Ni-Fe BASED CATHODE FUNCTIONAL LAYERS FOR SOLID OXIDE ELECTROCHEMICAL CELLS

Abstract

To provide solid oxide electrochemical cells improved in electrochemical properties, such as stability and catalytic activity, by using a cathode functional layer material with suppressed reactions with water or with chromium gas species.SOLUTION: A solid oxide electrochemical cell 500 includes a solid oxide electrolyte 312, an anode 314 located on a first side of the solid oxide electrolyte 312, and a cathode 316 located on a second side of the solid oxide electrolyte 312. The cathode 316 includes lanthanum nickel ferrite.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This disclosure relates, in general terms, to fuel cell stacks and, in particular, to electrochemical battery cathode materials. [Background technology]

[0002] In high-temperature fuel cell systems, such as solid oxide fuel cell (SOFC) systems, the oxidizer flow passes through the cathode side of the fuel cell, and the fuel flow passes through the anode side. The oxidizer flow is typically air, and the fuel flow may be a hydrocarbon fuel, such as methane, natural gas, pentane, ethanol, or methanol. The fuel cell operates at a typical temperature of 750°C to 950°C, allowing negatively charged oxygen ions to move from the cathode flow stream to the anode flow stream, where the ions combine with free hydrogen or hydrogen in hydrocarbon molecules to produce water vapor, and / or with carbon monoxide to produce carbon dioxide. Excess electrons from the negatively charged ions are returned to the cathode side of the fuel cell via an electrical circuit completed between the anode and cathode, resulting in an electric current flowing through the circuit.

[0003] A fuel cell stack may have internal or external manifolds for fuel and air. In an internal manifold stack, fuel and air are distributed to each cell using risers contained within the stack. In other words, the gases flow through openings or holes in the support layer of each fuel cell, such as the electrolyte layer, and through the gas flow separators in each cell. In an external manifold stack, the stack has openings at the fuel and air inlet and outlet sides, and the fuel and air are introduced and recovered independently of the stack hardware. For example, the inlet and outlet fuel and air flow through separate passages between the stack and the manifold housing in which the stack is located.

[0004] Fuel cell stacks are often constructed from multiple cells in the form of planar elements, tubes, or other geometries. Fuel and air must be supplied to an electrochemically active surface, which can be large. One component of a fuel cell stack is the so-called gas flow separator (called a gas flow separator plate in planar stacks), which separates the individual cells within the stack. The gas flow separator plate separates the fuel, such as hydrogen or hydrocarbon fuel, flowing to the fuel electrode (i.e., anode) of one cell in the stack from the oxidizer, such as air, flowing to the air electrode (i.e., cathode) of an adjacent cell in the stack. Often, the gas flow separator plate is also used as an interconnect, electrically connecting the fuel electrode of one cell to the air electrode of an adjacent cell. In this case, the gas flow separator plate acting as an interconnect is formed from or contains a conductive material. [Overview of the Initiative]

[0005] In one embodiment, a solid oxide electrochemical battery includes a solid oxide electrolyte, an anode located on a first side of the solid oxide electrolyte, and a cathode located on a second side of the solid oxide electrolyte, the cathode comprising lanthanum nickel ferrite.

[0006] In another embodiment, a method for manufacturing a solid oxide electrochemical battery includes the steps of supplying a solid oxide electrolyte, forming an anode on a first side of the solid oxide electrolyte, and forming a cathode containing lanthanum nickel ferrite on a second side of the solid oxide electrolyte. [Brief explanation of the drawing]

[0007] The accompanying drawings incorporated herein and constituting part thereof illustrate exemplary embodiments of the present invention and, together with the above general description and the following detailed description, are useful in illustrating the features of the present invention. [Figure 1A] This is a perspective view of a conventional fuel cell column. [Figure 1B] This is a perspective view of one counterflow solid oxide fuel cell stack included in the column of Figure 1A. [Figure 1C] Figure 1B is a side cross-sectional view of a portion of the stack. [Figure 2A] Figure 1B is a top view of the air side of a conventional interconnect in the stack. [Figure 2B] Figure 1B is a top view of the fuel side of a conventional interconnect. [Figure 3A] This is a perspective view of a fuel cell stack according to various embodiments of the present disclosure. [Figure 3B] This is an exploded perspective view of a portion of the stack in Figure 3A according to various embodiments of the present disclosure. [Figure 3C] This is a top view of the fuel side of an interconnect included in the stack shown in Figure 3A, according to various embodiments of the present disclosure. [Figure 3D] This is a schematic diagram of a fuel cell included in the stack shown in Figure 3A, according to various embodiments of the present disclosure. [Figure 4A] This is a plan view showing the air side of the cross-flow type (direct flow type) interconnect shown in Figure 3C, according to various embodiments of the present disclosure. [Figure 4B] This is a plan view showing the fuel side of the cross-flow interconnect shown in Figure 3C, according to various embodiments of the present disclosure. [Figure 5] This is a schematic diagram of an electrochemical battery according to various embodiments of the present disclosure. [Figure 6] This figure shows the standardized area resistivity degradation of an embodiment battery having a lanthanum nickel ferrite-based cathode functional layer (CFL) and a comparative battery having a lanthanum strontium manganese-based CFL, according to various embodiments of the present disclosure. [Figure 7] This figure shows the ohm resistance of the embodiment battery and the comparison battery according to various embodiments of the present disclosure. [Modes for carrying out the invention]

[0008] Various embodiments will be described in detail with reference to the accompanying drawings. The drawings are not necessarily to scale and are intended to illustrate various features of the invention. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or similar components. References to specific examples and embodiments are illustrative and not intended to limit the scope of the invention or the claims.

