JPH0896820A - Fuel cell - Google Patents

Abstract

PURPOSE: To Provide a fuel cell in which diffusion of fuel in an electrode is increased to enhance utilization factor of the electrode, and contact resistance is decreased to enhance efficiency. CONSTITUTION: Recesses and projections of 5-500μm, preferably 10-200μm are formed on the end surface 46, coming in contact with a gas diffusion electrode 30, of a rib 42 of a current collecting electrode 40, on the side surface 47 of the rib 42, and on the surface 48 of the rib 42. When compression load is applied to the stacking direction of a fuel cell, the recesses and projections form low surface pressure parts in a contact part 34, which comes in contact with the end surface 46 of the rib 42 of the current collecting electrode 40, of the gas diffusion electrode 30. Oxidizing gas or fuel gas in a gas flow path 44 diffuses inside the contact part 34 of the gas diffusion electrode 30 through the low surface pressure part from the edge of the end surface 46 of the rib 42. As a result, the area of the gas diffusion electrode 30 contributing to electrochemical reaction is enlarged, and a fuel cell with high efficiency can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more specifically, to a fuel flow path composed of an electrolyte layer, electrodes for sandwiching the electrolyte layer to form a power generation layer, and electrodes sandwiching the power generation layer for the fuel cell. And a collector electrode having a rib portion that forms the fuel cell.

[0002]

2. Description of the Related Art Conventionally, this type of fuel cell has a size of 1 μm.
One using a gas diffusion electrode having many pores of about m to 100 μm has been proposed (for example, JP-A-6-3.
6771 and JP-A-3-93165). In these fuel cells, by providing many pores in the gas diffusion electrode, the fuel gas is smoothly supplied to the electrolyte layer,
The power generation characteristics in the high current density region are improved.

Such a gas diffusion electrode, for example, Japanese Unexamined Patent Publication (Kokai) No.
In the gas diffusion electrode described in JP-A-36771, an inorganic salt powder is mixed with a material forming the gas diffusion electrode to form a sheet, which is then sintered, and the inorganic salt powder is extracted from a sintered product into a solvent. It is removed to obtain the desired porosity.

[0004]

However, in a fuel cell using such a gas diffusion electrode, since the gas diffusion electrode is formed by sintering, it lacks flexibility and causes contact failure due to manufacturing error or the like. There was a problem that resistance increased. In addition, since the gas diffusion electrode has many pores, it is fragile and low in strength.

In order to solve these problems, it is conceivable to use a soft and breathable carbon cloth (woven cloth made of carbon fibers) for the gas diffusion electrode. However, a gas diffusion electrode made of this carbon cloth is laminated with a collector electrode having a rib that forms a fuel gas flow path together with the gas diffusion electrode to form a fuel cell, and in order to reduce the contact resistance of the fuel cell, When a pressing load is applied in the stacking direction, the portion of the gas diffusion electrode that is in contact with the rib of the collector electrode is compressed and densified by the pressing load, and the air permeability is reduced. Therefore, the diffusion of the fuel gas to the densified portion is hindered, it becomes difficult to contribute to the electrochemical reaction, and there arises a problem that the utilization rate of the gas diffusion electrode becomes low. In order to improve the diffusion of the fuel gas to the portion of the gas diffusion electrode that contacts the rib of the collector electrode, it is possible to provide pores in the rib of the collector electrode, but it was densified by the pressing load of the gas diffusion electrode. The improvement of fuel gas permeability in the part cannot be expected.

An object of the fuel cell of the present invention is to solve such problems, improve the fuel diffusion of the electrode to increase the utilization factor of the electrode, and reduce the contact resistance to provide an efficient fuel cell. And adopted the following configuration.

[0007]

A first fuel cell of the present invention is a fuel cell comprising an electrolyte layer, electrodes for sandwiching the electrolyte layer to form a power generation layer, and sandwiching the power generation layer for holding fuel. In a fuel cell comprising a collecting electrode having a rib portion forming a flow path, the fuel in the flow path is in contact with the electrode from an edge of a contact surface of the rib portion which contacts the contact surface by a predetermined dimension or more. It is characterized in that the contact surface has a non-flat shape so as to diffuse to the contacted portion of the electrode.

A second fuel cell of the present invention comprises an electrolyte layer,
In a fuel cell, comprising: an electrode that sandwiches the electrolyte layer to form a power generation layer; and a collector electrode that sandwiches the power generation layer and has a rib portion that forms a fuel flow path with the electrode, in contact with the electrode A plurality of grooves that cross the rib portion are formed on the contact surface of the rib portion.

A third fuel cell of the present invention comprises an electrolyte layer,
In a fuel cell, comprising: an electrode that sandwiches the electrolyte layer to form a power generation layer; and a collector electrode that sandwiches the power generation layer and has a rib portion that forms a fuel flow path with the electrode, in contact with the electrode A groove is formed on the contact surface of the rib portion within a predetermined dimension from the edge of the contact surface.

A fourth fuel cell of the present invention comprises an electrolyte layer and
In a fuel cell, comprising: an electrode that sandwiches the electrolyte layer to form a power generation layer; and a collector electrode that sandwiches the power generation layer and has a rib portion that forms a fuel flow path with the electrode, in contact with the electrode The contact surface of the rib portion is formed in a protruding shape.

