High power density solid oxide fuel cell having a graded anode

  • US 6,228,521 B1
  • Filed: 12/08/1998
  • Issued: 05/08/2001
  • Est. Priority Date: 12/08/1998
  • Status: Expired due to Term
First Claim
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1. A method to produce an improved high power density solid oxide fuel cell having a graded anode, which method comprises:

  • (a) obtaining a powder mixture of nickel oxide and YSZ, said YSZ having a composition of between about 5 and 15 mole percent of Y2O3 doped ZrO2, wherein the ratio of nickel oxide to YSZ is between about 70 to 90 volume percent of the total volume;

    (b) creating a pellet of thickness of between about 100 and 3000 μ

    m by consolidation of the powder mixture of step (a);

    (c) forming a powder mixture of nickel oxide and YSZ, said powder mixture having between about 50 and 65 volume percent of nickel oxide to the total mixture;

    (d) forming a slurry of the powder mixture of step (c) with water, a volatile organic liquid or mixtures thereof optionally subjecting the obtained slurry to mixing;

    (e) contacting the pellet of step (b) with the slurry of step (d) followed by evaporation of the volatile liquid only when it is present to produce a graded pellet;

    (f) depositing a layer of YSZ on the top surface of the graded pellet of step (e);

    (g) sintering the pellet of step (f) in air at between about 1100 and 1500°

    C. producing densification of the pellet in three layers, said layers comprising YSZ electrolyte, NiO plus YSZ inner electrode layer and NiO plus YSZ outer anode and support, wherein said YSZ electrolyte layer has porosity of less than 4% by volume, (h) obtaining a powdered mixture LSM by calcining a mixture of at least three components having MnO2 as a first component;

    a second component selected from the group consisting of La2O3, Y2O3, any other rare earth element oxide, or combinations thereof; and

    a third component selected from the group consisting of SrCO3, CaCO3, BaCO3, MgCO3 or combinations thereof at between about 800 and 1200°

    C.;

    (i) obtaining and calcining a powdered YSZ at between 1000 and 1300°

    C.;

    (j) producing a powder mixture of LSM and YSZ which is mixed with a organic liquid;

    (k) successively coating the top of the pellet of step (g) with the mixture of step (j) followed by heating at between about 350 and 500°

    C. in air or oxygen to produce a layer of between about 5 and 100 micrometers in thickness;

    (l) heating the coated pellet produced in step (k) at between about 1000 and 1400°

    C. to create the unreduced fuel cell; and

    (m) contacting the unreduced fuel cell of step (l) at between about 500°

    C. and 1000°

    C. with a mixture of water and hydrogen;

    thereby producing a reduced fuel cell wherein the thicker anode which has an open porosity of between about 30 and 40 volume percent, and the thinner anode which has a porosity of between about 20 to 29.9 volume percent.

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