JP7578018B2 - Fuel cell and fuel cell stack - Google Patents

Description

The present invention relates to a fuel cell and a fuel cell stack that constitute a solid oxide fuel cell.

Patent document 1 describes a fuel cell stack made up of cells in which current collectors with lattice-shaped openings are joined to both sides of a flat electrode reactant. In addition, in the fuel cell stack of Patent document 1, adjacent cells are electrically connected by connecting the external lead-out terminals located point-symmetrically in each cell with the current collectors.

Japanese Patent Application Publication No. 06-060905

The electrode catalyst layer of a fuel cell is generally formed of a thin film of several tens of microns, so there is a large ohmic loss when current flows in the surface direction. If a current collector with lattice-shaped openings is used as the current collector, current flows through the current collector in the lattice part connected to the current collector. However, in the opening part, the current flows in the surface direction within the electrode catalyst layer. Therefore, when a current collector with lattice-shaped openings is used, there is a large ohmic loss. As a result, there is a problem of loss of generated power (energy) from the fuel cell stack.

The present invention aims to provide a solid oxide fuel cell and a fuel cell stack that reduce ohmic losses.

A fuel cell according to an embodiment of the present invention is a fuel cell constructed by stacking an anode layer, a cathode layer, and a solid electrolyte layer sandwiched between the anode layer and the cathode layer. The fuel cell further includes a first metal porous body layer, a first metal frame, a second metal porous body layer, and a second metal frame. The first metal porous body layer is formed in a flat plate shape by a metal porous body having a plurality of pores communicating in the surface direction, sandwiches the anode layer together with the solid electrolyte layer, and supplies anode gas to the anode layer through the plurality of pores. The first metal frame is electrically connected to the anode layer through the first metal porous body layer by electrically connecting to the outer periphery of the first metal porous body layer, and supports the first metal porous body layer. The second metal porous body layer is formed in a flat plate shape by a metal porous body, sandwiches the cathode layer together with the solid electrolyte layer, and supplies cathode gas to the cathode layer through the plurality of pores. The second metal frame is electrically connected to the second metal porous layer at the outer periphery of the second metal porous layer, thereby electrically connecting to the cathode layer via the second metal porous layer and supporting the second metal porous layer.

The present invention provides a solid oxide fuel cell and a fuel cell stack with reduced ohmic losses.

FIG. 1 is an external perspective view of a cell stack. FIG. 2 is an exploded perspective view of the cell stack. FIG. 3 is an exploded perspective view of the cell. FIG. 4 is a cross-sectional view of the cell. FIG. 5 is a partial cross-sectional view of the stack. FIG. 6 is an explanatory diagram showing the flow of the anode gas. FIG. 7 is an explanatory diagram showing the flow of the cathode gas. FIG. 8 is an explanatory diagram showing a mode of supply of anode gas and cathode gas via a metal porous layer. FIG. 9 is an explanatory diagram showing paths along which current flows in a cell and a cell stack. FIG. 10 is a cross-sectional view of the cell of the first comparative example. FIG. 11 is an explanatory diagram showing a path of a current flowing through a cell of the first comparative example. FIG. 12 is an explanatory diagram showing a defect caused by misalignment of a grid current collector. FIG. 13 is a schematic cross-sectional view of a cell stack and a cell according to a second comparative example. FIG. 14 is an explanatory diagram showing the shape of the active area, the installation range of the bus bar, and the current path. FIG. 15 is an explanatory diagram showing the installation range of the busbar and the current path. FIG. 16 is a graph showing the temperature distribution in the active area.

The following describes an embodiment of the present invention with reference to the drawings.

[Cell stack structure]
FIG. 1 is an external perspective view of a cell stack 100. The cell stack 100 is a fuel cell stack (solid oxide fuel cell stack) used in a solid oxide fuel cell (SOFC). The cell stack 100 is formed by arranging a plurality of solid oxide fuel cells (fuel cell) in a stacked manner and electrically connecting each of the solid oxide fuel cell cells. A fuel cell system is configured using one or a plurality of cell stacks 100. Hereinafter, each solid oxide fuel cell constituting the cell stack 100 will be referred to as a fuel cell, or more simply, a cell 10. The cell 10 may generally be referred to as a single cell.

As shown in FIG. 1, the cell stack 100 is generally flat overall. Therefore, the cells 10 that make up the cell stack 100 are also flat. The cell stack 100 is generally rectangular, and the surface perpendicular to the stacking direction of the cells 10 (hereinafter referred to as the stacking direction) is generally rectangular.

Hereinafter, with respect to the cell stack 100 and cells 10, etc., the surface perpendicular to the stacking direction of the cells 10 will simply be referred to as the surface, without distinction between the front and back. The short direction of the surface will be the X direction, the long direction will be the Y direction, and the stacking direction of the cells 10 will be the Z direction. In the cell stack 100 and cells 10, etc., the surfaces parallel to the Z direction will be referred to as the side. Also, with respect to the cell stack 100 and cells, etc., the X direction, Y direction, and Z direction may be referred to as the horizontal direction, vertical direction, and height direction (or thickness direction), respectively. The positive direction of each of the X, Y, and Z directions is defined to form a right-handed system.

The negative end in each of the X, Y and Z directions is called the "base end" and the positive end is called the "tip end". With respect to the direction of the cell stack 100 and the cells 10, etc., "up" refers to the positive side in the Z direction and "down" refers to the negative side in the Z direction. With respect to the length of the cell stack 100 and the cells 10, etc., the length in the X direction is called the "length" and the length in the Y direction is called the "width". In this embodiment, the direction in which the anode gas and cathode gas flow within the cell stack 100 is the positive side in the Y direction. The Z direction is the thickness direction of the cell stack 100. Note that the cross-sectional views of this embodiment shown below in Figure 4 and other figures are taken at the position indicated by A-A in Figure 1.

The cell stack 100 has an inlet 11, an outlet 12, an active area 13, and bus bars 14 and 15.

The inlet 11 is a gas supply hole for supplying anode gas and cathode gas to the cell stack 100. In this embodiment, the inlet 11 is provided on the X-direction base end side of the cell stack 100. The anode gas is a fuel or a reformed fuel (reformed fuel), for example, a hydrocarbon fuel such as hydrogen or methane. The cathode gas is a so-called oxidizer, for example, air. In this embodiment, the inlet 11 has, as gas supply holes, an anode gas supply hole 16b for supplying anode gas, and cathode gas supply holes 16a and 16c for supplying cathode gas. In the inlet 11 of this embodiment, the cathode gas supply hole 16a, the anode gas supply hole 16b, and the cathode gas supply hole 16c are arranged in a row in this order. However, the number and arrangement of the anode gas supply holes and the cathode gas supply holes are arbitrary.

The outlet 12 is a gas exhaust hole for exhausting anode off-gas and cathode off-gas. In this embodiment, the outlet 12 is provided at the tip side of the cell stack 100 in the X direction. The anode off-gas and cathode off-gas are anode gas, etc., and cathode gas, etc., exhausted from the cell stack 100. In this embodiment, the outlet 12 includes, as gas exhaust holes, an anode off-gas exhaust hole 17b for exhausting anode off-gas, and cathode off-gas exhaust holes 17a and 17c for exhausting cathode off-gas. The cathode off-gas exhaust hole 17a, the anode off-gas exhaust hole 17b, and the cathode off-gas exhaust hole 17c are arranged in a row in this order. However, the number and arrangement of the anode off-gas exhaust holes and the cathode off-gas exhaust holes are arbitrary.

In the following, the gas supply holes constituting the inlet 11 and the gas exhaust holes constituting the outlet 12 are collectively referred to as gas flow holes. In addition, when it is not necessary to distinguish between anode gas and cathode gas in the explanation, anode gas, anode off-gas, cathode gas, and cathode off-gas are collectively referred to simply as gas.

The active area 13 is the area where electricity is actually generated using the anode gas and cathode gas. The active area 13 is formed between the inlet 11 and the outlet 12, i.e., in the central part of the cell stack 100.

The bus bars 14 and 15 are current collectors that electrically connect the cells 10 that make up the cell stack 100, thereby collecting the power generated by the cells 10. The bus bars 14 and 15 are made of, for example, metal, and have electrical conductivity that is sufficient to substantially prevent the loss of power generated by power generation. The bus bar 14 is attached to the side surface on the positive side in the X direction along the longitudinal direction of the cell stack 100. The bus bar 15 is attached to the side surface on the negative side in the X direction along the longitudinal direction of the cell stack 100. In this embodiment, the bus bars 14 and 15 connect the stacked cells 10 in series.