A fifth fuel cell of the present invention comprises an electrolyte layer,
In a fuel cell comprising an electrode that sandwiches the electrolyte layer to form a power generation layer and a collector electrode that sandwiches the power generation layer and has a rib portion that forms a fuel flow path with the electrode, is in contact with the electrode Conductive fibers are implanted on the contact surface of the rib portion.

[0012]

In the first fuel cell of the present invention constructed as described above, the contact surface of the rib portion of the collecting electrode which comes into contact with the electrode is made non-flat, so that the fuel in the flow path is protected from the contact surface. From the edge of the electrode to the contacted portion of the electrode that contacts this contact surface by a predetermined size or more. As a result, the area of the electrode that can contribute to the electrochemical reaction is increased, and an efficient fuel cell is obtained. The predetermined dimension here is set to a value larger than the dimension at which the fuel in the flow path can diffuse from the edge of the contact surface to the contacted portion of the electrode when the contact surface of the rib portion of the collecting electrode is made flat. It is determined by the material, structure, flexibility, permeability of the electrode, the surface pressure of the contacted portion of the electrode due to the pressing load acting in the stacking direction of the fuel cell, and the like.

In the second fuel cell of the present invention, the fuel in the flow path comes into contact with the contact surface through a plurality of grooves formed in the contact surface of the rib contacting the electrodes and traversing the ribs. It diffuses to the contacted part of the electrode.

In the third fuel cell of the present invention, the groove formed within a predetermined dimension from the edge of the contact surface of the rib portion contacting the electrode has an edge portion of the contacted portion of the electrode contacting the contact surface. Make a part with low surface pressure within the specified dimension. As a result, the fuel in the flow path diffuses from the edge of the contact surface of the rib to the low contact pressure portion of the contacted portion of the electrode, and the fuel that has diffused to this low contact pressure portion is further absorbed inside the contacted portion. Spread to. The predetermined size here means that the fuel in the flow channel diffuses from the edge of the contact surface of the rib to the contacted part of the electrode when the groove is not formed on the contact surface of the rib of the collecting electrode. It is set as a value smaller than the obtained size, and is determined by the material, structure, flexibility, permeability of the electrode, the surface pressure of the contacted part of the electrode due to the pressing load applied in the stacking direction of the fuel cell, etc. .

In the fourth fuel cell of the present invention, the protruding contact surface of the rib portion in contact with the electrode acts on the contacted portion of the electrode in contact with the contact surface based on this protruding shape. Change. As a result, the fuel in the flow path diffuses inward from the edge of the contact surface of the rib portion through the low contact pressure portion of the contacted portion of the electrode.

In the fifth fuel cell of the present invention, the conductive fibers planted on the contact surface of the rib portion in contact with the electrode change into the surface pressure acting on the contacted portion of the electrode in contact with this contact surface. give. As a result, the fuel in the flow path diffuses inward from the edge of the contact surface of the rib portion through the low contact pressure portion of the contacted portion of the electrode. In addition, the fibers having conductivity, which are implanted on the contact surface of the rib portion, form a layer having a plurality of minute gaps at the contact portion between the contact surface of the rib and the contacted portion of the electrode. Therefore, the fuel diffuses from the gap of this layer to the contacted portion of the electrode. Furthermore, when the electrode is formed of fibers such as carbon cloth, the conductive fibers implanted on the contact surface of the rib portion are entangled with the fibers of the electrode and reduce the contact resistance between the electrode and the collecting electrode. .

[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 is an explanatory view illustrating the configuration of a unit cell 10 that constitutes a fuel cell that is a preferred embodiment of the present invention, and FIG. 2 is an enlarged explanatory view showing an enlarged portion of a broken line circle in FIG. is there. The unit cell 10 is a polymer electrolyte fuel cell unit cell, and as shown in FIG. 1, an electrolyte membrane 20 and two gas diffusion electrodes 30 that sandwich the electrolyte membrane 20 from both sides to form a sandwich structure. , And two collector electrodes 40 sandwiching this sandwich structure from both sides.

The electrolyte membrane 20 is made of a polymer material such as a fluorine resin and has a thickness of 100 μm to 20 μm.
It is a 0 μm ion-exchange membrane and exhibits good electric conductivity in a wet state. The two gas diffusion electrodes 30 are both formed of carbon cloth woven with threads made of carbon fibers. On the surface of the carbon cloth on the side of the electrolyte membrane 20 and the gap, carbon powder carrying platinum or an alloy of platinum and another metal is kneaded to form a catalyst layer 32 (see FIG. 2). The electrolyte membrane 20 and the two gas diffusion electrodes 30 have a sandwich structure in which the two gas diffusion electrodes 30 sandwich the electrolyte membrane 20 at 100 ° C.
To 160 ° C., preferably 110 to 130 ° C., 1 MPa {10.2 kgf / cm ² } to 20 MPa
{204 kgf / cm ² } preferably 5 MPa {51 kgf / c
They are joined by a hot pressing method in which a pressure of m ² } to 10 MPa {102 kgf / cm ² } is applied to join.

The collector electrode 40 is made of dense carbon which is made compact by compressing carbon to make it gas impermeable. A plurality of ribs 42 arranged in parallel with each other are formed on the left and right surfaces (laminating surfaces) of FIG. 1 that are in contact with the gas diffusion electrode 30 of the collecting electrode 40 so as to be orthogonal to each other. The rib 42 forms a gas flow channel 44 with the surface of the gas diffusion electrode 30 to form a flow channel of an oxidizing gas containing oxygen or a fuel gas containing hydrogen. Two collector electrodes 40
Are arranged so that the ribs 42 facing each other with the electrolyte membrane 20 and the two gas diffusion electrodes 30 sandwiched therebetween are orthogonal to each other.

