JPH08203546A - Manufacture of fuel cell and flow path formation member used for it - Google Patents

Abstract

PURPOSE: To improve output voltage of a fuel cell in a high current density range so as to improve energy efficiency of a whole system. CONSTITUTION: A flow path for gas is formed between ribs and the surface of a gas diffusion electrode by forming a plurality of linear ribs in a current collecting body 15 of a fuel cell 10. One side of the current collecting body 15, which contacts with a cathode 12, forms an oxygen containing gas flow path 17a with the surface of the cathode 12 and the other side of the current collecting body 15, which contacts with an anode 13, forms a hydrogen containing gas flow path 17b with the anode 13. The crown width Wma of the oxygen containing gas flow path 17a is formed narrower than the crown width Wmb of the hydrogen containing gas flow path 17b. Such constitution can narrow the width of the crown part which is inferior in gas diffusion performance in the oxygen containing gas flow path 17a. Gas diffusion performance in the side of the oxygen containing gas flow path 17a is thus improved more than that of the hydrogen containing gas flow path 17b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell for supplying gas to a gas diffusion electrode from a flow channel formed in a flow channel forming member to obtain electromotive force from a chemical reaction of the gas, and a fuel cell for use in the fuel cell. The present invention relates to a method for manufacturing a flow path forming member.

[0002]

2. Description of the Related Art Conventionally, a fuel cell has been known as a device for directly converting the energy of fuel into electrical energy. For example, in a polymer electrolyte fuel cell, a pair of electrodes composed of a catalytic reaction layer and a gas diffusion layer are pressure-bonded to an electrolyte membrane that exhibits ionic conductivity in a humidified state, and a fuel such as hydrogen is attached to the surface of one electrode. A gas is brought into contact with the surface of the other electrode, and an oxygen-containing gas containing oxygen is brought into contact with the surface of the other electrode, and the electrochemical reaction that takes place at this time is utilized to extract electric energy from between the electrodes. Thus
The fuel cell can obtain a constant electromotive force as long as the fuel gas and the oxygen-containing gas are supplied.

By the way, in this fuel cell, the voltage actually obtained is lowered by a polarization phenomenon by drawing a current. The polarization phenomenon includes resistance polarization due to ionic conduction resistance and contact resistance of the electrolyte membrane, activation polarization due to catalytic activity, and concentration polarization due to diffusion control of the reaction gas,
In order to improve battery performance, it is important to reduce these polarizations.

On the other hand, in the above-mentioned fuel cell, the fuel gas and the oxygen-containing gas are supplied to the electrode surface by a member called a current collector that also serves as a flow path for these gases and a collector electrode. The current collector is generally one having a plurality of straight flow channel grooves on the surface in contact with the electrode, and a current collector provided on the fuel electrode side and a current collector provided on the oxygen electrode side. Is provided with flow channel grooves having the same shape, flow channel width and pitch width (distance between flow channels).

[0005]

However, since the oxygen-containing gas, air, is inferior in diffusibility to the fuel gas, hydrogen, the flow path groove of the current collector described above is provided on the oxygen electrode side and the hydrogen electrode side. In the conventional configuration in which the same is used, the problem that the diffusion of the oxygen-containing gas becomes poor on the oxygen electrode side in the high current density region, the concentration polarization increases, and the output voltage of the fuel cell decreases .

To restore the lowered output voltage of the fuel cell, it is necessary to increase the actual gas flow rate or the gas pressure higher than the theoretical gas flow rate according to the load.
For that reason, drive energy is required, and a secondary problem that the energy efficiency of the entire system deteriorates occurs.

The fuel cell of the present invention has been made in view of these problems, and an object thereof is to improve the output voltage of the fuel cell in a high current density region, and to improve the energy efficiency of the entire system. I am trying. The manufacturing method of the flow path forming member of the present invention aims to improve the output voltage of the fuel cell in the high current density region by manufacturing the flow path forming member used in the fuel cell, and thus the energy efficiency of the entire system. The purpose is to improve.

[0008]

In order to achieve such an object, the following constitution is adopted as a means for solving the above problems.

That is, in the fuel cell according to claim 1 of the present invention, a joined body sandwiching an electrolyte membrane between two electrodes, a hydrogen-containing gas passage and an oxygen-containing gas passage in contact with the joined body are provided. In a fuel cell having a flow path forming member for forming
The peak width of the flow path of the oxygen-containing gas formed in the flow path forming member is narrower than the peak width of the flow path of the hydrogen-containing gas formed in the flow path forming member.

In the fuel cell having such a structure, the flow path of the hydrogen-containing gas and the flow path of the oxygen-containing gas may be formed by an array of a plurality of convex members (claim 2).

