Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
  • H01M8/2425—High-temperature cells with solid electrolytes
  • H01M8/2428—Grouping by arranging unit cells on a surface of any form, e.g. planar or tubular
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/8605—Porous electrodes
  • H01M4/8621—Porous electrodes containing only metallic or ceramic material, e.g. made by sintering or sputtering
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0236—Glass; Ceramics; Cermets
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
  • H01M8/023—Porous and characterised by the material
  • H01M8/0241—Composites
  • H01M8/0245—Composites in the form of layered or coated products
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M8/1213—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the electrode/electrolyte combination or the supporting material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
  • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
  • H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
  • H01M8/1253—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides the electrolyte containing zirconium oxide
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
  • H01M8/2425—High-temperature cells with solid electrolytes
  • H01M8/243—Grouping of unit cells of tubular or cylindrical configuration
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
  • H01M4/9025—Oxides specially used in fuel cell operating at high temperature, e.g. SOFC
  • H01M4/9033—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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
  • H01M4/90—Selection of catalytic material
  • H01M4/9041—Metals or alloys
  • H01M4/905—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC
  • H01M4/9066—Metals or alloys specially used in fuel cell operating at high temperature, e.g. SOFC of metal-ceramic composites or mixtures, e.g. cermets
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to a solid oxide fuel cell and processes of forming the same.
• a fuel cell is an energy conversion device that transforms chemical energy into electric power through the electrochemical oxidation of fuel.
• a typical fuel cell includes a cathode, an anode, and an electrolyte between the cathode and the anode.
• SOFCs solid oxide fuel cells
• SOFCs use a hard, ceramic compound metal oxide as an electrolyte.
• oxygen gas (O 2 ) is reduced to oxygen ions (O 2 ) at the cathode, and a fuel gas such as hydrogen (H 2 ) or a hydrocarbon such as methane (CH 4 ) is oxidized with the oxygen ions to form water and carbon dioxide (from hydrocarbon) at the anode.
• a fuel gas such as hydrogen (H 2 ) or a hydrocarbon such as methane (CH 4 ) is oxidized with the oxygen ions to form water and carbon dioxide (from hydrocarbon) at the anode.
• the design of a fuel cell is typically based on its support structure and shape.
• US Patent Publication No. 2004/0219411 describes an anode-supported fuel cell, which is also known as a flat-tubular fuel cell because of the flat-tubular shape of the anode.
• the anode is typically the thickest layer of the fuel cell, and therefore, provides the support for forming other layers of the fuel cell.
• FIG. 1 illustrates a solid oxide fuel cell (SOFC) according to an embodiment
• FIG. 2 illustrates an SOFC stack according to another embodiment. DETAILED DESCRIPTION
• an SOFC can include a cathode having a thickness capable of providing structural support for other layers of the SOFC.
• the SOFC can include a cathode having channels formed therein.
• FIG. 1 illustrates a solid oxide fuel cell (SOFC) 100 in accordance with an embodiment.
• the SOFC 100 can include a cathode 109.
• the cathode 109 can be planar.
• the cathode 109 can include an upper surface and a lower surface opposite the upper surface, wherein the upper surface and lower surface are substantially parallel to each other.
• the cathode 109 can have a particular thickness.
• a cathode 109 having a thickness of less than 0.6 mm may not provide enough structural support for the entire SOFC 100 and may not allow for the inclusion of adequately- sized channels to formed in the cathode 109.
• a thickness of greater than 5.0 mm may increase production cost and ionic/electrical resistance without any significant increase in power density of the SOFC 100. Therefore, in accordance with an embodiment, the cathode 109 can have a thickness of at least 0.6 mm, such as at least 1.0 mm, at least 1.5 mm, or even at least 2.0 mm.
• the cathode 109 may include a thickness of not greater than 5.0 mm, such as not greater than 4.0 mm, not greater than 3.0 mm, or even not greater than 2.0 mm.
• the cathode 109 can have a thickness that is within a range of any minimum or maximum value indicated above, such as, for example, within a range of 0.6 mm to 5 mm, 1.0 mm to 2.0 mm, or 0.6 mm to 1.5 mm.
• the cathode 109 can include channels 111 to help provide more uniform delivery or distribution of a fluid (e.g., oxygen or air) across the cathode 109. More uniform delivery or distribution of a fluid may provide for greater power density of the SOFC 100 that capable in an SOFC that does not have channels formed therein.
• the channels 111 can be formed in the cathode bulk layer 110 of the cathode 109.
