Fuel cell stacks including improved dielectric layers

Abstract

To provide solid oxide fuel cell stacks with interconnects designed to maximize fuel utilization and fuel cell active area.SOLUTION: A fuel cell stack comprises: stacked solid oxide fuel cells; interconnects 400 disposed between the fuel cells; and dielectric layers 440 disposed on the interconnects, the dielectric layers comprising a first glass-containing component and a corrosion barrier material. The dielectric layers have the weight ratio of (the first glass-containing component):(the corrosion barrier material) ranging from 5:95 to 60:40. The first glass-containing component is at least 50% amorphous, after sintering at a temperature in the range from about 950°C to about 1050°C for at least 15 minutes. The corrosion barrier material comprises zirconium silicate (ZrSiO4), potash feldspar (KAlSi3O8), alumina (Al2O3), lanthanum trisilicate (La2Si3O9), silicon carbide, or any combination thereof.SELECTED DRAWING: Figure 5D

Description

Technical Field

[0001] The present disclosure relates to fuel cell dielectric layers, and particularly to dielectric layers containing amorphous components.

Background Art

[0002] In high-temperature fuel cell systems, such as solid oxide fuel cell (SOFC) systems, an oxidant stream passes through the cathode side of the fuel cell, and a fuel stream passes through the anode side of the fuel cell. The oxidant stream is typically air, and the fuel stream 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, enabling the movement of negatively charged oxygen ions from the cathode flow stream to the anode flow stream, where the ions combine with hydrogen in free hydrogen or hydrocarbon molecules to produce water vapor and / or combine with carbon monoxide to produce carbon dioxide. Excess electrons from the negatively charged ions are returned to the cathode side of the fuel cell through a completed electrical circuit between the anode and the cathode, resulting in an electric current flowing through the circuit.

[0003] The fuel cell stack can include manifolds for fuel and air, either internally or externally. In an internal manifold type stack, fuel and air are distributed to each cell using risers contained within the stack. In other words, the gas flows through the openings or pores of the support layer of each fuel cell, such as the electrolyte layer, and the gas flow separator of each cell. Also, in an external manifold type stack, the stack has openings on the inlet and outlet sides for fuel and air, and the fuel and air are introduced and recovered independently of the stack hardware. For example, the inlet and outlet fuels and air flow through separate passages between the stack and the manifold housing in which the stack is disposed.

[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] According to various embodiments of the present disclosure, a fuel cell stack comprises stacked solid oxide fuel cells, interconnects disposed between the fuel cells, and a dielectric layer disposed on the interconnects, comprising a first glass-containing component and a corrosion barrier material, wherein the dielectric layer has a weight ratio of the first glass-containing component to the corrosion barrier material in the range of about 5:95 to about 60:40, the first glass-containing component being at least 50% amorphous (e.g. by volume) after being sintered at a temperature in the range of about 950°C to about 1050°C for at least 15 minutes, and the corrosion barrier material comprises zirconium silicate (ZrSiO4), potassium feldspar (KAlSi3O8), alumina (Al2O3), lanthanum trisilicate (La2Si3O9), silicon carbide, or any combination thereof.

[0006] According to various embodiments of the present disclosure, a fuel cell stack comprises stacked solid oxide fuel cells, each fuel cell comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode; a cross-flow interconnect disposed between the fuel cells and including fuel ports; a peripheral seal disposed between the fuel side of the interconnect and the fuel side of the fuel cell; a riser seal surrounding the fuel ports disposed between the air side of the interconnect and the air side of the fuel cell; and an electrolyte reinforcement layer disposed directly on the electrolyte and comprising at least one of yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (SSZ), magnesia, zirconia, ZrSiO4, alumina, or a combination thereof.

[0007] According to various embodiments of the present disclosure, a fuel cell stack comprises stacked solid oxide fuel cells, each fuel cell comprising an anode, a cathode, and an electrolyte disposed between the anode and the cathode; a cross-flow interconnect disposed between the fuel cells, each interconnect having an air side, an opposing fuel side, and fuel holes extending through the opposing sides of the interconnect, the air side each including an airflow range and a riser seal surface surrounding the fuel holes; a perimeter seal disposed between the fuel side of the interconnect and the fuel side of the fuel cells; a riser seal disposed between the air side of the interconnect and the air side of the fuel cells and completely covering the riser surface; and a dielectric layer disposed between the riser seal surface and the riser seal and covering at least less than 50% of the riser seal surface. [Brief explanation of the drawing]

[0008] 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] Figure 1A is a perspective view of one counterflow solid oxide fuel cell (SOFC) stack included in the column. [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] This 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] Figure 3A is a disassembled perspective view of a portion of the stack. [Figure 3C] Figure 3A is a plan view of the fuel side of the interconnect included in the stack. [Figure 3D] Figure 3A is a schematic diagram of the fuel cell included in the stack. [Figure 4A] This is a top view showing the air side of the cross-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 5A] This is a plan view showing the air side of the interconnect in Figure 3C. [Figure 5B] This is a plan view showing a variation of the interconnect in Figure 5A. [Figure 5C] This is a plan view showing the air side of an interconnect according to various embodiments of the present disclosure. [Figure 5D] This is a plan view showing the air side of an interconnect according to various embodiments of the present disclosure. [Figure 6A] Figures 4A and 4B show two interconnects according to various embodiments of the present disclosure, as well as a fuel cell as incorporated into the fuel cell stack shown in Figure 3A, in a perspective cross-sectional view. [Figure 6B] Figure 6A is a top view showing the overlap between the fuel cell and the seal on the fuel side of the interconnect. [Figure 7A] This is a top view showing the fuel side of a fuel cell according to various embodiments of the present disclosure. [Figure 7B] Figure 7B is a top view showing the air side of the fuel cell. [Modes for carrying out the invention]

[0009] 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. In this specification, ranges may be expressed as from a certain value "about" and / or from another specific value "about". Where such ranges are expressed, the examples include from a certain value and / or from another specific value. Similarly, where 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] Figure 1A is a perspective view of a conventional fuel cell column 30, Figure 1B is a perspective view of a counterflow type solid oxide fuel cell (SOFC) stack 20 included in the column 30 of Figure 1A, and Figure 1C is a side cross-sectional view of a portion of the stack 20 of Figure 1B.

