JP2841340B2 - Solid electrolyte fuel cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid electrolyte fuel cell, and more particularly to a high output fuel cell having a large contact area between oxygen or fuel gas and a solid electrolyte plate.

[Conventional technology]

The high-temperature solid electrolyte fuel cell has no erosion of surrounding materials due to the electrolyte, no decomposition, evaporation, and dissipation of the electrolyte itself, and can use a liquid material to simplify the cell structure.
It can be used as fuel without reforming natural gas or coal gas because it operates at ~ 1000 ° C.It is expected to be a fuel cell with low internal resistance, high output and high energy utilization. ing. Conventionally, as such a solid electrolyte fuel cell, a zirconia electrolyte is made into a flat plate type so that a power density per volume is improved.

FIG. 4 is a view showing an example of such a conventional highly integrated flat type fuel cell. In the figure, reference numerals 21 and 22 denote external terminals, 23 and 24 denote external terminal gas passages, and 25 and 26 denote a three-layer structure. A plate, 27 is an interconnector, and 28 and 29 are gas passages.

In the figure, three-layer structures 25 and 26 are thin solid electrolyte plates made of, for example, zirconia (ZrO ₂ ), and porous electrodes (anodes) forming an air electrode (cathode) and a fuel electrode (anode) on both surfaces thereof. The porous electrode material to be formed is applied, and the external terminals 21 and 22 and the interconnector 27 are laminated so as to sandwich them.
A unit cell is composed of the layer structure plate 25 and the interconnector 27,
Similarly, an interconnector 27, a three-layer structure plate 26, an external terminal 24
Constitute a unit cell, and these are arranged in two stages in series.
Of course, an N-stage series configuration can be obtained by increasing the number of stacked unit cells.

In such a configuration, when oxygen or air is supplied to the gas passages 23 and 29, for example, hydrogen is supplied to the gas passages 24 and 28, and the external terminals 21 and 22 are connected through an external circuit (not shown).
Oxygen is ionized to react with fuel and flows through the solid electrolyte plates 25 and 26.At this time, oxygen takes in electrons at the air electrode to become oxygen ions, and at the fuel electrode side, the ions react with fuel to emit electrons. In the external circuit, the air electrode is (+) and the fuel electrode is (-).
A current flows from 21 to the external terminal 22. This is represented by the following chemical formula.

^{_{Cathode: 1 / 2O 2 + 2e -}} → O 2- ^{_{anode: H 2 + O 2- → H}} 2 O + 2e - overall electrode reaction becomes _{1 / 2O 2 + H 2 →} H 2 O. In the case of using carbon monoxide as the fuel, the fuel _{^{electrode: CO + O 2- → CO 2}} + 2e - , and the overall electrode reaction becomes _{CO + 1 / 2O 2 → CO} 2.

Further, a plurality of channels having a rectangular cross section formed of a honeycomb structure are formed by partitioning the walls with the electrode material and the wall made of the solid electrolyte, and the fuel gas and the oxygen gas are caused to flow by flowing the fuel gas and the oxygen gas into the adjacent channels of the honeycomb structure. A device that increases the contact area with the solid electrolyte to obtain high output has also been proposed as a solid electrolyte fuel cell having a structure of MODE1 by the Argonne Research Institute of the United States (Japanese Patent Laid-Open No. 61-269868).

The operation results of the flat plate fuel cell have been reported by the present applicant, the Argonne Research Institute of the United States (MODE0), Z-Tech, W, R, Grac, and the like. Not reported.

[Problems to be solved by the invention]

By the way, in order to increase the power density per volume of the fuel cell, it is essential to increase the contact area between the solid electrolyte and the fuel gas, but in the conventional solid electrolyte fuel cell, the fuel gas and the solid electrolyte Contact surface with 2
Due to the dimensional nature, there is a limit to the increase in the contact area, which is not always sufficient to increase the power density per volume.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a solid electrolyte fuel cell capable of further increasing a contact area between a fuel gas and a solid electrolyte and further increasing a power density per volume. And

[Means for solving the problem]

The solid electrolyte fuel cell of the present invention is obtained by processing a plate of partially stabilized zirconia (PSZ) mainly composed of tetragonal crystals into an uneven shape,
It is characterized in that the contact area with the fuel gas is increased three-dimensionally by using a solid electrolyte in which both the front and back surfaces of the SZ plate have a projection structure.

That is, a gas containing oxygen is supplied to one surface of the solid electrolyte coated with the electrode constituent material, and a fuel gas is supplied to the other surface, and the oxygen and the fuel are chemically reacted through the solid electrolyte plate to generate an electric output. In a fuel cell in which cells to be generated are stacked, irregularities are provided on a solid electrolyte plate, and a current collector is provided on both sides of the solid electrolyte plate so as to be in contact with each top of the irregularities to form a cell. I do.

FIG. 1, FIG. 2, and FIG. 3 are views for explaining the solid oxide fuel cell of the present invention. In the figure, 1 and 2 are solid electrolytes having a protruding structure, 3 and 4 are end wall portions, and 11 and 12 are current collectors.

First, in order to minimize the resistance of the PSZ to be used, for example, the thickness t (FIG. 3) is set to 0.1 to 0.3 mm, especially 0.1 mm.
2 mm, adding Y ₂ O ₃ of 3～4Mol% as a dopant.
As shown in FIG. 1, the solid electrolyte has a projection structure in which the front and rear surfaces of a PSZ plate are made uneven, like an egg container for storing eggs in a predetermined number unit. As described above, the solid electrolytes 1 and 2 having the projections and depressions on both the front and back surfaces may be formed into a structure by firing a single molded green compact formed by casting, injection molding, or cold pressing. In addition, there is a method of stacking green compacts before firing. However, if an attempt is made to increase the number of stacking layers, the raw material has a very fragile PSZ with low strength, and the lower layer is broken, so firing is preferable. The anode material on one side of the projection structure, for example, Ni / ZrO ₂ cermet was applied fabricated in a thickness of 0.1 to 1 mm, the other cathode material on the surface, for example, La _1-x Sr _x MnO ₃ and 0.1 to 1 mm thickness To make a coating. In the production of the anode and the cathode, there is no problem even if the structure of the projection is raw or after firing.

