JP2019114563A - Fuel cell stack - Google Patents

Abstract

To provide a fuel cell stack capable of suppressing damage caused by thermal stress.SOLUTION: In a fuel cell stack 1, a plurality of fuel battery cells 2 are laminated and arranged. The fuel battery cell 2 includes: a solid electrolyte layer; an anode layer arranged on one face side of the solid electrolyte layer; and a cathode layer arranged on the other face side of the solid electrolyte layer. The cathode layer includes: a functional layer 230 functioning as an electrode; and a contact layer 231 applied to the surface 232 of the functional layer 230. The contact layer 231 is made of only a contact member which is linearly applied to the surface 232 of the functional layer 230. In the contact member, a plurality of linear contact members 231b are contained, formed so as to extend in the direction along the composite vector of a fuel gas flow direction and an oxidant gas flow direction. A wire interval of the linear contact member 231b becomes narrower toward the downstream side of the composite vector.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a fuel cell stack in which fuel cells are stacked.

  Conventionally, there is a fuel cell stack described in Patent Document 1. In the fuel cell stack described in Patent Document 1, fuel cells are stacked. The fuel cell has a first electrode, a second electrode, and a solid electrolyte. The first electrode is an anode. The second electrode is a cathode. The solid electrolyte is disposed between the first electrode and the second electrode. The fuel cell described in Patent Document 1 has a fuel gas inlet, a fuel gas outlet, an air inlet, and an air outlet. The fuel gas inlet is provided to the first electrode and supplies the fuel gas to the first electrode. The fuel gas outlet is disposed to face the fuel gas inlet. The air inlets are provided at at least two locations on the fuel gas inlet side of one of the side edges of the pair of side edges opposed to each other along the flow direction of the fuel gas on the second electrode side. The air inlet supplies air to the second electrode. The air outlet is provided on the fuel gas outlet side of the other outer edge of the second electrode facing the air inlet.

JP 2002-141081 A

  By the way, in the fuel cell described in Patent Document 1, the fuel gas flowing into the first electrode from the fuel gas inlet flows to the fuel gas outlet while reacting chemically. When the fuel gas chemically reacts, the fuel gas becomes lean accordingly. As a result, the fuel gas becomes thinner as it goes from the fuel gas inlet to the fuel gas outlet. Such a change in the concentration of the fuel gas makes the heat generation distribution of the fuel cell uneven. Specifically, the calorific value increases as the concentration of the fuel gas increases. On the other hand, the lower the concentration of the fuel gas, the lower the calorific value. When such a nonuniform heat generation distribution is generated in the fuel cell, thermal stress is generated from the fuel cell as a starting point. The thermal stress damages each component. In particular, damage to the gas seal immediately leads to failure of the fuel cell stack.

  The present invention has been made in view of the above circumstances, and an object thereof is to suppress a thermal stress originating from a fuel cell to thereby suppress a fuel cell stack capable of suppressing a damage caused by the thermal stress. It is to provide.

  In order to solve the above-mentioned subject, a fuel cell stack (1) in which a plurality of fuel cells (2) are stacked is provided with a metal member (3) disposed between adjacent fuel cells. The fuel cell comprises a solid electrolyte layer (21), an anode layer (20) disposed on one side of the solid electrolyte layer, and a cathode layer (23) disposed on the other side of the solid electrolyte layer. There is. The cathode layer has a functional layer (230) functioning as an electrode, and a contact layer (231) applied to the surface of the functional layer in order to reduce the contact resistance at the contact portion with the metal member. The contact layer consists only of the contact material applied linearly on the surface of the functional layer. The contact material includes a plurality of linear contact materials (231 b) formed to extend in a direction along the composite vector of the flow direction of the fuel gas and the flow direction of the oxidant gas. As the line spacing of the linear contact material becomes narrower toward the downstream side in the direction of the composite vector, the coating distribution of the contact layer becomes uneven. The non-uniform distribution of application of the contact layer results in the non-uniform distribution of resistance of the cathode layer.