Figure 2 is an exploded perspective view of the cell stack 100. As shown in Figure 2, the cell stack 100 has a stack structure in which multiple cells 10 and gasket assemblies 18a, 18b are stacked alternately.

Each cell 10 has openings at positions corresponding to the inlet 11 and the outlet 12. That is, each cell 10 has a plurality of openings that form an anode gas supply hole 16b and cathode gas supply holes 16a, 16c, respectively, corresponding to the inlet 11. Similarly, each cell 10 has a plurality of openings that form an anode off-gas exhaust hole 17b and cathode off-gas exhaust holes 17a, 17c, respectively, corresponding to the outlet 12.

The structure of each cell 10 is the same, and the electrode catalyst layer 32 is exposed in the active area 13 of each cell 10. The electrode catalyst layer 32 is a laminate in which an anode electrode, a solid electrolyte, a cathode electrode, etc. are stacked, and the surface of the electrode catalyst layer 32 is divided into a surface that functions as an anode and a surface that functions as a cathode. Therefore, the cell 10 also has a front and back. Hereinafter, the surface of the cell 10 that functions as an anode is referred to as the anode surface 22, and the surface that functions as a cathode is referred to as the cathode surface 23. The cell stack 100 has a cell arrangement in which multiple cells 10 are stacked alternately while being inverted so that the anode surfaces 22 face each other and the cathode surfaces 23 face each other. The structure of the cell 10 and the layer structure of the electrode catalyst layer 32 will be described in detail later.

In addition, in the above cell arrangement, two adjacent cells 10 are spaced apart at a predetermined distance. The distance between the cells 10 is adjusted by the thickness of the gasket assemblies 18a, 18b disposed between the cells 10.

The gasket assembly 18a is made of an insulator and is arranged in the above cell arrangement where the anode faces 22 of adjacent cells 10 face each other. In other words, the gasket assembly 18a is for the anode. The gasket assembly 18a includes an outer edge sealant 26, a gas flow hole sealant 27, and a vent support 28 (gas flow support).

When the cell stack 100 is formed, the peripheral sealing material 26 contacts adjacent cells 10 to seal the space between those cells 10 (hereinafter referred to as the inter-cell space). Therefore, the peripheral sealing material 26 isolates the inter-cell space from the outside world (outside the cell stack 100).

The gas flow hole sealing material 27 seals a portion of the gas flow holes that form the inlet 11 and the outlet 12 at their outer periphery. More specifically, the gas flow hole sealing material 27 has an opening that forms a gas flow hole, for example, in its center. Therefore, the gas flow hole sealing material 27 does not impede the flow of gas in the stack direction. On the other hand, when the cell stack 100 is formed, the gas flow hole sealing material 27 is sandwiched between the upper and lower cells 10, thereby blocking the flow of gas into and out of the inter-cell space.

In the anode gasket assembly 18a, the gas flow hole sealant 27 seals the outer periphery of the cathode gas supply holes 16a, 16c and the cathode off-gas exhaust holes 17a, 17c. That is, the gas flow hole sealant 27 of the gasket assembly 18a blocks the flow of cathode gas into and out of the inter-cell space while allowing the flow of cathode gas and cathode off-gas in the stack direction.

When the cell stack 100 is formed, the ventilation support material 28 supports the upper and lower cells 10 at the outer periphery of some of the gas flow holes. Like the gas flow hole sealing material 27, the ventilation support material 28 has an opening that forms a gas flow hole, for example, in its center. Therefore, the ventilation support material 28 does not impede the flow of gas in the stack direction. On the other hand, unlike the gas flow hole sealing material 27, the ventilation support material 28 has multiple ventilation grooves (gas passage grooves) radially from the opening, for example. Therefore, the ventilation support material 28 does not impede the flow of gas. Therefore, the ventilation support material 28 supports the upper and lower cells 10 in a manner that allows ventilation (gas passage).

In the anode gasket assembly 18a, the ventilation support material 28 supports the upper and lower cells 10 on the outer periphery of the anode gas supply hole 16b and the anode off-gas exhaust hole 17b. This allows the anode gas and anode off-gas to flow into and out of the inter-cell space.

The gasket assembly 18b is disposed at a location where the cathode faces 23 of adjacent cells 10 face each other in the cell arrangement described above. In other words, the gasket assembly 18b is for the cathode.

The gasket assembly 18b for the cathode is formed of an insulator, similar to the gasket assembly 18a for the anode, and includes an outer edge sealant 26, a gas flow hole sealant 27, and a ventilation support material 28. However, in the gasket assembly 18b, the gas flow hole sealant 27 seals the outer periphery of the anode gas supply hole 16b and the anode off-gas exhaust hole 17b. In the gasket assembly 18b for the cathode, the ventilation support material 28 supports the upper and lower cells 10 on the outer periphery of the cathode gas supply holes 16a, 16c and the cathode off-gas exhaust holes 17a, 17c. Therefore, the gasket assembly 18b blocks the flow of anode gas into and out of the inter-cell space, and allows the flow of cathode gas.

[Structure of cell and electrode catalyst layer]
Fig. 3 is an exploded perspective view of the cell 10. As shown in Fig. 3, the cell 10 includes a first metal frame 31, an electrode catalyst layer 32, a seal cell 33, and a second metal frame .

The first metal frame 31 is a metal support that supports the electrode catalyst layer 32 at its outer periphery 48 (see FIG. 4). The first metal frame 31 is electrically connected to the electrode catalyst layer 32 at the outer periphery 48 (see FIG. 4) of the electrode catalyst layer 32. Specifically, the first metal frame 31 supports the electrode catalyst layer 32 while electrically connecting it to the electrode catalyst layer 32 on the anode layer 41 side of the electrode catalyst layer 32. Therefore, the first metal frame 31 is connected to the first metal porous layer 45. As a result, the first metal frame 31 is electrically connected to the anode layer 41 via the first metal porous layer 45 and supports the first metal porous layer 45. As a result, the first metal frame 31 constitutes a current collector that becomes the anode electrode in the cell 10.

The first metal frame 31 also exposes the electrode catalyst layer 32 through an opening provided in the center. That is, the surface of the cell 10 on which the first metal frame 31 is provided is the anode surface 22, and the first metal porous layer 45 is exposed. At least the portion of the electrode catalyst layer 32 exposed from the first metal frame 31 forms the active area 13. In addition, the first metal frame 31 has openings that form gas flow holes and connection parts that connect to the bus bars 14 and 15.

The electrode catalyst layer 32 assists the reaction between the anode gas and the cathode gas by isolating the anode gas and the cathode gas while allowing the conduction of certain ions. The electrode catalyst layer 32 includes, as the basic structure for reacting the anode gas and the cathode gas, at least an anode electrode layer 41, a solid electrolyte layer 43 (see FIG. 4), and a cathode electrode layer 42 (see FIG. 4) stacked in this order (hereinafter referred to as the basic stack 44 (see FIG. 4)).

The seal cell 33 is a sealing member that seals the side of the electrode catalyst layer 32 when the cell 10 is formed. The seal cell 33 is also formed of an insulator, and is sandwiched between the first metal frame 31 and the second metal frame 34 when the cell 10 is formed. Therefore, the seal cell 33 also functions as an insulating support for the first metal frame 31 and the second metal frame 34. Therefore, the seal cell 33 has an opening that exposes the entire surface of the electrode catalyst layer 32. The seal cell 33 also has an opening that forms a gas flow hole.

The second metal frame 34 is a metal support that supports the electrode catalyst layer 32. The second metal frame 34 is electrically connected to the electrode catalyst layer 32 at the outer periphery 49 of the electrode catalyst layer 32. Specifically, the second metal frame 34 is connected to and supports the electrode catalyst layer 32 on the cathode layer 42 side of the electrode catalyst layer 32. Therefore, the second metal frame 34 is connected to the second metal porous layer 46. As a result, the second metal frame 34 is electrically connected to the cathode layer 42 via the second metal porous layer 46 and supports the second metal porous layer 46. As a result, the second metal frame 34 constitutes a current collector that serves as the cathode electrode in the cell 10.

The second metal frame 34 also exposes the electrode catalyst layer 32 through an opening provided in the center. That is, the surface of the cell 10 on which the second metal frame 34 is provided is the cathode surface 23, and the second metal porous layer 46 is exposed. At least the portion of the electrode catalyst layer 32 exposed from the second metal frame 34 forms the active area 13. In addition, the second metal frame 34 has openings that form gas flow holes and connection parts that connect to the bus bars 14, 15.

