JPH11204118A - Fuel cell separator and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply water for humidifying an electrolytic membrane at low cost and enhance energy efficiency of a fuel cell power generating system by providing a plurality of protrusions in a gas flow passage for gas supply on a separator, and forming a water reservoir part in its opened shape on an electrode side. SOLUTION: An electrolytic membrane is sandwiched between a pair of electrodes, a separator for forming a gas flow passage is provided in contact with this electrode. A plurality of protrusions 43 are protruded on a bottom face of this separator, a gap is used as a gas flow passage, and a horizontal side face 43a of the protrusions 43 vertically facing the vertical, downward flow of gas is used as a water reservoir part of a reaction generation water W of a fuel cell. Furthermore, the protrusions 43 are constituted by forming vertical, downward cavities as required, or can be formed into a V-bent shape. At this water reservoir part, a water absorptive resin is preferably arranged, and irregularities may be provided on a wall face. Thereby, the generated water W collected at the water reservoir part migrates to an electrolyte membrane via an electrode and is maintained in proper wetted state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell separator in contact with a pair of electrodes sandwiching an electrolyte membrane, and a fuel cell including the fuel cell separator.

[0002]

2. Description of the Related Art In a polymer electrolyte fuel cell, which is one type of fuel cell, as shown in the following formulas (1) and (2), the reaction of converting hydrogen gas into hydrogen ions and electrons at the anode is performed at the cathode. A reaction for producing water from oxygen gas, hydrogen ions and electrons is performed.

Anode reaction (fuel electrode): H ₂ → 2H ⁺ + 2e ⁻ (1) Cathode reaction (oxygen electrode): 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)

[0004] Hydrogen ions generated at the anode are hydrated (H ⁺ · xH ₂ O) and move to the cathode through the electrolyte membrane. For this reason, in the vicinity of the anode-side surface of the electrolyte membrane, water becomes insufficient, and it is necessary to replenish the insufficient water in order to perform the above-mentioned reaction continuously. Electrolyte membranes used in polymer electrolyte fuel cells have good electrical conductivity in the wet state, but when the water content decreases, the electrical resistance of the electrolyte membrane increases and it does not function sufficiently as an electrolyte. Stops the electrode reaction.

[0005] The replenishment of the water is generally performed by humidifying the fuel gas. As a device for humidifying the fuel gas, a humidifier (bubbler) for bubbling and humidifying the fuel gas is well known. The humidifier is used to humidify the fuel gas to wet the electrolyte membrane.

[0006]

However, the bubbler must be heated by an electric heater and consumes considerable energy. Therefore, when considered as a fuel cell power generation system, there is a problem that the energy efficiency is extremely low.

The present invention has been made in view of such a problem, and has as its object to increase the energy efficiency of a fuel cell power generation system by reducing the energy consumption required for supplying water to an electrolyte membrane.

[0008]

A fuel cell separator according to the present invention is in contact with a pair of electrodes sandwiching an electrolyte membrane and has a gas flow path for gas supply on the electrode side. The gist of the invention is that a water reservoir for holding water is formed in the gas flow path.

The fuel cell separator having the above structure (hereinafter referred to as “separator”)
According to the basic configuration of the fuel cell separator), the water in the gas flow path is retained in the water reservoir. The moisture in the gas flow path originally corresponds to the moisture contained in the gas flow path, and when the gas flow path is a flow path of an oxygen-containing gas, the water generated in the oxygen electrode corresponds. These waters are stored in the water pool. The water in the water reservoir appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface. For this reason, in the fuel cell using the fuel cell separator, the electrolyte membrane can be kept in a good wet state without using a special humidifier such as a bubbler.

Therefore, the fuel cell using the fuel cell separator has excellent energy efficiency because no humidifier is used.

[0011] In the fuel cell separator having the above-mentioned basic structure, the water reservoir may have a shape opened toward the electrode.

According to the fuel cell separator of this configuration, when assembled to the fuel cell, the water reservoir is in a state of communicating with the electrode, so that the water generated by the electrode tends to accumulate in the water reservoir.

[0013] In the fuel cell separator having the above basic configuration, the gas flow path is formed by a plurality of projections projecting from the flow path bottom surface, and the gas flow path is formed when the fuel cell separator is assembled to the fuel cell. The direction of the gas flow by the gas flow path is determined so as to be vertically downward, and the water pool portion, on the convex portion, faces the direction of the gas flow, and forms a surface that is perpendicular to the direction of the gas flow. It is possible to be constituted.

According to the fuel cell separator having this structure, the predetermined surface of the convex portion is horizontal because it is opposed to and perpendicular to the direction of the gas flow vertically below. For this reason, the water in the gas flow path is held on the horizontal surface with surface tension. The retained water appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface.