A fuel cell according to a third aspect of the present invention is provided with a plurality of bonded bodies sandwiching an electrolyte membrane between a hydrogen electrode and an oxygen electrode and between the bonded bodies, and the bonded body on one side. Forming a flow path of a hydrogen-containing gas in contact with the hydrogen electrode of
In a fuel cell including a flow path forming member that forms a flow path of an oxygen-containing gas in contact with the oxygen electrode of the joined body on the other side, a flow path of the oxygen-containing gas formed in the flow path forming member The crest width is made narrower than the crest width of the flow path of the hydrogen-containing gas formed in the flow path forming member, and the crest part on the other side is internally present in the trough part on one side of both the flow paths. As described above, the both flow paths are arranged.

A manufacturing method according to a fourth aspect of the present invention is a method for manufacturing the flow path forming member used in the fuel cell according to the third aspect, the first mold material having a plurality of grooves, and It is characterized in that a step of pressurizing and compressing the flow path forming member material is provided by a second mold material having a plurality of grooves in which groove troughs are located relatively to the groove ridges of the first mold material.

[0013]

According to the fuel cell of the present invention configured as described above, the peak width of the flow path of the oxygen-containing gas formed in the flow path forming member is equal to that of the hydrogen containing gas formed in the flow path forming member. Since the width of the gas flow passage is narrower than that of the gas flow passage, the width of the portion (peak portion) where the gas diffusibility is poor in the flow passage of the oxygen-containing gas becomes narrow. Therefore, the diffusivity of the gas on the oxygen-containing gas side can be improved more than on the flow path side of the hydrogen-containing gas.
As a result, in the high current density region, it works to eliminate the deterioration of the diffusion of the oxygen-containing gas.

According to the fuel cell of the second aspect, since the gas flow path is formed by the array of the plurality of convex members, the gas flow is not limited to a straight groove but in one predetermined direction. , It becomes possible to flow in the other direction in a grid pattern. Therefore, the contact area of the gas with the electrode surface is increased and the generated water or the like generated at the electrode is easily discharged.

According to the fuel cell of the third aspect, the peak width of the flow path of the oxygen-containing gas formed in the flow path forming member is the peak width of the flow path of the hydrogen-containing gas formed in the flow path forming member. Since it is narrower than the above, it works so as to eliminate the deterioration of the diffusion of the oxygen-containing gas in the high current density region, as in the first aspect. Furthermore, since both flow paths are arranged so that the valleys on the one side of both the flow paths of the oxygen-containing gas and the hydrogen-containing gas are mutually present in the valleys on the other side, the flow path forming member Reduce the thickness.

According to the method of manufacturing a flow path forming member according to claim 4, the flow path forming member material is pressure-compressed by the pair of first and second mold materials, whereby the flow path to the groove troughs of these mold materials. The fluidity of the forming member material is improved so that the flow path forming member has a high filling property.

[0017]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above.

FIG. 1 shows a fuel cell 10 as a first embodiment.
It is a structural diagram showing a single cell of. FIG. 2 is a front view of the single cell. The fuel cell 10 is a polymer electrolyte fuel cell, and as shown in FIG. 1, a single cell is used as an electrolyte membrane 11 and a gas diffusion electrode having a sandwich structure in which the electrolyte membrane 11 is sandwiched from both sides. The cathode 12 and the anode 13 and this sandwich structure (joint body)
Cathode 12 and anode 1 while sandwiching 20 from both sides
3 and a current collector 15 as a flow path forming member that forms a flow path for the oxygen-containing gas and the hydrogen-containing gas.

The electrolyte membrane 11 is made of a polymer material such as a fluorine resin and has a thickness of 50 μm to 20 μm.
It is an ion exchange membrane of 0 [μm] and exhibits good electric conductivity in a wet state. Here, Nafion 115 manufactured by EI DuPont, USA is used. The cathode 12 and the anode 13 are formed of a carbon cloth woven with a yarn in which the surface of the carbon fiber is coated with polytetrafluoroethylene and the untreated carbon fiber is in a ratio of 1: 1. Since polytetrafluoroethylene exhibits water repellency, the surfaces of the cathode 12 and the anode 13 are not covered with water and hinder gas permeation. On the surface of the carbon cloth on the electrolyte membrane 11 side and in the gap, carbon powder carrying platinum or an alloy of platinum and another metal is kneaded to form a catalytic reaction layer.

