U.S. patent application number 14/255716 was filed with the patent office on 2014-08-14 for all ceramics solid oxide fuel cell.
This patent application is currently assigned to Technical University of Denmark. The applicant listed for this patent is Technical University of Denmark. Invention is credited to Peter Halvor Larsen.
Application Number | 20140223730 14/255716 |
Document ID | / |
Family ID | 39679443 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140223730 |
Kind Code |
A1 |
Larsen; Peter Halvor |
August 14, 2014 |
ALL CERAMICS SOLID OXIDE FUEL CELL
Abstract
The present invention provides an all ceramics solid oxide cell,
comprising an anode layer, a cathode layer, and an electrolyte
layer sandwiched between the anode layer and the cathode layer,
wherein the electrolyte layer comprises doped zirconia and has a
thickness of from 40 to 300 .mu.m; wherein the anode layer and the
cathode layer both comprise doped ceria or both comprise doped
zirconia; and wherein the multilayer structure formed of the anode
layer, the electrolyte layer and the cathode layer is a symmetrical
structure. The present invention further provides a method of
producing said solid oxide cell.
Inventors: |
Larsen; Peter Halvor;
(Roskilde, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Technical University of Denmark |
Kgs. Lyngby |
|
DK |
|
|
Assignee: |
Technical University of
Denmark
Kgs. Lyngby
DK
|
Family ID: |
39679443 |
Appl. No.: |
14/255716 |
Filed: |
April 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12922911 |
Dec 8, 2010 |
8741425 |
|
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PCT/EP2009/002010 |
Mar 18, 2009 |
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14255716 |
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Current U.S.
Class: |
29/623.5 ;
29/623.1 |
Current CPC
Class: |
H01M 4/905 20130101;
H01M 8/1226 20130101; H01M 8/1286 20130101; H01M 4/8885 20130101;
H01M 4/9025 20130101; Y10T 29/49115 20150115; Y02P 70/50 20151101;
Y10T 29/49108 20150115; H01M 4/8621 20130101; Y10T 428/24942
20150115; H01M 4/8892 20130101; Y02E 60/50 20130101; H01M 4/8657
20130101 |
Class at
Publication: |
29/623.5 ;
29/623.1 |
International
Class: |
H01M 4/88 20060101
H01M004/88 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2008 |
EP |
08005045.3 |
Claims
1-13. (canceled)
14. A method of producing an all ceramics solid oxide cell, the
solid oxide cell comprising an anode layer, a cathode layer, and an
electrolyte layer sandwiched between the anode layer and the
cathode layer, wherein: the electrolyte layer comprises doped
zirconia and has a thickness of from 40 to 300 .mu.m; the anode
layer and the cathode layer both comprise doped ceria or both
comprise doped zirconia; and the multilayer structure formed of the
anode layer, the electrolyte layer and the cathode layer is a
symmetrical structure, the method comprising: (a) providing a first
electrode precursor layer; (b) forming an electrolyte layer on top
of the first electrode precursor layer; (c) forming a second
electrode precursor layer on top of the electrolyte layer; and (d)
sintering the obtained multilayer structure.
15. The method of claim 14, wherein the sintering temperature
ranges from 1000.degree. C. to 1300.degree. C.
16. The method of claim 14, further comprising the step of
impregnating the electrode precursor layer which will form the
cathode layer with a barrier material.
17. The method of claim 16, wherein the barrier material is
selected from (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (i.e. CGO10)
and (Ce.sub.0.9Sm.sub.0.1)O.sub.2-.delta..
18. The method of claim 14, further comprising impregnating the
first electrode precursor layer and the second electrode precursor
layer with a catalyst or catalyst precursor material so as to form
the cathode layer and the anode layer.
19. The method of claim 18, wherein the catalyst or catalyst
precursor for the electrode precursor layer which will form the
cathode layer is selected from manganites, ferrites, cobaltites and
nickelates, doped ceria, doped zirconia and mixtures thereof.
20. The method of claim 19, wherein the catalyst or catalyst
precursor for the electrode precursor layer which will form the
anode layer is selected from Ni, Fe.sub.xNi.sub.1-x alloys and a
mixture of Ni and doped ceria/zirconia or a mixture of Cu and Cu
and/or doped zirconia/ceria, and
Ma.sub.sTi.sub.1-xMb.sub.xO.sub.3-.delta. or
LnCr.sub.1-xM.sub.xO.sub.3-.delta., wherein: Ma is Ba, Sr or Ca; Mb
is V, Nb, Ta, Mo, W, Th or U; s ranges from 0 to 0.5; and M is T,
V, Mn, Nb, Mo, W, Th or U.
21. The method of claim 15, further comprising the step of
impregnating the electrode precursor layer which will form the
cathode layer with a barrier material.
22. The method of claim 15, further comprising the step of
impregnating the first electrode precursor layer and second
electrode precursor layer with a catalyst or catalyst precursor
material so as to form the cathode layer and the anode layer.
23. The method of claim 16, further comprising the step of
impregnating the first electrode precursor layer and second
electrode precursor layer with a catalyst or catalyst precursor
material so as to form the cathode layer and the anode layer.
24. The method of claim 17, further comprising the step of
impregnating the first electrode precursor layer and second
electrode precursor layer with a catalyst or catalyst precursor
material so as to form the cathode layer and the anode layer.
25. The method of claim 14, wherein the thickness of the anode
layer and the cathode layer is 150 .mu.m or less.
26. The method of claim 14, wherein the electrolyte layer comprises
more than one layer.
27. The method of claim 14, wherein the anode layer and the cathode
layer each comprise more than one layer.
28. The method of claim 14, wherein the anode layer and the cathode
layer have a porosity ranging from 20% to 80%.
29. The method of claim 14, wherein the anode or the cathode layer,
or both, is impregnated with a barrier material.
Description
TECHNICAL FIELD
[0001] The present invention relates to an all ceramics solid oxide
cell (SOC) and a method for preparing same.
BACKGROUND ART
[0002] Solid oxide cells (SOCs) generally include cells designed
for different applications, such as solid oxide fuel cells (SOFCs)
or solid oxide electrolysis cells (SOECs). Due to their common
basic structure, the same cell may, for example, be used in SOFC
applications as well as SOEC applications. Since in SOFCs fuel is
fed into the cell and converted into power, while in SOECs power is
applied to produce fuel, these cells are often referred to as
`reversible` SOCs.
[0003] Solid oxide cells may have various designs. Typical
configurations include an electrolyte layer being sandwiched
between two electrodes. During operation of the cell, usually at
temperatures of about 500.degree. C. to about 1100.degree. C., one
electrode is in contact with oxygen or air, while the other
electrode is in contact with a fuel gas.
[0004] The most common manufacture processes suggested in the prior
art comprise the manufacture of single cells. Generally, a support
is provided, on which an electrode layer is formed, followed by the
application of an electrolyte layer. The so formed half cell is
dried and afterwards sintered, in some cases in a reducing
atmosphere. Finally, a second electrode layer is formed thereon so
as to obtain a complete cell. Alternatively, one of the electrode
layers or the electrolyte layer may be used as a support layer,
having a thickness of about 300 .mu.m or more.
[0005] This approach usually requires a relatively thick support
layer to provide mechanical stability of the obtained cell, thereby
increasing the overall thickness of the single cells. It has been
suggested to form the support from metals or metal alloys, which
are less brittle than ceramic materials and therefore superior in
mechanical stability. However, disadvantageously it has been found
that due to the metallic materials used, poisoning of the catalyst
in the adjacent electrode layer due to migration from the support,
especially if chromium is used in the support, may occur.
Furthermore, metal supports are not suitable for SOCs intended for
high temperature applications in the range up to about 1000.degree.
C.
[0006] If alternatively one of the electrodes is also used as the
support layer, on the one hand the overall thickness of said layer
determines the mechanical stability of the cell, i.e. the layer
must be sufficiently thick; on the other hand the layer thickness
influences the gas diffusion through the electrode layer and should
therefore be sufficiently thin. Furthermore, in order to produce
cells as cost effective as possible, the amount of materials used
for each layer should be kept to a minimum.
