JP2000021424A - Current collector body for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve current collecting performance by enlarging the contact area with electrodes an the cross-sectional area of a gas passage, by forming the gas passage on the contact surface with the electrodes of a pair of current collectors having the gas passage also serving as a gas chamber of reactive gas on the opposite surface to a pair of electrodes for sandwiching a solid electrolyte film, and providing the recessed part having a cross-sectional shape having the inside widening more than the opening part. SOLUTION: A gas passage 31 of the recessed part, having a cross section having the inside widening more than the opening part contacting with electrodes, is arranged in a lattice shape on both surfaces of a current collector 11, such as stainless steel having a construction material which is hardly degraded by transmission and reaction heat of reactive gas. Thus, the contact area with the electrodes becomes large to increase a flow rate of the reactive gas. The curved starting part having the inside starting to widen more than a width of an opening is deisrably arranged in the opening part of the gas passage 31, so that the tip of the opening part does not turn into an easily foldable acute angle shape. It is recommended that the tip of the opening part be properly rounded to prevent the defect. The current collector is manufactured by performing etching processing, after masking a position of the thick part 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell which has electrodes on both sides of a solid electrolyte membrane, and supplies fuel gas to one of the electrodes and oxidant gas to the other electrode to extract electricity. Current collector.

[0002]

2. Description of the Related Art As can be seen from air pollution caused by exhaust gas from factories and automobiles, and hot wastewater discharged from power plants, various environmental loads occur during the process from energy consumption to emission. ing. 2. Description of the Related Art With an increase in interest in the global environment in recent years, energy with less impact on the global environment has been demanded, and a fuel cell has been cited as one of them.

[0003] In general, a fuel cell uses hydrogen as its main fuel,
The energy obtained when the hydrogen chemically reacts with the oxygen is extracted as electric power. Unlike conventional engines and turbines, this fuel cell is not restricted by the efficiency of the Carnot cycle, has high power generation efficiency, and has a high NO.
It is a clean power source that emits very little x, SOx and the like.

A fuel cell is a chemical cell in that chemical energy is converted into electric energy. However, unlike a general chemical cell, a reactant is continuously supplied from the outside, and a reaction product is continuously supplied to the outside. , It can be operated for a very long time and does not need to be charged. There are several types of fuel cells, one of which is a polymer electrolyte fuel cell. This polymer electrolyte fuel cell has the characteristics that the operating temperature is low (100 ° C. or less) and the power density is high (about 60%). A polymer electrolyte fuel cell has a proton exchange polymer electrolyte membrane, an electrode including a catalyst formed to sandwich the electrolyte membrane, and a current collector that sandwiches the electrode and collects electricity generated by the electrode. It is composed of the body. The current collector has a gas flow path having a gas diffusion function of introducing a reactive gas serving as a raw material for an electrode reaction to a surface facing the electrode and diffusing the reactive gas to the electrode.

In this polymer electrolyte fuel cell, a fuel gas containing hydrogen or hydrogen gas is supplied to one side of an electrolyte membrane, and an oxide gas containing oxygen such as air is supplied to the other side of the electrolyte membrane. Hydrogen and oxygen react gently. In the reaction path of both gases, hydrogen in the fuel gas becomes protons (H ⁺ ) and electrons (e ⁻ ) at the electrode (hydrogen electrode), and the protons move through the electrolyte membrane, and the transferred protons are oxidized. This is a reaction in which oxygen in the source gas reacts with electrons from the electrode (oxygen electrode) to generate water (H ₂ O).

Hydrogen electrode: H ₂ → 2H ⁺ + 2e ⁻ Oxygen electrode: 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O Entire: H ₂ + 1 / 2O ₂ → H ₂ O Polymer electrolyte fuel cell In the case of (1), the output power of a single cell composed of one electrolyte membrane is less than 1.0 V. Usually, a predetermined number of the single cells are stacked in series to form a fuel cell. When the single cells are stacked in series as described above, the current collector can be shared between adjacent cells.
When the current collector is shared, the reactive gas is formed so as not to pass through the current collector. In this case, gas flow paths are provided on both sides of the current collector, and the fuel gas and the oxide gas flowing through the gas flow paths on both sides are sufficiently isolated so as not to contact and mix.

