U.S. patent application number 16/495231 was filed with the patent office on 2020-01-09 for manufacturing method for electrochemical element and electrochemical element.
The applicant listed for this patent is Osaka Gas Co., Ltd.. Invention is credited to Mitsuaki Echigo, Kyohei Manabe, Kazuyuki Minami, Hisao Ohnishi, Yuji Tsuda.
Application Number | 20200014051 16/495231 |
Document ID | / |
Family ID | 63584465 |
Filed Date | 2020-01-09 |
United States Patent
Application |
20200014051 |
Kind Code |
A1 |
Echigo; Mitsuaki ; et
al. |
January 9, 2020 |
Manufacturing Method for Electrochemical Element and
Electrochemical Element
Abstract
Provided is a low-cost electrochemical element that has
excellent performance, reliability, and durability. Also, provided
is a manufacturing method for an electrochemical element including
a metal substrate (metal support) and an electrode layer formed
on/over the metal substrate. The method includes an electrode layer
forming step of forming an electrode layer having a region with a
surface roughness of 1.0 .mu.m or less on/over the metal substrate,
and an electrolyte layer forming step of forming an electrolyte
layer by spraying aerosolized metal oxide powder onto the electrode
layer.
Inventors: |
Echigo; Mitsuaki;
(Osaka-shi, JP) ; Ohnishi; Hisao; (Osaka-shi,
JP) ; Tsuda; Yuji; (Osaka-shi, JP) ; Manabe;
Kyohei; (Osaka-shi, JP) ; Minami; Kazuyuki;
(Osaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Osaka Gas Co., Ltd. |
Osaka-shi |
|
JP |
|
|
Family ID: |
63584465 |
Appl. No.: |
16/495231 |
Filed: |
March 22, 2018 |
PCT Filed: |
March 22, 2018 |
PCT NO: |
PCT/JP2018/011442 |
371 Date: |
September 18, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/8807 20130101;
Y02E 60/10 20130101; H01M 8/1253 20130101; H01M 8/1246 20130101;
H01M 2300/0077 20130101; Y02E 60/50 20130101; H01M 2300/0074
20130101; H01M 2004/021 20130101; H01M 8/1286 20130101; H01M
2008/1293 20130101; Y02P 70/50 20151101 |
International
Class: |
H01M 8/1246 20060101
H01M008/1246 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2017 |
JP |
2017-056732 |
Claims
1. A manufacturing method for an electrochemical element including
a metal support and an electrode layer formed on/over the metal
support, the method comprising: an electrode layer forming step of
forming an electrode layer having a region with a surface roughness
(Ra) of 1.0 .mu.m or less on the metal support; and an electrolyte
layer forming step of forming an electrolyte layer by spraying
aerosolized metal oxide powder onto the electrode layer.
2. A manufacturing method for an electrochemical element including
a metal support, an electrode layer formed on/over the metal
support, and an intermediate layer formed on/over the electrode
layer, the method comprising: an intermediate layer forming step of
forming an intermediate layer having a region with a surface
roughness (Ra) of 1.0 .mu.m or less on the electrode layer; and an
electrolyte layer forming step of forming an electrolyte layer by
spraying aerosolized metal oxide powder onto the intermediate
layer.
3. The manufacturing method for an electrochemical element
according to claim 2, wherein the electrolyte layer contains
stabilized zirconia.
4. An electrochemical element provided with a dense electrolyte
layer formed by spraying aerosolized metal oxide powder onto an
electrode layer that is formed on/over a metal support and has a
region with a surface roughness (Ra) of 1.0 .mu.m or less.
5. An electrochemical element provided with a dense electrolyte
layer formed by spraying aerosolized metal oxide powder onto an
intermediate layer that is formed on/over an electrode layer
on/over a metal support and has a region with a surface roughness
(Ra) of 1.0 .mu.m or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to a manufacturing method for
an electrochemical element, and an electrochemical element.
BACKGROUND ART
[0002] A conventional metal-supported solid oxide fuel cell (SOFC)
is obtained by forming an anode electrode layer on/over a porous
metal support obtained by sintering Fe--Cr based alloy powder, and
forming an electrolyte layer on/over the anode electrode layer.
PRIOR ART DOCUMENTS
Non-Patent Document
[0003] Non-Patent Document 1: Jong-Jin Choi and Dong-Soo Park,
"Preparation of Metal-supported SOFC using Low Temperature Ceramic
Coating Process", Proceedings of 11th European SOFC & SOE
Forum, A1502, Chapter 09--Session B15--14/117-20/117 (1-4 Jul.
2014)
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0004] However, as disclosed in Non-Patent Document 1, it is
necessary to prepare an anode electrode layer subjected to heating
treatment at a high temperature of 1300.degree. C. in order to form
a zirconia-based electrolyte in a low temperature range.
Accordingly, damage to the metal support is unavoidable, and it is
necessary to provide, through heating treatment at 1200.degree. C.,
an expensive LST (LaSrTiO.sub.3) diffusion preventing layer for
preventing elements that poison a cell from diffusing from the
metal support, and this poses problems of reliability, durability,
and cost.
[0005] The present invention was achieved in light of the foregoing
problems, and an object of the present invention is to provide a
low-cost electrochemical element that has excellent performance,
reliability, and durability.
Means for Solving Problem
[0006] A characteristic configuration of a manufacturing method for
an electrochemical element for achieving the object is a
manufacturing method for an electrochemical element including a
metal support and an electrode layer formed on/over the metal
support, the method including an electrode layer forming step of
forming an electrode layer having a region with a surface roughness
(Ra) of 1.0 .mu.m or less on/over the metal support, and an
electrolyte layer forming step of forming an electrolyte layer by
spraying aerosolized metal oxide powder onto the electrode
layer.
[0007] With the above-mentioned characteristic configuration, the
electrode layer is suitable for an electrolyte layer formation
process performed in a low temperature range, thus making it
possible to form an electrochemical element including an electrode
layer and an electrolyte layer on/over a metal support without
providing an expensive LST diffusion preventing layer. It is also
possible to manufacture an electrochemical element that has
excellent reliability and durability as well as high adhesion
strength between the electrode layer and the electrolyte layer.
[0008] A characteristic configuration of a manufacturing method for
an electrochemical element for achieving the object is a
manufacturing method for an electrochemical element including a
metal support, an electrode layer formed on/over the metal support,
and an intermediate layer formed on/over the electrode layer, the
method including an intermediate layer forming step of forming an
intermediate layer having a region with a surface roughness (Ra) of
1.0 .mu.m or less on/over the electrode layer, and an electrolyte
layer forming step of forming an electrolyte layer by spraying
aerosolized metal oxide powder onto the intermediate layer.
[0009] With the above-mentioned characteristic configuration, the
intermediate layer is suitable for an electrolyte layer formation
process performed in a low temperature range, thus making it
possible to form an electrochemical element including an electrode
layer, an intermediate layer, and an electrolyte layer on/over a
metal support without providing an expensive LST diffusion
preventing layer. It is also possible to manufacture an
electrochemical element that has excellent reliability and
durability as well as high adhesion strength between the
intermediate layer and the electrolyte layer.
[0010] In another characteristic configuration of the
electrochemical element according to the present invention, the
electrolyte layer contains stabilized zirconia.
[0011] With the above-mentioned characteristic configuration, the
electrolyte layer contains stabilized zirconia, thus making it
possible to realize an electrochemical element having excellent
performance that can be used in a high temperature range of about
650.degree. C. or higher, for example.
