JP2014216110A - Cell structure of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell structure of a fuel cell which reduces possibility of degradation and damage of a membrane electrode assembly.SOLUTION: The cell structure includes: a rectangular electrode body 100 which includes a rectangular membrane electrode assembly and rectangular first and second gas diffusion layers arranged both sides of the membrane electrode assembly; and a seal member 120 having a rectangular opening and covering an outer peripheral portion of a first gas diffusion layer 104c by arranging the first gas diffusion layer 104c on the opening. The electrode body 100 is arranged so that, with respect to the seal member, a distance D1 between a first outer peripheral end of the first gas diffusion layer 104c located on a side of a supply port 114i of a fuel gas and a first inner peripheral end of the seal member 120 is smaller than a distance D2 between a second outer peripheral end of the first gas diffusion layer 104c located on a side of a discharge port 114o of the fuel gas and a second inner peripheral end of the seal member 120.

Description

  The present invention relates to fuel cell technology.

  The fuel cell includes a membrane electrode assembly and a gas diffusion layer. A fuel cell is formed by stacking a plurality of single cells and applying a predetermined load from both sides in the stacking direction. In the fuel cell, a gas seal member (gasket) is provided on the outer periphery of the electrolyte membrane in order to suppress cross leakage between both electrodes of the fuel gas and the oxidizing gas. As one of such fuel cells, there is known a fuel cell in which a gas diffusion layer disposed on one electrode is formed smaller than a gas diffusion layer and an electrolyte membrane disposed on the other electrode (for example, , See Patent Document 1). Moreover, in the technique of patent document 1, suppression of the cross leak of fuel gas and oxidizing gas is aimed at by providing a gasket.

Japanese Patent Laid-Open No. 2007-066766

  When the gasket is provided so as to be in contact with the outer periphery of the smaller gas diffusion layer, the gap between the outer periphery of the smaller gas diffusion layer and the gasket is caused by, for example, the accuracy of formation of the gas diffusion layer or the gasket. There was a case where a gap occurred.

  If a gap exists between the outer periphery of the gas diffusion layer and the gasket, the membrane electrode assembly is exposed in this gap. In a polymer electrolyte fuel cell, for example, when the fuel cell repeats power generation and stoppage, the membrane electrode assembly causes a state change between a wet state and a dry state. Here, sufficient external force is not applied to the exposed portion (exposed portion) of the membrane electrode assembly even when a predetermined load is applied from both sides of the fuel cell. Therefore, when the membrane electrode assembly is in a wet state, there is a possibility that the exposed portion swells and deforms greatly to cause buckling. In addition, when the membrane / electrode assembly is in a dry state, the exposed portion may contract and crack. As described above, the membrane electrode assembly may be deteriorated or damaged by repeated deformation of the membrane electrode assembly.

  Here, by filling the gap with the resin, the swelling of the membrane electrode assembly in a wet state may be suppressed in some cases. FIG. 15 is a schematic cross-sectional view showing an example of the structure of a single cell in which a gap is filled with resin. The single cell 10R includes a second gas in which a first gas diffusion layer 104c disposed on a cathode 103c of a membrane electrode assembly (MEA) 101 is disposed on an anode 103a of the membrane electrode assembly 101. The diffusion layer 104 a and the membrane electrode assembly 101 are formed smaller than the electrolyte membrane 102. A first water repellent layer 105c is formed on the surface of the first gas diffusion layer 104c on the side in contact with the cathode 103c, and the surface of the second gas diffusion layer 104a on the side in contact with the anode 103a is on the first surface. Two water-repellent layers 105a are formed.

  In the single cell 10R, a seal member 120 is formed on the outer periphery of the first gas diffusion layer 104c so as to be sandwiched between the first separator 110c and the second separator 110a. Further, the single cell 10R is filled with a resin as the filler 130 in the gap formed between the seal member 120 and the first gas diffusion layer 104c, and the swelling of the membrane electrode assembly 101 in a wet state is suppressed. Is done.

  However, when the filling amount of the filler 130 is small and the thickness of the layer formed by the filler 130 (hereinafter also referred to as “filler layer”) becomes thin, the following problem may occur.

  When the thickness of the filler layer is reduced, when the plurality of single cells 10R are stacked and assembled, the part of the membrane electrode assembly 101 where the load overlaps with the filler 130 (corresponding MEA part) ) May not be enough. In this case, since it becomes insufficient to suppress the swelling of the electrolyte membrane 20, the membrane electrode assembly 101 may buckle and the membrane electrode assembly may be deteriorated or damaged.

  Further, when the pressure of the fuel gas on the anode 103a side is larger than the pressure of the oxidizing gas on the cathode 103c side, and the gap exists in a place where the gas differential pressure between the electrodes between the anode 103a and the cathode 103c is large. In this case, a stress is generated on the membrane electrode assembly 101 by the differential pressure of gas between the electrodes (hereinafter also referred to as “inter-electrode differential pressure”). As a result, mechanical deformation corresponding to the generated stress is likely to occur in the gap portion of the membrane electrode assembly 101. When the filler 130 is sufficiently filled in the gap, the stress generated in the membrane electrode assembly 101 is suppressed by the load applied from the formed filler layer, thereby deforming the membrane electrode assembly 10. It can be sufficiently suppressed. However, when the filling amount of the filler 130 decreases, the stress applied to the membrane electrode assembly 101 cannot be suppressed by the load applied from the formed filler layer. This is because the deformation may not be sufficiently suppressed. Note that the pressure difference between the electrodes is higher at the fuel gas pressure than the oxidizing gas pressure and is usually larger at the fuel gas introduction side (inlet side) to the single cell. When the filling amount of the filling material into the gap existing in is reduced, the membrane electrode assembly is likely to be deformed. As described above, even when the gap is filled with the filler, the membrane electrode assembly may be deteriorated or damaged due to the differential pressure between the electrodes.

