JPH1173979A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately humidify a reaction gas without leading to a reduction in generating efficiency or an increase in required space, and hold an electrolyte film in a prescribed wet state by injecting a part of a cooling water to be supplied to a cooling water passage for at least one of a fuel gas passage and an oxidizing agent gas passage. SOLUTION: A separator 2A for partitioning a cooling water passage from a fuel gas passage in a fuel battery layer product has a through-hole 5, and a porous member 3 supported by a spacer 4 is arranged adjacent to the through- hole 5. A part of the cooling water flowing in a cooling water passage between the separator 2A and a separator 2 is injected into the fuel gas passage between the separator 2A and an electrolyte film 1 through the porous member 3 adjacent to the through-hole 5. Since a fuel gas, when it enters an electrode surface, water is immediately injected, supplied, and then it is humidified so that a, electrolyte film 1 is held in wet state, and the reduction in characteristic performance due to lack of moisture is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell which generates electric power by an electrochemical reaction using a solid polymer membrane as an electrolyte.

[0002]

2. Description of the Related Art FIG. 6 is an exploded sectional view of a main part showing a basic structure of a fuel cell stack of a generally used solid polymer electrolyte fuel cell. A catalyst layer (not shown) containing a noble metal, mainly platinum, is joined to both sides of an electrolyte membrane 1 made of a solid polymer membrane, and a porous gas diffusion layer 7 is arranged on both outer surfaces thereof to form a membrane electrode assembly (MEA; Membrane). Electrode
Assembly) is configured. On both surfaces of the membrane / electrode assembly, gas channel plates 8 having grooves formed therein for supplying a reaction gas to the catalyst layer, that is, a fuel gas containing hydrogen and an oxidizing gas containing oxygen, are arranged. Are sandwiched between the separators 2 to form a single cell. When fuel gas and oxidant gas are supplied to generate electricity by electrochemical reaction,
Since heat is generated at the same time, cooling water is supplied to the cooling water flow path plate 9 provided for each cell or every several cells to remove this heat generation and to use the fuel cell stack at a predetermined temperature. . Seal rubbers 6 are disposed around the reaction gas flow path and the cooling water flow path of each cell, respectively, and serve to seal the reaction gas and the cooling water. Separator 2
Since it is necessary to have conductivity and gas impermeability, a dense carbon material or a metal material is usually used. Further, a porous carbon material is generally used for the gas flow channel plate 8, and a porous carbon material or a non-porous carbon material is generally used for the cooling water flow channel plate 9.

FIG. 7 is a plan view showing the basic structure of the stacking surface of the fuel cell stack shown in FIG.
FIG. 3B is a plan view of the separator 2. As shown in FIGS. 7A and 7B, fuel cell inlet manifold 10, oxidant gas inlet manifold 11, and cooling water inlet manifold communicating with each other in the stacking direction are provided at four corners of the fuel cell stack. 12, fuel gas outlet manifold 13, oxidant gas outlet manifold 14,
A cooling water outlet manifold 15 is provided and is air-tightly separated from each other by a seal rubber 6. In the gas flow path plate 8 to which the fuel gas is supplied, as shown in FIG. 7A, the fuel gas flows through the zigzag gas flow path from the fuel gas inlet manifold 10 to the fuel gas outlet manifold 13. And contribute to power generation. Although not shown in the figure, both the oxidizing gas and the cooling water
Similarly, it flows in a zigzag manner from the inlet side manifold to the diagonally arranged outlet side manifold to contribute to power generation and cooling.

[0004]

By the way, the electrolyte membrane 1 made of a solid polymer membrane increases in resistance when dried, and the generated cell voltage decreases, so that desired characteristics cannot be obtained. It is necessary to operate while keeping it moist.
Therefore, a method of keeping the electrolyte membrane 1 wet by humidifying and supplying the reaction gas is generally used. A humidification tank is provided outside the fuel cell stack, and the reaction gas is passed through warm water. After humidification, the reaction gas is supplied to the fuel cell stack, or a humidifying section is provided inside the fuel cell stack, and the reaction gas is brought into contact with the cooling water and the reaction gas through a moisture-permeable diaphragm. A method of humidifying and supplying is adopted.

