KR101963980B1 - Cathode powder for solid oxide fuel cell and method of the same - Google Patents

Abstract

According to the present invention, the cathode powder for a solid oxide fuel cell can be represented by a compound of chemical formula 1, wherein Sm is substituted for Nd to satisfy the relational formula 1. The chemical formula 1 can be expressed as {Sm_(1-x)Nd_x}Ba_(1-y)Sr_yCo_zO_(5+d). In the chemical formula 1, x, y, z satisfy inequations, 0 < x < 1, 0.4 <= y <= 0.6, and 1.9 <= z <= 2.1, and d is a positive integer exceeding zero while being equal to or less than one for representing the electrical neutrality of the compound of the chemical formula 1. The relational formula 1 can be expressed as EC >= 400, wherein EC is the electric conductivity measured in units of S/cm at 500°C after compressing and molding the cathode powder to manufacture a bar-shaped product in the size of 5.5 mm × 4 mm × 24 mm.

Description

Technical Field [0001] The present invention relates to a cathode powder for a solid oxide fuel cell,

More particularly, the present invention relates to an air electrode powder for a solid oxide fuel cell having a double layer perovskite structure and a method for manufacturing the same.

Solid Oxide Fuel Cell (SOFC), which operates at a high temperature, exhibits excellent electrical conductivity and catalytic properties as well as an advantage of increasing the activity of electrodes and electrolytes due to high temperature operating environment characteristics. However, Problems of high temperature stability, chromium poisoning, durability of the metal material constituting the SOFC, and oxidation are caused.

In order to solve these problems, researches on SOFC single cells and stacks are being conducted using various methods. In order to reduce the long-term stability and operating cost, a middle-temperature solid oxide fuel cell (SOFC) oxide fuel cell, IT-SOFC).

However, when operating at a high temperature, the performance is deteriorated due to the increase of the electrolyte resistance and the polarization resistance of the electrode. In particular, research and development of a new air electrode is essential because the performance deterioration due to the increase of the polarization resistance of the air electrode is dominant compared with the increase of the polarization resistance of the electrolyte and the fuel electrode.

Recently, a layered perovskite oxide, which shows the chemical structure of AA'B ₂ O _{5 + d} , is applied as an air electrode of an intermediate-temperature solid oxide fuel cell (IT-SOFC) have. Among them, A-site mainly substitutes Lanthanide element such as Ce, Pr, Nd, Pm, Sm and Gd, and the study of substituting Ba and Sr in A'-site has been carried out. B-site has been studied to improve the performance by improving the compatibility between cathodes and electrolytes by lowering the coefficient of thermal expansion by replacing Co, Fe, Mn, Ni and Cu.

These studies were though, AA'B ₂ O layered perovskite Oxide showing the chemical structure of the _{5 + d,} so should proceed for a long time in the heat treatment condition of high temperature is low in the efficiency of the process, typically after the final intermediate image is shown AA'B ₂ Since the layered perovskite oxide having the chemical structure of O _{5 + d} is produced, the particle size of the final cathode electrode powder is too large. Also, when the particle size of the air electrode powder is coarsened, there is a problem that the reducing power for reducing oxygen molecules is reduced.

Korean Patent Publication No. 10-2017-0044462

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to improve the electrical conductivity and the area specific resistance (ASR) by substituting Sm and Nd in the A site in the chemical structure of AA'B ₂ O _{5 +} Wherein the solid oxide fuel cell comprises a cathode active material.

The present invention also includes an air electrode for a solid oxide fuel cell using the above-described cathode electrode powder for a solid oxide fuel cell.

On the other hand, other unspecified purposes of the present invention will be further considered within the scope of the following detailed description and easily deduced from the effects thereof.

In order to achieve the above object, an air electrode powder for a solid oxide fuel cell according to an embodiment of the present invention is represented by the following chemical formula 1, wherein Nd is substituted for the Sm site,

[Chemical Formula 1]

(Sm _{1 - x} Nd _x ) Ba _{1 - y} Sr _y Co _z O _{5 + d}

(In the formula 1, 0 <x <1, 0.4 ≤ y ≤ 0.6, 1.9 ≤ z ≤ 2.1, and d is a positive number of more than 0 and 1 or less.

[Relation 1]

EC ≥ 400

(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)

In the cathode electrode powder for a solid oxide fuel cell according to an embodiment of the present invention, x may be 0.5? X? 0.9.

In the cathode powder for a solid oxide fuel cell according to an embodiment of the present invention, the cathode powder for a solid oxide fuel cell may have a tetragonal crystal structure.

