JP2023101175A - Fuel battery cell - Google Patents

Abstract

To prevent elution of a medium temperature membrane by liquid water by using a resin sheet to replenish liquid water that flows back through a manifold or outside a stack in a fuel battery cell.SOLUTION: A fuel battery cell has a membrane electrode assembly, a resin sheet for fixing a peripheral part of the membrane electrode assembly, and a pair of separators for sandwiching the resin sheet. The resin sheet has a first opening formed that constitutes a portion of a manifold when the fuel battery cell is stacked. The separators have a second opening formed that constitutes the other portion of the manifold when the fuel battery cell is stacked. The size of the first opening is smaller than the size of the second opening. The resin sheet has an overhang portion that extends inwardly on the edge of the second opening. At least a portion of the overhang portion is formed in a mesh-like shape.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to the technical field of fuel cells having a structure in which a resin sheet is sandwiched between separators.

When applying a power generation membrane with an operating temperature of 100° C. or higher (hereinafter referred to as a "medium temperature membrane") to this type of fuel cell, water cooled and liquefied after the fuel cell system stops operating (hereinafter referred to as such Water in a liquid state is called "liquid water") flows back into the cell from the manifold or piping, the medium-temperature film is eluted. In order to prevent such elution, fuel cells having various structures as described below have been proposed.

That is, a porous water absorption tube is arranged in the oxidant gas communication hole on the outlet side of the fuel cell stack to discharge water to the outside by capillary action and air pressure difference (see Patent Documents 1 and 2). , a porous body arranged so as to block the cross section of the drainage channel (see Patent Document 3), the most downstream part in the flow direction of the fuel gas in the anode side gas channel, and the oxidant gas in the cathode side gas channel provided with a generated water capturing portion for capturing generated water at least one of the most downstream portions in the flow direction (see Patent Document 4), disposed between the gas flow path forming member and the separator, A porous body part of which covers the discharge port, and includes a hydrophilic porous body having a void communicating with the discharge port (see Patent Document 5), or gas on the cathode side A proposal has been made to provide a hydrophilic porous flow path between the diffusion layer and the separator (see Patent Document 6).

JP-A-2001-118596 JP 2009-152217 A JP-A-2005-166545 Japanese Unexamined Patent Application Publication No. 2009-218051 JP-A-2009-277385 JP 2010-015725 A

However, the above patent documents have various technical problems as described below.

That is, according to the knowledge of the inventor of the present application, according to Patent Documents 1 and 2, the number of parts increases. According to Patent Document 3, the pressure loss increases and the number of parts increases. According to Patent Document 4, the separator needs a space for the generated water trapping section. According to Patent Document 5, parts for drainage, flow paths, and space are required, which increases the cost and the number of parts. Alternatively, according to Patent Literature 6, water remains in the vicinity of the membrane or the medium-temperature membrane is eluted by water entering from the manifold, because no devises are made for drainage and water collection.

The present invention has been devised, for example, in view of the above-mentioned technical problems. An object of the present invention is to provide a fuel cell capable of preventing elution of a medium temperature membrane.

In one aspect of the fuel cell according to the present invention, in order to solve the above problems, a membrane electrode assembly, a resin sheet for fixing the peripheral portion of the membrane electrode assembly, and a pair of separators sandwiching the resin sheet are provided. wherein the resin sheet is formed with a first opening that constitutes a part of a manifold when the fuel cells are stacked, and each of the pair of separators is provided with the A second opening is formed that forms another part of the manifold when the fuel cells are stacked, the size of the first opening is smaller than the size of the second opening, and the resin sheet is: At least a portion of the protruding portion has a protruding portion that protrudes from the edge of the second opening to the inside of the second opening due to a difference in size between the first opening and the second opening. is formed in a mesh shape.