[0011] Referring to FIGS. 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 (such as an anode splitter plate (ASP) 36). Further, the column 30 may 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) disposed below via a ceramic connector 39. The fuel inlet conduit 32 is fluidly connected to the ASP 36 and configured to provide a fuel supply to each ASP 36, and the anode exhaust conduit 34 is fluidly connected to the ASP 36 and configured to receive anode fuel exhaust from each ASP 36.

[0012] The ASP 36 is disposed between the stacks 20 and configured to provide a fuel supply including a hydrocarbon fuel to the stacks 20 and to receive anode fuel exhaust from the stacks 20. For example, the ASP 36 may be fluidly connected to internal fuel riser holes 22 formed within the stacks 20 as described below.

[0013] Referring to FIG. 1C, the stack 20 includes a plurality of fuel cells 1 separated by an interconnect 10, which may also be referred to as a gas flow separator plate or a bipolar plate. Each fuel cell 1 includes a cathode electrode 3, a solid oxide electrolyte 5, and an anode electrode 7.

[0014] 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. FIG. 1C shows that the lower fuel cell 1 is disposed between two interconnects 10.

[0015] 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.

[0016] 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.

[0017] 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 a raised platform without ribs or passages. The surface of the peripheral region may be coplanar with the top of the rib 12.

[0018] 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, as indicated by the arrow. The second direction B may be perpendicular to the first direction A (see Figure 2A).

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Cross-flow fuel cell system 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 plan 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.

[0026] 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”.

[0027] 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. The interconnect 400 can typically 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% by weight (e.g., 95%) of chromium. The interconnect 400 may also contain less than about 10% by weight of iron, for example, about 4–6% by weight (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.

[0028] 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.

[0029] 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.

[0030] The stack 300 may include side baffles 302, a fuel plenum 304, 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 304 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 304 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 304 may be connected to a fuel inlet / outlet conduit 308 located below the fuel plenum 304.

[0031] 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.

[0032] 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 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. Note that while two fuel inlets and two fuel outlets 402, 404 are shown, there may be one fuel inlet 402 and one fuel outlet 404, or there may be three or more fuel inlets and three or more fuel outlets 402, 404. 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.

[0033] 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.

[0034] 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 provide the anode exhaust received from the fuel cell 310 to the fuel plenum 304.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 containing a perovskite, such as lanthanum strontium manganite (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.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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).

[0043] The seals 424,434 may include a glass or ceramic sealing material, as described in detail below. 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.

[0044] Figure 5A is a plan view showing the air side of the interconnect 400 without the riser seal 424 according to various embodiments of the present disclosure, and Figures 5B to 5D are plan views showing variations of the interconnect 400 in Figure 5A.

[0045] In conventional fuel cell stacks, the fuel cell electrolyte completely covers the interconnects, so that the fuel cell electrolyte acts as a dielectric layer between adjacent interconnects. In a cross-flow design, portions of multiple interconnects 400 may be located in interconnect regions corresponding to the outer periphery of the fuel cell, for example, the riser seal surface 422. In these regions, electrical short circuits can occur between interconnects if the stack is tilted or if the seals become conductive over time. Leakage currents can also lead to seal degradation over time. Thus, various embodiments provide a dielectric layer that protects against electrical short circuits and / or seal degradation.

[0046] Referring to Figures 5A and 5B, the interconnect 400 may include a dielectric layer 440 disposed on the riser seal surface 422. In this specification, the dielectric layer 440 may also be referred to as a corrosion barrier layer (CBL) because it can reduce the diffusion of contaminants into adjacent seals. Each dielectric layer 440 may be annular, as shown in Figure 5A, and may cover the entire or substantially entire corresponding riser seal surface 422. For example, in the embodiment of Figure 5A, the dielectric layer 440 may be D-shaped and have substantially the same shape as the riser seal 424 shown in Figure 4A, which is disposed on it.

[0047] In another embodiment, as shown in Figure 5B, the dielectric layer 440 may be C-shaped and may cover only the outer region 422E of the corresponding riser seal surface 422, for example, the portion adjacent to the outer periphery of the interconnect 400. The C-shaped dielectric layer 440 may include two parallel portions extending perpendicular to the direction of the air ribs 406 and air passages 408, and one connecting portion extending parallel to the direction of the air ribs 406 and air passages 408 and connecting the two parallel portions. The dielectric layer 440 forms an electrical insulation barrier between adjacent interconnects 400, preventing electrical short circuits if the corresponding stack is tilted or the seal becomes conductive. In the embodiment of Figure 5B, each riser seal surface 422 has an inner region 422I including the portion of the riser seal surface 422 located closest to the corresponding airflow range 420, and an outer region 422E including the portion of the riser seal surface 422 located furthest from the corresponding airflow range 420. In this embodiment, the dielectric layer covers at least 95% of each outer region 422E, but is omitted in the inner region 422I.

[0048] In another embodiment, as shown in Figure 5C, the dielectric layer 440 may be a D-shaped structure formed of relatively narrow (i.e., thin) wire sealing material, so that the dielectric layer 440 covers less than 50% of the entire riser seal surface 422 covered by the riser seal 424, for example, about 25% to about 50%, or 30% to 45% of the surface area covered by the riser seal 424.

[0049] During sintering, the relatively thin dielectric layer 440 may allow adjacent riser seals to overflow from the dielectric layer 440, thereby enabling at least a portion of the riser seal material to directly contact the riser seal surface 422. In this way, the relatively thin dielectric layer 440 may enable enhanced seal-to-interconnect adhesion while still preventing electrical contact (i.e., short circuits) between adjacent interconnects 400 in the stack.