In the fuel cell separator having the above-mentioned basic structure, the gas flow path is formed by a plurality of projections projecting from the bottom of the flow path, and the pool is formed on the projection by the projection of the fuel cell separator. It may be configured such that a recess having a depth that is vertically downward is formed when the fuel cell is assembled.

According to the fuel cell separator having this configuration, water in the gas flow path is held in the depression formed in the projection. The retained water appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface.

In the fuel cell separator having the above-described structure, the convex portion is formed by bending a horizontally long rectangular parallelepiped into a V-shape, and the water pool portion is formed by a bent portion of the convex portion. You can also.

According to the fuel cell separator having this structure, the water in the gas flow path is held inside the V-shaped bent portion. The retained water appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface.

In the fuel cell separator having the above-mentioned basic structure, it is possible to adopt a structure in which a water-absorbing resin is provided in the water reservoir.

According to the fuel cell separator having this configuration, more water can be retained in the water pool. For this reason, the electrolyte membrane can be further wetted, and the fuel cell can be made more excellent in energy efficiency.

Further, in the fuel cell separator having the above-mentioned basic structure, the water reservoir may be formed by providing at least one wall surface of the gas flow channel with irregularities.

According to the fuel cell separator having this structure, it is possible to retain the moisture in the gas on the surface having irregularities. The retained water appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface.

The first fuel cell of the present invention comprises a joined body sandwiching an electrolyte membrane between a pair of electrodes, and a separator in contact with the joined body and having a gas flow path for gas supply on the electrode side. In the fuel cell, the separator includes a flow path bottom surface facing the surface of the electrode, and a plurality of protrusions protruding from the flow path bottom surface and reaching the surface of the electrode, wherein the protrusion is formed of the gas. The gist of the present invention is that the flow direction is arranged vertically downward, and an upward surface perpendicular to the gas flow direction is provided.

According to the fuel cell having this configuration, the predetermined surface of the convex portion of the separator is upward because it is vertically upward with respect to the direction of gas flow below vertically. For this reason, the water in the gas flow path is held on the horizontal surface with surface tension. The retained water appropriately moisturizes the gas and wets the electrolyte membrane through the electrode surface. Therefore, in this fuel cell, the electrolyte membrane can be kept in a good wet state without using a special humidifier such as a bubbler.

Therefore, this fuel cell is excellent in energy efficiency because no humidifier is used.

A second fuel cell according to the present invention has a joined body in which an electrolyte membrane is sandwiched between a pair of electrodes, and a gas flow path for contacting the joined body and supplying an oxygen-containing gas on the one electrode side. In a fuel cell including a separator, the separator includes a flow path bottom surface facing the surface of the electrode, and a plurality of protrusions protruding from the flow path bottom surface and reaching the surface of the electrode, wherein the protrusion is The gist of the present invention is to provide a water reservoir provided at a contact portion with the surface of the electrode for holding water.

According to the fuel cell having this configuration, the water generated on the electrode side to which the oxygen-containing gas is supplied is stored in the water reservoir provided at the contact portion of the projection with the electrode surface. The water in the water reservoir appropriately moisturizes the gas and wets the electrolyte membrane via the electrode surface. Therefore, in this fuel cell, the electrolyte membrane can be kept in a good wet state without using a special humidifier such as a bubbler.

Accordingly, this fuel cell is excellent in energy efficiency because no humidifier is used.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, embodiments of the present invention will be described below based on examples. A polymer electrolyte fuel cell (hereinafter, simply referred to as a fuel cell) 10 according to a first preferred embodiment of the present invention has a single cell 20 as a bonded body as a basic unit, and has a stack structure in which the single cells 20 are stacked. have. FIG. 1 is an explanatory diagram schematically showing a cross section of the single cell 20. As shown in FIG. The single cell 20 of the fuel cell 10 includes the electrolyte membrane 2
1, an anode 22 and a cathode 23, and separators 24 and 25.

The anode 22 and the cathode 23 are gas diffusion electrodes having a sandwich structure sandwiching the electrolyte membrane 21 from both sides. The separators 24 and 25 sandwich the sandwich structure from both sides while further sandwiching the sandwich structure.
A flow path for the fuel gas and the oxygen-containing gas is formed between the fuel cell 2 and the cathode 23. Anode 22 and separator 2
4, a fuel gas flow path 24P is formed, and between the cathode 23 and the separator 25, an oxygen-containing gas flow path 25P is formed.