[0009] In this specification, a range may be expressed as from a certain value "about" and / or from another specific value "about". When such a range is expressed, the example includes from a certain value and / or from another specific value. Similarly, when a value is expressed as an approximation by using "about" or "substantially" immediately before it, it will be understood that a particular value takes on a different form. In some embodiments, the value "about X" may include values ​​of + / -1%X. Furthermore, each endpoint of a range is understood to be significant in relation to other endpoints and independently of other endpoints.

[0010] Some embodiments of this disclosure relate to SOFCs including a Ni-Fe-based perovskite material, such as a cathode functional layer (CFL) having lanthanum nickel ferrite. Such materials have improved stability in the presence of water vapor and / or chromium vapor and exhibit reduced area resistivity degradation compared to lanthanum strontium manganite (LSM)-based CFLs. The disclosed embodiments relate to the perovskite material LaNi 1-y Fe y O 3-δ and La 1-x Ca x Ni 1-y Fe y O 3-δNi-Fe including the same, and a mixture of Ni-Fe containing such perovskite materials and other non-perovskite type ion-conductive ceramic materials, such as scandia-stabilized zirconia (SSZ), samaria-doped ceria (SDC), gadolinia-doped ceria (GDC), or CFL having zirconia stabilized with Sc-Ce-Y or Sc-Ce-Yb. The weight ratio of the Ni-Fe perovskite phase: other ceramic phases may be variable between 3:7 and 7:3. The disclosed embodiments further include, in the SOFC cathode, a more conductive perovskite material, such as LSM (e.g., (La 1-x Sr x ) y MnO 3-δ ), lanthanum strontium cobaltite (LSCo) or lanthanum strontium cobalt ferrite (LSCF, e.g., La 1-x Sr x Co 1-y Fe y O 3-δ ), and a CFL based on Ni-Fe perovskite combined with a cathode current collector layer (CCL).

[0011] FIG. 1A is a perspective view of a conventional fuel cell column 30, FIG. 1B is a perspective view of one counterflow type SOFC stack 20 included in the column 30 of FIG. 1A, and FIG. 1C is a partial side cross-sectional view of the stack 20 of FIG. 1B.

[0012] Referring to Figures 1A and 1B, the column 30 may include one or more stacks 20, a fuel inlet conduit 32, an anode exhaust conduit 34, and an anode feed / return assembly 36 (e.g., an anode splitter plate (ASP) 36). The column 30 may also include a side baffle 38 and a compression assembly 40. The side baffle 38 may be coupled to the compression assembly 40 and a stack component (not shown) located below it via a ceramic connector 39. The fuel inlet conduit 32 is fluid-connected to the ASPs 36 and configured to provide fuel to each ASP 36, and the anode exhaust conduit 34 is fluid-connected to the ASPs 36 and configured to receive anode fuel exhaust from each ASP 36.

[0013] The ASP36 is positioned between the stacks 20 and configured to provide the stacks 20 with a fuel supply containing hydrocarbon fuel and to receive anode fuel exhaust from the stacks 20. For example, the ASP36 may be fluidly connected to an internal fuel riser passage 22 formed within the stacks 20, as described below.

[0014] Referring to Figure 1C, the stack 20 includes a plurality of fuel cells 1 separated by interconnects 10, which are sometimes called gas flow separator plates or bipolar plates. Each fuel cell 1 includes a cathode electrode 3, a solid oxide electrolyte 5, and an anode electrode 7.

[0015] Each interconnect 10 electrically connects adjacent fuel cells 1 within the stack 20. In particular, the interconnect 10 can electrically connect the anode electrode 7 of one fuel cell 1 to the cathode electrode 3 of an adjacent fuel cell 1. Figure 1C shows that the lower fuel cell 1 is positioned between two interconnects 10.

[0016] Each interconnect 10 includes ribs 12 that at least partially define the fuel passage 8A and the air passage 8B. The interconnect 10 can act as a gas-fuel separator, separating fuel, such as hydrocarbon fuel, flowing to the fuel electrode (i.e., anode 7) of one cell in the stack from the oxidizer, such as air, flowing to the air electrode (i.e., cathode 3) of an adjacent cell in the stack. One end of the stack 20 may be provided with an air end plate or a fuel end plate (not shown) for supplying air or fuel to the end electrode, respectively.

[0017] Figure 2A is a plan view of the air side of a conventional interconnect 10, and Figure 2B is a plan view of the fuel side of the interconnect 10. Referring to Figures 1C and 2A, the air side includes an air passage 8B. Air flows through the air passage 8B to the cathode electrode 3 of the adjacent fuel cell 1. In particular, air can flow across the interconnect 10 in a first direction A indicated by the arrow.

[0018] A ring seal 23 may surround the fuel port 22A of the interconnect 10 to prevent fuel from contacting the cathode electrode. A strip-shaped peripheral seal 24 is positioned around the air-side peripheral portion of the interconnect 10. The seals 23 and 24 may be made of glass material. The peripheral portion may be in the form of a raised, elevated portion that does not include ribs or passages. The surface of the peripheral region may be coplanar with the top of the rib 12.

[0019] Referring to Figures 1C and 2B, the fuel side of the interconnect 10 may include a fuel passage 8A and a fuel manifold 28 (e.g., a fuel plenum). Fuel flows from one of the fuel holes 22A into the adjacent manifold 28, through the fuel passage 8A, and to the anode 7 of the adjacent fuel cell 1. Excess fuel can flow into the other fuel manifold 28 and then into the adjacent fuel hole 22A. In particular, fuel can flow across the interconnect 10 in a second direction B indicated by the arrow. The second direction B may be perpendicular to the first direction A (see Figure 2A).

[0020] A frame-shaped seal 26 is positioned in the fuel-side peripheral region of the interconnect 10. The peripheral region may be a raised, elevated portion that does not include ribs or passages. The surface of the peripheral region may be coplanar with the top of the rib 12.

