U.S. patent application number 10/158085 was filed with the patent office on 2002-10-10 for electrochemical cell having gas flow channels surrounded by solid electrolyte and interconnector.
This patent application is currently assigned to NGK Insulators, Ltd.. Invention is credited to Kawasaki, Shinji, Okumura, Kiyoshi.
Application Number | 20020146611 10/158085 |
Document ID | / |
Family ID | 26436757 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020146611 |
Kind Code |
A1 |
Kawasaki, Shinji ; et
al. |
October 10, 2002 |
ELECTROCHEMICAL CELL HAVING GAS FLOW CHANNELS SURROUNDED BY SOLID
ELECTROLYTE AND INTERCONNECTOR
Abstract
An electrochemical cell including at least one dense solid
electrolyte body, at least two dense interconnectors for collecting
current flowing the cell, cathodes and anodes, wherein the at least
one dense solid electrolyte body and at least two dense
interconnectors constitute a structural body, a plurality of first
gas flow channels and a plurality of second gas flow channels both
extend in a given direction, and are each defined and surrounded by
a part of the at least one solid electrolyte body and a part of the
at least two interconnectors, the anodes are formed on respective
walls defined by a part of at least one solid electrolyte body and
a part of at least two interconnectors and constituting the
respective first gas flow channels, the cathodes are formed on
respective walls defined by a part of at least one solid
electrolyte body and a part of at least two interconnectors and
constituting the respective second gas flow channels, every anode
is opposed to an adjacent cathode or adjacent cathodes via a solid
electrolyte body, and every cathode is opposed to an adjacent anode
or adjacent anodes via a solid electrolyte body.
Inventors: |
Kawasaki, Shinji; (Nagoya
City, JP) ; Okumura, Kiyoshi; (Kasugai City,
JP) |
Correspondence
Address: |
PARKHURST & WENDEL, L.L.P.
1421 PRINCE STREET
SUITE 210
ALEXANDRIA
VA
22314-2805
US
|
Assignee: |
NGK Insulators, Ltd.
Nagoya City
JP
|
Family ID: |
26436757 |
Appl. No.: |
10/158085 |
Filed: |
May 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10158085 |
May 31, 2002 |
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09456884 |
Dec 8, 1999 |
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09456884 |
Dec 8, 1999 |
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08861010 |
May 21, 1997 |
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6025084 |
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Current U.S.
Class: |
429/482 ;
264/618; 427/115; 429/490; 429/497; 429/513; 429/517; 429/535;
502/101 |
Current CPC
Class: |
C25B 9/70 20210101; Y02P
70/50 20151101; C04B 2111/00129 20130101; C25B 1/04 20130101; H01M
8/1246 20130101; Y02E 60/36 20130101; Y02E 60/50 20130101; C04B
38/0009 20130101; B01D 53/326 20130101; H01M 8/2435 20130101; C04B
2111/00853 20130101; C04B 38/0009 20130101; C04B 35/48
20130101 |
Class at
Publication: |
429/31 ; 429/38;
264/618; 429/32; 427/115; 502/101 |
International
Class: |
H01M 008/12; H01M
008/10; H01M 008/02; H01M 004/88 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 1996 |
JP |
8-128246 |
Apr 14, 1997 |
JP |
9-95539 |
Claims
What is claimed is:
1. An electrochemical cell comprising at least one dense solid
electrolyte body, at least two dense interconnectors for collecting
current flowing the cell, cathodes and anodes, wherein said at
least one dense solid electrolyte body and at least two dense
interconnectors constitute a structural body, a plurality of first
gas flow channels and a plurality of second gas flow channels both
extend through the structure body in a given direction, and are
each defined and surrounded by a part of said at least one solid
electrolyte body and a part of said at least two interconnectors,
the anodes are formed on respective walls defined by said part of
at least one solid electrolyte body and said part of at least two
interconnectors and constituting the respective first gas flow
channels, the cathodes are formed on respective walls defined by
said part of at least one solid electrolyte body and said part of
at least two interconnectors and constituting the respective second
gas flow channels, every anode is opposed to an adjacent cathode or
adjacent cathodes via a solid electrolyte body and every cathode is
opposed to an adjacent anode or adjacent anodes via a solid
electrolyte body.
2. The electrochemical cell set forth in claim 1, wherein as viewed
in a direction orthogonal to the flow channels, every first gas
flow channel excluding those in extremely opposite sides of the
structural body is adjacent to four second gas flow channels,
whereas every second gas flow channels excluding those in said
extremely opposite sides is adjacent to four first gas flow
channels.
3. The electrochemical cell set forth in claim 1 or 2, wherein the
cross sectional view of each of the first and second gas flow
channels is one selected from the group consisting of an isosceles
triangular shape, an equilateral triangular shape, a rectangular
shape, a square shape and an equilateral hexagonal shape.
