JP2015170398A - Solid-state polymer electrolytic fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer electrolytic fuel battery having excellent durability in which when a polymer electrolyte membrane affecting durability is pinched by a frame body in a single battery module configured by sandwiching a membrane electrode assembly between a pair of separators through a gasket, a sub seal is disposed to prevent further increase of the gap, thereby protecting the polymer electrolyte membrane, and even when the sub seal is additionally disposed, the fastening pressure is not increased, and membrane deterioration caused by direct contact of the polymer electrolyte membrane with gas does not occur.SOLUTION: In order to prevent further increase of a gap when MEA 5 is pinched and held by two frame bodies, a sub seal 7B having small reaction force is disposed between a main seal 7A and the tip portion at the power generation area side of the frame body, thereby achieving a solid polymer electrolytic battery having excellent durability in which membrane deterioration caused by direct contact of the polymer electrolyte membrane with gas does not occur.

Description

  The present invention relates to a solid polymer electrolyte fuel cell, and more particularly to the structure of an electrode-membrane-frame assembly of a fuel cell.

  A solid polymer electrolyte fuel cell (hereinafter sometimes referred to as “PEFC”) uses a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air to react electrochemically. And a device that generates heat at the same time.

  Basic components of the PEFC include a polymer electrolyte membrane that selectively transports hydrogen ions, and an anode electrode and a cathode electrode formed on both sides of the polymer electrolyte membrane. These electrodes have a catalyst layer formed on the surface of the polymer electrolyte membrane, and a gas diffusion layer (GDL) having both air permeability and electronic conductivity disposed outside the catalyst layer. Such an assembly in which the polymer electrolyte membrane and the electrode are integrally joined together is called an electrolyte membrane-electrode assembly (MEA).

  Further, a frame is fitted on the outer edge of the MEA to form an electrode-membrane-frame assembly. On the other hand, on both sides of the MEA, conductive separators are disposed for mechanically sandwiching and fixing the MEAs and electrically connecting adjacent MEAs in series. In the portion of the separator that comes into contact with the MEA, a gas flow path is formed for supplying a reaction gas to each electrode and carrying away generated water and surplus gas. A structure in which an MEA is sandwiched between a pair of separators is referred to as a single battery module (single cell).

  Further, in order to supply the reaction gas to the gas flow path, a manifold hole is provided at the edge of the separator to distribute the reaction gas. Furthermore, the electrode forming part in the MEA, that is, between the pair of separators is surrounded so as to surround the outer periphery of the power generation region so that the reaction gas supplied to the gas flow path does not leak to the outside or mix. A sealing member (gasket) is disposed.

  Incidentally, one of the important issues in PEFC is the improvement of gas utilization efficiency. Factors that reduce the utilization efficiency include gas cross leak, gas external leak, and gas shortcut.

  Specifically, the cross leak is a state as described below. Due to these, the gas utilization efficiency decreases, the PEFC efficiency (power generation efficiency) decreases, and the membrane deteriorates.

  1) A hole is opened in the MEA.

  2) The fuel gas on the anode side passes through the surface of the MEA, wraps around the end of the MEA, and escapes to the cathode side.

  3) The cathode side oxidant gas passes through the surface of the MEA, wraps around the end of the MEA, and escapes to the anode side.

  Gas external leakage means that the sealing and sealing properties cannot be maintained due to problems such as unevenness of the surface in contact with the sealing seal and straddling different materials. Efficiency (power generation efficiency) decreases.

  As for the gas shortcut, the MEA may have a gap between the inner edge of the gasket and the outer edge of the electrode layer due to limitations in processing steps.

  When such a gap exists, fuel gas and oxidant gas leak into the gap during PEFC operation, and the leaked fuel gas and oxidant gas are discharged to the outside with little exposure to the MEA. Will be. As a result, the utilization efficiency of the fuel gas and the oxidant gas is reduced, that is, the PEFC efficiency (power generation efficiency) is reduced.

  In recent years, with the cost reduction, injection molding is often used in the process. However, when direct injection molding is applied to the MEA, excessive heat and pressure are applied, and a hole is opened. It is expected that the durability time will be affected, leading to a decline in durability performance.

  In order to solve such a problem, the electrode-membrane-frame assembly of a conventional solid polymer electrolyte fuel cell is a combination of a frame holding MEA and an elastic gasket material, or two colors A structure that solves the above-mentioned problems and reduces excessive heat and pressure load by direct injection molding to MEA is disclosed by combining products integrated by methods such as molding into MEA integrated products. (For example, refer to Patent Document 1 and Patent Document 2).

  FIG. 15 is a diagram showing an electrode-membrane-frame assembly of a conventional fuel cell described in Patent Document 1. As shown in FIG. FIG. 15 corresponds to FIG.

  In addition, “′” is added to distinguish from the code of the present invention. Further, in FIG. 15, the upper portions are drawn slightly apart from each other for easy viewing.