Specifically, as the carbon powder carrying platinum, the weight of platinum is 40 [%] with respect to the weight of carbon powder.
(Wt%) is used, and this platinum-supporting carbon powder is used in an amount of 0.4 [mg / cm ² ] of platinum, and the fluorine-based cation exchange resin solution (solid content of Nafion is 5 [ %]) Is added and mixed in an amount such that the resin solid content is equivalent to 50 [%] to form a catalytic reaction layer.

The electrolyte membrane 11, the cathode 12 and the anode 13 are 100 ° C. to 160 ° C. with the electrodes 12 and 13 sandwiching the electrolyte membrane 11 in a sandwich structure.
1MP at a temperature of 110 ° C to 130 ° C
a {10.2 kgf / cm ² } to 20 MPa {102 kgf
/ Cm ² }, preferably 5 MPa {51 kgf / cm ² } or 1
Bonding is performed by a hot pressing method in which a pressure of 0 MPa {102 kgf / cm ² } is applied to bond.

The current collector 15 is formed of a dense carbon plate. The current collector 15 is formed with a plurality of ribs, and the ribs and the surface of the gas diffusion electrode form a straight gas flow path 17 having a rectangular cross section. The current collector 15 on the side in contact with the cathode 12 forms a flow path for the oxygen-containing gas with the surface of the cathode 12 and
The oxygen-containing gas flow path 17a that forms the water collecting path of the water generated in step (1) is formed, while the current collector 15 on the side in contact with the anode 13 is formed.
Forms a hydrogen-containing gas flow path 17b which forms a flow path for a mixed gas of hydrogen gas, which is a hydrogen-containing gas, and steam with the surface of the anode 13. The oxygen-containing gas passage 17a and the hydrogen-containing gas passage 17b are formed so that their directions are parallel to each other, and as shown in FIG. Portion) width Wma is formed to be narrower than the mountain width Wmb of the hydrogen-containing gas passage 17b.

FIG. 3 is an explanatory view showing the relative positional relationship between the oxygen-containing gas passage 17a and the hydrogen-containing gas passage 17b in the fuel cell 10. In this figure, the hatched portion shows the junction of the peak portion of the oxygen-containing gas flow channel 17a with the cathode surface, and the non-hatched portion (including the hatched portion) is the anode of the peak portion of the hydrogen-containing gas flow channel 17b. The joint with the surface is shown. Also from this figure, the oxygen-containing gas flow channel 17a and the hydrogen-containing gas flow channel 17b have the directions parallel to each other, and the peak width W of the oxygen-containing gas flow channel 17a is W.
It can be seen that ma is narrower than the mountain width Wmb of the hydrogen-containing gas passage 17b.

Specifically, the peak width Wma of the oxygen-containing gas passage 17a is 0.5 [mm] and the valley width Wga thereof is 1.5.
[Mm], and the mountain width Wmb of the hydrogen-containing gas passage 17b
Is 1.0 [mm] and its valley width Wgb is 1.0 [mm]. The current collector 15 having such a configuration and the bonded body 20 are seal-bonded with an adhesive.

The electrolyte membrane 11 and the cathode 1 described above
2, the anode 13 and the current collector 15 have a single cell structure of the fuel cell 10. In practice, a plurality of sets of the current collector 15, the cathode 12, the electrolyte membrane 11, the anode 13, and the current collector 15 are arranged in this order. The fuel cell 10 is constructed by stacking.

The fuel cell 10 thus constructed carries out the electrochemical reaction represented by the following equations (1) and (2) to directly convert chemical energy into electrical energy.

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

This electrochemical reaction is carried out in the oxygen-containing gas flow path 1
The oxygen-containing gas flowing through 7a diffuses into the catalytic reaction layer of the cathode 12, and the hydrogen-containing gas flowing through the hydrogen-containing gas flow path 17b diffuses into the catalytic reaction layer of the anode 13 so that the oxygen-containing gas continuously flows. Here, the gas diffusivity to the catalytic reaction layer was evaluated by the ammonia gas diffusion method using a straight straight gas passage having a rectangular cross section, and will be described below.

The ammonia gas diffusion method is a method in which diazo photosensitive paper is assembled in the cell instead of the catalytic reaction layer and ammonia vapor is caused to flow in the gas passage to evaluate the diffusivity of ammonia gas. When the ammonia gas diffuses into the diazo photosensitive paper, the diffused area changes its color to blue. Therefore, by measuring this discolored area, the diffusivity of the ammonia gas in the gas flow path can be examined. The result of the evaluation is shown in FIG. As shown in FIG.
Gas is less likely to diffuse on the pressure-bonding surface between the mountain portion M2 of the gas flow path M1 and the gas diffusion electrode M3, and 0.2 [m from the end of the mountain portion M2.
The diffusion of gas was observed only in the area inside only [m]. The thicknesses of the gas diffusion layer, the catalytic reaction layer and the electrolyte membrane at this time are 0.3 [mm], 0.01 [mm], 0.
It was set to 12 [mm].

