JP5281390B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell, and in particular, suppresses a change in the amount of interface caused by Ni grain growth in a fuel electrode conductive layer of a cell, and at the same time, conductance of a lead portion for current collection. The present invention relates to a solid oxide fuel cell capable of ensuring the above.

  Fuel cells, which are power generation devices that use a power generation method based on an electrochemical reaction, are attracting attention in various fields because they have excellent power generation efficiency and environmental friendliness.

As one of the fuel cells, a solid oxide fuel cell having an operating temperature of about 700 to 1000 ° C. is known.
The solid oxide fuel cell includes an element unit that generates electric power and a lead unit that collects the electric power generated by the element unit and extracts the electric power to the outside of the solid oxide fuel cell.

  The element portion includes a cylindrical substrate tube, a plurality of cells provided on the outer surface of the substrate tube, and an interconnector that electrically connects adjacent cells. The cells are laminated in the order of the fuel electrode conductive layer, the electrolyte, and the air electrode conductive layer in this order from the outer surface side of the base tube, and if necessary, the fuel electrode reaction layer, the electrolyte, and the fuel electrode conductive layer. An air electrode reaction layer is interposed between the air electrode conductive layer and the air electrode conductive layer. The interconnector electrically connects the air electrode conductive layer of one cell and the fuel electrode conductive layer of an adjacent cell.

  The base tube is calcia stabilized zirconia (CSZ), the fuel electrode conductive layer is a composite material of nickel (Ni) and yttria stabilized zirconia (YSZ), the electrolyte is yttria stabilized zirconia (YSZ), and the air electrode conductive layer is lanthanum ( An example of the material is La) -based compound.

  The base tube extends not only to the element portion but also to the lead portion, and the lead portion is formed on the outer surface of the base tube.

When a fuel such as hydrogen is supplied to the inside of the base tube of the solid oxide fuel cell and an oxidizing agent such as air or oxygen is supplied to the air electrode conductive layer side outside the base tube, the operating temperature is about 700 to 1000 ° C. Oxygen ions (O ²⁻ ) can move through the electrolyte and take out electricity. The extracted electricity is collected in the lead portion and extracted outside.

  In the solid oxide fuel cell configured as described above, conventionally, the fuel electrode conductive layer and the lead portion of the cell are made of the same material.

As described above, for example, a composite material of Ni and YSZ is used as the material constituting the fuel electrode conductive layer and the lead portion.
The fuel electrode conductive layer is a film for the purpose of energizing electrons reacted at the interface between the three layers. However, if the operating temperature is maintained at a high temperature of about 700 ° C. to 1000 ° C. for a long time, a composition change called Ni grain growth occurs. It has been found that the amount of interface changes, i.e. there is a problem with durability. As a countermeasure to the change in the interface amount, for example, a method of reducing the Ni content that bears the conductive path, or reducing the continuity of Ni by highly dispersing Ni can be considered. As a result, the conductivity decreases, and the conductivity of the lead portion formed of the same material cannot be sufficiently ensured.
That is, from the viewpoint of durability of the fuel electrode conductive layer accompanied by a reaction, it is preferable to use a material whose conductivity of the fuel electrode conductive layer is lowered, but when such a material is used, the fuel electrode conductive layer and the lead portion are used. Since the same substance is used, the conductivity of the lead portion without reaction is also lowered, and the output of the entire solid oxide fuel cell is lowered.

  Patent Document 1 discloses a first fuel cell that is operated in a temperature range of 900 to 1000 ° C. using a stabilized zirconia-based material as an electrolyte on a substrate tube, and a ceria-based or lanthanum gallate-based electrolyte as an electrolyte on the substrate tube. A solid oxide fuel cell comprising a second fuel cell that is operated in a temperature range of 600 to 900 ° C. using any one of the above materials is disclosed.

