JP7040303B2 - Fuel cell - Google Patents

Description

The present invention relates to a fuel cell having an adhesive layer.

As a fuel cell of this type, any one of a membrane electrode assembly in which an electrolyte membrane is sandwiched between a cathode side catalyst layer and an anode side catalyst layer, and a cathode side diffusion layer and an anode side diffusion layer in which a membrane electrode assembly is sandwiched. One diffusion layer formed to be smaller than the electrolyte membrane is disclosed (see Patent Document 1). This fuel cell is further outside the outer peripheral end face of one of the smaller diffusion layers, and is a stack of an electrolyte film, a cathode side catalyst layer, an anode side catalyst layer, a cathode side diffusion layer, and an anode side diffusion layer. An adhesive layer as a support layer is provided between the sealing member arranged at a position corresponding to the electrolyte membrane in the direction and the outer peripheral end surface of the sealing member and one of the small diffusion layers.

JP-A-2017-126448

However, in the fuel cell described in Patent Document 1, a gap is likely to be formed between the adhesive layer and any of the catalyst layers in manufacturing. When such a gap is formed, the membrane electrode assembly at the position corresponding to the gap is exposed. Since the thin membrane electrode assembly is not supported in the exposed part, when stress is concentrated during repeated operation and rest, the membrane electrode assembly may tear or the membrane (bond) may be invaded by water or water vapor. There is a problem that it swells and contracts and breaks due to fatigue.

The present invention has been made to solve such a problem. By making it difficult to expose the membrane electrode assembly, it prevents stress concentration, makes it difficult for water to enter, and tears the membrane of the membrane electrode assembly. The challenge is to provide a fuel cell that is unlikely to occur.

The fuel cell according to the present invention sandwiches a membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of catalyst layers consisting of a cathode side and an anode side, and the membrane electrode assembly, and one diffusion layer is the membrane electrode assembly. A pair of diffusion layers consisting of a cathode side and an anode side smaller than the body, and a resin sheet having an end facing the end of the one diffusion layer smaller than the membrane electrode assembly are provided, and the diffusion of the one. A fuel cell having an adhesive layer between the end of the layer and the end of the resin sheet, and the end of any one of the pair of catalyst layers is the diffusion layer of the one. It is located inside in the plane direction from the end portion, and is characterized by having a region where the adhesive layer and the one catalyst layer overlap between the stacking directions of the pair of diffusion layers.

The fuel cell according to the present invention faces a membrane electrode assembly, a pair of diffusion layers having a cathode side and an anode side in which one diffusion layer is smaller than the membrane electrode assembly, and the end of one diffusion layer. A resin sheet having an end portion is provided, and an adhesive layer is provided between the end portion of one diffusion layer and the end portion of the resin sheet, and the end portion of one catalyst layer is from the end portion of one diffusion layer. Is also located inside in the plane direction, and has a region where the adhesive layer and one catalyst layer overlap between the stacking directions of the pair of diffusion layers. With this configuration, it becomes difficult to form a gap between the adhesive layer and one of the catalyst layers, and it becomes difficult to expose the membrane electrode assembly. As a result, the membrane electrode assembly is less likely to tear when stress is concentrated, and the membrane electrode assembly swells and contracts due to the intrusion of water generated in the fuel cell, resulting in fatigue fracture.

According to the present invention, by making the membrane electrode assembly difficult to expose, it is possible to provide a fuel cell in which the membrane tearing of the membrane electrode assembly is unlikely to occur due to stress concentration or water infiltration.

FIG. 3 is a partial cross-sectional view of a fuel cell according to an embodiment of the present invention. The process diagram which shows the bonding process of the fuel cell which concerns on embodiment of this invention. It is a partial cross-sectional view of the fuel cell according to the embodiment of the present invention, FIG. 3A shows a state in which MEA is set, and FIG. 3B shows an adhesive applied to an end portion of MEA. A state is shown, FIG. 3C shows a state in which a resin sheet is installed, and FIG. 3D shows a state in which a cathode side gas diffusion layer is installed. Partial cross-sectional view of a conventional fuel cell.

