JP2751434B2 - Fuel cell separator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell separator used for partitioning cells of a fuel cell used in an energy sector in which chemical energy of a fuel is directly converted into electric energy. .

[Prior Art] Among the fuel cells that have been proposed to date, a molten carbonate fuel cell is, as shown in FIG. 12, an example of a tile in which molten carbonate is impregnated into a porous material (electrolyte). Plate) 1 as cathode (oxygen electrode) 2 and anode (fuel electrode)
3 sandwiched between both electrodes, and oxidized gas OG on the cathode 2 side
And a fuel gas FG is supplied to the anode 3 side so that power is generated by a chemical reaction between the cathode 2 and the anode 3. To form a stack.

In the case of an internal manifold type fuel cell, the separator 4 serving as a partition when stacking the cells I of the fuel cell is formed with irregularities serving as gas passages on the front and back surfaces in a central portion excluding a peripheral portion. Are provided with manifolds 5 and 6 for supply and discharge of oxidizing gas and manifolds 7 and 8 for supply and discharge of fuel gas, which are provided as wet seal portions so that different gases flow on both front and back surfaces of the separator 4. The gas supply / discharge manifold is connected to a central gas passage. Reference numeral 9 denotes a mask plate in which a central portion is cut out and arranged around the separator 4.

The separator 4 may be formed by etching, machining, excavating, pressing, or the like for forming gas passages in the center of the separator, or by disposing a corrugated plate on both sides of a center plate. There is a corrugated type in which a gas passage is formed.

An example of the corrugated separator of the internal manifold type is a manifold for an oxidizing gas and a fuel gas at a peripheral portion as shown in FIGS. 13 and 14.
Center plate 10 provided with 11 and 12; corrugated plates 14 and 15 arranged on both sides of center plate 10 to form gas passages; And the above manifold 1
Mask plates 13a, 13b, which are arranged on the upper and lower surfaces around the center plate 10 in the form of cutouts of parts 1 and 12, and whose outer edges are joined over the entire circumference, are arranged above and below the periphery of the center plate 10. Support plates 16a, 1 superposed inside the mask plates 13a, 13b
6b, and a manifold 11 for the oxidizing gas.
In the part, the peripheral edge of the manifold of the mask plate 13a is bent and joined to the center plate 10 so that the oxidizing gas OG flows to the electrode reaction section through the corrugated plate 15 as shown by an arrow in FIG. In the part of the manifold 12 for fuel gas, the mask plate
The peripheral edge of the manifold 13b is bent and joined to the center plate 10 so that the fuel gas FG flows through the corrugated plate 14 as shown by an arrow in FIG. 14 to the electrode reaction section.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned conventional corrugated separator, since the two mask plates 13a and 13b are overlapped on both surfaces of the center plate 10, the separator is used as a separator. There is a problem that the number of parts is large, and both mask plates 13a and 13b are manifolds.
Since the parts 11 and 12 are bent inward by pressing and joined to the center plate 10,
There is a problem that the press work is required for the mask plates 13a and 13b, the number of work is large, and the press work requires much time and cost.

Therefore, the present invention replaces the conventional separator of the type in which one center plate and two mask plates are superimposed and joined all over the periphery, and the mask plate is bent at the manifold portion and joined to the center plate. It is an object of the present invention to provide a fuel cell separator which can be manufactured easily and at low cost, and which can improve the corrosion resistance and extend the life of the fuel cell.

[Means for Solving the Problems] In order to solve the above problems, the present invention arranges one separator plate manufactured by press molding, and arranges the separator plate on both sides so as to sandwich a peripheral portion of the separator plate. It is composed of two flat plate-shaped mask plates, and the separator plate has unevenness for forming a gas passage on the front and back surfaces in a central portion and has a manifold in a peripheral portion, and the two mask plates are: A heat-resistant clad material in which a high-aluminum ferrite layer having an aluminum content of 12% or more and heat-resistant steel are diffusion-bonded to the outer surface is used so that the high-aluminum ferrite layer is positioned outside, and a manifold is further provided. The above-mentioned separator plate and the inner surface side of the two mask plates are laser-welded at the outer edge portion and the manifold portion. And it formed. The two mask plates use a flat heat-resistant clad material in which a high aluminum ferrite layer and a heat-resistant steel are diffusion-bonded. The clad ratio of the high aluminum ferrite layer is 10% or less, and the depth is (Thickness) 50 ~
It is preferably about 100 μm. The separator plate uses a clad material of nickel and heat-resistant steel, and the clad ratio of the nickel layer is 0.2 to 20%. Further, the separator plate is made of a heat-resistant clad material in which a high-aluminum ferrite layer having an aluminum content of 12% or more is diffusion-bonded to the surface of the heat-resistant steel in contact with the anode gas.

