membrane electrode structure 1 is increased between the anode side and the cathode side. Will be equal. Thereby, it becomes difficult to produce the deformation | transformation of the membrane electrode structure 1, and the failure | damage of the electrolyte membrane 4 can be prevented more reliably.

  The fuel cell C shown in FIG. 8 (A) has the same basic configuration as that of the previous embodiment, and each electrode end face (fuel) including the seal bases MA and MC of the gas seal member 3 and the gas diffusion layers 6A and 6C. Between the polar layer 5A and the air electrode layer 5C, there are gaps 9,9. The gap 9 has a dimension S in the battery inside / outside direction, the displacement of the seal elastic portions EA, EC accompanying the swelling and shrinking of the electrolyte membrane 4, and the displacement of the electrode end portion accompanying the swelling and shrinking of the electrode layers (5A, 5C). It is more than the difference.

  Here, in the fuel cell C described above, the gas diffusion layers 6A and 6C of the membrane electrode structure 1 hardly swell and contract. Even if the gas diffusion layers 6A and 6C swell and contract, they are much smaller than the electrolyte membrane 4 and the like. is there. Therefore, the fuel cell C is provided with the gap 9 as described above, so that when the membrane electrode structure 1 is displaced in the in-plane direction as shown in FIG. This prevents the layers 6A and 6C from interfering with each other and applying stress to the electrolyte membrane 4 and the electrode layers (5A and 5C).

  Moreover, in the fuel cell C, the gap 9 is provided, so that even when the electrolyte membrane 4 and the electrode layers (5A, 5C) have different swelling rates, the electrode layer (5A, 5C) and the gas sealing material 3 Contact can be avoided. In this way, the fuel cell C can more reliably prevent the electrolyte membrane 4 from being damaged.

  The fuel cell C shown in FIG. 9 has the same basic configuration as the previous embodiment, and at least each of the seal elastic portions EA, EC in the gas seal member 3 is formed of an adhesive having elasticity after curing. . As the adhesive, as described above, an adhesive containing any one of a synthetic rubber resin, a silicon resin, a urethane resin, an olefin resin, an acrylic resin, and an epoxy resin can be used.

  The fuel cell C can obtain the same effect as that of the previous embodiment, and can have the seal elastic portions EA and EC in various shapes according to the structure of the fuel cell. For example, even when there is a step between the seal bases MA and MC and the gas diffusion layers 6A and 6C as shown in the figure, it can be easily dealt with. Further, during the assembly process of the fuel cell C, it is possible to apply and form the seal elastic portions EA and EC, and to adhere to the separators 2A and 2C, thereby contributing to further improvement in productivity.

  The configuration of the fuel cell of the present invention is not limited to the above-described embodiments, and details of the configuration can be changed as appropriate without departing from the gist of the fuel cell, for example, on the anode side and the cathode side. In consideration of the differential pressure, the seal elastic portions EA and EC may have different shear stresses and shear forces. Moreover, although the gas sea member 3 of the said embodiment is comprised by the seal base part and the seal elastic part, you may comprise only a seal elastic part.

DESCRIPTION OF SYMBOLS 1 Membrane electrode structure 2A Anode separator 2C Cathode separator 3 Gas seal member 4 Electrolyte membrane 5A Fuel electrode layer (electrode layer)
5C Air electrode layer (electrode layer)
6A Gas diffusion layer on the anode side 6C Gas diffusion layer on the cathode side 9 Crevice C Fuel cell EA Seal elastic part on the anode side EC Elastic seal part on the cathode side e Extension part M Seal base MA Seal base on the anode side MC Cathode side Seal base

Claims (8)

A membrane electrode structure;
An anode-side and cathode-side separator that sandwiches the membrane electrode structure;
A gas seal member that closes between the peripheral portion of the membrane electrode structure and each separator,
A fuel cell characterized in that at least a part of the gas seal member including a portion in contact with the separator is formed of a seal elastic portion that deforms following the displacement in the in-plane direction of the membrane electrode structure.   2. The fuel cell according to claim 1, wherein the seal elastic portion has an extending portion that is sandwiched between the membrane electrode structure and the separator.   3. The fuel cell according to claim 1, wherein the seal elastic portion is made of the same material, and has the same thickness dimension and the same width dimension in the cell inside / outside direction.   3. The fuel cell according to claim 1, wherein the seal elastic portion is made of the same material and has the same ratio of a thickness dimension to a width dimension in the cell inside / outside direction.   2. The membrane electrode structure has an anode-side and a cathode-side gas diffusion layer on both surfaces thereof, and a gap between the gas seal member and an electrode end surface including each gas diffusion layer. The fuel cell of any one of -4.   The fuel cell according to any one of claims 1 to 5, wherein at least a seal elastic portion in the gas seal member is formed of an adhesive having elasticity after curing.   A fuel cell stack comprising a plurality of the fuel cells according to any one of claims 1 to 6 stacked.   A vehicle comprising the fuel cell stack according to claim 7 as a power source.

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