The gas flow passage formed on the surface of the current collector is a groove having a concave cross section or a trapezoidal shape whose width becomes narrower toward the inside. It spreads in the form of a lattice.

[0008]

Since a fuel cell is a battery that obtains power from reaction energy in which hydrogen in a fuel gas reacts with oxygen in an oxide gas, the output power of this battery is a reaction amount of hydrogen and oxygen. Depends on. In addition, the current collection efficiency is improved by increasing the contact area between the current collector and the electrode surface, and the power generation capability is also improved.

Since the cross section of the gas flow channel formed on the surface of the current collector is concave, if the concave portion of the gas flow channel is widened to increase the amount of reactive gas introduced, the current collector and Since the contact area with the electrode surface is reduced, the current collection efficiency is reduced. Conversely, when the contact area between the current collector and the electrode surface is increased, the cross-sectional area of the concave portion of the gas flow path is reduced, so that the amount of reactive gas introduced is reduced, and the reaction amount contributing to the electrode reaction is reduced. Because of the decrease, the power generation efficiency decreases.

The present invention has been made in view of the above circumstances, and has as its object to provide a current collector for a fuel cell having a large contact area with an electrode and a large cross-sectional area of a gas flow path.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have repeatedly studied the current collector of a fuel cell, more specifically, the cross-sectional shape of a gas flow channel provided in the current collector. It has been found that the problem can be solved by forming the concave portion of the gas flow path into a shape having a wide inside. That is, the current collector of the present invention comprises a solid electrolyte membrane, a pair of electrodes sandwiching the solid electrolyte membrane from both sides, and a gas chamber in which a reactive gas which is located opposite to the electrode and causes an electrode reaction with the electrode is introduced. And a pair of current collectors provided on the surface facing the electrodes, the current collectors being used in a fuel cell. Is formed, and the cross-sectional shape of the concave portion is such that the inside of the concave portion is wider than the opening of the concave portion.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The current collector of the present invention has a concave portion serving as a gas flow path formed on a contact surface with an electrode, and the cross section of the concave portion is smaller than the opening opening on the contact surface with the electrode. Its inside has a widened shape. As the current collector, any material may be used as long as it has characteristics such that the introduced reactive gas does not permeate, has high current collecting performance, and does not deteriorate due to the reaction heat of the reactive gas. .

The cross-sectional shape of the gas flow path is such that the inside thereof is wider than the opening opening on the contact surface with the electrode. Because the inside is wide, the cross-sectional area of the gas passage can be increased, and the flow rate of the reactive gas can be increased.
As a result, the reaction amount is increased to improve the power generation capacity. In addition, the contact area with the electrode is increased, and the current collecting performance of the current collector is improved.

The cross-sectional shape of the gas flow path may be any shape as long as the gas flow path has a shape in which the inside is wider than an opening opening on the contact surface with the electrode. Examples of the cross-sectional shape of the gas flow path include an elliptical shape in which the width of the opening of the gas flow path is shorter than the long diameter, and a trapezoidal shape in which the opening of the gas flow path is the upper bottom. The gas flow path
It is preferable that the inside of the concave portion starts from a bending start portion where the width starts to widen from the width of the opening portion of the concave portion. Here, the opening indicates the area from the opening of the current collector surface to the starting point of the curve, and the width of the opening indicates the area of the current collector in which the concave portion is opened. When the bending start portion is located on the surface of the current collector, that is, when the concave portion opens and the inside of the current collector begins to spread, the opening becomes an acute angle, and the acute-angled tip of the opening is easily broken and falls off. Become. When the tip falls off, the contact area between the current collector and the electrode decreases, so that the current collecting performance of the current collector decreases. In addition, if the falling pieces generated by the falling fall in the gas flow path, the falling pieces may obstruct the gas flow and reduce the amount of gas introduced into the electrode surface, leading to a decrease in the output of the fuel cell. Become. For this reason, by setting the bending start portion inside the current collector from the opening of the gas flow path, a cross section that defines the opening of the concave portion of the gas flow path has a width, and the tip thereof is prevented from falling off. .