Although the separators 24 and 25 each have a flow path formed on only one side in FIG. 1, actually, a convex portion to be described later is formed on both sides thereof, and one side has an anode 22.
And a fuel gas flow path 24P is formed between them, and the other surface forms an oxygen-containing gas flow path 25P with the cathode 23 provided in the adjacent single cell. Thus, the separators 24, 25
Has a function of forming a gas flow path with the gas diffusion electrode and separating the flow of the fuel gas and the oxygen-containing gas between adjacent single cells. Of course, single cell 20
Are stacked to form a stack structure, the two separators located at both ends of the stack structure have protrusions formed only on one surface in contact with the gas diffusion electrode.

Here, the electrolyte membrane 21 is a proton-conductive ion-exchange membrane formed of a solid polymer material, for example, a fluorine-based resin, and shows good electric conductivity in a wet state. In this embodiment, a Nafion membrane (manufactured by DuPont) is used.
It was used. Platinum as a catalyst or an alloy composed of platinum and another metal is applied to the surface of the electrolyte membrane 21. As a method of applying the catalyst, a carbon powder supporting platinum or an alloy composed of platinum and another metal is prepared, the carbon powder supporting the catalyst is dispersed in an appropriate organic solvent, and an appropriate amount of an electrolyte solution is added. A method of forming a paste and performing screen printing on the electrolyte membrane 21 is employed.

The alloy catalyst comprising platinum and another metal includes platinum as the first component and ruthenium, nickel, cobalt, indium, iron, chromium as the second component.
Some include alloys of one or more of manganese and the like.

The anode 22 and the cathode 23 are both formed of carbon cloth woven with carbon fiber yarns. In the present embodiment, the anode 22 and the cathode 23 are formed of carbon cloth, but a configuration formed of carbon paper or carbon felt made of carbon fiber is also suitable.

The electrolyte membrane 21 and the anode 22 and the cathode 23 are integrated by thermocompression bonding. That is, the electrolyte membrane 21 coated with a catalyst such as platinum is sandwiched between the anode 22 and the cathode 23, and they are pressed together while being heated to 120 to 130 ° C. As a method of integrating the electrolyte membrane 21 with the anode 22 and the cathode 23, a method by adhesion may be used in addition to thermocompression bonding. When sandwiching the electrolyte membrane 21 between the anode 22 and the cathode 23, a proton conductive solid polymer solution (for example, Aldrich Chee) is formed between each electrode and the electrolyte membrane 21.
When bonding is performed using Nafion Solution (Micical Co., Ltd.), each electrode and the electrolyte membrane 21 are fixed to each other as an adhesive in the process of solidification of the proton conductive solid polymer solution.

The separators 24 and 25 are formed of a gas-impermeable conductive member, for example, dense carbon which is made by compressing carbon to be gas-impermeable. Separator 2
4 and 25 have anodes 22 on both sides thereof, as described above.
And the surface of the cathode 23 of the adjacent single cell to form an oxygen-containing gas channel 25P.

The shapes of the separators 24 and 25 are as follows. Since the separators 24 and 25 have the same shape, here, the oxygen-containing gas flow path 25P
Will be described by way of an example of the separator 25 that forms. FIG.
Is a plan view of the separator 25. FIG. As shown
The separator 25 is formed as a quadrangular plate-like member, and has slots 31 and 33 near the edges of two opposing sides.
Are provided, and elongated holes 35 and 37 are provided near the edges of the other two sides, respectively.

The slots 31 and 33 facing the diagonal line form two oxygen-containing gas supply / discharge passages that penetrate the fuel cell 10 in the stacking direction when they are stacked. Two fuel gas supply / discharge passages penetrating in the stacking direction are formed.

The elongated holes 31, 33,
A step surface 41 which is one step lower than the plane portion is formed inside the plane portion of the outer edge provided with 35 and 37.
On the step surface 41, a plurality of rectangular parallelepiped convex portions 43 having a width of 2 [mm], a length of 2 [mm], and a height of 1 [mm] are regularly arranged. Each convex part 4
3 is oriented such that the upward side surface 43a of the projection 43 is perpendicular to the direction X from the long hole 31 to the long hole 33. The projection 43, the step surface 41, and the surface of the cathode 23 form a gas flow path dispersed in a plurality of directions. The long holes 31 and 33 are on the same height as the step surface 41, and the oxygen-containing gas is sent from the long holes 31 and 33 to the gas flow path. These oxygen-containing gas channels correspond to the oxygen-containing gas channel 25P shown in FIG.

A step surface and a projection (not shown) having the same shape as the step surface 41 and the projection 43 are formed on the other of the laminated surfaces of the separator 25 (the back surface in FIG. 2). The step surface and the projection and the surface of the anode 22 form a fuel gas flow path. The fuel gas is supplied or discharged from the fuel gas supply / discharge passage formed by the slots 35 and 37 to the fuel gas passage. It should be noted that such a fuel gas flow path corresponds to the fuel gas flow path 24P shown in FIG.