  In the joined body of Patent Document 1, there are a first frame body 6A ′ and a second frame body 6B ′ separately made of a predetermined resin material, and the first frame body 6A ′ and the second frame body. The polymer electrolyte membrane 5A ′ portion where the catalyst layer 5B is not applied is sandwiched between the bodies 6B ′, and the polymer electrolyte membrane 5A ′ portion where the catalyst layer 5B is not applied between the GDL and the frame is sealed with the membrane The MEA integrated product is configured by blocking with a stopper.

  The MEA integrated product is sandwiched between an anode separator 2 'and a cathode separator 3' to constitute a unit cell 10 '. The first frame 6A 'is provided with a membrane sealing member (main seal 7A') for preventing cross leakage on the side where the polymer electrolyte membrane 5A 'contacts. Further, a structure in which a first frame 6A 'and a separator sealing member 7D' for sealing between the anode separator 2 'and the cathode separator 3' is proposed.

  FIG. 16 is a partially enlarged sectional view of a conventional fuel cell described in Patent Document 2. FIG. 16 corresponds to FIG. Note that “′” is added to distinguish from the code of the present invention.

  In the structure of Patent Document 2, as in Claim 1 of the same document, the outer edge portion 5Ba ′ of the catalyst layer is outside the outer edge portion 5Ca ′ of the GDL 5C ′ and from the center portion of the gasket (main seal 7A ′). Is also provided to be located inside. Further, as described in claim 5 of the same document, if there is a distance of twice or more the thickness of the gasket (main seal 7A ′) between the gasket (main seal 7A ′) and the end of the power generation region. Has been.

  FIG. 17 is a partially enlarged cross-sectional view schematically showing the configuration of the fuel cell according to the eighth embodiment described in Patent Document 2. As shown in FIG. FIG. 17 corresponds to FIG. In addition, “′” is added to distinguish from the code of the present invention.

  In claim 6 of this Patent Document 2, it is described in FIG. 17 that the first frame body 6A, the second frame body 6B and the separators 2 ′ and 3 ′ are fixed with an adhesive 40 in order to bring them into close contact with each other. Yes.

JP 2009-021217 A Japanese Patent No. 5302481

  However, in the conventional configuration of Patent Document 1, the catalyst layer does not exist in a region in contact with the frame. There is an elastic body between the frame directly under the gasket and the polymer electrolyte membrane, and a gap is generated between the frame and the polymer electrolyte membrane. Accordingly, there is a problem that the membrane is deteriorated due to direct gas contact with the polymer electrolyte membrane and the durability is remarkably lowered.

  Moreover, in the said patent document 2, the outer edge part of a catalyst layer is between a gasket and the edge part of an electric power generation area | region, It is disclosed that the width | variety has a distance more than twice the thickness of a gasket, A technique is also disclosed in which the frame and the separator are fixed with an adhesive between the widths and the frame and the separator are in close contact with each other. For this reason, the gasket has a large reaction force for preventing the gas from leaking outside or cross leak, and the electrode side of the frame is opened.

  Also, since the frame is pulled by the separator to the separator, a gap is generated between the frame and the polymer electrolyte membrane, and membrane deterioration occurs due to direct gas contact with the polymer electrolyte membrane, resulting in a significant decrease in durability. The problem also arises.

  The present invention solves the above-described conventional problems, and eliminates a gap between the frame body and the polymer electrolyte membrane without increasing the fastening pressure of the fuel cell module with a simple gasket shape. An object of the present invention is to provide a solid polymer electrolyte fuel cell excellent in durability, in which membrane deterioration due to direct gas contact does not occur.

The solid polymer electrolyte fuel cell of the present invention has the following characteristics.
[1] a polymer electrolyte membrane, a catalyst layer provided on each surface of the polymer electrolyte membrane, a gas diffusion layer provided on the surface of the catalyst layer,
The point which has a pair of frame provided so that the outer periphery of the said polymer electrolyte membrane might be pinched | interposed, and a pair of separator provided on the said gas diffusion layer. In [1],
[2] Of the pair of separators, on the surface on the side where the polymer electrolyte membrane is disposed and on the outer side of the gas diffusion layer, the main seal provided in an annular shape, and the inner edge of the frame Is provided with a sub seal provided on the outer side and on the inner side of the center portion of the main seal.

  As described above, the simple gasket shape of this configuration can eliminate the gap between the frame and the polymer electrolyte membrane without increasing the fastening pressure of the fuel cell module, and the membrane degradation of the polymer electrolyte membrane can be prevented. A solid polymer electrolyte fuel cell which is suppressed and excellent in durability can be provided.