• the cathode bulk layer 110 can include a thickness capable of having channels 111 formed therein, such as a thickness of at least 0.6 mm, at least at least 1.0 mm, at least 1.5 mm, or at least 2.0 mm.
• the cathode bulk layer 110 may include a thickness of not greater than 5.0 mm, such as not greater than 4.0 mm, or not greater than 3.0 mm, or not greater than 2.0 mm.
• the cathode bulk layer 110 can have a thickness that is within a range of any minimum or maximum value indicated above, such as, for example, within a range of 0.6 mm to 5 mm, 1.0 mm to 2.0 mm, or 0.6 mm to 1.5 mm.
• the channels 111 can be of any desired shape, such as, for example, circular, rectangular, or oblong. In the case in which the channels 111 are circular, they can have a particular diameter. The diameter may be chosen for particular flow and pressure characteristics. For example, a diameter of less than 0.5 mm may not be large enough to provide adequate fluid flow through the channels. In an embodiment, the diameter of the channels 111 can be at least 0.5 mm, such as at least 1.0 mm, or even at least 1.5 mm. In a non- limiting embodiment, the diameter of the channels 111 may be not greater than 2.0 mm, such as not greater than 1.5 mm, or even not greater than 1.0 mm.
• the cathode 109 may have channels 111 of a diameter within a range of any minimum or maximum value indicated above, such as, for example, within a range of from 0.5 mm to 2.0 mm, 0.5 to 1.5mm, or 1.5 to 1.0 mm.
• the channels can have a rectangular shape, or even an oblong shape, as viewed from a cross section of FIG. 1, and can have a minimum dimension (e.g. height or width) and a maximum dimension (e.g., other of the height or width of the channels 111) separately within a range of any of the aforementioned diameters indicated with respect to circular channels.
• the channels 111 can have a rectangular or oblong shape having a height of from 0.5 mm to 2.0 mm and a width of from 0.5 mm to 2.0 mm.
• the rectangular or oblong channels 111 can have a height of 0.5 mm and a width of 1.5mm.
• the channels 111 can have a height (or diameter) of at least 50% of the thickness of the cathode bulk layer 110.
• the channels 11 can have a height of not greater than 90% of the thickness of the cathode bulk layer 110, such as not greater than 75% or nor greater than 60% of the thickness of the cathode bulk layer 110.
• the channels 111 can have a height that is within a range of any minimum of maximum value indicated above.
• the channels 111 can have a height that is within a range of 50-60% of the thickness of the cathode bulk layer 110.
• a cathode bulk layer 110 can have a channel of having a thickness of 1 mm and can have a channel height of 0.50 mm to 0.60 mm.
• a minimum thickness of the cathode 109 may be at least 0.05 mm thicker than the dimension of the channels 111 in the thickness direction (e.g., diameter or height of the channels 111 as viewed from the cross section illustrated in FIG. 1).
• the minimum thickness of the cathode 109 may be at least 0.1 mm thicker, such as 0.5 mm thicker, or even at least 1.0 mm thicker, than the dimension of the channels 111 in the thickness direction. Such a minimum thickness can help ensure that structural integrity is maintained in a cathode 109 having channels therein.
• the minimum thickness of the cathode 109 having channels 111 therein may also be dependent on the strength or porosity of the cathode 109 in that a cathode having greater porosity or less strength may require a greater minimum thickness to provide adequate structural integrity.
• the SOFC 100 can include a flat tubular anode 101 having a particular thickness.
• the thickness of the cathode 109 and the flat- tubular anode 101 can be defined with respect to each other.
• the cathode 109 can have a thickness (Th c ) and the flat- tubular anode 101 can have a thickness (Th a ).
• a ratio (Th c )/(Th a ) can be at least at least at least 0.50, such as at least 0.75, or even at least 1.0. In a non-limiting embodiment, the ratio
• (Th c )/(Th a ) may be not greater than 1.50, such as not greater thanl.25, or even not greater than 1.0.
• the ratio (Th c )/(Th a ) can be within a range of any minimum or maximum ratio described above, such as, for example, within a range of 0.50 to 1.5, or 0.75 to 1.25. In a certain embodiment, the ratio
• (Th c )/(Th a ) can be about 1.0, indicating that the cathode 109 and the flat- tubular anode 101 have the same thicknesses.
• the use of electrodes having a ratio (Th c )/(Th a ) within a range of 0.50 to 1.5, or more particularly 0.75 to 1.25 may reduce geometric issues such as curvature of one or more components of the SOFC 100 resulting during formation or use.