4. A process for producing the electrochemical cell set forth in
claim 1 or 2, comprising the steps of forming a green molded body
of said structural body by simultaneously extrusion molding a body
for said at least one electrolyte body and a body for said at least
two interconnectors, obtaining the structural body by firing said
green molded body, and forming said anodes and cathodes on said
respective walls defined by said part of at least two
interconnectors and constituting the respective first and second
gas flow channels, respectively.
5. A process for producing the electrochemical cell set forth in
claim 3, comprising the steps of forming a green molded body of
said structural body by simultaneously extrusion molding a body for
said at least one electrolyte body and a body for said at least two
interconnectors, obtaining the structural body by firing said green
molded body, and forming said anodes and cathodes on said
respective walls defined by said part of at least one solid
electrolyte body and said part of at least two interconnectors and
constituting the respective first and second gas flow channels,
respectively.
6. A process for producing the electrochemical cell set forth in
claim 1 or 2, comprising the steps of forming a green molded body
of said structural body by simultaneously extrusion molding a body
for said at least on electrolyte body and a body of said at least
two interconnectors, applying respective materials for said anodes
and cathodes on said respective walls defined by said part of at
least one solid electrolyte body and said part of at least two
interconnectors and constituting the respective first and second
gas flow channels, respectively, and firing the green molded body
together with the materials applied.
7. A process for producing the electrochemical cell set forth in
claim 3, comprising the steps of forming a green molded body of
said structural body by simultaneously extrusion molding a body for
said at least one electrolyte body and a body of said at least two
interconnectors, applying respective materials for said anodes and
cathodes on said respective walls defined by said part of at least
one solid electrolyte body and said part of at least two
interconnectors and constituting the respective first and second
gas flow channels, respectively, and firing the green molded body
together with the materials applied.
8. An electrochemical device provided with the electrochemical cell
or cells set forth in claim 1 or 2.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to electrochemical cells such
as solid oxide fuel cells (SOFCs), steam electrolysis cells, oxygen
pumps, and NOx decomposition cells. The invention also relates to a
producing process for the production of such electrochemical cells,
and electrochemical devices using such electrochemical cells.
[0003] (2) Related Art Statement
[0004] The solid oxide fuel cells (SOFCs) are broadly classified
into the so-called flat planar type and the so-called tubular type.
Although it is said that the tubular type SOFC is most likely to be
practically used, the flat planar type SOFC is more advantageous
from the standpoint of the output density per unit volume. However,
in the flat planar type SOFC, an electric power-generating stack is
constructed by alternatively laminating so-called separators and
electric power-generating layers, but the SOFC thus produced has a
difficult problem in sealing.
[0005] On the other hand, so-called integrated (monolithic) type
SOFCs different from the above type SOFCs are proposed. The
above-mentioned tubular SOFC and the flat planar type SOFC are of a
design in which separate unit cells are laminated successively one
upon another. To the contrary, the monolithic type SOFC was
proposed by Argonne National Laboratory in the United States, is
obtained by preliminarily preparing green sheets of respective
components of the SOFC, forming a laminate through laminating the
above green sheets of the components in a given shape, and
sintering the entire laminate. The monolithic type SOFCs include a
parallel flow type (co-flow type) and an orthogonal flow type
(cross flow type). It is expected that the monolithic type SOFC can
realize an extremely high output density of as high as around 8
kW/kg ("Fuel Cell Generation" published by CORONA PUBLISHING CO.,
LTD. in May 20, 1994).
[0006] Among them, the parallel flow type SOFC is constructed such
that corrugated three layers of a fuel electrode, a solid
electrolyte and an air electrode are integrated, and the thus
integrated corrugated laminate is sandwiched by flat planar
interconnectors. The orthogonal flow type SOFC is constructed such
that the flat planar electrodes and electrolyte plate are laminated
and sandwiched between corrugated interconnector. However, these
fine constructions are so complicated that it is difficult to form
a molded body by laminating respective green sheets of the air
electrode, the fuel electrode, the solid electrolyte and the
interconnector. In addition, since the air electrode, the fuel
electrode, the solid electrolyte and the interconnector have
utterly different porosities, characteristics, and optimum
sintering temperatures, it is extremely difficult to finish SOFC
components having their respective favorable characteristics by
simultaneous sintering. Consequently, although the monolithic type
SOFC has been proposed well before, it has been considered
difficult to practically use such a monolithic type SOFC, and it is
a present situation that such monolithic SOFC cells are still in a
trial stage.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide
electrochemical cells having a large electrode area per unit volume
and a high efficiency. Further, it is another object of the present
invention to provide a new electrochemical cell structure which is
structurally relatively simple, needs not special structurally
sealing mechanism, and can be produced by simultaneous sintering.
It is a further object to provide a process for producing such an
electrochemical cell, and also to provide an electrochemical device
using such an electrochemical cell or such electrochemical
cells.
