Patent Publication Number: US-2023155157-A1

Title: Fuel cell column including stress mitigation structures

Description:
FIELD 
     The present disclosure is directed to fuel cell columns in general, and to fuel cell columns including stress mitigation structures. 
     BACKGROUND 
     In a high temperature fuel cell system, such as a solid oxide fuel cell (SOFC) system, an oxidizing flow is passed through the cathode side of the fuel cell while a fuel flow is passed through the anode side of the fuel cell. The oxidizing flow is typically air, while the fuel flow can be a hydrocarbon fuel, such as methane, natural gas, pentane, ethanol, or methanol. The fuel cell, operating at a typical temperature between 750° C. and 950° C., enables the transport of negatively charged oxygen ions from the cathode flow stream to the anode flow stream, where the ion combines with either free hydrogen or hydrogen in a hydrocarbon molecule to form water vapor and/or with carbon monoxide to form carbon dioxide. The excess electrons from the negatively charged ion are routed back to the cathode side of the fuel cell through an electrical circuit completed between anode and cathode, resulting in an electrical current flow through the circuit. 
     Fuel cell stacks may be either internally or externally manifolded for fuel and air. In internally manifolded stacks, the fuel and air are distributed to each cell using risers contained within the stack. In other words, the gas flows through openings or holes in the supporting layer of each fuel cell, such as the electrolyte layer, and gas flow separator of each cell. In externally manifolded stacks, the stack is open on the fuel and air inlet and outlet sides, and the fuel and air are introduced and collected independently of the stack hardware. For example, the inlet and outlet fuel and air flow in separate channels between the stack and the manifold housing in which the stack is located. 
     Fuel cell stacks are frequently built from a multiplicity of cells in the form of planar elements, tubes, or other geometries. Fuel and air have to be provided to the electrochemically active surface, which can be large. One component of a fuel cell stack is the gas flow separator (referred to as a gas flow separator plate in a planar stack) that separates the individual cells in the stack. The gas flow separator plate separates fuel, such as hydrogen or a hydrocarbon fuel, flowing to the fuel electrode (i.e., anode) of one cell in the stack from oxidant, such as air, flowing to the air electrode (i.e., cathode) of an adjacent cell in the stack. Frequently, the gas flow separator plate is also used as an interconnect which electrically connects the fuel electrode of one cell to the air electrode of the adjacent cell. In this case, the gas flow separator plate functions as an interconnect and is made of or contains an electrically conductive material. 
     SUMMARY 
     According to various embodiments of the present disclosure, a fuel cell column includes a stack of alternating fuel cells and interconnects, where the interconnects separate adjacent fuel cells in the stack and contain fuel and air channels which are configured to provide respective fuel and air to the fuel cells. a manifold plate containing a bottom inlet hole and a bottom outlet hole located in a bottom surface of the manifold plate, top outlet holes and top inlet holes formed in opposing sides of a top surface of the manifold plate, outlet channels fluidly connecting the top outlet holes to the bottom inlet hole, and inlet channels fluidly connecting the top inlet holes to the bottom outlet hole, and a mitigation structure configured to reduce stress applied to the stack due to at least one of a shape mismatch or coefficient of thermal expansion mismatch between the stack and the manifold plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the features of the invention. 
         FIG.  1 A  is a perspective view of a conventional fuel cell column,  FIG.  1 B  is a perspective view of one counter-flow solid oxide fuel cell (SOFC) stack included in the column of  FIG.  1 A , and  FIG.  1 C  is a side cross-sectional view of a portion of the stack of  FIG.  1 B . 
         FIG.  2 A  is a top view of the air side of a conventional interconnect of the stack of  FIG.  1 B , and  FIG.  2 B  is a top view of the fuel side of the conventional interconnect. 
         FIG.  3 A  is a perspective view of a fuel cell stack, according to various embodiments of the present disclosure,  FIG.  3 B  is an exploded perspective view of a portion of the stack of  FIG.  3 A ,  FIG.  3 C  is a top view of the fuel side of an interconnect included in the stack of  FIG.  3 A , and  FIG.  3 D  is a schematic view of a fuel cell included in the stack of  FIG.  3 A . 
         FIGS.  4 A and  4 B  are plan views showing, respectively, an air side and a fuel side of the cross-flow interconnect of  FIG.  3 C , according to various embodiments of the present disclosure. 
         FIG.  5 A  is an exploded top perspective view of a fuel flow structure, according to various embodiments of the present disclosure, and  FIG.  5 B  is an exploded bottom perspective view of the fuel flow structure of  FIG.  5 A . 
         FIG.  6 A  is a top view of a seal plate of  FIGS.  5 A and  5 B , and  FIG.  6 B  is a cross-sectional view taken along line L 3  of  FIG.  6 A . 
         FIG.  7 A  is a bottom view of a manifold plate of  FIGS.  5 A and  5 B ,  FIG.  7 B  is a cross-sectional view taken along line L 4  of  FIG.  7 A , and  FIG.  7 C  is a schematic top view of the manifold plate of  FIG.  7 A . 
         FIG.  8 A  is a vertical cross-sectional view taken along line L 1  of  FIG.  5 A , showing an assembled fuel plenum and inlet conduit, and  FIG.  8 B  is a vertical cross-sectional view or along line L 2  of  FIG.  5 A , showing the assembled fuel plenum and outlet conduit. 
         FIG.  9 A  is a simplified exploded side view of a fuel cell column, according to various embodiments of the present disclosure,  FIG.  9 B  is a simplified exploded side view of a modified version of the fuel cell column of  FIG.  9 A , and  FIG.  9 C  is a photograph of an example of a conductive mesh of  FIG.  9 B . 
         FIG.  10 A  is a simplified exploded side view of a fuel cell column, according to various embodiments of the present disclosure, and  FIG.  10 B  is a bottom view of one embodiment of the bottom termination plate of  FIG.  10 A . 
         FIGS.  11 - 13    are a simplified exploded side views of fuel cell columns, according to various embodiments of the present disclosure. 
         FIG.  14 A  is a simplified exploded side view of a fuel cell column, according to various embodiments of the present disclosure, and  FIG.  14 B  is a photograph of an example of a conductive mesh of  FIG.  14 A . 
     
    
    
     DETAILED DESCRIPTION 
     The 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 numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about” or “substantially” it will be understood that the particular value forms another aspect. In some embodiments, a value of “about X” may include values of +/−1% X. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
       FIG.  1 A  is a perspective view of a conventional fuel cell column  30 ,  FIG.  1 B  is a perspective view of one counter-flow solid oxide fuel cell (SOFC) stack  20  included in the column  30  of  FIG.  1 A , and  FIG.  1 C  is a side cross-sectional view of a portion of the stack  20  of  FIG.  1 B . 
     Referring to  FIGS.  1 A and  1 B , the column  30  may include one or more stacks  20 , a fuel inlet conduit  32 , an anode exhaust conduit  34 , and anode feed/return assemblies  36  (e.g., anode splitter plates (ASP&#39;s)  36 ). The column  30  may also include side baffles  38  and a compression assembly  40 . The side baffles  38  may be connected to the compression assembly  40  and an underlying stack component (not shown) by ceramic connectors  39 . The fuel inlet conduit  32  is fluidly connected to the ASP&#39;s  36  and is configured to provide the fuel feed to each ASP  36 , and anode exhaust conduit  34  is fluidly connected to the ASP&#39;s  36  and is configured to receive anode fuel exhaust from each ASP  36 . 
     The ASP&#39;s  36  are disposed between the stacks  20  and are configured to provide a hydrocarbon fuel containing fuel feed to the stacks  20  and to receive anode fuel exhaust from the stacks  20 . For example, the ASP&#39;s  36  may be fluidly connected to internal fuel riser channels  22  formed in the stacks  20 , as discussed below. 
     Referring to  FIG.  1 C , the stack  20  includes multiple fuel cells  1  that are separated by interconnects  10 , which may also be referred to as 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 . 
     Each interconnect  10  electrically connects adjacent fuel cells  1  in the stack  20 . In particular, an interconnect  10  may electrically connect the anode electrode  7  of one fuel cell  1  to the cathode electrode  3  of an adjacent fuel cell  1 .  FIG.  1 C  shows that the lower fuel cell  1  is located between two interconnects  10 . 
     Each interconnect  10  includes ribs  12  that at least partially define fuel channels  8 A and air channels  8 B. The interconnect  10  may operate as a gas-fuel separator that separates a fuel, such as a hydrocarbon fuel, flowing to the fuel electrode (i.e. anode  7 ) of one cell in the stack from oxidant, such as air, flowing to the air electrode (i.e. cathode  3 ) of an adjacent cell in the stack. At either end of the stack  20 , there may be an air end plate or fuel end plate (not shown) for providing air or fuel, respectively, to the end electrode. 
       FIG.  2 A  is a top view of the air side of the conventional interconnect  10 , and  FIG.  2 B  is a top view of a fuel side of the interconnect  10 . Referring to  FIGS.  1 C and  2 A , the air side includes the air channels  8 B. Air flows through the air channels  8 B to a cathode electrode  3  of an adjacent fuel cell  1 . In particular, the air may flow across the interconnect  10  in a first direction A as indicated by the arrows. 
     Ring seals  23  may surround fuel holes  22 A of the interconnect  10 , to prevent fuel from contacting the cathode electrode. Peripheral strip-shaped seals  24  are located on peripheral portions of the air side of the interconnect  10 . The seals  23 ,  24  may be formed of a glass material. The peripheral portions may be in the form of an elevated plateau which does not include ribs or channels. The surface of the peripheral regions may be coplanar with tops of the ribs  12 . 