As a result of this evaluation, in the straight gas flow passage having a rectangular cross section, gas diffusion is observed only in the valley portion of the gas flow passage and a portion slightly invaded from the end portion of the mountain portion, and the mountain portion is It turned out that almost no gas diffusion was seen.

In the fuel cell 10 of the first embodiment described so far, in the current collector 15, the peak width Wma of the oxygen-containing gas passage 17a on the cathode 12 side is set to the anode 13.
Since it is configured to be narrower than the mountain width Wmb of the hydrogen-containing gas passage 17b on the side, the width of the mountain portion having poor gas diffusibility in the oxygen-containing gas passage 17a can be narrowed. Therefore, the gas diffusivity on the oxygen-containing gas flow channel 17a side can be enhanced more than on the hydrogen-containing gas flow channel 17b side. As a result, the actual reaction area of the cathode 12 can be made larger than the actual reaction area of the anode 13.

In general, the oxygen-containing gas is inferior in diffusivity to the hydrogen-containing gas. Therefore, in the conventional structure in which the peak width and the groove width of the gas flow path are the same on the cathode side and the anode side, in the high current density region. However, the diffusion of the oxygen-containing gas becomes poor on the cathode side, and the output voltage of the fuel cell decreases. On the other hand, in the first embodiment, since the actual reaction area of the cathode 12 can be made larger than the actual reaction area of the anode 13, it is possible to prevent the output voltage from decreasing in the high current density region. It produces the effect you just said. Also, since it is possible to prevent the output voltage from decreasing, the ratio (the stoichiometric ratio) between the theoretical gas flow rate and the actual gas flow rate can be increased as in the conventional case.
Since there is no need to increase the gas pressure, the power consumption by the compressor or blower for that purpose can be suppressed, and the energy efficiency of the entire system can be improved.

By the way, in this embodiment, the cathode 12
It has been described that the actual reaction area of (1) is larger than the actual reaction area of the anode 13, but the extent of increase was examined by the above-mentioned ammonia gas diffusion method. As a result, when the electrode area was set to 144 [cm ² ], straight grooves having a peak width and a valley width of both 1.0 [mm] were formed on the anode 13 side, so the actual reaction area was 100. [Cm
² ] (converted as an electrode utilization rate of 69 [%]), and since a straight groove having a peak width of 0.5 [mm] and a valley width of 1.5 [mm] is formed on the cathode 12 side. The actual reaction area is 137 [cm ² ] (95 [%] when converted as the electrode utilization rate). Therefore, it was found from this actual measurement result that the actual reaction area of the cathode 12 was considerably larger than the actual reaction area of the anode 13.

The second embodiment of the present invention will be described below. The second embodiment relates to a fuel cell having almost the same configuration as the fuel cell 10 of the first embodiment, and the direction of the oxygen-containing gas passage formed in the current collector is different from that of the first embodiment. Be different. That is, in the first embodiment, the oxygen-containing gas channel 1
Although the direction of 7a and the direction of the hydrogen-containing gas flow path 17b are configured to be parallel to each other, in the second embodiment, the direction of the oxygen-containing gas flow path and the direction of the hydrogen-containing gas flow path are orthogonal to each other. Is configured to.

FIG. 5 shows a fuel cell 11 as a second embodiment.
FIG. 3 is a structural diagram showing a single cell of 0. As shown in FIG.
A hydrogen-containing gas channel 117b extending in the x direction in the drawing is formed in the current collector 115 bonded to the anode 113 side, and a current collector 115 bonded to the cathode 112 side is in the y direction in the drawing. And an oxygen-containing gas flow path 117a extending in the direction is formed. That is, the fuel cell 110 of the second embodiment.
In the fuel cell 10 of the first embodiment, the current collector 15 on the cathode 12 side is rotated 90 degrees clockwise around the y-axis in the figure, so that the direction of the oxygen-containing gas flow path 117a and the hydrogen flow path are reduced. It is configured such that the directions of the containing gas channels 117b are orthogonal to each other.