According to another aspect of the present invention, there is provided a method of manufacturing an air electrode powder for a solid oxide fuel cell, comprising the steps of: a) mixing a metal salt and a combustion material to obtain a metal salt mixed solution; b) heating the metal salt mixed solution to produce a raw material powder; and c) calcining the raw material powder to produce a cathode powder for a solid oxide fuel cell, wherein the cathode powder for a solid oxide fuel cell is represented by the following Formula 1, Can:

[Chemical Formula 1]

(Sm _{1 - x} Nd _x ) Ba _{1 - y} Sr _y Co _z O _{5 + d}

(In the formula 1, 0 <x <1, 0.4 ≤ y ≤ 0.6, 1.9 ≤ z ≤ 2.1, and d is a positive number of more than 0 and 1 or less.

[Relation 1]

EC ≥ 400

(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)

In the method of manufacturing an air electrode powder for a solid oxide fuel cell according to an embodiment of the present invention, the metal salt may include a stoichiometric ratio of samarium (Sm) nitrate, neodymium (Nd) nitrate, strontium (Sr) nitrate and cobalt (Co) nitrate.

In the method of manufacturing the cathode powder for a solid oxide fuel cell according to an embodiment of the present invention, the calcination temperature may be 600 to 1100 ° C in the step c).

The present invention also includes a cathode for a solid oxide fuel cell comprising the above-described cathode electrode powder for a solid oxide fuel cell.

According to another aspect of the present invention, there is provided a method of manufacturing a cathode for a solid oxide fuel cell, comprising: preparing an electrolyte support; Coating the electrolyte support with an air electrode paste containing an air electrode powder for a solid oxide fuel cell; And sintering the coated electrolyte support.

In the method of manufacturing an air electrode for a solid oxide fuel cell according to an embodiment of the present invention, the air electrode paste may include a dispersant and a resin solution.

As described above, the electrical conductivity of the air electrode powder for a solid oxide fuel cell according to the present invention can be improved by replacing Nd in the Sm site.

In addition, solid oxide fuel cell air electrode powder production process according to the present invention is to obtain a pure crystal phase at a lower calcining temperature than conventional solid-phase sintering method, Sm and Nd yi A place in the chemical structure of AA'B ₂ O _{5 + d} (A- site to form a single-phase solid solution.

Further, since the air electrode powder for a solid oxide fuel cell according to the present invention has a uniform and fine grain size, the air electrode for a solid oxide fuel cell using such an air electrode powder can have a finer pore structure, Breakage of the porous structure due to thermal shock can be prevented.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

1 is an XRD graph of an air electrode powder for a solid oxide fuel cell produced in Examples 1 to 9 and Comparative Example 1 of the present invention.
2 is an XRD graph of the cathode powder for solid oxide fuel cells prepared in Examples 10 to 14 and Comparative Examples 3 to 8 of the present invention.
3 is an XRD graph of the cathode powder for a solid oxide fuel cell manufactured in Examples 14 to 16 of the present invention.
4 is a SEM photograph of an air electrode powder for a solid oxide fuel cell manufactured in Example 8 of the present invention.
5A is a high-magnification SEM photograph of an air electrode powder for a solid oxide fuel cell manufactured in Example 7 of the present invention.
FIG. 5B is a high-magnification SEM photograph of the cathode powder for a solid oxide fuel cell manufactured in Example 8 of the present invention. FIG.
5C is a high-magnification SEM photograph of the air electrode powder for a solid oxide fuel cell manufactured in Example 9 of the present invention.
6A is a SEM photograph showing the surface of the air electrode for a solid oxide fuel cell manufactured in Example 24 of the present invention.
6B is an SEM photograph showing cut surfaces of an air electrode and an electrolyte support after cutting the half-cell fabricated in Example 24 of the present invention.
7 is a graph showing electric conductivity measurement results of the air electrode powder for a solid oxide fuel cell manufactured in Examples 1 to 9 and Comparative Example 1 of the present invention.
Fig. 8 is a diagram showing the results of area specific resistance measurement of the half-cells produced in Examples 17 to 25 and Comparative Example 9 of the present invention.

Hereinafter, the present invention will be described in detail. The following embodiments and drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. In addition, unless otherwise defined in the technical and scientific terms used herein, unless otherwise defined, the meaning of what is commonly understood by one of ordinary skill in the art to which this invention belongs is as follows, A description of known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted. Further, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing depicted in the accompanying drawings.

As used herein, the term " moderate temperature " may mean a temperature of about 400 to 750 C, " middle temperature " means a temperature of about 550 to 750 C, .