The fuel cell 10 according to the embodiment to which the fuel cell according to the present invention is applied will be described with reference to the drawings.

As shown in FIG. 1, the fuel cell 10 has a membrane electrode assembly (MEA: Membrane Electrode Assembly, hereinafter referred to as MEA) 11 and a cathode side gas diffusion layer (GDL: Gas Diffusion Layer, hereinafter referred to as GDL) 12. It is composed of an anode side GDL 13, a resin sheet 14, an adhesive layer 15, a cathode side separator 16, and an anode side separator 17. The cathode side GDL 12 and the anode side GDL 13 according to the present embodiment correspond to a pair of diffusion layers in the fuel cell according to the present invention.

The MEA 11 is composed of a bonded body of an electrolyte membrane 21, a cathode side catalyst layer 22, and an anode side catalyst layer 23. The electrolyte membrane 21 is made of a polyelectrolyte resin which is a solid polymer material such as perfluorosulfonic acid (PFSA) ionomer, and is composed of an ion exchange membrane using a polymer membrane having ionic conductivity as an electrolyte. The electrolyte membrane 21 has a function of blocking the flow of electrons and gas and transferring protons from the anode-side catalyst layer 23 to the cathode-side catalyst layer 22.

The catalyst layer 22 on the cathode side is made of a conductive carrier carrying a catalyst such as platinum or a platinum alloy. For example, an electrode formed by coating carbon particles such as catalyst-supported carbon particles with an ionomer having proton conductivity. It consists of a catalyst layer. The ionomer is made of a polyelectrolyte resin which is a solid polymer material such as a fluororesin having the same quality as the electrolyte membrane, and has proton conductivity due to its ion exchange group. The cathode-side catalyst layer 22 has a function of generating water from protons, electrons, and oxygen. The end portion 22a of the cathode side catalyst layer 22 is located inside the end portion 12a of the cathode side GDL 12 in the plane direction, that is, on the right side of the paper surface of FIG.

The anode-side catalyst layer 23 is made of the same material as the cathode-side catalyst layer 22, but unlike the cathode-side catalyst layer 22, it has a function of decomposing hydrogen gas (H ₂ ) into protons and electrons. .. The cathode side catalyst layer 22 and the anode side catalyst layer 23 according to the present embodiment correspond to a pair of catalyst layers in the fuel cell according to the present invention.

The cathode side GDL 12 is formed of a material having gas permeability and conductivity, for example, a carbon fiber such as carbon paper or a porous fiber base material such as graphite fiber. The cathode side GDL 12 is bonded to the outside of the cathode side catalyst layer 22, and has a function of diffusing air as an oxidant gas to make it uniform and spreading it to the cathode side catalyst layer 22. The cathode side GDL 12 is formed smaller than the MEA 11, and the end portion 12a of the cathode side GDL 12 is located on the right side of the paper surface of FIG. 1 with respect to the end portion 11a of the MEA 11.

The cathode side GDL 12 has a microporous layer (MPL: Micro Porous Layer, hereinafter referred to as MPL) 12b formed on the cathode side catalyst layer 22 side. The MPL12b is made of a so-called MPL paste, specifically, a coating thin film containing a water-repellent resin such as polytetrafluoroethylene (PTFE) and a conductive material such as carbon black as main components. The MPL 12b has a function of circulating hydrogen (H) gas, a function of retaining a larger amount of water (H ₂ O) in the electrolyte membrane 21, and a function of efficiently discharging excess water in the MEA 11.

Like the cathode side GDL 12, the anode side GDL 13 is formed of a material having gas permeability and conductivity, for example, a carbon fiber such as carbon paper or a porous fiber base material such as graphite fiber. The anode-side GDL 13 is bonded to the outside of the anode-side catalyst layer 23, and has a function of diffusing hydrogen gas as a fuel gas to make it uniform and spreading it to the anode-side catalyst layer 23. The anode-side GDL13 has an MPL13a made of MPL paste, like the cathode-side GDL12.