[0012] In a characteristic configuration of an electrochemical
element according to the present invention, a dense electrolyte
layer is formed by spraying aerosolized metal oxide powder onto an
electrode layer that is formed on/over a metal support and has a
region with a surface roughness (Ra) of 1.0 .mu.m or less.
[0013] With the above-mentioned characteristic configuration, the
electrode layer is suitable for an electrolyte layer formation
process performed in a low temperature range, thus making it
possible to form an electrochemical element including an electrode
layer and an electrolyte layer on/over a metal support without
providing an expensive LST diffusion preventing layer. It is also
possible to configure an electrochemical element that has excellent
reliability and durability as well as high adhesion strength
between the electrode layer and the electrolyte layer.
[0014] In a characteristic configuration of an electrochemical
element according to the present invention, a dense electrolyte
layer is formed by spraying aerosolized metal oxide powder onto an
intermediate layer that is formed on/over an electrode layer
on/over a metal support and has a region with a surface roughness
(Ra) of 1.0 .mu.m or less.
[0015] With the above-mentioned characteristic configuration, the
intermediate layer is suitable for an electrolyte layer formation
process performed in a low temperature range, thus making it
possible to form an electrochemical element including an electrode
layer, an intermediate layer, and an electrolyte layer on/over a
metal support without providing an expensive LST diffusion
preventing layer. It is also possible to configure an
electrochemical element that has excellent reliability and
durability as well as high adhesion strength between the
intermediate layer and the electrolyte layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram showing a configuration of an
electrochemical element.
[0017] FIG. 2 is an electron micrograph of a cross section of the
electrochemical element.
BEST MODES FOR CARRYING OUT THE INVENTION
First Embodiment
[0018] Hereinafter, an electrochemical element E and a solid oxide
fuel cell (SOFC) according to this embodiment will be described
with reference to FIG. 1. The electrochemical element E is used as
a constituent element of a solid oxide fuel cell that receives a
supply of air and fuel gas containing hydrogen and generates power,
for example. It should be noted that when the positional
relationship between layers and the like are described in the
description below, a counter electrode layer 6 side may be referred
to as "upper portion" or "upper side", and an electrode layer 2
side may be referred to as "lower portion" or "lower side", with
respect to an electrolyte layer 4, for example. In addition, in a
metal substrate 1, a surface on/over which the electrode layer 2 is
formed may be referred to as "front side", and a surface on/over an
opposite side may be referred to as "back side".
[0019] Electrochemical Element
[0020] As shown in FIG. 1, the electrochemical element E includes a
metal substrate 1 (metal support), an electrode layer 2 formed
on/over the metal substrate 1, an intermediate layer 3 formed
on/over the electrode layer 2, and an electrolyte layer 4 formed
on/over the intermediate layer 3. The electrochemical element E
further includes a reaction preventing layer 5 formed on/over the
electrolyte layer 4, and a counter electrode layer 6 formed on/over
the reaction preventing layer 5. Specifically, the counter
electrode layer 6 is formed above the electrolyte layer 4, and the
reaction preventing layer 5 is formed between the electrolyte layer
4 and the counter electrode layer 6. The electrode layer 2 is
porous, and the electrolyte layer 4 is dense.
[0021] Metal Substrate
[0022] The metal substrate 1 plays a role as a support that
supports the electrode layer 2, the intermediate layer 3, the
electrolyte layer 4, and the like and maintains the strength of the
electrochemical element E. A material that has excellent electron
conductivity, thermal resistance, oxidation resistance, and
corrosion resistance is used as the material for forming the metal
substrate 1. Examples thereof include ferrite-based stainless
steel, austenite-based stainless steel, and nickel-based alloys. In
particular, alloys containing chromium are favorably used. It
should be noted that although a plate-shaped metal substrate 1 is
used as the metal support in this embodiment, a metal support
having another shape such as a box shape or cylindrical shape can
also be used.
[0023] It should be noted that the metal substrate 1 need only have
a strength sufficient for serving as the support for forming the
electrochemical element, and can have a thickness of approximately
0.1 mm to 2 mm, preferably approximately 0.1 mm to 1 mm, and more
preferably approximately 0.1 mm to 0.5 mm, for example.
[0024] The metal substrate 1 is provided with a plurality of
through holes 1a that penetrate the surface on the front side and
the surface on the back side. It should be noted that the through
holes 1a can be provided in the metal substrate 1 through
mechanical, chemical, or optical piercing processing, for example.
The through holes 1a have a function of transmitting gas from the
surface on the back side of the metal substrate 1 to the surface on
the front side thereof. Porous metal can also be used to impart gas
permeability to the metal substrate 1. A metal sintered body, a
metal foam, or the like can also be used as the metal substrate 1,
for example.
[0025] A metal oxide thin layer 1b serving as a diffusion
suppressing layer is provided on/over the surfaces of the metal
substrate 1. That is, the diffusion suppressing layer is formed
between the metal substrate 1 and the electrode layer 2, which will
be described later. The metal oxide thin layer 1b is provided not
only on/over the surface of the metal substrate 1 exposed to the
outside but also the surface (interface) that is in contact with
the electrode layer 2 and the inner surfaces of the through holes
1a. Element interdiffusion that occurs between the metal substrate
1 and the electrode layer 2 can be suppressed due to this metal
oxide thin layer 1b. For example, when ferrite-based stainless
steel containing chromium is used in the metal substrate 1, the
metal oxide thin layer 1b is mainly made of a chromium oxide. The
metal oxide thin layer 1b containing the chromium oxide as the main
component suppresses diffusion of chromium atoms and the like of
the metal substrate 1 to the electrode layer 2 and the electrolyte
layer 4. The metal oxide thin layer 1b need only have such a
thickness that allows both high diffusion preventing performance
and low electric resistance to be achieved. For example, it is
preferable that the thickness is on the order of submicrons, and
specifically, it is more preferable that the average thickness is
approximately 0.3 .mu.m or more and 0.7 .mu.m or less. It is more
preferable that the minimum thickness is about 0.1 .mu.m or
more.
[0026] Also, it is preferable that the maximum thickness is about
1.1 .mu.m or less.
[0027] The metal oxide thin layer 1b can be formed using various
techniques, but it is favorable to use a technique of oxidizing the
surface of the metal substrate 1 to obtain a metal oxide. Also, the
metal oxide thin layer 1b may be formed on/over the surface of the
metal substrate 1 by using a PVD technique such as a sputtering
technique or PLD technique, a CVD technique, or a spray coating
technique (a technique such as thermal spraying technique, an
aerosol deposition technique, an aerosol gas deposition technique,
a powder jet deposition technique, a particle jet deposition
technique, or a cold spraying technique), or may be formed by
plating and oxidation treatment. Furthermore, the metal oxide thin
layer 1b may also contain a spinel phase that has high electron
conductivity, or the like.
[0028] When a ferrite-based stainless steel material is used to
form the metal substrate 1, its thermal expansion coefficient is
close to that of YSZ (yttria-stabilized zirconia), GDC
(gadolinium-doped ceria; also called CGO), or the like, which is
used as the material for forming the electrode layer 2 and the
electrolyte layer 4. Accordingly, even if low and high temperature
cycling is repeated, the electrochemical element E is not likely to
be damaged. Therefore, this is preferable due to being able to
realize an electrochemical element E that has excellent long-term
durability.