     Referring to  FIGS.  1 C and  2 B , the fuel side of the interconnect  10  may include the fuel channels  8 A and fuel manifolds  28  (e.g., fuel plenums). Fuel flows from one of the fuel holes  22 A, into the adjacent manifold  28 , through the fuel channels  8 A, and to an anode  7  of an adjacent fuel cell  1 . Excess fuel may flow into the other fuel manifold  28  and then into the adjacent fuel hole  22 A. In particular, the fuel may flow across the interconnect  10  in a second direction B, as indicated by the arrows. The second direction B may be perpendicular to the first direction A (see  FIG.  2 A ). 
     A frame-shaped seal  26  is disposed on a peripheral region of the fuel side of the interconnect  10 . The peripheral region may be an elevated plateau which does not include ribs or channels. The surface of the peripheral region may be coplanar with tops of the ribs  12 . 
     Accordingly, a conventional counter-flow fuel cell column, as shown in  FIGS.  1 A,  1 B,  1 C,  2 A, and  2 B , may include complex fuel distribution systems (fuel rails and anode splitter plates). In addition, the use of an internal fuel riser may require holes in fuel cells and corresponding seals, which may reduce an active area thereof and may cause cracks in the ceramic electrolytes of the fuel cells  1 . 
     The fuel manifolds  28  may occupy a relatively large region of the interconnect  10 , which may reduce the contact area between the interconnect  10  and an adjacent fuel cell by approximately 10%. The fuel manifolds  28  are also relatively deep, such that the fuel manifolds  28  represent relatively thin regions of the interconnect  10 . Since the interconnect  10  is generally formed by a powder metallurgy compaction process, the density of fuel manifold regions may approach the theoretical density limit of the interconnect material. As such, the length of stroke of a compaction press used in the compaction process may be limited due to the high-density fuel manifold regions being incapable of being compacted further. As a result, the density achieved elsewhere in the interconnect  10  may be limited to a lower level by the limitation to the compaction stroke. The resultant density variation may lead to topographical variations, which may reduce the amount of contact between the interconnect  10  a fuel cell  1  and may result in lower stack yield and/or performance. 
     Another important consideration in fuel cell system design is in the area of operational efficiency. Maximizing fuel utilization is a key factor to achieving operational efficiency. Fuel utilization is the ratio of how much fuel is consumed during operation, relative to how much is delivered to a fuel cell. An important factor in preserving fuel cell cycle life may be avoiding fuel starvation in fuel cell active areas, by appropriately distributing fuel to the active areas. If there is a maldistribution of fuel such that some flow field channels receive insufficient fuel to support the electrochemical reaction that would occur in the region of that channel, it may result in fuel starvation in fuel cell areas adjacent that channel. In order to distribute fuel more uniformly, conventional interconnect designs include channel depth variations across the flow field. This may create complications not only in the manufacturing process, but may also require complex metrology to measure these dimensions accurately. The varying channel geometry may be constrained by the way fuel is distributed through fuel holes and distribution manifolds. 
     One possible solution to eliminate this complicated geometry and the fuel manifold is to have a wider fuel opening to ensure much more uniform fuel distribution across the fuel flow field. Since fuel manifold formation is a factor in density variation, elimination of fuel manifolds should enable more uniform interconnect density and permeability. Accordingly, there is a need for improved interconnects that provide for uniform contact with fuel cells, while also uniformly distributing fuel to the fuel cells without the use of conventional fuel manifolds. 
     Owing to the overall restrictions in expanding the size of a hotbox of a fuel cell system, there is also a need for improved interconnects designed to maximize fuel utilization and fuel cell active area, without increasing the footprint of a hotbox. 
     Cross-Flow Fuel Cell Systems 
       FIG.  3 A  is a perspective view of a fuel cell column  200 , according to various embodiments of the present disclosure,  FIG.  3 B  is an exploded perspective view of a portion of the column  200  of  FIG.  3 A ,  FIG.  3 C  is a top view of the fuel side of an interconnect  400  included in the column  200 , and  FIG.  3 D  is a schematic view of a fuel cell included in the column  200 . 
     Referring to  FIGS.  3 A- 3 D , the fuel cell column  200  includes at least one fuel cell stack  300  that includes multiple fuel cells  310  that are separated by interconnects  400 , which may also be referred to as gas flow separator plates or bipolar plates. One or more columns  200  may be thermally integrated with other components of a fuel cell power generating system (e.g., one or more anode tail gas oxidizers, fuel reformers, fluid conduits and manifolds, etc.) in a common enclosure or “hotbox.” 
     The interconnects  400  are made from an electrically conductive metal material. For example, the interconnects  400  may comprise a chromium alloy, such as a Cr—Fe alloy. The interconnects  400  may typically be fabricated using a powder metallurgy technique that includes pressing and sintering a Cr—Fe powder, which may be a mixture of Cr and Fe powders or an Cr—Fe alloy powder, to form a Cr—Fe interconnect in a desired size and shape (e.g., a “net shape” or “near net shape” process). A typical chromium-alloy interconnect  400  comprises more than about 90% chromium by weight, such as about 94-96% (e.g., 95%) chromium by weight. An interconnect  400  may also contain less than about 10% iron by weight, such as about 4-6% (e.g., 5%) iron by weight, may contain less than about 2% by weight, such as about zero to 1% by weight, of other materials, such as yttrium or yttria, as well as residual or unavoidable impurities. 
     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 the cathode  316  may be printed on the electrolyte  312 . In other embodiments, a conductive layer  318 , such as a nickel mesh, may be disposed between the anode  314  and an adjacent interconnect  400 . The fuel cell  310  does not include through-holes, such as the fuel holes of conventional fuel cells. Therefore, the fuel cell  310  avoids cracks that may be generated due to the presence of such through-holes. 
     An upper most interconnect  400  and a lowermost interconnect  400  of the column  200  may be different ones of an air end plate or fuel end plate including features for providing air or fuel, respectively, to an adjacent end fuel cell  310 . As used herein, an “interconnect” may refer to either an interconnect located between two fuel cells  310  or an end plate located at an end of the stack and directly adjacent to only one fuel cell  310 . Since the column  200  does not include ASPs and the end plates associated therewith, the column  200  may include only two end plates. As a result, stack dimensional variations associated with the use of intra-column ASPs may be avoided. 
     The column  200  may include side baffles  302 , a fuel plenum  350 , and a compression assembly  306 . The side baffles  302  may be formed of a ceramic material and may be disposed on opposing sides of the fuel cell column  200  containing stacked fuel cells  310  and interconnects  400 . The side baffles  302  may connect the fuel plenum  350  and the compression assembly  306 , such that the compression assembly  306  may apply pressure to the column  200 . The side baffles  302  may be curved baffle plates, such each baffle plate covers at least portions of three sides of the fuel cell column  200 . For example, one baffle plate may fully cover the fuel inlet riser side of the column  200  and partially covers the adjacent front and back sides of the stack, while the other baffle plate fully covers the fuel outlet riser side of the stack and partially covers the adjacent portions of the front and back sides of the stack. The remaining uncovered portions for the front and back sides of the stack allow the air to flow through the column  200 . The curved baffle plates provide an improved air flow control through the stack compared to the conventional baffle plates  38  which cover only one side of the stack. The fuel plenum  350  may be disposed below the column  200  and may be configured to provide a hydrogen-containing fuel feed to the column  200 , and may receive an anode fuel exhaust from the column  200 . The fuel plenum  350  may be connected to fuel inlet and outlet conduits  320  which are located below the fuel plenum  350 . 
     Each interconnect  400  electrically connects adjacent fuel cells  310  in the column  200 . In particular, an interconnect  400  may electrically connect the anode electrode of one fuel cell  310  to the cathode electrode of an adjacent fuel cell  310 . As shown in  FIG.  3 C , each interconnect  400  may be configured to channel air in a first direction A, such that the air may be provided to the cathode of an adjacent fuel cell  310 . Each interconnect  400  may also be configured to channel fuel in a second direction F, such that the fuel may be provided to the anode of an adjacent fuel cell  310 . Directions A and F may be perpendicular, or substantially perpendicular. As such, the interconnects  400  may be referred to as cross-flow interconnects. 
     The interconnect  400  may include fuel holes that extend through the interconnect  400  and that are configured for fuel distribution. For example, the fuel holes may include one or more fuel inlets  402  and one or more fuel (e.g., anode exhaust) outlets  404 , which may also be referred to as anode exhaust outlets  404 . The fuel inlets and outlets  402 ,  404  may be disposed outside of the perimeter of the fuel cells  310 . As such, the fuel cells  310  may be formed without corresponding through-holes for fuel flow. The combined length of the fuel inlets  402  and/or the combined length of the fuel outlets  404  may be at least 75% of a corresponding length of the interconnect  400  e.g., a length taken in direction A. 
     In one embodiment, each interconnect  400  contains two fuel inlets  402  separated by a neck portion  412  of the interconnect  400 , as shown in  FIG.  3 B . However, more than two fuel inlets  402  may be included, such as three to five inlets separated by two to four neck portions  412 . In one embodiment, each interconnect  400  contains two fuel outlets  404  separated by a neck portion  414  of the interconnect  400 , as shown in  FIG.  3 B . However, more than two fuel outlets  404  may be included, such as three to five outlets separated by two to four neck portions  414 . 