The resin sheet 14 is made of synthetic resin, is formed in a frame shape, and is bonded to the electrolyte membrane 21. The resin sheet 14 prevents so-called cross leaks and electrical short circuits between catalyst electrodes, in which hydrogen gas (H ₂ ) at the fuel electrode and oxygen gas (O ₂ ) at the air electrode pass through the electrolyte membrane in a small amount. Has a function for.

The adhesive layer 15 is made of a liquid adhesive member having higher rigidity and higher elasticity than the electrolyte membrane 21. Examples of the liquid adhesive member include an adhesive made of an epoxy resin. The adhesive layer 15 is formed between the end portion 12a of the cathode side GDL 12 and the end portion 14a of the resin sheet 14, between the cathode side GDL 12 and the cathode side catalyst layer 22 in the stacking direction, and the resin in the stacking direction through the bonding step described later. It is formed between the sheet 14 and the electrolyte membrane 21.

The cathode side separator 16 is formed of a metal plate such as an iron steel plate, a stainless steel plate, and an aluminum plate. The cathode side separator 16 is bonded to the cathode side GDL 12 and the resin sheet 14, and an oxidant gas flow path 16a through which air as an oxidant gas flows is formed along the surface of the cathode side GDL 12. A titanium (Ti) thin film is formed on the surface of the cathode side separator 16, and a carbon layer is formed on the titanium thin film.

Like the cathode side separator 16, the anode side separator 17 is formed of a metal plate such as an iron steel plate, a stainless steel plate, and an aluminum plate. The anode-side separator 17 is bonded to the anode-side GDL 13 and the resin sheet 14, and a fuel gas flow path 17a through which hydrogen as a fuel gas flows is formed along the surface of the anode-side GDL 13. Similar to the surface of the cathode side separator 16, a titanium (Ti) thin film is formed on the surface of the anode side separator 17, and a carbon layer is formed on the titanium thin film.

Next, the bonding process of the adhesive layer 15 of the fuel cell 10 will be described with reference to the drawings.

As shown in FIG. 2, the bonding step of the adhesive layer 15 includes a step of setting the MEA, a step of applying an adhesive to the MEA, a step of installing a resin sheet, and a step of installing a diffusion layer. It is composed of. Each step is performed in sequence.

In the step of setting the MEA, as shown in FIG. 3A, the MEA 11 and the anode-side GDL 13 are set on a mounting table such as a table (not shown) (step S1). The anode-side GDL 13 is located on the side in contact with the mounting table, and the previously small cathode-side catalyst layer 22 of the MEA 11 is located on the upper side.

In the step of applying the adhesive to the MEA, as shown in FIG. 3B, the outer peripheral portion of the cathode side catalyst layer 22 and the electrolyte film 21 including the end portion 22a of the cathode side catalyst layer 22 constituting the MEA 11 is covered. The adhesive is applied to form the adhesive layer 15 (step S2). The adhesive layer 15 overlaps with the outer peripheral portion of the cathode side catalyst layer 22 within a predetermined range.

In the step of installing the resin sheet 14, as shown in FIG. 3C, the region inside from the end 14a of the resin sheet 14 and the region inside from the end 13b of the anode side GDL 13 overlap each other. In addition, the resin sheet 14 is installed on the coated adhesive layer 15 (step S3). As a result, the adhesive layer 15 has a region 15b that overlaps with the resin sheet 14 in the stacking direction. If it is necessary to cure the adhesive, it may be cured in this step.

In the step of installing the diffusion layer, as shown in FIG. 3D, the end portion 14a of the resin sheet 14 and the end portion 12a of the cathode side GDL 12 are at positions facing each other with a gap L1 and the cathode. The cathode side GDL 12 is installed at a position where the distance between the end portion 12a of the side GDL 12 and the end portion 22a of the cathode side catalyst layer 22 is L2. In this case, the adhesive layer 15 may protrude.

By this installation, the adhesive layer 15 overlaps with the cathode side GDL 12, and further, the adhesive layer 15 has a region 15a overlapping with the cathode side catalyst layer 22 between the cathode side GDL 12 and the anode side GDL 13 in the stacking direction. There is. If it is necessary to cure the adhesive, it may be cured in this step.