1 is a partially exploded perspective view showing a schematic structure of an electrode-membrane-frame assembly of a solid polymer electrolyte fuel cell according to an embodiment of the present invention. The front view which looked at the electrode-membrane-frame assembly of the polymer electrolyte fuel cell which comprises the cell of FIG. 1 from the anode separator side surface 1 is a front view of the electrode-membrane-frame assembly of the solid polymer electrolyte fuel cell constituting the cell of FIG. 1 as viewed from the cathode separator side surface. FIG. 2 is a partially exploded sectional view of the electrode-membrane-frame assembly in FIG. 2 is a partially exploded cross-sectional view of the electrode-membrane-frame assembly in FIG. The front view which looked at the anode separator of FIG. 1 in Embodiment 1 from the anode side surface The front view which looked at the cathode separator of FIG. 1 in Embodiment 1 from the cathode side surface Partial sectional view taken along the line CC of FIG. 6 in the first embodiment. The front view which looked at the anode separator of FIG. 1 in Embodiment 2 from the anode side surface Partial sectional view taken along arrow DD in FIG. 9 in the second embodiment. Partial sectional view taken along line EE of FIG. 9 in the second embodiment. Partial sectional view taken along arrow E'-E 'in FIG. The front view which looked at the cathode separator of FIG. 1 in Embodiment 2 from the cathode side surface Sectional drawing which cut | disconnected cell 10 in the arrow FF part of the front view which looked at the electrode-membrane-frame assembly of the solid polymer electrolyte fuel cell of FIG. The figure which shows Embodiment 1 of the electrode-membrane-frame assembly of the conventional solid polymer electrolyte fuel cell described in patent document 1 Partially enlarged sectional view of a conventional fuel cell described in Patent Document 2 Partially enlarged sectional view schematically showing the structure of the fuel cell according to the eighth embodiment described in Patent Document 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
Embodiments according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a perspective view schematically showing a part of the structure of the PEFC according to Embodiment 1 of the present invention in an exploded manner.

  2 is a front view of the electrode-membrane-frame assembly 1 viewed from the anode separator 2 side, and FIG. 3 is a front view of the electrode-membrane-frame assembly 1 viewed from the cathode separator 3 side. . 4 is a partial cross-sectional view taken along the line AA in FIG. 2, and FIG. 5 is a cross-sectional view taken along the line BB in FIG. In FIG. 4 and FIG. 5, the right half is slightly disassembled and displayed.

  Further, the following drawings are drawings of a separator member that sandwiches the electrode-membrane-frame assembly 1 from the anode side and the cathode side. That is, FIG. 6 is a front view of the anode separator of FIG. 1 as viewed from the anode side surface, and is a view when the main seal 7A and the sub seal 7B are integrated.

  FIG. 7 is a front view of the cathode separator of FIG. 1 as viewed from the cathode side surface, and is a view when the main seal 7A and the sub seal 7B are integrated.

  As shown in FIG. 1, the PEFC 100 is configured by stacking a plurality of cells (single battery modules) 10. Although not shown, a current collector plate, an insulating plate, and an end plate (end plate) are attached to the outermost cell 10 positioned on both ends of the plurality of stacked cells 10, and the plurality of cells 10 are arranged on both sides. From the above, it is fastened by a fastening bolt and a nut (both not shown) that pass through the bolt hole 4.

  In the first embodiment, 60 cells 10 are stacked and fastened with a fastening force of 10 kN by bolts and nuts inserted through the bolt holes 4. In the first embodiment, a structure in which a plurality of cells 10 are stacked will be described as an example. However, a PEFC may be configured by one cell.

  The cell 10 is configured such that the electrode-membrane-frame assembly 1 is sandwiched between an anode separator 2 and a cathode separator 3 which are a pair of conductive separators. More specifically, gaskets (main seal 7A and sub-seal 7B), which are examples of sealing members, are disposed on both surfaces of the frame 6 positioned at the peripheral edge of the electrode-membrane-frame assembly 1. Thus, the cell 10 is configured by being sandwiched between the pair of separators 2 and 3 (see FIGS. 4 and 5).

  Thereby, the diffusion layer 5C (see FIG. 4) of the membrane electrode assembly (MEA) 5 which is a joined body of the electrode and the electrolyte membrane is in contact with the surfaces of the separators 2 and 3, and the fuel gas flow path of the anode separator 2 The fuel gas flow channel and the oxidant gas flow channel are defined by the diffusion layer contact portion 21A of the groove 21, the diffusion layer contact portion 31A of the oxidant gas flow channel groove 31 of the cathode separator 3, and the respective diffusion layers 5C. Is done.

  As a result, the fuel gas flowing through the diffusion layer abutting portion 21A comes into contact with the diffusion layer 5C on the anode separator 2 side to cause an electrochemical reaction of the PEFC 100. In the stacked cells 10, adjacent MEAs 5 are electrically connected to each other in series or in parallel. A pair of through-holes through which fuel gas and oxidant gas circulate, that is, fuel gas manifold holes 12, 22, and 32, are formed in the frame 6 at the periphery of the separators 2 and 3 and the electrode-membrane-frame assembly 1. In addition, oxidant manifold holes 13, 23, and 33 are provided. In the state where the cells 10 are stacked, these through holes are stacked to form a fuel gas manifold and an oxidant manifold.