     The fuel inlets  402  of adjacent interconnects  400  may be aligned in the column  200  to form one or more fuel inlet risers  403 . The fuel outlets  404  of adjacent interconnects  400  may be aligned in the column  200  to form one or more fuel outlet risers  405 . The fuel inlet riser  403  may be configured to distribute fuel received from the fuel plenum  350  to the fuel cells  310 . The fuel outlet riser  405  may be configured to provide anode exhaust received from the fuel cells  310  to the fuel plenum  350 . 
     Unlike the flat related art side baffles  38  of  FIG.  1 A , the side baffles  302  may be curved around edges of the interconnects  400 . In particular, the side baffles  302  may be disposed around the fuel inlets  402  and outlets  404  of the interconnects  400 . Accordingly, the side baffles may more efficiently control air flow through air channels of the interconnects  400 , which are exposed between the side baffles  302  and are described in detail with regard to  FIGS.  4 A and  4 B . 
     In various embodiments, the column  200  may include at least 30, at least 40, at least 50, or at least 60 fuel cells, which may be provided with fuel using only the fuel risers  403 ,  405 . In other words, as compared to a conventional fuel cell system, the cross-flow configuration allows for a large number of fuel cells to be provided with fuel, without the need for ASP&#39;s or external stack fuel manifolds, such as external conduits  32 ,  34  shown in  FIG.  1 A . 
     Each interconnect  400  may be made of or may contain electrically conductive material, such as a metal alloy (e.g., chromium-iron alloy) which has a similar coefficient of thermal expansion to that of the solid oxide electrolyte in the cells (e.g., a difference of 0-10%). For example, the interconnects  400  may comprise a metal (e.g., a chromium-iron alloy, such as 4-6 weight percent iron, optionally 1 or less weight percent yttrium and balance chromium alloy), and may electrically connect the anode or fuel-side of one fuel cell  310  to the cathode or air-side of an adjacent fuel cell  310 . An electrically conductive contact layer, such as a nickel contact layer (e.g., a nickel mesh), may be provided between anode and each interconnect  400 . Another optional electrically conductive contact layer may be provided between the cathode electrodes and each interconnect  400 . 
     A surface of an interconnect  400  that in operation is exposed to an oxidizing environment (e.g., air), such as the cathode-facing side of the interconnect  400 , may be coated with a protective coating in order to decrease the growth rate of a chromium oxide surface layer on the interconnect and to suppress evaporation of chromium vapor species which can poison the fuel cell cathode. Typically, the coating, which can comprise a perovskite such as lanthanum strontium manganite (LSM), may be formed using a spray coating or dip coating process. Alternatively, other metal oxide coatings, such as a spinel, such as an (Mn, Co) 3 O 4  spinel (MCO), can be used instead of or in addition to LSM. Any spinel having the composition Mn 2-x Co 1+x O 4  (0≤x≤1) or written as z(Mn 3 O 4 )+(1-z)(Co 3 O 4 ), where (⅓≤z≤⅔) or written as (Mn, Co) 3 O 4  may be used. In other embodiments, a mixed layer of LSM and MCO, or a stack of LSM and MCO layers may be used as the coating. 
       FIGS.  4 A and  4 B  are plan views showing, respectively, an air side and a fuel side of the cross-flow interconnect  400 , according to various embodiments of the present disclosure. 
     Referring to  FIG.  4 A , the air side of the interconnect  400  may include ribs  406  configured to at least partially define air channels  408  configured to provide air to the cathode of a fuel cell  310  disposed thereon. The air side of the interconnect  400  may be divided into an air flow field  420  including the air channels  408 , and riser seal surfaces  422  disposed on two opposing sides of the air flow field  420 . One of the riser seal surfaces  422  may surround the fuel inlets  402  and the other riser seal surface  422  may surround the fuel outlets  404 . The air channels  408  and ribs  406  may extend completely across the air side of the interconnect  400 , such that the air channels  408  and ribs  406  terminate at opposing peripheral edges of the interconnect  400 . In other words, when assembled into a column  200 , opposing ends of the air channels  408  and ribs  406  are disposed on opposing (e.g., front and back) outer surfaces of the stack, to allow the blown air to flow through the stack. Therefore, the stack may be externally manifolded for air. 
     Riser seals  424  may be disposed on the riser seal surface  422 . For example, one riser seal  424  may surround the fuel inlets  402 , and one riser seal  424  may surround the fuel outlets  404 . The riser seals  424  may prevent fuel and/or anode exhaust from entering the air flow field  420  and contacting the cathode of the fuel cell  310 . The riser seals  424  may also operate to prevent fuel from leaking out of the fuel cell stack  100  (see  FIG.  3 A ). 
     Referring to  FIG.  4 B , the fuel side of the interconnect  400  may include ribs  416  that at least partially define fuel channels  418  configured to provide fuel to the anode of a fuel cell  310  disposed thereon. The fuel side of the interconnect  400  may be divided into a fuel flow field  430  including the fuel channels  418 , and a perimeter seal surface  432  surrounding the fuel flow field  430  and the fuel inlets and outlets  402 ,  404 . The ribs  416  and fuel channels  418  may extend in a direction that is perpendicular or substantially perpendicular to the direction in which the air-side channels  408  and ribs  406  extend. 
     A frame-shaped perimeter seal  434  may be disposed on the perimeter seal surface  432 . The perimeter seal  434  may be configured to prevent air entering the fuel flow field  430  and contacting the anode on an adjacent fuel cell  310 . The perimeter seal  434  may also operate to prevent fuel from exiting the fuel risers  403 ,  405  and leaking out of the fuel cell column  200  (see  FIGS.  3 A and  3 B ). 
     The seals  424 ,  434  may comprise a glass or ceramic seal material. The seal material may have a low electrical conductivity. In some embodiments, the seals  424 ,  434  may be formed by printing one or more layers of seal material on the interconnect  400 , followed by sintering. 
     Fuel Flow Structures 
     As shown in  FIG.  1 A , in a conventional fuel cell system, fuel and fuel exhaust are provided to and received from a fuel cell stack through metal anode splitter plates  36 . The anode splitter plates  36  which are fluidly connected to one another by the fuel inlet conduit  32  and the anode exhaust conduit  34 . The conduits  32 ,  34  include metal tubes that are welded to the anode splitter plates  36  and to ceramic components that serve as dielectric breaks. As such, fluidly connecting the anode splitter plates  36  relies upon expensive dielectric components and a significant amount of on-site welding. Therefore, there is a need for a more cost effective method for providing fuel to, and receiving fuel exhaust from, a fuel cell stack. 
       FIG.  5 A  is an exploded top perspective view of a fuel flow structure  500 , according to various embodiments of the present disclosure, and  FIG.  5 B  is an exploded bottom perspective view of the fuel flow structure  500  of  FIG.  5 A . Referring to  FIGS.  5 A and  5 B , the fuel flow structure  500  includes fuel conduits  320  and a fuel plenum  350 . The fuel plenum  350  may include a seal ring  354 , glass or glass ceramic seals  356 , a base plate  360 , a dielectric layer  364 , a cover plate  366 , a seal plate  370 , and a manifold plate  380 . 
     The fuel plenum  350  may be configured to form a fluid-tight connection with the fuel conduits  320 . The fuel conduits  320  may include an inlet conduit  320 A configured to provide fuel to the fuel plenum  350 , and an outlet conduit  320 B configured to receive fuel exhaust from the fuel plenum  350 . The fuel conduits  320  may include metal tubes  322 , metal bellows  324 , and dielectric rings  326 . The metal tubes  322  may be coupled to the bellows  324  and the dielectric rings  326  by brazing, welding, or press-fitting, for example. The bellows  324  may act to compensate for differences in coefficients of thermal expansion between fuel cell components by deforming to absorb stress. In alternate embodiments, the metal tubes  322  may themselves include, or be made entirely of bellows, rather than be coupled with the bellows  324  such that the metal tubes/bellows  322  may be directly coupled with the dielectric ring  326 . The dielectric rings  326  may operate as dielectric breaks, to prevent current from being conducted through the fuel conduits  320  and electrically shorting a fuel cell stack disposed on the fuel plenum  350 . 
     The base plate  360 , dielectric layer  364 , and cover plate  366  may respectively include inlet holes  361 A,  365 A,  367 A and outlet holes  361 B,  365 B,  367 B, which may be through-holes that extend through the respective plates and layer. The base plate  360  may include protrusions  362  configured to mate with ceramic connectors  39 , as shown in  FIG.  1 A . The base plate  360  and the cover plate  366  may be formed of a densified dielectric material. For example, the base plate  360  and the cover plate  366  may be formed of a substantially non-porous, electrically-insulating ceramic material, such as alumina, zirconia, yttria stabilized zirconia (YSZ) (e.g., 3% yttria stabilized zirconia), or the like. The base plate  360  and the cover plate  366  may be rigid plates configured to provide support to the dielectric layer  364 . 
     In some embodiments, the dielectric layer  364  may be formed of a ceramic material having a higher dielectric constant than the ceramic materials of the base plate  360  and/or the cover plate  366 . In other words, the dielectric layer  364  may be able to withstand a higher maximum electric field without electrical breakdown and becoming electrically conductive (i.e., have a higher breakdown voltage) than the base plate  360  and the cover plate  366 . For example, the dielectric layer  364  may be formed of one or more layers of a porous ceramic yarn or fabric that is highly electrically insulating at high temperatures, such as Nextel ceramic fabrics numbers  312 ,  440  or  610 , available from 3M Co. 