  Deterioration or damage of the membrane electrode assembly is undesirable because it can cause cross leak of fuel gas and oxidizing gas. Therefore, even when the state of the membrane electrode assembly changes between a wet state and a dry state, and even when the filling amount of the filler in the gap is small, the deterioration and damage of the membrane electrode assembly is suppressed. Technology was desired. Further, in the fuel cell, it has been desired to suppress the number of parts, simplify the manufacturing process, reduce the manufacturing cost, and the like.

  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.

(1) According to one form of this invention, the cell structure of a fuel cell is provided. This cell structure is a rectangular electrode body comprising a rectangular membrane electrode assembly, and rectangular first and second gas diffusion layers disposed on both sides of the membrane electrode assembly, The first gas diffusion layer has a smaller area than the second gas diffusion layer, and the outer periphery of the first gas diffusion layer includes the outer periphery of the membrane electrode assembly and the second gas diffusion layer. An electrode body positioned inside the outer peripheral portion of the first gas diffusion layer; a sealing member having a rectangular opening, wherein the first gas diffusion layer is disposed in the opening by disposing the first gas diffusion layer A seal member covering the outer peripheral portion of the first gas diffusion layer; a filler filled between an outer peripheral end portion of the first gas diffusion layer and an inner peripheral end portion of the seal member; on the surface of the seal member and the first A groove-like acid which is disposed on the surface of the gas diffusion layer and allows an oxidizing gas to flow along the surface of the first gas diffusion layer A first separator having a gas flow path; a groove shape disposed on the surface of the seal member and on the surface of the second gas diffusion layer and for allowing fuel gas to flow along the surface of the second gas diffusion layer A second separator having a fuel gas flow path; and on the outer peripheral side of the first side of the electrode body, the fuel gas supply port for supplying the fuel gas from the outside to the fuel gas flow path; A fuel gas exhaust port for exhausting the fuel gas from the fuel gas flow path to the outside, on the outer peripheral side of the second side facing the first side. The electrode body has an interval between the first outer peripheral end of the first gas diffusion layer located on the fuel gas supply port side and the first inner peripheral end of the seal member. It arrange | positions so that it may become smaller than the space | interval between the 2nd outer peripheral edge part of the said 1st gas diffusion layer located in the gas discharge port side, and the 2nd inner peripheral edge part of the said sealing member. . According to the cell structure of this embodiment, it is possible to reduce the stress applied to the membrane electrode assembly located in the gap between the first gas diffusion layer and the seal member on the fuel gas supply port side. Thereby, the possibility that the membrane electrode assembly is deformed can be reduced, and the possibility that the membrane electrode assembly is deteriorated or damaged can be reduced.

(2) In the cell structure of the above aspect, the cell body is further provided on the outer peripheral side of a third side perpendicular to the first side of the electrode body, and the oxidizing gas is supplied to the oxidizing gas channel from the outside. A supply port for the oxidizing gas; and an exhaust port for the oxidizing gas, which is disposed on the outer peripheral side of the fourth side facing the third side, and discharges the oxidizing gas from the oxidizing gas flow path to the outside. A distance between a third outer peripheral end portion of the first gas diffusion layer and a third inner peripheral end portion of the seal member, the electrode body being located on the discharge port side of the oxidizing gas. Is larger than the interval between the fourth outer peripheral end of the fourth gas diffusion layer located on the supply port side of the oxidizing gas and the fourth inner peripheral end of the seal member, It may be arranged. According to the cell structure of this embodiment, since the pressure difference between the pressure of the fuel gas and the pressure of the oxidizing gas can be reduced on the fuel gas supply port side, the gap between the first gas diffusion layer and the seal member can be reduced. It is possible to more effectively reduce the stress applied to the membrane electrode assembly located in the gap. Thereby, the possibility that the membrane electrode assembly is deformed can be reduced, and the possibility that the membrane electrode assembly is deteriorated or damaged can be reduced.

  Note that the present invention can be realized in various forms, for example, in the form of a cell structure of a fuel cell, a fuel cell, a vehicle equipped with the fuel cell, and the like.

It is explanatory drawing which shows schematic structure of the fuel cell system in one Embodiment. It is explanatory drawing which shows schematic structure of a single cell. It is a schematic sectional drawing which expands and shows the part of area | region A1 among the peripheral parts of the schematic cross section of the single cell shown in FIG.2 (c). It is a schematic sectional drawing which expands and shows the part of area | region A2 among the peripheral parts of the schematic cross section of the single cell shown in FIG.2 (c). It is explanatory drawing which shows the outline of the manufacturing method of a fuel cell. It is a top view which shows the arrangement | positioning relationship between the sealing member and the 1st gas diffusion layer in sample # 1. It is a top view which shows the arrangement | positioning relationship between the sealing member and the 1st gas diffusion layer in sample # 2. It is a top view which shows the arrangement | positioning relationship between the sealing member in sample # 3, and a 1st gas diffusion layer. It is a top view which shows the arrangement | positioning relationship between the sealing member in sample # 4, and a 1st gas diffusion layer. It is the table | surface which put together the clearance gap in each sample. It is a table | surface which shows the tensile stress assumed in the a part and c part of each sample. It is a schematic diagram which shows the model of a deformation | transformation of a membrane electrode assembly. It is a graph which shows the relationship between the clearance gap and the tensile stress (sigma) in each using the inter-electrode differential pressure of a part and the inter-electrode differential pressure of c part as parameters. It is the table | surface which put together the relationship between the clearance gap in a part and c part, the interpolar pressure difference (DELTA) p, and the tensile stress (sigma) based on FIG. It is a schematic sectional drawing which shows an example of the structure of the single cell which filled the clearance gap with resin.

A1: Fuel cell configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 5 according to an embodiment. The fuel cell system 5 includes a fuel cell 200, a hydrogen tank 50, an air compressor 40, and a control unit 26. The hydrogen tank 50 stores hydrogen as fuel gas. The air compressor 40 supplies compressed air as an oxidizing gas to the fuel cell 200. The control unit 26 controls the entire fuel cell system 5.

