Patent Publication Number: US-2023163324-A1

Title: Cell, cell stack device, module, and module housing device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cell, a cell stack device, a module, and a module housing device. 
     BACKGROUND OF INVENTION 
     In recent years, various fuel cell stack devices each including a plurality of fuel cells have been proposed as next-generation energy. In this technology, the plurality of fuel cells are each a type of cell capable of obtaining electrical power by using, as a reactive gas, a fuel gas such as a hydrogen-containing gas, and an oxygen-containing gas such as air. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: JP 2015-162357 A 
     SUMMARY 
     A cell according to an aspect of an embodiment includes an element portion and a support substrate. The support substrate includes a gas-flow passage through which the reactive gas flows in a first direction, and supports the element portion. The element portion includes a first portion having a first length in a second direction intersecting the first direction, and a second portion located on a downstream side in the gas-flow passage relative to the first portion, the second portion having a second length in the second direction different from the first length in the second direction. 
     Also, a cell stack device of the present disclosure includes a cell stack including a plurality of the cells described above. 
     Further, a module of the present disclosure includes the cell stack device described above and a storage container in which the cell stack device is stored. 
     Additionally, a module housing device of the present disclosure includes the module described above, an auxiliary device for operating the module, and an external case that houses the module and the auxiliary device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a horizontal cross-sectional view illustrating an example of a cell according to a first embodiment. 
         FIG.  1 B  is a side view illustrating an example of the cell according to the first embodiment when viewed from an air electrode side. 
         FIG.  1 C  is a side view illustrating an example of the cell according to the first embodiment when viewed from an interconnector side. 
         FIG.  2 A  is a perspective view illustrating an example of a cell stack device according to the first embodiment. 
         FIG.  2 B  is a cross-sectional view taken along a line X-X illustrated in  FIG.  2 A . 
         FIG.  2 C  is a top view illustrating an example of the cell stack device according to the first embodiment. 
         FIG.  3    is a side view illustrating an example of a cell according to a variation of the first embodiment when viewed from an air electrode side. 
         FIG.  4    is an exterior perspective view illustrating an example of the module according to the first embodiment. 
         FIG.  5    is an exploded perspective view schematically illustrating an example of a module housing device according to the first embodiment. 
         FIG.  6 A  is a cross-sectional view illustrating an example of a cell stack device according to a second embodiment. 
         FIG.  6 B  is a horizontal cross-sectional view illustrating an example of a cell according to the second embodiment. 
         FIG.  6 C  is a side view illustrating an example of the cell according to the second embodiment when viewed from an air electrode side. 
         FIG.  7 A  is a side view illustrating an example of a cell according to a variation of the second embodiment when viewed from an air electrode side. 
         FIG.  7 B  is a side view illustrating another example of a cell according to a variation of the second embodiment when viewed from an air electrode side. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of a cell, a cell stack device, a module, and a module housing device disclosed herein will be described in detail with reference to the accompanying drawings. The disclosure is not limited by the following embodiments. 
     Note that the drawings are schematic and that the dimensional relationships between elements, the proportions thereof, or the like may differ from actual dimensions and the like. Further, the dimensional relationships, proportions, or the like may differ between drawings. 
     First Embodiment 
     Configuration of Cell 
     First, with reference to  FIGS.  1 A to  1 C , a solid oxide fuel cell will be described as an example of a cell according to a first embodiment. 
       FIG.  1 A  is a horizontal cross-sectional view illustrating an example of a cell  1  according, to the first embodiment,  FIG.  1 B  is a side view illustrating an example of the cell  1  according to the first embodiment when viewed from an air electrode  5  side, and  FIG.  1 C  is a side view illustrating an example of the cell  1  according to the first embodiment when viewed from an interconnector  6  side. Note that  FIGS.  1 A to  1 C  each illustrate an enlarged portion of a configuration of the cell  1 . 