     In other embodiments, the dielectric layer  364  may be formed of a ceramic matrix composite (CMC) material, or any comparable material that has high dielectric strength, due to having a high surface area to volume ratio. The CMC may include, for example, a matrix of aluminum oxide (e.g., alumina), zirconium oxide or silicon carbide. Other matrix materials may be selected as well. The fibers may be made from alumina, carbon, silicon carbide, or any other suitable material. In one embodiment, both matrix and fibers may comprise alumina. Accordingly, the dielectric layer  364  may be configured to operate as a dielectric break to prevent electrical conduction through the fuel plenum  350 . 
     The cover plate  366  and the base plate  360  may have a higher density than the dielectric layer  364 . For example, the cover plate  366  and/or the base plate  360  may be formed of a fully dense ceramic material, such as 97% to 99.5% dense alumina, or the like. The cover plate  366  is configured to separate the seal plate  370  from the dielectric layer  364 . As such, the cover plate  366  may be configured to prevent the diffusion of metallic species from the seal plate  370  into the dielectric layer  364 . For example, the cover plate  366  may reduce and/or prevent the diffusion of chromium species (e.g., chromium oxides) from the seal plate  370  into the dielectric layer  364 , in order to prevent the chromium species from reducing the dielectric strength of the dielectric layer  364  and/or otherwise degrading the structural integrity of the dielectric layer  364 . 
     The seal plate  370  and the manifold plate  380  may be formed of a metal or metal alloy, such as stainless steel, that may be easily welded to the fuel conduits  320 . For example, the seal plate  370  and/or the manifold plate  380  may be formed of 446 stainless steel or the like. 446 stainless steel includes 23 to 27 weight % Cr, 1.5 weight % or less Mn, 1 weight % or less of one or more of Si, Ni, C, P and/or S, and balance Fe. In some embodiments, the seal plate  370  and/or the manifold plate  380  may be formed by brazing multiple metal sub-plates together. In embodiments formed using metal sub-plates, each of the sub-plates may be cut to form various structures, such as holes and/or channels, prior to, or after, the brazing process. In some embodiments, laser cutting or the like may be used to cut such structures. 
     The seal plate  370  and the manifold plate  380  may respectively include coatings  372 ,  382  on one or both sides, such as at least on the sides of the plates  370 ,  380  that face each other. The coatings  372 ,  382  may have a thickness ranging from about 75 μm to about 200 μm, such as from about 100 μm to about 175 μm, from about 110 μm to about 140 μm, or about 120 μm. Typically, the coatings  372 ,  382  may comprise a metal oxide material, such as a perovskite material, for example, lanthanum strontium manganite (LSM). Alternatively, other metal oxide coatings, such as a spinel, such as an (Mn, Co) 3 O 4  spinel (MCO), can be used instead of or in addition to LSM. Any spinel having the composition Mn 2-x Co 1+x O 4  (0≤x≤1) or written as z(Mn 3 O 4 )+(1-z)(Co 3 O 4 ), where (⅓≤z≤⅔) or written as (Mn, Co) 3 O 4  may be used. In other embodiments, a mixed layer of LSM and MCO, or a stack of LSM and MCO layers may be used as the coatings  372 ,  382 . The coatings  372 ,  382  may be formed using a spray coating or dip coating process and may be applied to substantially all the outer surfaces of the seal plate  370  and the manifold plate  380 . 
     The seal plate  370  may include an inlet hole  374 A and an outlet hole  374 B, which may be through-holes that extend between top and bottom surfaces thereof. The manifold plate  380  may include a bottom inlet hole  384 A and a bottom outlet hole  384 B formed in the bottom surface thereof, and top inlet holes  390 A and top outlet holes  390 B, which may be formed in the top surface thereof, on opposing sides of the manifold plate  380 . While three top inlet holes  390 A and three top outlet holes  390 B are shown, the present disclosure is not limited to any particular number of top outlet and inlet holes  390 A,  390 B. For example, the manifold plate  380  may include two, four, five or more top inlet holes  390 A, and may include two, four, five or more top outlet holes  390 B, depending on a number of fuel inlets and outlets included in the interconnects  400  of a corresponding fuel cell stack. For example, if the interconnects has three inlets and three outlets, then the manifold plate  380  has three inlet holes  390 A and three outlet holes  390 B. 
     The base plate  360 , dielectric layer  364 , cover plate  366 , seal plate  370 , and manifold plate  380  may be stacked on one another, such that the inlet holes  361 A,  365 A,  367 A,  374 A,  384 A are aligned to form an inlet conduit passage  352 A, and the outlet holes  361 B,  365 B,  367 B,  374 B,  384 B are aligned to form an outlet conduit passage  352 B. The inlet and outlet conduits  320 A,  320 B may be inserted into the respective inlet and outlet conduit passages  352 A,  352 B such that ends  328  of the inlet and outlet conduits  320 A,  320 B may extend up to and/or past the top surface of the seal plate  370 . 
       FIG.  6 A  is a top view of the seal plate  370 , and  FIG.  6 B  is a cross-sectional view taken along line L 3  of  FIG.  6 A . Referring to  FIGS.  6 A and  6 B , an inlet seal region  378 A and an outlet seal region  378 B may be respectively formed around the inlet hole  374 A and an outlet hole  374 B in areas where the coating  372  is not applied to the top surface of the seal plate  370 . As such, the inlet and outlet seal regions  378 A,  378 B may have a depth D2 equal to the thickness of the coating  372 , such as a depth D2 of about 120 μm. 
       FIG.  7 A  is a bottom view of the manifold plate  380 ,  FIG.  7 B  is a cross-sectional view taken along line L 4  of  FIG.  7 A , and  FIG.  7 C  is a schematic top view of the manifold plate  380 , according to various embodiments of the present disclosure. Referring to  FIGS.  7 A- 7 C , inlet and outlet recesses  386 A,  386 B may be formed in the bottom surface of the manifold plate  380 , respectively surrounding the bottom inlet and outlet holes  384 A,  384 B. The inlet and outlet recesses  386 A,  386 B may have a depth D3 ranging from about 0.5 mm to about 6 mm. 
     Inlet and outlet seal regions  388 A,  388 B may be respectively formed around the inlet and outlet recesses  386 A,  386 B, in areas where the coating  382  is not applied to the bottom surface of the manifold plate  380 . As such, the inlet and outlet seal regions  388 A,  388 B may have a depth D4 equal to the thickness of the coating  382 , such as a depth D4 of about 120 μm. 
     The manifold plate  380  may also include internal inlet channels  392 A and outlet channels  392 B. The inlet channels  392 A may fluidly connect the bottom inlet hole  384 A to respective top inlet holes  390 A. The outlet channels  392 B may fluidly connect the bottom outlet hole  384 B to respective top outlet holes  390 B. The inlet channels  392 A may be configured such that substantially equal amounts of fuel (e.g., equal fuel flow rates) are provided to each top inlet hole  390 A from the common bottom inlet hole  384 A. The outlet channels  392 B may be configured such that substantially equal amounts of fuel exhaust are provided from each top outlet hole  390 B to the common bottom outlet hole  384 B. 
     In addition, the manifold plate  380  may include an electrical contact  381 . The manifold plate  380  may be electrically connected to the bottom of a fuel cell stack, and the electrical contact  381  may extend laterally from the manifold plate  380  and may be configured to provide a connection point for connecting the manifold plate  380  to a current collection circuit. 
       FIG.  8 A  is a vertical cross-sectional view taken along line L 1  of  FIG.  5 A , showing the assembled fuel plenum  350  and inlet conduit  320 A, and  FIG.  8 B  is a vertical cross-sectional view or along line L 2  of  FIG.  5 A , showing the assembled fuel plenum  350  and outlet conduit  320 B. 
     Referring to  FIGS.  5 A,  5 B,  8 A, and  8 B , the base plate  360 , dielectric layer  364 , cover plate  366 , seal plate  370 , and manifold plate  380  are stacked on one another, thereby forming the inlet conduit passage  352 A and the outlet conduit passage  352 B. The inlet conduit  320 A may be inserted in the inlet conduit passage  352 A, facing the bottom inlet hole  384 A. The outlet conduit  320 B may be inserted in the outlet conduit passage  352 B, facing the bottom outlet hole  384 B. 
     A first seal ring  354 A may be disposed in the inlet recess  386 A on the bottom surface of the manifold plate  380  and around the inlet conduit  320 A. A second seal ring  354 B may be disposed in the outlet recess  386 B on the bottom surface of the manifold plate  380  and around the outlet conduit  320 B. The inlet and outlet conduits  320 A,  320 B may be welded to the seal plate  370 . In particular, the welding process may include welding the first and second seal rings  354 A,  354 B to the inlet and outlet conduits  320 A,  320 B, and welding the first and second seal rings  354 A,  354 B to the surface of the seal plate  370  to ensure that a fluid-tight seal is formed between the inlet and outlet conduits  320 A,  320 B and the seal plate  370 . 
     A first glass or glass ceramic seal  356 A may be disposed in the inlet seal region  378 A of the seal plate  370 , and a second glass or glass ceramic seal  356 B may be disposed in the inlet seal region  388 A of the manifold plate  380 . A third glass or glass ceramic seal  356 C may be disposed in the outlet seal region  378 B of the seal plate  370 , and a fourth glass or glass ceramic seal  356 D may be disposed in the outlet seal region  388 B of the manifold plate  380 . However, in other embodiments, a single glass or glass ceramic seal may be used. The seals  356 A- 356 D may be heated to soften the seals  356 A- 356 D, such that the seals  356 A- 356 D form a fluid-tight connections that physically connect the seal plate  370  to the manifold plate  380 . 