[0007] US-A-2004/0166380 (Gorte et al) relates to porous electrodes
for use in SOFCs, wherein the electrodes are comprised primarily of
a ceramic material and an electrochemically conductive material.
The electrodes are prepared by impregnating a porous ceramic
material with precursors of the electrochemically conducting
material. The focus is especially on providing a cathode comprising
a porous ceramic matrix and an electrochemically conducting
material dispersed at least partially within the porous ceramic
matrix, wherein the porous ceramic matrix includes a plurality of
pores having a pore size of at least about 0.5 .mu.m.
[0008] US-A-2004/0018409 (Hui et al) discloses a SOFC comprising a
dense electrolyte disposed between a porous anode and a porous
cathode. The electrolyte may preferably be yttria stabilized
zirconia. The anode may be formed from yttrium-doped strontium
titanate, yttrium-doped strontium titanate and nickel, doped ceria,
lanthanum-doped ceria and nickel or yttria stabilized zirconia and
nickel. The cathode may be formed from strontium-doped lanthanum
manganite or doped lanthanum ferrite. The SOFC may further comprise
Interlayers' disposed between the electrodes and the electrolyte.
Said layers are dense layers which function as a barrier layer. The
interlayers further do not comprise any catalyst material, and
since the layers are dense layers, they cannot function as
electrodes.
[0009] WO-A-2006/082057 (Larsen) relates to a SOFC comprising an
electrolyte layer sandwiched in between two electrode layers, and
further a metallic support for mechanical stability of the
cell.
[0010] US-A-2004/0101729 (Kearl) relates to a SOFC with a thin film
electrolyte in combination with both, a thick film anode/fuel
electrode and a thick film cathode/air electrode. The cathode
preferably comprises a material, such as silver, or a material
having a perovskite structure, such as lanthanum strontium
manganite, lanthanum strontium ferrite, lanthanum strontium
cobaltite, LaFeO.sub.3/LaCoO.sub.3, YMnO.sub.3, CaMnO.sub.3,
YfeO.sub.3, and mixtures thereof. The cell may further comprise
interfacial layers between the electrodes and the electrolyte
layer. Said interfacial layers do not comprise any catalyst
material, and since the layers are dense layers, they cannot
function as electrodes.
[0011] WO-A-98/49738 (Wallin et al) discloses a composite oxygen
electrode/electrolyte structure for a solid state electrochemical
device having a porous composite electrode in contact with a dense
electrolyte membrane, said electrode comprising: [0012] (a) a
porous structure having interpenetrating networks of an
ionically-conductive material and an electronically-conductive
material; and [0013] (b) an electrocatalyst different from the
electronically-conductive material, dispersed within the pores of
the porous structure.
[0014] WO-A-2007/011894 (Hertz et al) discloses a thin-film
composite material with nanometer-scale grains, comprising a
thin-film layer that includes: [0015] a) an electronic conductor;
and [0016] b) an ionic conductor.
[0017] US-A-2003/0082436 (Hong et al) relates to an electrode for a
SOFC, sensor or solid state device, comprising an electrode coated
with an oxygen ion conducting ceramic ceria film. The electrolyte
may be a YSZ electrolyte sandwiched by Pt-LSM electrodes.
[0018] U.S. Pat. No. 5,543,239 (Virkar et al) discloses an improved
electrode/electrolyte structure having an enhanced three-faced
boundary length for use as a fuel cell, a catalyst or a sensor,
wherein said structure comprises: [0019] a) a substrate layer
consisting of the dense electrolyte material; [0020] b) a porous
surface layer of said dense electrolyte material over the dense
electrolyte substrate layer; [0021] c) an electrocatalyst material
on and within the porous surface layer of electrolyte, wherein the
electrocatalyst material is continuous on the surface of the porous
electrolyte, creating enhanced three-faced boundaries with gas
present; and [0022] d) said structure is integrally connected or
attached to a porous anode.
[0023] US-A-2006/0093884 (Seabaugh et al) relates to a ceramic
laminate structure including partially stabilized zirconia
electrode layers, sandwiching a fully stabilized zirconia
electrolyte layer.
[0024] US-A-2008/0038611 (Sprenkle et al) discloses an electrode
supported electrolyte membrane for an electrochemical cell
comprising: [0025] a substantially continuous layer of a ceramic
ion conducting electrolyte supported on a conductive electrode
substrate, wherein the substrate includes an active electrode layer
and a bulk electrode layer; [0026] a backing structure on a face of
the bulk electrode layer opposite the electrolyte layer with a
thermal expansion coefficient approximately equal to the thermal
expansion coefficient of the electrolyte layer.
[0027] EP-A-1482584 (Komada et al) teaches an electrode for a solid
oxide cell wherein: [0028] the electrode comprises a skeleton
constituted of a porous sintered compact having a three dimensional
network structure, the porous sintered compact being made of an
oxide ion conducting material and/or a mixed oxide ion conducting
material; [0029] grains made of an electron conducting material
and/or a mixed oxide ion conducting material are adhered onto the
surface of said skeleton; and [0030] said grains are baked inside
the voids of said porous sintered compact under the conditions such
that the grains are filled inside the voids.
[0031] In view of the disadvantages of the SOC compositions of the
prior art, there is still a desire for improved SOCs which are
durable, have good mechanical stability, do not suffer from the
above described drawbacks of the SOCs of the prior art, may be used
in a wide temperature range up to 1000.degree. C. or above, and
which have an overall excellent life time.
OBJECT OF THE PRESENT INVENTION
[0032] It was therefore the objective problem underlying the
present invention to provide an SOC have an enhanced electrode
performance and excellent lifetime without sacrificing mechanical
stability of the cell, and to provide a method of producing
same.
SUMMARY
[0033] The above problem is solved by an all ceramics solid oxide
cell, comprising an anode layer, a cathode layer, and an
electrolyte layer sandwiched between the anode layer and the
cathode layer, [0034] wherein the electrolyte layer comprises doped
zirconia and has a thickness of from 40 to 300 .mu.m, [0035]
wherein the anode layer and the cathode layer both comprise doped
ceria or both comprise doped zirconia; and [0036] wherein the
multilayer structure formed of the anode layer, the electrolyte
layer and the cathode layer is a symmetrical structure.
[0037] The above problem is further solved by a method of producing
the above all ceramics solid oxide cell, comprising the steps of:
[0038] providing a first electrode precursor layer; [0039] forming
an electrolyte layer on top of the first electrode precursor layer;
[0040] forming a second electrode precursor layer on top of the
electrolyte layer; and [0041] sintering the obtained multilayer
structure.
[0042] Preferred embodiments are set forth in the subclaims and the
following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 illustrates a SOC in accordance with the present
invention, comprising an electrolyte layer 1 sandwiched by two
electrode layers 2, 3.
[0044] FIG. 2 illustrates a SOC in accordance with the present
invention, comprising an electrolyte layer 4 sandwiched by
electrode layers 5 to 8.
[0045] FIG. 3 illustrates another embodiment of an SOC in
accordance with the present invention, comprising two electrolyte
layers 9, 10 and two electrode layers 11 and 12.
[0046] FIG. 4 illustrates an SOC in accordance with the present
invention, having a corrugated pattern, comprising an electrolyte
layer 13 sandwiched by two electrode layers 14, 15.
DETAILED DESCRIPTION OF THE INVENTION
[0047] SOC of the Invention
[0048] The invention provides an all ceramics solid oxide cell,
comprising an anode layer, a cathode layer, and an electrolyte
layer sandwiched between the anode layer and the cathode layer,
[0049] wherein the electrolyte layer comprises doped zirconia and
has a thickness of from 40 to 300 .mu.m; [0050] wherein the anode
layer and the cathode layer both comprise doped ceria or both
comprise doped zirconia; and [0051] wherein the multilayer
structure formed of the anode layer, the electrolyte layer and the
cathode layer is a symmetrical structure.
