Patent Description:
The increased use of electrical power in aircraft systems and propulsion requires advanced electrical storage systems and/or a chemical to electrical power conversion system to generate adequate amounts of electrical power. Both high system efficiency and high power density of the conversion system are required.

Fuel cell based power systems, such as solid oxide fuel cell (SOFC) based power systems, are able to achieve electrical efficiencies of <NUM>% or greater. Further, SOFC power systems can operate with a variety of fuels and are scalable to achieve different power levels. Current, state of the art SOFC systems, however, have relatively low power densities of less than about <NUM> watts per kilogram, and relatively slow startup times typically exceeding <NUM> minutes. For aircraft and aerospace applications, increased power densities and reduced startup times are required.

<CIT> discloses a fuel cell stack including multiple fuel cells that are separated by interconnects, that are gas flow separator plates. Each interconnect includes ribs that at least partially define fuel channels and air channels.

In one embodiment, a solid oxide fuel cell or solid oxide electrolyzer includes a plurality of fuel cell layers stacked along a stacking axis. Each fuel cell layer including a stacked arrangement of elements including a cathode, an anode, an electrolyte located between the anode and the cathode, a support layer positioned at the anode opposite the electrolyte, and a separator plate located at the support layer opposite the anode. The separator plate is configured to contact the cathode of an adjacent fuel cell layer of the plurality of fuel cell layers. The separator plate defines a plurality of anode flow channels configured to deliver a fuel therethrough and a plurality of cathode flow channels configured to deliver an air flow therethrough. The separator plate is formed from a bulk metallic glass material.

Additionally or alternatively, in this or other embodiments an electrical conductivity of the separator is attained via crystallization of the bulk metallic glass material.

Additionally or alternatively, in this or other embodiments the bulk metallic glass material is corrosion resistant.

Additionally or alternatively, in this or other embodiments the separator plate includes a coating applied to the bulk metallic glass material.

Additionally or alternatively, in this or other embodiments the plurality of anode flow channels at least partially overlap the plurality of cathode flow channels along the stacking axis.

Additionally or alternatively, in this or other embodiments the electrolyte is formed from a solid oxide material.

Additionally or alternatively, in this or other embodiments the separator plate defines the plurality of anode flow channels at a first side of the separator plate and the plurality of cathode flow channels at a second side of the separator plate opposite the first side.

Additionally or alternatively, in this or other embodiments the bulk metallic glass material is one or more of a Fe-Cr-Mo-C-B based bulk metallic glass material, a Zr based bulk metallic glass material, or a bulk metallic glass composite material.

In another embodiment, a fuel cell layer of a multi-layer fuel cell includes a cathode, an anode, an electrolyte located between the anode and the cathode, a support layer positioned at the anode opposite the electrolyte, and a separator plate positioned at the support layer opposite the anode. The separator plate is configured to contact the cathode of an adjacent fuel cell layer. The separator plate defines a plurality of anode flow channels configured to deliver a fuel therethrough and a plurality of cathode flow channels configured to deliver an air flow therethrough. The separator plate is formed from a bulk metallic glass material.

Additionally or alternatively, in this or other embodiments the separator plate includes a plurality of curved portions separated by flat support portions, with the support portions interfacing with the support layer and curved portions <NUM> contacting the cathode of the adjacent fuel cell layer.

In yet another embodiment, a method of assembling a multi-layer fuel cell includes assembling a plurality of fuel cell layers, each fuel cell layer including a cathode, an anode, an electrolyte located between the anode and the cathode, a support layer positioned at the anode opposite the electrolyte, and a separator plate positioned at the support layer opposite the anode. The separator plate is configured to contact the cathode of an adjacent fuel cell layer. The separator plate defines a plurality of anode flow channels configured to deliver a fuel therethrough and a plurality of cathode flow channels configured to deliver an air flow therethrough. The separator plate is formed from a bulk metallic glass material. The plurality of fuel cell layers are arranged along a stacking axis, the separator plate is heated to a temperature greater than a glass transition temperature of the bulk metallic glass material, a compressive load is applied to the plurality of fuel cell layers, and the bulk metallic glass material is thermoplastically flowed thereby increasing a contact area of the separator plate to the cathode of the adjacent fuel cell layer.

Additionally or alternatively, in this or other embodiments the bulk metallic glass material is one of a Fe-Cr-Mo-C-B based bulk metallic glass material, a Zr based bulk metallic glass material, or a bulk metallic glass composite.

Additionally or alternatively, in this or other embodiments the glass transition temperature is below <NUM> degrees Celsius.

Additionally or alternatively, in this or other embodiments thermoplastic flow of the bulk metallic glass material improves a contact area between the separator plate and the support layer.