[0008] An electrochemical cell according to the present invention
includes at least one dense solid electrolyte body, at least two
dense interconnectors for collecting current flowing in the cell,
cathodes and anodes, wherein said at least one dense solid
electrolyte body and at least two dense interconnectors constitute
a structural body, a plurality of first gas flow channels and a
plurality of second gas flow channels both extend through the
structural body in a given direction, and are each defined and
surrounded by a part of said at least one solid electrolyte body
and a part of said at least two interconnectors, the anodes are
formed on respective walls defined by said part of at least one
solid electrolyte body and said part of at least two
interconnectors and constituting the respective first gas flow
channels, the cathodes are formed on respective walls defined by
said part of at least one solid electrolyte body and said part of
at least two interconnectors and constituting the respective second
gas flow channels, every anode is opposed to an adjacent cathode or
adjacent cathodes via a solid electrolyte body, and every cathode
is opposed to an adjacent anode or adjacent anodes via a solid
electrolyte body.
[0009] According to the electrochemical cell of the present
invention, it is preferable that as viewed in a direction
orthogonal to the flow channels, every first gas flow channels
excluding those in extremely opposite sides of the honeycomb
structural body is adjacent to four second gas flow channels,
whereas every second gas flow channels excluding those in extremely
opposite sides is adjacent to four first gas flow channels.
[0010] The process for producing the electrochemical cell according
to the present invention is characterized by including the steps of
forming a green molded body of said structural body by
simultaneously extrusion molding a body for said at least one
electrolyte body and a body for said at least two interconnectors,
obtaining the structural body by firing said green molded body, and
forming said anodes and cathodes on said respective walls defined
by said part of at least one solid electrolyte body and said part
of at least two interconnectors and constituting the respective
first and second gas flow channels, respectively.
[0011] Another aspect of the process for producing the
electrochemical cell according to the present invention is
characterized by including the steps of forming a green molded body
of said structural body by simultaneously extrusion molding a body
for said at least one electrolyte body and a body for said at least
two interconnectors, applying respective materials for said anodes
and cathodes on said respective walls defined by said part of at
least one solid electrolyte body and said part of at least two
interconnectors and constituting the respective first and second
gas flow channels, respectively, and firing the green molded body
together with the materials applied.
[0012] The present invention is also related to an electrochemical
device provided with the electrochemical cell or cells set forth
above.
[0013] Having repeatedly made investigations to produce solid oxide
fuel cells having a monolithic structure and a high electric
power-generating efficiency, the present inventors have reached the
technical idea that in order to produce such a solid oxide fuel
cell, a honeycomb structural body is formed by integrating at least
one dense solid electrolyte body and at least two dense
interconnectors, and electrodes are formed on walls of channels
extending through the honeycomb structural body.
[0014] According to the thus constructed electrochemical cell, the
power-generating efficiency per unit volume is extremely high, and
gas-tightness of the channels of the honeycomb structure are
independently assured by the dense solid electrolyte body and the
interconnectors, so that a power-generating device having a
seal-less structure can be readily produced. In addition, the
honeycomb-molded body to constitute at least one solid electrolyte
body and at least two interconnectors can be produced by
simultaneous extrusion molding. Further, since the solid
electrolyte body and the interconnector are both required to be
dense or gas-tight, it is easy to integrally sinter them without
necessitating fine control of their porosities to fall in their
respective specific ranges as in the case of the air electrode or
fuel electrode.
[0015] Furthermore, since the interconnector and the solid
electrolyte body are both made of their respective dense materials
with high relative densities, the honeycomb structure body
constituted by these dense materials has a high structural
strength.
[0016] The air electrode and the fuel electrode may be formed by
feeding respective materials for the air electrode and the fuel
electrode into the channels of the honeycomb structural body formed
above, attaching the materials upon the respective walls of the
channels, and sintering the attached materials.
[0017] The present inventors applied the above structure to
electrochemical cells other than the SOFC, for example, the steam
electrolysis cell, and they confirmed that the efficiency per unit
volume, e.g., electrolysis efficiency can be also largely enhanced,
and the above mentioned function and effects can be obtained.
