Structures and fabrication techniques for solid state electrochemical devices

• US 7,351,488 B2
• Filed: 06/20/2006
• Issued: 04/01/2008
• Est. Priority Date: 07/31/1999
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Jacobson, Craig P., Visco, Steven J., DeJonghe, Lutgard C.
• Primary Examiner(s): Bell; Bruce F.
• Application Number:
  US11/471,774
• Publication Number:
  US 20060234112A1
• Time in Patent Office: 651 Days
• Field of Search: 429/30, 429/33, 429/40, 429/41, 429/44, 429/45
• US Class Current: 429/486
• CPC Class Codes: B01D 2257/108 Hydrogen
• CPC Class Codes: B01D 53/326 in electrochemical cells
• CPC Class Codes: C25B 9/00 Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 2300/0074 Ion conductive at high temperature
• CPC Class Codes: H01M 4/8885 Sintering or firing
• CPC Class Codes: H01M 4/9025 Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
• CPC Class Codes: H01M 4/9033 Complex oxides, optionally doped, of the type M1MeO3, M1 being an alkaline earth metal or a rare earth, Me being a metal, e.g. perovskites
• CPC Class Codes: H01M 4/905 specially used in fuel cell operating at high temperature, e.g. SOFC
• CPC Class Codes: H01M 4/9066 of metal-ceramic composites or mixtures, e.g. cermets
• CPC Class Codes: H01M 8/004 Cylindrical, tubular or wound
• CPC Class Codes: H01M 8/1213 characterised by the electrode/electrolyte combination or the supporting material
• CPC Class Codes: H01M 8/1226 characterised by the supporting layer
• CPC Class Codes: H01M 8/1231 with both reactants being gaseous or vaporised
• 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: H01M 8/1266 the electrolyte containing bismuth oxide
• CPC Class Codes: H01M 8/2432 Grouping of unit cells of planar configuration
• CPC Class Codes: H01M 8/2483 characterised by internal manifolds
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49115 : including coating or impregnating

Abstract

Porous substrates and associated structures for solid-state electrochemical devices, such as solid-oxide fuel cells (SOFCs), are low-cost, mechanically strong and highly electronically conductive. Some preferred structures have a thin layer of an electrocatalytically active material (e.g., Ni—YSZ) coating a porous high-strength alloy support (e.g., SS-430) to form a porous SOFC fuel electrode. Electrode/electrolyte structures can be formed by co-firing or constrained sintering processes.

Claims

1. A solid oxide fuel cell, comprising:

a sintered substrate consisting essentially of a material selected from the group consisting of a porous non-noble transition metal, a porous non-noble transition metal alloy, and a porous cermet incorporating one or more of a non-noble, non-nickel transition metal and a non-noble transition metal alloy;

a first porous electrode material having high electrocatalytic activity on the substrate;

an electrolyte comprising a dense, sintered coating of a ceramic material on the electrode; and

a second porous electrode on the electrolyte.

2. The fuel cell of claim 1, wherein said substrate material is a porous non-noble transition metal alloy selected from the group consisting of low-chromium ferritic steels and intermediate-chromium ferritic steels.

3. The fuel cell of claim 2, wherein said substrate material is a low-chromium ferritic steel having has 11-15% Cr.

4. The fuel cell of claim 3, wherein the low-chromium ferritic is selected from the group consisting of stainless steel types 405, 409 and 410.

5. The fuel cell of claim 2, wherein said substrate material is an intermediate-chromium ferritic steel having has 16-18% Cr.

6. The fuel cell of claim 5, wherein the intermediate-chromium ferritic steel is selected from the group consisting of stainless steel types 430 and 434.

7. The fuel cell of claim 1, wherein said substrate is planar.

8. The fuel cell of claim 1, wherein said substrate is tubular.

9. The fuel cell of claim 1, wherein the material having high electrocatalytic activity comprises Ni and an ionic conductor.

10. The fuel cell of claim 9, wherein the material having high electrocatalytic activity is Ni—

YSZ.

11. The fuel cell of claim 1, wherein said electrolyte coating comprises a material selected from the group consisting of at least one of yttria stabilized zirconia, scandia stabilized zirconia, doped ceria, gadolidia doped ceria, La_0.8Sr_0.2Ga_0.85Mg_0.15O_2.825 and (Bi₂O₃)_0.75(Y₂O₃)_0.25.