As used herein, the term " SBSCO & _{quot ; 5} Sr _{0 . 5} Co ₂ O _{5 + d} , and "NBSCO" may mean NdBa _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} .

The cathode electrode powder for a solid oxide fuel cell according to an embodiment of the present invention is represented by the following formula (1).

[Chemical Formula 1]

(Sm _{1 - x} Nd _x ) Ba _{1 - y} Sr _y Co _z O _{5 + d}

(In the formula 1, 0 <x <1, 0.4 ≤ y ≤ 0.6, 1.9 ≤ z ≤ 2.1, and d is a positive number of more than 0 and 1 or less.

Also, the air electrode powder for a solid oxide fuel cell according to the present invention has electric conductivity satisfying the following relational expression 1 by replacing Nd in the Sm site of the formula (1).

[Relation 1]

EC ≥ 400

(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)

Accordingly, the cathode material for a solid oxide fuel cell according to the present invention can prevent performance deterioration due to increase in the electrolyte resistance and the polarization resistance of the electrode when the cathode material used in the existing high temperature operating environment is operated in the middle and low temperature range have.

In addition, according to another embodiment of the present invention, the cathode electrode powder for a solid oxide fuel cell may have the following formula: x = 0.5? X? 0.9. When the category of x is satisfied, the cathode powder for a solid oxide fuel cell according to the present invention can have a higher electric conductivity effect.

In detail, the air electrode powder for a solid oxide fuel cell according to the present invention may have an EC value of 600 or more in the above relational expression (1). Accordingly, the present invention can stably operate in an intermediate low temperature region of 500 or more and exhibits an effect of significantly increasing the electric conductivity.

Also, the cathode powder for a solid oxide fuel cell according to the present invention may have a tetragonal crystal structure.

Specifically, by substituting the above-mentioned Nd for the Sm site, the lattice constant of the above-mentioned formula (1) increases. That is, when Nd is substituted with a small amount of x = 0.4 or less in the Sm site, the crystal structure of the present invention is maintained in an orthorhombic system crystal structure, and the mobility of electrons is decreased.

However, when the Nd is substituted with an excess of x = 0.5 or more in the Sm moiety, the crystal structure changes into a tetragonal system crystal structure showing high symmetry in the orthorhombic crystal structure, Thereby exhibiting higher electrical conductivity.

Also, according to another embodiment of the present invention, the cathode electrode powder for a solid oxide fuel cell may have a composition of 0.7? X? 0.8 in the formula (1). When the category of x is satisfied, the cathode powder for a solid oxide fuel cell according to the present invention can have a higher electric conductivity effect.

In detail, the air electrode powder for a solid oxide fuel cell according to the present invention may have an EC value of 650 or more in the above relational expression (1). Accordingly, the present invention can stably operate in an intermediate and low temperature range of 500 DEG C or higher and exhibits an effect of significantly increasing the electric conductivity.

The present invention also includes a method for producing the above-described cathode electrode powder for a solid oxide fuel cell.

According to another aspect of the present invention, there is provided a method of manufacturing an air electrode powder for a solid oxide fuel cell, comprising the steps of: a) mixing a metal salt and a combustion raw material to obtain a metal salt mixed solution; b) heating the mixed metal salt solution to obtain a raw material powder; and c) calcining the raw material powder to produce a cathode powder for a solid oxide fuel cell, wherein the cathode powder for a solid oxide fuel cell is represented by the following Formula 1, Can:

[Chemical Formula 1]

(Sm _{1 - x} Nd _x ) Ba _{1 - y} Sr _y Co _z O _{5 + d}

(In the formula 1, 0 <x <1, 0.4 ≦ y ≦ 0.6, 1.9 ≦ z ≦ 2.1, and d is a positive number of 0 or 1 or less.

[Relation 1]

EC ≥ 400

(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)

Further, in the method of manufacturing an air electrode powder for a solid oxide fuel cell according to an embodiment of the present invention, in the step a), the metal salt may include a stoichiometric ratio of Sm nitrate, Nd nitrate , A mixture of Sr nitrate and Co nitrate is preferable for attaining the aimed effect in the present invention.

Further, in the step a), the metal salt mixed solution may include a solvent. The solvent may be such that it can be homogeneously mixed with the metal salt. In the present invention, the solvent is not particularly limited, but may be a polar solvent capable of dissolving a metal salt such as water or distilled water.