[0052] The solid oxide cell of the present invention includes solid
oxide fuel cells as well as solid oxide electrolysis cells. By "all
ceramics" in the sense of the present invention it is referred to a
SOC which does not comprise a metallic layer or a layer comprising
in part metal components other than catalyst material. Thus, the
cell of the present invention does not comprise any metallic
support or any layers which are at least partly or completely
formed from metals or metal alloys. Advantageously, poisoning of
the electrode layers and the catalyst therein due to migration of
species from metals is effectively avoided. Furthermore, the cell
is suitable to be used under operation conditions such as
temperatures up to about 1000.degree. C. or above if desired. In
particular, the "all ceramics" solid oxide cell does not comprise
any metal other than catalyst material being introduced by
impregnation of the electrode precursor layers after sintering.
Instead, the "all ceramics" solid oxide cell only comprises
non-metallic components except for catalyst material.
[0053] The SOC of the present invention specifically comprises a
doped zirconia electrolyte layer which is sandwiched between two
porous doped ceria electrode layers or between two porous doped
zirconia electrode layers. Due to this configuration, doped
zirconia as the electrolyte layer is solely an ionic conductor,
whereas doped ceria in the layer forming the cathode provides a
better ionic conductivity and less reactivity with the cathode
materials than doped zirconia. As for the anode, doped ceria
becomes a mixed conductor, i.e. conductor of both, electrons and
ions, and thereby enhances the anode performance as compared to an
anode based on doped zirconia. Thereby, an enhanced electrode
performance is provided.
[0054] In the cell of the present invention, the multilayer
structure formed of the anode layer, the electrolyte layer and the
cathode layer is a symmetrical structure. "Symmetrical" in the
sense of the present invention refers to the anode and cathode
(precursor) layers being porous and both layers being identical in
the ceria composition, and in the thickness of each electrode
(precursor) layer, thus sandwiching the electrolyte layer so as to
form a symmetrical structure. This ensures that the mechanical
forces exerted on the electrolyte layer during the temperature
cycling in use from both sides are symmetrical. Furthermore, since
the thermal expansion of the electrode layers is larger than the
thermal expansion of the electrolyte layer sandwiched in between,
the electrolyte layer is under compression during cooling of the
cell. Both advantageously result in an improved mechanical strength
of the cell. If electrodes comprising doped zirconia are used, the
thermal expansion coefficient (TEC) of the layers is preferably
adjusted by the concentration of the dopant or by employing a
suitable dopant to ensure that the TEC of the electrodes is higher
than the TEC of the electrolyte layer.
[0055] Of course, the final cathode and anode layer differentiate
in the catalyst used, which however has no influence on the
symmetrical character of the cell, as is immediately evident to a
person skilled in the art. More specifically, the presence of a
different catalyst does not have any influence on the layer
thickness, porosity or ceria composition of each layer.
[0056] When referring to the "electrode precursor layers" in the
sense of the present invention, it is referred to the electrode
layers during the manufacture of the cell after sintering but prior
to the impregnation with a catalyst material, as will be described
below in connection with the method of the present invention. Prior
to the impregnation with catalyst material, which is a preferred
embodiment, the electrode layers are identical in the ceria or
zirconia composition, and in the thickness, as described above.
They are formed into the final electrode layers, i.e. the cathode
layer and the anode layer, by selecting the respective catalyst
materials and impregnating the layers therewith, which define the
function of the electrode layer.
[0057] Thus, "Symmetrical" in the sense of the present invention
refers to the cell comprising an anode layer and cathode layer
which are identical in the ceria or zirconia composition, and in
the thickness, and only differ in terms of the catalyst.
[0058] As may be seen from FIG. 1, the electrode layers may be
formed as single layers 2 and 3. However, as may be seen from FIG.
2, the electrode layers, i.e. the anode layer and the cathode
layer, may also be formed as a multilayer structure comprising the
same number of layers on each side. As shown in FIG. 2, each
electrode comprises two layers 5, 7 and 6, 8. Each electrode may of
course have more than two layers if desired without compromising
the symmetry of the multilayer structure as described above.
[0059] Electrolyte Layer
[0060] The thickness of the electrolyte layer comprising doped
zirconia is from 40 to 300 .mu.m, preferably from 50 to 280 .mu.m
in the dry state. It is more preferred that the thickness is up to
200, even more preferred up to 250 .mu.m, and even more preferably
up to 150 .mu.m. The thickness depends on the intended operational
temperature and the requirements of ionic conductivity and
mechanical strength of the later application of the cell. Contrary
to SOCs of the prior art, wherein the electrolyte layers should be
as thin as possible, the electrolyte layer of the SOC of the
present invention may be comparatively thick, i.e. up to 300 .mu.m,
thus allowing for thinner electrode layers without compromising the
mechanical stability.
[0061] In another preferred embodiment, the electrolyte layer of
the thin reversible solid oxide fuel cell is a multilayer structure
comprising at least two layers, as illustrated by layers 9 and 10
in FIG. 3. The overall thickness of said multilayer structure is
still in the above range.
[0062] Electrode Layers
[0063] The thickness of the electrode layers, i.e. the anode layer
and the cathode layer, comprising doped ceria is preferably 150
.mu.m or less in the dry state, more preferably 100 .mu.m or less,
and even more preferably 50 .mu.m or less. As the electrolyte layer
in some cases provides the mechanical stability, the electrode
layers may be relatively thin. Furthermore, the electrode layers
are preferably at least 1 .mu.m thick, more preferably 10 .mu.m,
and most preferably 20 .mu.m. As the cell has a symmetrical
character, the thickness of the anode layer and the cathode layer
is of course identical, as defined above.
[0064] The electrode precursor layers prior to impregnation with a
catalyst preferably have a porosity of from 20 to 80%, more
preferably from 30 to 70%, and even more preferably from 40 to 60%
as determined by mercury porosimetry.
[0065] In a more preferred embodiment, the electrode precursor
layers comprise two different layers each, as shown in FIG. 2. The
electrode precursor layers may comprise more than two layers each,
while maintaining an overall symmetrical cell structure.
[0066] Since the final cell structure is a symmetrical structure,
with the electrolyte layer being sandwiched by the electrode layers
as described above, the electrolyte layer having a smaller TEC than
the electrode layers in contact with the electrolyte layer will be
under compression during cooling. Consequently, the cell exhibits
an improved stability, resulting in a longer cell life.
[0067] In a further preferred embodiment, the manufactured cell
structure is profiled prior to sintering so as to obtain a
patterned structure. Patterned structures include a ribbon
structure or egg tray structure, as illustrated by FIG. 4. The
pattern may be used to provide gas channels in the cell during
later use if desired. If present, said pattern contributes to the
overall stiffness and handling strength of the cell. The profiling
of the cell further increases the power/volume performance of the
stack which is highly advantageous in certain applications. How to
profile a cell structure is well known to a person skilled in the
art.
[0068] When a catalyst is present in the electrode layers,
preferably the catalyst or precursor thereof for the impregnation
of the electrode precursor layer which will function as the cathode
layer is selected from the group consisting of manganites,
ferrites, cobaltites and nickelates or mixtures thereof.
(La.sub.1-xSr.sub.x).sub.sMnO.sub.3-.delta. and
(A.sub.1-xB.sub.x).sub.sFe.sub.1-yCo.sub.yO.sub.3-.delta. where
A=La, Gd, Y, Sm, Ln or mixtures thereof, and B.dbd.Ba, Sr, Ca, or
mixtures thereof, and Ln=lanthanides. Examples include lanthanum
strontium manganate, lanthanide strontium iron cobalt oxide,
(La.sub.1-xSr.sub.x)MnO.sub.3-.delta.,
(Ln.sub.1-xSr.sub.x)MnO.sub.3-.delta.,
(La.sub.1-xSr.sub.x)Fe.sub.1-yCo.sub.yO.sub.3-.delta.,
(Ln.sub.1-xSr.sub.x)Fe.sub.1-yCo.sub.yO.sub.3-.delta.,
(Y.sub.1-xCa.sub.x)Fe.sub.1-yCo.sub.yO.sub.3-.delta.,
(Gd.sub.1-xSr.sub.x)Fe.sub.1-yCo.sub.yO.sub.3-.delta.,
(Gd.sub.1-xCa.sub.x)Fe.sub.1-yCo.sub.yO.sub.3-.delta., or mixtures
thereof. In the formula, x is from about 0 to 1, more preferably
from about 0.1 to 0.5, and most preferably from 0.2 to 0.4. Y is
from about 0 to 1, more preferably from about 0.1 to 0.5, and most
preferably from 0.2 to 0.3. S is preferably from 0.7 to 1.