FIG. 6 is an explanatory diagram showing the relative positional relationship between the oxygen-containing gas passage 117a and the hydrogen-containing gas passage 117b in the fuel cell 110. In this figure, the hatched portion indicates the joint portion with the cathode surface of the peak portion of the oxygen-containing gas flow channel 17a, and the non-hatched portion indicates the joint portion with the anode surface of the peak portion of the hydrogen-containing gas flow channel 17b. Show. Also from this figure, the oxygen-containing gas channel 11
It can be seen that the directions of 7a and the hydrogen-containing gas passage 117b are orthogonal to each other. Moreover, as shown in this figure,
Similar to the first embodiment, the mountain width Wma of the oxygen-containing gas flow channel 117a is narrower than the mountain width Wmb of the hydrogen-containing gas flow channel 17b.

As described above, in the fuel cell 110 of the second embodiment, the peak width Wma of the oxygen-containing gas flow path 117a on the cathode 112 side is the peak width Wmb of the hydrogen-containing gas flow path 117b on the anode 113 side. Since it is configured to be narrower than that of the oxygen-containing gas passage 117a, the peak portion having poor gas diffusibility is narrowed on the oxygen-containing gas passage 117a side, and the hydrogen-containing gas passage 117b is formed.
The gas diffusivity on the oxygen-containing gas flow path 117a side can be enhanced more than on the side. As a result, the actual reaction area of the cathode 112 can be made larger than the actual reaction area of the anode 113.

Therefore, the fuel cell 110 according to the second embodiment.
Then, like the first embodiment, it is possible to prevent the output voltage of the fuel cell from decreasing in the high current density region, and
It is also possible to suppress the special power consumption in the high current density region and improve the energy efficiency of the entire system.

Another embodiment of the above-described first embodiment will be described below. This embodiment has substantially the same configuration as the fuel cell 10 of the first embodiment, and the difference from the first embodiment is that, as shown in FIG. 7, one current collector 215 is used.
In addition, the oxygen-containing gas channel 217a and the hydrogen-containing gas channel 21
7b and two bonded bodies 220 are formed.
The difference is that A and 220B are connected by one current collector 215. As in the first embodiment, the peak width Wma of the oxygen-containing gas flow passage 217a is equal to the hydrogen-containing gas flow passage 21.
It is narrower than the mountain width Wmb of 7b. For this reason, also in the embodiment of this another aspect, the same effect as that of the first and second embodiments is achieved.

In place of this alternative embodiment, both the oxygen-containing gas flow path and the hydrogen-containing gas flow path are formed in one current collector, and the oxygen-containing gas flow is the same as in the second embodiment. The directions of the passage and the hydrogen-containing gas passage may be orthogonal to each other.

The third embodiment of the present invention will be described below. The third embodiment relates to a fuel cell having substantially the same structure as the fuel cell 10 of the first embodiment, and the shape of the current collector is different from that of the first embodiment. The current collector of the third embodiment constitutes a gas flow path with a plurality of convex portions, and FIG. 8 is a plan view of the current collector. As shown in FIG. 8, the current collector 315 is formed as an octagonal plate-shaped member,
Near the edges of four hypotenuses out of the eight sides of the current collector 15,
Along the sides, elongated holes 321, 323 and holes 32
5,327 are formed. The holes 321, 323 and the holes 325, 327 are provided with two hydrogen-containing gas supply / exhaust passages that penetrate the fuel cell in the stacking direction when stacked.
Two oxygen-containing gas supply / discharge channels are formed. Current collector 315
Holes 321 and 323 on one of the stacking surfaces (display surface in FIG. 8) of
As shown in the drawing, a step surface 331 that is one step lower than the plane of the outer edge is formed between and.
A plurality of cubic ribs (projections) 333 each having a side of 1 [mm] are regularly arranged.

The cubic ribs 333 are arranged in a grid pattern in the horizontal direction and the vertical direction.
3 and the step surface 331 and the surface of the gas diffusion electrode form a flow path of the oxygen-containing gas.

The other side of the laminated surface of the current collector 315 (see FIG. 8).
Between the holes 325 and 327 (on the back surface of the same), the step surface 331 and the rib 3 formed between the holes 321 and 323.
A step surface and a rib (343: FIG. 9) having the same shape as 33 are formed. The step surface, the rib and the surface of the gas diffusion electrode form a flow path for the hydrogen-containing gas.

FIG. 9 is an explanatory view showing the relative positional relationship between the oxygen-containing gas passage and the hydrogen-containing gas passage in the current collector 315. In this figure, the hatched portion shows the joint portion of the rib 333 forming the oxygen-containing gas flow path with the cathode surface, and the non-hatched portion (including the hatched portion) shows the rib 343 forming the hydrogen-containing gas flow path. 3 shows a joint portion with the anode surface. As shown in this figure, the mountain width Wma of the oxygen-containing gas flow channel formed by the rib 333 is narrower than the mountain width Wmb of the hydrogen-containing gas flow channel formed by the rib 343. In addition, specifically, the mountain width Wma of the oxygen-containing gas flow path is 0.5 [m
m], and the valley width Wga is 1.5 [mm],
On the other hand, the mountain width Wmb of the hydrogen-containing gas channel is 1.0 [m
m] and its valley width Wgb is 1.0 [mm].