  As in the above configuration, if the cathode layer is provided with a non-uniform resistance distribution, the amount of generated heat is increased in the region of high resistance value in the cathode layer because the current flowing during power generation is increased. On the other hand, in the region where the resistance value is low in the cathode layer, the amount of heat generated is reduced because the current flowing during power generation is reduced. Therefore, if a resistance distribution is provided in the cathode layer such that the calorific value caused by the concentration of hydrogen and air and the calorific value caused by the magnitude of the current at the time of power generation are inversely correlated, the fuel cell is consequently obtained. The calorific value of the cell can be made uniform. That is, the heat generation distribution of the fuel cell can be made uniform. Therefore, since the thermal stress originating from the fuel cell can be suppressed, damage to the fuel cell stack due to the thermal stress can be suppressed.

  In addition, the code | symbol in the parentheses as described in said means and a claim is an example which shows a correspondence with the specific means as described in embodiment mentioned later.

  According to the present invention, damage to the fuel cell stack due to thermal stress can be suppressed.

FIG. 2 is a cross-sectional view showing a cross-sectional structure of a fuel cell stack according to a first embodiment. It is a top view which shows the temperature distribution which arises in the conventional fuel cell. It is a top view which shows resistance distribution of the fuel cell of 1st Embodiment. It is a top view which shows the density distribution of the contact layer of the fuel cell of 1st Embodiment. It is an enlarged view which shows the expansion structure of the area | region S of FIG. It is an enlarged view which shows the expansion structure of the area | region S of FIG. It is a top view which shows the planar structure of the anode layer in the fuel cell of 2nd Embodiment. It is a top view which shows the planar structure of the anode layer in the fuel cell of the modification of 2nd Embodiment. It is a top view which shows the density distribution of the contact layer of the fuel cell of 3rd Embodiment. It is a top view which shows the density distribution of the contact layer of the fuel cell of 4th Embodiment.

First Embodiment
Hereinafter, an embodiment of a fuel cell stack will be described. First, an outline of the fuel cell stack 1 of the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the fuel cell stack 1 of the present embodiment has a structure in which solid oxide fuel cells 2 and separators 3 are alternately stacked. Hereinafter, the solid oxide fuel cell 2 is referred to as "SOFC 2". The direction in which the SOFC 2 and the separator 3 are stacked is referred to as a stacking direction A. The SOFC 2 and the separator 3 have a rectangular cross-sectional shape perpendicular to the stacking direction A. In the fuel cell stack 1 of the present embodiment, hydrogen is used as the fuel gas supplied to the SOFC 2. In addition, air, more specifically, oxygen in the air, is used as the oxidant gas supplied to the SOFC 2.

  The separator 3 is disposed between the SOFCs 2 and 2 adjacent in the stacking direction A. The separator 3 is made of a metal such as a ferrite metal. In the present embodiment, the separator 3 corresponds to a metal member. The separator 3 has a function of separating hydrogen and air supplied to the SOFC 2 and a function of electrically connecting each SOFC 2. A fuel gas channel 30 is formed on one surface of the separator 3 in the stacking direction A. The fuel gas flow passage 30 allows hydrogen to flow in the direction indicated by the arrow B in the drawing, that is, in the direction from one side of the separator 3 to the other side. The hydrogen flow direction B is orthogonal to the stacking direction A. In the present embodiment, the hydrogen flow direction B corresponds to the flow direction of the fuel gas. An air channel 31 is formed on the other surface of the separator 3 in the stacking direction A. The air flow path 31 circulates air in the direction indicated by the arrow C in the figure. The air flow direction C is a direction orthogonal to both the stacking direction A and the hydrogen flow direction B. In the present embodiment, the air flow direction C corresponds to the flow direction of the oxidant gas. As described above, in the fuel cell stack 1 of the present embodiment, a so-called cross flow type supply method is adopted in which the hydrogen flow direction B and the air flow direction C are orthogonal to each other.

  The SOFC 2 has a structure in which an anode layer 20, a solid electrolyte layer 21, an intermediate layer 22, and a cathode layer 23 are laminated in this order. That is, the anode layer 20 is disposed on one side of the solid electrolyte layer 21. The cathode layer 23 is disposed on the other surface side of the solid electrolyte layer 21. The SOFC 2 generates electric power based on a chemical reaction between hydrogen supplied from the fuel gas channel 30 to the anode layer 20 and oxygen in the air supplied from the air channel 31 to the cathode layer 23.

The cathode layer 23 includes a functional layer 230 and a contact layer 231.
The functional layer 230 is configured of a porous thin plate-like fired body. The functional layer 230 is made of, for example, a prosquito based oxide. In the functional layer 230, oxygen ions are generated by receiving oxygen transmitted from the separator 3 in the air. That is, the functional layer 230 has a function as an electrode that reduces oxygen in the air.

