JP5137416B2 - Current collecting material for fuel electrode, solid oxide fuel cell unit cell and solid oxide fuel cell - Google Patents

Description

  The present invention relates to a current collecting material for a fuel electrode, a solid oxide fuel cell single cell, and a solid oxide fuel cell.

  A solid oxide fuel cell (hereinafter referred to as “SOFC”) is a fuel cell using a solid electrolyte exhibiting oxygen ion conductivity as an electrolyte. The basic elements of the SOFC are a fuel electrode, a solid electrolyte, and an air electrode, and a structure in which these three elements are sequentially stacked and joined is called a single cell.

  In general, in a fuel cell, a plurality of single cells are used as an aggregate, and this aggregate is used as a power generator. In the SOFC, a flat or tubular unit cell is usually electrically connected in series and in parallel to form a power generator.

  Here, when a plurality of flat single cells are connected in series, the fuel gas and the oxidant gas alternately flow in contact like fuel gas / oxidant gas / fuel gas. Therefore, when stacking a plurality of flat single cells, a separator for separating both gases is sandwiched between each single cell, and the combination of the single cell and the separator is a repeating unit.

  In addition to the role of separating the fuel gas and the oxidant gas, the separator also has a role of electrically connecting the single cells. In order to flow the fuel gas to the fuel electrode on one side and the oxidant gas to the air electrode on the other side across the separator, the separator is generally formed with a gas flow path for refluxing each gas. .

  In this type of flat type SOFC, in addition to the electric resistance of a single cell, a contact resistance between the single cell and the separator is added.

  In particular, the latter contact resistance is not negligible and is important for battery design. This is because even if the original power generation performance of the single cell is excellent, if the contact resistance between the single cell and the separator is large, the current collection efficiency is lowered and the power generation performance of the SOFC as a whole is impaired. .

  Therefore, conventionally, when stacking single cells using separators, attempts have been made to reduce the contact resistance between the single cells and the separator.

  For example, it is conventionally known that a nickel layer is interposed as a current collecting layer between a fuel electrode of a single cell and a separator.

  Further, for example, Patent Document 1 uses a two-layered fuel electrode composed of a first electrode on the solid electrolyte side and a current collecting layer on the separator side, and the size of nickel particles in the current collecting layer is as follows: A technique is disclosed in which the contact resistance between the fuel electrode of a single cell and the separator is reduced and the current collecting property is increased by making the size smaller than the size of nickel particles in the first electrode layer.

Japanese Patent Laid-Open No. 10-21930

  However, an SOFC in which a nickel layer is interposed as a current collecting layer between the fuel electrode of a single cell and a separator has a problem that the single cell is easily broken when started and stopped.

  This is because when exposed to a high temperature during power generation (for example, about 800 ° C.), the single cell and the separator are fixed by the nickel layer, and when the power generation is stopped and cooled in this state, the coefficient of thermal expansion differs. It is considered that this is because the single cell and the separator contract in a state where they are physically fixed, and therefore, the single cell and the separator are cracked by the stress due to the difference in thermal expansion between them.

  In particular, when a metal separator mainly using a metal such as ferritic stainless steel is used, the single cell is easily cracked.

  This is thought to be because the nickel in the current collecting layer diffuses and is firmly fixed in the stainless steel as a separator material due to the high temperature during power generation.

  On the other hand, the fuel electrode according to the technique of Patent Document 1 is a hard structure in which the current collecting layer and the electrode first layer are both sintered. Therefore, even if this fuel electrode and a separator, which is also a hard structure, are laminated, a gap is generated between them, and it is considered difficult to sufficiently reduce the contact resistance.

  The present invention has been made in view of the above problems, and a problem to be solved by the present invention is to provide a current collecting material for a fuel electrode capable of suppressing cracking of a single cell without greatly impairing power generation performance. It is in. It is another object of the present invention to provide a solid oxide fuel cell unit cell and a solid oxide fuel cell using the same.