     In the example illustrated in  FIGS.  1 A to  1 C , the cell  1  is hollow and flat plate-shaped, and has a long thin plate shape. As illustrated in  FIG.  1 B , the shape of the entire cell  1  when viewed from the side is a rectangle having a side length of, for example, 5 cm to 50 cm in a length direction L and a length of, for example, 1 cm to 10 cm in a width direction W orthogonal to the length direction L. The thickness of the entire cell  1  in a thickness direction T is, for example, 1 mm to 5 mm. 
     As illustrated in  FIG.  1 A , the cell  1  includes a support substrate  2  that is electrically conductive, an element portion  7 , and the interconnector  6 . The support substrate  2  has a pillar shape having a pair of flat surfaces n 1  and n 2  on opposite sides from each other, and a pair of arc-shaped side surfaces m connecting the flat surfaces n 1  and n 2 . 
     The element portion  7  is located on the flat surface n 1  of the support substrate  2 . The element portion  7  includes a fuel electrode  3 , a solid electrolyte layer  4 , and the air electrode  5 . Additionally, in the example illustrated in  FIG.  1 A , the interconnector  6  is located on the flat surface n 2  of the cell  1 . 
     Further, as illustrated in  FIG.  1 B , the air electrode  5  does not extend to the lower end or the upper end of the cell  1 . At a lower end portion of the cell  1 , only the solid electrolyte layer  4  is exposed to the surface. The shape of the air electrode  5  in a side view will be described later. 
     Furthermore, as illustrated in  FIG.  1 C , the interconnector  6  may extend to the lower end and the upper end of the cell  1 . At the lower end portion of the cell  1 , the interconnector  6  and the solid electrolyte layer  4  are exposed to the surface. Note that, as illustrated in  FIG.  1 A , the solid electrolyte layer  4  is exposed at the surfaces of the pair of arc-shaped side surfaces m of the cell  1 . The interconnector  6  may not extend to the lower end of the cell  1 . 
     Hereinafter, each constituent member constituting the cell  1  will be described. 
     The support substrate  2  includes gas-flow passages  2   a  through which a reactive gas flows. An example of the support substrate  2  illustrated in  FIG.  1 A  includes six of the gas-flow passages  2   a.  The gas-flow passages  2   a  are located along the length direction L (see  FIG.  1 B ) that intersects the width direction W The support substrate  2  has gas permeability, and allows the reactive gas flowing in the gas-flow passages  2   a  to permeate to the fuel electrode  3 . The support substrate  2  may have electrical conductivity. The support substrate  2  having electrical conductivity causes electricity generated in the element portion to be collected in the interconnector  6 . 
     The air electrode  5  includes portions  5   a.  and  5   b . The portion  5   b  is located on one end side of the cell  1  in the length direction L, and the portion  5   a  is located on the other end side in the length direction L. The portions  5   a  and  5   b  each have a predetermined length in the width direction W, and each extend in the length direction L. 
     In the example illustrated in  FIG.  1 B , the fuel gas as the reactive gas flows through the gas-flow passage  2   a  located along the length direction L from the one end side to the other end side of the cell  1 . That is, the portion  5   b  is located on an upstream side in the gas-flow passage  2   a  through which the fuel gas flows, and the portion  5   a  is located on a downstream side in the gas-flow passage  2   a.    
     Here, the element portion  7  refers to a portion where the fuel electrode  3  and the air electrode  5  overlap with each other with the solid electrolyte layer  4  interposed therebetween. That is, in the present embodiment, the element portion  7  viewed in plan view matches the portion where the air electrode  5  is located. In the element portion  7 , heat is generated during power generation. The heat generation amount in the element portion  7  correlates to the power generation amount. Thus, when the length of the element portion  7  in the width direction W is made constant, the heat generation amount is approximately the same over the entire length direction L. 
     However, a portion of the heat generated at the one end side of the cell  1  is transmitted along the flow of the fuel gas to the other end side of the cell  1  on the downstream side in the gas-flow passage  2   a , so that a temperature gradient tends to occur in the cell  1  along the length direction L. That is, the other end side of the cell  1  located on the downstream side in the gas-flow passage  2   a  is more likely to be higher in temperature than the one end side located on the upstream side. When a temperature gradient occurs in the cell  1 , on the other end side where the temperature becomes high, the power generation amount and the heat generation amount are larger than that on the one end side and deterioration progresses further. Thus, there is a concern that the battery performance of the cell  1  will deteriorate. 