  The contact layer 231 is applied to the surface 232 in contact with the separator 3 in the functional layer 230. The contact layer 231 is made of, for example, LNF (lanthanum nickel ferrite). The contact layer 231 has a function of reducing the contact resistance at the contact portion of the separator 3 while securing the conductivity of the functional layer 230 and the separator 3.

  The intermediate layer 22 is formed of a thin plate-like fired body. The intermediate layer 22 is made of, for example, GDC (gadolinium-doped ceria) or SDC (samarium-doped ceria). The intermediate layer 22 has a phenomenon that a high resistance layer is formed between the solid electrolyte layer 21 and the cathode layer 23 when the solid electrolyte layer 21 and the cathode layer 23 react with each other when manufacturing or operating the fuel cell stack 1. It has a suppressing function.

  The solid electrolyte layer 21 is made of a dense thin plate-like fired body. The solid electrolyte layer 21 is made of, for example, YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), SDC, GDC, and a prosquito-based oxide. The solid electrolyte layer 21 has a function of transferring oxygen ions generated in the cathode layer 23 to the anode layer 20.

The anode layer 20 is made of a porous thin plate-like fired body. The anode layer 20 is made of, for example, a metal such as Ni (nickel) or a cermet of a metal such as Ni and a ceramic. The cermet is, for example, Ni metal such as YSZ and ZrO ₂ based ceramics. In the anode layer 20, water is generated by a chemical reaction between oxygen ions (O ^2- ) moving from the cathode layer 23 through the solid electrolyte layer 21 and hydrogen supplied from the fuel gas flow path 30. Be done. The electrons emitted during this chemical reaction cause the SOFC 2 to generate electricity. That is, the anode layer 20 has a function as an electrode that oxidizes hydrogen.

  The SOFC 2 includes a diffusion layer 4 disposed between the anode layer 20 and the separator 3. The diffusion layer 4 is made of, for example, a porous metal such as Ni mesh. The diffusion layer 4 has conductivity between the separator 3 and the anode layer 20 and gas permeability that enables supply of hydrogen to the anode layer 20.

  Incidentally, as shown in FIG. 2, in the conventional fuel cell stack 5, the inventor has confirmed that the heat generation distribution of the SOFC 6 becomes uneven by experiments, simulation analysis and the like. FIG. 2 shows the planar structure of the conventional SOFC 6 as viewed from the cathode layer 60 side. In addition, in FIG. 2, illustration of the separator is abbreviate | omitted for convenience. The dashed dotted line in FIG. 2 represents the isotherm. As shown in FIG. 2, assuming that the composite vector of the hydrogen flow direction B and the air flow direction C is “D”, the heat generation distribution that the temperature decreases as it goes in the direction substantially equivalent to the composite vector D is generated in SOFC 6 . In other words, the SOFC 6 has a heat generation distribution in which the temperature rises as it goes in the direction opposite to the composite vector D. This is considered to be due to the following reasons.

  In the fuel cell stack, in order to improve the utilization rate of hydrogen which is a fuel gas and achieve high efficiency, the air may be supplied excessively, while the amount of supplied hydrogen may be suppressed. In this case, since hydrogen is insufficient toward the downstream side in the hydrogen flow direction B, power generation is less likely to occur. Further, the region where power generation is most likely to occur is the region where the concentration of hydrogen and air is the highest, that is, the region in the opposite direction of the composite vector D. The regions with high concentrations of hydrogen and air are also regions with high partial pressures of hydrogen and air. In the area where power generation is likely to occur, the calorific value is large. Therefore, the heat generation distribution in which the temperature rises in the opposite direction to the composite vector D is generated in the SOFC 6. When an exothermic distribution due to the concentration of hydrogen and air occurs in the SOFC 6, thermal stress is generated in the SOFC 6. This causes the fuel cell stack 1 to be damaged.