  The fuel cell 200 is a polymer electrolyte fuel cell. The structure of the fuel cell 200 is a stack structure in which a plurality of single cells 10 are stacked. The fuel cell 200 includes an end plate 21, an insulating plate 22, and a current collector plate 23 in addition to the plurality of single cells 10. On both sides in the stacking direction (Z-axis direction), current collector plate 23, insulating plate 22 and end plate 21 are arranged in this order from the single cell 10 side toward the outside. The two end plates 21 are fastened with a predetermined fastening force (load) by a tension rod 24 and a nut 25. Thereby, a predetermined force is applied to each single cell 10 from both sides in the stacking direction. At least one of the nuts 25 is provided with a drive unit 27 for adjusting the fastening force by rotating the nut 25.

  Each single cell 10 generates power by an electrochemical reaction between a fuel gas (hydrogen) and an oxidizing gas (oxygen contained in air). Hydrogen as fuel gas stored in the hydrogen tank 50 flows through the hydrogen gas supply path 53 after being decompressed by the decompression valve 51. The flowing hydrogen is adjusted to a predetermined pressure by a pressure adjusting valve 52 provided in the hydrogen gas supply path 53 and supplied to the fuel cell 200. A gas containing hydrogen (anode supply gas) supplied to the fuel cell 200 is supplied to each single cell 10 via an anode gas supply manifold (not shown) formed inside the fuel cell 200, and It is used for power generation in the cell 10. Gas (anode exhaust gas) containing hydrogen that has not been used in each single cell 10 is collected through an anode gas discharge manifold (not shown) formed inside the fuel cell 200. Then, the anode exhaust gas is discharged outside the fuel cell 200 through the anode exhaust gas passage 54. The fuel cell system 5 may have a configuration in which anode exhaust gas is recirculated to the supply side.

  The air pressurized by the air compressor 40 is supplied to the fuel cell 200 via the oxidizing gas supply path 41. Air containing oxygen (cathode supply gas) supplied to the fuel cell 200 is supplied to each single cell 10 via a cathode gas supply manifold (not shown), and is used for power generation in each single cell 10. Air (cathode exhaust gas) that has not been used in each single cell 10 is collected via a cathode gas exhaust manifold (not shown) and exhausted to the outside of the fuel cell 200 via a cathode exhaust gas channel 48.

  The refrigerant circulation pump 46 supplies the refrigerant to the fuel cell 200 via the refrigerant circulation channel 47. The coolant heated by the fuel cell 200 is cooled by the radiator 45 and supplied to the fuel cell 200 again. The cooling medium is supplied to each single cell 10 via a refrigerant supply manifold (not shown), and cools each single cell 10. The cooling medium after passing through each single cell 10 is collected via a refrigerant discharge manifold (not shown) and circulates to the radiator 45 via the refrigerant circulation passage 43. As the cooling medium, water or non-freezing water such as a mixed solution of water and ethylene glycol can be used. In this embodiment, liquid is used as the cooling medium, but air may be used as the cooling medium.

  The control unit 26 is a computer that includes a CPU, a memory, and the like (not shown). The control unit 26 receives signals from temperature sensors, pressure sensors, voltmeters, and the like arranged in each unit of the fuel cell system 5 and controls the entire fuel cell system 5 based on the received signals.

  FIG. 2 is an explanatory diagram showing a schematic configuration of the single cell 10. 2A shows a schematic plan view of the single cell 10 viewed from the cathode side, and FIG. 2B shows a schematic plan view of the inside of the single cell 10 viewed from the cathode side. FIG.2 (c) has shown the schematic AA arrow cross section shown to Fig.2 (a). FIG. 3 is an enlarged schematic cross-sectional view showing a region A1 in the peripheral edge of the schematic cross section of the single cell 10 shown in FIG. FIG. 4 is an enlarged schematic cross-sectional view showing a region A2 in the peripheral edge of the schematic cross section of the single cell 10 shown in FIG.

  As shown in FIG. 2, the single cell 10 includes an electrode body 100 and first and second separators 110 c and 110 a disposed so as to sandwich both surfaces of the electrode body 100. The single cell 10 includes a seal member 120 disposed so as to cover the outer periphery of the electrode body 100.

  The electrode assembly 100 includes a membrane electrode assembly (MEA) 101, a first gas diffusion layer 104c, and a second gas diffusion layer 104a, as shown in FIGS. Prepare. The membrane electrode assembly 101 includes an electrolyte membrane 102 and a cathode 103c and an anode 103a disposed on both surfaces of the electrolyte membrane. The electrolyte membrane 102 is a proton-conductive ion exchange membrane formed of a solid polymer material, for example, a fluorine-based resin including perfluorocarbon sulfonic acid, and exhibits good electrical conductivity in a wet state. Each of the cathode 103c and the anode 103a includes, for example, platinum or a platinum alloy as a catalyst. More specifically, the cathode 103 c and the anode 103 a include carbon particles supporting the catalyst and an electrolyte similar to the polymer electrolyte that constitutes the electrolyte membrane 102. 2 to 4, members with “c” at the end of the reference numerals are members on the cathode 103 c side, and members with “a” are members on the anode 103 a side.

  The first gas diffusion layer 104c and the second gas diffusion layer 104a are arranged so as to sandwich the membrane electrode assembly 101 from both sides. A first water repellent layer 105c is provided on the surface of the first gas diffusion layer 104c that contacts the cathode 103c. A second water repellent layer 105a is provided on the surface of the second gas diffusion layer 104a that is in contact with the anode 103a.

  The first and second gas diffusion layers 104c and 104a are formed of a conductive member having gas permeability. Examples of the conductive member include carbon paper, carbon cloth, metal mesh, and foam metal. The first and second gas diffusion layers 104c and 104a are both formed as flat plate members. By providing the first and second gas diffusion layers 104c and 104a, it is possible to improve the gas supply efficiency to the electrode and to improve the current collecting property between the first and second separators 110c and 110a and the electrode. it can. Further, the electrolyte membrane 102 can be protected by the first and second gas diffusion layers 104c and 104a.