[0029] Electrode Layer
[0030] As shown in FIG. 1, the electrode layer 2 can be provided as
a thin layer in a region that is larger than the region provided
with the through holes 1a, on/over the front surface of the metal
substrate 1. When it is provided as a thin layer, the thickness can
be set to approximately 1 .mu.m to 100 .mu.m, and preferably 5
.mu.m to 50 .mu.m, for example. This thickness makes it possible to
ensure sufficient electrode performance while also achieving cost
reduction by reducing the used amount of expensive electrode layer
material. The region provided with the through holes 1a is entirely
covered with the electrode layer 2. That is, the through holes 1a
are formed inside the region of the metal substrate 1 in which the
electrode layer 2 is formed. In other words, all the through holes
1a are provided facing the electrode layer 2.
[0031] A composite material such as NiO-GDC, Ni-GDC, NiO--YSZ,
Ni--YSZ, CuO--CeO.sub.2, or Cu--CeO.sub.2 can be used as the
material for forming the electrode layer 2, for example. In these
examples, GDC, YSZ, and CeO.sub.2 can be called the aggregate of
the composite material. It should be noted that it is preferable to
form the electrode layer 2 using low-temperature heating (not
performing heating treatment in a high temperature range of higher
than 1100.degree. C., but rather performing a wet process using
heating treatment in a low temperature range, for example), a spray
coating technique (a technique such as a thermal spraying
technique, an aerosol deposition technique, an aerosol gas
deposition technique, a powder jet deposition technique, a particle
jet deposition technique, or a cold spraying technique), a PVD
technique (e.g., a sputtering technique or a pulse laser deposition
technique), a CVD technique, or the like. Due to these processes
that can be used in a low temperature range, a favorable electrode
layer 2 is obtained without using heating in a high temperature
range of higher than 1100.degree. C., for example. Therefore, this
is preferable due to being able to prevent damage to the metal
substrate 1, suppress element interdiffusion between the metal
substrate 1 and the electrode layer 2, and realize an
electrochemical element that has excellent durability. Furthermore,
using low-temperature heating makes it possible to facilitate
handling of raw materials and is thus more preferable.
[0032] The inside and the surface of the electrode layer 2 are
provided with a plurality of pores in order to impart gas
permeability to the electrode layer 2.
[0033] That is, the electrode layer 2 is formed as a porous layer.
The electrode layer 2 is formed to have a denseness of 30% or more
and less than 80%, for example. Regarding the size of the pores, a
size suitable for smooth progress of an electrochemical reaction
can be selected as appropriate. It should be noted that the
"denseness" is a ratio of the material of the layer to the space
and can be represented by a formula "1-porosity", and is equivalent
to relative density.
[0034] Intermediate Layer
[0035] As shown in FIG. 1, the intermediate layer 3 can be formed
as a thin layer on/over the electrode layer 2 so as to cover the
electrode layer 2. When it is formed as a thin layer, the thickness
can be set to approximately 1 .mu.m to 100 .mu.m, preferably
approximately 2 .mu.m to 50 .mu.m, and more preferably
approximately 4 .mu.m to 25 .mu.m, for example. This thickness
makes it possible to ensure sufficient performance while also
achieving cost reduction by reducing the used amount of expensive
intermediate layer material. YSZ (yttria-stabilized zirconia), SSZ
(scandium-stabilized zirconia), GDC (gadolinium-doped ceria), YDC
(yttrium-doped ceria), SDC (samarium-doped ceria), or the like can
be used as the material for forming the intermediate layer 3. In
particular, ceria-based ceramics are favorably used.
[0036] It is preferable to form the intermediate layer 3 using
low-temperature heating (not performing heating treatment in a high
temperature range of higher than 1100.degree. C., but rather
performing a wet process using heating treatment in a low
temperature range, for example), a spray coating technique (a
technique such as a thermal spraying technique, an aerosol
deposition technique, an aerosol gas deposition technique, a powder
jet deposition technique, a particle jet deposition technique, or a
cold spraying technique), a PVD technique (e.g., a sputtering
technique or a pulse laser deposition technique), a CVD technique,
or the like. Due to these film formation processes that can be used
in a low temperature range, an intermediate layer 3 is obtained
without using heating in a high temperature range of higher than
1100.degree. C., for example. Therefore, it is possible to prevent
damage to the metal substrate 1, suppress element interdiffusion
between the metal substrate 1 and the electrode layer 2, and
realize an electrochemical element E that has excellent durability.
Furthermore, using low-temperature heating makes it possible to
facilitate handling of raw materials and is thus more
preferable.
[0037] It is preferable that the intermediate layer 3 has oxygen
ion (oxide ion) conductivity. It is more preferable that the
intermediate layer 3 has both oxygen ion (oxide ion) conductivity
and electron conductivity, namely mixed conductivity. The
intermediate layer 3 that has these properties is suitable for
application to the electrochemical element E.
[0038] Surface Roughness (Ra) of Intermediate Layer
[0039] In this embodiment, the intermediate layer 3 has a region
with a surface roughness (Ra) of 1.0 .mu.m or less. This region may
correspond to all or a part of the surface of the intermediate
layer 3. An electrochemical element E that has excellent
reliability and durability as well as high adhesion strength
between the intermediate layer 3 and the electrolyte layer 4 can be
configured due to the intermediate layer 3 having a region with a
surface roughness (Ra) of 1.0 .mu.m or less. It should be noted
that the intermediate layer 3 more preferably has a region with a
surface roughness (Ra) of 0.5 .mu.m or less, and even more
preferably 0.3 .mu.m or less. The reason for this is that an
electrochemical element E that has excellent reliability and
durability as well as higher adhesion strength between the
intermediate layer 3 and the electrolyte layer 4 can be configured
if the intermediate layer 3 is smoother in terms of the surface
roughness.
[0040] Electrolyte Layer
[0041] As shown in FIG. 1, the electrolyte layer 4 is formed as a
thin layer on/over the intermediate layer 3 so as to cover the
electrode layer 2 and the intermediate layer 3. Specifically, as
shown in FIG. 1, the electrolyte layer 4 is provided on/over both
the intermediate layer 3 and the metal substrate 1 (spanning the
intermediate layer 3 and the metal substrate 1). Configuring the
electrolyte layer 4 in this manner and joining the electrolyte
layer 4 to the metal substrate 1 make it possible to allow the
electrochemical element to have excellent toughness as a whole.
[0042] Also, as shown in FIG. 1, the electrolyte layer 4 is
provided in a region that is larger than the region provided with
the through holes 1a, on/over the front surface of the metal
substrate 1. That is, the through holes 1a are formed inside the
region of the metal substrate 1 in which the electrolyte layer 4 is
formed.
[0043] The leakage of gas from the electrode layer 2 and the
intermediate layer 3 can be suppressed in the vicinity of the
electrolyte layer 4. A description of this will be given. When the
electrochemical element E is used as a constituent element of a
SOFC, gas is supplied from the back side of the metal substrate 1
through the through holes 1a to the electrode layer 2 during the
operation of the SOFC. In a region where the electrolyte layer 4 is
in contact with the metal substrate 1, leakage of gas can be
suppressed without providing another member such as a gasket. It
should be noted that although the entire vicinity of the electrode
layer 2 is covered with the electrolyte layer 4 in this embodiment,
a configuration in which the electrolyte layer 4 is provided
on/over the electrode layer 2 and the intermediate layer 3 and a
gasket or the like is provided in its vicinity may also be
adopted.
