WO2018030691A1 - Method for manufacturing composite powder in core-shell structure for solid oxide fuel cell - Google Patents

Abstract

The present invention relates to a composite powder in a core-shell structure for a solid oxide fuel cell (SOFC), and more specifically, to a composite powder in a core-shell structure for a solid oxide fuel cell (SOFC) having a novel structure in which nickel, zirconium, and yttrium are stably formed in the core-shell structure, thereby preventing deformation due to the coarsening and shrinking of nickel when an anode is operated at a high temperature while enhancing sintering properties and electrical conductivity.

Description

Method for producing composite powder of core-shell structure for solid oxide fuel cell

The present invention relates to a composite powder of a core-shell structure for a solid oxide fuel cell (SOFC) and a method of manufacturing the same, and more particularly to nickel, zirconium, and yttrium, which are stably formed in a core shell structure, so that the anode is heated at a high temperature. The present invention relates to a method for producing a composite powder of a core-shell structure for a solid oxide fuel cell (SOFC) having a novel structure that can improve sintering and electrical conductivity while preventing deformation due to coarsening and shrinkage of nickel during operation.

As fossil raw materials are gradually depleted, the demand for new energy sources is increasing. Solid Oxide Fuel Cell, which converts chemical energy directly into electrical energy, has high energy conversion efficiency, and it is possible to use various fuels by its own internal reforming. As it can be improved, it is attracting attention as a next generation energy source.

Solid oxide fuel cell is a structure that uses high oxygen ion conductivity of oxide electrolyte and connects anodes in series, and requires spatial separation of hydrogen and oxygen in order to use electron transfer. It is a battery that uses an electric current generated by chemical bonds to induce electrons to move to another pole. As a fuel electrode material, nickel oxide (NiO) and stabilized zirconia (YSZ) are generally used as a mixture, and an electrolyte is used. Yttria (Y2O3), ceria (CeO2), Scandia (Sc2O3), gadolinium oxide (Gd2O3), etc., are added to zirconia (ZrO2) and ceria (CeO2), and the material uses high thermal stability and ion conductivity at high temperatures. have. A unit cell of a solid oxide fuel cell (SOFC) is made of solid electrolytes with a cathode on one side and a cathode on the other.

Yttria-stabilized zirconia (YSZ), which is stabilized by addition of nickel or nickel oxide and yttria, is used as a fuel electrode of a solid oxide fuel cell which is commonly used at present. Nickel is an excellent conductor of electrons in the high-temperature reduction atmosphere and acts as a transport path for electrons. Yttria stabilized zirconia prevents coarsening of the skeleton and nickel particles that maintain the microstructure, and adjusts the thermal expansion coefficient to be similar to other components. It forms an oxygen ion path and serves as an excellent ion conductor.

The anode mixed with nickel oxide and stabilized zirconia has a simple mixing method, but since the attraction force between stabilized zirconia and stabilized zirconia, nickel oxide and nickel oxide, or stabilized zirconia and nickel oxide is different from each other, the two powders under the same dispersion conditions At the same time it is not dispersed and aggregation of the powders occurs. In particular, homogeneous aggregation of relatively large powders, where there is a difference in size of the powders, can lead to microstructure non-uniformity of the anode. In addition, about 30% of volume shrinkage occurs during heat treatment in a reducing atmosphere using nickel oxide and stabilized zirconia. As the volume shrinkage occurs, electrical conductivity decreases due to the decrease in strength of the anode and the occurrence of cracks. When nickel (Ni) and stabilized zirconia are used, volume shrinkage does not occur and does not cause deterioration in the reducing atmosphere. It has advantages

Non-uniformities such as shape, size, and cohesion of the raw materials constituting the anode may adversely affect the properties of the anode, such as electrical conductivity, fuel permeability, and three-phase interface activity, which may degrade the durability, mechanical properties, and output characteristics of the unit cell. do. In addition, the grain size and pores are non-uniform in size, and densification and coarsening of Ni occur. The coarsening of Ni generated in this way causes volume change by thermal cycle and redox reaction, resulting in damage of electrolyte, Ni, YSZ and Due to the reduction of the three-phase interface consisting of pores, the electrochemical activity is reduced to reduce the output of the unit cell.