In addition, end walls 3 and 4 are provided on four sides of the solid electrolyte having the projection structure. In order to form gas flow paths orthogonal to each other on both sides of the solid electrolyte, the end wall portions extend in opposite directions to the end side portions 3 and the end wall portions 4 and have a structure overlapping at four corners.

The unit cell thus completed is sandwiched between current collectors 11 and 12 from above and below as shown in FIG. 2, and a glass seal is formed between the current collectors 11 and 12 and the end walls 3 and 4 (13 and 14 in the figure). To prevent gas leakage. The current collectors 11, 12 and the unit cell are in electrical contact with each other at the top of the protrusion as shown in FIG. By repeating and laminating this structure, a series connection structure can be formed. As the current collector, a heat-resistant alloy or ceramic coated with a conductive material is used.
Particularly, a nickel-based or chromium-based alloy containing chromium is preferable.

The material of the end wall may be either the current collector or PSZ, or may be integrally formed with either the current collector or PSZ. And since the protruding structure and the current collecting material are accumulated one after another, its own weight mainly concentrates on the four corners of the end wall material. preferable.

As shown in FIG. 3, the running distance of the currents J ₁ and J _{2 on} both sides of the solid electrolyte plate is the maximum distance between the contact portions with the electric materials 11 and 12 (the distance between P _{1 and} P _{2 in the} figure). . Therefore, in order to minimize the power loss due to the resistance of the electrodes, the height h of the projection structure is designed so that the distance traveled by the current is reduced, and the number of projections is designed so that the contact area with the gas is maximized. .

[Action]

In the solid electrolyte fuel cell of the present invention, the solid electrolyte plate is processed into an uneven shape and the front and rear surfaces are formed into a projection structure, so that the contact surface between the oxygen or fuel gas and the solid electrolyte can be increased three-dimensionally. Therefore, the power density per volume can be greatly improved.

〔Example〕

FIG. 1 shows an embodiment in which the running wall portion is integrally formed of the same material as the projecting structure material PSZ.

In this embodiment, the height h of the projection structure is 2 mm,
The thickness t of the projection was 0.2 mm, and the four corners of the end wall were 2 mm. Further, sides a and b of the projection structure were set to 50 mm.

As the current collector, a plate of La _0.8 Ca _0.2 CrO ₃ having a thickness of 1 mm was used, and the protrusion structure was sandwiched from above and below as shown in FIG.

 The projection structure shown in FIG. 1 was manufactured as follows.

Using 3 mol% Y ₂ O ₃ doped zirconia powder as a material, using a slurry usually prepared for a doctor blade,
A slip having a thickness of 0.2 mm was formed by a doctor blade method, and the slip was pressed against a protruding mold to be molded. This was produced by firing under normal firing conditions.

In FIG. 2, electrodes are applied to both surfaces of the projection structure. The space between the current collector and the projection structure was sealed with glass that liquefies at 1000 ° C. The cell of this structure was heated to 1000 ° C., where and H ₂ on the anode side flow of O ₂ on the cathode side was measured output is taken out the lead terminals by the current collector,
An output of 10 W was obtained. Converting this to volume density, 1KW /
And extremely high density.

〔The invention's effect〕

As described above, according to the present invention, the structure of the solid electrolyte fuel cell is a three-dimensional structure that is favorably selected, and has a significantly higher volume power density than a conventional two-dimensional fuel cell such as a mainstream cylinder or flat plate. It can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a projection structure of a solid electrolyte of the present invention.
FIG. 3 is a perspective view of a unit cell of the solid oxide fuel cell according to the present invention, FIG. 3 is a view for explaining a current path of an electrolyte wall, and FIG. 4 is a view showing a configuration of a conventional flat fuel cell. 1, 2,..., Solid electrolyte having a protruding structure, 3, 4,.
1, 12 …… Current collector.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuaki Tagaya 1-3-1 Nishitsurugaoka, Oimachi, Iruma-gun, Saitama Prefecture Toa Fuel Industry Co., Ltd. (72) Fumiya Ishizaki Oimachi, Iruma-gun, Saitama 1-3-1 Nishitsurugaoka Research Institute, Toa Fuel Industry Co., Ltd. (72) Inventor Hiroshi Seto 1-3-1 Nishitsurugaoka, Oimachi, Iruma-gun, Saitama Prefecture Toa Fuel Industry Co., Ltd. (72) Inventor Satoshi Sakurada 1-3-1 Nishi-Tsurugaoka, Oi-machi, Iruma-gun, Saitama Prefecture (56) References Hikaru 2-92666 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , (DB name) H01M 8/00-8/24

Claims (1)

(57) [Claims] An oxygen-containing gas is supplied to one surface of a solid electrolyte coated with an electrode constituent material, and a fuel gas is supplied to the other surface. In a fuel cell in which cells that generate output are stacked, a solid electrolyte is processed into a projection structure so that projections that are alternately and vertically oriented in a conical shape are two-dimensionally distributed, and the projection structure is formed. A solid electrolyte fuel cell, wherein a current collector is provided so as to be in contact with each top of both sides of the body to form a cell.