[0021] Therefore, conventional counterflow fuel cell columns, such as those shown in Figures 1A, 1B, 1C, 2A, and 2B, may include a complex fuel distribution system (fuel rails and anode splitter plate). Furthermore, the use of an internal fuel riser may require holes in the fuel cell and corresponding seals, thereby reducing the working surface area of ​​the fuel cell and potentially causing cracks in the ceramic electrolyte of the fuel cell 1.

[0022] The fuel manifold 28 may occupy a relatively large area of ​​the interconnect 10, which could reduce the contact area between the interconnect 10 and adjacent fuel cells by approximately 10%. Also, because the fuel manifold 28 is relatively deep, it corresponds to a relatively thin area of ​​the interconnect 10. Since the interconnect 10 is generally formed by a powder metallurgy compression process, the density of the fuel manifold area may approach the theoretical density limit of the interconnect material. Therefore, the length of the compression press stroke used in the compression process is limited because the high-density fuel manifold area cannot be further compressed. As a result, the compression stroke limitation may limit the density achieved elsewhere in the interconnect 10 to a lower level. The resulting density variation may lead to localized variability, which could reduce the amount of contact between the interconnect 10 and the fuel cell 1, potentially degrading the stack's yield and / or performance.

[0023] Another important consideration in the design of fuel cell systems is the area of ​​operational efficiency. To achieve operational efficiency, maximizing fuel utilization is a crucial factor. Fuel utilization is the ratio of the amount of fuel consumed during operation to the amount of fuel supplied to the fuel cell. A key factor in maintaining the cycle life of a fuel cell may be avoiding fuel depletion in the fuel cell's area of ​​action by properly distributing fuel across the area of ​​action. If there is an uneven distribution of fuel, such that some flow range passages do not receive enough fuel to support the electrochemical reactions occurring in the area of ​​that passage, it can lead to fuel depletion in the fuel cell area adjacent to that passage. To distribute fuel more uniformly, conventional interconnect designs include deviations in passage depth across the entire flow range. This not only introduces complexity in the manufacturing process but can also require complex measurements to accurately determine these dimensions. The distribution of fuel through fuel ports and distribution manifolds can constrain various passage geometries.

[0024] One possible solution to overcome this complex geometry and fuel manifold is to have a wider fuel opening to ensure more uniform fuel distribution across the entire fuel flow range. Since the formation of the fuel manifold is a source of density variation, eliminating the fuel manifold should allow for more uniform density and permeability in the interconnect. Therefore, there is a need for an improved interconnect that provides uniform contact with the fuel cell while distributing fuel uniformly to the fuel cell without using a conventional fuel manifold.

[0025] Due to the overall constraints on increasing the size of the hotbox in fuel cell systems, there is also a need for improved interconnects designed to maximize fuel utilization and the working area of ​​the fuel cell without increasing the hotbox footprint.

[0026] Figure 3A is a perspective view of a fuel cell stack 300 according to various embodiments of the present disclosure. Figure 3B is an exploded perspective view of a portion of the stack 300 in Figure 3A. Figure 3C is a top view of the fuel side of the interconnect 400 included in the stack 300. Figure 3D is a schematic diagram of the fuel cell included in the stack 300.

[0027] Referring to Figures 3A to 3D, the fuel cell stack 300, which may also be called a fuel cell column because it does not have an ASP, includes a plurality of fuel cells 310 separated by an interconnect 400, which may also be called a gas flow separator plate or bipolar plate. One or more stacks 300 may be thermally integrated with other components of the fuel cell power generation system (e.g., one or more anode exhaust gas oxidizers, fuel reformers, fluid conduits and manifolds, etc.) within a common enclosure or “hot box”.

[0028] The interconnect 400 is formed from a conductive metallic material. For example, the interconnect 400 may include a chromium alloy, such as a Cr-Fe alloy. Typically, the interconnect 400 can be manufactured using powder metallurgy techniques, including pressing and sintering of Cr-Fe powder, which may be a mixture of Cr powder and Fe powder or Cr-Fe alloy powder, to form a Cr-Fe interconnect of the desired size and shape (e.g., a "net-shape" or "near-net-shape" process). A typical chromium alloy interconnect 400 contains more than about 90% by weight of chromium, for example, about 94–96% (e.g., 95%) of chromium. The interconnect 400 may also contain less than about 10% by weight of iron, for example, about 4–6% (e.g., 5%) of iron, less than about 2% by weight of other materials, for example, about 0–1% by weight, such as yttrium or yttria, and residual or unavoidable impurities.

[0029] Each fuel cell 310 may include a solid oxide electrolyte 312, an anode 314, and a cathode 316. In some embodiments, the anode 314 and cathode 316 are printable on the electrolyte 312. In other embodiments, a conductive layer 318, such as a nickel mesh, may be placed between the anode 314 and the adjacent interconnect 400. The fuel cell 310 does not have through holes like the fuel holes of conventional fuel cells. Therefore, the fuel cell 310 avoids cracks that may occur due to the presence of such through holes.

[0030] The uppermost and lowermost interconnects 400 of the stack 300 may be different forms of air-side endplates or fuel-side endplates, each characterized for supplying air or fuel to an adjacent end fuel cell 310. As used herein, “interconnect” may mean either an interconnect located between two fuel cells 310, or an endplate located at the end of the stack and directly adjacent to only one fuel cell 310. Since the stack 300 does not include an ASP and its associated endplates, the stack 300 can only contain two endplates. As a result, deviations in stack dimensions associated with the use of an in-column ASP can be avoided.

