JPH02288161A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To reduce internal resistance and to increase power generation capacity by filling a gas permeable conductive material in at least one gas passage. CONSTITUTION:Oxygen electrodes 2 are, respectively, formed in the inner circumferences of solid electrolytes 1 and fuel electrodes 3 are respectively, formed in their greater parts of the outer circumferences. Inter-connectors 4 electrically being in connection with the oxygen electrodes 2 are, respectively, projected to the outside to connect two or more fuel cells in series by sequentially being in contact with the fuel electrodes 3 of other fuel cells. Gas permeable conductive material 8 are, respectively, filled in oxidizing gas passages 6 inside the oxygen electrodes 2. Current flows from the fuel electrodes 3 to the inter- connectors 4 through the oxygen electrodes 2 and the conductive materials 8, respectively. Since electric conductivity of the conductive materials 8 are high, electric conductivity of the cells are increased as a whole. The internal resistance in each unit cell is reduced and powder generating capacity is increased.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention arranges a porous fuel electrode and an oxygen electrode with a solid electrolyte sandwiched between them, and performs an electrochemical reaction between a fuel gas and an oxidizing gas with the solid electrolyte sandwiched therebetween. This invention relates to fuel cells that generate electric power.

As is well known, conventional solid electrolyte fuel cells utilize the fact that materials such as yttria-stabilized zirconia exhibit ionic conductivity at high temperatures. Electromotive force is obtained through electrochemical reactions accompanying movement. This is illustrated in principle as shown in FIGS. 3 to 5, and the one shown in FIG. 3 is a so-called cylindrical fuel cell. That is, a porous oxygen electrode 2 is formed on the inner circumferential side of a cylindrical solid electrolyte 1, and a porous fuel electrode 3 is formed on the outer circumferential side of the solid electrolyte 1.
is formed, and in order to connect adjacent cells in series, an interconnector 4 electrically connected to the oxygen electrode 2 is provided protruding outside while insulated from the fuel electrode 3. and other cell fuel electrodes 3
and are electrically connected through a conductive material 5 such as N1 felt.

The inner circumferential side of the M elementary electrode 2 is used as an oxidizing gas flow path 6 for air, oxygen, etc., and the outer circumferential side of the fuel Ta #A3 is used as a fuel gas flow path 7 for flowing fuel gas such as hydrogen gas or carbon monoxide gas. It is said that

Furthermore, the one shown in Fig. 4 is a so-called flat plate type fuel cell.
The solid electrolyte 11 is formed to have an uneven cross section such as a waveform, and an oxygen electrode 12 is formed on the lower side of the solid electrolyte 11 in FIG. 4, and a fuel electrode 13 is formed on the upper side. The fuel electrodes 13 and the oxygen electrodes 12 are sandwiched by plate-shaped interconnectors 14 and stacked in multiple stages, so that the upper and lower fuel electrodes 13 and the oxygen electrodes 12 are electrically connected via the interconnectors 14 and connected in series. And M elementary electrode 1
The portion surrounded by 2 is an oxidizing gas flow path 16,
Further, the portion surrounded by the fuel electrode 13 is defined as a fuel gas flow path 17 .

Furthermore, the one shown in FIG. 5 shows another example of a flat plate type fuel cell, in which the solid electrolyte 21 and the oxygen electrodes 22 and fuel electrodes 23 arranged on both sides thereof are each formed in a flat plate shape, and Fj A rectangular notch is formed in the portion of the elementary electrode 22 and the fuel electrode 23 on the opposite side from the solid electrolyte 21, and the solid electrolyte 21, oxygen electrode 22, and fuel electrode 23 having the above-described structure are integrated. are sequentially stacked with a flat plate-like interconnector 24 in between, so that the notch becomes a hollow passage, the rectangular hollow passage on the oxygen electrode 22 side becomes the oxidizing gas flow passage 26, and the rectangular hollow passage on the fuel electrode 23 side becomes a hollow passage. The hollow passage serves as a fuel gas passage 27.