• embodiments herein can include a ratio (Th c )/(Th a ) within a range of 0.50 to 1.5, or more particularly 0.75 to 1.25, the cathode 109 can be thick enough to provide structural support to the SOFC similarly to a relatively thick anode 101 of an embodiment.
• the SOFC 101 in accordance with an embodiment may be categorized as an electrode- supported fuel cell.
• the size and shape (e.g., diameter, width, height) of the cathode channels 111 or anode channels 108 can affect pressure drop within the cathode 109 or anode 101, respectively.
• the pressure drop increases, parasitic power consumption increases and there may be insufficient pressure for the fuel or oxidant to flow through the entire length of the channels as intended.
• channel size is relatively small, pressure drop will be relatively high.
• the pressure drop across the channels may be regulated to obtain needed or desired flow characteristics.
• the channels 111 or channels 108 may have a pressure drop that is not greater than 1.5 kPa, such as not greater than 1 kPa, or even not greater than 0.5 kPa. In an embodiment, the channels 111 or channels 108 may have a pressure drop that is at least O.OlkPa.
• the cathode 109 can include a cathode bulk layer 110 and a cathode functional layer 104.
• the cathode bulk layer 110 can include a greater percent porosity than the cathode functional layer 104.
• the porosity of the cathode bulk layer 110 can aid in the transport of fluid (e.g., air or oxygen) through the cathode 109 and toward the electrolyte 103 where the electrochemical reaction of the cell takes place.
• the porosity of cathode functional layer 104 can help to provide a greater density of triple phase boundaries (TPBs) at the interface of the cathode 109 and the electrolyte layer 103.
• TPBs triple phase boundaries
• TPBs are the confined spatial sites where electrolyte, gas, and electrically connected catalyst regions contact and where the oxygen reduction reaction and the hydrogen oxidation reaction of the fuel cell take place.
• the cathode functional layer 104 is disposed between, and can be in direct contact with, the cathode bulk layer 110 and the electrolyte 103.
• the cathode bulk layer 110 can have a particular total porosity, including both open porosity and closed porosity. Porosity can be calculated based on Archimedes Principle. In a particular embodiment, the majority of the total porosity is open porosity that creates an interconnected network of pores to allow fuel to traverse through the cathode bulk layer 110 toward the electrolyte 103. A total porosity of less than 25 vol% may provide insufficient interconnected porosity, while a total porosity of greater than 50% may provide insufficient structural integrity of the cathode bulk layer 110. In an embodiment, the cathode bulk layer 110 can have a total porosity of at least 25 vol%, such as at least 30 vol%, or even at least 40 vol%.
• the cathode bulk layer 110 may have a total porosity of not greater than 50 vol%, such as not greater than 40 vol%.
• a total porosity that is within a range of any minimum or maximum value indicated above, such as, for example, within a range from 25 vol% to 40 vol%.
• the cathode functional layer 104 can have a total porosity of at least 10 vol%, such as at least 15 vol%, or even at least 20 vol%. In a non-limiting embodiment, the cathode functional layer 104 may have a total porosity that is not greater than 35 vol%, such as not greater than 25 vol%, or even not greater than 20 vol%. The cathode functional layer 104 can have a total porosity that is within a range of any minimum or maximum value indicated above, such as, for example, within a range from 15 vol% to 25 vol%.
• the cathode bulk layer 110 can include a majority of the thickness of the cathode 109, and the cathode functional layer 104 can include a minority of the thickness.
• the cathode bulk layer 110 can include at least 90% of the total thickness of the cathode 109, such as at least 95%, or even at least 99% of the total thickness of the cathode 109.
• the cathode functional layer 104 may include a thickness that is not greater than 10% of the thickness of the cathode 109, such as not greater than 5%, or even not greater than 1% of the total thickness of the cathode 109.
• the cathode functional layer 104 can have a thickness of at least 15 microns and not greater than 50 microns. If the cathode functional layer 104 is too thin (i.e., less than 15 microns thick), the cathode functional layer 104 will not have enough volume for electro-chemical activity. However, if the cathode functional layer 104 is too thick (i.e., greater than 50 microns), the thickness could prevent gas diffusion through the cathode functional layer 104.
• the cathode bulk layer 110 can be directly bonded to the cathode functional layer 104. In another embodiment, the cathode bulk layer 110 can be bonded to the cathode functional layer 104 by a cathode bond layer 107.