  As described above, the fuel gas passage groove 21 is provided on the inner main surface of the anode separator 2 so as to connect the pair of fuel gas manifold holes 22, 22. An oxidant gas passage groove 31 is formed on the inner main surface of the cathode separator 3 so as to connect the pair of oxidant gas manifold holes 33 and 33. That is, the oxidant gas and the fuel gas are branched from the one manifold, that is, the supply-side manifold, to the flow channel grooves 21 and 31, respectively, and flow to the other manifold, that is, the discharge-side manifold. Composed.

  The fuel gas channel groove 21 has a diffusion layer contact portion 21A formed on a surface portion that contacts the diffusion layer 5C in the assembled state of the cell 10 and a pair of connection portions 21B that are communication channel grooves. . The connecting portion 21B is formed so that a portion that contacts the diffusion layer 5C is connected to a portion that faces the periphery of the diffusion layer 5C.

  Similarly, the oxidant gas flow channel groove 31 includes a diffusion layer contact portion 31A formed on a surface portion that contacts the diffusion layer 5C in the assembled state of the cell 10 and a pair of communication portions that are communication flow channel grooves. 31B. The connecting portion 31B is formed so as to connect between a portion in contact with the diffusion layer 5C and a portion facing the periphery of the diffusion layer 5C. Here, the communication portions 21B and 31B are formed so as to connect the pair of manifold holes 22 and 33 and the diffusion layer contact portions 21A and 31A.

  As a result, the oxidant gas and the fuel gas branch from the supply-side fuel gas manifold hole 22 and the oxidant gas manifold hole 33 to the connecting portions 21B and 31B, respectively, and flow into the connecting portions 21A and 31A, respectively. In contact with each diffusion layer 5C, an electrochemical reaction occurs. The surplus gas and reaction product components are discharged to the exhaust-side fuel gas manifold hole via the connecting portions 21B and 31B connected to the discharge-side fuel gas manifold hole 22 and the oxidant gas manifold hole 33. 22 and the oxidant gas manifold hole 33 are discharged.

  A main seal 7A and a sub-seal 7B are disposed on both main surfaces of the frame 6 of the electrode-membrane-frame assembly 1. The main seal 7A is disposed so that the oxidant gas and the fuel gas do not flow out from the predetermined flow path grooves 21 and 31. That is, the main seal 7A is disposed so as to surround the periphery of the manifold holes 12, 13, and 14 and the periphery of the frame. Here, on the anode separator 2 side, in the assembled state of the cell 10, the main seal 7A and the sub seal 7B are not disposed at the position where the connecting portion 21B of the fuel gas flow channel 21 abuts.

  In addition, a main seal 7A and a sub seal 7B are disposed so that the fuel gas manifold hole 12 and the MEA 5 are integrally surrounded. Similarly, on the cathode separator 3 side (see FIG. 3), in the assembled state of the cell 10, the main seal 7A and the sub seal 7B are disposed at a position P where the connecting portion 31B of the oxidant gas flow channel 31 abuts. Not.

  Further, the main seal 7A prevents the flow of the fuel gas flowing between the fuel gas manifold hole 22 and the MEA 5 and the flow of the oxidizing gas flowing between the oxidant gas manifold hole 33 and the MEA 5 from being disturbed. The fuel gas and the oxidant gas are prevented from leaking out of the fuel gas channel 21 and the oxidant gas channel 31.

  In FIG. 1, the meander structure of the flow grooves 21 and 31 of the diffusion layer contact portions 21A and 31A of the main seal 7A, the sub seal 7B, and the separators 2 and 3 is shown as a schematic configuration.

  In the PEFC 100 of the first embodiment, the case where the manifold holes are formed by the through holes of the separator will be described. Instead of this, the so-called external manifold, that is, the outside of the separator is formed. There is also a configuration with manifolds. From the viewpoint of downsizing the PEFC 100 and simplicity of the external configuration, it is preferable that the manifold is formed by a through hole of the separator.

  Further, two pairs in which water circulates in the peripheral portions of the separators 2 and 3 and the electrode-membrane-frame assembly 1 like the fuel gas manifold holes 12, 22, 32 and the oxidant gas manifold holes 13, 23, 33. Water manifold holes 14, 24, and 34 that form the manifolds are provided. Thus, in the state where the cells 10 are stacked, these manifold holes are stacked to form two pairs of water manifold holes.

  Here, a schematic plan view of the electrode-membrane-frame assembly 1 is shown in FIG. 2, a cross-sectional view taken along the line AA in the electrode-membrane-frame assembly 1 of FIG. 2 is shown in FIG. -B sectional view is shown in FIG. The fuel gas manifold hole 12 in FIG. 5 is drawn slightly smaller. Also, in FIGS. 4 and 5, the right half is drawn slightly apart.

  As shown in FIGS. 4 and 5, the MEA 5 includes a polymer electrolyte membrane 5A that selectively transports hydrogen ions, and a pair of electrode layers 5D (anode and cathode electrodes) formed on both surfaces of the polymer electrolyte membrane 5A. Layer). The electrode layer 5D is mainly composed of carbon powder carrying a platinum catalyst as a main component, and a catalyst layer 5B formed on the surface of the polymer electrolyte membrane 5A, and air permeability and conductivity formed on the outer surface of the catalyst layer 5B. A diffusion layer 5C having both of the above. The catalyst layer 5B may have a two-layer structure of a water repellent carbon layer and a platinum carbon layer (not shown).

