JP2017045637A - Membrane electrode assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems of a conventional membrane electrode assembly that the dew condensation water or gas may leak to the outside, and chemical durability of an electrolyte membrane decreases.SOLUTION: A membrane electrode assembly 1 constituting a single cell C of solid polymer includes an electrolyte membrane 2 having anode and cathode electrodes EA, EC, and a frame F integrated with the periphery of the electrolyte membrane 2. The frame F includes a first frame F1 corresponding to the external dimension of the single cell C, and a second frame F2 corresponding only to the peripheral region of the electrolyte membrane 2 and clamping the periphery thereof between the first frame F1. The first frame F1 is thicker than the second frame F2. Consequently, leakage of the dew condensation water or gas to the outside is prevented, and chemical durability of the electrolyte membrane is maintained.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an improvement of a membrane electrode assembly used for a single cell of a polymer electrolyte fuel cell.

  As a conventional membrane electrode assembly, there is one described in Patent Document 1 under the name of a fuel cell. The membrane electrode assembly described in Patent Document 1 has a structure in which an electrolyte membrane made of a solid polymer is sandwiched between an anode side electrode and a cathode side electrode. The electrolyte membrane has an outer peripheral edge extending outward from between both electrodes. And in patent document 1, the structure which provided the protective film which has the same structure in both surfaces of the outer periphery part of an electrolyte membrane, and the structure which provided the reinforcement film in the single side | surface of the outer periphery part of a solid polymer electrolyte membrane Have been described.

JP 2011-165432 A

  However, in the conventional membrane electrode assembly as described above, in the configuration in which the protective film is provided on both surfaces of the outer peripheral edge portion of the electrolyte membrane, for example, dew condensation water generated in the manifold hole portion or gas flowing through the manifold hole is There is a problem in that there is a risk of leakage through the adhesive layer of the protective film. On the other hand, in the configuration in which the reinforcing film is provided on one surface of the outer peripheral edge of the electrolyte membrane, the protective function of the end portion of the electrolyte membrane is lost, and the electrolyte membrane is easily bent, so that a difference in wettability occurs in the electrolyte membrane. There is a problem in that the chemical durability of the electrolyte membrane is lowered due to the movement of additives.

  The present invention has been made in view of the above-described conventional situation, and has a structure in which only the periphery of the electrolyte membrane is sandwiched between two frames, and prevents leakage of condensed water and gas to the outside, An object of the present invention is to provide a membrane electrode assembly capable of maintaining the chemical durability of an electrolyte membrane by protecting the end portion of the electrolyte membrane while preventing bending.

  A membrane electrode assembly according to the present invention is a membrane electrode assembly constituting a single cell of a polymer electrolyte fuel cell, and includes an electrolyte membrane having anode and cathode electrodes, and a frame integrated around the electrolyte membrane. And. The membrane electrode assembly includes a first frame having a size corresponding to the outer dimension of the single cell, and a size corresponding only to a peripheral region of the electrolyte membrane, and between the first frame and the first frame. And a second frame sandwiching the periphery of the electrolyte membrane, wherein the first frame has a thickness larger than the thickness of the second frame.

  The membrane electrode assembly according to the present invention has a structure in which only the periphery of the electrolyte layer is sandwiched between a first frame having a relatively large area and thickness and a second frame having a relatively small area and thickness. Therefore, the entire periphery of the electrolyte membrane is held by the first and second frames while ensuring the strength of the entire frame by the first frame, and the end portions of the electrolyte membrane are covered by both frames. . In this membrane electrode assembly, manifold holes for fluid can be formed in the first frame, and since only the first frame exists in a single layer, the manifold hole portion leaks condensed water and gas. There will be no route.

  In this way, the membrane electrode assembly described above can prevent condensation water and gas from leaking to the outside, and prevents bending while protecting the end portion of the electrolyte membrane, thereby preventing chemical durability of the electrolyte membrane. Sex can be maintained.

It is a top view of the decomposition | disassembly state which shows the single cell provided with the membrane electrode assembly concerning this invention. It is a disassembled perspective view (A) and (B) sectional drawing explaining 1st Embodiment of a membrane electrode assembly. It is sectional drawing (A)-(D) of the principal part explaining 4 examples of an adhesion layer as 2nd Embodiment of a membrane electrode assembly. It is sectional drawing of the single cell explaining 3rd Embodiment of a membrane electrode assembly. It is a disassembled perspective view (A) explaining 4th Embodiment of a membrane electrode assembly, and sectional drawing (B) of the principal part. It is a disassembled perspective view (A) explaining 5th Embodiment of a membrane electrode assembly, and sectional drawing (B) of the principal part. It is a disassembled perspective view (A) explaining 3 examples of a 2nd frame as 6th Embodiment of a membrane electrode assembly, and sectional drawing (B)-(D) of the principal part. It is sectional drawing of the single cell explaining 7th Embodiment of a membrane electrode assembly.