According to one aspect of the fuel cell according to the present invention, it is possible to replenish the liquid water flowing back through the outside of the stack and the manifold with the resin sheet. This can prevent or reduce the elution of the intermediate temperature film by the liquid water. Moreover, since the resin sheet is an essential constituent member of the fuel cell, the number of parts is not increased for such water replenishment.

Such functions and effects of the present invention will be made clearer by the embodiments of the invention described below.

1 is a diagram showing a schematic configuration of a fuel cell system according to an embodiment; FIG. It is a figure which shows the structure of the fuel cell which concerns on embodiment. It is the elements on larger scale which expand and show a part of manifold which concerns on embodiment by planarly viewing.

An embodiment of a fuel cell comprising a plurality of fuel cells will be described with reference to FIGS. 1 to 3. FIG.

(Schematic configuration of fuel cell system)
In FIG. 1, a fuel cell system 100 includes a fuel cell stack 30 that generates power through an electrochemical reaction, an oxidizing gas system device 10 that supplies an oxidizing gas to the fuel cell stack 30, and a fuel gas to the fuel cell stack 30. A fuel gas system device 20 for supplying fuel gas, a cooling system device 50 for cooling the fuel cell stack 30 , and a control unit 90 for controlling the fuel cell system 100 are provided.

The fuel cell stack 30 includes a laminate formed by stacking a plurality of fuel cells 31 (see FIG. 2) each having an anode, a cathode, an electrolyte membrane, a separator, and the like. Details of the fuel cell stack 30 will be described later.

The oxidizing gas system equipment 10 includes an air cleaner 11 , an air compressor 12 , a valve 13 , an intake pipe 14 and an exhaust pipe 15 . Air sucked from the air cleaner 11 is compressed by the air compressor 12 and supplied to the cathode of the fuel cell stack 30 as an oxidant gas. Exhaust gas from the cathode (hereinafter also referred to as “cathode offgas” as appropriate) is introduced into the diluter 25 via the exhaust pipe 15 . Incidentally, the intake pipe 14 may be provided with, for example, a dehydrator, a heater, and the like.

The fuel gas system equipment 20 includes a fuel tank 21 , a valve 22 , an intake pipe 23 , an exhaust pipe 24 and a diluter 25 . High-pressure hydrogen stored in the fuel tank 21 is supplied to the anode of the fuel cell stack 30 as fuel gas. The pressure and amount of hydrogen supplied to the fuel cell stack 30 are adjusted by the valve 22, for example. Exhaust gas from the anode (hereinafter also referred to as “anode off-gas” as appropriate) is introduced into a diluter 25 via an exhaust pipe 24 . The diluter 25 dilutes the concentration of hydrogen contained in the anode off-gas by mixing the cathode off-gas and the anode off-gas. The exhaust gas discharged from the diluter 25 is discharged outside the fuel cell system 100 .

The fuel gas system device 20 may be configured to lead the anode off-gas to the intake pipe 23 again and circulate it in the fuel cell stack 30 . Further, the fuel gas system device 20 may have a so-called anode dead end configuration that does not have an anode off-gas discharge path. Alternatively, the oxidant gas system device 10 and the fuel gas system device 20 may each have an off-gas discharge route individually.

The cooling system device 50 includes a radiator 51 , a circulation pump 52 and piping 53 . Cooling water is circulated between the fuel cell stack 30 and the radiator 51 via a pipe 53 by a circulation pump 52 .

Each component described above (for example, the compressor 12 , the valve 13 , the valve 22 , the circulation pump 52 , etc.) is controlled by the control unit 90 . The control unit 90 is configured as a microcomputer internally provided with a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The control unit 90 controls overall operation of the fuel cell system 100, for example, by loading a program stored in ROM into RAM and executing the program.

(Schematic configuration of fuel cell stack)
The configuration of the fuel cell stack 30 will be explained with reference to FIG. The fuel cell stack 30 includes a stack of a plurality of fuel cells 31 each having a membrane electrode assembly (MEA) 61 , a gas diffusion layer 63 , and separators 71 and 72 . The laminate is sandwiched by terminals, insulators and end plates (not shown) from both ends thereof. Note that the fuel cell stack 30 is not limited to a configuration in which a plurality of fuel cells 31 are stacked, and may be configured with a single fuel cell 31 .