  The anode separator 2 and the cathode separator 3 have a flat plate shape, and the surface in contact with the electrode-membrane-frame assembly 1, that is, the inner surface is more specifically the shape of the electrode-membrane-frame assembly 1. Has steps 2a and 3a so that the central portion protrudes in a trapezoidal shape according to the step generated by the difference between the thickness of the frame 6 and the thickness of the MEA 5.

  That is, the thickness of the frame body 6 is larger than the total thickness of the polymer electrolyte membrane 5A, the catalyst layer 5B, and the diffusion layer 5C, and thus a step is formed. 3a is attached, but it is not completely fitted, and a gap remains as shown in the left part of FIG. Gaskets (main seal 7A, sub seal 7B) are sandwiched between the gaps.

  Here, for example, glassy carbon (thickness 3 mm) manufactured by Tokai Carbon Co., Ltd. is used for the anode separator 2 and the cathode separator 3. In the separators 2 and 3, various manifold holes 22, 23, 32, 33, 34 and bolt holes 4 penetrate through the separators 2 and 3 in the thickness direction.

  A fuel gas channel groove 21 and an oxidant gas channel 31 are formed on the inner surfaces of the separators 2 and 3, and a water channel groove (not shown) is formed on the back surfaces of the separators 2 and 3. Various manifold holes 22, 23, 24, 32, 33, 34, bolt holes 4, fuel gas flow channel 31, water flow channel 50 and the like are formed by cutting or molding.

  Here, the water channel groove is formed so as to connect the two pairs of water manifold holes 24 and 34. That is, each of the water branches from one manifold hole, that is, the supply-side manifold hole, to the water flow channel groove, and flows to the other manifold hole, that is, the drain-side manifold hole. Thereby, the cell 10 can be maintained at a predetermined temperature suitable for the electrochemical reaction by the heat transfer capability of water.

  Similarly to the fuel gas and the oxidant gas, the water supply / discharge passage for cooling is formed without forming the water manifold holes 14, 24, 34 in the peripheral portions of the separators 2, 3 and the electrode-membrane-frame assembly 1. An external manifold structure may be used. Furthermore, the cell 10 may be stacked by inserting a cooling unit in which cooling water circulates between adjacent cells without forming a water flow channel groove on the back of the separators 2 and 3.

  As shown in FIGS. 4 and 5, the frame body 6 includes a first frame body 6A, a second frame body 6B, and third frame bodies 6C, 6C-1, and 6C-2. On the other hand, in the MEA 5, since the size of the polymer electrolyte membrane 5A is larger than the size of the catalyst layer 5B and the diffusion layer 5C formed on both surfaces thereof, only the peripheral portion of the polymer electrolyte membrane 5A is outward. It has a shape that protrudes and is exposed. Then, between the first frame body 6A and the second frame body 6B, the exposed peripheral portion of the polymer electrolyte membrane 5A is disposed and sandwiched between the both frame bodies 6A and 6B. A configuration in which the MEA 5 is held by the frame 6 is realized.

  Further, third frames 6C, 6C-1, and 6C-2 for integrating the first frame body 6A and the second frame body 6B are formed. The third frames 6C, 6C-1, and 6C-2 are welded at the welded portion 15 so as to straddle the joints formed by fitting the second frame 6B. Accordingly, the first frame body 6A, the second frame body 6B, and the third frame bodies 6C, 6C-1, and 6C-2 are mechanically integrated, and the MEA 5 is held.

  The first frame 6A and the second frame 6B are formed in advance by injection molding using a thermoplastic resin material. The relationship between the MEA 5 held by the frames 6A and 6B, the main seal 7A, and the sub seal 7B will be described.

  4 is a partially exploded cross-sectional view of the electrode-membrane-frame assembly of FIG. As shown in the figure, when the MEA 5 is held between two frames, the fuel gas is prevented from passing between the frame and the MEA 5 and the oxidant gas is prevented from escaping to the fuel gas side. There is a need to. Further, since the gas passing between the frame body and the MEA 5 moves through the catalyst layer 5B, the polymer electrolyte membrane 5A portion must be pressed directly under the main seal 7A. The center of the main seal 7A is arranged at a position 3 to 7 mm away from the tip.

  Moreover, since this main seal 7A serves as both for preventing an external leak, the reaction force of a gasket needs 2-10 N / mm. When the cells 10 are stacked, it is assumed that the anode separator 2 and the cathode separator 3 are displaced from each other, and the main seal 7A and the power generation area side of the frame body are not opened so that the tip of the power generation area side of the frame body is not opened. The sub seal 7B is disposed between the tip portions.

  Since the sub seal 7B is only for preventing the frame from opening, the reaction force does not need to be applied as much as the main seal 7A. The main seal 7A must be closed because it is necessary to stop external leakage, but the sub-seal 7B does not need to be closed because the sub seal 7B may be disposed so as not to open the frame. It is desirable that the main seal 7A and the sub seal 7B are partially connected.