Referring to <FIG>, shown is a schematic illustration of an embodiment of a fuel cell (<NUM>). In some embodiments, the fuel cell <NUM> is an oxygen-ion conducting solid oxide fuel cell or a proton conducting solid oxide fuel cell. The fuel cell <NUM> includes an anode <NUM> and a cathode <NUM> with an electrolyte <NUM> disposed between the anode <NUM> and the cathode <NUM>. In the case of the solid oxide fuel cell <NUM>, the electrolyte <NUM> is a solid oxide material, such as for example, a ceramic material. A flow of fuel is introduced to the fuel cell <NUM> along with a flow of air. Chemical reactions of the fuel and air with the electrolyte <NUM> produces electricity. In some embodiments, an operating temperature of the fuel cell <NUM> is in the range of <NUM> -<NUM> degrees Celsius, while in other embodiments the operating temperature is in the range of <NUM>-<NUM> degrees Celsius. The flow of fuel may comprise, for example, natural gas, coal gas, biogas, hydrogen, or other fuels such as jet fuel.

Referring now to <FIG>, the fuel cell <NUM> includes a plurality of fuel cell layers <NUM> stacked along a stacking axis <NUM>. In some embodiments, each fuel cell layer <NUM> has a rectangular shape. It is to be appreciated, however, that the fuel cell layers <NUM> may have other polygonal shapes or may be, for example, circular, elliptical or oval in shape. As shown in <FIG>, each fuel cell layer <NUM> includes a separator plate <NUM> and a support <NUM> located over the separator plate <NUM>. An anode <NUM>, electrolyte <NUM> and a cathode <NUM> are stacked atop the support <NUM> in that order. In some embodiments, the electrolyte <NUM> is formed from a solid oxide material, such as a ceramic material. The fuel cell layers <NUM> are stacked such that the cathode <NUM> contacts the separator plate <NUM> of the neighboring fuel cell layer <NUM>.

The separator plate <NUM> is compliant and lightweight and is shaped to define a plurality of anode flow channels <NUM> and a plurality of cathode flow channels <NUM> and separate the anode flow channels <NUM> from the cathode flow channels <NUM>. The plurality of anode flow channels <NUM> are defined at a first side of the separator plate <NUM> and the plurality of cathode flow channels <NUM> are defined at a second side of the separator plate <NUM> opposite the first side. As illustrated the anode flow channels <NUM> and the cathode flow channels <NUM> at least partially overlap along the stacking axis <NUM>. This improves a density of the fuel cell <NUM> along the stacking axis <NUM>.

Compliance of the separator plate <NUM> ensures good contact with the cathode <NUM> for high electrical performance, and the separator plate <NUM> is configured for light weight to enable high power density of the fuel cell <NUM>. The fuel flows through the anode flow channels <NUM> and the air flows through the cathode flow channels <NUM>. When the fuel cell <NUM> is operated as an electrolyzer the reactant may be different. For example, for a steam electrolyzer with oxygen-ion conducting electrolyte, steam flows through the anode flow channels <NUM>, and oxygen is generated at the cathode. For a steam electrolyzer with a proton conducting electrolyte, steam flows through the cathode flow channels <NUM>, and hydrogen is generated at the anode.

In some embodiments, such as in <FIG>, the separator plate <NUM> includes a plurality of curved portions <NUM> separated by flat support portions <NUM>, with the support portions <NUM> interfacing with the support <NUM> and curved portions <NUM> contacting the cathode <NUM> of the neighboring fuel cell layer <NUM>. The waveform shape of the separator plate <NUM> with the plurality of curved portions <NUM> allows for greater levels of fuel flow coverage to the anode <NUM> and a greater level of airflow coverage to the cathode <NUM>. In other embodiments, the curved portions <NUM> may have other shapes, such as rectilinear as shown in <FIG>. The separator plate <NUM> may be formed from corrugated sheet stock with features on the order of millimeters to centimeters. Alternatively, the separator plate <NUM> may be formed from sheet material by, for example, stamping, extrusion, folding, bending, roll forming, hydroforming, or the like. Other methods may include injection molding or additive manufacturing methods including laser powder bed fusion, electron beam melting, directed energy deposition, or laminated object manufacture. In still other embodiments, the separator plate may be formed at least partially by a process such as ultraviolet lithography and etching which may be used to form features with a resolution below <NUM> microns, or by micro-EDM (electrical discharge machining) or laser micromachining, both of which that may be utilized to produce features with a resolution in the range of <NUM> to <NUM> microns.