Figure 4 is a cross-sectional view of the cell 10. As shown in Figure 4, the electrode catalyst layer 32 includes a basic laminate 44 consisting of an anode layer 41, a cathode layer 42, and a solid electrolyte layer 43 sandwiched between the anode layer 41 and the cathode layer 42.

The anode layer 41 is a flat thin film that functions as a so-called fuel electrode. The anode layer 41 is formed, for example, from ceramic or a cermet made of ceramic and metal. The anode layer 41 has gas permeability, electrical conductivity, and ion conductivity that allow the anode gas to pass through it, to the extent that it can function as a fuel electrode. The anode layer 41 also functions as a catalyst that promotes the reaction between the anode gas and oxide ions (e.g., oxygen ions) that have been transmitted through the solid electrolyte layer 43.

The cathode layer 42 is a flat thin film that functions as a so-called oxidizer electrode (air electrode). The cathode layer 42 is formed, for example, from a metal oxide. The cathode layer 42 has gas permeability, electrical conductivity, and ion conductivity that allow the cathode gas to pass through, to the extent that it can function as an oxidizer electrode. The cathode layer 42 also functions as a catalyst that promotes ionization of the oxidizer (e.g., oxygen) contained in the cathode gas.

The solid electrolyte layer 43 is a flat thin film of a solid electrolyte having ion conductivity, and conducts oxidant ions. The solid electrolyte layer 43 is formed, for example, from a solid oxide ceramic. Ceramics refers to sintered bodies of inorganic materials, and include not only nonmetallic oxides but also metallic oxides.

The electrode catalyst layer 32 of this embodiment further includes a first metal porous layer 45 and a second metal porous layer 46 in addition to the basic laminate 44.

The first metal porous layer 45 is a flat metal thin film formed to uniformly cover the anode layer 41 at least in the active area 13, and supports the basic laminate 44 from the anode layer 41 side. Therefore, in the layer structure of the electrode catalyst layer 32, the first metal porous layer 45 sandwiches the anode layer 41 together with the solid electrolyte layer 43. The first metal porous layer 45 is formed thicker than the anode layer 41 to the extent that it can support the basic laminate 44. For example, the first metal porous layer 45 is formed thicker than the anode layer 41 by about one order of magnitude.

The first metal porous layer 45 is formed of a metal porous body. The metal porous body is a porous body made of metal. The first metal porous layer 45 is formed of, for example, stainless steel (SUS) containing nickel, chromium, etc. Also, the porous body refers to a member that contains countless tiny pores (not shown) arranged substantially randomly, and these pores are substantially randomly connected. Therefore, the multiple pores contained in the first metal porous layer 45 are connected in the surface direction (XY plane direction). Also, the multiple pores contained in the first metal porous layer 45 are connected between the surfaces, and the distribution of the pores in the surface is substantially uniform.

Therefore, the first metal porous layer 45 is a good conductor with uniform electrical conductivity in the surface direction (XY in-plane direction) and thickness direction (Z direction), and behaves as a substantially continuous metal plate overall. In addition, the first metal porous layer 45 allows the anode gas to pass substantially uniformly from one exposed surface (the surface on the negative side in the Z direction) to the other surface (the surface on the positive side in the Z direction) joined to the anode layer 41 through the multiple pores. Therefore, when the anode gas is supplied to one exposed surface, the first metal porous layer 45 supplies the anode gas to the anode layer 41 through the multiple pores.

The second metal porous layer 46 is a flat metal thin film formed to uniformly cover the cathode layer 42 at least in the active area 13, and supports the basic laminate 44 from the cathode layer 42 side. Therefore, in the layer structure of the electrode catalyst layer 32, the second metal porous layer 46 sandwiches the cathode layer 42 together with the solid electrolyte layer 43. The first metal porous layer 45 is formed thicker than the cathode layer 42 to the extent that it can support the basic laminate 44. For example, the second metal porous layer 46 is formed thicker than the cathode layer 42 by about one order of magnitude.

The second metal porous layer 46 is formed of a metal porous body, similar to the first metal porous layer 45. Therefore, the second metal porous layer 46 is a good conductor having uniform electrical conductivity in the surface direction (XY in-plane direction) and thickness direction (Z direction), and behaves as a substantially continuous metal plate as a whole. In addition, the multiple pores contained in the second metal porous layer 46 are connected in the surface direction (XY in-plane direction). The multiple pores contained in the second metal porous layer 46 are connected between the surfaces, and the distribution of the pores in the surface is substantially uniform. Therefore, the second metal porous layer 46 allows the cathode gas to pass through substantially uniformly from one exposed surface (surface on the positive side of the Z direction) to the other surface (surface on the negative side of the Z direction) joined to the cathode electrode layer 42 through the multiple pores. Therefore, when cathode gas is supplied to one exposed surface, the second metal porous layer 46 supplies the cathode gas to the cathode layer 42 through the multiple pores.

As described above, the electrode catalyst layer 32 has a structure in which the first metal porous layer 45 and the second metal porous layer 46 support the basic laminate 44 from both sides. The electrode catalyst layer 32 is also joined to the first metal frame 31 and the second metal frame 34 by the first metal porous layer 45 and the second metal porous layer 46. Specifically, the first metal porous layer 45 is electrically connected to the first metal frame 31 at a part or all of its outer periphery 48. In this embodiment, in order to better reduce the electrical resistance (ohmic loss) at the connection portion, the first metal porous layer 45 and the first metal frame 31 are joined by a metal joining method such as welding at almost the entirety of the outer periphery 48. Similarly, the second metal porous layer 46 is electrically connected to the second metal frame 34 at a part or all of its outer periphery 49. In this embodiment, in order to better reduce electrical resistance (ohmic loss) at the connection portion, the second metal porous layer 46 and the second metal frame 34 are joined by a metal joining method such as welding around almost the entire outer periphery 49.

As described above, cell 10 is a so-called metal-supported cell. In a typical conventional metal-supported cell, only one of the anode layer 41 side or the cathode layer 42 side is supported by a metal support. In contrast, cell 10 in this embodiment is supported by metal supports on both the anode side and the cathode side. Therefore, while a typical conventional metal-supported cell is a one-sided metal-supported cell, cell 10 in this embodiment is, so to speak, a two-sided metal-supported cell.

The specific method for forming the first metal porous layer 45 and the second metal porous layer 46 is arbitrary. Therefore, the first metal porous layer 45 and the second metal porous layer 46 can be formed from felt or nonwoven fabric made of metal fibers, or a sintered body of metal particles. However, it is preferable that the first metal porous layer 45 and the second metal porous layer 46 are sintered bodies of metal particles. Compared to cases using other methods, sintered bodies of metal particles have excellent electrical conductivity and rigidity (strength). For this reason, it is preferable that the first metal porous layer 45 and the second metal porous layer 46 are treated bodies of metal particles.

In this embodiment, the first metal porous layer 45 and the second metal porous layer 46 are formed as a sintered body integral with the basic laminate 44 by co-firing. Specifically, first, a first metal porous body slurry, an anode slurry, an electrolyte slurry, a cathode slurry, and a second metal porous body slurry are prepared as slurries for forming each layer of the electrode catalyst layer 32. Next, each slurry is formed into a sheet, and the sheets are laminated and stuck together in the stacking order in the electrode catalyst layer 32 to form a molded slurry laminate. The molded slurry laminate is then degreased and co-fired to form the electrode catalyst layer 32.

[Detailed structure of cell stack]
5 is a partial cross-sectional view of the cell stack 100. As shown in Fig. 5, due to the cell arrangement in which the anode surfaces 22 face each other and the cathode surfaces 23 face each other, and the internal structure of the gasket assemblies 18a, 18b, the inter-cell space between the opposing anode surfaces 22 becomes an anode gas flow path FPa through which the anode gas flows. Similarly, the inter-cell space between the opposing cathode surfaces 23 becomes a cathode gas flow path FPc through which the cathode gas flows.

The anode gas flow path FPa supplies anode gas to two adjacent cells 10. That is, in the cell stack 100, the anode gas flow path FPa serves two cells 10. The height H1 of the anode gas flow path FPa can be adjusted as desired by the thickness of the gasket assembly 18a. Therefore, the cross-sectional area of the anode gas flow path FPa can be adjusted as desired.

The cathode gas flow path FPc supplies cathode gas to two adjacent cells 10. That is, in the cell stack 100, the cathode gas flow path FPc serves two cells 10. The height H2 of the cathode gas flow path FPc can be adjusted as desired by the thickness of the gasket assembly 18b. Therefore, the cross-sectional area of the cathode gas flow path FPc can also be adjusted as desired.