     The inlet seal regions  378 A,  388 A may overlap to form an inlet seal area  358 A, and the outlet seal regions  378 B,  388 B may overlap to form an outlet seal area  358 B. The first and second seals  356 A,  356 B may be stacked on one another in the inlet seal area  358 A, and the third and fourth seals  356 C,  356 D may be stacked on one another in the outlet seal area  358 B. The coatings  372 ,  382  may be stacked on one another. As such, the height of the inlet and outlet seal areas  358 A,  358 B may be equal to the combined thickness of the coatings  372 ,  382 . 
     The inlet and outlet seal areas  358 A,  358 B may provide space for the glass or glass ceramic seals  356 A- 356 D to expand laterally when heated to fuel cell system operating temperatures, thereby reducing stress applied to the glass or glass ceramic seals  356 A- 356 D over time. In addition, since the seal plate  370  and the manifold plate  380  may be formed of the same materials, the seal plate  370  and the manifold plate  380  may have matched coefficients of thermal expansion (CTEs). Therefore, stress applied to the glass or glass ceramic seals  356 A- 356 D over time may be further reduced. 
     The glass or glass ceramic seals  356 A- 356 D may be formed of a high-temperature glass or glass ceramic material, such as a silicate or aluminosilicate glass or glass ceramic material. In some embodiments, the glass or glass ceramic seals  356 A- 356 D may be formed of a silicate glass or glass ceramic seal material comprising SiO 2 , BaO, CaO, Al 2 O 3 , K 2 O, and/or B 2 O 3 . For example, the seal material may include, by weight: SiO 2  in an amount ranging from about 40% to about 60%, such as from about 45% to about 55%; BaO in an amount ranging from about 10% to about 35%, such as from about 15% to about 30%; CaO in an amount ranging from about 5% to about 20%, such as from about 7% to about 16%; Al 2 O 3  in an amount ranging from about 10% to about 20%, such as from about 13% to about 15%; and B 2 O 3  in an amount ranging from about 0.25% to about 7%, such as from about 0.5% to about 5.5%. In some embodiments, the seal material may additionally include K 2 O in an amount ranging from about 0.5% to about 1.5%, such as from about 0.75% to about 1.25%. 
     In some embodiments, the glass or glass ceramic seals  356 A- 356 D may be formed of a silicate glass or glass ceramic seal material comprising SiO 2 , B 2 O 3 , Al 2 O 3 , CaO, MgO, La 2 O 3 , BaO, and/or SrO. For example, the seal material may include, by weight: SiO 2  in an amount ranging from about 30% to about 60%, such as from about 35% to about 55%; B 2 O 3  in an amount ranging from about 0.5% to about 15%, such as from about 1% to about 12%; Al 2 O 3  in an amount ranging from about 0.5% to about 5%, such as from about 1% to about 4%; CaO in an amount ranging from about 2% to about 30%, such as from about 5% to about 25%; MgO in an amount ranging from about 2% to about 25%, such as from about 5% to about 20%; and La 2 O 3  in an amount ranging from about 2% to about 12%, such as from about 5% to about 10%. In some embodiments, the seal material may additionally include BaO in an amount ranging from about 0% to about 35%, such as from about 0% to about 30%, or from about 0.5% to about 30%, including about 20% to about 30%, and/or SrO in an amount ranging from about 0% to about 20%, such as from about 0% to about 15%, of from about 0.5% to about 15%, including about 10% to about 15%. In some embodiments, the seal material may additionally include at least one of BaO and/or SrO in a non-zero amount such as at least 0.5 wt. %, such as both of BaO and SrO in a non-zero amount, such at least 0.5 wt. %. However, other suitable seal materials may be used. 
     When assembled in a fuel cell stack, such as the fuel cell column  200  of  FIGS.  3 A- 3 C , the top inlet holes  390 A may be fluidly connected to the fuel inlets  402  of the interconnect  400  of the column  200 , and the top outlet holes  390 B may be fluidly connected to the fuel outlets  404  of the interconnects  400 , as shown in  FIG.  4 A . For example, a glass or glass ceramic seal  424  may be disposed between the top inlet holes  390 A and the fuel inlets  402  of an adjacent interconnect  400 , and a glass or glass ceramic seal  424  may be disposed between the top outlet holes  390 B and the fuel outlets  404  of the adjacent interconnect  400 , in order to provide fluid-tight connections. 
     While solid oxide fuel cells are described above in various embodiments, embodiments can include any other fuel cells, such as molten carbonate, phosphoric acid or PEM fuel cells. 
       FIG.  9 A  is a simplified exploded side view of a fuel cell column  600 , according to various embodiments of the present disclosure. Referring to  FIG.  9 A , the column  600  may include a fuel cell stack  300 , a top termination plate  610 , a seal plate  370 , a manifold plate  380 , and a compression assembly  306 . Although not shown in  FIG.  9 A , the column  600  may include other components, such as baffle plates  302 , a base plate  360 , dielectric layers  364 , and a cover plate  366 , as shown in the  FIGS.  3 A,  5 A, and  5 B . 
     The fuel cell stack  300  may include fuel cells  310  separated by interconnects  400 . The fuel cells and interconnects  400  may be arranged in an “even” configuration shown in  FIG.  9 A , where fuel cells of the stack  300  are arranged cathode side up (i.e., air sides of the interconnects  400  face the top termination plate  610  and fuel sides of the interconnects  400  face the manifold plate  380 ). In contrast, a stack having an “odd” configuration includes fuel cells arranged anode side up (i.e., fuel sides of the interconnects  400  face the top termination plate  610  and air sides of the interconnects  400  face the manifold plate  380 ), as shown in  FIG.  12   . The top termination plate  610  of a first stack  300  in the “even” configuration in a first column  600  may be electrically connected by a conductive jumper or wire to the top termination plate  610  of a second stack  300  in the “odd” configuration in a laterally adjacent second column  600 . The manifold plates  380  of the first and second columns  600  may be electrically connected to respective positive and negative electrical terminals of the system. 
     The top termination plate  610  disposed between the stack  300  and the compression assembly  306 . The top termination plate  610  may be bonded to an uppermost interconnect  400 U of the stack  300  by manifold seals  614 , which may be ring-shaped glass or glass-ceramic seals similar to the seals  424  described above. The top termination plate  610  may be form by the same processes and materials as the interconnects  400 . For example, the top termination plate  610  may be formed of a Cr—Fe alloy by a power metallurgy process. 
     The top and bottom surfaces of the top termination plate  610  may be coated with a protective coating  612 , in order to decrease the growth rate of a chromium oxide surface layer on the interconnect and to suppress evaporation of chromium vapor species which can poison the fuel cell cathode. The coating  612  may have a thickness ranging from about 40 μm to about 90 μm, such as from about 50 μm to about 80 μm, or about 65 μm. The coating  612  may comprise a perovskite material, such as lanthanum strontium manganite (LSM). The coating  612  may be formed using dip coating or a spray coating process, such as an atmospheric plasma spraying (“APS”) or thermal spraying. Alternatively, other metal oxide coatings, such as a spinel, such as a (Mn, Co) 3 O 4  spinel (MCO), can be used instead of or in addition to LSM. Any spinel having the composition Mn 2-x Co 1+x O 4  (0≤x≤1) or written as z(Mn 3 O 4 )+(1-z)(Co 3 O 4 ), where (⅓≤z≤⅔) or written as (Mn, Co) 3 O 4  may be used. In other embodiments, a mixed layer of LSM and MCO, or a stack of LSM and MCO layers may be used as the coating  612 . 
     A protective coating  618  may be formed on the top surface of an uppermost interconnect  400 U of the stack  300 . The coating  618  may be formed of the same material as the coating  612  of the top termination plate  610 . In some embodiments, the coating  618  may be formed by APS or contact printing and may have a thickness ranging from about 10 μm to about 50 μm, such as from about 20 μm to about 40 μm, or about 30 μm. For example, the coating  618  may have the same area and perimeter (i.e., outer horizontal shape) as the coating  612  on the bottom of the top termination plate  610 , which may have the same area and perimeter as the fuel cells of the stack  300 . 
     The manifold plate  380  may be disposed between the seal plate  370  and the stack  300 . A protective coating  382  may be formed on the bottom surface of the manifold plate  380 . The coating  382  may be formed of the same material as the coating  612  of the top termination plate  610 . The manifold plate  380  may be connected to the seal plate  370  using one or more seals  356 , which may be formed of a glass or glass-ceramic seal material. For example, two ring-shaped seal  356 , may be stacked on one another to seal fuel inlet and outlet holes of the manifold plate  380  and the seal plate  370 . In some embodiments, the seals  356  may be tape cast seals having a thickness ranging from about 100 μm to about 300 μm, such as from about 150 μm to about 250 μm, or about 200 μm, prior to sintering and compression. In some embodiments, ceramic seals  354  may be disposed inside the ring seals  356 , as shown in  FIGS.  8 A and  8 B . 
     A lowermost interconnect  400 L of the stack  300  may interface with the manifold plate  380 . In particular, the lowermost interconnect  400 L may be bonded to the manifold plate  380  by a peripheral seal  634 . The peripheral seal  634  may be a frame-shaped seal formed by dispensing a green glass or glass-ceramic seal material around the perimeter of a conductive compliant layer  630 . The green seal material may be cured by heat or UV light, for example. The compliant layer  630  may be formed of a conductive compliant metal material, such as a metal mesh, such as a nickel or nickel alloy mesh, and may be configured to electrically connect the lowermost interconnect  400 L and the manifold plate  380 . The compliant layer  630  may also be referred to herein as a “compliant metal mesh” or a “metal mesh”. 