• the cathode bond layer 107 can include characteristics such as electrical connectivity, gas permeability, mechanically strength, and thermal stability throughout the operational temperature range of the SOFC 100. For example, the cathode bond layer 107 can improve electrical contact and conductivity between the cathode bulk layer 110 and the cathode functional layer 104 by bonding the cathode bulk layer 110 directly to the cathode functional layer 104.
• the cathode bond layer 107 can thereby improve the dimensional tolerance between the cathode bulk layer 110 and the cathode functional layer 104 to enhance the physical integrity (i.e., mechanical strength) of the SOFC 100.
• the cathode bond layer 107 can include a thickness of at least 15 microns, such as at least 20 microns, or at least 25 microns.
• the cathode bond layer 107 may have a thickness that is not greater than 300 microns, such as not greater than 200 microns, no greater than 100 microns, not greater than 50 microns, or no greater than 30 microns.
• the cathode bond layer 107 can have a thickness that is within a range of any minimum or maximum value indicated above, such as, for example, within a range from 15 microns to 30 microns. In a particular embodiment, the cathode bond layer 107 can have the same thickness as the cathode functional layer 104.
• the cathode bond layer 107 can include a variety of materials, which may or may not include materials in common with the layers to which it is bonded (e.g., cathode layer and interconnect layer).
• the cathode bond layer 107 can have a similar CTE to the adjacent layer, and thus provide thermal stability of the entire cathode 109.
• the cathode bond layer 107 can include a lanthanum strontium manganite (LSM) material, , a lanthanum chromite material, a lanthanum strontium cobaltite (LSC) material, or a combination thereof.
• LSM lanthanum strontium manganite
• LSC lanthanum strontium cobaltite
• the cathode 109 can be made of a doped lanthanum manganite material.
• the doped lanthanum manganite material can have a general composition represented by the formula, (La 1 _ x A x ) y MnO 3 , where the dopant material is designated by "A" and is substituted within the material for lanthanum (La), on the A-sites of a perovskite crystal structure.
• the dopant material can include an element, such as Mg, Ba, Sr, Ca, Co, Ga, Pb, Z, or any mixture thereof.
• the dopant is Sr
• the cathode 109 may include a lanthanum strontium manganite material, known generally as LSM.
• the cathode 109 can consist essentially of LSM.
• the term “consist essentially of,” “consists essentially of,” or “consisting essentially of” means that the described material(s) is (are) limited to that (those) specified and to any other material(s) that do not materially affect the basic characteristics of the specified material(s).
• the value of x within the doped lanthanum manganite composition (La ⁇ x A x ) y MnO 3 represents the amount of dopant "A" substituted for La within the structure.
• x is not greater than about 0.5, such as not greater than about 0.4, not greater than about 0.3, not greater than about 0.2, or even not greater than about 0.1.
• the value of x can be greater than about 0.05.
• the value of x can be within a range of from about 0.4 to 0.05.
• y is not greater than about 1.0, and the ratio of La/Mn is not greater than about 1.0.
• the cathode bulk layer 110 and the cathode functional layer 104 of the cathode 109 can include the same or different materials.
• Components of an SOFC may be susceptible to damage caused by fluctuations in temperature during their formation or use.
• materials employed to form the various components including ceramics of differing compositions, exhibit distinct material, chemical, and electrical properties that can result in breakdown and failure of the SOFC article.
• an anode material including equal parts nickel oxide (NiO) and yttria stabilized zirconia (YSZ) can have an average CTE of about of 12.5xl0 "6 0 C ⁇
• a cathode material including LSM can have an average CTE of from about 12.2xl0 "6 °C _1 to about 12.4xl0 "6 °C _1 .
• a CTE of an electrolyte material including YSZ is generally in a range of from about 10.5xl0 ⁇ 6 °C _1 to about 1 lxlO "6 °C _1 .
• the difference between the CTEs of the various materials of different layers of the SOFC would generate a large thermal mismatch stress in the SOFC.
• Using CTE matched layers between the cathode and anode layers may reduce the occurrence of curvature of SOFC layers that could otherwise result with mismatched CTEs.
• a fuel cell in which both the anode and the cathode are relatively thick are particularly susceptible to coefficient of thermal expansion (CTE) mismatches between adjacent components to the anode or cathode, which can lead to failure of the fuel cell, particularly at operating temperatures of 780 °C to 950 °C.