In order to solve the above problems, a current collecting material for a fuel electrode according to the present invention is interposed between a fuel electrode of a solid oxide fuel cell and a separator, and comprises a nickel powder, a nickel alloy powder, and a nickel oxide powder. one or the two or more than consisting of nickel-based powders are selected, and a powder of a material that does not stick to the separator at a temperature during cell power generation, the said nickel powder volume ratio of the material powder (the nickel the volume of the volume / the material powder of the powder) is in the range of 87 / 13-99 / 1, the material powder and the particle size ratio (particle size of the particle diameter / the nickel powder of the material powder of the nickel powder ) Is in the range of 6/1 to 2/1.

  The material powder is preferably an oxide powder.

  The material powder may be one or more selected from stabilized zirconia powder, ceria solid solution powder, alumina powder, and lanthanum gallate composite oxide powder.

  The fuel electrode current collecting material preferably further contains a binder.

  In the solid oxide fuel cell unit cell according to the present invention, a fuel electrode is laminated on one surface of a solid electrolyte exhibiting oxygen ion conductivity, and an air electrode is laminated on the other surface, and on the surface of the fuel electrode, The gist is that the fuel electrode current collecting material is formed in an unfired state.

  The gist of the solid oxide fuel cell according to the present invention is that the single cells are stacked in multiple stages via separators.

  At this time, the separator is preferably a metal separator.

The current collector material for a fuel electrode according to the present invention includes the nickel-based powder and a powder of a material that does not adhere to the separator at a temperature during battery power generation, and the volume ratio between the nickel-based powder and the material powder is specific. It is within the range.

  Therefore, the crack of a single cell can be suppressed by using this for the current collection material between the fuel electrode and separator of a single cell.

  This is because, in the current collecting material, in addition to the nickel-based powder, powder of a material that does not adhere to the separator at the temperature during battery power generation is mixed, so that the interface between nickel and the material is fine at the time of battery start / stop. This is considered to be because the stress caused by the sticking can be relieved, for example, by cracking.

Further, even when an insulating material is selected as the material powder, for example, the volume ratio between the nickel-based powder and the material powder is within a specific range, so that the current collecting property is reduced. It is difficult to let it. Therefore, the power generation performance is not greatly impaired.

  In addition, when the current collecting material is formed in an unfired state on the surface of the fuel electrode of a single cell and used as it is laminated with a separator, the current collecting material in the unfired and soft state is crushed. It becomes easy to fill a gap generated between the fuel electrode and the separator. Therefore, according to the said current collection material, there exists an advantage that it becomes easy to reduce contact resistance.

  Here, when the particle size of the material powder is larger than the particle size of the nickel-based powder, it becomes easy to suppress cracking of the single cell. This is considered to be because the stress relaxation due to the fixing is more likely to occur.

  Moreover, when the said material powder is an oxide powder, there exists an advantage that the freedom degree which selects the material which does not adhere to a separator at the temperature at the time of battery power generation becomes high.

  Moreover, when the said current collection material contains the binder further, fluidity | liquidity or plasticity improves. Therefore, there is an advantage that it becomes easier to fill a gap generated between the fuel electrode and the separator and the contact resistance can be further reduced. In addition, there is an advantage that, after being attached to the surface of the single cell, it is difficult to drop off.

  In the solid oxide fuel cell single cell according to the present invention, the current collecting material is formed in an unfired state on the surface of the fuel electrode. Therefore, if this is laminated | stacked in many steps through a separator, it will become easy to fill the gap which arises between a fuel electrode and a separator by collapsing the current collection material which is unfired and is in a soft state. Therefore, it becomes easy to reduce contact resistance.

  In the solid oxide fuel cell according to the present invention, the single cell is stacked in multiple stages via separators. Therefore, even when a temperature cycle by starting and stopping the battery is applied, cracking of the single cell can be suppressed and stable power generation can be performed. Therefore, it has high reliability.

  Hereinafter, the fuel electrode current collector material (hereinafter sometimes referred to as “the current collector material”), a solid oxide fuel cell single cell (hereinafter referred to as “the present SOFC single cell”) according to the present embodiment. )) And a solid oxide fuel cell (hereinafter sometimes referred to as “the present SOFC”) will be described in detail.