[0069] Furthermore, electrolyte materials such as doped zirconia or
doped ceria may be impregnated into the electrode precursor layer
designated as the cathode if desired, alone or in combination with
any of the materials mentioned above.
[0070] When a catalyst is present in the electrode layers, it is
also preferred that the catalyst or precursor thereof for the
impregnation of the electrode precursor layer which will function
as the anode layer is selected from the group consisting of Ni,
Fe.sub.xNi.sub.1-x alloys and a mixture of Ni and doped
ceria/zirconia or a mixture of Cu and Cu and doped zirconia/ceria.
Alternatively Ma.sub.sTi.sub.1-xMb.sub.xO.sub.3-.delta., Ma=Ba, Sr,
Ca; Mb.dbd.V, Nb, Ta, Mo, W, Th, U; 0.ltoreq.s.ltoreq.0.5; or
LnCr.sub.1-xM.sub.xO.sub.3-.delta., M=T, V, Mn, Nb, Mo, W, Th, U
may be used. In the formula, x is from about 0 to 1, more
preferably from about 0.1 to 0.5, and most preferably from 0.2 to
0.3.
[0071] Moreover, electrocatalytic active electrolyte materials such
as doped ceria may be impregnated into the anode if desired, alone
or in combination with any of the materials mentioned above.
[0072] Optional Barrier Layer
[0073] In another preferred embodiment, the electrode precursor
layer designated as the cathode is impregnated with barrier
material. By providing a barrier material that is deposited on the
surfaces in the electrode precursor layer and electrolyte layer by
impregnation through the cathode precursor layer, interface
reactions between cathode materials and the electrolyte material at
elevated temperatures, for example during the operation of the
cell, is effectively prevented. This eliminates undesired reactions
between cathode and electrolyte materials, particularly between La
and/or Sr oxides in the cathode layer, and ZrO.sub.2 in the
electrode precursor layer and electrolyte layer, which otherwise
would result in the formation of electrically insulating interface
layers in the cell and thereby reduce its electrochemical
activity.
[0074] Preferably, the barrier material comprises ceria, more
preferably doped ceria such as
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (i.e. CGO10) or
(Ce.sub.0.9Sm.sub.0.1)O.sub.2-.delta. (i.e. CSO10).
[0075] The precursor solution or suspension of the barrier material
is preferably a nitrate solution of doped ceria, for instance a
nitrate solution of Gd doped ceria
((Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta.), or a colloidal suspension
of doped ceria particles having average diameter of 2 to 100 nm,
preferably 30 to 100 nm, more preferably 30 to 80 nm.
METHOD OF THE INVENTION
[0076] The present invention further provides a method of producing
the above described all ceramics solid oxide cell, comprising the
steps of: [0077] providing a first electrode precursor layer;
[0078] forming an electrolyte layer on top of the first electrode
precursor layer; [0079] forming a second electrode precursor layer
on top of the electrolyte layer; and [0080] sintering the obtained
multilayer structure.
[0081] The cell may be manufactured using standard ceramic
processing techniques as well as advanced colloidal and chemical
processing as proposed as known to a person skilled in the art.
Preferably, the sintering temperature is in the range of 1000 to
1300.degree. C.
[0082] Preferably, the method further comprises the step of
impregnation of the electrode precursor layers with the above
mentioned electrochemically active materials.
[0083] Optional Barrier Layer
[0084] In another preferred embodiment, the cathode precursor layer
is impregnated with a barrier material prior to impregnation with a
catalyst material. As indicated above, by providing a barrier
material that is deposited on the surfaces in the electrode
precursor layer and electrolyte layer by impregnation through the
cathode precursor layer, interface reactions between air electrode
(cathode) materials and the electrolyte material are prevented.
This advantageously eliminates undesired reactions between cathode
and electrolyte materials, particularly between La and/or Sr oxides
in the cathode and ZrO.sub.2 in the electrolyte, which tend to
react and form electrically insulating interface layers in the cell
and thereby reduce its electrochemical activity.
[0085] Preferably, the barrier material comprises ceria, more
preferably doped ceria such as
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (i.e. CGO10) or
(Ce.sub.0.9Sm.sub.0.1)O.sub.2-.delta. (i.e. CSO10).
[0086] Even more preferred is the step of impregnating a precursor
solution or suspension of a barrier material at least into the
cathode precursor layer and subsequently conducting a heat
treatment. Afterwards, the electrodes are impregnated with the
catalyst or catalyst precursor as mentioned above.
[0087] Advantages
[0088] The all ceramics solid oxide cell of the present invention
comprises a combination of a zirconia based electrolyte and ceria
or zirconia based electrode (precursor) layers which results in:
[0089] Enhanced electrode performance due to the substitution of
zirconia in electrodes with ceria; [0090] The cell being suitable
for use in a wide temperature range of applications, i.e. from
500-1100.degree. C.; [0091] Durable all ceramics cells without the
requirement of an additional support layer, especially a metal
support layer; [0092] The cell manufacturing process only requires
one sintering step, making the production more cost effective;
[0093] The electrodes are impregnated after sintering of the cell,
thus ensuring fine microstructures and in return a high
performance; [0094] The zirconia based electrolyte is under
compressional forces from both sides due to the higher thermal
expansion coefficient of ceria compared to zirconia, or due to the
higher thermal expansion coefficient of the doped zirconia
electrode layers compared to the zirconia electrolyte layer, and
will consequently increase the mechanical strength of the cell;
[0095] The cells have an improved lifetime.
[0096] The present invention will now be described by the following
examples. The invention is however intended to be not limited
thereto.
EXAMPLES
Example 1
Manufacture of a SOC
[0097] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0098] Layer 1: The suspension comprises
Ce.sub.0.9Gd.sub.0.1O.sub.2 (CGO10) powder mixed with 10 vol % of
graphite pore former. The green thickness is about 40 .mu.m. The
sintered porosity of the layer is about 50% with an average pore
size around 2-3 .mu.m.
[0099] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the electrolyte is about 25 .mu.m. The sintered
density of the layer is >96 of the theoretical density.
[0100] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (1) sandwiched between two electrode precursor layers (2, 3),
as shown in FIG. 1. The lamination is performed by the use of
heated rolls in a double roll set-up and takes place in one pass.
The obtained structure is symmetrical, as indicated in FIG. 1.
[0101] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0102] The fourth step comprises sintering. The laminate is heated
with an increase of the temperature of about 50.degree. C./h to
about 500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with an
increase of the temperature of 100.degree. C./h, and left for 5
hours before cooling to room temperature.
[0103] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side. A nitrate solution of La, Sr,
Co and Fe is vacuum infiltrated into the porous structure. The
infiltration is performed six times with an intermediate heating
step for decomposition of the nitrates. The resulting composition
of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(CO.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0104] In the sixth step the anode is impregnated. The impregnated
cathode side is masked prior to impregnation of the anode. A
nitrate solution of Ni, Ce and Gd is vacuum infiltrated into the
porous structure. The infiltration is performed five times with an
intermediate heating schedule between each infiltration for
decomposition of the impregnated nitrates. The resulting
composition of the impregnated anode part is 40 vol % Ni and 60 vol
% (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after reduction of
NiO).
[0105] The so formed cell has a thickness of about 100 .mu.m and is
ready to be built into a stack of cells. No heat treatment prior to
stacking is required.
Example 2
Manufacture of a SOC
[0106] The cell is produced as outlined above for Example 1, with
the exception that in step five the cathode is impregnated. The
sintered cell is masked on one side. A colloidal suspension of
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta.
and (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (CGO10) is vacuum
infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating step.
