Phase stable doped zirconia electrolyte compositions with low degradation

• US 9,413,024 B2
• Filed: 10/16/2013
• Issued: 08/09/2016
• Est. Priority Date: 01/26/2010
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Armstrong, Tad, El Batawi, Emad, Janousek, Martin, Pillai, Manoj
• Primary Examiner(s): Slifka, Sarah A
• Assistant Examiner(s): THOMAS, BRENT C
• Application Number:
  US14/055,557
• Publication Number:
  US 20140051010A1
• Time in Patent Office: 1,028 Days
• Field of Search: 429/428, 429/496
• US Class Current: 1/1
• CPC Class Codes: C01G 25/006 Compounds containing, besides zirconium, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C01G 25/02 Oxides
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3246 Stabilised zirconias, e.g. YSZ or cerium stabilised zirconia
• CPC Class Codes: C04B 2235/762 Cubic symmetry, e.g. beta-SiC
• CPC Class Codes: C04B 35/48 based on zirconium or hafnium oxides, zirconates, zircon or hafnates
• CPC Class Codes: C04B 35/486 Fine ceramics
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/1246 the electrolyte consisting of oxides
• CPC Class Codes: H01M 8/1253 the electrolyte containing zirconium oxide
• CPC Class Codes: H01M 8/126 the electrolyte containing cerium oxide
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A solid oxide fuel cell (SOFC) includes a cathode electrode, a solid oxide electrolyte, and an anode electrode. The electrolyte and/or electrode composition includes zirconia stabilized with (i) scandia, (ii) ceria, and (iii) at least one of yttria and ytterbia. The composition does not experience a degradation of ionic conductivity of greater than 15% after 4000 hrs at a temperature of 850° C.

Claims

1. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising;

a formula (ZrO₂)_1-w-x-b(Sc₂O₃)_w(CeO₂)_x(Yb₂O₃)_b, where;

w=0.1;

x=0.01 and b=0.01;

or

w=0.1;

x=0.01 and b=0.005;

or

w=0.1;

x=0.005 and b=0.005;

wherein;

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition does not experience a degradation of ionic conductivity of greater than 15% after 4000 hrs and at a temperature of 850°

C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850°

C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850°

C.

2. The composition of claim 1, wherein:

the composition is utilized as an electrolyte layer of a planar solid oxide fuel cell comprising the anode and the cathode;

the electrolyte layer supports the anode and cathode;

the solid oxide fuel cell is located in a solid oxide fuel cell stack adjacent to an interconnect comprising at least 94 wt % Cr, 4-6 wt % Fe and 0-1 wt % Y; and

a coefficient of thermal expansion of the electrolyte differs by 1% or less from a coefficient of thermal expansion of the interconnect.

3. The composition of claim 1, wherein w=0.1;

x=0.01 and b=0.01.

4. The composition of claim 1, wherein w=0.1;

x=0.01 and b=0.005.

5. The composition of claim 1, wherein w=0.1;

x=0.005 and b=0.005.

6. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising a formula (ZrO₂)_1-w-x-b(Sc₂O₃)_w(CeO₂)_x(Yb₂O₃)_b, where:

0.09≦

w≦

0.11;

0.005<

x<

0.015 and 0.0025<

b≦

0.015;

wherein;

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition does not experience a degradation of ionic conductivity of greater than 15% after 4000 hrs and at a temperature of 850°

C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850°

C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850°

C.

7. The composition of claim 6, wherein:

0.01≦

x≦

0.015 and 0.005≦

b≦

0.0125.

8. The composition of claim 7, wherein:

0.005≦

b≦

0.01.

9. The composition of claim 8, wherein:

w=0.1, b=0.01 and x=0.01.

10. The composition of claim 6, wherein:

0.005≦

x≦

0.0125 and 0.0025≦

b≦

0.01.

11. The composition of claim 6, wherein:

0.0025≦

b≦

0.0125.

12. The composition of claim 11, wherein:

0.005≦

x≦

0.01 and 0.005≦

b≦

0.01.

13. The composition of claim 8, wherein:

w=0.1 and x=0.01.

14. A planar fuel cell comprising the electrolyte of the composition of claim 6.

15. A scandia stabilized zirconia electrolyte composition for a solid oxide fuel cell, comprising:

a formula (ZrO₂)_1-w-x-b(Sc₂O₃)_w(CeO₂)_x(Yb₂O₃)_b, where w=0.1;

x=0.01 and b=0.01;

wherein;

the scandia stabilized zirconia electrolyte composition consists of a single layer located in direct contact with an anode on a first major surface of the single layer and in direct contact with a cathode on a second major surface of the single layer;

the composition experiences a degradation of ionic conductivity of 1-5% after 4000 hrs and at a temperature of 850°

C.;

the composition comprises a cubic phase which substantially lacks tetragonal phase domains after operating in a solid oxide fuel cell at 850°

C. for at least 4000 hours in at least one of air or hydrogen ambient; and

the composition does not experience a cubic to rhombohedral phase transition at a temperature of about 25 to 850°

C.

16. The composition of claim 15, wherein the composition have a starting ionic conductivity of 0.14 S/cm or greater.

17. The composition of claim 16, wherein the composition have a starting ionic conductivity of 0.16 to 0.17 S/cm.