[0005] When the reaction gas is supplied by being humidified as described above, the electrolyte membrane 1 is kept wet and a predetermined cell voltage can be obtained. In the method of humidifying by providing a humidifying tank, not only the humidifying tank, but also heating the piping of the reaction gas from the humidifying tank to the fuel cell stack to a predetermined temperature or higher,
Since it is necessary to keep heat, there is a problem that a large amount of power is required and the power generation efficiency of the fuel cell is reduced.
Also, since the heated temperature is easily affected by the ambient temperature,
There is a drawback that the temperature fluctuates and the humidification amount fluctuates.

In the latter method, a humidifying section is provided inside the fuel cell stack, and the reaction gas is humidified by contacting with cooling water through a diaphragm. When the number of single cells to be stacked increases, the proportion increases. Since the humidifying section needs to be enlarged, the size of the fuel cell stack, and hence the size of the power generation system, increases, and the required space increases.

[0007] The present invention has been made in view of these difficulties of the prior art, and an object thereof is to provide a reaction gas that is appropriately humidified and supplied without lowering the power generation efficiency and increasing the required space. An object of the present invention is to provide a solid polymer electrolyte fuel cell in which an electrolyte membrane is maintained in a predetermined wet state and excellent cell characteristics are obtained.

[0008]

In order to achieve the above-mentioned object, according to the present invention, a fuel gas is provided on both sides of a membrane electrode assembly in which a catalyst layer is joined to both main surfaces of a flat solid polymer electrolyte membrane. A fuel cell stack is formed by arranging a flow path and an oxidizing gas flow path, stacking a plurality of unit cells formed by being sandwiched by separators made of a gas impermeable material, and forming hydrogen into the fuel gas flow path. The fuel gas contained, and the oxidizing gas containing oxygen is supplied to the oxidizing gas flow path to generate power by an electrochemical reaction, and the cooling flows through a cooling water flow path formed by a single cell and a separator. In a solid polymer electrolyte fuel cell used while being maintained at a predetermined temperature with water, (1) cooling supplied to a cooling water flow path to at least one of a fuel gas flow path and an oxidizing gas flow path Equipped with a water injection part to inject a part of water (2) For example, a through hole provided in a separator between a cooling water flow path and a gas flow path, or a series connection body of a similar through hole and a porous member adjacent to the through hole is used. This is the water injection section.

(3) Alternatively, a through-hole or a through-groove provided in a seal member between a gas inlet and a cooling water inlet manifold for communicating a plurality of unit cells of the fuel cell stack with the separator, or the inside thereof. These through holes or through grooves in which a porous member is disposed are referred to as the above-mentioned water injection portions. (4) Alternatively, in the vicinity of the cooling water inlet manifold that connects the plurality of single cells of the fuel cell stack and the separator, the gas passage is formed narrow by projecting the separator from the cooling water passage to the gas passage. Then, a porous member is disposed in the narrow portion to form the above-mentioned water injection portion.

As described in (1) above, the gas flow path of each single cell of the fuel cell stack may be provided with a water injection portion formed as described in (2), (3) or (4), for example. For example, water can be injected into the gas flow path without increasing the size and weight of the fuel cell stack. The injection amount is basically determined by the size of the through hole and the selection of the porous member, and is adjusted by controlling the pressure of the cooling water supply system. Accordingly, an appropriate amount of water can be continuously supplied to the inside of each unit cell, and the electrolyte membrane is kept moist at all times to obtain predetermined cell characteristics.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> FIG. 1 is a sectional view showing a basic configuration of a water injection portion of a fuel cell stack according to Embodiment 1 of the present invention. As shown in the figure, in the present embodiment, a through hole 5 is provided in a separator 2A separating a cooling water flow path and a fuel gas flow path, and a porous member 3 supported by a spacer 4 adjacent to the through hole 5 is provided. Is arranged. Therefore, a part of the cooling water flowing through the cooling water flow path between the separator 2A and the separator 2 passes through the porous member 3 adjacent to the through hole 5 as shown by the solid line in the figure, and Is injected into the fuel gas flow path between the fuel gas and the electrolyte membrane 1.