  FIG. 4 shows an example in which the reaction rate is lowered by reducing the compression rate.

  FIG. 5 is a cross-sectional view taken along line BB in FIG. 2, which is a front view of the electrode-membrane-frame assembly 1 as viewed from the anode side surface. As shown in FIG. 5, the main seal 7A and the sub-seal 7B cannot be disposed in the flow path portion. Therefore, a rib 8B is raised from the frame body side to receive the reaction force in the portion where the main seal 7A and the sub-seal 7B are present. Can be prevented from opening.

  On the separator, a main seal 7A and a sub seal 7B, which are examples of a sealing member, are arranged. The main seal 7A and the sub seal 7B may or may not be integrated with the first frame 6A and the second frame 6B. Further, it may or may not be integrated with the separator.

  The main seal 7A and the sub seal 7B are made of an elastic body, and are deformed by placing and pressing the electrode-membrane-frame assembly 1 between a pair of separators 2 and 3, and as shown in FIG. The periphery (that is, between the MEA 5 and the separators 2 and 3) and the periphery of the manifold hole are sealed (sealed). Similarly, in the fuel gas manifold hole 12 and the oxidant manifold hole 13, the periphery of each manifold hole is sealed by the main seal 7A.

  Hereinafter, the shapes of the main seal 7A and the sub seal 7B will be described in detail.

  FIG. 6 is a front view of the anode separator of FIG. 1 as viewed from the anode side surface. A composite gasket portion 7 in which a main seal 7A and a sub seal 7B are combined is disposed around a fuel gas passage groove 21A in the power generation area in the figure. The sub seal 7B is not closed because it does not exist in the flow path as shown in the figure.

  FIG. 8 is a partial cross-sectional view taken along the line CC in FIG. 6 in the first embodiment. The height of the main seal 7A is HA, the tip R is RA, the height of the sub seal 7B is HB, and the tip R is RB. Moreover, the following can be said when the dimension of HP is the dimension after compression of the seal.

  An example in which the reaction force of the sub seal 7B is designed to be smaller than the reaction force of the main seal 7A will be described below.

  When HA = HB, the compression ratios are equal, so the reaction force can be reduced by setting RA> RB.

  When HA> HB, the reaction force can be reduced even if RA = RB. However, in this case, if the compression ratio becomes too small, the sub seal 7B may not function due to component tolerance and assembly tolerance. Because there is, attention is necessary.

  The frame body 6 (the first frame body 6A, the second frame body 6B, the third frame bodies 6C, 6C-1, and 6C-2) is formed of a thermoplastic resin. This thermoplastic resin is chemically clean and stable below the operating temperature of PEFC 100, and has a moderate elastic modulus and a relatively high weight deflection temperature.

  For example, when the width of the fuel gas channel 21 and the oxidant gas channel 31 of the separators 2 and 3 is about 1 to 2 mm and the thickness of the frame 6 is about 1 mm or less, the compression elastic modulus of the frame 6 is at least It is preferable that it is 2000 MPa or more. Here, the elastic modulus refers to a compressive elastic modulus measured by a compressive elastic modulus measuring method defined in JIS-K7181.

  Moreover, since the operating temperature of PEFC100 is generally 90 ° C. or lower, the deflection load temperature of the frame 6 is preferably 120 ° C. or higher. The frame 6 is preferably made of a material having high mechanical strength and high heat resistance.

  For example, a so-called super engineering plastic grade is suitable, and examples thereof include modified polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), crystalline polymer (LCP) polyether nitrile (PEN) and the like. .

  These are suitable materials having a compression modulus of several thousand to several tens of thousands of MPa and a deflection load temperature of 120 ° C. or more. Further, even a widely used resin material is not suitable, for example, polypropylene (GFPP) filled with a glass filler because the glass filler may pierce the polymer electrolyte membrane. In the first embodiment, modified PPE (Asahi Kasei Chemicals Corporation Zylon 500H), which is a thermoplastic resin, is used.

  The main seal 7A and the sub seal 7B are made of rubber such as fluoro rubber, EPDM, or AEM, a plastic resin, or a thermoplastic elastomer as an elastic body. The main seal 7A and the sub-seal 7B are chemically stable under the operating conditions of the PEFC 100, and have particularly hot water resistance and acid resistance derived from the polymer electrolyte membrane, such as not causing hydrolysis.

  For example, the compression elastic modulus of the gasket 7 is preferably 200 MPa or less. In the first embodiment, fluororubber is used in order to ensure good sealing performance at the fastening load of PEFC100.

  A general sealing member 9 such as a squeezed packing made of a heat-resistant material is disposed around the various manifold holes on the back surfaces of the anode separator 2 and the cathode separator 3. This prevents the fuel gas, the oxidant gas, and the water from flowing out from the connection portion between the cells 10 of the various manifold holes 22, 23, 24, 32, 33, 34 between the adjacent cells 10.