[0044] YSZ (yttria-stabilized zirconia), SSZ (scandium-stabilized
zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria),
SDC (samarium-doped ceria), LSGM (strontium- and magnesium-doped
lanthanum gallate), or the like can be used as the material for
forming the electrolyte layer 4. In particular, zirconia-based
ceramics are favorably used. Using zirconia-based ceramics for the
electrolyte layer 4 makes it possible to increase the operation
temperature of the SOFC in which the electrochemical element E is
used compared with the case where ceria-based ceramics are used.
For example, when the electrochemical element E is used in the
SOFC, by adopting a system configuration in which a material such
as YSZ that can exhibit high electrolyte performance even in a high
temperature range of approximately 650.degree. C. or higher is used
as the material for forming the electrolyte layer 4, a
hydrocarbon-based raw fuel material such as city gas or LPG is used
as the raw fuel for the system, and the raw fuel material is
reformed into anode gas of the SOFC through steam reforming or the
like, it is thus possible to construct a high-efficiency SOFC
system in which heat generated in a cell stack of the SOFC is used
to reform raw fuel gas.
[0045] It is preferable to form the electrolyte layer 4 using an
aerosol deposition technique. Due to such a film formation process
that can be used in a low temperature range, an electrolyte layer 4
that is dense and has high gas-tightness and gas barrier properties
is obtained without using heating in a high temperature range of
higher than 1100.degree. C., for example. Therefore, it is possible
to prevent damage to the metal substrate 1, suppress element
interdiffusion between the metal substrate 1 and the electrode
layer 2, and realize an electrochemical element E that has
excellent performance and durability.
[0046] The electrolyte layer 4 is given a dense configuration in
order to block gas leakage of anode gas and cathode gas and exhibit
high ion conductivity. The electrolyte layer 4 preferably has a
denseness of 90% or more, more preferably 95% or more, and even
more preferably 98% or more. When the electrolyte layer 4 is formed
as a uniform layer, the denseness is preferably 95% or more, and
more preferably 98% or more. When the electrolyte layer 4 has a
multilayer configuration, at least a portion thereof preferably
includes a layer (dense electrolyte layer) having a denseness of
98% or more, and more preferably a layer (dense electrolyte layer)
having a denseness of 99% or more. The reason for this is that an
electrolyte layer that is dense and has high gas-tightness and gas
barrier properties can be easily formed due to such a dense
electrolyte layer being included as a portion of the electrolyte
layer even when the electrolyte layer has a multilayer
configuration.
[0047] Reaction Preventing Layer
[0048] The reaction preventing layer 5 can be formed as a thin
layer on/over the electrolyte layer 4. When it is formed as a thin
layer, the thickness can be set to approximately 1 .mu.m to 100
.mu.m, preferably approximately 2 .mu.m to 50 .mu.m, and more
preferably approximately 4 .mu.m to 25 .mu.m, for example. This
thickness makes it possible to ensure sufficient performance while
also achieving cost reduction by reducing the used amount of
expensive reaction preventing layer material. The material for
forming the reaction preventing layer 5 need only be capable of
preventing reactions between the component of the electrolyte layer
4 and the component of the counter electrode layer 6. For example,
a ceria-based material or the like is used. Introducing the
reaction preventing layer 5 between the electrolyte layer 4 and the
counter electrode layer 6 effectively suppresses reactions between
the material constituting the counter electrode layer 6 and the
material constituting the electrolyte layer 4 and makes it possible
to improve long-term stability in the performance of the
electrochemical element E. Forming the reaction preventing layer 5
using, as appropriate, a method through which the reaction
preventing layer 5 can be formed at a treatment temperature of
1100.degree. C. or lower makes it possible to suppress damage to
the metal substrate 1, suppress element interdiffusion between the
metal substrate 1 and the electrode layer 2, and realize an
electrochemical element E that has excellent performance and
durability, and is thus preferable. For example, the reaction
preventing layer 5 can be formed using, as appropriate,
low-temperature heating (not performing heating treatment in a high
temperature range of higher than 1100.degree. C., but rather
performing a wet process using heating treatment in a low
temperature range, for example), a spray coating technique (a
technique such as a thermal spraying technique, an aerosol
deposition technique, an aerosol gas deposition technique, a powder
jet deposition technique, a particle jet deposition technique, or a
cold spraying technique), a PVD technique (e.g., a sputtering
technique or a pulse laser deposition technique), a CVD technique,
or the like. In particular, using low-temperature heating, an
aerosol deposition technique, or the like makes it possible to
realize a low-cost element and is thus preferable. Furthermore,
using low-temperature heating makes it possible to facilitate
handling of raw materials and is thus more preferable.
[0049] Counter Electrode Layer
[0050] The counter electrode layer 6 can be formed as a thin layer
on/over the electrolyte layer 4 or the reaction preventing layer 5.
When it is formed as a thin layer, the thickness can be set to
approximately 1 .mu.m to 100 .mu.m, and preferably approximately 5
.mu.m to 50 .mu.m, for example. This thickness makes it possible to
ensure sufficient electrode performance while also achieving cost
reduction by reducing the used amount of expensive counter
electrode layer material. A complex oxide such as LSCF or LSM can
be used as the material for forming the counter electrode layer 6,
for example. The counter electrode layer 6 constituted by the
above-mentioned material functions as a cathode.
[0051] It should be noted that forming the counter electrode layer
6 using, as appropriate, a method through which the counter
electrode layer 6 can be formed at a treatment temperature of
1100.degree. C. or lower makes it possible to suppress damage to
the metal substrate 1, suppress element interdiffusion between the
metal substrate 1 and the electrode layer 2, and realize an
electrochemical element E that has excellent performance and
durability, and is thus preferable. For example, the counter
electrode layer 6 can be formed using, as appropriate,
low-temperature heating (not performing heating treatment in a high
temperature range of higher than 1100.degree. C., but rather
performing a wet process using heating treatment in a low
temperature range, for example), a spray coating technique (a
technique such as a thermal spraying technique, an aerosol
deposition technique, an aerosol gas deposition technique, a powder
jet deposition technique, a particle jet deposition technique, or a
cold spraying technique), a PVD technique (e.g., a sputtering
technique or a pulse laser deposition technique), a CVD technique,
or the like. In particular, using low-temperature heating, a spray
coating technique, or the like makes it possible to realize a
low-cost element and is thus preferable. Furthermore, using
low-temperature heating makes it possible to facilitate handling of
raw materials and is thus more preferable.
[0052] Solid Oxide Fuel Cell
[0053] The electrochemical element E configured as described above
can be used as a power generating cell for a solid oxide fuel cell.
For example, fuel gas containing hydrogen is supplied from the back
surface of the metal substrate 1 through the through holes 1a to
the electrode layer 2, air is supplied to the counter electrode
layer 6 serving as a counter electrode of the electrode layer 2,
and the operation is performed at a temperature of 600.degree. C.
or higher and 850.degree. C. or lower, for example. Accordingly,
the oxygen O.sub.2 included in air reacts with electrons e.sup.- in
the counter electrode layer 6, thus producing oxygen ions O.sup.2-.
The oxygen ions O.sup.2- move through the electrolyte layer 4 to
the electrode layer 2. In the electrode layer 2, the hydrogen
H.sub.2 included in the supplied fuel gas reacts with the oxygen
ions O.sup.2-, thus producing water H.sub.2O and electrons e.sup.-.