As shown in FIG. 2, the rib 42 of the collecting electrode 40 is formed.
In the end face 46 that contacts the gas diffusion electrode 30, the side face 47 of the rib 42, and the face 48 between the ribs 42, unevenness of 5 μm to 500 μm, preferably 10 μm to 200 μm is formed.

The collector electrode 40 of this embodiment was manufactured as follows. First, a dense carbon plate material that is a material of the collecting electrode 40 is formed into a desired shape, for example, a square shape,
The laminated surface is a diamond electrodeposited stone with a width of 2 mm and a depth of 1
A mm 42 groove is cut to form a rib 42. Next, grindstone # 60 (particle size 425 μ
m) jet gun (nozzle diameter 8.33, jet diameter 4.3)
7) is used to form irregularities of 10 μm to 100 μm by surface treatment (liquid honing) which is sprayed at an air pressure of 400 kPa (4 Kgf / cm ² ). The surface roughness (Rz / Rmax) of the laminated surface of the collector electrode 40 thus formed is 20.
It was / 50. Here, the size of the irregularities is determined by the thickness and flexibility of the gas diffusion electrode 30, the surface pressure acting in the stacking direction of the unit cells 10, the strength required for the collector electrode 40, and the like.

In the unit cell 10 thus constructed, if the oxidizing gas and the fuel gas are caused to flow through the pair of gas passages 44 facing each other with the electrolyte membrane 20 and the two gas diffusion electrodes 30 interposed therebetween, the electrochemical reaction shown by the following formula Is performed to convert chemical energy directly into electrical energy.

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

At this time, the oxidizing gas or the fuel gas in the gas flow path 44 diffuses into the gas diffusion electrode 30 as follows and contributes to the electrochemical reaction. In the portion of the gas diffusion electrode 30 facing the gas passage 44, the oxidizing gas or the fuel gas diffuses directly from the gas passage 44. On the other hand, the gas diffusion electrode 3
In the conventional example in which the end surface 46 of the collector electrode 40, which is in contact with the end surface 46 of the rib 42 of the collector electrode 40, is flat and has no unevenness, the contact portion 34 is compressed and densified by the pressing load from the end surface 46. The oxidizing gas or the fuel gas diffuses only in the range corresponding to the degree of densification of the contact portion 34,
In the unit cell 10 of the example, although it is densified by the pressure load from the end face 46, the unevenness formed on the end face 46 causes a portion having a low surface pressure. Therefore, as shown by the arrow in FIG. The gas passes from the edge portion of the end surface 46 of the rib 42 through a portion having a low surface pressure to the contact portion 3 of the gas diffusion electrode 30.
It spreads to the inside of 4.

Here, the range in which the oxidizing gas or the fuel gas diffuses in the contact portion 34 of the conventional example is 0.3 mm in thickness of the gas diffusion electrode 30, 2 mm in width of the rib 42, and 2 mm in interval between the ribs 42. And the surface pressure is 2 MPa (20.4 Kgf / c
According to the experimental result under the condition of m ² ), the range was about 0.2 mm from the edge of the end face 46 of the rib 42. Therefore, the width of the contact portion 34 of the gas diffusion electrode 30 is also 2 mm, but in the area having a width of about 1.6 mm centering on the center, the oxidizing gas or the fuel gas is not diffused, so that the electrochemical reaction described above is performed. Do not do. The contact portion 3 of the conventional example
The range in which the oxidizing gas or the fuel gas diffuses in 4 is determined by the properties and surface pressure of the gas diffusion electrode 30.

FIG. 3 shows a unit cell 10 of this embodiment and a unit cell whose collector electrode has a flat end surface (hereinafter referred to as "conventional unit cell").
Say. 5 is a graph illustrating the relationship between the current density and the cell voltage in FIG. In the graph, the curve A shows the relationship between the cell density and the current density of the conventional battery, and the curve B shows the relationship between the current density and the cell voltage. In addition, a grindstone # 700 (particle diameter 25 μm) was obtained by the same process as the process of forming unevenness on the laminated surface of the collecting electrode 40 of the example.
The relationship between the cell voltage and the current density of the unit cell using the collecting electrode having the surface roughness of the rib of 3/5 using the curve C and the end surface of the rib using the grindstone # 150 (particle size 100 μm) The relationship between the cell voltage and the current density of the unit cell using the collecting electrode having the surface roughness of 10/20 is shown as a curve D. As shown in the figure, in each of the unit cells in which irregularities are formed on the laminated surface of the collector electrode, the improvement in performance is recognized in comparison with the conventional unit cell in which no irregularities are formed. The unit cell 10 of the example having the surface roughness of 20/50 was found to have improved performance even when compared with the unit cells shown as the curve C and the curve D having the low surface roughness. The improvement in the density region is remarkable.

As described above, such improvement in performance is as follows.
Oxidizing gas or fuel gas also diffuses inside the contact portion 34 of the gas diffusion electrode 30 to increase the utilization rate of the gas diffusion electrode 30, and due to the unevenness formed on the end surface 46 of the collection electrode 40, gas diffusion with the collection electrode 40 occurs. This is because the contact area with the electrode 30 increases and the contact resistance decreases.

Further, the unevenness formed on the side surface 47 of the rib 42 of the collector electrode 40 and the surface 48 between the ribs 42 disturbs the flow of the oxidizing gas or the fuel gas and increases the diffusibility to the gas diffusion electrode 30. .