When the cell stack 100 generates power, for example, the flow rate of the cathode gas is usually greater than the flow rate of the anode gas. For this reason, in this embodiment, the pressure loss of the anode gas in the anode gas flow path FPa and the pressure loss of the cathode gas in the cathode gas flow path FPc are individually adjusted according to the flow rates of the anode gas and the cathode gas. Specifically, the height H2 of the cathode gas flow path FPc is set higher than the height H1 of the anode gas flow path FPa. That is, the gasket assembly 18b is formed thicker than the gasket assembly 18a, and as a result, H2>H1. As a result, in the cell stack 100, the cross-sectional area of the cathode gas flow path FPc is greater than the cross-sectional area of the anode gas flow path FPa. In this way, when the pressure loss in the anode gas flow path FPa and the cathode gas flow path FPc is reduced, the power consumption of devices that supply the anode gas and cathode gas to the cell stack 100, such as blowers and pumps (not shown), is reduced. Furthermore, when the pressure loss of the anode gas and cathode gas is appropriately adjusted, the power generation reaction and the like in the active area 13 occurs almost uniformly. Therefore, by reducing the pressure loss of the anode gas and cathode gas, temperature distribution is less likely to occur in the active area 13.

The bus bars 14, 15 are joined to the first metal frame 31 and the second metal frame 34 of each cell 10 by metal joining such as welding. In this way, the bus bars 14, 15 electrically connect adjacent cells 10.

In this embodiment, the bus bar 14 connects the first metal frame 31, which is the anode of a certain cell 10 (the cell 10 in the middle row of FIG. 5), to the cell 10 in the upper row of FIG. 5 adjacent to this cell 10, at the second metal frame 34, which is the cathode. The bus bar 15 connects the cell 10 in the middle row of FIG. 5, to which the bus bar 14 connects to the first metal frame 31, at the second metal frame 34, which is the cathode. Furthermore, the bus bar 15 connects the cell 10 in the lower row of FIG. 5, to which the bus bar 14 connects to the second metal frame 34, at the first metal frame 31, which is the anode. In other words, the bus bar 14 connects two adjacent cells 10 in series, and the bus bar 15 further connects the set of cells 10 connected in series by the bus bar 14 in series. Conversely, it can be said that the bus bar 15 connects two adjacent cells 10 in series, and the bus bar 14 further connects the sets of cells 10 connected in series by the bus bar 15 in series.

[Anode and cathode gas flows]
6 is an explanatory diagram showing the flow of the anode gas. As shown by the thick arrows in FIG. 6, the anode gas flowing through the anode gas supply holes 16b is jetted radially from the ventilation grooves of the ventilation support material 28 into the anode gas flow path FPa. As a result, the anode gas is supplied to the anode gas flow path FPa. In the anode gas flow path FPa, the anode gas flows substantially parallel to and substantially uniformly along the anode surface 22 toward the positive side in the X direction. The anode gas is then discharged to the anode off-gas discharge hole 17b through the ventilation grooves of the ventilation support material 28 provided in correspondence with the anode off-gas discharge hole 17b.

Figure 7 is an explanatory diagram showing the flow of cathode gas. As shown by the thick dashed arrows in Figure 7, the cathode gas flowing through the cathode gas supply holes 16a and 16c is ejected radially from the two ventilation support materials 28 through their respective ventilation grooves. This allows the cathode gas to be supplied to the cathode gas flow path FPc. In the cathode gas flow path FPc, the cathode gas flows almost parallel to and almost uniformly along the cathode surface 23 toward the positive side of the X direction. The cathode gas is then discharged to the cathode off-gas exhaust hole 17a and the cathode off-gas exhaust hole 18c through the ventilation grooves of the two ventilation support materials 28 provided corresponding to the cathode off-gas exhaust holes 17a and 17c, respectively.

Figure 8 is an explanatory diagram showing the supply state of anode gas and cathode gas through the metal porous layer. As shown in Figure 8, the anode gas comes into contact with the first metal porous layer 45 while flowing through the anode gas flow path FPa as described above. As a result, the anode gas passes through the pores of the first metal porous layer 45 and is supplied to the anode layer 41. Since the extremely small pores of the first metal porous layer 45 are uniformly formed, the anode gas is supplied uniformly to the entire surface of the anode layer 41 at least within the range of the active area 13. That is, at least in the active area 13, there is no part where the anode gas does not reach the anode layer 41 due to the presence of the first metal porous layer 45. Therefore, the anode gas reaches the entire surface of the anode layer 41 substantially uniformly.

In addition, while the cathode gas flows through the cathode gas flow path FPc as described above, it comes into contact with the second metal porous layer 46. As a result, the cathode gas passes through the pores of the second metal porous layer 46 and is supplied to the cathode layer 42. Since the extremely small pores of the second metal porous layer 46 are uniformly formed, the cathode gas is supplied uniformly to the entire surface of the cathode layer 42 at least within the range of the active area 13. In other words, at least in the active area 13, there is no part where the cathode gas does not reach the cathode layer 42 due to the presence of the second metal porous layer 46. Therefore, the cathode gas reaches the entire surface of the cathode layer 42 substantially uniformly.

[Current flow in cells and cell stacks]
Fig. 9 is an explanatory diagram showing paths along which current flows in a cell 10 and a cell stack 100. As shown by the bold arrow in Fig. 9, in a certain cell 10 in the lower part of Fig. 9, current flows into the second metal frame 34, which is the cathode, via the bus bar 14. This current flows in the planar direction along the second porous metal layer 46 connected to the second metal frame 34. This is because the second porous metal layer 46 is a good conductor and has a lower electrical resistance than the cathode layer 42.

In addition, as shown by the thick dashed arrow, when the cell 10 generates electricity, the current that flows into the second metal porous layer 46 and the current generated by the power generation flow through the basic laminate 44 (cathode layer 42, solid electrolyte layer 43, and anode layer 41) and into the first metal porous layer 45.

Here, the basic laminate 44 is thinner and less conductive than the first metal porous layer 45 and the second metal porous layer 46. Therefore, the electrical resistance in the surface direction of the basic laminate 44 is greater than the electrical resistance in the surface direction of the first metal porous layer 45 and the second metal porous layer 46. In addition, since the first metal porous layer 45 and the second metal porous layer 46 supply the anode gas and the cathode gas to the active area 13 almost uniformly, power is generated almost uniformly in the entire range of the active area 13. For these reasons, the propagation of current in the surface direction is carried out exclusively by the first metal porous layer 45 and the second metal porous layer 46. Therefore, in the cell 10, the current flow in the basic laminate 44 is almost perpendicular to the surface of the electrode catalyst layer 32.

The current that flows into the first metal porous layer 45 propagates in the planar direction along the first metal porous layer 45. It then propagates through the bus bar 15 and flows into the second metal frame 34 of the adjacent cell 10 in the upper row of Figure 9.

As shown by the thick arrow, the current that flows into the adjacent cell 10 flows into the second metal porous layer 46 in the same manner as the cell 10 in the lower row of Figure 9, and flows in the direction of its surface. Then, as this adjacent cell 10 generates power, the current that has flowed in and the current generated by the power generation flows almost vertically through the basic stack 44, as shown by the thick dashed arrow, and flows into the first metal porous layer 45. The current that has flowed into the first metal porous layer 45 propagates in the direction of its surface, propagates through the first metal frame 31 and bus bar 14, and flows into the second metal frame 34 of the next cell 10. The above process is then repeated.

[Function of Cell and Cell Stack]
The operation of the cell 10 and the cell stack 100 configured as described above will be explained below by comparing a first comparative example with a second comparative example.

(1) Comparison with First Comparative Example Fig. 10 is a cross-sectional view of a cell 210 of the first comparative example. The cell 210 of the first comparative example is a cell in which the first metal porous layer 45 and the second metal porous layer 46 of the cell 10 according to the above embodiment are replaced with a lattice current collector 211 having lattice-shaped openings, and the other configuration is the same as that of the above embodiment. In the first comparative example, the cell 210 is arranged in the same manner as in the above embodiment to form a cell stack.

The lattice collector 211 is formed by providing a number of openings in a metal sheet. Therefore, the anode gas and the cathode gas are blocked by the lattice collector 211. That is, as shown in FIG. 10, the anode gas reaches the anode layer 41 only at the openings of the lattice collector 211. Similarly, the cathode gas reaches the cathode layer 42 only at the openings of the lattice collector 211. Therefore, the two lattice collectors 211 are aligned so that the positions of the openings are aligned. The active area in the cell 210 of the first comparative example is limited to the range in the Z direction where the openings of the two lattice collectors 211 are aligned.