Therefore, in each of the above-mentioned fuel cells, the oxidizing gas passage 6.1
For example, let air flow through 6.26, and the fuel gas passage 7
．． For example, if hydrogen gas is flowed through 17.27, solid electrolyte 1
,11.Due to the difference in oxygen concentration on both sides of 21,
An electrochemical reaction occurs between oxygen in the air and hydrogen gas, that is, oxygen ions react with hydrogen through the solid electrolyte 1, 11.21, and an electromotive force is generated accordingly.

By the way, the theoretical value of the electromotive force generated in each unit cell is slightly more than 1 volt, so in the configuration shown in FIG. 3, a plurality of unit cells are connected in series via an interconnector 4 and a conductive material 5, Furthermore, in the configurations shown in FIGS. 4 and 5, the flat interconnector 14.2
By connecting multiple cells in series through 4,
Obtaining the required voltage. Although not specifically shown in Figure 3, the required current is obtained by connecting multiple single cells in parallel, and in the fuel cells shown in Figures 4 and 5, multiple single cells are connected in parallel. The configuration is connected in parallel.

Problems to be Solved by the Invention However, in order to increase the power that can be obtained as much as possible, it is sufficient to increase the electromotive force of each cell, but there is a limit to the electromotive force that can be obtained from each cell. Furthermore, internal resistance is a major factor in reducing the extractable power, and by reducing this internal resistance, the extractable power can be increased. However, when the individual cells are connected in series and parallel as described above, the current flows from the interconnector 4, 14.24 to the oxygen electrode 2.
and solid electrolyte 1.11.21 and fuel electrode 3,
13.23, the current flow path is complicatedly curved,
And longer. Furthermore, each electrode does not necessarily have a sufficiently wide cross-sectional area, and materials are selected based on other factors such as heat resistance, reduction resistance, and oxidation resistance, and as a result, the resistance of each electrode and solid electrolyte increases. This could not be ignored, and there was room for further improvement in order to increase the generated power.

This invention was made against the background of the above-mentioned circumstances.
The object of the present invention is to provide a solid electrolyte fuel cell that can reduce internal resistance and increase generated power.

Means for Solving the Problems In order to achieve the above object, the present invention provides a fuel electrode and an oxygen electrode with a solid electrolyte sandwiched between them, and forms a fuel gas flow path for flowing fuel gas to the fuel electrode side. In a solid electrolyte fuel cell in which an oxidizing gas channel is formed to flow an oxidizing gas containing oxygen to the oxygen electrode side, a ventilated four-electrode is provided in at least one of the fuel gas channel and the oxidizing gas channel. It is characterized by being filled with a flexible material.

Further, in the present invention, a felt material containing Ni or an alloy thereof may be used as the conductive material, and the fuel gas flow path may be filled with this felt material.

Function: Also in the fuel cell of the present invention, an electrochemical reaction occurs between the oxidizing gas and the fuel gas via the solid electrolyte, and an electromotive force is generated so that the oxygen electrode becomes the anode and the fuel electrode becomes the cathode. and the current flows through each electrode. In addition, when these fuel cells are connected in series, an interconnector is used to connect the oxygen electrode of one cell to the fuel electrode of the other cell. In this case, in the fuel cell of the present invention, Because at least one of the gas flow paths is filled with a conductive material that is breathable, the current flows not only through the material that makes up the electrode, but also through the filled conductive material that has air permeability. ,the result,
Since the current flow path is short and has a large area, the internal resistance of the fuel cell as a whole is reduced.

Example Next, the present invention will be explained based on examples.

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and shows a cylindrical self-supporting fuel cell. That is, in FIG. 1, reference numeral 1 indicates a solid electrolyte, an oxygen electrode 2 is formed on the inner peripheral side thereof, and a fuel electrode 3 is formed on most of the outer peripheral surface of the solid electrolyte 1. Further, an interconnector 4 electrically connected to the oxygen electrode 2 is formed to protrude to the outside,
A plurality of fuel cells are connected in series by bringing this interconnector 4 into contact with the fuel electrodes 3 of other fuel cells. A hollow portion inside the oxygen electrode 2 serves as an oxidizing gas flow path 6, and the inside thereof is filled with an air-permeable conductive material 8. As this conductive material 8, l
a Mn 03 and laC.