The unit cell 1 of the fuel cell of the embodiment described above
According to No. 0, by forming the unevenness on the end surface 46 of the rib 42, it is possible to improve the performance of the unit cell 10 and thus the fuel cell. That is, the unevenness formed on the end surface 46 causes a portion having a low surface pressure in the contact portion 34, and causes the oxidizing gas or the fuel gas to diffuse from the portion having a low surface pressure to the inside of the contact portion 34. Therefore, the area of the gas diffusion electrode 30 that contributes to the electrochemical reaction is increased, and the utilization rate of the gas diffusion electrode 30 is increased, so that the power generation efficiency can be increased.
Further, by forming the unevenness on the end surface 46 of the rib 42, the contact area between the collector electrode 40 and the gas diffusion electrode 30 is increased, and thus the contact resistance is decreased and the internal resistance of the fuel cell can be decreased. it can. Besides this, rib 4
By forming irregularities also on the side surface 47 of the second side and the surface 48 between the ribs 42, the flow of the oxidizing gas or the fuel gas is disturbed, the diffusivity to the gas diffusion electrode 30 is increased, and the performance of the fuel cell is improved. Can be made.

In the embodiment, the side surface 47 and the surface 48 of the rib 42 are provided with the concavities and convexities in addition to the end surface 46, but it is also possible to form the concavities and convexities other than the end surface 46. Further, in the embodiment, the concavities and convexities are formed on the end faces 46 and the like of the ribs 42 by using liquid honing. The unevenness may be formed by a method provided beforehand.

Next, a single cell 110 of a fuel cell which is a second embodiment of the present invention will be described. The unit cell 110 of the second embodiment has the same configuration as the unit cell 10 of the first embodiment except that the collector electrode 140 is used instead of the collector electrode 40. Therefore, the same components as those of the unit cell 10 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 4 shows the unit cell 110 of the second embodiment shown in FIG.
It is an expansion explanatory view which expanded and showed the part equivalent to a dashed circle in the inside. FIG. 5 is an enlarged explanatory view showing a part (5-5 surface in FIG. 4) of the laminated surface of the collecting electrode 140 in an enlarged manner. Like the collector electrode 40 of the first embodiment, the collector electrode 140 of the second embodiment is formed of dense carbon, and a plurality of ribs 14 arranged in parallel are provided on the two laminated surfaces thereof.
2 are formed in a mutually orthogonal arrangement. The ribs 142 form a gas flow path 144 that forms a flow path for the oxidizing gas or the fuel gas together with the surface of the gas diffusion electrode 30.
The end surface 146 of the rib 142, which is in contact with the gas diffusion electrode 30, has a width of 0.2 mm and a depth of 0.2 mm in a direction perpendicular to the longitudinal direction of the rib 142, that is, across the rib 142.
A plurality of thin grooves 148 are formed at intervals of 0.2 mm (see FIG. 5).

The unit cell 1 of the second embodiment thus constructed
When an oxidizing gas and a fuel gas are caused to flow through a pair of gas flow passages 144 that face each other with the electrolyte membrane 20 and the two gas diffusion electrodes 30 sandwiched therebetween, the electrochemical reaction described above is performed and the chemical energy is directly converted into electrical energy. To do. At this time, the end surface 1 of the rib 142 of the collector electrode 140 of the gas diffusion electrode 30 is
As shown by the arrow in FIG. 4, the oxidizing gas or fuel gas in the gas flow path 144 is applied to the end surface 1 at the contact portion 34 that contacts the end surface 1.
Diffused through the narrow groove 148 that traverses the rib 142 formed on the nozzle 46. Further, since the gas diffusion electrode 30 is formed of carbon cloth having relatively high flexibility, the gas diffusion electrode 30 bites into the narrow groove 148, and the narrow groove 148.
The gas diffusion electrode 30 comes into contact with the formation surface of the. As a result, the contact area between the collector electrode 140 and the gas diffusion electrode 30 is smaller than that of the narrow groove 1.
As compared with the case where 48 is not formed, the contact resistance between the collector electrode 140 and the gas diffusion electrode 30 becomes smaller, as compared with the case where 48 is not formed. Therefore, the depth of the narrow groove 148 is preferably set to a depth at which the gas diffusion electrode 30 comes into contact with the gas diffusion electrode 30, that is, the thickness of the gas diffusion electrode 30 or less.

FIG. 6 is a graph illustrating the relationship between the cell density and the current density of the unit cell 110 of the second embodiment and the unit cell of the conventional example. In the graph, curve A is the conventional single cell,
The curve E represents the relationship between the current density and the cell voltage of the unit cell 10 of the second embodiment. As shown, an end surface 146 of the rib 142 has a plurality of narrow grooves 148 extending across the rib 142.
The performance of the unit cell 110 formed with is improved compared to the conventional unit cell in which the narrow groove 148 is not formed. Especially, the performance is remarkably improved in the high current density region.