• CTE coefficient of thermal expansion
• Stress generation of SOFC components can also occur when cooling down from a sintering temperature (e.g., 1300-1400°C) to room temperature, particularly when two or more SOFC components (i.e., layers) are sintered together if there is any mismatch in the CTE among the two or more
• any temperature change (especially a temperature change that is too rapid) can cause fracture and consequent failure of the SOFC.
• a majority of the stress can generated by the mismatch between the CTEs of the flat-tubular anode 101 and the cathode 109, particularly the cathode bulk layer 110.
• the selection of a relatively thin (e.g. 30 microns to 100 microns) cathode, such as that of a conventional anode-supported fuel cell is typically not based on the CTE characteristics of the cathode material because such a consideration is not imperative at such small cathode thicknesses.
• the cathode 109 can be chosen to have a CTE that is well-matched to one or more other layers of the SOFC 100, particularly to that of the flat-tubular anode 101.
• CTE mismatch between the flat-tubular anode 101 and the cathode 109 may be determined based on the following formula: [(CTE a - CTE d )/CTE a ] x 100%, wherein CTE a is the CTE of the anode, and CTE C is the CTE of the cathode.
• the CTE mismatch may be not greater than about 5%, such as not greater than about 4%, not greater than about 3%, not greater than about 2%, or even not greater than about 1%. In a particular embodiment, the CTE mismatch may be at least about 0.001%.
• a cathode bond layer 106 can be used to bond a cathode from another subcell to the interconnect 105.
• a bond layer should be porous and thin to allow for a high oxygen partial pressure at an interface between the bond layer 106 and the interconnect 105.
• a cathode bond layer can improve electrical contact between the interconnect 105 and an adjacent cathode that is bonded thereto.
• the cathode bond layer 106 can also improve the dimensional tolerance between the interconnect 105 and the adjacent cathode to enhance the physical integrity of the SOFC 100.
• the cathode bond layer 106 can include a variety of materials, which may or may not include materials in common with the layers to which it is bonded (e.g., cathode layer and interconnect layer).
• the cathode bond layer 106 can include a lanthanum strontium manganite (LSM) material, , a lanthanum chromite material, a lanthanum strontium cobaltite (LSC) material, or a combination thereof.
• LSM lanthanum strontium manganite
• LSC lanthanum strontium cobaltite
• the cathode bond layer 106 can include a thickness of at least 15 microns, such as at least 25 microns, at least 50 microns, at least 100 microns 200 microns, at least 300 microns.
• the cathode bond layer 106 may have a thickness that is not greater than 300 microns.
• the cathode bond layer 106 can have a thickness that is within a range of any minimum or maximum value indicated above, such as, for example, within a range from 15 microns to 300 microns, or 100 microns to 300 microns.
• SOFC 100 can include a flat- tubular anode 101.
• the flat-tubular anode 101 can include a thickness of at least 0.6 mm.
• the minimum thickness of the anode 101 may be at least 0.5 mm thicker, or even at least 1.0 mm thicker, than the dimension of the channels in the thickness direction.
• the flat- tubular anode 101 may include a thickness of not greater than 5.0 mm, such as not greater than 4 mm, not greater than 3 mm, not greater than 2 mm, or even not greater than 1.5 mm.
• the flat-tubular anode 101 can have a thickness that is within a range of any minimum or maximum value indicated above.
• the flat-tubular anode 101 can have a thickness within a range from 0.6 mm to 1.5 mm.
• the flat-tubular anode 101 can have a shape that is defined at least in part by an exterior surface 102.
• the exterior surface 102 can be substantially flat at one portion of the flat-tubular anode 101, and substantially rounded at another portion of the flat- tubular anode 101.
• the exterior surface 102 can be substantially flat at a portion of the flat-tubular anode 101 that contacts an interconnect 105.
• the exterior surface 102 can be substantially rounded at opposite ends of the flat- tubular anode 101, as generally illustrated in FIG. 1. The rounded ends may help the electrolyte 103 to have a more uniform thickness along the ends of the flat-tubular anode 101.
• the flat-tubular anode 101 can include channels 108 for the delivery of a fluid (e.g., fuel) to the SOFC 100 from an external source.
• a fluid e.g., fuel
• the channel 108 can include the shapes and dimensions as discussed herein with respect to cathode channels 111.
• the flat-tubular anode 101 can include a particular porosity.
• the total porosity can include both open porosity and closed porosity.
• the majority of porosity of the flat-tubular anode 101 is open porosity that creates an interconnected network of pores to allow for fluid (e.g., fuel) to traverse through the anode 101 to the electrolyte 103.