The gas flow passage preferably has a rounded cross section at the opening of the recess. Since the cross section of the opening is rounded, the contact portion between the current collector and the electrode becomes smooth, and the loss of the opening can be suppressed. In addition, the opening of the opening is also prevented from falling into the inside in the same manner. The gas flow path extends on the surface of the surface portion so that the reactive gas is diffused on the electrode surface. The form spreading on the surface of the surface layer of the gas flow path may be any form as long as the reactive gas is diffused. That is, the gas flow path can be spread in various forms such as a form in which a plurality of gas flow paths are arranged in parallel, a form in which the gas flow path is spread in a lattice, a zigzag form, and a spiral form.

The current collector for a fuel cell according to the present invention comprises: a solid electrolyte membrane; a pair of electrodes sandwiching the solid electrolyte membrane from both sides;
A fuel cell having a pair of current collectors provided on a surface facing the electrodes, the gas channels serving as gas chambers for introducing a reactive gas which is positioned to face the electrodes and to cause an electrode reaction with the electrodes. Used for In the current collector of the present invention, it is preferable that concave portions serving as gas flow paths are formed on both surfaces thereof. By providing the concave portions on both surfaces of the current collector, when a plurality of single cells made of one solid electrolyte membrane are connected in series, the adjacent cells can share the current collector.

[0017]

The present invention will be described below with reference to examples. (Example 1) As an example of the present invention, a current collector 11 in which a gas flow path 31 shown in FIG. 2 showing a perspective view of FIG. 1 and a cross section taken along line II of FIG. . The current collector 11 has a gas passage 31 formed in a lattice pattern on both sides of a stainless steel plate having a thickness of 1.3 mm. Here, the thickness of the current collector 11 refers to the thickness of the thick portion 51 that partitions the gas flow path 31. The gas flow path 31 is 200 ×
A substantially elliptical cross-sectional shape as shown in the cross-sectional view of FIG. 3 is provided on the surface of the 200-mm current collector 11 facing the electrode. The gas channel 31 has a width of 1 mm and a depth of 0.5 m
The groove has a shape in which a half circle having a diameter of 0.5 mm is attached to both side surfaces of a rectangular shape of m. At this time, the width of the opening 41 on the surface of the current collector 1 of the gas flow channel 31 was 1 mm, and the width of the widest widest portion 42 of the gas flow channel 31 was 1.5 mm.

The current collector 11 of this embodiment is manufactured by etching a stainless steel plate in which a portion to be the thick portion 51 of the current collector 11 is masked.
That is, after a 1 mm square masking is applied at 1 mm intervals on a surface of a 1.3 mm thick stainless steel plate facing the electrode, the stainless steel plate is immersed in an aqueous solution containing ferric chloride and nitric acid. The widened concave portion serving as a gas flow path was formed in a lattice shape. Thereafter, the stainless steel plate was pulled out of the aqueous solution, washed, and the masking was peeled off, to produce a current collector of the example.

(Embodiment 2) This embodiment is a current collector 12 in which gas channels 32 are provided in a grid pattern as in Embodiment 1, and this current collector 12 has a thickness of 1.3 mm. Gas passages 32 are provided on both sides of the stainless steel plate.
Here, the thickness of the current collector 12 refers to the thickness of the thick portion 52 that defines the concave portion of the gas flow path 32. The gas flow path 32
A substantially elliptical cross-sectional shape as shown in the cross-sectional view of FIG. 4 is provided on a surface of the current collector 12 of 200 × 200 mm facing the electrode. The gas passage 32 has a width of 0.36.
mm, depth 0.5mm on both sides of a rectangle 0.5mm deep
It has a shape with a semicircle of mm attached. At this time, the width of the opening 43 on the surface of the current collector 12 of the gas flow path 32 is
It was 0.36 mm, and the width of the widest widest part 44 of the gas flow path 32 was 0.86 mm.