In the graph, a curve F indicates a unit cell 210 using a collector electrode 240 (see FIGS. 7 and 8) of a type in which the direction of the narrow groove is the same as the longitudinal direction of the rib and the narrow groove does not cross the rib. 3 shows the relationship between the current density and the cell voltage. As shown in FIGS. 7 and 8, the collector electrode 240 has a plurality of fine grooves having the same width, depth, and spacing as the narrow grooves 148 of the collector electrode 140, which are parallel to the longitudinal direction of the rib 242 on the end surface 246 of the rib 242. A groove 248 is formed. As shown in the graph of FIG. 6, the unit cell 2 using this collecting electrode 240
Also in No. 10, as compared with the unit cell of the conventional example in which the narrow groove is not formed, the performance improvement is recognized, though not as much as the unit cell 110. This is because the gas diffusion electrode 30 bites into the narrow groove 248 to increase the contact area and reduce the contact resistance. In addition, since the narrow groove 248 is formed on the end face 246, the contact portion 34 of the gas diffusion electrode 30 is covered. This is because a band-shaped portion having a low pressure is formed, and the oxidizing gas and the fuel gas diffuse from the edge of the end surface 246 into the inside of the contact portion 34.

As described above, in the unit cell of the conventional example, the range in which the oxidizing gas or the fuel gas diffuses is limited depending on the degree of densification of the contact portion 34. If formed by the narrow groove 248 of the end face 246,
The oxidizing gas or the fuel gas in the gas flow path 244 is removed by the ribs 24.
2 from the edge of the end surface 246 of the contact portion 34 to the high surface pressure portion of the contact portion 34 to reach the low surface pressure portion and the narrow groove 248, and the low surface pressure portion and the narrow groove 248 also supply the oxidizing gas or the fuel gas. Is diffused. Therefore, even if it is densified, the fine grooves 2 are formed on the end surface 246 at intervals within a range in which diffusion is possible.
By forming 48, the oxidizing gas or the fuel gas can be diffused to the central portion of the contact portion 34. In the second embodiment, the thickness of the gas diffusion electrode 30 is 0.3 mm and the rib 24 is
The width of 2 is 2 mm, the distance between the ribs 242 is 2 mm, and the surface pressure is 2 MPa (20.4 Kgf / cm ² ).
Even if 4 is densified, the range in which the oxidizing gas or the fuel gas can diffuse is about 0.2 mm as described above.
Since the interval of 8 is 0.2 mm, the oxidizing gas or the fuel gas diffuses throughout the contact portion 34.

According to the unit cell 110 of the fuel cell of the second embodiment described above, the rib 142 is formed on the end surface 46 of the rib 142.
By forming the plurality of narrow grooves 148 that traverse each other, the oxidizing gas and the fuel gas in the gas flow path 244 can be diffused into the contact portion 34. As a result, it is possible to increase the utilization rate of the gas diffusion electrode 30 that contributes to the electrochemical reaction and improve the performance of the unit cell 110 and thus the fuel cell. Further, since the gas diffusion electrode 30 is embedded in the narrow groove 148 and contacts the surface where the narrow groove 148 is formed, the contact area between the collector electrode 140 and the gas diffusion electrode 30 can be increased to reduce the contact resistance.

In the unit cell 110 of the second embodiment, the width and depth of the narrow groove 148 and the distance between them are both 0.2 m.
Although m is used, any size may be used. However, in order to increase the contact area between the narrow groove 148 and the gas diffusion electrode 30, it is preferable that the depth thereof be equal to or less than the thickness of the gas diffusion electrode 30.

In the unit cell 110 of the second embodiment, the narrow groove 14
8 was formed in a direction perpendicular to the longitudinal direction of the rib 142,
It may be formed in any direction as long as it crosses the rib 142. Further, as in the collecting electrode 240 shown in FIGS. 7 and 8, it may be formed as a fine groove that does not cross the rib.
In this collecting electrode 240, since the fine groove 248 does not cross the rib 242, the oxidizing gas or the fuel gas does not diffuse through the fine groove 248 into the contact portion 34 of the gas diffusion electrode 30, but the contact portion 34 is Since the fine grooves 248 are formed in the end face 246 at intervals within a range in which the oxidizing gas or the fuel gas can be diffused even if the end face 24 of the rib 242 is densified.
The oxidizing gas or fuel gas that has permeated through the high surface pressure portion of the contact portion 34 from the edge portion of 6 diffuses to the inner portion of high contact surface pressure, so that the oxidizing gas or fuel gas reaches the central portion of the contact portion 34. Can be diffused. As a result,
The utilization rate of the gas diffusion electrode 30 that contributes to the electrochemical reaction can be increased. Even in the unit cell 210 using the collecting electrode 240, the gas diffusion electrode 30 is embedded in the narrow groove 248 and comes into contact with the surface where the narrow groove 248 is formed.
The contact area between the gas diffusion electrode 30 and the gas diffusion electrode 30 can be increased to reduce the contact resistance.

Next, a unit cell 310 of a fuel cell which is a third embodiment of the present invention will be described. The unit cell 310 of the third embodiment has the same configuration as the unit cell 10 of the first embodiment except that the collecting electrode 340 is used instead of the collecting electrode 40. Therefore, the same components as those of the unit cell 10 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 9 shows the unit cell 310 of the third embodiment shown in FIG.
It is an expansion explanatory view which expanded and showed the part equivalent to a dashed circle in the inside. Like the collector electrode 40 of the first embodiment, the collector electrode 340 of the third embodiment is formed of dense carbon, and a plurality of ribs 342 arranged in parallel are formed on the two laminated surfaces thereof. , Are formed so as to be orthogonal to each other. The rib 342 forms a gas flow path 34 that forms a flow path for the oxidizing gas or the fuel gas with the surface of the gas diffusion electrode 30.
4 is formed. An end portion 346 of the rib 342 of the collector electrode 340 that comes into contact with the gas diffusion electrode 30 is formed in a mountain shape by two tapered surfaces. Angle θ of the tapered surface shown in the figure
Is preferably in the range represented by the following formula, and the collector electrode 3 of the third embodiment is
In No. 40, the thickness of the gas diffusion electrode 30 was 0.3 mm, the coefficient for multiplying the gas diffusion electrode 30 was 0.7, and the width of the rib 342 was 2 mm.