The electrolyte membrane-electrode assembly 61 is a part where an electrochemical reaction of the fuel cell takes place, and has an anode, an electrolyte membrane and a cathode (not shown). The anode and cathode are formed by supporting a catalyst on a conductive carrier to form a three-phase interface of catalyst, electrolyte and reaction gas (fuel gas or oxidant gas). The gas diffusion layer 63 serves as a flow path for the reaction gas to be subjected to the electrochemical reaction in the electrolyte membrane-electrode assembly 61, and also collects current.
The structure in which the electrolyte membrane/electrode assembly 61 and the two gas diffusion layers 63 are integrated is called an electrolyte membrane/electrode/gas diffusion layer assembly (Membrane Electrode & Gas Diffusion Layer Assembly: MEGA). .

A sealing portion 62 is provided on the outer periphery of the electrolyte membrane-electrode assembly 61 and the gas diffusion layer 63 in order to ensure the sealing performance of the reactant gas flow path formed by the gas diffusion layer 63 . The seal portion 62 is provided with several through holes as shown. The through holes are also provided in the separators 71 and 72 in the same manner.

The separators 71 and 72 are parts forming a wall surface of the gas diffusion layer 63 which serves as a channel for reaction gas. As described above, the separators 71 and 72 and the seal portion 62 are provided with several through-holes in their outer peripheral portions. By connecting these through-holes, a fuel gas supply manifold 73 and a fuel gas discharge manifold 74 as fuel gas flow paths, an oxidant gas supply manifold 75 and an oxidant gas discharge manifold 76 as oxidant gas flow paths. , and a cooling water supply manifold 77 and a cooling water discharge manifold 78 as cooling water flow paths are formed.

The oxidant gas supplied from the intake pipe 14 of the oxidant gas system device 10 to the oxidant gas supply manifold 75 passes through gas flow paths and holes (not shown) formed inside the separator 72, and passes through the separator 72. It is supplied to the diffusion layer 63 and from the gas diffusion layer 63 to the cathode. Then, the cathode off-gas is discharged from the gas diffusion layer 63 to the oxidizing gas discharge manifold 76 through the holes of the separator 72 and the gas flow paths (not shown) formed inside the separator 72 . is led to the exhaust pipe 15 of the

The fuel gas supplied from the intake pipe 23 of the fuel gas system device 20 to the fuel gas supply manifold 73 passes through the gas flow path and holes (not shown) formed inside the separator 71 to the gas diffusion layer 63. , and from the gas diffusion layer 63 to the anode. Then, the anode off-gas is discharged from the gas diffusion layer 63 to the fuel gas discharge manifold 74 through the holes of the separator 71 and the gas passages (not shown) formed therein, and is discharged from the fuel gas system equipment 20. It is led to tube 24 .

Cooling water supplied from the cooling system device 50 to the cooling water supply manifold 77 is discharged to the cooling water discharge manifold 78 through flow paths (not shown) formed inside the separators 71 and 72, and again, It is guided to the cooling system equipment 50 .

The fuel cell system 100 can operate in a medium temperature range (eg, 100° C. to 200° C.). That is, the operating temperature of the fuel cell stack 30 is 100° C. or higher. In other words, in the present embodiment, the electrolyte membrane-electrode assembly 61 is configured as a "medium temperature membrane" which is a power generation membrane with an operating temperature of 100° C. or higher. During operation of the fuel cell system 100, water is generated on the cathode side of the fuel cell 31 (that is, on the separator 72 side) in the course of the electrochemical reaction. Since the operating temperature of the fuel cell stack 30 is 100° C. or higher, the water produced during the electrochemical reaction is gaseous.