[Operation] Since it is composed of three members, one separator plate and two mask plates, the structure is simplified and the weight can be reduced. When partitioning the fuel cell, the upper and lower parts sandwiching the separator plate are used. The mask plate is brought into contact with the tile, the cathode and anode electrodes are placed in the cutouts at the center of the mask plate, and different gases flowing on the front and back surfaces of the separator plate contact the electrodes to react. Furthermore, the heat-resistant clad material used for the two mask plates has an aluminum content of 12
% High aluminum ferrite layer, and the heat-resistant clad material used for the separator uses a high aluminum ferrite layer with an aluminum content of 12% or more on the surface in contact with the anode side, so that the corrosion resistance should be improved. Can be.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a fuel cell separator according to the present invention, in which a cathode 2 and an anode 3 are provided on both sides of a tile 1.
Used as a partition plate when stacking cells formed by laminating a plurality of cells into one separator plate
It is assumed that three members consisting of 17 and two mask plates 18a and 18b are superposed. That is, a separator plate 17 made of one thin plate manufactured by forming irregularities on both front and back surfaces by press molding, and the separator plate
The separator plate 17 comprises two mask plates 18a and 18b which sandwich the peripheral portion of 17 from both sides.
A gas passage is formed by pressing irregularities on both front and back surfaces in a central portion serving as an electrode reaction portion, and a gas passage is formed in a peripheral portion so that the gas passage is communicated with the gas passage in the central portion. A gas supply / discharge manifold 19 and a fuel gas supply / discharge manifold 20 are provided. In addition, the mask plates 18a and 18b have a configuration in which both the central portion serving as the electrode reaction portion is cut out and only the peripheral portion is provided, and manifolds 19 and 20 are provided in the peripheral portion so as to correspond to the manifolds 19 and 20. In addition, when the cells of the fuel cell are stacked, the portions in contact with the tile 1 are in contact with the molten carbonate and are corroded. Therefore, in order to prevent the corrosion, the mask plates 18a and 18b are provided with a high aluminum ferrite layer 18c. And the heat-resistant steel 18d as a base material is made of a flat heat-resistant clad material which is diffusion-bonded, so that the high aluminum ferrite layer 18c is positioned on the outer surface side in contact with the tile 1. Further, the one separator plate 17 and the two mask plates 18a and 18b sandwiching the same are integrally formed by laser welding.
The places where the separator plate 17 and the mask plates 18a and 18b are laser-welded are the outer edge and the manifold 19 and 20 parts, and the separator plate 17 and the mask plates 18a and 18b
The separator plate 17
(From the side opposite to the high aluminum ferrite layer 18c) so as to perform laser welding. 21 is a laser weld.

The separator plate 17 is made of nickel /
A heat-resistant steel clad material is used, and the separator plate 17 is arranged and used so that a heat-resistant steel layer is on the side where the oxidizing gas flows and a nickel layer is on the side where the fuel gas flows.

Next, the background in which the above-described one separator plate 17 and the two mask plates 18a and 18b constituting the fuel cell separator of the present invention were made of the above-described material, more specific description, and experimental results , Etc. will be described in detail.

The operating temperature of a molten carbonate fuel cell is 600 to 700
The separator is exposed to both oxidizing and reducing atmospheres in molten carbonate, which is as high as ° C. and is highly corrosive. As the corrosion of the separator proceeds, the lithium in the molten carbonate is consumed, and at the same time, the contact resistance increases and the life of the battery decreases.