     Therefore, in the present embodiment, the length of the element portion  7  in the width direction W as the second direction differs between the upstream side and the downstream side in the length direction L as the first direction. In an embodiment, the air electrode  5  serving as a first electrode includes the portion  5   b  and the portion  5   a , which is located on the downstream side in the gas-flow passage  2   a  relative to the portion  5   b  and has a smaller length in the width direction W as the second direction than the portion  5   b.  When a length of the element portion  7  corresponding to the portion  5   b  in the width direction W is defined as a first length, and a length of the element portion  7  corresponding to the portion  5   a  in the width direction W is defined as a second length, the second length is smaller than the first length. 
     This can reduce the to ten gradient in the cell  1  along the length direction L. Thus, according to the embodiment, a decrease in battery performance can be reduced. 
     The material of the support substrate  2  contains, for example, an iron group metal component and an inorganic oxide. For example, the iron group metal component may be Ni (nickel) and/or NiO. For example, the inorganic oxide may be a specific rare earth element oxide. 
     As the material of the fuel electrode  3 , a commonly known material may be used. As the fuel electrode  3 , porous electrically conductive ceramics, for example, ceramics that contain ZrO 2  in which calcium oxide, magnesium oxide, or a rare earth element oxide is solid-solved and Ni and/or NiO, may be used. As the rare earth element oxide, for example, Y 2 O 3  or the like is used. Hereinafter, ZrO 2  in which calcium oxide, magnesium oxide, or a rare earth element oxide is solid-solved may be referred to as stabilized zirconia. Stabilized zirconia also includes partially stabilized zirconia. 
     The solid electrolyte layer  4  is an electrolyte and bridges ions between the fuel electrode  3  and the air electrode  5 . At the same time, the solid electrolyte layer  4  has gas blocking properties, and reduces leakage of the fuel gas and the oxygen-containing gas. 
     The material of the solid electrolyte layer  4  may be, for example, ZrO 2  in which 3 mol % to 15 mol % of a rare earth element oxide is solid-solved. As the rare earth element oxide, for example, Y 2 O 3  or the like is used. Note that another material may be used as the material of the solid electrolyte layer  4 , as long as the material has the characteristic described above. 
     The material of the air electrode  5  is not particularly limited, as long as the material is commonly used for an air electrode. The material of the air electrode  5  may be, for example, an electrically conductive ceramic such as an ABO 3  type perovskite oxide. 
     The material of the air electrode  5  may be, for example, a composite oxide in which Sr and La coexist in an A site. Examples of such a composite oxide include La x Sn 1-x Co y Fe 1-y O 3 , La x Sr 1-x MnO 3 , La x Sr 1-x FeO 3 , and La x Sr 1-x CoO 3 . Here, x is 0&lt;x&lt;1, and y is 0&lt;y&lt;1. 
     Further, the air electrode  5  has gas permeability. The open porosity of the air electrode  5  may be, for example, 20% or more, and particularly may be in a range from 30% to 50%. 
     As the material of the interconnector  6 , a lanthanum chromite-based perovskite-type oxide (LaCrO 3 -based oxide), a lanthanum strontium titanium-based perovskite-type oxide (LaSrTiO 3 -based oxide), or the like may be used. These materials have electrical conductivity, and are neither reduced nor oxidized even when in contact with a fuel gas such as a hydrogen-containing gas or an oxygen-containing gas such as air. 
     Further, the interconnector  6  is dense, and reduces the leakage of both the fuel gas flowing through the gas-flow passages  2   a  located inside the support substrate  2  and the oxygen-containing gas flowing outside the support substrate  2 . The interconnector  6  may have a relative density of 93% or more, particularly 95% or more. 