JP-A-2005-79060

  However, the technique disclosed in Patent Document 1 can make effective use of a space in which a significant temperature difference from a power generation unit such as an end of a fuel cell tube occurs by changing the electrolyte material depending on the temperature range. In the region of the second fuel cell operated in the low temperature range of 600 to 900 ° C., the change in the amount of the interface in the fuel electrode conductive layer may be reduced, but the temperature range of 900 to 1000 ° C. is high. In the region of the first fuel cell operated at 1, the change in the interface amount in the fuel electrode conductive layer cannot be reduced.

  Therefore, in view of the problems of the prior art, the present invention suppresses the change in the amount of the interface due to the Ni grain growth in the fuel electrode conductive layer, ensures the durability of the fuel electrode conductive layer, and at the lead portion. It is an object of the present invention to provide a solid oxide fuel cell that can sufficiently ensure conductivity.

In order to solve the above problems, the present invention includes a fuel electrode conductive layer formed on a base tube, an electrolyte formed on the fuel electrode conductive layer, and an air electrode conductive layer formed on the electrolyte. Multiple cells,
A solid oxide fuel cell comprising an interconnector for electrically connecting adjacent cells of the plurality of cells, the solid oxide fuel cell having a lead portion that collects electric power generated by the cell, and conducting the fuel electrode Both the layer and the lead portion are materials containing nickel (Ni), and materials having at least one composition or structure are used to ensure the durability of the fuel electrode conductive layer and the conductivity of the lead portion. This is a basic feature.

  In this way, different materials for the fuel electrode conductive layer and the lead portion, more specifically, a fuel electrode conductive layer with a reaction is secured with a certain level of conductivity and a highly durable material for the reaction. By using a highly conductive material for the lead portion that is not accompanied, the interface amount change due to Ni grain growth in the fuel electrode conductive layer is suppressed, and sufficient conductivity is ensured in the lead portion. It is possible to provide a solid oxide fuel cell capable of

Further, the fuel electrode conductive layer and the lead portion are made of a material containing Ni or Ni-based alloy and yttria stabilized zirconia (YSZ), and the fuel electrode conductive layer is obtained by pulverizing the material. using highly dispersed organization, the lead unit may use a low dispersion tissue body obtained by sintering the material.

When the material used for the fuel electrode conductive layer is pulverized, the dispersibility of Ni is improved and the continuity of Ni is lowered. Therefore, Ni grain growth in the fuel electrode conductive layer can be suppressed, a change in the interface amount can be suppressed, and durability can be ensured. The pulverization is performed by, for example, mixing with a ball mill.
In addition, the material used for the lead portion can sinter so that Ni having a large particle size can be put into the structure, thereby improving the continuity of Ni. Therefore, sufficient conductivity can be ensured in the lead portion.

  Thereby, the material used for the fuel electrode conductive layer and the material used for the lead portion are different by applying different pretreatments to the composite material of Ni or Ni-based alloy and YSZ with the same material and mixing ratio. Can be a material. In other words, the composite material of Ni or Ni-based alloy and YSZ before the pretreatment can be made common for the fuel electrode conductive layer and for the lead portion, and the management of the material is easy.

  Further, the fuel electrode conductive layer and the lead portion are made of a material containing a composite material made of Ni or a Ni-based alloy and yttria-stabilized zirconia (YSZ), and the material used for the fuel electrode conductive layer is a material The content of NiO in the material is 30 to 60 vol%, and the material used for the lead portion is characterized in that the content of NiO in the material is 50 to 70 vol%.

  As a result, it is possible to suppress the change in the amount of the interface due to the grain growth of Ni in the fuel electrode conductive layer only by adjusting the blending ratio of Ni or a Ni-based alloy and YSZ without performing the structure control, and the fuel electrode conductivity. The durability of the layer can be ensured, and the conductivity in the lead portion can be sufficiently ensured, the material can be easily managed, and the production of the solid oxide fuel cell is easy.

  In addition, the fuel electrode conductive layer uses a material containing a composite material made of Ni or a Ni-based alloy and YSZ, and the lead portion contains Ni and is more conductive than the material used for the fuel electrode conductive layer. It is characterized by using a material with high properties.