The separator 25 having the above structure is arranged such that the step surface 41 is vertical when the fuel cell is assembled, with the long hole 31 being on the upper side and the long hole 33 being on the lower side. Determined to be located. Therefore, in the fuel cell 10 to which the separator 25 is attached, from the upper side to the lower side,
That is, the oxygen-containing gas is sent vertically downward, while the fuel gas is sent horizontally in the fuel gas direction.

The configuration of the unit cell 20, which is the basic structure of the fuel cell 10, has been described above. When the fuel cell 10 is actually assembled, the separator 24, the anode 2
2. A plurality of sets of the electrolyte membrane 21, the cathode 23, and the separator 25 are laminated in this order (100 sets in this embodiment), and a current collector plate (not shown) formed of a dense carbon or copper plate is provided at both ends thereof. The arrangement forms a stack structure.

As described above, the fuel cell 10 having the above-described configuration allows the fuel gas containing hydrogen to pass through the fuel gas passage 24P.
The oxygen-containing gas containing oxygen is supplied to the oxygen-containing gas flow path 25P.
To the anode 22 and the cathode 2
3 perform the electrochemical reaction shown in the above equations (1) and (2), and directly convert chemical energy into electric energy.

FIG. 3 is an explanatory view schematically showing the flow direction of the oxygen-containing gas in the separator 25 of the fuel cell 10 and the state of the generated water. In the fuel cell 10 of this embodiment, as shown in the figure, the oxygen-containing gas flows vertically downward (from the top to the bottom in the figure) by the separator 25, and the separator 25 moves in the direction of the flow of the oxygen-containing gas. The arbitrary side surface 43a of the convex portion 43 formed in the vertical direction is in a vertical direction. That is, one side surface 43a of the convex portion 43 is
It is horizontal. When the oxygen-containing gas is flowed, water is generated at the cathode 23 by the cathode reaction according to the above equation (2). In the fuel cell 10 of this embodiment, the generated water W Accumulates moderately.

FIG. 4 is an explanatory view schematically showing a cross section near the oxygen-containing gas flow path 25P. As can be seen from FIG. 4, the convex portion 43 forming the oxygen-containing gas flow path 25P is formed.
The generated water W appropriately accumulates on one side surface 43a, that is, in the concave portion of the oxygen-containing gas channel 25P. The generated water W accumulated near the surface of the cathode 23 appropriately moisturizes the oxygen-containing gas, moves from the cathode 23 to the electrolyte membrane 21, and works to keep the electrolyte membrane 21 in a favorable wet state.

Therefore, in the fuel cell 10 of this embodiment, the electrolyte membrane 21 can be kept sufficiently wet without using a special humidifier such as a bubbler. For this reason, the fuel cell 10 requires less energy consumption because the humidifier is not used, and requires less space. That is, the fuel cell 10 has an effect of being efficient in terms of energy consumption and space volume.

In particular, in this embodiment, since the portion of the separator 25 that holds the generated water W, that is, the side surface 43a of the projection 43 is in contact with the cathode 23, the water generated at the cathode 23 is removed. It also has the effect of being easy to store.

The cell performance of the fuel cell 10 of the first embodiment is compared with that of a conventional fuel cell. Here, a conventional fuel cell was provided with a separator having the following configuration.

FIG. 5 is an explanatory view schematically showing a plane of a conventional split rib type separator. As shown
This conventional separator has a configuration in which a plurality of rectangular parallelepiped convex portions A1 forming an oxygen-containing gas flow path are arranged at an angle of 45 degrees with respect to the vertically downward direction, and the flow direction of the oxygen-containing gas is vertically downward. The direction is inclined by 45 degrees with respect to the direction.

FIG. 6 is a graph showing the relationship between voltage and current density for the fuel cell 10 of the first embodiment and the conventional fuel cell. In FIG. 6, curve A shows the relationship between voltage and current density for fuel cell 10, and curve B shows the relationship between voltage and current density for the conventional fuel cell having a split rib separator. It is. A curve C shows the relationship between the voltage and the current density of the fuel cell of the second embodiment described later, which will be described later.
Note that this voltage-current density characteristic indicates that dry air (humidity 40 to 50) was used as an oxygen-containing gas for the fuel cell.
[%]).

As shown in FIG. 6, the fuel cell 10 of the first embodiment has a wider range of current densities in the measurement range than the above-mentioned conventional fuel cell using a split rib type separator. The characteristics were excellent. In particular, in the high current density region (0.5
[A / cm ² ] or more, the voltage drop was small, and improvement in gas diffusivity was observed.

Next, a second embodiment will be described. The second embodiment relates to a polymer electrolyte fuel cell having substantially the same configuration as the fuel cell 10 of the first embodiment. Only the shape and arrangement of the projections provided on the separator on the oxygen-containing gas side are described. Is different from the first embodiment.