[0031] The stack 300 may include side baffles 302, a fuel plenum 350, and a compression assembly 306. The side baffles 302 can be formed from a ceramic material and may be positioned on opposite sides of the fuel cell stack 300, which includes the stacked fuel cells 310 and interconnect 400. The side baffles 302 may connect the fuel plenum 350 and the compression assembly 306 so that the compression assembly 306 can apply pressure to the stack 300. The side baffles 302 may be curved baffle plates such that each baffle plate covers at least a portion of three sides of the fuel cell stack 300. For example, one baffle plate may completely cover the fuel inlet riser side of the stack 300 and partially cover adjacent front and back sides of the stack, while the other baffle plate may completely cover the fuel outlet riser side of the stack and partially cover adjacent front and back sides of the stack. The remaining uncovered portions of the front and back sides of the stack allow air to flow through the stack 300. The curved baffle plate improves control of the airflow through the stack compared to a conventional baffle plate 38 that covers only one side of the stack. The fuel plenum 350 may be located below the stack 300 and may be configured to supply hydrogen-containing fuel to the stack 300 and may receive anode fuel exhaust from the stack 300. The fuel plenum 350 may be connected to a fuel inlet and outlet conduit 320 located below the fuel plenum 350.

[0032] Each interconnect 400 electrically connects adjacent fuel cells 310 within the stack 300. In particular, an interconnect 400 can electrically connect the anode electrode of one fuel cell 310 to the cathode electrode of an adjacent fuel cell 310. As shown in Figure 3C, each interconnect 400 can be configured to supply air to the cathode of an adjacent fuel cell 310 by flowing air in a first direction A. Alternatively, each interconnect 400 can be configured to supply fuel to the anode of an adjacent fuel cell 310 by flowing fuel in a second direction F. Directions A and F may be orthogonal to each other, or substantially orthogonal to each other. Therefore, the interconnects 400 can be called cross-flow interconnects.

[0033] The interconnect 400 may include fuel ports extending through the interconnect 400 and configured for fuel distribution. For example, the fuel ports may include one or more fuel inlets 402 and one or more fuel (e.g., anode exhaust) outlets 404, which may also be called anode exhaust outlets 404. The fuel inlets 402 and fuel outlets 404 can be located outside the periphery of the fuel cell 310. Thus, the fuel cell 310 can be formed without corresponding through-holes for fuel flow. The total length of the fuel inlets 402 and / or the total length of the fuel outlets 404 may be at least 75% of the corresponding length of the interconnect 400, for example, the length in direction A.

[0034] In one embodiment, as shown in Figure 3B, each interconnect 400 includes two fuel inlets 402 separated by a neck portion 412 of the interconnect 400. However, there may be more than two fuel inlets 402, for example, three to five inlets separated by two to four neck portions 412. In one embodiment, as shown in Figure 3B, each interconnect 400 includes two fuel outlets 404 separated by a neck portion 414 of the interconnect 400. However, there may be more than two fuel outlets 404, for example, three to five outlets separated by two to four neck portions 414.

[0035] The fuel inlets 402 of adjacent interconnects 400 can be aligned within the stack 300 to form one or more fuel inlet risers 403. The fuel outlets 404 of adjacent interconnects 400 can be aligned within the stack 300 to form one or more fuel outlet risers 405. The fuel inlet risers 403 can be configured to distribute the fuel received from the fuel plenum 350 to the fuel cell 310. The fuel outlet risers 405 can be configured to supply the anode exhaust received from the fuel cell 310 to the fuel plenum 350.

[0036] Unlike the flat side baffle 38 of the related technology shown in Figure 1A, the side baffle 302 can be curved to surround the edge of the interconnect 400. In particular, the side baffle 302 can be positioned to surround the fuel inlet 402 and fuel outlet 404 of the interconnect 400. Thus, the side baffle can more efficiently control the airflow through the air passages of the interconnect 400 that are exposed between the side baffles 302 and described in detail with respect to Figures 4A and 4B.

[0037] In various embodiments, the stack 300 may include at least 30, at least 40, at least 50, or at least 60 fuel cells, which can be supplied with fuel using only fuel risers 403, 405. In other words, compared to conventional fuel cell systems, the cross-flow configuration can supply fuel to a large number of fuel cells without requiring an external fuel manifold, such as external conduits 32, 34, of the ASP or stack shown in Figure 1A.

[0038] Each interconnect 400 may be made of a conductive material, such as a metal alloy (e.g., chromium-iron alloy) having a coefficient of thermal expansion similar to that of the solid oxide electrolyte of the cell (e.g., a difference of 0-10%), or may contain such conductive material. For example, the interconnect 400 may contain a metal (e.g., 4-6% by weight of iron, optionally 1% or less by weight of yttrium, and a chromium-iron alloy such as equilibrium chromium alloy), and may electrically connect the anode side, i.e., the fuel side, of a given fuel cell 310 to the cathode side, i.e., the air side, of an adjacent fuel cell 310. A conductive contact layer, such as a nickel contact layer (e.g., nickel mesh), may be provided between the anode and each interconnect 400. Another optional conductive contact layer may be provided between the cathode electrode and each interconnect 400.

[0039] The surface of the interconnect 400, which is exposed to an oxidizing environment (e.g., air) during operation, for example, the side of the interconnect 400 facing the cathode, may be coated with a protective coating layer to reduce the growth rate of the chromium oxide surface layer of the interconnect and suppress the evaporation of chromium vapor species that degrade the fuel cell cathode. Typically, a coating layer that may contain a perovskite, such as LSM, can be formed using a thermal spray coating or dipping coating process. Alternatively, other metal oxide coatings such as spinel, such as (Mn,Co)3O4 spinel (MCO), can be used instead of or in addition to LSM. 2-x Co 1+xAny spinel having a composition expressed as O4(0≦x≦1) or z(Mn3O4)+(1-z)(Co3O4), where (1 / 3≦z≦2 / 3) or (Mn,Co)3O4 can be used. In other embodiments, a mixed layer of LSM and MCO or a stack of LSM and MCO layers can be used as the coating layer.