Examples of materials having higher conductivity than the material used for the fuel electrode conductive layer include Ni / MgAl ₂ O ₄ , Ni / YSZ / Al ₂ O ₃ , Ni / SDC (Samarium Doped Ceria), Ni / GDC (Gadolinium). Doped ceria).

  As a result, it is possible to suppress changes in the amount of the interface due to Ni grain growth in the fuel electrode conductive layer, to ensure the durability of the fuel electrode conductive layer, and to sufficiently ensure the conductivity in the lead portion. In addition to this, since the degree of freedom of the material is high, the material can be selected according to the manufacturing cost.

  As described above, according to the present invention, the change in the amount of the interface due to the Ni grain growth in the fuel electrode conductive layer is suppressed, the durability of the fuel electrode conductive layer is ensured, and the conductivity in the lead portion is increased. A solid oxide fuel cell that can be sufficiently secured can be provided.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

1 is an external view of a solid oxide fuel cell 2 in Example 1. FIG.
The solid oxide fuel cell 2 includes an element part (battery part) 4 that generates power and a lead part (energization) that collects the electric power generated by the element part 4 and takes it out of the solid oxide fuel cell 2 Part) 6.

FIG. 2 is a partial cross-sectional view of the element portion 4 in the solid oxide fuel cell.
The element unit 4 includes a cylindrical base tube 22, a plurality of cells 8 provided on the outer surface of the base tube 22, and an interconnector 10 that electrically connects adjacent cells 8. Each cell 8 is laminated in order of the fuel electrode conductive layer 12, the electrolyte 16, and the air electrode conductive layer 20 from the outer surface side of the base tube 22, and the fuel electrode is interposed between the fuel electrode conductive layer 12 and the electrolyte 16. An air electrode reaction layer 18 is interposed between the reaction layer 14, the electrolyte 16, and the air electrode conductive layer 20. The interconnector 10 electrically connects the air electrode conductive layer 20 of one cell 8 and the fuel electrode conductive layer 14 of another cell 8.

The base tube 22 is cylindrical and extends not only to the element portion 4 shown in FIG. 1 but also to the lead portion 6, and the lead portion 6 is formed on the outer surface of the base tube 22.
As an example of the material of each part, the base tube 22 may be calcia stabilized zirconia (CSZ), the electrolyte 16 may be yttria stabilized zirconia (YSZ), and the air electrode conductive layer may be lanthanum (La) compound.

When a fuel such as hydrogen is supplied to the inside of the base tube 22 of the solid oxide fuel cell 2 and an oxidant such as air or oxygen is supplied to the air electrode conductive layer 20 outside the base tube 22, the operating temperature is about 700. At ˜1000 ° C., oxygen ions (O ²⁻ ) can move through the electrolyte 16 and take out electricity.

A current flow during operation of the solid oxide fuel cell will be described. Oxygen ions obtained from the air electrode conductive layer 20 by supplying the oxidizing agent pass through the electrolyte 16 and react with hydrogen in the fuel electrode conductive layer 12 to generate water (H ₂ O) and release electrons. . At this time, the current flows through the fuel electrode conductive layer 12, the electrolyte 16, and the air electrode conductive layer 20, flows through the interconnector 10, and flows to the fuel electrode conductive layer 12 of the adjacent cell.
The air electrode reaction layer 18 is provided at the interface between the air electrode conductive layer 20 and the electrolyte 16 and is provided to improve the reactivity in the power generation reaction of the fuel cell.

The material of the lead portion 6 in the solid oxide fuel cell 2 configured as described above was prepared as follows.
First, NiO and YSZ powders are mixed by 50 vol%, and one or two or more of pulverization, sintering and granulation are combined one or more times to obtain a structure containing a desired particle size. Created the body. Here, the desired particle size means a particle size larger than the particle size of the structure forming the fuel electrode conductive layer described later.
Sintering is the joining of particles at high temperature, and the solid powder aggregate is solidified by heating at a temperature lower than the melting point to obtain a dense object called a sintered body. .
In addition, granulation means that fine powder is adhered and aggregated or compressed to form grains having a diameter larger than that of the fine powder.