The effect of the fuel cell 10 according to the embodiment configured as described above will be described.

The fuel cell 10 according to the present embodiment has a membrane electrode assembly 11, a cathode side GDL 12 smaller than the membrane electrode assembly 11, an anode side GDL 13, and an end portion 14a facing the end portion 12a of the cathode side GDL 12. It is provided with a resin sheet 14 having a cathode. The fuel cell 10 further has an adhesive layer 15 between the end portion 12a of the cathode side GDL 12 and the end portion 14a of the resin sheet 14, and the end portion 22a of the cathode side catalyst layer 22 is the end of the cathode side GDL 12. The adhesive layer 15 is located inside the portion 12a in the plane direction, is between the cathode side GDL 12 and the anode side GDL 13, and is between the cathode side GDL 12 and the cathode side catalyst layer 22 in the stacking direction. It has a region 15a that overlaps with the side catalyst layer 22.

With this configuration, since the adhesive layer 15 has a region 15a that overlaps with the cathode side catalyst layer 22, it becomes difficult to form a gap between the adhesive layer 15 and the cathode side catalyst layer 22, and the membrane electrode assembly 11 is exposed. The effect of making it difficult to do is obtained. As a result, the membrane electrode assembly 11 is less likely to swell and contract due to the tearing of the membrane electrode assembly when stress is concentrated and the intrusion of water generated in the fuel cell 10, resulting in fatigue fracture. Therefore, contact with the cathode side catalyst layer 22 or the anode side catalyst layer 23 of the invading water is unlikely to cause cracks between the membrane electrode assembly 11 and the cathode side catalyst layer 22 or the anode side catalyst layer 23. The effect of becoming is obtained.

The fuel cell 10 according to the present embodiment has an effect that the problem in the structure of the conventional fuel cell 100 shown in FIG. 4 can be solved.

The conventional fuel cell 100 includes a MEA 111, a cathode side GDL 112 having MPL 112a, an anode side GDL 113 having MPL 113a, a resin sheet 114, an adhesive layer 115, a cathode side separator 116, and an anode side separator 117. Has been done.

The conventional fuel cell 100 is manufactured by the first method or the second method. In the first method, first, an adhesive is applied to a portion where the resin sheet 114 and the MEA 111 are bonded, and the resin sheet 114 and the MEA 111 are bonded to each other. After that, the adhesive is filled in the gap between the resin sheet 114 and the cathode side GDL 112. In the second method, first, the adhesive is applied to the end portion of the MEA 111, and the resin sheet 114 and the cathode side GDL 112 are placed on the end portion to which the adhesive is applied.

In the first method, there are a plurality of steps, and the work of filling the narrow gap between the resin sheet 114 and the MEA 111 with the liquid adhesive is a relatively time-consuming work, and is used to fabricate the fuel cell 100. There is a problem that it takes time.

Further, in the second method, the adhesive can be applied once, which simplifies the process. However, regardless of whether the adhesive is installed from the resin sheet 114 or the cathode side GDL 112, the cathode side GDL 112 and MEA 111 are configured. Adhesive enters between the cathode side catalyst layer 122 and (a), or a gap is formed between the end of the adhesive layer 115 and the cathode side GDL 112 (b).

In the case of (a), since the surface of the MPL112a of the cathode side catalyst layer 122 and the cathode side GDL112 in contact with the adhesive is generally rough, the adhesiveness between the adhesive and the cathode side GDL112 and MEA111 is poor, and the cathode side. There is a problem that the cathode side GDL 112 and MEA 111 are peeled off from the adhesive when stress is generated in the portion of the catalyst layer 122 and the cathode side GDL 112. If the cathode side GDL112 or MEA111 is peeled off from the adhesive, there is a problem that the MEA111 becomes a single member and is easily torn.

In the case of (b), there is a problem that the MEA 111 is exposed without being covered with either the adhesive or the cathode side catalyst layer 122. In this case as well, there is a problem that the MEA111 becomes a single member and is easily torn. Further, since the MEA111 is exposed and the humidity of the outside air changes during power generation of the fuel cell composed of the fuel cell 100 in an unrestrained state, the MEA111 swells and contracts due to the intrusion of water or water vapor. There is a problem that MEA111 may tear.