FIG. 7 is an explanatory view schematically showing a plane of the separator used in the second embodiment. The protrusion 43 provided on the separator 25 of the first embodiment is a square column having a planar shape, whereas the separator used in the second embodiment is a column having a V-shaped plane. A plurality of convex portions 50 having such a shape are regularly arranged on the separator. Each projection 50 is as follows in detail. The protrusion 50 has a first rectangular parallelepiped having a width of 2 [mm], a length of 7 [mm], a height of 1 [mm], a width of 2 [mm], and a length of 5 [m].
m] and a second rectangular parallelepiped having a height of 1 [mm] in a key shape, and has a V-shape by setting the elevation angle θ with respect to the horizontal direction to 45 degrees. Further, the arrangement of the plurality of convex portions 50 is such that the convex portions 50 in the odd rows and the convex portions 50 in the even rows are not arranged on the same column, but the even rows are arranged between the columns of the adjacent convex portions 50 in the odd rows. Are arranged. The separator is provided with an oxygen-containing gas supply port and a discharge port (not shown) in the upward and downward directions in the drawing, as in the first embodiment, and is used when assembling to a fuel cell. In this configuration, the oxygen-containing gas flows vertically downward.

That is, according to the separator of the second embodiment, the oxygen-containing gas is configured to flow vertically downward, and then the V-shaped gas having an elevation angle of 45 degrees with respect to the horizontal direction is formed. The configuration is provided with the convex portion 50.

According to the separator having such a configuration, when the fuel cell is operated, the generated water generated on the cathode 23 side appropriately accumulates in the V-shaped portion of the projection 50. The generated water appropriately moisturizes the oxygen-containing gas, moves from the cathode 23 to the electrolyte membrane 21, and acts to keep the electrolyte membrane 21 in a good wet state.

Therefore, the fuel cell of the second embodiment can humidify the electrolyte membrane without using a humidifier, as in the first embodiment, and the efficiency is high in terms of energy consumption and space volume. It has the effect of being good.

Further, in this embodiment, since the V-shaped convex portion 50 for storing the generated water W in the separator is in contact with the cathode, there is also an effect that the water generated at the cathode can be easily stored.

The performance of the fuel cell of the second embodiment is shown by a curve C in FIG. As shown in the figure, the fuel cell of the second embodiment has all the measurement ranges compared with the fuel cell of the first embodiment (curve B) as well as the conventional fuel cell (curve A) described above. Over its current density. In particular, a high current density region (0.5 [A /
cm ² ] or more, and the gas diffusibility was improved.

In the second embodiment, the V-shaped convex portion is provided only on the separator on the oxygen electrode (cathode) side. The separator on the pole (anode) side may have the same V-shaped protrusion as the separator on the cathode side.

According to this configuration, the water originally contained in the fuel gas can be stored in the V-shaped portion of the projection. Therefore, it is not necessary to humidify the fuel gas using the humidifier, or it is possible to reduce the capacity of the humidifier. Therefore, according to such a fuel cell, there is an effect that energy consumption and space volume can be further reduced.

Next, a third embodiment will be described. The third embodiment differs from the fuel cell 10 of the first embodiment in the shape of the separator, and has the same other configuration.

FIG. 8 is a plan view of the separator 60 used in the third embodiment. As shown in the figure, the separator 60 is formed as a rectangular plate-like member, and is provided with two round holes 61 and 63 near the center, respectively.
Round holes 65, 66, 67, and 68 are provided near the four corners, respectively.

One round hole 61 near the center forms a supply flow path for an oxygen-containing gas that passes through the fuel cell in the stacking direction when stacked, and the other round hole 63 similarly passes through in the stacking direction. A fuel gas supply channel is formed. Opposite round holes 65 and 67 among the round holes at the four corners form an oxygen-containing gas discharge passage that passes through the fuel cell in the stacking direction when stacked, and the other round hole 66. , 68 form a fuel gas discharge passage which also penetrates in the stacking direction.

The round holes 65, 66, 67,
A plurality of annular ribs 71, 72, 73, 74, 7 having different diameters are provided on the inner surface 60 a of the outer edge provided with 68.
5, 76 (corresponding to the protrusions in the claims) are formed concentrically. Each of the ribs 71 to 76 has two slits 71s located at a position 180 degrees from the center of the concentric circle.
(72s, 73s, 74s, 75s, 76s) are provided, and the positions of the slits 71s to 76s are
It is a position where the ribs alternate with each other as they move from the center to the outer ribs. The slits 71 s to 76 s, the surface of the separator 60, and the surface of the cathode form an oxygen-containing gas supply passage. The oxygen-containing gas supply passage is supplied with an oxygen-containing gas from the round hole 61,
The oxygen-containing gas is discharged from the round holes 65 and 67.