The current collector 12 of this embodiment was prepared in the same manner as the current collector of the first embodiment. (Comparative Example) A comparative example is a conventional current collector in which a gas flow path 33 partitioned by a thick portion 53 having a tapered side surface so that the inside is narrower than an opening 45 on the surface is provided in a grid pattern. Body 13. This current collector 13 has a thickness of 1.3 m.
The gas passages 33 are provided on both sides of the stainless steel plate having a length of m. Here, the thickness of the current collector 13 refers to the thickness of the thick portion 53 that divides the concave portion of the gas flow path 33.
As shown in the cross-sectional view of FIG. 5, the gas flow path 33 has a trapezoidal cross section with a wide opening, a width of the opening is 1 mm, a width of the bottom is 0.5 mm, and a depth. 0.5mm
It has a groove shape. Further, the taper of the side surface of the gas flow path 3 is 0.25 m for a depth of 0.5 mm of the gas flow path 3.
m.

The current collector 33 of the comparative example is manufactured by a hydraulic press. That is, the thickness is 1.3 m
The m stainless steel plate was manufactured by press-forming with a hydraulic press using a press die having convex portions for forming concave portions formed on the current collector surface in a lattice shape. (Evaluation) According to the current collectors of Examples and Comparative Examples of the present invention,
The current collector was evaluated using the cross-sectional area of the gas channel and the size of the contact area with the electrode.

In the current collectors of Example 1 and Comparative Example, the width of the opening of the gas flow path was 1 mm, and the depth was 0.5 mm. The total area of contact with the electrodes was 100 cm ² . Cross-sectional area of the gas flow path, the first embodiment 0.696Mm ^2, the comparative example was 0.375 mm ^2. As described above, when the contact area between the current collector and the electrode is the same, the current collector of Example 1 has a gas flow channel having a cross-sectional area of about 1.9 times that of the comparative example. Increasing the cross-sectional area of the gas flow path increases the amount of reactive gas introduced by the gas flow path when used in a fuel cell, and increases the reaction amount and, consequently, the output power. .

The current collectors of Example 2 and Comparative Example each have a gas flow passage having a cross-sectional area of 0.375 mm ² . At this time, the current collectors of Example 2 and Comparative Example had a surface facing the electrode of 2.
When the size was 00 × 200 mm, the contact area of the current collector of Example 2 with the electrode was 216 cm ² , and the contact area of the comparative example was 1
00 cm ² . As described above, if the cross-sectional areas of the gas flow paths are the same, the current collector of the second embodiment can have a contact area with the electrode as large as about 2.2 times. Increasing the contact area between the current collector and the electrode improves the current collection performance of the power generated by the electrode reaction at the electrode surface when used in a fuel cell, and increases the power output of the fuel cell Will be done.

Further, as another embodiment, a current collector having a curved start portion in which a concave portion forming a gas flow channel starts to widen from an opening portion, and a cross-sectional shape of the concave portion forming a gas flow channel are as follows. Different current collectors were made. (Embodiment 3) In this embodiment, a concave portion forming a gas flow path 34 is formed in the cross-sectional shape shown in the cross-sectional view of FIG. 6, and the gas flow path 34 having this cross section is in contact with an electrode. The current collector 14 is opened in a lattice shape. The gas flow path 34 has an opening 64 that is formed on a straight line perpendicular to the current collector surface from the opening end 84 of the concave portion opened on the surface of the current collector to the bending start portion 74. From 74, the recess has a cross-sectional shape that expands to a substantially elliptical shape.