  The first and second water-repellent layers 105c and 105a include carbon particles and a water-repellent substance such as a fluororesin. Such first and second water-repellent layers 105c and 105a constitute water-repellent ink that is a mixed liquid containing carbon particles and a water-repellent substance, and constitute the first and second gas diffusion layers 104c and 104a. It is formed by applying to the surface of the conductive member to be dried, drying and firing. The first and second water repellent layers 105c and 105a push back the liquid water to be moved from the membrane electrode assembly 101 to the gas diffusion layers 104c and 104a to the membrane electrode assembly 101 side. It is possible to suppress the electrolyte membrane 102 from being deficient in water by pushing back the liquid water. Further, by repelling the liquid water, it is possible to prevent the pores provided in the first and second gas diffusion layers 104c and 104a from being blocked by the liquid water.

  As shown in FIGS. 2B, 3 and 4, in the present embodiment, the first gas diffusion layer 104c and the second gas diffusion layer 104a have different sizes (areas). In the present embodiment, the area of the first gas diffusion layer 104c is smaller than that of the second gas diffusion layer 104a. In addition, as shown in FIG. 2B, the outer peripheral end (outer peripheral edge) of the first gas diffusion layer 104 c is in the in-plane direction (plane direction) of the membrane electrode assembly 101. It is located on the inner side (center side) of the outer peripheral end and the outer peripheral end of the second gas diffusion layer 104a (indicated by a broken line frame).

  As shown in FIGS. 2C, 3, and 4, the first and second separators 110 c and 110 a are arranged so as to sandwich the electrode body 100 and the seal member 120 from both sides. The first and second separators 110c and 110a are formed of a gas impermeable conductive member. Examples of the conductive member include a carbon member such as dense carbon that has been made to be gas-impermeable by compressing carbon, and a metal member such as press-formed stainless steel. As shown in FIG. 2A, the outer shape of the first and second separators 110c and 110a is rectangular. Of the first and second separators 110c and 110a, on the surface facing the catalyst electrode layer (cathode 82 or anode 86), as shown in FIGS. 3 and 4, flow channel grooves 116c and 116a through which reaction gas flows are provided. A concavo-convex shape for forming is formed. The channel groove 116c forms an oxidizing gas channel for allowing the oxidizing gas to flow through the first gas diffusion layer 106c. The channel groove 116a forms a fuel gas channel through which the fuel gas flows with respect to the second gas diffusion layer 106a. Hereinafter, the channel groove 116c is also referred to as “oxidizing gas channel 116c”, and the channel groove 116a is also referred to as “fuel gas channel 116a”.

  The seal member 120 has a sheet shape and is formed of a synthetic resin (for example, polyolefin). Polypropylene or polyethylene can be used as the polyolefin. The thickness of the seal member 120 can be appropriately determined depending on the shape of the first and second gas diffusion layers 104c and 104a, the shape of the first and second separators 110c and 110a, and the like. For example, the thickness of the seal member 120 is about 100 to 300 μm. As shown in FIGS. 3 and 4, the seal member 120 is attached to the surface of the outer peripheral portion of the membrane electrode assembly 101 on the side where the first gas diffusion layer 104 c is disposed. The outer shape of the seal member 120 is rectangular as shown in FIG. In addition, a space (opening) for accommodating the first gas diffusion layer 104c is formed in the center of the seal member 120. The seal member 120 seals the oxidizing gas flow path.

  As shown in FIGS. 3 and 4, on the membrane electrode assembly 101 where the filler 130 is exposed in the gap so as to close the gap between the outer peripheral end of the first gas diffusion layer 104c and the seal member 120. Is provided. The filler 130 is disposed between the seal member 120 and the membrane electrode assembly 101 and is used for attaching the seal member 120 to the membrane electrode assembly 101. The filler 130 includes a thermosetting resin such as polyisobutylene, epoxy, or urethane.

  As shown in FIGS. 2 (a) and 2 (b), the first separator 110c, the seal member 120, and the second separator 110a constitute various manifolds formed inside the fuel cell 200 described above. A plurality of through holes are formed as described below. Although the plan view of the second separator 110a is omitted, the positions and shapes of the plurality of through holes formed in the second separator 110a are the same as those of the first separator 110a.

  In the first and second separators 110c and 110a, as shown in FIG. 2A, a plurality of cathode gas introduction through holes 112i constituting the cathode gas supply manifold are formed on one long side (the lower side in the figure). A plurality of cathode gas discharge through holes 112o constituting the cathode gas discharge manifold are formed along the other long side (the upper side in the figure). Therefore, the side where the cathode gas supply through hole 112i is provided is the oxidizing gas (air) inlet side, and the side where the cathode gas discharge through hole 112o is provided is the oxidizing gas outlet side. Further, the first separator 110c has a plurality of anode gas introduction through holes 114i constituting an anode gas supply manifold formed along one short side (left side in the figure) to constitute an anode gas discharge manifold. A plurality of anode gas discharge through holes 114o are formed along the other short side (right side in the figure). Accordingly, the fuel gas (hydrogen) inlet side on the side where the anode gas supply through hole 114i is provided, and the side where the anode gas discharge through hole 114o is provided is the fuel gas outlet side.

  Also in the seal member 120, as shown in FIG. 2B, a plurality of cathode gas introduction through holes 122i constituting the cathode gas supply manifold are formed along one long side (the lower side in the figure). A plurality of cathode gas discharge through holes 122o constituting the cathode gas discharge manifold are formed along the other long side (the upper side in the figure). The seal member 120 has a plurality of anode gas introduction through holes 124i constituting an anode gas supply manifold formed along one short side (the left side in the figure), and a plurality of anode gas discharge manifolds are formed. The anode gas discharge through hole 124o is formed along the other short side (the right side in the figure).

  Hereinafter, the cathode gas introduction through hole is also referred to as a “cathode gas supply manifold”, and the cathode gas discharge through hole is also referred to as a “cathode gas discharge manifold”. The anode gas introduction through hole is also referred to as “anode gas supply manifold”, and the anode gas discharge through hole is also referred to as “cathode gas discharge manifold”.