In the fuel cell provided with the current collector 315 having such a structure, the peak width Wma of the oxygen-containing gas flow path formed by the rib 333 is larger than the peak width Wmb of the hydrogen-containing gas flow path formed by the rib 343. Since the width is narrow, the mountain portion having poor gas diffusibility can be narrowed on the oxygen-containing gas channel side, and the gas diffusivity on the oxygen-containing gas channel side can be enhanced more than that on the hydrogen-containing gas channel side. As a result, the actual reaction area of the cathode can be made larger than the actual reaction area of the anode.

Therefore, in the fuel cell of the third embodiment,
Similar to the first and second embodiments, it is possible to prevent the output voltage of the fuel cell from decreasing in the high current density region, and to suppress the special power consumption in the high current density region,
It is also possible to improve the energy efficiency of the entire system.
In addition, by configuring the flow path with a plurality of convex portions, it is possible to increase the contact area of the gas with the electrode surface and improve the energy conversion efficiency of the fuel cell. Furthermore, as shown in the formula (1) above. It is possible to facilitate discharge of water generated by the reaction and humidifying water supplied from the outside.

Since the fuel cell 110 of the second embodiment and the fuel cell of the third embodiment described above were compared and evaluated with the conventional example,
Next, a description will be given. The fuel cell of the conventional example to be compared is of the straight groove type as in the second embodiment, and has a mountain width of 1 [m for both the hydrogen-containing gas flow path and the oxygen-containing gas flow path of the current collector.
m] and a valley width of 1 [mm] (hereinafter referred to as a first conventional example), and a peak width of 0.5 [mm] and a valley width of 1.5 [mm] (hereinafter referred to as a second conventional example). Call).

The relationship between the current density and the voltage when these fuel cells were operated at an operating temperature of 80 ° C. was investigated, and the results are shown in FIG. As is apparent from FIG. 10, in the fuel cell 110 of the second embodiment shown by the alternate long and short dash line and the fuel cell of the third embodiment shown by the solid line, a comparative example is shown over the entire current density of the measurement range. Of the first conventional fuel cell (2
The characteristics are superior to those of the fuel cell of the second conventional example (shown by the broken line) and the current density is 0.5 [A].
/ Cm ² ] or higher current density region, the difference is remarkable. That is, in the first and second examples, since the peak width of the oxygen-containing gas flow channel is narrower than the peak width of the hydrogen-containing gas flow channel, the gas diffusibility on the oxygen-containing gas flow channel side should be improved. Therefore, high battery performance could be obtained as is clear from FIG.

FIG. 11 shows the relationship between the voltage and the holding time when the fuel cell 110 of the second embodiment and the fuel cell of the third embodiment were operated at an operating temperature of 80 [° C.]. As is apparent from FIG. 11, the fuel cell 110 of the second embodiment shown by the one-dot chain line and the fuel cell of the third embodiment shown by the solid line are
It was confirmed that the high voltage was stably maintained for a long time as compared with the fuel cell of the first conventional example shown by the two-dot chain line and the fuel cell of the second conventional example shown by the broken line.

The fourth embodiment of the present invention will be described below. The fourth embodiment is a modification of the embodiment shown in FIG. 7, and the shape of the current collector is different from that of the embodiment shown in FIG. FIG. 12 shows a fuel cell 41 as the fourth embodiment.
FIG. 13 is a structural diagram showing a cell structure of No. 0, and FIG. 13 is a perspective view of a current collector 415 provided in the fuel cell 410.

As shown in both figures, in the fuel cell 410 of the fourth embodiment, one current collector 415 has both an oxygen-containing gas flow channel 417a and a hydrogen-containing gas flow channel 417b. In addition, the current collector 415 is arranged such that the gas flow passages are arranged such that the valleys on the one side of the gas flow passages on the other side are inside each other. That is,
The current collector 415 has a configuration in which a flat plate is modified so that rectangular irregularities are alternately repeated. In addition, this current collector 415
Width Wma of the oxygen-containing gas channel 417a formed in
Is the hydrogen-containing gas flow channel 41 as in the previous embodiments.
It is narrower than the mountain width Wmb of 7b.