FIG. 2 is a plan view of the stacking surface of the fuel cell stack showing the arrangement of the water injection section shown in FIG. 1, (a) is a plan view showing a gas channel plate, and (b) is a separator. It is a top view. In this figure, components having the same functions as those of the configuration of the conventional example shown in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted. The through-hole 5 of the separator 2A shown in FIG. 1 is disposed close to the fuel gas inlet manifold 10 as shown in FIG.
As shown in FIG. 2 (a), are disposed in the fuel gas flow path near the fuel gas inlet manifold 10 corresponding to the through holes 5.

Therefore, in this configuration, the fuel gas supplied from the fuel gas inlet manifold 10 is injected with the water permeated through the porous member 3 adjacent to the through hole 5 as soon as it enters the electrode surface, supplied and humidified. Since the flow is made to flow, the electrolyte membrane 1 is kept moist, and deterioration of the characteristics due to lack of water is prevented. In this embodiment, the amount of water injected is easily adjusted by permeating and pouring water through the porous member 3 adjacent to the through hole 5. However, the cooling water is supplied only through the through hole 5 without using the porous member 3. Water may be injected into the fuel gas. Further, in this embodiment, the cooling water is injected into the fuel gas to thereby keep the electrolyte membrane 1 wet. However, the cooling water is injected into the oxidizing gas by a similar configuration to wet the electrolyte membrane 1. It is good also as a structure which holds.

<Embodiment 2> FIG. 3 is a sectional view showing a basic configuration of a water injection portion of a fuel cell stack according to Embodiment 2 of the present invention. In the present embodiment, as shown in FIG. 7A, a water injection section is provided at a portion of the cooling water inlet manifold 12, which is disposed in communication with the end of the fuel cell stack in the stacking direction. FIG.
The space through which the cooling water flows in the cooling water inlet manifold 12 and the space through which the oxidizing gas flows between the separator 2 and the electrolyte membrane 1 are shown as extending in the vertical direction of the drawing. While the space is kept airtight, the space through which the cooling water flows in the cooling water inlet manifold 12 and the space through which the fuel gas flows located on the opposite surface of the electrolyte membrane 1 are formed by the spacers 4A which are sealing members for the two spaces. Member 3 supported in a through hole formed in
It communicates through the space of A. Therefore, as shown by the solid line in the figure, the cooling water is injected into the fuel gas flow path through the porous member 3A, and the humidified fuel gas is sent to the electrode surface, so that the electrolyte membrane becomes wet. Will be retained.

<Embodiment 3> FIG. 4 is a sectional view showing a basic configuration of a water injection portion of a fuel cell stack according to Embodiment 3 of the present invention. The difference between this embodiment and the second embodiment shown in FIG. 3 is that the porous member 3A is supported in the through hole formed in the spacer 4A in the second embodiment, That is, the quality member 3A is not provided. With this configuration, the pressure loss at the water injection section is relatively low, which is effective when the amount of injected water needs to be increased.

<Embodiment 4> FIG. 5 is a sectional view showing a basic structure of a water injection portion of a fuel cell stack according to Embodiment 4 of the present invention. The feature of the present embodiment is that the separator 2B is formed using a titanium material, and a portion adjacent to the cooling water inlet manifold 12 is formed so as to protrude toward the space through which the fuel gas or the oxidizing gas flows, and the fuel 2 is formed. The point is that the porous member 3B is arranged in a narrow part of the gas flow space to form a water injection part, and the cooling water is injected into the fuel gas. In this configuration, the spacer used in the second and third embodiments is not required.

In each of the above-described embodiments 2 to 4, the water injection section is configured to inject cooling water into the flow path of the fuel gas, but the present invention is not limited to this. The water injection section may be configured to inject water into the oxidant gas flow path, or the electrolyte membrane may be effectively dried even if the water injection section is configured to inject both fuel gas and oxidant gas. And the deterioration of the cell characteristics is avoided.