Referring again to <FIG> and also to the partially exploded view of <FIG>, fuel is distributed to the anode fuel channels <NUM> via a primary manifold <NUM> and a secondary manifold <NUM>. The primary manifold <NUM> extends between the fuel cell layers <NUM> to distribute fuel to each fuel cell layer <NUM> of the plurality of fuel cell layers <NUM>. Each fuel cell layer <NUM> includes a secondary manifold <NUM> located at, for example, a first end <NUM> of the anode flow channels <NUM>. The secondary manifold <NUM> is connected to the primary manifold <NUM> and the plurality of anode flow channels <NUM> to distribute fuel from the primary manifold <NUM> to each of the anode flow channels <NUM> of the fuel cell layer <NUM>. The anode flow channels <NUM> extend from the secondary manifold <NUM> at the first end <NUM> of the anode flow channels <NUM> to a collection manifold <NUM> at a second end <NUM> of the anode flow channels <NUM>. Fuel flows from the primary manifold <NUM> through the secondary manifold <NUM>, and through the anode flow channels <NUM> with anode byproducts such as water vapor and carbon dioxide exiting the anode flow channels <NUM> and flowing into the collection manifold <NUM>.

The support layer <NUM> is formed from a metal material in some embodiments, and includes a porous section <NUM> and a non-porous or solid section <NUM>, with the solid section <NUM> surrounding the porous section <NUM> and defining an outer perimeter of the support layer <NUM>. The porous section <NUM> may be formed by, for example, laser drilling of a metal sheet, sintering of metal powder, or additive manufacturing. The porous section <NUM> is located over the anode flow channels <NUM> to allow the fuel flow to reach the anode <NUM> through the porous section <NUM>. In some embodiments, a metal catalyst foam layer <NUM> is located between the separator plate <NUM> and the support layer <NUM>.

The separator plate <NUM> is formed from a bulk metallic glass material. The bulk metallic glass material of the separator plate <NUM> will have a glass transition temperature below about <NUM> degrees Celsius, a crystallization temperature preferably between <NUM> degrees and <NUM> degrees Celsius, and a melting temperature greater than <NUM> degrees Celsius. The material is desired to be electrically conductive, and available in a thin sheet less than <NUM> mils thick. In some embodiments, the material is less than <NUM> mils thick. Further, the material can have high oxidation resistance, or alternatively the separator plate <NUM> includes a coating to provide oxidation resistance. Example materials include Fe-Cr-Mo-C-B based bulk metallic glass materials, Zr based bulk metallic glass materials, or bulk metallic glass composites having, for example, carbon fibers or carbon nanotubes for increased electrical conductivity. In some instances, the requisite electrical conductivity may be achieved by crystallization of the bulk metallic glass.

<FIG> and <FIG> illustrate an assembly method of the fuel cell <NUM>. As shown in <FIG>, the fuel cell layers <NUM> are assembled and arranged along the stacking axis <NUM>. The fuel cell layers <NUM>, and more specifically the separator plates <NUM>, are heated to above the glass transition temperature of the bulk metallic glass material of the separator plates <NUM>. A compressive load is applied to the assembly, during which the bulk metallic glass material thermoplastically flows and conforms to the cathode <NUM> surface below the separator plate <NUM>, increasing contact area of the separator plate with the cathode. Further, the separator plate <NUM> better conforms to the support layer <NUM>.

Such thermoplastic forming of the separator plate <NUM> via the use of and heating of the bulk metallic glass material improves the interface between the separator plate <NUM> and the cathode <NUM>, and further reduces the contact resistance, improving performance of the fuel cell <NUM>. Also, the bulk metallic can fill small (sub micron) high aspect ratio cavities to bolster the contact area between the bulk metallic glass and the cathode <NUM>. The cathode <NUM> may be engineered specifically for the bulk metallic glass separator plate <NUM>. In one embodiment, the temperature may be raised after forming to crystallize the bulk metallic glass separator plate <NUM>, thereby attaining higher conductivity.

Further, the compressive load normally required to ensure good contact between the cathode <NUM> and the separator plate <NUM> can be significantly reduced, allowing for a reduced weight of the fuel cell <NUM> assembly. Further, weight of the system is reduced and assembly is simplified by removing or reducing the scale of associated fixturing required.

The fuel cell <NUM> configurations disclosed herein enable a high performance electrical power system for, for example, an aircraft, especially for long duration operation. The configurations further reduce startup times and provide power densities higher than <NUM> W/kg. While the embodiments described herein apply to solid oxide fuel cells, one skilled in the art will readily appreciate that disclosed embodiments of the separator plate <NUM> may be applied to and utilized in other structures such as a solid oxide electrolyzer cell.

Claim 1:
A fuel cell layer of a multi-layer fuel cell, comprising:
a cathode (<NUM>);
an anode (<NUM>);
an electrolyte (<NUM>) disposed between the anode and the cathode;
a support layer (<NUM>) disposed at the anode opposite the electrolyte;
a separator plate (<NUM>) disposed at the support layer opposite the anode, the separator plate configured to contact the cathode of an adjacent fuel cell layer, the separator plate defining a plurality of anode flow channels configured to deliver a fuel therethrough and a plurality of cathode flow channels configured to deliver an air flow therethrough;
wherein the separator plate is formed from a bulk metallic glass material and characterized in that the anode flow channels and the cathode flow channels at least partially overlap along a stacking axis direction of the multilayer fuel cell.