  As shown in FIG. 2A, air as the oxidizing gas flows from a cathode supply manifold 112i serving as an oxidizing gas (air) supply port to an oxidizing gas flow path 116c (FIG. 3) formed in the first separator 110a. , Refer to FIG. 4), flows along the short side direction (Y direction) of the electrode body 100, and is discharged to the outside of the single cell 10 through the cathode gas discharge manifold 112 o serving as an oxidizing gas discharge port. In contrast, hydrogen as a fuel gas is supplied from a fuel gas flow path 116a (see FIGS. 3 and 4) formed in the first separator 110c from an anode gas supply manifold 114i serving as a fuel gas (hydrogen) supply port. ), Flows along the long side direction (X direction) of the electrode body 100, and is discharged to the outside of the single cell 10 through the anogas discharge manifold 114o serving as a fuel gas discharge port. That is, the flow path direction of the oxidizing gas flow path is orthogonal to the flow path direction of the fuel gas flow path.

  The first separator 110c, the seal member 120, and the second separator 110a are further formed with a plurality of through holes for constituting a refrigerant supply manifold and a refrigerant discharge manifold. Since there is no particular need, illustration and description are omitted.

  A distance D1 shown in FIGS. 2C and 3 is a distance between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120 on the anode supply manifolds 114i and 124i side. A distance D2 shown in FIGS. 2C and 4 is a distance between the outer peripheral end portion of the first gas diffusion layer 104c and the inner peripheral end portion of the seal member 120 on the anode discharge manifolds 114o and 124o side. The present embodiment is characterized in that the electrode body 100 is arranged so that the distance D1 on the hydrogen supply side shown in FIG. 3 is smaller than the distance D2 on the hydrogen discharge side shown in FIG. ing. This arrangement structure will be further described later.

  FIG. 5 is an explanatory diagram showing an outline of a method for manufacturing the fuel cell 200. First, the membrane electrode assembly 101 is prepared (step S10). Next, the first gas diffusion layer 104c on which the first water-repellent layer 105c is formed is attached to the membrane electrode assembly 101, and the second gas diffusion layer 104a on which the second water-repellent layer 105a is formed. Is attached (step S12). That is, step S12 is a process of preparing the electrode body 100.

  Next, the liquid filler 130 is applied on the first surface 101c on the side where the first gas diffusion layer 104c is disposed in the outer peripheral portion from the outer peripheral edge to the inner peripheral edge of the membrane electrode assembly 101 (step S14). ). In FIG. 5, for convenience of illustration, the filler 130 is depicted as being applied outside the space S formed between the seal member 120 and the electrode body 100. The filler 130 is applied to the position of the space S. The amount of the filler 130 to be applied is preferably 1.2 to 2.0 times the volume of the space S. Since the amount of the filler 130 is 1.2 times or more the volume of the space S, the filler 130 can be reliably protruded outward from the gap M in step S16 described later. Further, since the amount of the filler 130 is 2.0 times or less of the volume of the space S, the possibility that the filler 130 protrudes excessively from the gap M in step S16 described later can be reduced. If the filler 130 protrudes excessively from the gap M, there may be a problem that the oxidizing gas flow path is blocked.

  Next, the sealing member 120 is disposed so as to surround the first gas diffusion layer 104c. At this time, as described above, the hydrogen supply side interval D1 (FIG. 3) is smaller than the hydrogen discharge side interval D2 (FIG. 4). Thereby, a part of the filler 130 is pushed out by the seal member 120. As a result, the first gas diffusion layer 104c from the first filling portion 131 sandwiched between the seal member 120 and the membrane electrode assembly 101 and the gap M is obtained. Thus, an exposed portion 132 that protrudes outward in the stacking direction of the membrane electrode assembly 101 is formed (step S16). In this step, for example, the seal member 120 is disposed on the filler 130 so that the seal member 120 and the applied filler 130 partially overlap when viewed in the stacking direction of the membrane electrode assembly 101. It can be realized by doing.

  Next, the first and second separators 110c and 110a are attached to both sides of the electrode body 100 (step S18). Specifically, an adhesive is applied to a portion of the first and second separators 110c and 110a that contacts the seal member 120, and the seal member 120 and the electrode body 100 are connected by the first and second separators 110c and 110a. Apply force in the direction of compression in the stacking direction. Thereby, the 1st and 2nd separator 110c, 110a and the sealing member 120 are attached. Further, at least the first separator 110c is heated to a temperature higher than the temperature at which the filler 130 is cured. Thereby, the filler 130 is cured and the filler 130 and the first separator 110c are attached. As a result, the single cell 10 is manufactured. The fuel cell 200 is manufactured by stacking a plurality of single cells 10.

  Here, as described in the problem, when the filling amount of the filler 130 is small, in the gap S (see step S14 in FIG. 5) between the seal member 120 and the first gas diffusion layer 104c. In addition, it may be difficult to suppress the deformation of the membrane electrode assembly 101 due to the stress generated by the gas differential pressure between the electrodes (interelectrode differential pressure). In contrast, in the present embodiment, as described above, the outer peripheral end portion of the first gas diffusion layer 104c on the hydrogen discharge side and the sealing member for the purpose of suppressing the deformation of the membrane electrode assembly due to the differential pressure between the electrodes. The electrode body 100 is arranged such that the distance D1 on the hydrogen supply side is smaller than the distance D2 between the inner peripheral end portion 120 (see FIGS. 2 to 4). In the arrangement structure of the seal member 120 and the electrode assembly 100, as will be described in the following embodiments, the pressure of the fuel gas is higher than the pressure of the oxidizing gas even when the filling amount of the filler 130 is small. It is possible to suppress the deformation of the membrane electrode assembly caused by such an inter-electrode differential pressure.

  In order to confirm the effect of suppressing the deformation of the membrane / electrode assembly according to the present embodiment, the following four types of samples # 1 to # 4 having different arrangement structures were evaluated.