  And it sinters or granulates as a pre-processing with respect to the structure | tissue obtained by performing 1 type or 2 types or more in combination among the said grinding | pulverization, sintering, and granulation once or several times, and predetermined. The low dispersion structure | tissue used for the lead part 6 was obtained by mixing the thing of the particle size of this, and also making it sinter.

The material for the fuel electrode conductive layer 12 was prepared as follows.
First, 50 vol% of NiO and YSZ powders were mixed, coarsely pulverized, pulverized, atomized, and mixed to obtain a highly dispersed structure. More specifically, a mixture obtained by mixing 50 vol% each of the Ni and YSZ powders was mixed with a pole mill, the particle size was refined, and fired to obtain a highly dispersed structure.

FIG. 3 shows images of the low dispersion structure and the high dispersion structure obtained as described above.
3A is an image diagram of a low dispersion tissue body, and FIG. 3B is an image diagram of a high dispersion tissue body. In FIG. 3A, it can be seen that the particle diameters of Ni and YSZ are both large and the dispersibility of the material is low. In FIG. 3B, it can be seen that the particle diameters of Ni and YSZ are fine and the dispersibility of the material is high.

  Thus, by using a highly dispersed structure in the fuel electrode conductive layer 12, the continuity of Ni is lowered, so that Ni grain growth in the fuel electrode conductive layer can be suppressed. By suppressing the grain growth of Ni, it is possible to suppress the change in the interface amount of the fuel electrode conductive layer due to the reaction of Ni by power generation, and to ensure the durability of the fuel electrode conductive layer.

  Further, by using a low dispersion structure in the lead portion 6, the continuity of Ni is improved, and therefore the conductivity in the lead portion can be sufficiently ensured.

  Therefore, it is possible to suppress the change in the amount of the interface due to the Ni grain growth in the fuel electrode conductive layer 12 to ensure the durability of the fuel electrode conductive layer 12 and sufficiently ensure the conductivity in the lead portion 6. Can do.

  Furthermore, the fuel electrode conductive layer 12 is obtained by subjecting the material used for the fuel electrode conductive layer 12 and the material used for the lead portion 6 to the same material and a compounding ratio of Ni and YSZ. And the material of the lead part 6 can be obtained. That is, since the composite material of Ni and YSZ before the treatment can be used in common for the fuel electrode conductive layer and the lead portion, the management of the material is easy.

  Since the solid oxide fuel cell in Example 2 is the same as the solid oxide fuel cell shown in FIGS. 1 and 2 except for the materials of the fuel electrode conductive layer 12 and the lead portion 6, the description thereof will be omitted. Are omitted, and the same reference numerals represent the same thing.

  The material of the fuel electrode conductive layer 12 and the lead portion 6 in the solid oxide fuel cell 2 configured as described above was examined.

11 samples shown in Table 1 were prepared by changing the volume ratio of NiO and YSZ in the composite material of NiO and YSZ and the particle size of ZrO ₂ in YSZ.

  For each of the 11 samples, the conductivity (S / cm) at temperatures of 600 ° C., 700 ° C., 800 ° C., 900 ° C., and 1000 ° C. was measured. The results are shown in FIG. The plot symbols in the legend in FIG. 4 represent the sample names FCR-1 to 11 in order from the top.

As shown in FIG. 4, the dielectric constant decreased as the NiO content decreased at any temperature at which the measurement was performed. From this, it can be said that the Ni grain growth rate can be reduced by reducing the content of NiO contained in the fuel electrode conductive layer 12.
Therefore, the anode conductive layer 12 was made of a composite material made of NiO and YSZ, and the content of NiO in the composite material was set to 30 to 60 vol%. When the content of NiO is smaller than 30 vol%, as shown in FIG. 4, the dielectric constant is too small to ensure the conductivity of the fuel electrode conductive layer 12. On the other hand, if the NiO content is greater than 60 vol%, the effect of reducing the Ni grain growth rate is not sufficient.