<First Embodiment>
The membrane electrode assembly 1 shown in FIG. 1 is generally called MEA (Membrane Electrode Assembly), and constitutes a single cell C of a polymer electrolyte fuel cell. As shown in FIG. 2, the membrane electrode assembly 1 includes a solid polymer electrolyte membrane 2 having anode and cathode electrodes EA and EC, and a frame F integrated around the electrolyte membrane 2.

  The electrode EA, EC in the membrane electrode assembly 1 is not limited in its configuration, but includes at least the respective catalyst layers CA, CC, and in addition, a gas diffusion layer indicated by phantom lines in FIG. It is a structure in which GA, GC, etc. are laminated. Both electrodes EA, EC are arranged in the center of the electrolyte membrane 2. Thereby, the electrolyte membrane 2 has the outer peripheral area | region 2A extended from both electrodes EA and EC in the perimeter, and the flame | frame F is integrated with the outer peripheral area | region 2A.

  The single cell C in the illustrated example has a rectangular shape and includes the frame F and the membrane electrode assembly 1 and a pair of separators 3 and 4 that sandwich them. In the single cell C, a gas flow path of an anode gas is formed between the frame F and the membrane electrode assembly 1 and one separator 3, and between the frame F and the membrane electrode assembly 1 and the other separator 4. A gas flow path for the cathode gas is formed. The anode gas is a hydrogen-containing gas, and the cathode gas is an oxygen-containing gas (for example, air).

  Each separator 3 and 4 is made of, for example, stainless steel, and is formed into an appropriate shape by press working, and at least a portion corresponding to the membrane electrode assembly 1 is formed in a cross-sectional uneven shape continuous in the long side direction. . Each of the separators 3 and 4 has a corrugated convex portion in contact with the membrane electrode assembly 1 in a portion having an uneven cross-sectional shape, and a gas flow communicating in the long side direction between the corrugated concave portion and the membrane electrode assembly 1. Form a road.

  The frame F and the separators 3 and 4 in the single cell C have manifold holes H1 to H6 that communicate with each other in a stacked state to form a fluid manifold. In the illustrated example, three manifold holes H1 to H3 and H4 to H6 are provided along the short sides on both sides of the single cell C, respectively.

  As an example, the left manifold holes H1 to H3 in FIG. 1 are for cathode gas supply (H1), coolant supply (H2), and anode gas discharge (H3) in order from the top. Moreover, the manifold holes H4 to H6 on the right side in FIG. 1 are for anode gas supply (H4), coolant discharge (H5), and cathode gas discharge (H6) in order from the top. The positional relationship between supply and discharge of the manifold holes H1 to H6 may be partially or entirely reversed.

  As shown by dotted lines in FIG. 2A, the frame F and the separators 3 and 4 in the single cell C are formed with seal line portions SL made of, for example, an adhesive around the outer periphery and the manifold holes H1 to H6. ing. These seal line portions SL prevent a fluid such as a gas from leaking to the outside and prevent other fluids from flowing into each flow path. Therefore, a part of the seal line portion SL arranged around the manifold holes H1 to H6 is opened as an inlet / outlet so that the corresponding fluid can flow through each flow path.

  The frame F is made of a non-conductive member and is made of, for example, resin. In this embodiment, as shown in FIG. 2, the frame F includes a first frame F1 and a second frame F2 made of a resin film. ing. The first frame F1 has a size corresponding to the outer dimension of the single cell C. The second frame F2 has a size corresponding only to the peripheral region of the electrolyte membrane 2, and sandwiches the periphery (the outer peripheral region 2A) of the electrolyte membrane 2 with the first frame F1.

  More specifically, the first frame F1 has a rectangular shape corresponding to the outer shape of the single cell C, and has a rectangular opening K1 serving as a region of the electrolyte membrane 2 at the center, and has short sides on both sides. The manifold holes H1 to H3 and H4 to H6 are formed along the side. The opening K1 of the first frame 1 has a long side dimension a1 and a short side dimension b1 that are smaller than the long side dimension a0 and the short side dimension b0 of the electrolyte membrane 2.