1. The current collection material The current collection material contains at least a nickel-based powder and a specific material powder.

  Specific examples of the nickel-based powder include nickel (Ni) powder, nickel alloy powder, and nickel oxide (NiO) powder. These may be contained alone or in combination of two or more.

  Preferably, nickel oxide (NiO) powder can be suitably used from the viewpoint of suppressing volume change due to oxidation during temperature rise. Nickel oxide becomes metallic nickel when exposed to a high-temperature reducing atmosphere during power generation, and exhibits good electronic conductivity.

  On the other hand, the specific material powder is a powder of a material that does not adhere to the separator at the temperature during battery power generation.

  Usually, in SOFC, the temperature during battery power generation is about 700 ° C to 1000 ° C. Therefore, even if it is a case where the said specific material powder is exposed to such temperature, it is good if it does not adhere to a separator.

  As the separator, specifically, for example, a metal separator made of stainless steel such as ferrite, a metal separator in which gold is plated and clad on the surface of stainless steel such as ferrite, lanthanum-chromium A separator made of an oxide can be exemplified.

  Preferably, a metal separator can be suitably used from the viewpoints of being able to be manufactured at a relatively low cost and having advantages such as a high degree of freedom in designing the gas flow path.

  As the specific material powder, an oxide powder can be preferably used from the viewpoint of a high degree of freedom in selecting a powder that does not adhere to the separator at the temperature during battery power generation.

The specific material powder may be either insulating or conductive (electronic conductive). In the current collecting material, as will be described later, the volume ratio of the nickel-based powder and the specific material powder is within a specific range, and the current collecting property is considered as a whole. Therefore, even if it shows insulation as a specific material powder, it can be used.

  Specific examples of the specific material powder include, for example, stabilized zirconia (including partially stabilized) powder, ceria-based solid solution powder, alumina powder, lanthanum gallate-based composite oxide powder, and the like. These may be used alone or in combination of two or more.

  Preferably, stabilized zirconia powder can be suitably used from the viewpoint of preventing mutual diffusion with stable zirconia in the fuel electrode.

Specific examples of the stabilized zirconia include oxides such as scandia (Sc ₂ O ₃ ), yttria (Y ₂ O ₃ ), ceria (CeO ₂ ), calcia (CaO), and magnesia (MgO). Examples include stabilized zirconia containing at least one or more. These may be used alone or in combination of two or more.

  Preferably, stabilized zirconia containing at least one oxide selected from scandia, yttria and ceria is preferable from the viewpoint of being frequently used as a stabilizing material used for stabilized zirconia in the fuel electrode.

Here, in this current collecting material, the volume ratio of the particular material powder and nickel powder (volume / volume specific material powder of nickel powder) are 85/15 or more.

When the volume ratio is less than 85/15, it is difficult to adhere to the separator. However, when a powder such as stabilized zirconia that is so small as to have negligible electronic conductivity is used, the ratio becomes excessive and current collection is performed. There is a tendency for sex to decline.

The lower limit of the volume ratio is preferably 86/14 or more, more preferably 87/13 or more, and still more preferably, from the viewpoint of ensuring sufficient current collection and making it difficult to reduce power generation performance. 88/12 or more, most preferably 89/11 or more.

The preferable upper limit of the volume ratio is 99/1 or less, 98/2 or less from the viewpoint of sufficiently suppressing the fixation with the separator and avoiding the cracking of the single cell to stably generate power. 97/3 or less, 96/4 or less, 95/5 or less, and the like.

  In addition, the particle size of the material powder is preferably larger than the particle size of the nickel-based powder from the viewpoint of easily suppressing single cell cracking. The reason why it is easy to suppress the cracking of the single cell is that when the battery is started and stopped, it becomes easier to cause stress relaxation due to sticking, such as a fine crack is likely to enter the interface between nickel and the material. it is conceivable that.