     In one embodiment, the compliant metal mesh may comprise an Inconel alloy, such as Inconel 625 alloy which includes between 20 and 23 wt. % Cr, between 8 and 10 wt. % Mo, between 3.15 and 4.15 wt. Nb+Ta, between 0 and 1 wt. % Co and balance Ni with background impurities (e.g., less than 1 wt. % Al, Ti, C, Fe, Mn, Si, P and/or S each). 
     The compliant metal mesh should have sufficient vertical compliance, electrical contact, and sufficient deformation under typical loads to support the stack in its cambered form. For example, the compliant metal mesh may include between 1.5 and 2.5 metal wires per millimeter (e.g., between 1.9 and 2.3 wires per mm), may have wire thickness between 125 and 200 microns (e.g., between 140 and 180 microns), and mesh thickness between 250 and 400 microns (e.g., between 280 and 350 microns). 
     If the mesh is too stiff (i.e., the compressibility is too low), then the number of knuckles (i.e., wire crossing locations where wires bend out of the plane of the mesh) may be reduced. For example, some of the knuckles may be intentionally skipped. For example, ever second, every third, every fourth, etc. knuckle may be skipped. Alternatively holes may be intentionally drilled or punched through the thickness of the mesh to reduce the number of knuckles. The holes may have a width (e.g., diameter for circular holes) that is at least four times larger than the spacing between the wires of the mesh. The holes may have any suitable shape (e.g., round, rectangular, irregular, etc.). The holes may be spaced at regular or irregular interval in the plane of the mesh. For example, the holes may take up between 10 and 30 percent of the total area of the mesh. 
     The column  600  may include a fuel inlet manifold  601 A and a fuel outlet manifold  601 B, which extend through openings formed in the seal plate  370 , the manifold plate  380 , and the stack  300 . The top termination plate  610  may include channels that connect the manifolds  601 A,  601 B. 
     The manifold plate  380  may be made of 446 alloy stainless steel, for reasons of low cost, manufacturability (e.g., easy brazing and welding), and desirable material properties, such as oxidation resistance and fracture toughness. Interconnects  400  may be formed by compressing a metal alloy, such as an Cr—Fe alloy, via a powder metallurgy (PM) process, for reasons of low cost, minimal variability in critical properties (e.g., flow channel cross-sectional area), and precise match of coefficient of thermal expansion (CTE) to the fuel cell electrolyte. 
     The CTE of the manifold plate  380  may be close to the CTE of the interconnects  400 . However, in some embodiments, the CTEs may not be precisely matched. As a result, during thermal cycling (e.g., shutdown/restart), thermal stress may build up between the manifold plate  380  and the stack  300 , due to differing rates of thermal expansion between the manifold plate  380  and the interconnects  400  located at the bottom of the stack  300  near the manifold plate  380 . This thermal stress may result in the fracturing of the peripheral seal  634 , or more detrimentally the fracturing of a seal between adjacent interconnects  400  or the fracturing one of the fuel cells  310  at the bottom of the stack  300 . 
     Furthermore, the shape (or “camber”) of the manifold plate  380  and the interconnects  400  may not match. In addition, the camber of the manifold plate  380  may be essentially flat upon manufacture, but can change with time at temperature, and such changes may be influenced by many factors including material creep, the shape of the interconnects  400 , the compressive load, and the internal structure of the manifold plate  400 . The camber of the interconnects  400  may be nonzero upon manufacture, and can also change with time, influenced by the same factors as the manifold plate  380 , as well as the hydrogen and water content of the fuel flow. Difference in the camber of the interconnects  400  and manifold plate  380  may also result in seal and/or fuel cell cracking/damage. This shape mismatch can also result in uneven electrical contact within cells  310  at the bottom of the stack  300 , which may result in poor cell performance, and/or poor contact to the manifold plate  380 , resulting in resistive losses at the termination plates or current collectors. Shaping the manifold plate  380  may be complex and expensive, and may not account for all interconnect  400  shapes. 
     Therefore, various embodiments may include a mitigation structure configured to reduce stress applied to the stack  300 , due to a shape mismatch and/or coefficient of thermal expansion mismatch, between the stack  300  and the manifold plate  380 . The mitigation structure may also be configured to reduce electrical disconnections between the stack  300  and the manifold plate  380 . 
     For example, in some embodiments, the thickness (i.e., height) of the peripheral seal  634  may be increased so as to be greater than the thicknesses of the other seals in the column  600  (e.g., thicker than the seals inside the stack  300 ). Without wishing to be bound to a particular theory, it is believed that the seal stress is a function of seal thickness. If the peripheral seal  634  is the thickest seal in the column  600 , then then peripheral seal  634  should be the first to break due to thermal stress applied to the column  600 . As such, the cracking of the peripheral seal  634  may relieve thermal stress and prevent damage to adjacent fuel cells  310  and/or seals inside the stack  300 . 
     In various embodiments, the peripheral seal  634  may be formed of a compliant seal material, such as vermiculite, mica, or a glass-mica material, which may be in a glass ceramic configuration containing an amorphous glass matrix embedding ceramic crystals. This compliant seal material may allow for differing expansion rates between the lowermost interconnect  400 L and the manifold plate  380 , thereby preventing or reducing thermal stress buildup. 
     In other embodiments, the thickness of the compliant layer  630  may be increased to compensate for thermal stress. For example, the compliant layer  630  may be formed of a mesh with wire thickness ranging from about 80 μm to about 200 μm, such as from about of about 100 μm to about 150 μm. The thicker compliant layer  630  is used in combination with a thicker peripheral seal  634  which surrounds the compliant layer  630 , and thus has about the same thickness as the compliant layer  630 . Therefore, the thickness of the peripheral seal  634  may range from about 80 μm to about 200 μm, such as from about of about 100 μm to about 150 μm. In one embodiment, the peripheral seal  634  may comprise a UV curable seal material with a dispensed seal dam. 
     In some embodiments an optional recess  383  may be formed in the top surface of the manifold plate  380 , to at least partially accommodate the increased thickness of the compliant layer  630 . In particular, the recess  383  may have a depth ranging from about 100 μm to about 150 μm, such as about 120 μm. The compliant layer  630  may be located at least partially in the recess  383 . 
     In various embodiments, an optional high-temperature tribological coating  616  may be deposited on the top surface of the manifold plate  380  and/or the bottom surface of the lowermost interconnect  400 L. The tribological coating  616  may be configured to reduce friction between the manifold plate and the lowermost interconnect  400 L, which may provide lower-friction sliding during thermal expansion, thereby further reducing the stress on the stack  300 . The tribological coating  616  may be a dense and smooth coating comprising an electrically-insulating ceramic material, such as alumina, zirconia, YSZ, or the like, or a loose powder coating comprising a perovskite material, such as lanthanum strontium manganite (LSM), for example. 
     Accordingly, the column  600  may include a mitigation structure configured to reduce stress applied to the stack  300 , due to a shape mismatch and/or coefficient of thermal expansion mismatch, between the stack  300  and the manifold plate  380 . The mitigation structure may also be configured to reduce electrical disconnections between the stack  300  and the manifold plate  380 . The mitigation structure may include the compliant layer  630 , the peripheral seal  634 , and/or the tribological coating  616 , which are configured to reduce thermal stress applied to the column  600 . 
       FIG.  9 B  is a simplified exploded side view of a fuel cell column  600 ′, according to various embodiments of the present disclosure.  FIG.  9 C  is a photograph of an example of a crimped conductive mesh that may be used in the column  6   oo ′ shown in  FIG.  9 B . The fuel cell column  600 ′ is a modified version of the column  600  of  FIG.  9 A . As such, only the difference therebetween will be discussed in detail. 
     Referring to  FIGS.  9 B and  9 C , the column  600 ′ may include a wire mesh  631  as a compliant layer that electrically connects the stack  300  to the manifold plate  380 . The mesh  631  may be formed of wire bent that is bent into a wave pattern, such as a herringbone wave pattern as shown in  FIG.  9 C . The mesh  631  may be crimped to create peaks and troughs of controllable height to control the thickness of the wire mesh  631 . For example, the mesh  631  may have a thickness ranging from about 1 mm to about 20 mm, such as from about 1 mm to about 10 mm. 
     In one embodiment, the crimped mesh  631  may be formed of a material other than pure nickel to provide improved vertical compliance and oxidation resistance. Therefore, in some embodiments, the mesh  631  may be formed of a metal alloy, such as the above described Inconel 625, 446 stainless steel, Inconel 600, Hastelloy X, Crofer 22, or the like. Inconel 600 alloy may include 14 to 17 weight percent chromium, 6 to 10 weight percent iron, optionally 1 weight percent or less of Mn, Cu, Si, C and/or S, and at least about 72 weight percent (i.e., balance) nickel. Hastelloy X alloy may include about 22 weight percent chromium, about 18 weight percent iron, about 9 weight percent molybdenum, 1 to 2 atomic percent cobalt, optionally 1 weight percent or less of W, C, Mn, Si, B, Nb, Al and/or Ti, and at least about 47 weight percent (i.e., balance) nickel. Crofer 22 alloy may include about 20 to 24 weight percent chromium, 0.3 to 0.8 weight percent manganese, 0.03 to 0.2 weight percent titanium, 0.04 to 0.2 weight percent lanthanum, optionally 1 weight percent or less of C, S, Si, Cu, P and/or Al, and at least 73 weight percent (i.e., balance) iron. 