[0018] These and other objects, features and advantages of the
present invention will be apparent from the following description
of the invention when taken in conjunction with the attached
drawings, with the understanding that any modifications, variations
and changes may be easily made by the skilled person in the art to
which the invention pertains.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
[0019] For a better understanding of the invention, reference is
made to the attached drawings, wherein:
[0020] FIG. 1 is a cross-sectional view illustrating a part of an
electrochemical cell 10A according to a first embodiment of the
present invention;
[0021] FIG. 2 is a cross-sectional view illustrating a part of an
electrochemical cell 10B according to a second embodiment of the
present invention;
[0022] FIG. 3 is a cross-sectional view illustrating a part of an
electrochemical cell 10C according to a third embodiment of the
present invention;
[0023] FIG. 4 is a cross-sectional view illustrating a part of an
electrochemical cell 10D according to a fourth embodiment of the
present invention;
[0024] FIG. 5 is a perspective view for illustrating the outer
configuration of one embodiment of the electrochemical cell
according to the present invention;
[0025] FIG. 6 is a sectional view for diagrammatically illustrating
a favorable embodiment of an electrochemical device to which an
electrochemical cell according to the present invention is
applied;
[0026] FIG. 7 is a sectional view for diagrammatically illustrating
another favorable embodiment of an electrochemical device to which
an electrochemical cell according to the present invention is
applied;
[0027] FIG. 8 is a diagrammatic view for illustrating the extrusion
molding process for producing a structural body for an
electrochemical cell according to the present invention;
[0028] FIGS. 9(a) through 9(h) diagrammatically illustrate the
embodiment in FIG. 8;
[0029] FIGS. 10(a) through 10(d) diagrammatically illustrate an
embodiment similar to FIG. 9(a) through FIG. 9(h); and
[0030] FIGS. 11 diagrammatically illustrates a sectional view of
the embodiment of FIGS. 10(a) through FIG. 10(d).
DETAILED DESCRIPTION OF THE INVENTION
[0031] The present invention will be explained in more detail with
reference to more specific embodiments to which the present
invention should not be limited.
[0032] The entire configuration of the honeycomb structural body is
not particularly limited to any configuration. Further, the
configuration of each channel in the honeycomb structural body is
not limited to a particular one. However, from the standpoint of
effectively utilizing the space, the cross-sectional shape of each
channel is preferably of such a shape as an isosceles triangular
shape, an equilateral triangular shape, a rectangular shape, a
square shape or an equilateral hexagonal shape that the sections of
the channels may fill a plane at an end side thereof. In addition,
the channels may be designed such that the channels having
different cross-sectional shapes such as an equilateral triangular
shape and an equilateral hexagonal shape may be adjacent to each
other.
[0033] The material of the interconnector is preferably a
perovskite-type complex oxide containing lanthanum, more preferably
lanthanum chromite, because lanthanum chromite has heat resistance,
oxidation resistance and reduction resistance.
[0034] The material of the solid electrolyte body is preferably
yttria-stabilized zirconia or yttria partially stabilized zirconia,
but other materials may be also used. In the case of an NOx
decomposition cell, cerium oxide is preferable, too.
[0035] A raw material for the anode and cathode is preferably a
pervskite-type complex oxide containing lanthanum, more preferably
lanthanum manganite or lanthanum cobaltite, most preferably
lanthanum manganite. Lanthanum chromite and lanthanum manganite may
be doped with strontium, calcium, chromium (for lanthanum
manganite), cobalt, iron, nickel or aluminum. Further, the raw
material may be palladium, platinum, ruthenium, a mixed powder of
platinum and zirconia, a mixed powder of palladium and zirconia, a
mixed powder of ruthenium and zirconia, a mixed powder of platinum
and cerium oxide, a mixed powder of palladium and cerium oxide, or
a mixed powder of ruthenium and cerium oxide.
[0036] The electrochemical cell according to the present invention
may be used as an oxygen pump to supply oxygen.
[0037] Further, the electrochemical cell according to the present
invention may be used as a high temperature steam electrolysis
cell. This cell may be also used as a device for producing
hydrogen, or may be used as a device for removing steam. In this
case, the following reactions occur at respective electrodes.
Cathode: H.sub.2O+2e.sup.-.fwdarw.H.sub.2+O.sup.2-
Anode: O.sup.2-.fwdarw.2e.sup.-+1/2O.sub.2
[0038] Furthermore, the electrochemical cell according to the
present invention may be used as an NOx decomposing cell. This
decomposing cell can be used as a purifier for exhaust gases from
an automobile or an electric power-generating apparatus. Although
the exhaust gases from the gasoline engines are now disposed of
with three-way catalysts, such three-way catalysts will be less
effective if the number of low mileage type engines such as lean
burn engines and diesel engines, That is, since the content of
oxygen in exhaust gases from those engines is large, such a
three-ay catalyst cannot well work with respect to low mirage type
engines.
[0039] If the electrochemical cell according to the present
invention is used as an NOx decomposing cell, it can remove oxygen
in exhaust gases through the solid electrolyte filmy body, and
simultaneously decompose NOx into N.sub.2 and O.sup.2- and remove
the oxygen produced by this decomposition. Besides the above
process, water vapor in the exhaust gases is electrolyzed into
hydrogen and oxygen, and this hydrogen reduces NOx into
N.sub.2.
[0040] If the electrochemical cell is used as the NOx decomposing
cell, the solid electrolyte filmy body is particularly preferably
made of a cerium oxide based ceramic material, whereas the cathode
material is preferably palladium or palladium-cerium oxide
cermet.