  At this time, the particle diameter is a value of 50% diameter in a volume-based integrated fraction measured in accordance with JIS R1629. The above JIS R1629 is a standard for a particle size distribution measuring method by a laser diffraction / scattering method of a fine ceramic material. Specifically, a method for measuring a particle size distribution using a scattering intensity distribution detected by irradiating laser light to fine ceramic raw material particles dispersed in a liquid phase is defined.

  As the particle size distribution measuring device by the laser diffraction / scattering method, for example, “Laser diffraction / scattering type particle size distribution measuring device” manufactured by Horiba, Ltd. can be used. If it is done, it will not specifically limit.

  The particle diameter of the material powder is preferably 6 to 15 μm, more preferably 7 to 14 μm, and even more preferably 8 to 12 μm, from the viewpoint of forming a microstructure that easily cracks.

  On the other hand, the particle diameter of the nickel-based powder is preferably 0.5 to 5 μm, more preferably 1 to 5 μm, and even more preferably 2 to 4 μm, from the viewpoint of increasing electrical conductivity. .

  In addition, the particle diameter ratio of the material powder / the particle diameter ratio of the nickel-based powder is preferably 6/1 to 2/1, more preferably 5 /, from the viewpoint of forming a microstructure that is easily cracked. 1 to 2.5 / 1, and even more preferably 4/1 to 3/1.

  The current collecting material may further contain a binder in addition to the above powders. By using a binder to form a slurry, the fluidity or plasticity of the current collecting material is improved. Therefore, it becomes easier to fill a gap generated between the fuel electrode and the separator, and the contact resistance can be further reduced. Further, it is difficult to drop off after the current collecting material is attached to the surface of the single cell. The binder disappears when the SOFC is heated for the first time.

  Specific examples of the binder include polyethylene glycol, polyvinyl butyral, polyethylene, polymethyl methacrylate, thinner, polyvinyl alcohol, and methyl cellulose. These may be contained alone or in combination of two or more.

The current collecting material can be obtained, for example, by mixing a nickel-based powder weighed so as to have the above volume ratio and a specific material powder by an appropriate mixing method. The said mixing method is not specifically limited, Various mixing methods, such as a ball mill, a sand mill, a vibration mill, a bead mill, can be illustrated. Further, the mixing may be performed in a dry manner, or may be performed in a wet manner by adding an appropriate solvent such as water or alcohol.

  When using a binder, a nickel-based powder and a specific material powder are mixed in advance to prepare a mixed powder, which is dispersed in the binder by applying ultrasonic waves or the like. In addition, a nickel-based powder, a specific material powder and a binder are kneaded together, or either a nickel-based powder or a specific material powder and a binder are kneaded, and the remaining powder is mixed. It may be added and further kneaded. In addition to the binder, various solvents such as organic solvents and water, dispersants, and the like can be used in combination as appropriate in the above preparation.

2. SOFC Single Cell In this SOFC single cell, a fuel electrode is stacked on one surface of a solid electrolyte exhibiting oxygen ion conductivity, and an air electrode is stacked on the other surface.

  The electrode (fuel electrode, air electrode) may be directly joined to the solid electrolyte, or the reaction between the electrolyte material and the electrode material may be suppressed between the electrode and the solid electrolyte. An intermediate layer or the like may optionally be interposed for the purpose of increasing the catalytic activity.

  Moreover, as a cell structure, a flat plate type is suitable. At this time, the flat plate type is roughly classified into two types, a self-supporting membrane type in which a solid electrolyte is self-supporting, and a supporting membrane type in which a fuel electrode or an air electrode also has a supporting function. It may be in a format and is not particularly limited.

  Here, in the present SOFC single cell, the current collecting material is formed in an unfired state on the outer surface of the fuel electrode (the surface opposite to the solid electrolyte).

  The current collecting material may cover the entire surface of the fuel electrode, or may partially cover the surface of the fuel electrode as long as the power generation performance does not deteriorate. Preferably, the entire surface of the fuel electrode is covered from the viewpoint of improving the current collecting property.