With these reactions, electromotive force is generated between the
electrode layer 2 and the counter electrode layer 6. In this case,
the electrode layer 2 functions as a fuel electrode (anode) of the
SOFC, and the counter electrode layer 6 functions as an air
electrode (cathode).
[0054] Manufacturing Method for Electrochemical Element
[0055] Next, a manufacturing method for the electrochemical element
E according to this embodiment will be described.
[0056] Electrode Layer Forming Step
[0057] In an electrode layer forming step, the electrode layer 2 is
formed as a thin film in a region that is broader than the region
provided with the through holes 1a, on/over the front surface of
the metal substrate 1. The through holes of the metal substrate 1
can be provided through laser processing or the like. As described
above, the electrode layer 2 can be formed using low-temperature
heating (a wet process using heating treatment in a low temperature
range of 1100.degree. C. or lower), a spray coating technique (a
technique such as a thermal spraying technique, an aerosol
deposition technique, an aerosol gas deposition technique, a powder
jet deposition technique, a particle jet deposition technique, or a
cold spraying technique), a PVD technique (e.g., a sputtering
technique or a pulse laser deposition technique), a CVD technique,
or the like. Regardless of which technique is used, it is desirable
to perform the technique at a temperature of 1100.degree. C. or
lower in order to suppress deterioration of the metal substrate
1.
[0058] The following is an example of the case where
low-temperature heating is performed as the electrode layer forming
step. First, a material paste is produced by mixing powder of the
material for forming the electrode layer 2 and a solvent
(dispersion medium), and is applied to the front surface of the
metal substrate 1. Then, the electrode layer 2 is obtained through
compression shape forming (electrode layer smoothing step) and
heating at a temperature of 1100.degree. C. or lower (electrode
layer heating step). Examples of compression shape forming of the
electrode layer 2 include CIP (Cold Isostatic Pressing) shape
forming, roll pressing shape forming, and RIP (Rubber Isostatic
Pressing) shape forming. It is favorable to perform heating of the
electrode layer 2 at a temperature of 800.degree. C. or higher and
1100.degree. C. or lower. The order in which the electrode layer
smoothing step and the electrode layer heating step are performed
can be changed. It should be noted that, when an electrochemical
element including an intermediate layer is formed, the electrode
layer smoothing step and the electrode layer heating step may be
omitted, and an intermediate layer smoothing step and an
intermediate layer heating step, which will be described later, may
include the electrode layer smoothing step and the electrode layer
heating step.
[0059] It should be noted that lapping shape forming, leveling
treatment, surface cutting treatment, surface polishing treatment,
or the like can also be performed as the electrode layer smoothing
step.
[0060] Diffusion Suppressing Layer Forming Step
[0061] The metal oxide thin layer 1b (diffusion suppressing layer)
is formed on/over the surface of the metal substrate 1 during the
heating step in the above-described electrode layer forming step.
It should be noted that it is preferable that the above-mentioned
heating step includes a heating step in which the heating
atmosphere satisfies the atmospheric condition that the oxygen
partial pressure is low because a high-quality metal oxide thin
layer 1b (diffusion suppressing layer) that has a high element
interdiffusion suppressing effect and has a low resistance value is
formed. In a case where a coating method that does not include
heating is performed as the electrode layer forming step, for
example, a separate diffusion suppressing layer forming step may
also be included. In any case, it is desirable to perform these
steps at a temperature of 1100.degree. C. or lower such that damage
to the metal substrate 1 can be suppressed. The metal oxide thin
layer 1b (diffusion suppressing layer) may be formed on/over the
surface of the metal substrate 1 during the heating step in an
intermediate layer forming step, which will be described later.
[0062] Intermediate Layer Forming Step
[0063] In an intermediate layer forming step, the intermediate
layer 3 is formed as a thin layer on/over the electrode layer 2 so
as to cover the electrode layer 2. As described above, the
intermediate layer 3 can be formed using low-temperature heating (a
wet process using heating treatment in a low temperature range of
1100.degree. C. or lower), a spray coating technique (a technique
such as a thermal spraying technique, an aerosol deposition
technique, an aerosol gas deposition technique, a powder jet
deposition technique, a particle jet deposition technique, or a
cold spraying technique), a PVD technique (e.g., a sputtering
technique or a pulse laser deposition technique), a CVD technique,
or the like. Regardless of which technique is used, it is desirable
to perform the technique at a temperature of 1100.degree. C. or
lower in order to suppress deterioration of the metal substrate
1.
[0064] The following is an example of the case where
low-temperature heating is performed as the intermediate layer
forming step. First, a material paste is produced by mixing powder
of the material for forming the intermediate layer 3 and a solvent
(dispersion medium), and is applied to the front surface of the
metal substrate 1. Then, the intermediate layer 3 is obtained
through compression shape forming (intermediate layer smoothing
step) and heating at a temperature of 1100.degree. C. or lower
(intermediate layer heating step). Examples of compression shape
forming to be performed on the intermediate layer 3 include CIP
(Cold Isostatic Pressing) shape forming, roll pressing shape
forming, and RIP (Rubber Isostatic Pressing) shape forming. It is
favorable to perform heating of the intermediate layer 3 at a
temperature of 800.degree. C. or higher and 1100.degree. C. or
lower. The reason for this is that this temperature makes it
possible to form an intermediate layer 3 that has high strength
while suppressing damage to and deterioration of the metal
substrate 1. It is more preferable to perform heating of the
intermediate layer 3 at a temperature of 1050.degree. C. or lower,
and more preferably 1000.degree. C. or lower. The reason for this
is that the lower the heating temperature of the intermediate layer
3 is, the more likely it is to further suppress damage to and
deterioration of the metal substrate 1 when forming the
electrochemical element E. It should be noted that the order in
which the intermediate layer smoothing step and the intermediate
layer heating step are performed can be changed.
[0065] It should be noted that lapping shape forming, leveling
treatment, surface cutting treatment, surface polishing treatment,
or the like can also be performed as the intermediate layer
smoothing step.
[0066] Electrolyte Layer Forming Step
[0067] In an electrolyte layer forming step, the electrolyte layer
4 is formed as a thin layer on/over the intermediate layer 3 so as
to cover the electrode layer 2 and the intermediate layer 3.
[0068] It is desirable to perform an aerosol deposition technique
as the electrolyte layer forming step in order to form a
high-quality electrolyte layer 4 that is dense and has high
gas-tightness and gas barrier properties in a temperature range of
1100.degree. C. or lower. In this case, aerosolized powder of the
material for forming the electrolyte layer 4 is sprayed onto the
intermediate layer 3 on/over the metal substrate 1, and the
electrolyte layer 4 is thus formed.
[0069] Reaction Preventing Layer Forming Step
[0070] In a reaction preventing layer forming step, the reaction
preventing layer 5 is formed as a thin layer on/over the
electrolyte layer 4. As described above, the reaction preventing
layer 5 can be formed using low-temperature heating (not performing
heating treatment in a high temperature range of higher than
1100.degree. C., but rather performing a wet process using heating
treatment in a low temperature range, for example), a spray coating
technique (a technique such as a thermal spraying technique, an
aerosol deposition technique, an aerosol gas deposition technique,
a powder jet deposition technique, a particle jet deposition
technique, or a cold spraying technique), a PVD technique (e.g., a
sputtering technique or a pulse laser deposition technique), a CVD
technique, or the like. Regardless of which technique is used, it
is desirable to perform the technique at a temperature of
1100.degree. C. or lower in order to suppress deterioration of the
metal substrate 1.