[0050] With respect to Figure 5D, each riser seal surface 422 may have an inner region 422I located between the airflow region 420 and the fuel inlet 402 or fuel outlet 404, in addition to the outer region 422E. The inner region 422I may include the portion of the riser seal surface 422 closest to the airflow region 420 (i.e., 1 / 2), and the outer region 422E may include the remaining portion of the riser seal surface 422 furthest from the airflow region 420 (i.e., 1 / 2). If the dielectric layer 440 is not utilized at all, the portion of the riser seal located in the inner region 422I may degrade more rapidly than the portion of the riser seal located in the outer region 422E. While we do not wish to be bound by any particular theory, it is conceivable that galvanic corrosion may occur in the inner portion of the riser seal based on reactions with gas-phase products, resulting in the formation of pores / voids in the riser seal, particularly in the inner portion of the riser seal, over time.

[0051] Therefore, in some embodiments, the dielectric layer 440 may include a relatively wide (i.e., thick) inner portion 440I covering the inner region 422I and a relatively narrow outer portion 440 covering the outer region 422E. As used with respect to Figures 5A to 5D, the widths of the dielectric layer 440 and portions 440I and 440E are dimensions parallel to the riser seal surface 422 (i.e., perpendicular to the axial direction of the fuel cell stack). In particular, the inner portion 440I may cover substantially the entire inner region 422I (i.e., at least 95% of the inner region 422I), while the outer portion 440E may cover less than 50% of the surface of the outer region 422E.

[0052] The inner portion 440I of the dielectric layer 440 substantially covers the entire inner region 422I, reducing gas-phase reactions and thereby preventing and / or reducing degradation of the overlap portion of the riser seal. By covering only a portion of the outer region 422E with the outer portion 440E of the dielectric layer, enhanced seal-to-interconnect adhesion can be provided.

[0053] Conventional dielectric layers may contain a ceramic component mixed with a glass component. The glass component may be a glass material configured to be sintered to provide cohesive and adhesive strength. For example, the glass component may include a quartz glass material or a glass ceramic material, such as a glass ceramic material such as BaO-CaO-Al2O3-B2O3-SiO2 (BCAS). However, the amount of glass component contained in such a material may be limited to about 15% by weight or less due to the relatively low dielectric strength of conventional glass component materials. Furthermore, the glass component may crystallize completely at relatively low temperatures. As a result, such conventional dielectric layers may lack sufficient adhesive and / or cohesive strength due to the crystallization of the glass component and may delaminate from adjacent seals during thermal cycling at fuel cell operating temperatures.

[0054] Therefore, various embodiments provide dielectric layer materials that have sufficient dielectric strength to prevent short circuits (e.g., leakage currents) between interconnects, and that provide sufficient sealing adhesion to prevent delamination during thermal cycling.

[0055] According to various embodiments, the dielectric layer 440 may contain a corrosion barrier material and a first glass-containing component that is at least partially amorphous. For example, the dielectric layer 440 may have a weight ratio of the first glass-containing component to the corrosion barrier material of about 5:95 to 60:40, for example, about 10:90 to about 50:50. In some embodiments, the barrier material and the first glass-containing component may exist as separate phases within the dielectric layer 440.

[0056] The first glass-containing component may include a glass or glass-ceramic material that completely or at least partially retains an amorphous / glassy state after sintering at a temperature of at least 940°C, for example, at a temperature of about 950°C to about 1050°C. For example, the first glass-containing component may have at least 50%, for example, at least 70%, at least 80%, or at least 90% amorphous phase by volume after sintering at a temperature above 940°C for at least 15 minutes. In some embodiments, the first glass-containing component may include a barium silicate glass-containing component, for example, Schott G018-281 (glass-ceramic sealant for SOFC applications) available from Schott AG, Mainz, Germany, calcium-magnesium-aluminosilicate (CMAS) glass or glass-ceramic material, or a combination thereof.

[0057] In some embodiments, the first glass-containing component may include a CMAS glass or glass-ceramic material comprising about 85% to about 95%, for example, in the range of about 87% to about 93%, or about 89.2%, in mol% based on oxides; about 2.5% to about 6.5%, for example, in the range of about 4.0% to about 5.0%, or about 4.6%, in the range of about 2.0% to about 5.0%, or about 3.5%, in the range of about 3.0% to about 4.0%, or about 3.5%, and about 1.2% to about 4.2%, for example, in the range of about 2.2% to about 3.2%, or about 2.7%, in the range of MgO.

[0058] The corrosion barrier material may include a glass-ceramic material comprising a ceramic component and a second glass-containing component. For example, the ceramic component may include zircon (zirconium silicate (ZrSiO4)), potassium feldspar (KAlSi3O8), alumina (Al2O3), lanthanum trisilicate (La2Si3O9), silicon carbide, and / or other heat-resistant dielectric materials. The second glass-containing component may include a quartz glass material or a glass-ceramic material, such as a BaO-CaO-Al2O3-B2O3-SiO2 (BCAS) glass-ceramic material.

[0059] For example, the corrosion barrier material may contain, based on the total weight of the corrosion barrier material, about 25% to about 50% by weight, e.g., about 30% to about 45% by weight, about 35% to about 40% by weight, or about 37.5% by weight of ZrSiO4; about 25% to about 50% by weight, e.g., about 30% to about 45% by weight, about 35% to about 40% by weight, or about 37.5% by weight of KAlSi3O8; about 2% to about 25% by weight, e.g., about 4% to about 20% by weight, about 5% to about 15% by weight, or about 10% by weight of Al2O3; and about 0% to about 15% by weight, e.g., about 10% to about 15% by weight, or about 12% to about 15% by weight of a second glass-containing component.

[0060] In some embodiments, the second glass-containing component is, based on the weight of oxides, silica (SiO2) in amounts ranging from about 30% to about 60%, for example, about 35% to about 55%, boron oxide (B2O3) in amounts ranging from about 0.5% to about 15%, for example, about 1% to about 12%, alumina (Al2O3) in amounts ranging from about 0.5% to about 5%, for example, about 1% to about 4%, and carbon oxide in amounts ranging from about 2% to about 30%, for example, about 5% to about 25%. It may contain calcium (CaO), barium oxide (BaO) in amounts ranging from approximately 0% to approximately 35%, for example, in the range of approximately 20% to approximately 30%, magnesium oxide (MgO) in amounts ranging from approximately 0% to approximately 25%, for example, in the range of approximately 5% to approximately 20%, strontium oxide (SrO) in amounts ranging from approximately 0% to approximately 20%, for example, in the range of approximately 10% to approximately 15%, and lanthanum oxide (La2O3) in amounts ranging from approximately 0% to approximately 12%, for example, in the range of approximately 5% to approximately 10%.