A rib (not shown) having the same shape as the ribs 71 to 76 is formed on the other of the laminated surfaces of the separator 60 (the back surface in FIG. 2). The ribs, the back surface of the separator 60, and the front surface of the anode 22 form a fuel gas flow path. The fuel gas flow path is supplied with fuel gas from the fuel gas supply / discharge flow path formed by the round holes 63, and the fuel gas flows into the fuel gas discharge flow path formed by the round holes 66 and 68. Gas is exhausted.

The separator 60 having the above structure is arranged such that the surface 60a of the separator 60 is in a vertical direction when assembled to a fuel cell. Therefore, in the fuel cell to which the separator 60 is attached, the oxygen-containing gas is sent toward the lower right and the upper left as a whole as shown by arrows in the figure.

In the fuel cell having the separator 60 having such a configuration, water generated on the cathode side is supplied to the annular rib 7.
It accumulates moderately near the lowermost points of 1 to 76. The accumulated water W keeps the oxygen-containing gas in an appropriate moisture level, moves from the cathode to the electrolyte membrane, and works to keep the electrolyte membrane in a good wet state.

Therefore, the fuel cell of the third embodiment can humidify the electrolyte membrane without using a humidifier, similarly to the first and second embodiments, and can save energy and space. Thus, the effect of efficiently humidifying the electrolyte membrane can be obtained. Further, in this embodiment, since the ribs 71 to 76 for storing the generated water W are annular, even when the fuel cell is rotated, the generated water W W
Can be stored. For this reason, a secondary effect such as excellent mobility is also exhibited.

In the third embodiment, the separator 2
5, a portion for storing the generated water W, that is, the rib 71
-76 are in contact with the cathode, so that there is an effect that water generated at the cathode is easily stored.

Next, modifications of the first to third embodiments will be described. FIG. 9 is an explanatory diagram schematically showing a cross section of a single cell of a fuel cell which is a modification of the first embodiment. As shown in the figure, the single cell 120 of the fuel cell of this modification has the same single cell configuration as that of the first embodiment, and furthermore, the oxygen formed by the projection 43 in the separator 25 on the cathode 23 side. This is a configuration in which the water-absorbing resin RE is applied to the entire inner wall of the contained gas flow path 25P.

Here, the water-absorbing resin is formed of a crosslinked polyacrylate, polyacrylonitrile-based or carboxymethylcellulose-based resin and has a thickness of 0.1 [m
m].

According to such a modification of the structure, the water W generated by the cathode 23 can be stored on the side surface 43a above the convex portion 43 by the same operation as in the first embodiment. The adsorptivity of the generated water W to the side surface 43a of the convex portion 43 is enhanced by the conductive resin RE. Further, in this modified example, a side surface 43a above the convex portion 43, which is a portion where the generated water is stored in the first embodiment.
Not only this, but the water absorbing resin RE is applied to the entire inner wall of the flow channel, so that the generated water W can be held with higher performance in the flow channel. Therefore, the humidifying ability of the electrolyte membrane 21 can be further improved.

In this modification, the water-absorbing resin RE is applied to the entire inner wall of the flow channel. Alternatively, the water-absorbing resin RE may be applied to the portion above the convex portion 43 where the generated water is stored in the first embodiment. It is also possible to adopt a configuration in which the water absorbent resin RE is applied only to the side surface 43a.

Further, the configuration for applying the water absorbing resin RE as described above may be applied to the second embodiment or the third embodiment. That is, the water-absorbent resin may be applied to the inside of the V-shape of the V-shaped protrusion, or the water-absorbent resin may be applied to the inside of the annular rib.

Next, a fourth embodiment will be described. The fourth embodiment relates to a polymer electrolyte fuel cell having substantially the same configuration as the fuel cell 10 of the first embodiment, and differs only in the configuration of the separator.

FIG. 10 is an explanatory view schematically showing a cross section of a single cell 120 of a fuel cell according to the fourth embodiment. As shown in the drawing, this single cell 120 has a sandwich structure in which an electrolyte membrane 21 is sandwiched between an anode 22 and a cathode 23, as in the first embodiment.
There are provided separators 124 and 125 that form a flow path for the fuel gas and the oxygen-containing gas, which are different from those of the first embodiment.

The separator 124 on the fuel electrode (anode) side
Has the same configuration as the conventional split rib type separator described above with reference to FIG. On the other hand, the separator 125 on the oxygen electrode (cathode) side has the same configuration as that of the above-described conventional split rib type separator, and further has the anode 2
2 or the concave portion 150 is provided on the upper surface portion 143a of the convex portion 143 which is in contact with the cathode 23. Convex part 1
43 is width 2 [mm], length 2 [mm], height 1 [m]
m], and the recess 150 has a hemispherical shape with a radius of 0.4 [mm].

