Structures and fabrication techniques for solid state electrochemical devices
View Patent ↗Provided are low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one embodiment the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another embodiment, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe, Cu and Ag, or alloys thereof.
1. A solid state electrochemical device, comprising:
an electrode or electrode support 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; and
an electrolyte comprising a sintered coating of a ceramic material on the substrate.
2. The device of claim 1 , wherein said substrate is planar.
3. The device of claim 1 , wherein said substrate is tubular.
4. The device of claim 1 , wherein said substrate material is a metal selected from the group consisting of transition metals chromium, iron, copper, and nickel.
5. The device of claim 1 , wherein said substrate material is an alloy selected from the group consisting of a low-chromium ferritic steel, an intermediate-chromium ferritic steel, a high-chromium ferritic steel, a chrome-based alloy, and a chrome-containing nickel-based alloy.
6. The device of claim 5 , wherein said alloy is selected from the group consisting of Cr5Fe1Y and a chrome-containing nickel-based alloy.
7. The device of claim 1 , wherein said substrate material is a cermet selected from the group consisting of at least one of La 1-x Sr x Mn y O 3-δ (1≧X≧0.05) (0.95≦y≦1.15) (LSM), La 1-x Sr x CoO 3-δ (1≧X≧0.10) (LSC), SrCo 1-x Fe x O 3-δ (0.30≧X≧0.20), La 0.6 Sr 0.4 Co 0.6 Fe 0.4 O 3-δ , Sr 0.7 Ce 0.3 MnO 3-δ , LaNi 0.6 Fe 0.4 O 3-δ , Sm 0.5 Sr 0.5 CoO 3-δ , yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), (CeO 2 ) 0.8 (Gd 2 O 3 ) 0.2 (CGO), La 0.8 Sr 0.2 Ga 0.85 Mg 0.15 O 2.825 (LSGM20-15), (Bi 2 O 3 ) 0.75 (Y 2 O 3 ) 0.25 and alumina, in combination with at least one of transition metals Cr, Fe, Cu, an alloy thereof, a low-chromium ferritic steel, an intermediate-chromium ferritic steel, a high-chromium ferritic steel, a chrome-based alloy and a chrome-containing nickel-based alloy.
8. The device of claim 7 , wherein the LSM is selected from the group consisting of La 0.8 Sr 0.2 MnO 3 , La 0.65 Sr 0.30 MnO 3-δ , La 0.45 Sr 0.55 MnO 3-δ .
9. The device of claim 7 , wherein said chrome based alloy is Cr5Fe1Y.
10. The device of claim 1 , wherein said coating material is solely an ionic conductor.
11. The device of claim 10 , wherein said coating comprises at least one of yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), doped ceria (CGO), La 0.8 Sr 0.2 Ga 0.85 Mg 0.15 O 2.825 (LSGM20-15) and (Bi 2 O 3 ) 0.75 (Y 2 O 3 ) 0.25 .
12. The device of claim 11 , wherein said coating is at least one YSZ of (ZrO 2 ) 0.92 (Y 2 O 3 ) 0.08 and (ZrO 2 ) 0.90 (Y 2 O 3 ) 0.10 ).
13. The device of claim 1 , wherein said coating is a mixed ionic electronic conductor.
14. The device of claim 13 , wherein said coating comprises at least one of SrCo 1-x Fe x O 3-δ (0.30≧X≧0.20), La 0.6 Sr 0.4 Co 0.6 Fe 0.4 O 3-δ , La 0.8 Sr 0.2 MnO 3 , La 0.65 Sr 0.30 MnO 3 , La 0.45 Sr 0.55 MnO 3 , Sr 0.7 Ce 0.3 MnO 3-δ , LaNi 0.6 Fe 0.4 O 3 , Sm 0.5 Sr 0.5 CoO 3 and La 1-x Sr x CoO 3-δ .