[0061] In some embodiments, the second glass-containing component may be omitted. For example, the first glass-containing component may substitute for the second glass-containing component, thereby the dielectric layer 440 may have a weight ratio of the first glass-containing component to the corrosion barrier material in the range of about 15:85 to about 70:30, for example, about 20:80 to about 60:40.

[0062] In another embodiment, the corrosion barrier material may contain about 30% to about 45%, for example, in the range of about 35% to about 40%, or about 39%, of SiO2 based on oxides; about 23% to about 33%, for example, in the range of about 25% to about 30%, or about 27%, of CaO; about 15% to about 25%, for example, in the range of about 18% to about 20%, or about 19%, of MgO; about 6% to about 7%, for example, about 6.5%, of Al2O3; about 4% to about 5%, for example, about 4.5%, of B2O3; about 0.5% to about 5%, for example, in the range of about 1.5% to about 3.5%, or about 2%, of La2O3; and about 0.5% to about 5%, for example, in the range of about 1.5% to about 3.5%, or about 2%, of ZrO2. The corrosion barrier material may contain trace amounts of impurities, such as Na2O, P2O5, SrO, BaO, Li2O, and / or K2O. In some embodiments, the corrosion barrier material may be at least 90% crystalline (for example, it may contain at least 90% or at least 95% by volume of one or more crystalline phases). For example, the corrosion barrier material may contain lanthanum trisilicate (La2Si3O9) as the first crystalline phase. The first crystalline phase is the crystalline phase having the largest volume percentage of all crystalline phases and may contain at least 50 volume percent of all crystalline phases.

[0063] In another embodiment, the corrosion barrier material is an oxide-based mol% of about 45% to about 55%, for example, in the range of about 47% to about 53%, or about 50.5% of SiO2, about 0.5% to about 3%, for example, in the range of about 1.5% to about 2.5%, or about 2.0% of CaO, about 1% to about 4%, for example, in the range of about 1% to about 2%, or about 1.5% of MgO, and an oxide-based mol% of about 2% to about 3%, for example, about 2.5% of A The corrosion barrier material may contain approximately 10% to 16% of l2O3, for example in the range of approximately 11% to 13%, or approximately 12% of B2O3, for example in the range of approximately 15% to 30%, for example in the range of approximately 18% to 24%, or approximately 21.5% of BaO, for example in the range of approximately 7% to 9%, or approximately 8% of La2O3, and approximately 0.5% to 3%, for example in the range of approximately 1.5% to 3.5%, or approximately 2% of ZrO2. The corrosion barrier material may contain trace amounts of impurities, such as Na2O, P2O5, SrO, BaO, Li2O, and / or K2O. In some embodiments, the corrosion barrier material may be at least 90% crystalline (for example, containing at least 90% or at least 95% of one or more crystalline phases). For example, the corrosion barrier material may contain lanthanum trisilicate (La2Si3O9) as the first crystalline phase. The crystalline corrosion barrier material may contain one or more second crystalline phases, such as zircon (ZrSiO4) and / or sunbornite (BaSi2O5).

[0064] The dielectric layer 440 may include ceramic support particles (e.g., hard, round ceramic particles) configured to act as physical support means to maintain separation between adjacent interconnects 400. For example, the support particles may be configured to maintain a minimum distance between adjacent interconnects 400 sufficient to prevent and / or reduce leakage current between adjacent interconnects 400 that may occur if the glass phase of the adjacent seal is excessively compressed. The support particles may include alumina, zircon (zirconium silicate (ZrSiO4)), stabilized zirconia (e.g., yttria-stabilized zirconia), or any combination thereof. The support particles may have an average particle size in the range of about 5 μm to about 50 μm, for example, about 10 μm to about 30 μm.

[0065] In some embodiments, to prevent the diffusion of Mn from the LSM / MCO material into the riser seal 424 and consequently prevent the riser seal 424 from becoming conductive, part or all of the LSM / MCO coating may be removed in the region around the riser seal 424 on the air side of the interconnect 400. In another embodiment, the riser seal 424 may be formed of a crystalline glass or glass-ceramic material that does not react with the LSM / MCO coating, such as the borosilicate glass-ceramic composition described above.

[0066] The dielectric layer 440 may be formed from a separate layer, such as a casting tape or a sintered layer, and may be placed between the interconnects 400 during fuel cell stack assembly. In another embodiment, the dielectric layer 440 may be formed by dispersing a dielectric material in the form of an ink, paste, or slurry, and then screen printing, pad printing, or aerosol spraying onto the interconnects 400. In some embodiments, the dielectric layer 440 may be formed by a thermal spraying process, such as an atmospheric plasma spraying (APS) process. For example, the dielectric layer 440 may contain alumina deposited by the APS process.

[0067] The dielectric layer 440 may be deposited directly on the interconnect 400. For example, the dielectric layer 440 may be placed directly on the riser seal surface 422, i.e., on the portion of the interconnect 400 around the fuel inlet 402 and fuel outlet 404 that is covered by the riser seal 424, except for a small overlapping region (e.g., a seam) where the dielectric layer 440 and the LSM / MCO coating overlap, but not covered by the LSM / MCO coating, so as to prevent Cr evaporation from the exposed surface of the interconnect 400. Thus, the LSM / MCO coating is placed on the interconnect 400 within the airflow region 420, including the air passage 408 and rib 406, but not on the riser seal surface 422 of the interconnect 400 surrounding the fuel inlet 402 and fuel outlet 404. The dielectric layer 440 is located on the riser seal surface of the interconnect 400 in the region surrounding the fuel inlet 402 and fuel outlet 404, which is not covered by the LSM / MCO coating, and on the edge of the LSM / MCO coating in the airflow range 420 adjacent to the riser seal surface 422. Alternatively, the dielectric layer 440 may be omitted, and no dielectric layer 440 is deposited around the fuel riser opening.