     In some embodiments, the mesh  631  may be fixed to the manifold plate  380 , for example by resistance welding. In particular, mesh  631  may be welded along welding lines WL that extend along troughs of the mesh  631  where the mesh  631  contacts the manifold plate  380 . Welding the mesh  631  to the manifold plate  380  enhances the elasticity of the mesh under load by creating a spring-like structure, which allows the mesh  631  to better adjust to changes to the camber-induced gap between the manifold plate  380  and the stack  300 . For example, changes in the power output of the stack  300  and/or reduction and oxidation processes within the stack  300 , may result in changes to the gap. However, the spring-like action of the mesh  631  allows the mesh  631  to remain in contact with and support the manifold plate  380  and the stack  300 , when changes to the gap occur. As such, the mesh  631  may be configured to function as a spring to maintain electrical contact and reduce the chance of cracking cells of the stack  300 , in a variety of operating conditions. 
       FIG.  10 A  is a simplified exploded side view of a fuel cell column  602 , according to various embodiments of the present disclosure.  FIG.  10 B  is a bottom view of one non-limiting embodiment of the bottom termination plate  620  of  FIG.  10 A . The column  602  may be similar to the column  600 . As such, only the differences therebetween will be discussed in detail. 
     Referring to  FIGS.  10 A and  10 B , the column  602  may additionally include a bottom termination plate  620  disposed between the stack  300  and the manifold plate  380  (e.g., below the compliant layer  630 ). The bottom termination plate  620  may be configured to act as a stress buffer by physically separating the stack  300  from the manifold plate  380 . The bottom termination plate  620  may also improve electrical contact with the stack  300 , thereby decreasing resistive losses. 
     The bottom termination plate  620  may be formed of for example a Cr—Fe alloy by a powder metallurgy process. The Cr—Fe alloy may comprise 4 to 6 weight percent iron and 94 to 96 weight percent chromium. Alternatively, the bottom termination plate  620  may be formed of another high-temperature metal alloy, such as Inconel 625, stainless steel 446, Haynes alloy (e.g., a nickel and chromium based alloy), ZMG232L iron chromium alloy comprising 22 to 24 weight percent Cr and at least 70 weight percent iron, or the like. A protective coating  622  may be formed on the bottom surface of the bottom termination plate  620  and/or the protective coating  616  may be formed on the top surface of the manifold plate  380 . The protective coating  622  may be formed by the same methods and use the same materials as the protective coating  612 . In some embodiments, the protective coating  622  may have a thickness ranging from about 40 μm to about 90 μm, such as from about 50 μm to about 80 μm, or about 65 μm. The bottom termination plate  620  may also include fuel inlet and outlet openings  624  configured to fluidly connect with corresponding fuel inlet and outlet holes of the manifold plate  380 . In some embodiments, the bottom termination plate  620  may include an electrical contact  628 . 
     In some embodiments, a tribological coating  616  may be used in addition to or in place of the protective coating  622 . For example, the electrically-insulating ceramic material, such as alumina, zirconia, yttria stabilized zirconia (YSZ) (e.g., 3% yttria stabilized zirconia), or the like 
     In some embodiments, the bottom termination plate  620  may be configured to operate as a buffer layer that physically separates the stack  300  and the manifold plate  380 . In particular, the bottom termination plate  620  may be configured to relieve thermal stress between the stack  300  and the manifold plate  380 . For example, as shown in  FIG.  10 B , the bottom termination plate  620  may comprise at least one compliant plate  621  that may be cut, scored, or split to form relief structures (e.g., cuts or grooves)  626  that allow for easy camber change. For example, the relief structures  626  may extend completely or partially through the bottom termination plate  620 . The relief structures (e.g., grooves)  626  may be formed in or adjacent to portions of the bottom termination plate  620  that contact the stack  300 . In some embodiments, the bottom termination plate  620  may be formed of multiple stacked compliant plates  621 , such as from 1 to 5 stacked relief structure plates, that are laterally separated from each other by the relief structures (e.g., cuts). In other embodiments, the manifold plate  380  may be configured to operate as a buffer layer. In particular, the manifold plate  380  may include one or more of the compliant plates  621 . 
     The column  602  may include stacked ring seals  636  configured to seal the fuel inlet and outlet openings  624  of the bottom termination plate  620  and corresponding inlet and outlet openings of the manifold plate  380 . The seals  636  may be formed of a glass or glass-ceramic material and may have a thickness ranging from about 100 μm to about 300 μm, such as from about 150 μm to about 250 μm, or about 200 μm, prior to sintering and compression. The protective coating  622  may be omitted from portions of the bottom termination plate  620  that contact the seals  636 . 
     Accordingly, the column  602  may include a mitigation structure configured to reduce stress applied to the stack  300 , due to a shape mismatch and/or coefficient of thermal expansion mismatch, between the stack  300  and the manifold plate  380 . The mitigation structure may also be configured to reduce electrical disconnections between the stack  300  and the manifold plate  380 . The mitigation structure may include the compliant layer  630 , the peripheral seal  634 , the seals  636 , and/or the bottom termination plate  620 . 
       FIG.  11    is a simplified exploded side view of a fuel cell column  604 , according to various embodiments of the present disclosure. The column  604  may be similar to the column  602 . As such, only the differences therebetween will be discussed in detail. 
     Referring to  FIG.  11   , the column  604  may include multiple conductive compliant layers, such as a first compliant layer  630 A and a second compliant layer  630 B. The compliant layers  630 A,  630 B may be formed of a respective conductive metal mesh, such as nickel mesh, for example. 
     In some embodiments, the compliant first and second layers  630 A,  630 B may be vertically separated from each other by a separator  644 , which may be formed of a metal sheet or foil, for example. For example, the separator  644  may be formed of Inconel 625, 446 stainless steel, Haynes alloy, ZMG232L alloy, or other suitable high temperature alloys. Without wishing to bound by a particular theory, it is believed that the first and second compliant layers  630 A,  630 B formed of a nickel mesh may be compressed and reduced in thickness to a different extent in different areas of the column  604 , and may thereby maintain electrical contact and compressive force across the entire areas thereof. The maximum extent of this deformation may determine the maximum curvature mismatch that can be accommodated. The deformation of the compliant layers  630 A,  630 B may depend on a variety of factors including wire thickness, oxidation state of the metal, compressive force applied, and/or other factors. Furthermore, stacking the first and second compliant layers  630 A,  630 B without the separator  644  may not increase the total compliance, since the mesh wires of the first and second compliant layers  630 A,  630 B may become interlaced, effectively creating a compliant layer of with double the wire density and a reduced thickness. 
     Therefore, separating the two compliant layers  630 A,  630 B with the separator  644  may effectively double the compliance. Multiple compliant layers  630 A,  630 B and separators  644  can be stacked in this way for even higher compliance. The separator  644  can be a continuous layer, or may be cut or split into 2, 4, or more pieces to improve compliance. In some embodiments, the separator  644  may include through holes. 
     The first compliant layer  630 A may be surrounded by a first peripheral seal  634 A, and the second compliant layer  62 BA may be surrounded by a second peripheral seal  634 B. The seals  634 A,  634 B may be formed of a glass or glass-ceramic material disposed over the perimeter of the manifold plate  380 . The seals  634 A,  634 B may have a “figure eight” horizontal configuration containing a perimeter and a seal dam. 
     In some embodiments, the column  604  may include a dummy solid oxide fuel cell between the two bottommost interconnects in the stack  300 . The dummy solid oxide fuel cell may be the same as the remaining solid oxide fuel cells  310  having a ceramic electrolyte in the stack  300 , except that the dummy solid oxide fuel cell is electrically bypassed by a spot-welded jumper or electrical contact (now shown) connecting the two bottommost interconnects. This way, if the dummy solid oxide fuel cell cracks due to CTE mismatch and/or camber, then it would not increase the resistance of the column  604  since the cracked dummy cell is electrically bypassed in the column  604 . 
     In other embodiments, the column  604  may include one or more optional dummy interconnects  640  that are similar to the interconnects  400  of the stack, but do not provide fuel or air to the fuel cells  310 . The dummy interconnect  640  may be a Cr—Fe alloy interconnect formed by powder metallurgy. 
     In yet other embodiments, the dummy interconnect  640  may be formed of a conductive high-temperature metal alloy, such as Inconel 625, SS446, Haynes alloy, ZMG232L alloy, or the like. In this case, the dummy interconnect  640  may have a shape of a fuel cell, and be located between the two bottommost interconnects  400  in the stack  300  in place of the bottom most solid oxide fuel cell in the stack  300 . The dummy interconnect  640  electrically shorts the two bottommost interconnects  400  in the stack  300 . The dummy interconnect  640  may include a protective coating  642  on the air side thereof. In particular, the protective coating  642  may be configured to reduce oxidation of the air side of the dummy interconnect  640 . In some embodiments, the protective coating  642  may be an LSM and/or MCO coating applied by APS or the like. In particular, a metal dummy interconnect  640  may provide improved resistance to breakage and/or fuel leakage, as compared to a ceramic dummy interconnect. 
     In various embodiments, the manifold plate  380  may include the recess  383  to at least partially accommodate the compliant layers  630 A,  630 B and/or the separator  644 . In particular, the recess  383  may have a depth ranging from about 100 μm to about 150 μm, such as about 120 μm. 
     Accordingly, the column  604  may include a mitigation structure configured to reduce stress applied to the stack  300 , due to a shape mismatch and/or coefficient of thermal expansion mismatch, between the stack  300  and the manifold plate  380 . The mitigation structure may also be configured to reduce electrical disconnections between the stack  300  and the manifold plate  380 . The mitigation structure may include the first compliant layer  630 A, the second compliant layer  630 B, the first peripheral seal  634 A, the second peripheral seal  634 B, and/or the dummy interconnect  640  or dummy fuel cell. 