An object of the present invention is to provide a cathode composite having a new structure of nickel yttria core-cell in order to solve the problem of the anode mixed with nickel oxide and stabilized zirconia.

Another object of the present invention is to provide a method for producing a fuel electrode having a novel structure according to the present invention.

The present invention to solve the above problems

A core portion composed of at least one component of Ni particles or NiO particles;

A shell portion formed around the core portion and composed of at least one component of yttrium, zirconium, cesium, cerium, scandium, lanthanum, strontium, gallium, magnesium, and gadolium; It provides a composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) comprising a.

In the composite powder of a core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention, the average diameter of the core portion is 0.1 to 5.0 μm, and the average thickness of the shell portion is 10 to 500 nm.

In the composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention, the shell portion is characterized in that it contains yttrium and zirconium.

The composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention is characterized in that 40 to 80% by weight of nickel, 1 to 10% by weight of yttrium, and 20 to 60% by weight of zirconium.

The composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention is characterized by having a specific surface area of 1 to 20 m ² / g.

The composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention is characterized in that the average particle size (D50) is 0.2 to 20um.

The present invention also provides

(A) preparing Ni or NiO and a zirconium precursor and a yttrium precursor; And

(B) adding ammonia water (NH 4 OH) to form a zirconium precursor and a yttrium precursor on the surface of the Ni or NiO by a coprecipitation reaction; It provides a method for producing a composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention comprising a.

In the method for preparing a composite powder of a core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention, the zirconium precursor is zirconium hydroxide (Zr (OH) ₄ ), and the yttrium precursor is yttrium nitrate Y (NO _3). ) ₃ ㆍ 6H ₂ O.

The present invention also provides

(A) forming a core-shell structure in which Ni or NiO, a zirconium precursor and a yttrium precursor are grown by yttria stabilized zirconia (YSZ) tetragonal crystals on the surface of Ni or NiO through a hydrothermal synthesis reaction; And

(B) drying the hydrothermally synthesized composite powder at a temperature of 100 ° C. or higher at a pH of 5 to 8; It provides a method for producing a composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) comprising the present invention.

The composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention is stably formed with a core shell structure of nickel, zirconium, and yttrium, which is caused by coarsening and shrinking of nickel when the anode is operated at a high temperature. It can improve sintering and electrical conductivity while preventing deformation.

1 is a SEM photograph of the particles produced in the Examples and Comparative Examples of the present invention.

Figure 2 is a graph measuring the electrical conductivity of the particles produced in the embodiment of the present invention by the probe method.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited by the following examples.

<Example 1>

In Example 1, a micro-sized nickel powder required for preparing a nickel / yttria stabilized zirconia core-shell structure powder was prepared using a liquid phase reduction method.

Comparative Example 1

In Comparative Example 1, in order to prepare a nickel / yttria stabilized zirconia core-shell structure powder, a micro-sized nickel powder and a nano-sized yttria stabilized zirconia powder were mixed at a speed of at least 4000 rpm for 30 minutes or more using a high speed mixing method. The core-shell composite structure was prepared as shown in FIG.

<Example 2>

In Example 2, in order to synthesize nano-sized yttria stabilized zirconia powder, zirconium chloride (ZrOCl2.8H2O) and yttrium nitrate (Y (NO3) 3.6H2O) were uniformly dissolved in distilled water using a starting material of the shell portion, and then in an aqueous solution state. Was prepared.