  Further, the upper limit of the film thickness of the current collecting material is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less, from the viewpoint of reducing loss due to resistance of the material itself. And good.

  On the other hand, the lower limit of the film thickness of the current collecting material is preferably 5 μm or more, more preferably 10 μm or more, and even more, from the viewpoint of obtaining a thickness necessary for filling the gap between the fuel electrode and the separator. Preferably, it is 15 μm or more.

  The material of the solid electrolyte, the material of the fuel electrode, the material of the air electrode, and the material of the intermediate layer constituting the present SOFC single cell are not particularly limited, and various materials can be applied.

  Specific examples of the solid electrolyte material include, for example, stabilized zirconia containing at least one oxide such as scandia, yttria, ceria, calcia, and magnesia, and a mixture of these stabilized zirconia and alumina. It can be illustrated as an example.

  More specifically, from the viewpoint of excellent balance between mechanical properties such as strength and toughness and oxygen ion conductivity, preferably 3 to 6 mol%, more preferably 4 to 6 mol% of scandia is used. Scandia-stabilized zirconia to be contained, and this scandia-stabilized zirconia preferably having 0.3 to 5% by weight, more preferably 0.5 to 3% by weight of alumina, etc. are suitable. It is.

  Moreover, as a fuel electrode material, a cermet of a catalyst and a solid electrolyte can be exemplified as a suitable example.

  Specific examples of the catalyst constituting a part of the cermet include nickel, nickel alloy, nickel oxide (NiO), Co, and Ru. These may be used alone or in combination.

  On the other hand, as a solid electrolyte constituting another part of the cermet, specifically, stabilized zirconia containing at least one oxide such as scandia, yttria, ceria, etc. may be exemplified as a suitable example. it can.

More specifically, from the viewpoint of excellent oxygen ion conductivity, preferably ScSZ containing 9 to 12 mol%, more preferably 10 to 11 mol% Sc ₂ O ₃ , Y ₂ in addition to this ScSZ. As a suitable example, one or both of O ₃ and CeO ₂ is preferably added at 2 mol% or less, more preferably 0.5 to 1 mol% in a small amount.

  The mixing ratio of the catalyst and the solid electrolyte in the fuel electrode material is preferably in the range of catalyst: solid electrolyte = 30: 70 wt% to 70:30 wt%, more preferably catalyst: second solid electrolyte. It is good to exist in the range of = 40: 60 weight%-60:40 weight%. This is because good electrode activity can be obtained and the cell is unlikely to warp due to a difference in thermal expansion.

Further, as the air electrode material, specifically, transition metal perovskite oxides such as LaSrMnO ₃ , LaCaMnO ₃ , LaSrCoO ₃ , LaSrCoFeO ₃ , PrSrMnO ₃ ; preferably 8 to 10 mol%, more preferably the yttria-stabilized zirconia containing 8-9 mol% yttria, preferably 9-12 mol%, more preferably, scandia-stabilized zirconia containing 10-11 mol% of _scandia, Gd ₂ O _{3, Y 2} Oxides such as O ₃ and Sm ₂ O ₃ are preferably 10 to 35 mol%, more preferably 15 to 30 mol%, and even more preferably 20 to 30 mol% of a solid electrolyte such as a ceria-based solid solution; Illustrate a composite with the above transition metal perovskite oxide as a suitable example Can do.

Further, as the intermediate layer material, specifically, for example, at least one oxide selected from Gd ₂ O ₃ , Y ₂ O ₃ and Sm ₂ O ₃ is preferably used, preferably 10 to 35 mol%. More preferably, a ceria-based solid solution containing 15 to 30 mol%, more preferably 20 to 30 mol%, can be exemplified as a suitable example.

  In order to obtain the present SOFC single cell, for example, the following may be performed. That is, for example, first, the solid electrolyte material is formed into a flat plate shape by a press forming method, a tape forming method, or the like, and sintered at an optimum temperature according to the composition. Next, the slurry containing the fuel electrode material is applied to one surface of the solid electrolyte by a screen printing method, a doctor blade method, a brush coating method, a spraying method, a dipping method, or the like, and an optimum temperature according to the composition. Sintered into a fuel electrode. Similarly, the slurry containing the air electrode material is applied to the other surface of the solid electrolyte and sintered to form an air electrode.