(Embodiment 4) In this embodiment, the recess forming the gas flow path 35 is formed in the cross-sectional shape shown in the cross-sectional view of FIG. 7, and the gas flow path 35 having this cross-section is in contact with the electrode. Current collector 15 which is opened in a grid on the contact surface to be formed. This gas flow path 35 is provided with the opening 6 of the current collector of the third embodiment.
4 is rounded. That is, the concave portion of the present embodiment has an opening portion 65 in which the concave portion from the open end 85 of the concave portion to the bending start portion 75 is rounded, and has a cross-sectional shape in which the concave portion is broadened from the bending start portion 75 to an almost elliptical shape. I have.

(Embodiment 5) In this embodiment, the recess forming the gas flow path 36 is formed in the cross-sectional shape shown in the cross-sectional view of FIG. 8, and the gas flow path 36 having this cross-section is in contact with the electrode. Current collector 16 which is opened in a grid on the contact surface to be formed. The concave portion formed in the current collector of this embodiment has a substantially pentagonal cross-sectional shape with one opening 66 formed in the current collector surface as one vertex. In other words, the concave portion of this embodiment is inclined from the bending start portion 76 to the bending stop portion 86 to increase its internal width, and the width of the bending stop portions 86 becomes the widest portion 46 and the widest portion 46. Has a cross-sectional shape that is spread in a rectangular shape with one side as a side. Also in this embodiment, the opening 66 of the concave portion and the corner inside the concave portion are rounded.

[0027]

According to the current collector of the present invention, since the cross-sectional shape of the gas flow path formed on the contact surface with the electrode is formed to be wider than the opening in the surface, the cross-sectional area of the gas flow path is increased. And the contact area with the electrode increases. Therefore, when this current collector is used in a fuel cell, the amount of reactive gas introduced through the gas flow path can be increased, and the current collection performance of electric power obtained by the electrode reaction can be improved. Therefore, the present invention has the effect of increasing the output of a fuel cell using the current collector of the present invention.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a current collector according to a first embodiment.

FIG. 2 is a cross-sectional view showing a cross section taken along line II of the current collector of the first embodiment shown in FIG.

FIG. 3 is a cross-sectional view illustrating a cross-sectional shape of a gas flow path of the current collector according to the first embodiment.

FIG. 4 is a cross-sectional view illustrating a cross-sectional shape of a gas channel of a current collector according to a second embodiment.

FIG. 5 is a cross-sectional view illustrating a cross-sectional shape of a gas flow path of a current collector of a comparative example.

FIG. 6 is a cross-sectional view illustrating a cross-sectional shape of a gas flow path of a current collector according to a third embodiment.

FIG. 7 is a cross-sectional view illustrating a cross-sectional shape of a gas flow path of a current collector according to a fourth embodiment.

FIG. 8 is a cross-sectional view illustrating a cross-sectional shape of a gas flow path of a current collector according to a fifth embodiment.

[Explanation of symbols]

11, 12, 13, 14, 15, 16 ... current collector 31, 32, 33, 34, 35, 36 ... gas flow path 41, 43, 45 ... opening 42, 44, 46
... widest part 51, 52, 53, 54, 55, 56 ... thick part 64, 65, 66 ... opening part 74, 75, 76
... Bending start portion 84 ... Open end 86 ... Bending stop portion

Claims (4)

[Claims] 1. A solid electrolyte membrane, a pair of electrodes sandwiching the solid electrolyte membrane from both sides, and a gas chamber which is located opposite to the electrode and into which a reactive gas causing an electrode reaction with the electrode is introduced. And a pair of current collectors provided on a surface facing the electrode, wherein the current collector is provided on the contact surface with the electrode. A current collector for a fuel cell, comprising a concave portion forming a flow path, wherein the cross-sectional shape of the concave portion is such that the inside of the concave portion is wider than the opening of the concave portion. 2. The current collector for a fuel cell according to claim 1, wherein the inside of the concave portion starts from a curved start portion where the width of the concave portion starts increasing from the width of the opening of the concave portion. 3. The current collector for a fuel cell according to claim 2, wherein the cross section of the opening of the recess is rounded. 4. The current collector for a fuel cell according to claim 1, wherein the concave portion is formed on both surfaces of the current collector.