12. The fuel cell of claim 11, wherein said coating comprises at least one YSZ.

13. The fuel cell of claim 12, wherein said at least one YSZ is selected from the group consisting of (ZrO₂)_0.92(Y₂O₃)_0.08 and (ZrO₂)_0.90(Y₂O₃)_0.10).

14. The fuel cell of claim 11, wherein said coating comprises doped ceria.

15. The fuel cell of claim 14, wherein said coating is gadolidia doped ceria (CGO).

16. The fuel cell of claim 15, wherein said gadolidia doped ceria has the formula (CeO₂)_0.8(Gd₂O₃)_0.2.

17. The fuel cell of claim 1, wherein the sintered coating is about 1 to 50 microns thick.

18. The fuel cell of claim 1, wherein the sintered coating about 5 to 20 microns thick.

19. The fuel cell of claim 1, wherein the dense, sintered coating is no more than 2% porous.

20. The fuel cell of claim 1, wherein said second electrode comprises a mixed ionic electronic conductor (MIEC).

21. The fuel cell of claim 20, wherein said MIEC is selected from the group consisting of SrCo_1-xFe_XO_3-δ

(0.30≧

X≧

0.20), La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

, La _0.8Sr_0.2MnO₃, La_0.65Sr_0.30MnO₃, La_0.45Sr_0.55MnO₃, Sr_0.7Ce_0.3MnO_3-δ

, LaNi_0.6Fe_0.4O₃, Sm_0.5Sr_0.5CoO₃ and La_1-xSr_xCoO_3-δ

.

22. The fuel cell of claim 21, wherein said MIEC is La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

.

23. The fuel cell of claim 1, further comprising a metallic interconnect bonded to said porous substrate.

24. The fuel cell of claim 1, wherein the material having high electrocatalytic activity comprises a mixed ionic electronic conductor (MIEC).

25. The fuel cell of claim 24, wherein said MIEC is selected from the group consisting of SrCo_1-xFe_XO_3-δ

(0.30≧

X≧

0.20), La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

, La_0.8Sr₀MnO₃, La_0.65Sr_0.30MnO₃, La_0.45Sr_0.55MnO₃, Sr_0.7Ce_0.3MnO_3-δ

, LaNi_0.6Fe_0.4O₃, Sm_0.5Sr_0.5CoO₃ and La_1-xSr_xCoO_3-δ

.

26. The fuel cell of claim 21, wherein said MIEC is La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

.

27. The fuel cell of claim 1, wherein said second electrode comprises Ni and an ionic conductor.

28. The fuel cell of claim 1, wherein:

the porous substrate comprises a sintered substrate consisting essentially of an intermediate-chromium ferritic steel;

the first porous electrode material having high electrocatalytic activity on the substrate is a fuel electrode material;

the dense, sintered electrolyte coating is a doped ceria on the fuel electrode; and

the second porous electrode is an air electrode.

29. The fuel cell of claim 28, wherein the intermediate-chromium ferritic steel is selected from the group consisting of stainless steel types 430 and 434.

30. The fuel cell of claim 29, wherein the first porous electrode material having high material having high electrocatalytic activity comprises Ni and an ionic conductor.

31. The fuel cell of claim 30, wherein the porous air electrode comprises a mixed ionic electronic conductor (MIEC).

32. The fuel cell of claim 31, wherein said MIEC is La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

.

33. The fuel cell of claim 32, further comprising a metallic interconnect bonded to said porous substrate.

34. The fuel cell of claim 1, wherein:

the porous substrate comprises a sintered substrate consisting essentially of an intermediate-chromium ferritic steel;

the first porous electrode material having high electrocatalytic activity on the substrate is an air electrode material;

the dense, sintered electrolyte coating is a doped ceria on the air electrode; and

the second porous electrode is a fuel electrode.

35. The fuel cell of claim 34, wherein the intermediate-chromium ferritic steel is selected from the group consisting of stainless steel types 430 and 434.

36. The fuel cell of claim 35, wherein the material having high electrocatalytic activity comprises a mixed ionic electronic conductor (MIEC).

37. The fuel cell of claim 36, wherein said MIEC is La_0.6Sr_0.4Co_0.6Fe_0.4O_3-δ

.

38. The fuel cell of claim 37, wherein the porous fuel electrode comprises Ni and an ionic conductor.

39. The fuel cell of claim 38, further comprising a metallic interconnect bonded to said porous substrate.