[0071] Counter Electrode Layer Forming Step
[0072] In a counter electrode layer forming step, the counter
electrode layer 6 is formed as a thin layer on/over the reaction
preventing layer 5. As described above, the counter electrode layer
6 can be formed using low-temperature heating (not performing
heating treatment in a high temperature range of higher than
1100.degree. C., but rather performing a wet process using heating
treatment in a low temperature range, for example), a spray coating
technique (a technique such as a thermal spraying technique, an
aerosol deposition technique, an aerosol gas deposition technique,
a powder jet deposition technique, a particle jet deposition
technique, or a cold spraying technique), a PVD technique (e.g., a
sputtering technique or a pulse laser deposition technique), a CVD
technique, or the like. Regardless of which technique is used, it
is desirable to perform the technique at a temperature of
1100.degree. C. or lower in order to suppress deterioration of the
metal substrate 1.
[0073] In this manner, the electrochemical element E can be
manufactured. That is, the manufacturing method for an
electrochemical element according to this embodiment is a
manufacturing method for an electrochemical element including a
metal substrate 1 (metal support), an electrode layer 2 formed
on/over the metal substrate 1, an intermediate layer 3 formed
on/over the electrode layer 2, and an electrolyte layer 4 on/over
the intermediate layer 3, and the method includes an intermediate
layer forming step of forming the intermediate layer 3 with a
surface roughness (Ra) of 1.0 .mu.m or less on/over the electrode
layer 2, and an electrolyte layer forming step of forming the
electrolyte layer 4 by spraying aerosolized metal oxide powder onto
the intermediate layer 3.
[0074] It should be noted that a configuration in which the
electrochemical element E does not include both or either of the
intermediate layer 3 and the reaction preventing layer 5 is also
possible. That is, a configuration in which the electrode layer 2
and the electrolyte layer 4 are in contact with each other, or a
configuration in which the electrolyte layer 4 and the counter
electrode layer 6 are in contact with each other is also possible.
In this case, in the above-described manufacturing method, the
intermediate layer forming step and the reaction preventing layer
forming step are omitted. It should be noted that it is also
possible to add a step of forming another layer or to form a
plurality of layers of the same type one on/over top of another,
but in any case, it is desirable to perform these steps at a
temperature of 1100.degree. C. or lower.
EXAMPLES
[0075] A metal substrate 1 was produced by providing a plurality of
through holes 1a through laser processing in a region with a radius
of 2.5 mm from the center of a crofer 22 APU metal plate having a
circular shape with a thickness of 0.3 mm and a diameter of 25 mm.
It should be noted that, at this time, the through holes 1a on the
surface of the metal substrate 1 were provided through laser
processing.
[0076] Next, a paste was produced by mixing 60 wt % of NiO powder
and 40 wt % of GDC powder and adding an organic binder and an
organic solvent (dispersion medium) thereto. The paste was used to
form an electrode layer 2 on/over a region with a radius of 3 mm
from the center of the metal substrate 1. It should be noted that
the electrode layer 2 was formed using screen printing. Then,
heating treatment was performed at 950.degree. C. on the metal
substrate 1 on/over which the electrode layer 2 was formed
(electrode layer forming step, diffusion suppressing layer forming
step).
[0077] Next, a paste was produced by adding an organic binder and
an organic solvent (dispersion medium) to fine powder of GDC. The
paste was used to form an intermediate layer 3, through screen
printing, on/over a region with a radius of 5 mm from the center of
the metal substrate 1 on which the electrode layer 2 was formed.
Next, the intermediate layer 3 having a flat surface was formed by
performing CIP shape forming with a pressure of 300 MPa on the
metal substrate 1 on/over which the intermediate layer 3 was formed
and then performing heating treatment at 1000.degree. C.
(intermediate layer forming step).
[0078] The electrode layer 2 and the intermediate layer 3 obtained
through the above-described steps had a thickness of about 20 .mu.m
and about 10 .mu.m, respectively. Moreover, the He leakage amount
of metal substrate 1 on/over which the electrode layer 2 and the
intermediate layer 3 were formed in this manner was 11.5
mL/minutecm.sup.2 under a pressure of 0.2 MPa.
[0079] Subsequently, powder of 8YSZ (yttria-stabilized zirconia)
with a mode diameter of about 0.7 .mu.m was aerosolized using dry
air at a flow rate of 13 L/min. The aerosol was introduced into a
chamber in which the pressure was set to 250 Pa, and then an
electrolyte layer 4 was formed by spraying the aerosol onto 15
mm.times.15 mm region on/over the metal substrate 1 on/over which
the electrode layer 2 and the intermediate layer 3 was formed, so
as to cover the intermediate layer 3 (aerosol deposition
technique). It should be noted that, at this time, the metal
substrate 1 was not heated (electrolyte layer forming step).
[0080] The electrolyte layer 4 obtained through the above-described
step had a thickness of approximately 3 to 4 .mu.m. The He leakage
amount of the metal substrate 1 on/over which the electrode layer
2, the intermediate layer 3, and the electrolyte layer 4 were
formed was measured under a pressure of 0.2 MPa. The determined He
leakage amount was smaller than the lower detection limit (1.0
mL/minutecm.sup.2). That is, compared with the He leakage amount
after forming the intermediate layer 3, the He leakage amount after
forming the electrolyte layer 4 decreased significantly and was
smaller than the lower detection limit. It was thus confirmed that
a high-quality electrolyte layer 4 that was dense and had increased
gas barrier properties was formed.
[0081] Next, a paste was produced by adding an organic binder and
an organic solvent (dispersion medium) to fine powder of GDC. The
paste was used to form a reaction preventing layer 5 on/over the
electrolyte layer 4 of the electrochemical element E using screen
printing.
[0082] Thereafter, the reaction preventing layer 5 was formed by
performing heating treatment at 1000.degree. C. on the
electrochemical element E on/over which the reaction preventing
layer 5 was formed (reaction preventing layer forming step).
[0083] Furthermore, a paste was produced by mixing GDC powder and
LSCF powder and adding an organic binder and an organic solvent
(dispersion medium) thereto. The paste was used to form a counter
electrode layer 6 on/over the reaction preventing layer 5 using
screen printing. Lastly, a final electrochemical element E was
obtained by heating, at 900.degree. C., the electrochemical element
E on/over which the counter electrode layer 6 was formed (counter
electrode layer forming step).
[0084] Hydrogen gas and air were respectively supplied to the
electrode layer 2 and the counter electrode layer 6, and the open
circuit voltage (OCV) of the obtained electrochemical element E
serving as a cell for a solid oxide fuel cell was measured. The
result was 1.07 V at 750.degree. C.
[0085] FIG. 2 shows an electron micrograph of a cross section of
the electrochemical element E. As is clear from the electron
micrograph, the dense electrolyte layer 4 was formed on/over the
smooth surface with a surface roughness (Ra) of 1.0 .mu.m or less
of the intermediate layer 3 on the side facing the electrolyte
layer, and it is thus clear that a cell for a solid oxide fuel cell
(electrochemical element E) that had favorable performance was
obtained.
[0086] Five samples were produced in the same manner, and the
surface roughnesses (Ra) of the intermediate layers 3 of these
samples were measured using a laser microscope. Table 1 shows the
results.