In addition, in the method of manufacturing an air electrode powder for a solid oxide fuel cell according to an embodiment of the present invention, in the step b), a combustion synthesis reaction between the metal salt and the combustion raw material occurs in the metal salt mixed solution, The metal salt mixed solution may be heated to about 200 to 400 캜 so that it can be made into an oxide of a powder form of about 1 탆 or less.

In the method of manufacturing an air electrode powder for a solid oxide fuel cell according to an embodiment of the present invention, in the step (c), the calcination temperature is 600 to 600 ° C at which the double layer perovskite crystal structure of the formula (1) 1200 deg. C is preferable for achieving the desired effect in the present invention. In detail, when the calcination temperature is less than 600 ° C, the cathode powder for a solid oxide fuel cell according to the present invention has difficulty in having a double layer perovskite crystal structure. In addition, when the calcination temperature is higher than 1200 ° C., the air electrode powder for a solid oxide fuel cell according to the present invention is not preferable since the above-described Ba (barium) is not only volatilized but also the air electrode containing Ba is melted.

Meanwhile, in the method of manufacturing an air electrode powder for a solid oxide fuel cell according to another embodiment of the present invention, in the step a), the combustion raw material may include glycine. That is, in the step a), a metal salt mixed solution may be obtained by mixing the metal salt and glycine with a solvent. At this time, the molar ratio of the metal salt and glycine is preferably in the range of 1: 2 to 4: metal salt: glycine. B) It is preferable to initiate the combustion synthesis reaction properly during the step and to obtain a homogeneous oxide raw material powder without unreacted.

On the other hand, the combustion synthesis method using glycine can obtain a small powder compared to the conventional solid phase synthesis method, and shows a merit that crystallinity and reproducibility are superior even when a relatively small powder is obtained. That is, the combustion synthesis method using glycine rapidly converts the precursor solution from the molecular state of the precursor solution directly to the final phase without forming a middle phase, so that a homogeneous nano-sized powder can be obtained at a low cost.

In addition, the combustion synthesis method using glycine is advantageous in that the pyrolysis power is relatively higher than that of the combustion synthesis method using citric acid, and the heat generation is easily generated. That is, since the air electrode powder prepared by the combustion synthesis method using glycine has a small particle size and uniformity, when the air electrode powder is applied to the air electrode, the initial particle size is small and the shape of the air electrode powder can be maintained even after sintering. A denser porous structure can be obtained with the increase of the three-phase interface.

The present invention also includes an air electrode for a solid oxide fuel cell comprising the aforementioned cathode electrode powder for a solid oxide fuel cell.

A cathode for a solid oxide fuel cell according to another aspect of the present invention may be formed on an electrolyte support.

In addition, the cathode for solid oxide fuel cells can be used as an electrolyte supporting body type unit cell.

As a specific, non-limiting example, the cathode for a solid oxide fuel cell is a porous structure having an average size of pores of about 0.5 to 5 탆, and the porous structure may be present in an amount of 5 to 50 vol% have.

According to one embodiment of the present invention, the area specific resistivity (ASR) of the air electrode for a solid oxide fuel cell is 1 to 4 Ωcm ² , Preferably in the range of 1.7 to 3.6 Ωcm ² , more preferably in the range of 1.75 to 3.53 Ωcm ² Lt; / RTI &gt;

The area specific resistivity (ASR) of the air electrode for a solid oxide fuel cell is 0.1 to 1 Ωcm ² , Preferably 0.2 to 0.7 [Omega] cm &lt; ² &gt; , More preferably in the range of 0.24 to 0.54 [Omega] cm &lt; ² &gt; Lt; / RTI &gt;

The area specific resistivity (ASR) of the air electrode for a solid oxide fuel cell is preferably 0.01 to 0.4 Ωcm ² And preferably 0.02 to 0.2 Ωcm ² , More preferably 0.043 to 0.098 Ωcm ² Lt; / RTI &gt;

The present invention also includes a method of manufacturing the above-described cathode for a solid oxide fuel cell.

According to another aspect of the present invention, there is provided a method of manufacturing a cathode for a solid oxide fuel cell, comprising: preparing an electrolyte support; Coating the electrolyte support with an air electrode paste containing an air electrode powder for a solid oxide fuel cell; And sintering the coated electrolyte support.

In detail, the electrolyte support may be any material capable of supporting the air electrode, but a ceria electrolyte support may be used in consideration of thermal stability and electrical conductivity. However, the present invention is not limited to the ceria electrolyte support.

The air electrode paste may include a dispersant, a resin solution, a solvent, and the like.

The dispersant is not particularly limited as long as it is known in the art. Examples of the dispersing agent include urethane resin, acrylic acid resin, pyrrolidone resin and polycarboxylic acid resin. More specific examples include KD-1 and polyvinyl pyrrolidone.