[0107] The obtained cell has a thickness of about 100 .mu.m and is
ready to be built into a stack of cells. No heat treatment prior to
stacking is required.
Example 3
Manufacture of a SOC
[0108] The manufacturing is carried out as described in Example 1
for steps one to four.
[0109] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a polymeric seal. A
colloidal suspension of
(La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta. and (CGO10) is
vacuum infiltrated into the porous structure. The infiltration is
performed four times with an intermediate drying between each
infiltration.
[0110] The cell is completed as described in Example 1. The
obtained cell has a thickness of about 100 .mu.m and is ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 4
Manufacture of a SOC
[0111] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0112] Layer 1: The suspension is based on
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. powder using charcoal as a
pore-former. The green thickness is about 40 .mu.m. The sintered
porosity of the layer is about 50% with an average pore size in the
range of 1-2 .mu.m.
[0113] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The green
thickness of the foil is about 12 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0114] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (1) sandwiched between two electrode precursor layers (2, 3),
as shown in FIG. 1. The lamination is performed by the use of
heated rolls in a double roll set-up and takes place in one
pass.
[0115] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0116] The fourth step comprises sintering. The laminate is heated
with an increase of the temperature of about 50.degree. C./h to
about 500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1150.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0117] The fifth step is the impregnation of a cathode barrier
layer. After sintering a nitrate solution of gadolinium doped ceria
(Gd.sub.0.1Ce.sub.0.9)O.sub.2-.delta. (barrier material) is
impregnated into the cathode precursor layer two times. After
impregnation the sample is heat treated for 1 hour at 400.degree.
C.
[0118] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side. A nitrate solution of La, Sr
and Co is vacuum infiltrated into the porous structure. The
infiltration is performed six times with an intermediate heating
step for decomposition of the nitrates. The resulting composition
of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97CoO.sub.3-.delta..
[0119] In the seventh step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
vacuum infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 40 vol %
Ni and 60 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0120] The so formed cell is about 100 .mu.m thick and ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 5
Manufacture of a SOC
[0121] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0122] Layer 1: The suspension comprises
(Ce.sub.0.85Gd.sub.0.15)O.sub.2-.delta. (CGO15) powder mixed with
10 vol % PMMA filler. The sintered thickness is about 25 .mu.m. The
sintered porosity of the layer is about 60% with an average pore
size in the range of 1-3 .mu.m.
[0123] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the electrolyte is about 150 .mu.m. The sintered
density of the layer is >96% of the theoretical density.
[0124] The cell is completed as described in Example 3. The so
formed cell is about 200 .mu.m thick and ready to be built into a
stack of cells. No heat treatment prior to stacking is
required.
Example 6
Manufacture of a SOC Having Multi Layer Electrodes
[0125] The first step comprises tape-casting of three layers; two
ceria containing electrode precursor layers (layer 1 and 2) and one
electrolyte layer (layer 3). Suspensions for tape-casting are
manufactured by means of ball milling of powders with polyvinyl
pyrrolidone (PVP), polyvinyl butyral (PVB) and EtOH+MEK as
additives. After control of particle size, the suspensions are
tape-cast using a double doctor blade set-up and the tapes are
subsequently dried. The relative thermal expansion coefficients
(TEC) of the layers are
TEC.sub.layer3<TEC.sub.layer1.ltoreq.TEC.sub.layer2.
[0126] Layer 1: The suspension comprises
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta.. 15 vol % graphite is used as
pore former. The sintered thickness is about 30 .mu.m. The sintered
porosity of the layer is about 50% with a pore size in the range of
2-5 .mu.m.
[0127] Layer 2: The suspension is based on
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta.. 10 vol % graphite is used as
a pore-former. The sintered thickness of the foil is about 25
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of 1-3 .mu.m.
[0128] Layer 3: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the foil is about 50 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0129] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (sandwiched between two electrode precursor layers on each
side in the order Layer 1-Layer 2-Layer 3-Layer 2-Layer 1. This
layer structure corresponds to layers 4 to 8 as shown in FIG. 2.
The lamination is performed by the use of heated rolls in a double
roll set-up and takes place in one pass.
[0130] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching of samples with an area of
about 600 cm.sup.2.
[0131] The cell is completed as described in Example 1. The
obtained cell is about 160 .mu.m thick and ready to be built into a
stack of cells. No heat treatment prior to stacking is
required.
Example 7
Manufacture of a Thin SOC Having Multi Layer Electrolyte
[0132] The first step comprises tape-casting of three layers; one
ceria containing electrode precursor layer (layer 1) and two
electrolyte layers (layers 2 and 3). Suspensions for tape-casting
are manufactured by means of ball milling of powders with polyvinyl
pyrrolidone (PVP), polyvinyl butyral (PVB) and EtOH+MEK as
additives. After control of particle size, the suspensions are
tape-cast using a double doctor blade set-up and the tapes are
subsequently dried. The relative thermal expansion coefficients
(TEC) of the layers are
TEC.sub.layer3<TEC.sub.layer1.ltoreq.TEC.sub.layer2.
[0133] Layer 1: Electrode precursor layer. The suspension is based
on (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta.. 10 vol % graphite is used
as a pore-former. The sintered thickness of the foil is about 50
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of 1-3 .mu.m.
[0134] Layer 2: Electrolyte layer. The suspension is based on
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta.. The sintered thickness of
the foil is about 10 .mu.m. The sintered porosity of the layer is
about 96%.
[0135] Layer 3: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the foil is about 5 .mu.m. The sintered density of the
layer is >96% of the theoretical density.
[0136] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (sandwiched between electrode precursor layers on each side
in the order Layer 1-Layer 2-Layer 3-Layer 2-Layer 1. The
lamination is performed by warm pressing at 120.degree. C.
[0137] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching of samples with an area of
about 600 cm.sup.2.
[0138] The fourth step comprises sintering. The laminate is heated
at an increase of the temperature of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0139] The fifth step is the impregnation of the cathode on the
side with the electrolyte layer (layer 3). The sintered cell is
masked on one side. A nitrate solution of La, Sr, Co and Fe is
infiltrated into the porous structure. The infiltration is
performed six times with an intermediate heating step for
decomposition of the nitrates. The resulting composition of the
impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0140] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 40 vol %
Ni and 60 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0141] The so formed cell has a thickness of about 125 .mu.m thick
and ready to be built into a stack of cells. No heat treatment
prior to stacking is required.
Example 8
Manufacture of a SOC Having a Multilayer Electrolyte
[0142] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0143] Layer 1: The suspension comprises
Ce.sub.0.9Gd.sub.0.1O.sub.2. The sintered thickness is about 30
.mu.m. The sintered porosity of the layer is about 30% with a pore
size in the range of 1-2 .mu.m.
[0144] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the foil is about 15 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0145] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising two electrolyte
layers (9, 10) sandwiched between two electrode precursor layers
(11, 12), as shown in FIG. 3. The lamination is performed by the
use of heated rolls in a double roll set-up and takes place in one
pass.
[0146] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0147] The fourth step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0148] The fifth step is the impregnation of a cathode barrier
layer. After sintering a nitrate solution of gadolinium doped ceria
(Gd.sub.0.1Ce.sub.0.9)O.sub.2-.delta. (barrier material) is
impregnated into the cathode precursor layer two times. After
impregnation the sample is heat treated for 1 hour at 400.degree.
C.
[0149] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A nitrate
solution of La, Sr, Co and Fe is infiltrated into the porous
structure. The infiltration is performed five times with an
intermediate heating step for decomposition of the nitrates. The
resulting composition of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0150] In the seventh step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A nitrate solution of
Cu, Ni, Ce and Gd is infiltrated into the porous structure. The
infiltration is performed six times with an intermediate heating
schedule between each infiltration for decomposition of the
impregnated nitrates. The resulting composition of the impregnated
anode part is 4 vol % Cu, 38 vol % Ni and 58 vol %
(Ce.sub.0.6Gd.sub.0.1)O.sub.2-.delta. (after reduction of NiO).
[0151] The obtained cell is about 90 .mu.m thick and ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 9
Manufacture of a SOC with a Patterned Profiled Structure
[0152] Steps one and two are carried out as described in Example
1.