According to the fuel cell having such a configuration, the water generated on the cathode 23 side accumulates in the recess 150.
The generated water appropriately moisturizes the oxygen-containing gas, moves from the cathode 23 to the electrolyte membrane 21, and keeps the electrolyte membrane 21 in a good wet state.

Therefore, the fuel cell according to the fourth embodiment can humidify the electrolyte membrane without using a humidifier, as in the first embodiment, and is efficient in terms of energy consumption and space volume. This has the effect that the electrolyte membrane can be humidified.

FIG. 11 is a graph showing the relationship between voltage and current density for the fuel cell of the fourth embodiment and a conventional fuel cell. In the figure, curve A shows the relationship between voltage and current density for the fuel cell of the fourth embodiment, and curve B shows the relationship between voltage and current density for a conventional fuel cell provided with a split rib type separator. It is a thing. As shown in the figure, the fuel cell of the fourth embodiment was superior to the conventional fuel cell in the characteristics over the entire current density in the measurement range.

Next, a fifth embodiment will be described. The fifth embodiment relates to a polymer electrolyte fuel cell having substantially the same configuration as the fuel cell 10 of the first embodiment, and differs only in the configuration of the separator.

FIG. 12 is an explanatory view schematically showing a cross section of a single cell 220 of the fuel cell according to the fifth embodiment. As shown in the drawing, this single cell 220 has a sandwich structure in which an electrolyte membrane 21 is sandwiched between an anode 22 and a cathode 23, similarly to the first embodiment, and a separator having a shape different from that of the first embodiment is provided outside thereof. 224,225
Is provided.

The separator 224 on the fuel electrode (anode) side
Is a conventionally known so-called straight type having a plurality of linear flow grooves, and is a fuel gas flow path 224P extending from the front side to the rear side of the drawing in FIG.
Are formed. The separator 225 on the oxygen electrode (cathode) side is the same straight type as the separator 224, and has an oxygen-containing gas channel 225P extending from top to bottom in FIG.

FIG. 13 is a perspective view in which a part of the separator 225 is cut away. As can be seen from FIG. 13, the separator 225 includes a plurality of oxygen-containing gas flow paths 225P formed from linear flow grooves, and the flow path bottom surface 225Pa of each oxygen-containing gas flow path 225P , A plurality of recesses 227 are provided at equal intervals in the flow channel direction. With this configuration, the channel bottom surface 225Pa is a surface having irregularities.

In FIG. 13, the separator 22
5, a separator 224 is fixed to the back surface, and the fixed component is assembled between adjacent sandwich structures (electrolyte membrane 21, anode and cathode 23).

According to the fuel cell having such a configuration, the generated water W (FIG. 12) generated on the cathode 23 side is formed in the concave portion 2 formed in the flow path bottom surface 225Pa of the oxygen-containing gas flow path 225P.
Collected in 27. The generated water W appropriately moisturizes the oxygen-containing gas, moves from the cathode 23 to the electrolyte membrane 21, and keeps the electrolyte membrane 21 in a good wet state.

Therefore, the fuel cell of the fifth embodiment can humidify the electrolyte membrane without using a humidifier, similarly to the first embodiment, and can efficiently consume energy and space. This has the effect that the electrolyte membrane can be humidified.

The configuration in which the bottom surface of the flow channel is provided with irregularities described using the fifth embodiment is not limited to the above-described straight type flow channel groove, and may be applied to a flow channel having another shape. Good. For example, a configuration may be adopted in which unevenness is provided on the bottom surface of a split rib type flow path, or a configuration in which unevenness is provided on the bottom surface of a so-called serpentine type flow path where the flow path is formed in a meandering shape.

Further, the configuration in which the above-mentioned unevenness is provided on the bottom surface of the flow channel may be applied to the first to third embodiments. That is, a configuration may be employed in which the bottom surface of the flow path formed by a plurality of convex portions having a horizontal surface is provided with irregularities.
The configuration may be such that the bottom surface of the flow path formed by the letter-shaped projections is provided with irregularities, or the configuration is such that the bottom surface of the flow path formed by the annular ribs is provided with unevenness.

Note that these irregularities do not necessarily have to be regular in size and arrangement as in the fifth embodiment.
Irregular sizes and irregular arrays may be used. Also,
A configuration in which a water-absorbing resin is applied to such an uneven surface may be adopted. The water-absorbing resin is the same as the example described above with reference to FIG.