The fuel cell 10 according to the present embodiment has an effect that each of the above problems in the structure of the conventional fuel cell 100 can be solved.

In the fuel cell 10 according to the present embodiment, there is a case where the adhesive layer 15 has a region 15a between the cathode side GDL 12 and the cathode side catalyst layer 22 so as to overlap with the cathode side catalyst layer 22. explained. In this case, the cathode side GDL 12, the adhesive layer 15, the cathode side catalyst layer 22, and the electrolyte membrane 21 are laminated in this order.

However, the fuel cell according to the present invention may have a structure other than the structure of the fuel cell 10 according to the embodiment. That is, the structure may be configured such that the adhesive layer 15 has a region 15a overlapping the cathode side catalyst layer 22 between the cathode side catalyst layer 22 and the electrolyte membrane 21. In this case, the cathode side GDL 12, the cathode side catalyst layer 22, the adhesive layer 15, and the electrolyte membrane 21 are laminated in this order.

Further, in the fuel cell 10 according to the present embodiment, as shown in FIG. 1, the cathode side separator 16, the cathode side GDL 12, the cathode side catalyst layer 22, the electrolyte film 21, and the anode side catalyst layer 23 are viewed from above the paper surface. , The case where the structure is configured in which the anode side GDL 13 and the anode side separator 17 are laminated in this order has been described.

However, the fuel cell according to the present invention may have a structure other than the structure of the fuel cell 10 according to the embodiment. That is, from the top of the paper, the anode-side separator 17 is replaced with the cathode-side separator 16, the anode-side GDL13 is replaced with the cathode-side GDL12, the anode-side catalyst layer 23 is replaced with the cathode-side catalyst layer 22, the anode-side catalyst is replaced with the anode-side catalyst. The layer 23 may be replaced with the cathode side catalyst layer 22, the anode side GDL 13 may be replaced with the cathode side GDL 12, and the anode side separator 17 may be replaced with the cathode side separator 16.

In this case, the anode-side GDL 13 is formed smaller than the MEA 11, and the end portion of the anode-side catalyst layer 23 is located inside the end portion 13b of the anode-side GDL 13 in the planar direction. Further, between the stacking direction of the anode side GDL 12 and the anode side catalyst layer 23, the adhesive layer 15 has a region 15a overlapping with the anode side catalyst layer 23. Also in this case, the same effect as that of the fuel cell 10 according to the embodiment can be obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs are designed without departing from the spirit of the present invention described in the claims. You can make changes.

10 ... Fuel cell, 11 ... MEA (membrane electrode assembly), 11a, 12a, 13b, 14a, 22a ... end, 12 ... cathode side GDL (pair of diffusion layers), 12b , 13a ... MPL, 13 ... Anode side GDL (pair of diffusion layers), 14 ... Resin sheet, 15 ... Adhesive layer, 15a, 15b ... Overlapping region, 16 ... Cathode side Separator, 16a ... Oxidizing agent gas flow path, 17 ... Anode side separator, 17a ... Fuel gas flow path, 21 ... Electrolyte film, 22 ... Cathode side catalyst layer (pair of catalyst layers) , 23 ... Anode side catalyst layer (pair of catalyst layers)

Claims (1)

A membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of catalyst layers consisting of a cathode side and an anode side, and a membrane electrode assembly in which one diffusion layer is smaller than the membrane electrode assembly on the cathode side and the anode side. A resin sheet which is a sealing member having a pair of diffusion layers composed of the same and an end portion facing the end portion of the one diffusion layer smaller than the membrane electrode assembly in a direction parallel to the in-plane of the diffusion layer. A fuel cell having an adhesive layer between the end of the one diffusion layer and the end of the resin sheet.
The end portion of one of the catalyst layers of the pair of catalyst layers is located inside the end portion of the one diffusion layer in the plane direction, and is located between the stacking directions of the pair of diffusion layers. A fuel cell having a region where the adhesive layer and one of the catalyst layers overlap each other.

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