O3 etc. can be used. and the fuel electrode 3
The outer circumferential side of the fuel gas passage 7 is a fuel gas passage 7 through which fuel gas such as hydrogen gas flows. Therefore, in the fuel cell shown in FIG. 1, an oxidizing gas such as air containing oxygen or pure oxygen gas is passed through the oxidizing gas flow path, and a fuel gas such as hydrogen gas, carbon monoxide gas, or methane is flowing through the fuel gas flow path 7. By flowing the solid electrolyte 1, an oxidation reaction occurs, and an electromotive force is generated accordingly. By connecting each fuel cell in series as described above, current flows from the oxygen electrode 2 of one cell to the fuel electrode 3 of the other cell, but in each fuel cell, a current flows from the fuel electrode 3 to the interconnector 4. The current flow takes place through the conductive material 8 filled in the oxygen electrode 2 and the oxidizing gas flow path 6, so that the current flows through the free flow path and the conductivity of the conductive material 8 Since the rate is high, the overall conductivity is high, and in terms of yA, the internal resistance of the fuel cell is reduced.

FIG. 2 shows another embodiment of the present invention, and the fuel cell shown here is an application of the present invention to the above-described flat plate type fuel cell shown in FIG. That is, in FIG. 2, each reference numeral indicates the same member as the member explained with reference to FIG. It is filled with a four-electroconductive material 28. Among these conductive materials 28, it is preferable that the conductive material 28 filled in the fuel gas flow path 27 is an air-permeable felt material containing N: or an alloy thereof. Therefore, in the configuration shown in FIG. 2, the flow of current through the I11 cells connected in series is not limited to each electrode material, but also through the conductive material 28 in each gas flow path 26, 27 as a flow path for current flow. flows, the overall electrical conductivity is high, and as a result, the internal resistance of the fuel cell is reduced. If the fuel gas passage 27 is filled with a particularly breathable conductive material 28 containing Ni or its alloy, the conductive material 28 will absorb unreformed gas such as methane. Since it also acts as a catalyst for reforming carbon oxide and hydrogen, the types of usable fuel gas are diversified and the usefulness of fuel cells is improved.

In each of the above embodiments, an example in which the present invention is applied to the conventional fuel cell shown in FIG. 3 and FIG. You can also.

Effects of the Invention As is clear from the above explanation, according to the fuel cell of the present invention, the internal resistance of each unit cell is reduced because the inside of the oxidizing gas flow path or the fuel gas flow path also serves as a current flow path. ,
As a result, it is possible to increase the power generation capacity. In addition, if a gas-permeable conductive material containing Ni or its alloy is used and filled in the fuel gas flow path, the conductive material acts as a catalyst for reforming the fuel gas. A fuel cell capable of internally reforming gas can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing one embodiment of the present invention, Fig. 2 is a diagram schematically showing another embodiment of the invention, and Fig. 3 is a diagram schematically showing a conventional cylindrical solid electrolyte fuel cell. 4 and 5 are diagrams each schematically showing a conventional flat plate solid electrolyte fuel cell. 1.21... Solid electrolyte, 2,22... Oxygen electrode, 3.23... Fuel electrode, 6,26... Oxidizing gas flow path, 7.27... Fuel gas flow path, 8 .28...
・Conductive material.

Claims (2)

[Claims] (1) A fuel electrode and an oxygen electrode are provided with a solid electrolyte sandwiched between them, and a fuel gas flow path is formed to flow fuel gas to the fuel electrode side, and an oxidizing gas flow path to flow an oxidizing gas containing oxygen to the oxygen electrode side. What is claimed is: 1. A solid electrolyte fuel cell in which at least one of the fuel gas flow path and the oxidizing gas flow path is filled with an air-permeable conductive material. (2) Ni is used as the conductive material in the fuel gas flow path.
2. The solid electrolyte fuel cell according to claim 1, wherein the solid electrolyte fuel cell is filled with a felt material containing the solid electrolyte fuel cell or an alloy thereof.