The dispersant may be contained in an amount of 5% by weight or less based on the total weight of the air electrode paste.

The resin solution may include a binder resin capable of imparting an adhesive force to the air electrode paste. The binder resin is not particularly limited as long as it is used in this field. As a specific, non-limiting example, the resin solution may comprise? -Terpineol and a PVB binder (BUTVAR).

The solvent may be any solvent known in the art and may be any solvent as long as it can prevent drying of the composition and control the fluidity of the composition during the production process. For example, acetone or the like can be used.

Meanwhile, in the method of manufacturing a cathode for a solid oxide fuel cell according to an embodiment of the present invention, in the step of sintering the coated electrolyte support, the sintering temperature is not particularly limited, but is preferably 1200 ° C or less, It is good for achieving a desired effect in the invention.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are only a few examples of the present invention, and the present invention is not limited by the following examples.

Example  1 to 9, Comparative Example  1 to 2

&Lt; Production of raw material powder using GNP (Glycine nitrate process)

A metal salt of samarium nitrate _{((Sm (NO 3) 3} · 6H 2 O), neodymium nitrate _{((Nd (NO 3) 3} · 6H 2 O), barium nitrate _{((Ba (NO 3) 2} ), strontium nitrate (( Sr (NO ₃ ) ₂ ) and cobalt nitrate ((Co (NO ₃ ) ₂ .6H ₂ O) were used and the metal salt was changed to (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _The weighed metal salt was dissolved in distilled water together with glycine (C ₂ H ₅ NO ₂ ). The weight of the metal salt was adjusted to _{5 + d} (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9) (Sm + Nd + Ba + Sr + Co metal salt): Glycine = 1: 3. The composition of the metal salt (Sm + Nd + Ba + Sr + Co metal salt) Respectively.

Thereafter, the mixture dissolved in distilled water was heated at a temperature of 300 ° C to evaporate the distilled water to prepare an oxide raw material powder.

&Lt; Preparation of air electrode powder &

Of the oxide raw material powder, air (air) and calcined in a 1100 ℃ 3 sigan atmosphere final double-layer perovskite structure _{(layered perovskite) (Sm 1 -} x Nd x) Ba 0. ₅ Sr _{0 . 5} Co ₂ O _{5 + d} (x = 0.8) cathode powder was prepared.

Chemical composition Abbreviations Example 1 Sm _0.9 Nd _0.1 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO1 Example 2 Sm _0.8 Nd _0.2 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO2 Example 3 Sm _0.7 Nd _0.3 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO3 Example 4 Sm _0.6 Nd _0.4 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO4 Example 5 Sm _0.5 Nd _0.5 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO5 Example 6 Sm _0.4 Nd _0.6 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO6 Example 7 Sm _0.3 Nd _0.7 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO7 Example 8 Sm _0.2 Nd _0.8 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO8 Example 9 Sm _0.1 Nd _0.9 Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} SNBSCO9 Comparative Example 1 SmBa _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} SBSCO Comparative Example 2 Ce _{0 . 9} Gd _{0 . 1} O _{2 + d} CGO91

Example  10 to 16

The oxide raw material powders described in Example 8 were heated at 600 ° C (Example 10), 700 ° C (Example 11), 800 ° C (Example 12), 900 ° C (Example 13) The procedure of Example 8 was repeated, except that the calcination was carried out at 1050 占 폚 (Example 15) and 1100 占 폚 (Example 16).

Comparative Example  3 to 8

(Comparative Example 3), 100 占 폚 (Comparative Example 4), 200 占 폚 (Comparative Example 5), 300 占 폚 (Comparative Example 6), 400 占 폚 (Comparative Example 7), and The same procedure as in Example 1 was conducted except that the heat treatment was performed at 500 占 폚 (Comparative Example 8).

Example  17 to 25, Comparative Example  9

&Lt; Production of air electrode paste &

(Sm _{1 - x} Nd _x ) Ba ₀ .05 produced in Examples 1 to 9 and Comparative Example 1 _{. 5} Sr _{0 . And 5} g of ₅ Co ₂ O _{5 + d} (x = 0 to 0.9) air electrode powder, respectively. Here, when x is 0, it is Comparative Example 9, and when x is 0.1, Example 17, when x is 0.2, Example 18, when x is 0.3, Example 19, , Example 21 when x is 0.5, Example 22 when x is 0.6, Example 23 when x is 0.7, Example 24 when x is 0.8, Example 25 when x is 0.9, to be.