[0041] FIGS. 1 to 4 are cross sectional views all illustrating
parts of electrochemical cells as preferred embodiments according
to the present invention as cut in a direction crossing channels.
In the electrochemical cell 10A of FIG. 1, first gas (e.g.
oxidative gas) flow channels 6A and second gas (e.g., fuel gas)
flow channels 7A all having an almost square cross section are
formed in a structural body 1A. A cathode 4A is formed on a
surrounding wall surface of each first gas flow channel 6A, whereas
an anode 5A is formed on that of each second gas flow channel 7A.
In FIG. 1, both the flow channels 6A and the flow channels 7A are
arranged vertically, while the gas flow channels 6A are opposed to
the respectively adjacent gas flow channels 7A in a lateral
direction via a solid electrolyte body 3A.
[0042] The structural body 1A also includes an interconnectors 2A
and the above solid electrolyte body 3A, and each of the flow
channels 6A and 7A is surrounded in a by a part of the
interconnector 2A and in the remaining half by a part of the solid
electrolyte body 3A. Consequently, each of the flow channels 6A and
7A is kept gas-tight in a cross-sectional direction thereof. In the
electrochemical cell 10A of FIG. 1, two pairs of the first gas flow
channel 6A rows and the second gas flow channels 7A rows are
arranged in the honeycomb structural body 1A, while the first gas
flow channels 6A rows and the second gas flow channel 7A rows are
alternatively arranged in the lateral direction, and the
interconnectors 2A are arranged at opposite sides of the structural
body 1A and between the two pair of the first gas flow channel 6A
rows and the second gas flow channels 7A rows.
[0043] In the electrochemical cell 10B of FIG. 2, first gas flow
channels 6B and second gas flow channels 7B all having an almost
square cross-sectional shape are formed in a structural body 1B. A
cathode 4B is formed on a surrounding wall surface of each of the
first gas flow channel 6B, and an anode 5B is formed on that of
each of the second gas flow channels 7B.
[0044] The first gas flow channels 6B and the second gas flow
channels 7B are arranged alternatively as viewed vertically in FIG.
2. As to the adjacent two rows, the first and second gas flow
channels 6B and 7B are staggered in every other row vertically by a
half of a side of each flow channel as viewed in the lateral
direction of FIG. 2. That is, one first gas flow channel 6B and one
second gas flow channel 7B in one row are half-by-half opposed to
one flow channel 6B in an adjacent row. Accordingly, each first
flow channel 6B is adjacent to four second flow channels 7B,
excluding those located at opposite sides of the structural body,
whereas each second flow channel 7B is adjacent to four first flow
channels, excluding those located at opposite sides of the
structural body. When the configuration in FIG. 2 is adopted, the
area of the electrodes can be increased, and efficiency of the
electrochemical cell, for example, power-generating efficiency,
electrolyzing efficiency, or oxygen-feeding efficiency can be
enhanced. Further, in order to obtain a given efficiency as
referred to above, the entire electrochemical device can be made
compact.
[0045] The structural body 1B also includes dense interconnectors
2B and dense solid electrolyte bodies 3B, and each of the flow
channels 6B and 7B is surrounded in a portion by a part of the
interconnector 2B and in the remaining portion by a part of the
solid electrolyte body 3B. Consequently, each of the flow channels
6B and 7B is kept gas-tight in a cross-sectional direction thereof.
In the electrochemical cell 10B of FIG. 2, the first gas flow
channel 6B zigzag lines and the second gas flow channels 7B zigzag
lines are alternatively arranged in the vertical direction, and the
interconnectors 2A are arranged at opposite sides of the structural
body 1A and between the two pair of the first gas flow channel 6A
lines and the second gas flow channels 7A lines.
[0046] In the electrochemical cell of FIG. 3, a structural body 10C
includes dense interconnectors 2C and dense solid electrolyte
bodies 3C vertically alternatively piled one upon another, and a
number of channels each having a triangular cross section are
formed among the interconnectors 2C and the solid electrolyte
bodies 3C in the structural body 10C. A pair of a line of first gas
flow channels 6C and a line of second gas flow channels 7C are
opposed to each other via each of the solid electrolyte bodies 3C,
and each of the first and second gas flow channels 6C and 7C is
surrounded by a part of the interconnector 2C and a part of the
solid electrolyte body 3C as shown in FIG. 3. As viewed vertically,
the lines of the first gas flow channels 6C and the lines of the
second gas flow channels are alternatively arranged. A cathode 4C
is formed on a surrounding wall surface of each first gas flow
channels 6C, and an adnode 5C formed on that of each of the second
gas flow channels 7C. Electric power is to be generated between a
pair of the adjacent first and second gas flow channels 6C and 7C
opposed to each other via the solid electrolyte body 3C. Between
the adjacent first gas flow channels 6C in each line and between
the adjacent second flow channels 7C in each line are formed
channels 8 each having an almost triangular cross section. Each of
the first and second gas flow channels 6C and 7C is kept by the
gas-tight interconnector 2C and the gas-tight solid electrolyte
body 3C as viewed in a crossing direction thereof.
