JPH03266365A - Solid oxide fuel cell separator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a separator for a solid oxide fuel cell.
In particular, this invention relates to separators for solid oxide fuel cells that are used as current collector plates for flat solid oxide fuel cells that are currently being developed as part of new power generation technology.

[Prior Art] As is well known, a flat solid electrolyte fuel cell has a fuel electrode formed on one side of a flat solid electrolyte and an oxidizer electrode (also called an air electrode) formed on the other side. This is a fuel cell power generation facility in which battery members called a three-layer battery membrane are stacked, and a flat separator (also called an interconnector) is arranged between each battery member to form an electric circuit.

Therefore, the separator of the above-mentioned flat solid oxide fuel cell serves as a partition wall between the fuel gas (reducing agent) and air (oxidizing agent), and also separates the fuel gas and air from the fuel electrode (which becomes the negative electrode). and a gas distribution means forming a supply path on the surface of the oxidizer electrode (which becomes the positive electrode), and further makes contact with the surface of each electrode for energization, and serves as a current collector plate that collects the generated current. It's something that works.

In addition, in the structure as described above, the separator can also be called a bipolar plate having gas distribution means from the viewpoint of a current collector plate.

Conventional examples of separators equipped with gas distribution means include 5
OFC Nagoya Symposium Proceedings, November 13-14, 1989;
5OFC-NAGOY^;Internationala
Symposium on 5olis Oxid
e Fuel Cell: Japan Fine Cer
amics Center).

FIG. 2 is a schematic perspective view showing the principle of a cell portion of a solid oxide fuel cell using a separator having a conventional gas flow means described on page 85 of this document. In the figure, 1 is a flat solid electrolyte made of Z r 02 (zirconia) stabilized with Y2O3, and 2 is a solid electrolyte made of N i
A fuel electrode (positive electrode) made of Z r O2 cermet,
3 is L a M n Oa or I n OS r O
The solid electrolyte 1, the fuel electrode 2 sandwiching the solid electrolyte 1, and the oxidizer electrode 3 integrally form a three-layer cell membrane. 4 and 5 are separators (current collector plates) made of conductive oxide or Ni-Cr alloy, which are used as end plates of the battery like the separator 4, and when laminating the battery three-layer membrane 10. It is used as a bipolar separator 9 with separators 4 and 5 placed back to back. The separators 4 and 5 are provided with a large number of grooves 6 and 6a that allow the fuel gas 7 and air 8 to flow in the gas traveling direction, and the open portions of the grooves 6 and 6a are the electrodes of the fuel electrode 2 and the oxidizer electrode 3, respectively. It is designed to ensure passages for supplying each gas to the surface. Note that instead of forming gas passages by grooves, a method is also used in which the gas passages are formed by regularly arranging dot-like protrusions.

The operation and operation of the solid oxide fuel cell configured as above
Since the principle is well known, its explanation will be omitted.

In reality, for example, the separator 4 is incorporated into a frame 11 for stacking the entire separator, as shown in the plan view of FIG. and a gas outlet 13 are provided, which together with the groove 6 constitute a gas distribution means. This also applies to the separator 5. Note that the outer flat portions of the grooves 6 and 6a are formed so as to come into contact with opposing electrode surfaces during stacking.

In addition, Utility Application No. 63-1144 filed by the same applicant as the present invention
No. 82 proposes, for example, a separator 4 in which a large number of point-like protrusions 14 are arranged, as shown in the plan view of the separator in FIG. is provided.

[Problems to be Solved by the Invention] In the conventional solid oxide fuel cell separator as described above, when the fuel gas or air is passed through the formed groove-like or dot-like convex region, it is necessary to As noted in Figures 3 and 4, there is a problem in that the gas flows in such a way that there are areas where the gas flow rate is high and areas where it is low. That is,
The gas density increases near the region connecting the gas inlet and outlet, and decreases as it moves outward. This phenomenon does not pose any particular problem in the case of batteries with a small area because fuel gas or air is evenly distributed on the electrode surface even with the conventional method, but in the case of batteries with a large area on a practical scale, fuel gas and air flows in a non-uniform distribution within the plane as described above, the battery reaction becomes non-uniform over the entire surface, which is unfavorable from the viewpoint of battery performance and thermal stress distribution. Figures 5 to 7 show some gas distribution means considered to prevent non-uniformity of gas flow.
The configuration and problems will be explained using diagrams.

FIG. 5 is a plan view showing the case of an external manifold in which the manifold is provided outside the frame 11, but it is necessary to provide a large number of gas inlets 12 and gas outlets 13, or to make them wide as shown. In this case, when configuring the fuel pipe and air pipe manifolds, their arrangement may interfere with each other, resulting in a very complicated structure, which is impractical.

Figure 6 shows a manifold 15.15a in the frame 11.
FIG. 2 is a plan view showing a case of an internal manifold in which gas is introduced through a gas inlet 12. In this case, as shown in the figure, in the structure of parallel flow (method in which fuel F and air A flow in the same direction), it is necessary to provide multiple stages of air and fuel passages. Since it can only be placed every other place to supply gas,
Gas inhomogeneity remains. In other words, in the case of an internal manifold structure, the gas inflow port cannot be enlarged, which also poses a practical problem.