       FIG.  12    is a simplified exploded side view of a fuel cell column  606 , according to various embodiments of the present disclosure. The column  606  may be similar to the column  600 . As such, only the differences therebetween will be discussed in detail. 
     Referring to  FIG.  12   , the fuel cell stack  300  of the column  606  may be in the odd configuration (as opposed to the stack  300  in the even configuration in the column  600  in  FIG.  9   ). As such, the air side of the lowermost interconnect  400 L may face the manifold plate  380 . The conductive compliant layer  630  and the peripheral seal  634  may be disposed between the top termination plate  610  the uppermost interconnect  400 U of the stack  300 . 
     The protective coating  612  may be formed on the upper surface of the top termination plate  610 , and may optionally be omitted from the bottom surface of the top termination plate  610  which faces the stack  300 . A second protective coating  618  may be formed on the bottom surface of a lowermost interconnect  400 L of the stack  300 . The coating  618  may be formed of the same materials as the coating  612  of the top termination plate  610 . In some embodiments, the coating  618  may be formed by contact printing and may have a thickness ranging from about 10 μm to about 50 μm, such as from about 20 μm to about 40 μm, or about 30 μm. For example, the coating  618  may have the same area and perimeter as the fuel cells  310  of the stack  300 . 
     The protective coating  382 , as described above with regard to  FIG.  5 A , may be disposed on the top and bottom surfaces of the manifold plate  380 . On the top surface of the manifold plate  380 , the coating  382  may have the same shape and area as the coating  618 . The coating  382  may be formed by the same methods and materials as the coating  612 . For example, the coating  382  may be formed of LSM applied by APS. The stack  300  may be connected to the manifold plate  380  by the ring-shaped manifold seals  614 . The coating  382  may be omitted from portions of the manifold plate  380  that contact the manifold seals  614 . 
     In some embodiments, the thickness of the coating  382  may be increased such that the coating  382  operates as a mitigation structure. For example, the coating  382  may have a thickness ranging from about 100 μm to about 550 μm, such as from about 120 μm to about 480 μm, or at least about 240 μm (e.g., 240 to 480 μm). 
       FIG.  13    is a simplified exploded side view of a fuel cell column  608 , according to various embodiments of the present disclosure. The column  608  may be similar to the column  604 . As such, only the differences therebetween will be discussed in detail. 
     Referring to  FIG.  13   , the fuel cell stack  300  of the column  608  may be in the odd configuration rather than in the even configuration shown in  FIG.  11   . As such, the air side of the lowermost interconnect  400 L may face the manifold plate  380 . The column  608  may include the first compliant layer  630 A, the second compliant layer  630 B, the first peripheral seal  634 A, the second peripheral seal  634 B, and the separator  644  located between the compliant layers  630 A and  630 B. 
     The column  608  may include a bottom termination plate  620  which separates the compliant layers  630 A,  630 B from the stack  300 . In particular, the bottom termination plate  620  may be configured to prevent the compliant layers  630 A,  630 B from being exposed to oxygen flowing though the stack  300 , in order to prevent oxidation of the compliant layers  630 A,  630 B. The bottom termination plate  620  may be formed of a conductive high-temperature metal alloy, such as Inconel 625, stainless steel 446, Haynes alloy, ZMG232L alloy, or the like. In some embodiments, the bottom termination plate  620  may include a spot-welded jumper (now shown). In other embodiments, the bottom termination plate  620  may be a dummy interconnect, similar to the chromium-iron alloy interconnects  400  formed by powder metallurgy which are located in the stack  300 . In still other embodiments, the bottom termination plate  620  may be formed of one or more compliant plates  621  containing relief structures  626 , as shown in  FIG.  10 B . 
     A protective coating  622  may be formed on the top surface of the bottom termination plate  620 , where the bottom termination plate  620  is exposed to air. The protective coating  622  may be similar to the protective coating  612 . For example, the coating  622  may be formed of LSM applied by APS. 
     In various embodiments, the top surface of any of the manifold plates  380  may be machined with an additional recess or pocket  383  to create the additional space for seals and/or the compliant layer(s)  630 A and/or  630 B. For example, a recess having a depth ranging from 80 μm to about 160 μm, such as from about 100 μm to about 140 μm, can be formed in the top of the manifold plate  380 . 
     In various embodiments, any of the manifold plates  380  described above may include relief structures, similar to the relief structures  626  shown in  FIG.  10 B . For example, any of the manifold plates  380  may contain grooves or may be formed of two or more plates laterally separated by relief structures (e.g., cuts) in order to facilitate expansion and contraction of the manifold plate  380 , and thereby reduce thermal stress applied to the corresponding fuel cells  310 . 
     Accordingly, the column  606  includes a mitigation structure configured to reduce stress applied to the stack  300 , due to a shape mismatch and/or coefficient of thermal expansion mismatch, between the stack  300  and the manifold plate  380 . The mitigation structure may also be configured to reduce electrical disconnections between the stack  300  and the manifold plate  380 . The mitigation structure may include the seals  614 ,  634 A,  634 B, the compliant layers  630 A,  630 B, the separator  644 , the bottom termination plate  620 , and/or the coating  622 . 
     In various embodiments, the thickness of one or more conductive layers  318  (see  FIGS.  3 A,  3 D ) of the fuel cell stack  300  may be increased to provide increased compliancy. For example, the conductive layer  318  (e.g., a nickel mesh) between the bottommost fuel cell  310  and at least one of the bottommost two interconnects  400  of the stack may be increased to at least 80 μm, such as to from about 100 μm to about 160 μm, to absorb thermal stress and prevent damage to the stack  300 . Thus, the nickel mesh between the bottom two interconnects may be thicker than the nickel meshes located between the remaining interconnects  400  and fuel cells  310  throughout the rest of the stack  300 . Thus, in one embodiment, metal meshes are located between the interconnects  400  and the fuel cells  310  in the stack  300 . In this embodiment, the mitigation structure comprises a bottom metal mesh located between the bottommost fuel cell and at least one of two bottommost interconnects in the stack, where the bottom metal mesh has a greater thickness than other metal meshes in the stack  300 . 
       FIG.  14 A  is a simplified exploded side view of a fuel cell column  609 , according to various embodiments of the present disclosure.  FIG.  14 B  is a photograph of a conductive mesh that may be used in the column  609  shown in  FIG.  14 A . The fuel cell column  609  is similar to the column  606  of  FIG.  12   . As such, only the difference therebetween will be discussed in detail. 
     Referring to  FIGS.  14 A and  14 B , the column  609  may include a wire mesh  631  as a compliant layer that electrically connects the stack  300  to the manifold plate  380 . The mesh  631  may be formed of wire bent that is bent into a wave pattern, such as a herringbone wave pattern as shown in  FIG.  14 B . The mesh  631  may be crimped to create peaks and troughs of controllable height to control the thickness of the wire mesh  631 . For example, the mesh  631  may have a thickness ranging from about 1 mm to about 20 mm, such as from about 1 mm to about 10 mm. The mesh  631  may be crimped to create peaks and troughs of controllable height to control the thickness of the wire mesh  631 . For example, the mesh  631  may have a thickness ranging from about 1 mm to about 20 mm, such as from about 1 mm to about 10 mm. 
     As described above, this mesh  631  may be formed of a material other than pure nickel. The mesh  631  may be formed of a metal alloy, such as Inconel 625, stainless steel 446, Inconel 600, Hastelloy X, Crofer 22, or the like. 
     In some embodiments, the mesh  631  may be fixed to the manifold plate  380 , for example by resistance welding. In particular, mesh  631  may be welded directly to an uncoated planar surface of the manifold plate  380 , along welding lines WL that extend along troughs of the mesh  631  where the mesh  631  contacts the manifold plate  380 . Welding the mesh  631  to the manifold plate  380  enhances the elasticity of the mesh under load by creating a spring-like structure, which allows the mesh  631  to adjust to changes to the camber-induced gap between the manifold plate  380  and the stack  300 . For example, changes in the power output of the stack  300  and/or reduction and oxidation processes within the stack  300 , may result in changes to the gap. However, the spring-like action of the mesh  631  allows the mesh  631  to remain in contact with and support the manifold plate  380  and the stack  300 , when changes to the gap occur. As such, the mesh  631  may be configured to function as a spring to maintain electrical contact and reduce the chance of cracking cells of the stack  300 , in a variety of operating conditions. 
     In various embodiments, a peripheral seal  634 , as described above with respect to  FIG.  9 A , may optionally be applied around the mesh  631 , in order to limit air exposure and/or oxidation of the mesh  631 . 
     In some embodiments, the mesh  631  may also be used in place of the compliant layer  630  at the top of the stack  300 . For example, the mesh  631  may be welded to the top termination plate  610 . In other embodiments, the mesh  631  may be disposed between the top of the stack  300  and the termination plate  610 , in the even configurations as shown in  FIGS.  9 A- 11   , or in place of any of the compliant layers  630  disclosed herein. 
     The manifold plates, coatings, and/or compliant layers disclosed herein may protect fuel cell stacks from damage due to CTE variations between the manifold plates and corresponding fuel cell stacks. 
     Fuel cell systems of the embodiments of the present disclosure are designed to reduce greenhouse gas emissions and have a positive impact on the climate. 
     The foregoing method descriptions are provided merely as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be appreciated by one of skill in the art the order of steps in the foregoing embodiments may be performed in any order. Words such as “thereafter,” “then,” “next,” etc. are not necessarily intended to limit the order of the steps; these words may be used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles “a,” “an” or “the” is not to be construed as limiting the element to the singular. Further, any step or component of any embodiment described herein can be used in any other embodiment. 
     The preceding description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.