     Configuration of Cell Stack Device 
     Next, a cell stack device  10  according to the present embodiment that uses the cell  1  described above will be described with reference to  FIGS.  2 A to  2 C .  FIG.  2 A  is a perspective view illustrating an example of the cell stack device  10  according to the first embodiment,  FIG.  2 B  is a cross-sectional view taken along a line A-A illustrated in  FIG.  2 A , and  FIG.  2 C  is a top view illustrating an example of the cell stack device  10  according to the first embodiment. 
     As illustrated in  FIG.  2 A , the cell stack device  10  includes a cell stack  11  that includes a plurality of the cells  1  arrayed (stacked) in the thickness direction T (see  FIG.  1 A ) of the cell  1 , and fixing members  12 . 
     The fixing member  12  includes a bonding material  13  and a support member  14 . The support member  14  supports the cells  1 . The bonding material  13  bonds the cells  1  with the support member  14 . Further, the support member  14  includes support bodies  15  and a gas tank  16 . The support bodies  15  and the gas tank  16 , as the support member  14 , are made of metal and are electrically conductive. 
     As illustrated in  FIG.  2 B , the support body  15  includes an insertion hole  15   a  into which the lower end portions of the plurality of cells  1  are inserted. The lower end portions of the plurality of cells  1  and an inner wall of the insertion hole  15   a,  are bonded by using the bonding material  13 . 
     The gas tank  16  includes opening portions through which a reactive gas is supplied to the plurality of cells  1  via the insertion hole  15   a , and recessed grooves  16   a  located around the opening portions. An outer peripheral end portion of each support body  15  is fixed to the gas tank  16  by a fixing material  21  filled in the recessed grooves  16   a  of the gas tank  16 . 
     In the example illustrated in  FIG.  2 A , the fuel gas is stored in an internal space  22  formed by the support bodies  15  and the gas tank  16 , which constitute the support member  14 . The gas tank  16  includes a gas flow pipe  20  connected thereto. The fuel gas is supplied to the gas tank  16  through this gas flow pipe  20 , and is supplied from the gas tank  16  to the gas-flow passages  2   a  (see  FIG.  1 A ) inside the cell  1 . The fuel gas supplied to the gas tank  16  is produced by a reformer  102  (see  FIG.  4   ), which will be described below. 
     A hydrogen-rich fuel gas can be produced, for example, by steam reforming a raw fuel. When the fuel gas is produced by the steam reforming, the fuel gas contains water vapor. 
     In the example illustrated in  FIG.  2 A , two rows of the cell stacks  11  each including a plurality of the cells  1 , two support bodies  15 , and the gas tank  16  are provided. The two rows of cell stacks  11  each have a plurality of the cells  1 . Each of the cell stacks  11  is fixed to a corresponding one of the support bodies  15 . An upper surface of the gas tank  16  includes two through holes. Each of the support bodies  15  is disposed in a corresponding one of the through holes. The internal space  22  is formed by the one gas tank  16  and the two support bodies  15 . 
     The insertion hole  15   a  has, for example, an oval shape in a top surface view. The length of the insertion hole  15   a,  for example, in an arrangement direction of the cells  1 , that is, the thickness direction T of the cells  1 , is greater than the distance between two end current collection members  17  located at two ends of the cell stack  11 . The width of the insertion hole  15   a  is, for example, greater than the length of the cell  1  in the width direction W (see  FIG.  1 A ). Note that the shape of the insertion hole  15   a.  may be substantially rectangular in the arrangement direction of the cells  1 . 
     As illustrated in  FIG.  2 B , the bonding material  13  is filled and solidified in a bonding portion between the inner wall of the insertion hole  15   a  and the lower end portions of the cells  1 . As a result, the inner wall of the insertion hole  15   a  and the lower end portions of the plurality of cells  1  are bonded and fixed, and the lower end portions of the cells  1  are bonded and fixed to each other. The gas-flow passages  2   a  of each cell  1  communicate with the internal space  22  of the support member  14  at a lower end portion of the cell  1 . 
     As the bonding material  13  and the fixing material  21 , a material having low electrical conductivity such as glass can be used. As a specific material of the bonding material  13  and the fixing material  21 , an amorphous glass or the like may be used, or particularly, a crystallized glass or the like may be used. 