Moreover, the lead part 6 used the composite material which consists of NiO and YSZ, and set the minimum of content of NiO in this composite material to 50 vol%. As can be seen from FIG. 4 and FIG. 5 described later, when the NiO content is 50 vol% or more, the dielectric constant is about 500 S / cm in the range of 700 to 1000 ° C., which is the operating temperature of the solid oxide fuel cell 2. That's it. If the dielectric constant of 500 S / cm or more can be achieved, the conductivity of the lead portion 6 does not become the rate-determining factor of the performance of the solid oxide fuel cell because of the dielectric constant of other materials forming the solid oxide fuel cell. A decrease in performance can be prevented. That is, the lead portion 6 can ensure sufficient conductivity.
FIG. 5 is a table summarizing the coefficient of thermal expansion when the mixing ratio (vol%) of NiO / YSZ is changed. As can be seen from FIG. 5, when the NiO content is 75 vol% or more, the thermal expansion coefficient may exceed 14.0 × 10 ⁻⁶ K ^−1, and it cannot be used practically. Therefore, the NiO content of 70 vol% at which the thermal expansion coefficient does not exceed 14.0 × 10 ⁻⁶ K ⁻¹ at the maximum is set as the upper limit of the NiO content of the lead portion 6.
In summary, the lead portion 6 was made of a composite material made of Ni and YSZ, and the content of NiO in the composite material was set to 50 to 70 vol%.

Based on the values set in this way, a composite material made of NiO and YSZ having a NiO content of 30 to 60 vol% is used for the fuel electrode conductive layer 12, and the NiO content is 50 for the lead portion 6. A composite material composed of NiO and YSZ, which was ˜70 vol%, was used.
This suppresses the change in the amount of the interface due to the NiO grain growth in the fuel electrode conductive layer 12 to ensure the durability of the fuel electrode conductive layer 12 and sufficiently ensure the conductivity in the lead portion 6. be able to.

  Further, the problem can be solved by adjusting the blending ratio of NiO and YSZ without controlling the structure, the material can be easily managed, and the production of the solid oxide fuel cell is easy.

  Since the solid oxide fuel cell 2 in Example 3 is the same as the solid oxide fuel cell 2 shown in FIGS. 1 and 2 except for the materials of the fuel electrode conductive layer 12 and the lead portion 6, The description thereof is omitted, and the same reference numerals represent the same thing.

  As a material for the fuel electrode conductive layer 12, a composite material made of Ni and YSZ was used. Thereby, the grain growth rate of Ni can be suppressed.

As the material of the lead portion 6, a material having higher conductivity than the fuel electrode conductive layer 12 was used. Specifically, Ni / MgAl ₂ O ₄ was used. Ni / MgAl ₂ O ₄ has a dielectric constant of about 2000 to 3000 S / cm at 900 ° C., and has higher conductivity than Ni / YSZ whose dielectric constant at 900 ° C. is about 500 S / cm.
In addition to Ni / MgAl ₂ O ₄ , Ni / YSZ / Al ₂ O ₃ , NiO / MgAl ₂ O ₄ , NiO / SDC, NiO / GDC, or the like can be used. For example, Ni / YSZ / Al ₂ O ₃ has a dielectric constant of about 1000 to 2000 S / cm at 900 ° C.
Further, the coefficient of thermal expansion of each of the substances is
Ni / YSZ (50/50) 12.0-13.0 × 10 ⁻⁶ K ⁻¹
Ni / YSZ / Al ₂ O ₃ (63/21/14) 11.0 to 12.0 × 10 ⁻⁶ K ⁻¹
NiO / MgAl ₂ O ₄ (60/40) 10.5 to 11.0 × 10 ⁻⁶ K ⁻¹
This is a practical range.
However, the numerical value in the parenthesis is a volume ratio of each component.