[0153] In the third step, the laminated tapes are cut into pieces.
This is done by knife punching resulting in sintered areas in the
range up to 40.times.40 cm.sup.2.
[0154] In the fourth step the laminated structures are given an egg
tray pattern profiled structure by pressing, electrolyte layer (13)
and two electrode precursor layers (14,15), as shown in FIG. 4.
[0155] The fifth step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0156] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A nitrate
solution of La, Sr, Co and Fe is infiltrated into the porous
structure. The infiltration is performed six times with an
intermediate heating step for decomposition of the nitrates. The
resulting composition of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0157] In the seventh step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A nitrate solution of
Ni, Ce and Gd is infiltrated into the porous structure. The
infiltration is performed seven times with an intermediate heating
schedule between each infiltration for decomposition of the
impregnated nitrates. The resulting composition of the impregnated
anode part is 50 vol % Ni and 50 vol %
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after reduction of NiO).
[0158] The obtained cell is ready to be built into a stack of
cells. No heat treatment prior to stacking is required.
Example 10
Manufacture of a SOC
[0159] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0160] Layer 1: The suspension comprises pre-calcined
(Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. and 10 vol % charcoal as a
pore-former. The sintered thickness is about 20 .mu.m. The sintered
porosity of the layer is about 50% with a pore size in the range of
about 2 .mu.m.
[0161] Layer 2: The suspension is based on YSZ powder. The sintered
thickness of the foil is about 75 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0162] Step two to four are carried out as described in Example
1.
[0163] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta.
and (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (CGO10) (2:1 volume
ratio) is vacuum infiltrated into the porous structure. The
infiltration is performed four times with an intermediate heating
step.
[0164] In the sixth step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A colloidal suspension
of NiO and Ce.sub.0.9Gd.sub.0.1O.sub.2 is vacuum infiltrated into
the porous structure. The infiltration is performed five times with
an intermediate drying between each infiltration. The volume ratio
of NiO:CGO is 1:2.
[0165] The obtained membrane is about 100 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
Example 11
Manufacture of a SOC
[0166] The first step comprises co-casting of a three-layered
structure (layer 1 and 3--electrode precursor layer, and layer
2--electrolyte layer) with intermediate drying after tape-casting
of each layer. Suspensions for tape-casting are manufactured by
means of ball milling of powders with polyvinyl pyrrolidone (PVP),
polyvinyl butyral (PVB) and EtOH+MEK as additives. After control of
particle size, the suspensions are tape-cast using a double doctor
blade set-up as described below and the cast is subsequently
dried.
[0167] Suspension 1, Layer 1 and 3: The suspension comprises
pre-calcined (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. and 10 vol %
charcoal as a pore-former. The sintered thickness is about 40
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of about 2 .mu.m.
[0168] Suspension 2, Layer 2: The suspension is based on doped
zirconia. The sintered thickness of the foil is about 100 .mu.m.
The sintered density of the layer is >96% of the theoretical
density.
[0169] Layer 1 is tape-cast onto a polymeric foil. After drying,
Layer 2 is tape-cast directly onto Layer 1, and after a subsequent
drying Layer 3 (Suspension 1) is tape-cast directly onto the two
layered structure comprising Layer 1 og Layer 2.
[0170] In the second step, the co-cast tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 200-500 cm.sup.2.
[0171] The third step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1150.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0172] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta.
and (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (CGO10) (2:1 volume
ratio) is vacuum infiltrated into the porous structure. The
infiltration is performed four times with an intermediate heating
step.
[0173] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
vacuum infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 50 vol %
Ni and 50 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0174] The obtained membrane is about 180 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
Example 12
Manufacture of a SOC
[0175] The first step comprises co-casting of a three-layered
structure (layer 1 and 3--electrode precursor layer, and layer
2--electrolyte layer) without intermediate drying. Suspensions for
tape-casting are manufactured by means of ball milling of powders
with polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB) and
EtOH+MEK as additives. After control of particle size, the
suspensions are tape-cast using a double doctor blade set-up as
described below and the cast is subsequently dried.
[0176] Suspension 1, Layer 1 and 3: The suspension comprises
pre-calcined (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. and 10 vol %
charcoal as a pore-former. The sintered thickness is about 50
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of about 2 .mu.m.
[0177] Suspension 2, Layer 2: The suspension is based on doped
zirconia. The sintered thickness of the foil is about 200 .mu.m.
The sintered density of the layer is >96% of the theoretical
density.
[0178] Three doctor blade set-ups are place in series on a
polymeric film and the three layers are tape-cast directly onto one
another. Layer 1 (Suspension 1) Layer 2 (Suspension 2) and Layer 3
(Suspension 1).
[0179] In the second step, the co-cast tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 200-500 cm.sup.2.
[0180] The third step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1150.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0181] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta.
and (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (CGO10) (2:1 volume
ratio) is vacuum infiltrated into the porous structure. The
infiltration is performed four times with an intermediate heating
step.
[0182] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
vacuum infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 50 vol %
Ni and 50 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0183] The obtained membrane is about 300 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
Example 13
Manufacture of a SOC
[0184] The first step comprises tape-casting of two layers (layer
1-electrode precursor layer, and layer 2-electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0185] Layer 1: The suspension comprises
Zr.sub.0.88Y.sub.0.12O.sub.2-.delta. powder mixed with 10 vol % of
graphite pore former. The green thickness is about 40 .mu.m. The
sintered porosity of the layer is about 50% with an average pore
size around 2-3 .mu.m.
[0186] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the electrolyte is about 25 .mu.m. The sintered
density of the layer is >96 of the theoretical density.
[0187] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (1) sandwiched between two electrode precursor layers (2, 3),
as shown in FIG. 1. The lamination is performed by the use of
heated rolls in a double roll set-up and takes place in one pass.
The obtained structure is symmetrical, as indicated in FIG. 1.
[0188] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0189] The fourth step is the sintering of the laminate. The
laminate is heated with an increase of the temperature of about
50.degree. C./h to about 500.degree. C. in a flowing air
atmosphere. After 2 hours of soaking, the furnace is heated to
about 1200.degree. C. with an increase of the temperature of
100.degree. C./h, and left for 5 hours before cooling to room
temperature.
[0190] In the fifth step the cathode is impregnated. The sintered
cell is masked on one side. A nitrate solution of La, Sr, Co and Fe
is vacuum infiltrated into the porous structure. The infiltration
is performed six times with an intermediate heating step for
decomposition of the nitrates. The resulting composition of the
impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0191] In the sixth step the anode is impregnated. The impregnated
cathode side is masked prior to impregnation of the anode. A
nitrate solution of Ni, Ce and Gd is vacuum infiltrated into the
porous structure. The infiltration is performed five times with an
intermediate heating schedule between each infiltration for
decomposition of the impregnated nitrates. The resulting
composition of the impregnated anode part is 40 vol % Ni and 60 vol
% (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after reduction of
NiO).
[0192] The so formed cell has a thickness of about 100 .mu.m and is
ready to be built into a stack of cells. No heat treatment prior to
stacking is required.
Example 14
Manufacture of a SOC
[0193] The cell is produced as outlined above for Example 13, with
the exception that in step five the cathode is impregnated. The
sintered cell is masked on one side. A colloidal suspension of
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta.
and (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (CGO10) is vacuum
infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating step.
[0194] The obtained cell has a thickness of about 100 .mu.m and is
ready to be built into a stack of cells. No heat treatment prior to
stacking is required.
Example 15
Manufacture of a SOC
[0195] The manufacturing is carried out as described in Example 13
for steps one to four.
[0196] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a polymeric seal. A
colloidal suspension of
(La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta. and (CGO10) is
vacuum infiltrated into the porous structure. The infiltration is
performed four times with an intermediate drying between each
infiltration.
[0197] The cell is completed as described in Example 13. The
obtained cell has a thickness of about 100 .mu.m and is ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 16
Manufacture of a SOC
[0198] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0199] Layer 1: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder using
charcoal as a pore-former. The green thickness is about 40 .mu.m.