     As the crystallized glass, for example, any of SiO 2 —CaO-based, MgO—B 2 O 3 -based, La 2 O 3 —B 2 O 3 —MgO-based, La 2 O 3 —B 2 O 3 —ZnO-based, and SiO 2 —CaO —ZnO-based materials may be used, or particularly, a SiO 2 —MgO-based material may be used. 
     Further, as illustrated in  FIG.  2 B , electrically conductive members  18  are interposed between adjacent cells  1  of the plurality of cells  1 . The electrically conductive member  18  electrically connects in series the fuel electrode  3  of one of the adjacent cells  1  with the air electrode  5  of the other of the adjacent cells  1 . More specifically, the electrically conductive member  18  connects the interconnector  6  electrically connected to the fuel electrode  3  of one of the adjacent cells  1 , and the air electrode  5  of the other of the adjacent cells  1 . 
     Further, as illustrated in  FIG.  2 B , the end current collection members  17  are electrically connected to the cells  1  located at the outermost sides in the arrangement direction of the plurality of cells  1 . The end current collection members  17  are each connected to an electrically conductive portion  19  protruding outward from the cell stack  11 . The electrically conductive portion  19  collects electricity generated by power generation of the cells  1 , and draws the electricity to the outside. Note that the end current collection members  17  are not illustrated in  FIG.  2 A . 
     Further, as illustrated in  FIG.  2 C , in the cell stack device  10 , two cell stacks  11 A and  11 B, which are connected in series, function as one battery. Thus, the electrically conductive portion  19  of the cell stack device  10  is divided into a positive electrode terminal  19 A, a negative electrode terminal  19 B, and a connection terminal  19 C. 
     The positive electrode terminal  19 A functions as a positive electrode when the electrical power generated by the cell stack  11  is output to the outside, and is electrically connected to the end current collection member  17  on a positive electrode side in the cell stack  11 A. The negative electrode terminal  19 B functions as a negative electrode when the electrical power generated by the cell stack  11  is output to the outside, and is electrically connected to the end current collection member  17  on a negative electrode side in the cell stack  11 B. 
     The connection terminal  19 C electrically connects the end current collection member  17  on a negative electrode side in the cell stack  11 A and the end current collector  17  on a positive electrode side in the cell stack  11 B. 
     Variation 
       FIG.  3    is a side view illustrating an example of a cell according to a variation of the first embodiment when viewed from an air electrode side. As illustrated in  FIG.  3   , the air electrode  5  differs from the air electrode  5  according to the above-described embodiment in that the air electrode  5  has a substantially trapezoidal shape in which an end portion  5   c  on a downstream side in the gas-flow passage  2   a  (see  FIG.  1 A ) through which the fuel gas flows has a length in the width direction W smaller than an end portion  5   d  on an upstream side. The end portion of the element portion  7 , which is located on the upstream side in the gas-flow passage  2   a  and corresponds to the end portion  5   d,  corresponds to a first portion of the element portion  7  in the cell  1  according to the embodiment. The end portion of the element portion  7 , which is located on the downstream side in the gas-flow passage  2   a  and corresponds to the end portion  5   c,  corresponds to a second portion of the element portion  7  in the cell  1  according to the embodiment. Additionally, when the length of the first portion in the width direction W is defined as a first length, and the length of the second portion in the width direction W is defined as a second length, the second length is smaller than the first length. 
     In this way, the temperature gradient along the length direction L of the cell  1  can also be reduced by continuously varying the length of the element portion  7  in the width direction W. Accordingly, the cell  1  according to the present variation can reduce a decrease in battery performance. 
     Note that in the cell  1  according to the above-described embodiment and the variation, the second portion of the element portion  7  is located at the end portion on the downstream side in the gas-flow passage  2   a.  but may be located in a region on the downstream side in the gas-flow passage  2   a  relative to the first portion. 
     Module 
     Next, a module  100  according to the embodiment of the present disclosure in which the above-mentioned cell stack device  10  is used will be described with reference to  FIG.  4   .  FIG.  4    is an exterior perspective view illustrating the module according to the embodiment, and illustrates a state in which a front surface and a rear surface, which are portions of a storage container  101 , are removed and the cell stack device  10 , which is a fuel cell stored inside the module, is extracted to the rear. 