Therefore, according to the present invention, in manufacturing the separator plate 17, in a reducing atmosphere and molten carbonate, valuable nickel (Ni) (for example, Inconel 201) and a heat-resistant steel (for example, SUS 316L, SUS 310S,
(Inconel 825, etc.). FIG. 2 shows a cross section of a part of the separator plate 17, in which 17a is a nickel layer and 17b is a layer of heat-resistant steel. In the above, Ni and the heat-resistant steel have different coefficients of thermal expansion, so that when the temperature is raised, a bimetal phenomenon occurs, and there is a possibility that thermal deformation may occur during the manufacturing process and during battery operation. Therefore,
Cladding ratio of Ni to heat-resistant steel (Ni thickness / total thickness) 0.2 to 20
%. If it is set to 0.2% or less, the corrosion resistance of Ni will not be exhibited, and if it is set to 20% or more, bending will occur when the temperature is increased due to the difference in thermal expansion coefficient with heat-resistant steel, and this will increase the cost. It is preferable to set the above to 0.2 to 20%.

Next, as for the mask plates 18a and 18b, the wet seal portion (outer peripheral portion) where the mask plate contacts the tile 1 impregnated with the electrolyte has a different oxygen concentration distribution, so that a local battery is generated and corrosion proceeds. In order to prevent this, a high aluminum material or the like which has a small electric conductivity and produces a dense scale layer is effective. Therefore, a high aluminum ferrite layer 18c is provided. Examples of the method of diffusing the high aluminum ferrite layer 18c on the surface of the heat-resistant steel 18d as a base material include a pack cementation method, a spraying method → baking → diffusion treatment, and the like. And the high aluminum diffusion layer has a large electric resistance, so that electric welding cannot be performed and welding cracks easily occur.

Therefore, the present inventors prototyped a clad material in which a high-aluminum ferrite steel sheet and heat-resistant steel were diffusion-bonded, and performed a corrosion test. In other words, as a result of making the same material as the material used as the mask plate and conducting a corrosion test,
The results shown in the photographs of FIGS. 4 to 9 were obtained.

In the above corrosion test, the test conditions were as follows: Material: High Al ferritic stainless steel (about 150 μm) / SUS 310S clad (t = 1.5 mm) Atmosphere: Gas phase-Fuel gas Liquid phase-Carbonate Immersion temperature: 650 ° C Immersion time: The test was performed under the conditions of 197 hours and when the aluminum concentration (content) of the high aluminum ferritic steel was 4%, 8%, and 12%.

First, in the case of an aluminum content of 4%, in the gas phase (portion wetted with carbonate), that is, in the gas flowing portion (electrode reaction zone), FIG. Slight corrosion was observed on the surface as shown in the photograph at 400 × magnification), but in the liquid phase, that is, in the wet seal portion, the fifth corrosion was observed.
As shown in the figure (a photograph in which the cross section of the structure in the liquid phase portion was viewed at a magnification of 400), it was confirmed that the structure was considerably corroded.

Also in the case of an aluminum content of 8%, slight corrosion was observed on the surface in the gas phase as shown in FIG. 6 and considerable corrosion was observed on the surface in the liquid phase as shown in FIG. 6 and 7 show cross sections of the tissue taken at a magnification of 400 ×.

Next, as a result of a test with an aluminum content of 12%, slight corrosion was observed on the surface as shown in FIG. 8 in the gas phase, but as shown in FIG. 9 in the liquid phase (wet seal portion). Little corrosion was seen. FIGS. 8 and 9 both show a tissue section at a magnification of 400 ×.

From these test results, it was confirmed that when the aluminum content of the high aluminum ferritic steel was 12% or more, the corrosion resistance was improved.

Next, the thickness of the high-aluminum ferrite layer 18c having an aluminum content of 12% or more is determined by adjusting the cladding ratio to prevent thermal deformation caused by a difference in thermal expansion between the heat-resistant steel 18d as a base material and the ferrite layer 18c. 10% or less, ferrite layer
The thickness of 18c should be 50-100μ or less. High aluminum ferritic steels have a body-centered cubic system and have a high aluminum diffusion rate, whereas heat-resistant steels are generally face-centered cubic and therefore have a low aluminum diffusion rate. As a result, since the aluminum concentration in the ferrite is made uniform, the corrosion resistance effect can be maintained.