  The second frame F2 has a rectangular shape that is slightly larger than the outer shape of the electrolyte membrane 2, has a certain width including all sides of the electrolyte membrane 2, and has an opening K2 at the center thereof. The opening K2 of the second frame F2 has the same long side dimension a2 and short side dimension b2 as the opening K1 of the first frame F1.

  In the frame F, as shown in FIG. 2B, the first frame F1 has a thickness T1 larger than the thickness T2 of the second frame F2. Both electrodes EA, EC provided on the electrolyte membrane 2 have vertical and horizontal dimensions that are slightly smaller than the openings K1, K2 of the frame F.

  The membrane electrode assembly 1 having the above-described configuration includes only the periphery of the electrolyte membrane 2 with the first frame F1 having a relatively large area and thickness and the second frame F2 having a relatively small area and thickness. It becomes the structure which pinched. Accordingly, the membrane electrode assembly 1 uniformly holds the entire circumference of the electrolyte membrane 2 by the first and second frames F1 and F2 while ensuring the strength of the entire frame F by the first frame F1. . Further, the end portion of the electrolyte membrane 2 is covered with both frames F1 and F2 over the entire circumference (a state where an edge cap is formed).

  As described above, the membrane electrode assembly 1 has fluid manifold holes H1 to H6 formed in the first frame F1, and the manifold holes H1 to H6 are formed of a single layer only in the first frame F1. Because it exists, there will be no leakage of condensed water or gas. Thereby, the membrane electrode assembly 1 can prevent the situation where the dew condensation water produced in the manifold holes H1 to H6 and the gas flowing through the manifold holes H1 to H6 leak to the outside.

  Further, since the membrane electrode assembly 1 covers and uniformly holds the entire circumference of the electrolyte membrane 2 by the both frames F1, F2, it is possible to prevent bending while protecting the end portion of the electrolyte membrane 2. 2 can suppress the difference in wetting and the movement of the additive, and can maintain the chemical durability and chemical durability of the electrolyte membrane 2 well.

  3-8 is a figure explaining the 2nd-7th embodiment of the membrane electrode assembly concerning this invention. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

Second Embodiment
FIG. 3 is a view for explaining four examples of adhesive layers in the membrane electrode assembly according to the present invention.
That is, in the membrane electrode assembly 1, as shown in FIG. 3A, at least the second frame F2 of the first and second frames F1, F2 bonds the electrolyte membrane 2 and the frames F, F2 to each other. It has the adhesive layer B to do.

  The membrane electrode assembly 1 can obtain the same operation and effect as the previous embodiment, and can reliably protect the end of the electrolyte membrane 2 with the minimum amount of adhesive material. In addition, the bonding work is easy. Thereby, shortening of manufacturing time and reduction of manufacturing cost can be realized.

  In addition, as shown in FIG. 3B, the membrane electrode assembly 1 has at least the first frame F1 of the first and second frames F1 and F2 bonded to the electrolyte membrane 1 and the frames F1 and F2. It has the adhesive layer B to do.

  The membrane electrode assembly 1 can obtain the same operations and effects as those of the previous embodiment, and can improve the gas sealing property and reduce the gas flow rate that does not contribute to the reaction. It can contribute to improvement.

  Further, as shown in FIG. 3C, the membrane electrode assembly 1 may be configured to have an adhesive layer B on both the first and second frames F1 and F2, or as shown in FIG. The adhesive layer B may be provided on the entire surface of the first frame F1.

  In the membrane electrode assembly 1 described above, the same actions and effects as in the previous embodiment can be obtained, and further improvement in gas sealing performance and further reduction in gas flow rate that does not contribute to the reaction can be realized. If the adhesive layer B is provided on the entire surface of the first frame F1, it is possible to perform bonding with a separator (not shown) at the same time.

<Third Embodiment>
The membrane electrode assembly 1 shown in FIG. 4 constitutes a single cell C together with a pair of separators 3 and 4 sandwiching the membrane electrode assembly 1. The membrane electrode assembly 1 forms an anode gas flow channel Fa with the upper anode side separator 3 in the figure, and forms a cathode gas flow channel Fc with the lower cathode side separator 4 in the figure. To do.

  In the membrane electrode assembly 1 of this embodiment, the first frame F is disposed on the anode electrode EA side (upper side in the drawing) of the electrolyte membrane 2. The single cell C provided with the membrane electrode assembly 1 has a thickness on the cathode side where the supply amount of gas is larger than that on the anode side by disposing the first frame F1 having a relatively large thickness on the anode side. The second frame F2 having a relatively small is disposed.