TABLE-US-00001 TABLE 1 Surface roughness (Ra) of intermediate layer
Calculated value for Calculated value for 259-.mu.m width 642-.mu.m
width Sample 1 0.064 .mu.m to 0.104 .mu.m 0.139 .mu.m to 0.196
.mu.m Sample 2 0.066 .mu.m to 0.224 .mu.m 0.117 .mu.m to 0.209
.mu.m Sample 3 0.066 .mu.m to 0.224 .mu.m 0.117 .mu.m to 0.209
.mu.m Sample 4 0.117 .mu.m to 0.209 .mu.m 0.221 .mu.m to 0.156
.mu.m Sample 5 0.152 .mu.m to 0.210 .mu.m 0.087 .mu.m to 0.124
.mu.m
[0087] In all the samples, the surface roughness (Ra) of the
intermediate layer 3 was 1.0 .mu.m or less, and a favorable
electrolyte layer 4 could be formed on/over the intermediate layer
3.
[0088] Next, regarding samples in which there was difficulty in
forming the electrolyte layer 4 in which a favorable electrolyte
layer 4 could not be formed on/over the intermediate layer 3 and
whose open circuit voltages (OCVs) did not reach 1 V or higher at
750.degree. C., the surface roughnesses (Ra) of the intermediate
layers 3 were measured using a laser microscope. Table 2 shows the
results.
TABLE-US-00002 TABLE 2 Surface roughness (Ra) of intermediate layer
Calculated value for Calculated value for 259-.mu.m width 642-.mu.m
width Sample 6 1.624 .mu.m to 2.499 .mu.m 1.350 .mu.m Sample 7
3.718 .mu.m to 8.230 .mu.m 2.596 .mu.m to 6.094 .mu.m
[0089] In both samples, the surface roughness (Ra) of the
intermediate layer 3 was greater than 1.0 .mu.m.
[0090] It was shown from the above results that setting the surface
roughness (Ra) of the intermediate layer 3 to 1.0 .mu.m or less
makes it possible to form a favorable electrolyte layer.
Second Embodiment
[0091] An electrochemical element E according to this embodiment
has a configuration in which the intermediate layer 3 is not
provided, that is, the electrode layer 2 and the electrolyte layer
4 are in contact with each other. Therefore, in the manufacturing
method for the electrochemical element E, the intermediate layer
forming step is omitted.
[0092] The electrochemical element E according to this embodiment
includes the metal substrate 1 (metal support), the electrode layer
2 formed on/over the metal substrate 1, and the electrolyte layer 4
formed on/over the electrode layer 2. The electrochemical element E
further includes the reaction preventing layer 5 formed on/over the
electrolyte layer 4, and the counter electrode layer 6 formed
on/over the reaction preventing layer 5. Specifically, the counter
electrode layer 6 is formed above the electrolyte layer 4, and the
reaction preventing layer 5 is formed between the electrolyte layer
4 and the counter electrode layer 6. The electrode layer 2 is
porous, and the electrolyte layer 4 is dense.
[0093] In this embodiment, the electrode layer 2 has a region with
a surface roughness (Ra) of 1.0 .mu.m or less. This region may
correspond to all or a part of the surface of the electrode layer
2. An electrochemical element E that has excellent reliability and
durability as well as high adhesion strength between the electrode
layer 2 and the electrolyte layer 4 can be configured due to the
electrode layer 2 having a region with a surface roughness (Ra) of
1.0 .mu.m or less. It should be noted that the electrode layer 2
more preferably has a region with a surface roughness (Ra) of 0.5
.mu.m or less, and even more preferably 0.3 .mu.m or less. The
reason for this is that an electrochemical element E that has
excellent reliability and durability as well as higher adhesion
strength between the electrode layer 2 and the electrolyte layer 4
can be configured if the electrode layer 2 is smoother in terms of
the surface roughness.
[0094] Manufacturing Method for Electrochemical Element
[0095] Next, a manufacturing method for the electrochemical element
E according to this embodiment will be described. The
electrochemical element E according to this embodiment does not
include the intermediate layer 3. Accordingly, in the manufacturing
method for the electrochemical element E according to this
embodiment, the electrode layer forming step (diffusion suppressing
layer forming step), the electrolyte layer forming step, the
reaction preventing layer forming step, and the counter electrode
layer forming step are performed in the stated order.
[0096] Electrode Layer Forming Step
[0097] In the electrode layer forming step, the electrode layer 2
is formed as a thin film in a region that is broader than the
region provided with the through holes 1a, on/over the front
surface of the metal substrate 1. The through holes of the metal
substrate 1 can be provided through laser processing or the like.
As described above, the electrode layer 2 can be formed using
low-temperature heating (a wet process using heating treatment in a
low temperature range of 1100.degree. C. or lower), a spray coating
technique (a technique such as a thermal spraying technique, an
aerosol deposition technique, an aerosol gas deposition technique,
a powder jet deposition technique, a particle jet deposition
technique, or a cold spraying technique), a PVD technique (e.g., a
sputtering technique or a pulse laser deposition technique), a CVD
technique, or the like. Regardless of which technique is used, it
is desirable to perform the technique at a temperature of
1100.degree. C. or lower in order to suppress deterioration of the
metal substrate 1.
[0098] The following is an example of the case where
low-temperature heating is performed as the electrode layer forming
step. First, a material paste is produced by mixing powder of the
material for forming the electrode layer 2 and a solvent
(dispersion medium), and is applied to the front surface of the
metal substrate 1. Then, the electrode layer 2 is obtained through
compression shape forming (electrode layer smoothing step) and
heating at a temperature of 1100.degree. C. or lower (electrode
layer heating step). Examples of compression shape forming of the
electrode layer 2 include CIP (Cold Isostatic Pressing) shape
forming, roll pressing shape forming, and RIP (Rubber Isostatic
Pressing) shape forming. It is favorable to perform heating of the
electrode layer 2 at a temperature of 800.degree. C. or higher and
1100.degree. C. or lower. The reason for this is that this
temperature makes it possible to form an electrode layer 2 that has
high strength while suppressing damage to and deterioration/over of
the metal substrate 1. It is more preferable to perform heating of
the electrode layer 2 at a temperature of 1050.degree. C. or lower,
and more preferably 1000.degree. C. or lower. The reason for this
is that the electrochemical element E can be formed with damage to
and deterioration of the metal substrate 1 being further suppressed
as the heating temperature of the electrode layer 2 is reduced.
[0099] It should be noted that lapping shape forming, leveling
treatment, surface cutting treatment, surface polishing treatment,
or the like can also be performed as the electrode layer smoothing
step.
[0100] In this manner, the electrochemical element E can be
manufactured. That is, the manufacturing method for an
electrochemical element according to this embodiment is a
manufacturing method for an electrochemical element including a
metal substrate 1 (metal support), an electrode layer 2 formed
on/over the metal substrate 1, and an electrolyte layer 4 formed
on/over the electrode layer 2, and the method includes an electrode
layer forming step of forming the electrode layer 2 with a surface
roughness (Ra) of 1.0 .mu.m or less on the metal substrate 1, and
an electrolyte layer forming step of forming the electrolyte layer
4 by spraying aerosolized metal oxide powder onto the electrode
layer 2.