Figure 7 shows crossflow flow in the internal manifold.
This is a plan view showing the case w), and if the gas inlets 15.15a are provided on the four sides of the frame 11 in this way, a wide gas inlet hole 12 or the like can be used. However, the cross-flow method has the problem that it is difficult to operate because the uniformity of the reaction is lost and the thermal stress distribution becomes non-uniform within the plane.

This invention was made to solve the above problems, and by improving the shape and arrangement of the protrusions provided on the separator, the number of supply pipes is reduced, a simple structure is sufficient, and the gas flow is improved. The object of the present invention is to provide a separator for a solid oxide fuel cell with good uniformity.

[Means for Solving the Problems] A separator for a solid oxide fuel cell according to the present invention has the following features:
A region on the surface of a separator that is used as a current collector plate and has a gas flow means for fuel and air that communicates with a gas inlet and a gas outlet in a direction in which the dimension in the gas traveling direction is perpendicular to the gas traveling direction. A bank-like protrusion for gas dispersion with a size smaller than that is provided.

In addition, the separator of a solid oxide fuel cell according to another aspect of the present invention is used as a current collector plate and has a gas flow means for fuel and air on the surface of the separator. It is provided with densely dotted gas dispersion protrusions, and in this case, baffle plate-like dispersion protrusions may be used instead of the dot-like dispersion protrusions.

[Function] In the first invention of this invention, since the shape of the protrusions provided on the surface of the separator is a linear body having a long dimension in the direction perpendicular to the direction in which the gas travels, the protrusions with the impeding property prevent the gas from flowing. Since there is a greater chance that the gas will deviate laterally, the gas will proceed while being dispersed laterally with respect to the direction of gas movement, so the gas will be distributed evenly within the separator surface and a uniform density of gas will be supplied to the electrode surface. be done.

In addition, in another invention, the dispersion protrusions are arranged so that the protrusions of the same shape are arranged more densely in the region near the gas inlet than in the far region, so that the gas is strongly dispersed on the inlet side of the gas flow surface of the separator. Since the gas then travels between the normally relatively uniformly arranged protrusions, the gas is evenly distributed on the separator surface and a uniform density of gas is supplied to the electrode surface.

[Example] Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing a general example of a solid oxide fuel cell assembled using a separator according to the present invention. In the figure, the gas flow mode is parallel flow, and the battery has two unit cells with one separator and two
This is shown as an example of a case in which two end plate separators are laminated. Further, the same or equivalent parts as in the conventional example shown in FIG. 2 are denoted by the same reference numerals as in the embodiment shown in the following drawings, and the explanation thereof will be omitted.

In FIG. 1, the surface (including the back surface in the case of bipolar) of the separator 4 and the bipolar separator 9 incorporated inside the frame 11 has a large number of dots or Linear protrusions or gas dispersion protrusions 2
1 is provided. When the tip (base) of this protrusion 21 is stacked to form a battery unit, it is formed at such a height that it comes into contact with the outer electrode of the battery three-layer membrane 10 to collect current. . The fuel gas 7 and air 8 enter through the gas inlet 12 provided on the frame 11, flow through the gap between the protrusions 21, and flow out through the gas outlet 13 provided on the opposite side, so that the respective reaction gases are deposited on the electrode surface. It is designed to supply The protrusions 21 are formed in a desired shape and arrangement from the separator 4 by, for example, a well-known process such as etching. Therefore, the frame 11 is generally also made of the same material as the separator 4. That is, the protrusion 21, the separator 4, and the frame 11 are integrally molded from the same material. Go.

Embodiment 1: For example, instead of the grooves 6 (FIG. 2), the separator 4 is provided with a linear protrusion 22 whose dimension in the gas traveling direction is longer than the dimension in the direction perpendicular to the gas traveling direction. be. The lengthwise size of the protrusion 22 is not particularly specified, and the protrusion 22 is formed at the gas inlet 1
When viewed from the 2 side, the protrusions 22 are arranged relatively regularly so that there is a predetermined gap or are different from each other, and the protrusions 22 as a whole are formed by protrusions for gas dispersion that function as baffles even if they differ in size. It is what was done. In other words, the gas (fuel or air) entering from the gas inlet 12
As the gas moves through the gap between the protrusions 22 as shown by the arrow drawn in the separator 4, this gas dispersion results in uniform gas distribution. Such electrodes 2, 3
Uniform supply of reactive gas to the surface of the electrode allows the cell reaction to proceed uniformly over the entire surface of the electrode, which prevents the reaction surface from collapsing locally, improving cell performance and ensuring a uniform thermal stress distribution. This will prevent the battery from interfering with operation.