The current collector 4 of the fuel cell 410 having such a structure
The manufacturing method of 15 will be described in detail below. In addition,
The current collector 415 is manufactured using the thermally expanded graphite powder manufactured as follows. A natural scaly graphite powder is prepared, and the graphite powder is wet-oxidized by immersing the graphite powder in concentrated sulfuric acid, concentrated nitric acid, mixed acid, or the like. Then, when this graphite powder is rapidly heated at a high temperature of 900 [° C.] or higher, the distance between layers in the crystal structure of graphite is 50 to 500.
It expands twice to form a thermally expanded graphite powder. A current collector 415 is manufactured using this thermally expanded graphite powder as a material.

In manufacturing the current collector 415, first, a press jig 500 including an outer frame 501, an upper mold 503 and a lower mold 505 shown in FIG.
The thermally expanded graphite powder C is put in 0. This press jig 50
A plurality of straight convex portions 503L and 505L are formed on the upper mold 503 and the lower mold 505 of 0, and the relative horizontal positional relationship between the convex portions 503L and 505L is as follows.
Convex portion 503L formed on one side mold 503 (505)
In the valley between (505L), the other mold 505 (503)
The relationship is such that the protrusions of the straight grooves 505L (503L) formed in the above are relatively positioned.

Next, the upper mold 50 of this press jig 500.
A vertically downward load is applied to 3 (the lower die 505 is fixed) to press and compress the thermally expanded graphite powder C. The pressure for pressing the upper mold 503 was 1.0 [ton / cm ² ]. As a result, the current collector 415 having the above-described configuration is manufactured.

As described above in detail, in the fuel cell 410 of the fourth embodiment, the peak width W of the oxygen-containing gas passage 417a is W.
Since ma is configured to be narrower than the mountain width Wmb of the hydrogen-containing gas passage 417b, the oxygen-containing gas passage 417 is formed.
On the a side, the mountain portion having poor gas diffusivity can be narrowed to enhance the gas diffusivity on the oxygen-containing gas flow channel 417a side than on the hydrogen-containing gas flow channel 417b side. As a result, the actual reaction area of the cathode 412 can be made larger than the actual reaction area of the cathode 413.

Therefore, the fuel cell 410 of this fourth embodiment is used.
Then, as in the previous examples, it is possible to prevent the output voltage of the fuel cell from decreasing in the high current density region.
Further, it is possible to suppress the special power consumption in the high current density region and improve the energy efficiency of the entire system. Further, the current collector 415 of the fuel cell 410 includes an oxygen-containing gas flow channel 417 a and a hydrogen-containing gas flow channel 417.
Since both gas flow passages 417a and 417b are formed so that the peaks on the other side are present in the valleys on the one side of b, it is possible to reduce the thickness of the current collector 415. As a result, the stack of the fuel cell 410 can be made compact.

Furthermore, the current collector 415 is attached to the pressing jig 5
It is possible to improve the filling property of the thermally expansive graphite powder by using the No. 00 to manufacture by press molding. Therefore,
According to the current collector 415, high packing can be easily achieved, high strength can be ensured, and the function as the gas separator is not impaired.

In the above-described first to fourth embodiments, the peak width Wma of the oxygen-containing gas flow path 17a is 0.5 [mm] and the peak width Wmb of the hydrogen-containing gas flow path 17b is 1.0 [mm]. However, these values are not necessarily limited to these values, and the point is that the mountain width Wma of the oxygen-containing gas flow channel 17a may be narrower than the mountain width Wmb of the hydrogen-containing gas flow channel 17b. In consideration of gas diffusivity, the peak width Wma of the oxygen-containing gas flow path 17a is preferably 1
It is desirable to set it to [mm] or less.

The embodiment of the present invention has been described above.
The present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

[0060]

As described above, in the fuel cell according to the first to third aspects, the gas diffusibility in the gas flow passage of the flow passage forming member is set to be closer to the oxygen-containing gas passage than to the hydrogen-containing gas passage. Can be increased. As a result, in the high current density region, it is possible to prevent the occurrence of the problem that the diffusion of the oxygen-containing gas becomes poor and the output voltage decreases. Further, since it is possible to prevent the output voltage from decreasing, it is not necessary to increase the actual gas flow rate or the gas pressure higher than the theoretical gas flow rate as in the conventional case. The consumption can be suppressed and the energy efficiency of the entire system can be improved.

Further, in the fuel cell according to the second aspect, since the gas flow path is formed by the array of the plurality of convex members, it is possible to increase the contact area of the gas with the electrode surface, and further, It is possible to easily discharge the generated water generated at the electrodes and the supplied humidifying water.

According to the fuel cell of the third aspect, the thickness of the flow path forming member can be reduced, and as a result, the entire stack can be made compact.