• a total porosity less than 25 vol% may provide inadequate interconnected porosity, while a total porosity of greater than 60% may provide insufficient structural integrity of the flat-tubular anode 101.
• the flat-tubular anode 101 can have a total porosity of at least 25 vol%, such as at least 30 vol%, or even at least 40 vol%. In a non-limiting embodiment, the flat-tubular anode 101 may have a total porosity of not greater than 50 vol%, such as not greater than 40 vol%. A skilled artisan will appreciate from the description herein that the flat- tubular anode 101 can have a total porosity that is within a range of any minimum or maximum value indicated above, such as, for example, within a range from 25 vol% to 40 vol%.
• Ni cermet generally refers to a ceramic metal composite that includes Ni, such as about 20 wt %-70 wt % of Ni.
• Ni cermet is a material that includes Ni (or NiO) and yttria- stabilized zirconia (YSZ).
• YSZ can include ZrO 2 containing anywhere from 3 mol% to 15 mol% of Y 2 O 3 .
• YSZ can include 8 mol% Y 2 O 3 (8YSZ).
• the flat-tubular anode 101 can include Ni, NiO, YSZ, or any combination thereof.
• the SOFC 100 can include an electrolyte layer 103.
• the electrolyte layer 103 can be disposed over a portion of the exterior surface 102 of the flat-tubular anode 101.
• the electrolyte layer 103 can be disposed over at least 50% of the exterior surface 102 of the flat-tubular anode 103.
• the electrolyte layer 103 can be disposed over at least 60% of the exterior surface 102 of the flat-tubular anode 103, such as at least 65%, at least 75%, at least 80%, at least 90%, or even at least 95%.
• the electrolyte layer 103 may be disposed over not greater than 95% of the exterior surface 102 of the flat-tubular anode 101.
• the electrolyte layer 103 may be disposed over not greater than 90% of the exterior surface 102 of the flat-tubular anode 103, such as not greater than 85%, not greater than 80%, not greater than 75%, not greater than 70%, not greater than 65%, not greater than 60%, or even not greater than 50%.
• the electrolyte layer 103 can be disposed over the exterior surface 102 of the flat-tubular anode 101 within any range of minimum or maximum values indicated above.
• the electrolyte layer 103 can be disposed over at least one of the rounded portions of the flat-tubular anode 101, as shown in FIG. 1. In other particular embodiments, the electrolyte layer 103 can be disposed only on one or more of the flat portions of the flat- tubular anode 101. In a certain embodiment, the electrolyte layer 103 can be disposed only between the flat- tubular anode 101 and the cathode 109.
• a ZrO2 based material such as a Sc 2 O 3 -d
• Lao .8 Sro .2 Gao .8 Mgo . i 5 COo .05 O 5 , Lao . 9Sro . iGao .8 Mgo.2O5, LaSrGaO 4 , LaSrGa 3 O 7 or La 0 .9A 0. iGa 3 where A Sr, Ca or Ba); or any mixture thereof.
• Another example includes doped yttrium- zirconate (e.g., YZr 2 O 7 ), doped gadolinium-titanate (e.g., Gd 2 Ti 2 O 7 ), brownmillerites (e.g., Ba 2 In 2 O 6 or Ba 2 In 2 O 5 ), or the like.
• the thickness of the electrolyte layer 103 can be at least 5 microns, such as at least 10 microns, at least 30 microns, at least 50 microns, at least 80 microns, or even at least 100 microns.
• the thickness of the electrolyte layer 103 may be not greater than 120 microns, such as not greater than 100 microns, not greater than 80 microns, not greater than 50 microns, not greater than 30 microns, or even not greater than 10 microns.
• the thickness of electrolyte layer 103 can be in a range of about 5 microns to about 20 microns, such as of about 5 microns to about 10 microns. In another specific embodiment, the thickness of electrolyte layer 103 is thicker than about 100 microns.
• the separation of the fuel gas in flat-tubular anode 101 and oxidizer gas in cathode 109 by the electrolyte layer 103 creates an oxygen partial pressure gradient. This gradient causes oxygen ions to be transported across the electrolyte layer 103 and to react with the fuel in the flat- tubular anode 101.
• the anode 101, cathode 109, and electrolyte 103 together can form a subcell.
• another flat-tubular anode, cathode, and electrolyte can form another subcell.
• Two or more subcells according to embodiments described herein can be stacked one upon another. For example, as illustrated in FIG.