  Then, the current collecting material is applied to the surface of the fuel electrode by a screen printing method, a doctor blade method, a brush coating method, a spray method, a dipping method, or the like. Thereby, this SOFC can be obtained.

  In applying the current collecting material, a binder or the like may be applied to the surface of the fuel electrode in advance. This is because the pores of the fuel electrode, which is a fired body, are impregnated with the binder, thereby increasing the flatness of the surface of the fuel electrode and facilitating the application of the current collecting material in a relatively uniform manner.

3. This SOFC
The present SOFC is obtained by stacking a large number of the above-mentioned SOFC single cells through separators. Therefore, the current collecting material contained in the battery remains unfired in a state before being used for power generation .

  As the separator, those already described above can be used.

  Hereinafter, the fuel electrode current collecting material, the SOFC single cell, and the SOFC according to the present invention will be described more specifically with reference to examples.

1. Production of current collecting material for fuel electrode according to Example and Comparative Example (Example 1)
Nickel oxide (NiO) powder (50% diameter: 3 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and stabilized zirconia having a composition of 11 mol% Sc ₂ O ₃ -89 mol% ZrO ₂ (50% diameter: 10 μm, First Rare Element Chemical Industry Co., Ltd. (hereinafter referred to as “11ScSZ”) was weighed so as to be 88 vol% and 12 vol%, respectively.

  Next, nickel oxide powder and 11ScSZ powder were placed in a polyethylene pot together with zirconia balls and ethanol, mixed for 24 hours, and then the obtained slurry was removed from the pot and dried.

  Next, a binder (polyethylene glycol) was added to the obtained mixed powder to prepare a slurry, and a fuel electrode current collecting material according to Example 1 was obtained.

(Comparative Example 1)
A binder (polyethylene glycol) is added to nickel oxide (NiO) powder (50% diameter: 1 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) to prepare a slurry, and the current collecting material for a fuel electrode according to Comparative Example 1 is prepared. Obtained.

(Comparative Example 2)
Example except that nickel oxide (NiO) powder (50% diameter: 3 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 11ScSZ were weighed and mixed to 80 vol% and 20 vol%, respectively. The fuel electrode current collector material according to Comparative Example 1 was obtained in the same manner as the production of the fuel electrode current collector material according to Example 1.

  The 50% diameter is a value measured according to JIS R1629 using a “laser diffraction / scattering particle size distribution analyzer” manufactured by Horiba, Ltd.

2. Production of SOFC single cells according to Examples and Comparative Examples (Example 1C)
As a solid electrolyte material, a stabilized zirconia having a composition of 4 mol% Sc ₂ O ₃ -96 mol% ZrO ₂ (manufactured by Daiichi Elemental Chemical Co., Ltd., hereinafter referred to as “4ScSZ”) is used, and a binder (methylcellulose) is used. ) To form a slurry, and a green sheet was formed using a doctor blade method. And this green sheet was baked at 1350 degreeC for 2 hours, and the solid electrolyte board about 150 micrometers thick was produced.

Next, nickel oxide (NiO) powder (manufactured by Nacalai Tesque) and stabilized zirconia having a composition of 10 mol% Sc ₂ O ₃ -1 mol% CeO ₂ -89 mol% ZrO ₂ (manufactured by Daiichi Rare Element Chemical Industries, Ltd.) (Hereinafter referred to as “10Sc1CeSZ”) The powder was weighed so that the weight ratio in terms of Ni and ZrO ₂ was 4: 6, mixed in a ball mill for 24 hours, and then dried to obtain a fuel electrode material. Then, a binder (polyethylene glycol) was added to the fuel electrode material to form a slurry, which was applied to one surface of the solid electrolyte plate using a screen printing method. And this was baked at 1350 degreeC for 2 hours, and it was set as the fuel electrode about 25 micrometers thick.