  FIG. 6 is a plan view showing the positional relationship between the seal member 120 and the first gas diffusion layer 104c in sample # 1. In sample # 1, the outer peripheral end of the first gas diffusion layer 104c is the hydrogen supply side as the fuel gas (anode gas) and the air discharge side as the oxidizing gas (cathode gas), and the inner peripheral end of the seal member 120 It is the sample arrange | positioned so that a part may be contacted. In sample # 1, the distance between the outer peripheral end portion of the first gas diffusion layer 104c and the inner peripheral end portion of the seal member 120 is made smaller on the hydrogen supply side than on the hydrogen discharge side, and the air supply side is discharged on the air. It is an example of the structure made small compared with the side.

  FIG. 7 is a plan view showing the positional relationship between the seal member 120 and the first gas diffusion layer 104c in sample # 2. Sample # 2 is a sample arranged so that the outer peripheral end portion of the first gas diffusion layer 104c is in contact with the inner peripheral end portion of the seal member 120 on the hydrogen discharge side and the air supply side. In sample # 2, the distance between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120 is larger on the hydrogen supply side than on the hydrogen discharge side, and the air discharge side is supplied with air. It is an example of the structure enlarged compared with the side.

  FIG. 8 is a plan view showing the positional relationship between the seal member 120 and the first gas diffusion layer 104c in sample # 3. Sample 3 is a sample arranged so that the outer peripheral end of the first gas diffusion layer 104c contacts the inner peripheral end of the seal member 120 on the hydrogen discharge side and the air discharge side. In sample # 3, the distance between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120 is larger on the hydrogen supply side than on the hydrogen discharge side, and the air discharge side is supplied with air. It is an example of the structure made small compared with the side.

  FIG. 9 is a plan view showing the positional relationship between the seal member 120 and the first gas diffusion layer 104c in sample # 4. Sample # 4 is a sample arranged so that the outer peripheral end of the first gas diffusion layer 104c is in contact with the inner peripheral end of the seal member 120 on the hydrogen supply side and the air supply side. In sample # 4, the distance between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120 is made smaller on the hydrogen supply side than on the hydrogen discharge side, and the air discharge side is supplied with air. It is an example of the structure enlarged compared with the side.

  As described above, in sample # 1 and sample # 4, the hydrogen supply side is the hydrogen discharge side as the gap (gap) between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120. The sample is arranged so that the outer peripheral end portion of the first gas diffusion layer 104c is in contact with the inner peripheral end portion of the seal member 120 on the hydrogen supply side so as to be smaller. On the other hand, in sample # 2 and sample # 3, the hydrogen supply side is the hydrogen discharge side as the gap (gap) between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120. In this sample, the outer peripheral end portion of the first gas diffusion layer 104c is arranged so as to come into contact with the inner peripheral end portion of the seal member 120 on the hydrogen discharge side so as to be larger.

  However, in consideration of the structure of the first gas diffusion layer 104c, even if the outer peripheral end portion of the first gas diffusion layer 104c is arranged so as to contact the inner peripheral end portion of the seal member 120, it is about 0.5 mm. A gap is generated. This is because the surface (the surface along the Z direction) that contacts the seal member 120 at the outer peripheral end of the first gas diffusion layer 104c has irregularities, and the convex portion contacts the seal member 120, but the concave portion does not seal. This is because a gap is formed without contacting the member 120.

  FIG. 10 is a table summarizing the gaps in each sample. In sample # 1, since the outer peripheral end portion of the first gas diffusion layer 104c is arranged to contact the inner peripheral end portion of the seal member 120 on the hydrogen supply side, the gap between the a portion and the c portion in the X direction is arranged. The (interval) is 0.5 mm, and the gap in the X direction between the b part and the d part is 1.5 mm. In sample # 1, since the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end of the seal member 120 on the air discharge side, the gap in the Y direction between the a part and the b part is 0. The gap in the Y direction between the c part and the d part is 1.5 mm.

  In sample # 2, since the outer peripheral end portion of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen discharge side, the gap between the a portion and the c portion in the X direction is arranged. Is 1.5 mm, and the gap in the X direction between the b part and the d part is 0.5 mm. In sample # 2, since the outer peripheral end of the first gas diffusion layer 104c is arranged to contact the inner peripheral end of the seal member 120 on the air supply side, the Y direction of the a part and the b part The gap in the Y direction between the c part and the d part is 0.5 mm.

  In sample # 3, since the outer peripheral end portion of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen discharge side, the gap between the a portion and the c portion in the X direction is arranged. Is 1.5 mm, and the gap in the X direction between the b part and the d part is 0.5 mm. Further, in sample # 3, the outer peripheral end of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end of the seal member 120 on the air discharge side. The gap in the Y direction between the c part and the d part is 1.5 mm.

  In sample # 4, since the outer peripheral end portion of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen supply side, the gap between the a portion and the c portion in the X direction is arranged. Is 0.5 mm, and the gap in the X direction between the b part and the d part is 1.5 mm. Further, in sample # 4, since the outer peripheral end of the first gas diffusion layer 104c is arranged to contact the inner peripheral end of the seal member 120 on the air supply side, the Y direction of the a part and the b part The gap in the Y direction between the c part and the d part is 0.5 mm.

  The gas pressure of hydrogen supplied from the hydrogen supply port (anode gas supply manifold) is set to 300 kPa, the gas pressure of hydrogen discharged to the hydrogen discharge port (anode gas discharge manifold) is set to 100 kPa, and the air supply port (cathode gas). The gas pressure of air supplied from the supply manifold) was 200 kPa, and the gas pressure of air discharged to the air discharge port (cathode gas discharge manifold) was 100 kPa. In this case, the gas differential pressure (electrode differential pressure) Δp generated in each part a to d is a part: +200 kPa, b part: 0 kPa, c part: +100 kPa, d part: -100 kPa. When the sign of the differential pressure is “+”, it indicates that (hydrogen pressure at the anode)> (air pressure at the cathode). Therefore, in the a part and the c part, there is a possibility that the deformation of the membrane electrode assembly is caused by the stress applied to the membrane electrode assembly in accordance with the interelectrode differential pressure Δp.