[0040] Figures 4A and 4B are plan views showing the air side and fuel side, respectively, of a cross-flow interconnect 400 according to various embodiments of the present disclosure. Referring to Figure 4A, the air side of the interconnect 400 may include ribs 406 configured to at least partially define an air passage 408 configured to supply air to the cathode of a mounted fuel cell 310. The air side of the interconnect 400 can be divided into an airflow range 420 including the air passage 408 and riser seal surfaces 422 located on two opposite sides of the airflow range 420. One of the riser seal surfaces 422 may surround a fuel inlet 402, and the other riser seal surface 422 may surround a fuel outlet 404. The air passage 408 and ribs 406 can extend entirely across the air side of the interconnect 400, such that the air passage 408 and ribs 406 terminate at opposite peripheries of the interconnect 400. In other words, when assembled into the stack 300, the opposite ends of the air passages 408 and ribs 406 are positioned on opposite (e.g., front and back) outer surfaces of the stack, allowing the blown air to flow through the stack. Therefore, the stack may be equipped with an external air manifold.

[0041] A riser seal 424 may be positioned on the riser seal surface 422. For example, one riser seal 424 may surround the fuel inlet 402, and another riser seal 424 may surround the fuel outlet 404. The riser seal 424 can prevent fuel and / or anode exhaust from entering the airflow range 420 and coming into contact with the cathode of the fuel cell 310. The riser seal 424 can also function to prevent fuel from leaking out of the fuel cell stack 100 (see Figure 3A).

[0042] Referring to Figure 4B, the fuel side of the interconnect 400 may include a rib 416 that at least partially defines a fuel passage 418 configured to supply fuel to the anode of the mounted fuel cell 310. The fuel side of the interconnect 400 can be divided into a fuel flow range 430 including the fuel passage 418 and a surrounding sealing surface 432 surrounding the fuel flow range 430 as well as the fuel inlet 402 and fuel outlet 404. The rib 416 and the fuel passage 418 may extend in a direction perpendicular or substantially perpendicular to the direction in which the air-side passage 408 and the rib 406 extend.

[0043] A frame-shaped perimeter seal 434 may be positioned on the perimeter sealing surface 432. The perimeter seal 434 can be configured to prevent air from entering the fuel flow range 430 and coming into contact with the anode of an adjacent fuel cell 310. The perimeter seal 434 can also function to prevent fuel from leaving the fuel risers 403, 405 and leaking out of the fuel cell stack 300 (see Figures 3A and 3B).

[0044] The seals 424,434 may include a glass or ceramic sealing material. The sealing material may have low conductivity. In some embodiments, the seals 424,434 can be formed by printing one or more layers of the sealing material onto the interconnect 400 and then sintering them.

[0045] Figure 5 is a schematic diagram of an electrochemical battery 500 according to various embodiments of the present disclosure. The electrochemical battery 500 may include a solid oxide fuel cell (SOFC) or a solid oxide electrolytic cell (SOEC). In a solid oxide electrolytic cell, a voltage is applied between the anode and the cathode, and a water-containing flow is supplied to the anode. The water is electrolyzed into hydrogen and oxygen at the anode. Oxygen ions are transported to the cathode via the electrolyte. An oxygen-containing exhaust flow is supplied from the cathode. A hydrogen-containing flow is supplied from the anode.

[0046] The electrochemical battery 500 includes a solid oxide electrolyte 312, an anode 314 having an anode current collector layer 314a and an anode functional layer 314b, and a cathode 316 having a CFL 316a and a cathode current collector layer (CCL) 316b.

[0047] The electrolyte 312 may contain ion-conducting ceramics, such as doped zirconia, doped ceria, and / or any other suitable ion-conducting ceramic oxide material. For example, the electrolyte 312 may contain yttria-stabilized zirconia (YSZ), yttria-ceria-stabilized zirconia (YCSZ), scandia-stabilized zirconia (SSZ), ytterbia-ceria-scandia-stabilized zirconia (YbCSSZ), or mixtures thereof. As disclosed in U.S. Patent No. 8,580,456, incorporated herein by reference, scandia may be present in an amount of 9 to 11 mol%, e.g., 10 mol%, ceria may be present in an amount greater than 0 and less than or equal to 3 mol%, e.g., 0.5 mol% to 2.5 mol%, e.g., 1 mol%, and ytterbia may be present in an amount greater than 0 and less than or equal to 2.5 mol%, e.g., 0.5 mol% to 2 mol%, e.g., 1 mol%. Yttria may be present in YCSZ in an amount of 8–10 mol%, and optionally ceria in an amount of 0–3 mol%. In another embodiment, the electrolyte may contain samaria, gadolinia, or yttria-doped ceria.

[0048] The anode 314 is located on the first side of the electrolyte 312. The anode functional layer 314b is located between the anode current collector layer 314a and the first side of the electrolyte 312. The anode 314 may contain at least one cermet comprising a metal phase and a ceramic phase. The metal phase may contain a metal catalyst, and the ceramic phase may contain one or more ceramic materials. The ceramic phase of the anode 40 may contain any suitable ion-conducting ceramic material, such as doped ceria and / or doped zirconia. For example, the ceramic phase may include, but is not limited to, gadolinia-doped ceria (GDC), samaria-doped ceria (SDC), praseodymia-doped ceria (PDC), ytterbia-doped ceria (YDC), scandia-stabilized zirconia (SSZ), ytterbia-ceria-scandia-stabilized zirconia (YCSSZ), yttria-stabilized zirconia (YSZ), etc. For example, the ceramic material may contain doped ceria, such as samaria, gadolinia, and / or praseodymia, or CeO2 doped with 10-20 mol% Sm2O3, Gd2O3, and / or Pr2O3. The metallic phase may contain a metal catalyst that acts as a conductor, such as nickel (Ni). The metal catalyst may be in a metallic state or an oxide state. For example, when the metal catalyst is in an oxidized state, it forms a metal oxide. Therefore, the anode can be annealed in a reducing atmosphere before and / or during operation of the fuel cell to reduce the metal catalyst to a metallic state. The anode functional layer 314b has a lower ratio of nickel-containing phase to ceramic phase than the anode current collector layer 314a.