[0047] In the electrochemical cell 10D of FIG. 4, a structural body
ID includes gas-tight interconnectors 2D and gas-tight solid
electrolyte bodies 3D laterally alternatively piled one upon
another and forming zigzag lines of first gas flow channels 6D and
zigzag lines of second gas flow channels 7D in which the former
zigzag lines are opposed to corresponding latter zigzag lines via
the respective solid electrolyte bodies 3D as shown. The first and
second gas flow channels 6D and 7D each have an almost equilateral
hexagonal cross sectional shape, and are arranged in a honeycomb
fashion. A cathode 4D is formed on a surrounding wall surface of
each first gas flow channel 6D, and an anode 5D formed on that of
each second gas flow channel 7D. Each of the first and second gas
flow channels 6D and 7D is surrounded and kept gas-tight as viewed
in a crossing direction thereof by a part of the gas-tight
interconnector 2D and a part of the gas-tight solid electrolyte
body 3D.
[0048] In the present invention, the channels in the honeycomb
structural body can be easily shaped if the dimension of them in
the cross section is not less than 1 mm. Further, the dimension of
the channel in the cross section is preferably not more than 5 mm,
because in this case, the electric resistance of the
electrochemical cell unit decreases and the area of the electrodes
per unit volume increases. From this point of view, the dimension
of each channel is more preferably not more than 3 mm.
[0049] The entire shape-of the honeycomb structural body is not
limited to any particular one. However, as viewed diagrammatically
three-dimensionally in FIG. 5, a big capacity can be easily
realized if the lateral and vertical dimensions "a" and "b" are not
less than 5 cm, whereas excessive increase in the pressure required
for the extrusion molding can be prevented if the dimensions "a"
and "b" are not more than 30 cm. If the longitudinal dimension "c"
is less than 10 cm, the ratio of end portions not contributing to
power generation, electrolysis or oxygen feeding increases to
deteriorate the efficiency of the electrochemical cell. Therefore,
the longitudinal dimension "c" is preferably not less than 10 cm.
If the longitudinal dimension "c" is not more than 100 cm, handling
is easy at the time of extrusion molding.
[0050] The entire shape of an electrochemical device using the
electrochemical cell according to the present invention is not
limited to any particular one. In the electrochemical cell
according to the present invention, the flow channels are each
surrounded by a part of the gas-tight interconnectors and a part of
the gas-tight solid electrolyte body (bodies). Therefore, the
electrochemical device preferably has a seal-less structure
utilizing that of the electrochemical cell. Preferred embodiments
of such seal-less structures are diagrammatically shown in FIGS. 6
and 7, respectively, in which interconnectors and solid electrolyte
bodies are omitted. In the electrochemical device of FIG. 6, a
first gas and a second gas are flown in opposite directions,
respectively. In the electrochemical device of FIG. 6, the
electrochemical cell 10A (10B, 10C, 10D) is placed in a can 13 of
the electrochemical device such that a gas chamber 15 and a gas
chamber 16 are defined at opposite sides of the can 13 as shown. An
exhaust opening 17 for the first gas and an exhaust opening 18 for
the second gas are formed in the can 13.
[0051] The first gas flow channels 6A (6B, 6C, 6D) of the
electrochemical cell are extended in a right direction of FIG. 6,
and their extensions 11 are opened to a first gas feed mechanism
(not shown) outside the can 13. On the other hand, the second gas
flow channels 7A (7B, 7C, 7D) are extended in a left direction of
FIG. 6, and their extensions 12 are opened to a second gas feed
mechanism (not shown) outside the can 13.
[0052] The first gas is fed to the extensions 11 of the first gas
flow channels 6A as shown by arrows A, flown inside the flow
channels 6A and further in the gas chamber 16 as shown by arrows B,
and discharged through the exhaust opening 17. On the other hand,
the second gas is fed to the extensions 12 of the second gas flow
channels 7A as shown by arrows C, flown inside the flow channels 7A
and further in the gas chamber 15 as shown by arrow D, and
discharged through the exhaust opening 18.
[0053] In the electrochemical device of FIG. 7, the first gas and
the second gas are flown in the same direction. The electrochemical
cell 10A (10B, 10C, 10D) is placed in a can 13 such that a first
gas chamber 30 and a combustion chamber 31 are defined at left and
right sides of the electrochemical cell inside the can 13,
respectively. A first gas feed opening 19, a first gas exhaust
opening 20, and a combustion gas exhaust opening 21 are formed in
the can 13 as shown.
[0054] The second gas flow channels 7A (7B, 7C, 7D) of the
electrochemical cell are extended in a left direction of FIG. 7,
and their extensions 12 are opened to a second gas feed mechanism
outside the can 13. None of the first gas flow channels 16 are
extended outwardly from the electrochemical cell.