  FIG. 11 is a table showing the tensile stress assumed in part a and part c of each sample. Each tensile stress shown in FIG. 11 can be obtained by calculation as shown below.

FIG. 12 is a schematic diagram showing a model of deformation of a membrane electrode assembly (MEA). As shown in FIG. 12, when an external force p is applied to the area of radius a centering on the virtual center axis (one-dot chain line) perpendicular to the membrane electrode assembly, in the area of radius a centering on the virtual center axis It is assumed that deformation of the membrane electrode assembly occurs. In this case, the tensile stress σ _r and the tensile stress σ _θ in polar coordinates (r, θ) represented by the distance r from the virtual center axis before deformation of the membrane electrode assembly and the angle θ around the virtual center axis are: It is represented by the following formula (1) as a.
σ = σ _r = σ _θ = (B _0/4 (E · p ² · r ² / t ² ) ^1/3
= (B _0/4 (E · p ² · a ² / t ² ) ^1/3 (1)
E is the Young's modulus of the membrane electrode assembly used, and B ₀ is a constant, for example, Poisson's ratio ν = 0.4 and B ₀ = 1.777. T is the film thickness of the membrane electrode assembly.

  The above formula (1) is a formula in which a formula of tensile stress (hereinafter, also simply referred to as “stress”) σ in general material mechanics is applied to a membrane electrode assembly (Journal of Power Sources 194 (2009)). 873-879).

Here, the stress generated in the membrane electrode assembly in the gap between the inner peripheral end portion of the seal member 120 and the outer peripheral end portion of the first gas diffusion layer 104c is the deformation in the membrane electrode assembly shown in FIG. The relationship between the gap and the tensile stress σ (= σ _r ) is calculated from the above equation (1) by regarding the diameter (2a) of the region of 2 as the size of the gap and setting the external force p as the inter-electrode differential pressure Δp. be able to. FIG. 13 is a graph showing the relationship between the gap and the tensile stress σ in each of which the parameter is the inter-electrode differential pressure (Δp = 200 kPa) and the c-component differential pressure (Δp = 100 kPa). . FIG. 14 is a table summarizing the relationship among the gaps in the a part and the c part, the inter-electrode differential pressure Δp, and the tensile stress σ based on FIG.

  Based on the results obtained as described above (FIGS. 13 and 14), the tensile stress assumed in the a part and the c part of each sample shown in FIG. 11 is obtained. In sample # 1, the tensile stress in part c is 7.9 MPa, which is the same as in sample # 2 and sample # 3, and does not increase relative to sample # 2 and sample # 3. The size is less than half of 6.0 MPa with respect to 12.5 MPa of sample # 3. In sample # 4, the tensile stress in part a is 12.5 MPa, which is the same as in sample # 2 and sample # 3, and does not increase with respect to sample # 2 and sample # 3. 2 and 7.9 MPa of sample # 3, which is 3.8 MPa, less than half the size.

  Therefore, according to the structure in which the outer peripheral end portion of the first gas diffusion layer 104c is arranged so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen supply side as in sample # 1 and sample # 4, It is possible to suppress the stress generated in the membrane electrode assembly in accordance with the inter-electrode differential pressure in which the hydrogen pressure is higher than the air pressure, and it is possible to suppress the deformation of the membrane electrode assembly. Further, in the case of a structure in which the flow direction of the oxidizing gas (air) and the flow direction of the fuel gas (hydrogen) are orthogonal to each other, as in sample # 1, the outer peripheral end of the first gas diffusion layer 104c It is preferable that the structure is arranged so that the portion contacts the inner peripheral end of the seal member 120 on the air discharge side. In sample # 1, it is possible to suppress the stress generated in the membrane electrode assembly in response to the differential pressure between the electrodes where the hydrogen pressure is higher than the air pressure, compared to sample # 4. It is possible to further suppress deformation.

  Note that Sample # 1 and Sample # 4 are spaced on the hydrogen supply side from the distance (gap) between the outer peripheral end of the first gas diffusion layer 104c and the inner peripheral end of the seal member 120 on the hydrogen discharge side. As an example of an arrangement structure in which this is smaller, the outer peripheral end of the first gas diffusion layer 104c is arranged so as to contact the inner peripheral end of the seal member 120 on the hydrogen supply side. Even in the case of sample # 1 and sample # 4, as described above, a gap of about 0.5 mm is generated even in the portion arranged to contact. Considering this, it is not always necessary that the outer peripheral end portion of the first gas diffusion layer 104c be in contact with the inner peripheral end portion of the seal member 120 on the hydrogen supply side. The distance between the inner peripheral end of the seal member 120 on the hydrogen supply side and the outer peripheral end of the first gas diffusion layer 104c is such that the inner peripheral end of the seal member 120 on the hydrogen discharge side and the first gas diffusion layer 104c What is necessary is just to arrange | position so that it may become smaller than the space | interval with an outer peripheral edge part. According to this arrangement structure, it is possible to suppress the stress generated in the membrane electrode assembly at least in the gap at the position on the hydrogen supply side where the inter-electrode differential pressure increases, and to suppress deformation of the membrane electrode assembly. Is possible. However, as in sample # 1 and sample # 4, a structure in which the outer peripheral end portion of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen supply side is desirable.