11 is an explanatory diagram showing the path of the current flowing through the cell 210 of the first comparative example. As shown in FIG. 11, in a certain cell 210, the current flows into the lattice collector 211 on the cathode layer 42 side through the second metal frame 34 as shown by the thick arrow, and propagates along the lattice collector 211. However, since the lattice collector 211 has an opening, the current propagates in the surface direction through not only the lattice collector 211 but also the cathode layer 42. In other words, when the lattice collector 211 is used, a current flows through the cathode layer 42 in the surface direction to a certain extent. Since the cathode layer 42 is formed extremely thin, the electrical resistance in the surface direction is very high. Therefore, the current flowing in the surface direction through the cathode layer 42 generates energy loss (so-called ohmic loss) due to this high electrical resistance.

In addition, in the cell 210 of the first comparative example, the active area is limited to the opening, so the current that flows into the lattice collector 211 on the cathode layer 42 side and the current generated by power generation flow toward the anode layer 41 at the opening of the lattice collector 211, as shown by the thick dashed arrow. Therefore, the current that reaches the anode layer 41 propagates in the surface direction through the anode layer 41 and flows into the lattice collector 211 provided on the anode layer 41 side. And, since the anode layer 41 is formed extremely thin like the cathode layer 42, the electrical resistance in the surface direction is very high. Therefore, the current that reaches the anode layer 41 further generates ohmic loss due to this high electrical resistance.

When a cell stack is constructed using the cells 210 of the first comparative example, the above-mentioned ohmic losses occur in each cell 210. In particular, the more cells 210 are connected in series to ensure the desired output voltage, the greater the ohmic losses become.

Comparing the cell 10 according to this embodiment with the cell 210 according to the first comparative example, the cell 10 according to this embodiment uses the first metal porous layer 45 and the second metal porous layer 46, so there is almost no ohmic loss as occurs in the cell 210 according to the first comparative example. That is, according to the cell 10 according to this embodiment, the ohmic loss is reduced compared to the cell 210 according to the first comparative example. Since the cell stack is composed of multiple cells, this characteristic is more pronounced in the cell stack. That is, since the cell stack 100 according to this embodiment is composed of the cell 10, the ohmic loss is significantly reduced compared to the cell stack composed of the cell 210 according to the first comparative example. In particular, since the cell stack 100 according to this embodiment connects the cells 10 in series, the ohmic loss is particularly significantly reduced compared to the cell stack in which the cells 210 according to the first comparative example are connected in series.

In addition, in the cell 10 according to this embodiment, the entire area where the first metal porous layer 45 and the second metal porous layer 46 are exposed is the active area 13. Therefore, in the cell 10 according to this embodiment, the area of the electrode catalyst layer 32 that contributes to power generation is larger than that of the cell 210 of the first comparative example. As a result, the cell 10 according to this embodiment has better power generation efficiency per area, i.e., better power generation performance, than the cell 210 of the first comparative example. This feature becomes more pronounced by constructing the cell stack 100.

Figure 12 is an explanatory diagram showing a defect caused by misalignment of the lattice collector 211. As shown in Figure 12, in the cell 210 of the first comparative example, the front and back lattice collectors 211 are misaligned due to manufacturing errors or the like. In the cell 210 of the first comparative example, the active area is limited to the range where the openings of the two lattice collectors 211 are aligned. If the two lattice collectors 211 are misaligned in this way, the effective active area AE becomes even narrower than the openings of the lattice collectors 211.

In contrast, the cell 10 according to this embodiment uses a substantially uniform first metal porous layer 45 and second metal porous layer 46, so there is no misalignment as occurs with the lattice collector 211. Therefore, in the cell 10 according to this embodiment, almost the entire surface of the exposed electrode catalyst layer 32 becomes the active area 13. Therefore, compared to the cell 210 of the first comparative example, the cell 10 according to this embodiment can obtain good power generation performance without being dependent on extremely slight manufacturing errors, etc.

In addition, in the cell 210 of the first comparative example, localized stress occurs due to misalignment of the lattice collectors 211 on the front and back. This can cause cracks 212 in the basic laminate 44 (see FIG. 11). If cracks 212 occur, depending on the extent of the cracks, part or all of the cell 210 will no longer function. The cracks 212 can occur during manufacturing, such as when bonding the lattice collectors 211 to the basic laminate 44, and can also occur due to thermal expansion and contraction caused by repeated use and discontinuance of the cell 210.

In contrast, in the cell 10 according to this embodiment, the first metal porous layer 45 and the second metal porous layer 46 uniformly cover the anode layer 41 and the cathode layer 42, respectively. Therefore, the first metal porous layer 45 and the second metal porous layer 46 do not generate local stress in the basic laminate 44. Therefore, in the cell 10 according to this embodiment, cracks caused by the first metal porous layer 45 and the second metal porous layer 46 hardly occur in the basic laminate 44 during manufacturing and repeated use. Therefore, the cell 10 according to this embodiment is superior in manufacturing suitability to the cell 210 of the first comparative example. In addition, the cell 10 according to this embodiment is highly durable against thermal expansion and contraction and is stable against repeated use.

The cell 10 according to this embodiment has a layer structure in which the basic laminate 44 is sandwiched between the first metal porous layer 45 and the second metal porous layer 46, which are about one order of magnitude thicker than the basic laminate 44. When the electrode catalyst layer 32 expands and contracts, the expansion and contraction of the first metal porous layer 45 and the second metal porous layer 46 is dominant. In addition, the first metal porous layer 45 and the second metal porous layer 46 are arranged symmetrically with respect to the basic laminate 44, and are substantially the same in terms of properties related to expansion and contraction, warping, etc. For this reason, the cell 10 having the first metal porous layer 45 and the second metal porous layer 46 is unlikely to generate internal stress that causes warping (bending) of the basic laminate 44 during manufacturing or repeated use. From this perspective, the cell 10 according to this embodiment is also excellent in manufacturing suitability and stable against repeated use.

(2) Comparison with the Second Comparative Example FIG. 13 is a schematic cross-sectional view of a cell stack 300 and a cell 310 according to the second comparative example. The cell stack 300 and the cell 310 according to the second comparative example are of a typical conventional form. As shown in FIG. 13, the cell 310 is a so-called one-side metal support cell. That is, the cell 310 is configured by removing the first metal porous layer 45 and the first metal frame 31 from the cell 10 according to the present embodiment. Therefore, in the cell 310, the surface of the anode layer 41 is exposed on the anode layer 41 side, not the first metal porous layer 45. On the other hand, on the cathode layer 42 side, the second metal porous layer 46 is exposed, similar to the cell 10 according to the present embodiment.

The cell stack 300 is formed by stacking a number of cells 310 with separators 311 between them. In the cell stack 300, the cells 310 are stacked with the front and back facing in a fixed relationship. For example, in FIG. 13, the lower cell 310 is arranged with the second metal porous layer 46 facing the negative side of the Z direction and the anode layer 41 facing the positive side of the Z direction. The upper cell 310 is stacked on the lower cell 310 with the second metal porous layer 46 facing the negative side of the Z direction and the anode layer 41 facing the positive side of the Z direction, just like the lower cell 310.

The separator 311 has multiple grooves extending in parallel in the Y direction. The tops 311a and 311c of the separator 311 formed by these multiple grooves abut against the anode layer 41 and the second metal porous layer 46 of the adjacent cells 310 when the cell stack 300 is formed. As a result, the inter-cell space formed between the adjacent cells 310 is divided into multiple parallel sections by the separator 311. Of these sections, the section adjacent to the anode layer 41 is used as the anode gas flow path FPa. On the other hand, the section adjacent to the second metal porous layer 46 (cathode layer 42) is used as the cathode gas flow path FPc.

The separator 311 is made of, for example, metal. Therefore, the top 311a of the separator 311 abuts against the second metal porous layer 46, and the separator 311 is electrically connected to the cathode layer 42 of a certain cell 310 (cell 310 in the upper row of FIG. 13) through the second metal porous layer 46. The top 311c of the separator 311 abuts against the anode layer 41, and the separator 311 is electrically connected to the anode layer 41 of an adjacent cell 310 (cell 310 in the lower row of FIG. 13). The end of the separator 311 is provided so as to extend outside the inter-cell space. Therefore, the separator 311 functions as a current collector.