[0068] Fuel cell stacks and / or their components may be conditioned and / or sintered. Sintering of the stack may involve a process of heating, melting and / or reflowing a glass or glass-ceramic seal precursor for seal formation in the fuel cell stack, which may be carried out in air and / or an inert gas at an elevated temperature (e.g., 600-1000°C). "Conditioning" may involve a process of reducing a metal oxide (e.g., nickel oxide) in the anode electrode to a metal (e.g., nickel) in a cermet electrode (e.g., nickel and ceramic material, e.g., stabilized zirconia or doped ceria) and / or heating the stack 300 during performance characterization / testing, which may be carried out at an elevated temperature (e.g., 750-900°C) while the fuel flows through the stack. Sintering and conditioning of the fuel cell stack 300 may be carried out in the same thermal cycle (i.e., without cooling the stack to room temperature between sintering and conditioning).

[0069] Figure 6A is a perspective cross-sectional view of a fuel cell 310 as assembled in the two interconnects 400 of Figures 4A and 4B and the fuel cell stack 300 of Figure 3A, according to various embodiments of the present disclosure. Figure 6B is a top view showing the overlap between the fuel cell 310 and seals 424, 434 on the fuel side of the interconnect 400 of Figure 6A.

[0070] Referring to Figures 4A, 4B, 6A, and 6B, when assembled into a fuel cell stack, the fuel cell 310 is positioned between interconnects 400, so that the airflow range 420 and fuel flow range 430 of each interconnect 400 face each other. The riser seal 424 may contact the first opposing air-side of the fuel cell 310, and the perimeter seal 434 may contact the second opposing fuel-side of the fuel cell 310. The portions of the perimeter seal 434 adjacent to the fuel inlet 402 and fuel outlet 404 may overlap the corresponding portions of the riser seal 424. Furthermore, multiple portions of the fuel cell 310 may be positioned between the overlapping portions of the seals 424, 434, for example, at the corners of the fuel cell 310. Thus, the combined thickness of the overlapping portions of the fuel cell 310 and the seals 424, 434 may be greater than the thickness of the overlapping portions of the seals 424, 434.

[0071] Therefore, stress may be applied to the corners of the fuel cell 310 during assembly and / or sintering, which may result in damage to the fuel cell 310, such as cracks in the corners. Accordingly, various embodiments of the present disclosure provide methods and stack configurations configured to protect the fuel cell 310 from damage during the assembly and / or sintering process.

[0072] Furthermore, since the seals 424 and 434 overlap the corners of the fuel cell 310, gaps G can be formed along the perimeter of the fuel cell 310, between the corners of the fuel cell 310, below each riser seal 424 (e.g., below the electrolyte 312), and above the perimeter seal 434. When the stack 300 is compressed, a downward force can be transmitted through the interconnect 400 and the seals 424 and 430 to the unsupported edges of the fuel cell 310 adjacent to the gaps G, and this downward force can create a lever action by the adjacent gaps G.

[0073] According to various embodiments of the present disclosure, a conductive layer 318 (e.g., nickel mesh) may extend into the gap G to support the edges of the electrolyte 312. In some embodiments, the anode 314 and / or cathode 316 may also extend into the gap G in combination with the extension of the conductive layer 318 to cover the electrolyte on the underside of the riser seal 424. In another embodiment, one or more electrolyte reinforcing layers 325 may be formed on one or both sides of the electrolyte 312 on the underside of the riser seal 424.

[0074] The electrolyte reinforcement layer 325 may be formed of a dielectric material, such as a ceramic material comprising yttria-stabilized zirconia (YSZ) (e.g., 3% yttria-stabilized zirconia (3YSZ)), scandia-stabilized zirconia (SSZ), magnesia, zirconia, and / or alumina. In one embodiment, the electrolyte reinforcement layer 325 may contain about 65% to about 85% by weight, for example, about 75% by weight of 3YSZ and about 35% to about 15% by weight, for example, about 25% by weight of alumina.

[0075] In another embodiment, the electrolyte reinforcement layer 325 may contain a dielectric material comprising YSZ, alumina, and zircon additives. For example, the electrolyte reinforcement layer 325 may contain about 40% to about 60% by weight, for example, about 50% by weight of 3YSZ, about 15% to about 35% by weight, for example, about 25% by weight of alumina, and about 15% to about 35% by weight, for example, about 25% by weight of ZrSiO4.

[0076] The electrolyte reinforcement layer 325 may contain dielectric materials including sintering aids, such as metals or metal oxide materials, such as Ti, Mo, W, Mg, Hf, Rh, Co, Ni, Fe, Mn, Cu, Sn, oxides thereof, and combinations thereof. For example, the electrolyte reinforcement layer 325 may contain about 0.1 to about 80% by weight (e.g., 50 to 75% by weight) of stabilized zirconia, about 0.1 to about 60% by weight (e.g., 20 to 45% by weight) of alumina, and about 0.1 to about 30% by weight (e.g., 1 to 5% by weight) of sintering aids (e.g., metals or metal oxide materials).

[0077] The electrolyte reinforcement layer 325 may have substantially the same thickness as the anode 314 and / or cathode 316, and together with the conductive layer 318, can support the edges of the fuel cell 310. In some embodiments, the electrolyte reinforcement layer 325 may be located on the cathode side of the fuel cell 310 and may be formed of a chromium getter material, such as manganese cobalt oxide spinel. Thus, the electrolyte reinforcement layer 325 may be configured to remove chromium from the air supplied to the fuel cell 310.