[0049] The cathode 316 is positioned on the second side of the electrolyte 312. CFL316a is positioned between CCL316b and the second side of the electrolyte 312.

[0050] A comparison of SOFCs operating in the temperature range of 750°C to 850°C (e.g., conventional) cathodes are electro-ion mixed conductive perovskite type LSM phases, e.g., La 0.8 Sr 0.2 MnO3-δ (0≦δ≦0.1) or A-site deficient LSM perovskite phase, for example (La 0.8 Sr 0.2 ) 0.97 MnO 3-δ It may contain [unspecified element]. This material is suitable for CCL, but there may be some stability issues with the use of LSM for CFL. For example, water vapor or chromium vapor (CrO2(OH)2) can degrade the electrocatalytic properties of LSM. Although we do not wish to be bound by any particular theory, it is thought that the surface of LSM may dissociate in the presence of water, creating strontium-located regions and manganese-deficient regions, both of which can affect the surface catalytic properties. Furthermore, it is thought that Mn in LSM may react with chromium vapor to form a Mn-Cr spinel phase, which can degrade the surface catalytic properties and inhibit the three-phase boundary within the CFL. In CFLs where a three-phase boundary exists and oxide ion and charge transfer processes occur, improved electrochemical properties (e.g., stability and / or catalytic activity) are desirable.

[0051] Since both Sr and Mn in LSM perovskite readily react with water or chromium gas species, the inventors have recognized that it may be desirable to use a CFL containing an electrochemically active and conductive perovskite phase that is Sr and Mn-free (excluding unavoidable impurities or atoms diffused from CCL during SOFC production) or has reduced Sr and Mn content. Sr and / or Mn can be replaced whole or partially by nickel and iron in the perovskite material. Therefore, Sr and / or Mn may be omitted whole or at least partially in CFL316a. Thus, CFL316a may contain lanthanum nickel ferrite perovskite material.

[0052] In the two embodiments excluding Sr and Mn, the CFL lanthanum nickel ferrite perovskite material system is LaNi 1-y Fe y O 3-δ and La 1-x Ca x Ni1-y Fe y O 3-δ (where 0 ≦ δ ≦ 0.1). In the first system, a preferred composition is LaNi 1-y Fe y O 3-δ (where 0.2 < y < 1, for example 0.2 < y < 0.8, for example 0.4 < y < 0.6). Materials of this system have advantageous stability and electrochemical properties. Non-limiting examples include LaNi 0.4 Fe 0.6 O 3-δ , LaNi 0.5 Fe 0.5 O 3-δ , and LaNi 0.6 Fe 0.4 O 3-δ . In the second system, a part of La can be replaced by Ca. Preferred compositions include La 1-x Ca x Ni 1-y Fe y O 3-δ (where 0.05 < x < 0.3, for example 0.1 < x < 0.2, and 0.3 < y < 0.7, for example 0.5 < y < 0.7). Non-limiting examples include La 0.8 Ca 0.2 Ni 0.3 Fe 0.7 O 3-δ and La 0.9 Ca 0.1 Ni 0.4 Fe 0.6 O 3-δ . These lanthanum nickel ferrite perovskite materials may have a cubic perovskite lattice structure. For LaNi 0.4 Fe 0.6 O 3-δ , La 0.8 Ca 0.2 Ni 0.3 Fe 0.7 O 3-δ and La 0.9 Ca 0.1 Ni 0.4 Fe 0.6 O 3-δ , it was confirmed by powder X-ray diffraction spectroscopy that the phases are cubic.

[0053] The conductivity of the lanthanum nickel ferrite perovskite material is lower than that of strontium-containing perovskite materials, such as LSM, lanthanum strontium cobaltite (LSCo), and lanthanum strontium cobalt ferrite (LSCF). Therefore, the lanthanum nickel ferrite perovskite material is preferably used for CFL316a rather than CCL316b, while the strontium-containing perovskite material (e.g., LSM, LSCo, or LSCF) is used for CCL316b. The lanthanum nickel ferrite perovskite material can be manufactured by forming a porous / sintered CFL316a on an electrolyte 312, and then forming CCL316b on the CFL316a.

[0054] In another embodiment, the lanthanum nickel ferrite perovskite material may be mixed with non-perovskite ion-conductive ceramic materials, such as scandia-stabilized zirconia (SSZ), Sm-doped ceria (SDC), Gd-doped ceria (GDC), or zirconia stabilized with Sc-Ce, Sc-Ce-Y, or Sc-Ce-Yb. Specific examples of non-perovskite ion-conductive ceramic materials include 89mol%ZrO2-10mol%Sc2O3-1mol%CeO2 ("10Sc1Ce"), Ce 0.8 Sm 0.2 O 2-δ Ce 0.8 Gd 0.2 O 2-δExamples include 88mol%ZrO2-10mol%Sc2O3-1mol%Yb2O3-1mol%CeO2 ("10Sc1Ce1Yb") and 88mol%ZrO2-10mol%Sc2O3-1mol%YO3-1mol%CeO2 ("10Sc1Ce1Y"). Generally, Sc-Ce-Y stabilized zirconia ("YbCSSZ" including the aforementioned 10Sc1Ce1Yb) can be mixed with lanthanum nickel ferrite perovskite materials. In YbCSSZ-stabilized zirconia, scandia may be present in an amount of 9-11 mol%, for example, 10 mol%, ceria may be present in an amount greater than 0 and less than or equal to 3 mol%, for example, 0.5 mol%-2.5 mol%, for example, 1 mol%, and ytterbia may be present in an amount greater than 0 and less than or equal to 2.5 mol%, for example, 0.5 mol%-2 mol%, for example, 1 mol%.