  Next, the manufacturing method of the electrode-membrane-frame assembly 1 of the first embodiment will be described.

  First, as shown in FIGS. 4 and 5, the catalyst layer 5B is formed on both surfaces of the central portion of the polymer electrolyte membrane 5A while exposing the peripheral edge, that is, not covering it. The end of the catalyst layer 5B is between the electrode side end of the frame and the main seal 7A line. Next, the diffusion layer 5C is formed. Even if the diffusion layer 5C is sandwiched by the frame body 6 and then attached to the catalyst layer 5B formed on the polymer electrolyte membrane 5A, the diffusion layer 5C is not yet sandwiched by the frame body 6. Alternatively, it may be formed by being attached to the catalyst layer 5B.

  Specifically, the catalyst layer 5B is formed as follows, for example. 35 g of water and 59 g of an alcohol dispersion of hydrogen ion conductive polymer electrolyte (9% FSS, manufactured by Asahi Glass Co., Ltd.) are mixed and stirred in 10 g of catalyst powder in which platinum is supported on Ketjen Black EC at a weight ratio of 1: 1. To prepare a catalyst layer ink.

  Next, the catalyst layer 5B is formed by coating and drying the catalyst layer ink to a thickness of 20 μm on both main surfaces of the polymer electrolyte membrane 5A using a general coating technique such as spray coating or screen coating. The Here, a perfluorocarbon sulfonic acid membrane (DUPONT Nafion 117 (registered trademark)) is used for the polymer electrolyte membrane 5A. Further, in the drawing, the structure for accurately disposing and temporarily fixing the polymer electrolyte membrane 5A on the step portion 6D of the first frame 6A is omitted.

  Next, a diffusion layer 5C is formed on the catalyst layer 5B. The diffusion layer 5C is configured by a porous body having a large number of fine pores. As a result, when the fuel gas or the oxidant gas enters the hole, the gas diffuses and easily reaches the catalyst layer 5B.

  In the first embodiment, for example, Carbel CL400 manufactured by Nippon Gore Co., Ltd., having a thickness of 400 μm) is placed on both main surfaces of the polymer electrolyte membrane 5A provided with the catalyst layer 5B. Then, the carbon fiber cloth is hot-pressed to form a diffusion layer 5C on the catalyst layer 5B on both main surfaces of the polymer electrolyte membrane 5A.

  On the other hand, as shown in FIGS. 2 to 5, the first frame 6 </ b> A is formed in advance by injection molding using a thermoplastic resin material. The power generation unit of the MEA 5 is an opening of the first frame 6A. The second frame 6B is also formed in advance by injection molding using a thermoplastic resin material. The power generation unit of the MEA 5 is an opening of the second frame 6B.

  In this way, the MEA 5, the first frame body 6A, and the second frame body 6B are prepared in advance. Then, the peripheral part of MEA5 is arrange | positioned on the step part 6D of 6 A of 1st frames. At that time, the alignment is performed so that the outermost edge of the MEA 5 is disposed outside the gasket line and the rib 8B. At this time, the first frame 6A and the MEA 5 may be temporarily fixed in this state.

  Next, the second frame 6B is fitted to the first frame 6A in which the MEA 5 is disposed. The peripheral edge of the MEA 5 is held between the first and second frame bodies 6A and 6B, and is inserted into a mold for forming the third frame bodies 6C, 6C-1 and 6C-2. The shapes of the frame bodies 6C, 6C-1, and 6C-2 are formed by injection molding, and the electrode-membrane-frame assembly 1 is finally formed. The cell 10 is completed by sandwiching the electrode-membrane-frame assembly 1 between the separators 2 and 3.

(Embodiment 2)
FIG. 9 is a front view of the anode separator of FIG. 1 according to the second embodiment of the present invention as viewed from the anode side surface. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  A composite gasket portion 7 in which the main seal 7A and the sub seal 7B are combined is disposed around the fuel gas passage groove 21A in the power generation area of FIG. As shown in the figure, the sub seal 7B is not closed because it does not exist in the flow path. Further, the sub-seal 7B in the figure is arranged so as not to continue actively in the circumferential direction. Thereby, the part which presses a frame body reduces, and reaction force falls. The range that is not pressed can be set by analysis based on the rigidity of the frame and the reaction force pressed by the sub seal 7B.

  FIG. 10 is a partial cross-sectional view taken along the line DD in FIG. 9 in the second embodiment. As in the first embodiment, the height of the main seal 7A is HA, the tip R is RA, the height of the sub seal 7B is HB, and the tip R is RB. Moreover, the following can be said when the dimension of HP is the dimension after compression of the seal.

  An example in which the reaction force of the sub seal 7B is designed to be smaller than the reaction force of the main seal 7A will be described below.

  When HA = HB, the compression ratios are equal, so the reaction force can be reduced by setting RA> RB.

  When HA> HB, the reaction force can be reduced even when RA = RB, but in this case, if the compression ratio becomes too small, the sub seal 7B does not function due to the tolerance of parts and the tolerance of assembly. There is a need for caution.