[0078] Figure 7A is a top view of the fuel side of a fuel cell 310 according to various embodiments of the present disclosure, and Figure 7B is a top view of the air side of the fuel cell 310 in Figure 7B. Referring to Figures 7A and 7B, in some embodiments, a dielectric electrolyte reinforcement layer 327 may be formed on the fuel side of the electrolyte 312 where the peripheral seal 434 overlaps the electrolyte 312. In particular, the electrolyte reinforcement layer 327 may be located directly on the fuel side of the electrolyte 312. A dielectric electrolyte reinforcement layer 329 may also be formed on the air side of the electrolyte 312 where the riser seal 424 overlaps the electrolyte 312. In particular, the electrolyte reinforcement layer 329 may be located directly on the air side of the electrolyte 312. The dielectric electrolyte reinforcement layer 329 may be formed in addition to or instead of the dielectric electrolyte reinforcement layer 327.

[0079] In particular, the electrolyte reinforcement layers 327 and 329 can be formed by printing a dielectric material onto the electrolyte 312. For example, the dielectric material can be printed onto the electrolyte 312 with a thickness ranging from about 5 μm to about 35 μm, for example, from about 10 μm to about 30 μm.

[0080] The dielectric material may be the same as the dielectric material of the electrolyte reinforcement layer 325. For example, the dielectric material may include YSZ (e.g., 3YSZ), SSZ, magnesia, zirconia, ZrSiO4 and / or alumina. In one embodiment, the reinforcement layers 327, 329 may contain about 65% to about 85% by weight, for example, about 70% to about 80% by weight, or about 75% by weight of 3YSZ and about 15% to about 35% by weight, for example, about 20% to about 30% by weight, or about 25% by weight of alumina, based on the total weight of the electrolyte reinforcement layers 327, 329.

[0081] In another embodiment, the electrolyte reinforcing layers 327,329 may contain about 40% to about 60% by weight, for example about 50% by weight of 3YSZ, about 15% to about 35% by weight, for example about 25% by weight of alumina, and about 15% to about 35% by weight, for example about 25% by weight of ZrSiO4, based on the total weight of the electrolyte reinforcing layers 327,329.

[0082] After printing, the electrolyte reinforcement layers 327,329 can be sintered. In particular, since dielectric materials may not contain glass material, the electrolyte reinforcement layers 327,329 can be sintered at relatively high temperatures, for example, in the range of about 1100°C to about 1300°C, for example, in the range of about 1150°C to about 1250°C, or at a temperature of about 1200°C. Therefore, the electrolyte reinforcement layers 327,329 may be completely or substantially completely crystalline. For example, the electrolyte reinforcement layers 327,329 may contain at least 90%, for example, at least 95%, or at least 99% by volume of crystalline phase, thereby providing reinforcement layers 327,329 with improved dielectric and mechanical properties compared to compositions containing glass material.

[0083] sealant Referring again to Figures 4A and 4B, the seals 424 and 434 can be configured to provide a number of different functions to the fuel cell system. For example, the seals 424 and 434 may act as airtight couplers between adjacent interconnects 400, thereby achieving high fuel utilization and minimal fuel leakage. The seals 424 and 434 may be configured to adequately accommodate the stresses arising from the thermal gradient during fuel cell operation. The seals 424 and 434 may be configured to have a CTE that matches the CTE of the interconnect 400 and / or the fuel cell. Furthermore, the seals 424 and 434 may be configured to withstand high operating temperatures over long periods and to have high chemical stability against other stack components in oxidizing and reducing atmospheres.

[0084] Therefore, seals 424,434 may be formed from a glass or glass / ceramic sealing material that provides good wettability and fluidity and retains an amorphous phase to allow self-recovery during thermal cycling. In some embodiments, the sealing material may have a coefficient of thermal expansion (CTE) that approximately matches the CTE of the interconnect 400 and the fuel cell. For example, the sealing material may have a CTE within ±10% or ±5% of the CTE of the fuel cell stack interconnect and / or the fuel cell. For example, when used in a fuel cell stack including an interconnect 400 and a fuel cell 310 having a CTE of about 10 ppm / °K, the sealing material may have a CTE in the range of about 9 parts per million (ppm) / °K to about 11 ppm / °K (1 ppm = 0.0001%).

[0085] The sealing material may be chemically inert to zirconia-based electrolyte materials, chromium-containing interconnect materials (e.g., Cr-Fe alloys containing 4-6 wt% Fe and the remainder chromium and impurities), and coatings containing manganese oxide, cobalt oxide, etc., which can chemically react with many other suitable sealing materials. The sealing material may have a sintering temperature of less than about 1000°C and may be stable at the SOFC system operating temperature (e.g., 700-900°C) when exposed to air and / or hydrogen. The sealing material may have a high dielectric constant, which may allow it to be configured to electrically insulate adjacent interconnects 400.

[0086] In some embodiments, seals 424,434 may be formed from a sealing material comprising a first component containing Si, Ca, Mg, and optionally Al. In some embodiments, the precursor of the first component may contain SiO2, CaO, MgO, and optionally Al2O3. The sealing material may optionally contain a second component. The precursor of the second component may contain a non-zero amount (e.g., at least 0.3 mol%) of B2O3, BaO, SrO, La2O3, ZrO2, and / or Y2O3. In some embodiments, the sealing material may contain oxides of Si, Ca, Al, and Mg as the first component, and optionally contain B2O3, BaO, SrO, La2O3, ZrO2, Y2O3, or any combination thereof as the second component. In some embodiments, the second component may be omitted from the sealing material (i.e., it may contain less than 0 to 0.3 mol% of the second component).

[0087] For example, the seal precursor may contain a first component in an amount ranging from about 70 mol% to about 100 mol%, for example, about 80 mol% to 100 mol%, about 90 mol% to about 100 mol%, or about 92.5 mol% to about 100 mol%, and the remaining second component. For example, the seal material may contain a second component in an amount ranging from about 20 mol% to 0 mol%, about 10 mol% to about 0.3 mol%, or about 7.5 mol% to about 0.85 mol%.