Comparing the cell 10 according to this embodiment with the cell 310 according to the second comparative example configured as described above, the cell 10 according to this embodiment is different in that the first metal porous layer 45 is provided on the anode layer 41 side, whereas the cell 310 according to the second comparative example does not have this. Therefore, in the cell 10 according to this embodiment, the current propagating in the surface direction on the anode layer 41 side flows through the first metal porous layer 45, which has low electrical resistance, whereas in the cell 310 according to the second comparative example, the current flows through the anode layer 41, which has high electrical resistance, before flowing into the separator 311. Therefore, in the cell 10 according to this embodiment, the ohmic loss is reduced compared to the cell 310 according to the second comparative example.

In addition, when comparing the cell stack 100 according to the present embodiment with the cell stack 300 according to the second comparative example, the cell stack 300 according to the second comparative example uses a separator 311, whereas the cell stack 100 according to the present embodiment does not use the separator 311. In the cell stack 300 according to the second comparative example, the separator 311 is used, and as a result, the anode gas flow path FPa and the cathode gas flow path FPc are divided into a plurality of narrowed flow paths. In contrast, in the cell stack 100 according to the present embodiment, the entire inter-cell space functions as one anode gas flow path FPa or cathode gas flow path FPc, so that the cross-sectional areas of these flow paths are larger than those of the cell stack 300 according to the second comparative example. Therefore, the cell stack 100 according to the present embodiment has a reduced pressure loss of the anode gas flowing through the anode gas flow path FPa and the pressure loss of the cathode gas flowing through the cathode gas flow path FPc compared to the cell stack 300 according to the second comparative example. As a result, the cell stack 100 according to this embodiment reduces the power consumption of devices that supply anode gas and cathode gas to the cell stack 100, such as blowers and pumps (not shown).

In the cell stack 300 of the second comparative example, each anode gas flow path FPa and cathode gas flow path FPc supplies anode gas and cathode gas to one cell 310. In contrast, in the cell stack 100 of this embodiment, one anode gas flow path FPa and cathode gas flow path FPc supplies anode gas and cathode gas to two adjacent cells 10, respectively. That is, the cell stack 100 of this embodiment is configured to combine the two flow paths required in the cell stack 300 of the second comparative example into one flow path. Therefore, the cell stack 100 of this embodiment can be formed thinner and smaller than the cell stack 300 of the second comparative example. In addition, the cell stack 100 of this embodiment can be highly integrated compared to the cell stack 300 of the second comparative example.

In particular, in the cell stack 100 according to this embodiment, the anode gas flow path FPa and the cathode gas flow path FPc are not divided into thin sections. In addition, the pressure loss of the anode gas and the cathode gas is reduced. Therefore, the heights H1, H2 of the anode gas flow path FPa and the cathode gas flow path FPc can be set lower than in the second comparative example. This also contributes to making the cell stack 100 according to this embodiment thinner, more compact, and more highly integrated.

[Active cell shape and busbar installation range]
In the cell 10 and cell stack 100 according to the above embodiment, the shape of the active area 13 and the installation range of the bus bars 14, 15 are arbitrary. However, it is preferable that the shape of the active area 13 and the installation range of the bus bars 14, 15 are determined as follows.

Figure 14 is an explanatory diagram showing the shape of the active area 13, the installation range of the bus bars 14, 15, and the current path. As shown in Figure 14, the width of the active area 13 is "W1" and the length of the active area 13 is "L1". In this case, it is preferable that the shape of the active area 13 has a high aspect ratio, in which the aspect ratio L1/W1, which is the ratio of the length L1 to the width W1, is greater than 1. For example, it is particularly preferable that the active area 13 is generally rectangular in shape, in which the length L1 is greater than the width W1.

In other words, when the flow direction (Y direction) of the anode gas and cathode gas is defined as a first direction and the direction perpendicular to this first direction (X direction) is defined as a second direction, it is preferable that the active area 13 has a shape that is longer in the first direction (Y direction) than in the second direction (X direction).

In this way, when the active area 13 is shaped to have a high aspect ratio, the anode gas is distributed well in the anode gas flow path FPa, and the anode gas flows almost uniformly within the anode gas flow path FPa. Similarly, the cathode gas is distributed well in the cathode gas flow path FPc, and the cathode gas flows almost uniformly within the cathode gas flow path FPc.

The bus bars 14 and 15 are attached to the cell array parallel to the first direction (Y direction), which is the flow direction of the anode gas and cathode gas. It is preferable that the length L2 of the bus bars 14 and 15 along the first direction (Y direction) is equal to or greater than the length L1 of the active area 13 along the first direction (Y direction).

In this way, when the length L2 of the busbars 14 and 15 is made equal to or greater than the length L1 of the active area 13, the generated electricity (current) flows through the active area 13 from one busbar 14 to the other busbar 15, generally parallel to the second direction (X direction), and uniformly in the first direction (Y direction), as shown by the bold arrow in FIG. 14. That is, the current density of the current flowing from the busbar 14 to the busbar 15 is almost uniform (constant) throughout the active area 13. Therefore, the heat generated by the current flow is generated uniformly in the active area 13, and the occurrence of local or overall heat distribution in the active area 13 is suppressed. Therefore, when the busbars 14 and 15 are made equal to or greater than the length L1 of the active area 13, electricity is generated uniformly and efficiently using the entire surface of the active area 13.

In particular, as described above, when the active area 13 has a high aspect ratio shape, the width W1 of the active area 13 is shorter than the length L1, so the distance that electricity generated by power generation travels through the active area 13 is short. This reduces ohmic loss in the active area 13. As a result, the recovery rate (utilization rate) of electricity generated by power generation is high. In other words, if the length L2 of the bus bars 14, 15 is made equal to or greater than the length L1 of the active area 13, the power generation performance of the cell stack 100 is improved.

It is particularly preferable that the length L2 of the busbars 14, 15 is approximately equal to the length L1 of the active area 13. This is because the length of the cells 10 and the cell stack 100 can be made as short as possible while improving the power generation performance of the cell stack 100 as described above. The length L2 of the busbars 14, 15 being "approximately equal" to the length L1 of the active area 13 means that the length L2 of the busbars 14, 15 has a length that can improve the power generation performance of the cell stack 100 as described above. Therefore, it is also acceptable for the length L2 of the busbars 14, 15 to be slightly shorter than the length L1 of the active area 13.

Figure 15 is an explanatory diagram showing the installation range of the bus bars 14, 15 and the current path. As shown in Figure 15, when the anode gas and cathode gas flow in parallel in the cell stack 100, the length L2 of the bus bars 14, 15 may be shorter than the length L1 of the active area 13. In this case, it is preferable that the bus bars 14, 15 are arranged unevenly on the upstream side of the anode gas and cathode gas (negative side in the Y direction) with respect to the active area 13. Note that "parallel" with respect to the flow of the anode gas and cathode gas means that the flow paths of the anode gas and cathode gas are approximately parallel and that the anode gas and cathode gas flow in the same direction.

In this way, when the bus bars 14, 15 are unevenly positioned on the upstream side of the anode gas and cathode gas, the current flowing through the active area 13 from the bus bar 14 to the bus bar 15 is concentrated in a part of the active area 13, as shown by the thick arrow. In the current concentration area 401 where the current is concentrated in this way, more heat (Joule heat) is generated than in the current sparse area 402 where the current is relatively sparse. When the anode gas and cathode gas flow in parallel, a temperature distribution may occur in the active area 13, but by unevenly positioning the bus bars 14, 15 as described above, the temperature distribution is corrected.

Figure 16 is a graph showing the temperature distribution of the active area 13. As shown by the dashed line in Figure 16, when the anode gas and cathode gas flow in parallel and in the same direction, a temperature distribution may occur in the active area 13 where the temperature increases from the inlet 11 to the outlet 12. For this reason, if the bus bars 14, 15 are biased upstream of the anode gas and cathode gas to generate a current concentration area 401 on the upstream side of the active area 13, the temperature of the current concentration area 401 will increase. As a result, as shown by the solid line, the temperature distribution of the active area 13 is corrected. Note that the two-dot dashed line in Figure 16 indicates the ideal temperature at which power generation efficiency is maximized.

Therefore, as described above, when the anode gas and cathode gas flow in parallel, distributing the bus bars 14, 15 on the upstream side improves the power generation performance of the cell 10 and the cell stack 100.