  As a result, in the single cell C provided with the membrane electrode assembly 1, the gas is distributed particularly in the frame F portion, that is, between the manifold holes H 1 to H 6 and the membrane electrode assembly 1 in the cathode-side flow path Fc. In this part, the pressure loss of the circulating gas can be minimized, and as a result, the power generation performance can be improved. The manifold holes H1 to H6 shown in FIG. 4 communicate with the manifold holes (not shown) on the separators 3 and 4 side, and the airtightness is maintained by the seal line part (see FIG. 1). And the cathode gas does not contact each other.

<Fourth embodiment>
In the membrane electrode assembly 1 shown in FIG. 5, the area of the opening K1 of the first frame F1 that is the region of the electrolyte membrane 2 is larger than the area of the opening K2 of the second frame F2. That is, as shown in FIG. 5A, the opening K1 of the first frame F1 has a longer side dimension a1 and a shorter side dimension b1 than the longer side dimension a2 and the shorter side dimension b2 of the second frame F2. Largely formed. In other words, the area of the opening K2 of the second frame F2 is smaller than the area of the opening K1 of the first frame F1.

  In this embodiment, as shown in FIG. 5B, the first frame F is disposed on the anode electrode EA side (the upper side in the drawing) of the electrolyte membrane 2. Further, the cathode-side electrode EC in the illustrated example includes a catalyst layer CC and a gas diffusion layer GC, and the inner peripheral portion of the second frame F2 is sandwiched between the electrolyte membrane 2 and the gas diffusion layer GC. It has become.

  The membrane electrode assembly 1 can obtain the same operations and effects as those of the previous embodiment, and also can reduce the differential pressure of gas generated between the anode-side channel Fa and the cathode-side channel Fb. Can be dealt with.

  That is, when the pressure of the anode side flow passage Fa becomes larger, the membrane electrode assembly 1 in the illustrated example has a cathode side (lower side in the figure) with respect to the load indicated by the arrow in the figure. ), The large deformation of the membrane electrode assembly 2 can be suppressed. Further, the end portion of the catalyst layer CC on the cathode side can be protected, thereby preventing the catalyst layer CC from deteriorating (carbon corrosion). Note that, contrary to the illustrated example, a configuration in which the first frame F1 is disposed on the cathode electrode EC side of the electrolyte membrane 2 is also possible.

<Fifth Embodiment>
The membrane electrode assembly 1 shown in FIG. 6 includes anode and cathode electrodes EA. The EC includes the respective catalyst layers CA and CC, and the area of the catalyst layer (CA) of the electrode (EA) disposed on the first frame F1 side is the catalyst layer of the electrode (EC) disposed on the second frame F2 side. It is larger than the area of (CC).

  More specifically, as shown in FIG. 6A, the membrane electrode assembly 1 has a catalyst layer CA of the cathode side electrode EC having a long side dimension a3 and a short side dimension b3 of the catalyst layer CA of the anode side electrode EA. It is larger than the long side dimension a4 and the short side dimension b4 of CC. In other words, the area of the catalyst layer CC of the electrode EC arranged on the second frame F2 side is smaller than the area of the catalyst layer CA of the electrode EA arranged on the first frame F1 side.

  The membrane electrode assembly 1 can obtain the same operation and effect as those of the previous embodiment, and in particular, can make maximum use of the reaction part of the anode side catalyst layer CA, further improving the power generation performance. Improvements can be made. Further, the end of the cathode catalyst layer CC can be protected to prevent the catalyst layer CC from deteriorating. Note that, contrary to the illustrated example, a configuration in which the first frame F1 is disposed on the cathode electrode EC side of the electrolyte membrane 2 is also possible.

<Sixth Embodiment>
In the membrane electrode assembly 1 shown in FIG. 7, the second frame F2 is formed of a plurality of strip-shaped frame members f1 to f8. In the second frame F2 shown in FIGS. 7A and 7B, two frame members f1 and f2 corresponding to the long side and two frame members f3 and f4 corresponding to the short side are formed in a rectangular frame shape. It is a combination. The second frame F2 shown in FIG. 7C is a combination of two frame members f5 and f6 corresponding to the long side and the short side in a rectangular frame shape. The second frame F2 shown in FIG. 7D is a combination of two frame members f7 and f8 corresponding to the short side and half of both long sides in a rectangular frame shape.

  The membrane electrode assembly 1 can realize a reduction in the yield and cost of the frame material as compared with the case where the opening is formed by cutting out one frame material, and the frame members f1 to f8 can be reduced. Since handling is easy, assembly workability improves. The configuration of the second frame F2 is not limited to the above embodiment, and the shape and number of frame members can be selected as appropriate.