Tan θ = (thickness of gas diffusion electrode 30 × 1
~ 0.5) / (width of rib 342 x 0.5)

Here, the denominator of the above equation is set to be equal to or less than the thickness of the gas diffusion electrode 30 because the entire end portion 346 is the gas diffusion electrode 3.
This is to make it contact 0. Gas diffusion electrode 30
This is because when the thickness is equal to or larger than the above, a part of the tapered surface of the rib 342 does not contact the gas diffusion electrode 30, and the width of the rib 342 is set to be useless. The reason why the thickness of the gas diffusion electrode 30 is 0.5 times or more is that the rib 342 is wider than the thickness of the gas diffusion electrode 30. Therefore, if it is smaller than this, an effective taper cannot be obtained. Because. Therefore, when the width of the rib 342 is not so wide as compared with the thickness of the gas diffusion electrode 30, it can be set to 0.5 times or less.

The unit cell 3 of the third embodiment thus constructed
When the oxidizing gas and the fuel gas are caused to flow through the pair of gas flow passages 344 facing each other with the electrolyte membrane 20 and the two gas diffusion electrodes 30 interposed therebetween, the same reaction as the electrochemical reaction shown in the first embodiment is performed. , Converts chemical energy directly into electrical energy. At this time, in the vicinity of the center of the contact portion 34 of the gas diffusion electrode 30, since the end portion 346 is formed in a chevron shape, a pressing load in the stacking direction applied to the fuel cell makes it more effective than the conventional unit cell. The inactivated region is densified so that the oxidizing gas or the fuel gas does not diffuse and does not contribute to the electrochemical reaction. However, since the degree of densification due to the pressing load is lower than that of the conventional unit cell except in the region, the oxidizing gas or the fuel gas in the gas flow path 344 has an edge portion as shown by an arrow in the figure. Diffuse from the edge of 346 along the tapered surface. Therefore, although there is a deactivation region, the area of the region contributing to the electrochemical reaction becomes large because the area is smaller than that of the conventional unit cell.
Improve fuel cell performance. In addition, since the end portion 346 has a chevron shape, the collector electrode 340 and the gas diffusion electrode 3 are
The contact area with 0 also becomes large and the contact resistance becomes small.

FIG. 10 is a graph illustrating the relationship between the cell density and the current density of the unit cell 310 of the third embodiment and the unit cell of the conventional example. In the graph, the curve A shows the relationship between the current density and the cell voltage of the conventional unit cell and the curve G shows the unit cell 310 of the third embodiment. As shown in the drawing, the unit cell 310 in which the end portion 346 of the rib 342 is formed in a mountain shape is
An improvement in the performance is recognized as compared with the unit cell of the conventional example in which 6 is flat.

According to the unit cell 310 of the fuel cell of the third embodiment described above, since the end portion 346 of the rib 342 is formed in a mountain shape, a region of the gas diffusion electrode 30 which is inactivated by densification is formed. The utilization rate of the gas diffusion electrode 30 contributing to the electrochemical reaction can be increased by reducing the size, and the performance of the unit cell 310 and thus the fuel cell can be improved. Further, since the end portion 346 of the rib 342 is formed in a mountain shape, the contact area between the collector electrode 340 and the gas diffusion electrode 30 can be increased to reduce the contact resistance.

In the unit cell 310 of the third embodiment, the end portion 346 of the rib 342 is mountain-shaped by the two tapered surfaces, but one taper surface is a one-sided sloped surface, a circular arc, or a convex shape. There is no problem with the configuration. Even in this case, it is preferable that the distance to the tip of the end portion 346 be equal to or less than the thickness of the gas diffusion electrode 30 so that the entire end portion 346 contacts the gas diffusion electrode 30.

Next, the unit cell 410 of the fuel cell according to the fourth embodiment of the present invention will be described. The unit cell 410 of the fourth embodiment has the same configuration as the unit cell 10 of the first embodiment except that the collecting electrode 440 is used instead of the collecting electrode 40. Therefore, the same components as those of the unit cell 10 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 11 is an enlarged explanatory view showing a portion corresponding to a broken line circle in FIG. 1 of the unit cell 410 of the fourth embodiment. Like the collector electrode 40 of the first embodiment, the collector electrode 440 of the fourth embodiment is formed of dense carbon, and a plurality of ribs 442 arranged in parallel are formed on the two laminated surfaces thereof. , Are formed so as to be orthogonal to each other. On the laminated surface on which the rib 442 is formed,
A conductive adhesive 450, for example, an epoxy adhesive or a carbon paste obtained by mixing carbon powder with a fluorine resin such as polytetrafluoroethylene, has a thickness of 5 μm.
A large number of short carbon fibers 452 having a length of m and a length of 100 μm are planted. The ribs 442 in which the short carbon fibers 452 are planted on the surface form a gas flow path 344 that forms a flow path for the oxidizing gas or the fuel gas together with the surface of the gas diffusion electrode 30.