     As illustrated in  FIG.  4   , the module  100  includes the storage container  101  and the cell stack device  10  stored in the storage container  101 . The reformer  102  is disposed above the cell stack device  10 . 
     The reformer  102  generates a fuel gas by reforming a raw fuel such as natural gas or kerosene, and supplies the fuel gas to the cell  1 . The raw fuel is supplied to the reformer  102  through a raw fuel supply pipe  103 . The reformer  102  may include a vaporizing unit  102   a  for vaporizing water and a reforming unit  102   b.  The reforming unit  102   b  includes a reforming catalyst (not illustrated) for reforming the raw fuel into a fuel gas. The reformer  102  can perform steam reforming, which is a highly efficient reformation reaction. 
     Then, the fuel gas generated by the reformer  102  is supplied to the gas-flow passages  2   a  (see  FIG.  1 A ) of the cell  1  through the gas flow pipe  20 , the gas tank  16 , and the support member  14 . 
     Furthermore, in the module  100  having the above-mentioned configuration, the temperature in the module  100  during normal power generation is approximately from 500° C. to 1000° C. due to combustion of the gas and power generation by the cells  1 . 
     With the module  100  having such a configuration, as mentioned above, the module  100  can be configured to suppress deterioration in battery performance by including the cell stack device  10  that reduces deterioration in battery performance. 
     Module Housing Device 
       FIG.  5    is an exploded perspective view illustrating an example of a module housing device according to the embodiment. A module housing device  110  according to the embodiment includes an external case  111 , the module  100  illustrated in  FIG.  4   , and an auxiliary device (not illustrated). The auxiliary device operates the module  100 . The module  100  and the auxiliary device are housed in the external case  111 . Note that some of the configuration is not illustrated in  FIG.  5   . 
     The external case  111  of the module housing device  110  illustrated in  FIG.  5    includes supports  112  and external plates  113 , A dividing plate  114  vertically partitions the interior of the external case  111 . The space above the dividing plate  114  in the external case  111  is a module housing chamber  115  in which the module  100  is housed, and the space below the dividing plate  114  in the external case  111  is an auxiliary device housing chamber  116  in which the auxiliary device configured to operate the module  100  is housed. Note that FIG.  5  does not illustrate the auxiliary device housed in the auxiliary device housing chamber  116 . 
     Further, the dividing plate  114  includes an air flow communication opening  117  that causes air in the auxiliary device housing chamber  116  to flow into the module housing chamber  115  side. The external plate  113  constituting the module housing chamber  115  includes an exhaust opening  118  for exhausting the air inside the module housing chamber  115 . 
     With the module housing device  110  having such a configuration, as described above, the module housing device  110  can reduce deterioration in battery performance by including, in the module housing chamber  115 , the module  100  that reduces deterioration in battery performance. 
     Second Embodiment 
     Subsequently, a cell stack device and a cell according to a second embodiment will be described with reference to  FIGS.  6 A to  6 C ,  FIG.  6 A  is a cross-sectional view illustrating an example of the cell stack device according to the second embodiment.  FIG.  6 B  is a horizontal cross-sectional view illustrating an example of the cell according to the second embodiment.  FIG.  6 C  is a side view illustrating an example of the cell according to the second embodiment when viewed from an air electrode side. 
     As illustrated in  FIG.  6 A , in the cell stack device  10 A according to the second embodiment, a plurality of support substrates  2 , each supporting a plurality of the element portions  7 , extend in the length direction L from a pipe  22   a  through which the fuel gas flows. This configuration constitutes each cell  1 A. The gas-flow passage  2   a  through which gas flows from the pipe  22   a  is provided inside the support substrate  2  constituting each cell  1 A. The cells  1 A are connected in series to each other via the electrically conductive member  18 . 