The embodiment of the present invention has been described above.
The present invention is not limited to these embodiments at all, and it is a matter of course that the present invention can be implemented in various modes without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a structure of a single cell 20 constituting a fuel cell 10 according to a first embodiment of the present invention.

FIG. 2 is a plan view of a separator 25.

FIG. 3 is an explanatory view schematically showing a flow direction of an oxygen-containing gas and a state of generated water W in a separator 25.

FIG. 4 is an explanatory diagram schematically showing a cross section near an oxygen-containing gas flow path 25P.

FIG. 5 is an explanatory view schematically showing a plane of a conventional split rib type separator.

FIG. 6 is a graph showing the relationship between voltage and current density for the fuel cell 10 of the first embodiment and a conventional fuel cell.

FIG. 7 is an explanatory view schematically showing a plane of a separator used in a second embodiment.

FIG. 8 is a plan view of a separator 60 used in a third embodiment.

FIG. 9 is an explanatory diagram schematically showing a cross section of a single cell of a fuel cell which is a modification of the first embodiment.

FIG. 10 shows a single cell 120 of a fuel cell as a fourth embodiment.
It is explanatory drawing which represents the cross section of FIG.

FIG. 11 is a graph showing the relationship between voltage and current density for the fuel cell of the fourth embodiment and a conventional fuel cell.

FIG. 12 shows a single cell 220 of a fuel cell as a fifth embodiment.
It is explanatory drawing which represents the cross section of FIG.

FIG. 13 is a perspective view in which a part of a separator 225 is cut away.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Solid polymer type fuel cell 20 ... Single cell 21 ... Electrolyte membrane 22 ... Anode 23 ... Cathode 24, 25 ... Separator 24P ... Fuel gas flow path 25 ... Cathode 25P ... Oxygen-containing gas flow path 31, 33, 35, 37 ... Elongated hole 41 ... Stepped surface 43 ... Protrusion 43a ... Side 50 ... Protrusion 60 ... Separator 60a ... Surface 61,63 ... Round hole 61,63,65,66,67,68 ... Round hole 71,72,73, 74, 75, 76: Ribs 71s to 76s: Slit 120: Single cell 124, 125: Separator 143: Convex part 150: Depressed part 220: Single cell 224, 225: Separator 224P: Fuel gas flow path 225P: Oxygen-containing gas flow Channel 225Pa Channel bottom 227 Concave part RE Water absorbent resin W Generated water

Claims (9)

[Claims] 1. A fuel cell separator having a pair of electrodes sandwiching an electrolyte membrane and having a gas flow path for gas supply on the electrode side, wherein a water reservoir for retaining water in the gas flow path. A separator for a fuel cell, wherein a part is formed. 2. The fuel cell separator according to claim 1, wherein the water reservoir has a shape open to the electrode. 3. The fuel cell separator according to claim 1, wherein the gas flow path is formed by a plurality of protrusions protruding from a flow path bottom surface, and the fuel of the fuel cell separator. At the time of assembling to a battery, the direction of the gas flow through the gas flow path is determined to be vertically downward, and the water pool portion faces the convex portion with respect to the direction of the gas flow, A fuel cell separator formed by forming a vertical surface. 4. The fuel cell separator according to claim 1, wherein the gas flow path is formed by a plurality of protrusions protruding from a flow path bottom surface, and the water reservoir is formed by the protrusion. A separator having a depth that is vertically lower when the fuel cell separator is assembled to the fuel cell. 5. The fuel cell separator according to claim 4, wherein the convex portion is formed by bending a horizontally long rectangular parallelepiped into a V-shape, and the water pool portion is formed by bending the convex portion. A fuel cell separator composed of parts. 6. The fuel cell separator according to claim 1, wherein a water-absorbing resin is provided in the water reservoir. 7. The fuel cell separator according to claim 1, wherein the water reservoir is formed by providing irregularities on at least one wall surface of the gas flow path. 8. A fuel cell comprising: a joined body sandwiching an electrolyte membrane between a pair of electrodes; and a separator in contact with the joined body and having a gas flow path for gas supply on the electrode side, wherein the separator comprises: A flow path bottom surface facing the electrode surface; and a plurality of protrusions protruding from the flow path bottom surface and reaching the electrode surface, wherein the flow direction of the gas is vertically downward. And a fuel cell having an upward surface perpendicular to the direction of flow of the gas. 9. A fuel cell comprising: a joined body sandwiching an electrolyte membrane between a pair of electrodes; and a separator in contact with the joined body and having a gas flow path for supplying an oxygen-containing gas on the one electrode side. The separator includes a flow channel bottom surface facing the surface of the electrode, and a plurality of protrusions projecting from the flow channel bottom surface and reaching the surface of the electrode, wherein the protrusion is in contact with the surface of the electrode. A fuel cell provided with a water reservoir for retaining water.