[0088] In various embodiments, the sealing material may contain a crystalline phase and an amorphous phase after the precursor material has been applied to the interconnect and sintered. For example, the sealing material may contain diopside ((CaO) 1-x (MgO) x )2(SiO2)2, in this case 0.3≦x≦1.0, and may include a crystalline phase containing at least one of (CaMgSi2O6), okermanite (Ca2MgSi2O7), monticerite (CaMgSiO4), wollastonite (CaSiO3), anorthite (CaAl2Si2O8), and / or magnesium aluminum silicate crystals. In one embodiment, the crystalline phase mainly consists of diopside (e.g., at least 50 mol%, e.g. 50-99 mol%, e.g. 60-95 mol%) of the crystalline phase, together with small amounts of anorthite, wollastonite, and magnesium aluminum silicate of the general formula MgOAl2O34SiO2 (e.g., 1-40%, e.g. 5-20 mol%).

[0089] In some embodiments, the sealing material may contain, by volume ratio, about 55% to about 85% crystalline phase and about 45% to about 25% amorphous phase, for example, about 60% to about 80% crystalline phase and about 40% to about 20% amorphous phase, about 65% to about 75% crystalline phase and about 35% to about 25% amorphous phase, or about 70% crystalline phase and about 30% amorphous phase.

[0090] In some embodiments, the seal precursor may contain SiO2 in an amount ranging from about 25% to about 55% based on oxides, for example, about 30% to about 50%, or about 32% to about 50%; CaO in an amount ranging from about 20% to about 45%, for example, about 21% to about 43%, or about 22% to about 41%; MgO in an amount ranging from about 5% to about 30%, for example, about 6% to about 27%, about 7% to about 27%, or about 5% to about 25%; and Al2O3 in an amount ranging from about 0% to about 15%, for example, about 0.5% to about 15%, or about 1% to about 14%.

[0091] In some embodiments, the seal precursor may include a CMAS material comprising about 85% to about 95%, for example, in the range of about 87% to about 93%, or about 89.2%, in mol% based on oxides; about 2.5% to about 6.5%, for example, in the range of about 4.0% to about 5.0%, or about 4.6%, in the range of about 2.0% to about 5.0%, or about 3.5%, in the range of about 3.0% to about 4.0%, or about 3.5%, in the range of about 1.2% to about 4.2%, for example, in the range of about 2.2% to about 3.2%, or about 2.7%, in the range of MgO.

[0092] The description of the method described above 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 the steps of the embodiments described above can be performed in any order. Words such as “then,” “next,” and “next” are not necessarily intended to limit the order of the steps and 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.

[0093] Furthermore, any process or component of any embodiment described herein may be used in any other embodiment.

[0094] 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. A fuel cell stack, a stacked solid oxide fuel cell; an interconnect disposed between the fuel cells; a dielectric layer disposed on the interconnect, the dielectric layer comprising a first glass-containing component and a corrosion barrier material; It contains the dielectric layer has a weight ratio of first glass-containing component to corrosion barrier material in a range of about 5:95 to about 60:40; the first glass-containing component is at least 50% amorphous after being sintered at a temperature in the range of about 950°C to about 1050°C for at least 15 minutes; The corrosion barrier material is zirconium silicate (ZrSiO ４ ), potassium feldspar (KAlSi ３ O ８ ), alumina (Al ２ O ３ ), lanthanum trisilicate (La ２ Si ３ O ９ ), silicon carbide, or any combination thereof; Fuel cell stack.

2. The first glass-containing component comprises a barium silicate glass or a calcium-magnesium-aluminosilicate (CMAS) material, the barium silicate glass or the calcium-magnesium-aluminosilicate (CMAS) material comprising, in mol % based on oxides: SiO in an amount ranging from about 87% to about 93% ２ , Al in an amount ranging from about 4.0% to about 5.0% ２ O ３ , CaO in an amount ranging from about 3.0% to about 4.0%, and MgO in an amount ranging from about 2.2% to about 3.2% The fuel cell stack of claim 1 , comprising:

3. The corrosion barrier material is, in mol % based on oxide, SiO in an amount ranging from about 30% to about 45% ２ , CaO in an amount ranging from about 23% to about 33%; MgO in an amount ranging from about 15% to about 25%; Al in an amount ranging from about 6% to about 7% ２ O ３ , B in an amount ranging from about 4% to about 5% ２ O ３ , La in an amount ranging from about 0.5% to about 5% ２ O ３ , and ZrO in an amount ranging from about 0.5% to about 5% ２ The fuel cell stack of claim 1 , comprising:

4. The corrosion barrier material is, in mol % based on oxide, SiO in an amount ranging from about 45% to about 55% ２ , CaO in an amount ranging from about 0.5% to about 3%; MgO in an amount ranging from about 1% to about 4%; Al in an amount ranging from about 2% to about 3% ２ O ３ , B in an amount ranging from about 4% to about 5% ２ O ３ , BaO in an amount ranging from about 15% to about 30%; La in an amount ranging from about 5% to about 10% ２ O ３ , and ZrO in an amount ranging from about 0.5% to about 3% ２ The fuel cell stack of claim 1 , comprising:

5. The corrosion barrier material comprises: about 30% to about 45% by weight of zirconium silicate; about 30% to about 45% by weight of potassium feldspar; about 4% to about 20% by weight alumina, and BaO-CaO-Al ２ O ３ -B ２ O ３ -SiO ２ (BCAS) about 10% to about 15% by weight of a second glass-containing component comprising a glass-ceramic material The fuel cell stack of claim 1 , comprising:

6. 10. The fuel cell stack of claim 1, wherein the dielectric layer further comprises support particles comprising alumina, zircon, or stabilized zirconia, the support particles having an average particle size ranging from about 10 μm to about 30 μm.

7. each of the interconnects having an air side, an opposing fuel side, and fuel holes extending through opposing sides of the interconnect; Each of the air sides includes an air flow area and a riser seal surface surrounding the fuel hole; the fuel cell stack further includes a riser seal completely covering the riser seal surface; the dielectric layer is disposed between the riser seal surface and the riser seal; The fuel cell stack according to claim 1 .