Next, La _0.6 Sr _0.2 Co _0.2 Fe _0.8 O ₃ is used as an air electrode material, (made by Seimi Chemical Co., Ltd.), and a binder (polyethylene glycol) is added to the slurry. And applied to the other surface of the solid electrolyte plate using a screen printing method. And this was baked at 1150 degreeC for 2 hours, and it was set as the air electrode of thickness about 25 micrometers.

  Next, the current collecting material for a fuel electrode according to Example 1 was applied on the surface of the fuel electrode by screen printing to form a layer having a thickness of about 25 μm.

  Thus, an SOFC single cell according to Example 1C in which the fuel electrode current collecting material according to Example 1 was formed in an unfired state on the outer surface of the fuel electrode was obtained.

(Comparative Example 1C)
A SOFC single cell according to Comparative Example 1C was obtained in the same manner as in the production of the SOFC single cell according to Example 1C, except that the fuel electrode current collecting material according to Comparative Example 1 was applied on the surface of the fuel electrode. It was.

(Comparative Example 2C)
A SOFC single cell according to Comparative Example 2C was obtained in the same manner as in the production of the SOFC single cell according to Example 1C, except that the fuel electrode current collecting material according to Comparative Example 2 was applied on the surface of the fuel electrode. It was.

3. Production of SOFCs according to Examples and Comparative Examples

(Example 1S)
The SOFC single cell according to Example 1C was sandwiched between a pair of metal separators (manufactured by Hitachi Metals, Ltd., “ZMG232”) (material: ferritic stainless steel) to produce an SOFC according to Example 1S. .

(Comparative Example 1S)
A SOFC according to Comparative Example 1S was obtained in the same manner as the SOFC according to Example 1S, except that the SOFC single cell according to Comparative Example 1C was used.

(Comparative Example 2S)
A SOFC according to Comparative Example 2S was obtained in the same manner as the SOFC according to Example 1S, except that the SOFC single cell according to Comparative Example 2C was used.

4). Power generation test 4.1 Power generation test <1>
Using the SOFCs according to Example 1S, Comparative Example 1S, and Comparative Example 2S, a power generation test was performed to confirm the difference in power generation performance depending on the mixing ratio of nickel oxide and stabilized zirconia in the current collecting material.

  In this power generation test, hydrogen (flow rate: 1 L / min) as fuel gas and air (flow rate: 2 L / min) as oxidant gas were supplied to each SOFC. The power generation temperature was 800 ° C., and the fuel gas used was humidified to 3% humidity through a bubbler humidified with an oil bath.

  FIG. 1 shows the relationship between the current and voltage of the SOFC according to Example 1S, Comparative Example 1S, and Comparative Example 2S.

As can be seen from FIG. That is, the SOFC according to Example 1S using the fuel electrode current collector material (nickel oxide / stabilized zirconia volume ratio = 88/12) according to Example 1 is the fuel electrode current collector material according to Comparative Example 1. It can be seen that almost the same power generation performance as the SOFC according to Comparative Example 1S using (nickel oxide = 100 vol%) is obtained.

On the other hand, the SOFC according to Comparative Example 2S using the current collecting material for fuel electrode according to Comparative Example 2 ( volume ratio of nickel oxide / stabilized zirconia = 80/20) is a ratio of stabilized zirconia that is insulating. Therefore, the power generation performance is greatly reduced. From this result, it is presumed that the volume ratio of nickel oxide / stabilized zirconia in the current collecting material is required to be at least 85/15 from the viewpoint of suppressing the decrease in power generation performance within an allowable range.

  Note that nickel oxide is reduced to nickel during power generation. Therefore, even when nickel or a nickel alloy is used instead of nickel oxide, it can be easily analogized that similar results can be obtained.

4.2 Power generation test <2>
Using the SOFC according to Example 1S and Comparative Example 1S, a power generation test for confirming the influence of the start / stop cycle on the power generation performance was performed. The power generation conditions were the same as in the above power generation test <1>.