The sintered porosity of the layer is about 50% with an average
pore size in the range of 1-2 .mu.m.
[0200] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The green
thickness of the foil is about 12 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0201] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (1) sandwiched between two electrode precursor layers (2, 3),
as shown in FIG. 1. The lamination is performed by the use of
heated rolls in a double roll set-up and takes place in one
pass.
[0202] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0203] The fourth step the laminate is sintered. The laminate is
heated with an increase of the temperature of about 50.degree. C./h
to about 500.degree. C. in a flowing air atmosphere. After 2 hours
of soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0204] The fifth step is the impregnation of a cathode barrier
layer. After sintering a nitrate solution of gadolinium doped ceria
(Gd.sub.0.1Ce.sub.0.9)O.sub.2-.delta. (barrier material) is
impregnated into the cathode precursor layer two times. After
impregnation the sample is heat treated for 1 hour at 400.degree.
C.
[0205] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side. A nitrate solution of La, Sr
and Co is vacuum infiltrated into the porous structure. The
infiltration is performed six times with an intermediate heating
step for decomposition of the nitrates. The resulting composition
of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97CoO.sub.3-.delta..
[0206] In the seventh step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
vacuum infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 40 vol %
Ni and 60 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0207] The so formed cell is about 100 .mu.m thick and ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 17
Manufacture of a SOC
[0208] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0209] Layer 1: The suspension comprises
Zr.sub.0.84Y.sub.0.16O.sub.2-.delta. powder mixed with 10 vol %
PMMA filler. The sintered thickness is about 25 .mu.m. The sintered
porosity of the layer is about 60% with an average pore size in the
range of 1-3 .mu.m.
[0210] Layer 2: The suspension is based on
Zr.sub.0.80Y.sub.0.20-.delta. powder. The sintered thickness of the
electrolyte is about 150 .mu.m. The sintered density of the layer
is >96% of the theoretical density.
[0211] The cell is completed as described in Example 15. The so
formed cell is about 200 .mu.m thick and ready to be built into a
stack of cells. No heat treatment prior to stacking is
required.
Example 18
Manufacture of a SOC Having Multi Layer Electrodes
[0212] The first step comprises tape-casting of three layers; two
zirconia containing electrode precursor layers (layer 1 and 2) and
one electrolyte layer (layer 3). Suspensions for tape-casting are
manufactured by means of ball milling of powders with polyvinyl
pyrrolidone (PVP), polyvinyl butyral (PVB) and EtOH+MEK as
additives. After control of particle size, the suspensions are
tape-cast using a double doctor blade set-up and the tapes are
subsequently dried. The relative thermal expansion coefficients
(TEC) of the layers are
TEC.sub.layer3<TEC.sub.layer1.ltoreq.TEC.sub.layer2.
[0213] Layer 1: The suspension comprises
Zr.sub.0.82Y.sub.0.18O.sub.2-.delta.. 15 vol % graphite is used as
pore former. The sintered thickness is about 30 .mu.m. The sintered
porosity of the layer is about 50% with a pore size in the range of
2-5 .mu.m.
[0214] Layer 2: The suspension is based on
Zr.sub.0.84Y.sub.0.16O.sub.2-.delta.. 10 vol % graphite is used as
a pore-former. The sintered thickness of the foil is about 25
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of 1-3 .mu.m.
[0215] Layer 3: The suspension is based on
Zr.sub.0.80Y.sub.0.20O.sub.2-.delta. powder. The sintered thickness
of the foil is about 50 .mu.m. The sintered density of the layer is
>96% of the theoretical density.
[0216] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (sandwiched between two electrode precursor layers on each
side in the order Layer 1-Layer 2-Layer 3-Layer 2-Layer 1. This
layer structure corresponds to layers 4 to 8 as shown in FIG. 2.
The lamination is performed by the use of heated rolls in a double
roll set-up and takes place in one pass.
[0217] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching of samples with an area of
about 600 cm.sup.2.
[0218] The cell is completed as described in Example 13. The
obtained cell is about 160 .mu.m thick and ready to be built into a
stack of cells. No heat treatment prior to stacking is
required.
Example 19
Manufacture of a Thin SOC Having Multi Layer Electrolyte
[0219] The first step comprises tape-casting of three layers; one
zirconia containing electrode precursor layer (layer 1) and two
electrolyte layers (layers 2 and 3). Suspensions for tape-casting
are manufactured by means of ball milling of powders with polyvinyl
pyrrolidone (PVP), polyvinyl butyral (PVB) and EtOH+MEK as
additives. After control of particle size, the suspensions are
tape-cast using a double doctor blade set-up and the tapes are
subsequently dried. The relative thermal expansion coefficients
(TEC) of the layers are
TEC.sub.layer3<TEC.sub.layer1.ltoreq.TEC.sub.layer2.
[0220] Layer 1: Electrode precursor layer. The suspension is based
on Zr.sub.0.82Y.sub.0.18O.sub.2-.delta.. 10 vol % graphite is used
as a pore-former. The sintered thickness of the foil is about 50
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of 1-3 .mu.m.
[0221] Layer 2: Electrolyte layer. The suspension is based on
Zr.sub.0.84Y.sub.0.16O.sub.2-.delta.. The sintered thickness of the
foil is about 10 .mu.m. The sintered porosity of the layer is about
96%.
[0222] Layer 3: Electrolyte layer. The suspension is based on
Zr.sub.0.80Y.sub.0.20O.sub.2-.delta. powder. The sintered thickness
of the foil is about 5 .mu.m. The sintered density of the layer is
>96% of the theoretical density.
[0223] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising an electrolyte
layer (sandwiched between electrode precursor layers on each side
in the order Layer 1-Layer 2-Layer 3-Layer 2-Layer 1. The
lamination is performed by warm pressing at 120.degree. C.
[0224] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching of samples with an area of
about 600 cm.sup.2.
[0225] The fourth step comprises sintering. The laminate is heated
at an increase of the temperature of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0226] The fifth step is the impregnation of the cathode on the
side with the electrolyte layer (layer 3). The sintered cell is
masked on one side. A nitrate solution of La, Sr, Co and Fe is
infiltrated into the porous structure. The infiltration is
performed six times with an intermediate heating step for
decomposition of the nitrates. The resulting composition of the
impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0227] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Ce and Gd is
infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 40 vol %
Ni and 60 vol % (Ce.sub.0.9Gd.sub.0.1)O.sub.2-.delta. (after
reduction of NiO).
[0228] The so formed cell has a thickness of about 125 .mu.m thick
and ready to be built into a stack of cells. No heat treatment
prior to stacking is required.
Example 20
Manufacture of a SOC Having a Multilayer Electrolyte
[0229] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0230] Layer 1: The suspension comprises
Zr.sub.0.76Sc.sub.0.2Y.sub.0.03O.sub.2-.delta.. The sintered
thickness is about 30 .mu.m. The sintered porosity of the layer is
about 30% with a pore size in the range of 1-2 .mu.m.
[0231] Layer 2: The suspension is based on
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. powder. The sintered
thickness of the foil is about 15 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0232] The second step comprises the lamination of the above
mentioned foils into a layered structure comprising two electrolyte
layers (9, 10) sandwiched between two electrode precursor layers
(11, 12), as shown in FIG. 3. The lamination is performed by the
use of heated rolls in a double roll set-up and takes place in one
pass.
[0233] In the third step, the laminated tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 12.times.12 to 30.times.30 cm.sup.2.
[0234] The fourth step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0235] The fifth step is the impregnation of a cathode barrier
layer. After sintering a nitrate solution of gadolinium doped ceria
(Gd.sub.0.1Ce.sub.0.9)O.sub.2-.delta. (barrier material) is
impregnated into the cathode precursor layer two times. After
impregnation the sample is heat treated for 1 hour at 400.degree.
C.