[0018]

As described above, according to the present invention, (1) the solid polymer electrolyte fuel cell is constructed as described in claim 1, so that the gas can be obtained without using any special device. Since an appropriate amount of water is continuously supplied to the inside of each single cell by injecting water into the flow channel, and the electrolyte membrane is maintained in a predetermined wet state,
A solid polymer electrolyte fuel cell having compact and excellent cell characteristics has been obtained.

(2) In particular, if the configuration is made as described in claims 2 to 6, water can be accurately injected into the gas flow path, and each unit cell can be provided without any special device. The solid polymer electrolyte type that has excellent cell characteristics and reduces the size and weight of the fuel cell stack because the appropriate amount of water is continuously supplied to the inside of the fuel cell and the electrolyte membrane is maintained in a predetermined wet state. It is suitable as a fuel cell.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a basic configuration of a water injection section of a fuel cell stack according to a first embodiment of the present invention.

FIGS. 2A and 2B are plan views of a stacking surface of a fuel cell stack showing an arrangement of a water injection section shown in FIG. 1, wherein FIG. 2A is a plan view showing a gas flow path plate, and FIG.

FIG. 3 is a cross-sectional view illustrating a basic configuration of a water injection section of a fuel cell stack according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a basic configuration of a water injection section of a fuel cell stack according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a basic configuration of a water injection section of a fuel cell stack according to a fourth embodiment of the present invention.

FIG. 6 is an exploded sectional view of a main part showing a basic configuration of a fuel cell stack of a generally used solid polymer electrolyte fuel cell;

7A and 7B are plan views showing a basic configuration of a stacking surface of the fuel cell stack shown in FIG. 6, wherein FIG. 7A is a plan view showing an example of a gas flow path plate, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2, 2A Separator 3, 3A, 3B Porous member 4, 4A Spacer 5 Through-hole 6, 6A Seal rubber 8 Gas passage plate 10 Fuel gas inlet manifold 11 Oxidant gas inlet manifold 12 Cooling water inlet manifold 13 Fuel gas Outlet manifold 14 Oxidant gas outlet manifold 15 Cooling water outlet manifold

Claims (6)

[Claims] A fuel gas flow path and an oxidizing gas flow path are arranged on both sides of a membrane electrode assembly in which a catalyst layer is bonded to both main surfaces of a flat solid polymer electrolyte membrane. A fuel cell stack is formed by stacking a plurality of single cells sandwiched by separators, and a fuel gas flow path contains hydrogen-containing fuel gas and an oxidant gas flow path contains oxygen-containing oxidation gas. In a solid polymer electrolyte fuel cell used by supplying an agent gas to generate power by an electrochemical reaction and maintaining a predetermined temperature by cooling water flowing through a cooling water channel formed by a single cell and a separator. A solid polymer, characterized in that at least one of the fuel gas flow path and the oxidizing gas flow path is provided with a water injection section for injecting a part of the cooling water supplied to the cooling water flow path. Electrolyte fuel cell. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the water injection section is a through hole provided in a separator between the cooling water flow path and the gas flow path. . 3. The water injection part comprises a series connection of a through hole provided in a separator between a cooling water flow path and a gas flow path, and a porous member adjacent to the through hole. The solid polymer electrolyte fuel cell according to claim 1, wherein 4. A through-hole provided in a seal member disposed between a gas inlet and a cooling water inlet manifold communicating the plurality of single cells of the fuel cell stack with the separator. Alternatively, the solid polymer electrolyte fuel cell according to claim 1, wherein the fuel cell is a through groove. 5. The solid polymer electrolyte fuel cell according to claim 4, wherein a porous member is disposed inside the through hole or the through groove provided in the seal member. 6. In a vicinity of a cooling water inlet manifold connecting a plurality of unit cells of a fuel cell stack and a separator, the separator projects from the cooling water flow path to the gas flow path, and the gas flow path is formed narrow. And the water injection part is
The solid polymer electrolyte fuel cell according to claim 1, comprising a porous member disposed in a narrow portion.