Next, 20 zirconia balls having a diameter of 10 mm were charged into a 150 ml mortar, and KD-1 or polyvinyl pyrrolidone, which is a dispersant, was added to 5 g of the air electrode powder in an amount of 5 wt% or less based on the total weight of the air electrode powder.

Further, a resin solution containing? -Terpineol and PVB binder (BUTVAR) was further added to the mortar and then wet ball milled to prepare an air electrode powder slurry. In wet ball milling, acetone was used as a solvent.

After removing the acetone in the air electrode powder slurry, an air electrode paste was prepared.

Finally, after the air electrode paste was coated by using a screen printing method to CGO91 electrolyte support sintered at _{1100 (Sm 1 - x Nd x} ) Ba 0. ₅ Sr _{0 . 5 C 2} O _{5 + d} (x = 0 ~ 0.9) cathode and a CGO 91 electrolyte support. Here, the CGO 91 electrolyte support was Ce _{0 . 9} Gd _{0 . 1} O _{2 -d} powder to a predetermined size and sintering at 1400 for about 4 hours. The sintered body is a circular sintered body having a diameter of 21 mm and a thickness of 2 mm.

Experimental Example

1) Determination of crystal structure

(Sm _{1 - x} Nd _x ) Ba ₀ .05 produced in Examples 1 to 9 and Comparative Example 1 _{. 5} Sr _{0 . The} results of XRD measurement of ₅ Co ₂ O _{5 + d} (x = 0 ~ 0.9) air electrode powder are shown in FIG.

The crystal structure of the cathode powder prepared in Examples 1 to 9 will be described with reference to FIG. As shown in FIG. 1, it can be seen that the substitution amount of Nd has SNBSCO crystal structure at x = 0 to 0.9. Especially, when the substitution amount of Nd is x = 0 to 0.4, the space group of the air electrode powder shows a structure of orthorhombic symmetry (SG Pmmm), but when the substitution amount of Nd is x = 0.5 to 0.9 It can be seen that the structure changes from tetragonal to tetragonal symmetry (SG P4 / mmm). The change of the crystal structure can be confirmed from the fact that the peaks split at 47˚, 54˚, 59˚, 69˚, and 79˚ are integrated into one.

The XRD measurement results of the (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) air electrode powder prepared in Examples 10 to 16 and Comparative Examples 3 to 8 are shown in FIGS. Respectively.

(Sm _1-x Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) cathode powder prepared in Examples 10 to 14 and Comparative Examples 3 to 8 with reference to FIG. 2 . As shown in FIG. 2, (Sm _{1 - x} Nd _x ) Ba _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} (x = 0.8) It can be seen that the crystal structure of the cathode powder is the crystal structure of the above oxide raw material powder. However, (Sm _{1 - x} Nd _x ) Ba ₀ .05 of Examples 10 to 14 having a heat treatment temperature of 600 ° C or higher _{. 5} Sr _{0 . 5} CO ₂ O _{5 + d} (x = 0.8) The cathode powder is crystallized to contain the SNBCO double layer perovskite crystal structure. In addition, since the (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) cathode powder according to the present invention can be produced by the GNP method and have a pure crystalline phase, Or problems of intermediate phase formation and crystallinity degradation, which have been problems in the combustion method using citric acid, can be solved.

The crystal structure of the (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) cathode powder prepared in Examples 14 to 16 is examined with reference to FIG. As shown in FIG. 3, in the air electrode powder prepared in Examples 14 and 15, an unknown unknown was finely detected at about 30 to 33 ° based on 2Θ, It can be seen that there is no unidentified peak and it has a pure crystal structure without secondary phase or intermediate phase.

2) Surface photo measurement

(Sm _{1 - x} Nd _x ) Ba _{0 . 5} Sr _{0 . The} results of SEM measurement of ₅ Co ₂ O _{5 + d} (x = 0.8) air electrode powder are shown in FIG.

Referring to FIG. 4, (Sm _{1 - x} Nd _x ) Ba _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} (x = 0.8) It can be seen that the cathode powder is formed by agglomerating grains having an average size of about 0.5 to 3 μm.

Fig. 5 (a), Fig. 5 (b) and Fig. 5 (c) show the microstructural characteristics in the case where Nd is replaced with an excess of x = 0.5 or more in the Sm site. 5 (a) is a high-magnification SEM photograph of Example 7 (Sm _1-x Nd _x ) Ba _{0 .5} Sr _0.5 Co ₂ O _{5 + d} (x = 0.7) _{8 (Sm 1-x Nd x} ) Ba 0 .5 Sr 0.5 and the high magnification SEM image of a _{Co 2 O 5 + d (x} = 0.8), Fig. 5 (c) is the embodiment _{9 (Sm 1-x Nd x} ) Ba _{0 .5} Sr _0.5 Co ₂ O _{5 + d} (x = 0.9).