The length L2 of the busbars 14 and 15 relative to the length L1 of the active area 13 is determined by suitability based on experiments, simulations, etc. In addition, when the busbars 14 and 15 are shorter than the active area 13, it is preferable that the busbars 14 and 15 are installed from the base end of the active area 13. However, even if the installation position of the busbars 14 and 15 is slightly shifted from the base end of the active area 13 and a current sparse area 402 occurs in the base end portion of the active area 13, the above-mentioned power generation performance improvement effect is achieved. Therefore, the busbars 14 and 15 may be installed so that, for example, when comparing the current sparse area 402 on the tip side with the current sparse area 402 on the base end side (not shown), the current sparse area 402 on the tip side is larger (longer).

When the cell 10 is a so-called internal reforming type, it is preferable that the reforming catalyst that reforms the fuel is provided in part or all of the current concentration area 401. Specifically, the first metal porous layer 45 of each cell 10 is configured to include the reforming catalyst in part or all of the current concentration area 401 formed in the active area 13 by the presence of the bus bars 14, 15. The reforming catalyst can be provided in the first metal porous layer 45 by a method such as coating or impregnation.

Because the fuel reforming reaction is an endothermic reaction, the temperature distribution shown by the dashed line in FIG. 16 becomes more pronounced. For this reason, as described above, if the reforming catalyst is provided within the current concentration area 401, the temperature drop due to the reforming reaction is compensated for by heat generated by the current concentration, and the temperature distribution of the cell 10 and cell stack 100 can be brought closer to the ideal temperature distribution. This improves the power generation performance of the cell 10 and cell stack 100 even when the cell 10 is an internal reforming type.

In the above embodiment, when constructing the cell stack 100, the multiple cells 10 are connected in series by the bus bars 14 and 15. However, some or all of the multiple cells 10 constituting the cell stack 100 may be connected in parallel depending on the desired current and voltage to be obtained by power generation. When connecting the cells 10 in parallel, the first metal frames 31 of adjacent cells 10 and the second metal frames 34 of adjacent cells 10 are connected by the bus bars 14 and 15. When connecting the cells 10 in parallel, the bus bars 14 and 15 can be omitted by forming some or all of the gasket assemblies 18a and 18b from a conductive material such as metal. For example, by forming the outer edge sealing material 26 of the gasket assemblies 18a and 18b from a conductive material, the first metal frames 31 of adjacent cells 10 and the second metal frames 34 of adjacent cells 10 are electrically connected to each other. In this way, by omitting the bus bars 14 and 15, the cells 10 and the cell stack 100 can be formed more easily and at a lower cost.

In the above embodiment, the flow directions of the anode gas and the cathode gas in the cell stack 100 are parallel, but the anode gas and the cathode gas can be made to flow in opposite directions. For example, an anode gas supply device (not shown) is connected to the cell 10 so that the anode gas flows from the anode gas supply hole 16b to the anode off-gas exhaust hole 17b as in the above embodiment. On the other hand, a cathode gas supply device (not shown) is connected to the cell 10 so that the cathode gas flows from the cathode off-gas exhaust holes 17a, 17c to the cathode gas supply holes 16a, 16c, in the opposite direction to the above embodiment. As a result, the anode gas and the cathode gas flow in opposite directions within the cell 10. With regard to the flow of the anode gas and the cathode gas, "opposite" means that the flow paths of the anode gas and the cathode gas are approximately parallel, and the anode gas and the cathode gas flow in opposite directions. Here, "opposite" may be referred to as anti-parallel.

As described above, the fuel cell (cell 10) according to this embodiment is a fuel cell configured by stacking an anode layer 41, a cathode layer 42, and a solid electrolyte layer 43 sandwiched between the anode layer 41 and the cathode layer 42. This fuel cell (cell 10) further includes a first metal porous layer 45, a first metal frame 31, a second metal porous layer 46, and a second metal frame 34. The first metal porous layer 45 is formed in a flat plate shape by a metal porous body having a plurality of pores communicating in the surface direction, and sandwiches the anode layer together with the solid electrolyte layer, and supplies anode gas to the anode layer through the plurality of pores. The first metal frame 31 is electrically connected to the anode layer 41 through the first metal porous layer 45 by electrically connecting at the outer periphery 48 of the first metal porous layer 45, and supports the first metal porous layer 45. The second metal porous layer 46 is formed into a flat plate shape using a porous metal body, and sandwiches the cathode layer 42 together with the solid electrolyte layer 43, and supplies cathode gas to the cathode layer 42 through a plurality of pores. The second metal frame 34 is electrically connected to the second metal porous layer 46 at the outer periphery 49 of the second metal porous layer 46, and is therefore electrically connected to the cathode layer 42 via the second metal porous layer 46 and supports the second metal porous layer 46.

In this way, the fuel cell (cell 10) according to this embodiment is supported on both the anode layer 41 side and the cathode layer 42 side by the first metal porous layer 45 and the second metal porous layer 46, which are good conductors and have gas permeability. Therefore, when the fuel cell generates electricity and current flows in the surface direction, the current flows not through the anode layer 41 or the cathode layer 42, which have high electrical resistance, but exclusively through the first metal porous layer 45 and the second metal porous layer 46, which have low electrical resistance. Therefore, compared to conventional fuel cells in which current flows in the surface direction through the anode layer 41 or the cathode layer 42, the ohmic loss is reduced in the fuel cell according to this embodiment. Therefore, the fuel cell according to this embodiment has good power generation performance in that the electricity generated by power generation can be extracted with low loss.

In addition, the first metal porous layer 45 and the second metal porous layer 46 do not impede the supply of anode gas to the anode layer 41 and the supply of cathode gas to the cathode layer 42. Therefore, the fuel cell (cell 10) according to this embodiment has a large active area 13. Therefore, the fuel cell according to this embodiment has good power generation performance in that it generates a large amount of power.

Furthermore, the first metal porous layer 45 and the second metal porous layer 46 are made of metal and support the basic laminate 44 consisting of the anode layer 41, the solid electrolyte layer 43, and the cathode layer 42 in a sandwiched manner, so that the fuel cell according to this embodiment has high strength. For this reason, the fuel cell according to this embodiment is less likely to develop defects such as cracks 212 even when used repeatedly with thermal expansion and contraction.

In the fuel cell (cell 10) according to this embodiment, the first metal porous layer 45 is formed to uniformly cover the anode layer 41, and the second metal porous layer 46 is formed to uniformly cover the cathode layer 42. Therefore, the active area 13 does not have any portion (opening, etc.) where the anode layer 41 and the cathode layer 42 are exposed. In other words, there is no portion where a current is forced to flow in the planar direction through the anode layer 41 or the cathode layer 42. Therefore, in the fuel cell according to this embodiment, ohmic loss is reduced over the entire surface of the active area 13. Therefore, the fuel cell according to this embodiment has good power generation performance.

In the fuel cell (cell 10) according to this embodiment, the first metal porous layer 45 and the second metal porous layer 46 have uniform electrical conductivity in the planar direction. That is, the first metal porous layer 45 and the second metal porous layer 46 each function as a substantially uniform metal plate as a whole. Therefore, even if the electricity generated by power generation flows in the planar direction through the first metal porous layer 45 and the second metal porous layer 46, there is almost no ohmic loss. Therefore, the fuel cell according to this embodiment has good power generation performance.

In the fuel cell (cell 10) according to this embodiment, the first metal porous layer 45 and the second metal porous layer 46 are sintered bodies of metal particles. Metal porous bodies formed by sintering metal particles have superior electrical conductivity compared to metal porous bodies manufactured by other methods. Therefore, since the first metal porous layer 45 and the second metal porous layer 46 are formed of sintered bodies of metal particles, the ohmic loss of the fuel cell according to this embodiment is particularly reduced. Therefore, the fuel cell according to this embodiment has good power generation performance.

The fuel cell stack (cell stack 100) according to this embodiment is formed using the above fuel cell (cell 10). This fuel cell stack has a cell arrangement in which a plurality of fuel cell cells are alternately stacked at a predetermined interval while being inverted so that the anode faces 22 face each other and the cathode faces 23 face each other when the surface of the fuel cell where the first metal porous layer 45 is exposed is the anode face 22 and the surface of the fuel cell where the second metal porous layer 46 is exposed is the cathode face 23. In addition, in the fuel cell stack, an anode gas flow path FPa through which the anode gas flows is formed in the space (inter-cell space) where the anode faces 22 face each other between adjacent fuel cell cells in the above cell arrangement. In addition, in the fuel cell stack, a cathode gas flow path FPc through which the cathode gas flows is formed in the space (inter-cell space) where the cathode faces 23 face each other between adjacent fuel cell cells in the above cell arrangement. And the fuel cell stack has a bus bar that electrically connects adjacent fuel cell cells in the above cell arrangement.