<Seventh embodiment>
A single cell C shown in FIG. 8 includes a frame F and a membrane electrode assembly 1 and a pair of separators 3 and 4 sandwiching them. The membrane electrode assembly 1 includes electrodes EA and EC on both surfaces of the electrolyte membrane 2, and each of the electrodes EA and EC includes a catalyst layer (not shown) and gas diffusion layers GA and GC disposed outside the catalyst layer.

  In the single cell C, the periphery of the electrolyte membrane 2 (outer peripheral region 2A) is sandwiched between the first and second frames F1 and F2 constituting the frame F, and the inner peripheral portion of the frame F is connected to the anode side and the cathode. The gas diffusion layers GA and GC on the side are sandwiched between the outer peripheral portions.

  Further, the frame F is provided with a stepped portion D that accommodates the second frame F2 on the inner peripheral portion of the first frame F1, and has a uniform thickness as a whole. An adhesive layer B having a fixing function and a sealing function is provided.

  A single cell C can be formed by stacking a plurality of single cells C to form a cell stack. At this time, adjacent separators 3 and 4 can be connected to each other by welding W. Further, in the illustrated unit cell C, the electrodes EA, EC and the separators 3, 4 are symmetrical with respect to the electrolyte membrane 2, whereas the first and second frames F 1, F 2 The thickness is different from each other. For this reason, the electrolyte membrane 2 is bent inside the frame F, but the shape of the electrodes EA, EC and the separators 3 and 4 is appropriately changed to make the electrolyte membrane 2 flat without bending. Is also possible.

  In the single cell C, in the membrane electrode assembly 1, it is possible to prevent bending while protecting the end of the electrolyte membrane 2, and to maintain the chemical durability and chemical durability of the electrolyte membrane 2 well. As a result, good power generation performance can be maintained over a long period of time.

  The configuration of the membrane electrode assembly according to the present invention is not limited to the above-described embodiments, and the details of the configurations may be changed as appropriate without departing from the gist of the present invention. Can be combined as appropriate.

  Moreover, in each said embodiment, although the 1st and 2nd frame illustrated the structure which consists of resin films, for example, what was injection-molded as a 1st frame with relatively large thickness, It is also possible to use different materials for the first and second frames. If the first and second frames made of a resin film are used, it is possible to reduce the thickness of a single cell and to reduce the size and weight of a fuel cell including a stack of single cells.

DESCRIPTION OF SYMBOLS 1 Membrane electrode assembly 2 Electrolyte membrane 3 Anode side separator 4 Cathode side separator B Adhesion layer C Single cell CA Anode side catalyst layer CC Cathode side catalyst layer EA Anode electrode EC Cathode electrode F frame F1 1st frame F2 2nd frame f1 f8 Frame member K1 Opening portion of first frame K2 Opening portion of second frame

Claims (8)

A membrane electrode assembly constituting a single cell of a polymer electrolyte fuel cell,
An electrolyte membrane having anode and cathode electrodes, and a frame integrated around the electrolyte membrane,
A first frame having a size corresponding to the outer dimension of the single cell and a size corresponding only to the peripheral region of the electrolyte membrane, and sandwiching the periphery of the electrolyte membrane between the first frame and the first frame. With two frames,
The membrane electrode assembly, wherein the first frame has a thickness larger than the thickness of the second frame.   2. The membrane electrode assembly according to claim 1, wherein at least the second frame of the first and second frames has an adhesive layer that adheres the electrolyte membrane and the frames.   2. The membrane electrode assembly according to claim 1, wherein at least the first frame of the first and second frames has an adhesive layer for bonding the electrolyte membrane and the frames.   The membrane electrode assembly according to any one of claims 1 to 3, wherein the first frame is disposed on the anode electrode side of the electrolyte membrane.   The membrane electrode assembly according to any one of claims 1 to 4, wherein an area of the opening portion of the first frame serving as the electrolyte membrane region is larger than an area of the opening portion of the second frame. The anode and cathode electrodes comprise respective catalyst layers;
6. The membrane electrode assembly according to claim 5, wherein the area of the catalyst layer of the electrode arranged on the first frame side is larger than the area of the catalyst layer of the electrode arranged on the second frame side.   The membrane electrode assembly according to any one of claims 1 to 6, wherein the second frame is formed of a plurality of strip-shaped frame members.   A single cell comprising the membrane electrode assembly according to claim 1 and a pair of separators sandwiching the membrane electrode assembly.

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