Figure 5 (a), Figure 5 (b), Figure 5 (c) above embodiment, when the respective Reference _{8 (Sm 1-x Nd x} ) Ba 0 .5 Sr 0.5 Co 2 O 5 + d (x = 0.8 ), Spherical nanoparticles having an average size of about 100 nm or less are uniformly distributed on the surface of the above-mentioned grains (or particles) (see Fig. 5 (b)). On the other hand, in Example 7 (Sm _1-x Nd _x ) Ba _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} (x = 0.7), nanoparticles relatively larger than those of Example 8 were formed, and the nanoparticles were relatively unevenly distributed on the surface of the grain compared to Example 8 . Further, in Example 9 (Sm _1-x Nd _x ) Ba _{0 . 5} Sr _{0 . The} nanoparticles having a size similar to that of Example 8 were formed on the surface of the above-mentioned grains in the composition of ₅ Co ₂ O _{5 + d} (x = 0.9). However, compared to Example 8, It can be seen that the

6 (a) and 6 (b) show SEM measurement results of the half-papers fabricated in Example 24 above. 6 (a) is an SEM photograph showing the surface of the (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) air electrode of the reversed-phase paper prepared in Example 24, b), after cutting if inverted produced in example _{24 (Sm 1 - x Nd x} ) Ba 0. ₅ Sr _{0 . 5} Co ₂ O _{5 + d} (x = 0.8) air electrode and the CGO 91 electrolyte support.

(Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) air electrode according to the present invention has a thickness of about 0.5 to 3 It is seen that grains having an average size of 탆 are formed by agglomeration with each other and have a porous structure in which pores having an average size of about 0.5 to 5 탆 are formed. Since the (Sm _{1 -x} Nd _x ) Ba _0.5 Sr _0.5 Co ₂ O _{5 + d} (x = 0.8) air electrode according to the present invention is produced by the GNP method as described above, the initial particles of the oxide raw material powder It is small in size and can have a fine structure even after calcination and sintering. Accordingly, (Sm _{1 - x} Nd _x ) Ba _{0 . 5} Sr _{0 . 5} CO ₂ O _{5 + d} (x = 0.8) The air electrode can improve the rate of oxygen reduction reaction by reducing the area resistivity and increasing the three phase interface at which the cathode reaction takes place.

3) Electrical Conductivity Measurement

(Sm _{1 - x} Nd _x ) Ba ₀ .05 produced in Examples 1 to 9 and Comparative Example 1 _{. 5} Sr _{0 .} Fig. 7 shows the result of measuring the electrical conductivity of the ₅ Co ₂ O _{5 + d} (x = 0 to 0.9) air electrode powder. Electrical conductivity measurement was carried out by charging 2 g of the cathode powder into a metal mold of 6 mm x 25 mm and compression molding to prepare a rectangular bar type electrical conductivity specimen of 5.5 mm x 4 mm x 24 mm and measuring with a Keithley 2400 Sourcemeter instrument. Specifically, the electric conductivity measurement method was a DC four terminal method, and a voltage was measured by applying a current. The electrical conductivity measurement temperature range was 50 to 900 占 폚, and was measured in an air atmosphere at 50 占 폚 intervals.

Referring to FIG. 7, a tetragonal symmetry (SG P4 / Z4) having a substitution amount of x = 0.5 to 0.9 is used as a substitute for an air electrode powder having an orthorhombic symmetry (SG Pmmm) mmm)) air electrode powder is more excellent in electric conductivity. Particularly, in Examples 1 to 9 and Comparative Example 1, Sm _{0 . 2} Nd _{0 . 8} Ba _{0 . 5} Sr _{0 . 5} Co ₂ O _{5 + d} cathode powder exhibits the highest relative conductivity at a measurement temperature of 50 to 2170 S / cm, 500 to 849 S / cm, and 700 to 516 S / cm.

4) Area Specific Resistance (ASR) measurement

Table 2 and FIG. 8 show the results of measurement of the area specific resistance of the half-papers fabricated in Examples 17 to 25 and Comparative Example 9. The impedance of the half-cell fabricated in Examples 17 to 25 and Comparative Example 9 was obtained using the 4-probe / 2-electrode method, and the result of dividing the real number side of the impedance by 2 was determined as the area specific resistance.