  Further, FIGS. 11 and 12 are partial cross-sectional views taken along arrow EE of the portion without the sub seal 7B of FIG. 9 in the second embodiment.

  In FIG. 11, EE and FIG. 12 are E′-E ′.

  In FIG. 11, only the main seal 7A is provided, and there is no shape connecting the sub seal 7B and the main seal 7A. Although it can be said that it is an effective means from the viewpoint of material reduction, the shape becomes more complicated and the formability of the sub seal 7B is affected.

  FIG. 12 shows an example in which the formability is improved by leaving the shape connecting the sub seal 7B and the main seal 7A in consideration of the influence of the formability.

  FIG. 13 is a front view of the cathode separator of FIG. 1 according to the second embodiment as viewed from the cathode side surface. Similar to the anode separator, the main seal 7A is provided around the fuel gas passage groove 31A in the power generation area of FIG. And a composite gasket portion 7 in which the sub seal 7B is combined.

  As shown in FIG. 13, the sub seal 7B is not closed because it does not exist in the flow path. Further, the sub-seal 7B in the figure is arranged so as not to continue actively in the circumferential direction. Thereby, the part which presses a frame body reduces, and reaction force falls. The range that is not pressed can be set by analysis based on the rigidity of the frame and the reaction force pressed by the sub seal 7B.

  14 is a cross-sectional view of the cell 10 taken along the line F-F in the front view of the electrode-membrane-frame assembly of the solid polymer electrolyte fuel cell of FIG. FIG.

  At this time, the sub seal 7B arranged on the anode separator 2 and the sub seal 7B arranged on the cathode separator 3 are arranged so that the non-pressing portions do not overlap. That is, the portion of the frame 6 of the electrode-membrane-frame assembly 1 is always pressed by either the sub seal 7B of the anode separator 2 or the sub seal 7B of the cathode separator 3. Moreover, it is also possible to insert a shape having another purpose, for example, a wrap-around prevention shape or a positioning shape, in a portion without the sub seal 7B.

  In the above-described embodiment, the main seal 7A and the sub seal 7B are integrated. However, the main seal 7A and the sub seal 7B may be independent from each other, that is, the main seal 7A and the sub seal 7B may not be connected. .

  In addition, among the various embodiments described above, any of the embodiments can be combined as appropriate to achieve the respective effects.

  Although the present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, various changes and modifications can be made. Such changes and modifications are to be understood as being included therein, so long as they do not depart from the scope of the present invention according to the appended claims.

  INDUSTRIAL APPLICABILITY The present invention can increase the utilization efficiency of fuel gas and oxidant gas, and can increase the yield in manufacturing, and thus is useful as a fuel cell used in a cogeneration system, an electric vehicle, and the like.

1 Electrode-membrane-frame assembly 2, 2 ′ anode separator 3, 3 ′ cathode separator 4 bolt hole 5 MEA (membrane electrode assembly)
5A Polymer electrolyte membrane 5B Catalyst layer 5C Diffusion layer 5D Electrode layer 6A, 6A ′ First frame 6B, 6B ′ Second frame 6C Third frame 7A ′ Film sealing member 7A Main seal 7B Sub seal 10 cell 10 'cell 15 welded part

Claims (8)

A polymer electrolyte membrane;
A catalyst layer provided on each surface of the polymer electrolyte membrane;
A gas diffusion layer provided on the surface of the catalyst layer;
A pair of frames provided so as to sandwich the outer periphery of the polymer electrolyte membrane;
A pair of separators provided on the gas diffusion layer,
A main seal provided in an annular shape on the surface of the pair of separators on the side where the polymer electrolyte membrane is disposed, and on the outer side of the gas diffusion layer;
A sub seal provided outside the inner edge of the frame and inside the center of the main seal;
A solid polymer electrolyte fuel cell. The solid polymer electrolyte fuel cell according to claim 1, wherein the main seal and the sub-seal are partially connected composite gasket members. 3. The solid polymer electrolyte fuel cell according to claim 1, wherein a maximum height from a bottom surface of the main seal is higher than a maximum height from a bottom surface of the sub seal. The reaction force by which the sub seal pushes the frame is smaller than the reaction force by which the main seal pushes the frame, and the compression rate is small.
The solid polymer electrolyte fuel cell according to any one of claims 1 to 3. The reaction force by which the sub seal part pushes the frame is smaller than the reaction force by which the main seal part pushes the frame, and the sub seal part is configured to be annular and intermittent.
The solid polymer electrolyte fuel cell according to any one of claims 1 to 4. The solid polymer electrolyte fuel cell according to any one of claims 1 to 5, wherein the main seal and the sub seal include a fluorine-based rubber. The solid polymer electrolyte fuel cell according to any one of claims 1 to 6, wherein the separator, the main seal, and the sub-seal are integrally formed joined bodies. The solid polymer electrolyte fuel cell according to any one of claims 1 to 7, wherein the sub seal is disposed only on an edge portion of the polymer electrolyte membrane sandwiched between the frames.

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