In this way, a composite material composed of Ni and YSZ was used for the fuel electrode conductive layer 12, and a material having higher conductivity than the fuel electrode conductive layer such as Ni / MgAl ₂ O ₄ was used for the lead portion 6.
Thereby, the change in the amount of the interface due to the Ni grain growth in the fuel electrode conductive layer 12 is suppressed, the durability of the fuel electrode conductive layer 12 is ensured, and the conductivity in the lead portion 6 is sufficiently ensured. be able to.

  Furthermore, since the freedom degree of material is high by this, material can be selected according to manufacture on a cost side.

  Solid oxide capable of suppressing the change in the amount of the interface due to Ni grain growth in the fuel electrode conductive layer, ensuring the durability of the fuel electrode conductive layer, and sufficiently ensuring the conductivity in the lead portion It can be used as a type fuel cell.

It is an external view of a solid oxide fuel cell. It is a partial cross section figure of the element part in a solid oxide fuel cell. 3A is an image diagram of a low dispersion tissue body, and FIG. 3B is an image diagram of a high dispersion tissue body. It is the graph which showed the relationship between a dielectric constant and temperature when changing the volume ratio of NiO and YSZ. It is the table | surface which put together the thermal expansion coefficient at the time of changing the compounding ratio (vol%) of NiO / YSZ.

Explanation of symbols

2 Solid Oxide Fuel Cell 4 Element Unit 6 Lead Unit 8 Cell 10 Interconnector 12 Fuel Electrode Conductive Layer 14 Fuel Electrode Reaction Layer 16 Electrolyte 18 Air Electrode Reaction Layer 20 Air Electrode Conductive Layer 22 Base Tube

Claims (4)

A plurality of cells including a fuel electrode conductive layer formed on a base tube, an electrolyte formed on the fuel electrode conductive layer, and an air electrode conductive layer formed on the electrolyte;
In a solid oxide fuel cell comprising an interconnector for electrically connecting adjacent cells among the plurality of cells,
A lead part for collecting the power generated in the cell;
Each of the fuel electrode conductive layer and the lead portion is a material containing nickel (Ni), and the materials having different compositions or structures are used to make the durability of the fuel electrode conductive layer and the conductivity of the lead portion. to ensure gender,
The anode conductive layer uses a highly dispersed structure of the material,
A solid oxide fuel cell , wherein a low dispersion structure of the material is used for the lead portion .   A plurality of cells including a fuel electrode conductive layer formed on a base tube, an electrolyte formed on the fuel electrode conductive layer, and an air electrode conductive layer formed on the electrolyte;
  In a solid oxide fuel cell comprising an interconnector for electrically connecting adjacent cells among the plurality of cells,
  A lead part for collecting the power generated in the cell;
  Each of the fuel electrode conductive layer and the lead portion is a material containing nickel (Ni), and the materials having different compositions or structures are used to make the durability of the fuel electrode conductive layer and the conductivity of the lead portion. Secure
  The material used for the fuel electrode conductive layer has a NiO content in the material of 30 to 60 vol%,
  A material used for the lead portion is a solid oxide fuel cell characterized in that the NiO content in the material is 50 to 70 vol%.   A plurality of cells including a fuel electrode conductive layer formed on a base tube, an electrolyte formed on the fuel electrode conductive layer, and an air electrode conductive layer formed on the electrolyte;
  In a solid oxide fuel cell comprising an interconnector for electrically connecting adjacent cells among the plurality of cells,
  A lead part for collecting the power generated in the cell;
  Both the fuel electrode conductive layer and the lead portion are materials containing nickel (Ni),
Using materials having different compositions or at least one structure, the durability and leakage of the anode conductive layer are improved.
Ensure the conductivity of the
The lead portion uses a material containing Ni and having higher conductivity than a material used for the fuel electrode conductive layer.   5. The material including a composite material made of Ni or a Ni-based alloy and yttria-stabilized zirconia (YSZ) is used for the fuel electrode conductive layer and the lead portion. A solid oxide fuel cell according to 1.

Images