The area specific resistivity (Ωcm ² ) Abbreviations 500 ℃ 600 ℃ 700 ℃ Comparative Example 9 SBSCO 3.311311 1.584893 0.57544 Example 17 SNBSCO1 2.22941 0.337551 0.068295 Example 18 SNBSCO2 3.532482 0.470999 0.0785 Example 19 SNBSCO3 3.06147 0.541652 0.09891 Example 20 SNBSCO4 2.590479 0.455302 0.0942 Example 21 SNBSCO5 1.764842 0.306147 0.05495 Example 22 SNBSCO6 2.103778 0.3925 0.07065 Example 23 SNBSCO7 1.978199 0.382455 0.07065 Example 24 SNBSCO8 1.750532 0.244135 0.04396 Example 25 SNBSCO9 2.621923 0.388186 0.058875

Referring to Table 2 and FIG. 8, the half-papers (Examples 17 to 25) made of the air electrode powder for a solid oxide fuel cell according to the present invention had higher area resistivity than those of Comparative Example 9 (SBSCO) Value is displayed.

In addition, a tetragonal symmetry (SG P4 / mmm) structure having a substitution amount of x = 0.5 to 0.9 as compared with an air electrode powder having an orthorhombic symmetry (SG Pmmm) structure in which the substitution amount of Nd is as small as x = It is found that the area specific resistance of the half-cell made of the air electrode powder of the present invention is better.

In particular, the Examples 17 to 25 and Comparative Example 9 in Example 24 of SNBSCO8 air electrode powder _{(Sm 0. 2 Nd 0.} 8 Ba 0. 5 Sr 0. 5 Co 2 O 5 + d) that is inverted with 500 ℃ from 1.75 Ωcm ^2, it can be seen at 550 ℃ from ^{0.244 Ωcm 2, 0.088 Ωcm 2,} 700 ℃ at 650 at 0.63 Ωcm ^2, 600 ℃ to 0.043 Ωcm ² to be seen, the lowest area specific resistance value.

Therefore, it has been confirmed that it is more preferable to achieve the object of the present invention by setting the x value to 0.7 to 0.85 in consideration of the electric conductivity and the area specific resistance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (9)

An air electrode powder for a solid oxide fuel cell, which is represented by the following formula (1), wherein Nd is substituted for the Sm site and satisfies the following relationship (1) and has a tetragonal crystal structure:
[Chemical Formula 1]
(Sm _1-x Nd _x ) Ba _1-y Sr _y Co _z O _{5 + d}
(In the formula 1, 0.7 <x? 0.85, 0.4? Y? 0.6, 1.9? Z? 2.1, and d is a positive number of more than 0 and 1 or less.
[Relation 1]
EC ≥ 650
(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)
delete delete A method of manufacturing an air electrode discharge for a solid oxide fuel cell according to claim 1,
a) mixing a metal salt and a combustion fuel to obtain a metal salt mixed solution;
b) heating the metal salt mixed solution to produce a raw material powder;
and c) calcining the raw material powder to prepare an air electrode powder for a solid oxide fuel cell
Wherein the cathode powder for a solid oxide fuel cell is represented by the following formula (1), Nd is substituted for the Sm site, and has a tetragonal crystal structure satisfying the following relational expression 1:
[Chemical Formula 1]
(Sm _1-x Nd _x ) Ba _1-y Sr _y Co _z O _{5 + d}
(In the formula 1, 0.7 <x? 0.85, 0.4? Y? 0.6, 1.9? Z? 2.1, and d is a positive number of more than 0 and 1 or less.
[Relation 1]
EC ≥ 650
(In the above relational expression 1, EC means the electrical conductivity measured at 500 ° C in the form of a bar having a size of 5.5 mm x 4 mm x 24 mm by compression-molding 2 g of the air electrode powder, and the unit of EC is S / cm.)
5. The method of claim 4,
Wherein the metal salt comprises a mixture of stoichiometric proportions of Sm nitrate, Nd nitrate, Sr nitrate and Co nitrate capable of producing the compound of formula (1).
5. The method of claim 4,
Wherein the calcining temperature in the step c) ranges from 600 to 1200 ° C.
An air electrode for a solid oxide fuel cell comprising an air electrode powder for a solid oxide fuel cell according to claim 1.
Preparing an electrolyte support;
Coating an air electrode paste comprising an air electrode powder for a solid oxide fuel cell according to claim 1 on the electrolyte support; And
And sintering the coated electrolyte support.
9. The method of claim 8,
Wherein the air electrode paste comprises a dispersant and a resin solution.

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