     As illustrated in  FIG.  6 B , the cell  1 A includes the support substrate  2 , a pair of the element portions  7 , and sealing portions  8 . The support substrate  2  has a pillar shape having a pair of flat surfaces n 1  and n 2  on opposite sides from each other, and a pair of arc-shaped side surfaces m connecting the flat surfaces n 1  and n 2 . 
     The pair of element portions  7  are located facing each other on the flat surfaces n 1  and n 2  of the support substrate  2 . Additionally, the sealing portions  8  are located in a manner to cover the side surfaces m of the support substrate  2 . 
     As illustrated in  FIG.  6 C , the cell  1 A includes a plurality of the air electrodes  5  on the flat surface side, for example. The plurality of air electrodes  5  include air electrodes  5 A to  5 C located along the length direction L of the cell  1 A. Each of the air electrodes  5 A to  5 C constitutes each element of the element portion  7 . The air electrode  5 C is located on one end of the cell  1 A in the length direction L, and the air electrode  5 A is located on the other end in the length direction L. The air electrode  5 B is located between the air electrodes  5 A and  5 C. The cell  1  may have a plurality of air electrodes on the flat surface n 2  side as well as on the flat surface n 1  side. 
     Furthermore, the fuel gas flows in the gas-flow passage  2   a  from one end side to the other end side of the cell  1 A. As described above, in the cell  1 A located on the downstream side in the gas-flow passage  2   a,  the temperature rises higher than on the upstream side, and there is a concern that battery performance is deteriorated due to this temperature gradient. 
     Accordingly, in the present embodiment, the length of the air electrode  5  in the width direction W located on the downstream side in the length direction L is reduced. In the embodiment, the length of the air electrode  5  serving as the first electrode in the width direction W is smaller in the element portion  7  located on the downstream side in the gas-flow passage  2   a  than in the element portion  7  located on the upstream side of the gas-flow passage  2   a.  Specifically, when the element portion  7  corresponding to the air electrode  5 A located on the downstream side in the gas-flow passage  2   a  is defined as a second element and the element portion  7  corresponding to the air electrode  5 C located on the upstream side in the gas-flow passage  2   a  relative to the air electrode  5 A is defined as a first element, a second length of the second element in the width direction W is smaller than a first length of the first element in the width direction W. 
     This can reduce the temperature gradient in the cell  1  along the length direction L. Thus, according to the embodiment, a decrease in battery performance can be reduced. 
     In the example illustrated in  FIG.  6 C , a third length, which is the length in the width direction W of a third element corresponding to the air electrode  5 B, is defined as the same as the first length, which is the length in the width direction W of the first element corresponding to air electrode  5 C. However, the third length may be the same as the second length, for example. 
     Variation 
       FIG.  7 A  is a side view illustrating an example of a cell according to a variation of the second embodiment when viewed from the air electrode side.  FIG.  7 B  is a side view illustrating another example of a cell according to a variation of the second embodiment when viewed from an air electrode side. 
     The cell  1 A illustrated in  FIG.  7 A  differs from the cell  1 A according to the above-described embodiment in that each element of the element portions  7  corresponding to the air electrodes  5 A to  5 C located along the length direction L has a different length in the width direction W. Specifically, the length in the width direction W of the element portion  7  corresponding to the air electrode  5  is smaller in the air electrode  5 B than in the air electrode  5 C located on the upstream side in the length direction L, and the length in the width direction W of the element portion  7  corresponding to the air electrode  5  is smaller in the air electrode  5 A than in the air electrode  5 B. 
     The cell  1 A illustrated in  FIG.  7 B  differs from the cell  1 A illustrated in  FIG.  7 A  in that each element of the element portions  7  corresponding to the air electrodes  5 A to  5 C has a substantially trapezoidal shape. In this shape, an end portion on the downstream side in the gas-flow passage  2   a  through which the fuel gas flows has a length in the width direction W smaller than that of an end portion on the upstream side. Specifically, the element portion  7  corresponding to the air electrode  5 A located on the downstream side in the gas-flow passage  2   a  is defined as a second element, and the element portion  7  corresponding to the air electrode  5 C located on the upstream side in the gas-flow passage  2   a  relative to the air electrode  5 A is defined as a first element. An upstream end of the first element is a first portion having a first length in the width direction W, and a downstream end of the first element is a second portion having a second length smaller than the first length in the width direction W. An upstream end of the second element is a third portion having a third length in the width direction W, and a downstream end of the second element is a fourth portion having a fourth length smaller than the third length in the width direction W. 