  Therefore, in the SOFC 2 of the present embodiment, the heat generation distribution of the SOFC 2 is made uniform by providing the cathode layer 23 with a non-uniform resistance distribution. Specifically, as shown in FIG. 3, the cathode layer 23 is provided with a resistance distribution such that the resistance value decreases as it goes in the direction of the composite vector D. In FIG. 3, the separator 3 is omitted for the sake of convenience. In the region of the cathode layer 23 where the resistance value is low, the amount of heat generated increases because the current flowing during power generation increases. On the other hand, in the region of the cathode layer 23 where the resistance value is high, the amount of heat generated is reduced because the current flowing during power generation is reduced. Therefore, if resistance distribution as shown in FIG. 3 is provided in the cathode layer 23, the calorific value due to the concentration of hydrogen and air and the calorific value due to the magnitude of the current at the time of power generation are inversely correlated. As a result, the calorific value of SOFC 2 can be made uniform.

Next, a specific structure of the cathode layer 23 of the present embodiment will be described.
In the cathode layer 23, a resistance distribution is provided by changing the density of the contact layer 231. Specifically, the contact layer 231 is applied so as to have a higher density toward the direction of the composite vector D. FIG. 4 is a diagram showing the density of the contact layer 231 in gray scale. In FIG. 4, it is shown that the density of the contact layer 231 is higher as the shade of gray scale becomes deeper.

  FIG. 5 is an enlarged view of a region S of the cathode layer 23 in FIG. As shown in FIG. 5, the contact layer 231 is formed of a plurality of contact materials 231 a applied in a dot shape on the surface 232 of the functional layer 230. As a method of applying the contact material 231a in a dot shape to the surface 232 of the functional layer 230, a coating method using a dispenser, a coating method based on screen printing, or the like can be used. The contact members 231a are arranged in a lattice. In the present embodiment, the density of the contact layer 231 is changed by changing the dot diameter d of the contact material 231a. The dot diameter d of the contact material 231a is the diameter of the contact material 231a. Specifically, the dot diameter d of the contact material 231a is larger as the density of the contact layer 231 shown in FIG. 4 is higher. Further, the dot diameter d of the contact material 231a is smaller as the density of the contact layer 231 is lower. The dot interval w of the contact material 231 a shown in FIG. 5 is constant in the entire region of the contact layer 231. The dot interval w is the center-to-center distance between adjacent contact members 231a and 231a.

  In the high density region of the contact layer 231, the contact resistance with the separator 3 is reduced as compared to the low density region. Thus, in the high density region of the contact layer 231, the resistance value of the cathode layer 23 can be reduced. Further, in the region where the contact layer 231 has a low density, the resistance value of the cathode layer 23 can be increased. Therefore, by changing the density of the contact layer 231 as shown in FIG. 4, it is possible to provide the cathode layer 23 with a resistance distribution as shown in FIG.

  According to the fuel cell stack 1 of the present embodiment described above, the actions and effects shown in the following (1) to (3) can be obtained.

  (1) The cathode layer 23 is provided with a non-uniform resistance distribution such that the resistance value becomes lower toward the combined vector D in the hydrogen flow direction B and the air flow direction C. That is, the cathode layer 23 has a nonuniform resistance distribution such that there is a region having a high resistance value and a region having a resistance value lower than the region having a high resistance value. As a result, the calorific value resulting from the concentration of hydrogen and air and the calorific value resulting from the magnitude of the current at the time of power generation are inversely correlated, and as a result, the calorific value of SOFC 2 can be made uniform. . That is, the heat generation distribution of SOFC 2 can be made uniform. Therefore, since the thermal stress originating from the SOFC 2 can be suppressed, damage to the fuel cell stack 1 due to the thermal stress can be suppressed. As a result, long-term stable operation of the fuel cell stack 1 can be ensured.

  In addition, since local heat generation at the contact portion between the cathode layer 23 and the separator 3 is suppressed via the contact layer 231, sintering of the contact layer 231 can be suppressed. When the contact layer 231 is sintered, the contact area between the functional layer 230 of the cathode layer 23 and air is reduced. Therefore, by suppressing the sintering of the contact layer 231, it is possible to suppress the decrease in the contact area between the functional layer 230 of the cathode layer 23 and the air. Thus, the life of the fuel cell stack 1 can be extended.

  (2) In the cathode layer 23, the application distribution of the contact layer 231 is not uniform, so the resistance distribution of the cathode layer 23 is not uniform. The application distribution of the contact layer 231 is set based on the hydrogen flow direction B and the air flow direction C. Thereby, the resistance distribution of the cathode layer 23 can be easily made uneven.