15. The device of claim 14 , wherein said coating is SrCo 0.75 Fe 0.25 O 3 .
16. The device of claim 1 , wherein the sintered coating is about 1 to 50 microns thick.
17. The device of claim 1 , wherein the sintered coating is about 3 to 30 microns thick.
18. The device of claim 1 , wherein the sintered coating is about 5 to 20 microns thick.
19. The device of claim 1 , wherein said sintered coating material and said substrate have substantially matched coefficients of thermal expansion.
20. The device of claim 1 , wherein said sintered coating comprises a solid electrolyte.
21. The device of claim 20 , further comprising an electrode formed on said solid electrolyte.
22. The device of claim 21 , further comprising a metallic interconnect bonded to said substrate.
23. The device of claim 1 , wherein an electrode layer is intermediate between said substrate and said sintered electrolyte.
24. The device of claim 23 , further comprising a second electrode formed on said solid electrolyte.
25. The device of claim 24 , further comprising a metallic interconnect bonded to said substrate.
26. The device of claim 1 , wherein said sintered substrate does not contain nickel.
27. The device of claim 1 , wherein the sintered coating is gas-tight and greater than about 90% densified.
28. The device of claim 27 , wherein the sintered coating is greater than about 95% densified.
29. The device of claim 27 , wherein the sintered coating is no more than 2% porous.
30. The device of claim 1 , wherein the sintered substrate consists essentially of a porous cermet incorporating one or more of transition metals Cr, Fe and Cu.
31. The device of claim 1 , wherein the substrate is a first electrode, the sintered coating is a solid electrolyte consisting essentially of a solely ionic conductor ceramic material, and further comprising a porous second electrode.
32. The device of claim 31 , wherein said substrate is planar.
33. The device of claim 31 , wherein said substrate is tubular.
34. The device of claim 31 , wherein said second electrode is an oxygen electrode.
35. The device of claim 31 , wherein said second electrode is a hydrogen electrode.
36. The device of claim 31 , further comprising a metallic interconnect.
37. The device of claim 31 , wherein the first electrode further comprises a thin layer of a material having high electrocatalytic activity on top of the sintered substrate.
38. The device of claim 37 , wherein the layer of material having high electrocatalytic activity comprises Ni-YSZ.
39. The device of claim 31 , wherein the sintered substrate consists essentially of a porous cermet incorporating one or more of transition metals Cr, Fe and Cu.
40. The device of claim 1 , wherein the substrate is a first electrode, the sintered coating is a proton-conducting thin film, and further comprising a porous second electrode.
41. The device of claim 40 , wherein said substrate is planar.
42. The device of claim 40 , wherein said substrate is tubular.
43. The device of claim 40 , wherein the first electrode further comprises a thin layer of a material having high electrocatalytic activity on top of the sintered substrate.
44. The device of claim 43 , wherein the layer of material having high electrocatalytic activity comprises Ni-YSZ.
45. The device of claim 40 , further comprising a metallic interconnect.
46. The device of claim 1 , wherein the substrate is a first electrode, the sintered coating is a mixed ionic electronic conductor, and further comprising a porous second electrode.
47. The device of claim 46 , wherein said substrate is planar.
48. The device of claim 46 , wherein said substrate is tubular.
49. The device of claim 46 , wherein the first electrode further comprises a thin layer of a material having high electrocatalytic activity on top of the sintered substrate.
50. The device of claim 49 , wherein the layer of material having high electrocatalytic activity comprises Ni-YSZ.
51. The device of claim 1 , wherein said substrate material has a fracture strength of at least about 5 Mpa.
52. The device of claim 51 , wherein said substrate material has a fracture strength of at least about 40 Mpa.
53. The device of claim 52 , wherein said substrate material has a fracture strength of at least about 100 Mpa.
54. The device of claim 1 , wherein said substrate material is chemically stable in an oxidizing environment at a temperature between about 400° C. and the material's melting point.
55. The device of claim 1 , wherein said substrate material forms an oxide scale having a growth rate constant of no more than about 1×10 −12 cm 2 /sec.