During operation of the fuel cell system 100, water produced during the electrochemical reaction is discharged to the outside of the fuel cell stack 30 as part of the cathode off-gas. On the other hand, when the operation of the fuel cell system 100 is stopped, the water produced in the course of the electrochemical reaction condenses inside the fuel cell stack 30 due to the temperature drop of the fuel cell stack 30. It becomes a liquid, or "liquid water".

For example, if the liquid water in the oxidizing gas discharge manifold 76 flows back into the fuel cell 31, if no countermeasures are taken, the electrolyte membrane-electrode assembly 61, which constitutes an example of the intermediate temperature membrane, There is a risk of deterioration such as elution with liquid water. However, in this embodiment, as will be described in detail below with reference to FIG. This prevents deterioration of the electrode assembly 61 due to liquid water.

That is, in FIG. 3, the inner wall of the oxidizing gas discharge manifold 76 (that is, the inner wall forming the flow path portion) is covered with a resin sheet 80 . This resin sheet 80 forms part of an insulator layer laminated between one fuel cell 31 and another fuel cell 31 in order to prevent short circuits or electrical conduction in the fuel cell stack 30. there is

The resin sheet 80 is formed with a first opening having a height of H1 and a width of W1, which constitutes a part of each of the oxidizing gas discharge manifolds 76 when the fuel cells 31 are stacked. Each of the separators 71 and 72 is formed with a second opening having a height of H2 and a width of W2, which constitutes another part of the oxidizing gas discharge manifold 76 when the fuel cells 31 are stacked. there is Here, the size of the first opening is smaller than the size of the second opening. H2 and W1<W2).

Therefore, due to the difference in size between the first opening and the second opening, the resin sheet 80 protrudes from the inner edge of the second opening to the inside of the second opening, as is apparent in FIG. It has a "protruding part" (a mesh-like part in FIG. 3). Especially in this embodiment, such a "protruding portion" is formed in a mesh shape. Here, the term "mesh" refers to a three-dimensional mesh having fine holes that can capture the liquid water 200 (see polka dots in FIG. 3) that cools and liquefies after the fuel cell system 100 stops operating as described above. It means that it has a typical fine lattice structure. As long as the resin sheet 80 has such a structure, the effects unique to the present invention can be obtained regardless of whether the resin sheet 80 is constructed from an existing resin or a resin that will be developed in the future. Therefore, as far as this is concerned, the type of resin that is the material of the resin sheet 80 and the type of structure do not matter.

As a specific example of the three-dimensional fine lattice structure of the resin sheet 80, a plurality of channel forming elements are continuously arranged along the flow direction of the gas or air, and a mesh channel formed of concave portions and convex portions. have In this case, the forming walls of the concave portion and the convex portion may be configured to have a shape continuously provided with a constant gradient with respect to the XY plane in FIG. Such a resin structure can also be referred to as a "3D fine mesh" or a "3D fine mesh channel" in view of its characteristics. Details of a specific example of such a three-dimensional fine lattice structure are disclosed in, for example, Japanese Patent Application Laid-Open No. 2012-243570 filed by the applicant of the present application. It should be noted that other portions of the resin sheet 80 excluding the above-mentioned "protruding portion" may be similarly formed in a mesh shape, or may be formed in a simple sheet shape exclusively for preventing short circuits or conduction instead of the mesh shape. may be formed.

The resin sheet 80 having the "protruding portion" as described above is used not only for the oxidant gas discharge manifold 76 shown as an example in FIG. The inner walls of various manifolds may be similarly provided.

As explained in detail above, according to the fuel cell according to the above embodiment, the liquid water 200 flowing backward through the outside of the stack and the oxidant gas discharge manifold 76 can be replenished with the mesh-like resin sheet 80 . can. This can prevent or reduce the elution of the electrolyte membrane-electrode assembly 61 by the liquid water 200 . Moreover, since the resin sheet 80 is an essential component in the existing fuel cell as a component for preventing short circuits or electrical conduction, the number of parts does not increase for such water replenishment.