[0055] The weight ratio of lanthanum nickel ferrite perovskite material to non-perovskite type ion-conducting ceramic material in CFL may be 3:7 to 7:3. For example, a CFL composition may contain 30 wt% lanthanum nickel ferrite and 70 wt% 10Sc1Ce1Yb, 40 wt% lanthanum nickel ferrite and 60 wt% 10Sc1Ce1Yb, 50 wt% lanthanum nickel ferrite and 50 wt% 10Sc1Ce1Yb, and 60 wt% lanthanum nickel ferrite and 40 wt% 10Sc1Ce1Yb. In another example, a CFL composition containing SDC may contain 30 wt% lanthanum nickel ferrite and 70 wt% SDC, 40 wt% lanthanum nickel ferrite and 60 wt% SDC, 50 wt% lanthanum nickel ferrite and 50 wt% SDC, and 60 wt% lanthanum nickel ferrite and 40 wt% SDC.

[0056] CFL316a can be printed (e.g., screen printed using ink) and sintered on the second side of electrolyte 312. CCL316b can be printed (e.g., screen printed using ink) and sintered on CFL316a and can mainly function as a current collecting layer. CCL316b may include LSM, LSCo, or LSCF. For example, the LSM composition may include A-site deficient type (La 1-x Sr x ) y MnO 3-δ (where 0.1 < x < 0.3 and 0.94 < y < 0.99). For example, it may include (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ .

[0057] An exemplary cathode 316 includes CFL316a of LaNi 0.4 Fe 0.6 O 3-δ and (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ of CCL316b, CCL of (La 0.8 Ca 0.2 Ni 0.3 Fe 0.7 and CFL, and CCL of (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ and may include CCL of (La 0.9 Ca 0.1 Ni 0.4 Fe 0.6 O 3-δ and (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ .

[0058] Another example of cathode 316 including composite CFL316a is 50 wt% LaNi 0.4 Fe 0.6 O 3-δ and 50 wt% Ce 0.8 Sm 0.2 O 2-δ(La 0.8 Sr 0.2 ) 0.98 MnO 3-δ CCL316b, 50 wt% LaNi 0.4 Fe 0.6 O 3-δ and CFL containing 50 wt% 89 mol% ZrO2 - 10 mol% Sc2O3 - 1 mol% CeO2 (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ CCL, as well as 50% by weight of LaNi 0.4 Fe 0.6 O 3-δ and CFL containing 50 wt% 88 mol% ZrO2 - 10 mol% Sc2O3 - 1 mol% Yb2O3 - 1 mol% CeO2 (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ CCL is one example.

[0059] If CCL316b contains LSCo or LSCF, then CCL316b is La 0.8 Sr 0.2 OO 3-δ La 0.8 Sr 0.2 Co 0.4 Fe 0.6 O 3-δ La 0.8 Sr 0.2 Co 0.2 Fe 0.8 O 3-δ La 0.6 Sr 0.4 Co 0.4 Fe 0.6 O 3-δ , or La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ It may include.

[0060] Embodiments of the CFL lanthanum nickel ferrite perovskite material system can be used in a reversible SOFC capable of generating power from fuel and air supplied to each anode and cathode in SOFC, SOEC, or fuel cell mode, and electrolyzing water when external power is supplied to the battery in electrolysis device mode.

[0061] SOFCs with LSM-based CCL316b and lanthanum nickel ferrite-based CFL316a were tested in an SOFC stack for various durations up to 2000 hours in a temperature range of 700°C to 850°C. To evaluate the performance and degradation of cathodes containing lanthanum nickel ferrite CFL, exemplary cathodes containing lanthanum nickel ferrite-based CFL and LSMC CL were tested head-to-head in a “Rainbow” SOFC stack containing SOFCs of both forms for direct comparison, along with LSM-based comparative cathodes containing LSM-based CFL and LSM CCL. In this non-limiting example, a “Type A” comparative SOFC containing a cathode with LSM CCL and CFL containing 50 wt% LSM and 50 wt% 10Sc1Ce1Yb was compared with LSM CCL and 50 wt% LaNi 0.4 Fe 0.6 O 3-δ It was compared to an exemplary SOFC of "Type B" that included a cathode with a CFL containing 50 wt% 10Sc1Ce1Yb.

[0062] Battery degradation is measured by the change in area resistivity over a predetermined period of time, and this is called area resistivity degradation (ASRD). ASRD is expressed in mΩcm. 2 The unit is expressed in / khr. The results of the stack test, as will be described in more detail below with reference to Figures 6 and 7, show that the exemplary Type B battery has a lower average degradation rate than the comparative Type A battery, and the median ASRD of the exemplary Type B battery is up to approximately 1.5 mΩcm higher than that of the comparative Type A battery. 2 This indicates that / khr is decreasing.

[0063] Figure 6 shows the standardized ASRD of SOFCs in a stack including exemplary Type B batteries numbered 6-10, 16-20, and 26-30, and comparative Type A batteries numbered 1-5, 11-15, 21-25, and 31. The standardized ASRD data shows that the exemplary Type B batteries had lower average ASRD rates than the comparative Type A batteries.