Example 2; FIG. 9 is a plan view showing an example separator according to an invention different from Example 1. In the figure, all of the protrusions 23 are of the conventional dot pattern, and most areas of the separator 4 are arranged in a normal manner with normal distances and intervals as shown in A. In the upstream region near the 12 side, as shown in B, a gas passage is formed by disposing protrusions 23 for gas dispersion that are denser than in the part A. Although the arrows along which the gas advances are omitted, due to the arrangement of the protrusions 23, the gas is significantly dispersed in the part B and then advances in the part A. As before, a uniform gas distribution is achieved on the electrode surface. Note that the distribution density of the protrusions 23 in the B part is preferably about 2 to 3 times that of the A part, depending on the size of the B part, but the area ratio of the B part to the A part is limited. shall not be carried out.

Example 3; Figure 1O shows an example of two separators in which baffle plate-like gas dispersion protrusions are arranged instead of the dot-like dispersion protrusions arranged densely on the upstream side shown in Example 2. , shown in FIG.

First, the separator structure shown in the embodiment of FIG. 10 has dot-like protrusions 23 similar to the part A shown in FIG. A plurality of gas dispersion protrusions 24 in the shape of a dogleg curve are arranged, for example, alternately.

In this case, as shown in the figure, it is preferable that the baffle plate-like protrusions 24 be arranged approximately at right angles to the gas traveling direction. With this configuration, the same gas dispersion as in Example 1.2 can be performed, and the electrode surface can be This achieved uniform gas distribution. Although the baffle plate is shown in a dogleg shape in FIG. 10, it may be in a straight shape as in the first embodiment. Moreover, even if the dot-like protrusions 23 are present between the baffle plates, there is no functional problem.

FIG. 11 shows an embodiment in which a groove-shaped projection 25 similar to that shown in the conventional example shown in FIG. This is an example. In this configuration, as in the embodiment of FIG. 10, uniform gas distribution to the electrode surface is achieved.

Although the present invention has been specifically explained above based on examples,
This invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof.

[Effects of the Invention] As described above, according to the present invention, protrusions are provided on the separator surface of a solid oxide fuel cell for uniformly distributing fuel and air on the electrode surface, and the protrusions are arranged in the direction of gas propagation. The shape and arrangement of the gas were improved by placing a horizontally elongated one in front of the gas, distributing the protrusions on the upstream side of the gas densely, and using baffle plate-like protrusions instead of densely distributing the gas. As a result, fuel and air were uniformly dispersed on the electrode surface. As a result, the overall performance of the battery is improved, the thermal stress distribution within the battery surface is made uniform, and the life and strength of the battery are improved.The number of gas supply ports can also be reduced, and the supply ports can be made with a small diameter. We were able to achieve improvements in the performance and structure of the battery, such as the ability to

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a general embodiment of a solid oxide fuel cell assembled using a separator according to the present invention, and FIG. 2 is a schematic perspective view showing the cell structure of a conventional solid oxide fuel cell in principle. , Figure 3. FIG. 4 is a plan view showing a convex structure of a conventional separator, FIGS. 5, 6, and 7 are plan views explaining problems in the convex structure of a conventional separator, and FIG. 8 is a claim. FIG. 9 is a schematic plan view of the separator according to the invention of claim 1; FIG. 9 is a schematic plan view of the separator according to the invention of claim 2; FIGS.
The figure is a schematic plan view of a separator having a baffle plate according to the invention of claim 3. In the figure, 1 is a solid electrolyte, 2 is a fuel electrode, 3 is an oxidizer electrode, 4 and 5 are separators, 6 and 6a are grooves, 7 is a fuel gas, 8 is air, 9 is a bipolar separator, and 10 is a three-layer battery membrane, 11 is the frame of the separator, 12 is the gas inlet, 13 is the gas outlet, 14 is the point-like protrusion, 15.15
a is a manifold, 21 is a protrusion, 22 is a linear protrusion, 2
3 is a point-like protrusion, and 24 is a baffle plate-like protrusion.

Claims (3)

[Claims] (1) Disposed as a current collector plate on both sides of a battery three-layer membrane consisting of a solid electrolyte and two electrodes sandwiching the solid electrolyte,
In a separator for a solid oxide fuel cell having a gas distribution means for supplying fuel gas and air to the surface of the electrode, a gas inlet of the gas distribution means is provided on the surface of the separator so as to be in contact with the surface of the electrode. A solid electrolyte fuel characterized in that a linear gas dispersion protrusion is provided on the surface of the area communicating with the gas outlet, the dimension of which is smaller in the direction in which the gas travels than in the direction perpendicular to the direction of travel of the gas. battery separator. (2) Disposed as a current collecting plate on both sides of a battery three-layer membrane consisting of a solid electrolyte and two electrodes sandwiching the solid electrolyte,
In a separator for a solid oxide fuel cell having a gas distribution means for supplying fuel gas and air to the surface of the electrode, a gas inlet of the gas distribution means is provided on the surface of the separator so as to be in contact with the surface of the electrode. 1. A separator for a solid oxide fuel cell, characterized in that dotted gas dispersion protrusions are provided more densely in a region closer to the surface than in a region farther from the surface. (3) The solid electrolyte type according to claim 2, characterized in that instead of providing the dot-like gas dispersion protrusions densely, baffle plate-like gas dispersion protrusions are provided in a region close to the gas inlet. Fuel cell separator.