[0055] The first gas is fed to the gas feed chamber 30 inside the
can 13 through the gas feed opening 19 as shown in an arrow E.
Alternatively, the first gas may be fed to the gas chamber 30 from
a direction vertical to the drawing paper, for example, from a
front side of the drawing paper. A part of the first gas is
discharged outside through the exhaust opening 20, whereas the
remainder is flown through the flow channels 6A of the
electrochemical cell as shown by arrows G, and discharged to the
combustion chamber 31 through downstream openings of the flow
channels 6A. On the other hand, the second gas is fed to the
extensions 12 of the second gas flow channels 7A as shown by arrows
F, flown through the flow channels 7A and discharged into the
combustion chamber 31. The combustion gas is flown as shown by
arrows H, and discharged through the exhaust opening 21.
[0056] When the electrochemical device is used as an electric
power-generating device (SOFC), current collectors 14 are set at
upper and lower end portions, respectively, in FIGS. 6 and 7.
Electric power is taken outside through these current collectors
14. A porous conductor having a buffering function, for example, a
felt, is preferably set between each current collector and the
SOFC, because stress is mitigated and contact electric resistance
is reduced in this case. Nickel is preferred as a material for the
felt and the current collectors.
[0057] A preferred embodiment of the process for producing the
electrochemical cell according to the present invention will be
explained with reference to a diagrammatic view of FIG. 8. In this
embodiment, a body constituting a green molded body for the
formation of the interconnectors and a body constituting a green
molded body for the formation of the solid electrolyte bodies are
continuously fed into a single die device so that the green molded
bodies of the interconnectors and the solid electrolyte bodies may
be extruded through the die device in a integrally joined fashion.
Then, the extruded body is integrally sintered.
[0058] In a particularly preferred embodiment, the body
constituting the green molded body for the formation of the
interconnectors and the body constituting the green molded body of
the solid electrolyte bodies are continuously fed into a single die
device such that the body constituting the green molded body for
the formation of the interconnectors is pushed toward the die
device through a first extruding mechanism, whereas the body
constituting the green molded body for the formation of the solid
electrolyte bodies is pushed toward the die device through a second
extruding mechanism. By so doing, the first extruding mechanism and
the second extruding mechanism can be mechanically adjusted with
respect to the extruding speed and the extruding pressure so that
peeling or curving of the extruded body may be prevented.
[0059] The green molded body of each of the inter-connector a and
the solid electrolyte body is preferably made by molding a mixture
in which an organic binder and water are mixed into a main
ingredient. As the organic binder, polyvinyl alcohol, methyl
cellulose, ethyl cellulose or the like may be used. The addition
amount of the organic binder is preferably 0.5 to 5 parts by
weight, if the weight of the main ingredient is taken as 10 parts
by weight.
[0060] In the embodiment of FIG. 8, a green shaped body 25 for the
formation of the interconnectors and a green shaped body 26 for the
formation of the solid electrolyte bodies are used. Each of the
green molded bodies has, for example, a cylindrical shape. The die
device 27 includes molding barrels 24A and 24B, a first die portion
27a and a second die portion 27b communicating with the molding
barrels 24A and 24B, respectively, plungers 23A and 23B slidably
arranged inside the molding barrels 24A and 24B, respectively, and
not shown dies arranged in the die portions 27a and 27b,
respectively. The green molded body 25 for the formation of the
interconnectors is placed in the molding barrel 24A, and the green
molded body 26 for the formation of the solid electrolyte bodies
placed in the molding barrel 24B.
[0061] The body 25 is pushed into the die portion 27a by moving a
shaft of the plunger 23A toward the die portion 27a, whereas the
body 26 is pushed into the die portion 27b by moving a shaft of the
plunger 23B toward the die portion 27b. The bodies are molded in
the form of the interconnectors and the solid electrolyte bodies
having the cross-sectional configuration as shown in FIG. 1, 2, 3
or 4. A reference numeral 28 denotes a honeycomb structural
body-extruding die. The thus extruded body may be fired at a firing
temperature of 1400.degree. C. to 1700.degree. C. A reference
numeral 28 is a honeycomb structural body-extruding die.
[0062] FIGS. 9(a) to 9(f) diagrammatically illustrating the
embodiment shown in FIG. 8. The molding from FIG. 9(a) to FIG. 9(c)
is effected by the die device 27, whereas the molding from FIG.
9(c) to FIG. 9(e) is effected by the honeycomb structural
body-extruding die 28. FIGS. 9(a) to 9(e) are sectional views taken
along lines IXa, IXb, IXc, IXd and IXe, respectively. Each of the
green shaped bodies 25 and 26 (FIG. 9(a)) is extruded into plural
planar bodies 29, 30 (FIG. 9(b)). The planar bodies 29 are inserted
between the planar bodies 30 at an inlet of the honeycomb-shaped
body extruding die 28 as shown in FIG. 9(c). Then, each of the
planar bodies 29 and 30 arrayed as in FIG. 9(c) is divided into a
row of rod-shaped bodies 29A and 30A in a matrix as shown in FIG.