In the collecting electrode 440 of the fourth embodiment, short carbon fibers 452 were planted on the laminated surface as follows. First, the adhesive 450 is applied to the laminated surface of the collecting electrode 440, and the collecting electrode 440 is connected to the ground or charged negatively. Then, positively charged short carbon fibers 452 are sprinkled on the laminated surface of the grounded or negatively charged collector electrode 440 coated with the adhesive 450. Then,
The short carbon fibers 452 are collected by electrostatic induction to the collecting electrode 440.
It is planted so as to stand on the adhesive 450 on the laminated surface of the.
Then, the adhesive 450 applied to the collecting electrode 440 is heated to a temperature of 1
The collector electrode 440 is completed by drying and curing at 50 ° C. for 30 minutes.

The unit cell 4 of the fourth embodiment thus constructed
When the oxidizing gas and the fuel gas are caused to flow through the pair of gas flow paths 444 facing each other with the electrolyte membrane 20 and the two gas diffusion electrodes 30 sandwiched therebetween, the same reaction as the electrochemical reaction shown in the first embodiment is performed. , Converts chemical energy directly into electrical energy.

At this time, the contact portion 34 of the gas diffusion electrode 30
The surface pressure is increased or decreased by the short carbon fibers 452 planted on the end surface 446 of the rib 442, and as shown by the arrow in the figure, the oxidizing gas or the fuel gas in the gas flow path 444 is discharged.
It diffuses from the end portion of 46 into the inside of the contact portion 34 through the low pressure portion. In addition, a layer having a minute gap due to the short carbon fibers 452 is formed at the contact portion between the contact portion 34 of the gas diffusion electrode 30 and the end surface 446, and an oxidizing gas or a fuel gas is generated inside the contact portion 34 from the gap of this layer. Spread. Further, the short carbon fibers 452 that are planted on the end surface 446 are entangled with the carbon fibers forming the gas diffusion electrode 30.
Therefore, the contact resistance between the collector electrode 440 and the gas diffusion electrode 30 becomes small. Further, the short carbon fibers 452 that are planted on the side surfaces of the ribs 442 that form the gas flow channel 444 disturb the flow of the oxidizing gas or the fuel gas in the gas flow channel 444, and the gas diffusion electrode 30 for the oxidizing gas or the fuel gas 30 To improve the diffusion.

FIG. 12 is a graph showing the relationship between the cell density and the current density of the unit cell 410 of the fourth embodiment and the unit cell of the conventional example. In the graph, the curve A shows the relationship between the current density and the cell voltage of the conventional unit cell and the curve H shows the unit cell 410 of the fourth embodiment. As shown, collector electrode 440
Cell 41 in which short carbon fibers 452 are planted on the laminated surface of
0 indicates that the performance is remarkably improved as compared with the conventional unit cell in which short carbon fibers are not implanted.

According to the unit cell 410 of the fuel cell of the fourth embodiment described above, short carbon fibers 452 are planted on the end surfaces 446 of the ribs 442, so that a low surface pressure portion is generated in the contact portion 34. The oxidizing gas or the fuel gas in the gas flow path 444 can be diffused from the edge portion of the end surface 446 into the inside of the contact portion 34 via the low surface pressure portion. In addition, the carbon short fiber 4 is attached to the end surface 446 of the rib 442.
By flocking 52, a layer having a minute gap is formed at the contact portion between the contact portion 34 and the end surface 446, so that the oxidizing gas or the fuel gas can be diffused into the contact portion 34 from the gap of this layer. it can. In this way, since the oxidizing gas or the fuel gas is diffused to the inside of the contact portion 34,
The utilization rate of the gas diffusion electrode 30 that contributes to the electrochemical reaction can be increased to improve the performance of the unit cell 410 and thus the fuel cell.

Further, the unit cell 41 of the fuel cell of the fourth embodiment
According to 0, since the short carbon fibers 452 of the end surface 446 of the rib 442 are entangled with the carbon fibers forming the gas diffusion electrode 30, the contact resistance can be reduced and the fuel cell with a small internal resistance can be obtained. Furthermore, since the short carbon fibers 452 are also planted on the side surfaces of the ribs 442 forming the gas flow passage 444, the short carbon fibers 452 disturb the flow of the oxidizing gas or the fuel gas in the gas flow passage 444, and the gas diffusion electrode 30 It is possible to improve the diffusion property to

In the fourth embodiment, the short carbon fibers 452 are also formed on the side surfaces of the ribs 442 forming the gas flow passage 444.
However, a structure in which only the end surfaces 446 of the ribs 442 are flocked may also be used. In the fourth embodiment, the short carbon fiber 452 has a thickness of 5 μm and a length of 100 μm.
The shape is not limited to this. The shape of the short carbon fibers is determined by the width and spacing of the ribs 442, the flexibility of the gas diffusion electrode 30, and the like.

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.

[0058]

As described above, according to the first fuel cell of the present invention, since the contact surface of the rib portion of the collecting electrode that comes into contact with the electrode has a non-flat shape, the fuel in the flow path is It is possible to diffuse from the edge portion of the contact surface to a contacted portion of the electrode which contacts the contact surface by a predetermined size or more. As a result, the area of the electrode that can contribute to the electrochemical reaction can be increased, and an efficient fuel cell can be obtained. Further, since the contact surface of the rib portion has a non-flat shape, the contact area can be made larger than that of a fuel cell having a flat contact surface, and a fuel cell having a small internal resistance can be obtained.