     In this way, the temperature gradient along the length direction L of the cell  1  can be reduced even by continuously varying the length of the air electrode  5  in the width direction W. Accordingly, the cell  1  according to the present variation can reduce a decrease in battery performance. 
     In the examples illustrated in  FIGS.  7 A and  7 B , the length in the width direction W of each element corresponding to each air electrode  5  is gradually changed from upstream to downstream in the gas-flow passage  2   a,  but no limitation is intended. For example, in  FIG.  7 A , the length in the width direction W of the element corresponding to the air electrode  5 B may be larger than the length in the width direction W of the second element corresponding to the air electrode  5 A, or may be smaller than the length in the width direction W of the first element corresponding to the air electrode  5 C. 
     In  FIG.  7 B  for example, at least one of the elements of the element portions  7  corresponding to the air electrodes  5 A to  5 C may have a substantially trapezoidal shape in plan view, as illustrated. 
     Other Variations 
     Subsequently, a cell stack device according to other variations of the embodiment will be described. 
     In the embodiments described above, a case where the hollow flat plate-shaped support substrate is used has been described as an example; however, the disclosure can also be applied to a cell stack device that uses a cylindrical support substrate. 
     Further, in the above-described embodiments, an example is illustrated in which the fuel electrode is provided on the support substrate and the air electrode is disposed on the surface of the cell. However, the disclosure can also be applied to an opposite arrangement, namely, to a cell stack device in which the air electrode is provided on the support substrate and the fuel electrode is disposed on the surface of the cell. 
     Further, in the above-described embodiment, the “cell”, the “cell stack device”, the “module”, and the “module housing device” are exemplified by a fuel cell, a fuel cell stack device, a fuel cell module, and a fuel cell device, respectively. However, these components may also be exemplified by an electrolytic cell, an electrolytic cell stack device, an electrolytic module, and an electrolytic device, respectively. 
     While the present disclosure has been described in detail, the present disclosure is not limited to the above-mentioned embodiments, and various changes, improvements, or the like can be made without departing from the gist of the present disclosure. 
     As described above, the cell  1  according to the embodiment includes the element portion  7  and the support substrate  2 . The support substrate  2  includes the gas-flow passages  2   a  through which the reactive gas flows in the first direction, and supports the element portion  7 . The element portion  7  includes a first portion having a first length in a second direction intersecting the first direction, and a second portion located on a downstream side in the gas-flow passage  2   a  relative to the first portion and having a second length different from the first length, in the second direction. This can enhance the durability of the cell  1 . 
     Also, the cell stack device  10  according to the embodiment includes a plurality of the cells described above. This can enhance the durability of the cell stack device  10 . 
     Further, the module  100  according to the embodiment includes the cell stack device  10  described above, and the storage container  101  in which the cell stack device  10  is stored. As a result, the module  100  can be configured to reduce a deterioration in battery performance. 
     Further, the module housing device  110  according to the embodiment includes the module  100  described above, the auxiliary device for operating the module  100 , and the external case that houses the module  100  and the auxiliary device. As a result, the module housing device  110  can be configured to reduce a deterioration in battery performance. 
     Note that the embodiments disclosed herein are exemplary in all respects and not restrictive. The above-described embodiments can be embodied in a variety of forms. Furthermore, the above-described embodiments may be omitted, replaced, or changed in various ways without departing from the scope of the appended claims and the gist thereof. 
     REFERENCE SIGNS LIST 
       1  Cell 
       10  Cell stack device 
       11  Cell stack 
       12  Fixing member 
       13  Bonding material 
       14  Support member 
       15  Support body 
       16  Gas tank 
       17  End current collection member 
       18  Electrically conductive member 
       100  Module 
       110  Module housing device