<Example 3>

The micro-sized nickel powder prepared by the method of Example 1 was calculated by mass ratio in the aqueous solution in which zirconium chloride and yttrium nitrate dissolved in Example 2 (nickel: yttria stabilized zirconia = 60 ~ 80: 40 ~ 50) Charged and stirred continuously. After confirming that the nickel powder was uniformly dispersed in the aqueous solution, ammonia water was added at a flow rate of 10 to 30 ml / min to proceed with the coprecipitation reaction. As the ammonia water was added, the aqueous solution became opaque, and it was confirmed that zirconium hydroxide and yttrium hydroxide were uniformly mixed with nickel powder. After the addition of the ammonia water, the mixture is stirred and distilled with distilled water until the pH reaches 8 again.

<Example 4>

In Example 4, the powder of the nickel / yttria stabilized zirconia core-shell structure of Examples 1 to 3 according to the present invention was added to a hydrothermal synthesizer, and then distilled water was poured by twice the powder and stirred evenly. The hydrothermal synthesizer was maintained at a temperature of 200 degrees for 8 hours to allow zirconium hydroxide and yttrium hydroxide to grow into zirconium oxide and yttrium oxide nanocrystals, respectively.

Example 5

In order to compare the powder prepared in Example 4 with the powder prepared in Comparative Example 1, FE-SEM was measured and the results are shown in FIG. 1 Before.

<Example 6>

In Example 6, in order to coat the nickel / yttria stabilized zirconia core-shell powder on the anode for the solid oxide fuel cell, carbon black was mixed and paste-processed. In order to observe the surface of the nickel / yttria stabilized zirconia core-shell powder, after the ball-mill process, the surface state of the core-shell powder prepared by the present invention and the powder prepared in the comparative example 1 was measured by FE-SEM. The results are shown in Figure 1 After.

The paste was prepared, and a measurement cell was prepared by coating a fuel electrode and an air electrode of a 200um YSZ electrolyte support. The anode was heat-treated in an air atmosphere at 1200 degrees, and the cathode was made of LSCF and GDC powder.

In the case of the anode manufactured in the present invention, the electrical conductivity value of 3054 S / cm2 at 750 degrees, and 2968 S / cm2 at 800 degrees, and the anode polarization resistance (ASR) at 0.05 극 ㎠ and the 750 degrees at 800 degrees. A value of 0.07 mm 2 was shown, and the results are shown in FIGS. 3 and 4.

In order to measure the cell characteristics, hydrogen gas was injected into the anode of the cell and oxygen was injected into the cathode of the cell, and the power density was measured by varying the current load in the temperature range of 700, 750, and 800 degrees. It was.

The composite powder of the core-shell structure for a solid oxide fuel cell (SOFC) according to the present invention is stably formed with a core shell structure of nickel, zirconium, and yttrium, which is caused by coarsening and shrinking of nickel when the anode is operated at a high temperature. It can improve sintering and electrical conductivity while preventing deformation.

Claims (3)

1. (A) preparing Ni or NiO and a zirconium precursor and a yttrium precursor; And

   (B) adding ammonia water (NH ₄ OH) to form a zirconium precursor and a yttrium precursor on the surface of the Ni or NiO by a coprecipitation reaction; Containing

   A method for producing a composite powder having a core-shell structure for a solid oxide fuel cell (SOFC).
2. The method of claim 1,

   The zirconium precursor is zirconium hydroxide (Zr (OH) ₄ ) And the yttrium precursor is yttrium nitrate Y (NO ₃ ) ₃ .6H ₂ O.

   A method for producing a composite powder having a core-shell structure for a solid oxide fuel cell (SOFC) according to claim 1.
3. (A) forming a core-shell structure in which Ni or NiO, a zirconium precursor and a yttrium precursor are grown by yttria stabilized zirconia (YSZ) tetragonal crystals on the surface of Ni or NiO through a hydrothermal synthesis reaction; And

   (B) drying the hydrothermally synthesized composite powder at a temperature of 100 ° C. or higher at a pH of 5 to 8; Containing

   A method for producing a composite powder having a core-shell structure for a solid oxide fuel cell (SOFC) according to claim 1.

Images