According to the second fuel cell of the present invention, the fuel in the flow path is brought into contact with the contact surface by forming a plurality of grooves on the contact surface of the rib portion that contacts the electrode. Can be diffused to the contacted part of the electrode. As a result, the area of the electrode that can contribute to the electrochemical reaction can be increased, and an efficient fuel cell can be obtained.

According to the third fuel cell of the present invention, since the groove is formed within a predetermined dimension from the edge of the contact surface of the rib portion that contacts the electrode, the fuel in the flow path is fed to the contact surface of the rib portion. It is possible to diffuse from the edge portion to the inside of the contacted portion of the electrode having a predetermined size or more. As a result, the area of the electrode that can contribute to the electrochemical reaction can be increased, and an efficient fuel cell can be obtained.

According to the fourth fuel cell of the present invention, by making the contact surface of the rib portion that comes into contact with the electrode into a protruding shape,
The fuel in the flow path can be diffused from the edge of the contact surface of the rib portion to the inside of the contacted portion of the electrode. As a result, the area of the electrode that can contribute to the electrochemical reaction can be increased, and an efficient fuel cell can be obtained.

According to the fifth fuel cell of the present invention, the fuel in the flow path is brought into contact with the contact surface of the rib portion by implanting electrically conductive fibers on the contact surface of the rib portion in contact with the electrode. It can be diffused into the contacted part. As a result, the area of the electrode that can contribute to the electrochemical reaction can be increased, and an efficient fuel cell can be obtained. In addition, when the electrode is formed of a fiber such as carbon cloth, the conductive fiber implanted on the contact surface of the rib portion is entangled with the fiber of the electrode, so that the contact resistance between the electrode and the collecting electrode is reduced. As a result, a fuel cell having a small internal resistance can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating the configuration of a unit cell 10 that constitutes a fuel cell that is a preferred embodiment of the present invention.

FIG. 2 is an enlarged explanatory view showing an enlarged part of a broken line circle in FIG.

FIG. 3 is a graph illustrating the relationship between the current density and the cell voltage in the unit cell 10 of the present example and the conventional unit cell.

FIG. 4 is an enlarged explanatory view of a part of the unit cell 110 according to the second embodiment.

FIG. 5 is an enlarged explanatory view showing an enlarged part of a laminated surface of a collector electrode 140 of the second embodiment.

FIG. 6 is a graph illustrating the relationship between the cell density and the current density of the unit cell 110 of the second example and the conventional unit cell.

FIG. 7 is an enlarged explanatory diagram of a modified example of the unit cell 110 according to the second embodiment.

FIG. 8 is a collector electrode 2 of a modified example of the unit cell 110 of the second embodiment.
It is an expansion explanatory view which expanded and showed a part of 40.

FIG. 9 is an enlarged explanatory view showing an enlarged part of the unit cell 310 of the third embodiment.

FIG. 10 is a graph illustrating the relationship between the current density and the cell voltage in the unit cell 310 of the third embodiment and the unit cell of the conventional example.

FIG. 11 is an enlarged explanatory view showing an enlarged part of the unit cell 410 of the fourth embodiment.

FIG. 12 is a graph illustrating the relationship between the cell density and the current density in the unit cell 410 of the fourth example and the unit cell of the conventional example.

[Explanation of symbols]

 10, 110, 210, 310, 410 ... Single cell 20 ... Electrolyte membrane 30 ... Gas diffusion electrode 32 ... Catalyst layer 34 ... Contact part 40, 140, 240, 340, 440 ... Collection electrode 42, 142, 242, 342, 442 ... Ribs 44, 144, 244, 344, 444 ... Gas flow paths 46, 146, 246 ... End surface 47 ... Side surface 48 ... Surface 148, 248 ... Fine groove 346 ... End portion 446 ... End surface 450 ... Adhesive 452 ... Carbon short fiber

Claims (5)

[Claims] 1. An electrolyte layer, an electrode for sandwiching the electrolyte layer to form a power generation layer, and a collector electrode having a rib portion for sandwiching the power generation layer and forming a fuel flow path with the electrode. In the fuel cell, the contact surface is formed so that the fuel in the flow path diffuses from an edge of the contact surface of the rib portion that contacts the electrode to a contacted portion of the electrode that contacts the contact surface by a predetermined size or more. A fuel cell having a non-flat shape. 2. An electrolyte layer, an electrode for sandwiching the electrolyte layer to form a power generation layer, and a collector electrode having a rib portion for sandwiching the power generation layer and forming a fuel flow path with the electrode. In the fuel cell, the fuel cell is characterized in that a plurality of grooves that cross the rib portion are formed on a contact surface of the rib portion that contacts the electrode. 3. An electrolyte layer, an electrode for sandwiching the electrolyte layer to form a power generation layer, and a collector electrode having a rib portion for sandwiching the power generation layer and forming a fuel flow path with the electrode. In the fuel cell, the groove is formed on the contact surface of the rib portion that comes into contact with the electrode within a predetermined dimension from the edge of the contact surface. 4. An electrolyte layer, an electrode for sandwiching the electrolyte layer to form a power generation layer, and a collector electrode having a rib portion for sandwiching the power generation layer and forming a fuel flow path with the electrode. In the fuel cell, the contact surface of the rib portion that comes into contact with the electrode is formed in a protruding shape. 5. An electrolyte layer, an electrode for sandwiching the electrolyte layer to form a power generation layer, and a collecting electrode having a rib portion for sandwiching the power generation layer and forming a fuel flow path with the electrode. In the fuel cell, conductive fibers are planted on the contact surface of the rib portion that contacts the electrode.