  Sample # 1 has a structure in which the flow path direction of the air as the oxidizing gas and the flow path direction of the hydrogen as the fuel gas are orthogonal to each other, and the outer periphery of the first gas diffusion layer 104c on the air supply side. As an example of an arrangement structure in which the interval on the air discharge side is smaller than the interval between the end portion and the inner peripheral end portion of the seal member 120, the outer peripheral end portion of the first gas diffusion layer 104c is on the air discharge side. The seal member 120 is disposed so as to be in contact with the inner peripheral end portion. Similarly, it is not always necessary that the outer peripheral end portion of the first gas diffusion layer 104c be in contact with the inner peripheral end portion of the seal member 120 on the air discharge side. The distance between the inner peripheral end of the seal member 120 on the air discharge side and the outer peripheral end of the first gas diffusion layer 104c is such that the inner peripheral end of the seal member 120 on the air supply side and the first gas diffusion layer 104c What is necessary is just to arrange | position so that it may become smaller than the space | interval with an outer peripheral edge part. According to this arrangement structure, it is possible to reduce the inter-electrode differential pressure applied to the membrane electrode assembly on the hydrogen supply side. As a result, the stress generated in the membrane electrode assembly in the gap between the hydrogen supply side and the air discharge side can be suppressed, and deformation of the membrane electrode assembly can be suppressed. However, as in sample # 1, a structure in which the outer peripheral end portion of the first gas diffusion layer 104c is disposed so as to contact the inner peripheral end portion of the seal member 120 on the hydrogen supply side and the air discharge side is desirable.

  In the above-described embodiment, the seal member 120 is described as an example of the structure provided on the side (cathode side) where the first gas diffusion layer 104c is disposed in the outer peripheral portion of the membrane electrode assembly 101. However, the outer peripheral end portion of the second gas diffusion layer 104a is located on the inner side of the outer peripheral end portion of the membrane electrode assembly 101, similarly to the first gas diffusion layer 104c. In the case where the seal member 120 is also provided on the side where the 104a is disposed (the anode side), the gap between the inner peripheral end of the seal member 120 and the outer peripheral end of the first gas diffusion layer 140c. The present invention can be similarly applied to the gap between the inner peripheral end of the seal member 120 and the outer peripheral end of the second gas diffusion layer 104a.

  In the above embodiment, the structure in which the flow direction of the fuel gas flow path is horizontal and the flow direction of the oxidation gas flow path is orthogonal to the vertical direction has been described as an example, but the structures may be reversed. In addition, the fuel gas flow channel and the oxidizing gas flow channel may have the same flow direction in the horizontal direction or the vertical direction. In this case, the flow directions of the fuel gas and the oxidizing gas are also in the same direction. You may face to the direction which mutually opposes.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 5 ... Fuel cell system 10, 10R ... Single cell 20 ... Electrolyte membrane 21 ... End plate 22 ... Insulating plate 23 ... Current collecting plate 24 ... Tension rod 25 ... Nut 26 ... Control part 27 ... Drive part 40 ... Air compressor 41 ... Oxidation Gas supply path 43 ... Refrigerant circulation path 45 ... Radiator 46 ... Refrigerant circulation pump 47 ... Refrigerant circulation path 48 ... Cathode exhaust gas path 50 ... Hydrogen tank 51 ... Pressure reducing valve 52 ... Pressure adjustment valve 53 ... Hydrogen gas supply path 54 ... Anode Exhaust gas path 100... Electrode body 101. Membrane electrode assembly (MEA)
DESCRIPTION OF SYMBOLS 102 ... Electrolyte membrane 103a ... Anode 103c ... Cathode 104a ... 2nd gas diffusion layer 104c ... 1st gas diffusion layer 105a ... 2nd water repellent layer 105c ... 1st water repellent layer 106a ... 2nd gas diffusion layer 106c ... first gas diffusion layer 110a ... second separator 110c ... first separator 116a ... fuel gas channel (channel groove)
116c ... oxidizing gas channel (channel groove)
DESCRIPTION OF SYMBOLS 120 ... Seal member 130 ... Filler 131 ... 1st filling part 131
132 ... second filling portion (exposed portion) 132
200 ... Fuel cell S ... Space M ... Gap

Claims (2)

A cell structure of a fuel cell,
A rectangular electrode assembly comprising a rectangular membrane electrode assembly and rectangular first and second gas diffusion layers arranged on both sides of the membrane electrode assembly, wherein the first gas The diffusion layer has a smaller area than the second gas diffusion layer, and the outer periphery of the first gas diffusion layer is smaller than the outer periphery of the membrane electrode assembly and the outer periphery of the second gas diffusion layer. An electrode body located inside;
A sealing member having a rectangular opening, the sealing member covering the outer periphery of the first gas diffusion layer by disposing the first gas diffusion layer in the opening;
A filler filled between an outer peripheral end of the first gas diffusion layer and an inner peripheral end of the seal member;
A first separator having an oxidizing gas flow path disposed on the surface of the sealing member and on the surface of the first gas diffusion layer and flowing an oxidizing gas along the surface of the first gas diffusion layer;
A second separator disposed on a surface of the seal member and a surface of the second gas diffusion layer, and having a fuel gas flow path for flowing a fuel gas along the surface of the second gas diffusion layer;
The fuel gas supply port for supplying the fuel gas from the outside to the fuel gas flow path, on the outer peripheral side of the first side of the electrode body;
The fuel gas exhaust port for exhausting the fuel gas from the fuel gas flow path to the outside, on the outer peripheral side of the second side facing the first side;
With
The electrode body has an interval between the first outer peripheral end of the first gas diffusion layer located on the fuel gas supply port side and the first inner peripheral end of the seal member. It arrange | positions so that it may become smaller than the space | interval between the 2nd outer peripheral edge part of the said 1st gas diffusion layer located in the gas discharge port side, and the 2nd inner peripheral edge part of the said sealing member. A cell structure of a fuel cell. The cell structure of the fuel cell according to claim 1, further comprising:
The oxidizing gas supply port for supplying the oxidizing gas from the outside to the oxidizing gas channel, on the outer peripheral side of a third side perpendicular to the first side of the electrode body;
The oxidizing gas exhaust port for exhausting the oxidizing gas from the oxidizing gas flow path to the outside, disposed on the outer peripheral side of the fourth side facing the third side;
With
The electrode body has an interval between a third outer peripheral end portion of the first gas diffusion layer located on the oxidizing gas discharge port side and a third inner peripheral end portion of the seal member. It arrange | positions so that it may become larger than the space | interval between the 4th outer peripheral end part of the said 4th gas diffusion layer located in the gas supply port side, and the 4th inner peripheral end part of the said sealing member. A cell structure of a fuel cell.

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