Additional Notes The following additional notes are disclosed with respect to the above-described embodiments.

[Appendix 1]
The fuel cell according to Supplementary Note 1 according to the present invention is a fuel cell having a membrane electrode assembly, a resin sheet for fixing a peripheral portion of the membrane electrode assembly, and a pair of separators sandwiching the resin sheet. The resin sheet is formed with a first opening that constitutes a part of a manifold when the fuel cells are stacked, and the fuel cells are stacked on each of the pair of separators. A second opening is formed which constitutes another part of the manifold when it is closed, the size of the first opening is smaller than the size of the second opening, and the resin sheet and the first opening are formed. Due to the difference in size from the second opening, there is a protruding portion protruding from the edge of the second opening to the inside of the second opening, and at least part of the protruding portion is formed in a mesh shape. It is characterized by being

According to the fuel cell described in Supplementary Note 1, the resin sheet can replenish the liquid water that cools and liquefies after the operation of the fuel cell system is stopped and flows backward through the outside of the stack and the manifold. This can prevent or reduce the elution of the intermediate temperature film by the liquid water. Moreover, since the resin sheet is an essential constituent member of the fuel cell, the number of parts is not increased for such water replenishment.

[Appendix 2]
In the fuel cell according to Appendix 2, at least a part of the protruding portion has a three-dimensional fine lattice structure with fine holes that can capture liquid water by capillary action, and is formed in the mesh shape. The fuel cell according to appendix 1, characterized in that

According to the fuel cell described in Supplementary Note 2, the liquid water condensed inside the fuel cell due to a drop in temperature can be efficiently captured by capillary action due to the fine holes or pores of the resin sheet, and the number of parts is relatively small. It is practically very advantageous from the viewpoint of being reduced and having a simple structure.

[Appendix 3]
The fuel cell according to Appendix 3 is a fuel cell characterized by having the fuel cell according to Appendix 1 or 2 above.

According to the fuel cell described in Supplementary Note 3, the deterioration due to the generation of liquid water in the fuel cell is reduced, the life as a whole is long, the number of parts is relatively reduced, and the structure is relatively simple. It is possible to realize a fuel cell that is excellent in terms of cost.

The present invention can be modified as appropriate without departing from the gist or idea of the invention that can be read from the scope of claims and the entire specification, and fuel cells with such modifications are also included in the technical concept of the present invention. .

DESCRIPTION OF SYMBOLS 10... Oxidant gas system apparatus 11... Air cleaner 12... Compressor 13, 22... Valves 14, 23... Intake pipe 15, 24... Exhaust pipe 20... Fuel gas system apparatus 21... Fuel tank 25... Diluter 30 Fuel cell stack 31 Fuel cell 50 Cooling system equipment 51 Radiator 52 Circulation pump 53 Piping 61 Electrolyte membrane/electrode assembly 62 Sealing part 63 Gas diffusion layer 71, 72 Separator 73 Fuel gas supply manifold 74 Fuel gas discharge manifold 75 Oxidant gas supply manifold 76 Oxidant gas discharge manifold 77 Cooling water supply manifold 78 Cooling Water discharge manifold, 80... resin sheet, 200... liquid water

Claims (1)

A fuel cell comprising a membrane electrode assembly, a resin sheet for fixing a peripheral portion of the membrane electrode assembly, and a pair of separators sandwiching the resin sheet,
The resin sheet is formed with a first opening that constitutes a part of a manifold when the fuel cells are stacked,
Each of the pair of separators is formed with a second opening that constitutes another part of the manifold when the fuel cells are stacked,
the size of the first opening is smaller than the size of the second opening;
The resin sheet has a protruding portion protruding from the edge of the second opening to the inside of the second opening due to a difference in size between the first opening and the second opening, and the protruding portion A fuel cell, wherein at least part of the portion is formed in a mesh shape.