According to the method of manufacturing the flow path forming member of the fourth aspect, it is possible to manufacture the flow path forming member having a high filling property. Therefore, by using the flow path forming member,
High packing and high strength can be achieved, and the function of gas impermeability is not impaired.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a single cell of a fuel cell 10 as a first embodiment of the present invention.

FIG. 2 is a front view of the single cell.

FIG. 3 is an oxygen-containing gas passage 17a in the fuel cell 10.
It is explanatory drawing which shows the relative positional relationship of the hydrogen containing gas flow path 17b.

FIG. 4 is an explanatory diagram showing the diffusivity of a gas flow channel examined by an ammonia gas diffusion method.

FIG. 5 is a structural diagram showing a single cell of a fuel cell 110 as a second embodiment of the present invention.

FIG. 6 is an oxygen-containing gas channel 11 in the fuel cell 110.
7a is an explanatory diagram showing a relative positional relationship between a hydrogen-containing gas flow path 117b and 7a. FIG.

FIG. 7 is a structural diagram showing a cell structure of a fuel cell as another mode of the first embodiment.

FIG. 8 is a current collector 31 provided in the fuel cell according to the third embodiment.
5 is a plan view of FIG.

9 is an explanatory diagram showing a relative positional relationship between an oxygen-containing gas passage and a hydrogen-containing gas passage in a current collector 315. FIG.

FIG. 10 is a graph showing the relationship between voltage and current density in the fuel cells of the second and third examples and the fuel cell of the conventional example.

FIG. 11 is a graph showing the relationship between voltage and holding time in the fuel cells of the second and third examples and the fuel cell of the conventional example.

FIG. 12 is a fuel cell 410 as a fourth embodiment of the present invention.
3 is a structural diagram showing the cell structure of FIG.

FIG. 13 is a perspective view of a current collector 415.

FIG. 14 is a press jig 5 used for manufacturing a current collector 415.
It is a schematic block diagram of 00.

[Explanation of symbols]

 10 ... Fuel cell 11 ... Electrolyte membrane 12 ... Cathode 13 ... Anode 15 ... Current collector 17 ... Gas channel 17a ... Oxygen-containing gas channel 17b ... Hydrogen-containing gas channel 20 ... Junction 110 ... Fuel cell 112 ... Cathode 113 ... Anode 115 ... Current collector 117a ... Oxygen-containing gas flow path 117b ... Hydrogen-containing gas flow path 215 ... Current collector 217a ... Oxygen-containing gas flow path 217b ... Hydrogen-containing gas flow path 220A, 220B ... Bonding body 315 ... Current collection Body 331 ... Step surface 333 ... Rib 343 ... Rib 410 ... Fuel cell 412 ... Cathode 415 ... Current collector 417a ... Oxygen-containing gas passage 417b ... Hydrogen-containing gas passage 500 ... Press jig 501 ... Outer frame 503 ... Upper mold 505 ... Lower mold

Claims (4)

[Claims] 1. A fuel comprising: a joined body sandwiching an electrolyte membrane between two electrodes; and a flow passage forming member which is in contact with the joined body and forms a flow passage for a hydrogen-containing gas and a flow passage for an oxygen-containing gas. In the battery, the peak width of the flow path of the oxygen-containing gas formed in the flow path forming member is narrower than the peak width of the flow path of the hydrogen-containing gas formed in the flow path forming member. And a fuel cell. 2. The fuel cell according to claim 1, wherein the flow path for the hydrogen-containing gas and the flow path for the oxygen-containing gas are:
A fuel cell formed by an array of a plurality of convex members. 3. A plurality of bonded bodies sandwiching an electrolyte membrane between a hydrogen electrode and an oxygen electrode, and a hydrogen-containing gas provided between the bonded bodies and in contact with the hydrogen electrode of one bonded body. And a flow channel forming member that forms a flow channel of an oxygen-containing gas in contact with the oxygen electrode of the joined body on the other side, wherein the flow channel forming member is formed. The peak width of the flow path of the oxygen-containing gas is made narrower than the peak width of the flow path of the hydrogen-containing gas formed in the flow path forming member, and the other is formed in the valley portion on one side of the both flow paths. A fuel cell, characterized in that the both flow paths are arranged such that the mountain portions on the side are inward of each other. 4. A method for manufacturing a flow path forming member used in the fuel cell according to claim 3, wherein the first mold member having a plurality of grooves and the groove ridges of the first mold member are relatively formed. A method for manufacturing a flow path forming member, comprising a step of pressurizing and compressing the flow path forming member material with a second mold material having a plurality of grooves in which groove troughs are located.