CORE-SHELL STRUCTURED COMPOSITE POWDER FOR SOLID OXIDE FUEL CELL

Abstract

The present invention relates to a core-shell structured composite powder for a solid oxide fuel cell (SOFC) and more particularly, to a core-shell structured composite powder for a SOFC having a new structure in which nickel, zirconium and yttrium are stably formed in a core shell structure to improve sinterability and conductivity while preventing a fuel electrode from being deformed due to coarsening and contraction of nickel during operation.

Claims

1. A core-shell structured composite powder for a solid oxide fuel cell (SOFC) comprising: a core portion composed of at least one of Ni particles or NiO particles; and a shell portion formed around the core portion and composed of at least one of yttrium, zirconium, cesium, cerium, scandium, lanthanum, strontium, gallium, magnesium and gadolinium.

2. The core-shell structured composite powder for the SOFC of claim 1, wherein the average diameter of the core portion is 0.1 to 5.0 m and the average thickness of the shell portion is 10 to 500 nm.

3. The core-shell structured composite powder for the SOFC of claim 1, wherein the shell portion may includes yttrium and zirconium.

4. The core-shell structured composite powder for the SOFC of claim 1, wherein the core-shell structured composite powder includes 40 to 80 wt % of nickel, 1 to 10 wt % of yttrium, and 20 to 60 wt % of zirconium.

5. The core-shell structured composite powder for the SOFC of claim 1, wherein a specific surface area is 1 to 20 m.sup.2/g.

6. The core-shell structured composite powder for the SOFC of claim 1, wherein an average particle size (D50) is 0.2 to 20 um.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 illustrates an SEM photograph of particles prepared in Examples of the present invention and Comparative Example.

[0025] FIG. 2 is a graph obtained by measuring conductivity of the particles prepared in Examples of the present invention by a probing method.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, the present invention will be described in more detail by Examples. However, the scope of the present invention is not limited to the following Examples.

Example 1

[0027] In Example 1, a micro-sized nickel powder required for the preparation of a core-shell structured powder of nickel/yttria-stabilized zirconia was prepared using liquid reduction.

Comparative Example 1

[0028] In Comparative Example 1, In order to prepare a core-shell structured powder of nickel/yttria-stabilized zirconia, a core-shell composite structure was prepared as illustrated in FIG. 1 by using and mixing a micro-sized nickel powder and a nano-sized yttria-stabilized zirconia powder at 4000 rpm or more for 30 minutes or more by using a high-speed mixing method.

Example 2

[0029] In Example 2, zirconium oxychloride (ZrOCl.sub.2.8H.sub.2O) and yttrium nitrate (Y(NO.sub.3).sub.3.6H.sub.2O) were evenly dissolved in distilled water as a starting material of the shell portion and prepared in an aqueous state in order to synthesize the nano-sized yttria-stabilized zirconia powder.

Example 3

[0030] The nano-sized nickel power prepared by the method in the Example 1 was added and continuously stirred in the aqueous solution in which zirconium oxychloride and yttrium nitrate were dissolved in Example 2 by calculating a mass ratio (Nickel:yttria-stabilized zirconia=60 to 80:40 to 50). 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 and subjected to the coprecipitation reaction. It was confirmed that the ammonia water was added, the aqueous solution was opaque and zirconium hydroxide and yttrium hydroxide were mixed uniformly with the nickel powder. When the addition of ammonia water was completed, stirring and filtration were repeated with distilled water until the pH was 8.

Example 4

[0031] In Example 4, the core-shell structured powders of the nickel/yttria stabilized zirconia of Examples 1 to 3 according to the present invention were added into a hydrothermal mixer, and distilled water was added twice as much as the powders and stirred evenly. A hydrothermal synthesizer was maintained at a temperature of 200 C. for 8 hours to allow zirconium hydroxide and yttrium hydroxide to grow into zirconium oxide and yttrium oxide nanocrystals, respectively.

Example 5

[0032] FE-SEM was measured to compare the powder prepared in Example 4 with the powder prepared in Comparative Example 1, and the results are illustrated in FIG. 1 Before.

Example 6

[0033] In Example 6, in order to coat the core-shell powder of nickel/yttria-stabilized zirconia on a fuel electrode for a solid oxide fuel cell, carbon black was mixed and ball-milled to be pasted. In order to observe the surface of the core-shell powder of nickel/yttria-stabilized zirconia, the surface states of the core-shell powder prepared by the present invention after the ball-milling process and the powder prepared by the method of Comparative Example 1 were measured by FE-SEM, and the results were illustrated in FIG. 1 After.

[0034] Paste was prepared and a fuel electrode and an air electrode of a 200 um YSZ electrolyte supporter were coated to prepare a measuring cell. The fuel electrode was annealed at 1200 C. in air atmosphere and the air electrode used LSCF and GDC powders.

[0035] In the case of the fuel electrode prepared in the present invention, conductivity values of 3054 S/cm.sup.2 at 750 C. and 2968 S/cm.sup.2 at 800 C. were shown, and the fuel electrode polarization resistance (ASR) was 0.05 Cm.sup.2 at 800 C. and 0.07 Cm.sup.2 at 750 C., and the results were illustrated in FIGS. 3 and 4.

[0036] While hydrogen gas and oxygen were injected into the fuel electrode and the air electrode of the cell prepared for measuring the cell characteristics, an output density was measured by varying the current load in a temperature range of 700, 750, and 800 C. and the results were illustrated in FIG. 4.