• SOFC 201 and SOFC 203 are subcells which can form a stack 200 having an interconnect 202 disposed between SOFC 201 and SOFC 203.
• An electrically conductive interconnect layer can be formed between an anode layer of one subcell and a cathode layer of an adjacent subcell to connect the subcells in series so that the electricity each subcell generates can be combined.
• a cathode bond layer 204 can be disposed between the interconnect 202 of SOFC 201 and the cathode 205 of SOFC 203. The pattern may be repeated multiple times to form a stack with a large number of individual subcells.
• the SOFC 100 can include an interconnect layer 105.
• the interconnect layer 105 can be disposed on the flat- tubular anode 101.
• the interconnect layer 105 can be in direct contact with the flat- tubular anode 101.
• the interconnect layer 105 can be planar along its entire length. In a particular embodiment, the
• interconnect layer 105 can be disposed over at least 20% of the exterior surface 102 of the flat-tubular anode 101, such as at least 30%. In a non-limiting embodiment, the interconnect layer 105 may be disposed over not greater than 50% of the exterior surface 102 of the flat-tubular anode 101, such as not greater than 40%, or not greater than 30%. A skill artisan will appreciate from the description herein that the interconnect layer 105 can be disposed over a portion of the exterior surface 102 of the flat-tubular anode 101 that is within a range of any of the minimum or maximum values indicated above.
• interconnect layer 105 can include a ceramic material, such as an inorganic material.
• the interconnect layer 105 can include an oxide material, such as a chromite or a titanate material. More particularly, the interconnect layer 105 can include lanthanum (La), manganese (Mn), strontium (Sr), titanium (Ti), niobium (Nb), calcium (Ca), gallium (Ga), cobalt (Co), yttria (Y), or any combination thereof.
• the interconnect layer 105 can include a chromium oxide-based material, nickel oxide-based materials, cobalt oxide-based materials, and titanium oxide-based materials (e.g., lanthanium strontium titanate).
• the interconnect layer 105 can be made of a material, such as LaSrCrO 3 , LaMnCrO 3 , LaCaCrO 3 , YCrO 3 , LaCrO 3 , LaCoO 3 , CaCrO 3 , CaCoO 3 , LaNiO 3 , LaCrO 3 , CaNiO 3 , CaCrO 3 , or any combination thereof.
• the interconnect layer 105 can include an LST-based material (e.g., alone or in combination with YST).
• the interconnect layer 105 may consist essentially of LST, such as, La 0.2 Sr 0.8 TiO 3 .
• the interconnect layer 105 can consist essentially of LST having one or more dopants, such as Nb.
• the interconnect material may include an A- site deficient material, wherein for example, the lattice sites typically occupied by lanthanum or strontium cations are vacant, and thus the material has a non- stoichiometric composition.
• the interconnect layer 105 can be a particularly thin, planar layer of material.
• the interconnect layer 105 may have an average thickness of not greater than about 100 microns, not greater than about 80 microns, not greater than about 50 microns, or even not greater than about 25 microns.
• the interconnect layer 105 can have an average thickness of at least about 1 micron, such as at least about 2 microns, at least about 5 microns, at least about 8 microns, or at least about 10 microns.
• the average thickness of the interconnect layer 105 can be within a range of from any of the minimum and maximum values noted above.
• an interconnect having a relatively thin titanate interconnect layer has been discovered by the inventors to perform better than a relatively thick titanate interconnect layer.
• the interconnect layer 105 including a titanate material may have a maximum average thickness of not greater than about 100 microns.
• each of the layers can be formed individually before assembling the layers in the SOFC subcell or jointly with other layers of the subcell through, for example, a co-sintering process. That is, the layers can be formed separately as green layers and assembled together into a subcell or stack. Alternatively, the layers may be formed in green state in succession on each other, such that a first green electrolyte layer is formed, and thereafter, a green electrode layer can be formed overlying the green electrolyte layer, and thereafter, a green interconnect layer can be formed overlying the green electrode layer. The method further including sintering the green SOFC cell in a single sintering process to form a sintered SOFC cell.
• green articles are reference to materials that have not undergone sintering to affect densification or grain growth.
• a green article is an unfinished article that may be dried and have low water content, but is unfired.
• a green article can have suitable strength to support itself and other green layers formed thereon.
• the layers described according to the embodiments herein can be formed through techniques including casting, deposition, printing, extruding, lamination, die-pressing, gel casting, spray coating, screen printing, roll compaction, injection molding, or any combination thereof.