When assembling the separator of the present invention, the separator plate 17 is sandwiched between the two mask plates 18a and 18b, and then the outer edge and the manifolds 19 and 20 are laser-welded. A laser beam is applied to the joint between the separator plate 17 and the mask plate 18a shown in FIG. 1 from the opposite side of the high aluminum ferrite layer 18c of the mask plate 18a as shown by an arrow to perform laser welding. A laser beam is applied to the joint between the outer edge of the plate 17 and the mask plate 18b from the opposite side of the high aluminum ferrite layer 18c in the direction of the arrow to perform laser welding to seal the wet seal portion. In the manifolds 19 and 20, the manifolds 19 and 20 are used to separate the separator plates 17 and 20, respectively.
Of the mask plate 18a or 18b is laser-welded in a ring shape from the separator plate 17 side. In such laser welding, the mask plates 18a,
The reason for irradiating the laser beam from the opposite side of each high aluminum ferrite layer 18c of 18b is to prevent the high aluminum ferrite steel from cracking because it is cracked when welded.

The present inventors prototyped a clad material in which a high-aluminum ferrite steel sheet and a heat-resistant steel were diffusion-bonded as in the case of the corrosion test, and performed a laser welding test. The results were as follows.

Welding material: SUS 304 used as separator plate,
High aluminum ferrite stainless steel (about 100μm, Al12%) / SUS 310S clad is used as the mask plate. Welding machine: CO ₂ laser machine. Welding method: Lap welding is performed with the clad material outside the separator plate side.

As a result of the test under the above welding conditions, a cross section of the welded portion as shown in FIG. 10 and the reference photograph was obtained, and the separator plate and the clad material could be laser-welded without affecting the clad material. The reference photograph is an enlarged photograph of the structure of the laser weld portion 21 between the separator plate and the mask plate.In the cross section of the weld portion 21, the upper thin portion is the separator plate, and the lower portion is the clad material. is there. As is clear from the above-mentioned FIG. 10 and the reference photograph, when welding is performed by irradiating a laser beam from the separator plate side, since the joint bead does not reach the high aluminum ferrite layer of the clad material, welding to the high aluminum ferrite layer is performed. No cracking occurs.

When a fuel cell is stacked in multiple layers using the separator of the present invention having the above-described configuration to form a stack, as shown in an example in FIG. 3, the tile 1 is sandwiched between both sides of the tile 1. The separator according to the present invention is punched on a cell having both cathode 2 and anode 3 electrodes.
Intervene so as to partition through 22,23. In this case, the punch plates 22, 23, the cathode 2 and the anode 3 are positioned inside the mask plates 18a, 18b integral with the separator plate 17 as shown in FIG. The separator plate 17 uniformly presses the tiles 1 through 22, 23, and the oxidizing gas OG supplied from the manifold 19 and the fuel gas FG supplied from the manifold 20 are supplied to the separator plate 17 for each stage. The oxidizing gas OG is brought into contact with the cathode 2 and the fuel gas is brought into contact with the anode 3 respectively. 24 is a manifold for cooling air.

In FIG. 3, the separator plate 17 and the mask plates 18a, 18b constituting the separator of the present invention are shown separated from each other, but as shown in FIG. 1, the outer edge and the manifold are welded by laser welding. Needless to say, it is used by joining. Further, the number of the manifolds 19 and 20 may be other than that shown in FIG. 3, and the case where the punch plates 22 and 23 are used is shown. However, the punch plates 22 and 23 may be omitted.

Next, FIG. 11 shows a cross section of a separator plate in another embodiment of the present invention. In the above embodiment, the separator plate 10 has a cross section as shown in FIG. Using a clad material with heat-resistant steel 17b, the nickel layer 17a on the side in contact with the fuel gas,
In addition, although an example in which the heat-resistant steel 17b is disposed so as to be in contact with the oxidizing gas and used is shown, as the separator plate 17, the surface of the heat-resistant steel 17b as a base material in contact with the fuel gas is replaced with a nickel layer. High aluminum ferrite layer 17
and a separator plate 17 made of a heat-resistant clad material having a high aluminum ferrite layer 17c diffusion-bonded to the surface thereof.
Is used as a separator.