9(d), and these rows of the rod-shaped bodies 29A and 30A are
converted into a honeycomb structural body 31 shown in FIG. 9(e).
FIG. 9(f) is an enlarged view of FIG. 9(c), FIG. 9(g) is an
enlarged view of FIG. 10(d), and FIG. 9(h) an enlarged view of FIG.
9(e) through a die not shown.
[0063] FIGS. 10(a) to 10(f) diagrammatically illustrate another
embodiment similar to that shown in FIG. 8 and FIGS. 9(a) to 9(h).
FIGS. 10(a) to 10(d) are sectional views taken along lines IXa,
IXb, IXc and IXd of FIG. 11, respectively. The embodiment in FIGS.
10(a) to 10(d) differs from that in FIGS. 8 and 9(a) to 9(h) in
that the steps in FIGS. 9(b) and 9(c) are modified. That is, each
of the green shaped bodies 25 and 26 (FIG. 9(a)) is extruded into
plural rod-shaped bodies 31 are inserted between the rod-shaped
bodies 32 at an inlet of the honeycomb-shaped body extruding die 28
as shown in FIG. 10(c). The thus arrayed rod-shaped bodies 31 and
32 are molded into a honeycomb structural body shown in FIG. 10(d).
In the embodiment of FIGS. 10(a) to 10(f) and FIG. 11, the die
device 27 may be integrally formed with the honeycomb structural
body-extruding die 28.
[0064] Then, an anode material or a cathode material is applied to
a surrounding wall surface of each of the channels through the thus
sintered body. Although this applying method is not limited to any
particular one, according to a preferred embodiment, slurries of
the anode material and the cathode material are poured into the
respectively intended channels, and discharged therethrough,
followed by drying. Thereby, their powdery materials are attached
to the respectively intended channels. Then, the resulting
honeycomb structural body in entirely fired at 1100.degree. C. to
1500.degree. C. to form anodes and cathodes.
[0065] The present inventors actually produced steam electrolysis
cells as shown in FIGS. 1 to 4. Their honeycomb structural bodies
and the interconnectors were prepared as mentioned above. The steam
electrolysis cells were produced by applying a platinum paste to
this honeycomb structural body.
[0066] More specifically, a slurry having fluidity was obtained by
adding polyethylene glycol into a commercially available platinum
paste. This slurry was poured into every channel, thereby attaching
the slurry onto the wall surfaces thereof. In this case, since the
anode and the cathode may be made of the same material, it is
unnecessary to pour different materials for the anodes and the
cathodes into respective channels as in the case of SOFC.
[0067] Since any platinum slurry attached to a place other than the
surrounding wall surfaces of the channels may cause short circuit,
such a slurry must be swept off. The thus obtained honeycomb
structural bodies were fixed, for example, at 1000.degree. C. for 1
hour, thereby forming platinum anodes and cathodes.
[0068] With respect to the thus produced steam electrolysis cells,
argon and argon containing steam were flown on the anode side and
the cathode side, respectively in the state that the cells were
heated to 1000.degree. C., while current was flown between the
anodes and the cathodes. Thereby, hydrogen could be generated.
[0069] Anodes and cathodes may be formed through immersing the
structural body into a slurry of a metal. For example, the
structural bodies 1A, 1B, 1C and 1D as explained above were
prepared. A fluidic slurry was obtained by adding polyethylene
glycol into a commercially available platinum paste. Each of the
structural bodies was immersed into this slurry.
[0070] At that time, the platinum slurry was attached to not only
surrounding wall surfaces of the channels but also end faces of the
structural body. If the structural bodies with the slurry thus
attached are fixed, the anodes and the cathodes may be shorted. For
this reason, portions near the respective end faces of the
structural body were removed by cutting. By so doing, unnecessary
platinum slurry can be easily removed from the structural body
without sweeping away it. The thus obtained honeycomb bodies were
fired at 1000.degree. C., thereby forming the anodes and the
cathodes made of platinum.
[0071] With respect to the thus produced steam electrolysis cells,
argon and argon containing steam were flown on the anode side and
the cathode side, respectively, in the state that the cells were
heated to 1000.degree. C., while current was flown between the
anodes and the cathodes. Thereby, hydrogen could be generated.
[0072] As having been explained above, according to the present
invention, the electrochemical cells which each have a large area
of the electrodes per unit voltage and high power-generating
efficiency, high electrolysis efficiency, high oxygen generating
efficiency or the like can be provided. Further, the
electrochemical cells are structurally relatively simple, and need
no special sealing mechanism and can be produced by simultaneous
sintering due to their structure.
* * * * *