[0236] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A nitrate
solution of La, Sr, Co and Fe is infiltrated into the porous
structure. The infiltration is performed five times with an
intermediate heating step for decomposition of the nitrates. The
resulting composition of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0237] In the seventh step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A nitrate solution of
Cu, Ni, Ce and Gd is infiltrated into the porous structure. The
infiltration is performed six times with an intermediate heating
schedule between each infiltration for decomposition of the
impregnated nitrates. The resulting composition of the impregnated
anode part is 4 vol % Cu, 38 vol % Ni and 58 vol %
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. (after reduction of
NiO).
[0238] The obtained cell is about 90 .mu.m thick and ready to be
built into a stack of cells. No heat treatment prior to stacking is
required.
Example 21
Manufacture of a SOC with a Patterned Profiled Structure
[0239] Steps one and two are carried out as described in Example
13.
[0240] In the third step, the laminated tapes are cut into pieces.
This is done by knife punching resulting in sintered areas in the
range up to 40.times.40 cm.sup.2.
[0241] In the fourth step the laminated structures are given an egg
tray pattern profiled structure by pressing, electrolyte layer (13)
and two electrode precursor layers (14,15), as shown in FIG. 4.
[0242] The fifth step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1200.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0243] The sixth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A nitrate
solution of La, Sr, Co and Fe is infiltrated into the porous
structure. The infiltration is performed six times with an
intermediate heating step for decomposition of the nitrates. The
resulting composition of the impregnated perovskite cathode is:
(La.sub.0.6Sr.sub.0.4).sub.0.97(Co.sub.0.2Fe.sub.0.8)O.sub.3-.delta..
[0244] In the seventh step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A nitrate solution of
Ni, Ce and Gd is infiltrated into the porous structure. The
infiltration is performed seven times with an intermediate heating
schedule between each infiltration for decomposition of the
impregnated nitrates. The resulting composition of the impregnated
anode part is 50 vol % Ni and 50 vol %
Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. (after reduction of
NiO).
[0245] The obtained cell is ready to be built into a stack of
cells. No heat treatment prior to stacking is required.
Example 22
Manufacture of a SOC
[0246] The first step comprises tape-casting of two layers (layer
1--electrode precursor layer, and layer 2--electrolyte layer).
Suspensions for tape-casting are manufactured by means of ball
milling of powders with polyvinyl pyrrolidone (PVP), polyvinyl
butyral (PVB) and EtOH+MEK as additives. After control of particle
size, the suspensions are tape-cast using a double doctor blade
set-up and the tapes are subsequently dried.
[0247] Layer 1: The suspension comprises pre-calcined YSZ and 10
vol % charcoal as a pore-former. The sintered thickness is about 20
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of about 2 .mu.m.
[0248] Layer 2: The suspension is based on YSZ powder. The sintered
thickness of the foil is about 75 .mu.m. The sintered density of
the layer is >96% of the theoretical density.
[0249] Step two to four are carried out as described in Example
13.
[0250] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.0.05O.sub.3-.delta.
and Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. (2:1 volume
ratio) is vacuum infiltrated into the porous structure. The
infiltration is performed four times with an intermediate heating
step.
[0251] In the sixth step the anode is impregnated. The cathode
impregnated side is masked by a rubber seal. A colloidal suspension
of NiO and Ce.sub.0.9Gd.sub.0.1O.sub.2 is vacuum infiltrated into
the porous structure. The infiltration is performed five times with
an intermediate drying between each infiltration. The volume ratio
of NiO:CGO is 1:2.
[0252] The obtained membrane is about 100 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
Example 23
Manufacture of a SOC
[0253] The first step comprises co-casting of a three-layered
structure (layer 1 and 3--electrode precursor layer, and layer
2--electrolyte layer) with intermediate drying after tape-casting
of each layer. Suspensions for tape-casting are manufactured by
means of ball milling of powders with polyvinyl pyrrolidone (PVP),
polyvinyl butyral (PVB) and EtOH+MEK as additives. After control of
particle size, the suspensions are tape-cast using a double doctor
blade set-up as described below and the cast is subsequently
dried.
[0254] Suspension 1, Layers 1 and 3: The suspension comprises
pre-calcined Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. and 10
vol % charcoal as a pore-former. The sintered thickness is about 40
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of about 2 .mu.m.
[0255] Suspension 2, Layer 2: The suspension is based on doped
zirconia. The sintered thickness of the foil is about 100 .mu.m.
The sintered density of the layer is >96% of the theoretical
density.
[0256] Layer 1 is tape-cast onto a polymeric foil. After drying,
Layer 2 is tape-cast directly onto Layer 1, and after a subsequent
drying Layer 3 (Suspension 1) is tape-cast directly onto the two
layered structure comprising Layer 1 og Layer 2.
[0257] In the second step, the co-cast tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 200-500 cm.sup.2.
[0258] The third step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1150.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0259] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta.
and Zr.sub.0.78Sc.sub.0.2Y.sub.0.02O.sub.2-.delta. (3:1 volume
ratio) is vacuum infiltrated into the porous structure. The
infiltration is performed four times with an intermediate heating
step.
[0260] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A nitrate solution of Ni, Zr and Y is
vacuum infiltrated into the porous structure. The infiltration is
performed five times with an intermediate heating schedule between
each infiltration for decomposition of the impregnated nitrates.
The resulting composition of the impregnated anode part is 50 vol %
Ni and 50 vol % Zr.sub.0.84Y.sub.0.16O.sub.2-.delta. (after
reduction of NiO).
[0261] The obtained membrane is about 180 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
Example 24
Manufacture of a SOC
[0262] The first step comprises co-casting of a three-layered
structure (layer 1 and 3--electrode precursor layer, and layer
2--electrolyte layer) without intermediate drying. Suspensions for
tape-casting are manufactured by means of ball milling of powders
with polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB) and
EtOH+MEK as additives. After control of particle size, the
suspensions are tape-cast using a double doctor blade set-up as
described below and the cast is subsequently dried.
[0263] Suspension 1, Layers 1 and 3: The suspension comprises
pre-calcined Zr.sub.0.80Y.sub.0.20O.sub.2-.delta. and 10 vol %
charcoal as a pore-former. The sintered thickness is about 50
.mu.m. The sintered porosity of the layer is about 50% with a pore
size in the range of about 2 .mu.m.
[0264] Suspension 2, Layer 2: The suspension is based on
Zr.sub.0.80Y.sub.0.20O.sub.2-.delta.. The sintered thickness of the
foil is about 200 .mu.m. The sintered density of the layer is
>96% of the theoretical density.
[0265] Three doctor blade set-ups are place in series on a
polymeric film and the three layers are tape-cast directly onto one
another. Layer 1 (Suspension 1) Layer 2 (Suspension 2) and Layer 3
(Suspension 1).
[0266] In the second step, the co-cast tapes are cut into square
pieces. This is done by knife punching resulting in sintered areas
in the range of 200-500 cm.sup.2.
[0267] The third step comprises sintering. The laminate is heated
at a temperature increase of about 50.degree. C./h to about
500.degree. C. in a flowing air atmosphere. After 2 hours of
soaking, the furnace is heated to about 1150.degree. C. with a
temperature increase of 100.degree. C./h and left for 5 hours
before cooling to room temperature.
[0268] The fifth step is the impregnation of the cathode. The
sintered cell is masked on one side by a rubber seal. A colloidal
suspension of (La.sub.0.75Sr.sub.0.25)Mn.sub.1.05O.sub.3-.delta.
and Zr.sub.0.80Y.sub.0.02O.sub.2-.delta. (2:1 volume ratio) is
vacuum infiltrated into the porous structure. The infiltration is
performed four times with an intermediate heating step.
[0269] In the sixth step the anode is impregnated. The cathode
impregnated side is masked. A colloidal suspension of NiO and
Zr.sub.0.80Y.sub.0.20O.sub.2-.delta. is vacuum infiltrated into the
porous structure. The infiltration is performed four times with an
intermediate drying between each infiltration. The resulting
composition of the impregnated anode part is 50 vol % Ni and 50 vol
% Zr.sub.0.80Y.sub.0.20O.sub.2-.delta. (after reduction of
NiO).
[0270] The obtained membrane is about 300 .mu.m thick and ready to
be built into a stack of cells. No heat treatment prior to stacking
is required.
* * * * *