According to this embodiment, since the surface of the separator plate 17 on the side in contact with the fuel gas is positively subjected to the corrosion resistance treatment, the corrosion resistance of the surface on the side in contact with the fuel gas is improved, and the life of the separator plate itself is extended. Can be achieved.

[Effects of the Invention] As described above, according to the fuel cell separator of the present invention, one separator plate manufactured by press molding and two flat mask plates sandwiching the separator plate are used. The above two mask plates are provided on the outer surfaces with a heat-resistant clad material obtained by diffusion bonding of a high aluminum ferrite layer having an aluminum content of 12% or more and heat resistant steel such that the high aluminum ferrite layer is positioned outside. Since it is used and has a manifold, and the separator plate and the inner surface side of the mask plate are integrated by laser welding at the peripheral part and the manifold part, it is easier and cheaper to manufacture than conventional separators It can be manufactured, and furthermore, the corrosion resistance is improved and the life of the fuel cell can be prolonged. The corrosion resistance of the separator plate is improved by using a heat-resistant clad material in which a high aluminum ferrite layer with an aluminum content of 12% or more is diffusion-bonded to the surface of the heat-resistant steel in contact with the fuel gas. An excellent effect of extending the life can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fuel cell separator of the present invention, FIG. 2 is a partially enlarged cross-sectional view showing a specific example of a separator plate in the separator of the present invention, and FIG. 3 is an assembled state of a fuel cell stack. FIGS. 4 to 9 are photographs of metal structures showing the results of corrosion tests on clad materials obtained by diffusion bonding of a high aluminum ferrite steel sheet and heat-resistant steel, and FIG. 10 is a photograph of a separator plate and a mask plate. Sectional view of a welded portion showing a laser welding test result, FIG. 11 is a partially enlarged sectional view showing another example of the separator plate in the separator of the present invention, FIG. 12 is a sectional view showing an example of a fuel cell, FIG. 13 and 14 show an example of a conventional separator, and are enlarged cross-sectional views of a manifold portion for an oxidizing gas and a manifold portion for a fuel gas. 1 ... tile, 2 ... cathode, 3 ... anode, 17 ...
… Separator plate, 18a, 18b …… Mask plate, 1
8c: High aluminum ferrite layer, 18d: Heat-resistant steel, 1
9,20: Manifold, 21: Laser weld.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takenori Watanabe 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima-Harima Heavy Industries, Ltd. (72) Inventor Toshio Kamada 3-1-1 Toyosu, Koto-ku, Tokyo No. 15 Ishikawa Shima-Harima Heavy Industries Co., Ltd. Tokyo Second Factory (72) Inventor Mitsuo Watanabe 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima Harima Heavy Industries Co., Ltd. Tokyo No. 2 Factory (56) References 63-53857 (JP, A) JP-A-63-53858 (JP, A) JP-A-59-141174 (JP, A) JP-A-2-192882 (JP, A)

Claims (2)

(57) [Claims] 1. A separator plate comprising: one separator plate manufactured by press forming; and two flat plate-shaped mask plates disposed on both sides so as to sandwich a peripheral portion of the separator plate. Is
The central part has irregularities for forming gas passages on both front and back sides, and the peripheral part has a manifold. The two mask plates have an aluminum content of 12% on the outer surface.
The heat-resistant clad material obtained by diffusion-bonding the high-aluminum ferrite steel and the heat-resistant steel is used so that the high-aluminum ferrite layer is positioned on the outside, has a manifold, and further has an inner surface of the separator plate and two mask plates. A fuel cell separator characterized by being integrated by laser welding the outer side and the manifold at the sides. 2. The heat-resistant cladding material according to claim 1, wherein a high-aluminum ferrite layer having an aluminum content of 12% or more is diffusion-bonded to the surface of the heat-resistant steel in contact with the anode gas as the separator plate. Fuel cell separator.