EXAMPLES
[0101] A metal substrate 1 was produced by providing a plurality of
through holes 1a through laser processing in a region with a radius
of 2.5 mm from the center of a crofer 22 APU metal plate having a
circular shape with a thickness of 0.3 mm and a diameter of 25 mm.
It should be noted that, at this time, the through holes 1a on the
surface of the metal substrate 1 were provided through laser
processing.
[0102] Next, a paste was produced by mixing 60 wt % of NiO powder
and 40 wt % of YSZ powder and adding an organic binder and an
organic solvent (dispersion medium) thereto. The paste was used to
form an electrode layer 2 on/over a region with a radius of 3 mm
from the center of the metal substrate 1. It should be noted that
the electrode layer 2 was formed using screen printing.
[0103] Next, CIP shape forming was performed with a pressure of 300
MPa on the metal substrate 1 on/over which the electrode layer 2
was formed, and then heating treatment was performed at
1050.degree. C. (electrode layer forming step, diffusion
suppressing layer forming step).
[0104] The electrode layer 2 obtained through the above-described
step had a thickness of about 20 .mu.m. Moreover, the He leakage
amount of metal substrate 1 on/over which the electrode layer 2 was
formed in this manner was 4.3 mL/minutecm.sup.2 under a pressure of
0.1 MPa.
[0105] Subsequently, powder of 8YSZ (yttria-stabilized zirconia)
with a mode diameter of about 0.7 .mu.m was aerosolized using dry
air at a flow rate of 4 L/min. The aerosol was introduced into a
chamber in which the pressure was set to 60 Pa, and then an
electrolyte layer 4 was formed by spraying the aerosol onto 15
mm.times.15 mm region on/over the metal substrate 1 on/over which
the electrode layer 2 was formed, so as to cover the electrode
layer 2 (aerosol deposition technique). It should be noted that, at
this time, the metal substrate 1 was not heated (electrolyte layer
forming step).
[0106] The electrolyte layer 4 obtained through the above-described
step had a thickness of approximately 5 to 6 .mu.m. The He leakage
amount of the metal substrate 1 on/over which the electrode layer 2
and the electrolyte layer 4 were formed in this manner was measured
under a pressure of 0.2 MPa. The determined He leakage amount was
smaller than the lower detection limit (1.0 mL/minutecm.sup.2). It
was thus confirmed that a high-quality electrolyte layer 4 that was
dense and had increased gas barrier properties was formed.
[0107] Next, a paste was produced by adding an organic binder and
an organic solvent (dispersion medium) to fine powder of GDC. The
paste was used to form a reaction preventing layer 5 on/over the
electrolyte layer 4 of the electrochemical element E using screen
printing.
[0108] Thereafter, the reaction preventing layer 5 was formed by
performing heating treatment at 1000.degree. C. on the
electrochemical element E on/over which the reaction preventing
layer 5 was formed (reaction preventing layer forming step).
[0109] Furthermore, a paste was produced by mixing GDC powder and
LSCF powder and adding an organic binder and an organic solvent
thereto. The paste was used to form a counter electrode layer 6
on/over the reaction preventing layer 5 using screen printing.
Lastly, a final electrochemical element E was obtained by heating,
at 900.degree. C., the electrochemical element E on/over which the
counter electrode layer 6 was formed (counter electrode layer
forming step).
[0110] Hydrogen gas and air were respectively supplied to the
electrode layer 2 and the counter electrode layer 6, and the open
circuit voltage (OCV) of the obtained electrochemical element E
serving as a cell for a solid oxide fuel cell was measured. The
result was 1.05 V at 750.degree. C.
[0111] Another sample was produced in the same manner, and the
surface roughness (Ra) of the electrode layer 2 of this sample was
measured using a laser microscope. Table 3 shows the results.
TABLE-US-00003 TABLE 3 Surface roughness (Ra) of electrode layer
Calculated value for Calculated value for 259-.mu.m width 642-.mu.m
width Sample 8 0.12 .mu.m to 0.165 .mu.m 0.237 .mu.m to 0.276
.mu.m
[0112] In Sample 8, the surface roughness (Ra) of the electrode
layer 2 was 1.0 .mu.m or less, and a favorable electrolyte layer 4,
a favorable reaction preventing layer 5, and a favorable counter
electrode layer 6 could be formed on/over the electrode layer
2.
[0113] It was shown from the above results that setting the surface
roughness (Ra) of the electrode layer 2 to 1.0 .mu.m or less makes
it possible to form a favorable electrolyte layer.
Other Embodiments
[0114] (1) Although the electrochemical elements E are used in a
solid oxide fuel cell in the above-described embodiments, the
electrochemical elements E can also be used in a solid oxide
electrolytic cell, an oxygen sensor using a solid oxide, and the
like.
[0115] (2) Although the present application is applied to a
metal-supported solid oxide fuel cell in which the metal substrate
1 serves as a support in the above-described embodiments, the
present application can also be applied to an electrode-supported
solid oxide fuel cell in which the electrode layer 2 or counter
electrode layer 6 serves as a support, or an electrolyte-supported
solid oxide fuel cell in which the electrolyte layer 4 serves as a
support. In such cases, the functions of a support can be obtained
by forming the electrode layer 2, counter electrode layer 6, or
electrolyte layer 4 to have a required thickness.
[0116] (3) In the above-described embodiments, a composite material
such as NiO-GDC, Ni-GDC, NiO--YSZ, Ni--YSZ, CuO--CeO.sub.2, or
Cu--CeO.sub.2 is used as the material for forming the electrode
layer 2, and a complex oxide such as LSCF or LSM is used as the
material for forming the counter electrode layer 6. With this
configuration, the electrode layer 2 serves as a fuel electrode
(anode) when hydrogen gas is supplied thereto, and the counter
electrode layer 6 serves as an air electrode (cathode) when air is
supplied thereto, thus making it possible to use the
electrochemical element E as a cell for a solid oxide fuel cell. It
is also possible to change this configuration and thus configure an
electrochemical element E such that the electrode layer 2 can be
used as an air electrode and the counter electrode layer 6 can be
used as a fuel electrode. That is, a complex oxide such as LSCF or
LSM is used as the material for forming the electrode layer 2, and
a composite material such as NiO-GDC, Ni-GDC, NiO--YSZ, Ni--YSZ,
CuO--CeO.sub.2, or Cu--CeO.sub.2 is used as the material for
forming the counter electrode layer 6. With this configuration, the
electrode layer 2 serves as an air electrode when air is supplied
thereto, and the counter electrode layer 6 serves as a fuel
electrode when hydrogen gas is supplied thereto, thus making it
possible to use the electrochemical element E as a cell for a solid
oxide fuel cell.
[0117] It should be noted that the configurations disclosed in the
above-described embodiments can be used in combination with
configurations disclosed in other embodiments as long as they are
compatible with each other. The embodiments disclosed in this
specification are illustrative, and embodiments of the present
invention are not limited thereto and can be modified as
appropriate without departing from the object of the present
invention.
INDUSTRIAL APPLICABILITY
[0118] The present invention can be applied to an electrochemical
element and a cell for a solid oxide fuel cell.
LIST OF REFERENCE NUMERALS
[0119] 1: Metal substrate (metal support) [0120] 1a: Through hole
[0121] 2: Electrode layer [0122] 3: Intermediate layer [0123] 4:
Electrolyte layer [0124] 5: Reaction preventing layer [0125] 6:
Counter electrode layer [0126] E: Electrochemical element
* * * * *