As described above, the fuel cell stack (cell stack 100) according to this embodiment is formed using the above-mentioned fuel cell (cell 10), so there is little ohmic loss in each fuel cell. In addition, the amount of electricity generated is large and the strength is high. For this reason, the cell stack 100 has good power generation performance.

In the fuel cell stack (cell stack 100) according to this embodiment, the bus bars 14, 15 electrically connect the first metal porous layer 45 and the second metal porous layer 46 between adjacent fuel cell cells in the above-mentioned cell arrangement, thereby connecting the fuel cell cells in series. Therefore, the fuel cell stack according to this embodiment has good power generation performance in that it can generate high voltage.

In addition, in the fuel cell stack (cell stack 100) according to this embodiment, the bus bars 14, 15 connect the first metal porous body layers and the second metal porous body layers 46 between adjacent fuel cell cells in the above-mentioned cell arrangement, respectively, thereby enabling the fuel cell cells to be connected in parallel. Therefore, the fuel cell stack according to this embodiment has good power generation performance in that it can generate a large current.

In the fuel cell stack (cell stack 100) according to this embodiment, the height H2 of the cathode gas flow path FPc, which is the spacing between the cathode surfaces 23, is greater than the height H1 of the anode gas flow path FPa, which is the spacing between the anode surfaces 22. Therefore, in the fuel cell stack according to this embodiment, the pressure loss of the anode gas in the anode gas flow path FPa and the pressure loss of the cathode gas in the cathode gas flow path FPc are both reduced. As a result, the equipment that supplies the anode gas and cathode gas to the cell stack 100 consumes less power.

In the fuel cell stack (cell stack 100) according to this embodiment, when the flow direction of the anode gas and cathode gas flowing in parallel or opposite directions is the first direction (Y direction) and the direction perpendicular to the first direction is the second direction (X direction), the active area 13 where power generation occurs is longer in the first direction than in the second direction. In this way, when the shape of the active area 13 is made to have a high aspect ratio, the distribution of the anode gas in the anode gas flow path FPa and the distribution of the cathode gas in the cathode gas flow path FPc are good. As a result, the fuel cell stack (cell stack 100) according to this embodiment has good power generation performance.

In the fuel cell stack (cell stack 100) according to this embodiment, the bus bars 14, 15 are attached parallel to the cell arrangement in the first direction (Y direction), and the length L2 of the bus bars 14, 15 along the first direction is equal to or greater than the length L1 of the active area 13 along the first direction. Therefore, the current density is uniform throughout the active area 13. As a result, the occurrence of local or global heat distribution in the active area 13 is suppressed, and power is generated uniformly and efficiently using the entire surface of the active area 13.

In the fuel cell stack (cell stack 100) according to this embodiment, when the anode gas and the cathode gas flow in parallel, the bus bars 14 and 15 are attached in parallel to the first direction (Y direction) with respect to the cell arrangement described above, and the length L2 of the bus bars 14 and 15 along the first direction may be shorter than the length L1 of the active area 13 along the first direction. In this case, the bus bars 14 and 15 are arranged so as to be biased toward the upstream side of the anode gas and the cathode gas with respect to the active area 13. In this way, when the anode gas and the cathode gas flow in parallel, the temperature distribution occurring in the active area 13 is corrected by biasing the bus bars 14 and 15 to the upstream side. As a result, the fuel cell stack according to this embodiment has good power generation performance.

In particular, in the above case, when the fuel cell is an internal reforming type, the first metal porous layer 45 is provided with a reforming catalyst that reforms the fuel in part or all of the range of the current concentration area 401 formed in the active area 13 by the presence of the bus bars 14, 15. In this way, when the reforming catalyst is provided in the range of the current concentration area 401, the temperature drop due to the reforming reaction is compensated for by heat generated by the current concentration, and the temperature distribution of the fuel cell stack can be made closer to the ideal temperature distribution. This improves the power generation performance of the fuel cell stack (cell stack 100) even when the fuel cell (cell 10) is an internal reforming type.

The above describes the embodiments of the present invention, but the configurations described in the above embodiments and each modified example are merely examples of application of the present invention and are not intended to limit the technical scope of the present invention.

10: Cell 11: Inlet 12: Outlet 13: Active area 14: Bus bar 15: Bus bar 18a: Gasket assembly 18b: Gasket assembly 31: First metal frame 32: Electrode catalyst layer 34: Second metal frame 41: Anode layer 42: Cathode layer 43: Solid electrolyte layer 45: First metal porous layer 46: Second metal porous layer 100: Cell stack

Claims (12)

A fuel cell configured by stacking an anode layer, a cathode layer, and a solid electrolyte layer sandwiched between the anode layer and the cathode layer,
a first metal porous body layer formed in a flat plate shape using a metal porous body having a plurality of pores communicating in a surface direction, the first metal porous body layer sandwiching the anode layer together with the solid electrolyte layer, and supplying an anode gas to the anode layer through the plurality of pores;
a first metal frame that is electrically connected to the anode layer via the first metal porous body layer by being electrically connected to an outer periphery of the first metal porous body layer and that supports the first metal porous body layer;
a second metal porous layer formed in a flat plate shape using the metal porous body, sandwiching the cathode layer together with the solid electrolyte layer, and supplying a cathode gas to the cathode layer through a plurality of the pores;
a second metal frame that is electrically connected to the second metal porous body layer at an outer periphery of the second metal porous body layer, thereby electrically connecting to the cathode layer via the second metal porous body layer and supporting the second metal porous body layer;
A fuel cell comprising: The fuel cell according to claim 1 ,
the first metal porous layer is formed so as to uniformly cover the anode layer,
The second metal porous layer is formed so as to uniformly cover the cathode layer.
Fuel cell. 3. The fuel cell according to claim 1 or 2,
The first metal porous layer and the second metal porous layer have uniform electrical conductivity in the planar direction.
Fuel cell. The fuel cell according to any one of claims 1 to 3,
The first metal porous layer and the second metal porous layer are sintered bodies of metal particles.
Fuel cell. A fuel cell stack formed using the fuel cell according to any one of claims 1 to 4,
When a surface of the fuel cell where the first metal porous body layer is exposed is an anode surface and a surface of the fuel cell where the second metal porous body layer is exposed is a cathode surface,
a cell array in which a plurality of the fuel cell units are stacked alternately at predetermined intervals while being inverted so that the anode surfaces face each other and the cathode surfaces face each other;
an anode gas flow path formed in a space between adjacent fuel cells in the cell array where the anode surfaces face each other, and through which the anode gas flows;
a cathode gas flow path formed in a space between adjacent fuel cells in the cell array where the cathode surfaces face each other, and through which the cathode gas flows;
a bus bar electrically connecting adjacent fuel cell units in the cell array;
A fuel cell stack comprising: 6. The fuel cell stack according to claim 5,
The bus bar electrically connects the first metal porous body layer and the second metal porous body layer between adjacent fuel cell units in the cell array, thereby connecting the fuel cell units in series. 6. The fuel cell stack according to claim 5,
The bus bar connects the first metal porous body layers and the second metal porous body layers between adjacent fuel cell units in the cell arrangement, thereby connecting the fuel cell units in parallel. A fuel cell stack according to any one of claims 5 to 7,
a height of the cathode gas flow channel, which is the distance between the cathode surfaces, is greater than a height of the anode gas flow channel, which is the distance between the anode surfaces;
Fuel cell stack. A fuel cell stack according to any one of claims 5 to 8,
When a flow direction of the anode gas and the cathode gas flowing in parallel or opposite directions is defined as a first direction, and a direction perpendicular to the first direction is defined as a second direction, an active area in which power is generated is longer in the first direction than in the second direction.
Fuel cell stack. 10. The fuel cell stack of claim 9,
the bus bar is attached in parallel to the cell array in the first direction;
a length of the bus bar along the first direction is equal to or greater than a length of the active area along the first direction;
Fuel cell stack. 10. The fuel cell stack of claim 9,
When the anode gas and the cathode gas flow in parallel,
the bus bar is attached in parallel to the cell array in the first direction;
a length of the bus bar along the first direction is shorter than a length of the active area along the first direction;
the bus bar is provided unevenly on the upstream side of the anode gas and the cathode gas with respect to the active area;
Fuel cell stack. 12. The fuel cell stack of claim 11,
the first metal porous layer is provided with a reforming catalyst for reforming fuel in a part or the whole of a range of a current concentration area formed in the active area by the presence of the bus bar;
Fuel cell stack.

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