[0064] Figure 7 shows the ohmic resistance (area resistivity, ASR) obtained by electrochemical impedance spectroscopy for the SOFC stack in Figure 6. These measurements show that the ASRD of the exemplary Type B battery is lower than that of the comparative Type A battery, and is virtually ohmic (based on, for example, the sheet resistance Rs). The data characterize the increase in Rs that occurred during 1500 hours of SOFC stack operation for each battery in the SOFC stack. As shown in Figure 7, the exemplary Type B battery has a lower increase in Rs compared to the comparative Type A battery. Thus, the results in Figures 6 and 7 indicate that the performance of the exemplary battery is improved compared to the comparative battery.

[0065] The foregoing description is provided merely as an illustrative example and is not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As those skilled in the art will understand, the order of steps in the foregoing embodiments can be performed in any order. Words such as “then,” “next,” and “next” are not necessarily intended to limit the order of steps, and these words may be used to guide the reader through the description of the method. Furthermore, references to singular elements in a claim using, for example, the articles “a,” “an,” or “the” should not be interpreted as limiting the element to the singular form.

[0066] Furthermore, any process or component of any embodiment described herein may be used in any other embodiment. The fuel cell systems of the embodiments of this disclosure are designed to reduce greenhouse gas emissions and have a positive impact on the climate.

[0067] The above description of the disclosed embodiments is provided to enable those skilled in the art to manufacture or use the invention. Various variations of these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the scope of the invention. Accordingly, the invention is not intended to be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A solid oxide electrochemical cell comprising: a solid oxide electrolyte; an anode disposed on a first side of the solid oxide electrolyte; a cathode functional layer disposed directly on the second side of the solid oxide electrolyte; and It contains The cathode functional layer comprises a mixture of a lanthanum nickel ferrite perovskite material and a non-perovskite ion-conducting ceramic material; and a cathode current collecting layer disposed on the cathode functional layer, the cathode current collecting layer including a perovskite material; Solid oxide electrochemical cells.

2. 10. The solid oxide electrochemical cell of claim 1, wherein the cathode functional layer excludes strontium and manganese.

3. The lanthanum nickel ferrite has the formula LaNi １－ｙ Fe ｙ O ３－δ 10. The solid oxide electrochemical cell of claim 1, having the formula: where 0.2<y<1 and 0≦δ≦0.

1.

4. 4. The solid oxide electrochemical cell of claim 3, wherein 0.4<y<0.

6.

5. The lanthanum nickel ferrite has the formula La １－ｘ Ca ｘ Ni １－ｙ Fe ｙ O ３－δ 10. The solid oxide electrochemical cell of claim 1, having the formula: where 0.05<x<0.3, 0.3<y<0.7, and 0≦δ≦0.

1.

6. 10. The solid oxide electrochemical cell of claim 1, wherein said non-perovskite ionically conductive ceramic material comprises a stabilized zirconia material.

7. 7. The solid oxide electrochemical cell of claim 6, wherein the stabilized zirconia material comprises zirconia stabilized with 9-11 mol% scandia, greater than 0 and less than or equal to 3 mol% ceria, and greater than 0 and less than or equal to 2.5 mol% ytterbia.

8. 10. The solid oxide electrochemical cell of claim 1, wherein said non-perovskite ionically conductive ceramic material consists essentially of a doped ceria material.

9. 10. The solid oxide electrochemical cell of claim 1, wherein the weight ratio of said lanthanum nickel ferrite perovskite material to said non-perovskite ionically conductive ceramic material is from 3:7 to 7:

3.

10. 10. The solid oxide electrochemical cell of claim 1, wherein the cathode current collecting layer comprises lanthanum strontium manganite, lanthanum strontium cobaltite, or lanthanum strontium cobalt ferrite.

11. 10. The solid oxide electrochemical cell of claim 1, wherein the lanthanum nickel ferrite comprises a perovskite material having a cubic crystal lattice structure.

12. The solid oxide electrochemical cell of claim 1 , wherein the solid oxide electrochemical cell comprises a solid oxide fuel cell.

13. 10. The solid oxide electrochemical cell of claim 1, wherein the solid oxide electrochemical cell comprises a reversible solid oxide fuel cell.

14. 10. The solid oxide electrochemical cell of claim 1, wherein the solid oxide electrochemical cell comprises a solid oxide electrolysis cell.

15. The solid oxide electrochemical cell of claim 1, wherein the cathode current collecting layer covers the entire upper surface of the cathode functional layer.

16. 1. A method of manufacturing a solid oxide electrochemical cell, comprising: providing a solid oxide electrolyte; forming an anode on a first side of the solid oxide electrolyte; forming a cathode on a second side of the solid oxide electrolyte, the cathode comprising: a cathode functional layer disposed directly on the second side of the solid oxide electrolyte and comprising a mixture of a lanthanum nickel ferrite perovskite material and a non-perovskite ion-conducting ceramic material; and a cathode current collecting layer disposed on the cathode functional layer and comprising a perovskite material. The method includes:

17. The lanthanum nickel ferrite of the formula LaNi １－ｙ Fe ｙ O ３－δ (wherein 0.2<y<1 and 0≦δ≦0.1), or a compound of formula La １－ｘ Ca ｘ Ni １－ｙ Fe ｙ O ３－δ wherein 0.05<x<0.3, 0.3<y<0.7, and 0≦δ≦0.1; the cathode current collecting layer contains lanthanum strontium manganite, lanthanum strontium cobaltite, or lanthanum strontium cobalt ferrite; 17. The method of claim 16.

18. 17. The method of claim 16, wherein the solid oxide electrochemical cell comprises a solid oxide fuel cell or a solid oxide electrolysis cell.

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