  FIG. 2 shows the relationship between the current and voltage in the initial state and the relationship between the current and voltage after restart in the SOFC according to Comparative Example 1S. FIG. 3 shows the relationship between the current and voltage in the initial state and the relationship between the current and voltage after restart in the SOFC according to Example 1S.

  2 and 3, the following can be understood. That is, the power generation performance of the SOFC according to Comparative Example 1S using the fuel electrode current collecting material (nickel oxide = 100 vol%) according to Comparative Example 1 is greatly deteriorated after the temperature cycle.

  This is because the single cell and the metal separator are fixed by nickel, and in this state, the power generation is stopped and cooled, so that the single cell and the metal separator having different coefficients of thermal expansion are physically fixed. It is presumed that the single cell was cracked due to the shrinkage and the stress resulting from the difference in thermal expansion between the two.

On the other hand, the SOFC according to Example 1S using the fuel electrode current collecting material (Nickel oxide / stabilized zirconia volume ratio = 88/12) according to Example 1 almost changes in power generation performance before and after the temperature cycle. It can be seen that power generation is stable.

  This is because, in the current collecting material, in addition to nickel oxide powder, a specific proportion of stabilized zirconia powder that does not adhere to the separator at the temperature during battery power generation is mixed at a specific ratio, so that when the battery is started and stopped, the nickel and the material are mixed. This is presumably because the stress caused by the sticking could be relieved by the formation of fine cracks at the interface and the cracking of the single cells could be avoided.

  Further, in the SOFC according to Example 1S after restart, the current collecting material for the fuel electrode is a sintered body due to the temperature rise during power generation. Even in this case, since the power generation performance similar to that in the initial state can be obtained, even if the current collecting material for the fuel electrode becomes a sintered body, it is possible to suppress the cracking of the single cell and the increase in the contact resistance. I understand.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the case where a binder is included in the current collecting material is exemplified, but besides this, the current collecting material can be used in a dry powder state without using a binder, It is not particularly limited.

It is the figure which showed the relationship between the electric current and voltage of SOFC which concern on Example 1S, the comparative example 1S, and the comparative example 2S. It is the figure which showed the relationship between the electric current and voltage of an initial state in the SOFC which concerns on the comparative example 1S, and the relationship between the electric current and voltage after a restart. It is the figure which showed the relationship between the electric current and voltage of an initial state in the SOFC which concerns on Example 1S, and the relationship between the electric current and voltage after restart.

Claims (7)

Interposed between the anode and the separator of the solid oxide fuel cell,
Nickel powder, nickel alloy powder, and includes one or a more than consisting of nickel-based powder selected from nickel oxide powder, and a powder of a material that does not stick to the separator at a temperature during cell power generation,
In the range volume ratio (volume / volume the material powder of the nickel powder) is 87 / 13-99 / 1 and the material powder and the nickel powder,
A fuel electrode collection, wherein a particle diameter ratio of the material powder to the nickel-based powder (particle diameter of the material powder / particle diameter of the nickel-based powder) is in a range of 6/1 to 2/1. Electric material. The current collecting material for a fuel electrode according to claim 1, wherein the material powder is an oxide powder. 3. The material powder according to claim 1 or 2 , wherein the material powder is one or more selected from stabilized zirconia powder, ceria solid solution powder, alumina powder, and lanthanum gallate composite oxide powder. The collector material for fuel electrodes as described. The current collecting material for a fuel electrode according to any one of claims 1 to 3 , further comprising a binder. A fuel electrode is laminated on one side of the solid electrolyte exhibiting oxygen ion conductivity, and an air electrode is laminated on the other side,
A solid oxide fuel cell single cell, wherein the fuel electrode current collecting material according to any one of claims 1 to 4 is formed in an unfired state on the surface of the fuel electrode. A solid oxide fuel cell, wherein the solid oxide fuel cell single cell according to claim 5 is stacked in multiple stages via separators. The solid oxide fuel cell according to claim 6 , wherein the separator is a metal separator.

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