8. The fuel cell stack of claim 7 , wherein the dielectric layer covers less than 50% of the riser seal surface.

9. Each of the riser seal surfaces comprises: an inner region including a portion of the riser seal surface disposed nearest the corresponding air flow area; an outer region including a portion of the riser seal surface located farthest from the corresponding air flow area; It has the dielectric layer covers at least 95% of each inner region and less than 50% of each outer region; The fuel cell stack according to claim 7.

10. The present invention further includes an electrolyte reinforcement layer disposed directly on the electrolyte of the solid oxide fuel cell below the riser seal, the electrolyte reinforcement layer being made of yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (SSZ), magnesia, zirconia, ZrSiO ４ 8. The fuel cell stack of claim 7, comprising alumina, alumina, or a combination thereof.

11. A fuel cell stack, a stack of solid oxide fuel cells, each of the fuel cells including an anode, a cathode, and an electrolyte disposed between the anode and the cathode; a cross-flow interconnect having fuel holes and disposed between the fuel cells; a perimeter seal disposed between the fuel side of the interconnect and the fuel side of the fuel cell; a riser seal surrounding the fuel hole disposed between the air side of the interconnect and the air side of the fuel cell; The electrolyte is directly disposed on the substrate, and the substrate is selected from yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (SSZ), magnesia, zirconia, ZrSiO ４ an electrolyte reinforcement layer comprising at least one of SiO 2 , SiO 3 , alumina, or a combination thereof; a fuel cell stack comprising:

12. The electrolyte reinforcement layer has a weight of 10 ... About 65% to about 85% by weight of 3% yttria-stabilized zirconia (3YSZ), and about 15% to about 35% by weight alumina The fuel cell stack of claim 11 , comprising:

13. The electrolyte reinforcement layer has a weight of 10 ... about 40 wt. % to about 60 wt. % 3% yttria-stabilized zirconia (3YSZ); about 15% to about 35% by weight alumina, and about 15 wt. % to about 35 wt. % ZrSiO ４ The fuel cell stack of claim 11 , comprising:

14. 12. The fuel cell stack of claim 11, wherein the electrolyte reinforcement layer comprises at least 90% by volume of a crystalline phase.

15. The fuel cell stack of claim 11 , wherein the electrolyte reinforcement layer is disposed between the riser seal and the electrolyte.

16. The fuel cell stack of claim 11 , wherein the electrolyte reinforcement layer is disposed between the perimeter seal and the electrolyte.

17. A fuel cell stack, a stack of solid oxide fuel cells, each of the fuel cells including an anode, a cathode, and an electrolyte disposed between the anode and the cathode; cross-flow interconnects disposed between the fuel cells, each interconnect having an air side, an opposing fuel side, and fuel holes extending through opposing sides of the interconnect, the air side including an air flow area and a riser seal surface surrounding the fuel holes; a perimeter seal disposed between the fuel side of the interconnect and the fuel side of the fuel cell; a riser seal disposed between the air side of the interconnect and the air side of the fuel cell, the riser seal completely covering the riser seal surface; a dielectric layer disposed between the riser seal surface and the riser seal, the dielectric layer covering at least less than 50% of the riser seal surface; a fuel cell stack comprising:

18. 18. The fuel cell stack of claim 17, wherein the dielectric layer covers less than 50% of the entire riser seal surface.

19. Each of the riser seal surfaces comprises: an inner region including a portion of the riser seal surface disposed nearest the corresponding air flow area; an outer region including a portion of the riser seal surface located farthest from the corresponding air flow area; It has the dielectric layer covers at least 95% of each inner region and less than 50% of each outer region; 18. The fuel cell stack of claim 17.

20. the inner region includes one half of the riser seal surface disposed closest to the corresponding air flow area; the outer region includes the other half of the riser seal surface located farthest from the corresponding air flow area.

20. The fuel cell stack of claim 19.

21. A fuel cell stack dielectric layer, comprising: a first glass-containing component; and a corrosion barrier material; It contains the dielectric layer has a weight ratio of first glass-containing component to corrosion barrier material in a range of about 5:95 to about 60:40; the first glass-containing component is at least 50% amorphous after being sintered at a temperature in the range of about 950°C to about 1050°C for at least 15 minutes; The corrosion barrier material comprises lanthanum trisilicate (La ２ Si ３ O ９ ) Fuel cell stack dielectric layer.

22. The first glass-containing component is, in mol % based on oxides: SiO in an amount ranging from about 87% to about 93% ２ , Al in an amount ranging from about 4.0% to about 5.0% ２ O ３ , CaO in an amount ranging from about 3.0% to about 4.0%, and MgO in an amount ranging from about 2.2% to about 3.2% 22. The fuel cell stack dielectric layer of claim 21, comprising:

23. The corrosion barrier material is, in mol % based on oxide, SiO in an amount ranging from about 30% to about 45% ２ , CaO in an amount ranging from about 23% to about 33%; MgO in an amount ranging from about 15% to about 25%; Al in an amount ranging from about 6% to about 7% ２ O ３ , B in an amount ranging from about 4% to about 5% ２ O ３ , La in an amount ranging from about 0.5% to about 5% ２ O ３ , and ZrO in an amount ranging from about 0.5% to about 5% ２ 22. The fuel cell stack dielectric layer of claim 21, comprising:

24. The corrosion barrier material is, in mol % based on oxide, SiO in an amount ranging from about 45% to about 55% ２ , CaO in an amount ranging from about 0.5% to about 3%; MgO in an amount ranging from about 1% to about 4%; Al in an amount ranging from about 2% to about 3% ２ O ３ , B in an amount ranging from about 4% to about 5% ２ O ３ , BaO in an amount ranging from about 15% to about 30%; La in an amount ranging from about 5% to about 10% ２ O ３ , and ZrO in an amount ranging from about 0.5% to about 3% ２ 22. The fuel cell stack dielectric layer of claim 21, comprising:

25. A fuel cell stack, a stacked solid oxide fuel cell; an interconnect disposed between the fuel cells; a fuel cell stack dielectric layer of claim 21 disposed on the interconnect; a fuel cell stack comprising:

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