• the SOFC can include a cathode having a thickness capable of providing structural support for other layers of the SOFC.
• the SOFC can include a cathode having channels formed therein.
• Such aforementioned features are not capable in a conventional anode- supported cell having a relatively thin cathode (e.g., in a range of from 30 microns to 100 microns).
• Such a thin cathode is generally not thick enough to allow channels to be formed therein for actively supplying air or oxygen to the SOFC.
• a cathode of a conventional anode-supported fuel cell receives air or oxygen passively from the environment by the entire SOFC structure being placed within an enclosure that provides air or oxygen generally around the entire SOFC structure. Diffusion alone is used to distribute the air or oxygen across the thin cathode of the conventional anode-supported fuel cell, which may limit the power density of the cell. Moreover, such a thin cathode is generally not thick enough to provide for structural support of the SOFC and must rely on a relatively thick anode structure for support. Also, the cathode of an
• embodiment can serve to replace the Cr-felt current collector used for cell-cell connection in some convention anode-supported cells, which also tend to exhibit high degradation and low temperature constraint issues.
• a solid oxide fuel cell comprising: a flat- tubular anode; a cathode including a cathode bulk layer; and an electrolyte disposed between the flat-tubular anode and the cathode.
• a solid oxide fuel cell comprising: a flat-tubular anode; a cathode including channels; and an electrolyte disposed between the flat-tubular anode and the cathode.
• a solid oxide fuel cell comprising: a flat-tubular anode; a cathode including a thickness of at least 0.6 mm; and an electrolyte disposed between the flat-tubular anode and the cathode.
• Item 4 The solid oxide fuel cell of any of the above items, wherein the flat-tubular anode has a coefficient of thermal expansion (CTE a ), and the cathode has a coefficient of thermal expansion (CTE C ); wherein a CTE Mismatch is defined by the formula: [(CTE a - CTE c /CTE a ] x 100%, and wherein the CTE Mismatch is not greater than 5%.
• Item 5 The solid oxide fuel cell of any of the above items, wherein the cathode includes a coefficient of thermal expansion in a range of lO.OxlO "6 °C to 12.5xl0 "6 °C _1 .
• Item 6 The solid oxide fuel cell of any of the above items, wherein the cathode has a thickness (Th c ) and the flat-tubular anode has a thickness (Th a ), and wherein a ratio (Th c )/(Th a ) is in a range of 0.50 to 1.50.
• Item 7 The solid oxide fuel cell of any of the above items, wherein the cathode includes a thickness in a range of 0.6 mm to 5 mm.
• Item 8 The solid oxide fuel cell of any of the above items, wherein the cathode includes channels.
• Item 9 The solid oxide fuel cell of any of the above items, wherein the channels of the cathode have a diameter of at least 0.5 mm.
• Item 10 The solid oxide fuel cell of any of the above items, wherein the channels of the cathode have a diameter of not greater than 2 mm.
• Item 11 The solid oxide fuel cell of any of the above items, wherein the cathode is substantially planar.
• Item 12 The solid oxide fuel cell of any of the above items, wherein the cathode includes a cathode bulk layer and a cathode functional layer.
• Item 13 The solid oxide fuel cell of any of the above items, wherein the cathode includes LSM.
• Item 14 The solid oxide fuel cell of any of the above items, wherein the flat-tubular anode includes Ni, NiO, YSZ, or a combination thereof.
• Item 15 The solid oxide fuel cell of any of the above items, further comprising an interconnect disposed on the flat-tubular anode.
• Item 16 The solid oxide fuel cell of any of the above items, wherein the electrolyte is in contact with a rounded portion of the anode.
• Item 17 A solid oxide fuel cell stack comprising two or more of the solid oxide fuel cells according to any of the above items, wherein the two or more solid oxide fuel cells are stacked one upon the other.
• Item 18 The solid oxide fuel cell of item 17, further comprising a cathode bond layer disposed between the interconnect of a first solid oxide fuel cell and a cathode of a second solid oxide fuel cell.
• Item 19 The solid oxide fuel cell of item 18, wherein the cathode bond layer includes LSM.

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• 2015
  • 2015-05-27 JP JP2016571351A patent/JP2017522691A/ja active Pending
  • 2015-05-27 EP EP15803627.7A patent/EP3152794A4/en not_active Withdrawn
  • 2015-05-27 WO PCT/US2015/032561 patent/WO2015187416A1/en active Application Filing

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