  (3) In the contact layer 231, the application distribution of the contact layer 231 is not uniform because the dot diameter d of the contact material 231a is changed. Thereby, the resistance distribution of the cathode layer 23 can be easily made uneven.

(First modification)
Next, a first modification of the fuel cell stack 1 of the first embodiment will be described.
As shown in FIG. 6, in the contact layer 231 of the present modification, the contact materials 231a are arranged in a diagonal lattice. Also in the contact layer 231, the dot diameter d of the contact material 231a is larger as the density of the contact layer 231 shown in FIG. 4 is higher. Further, the dot interval w of the contact material 231 a is constant in the entire region of the contact layer 231. Even with such a configuration, the actions and effects shown in (1) to (3) of the first embodiment can be obtained.

(2nd modification)
Next, a second modification of the fuel cell stack 1 of the first embodiment will be described.
In the contact layer 231 of this modification, the dot diameter d of the contact material 231 a is constant over the entire area of the contact layer 231. On the other hand, the dot interval w of the contact material 231a shown in FIG. 5 is shorter as the density of the contact layer 231 shown in FIG. 4 is higher. Even with such a configuration, it is possible to provide the cathode layer 23 with a nonuniform resistance distribution such that the resistance value becomes lower toward the direction of the combined vector D in the hydrogen flow direction B and the air flow direction C. It is possible to obtain the actions and effects shown in (1) and (2) of the first embodiment. The configuration of this modification can also be applied to the fuel cell stack 1 of the first modification of the first embodiment.

(Third modification)
Next, a third modification of the fuel cell stack 1 of the first embodiment will be described.
In the contact layer 231 of this modification, the dot diameter d of the contact material 231a shown in FIG. 5 becomes larger and the dot interval w of the contact material 231a becomes shorter as the density of the contact layer 231 shown in FIG. 4 increases. It has become. Even with such a configuration, it is possible to provide the cathode layer 23 with a nonuniform resistance distribution such that the resistance value becomes lower toward the direction of the combined vector D in the hydrogen flow direction B and the air flow direction C. It is possible to obtain the actions and effects shown in (1) and (2) of the first embodiment. The configuration of this modification can also be applied to the fuel cell stack 1 of the first modification of the first embodiment.

Second Embodiment
Next, a second embodiment of the fuel cell stack 1 will be described. Hereinafter, differences from the first embodiment will be mainly described.

  As shown in FIG. 7, the contact layer 231 of the present embodiment is formed of a plurality of contact members 231 b linearly applied to the surface 232 of the functional layer 230. A plurality of contact members 231 b are provided to extend in the direction of the composite vector D. As a method of applying the contact material 231b in a linear shape on the surface 232 of the functional layer 230, a coating method using a dispenser, a coating method based on screen printing, or the like can be used. In the present embodiment, the density of the contact layer 231 is changed by changing the inter-line distance h1 of the contact material 231b. The line spacing h1 of the contact members 231b indicates the spacing between the adjacent contact members 231b and 231b. Specifically, as the hydrogen flow direction B and the air flow direction C are directed in the direction of the combined vector D, the inter-line distance h1 of the contact material 231b is shorter. Thereby, the density distribution as shown in FIG. 4 can be provided in the contact layer 231.

  According to the fuel cell stack 1 of the present embodiment described above, in addition to the actions and effects of (1) and (2) of the first embodiment, the actions and effects shown in the following (4) can be obtained .

  (4) In the contact layer 231, the application distribution of the contact layer 231 is uneven due to the change in the inter-line distance h1 of the contact material 231b. Thereby, the resistance distribution of the cathode layer 23 can be easily made uneven.

(Modification)
Next, a modification of the fuel cell stack 1 of the second embodiment will be described.
As shown in FIG. 8, the contact layer 231 of the present embodiment is formed of the contact materials 231 b and 231 c provided in a hatched manner on the surface 232 of the functional layer 230, in other words, in a cross shape. A plurality of contact members 231 b are provided to extend in the direction of the composite vector D. A plurality of contact members 231c are provided so as to extend in a direction substantially orthogonal to the extending direction of the contact members 231b. In the present modification, the density of the contact layer 231 is changed by changing the line spacing h1 of the contact material 231b and the line spacing h2 of the contact material 231c. The line spacing h1 of the contact members 231b indicates the spacing between the adjacent contact members 231b and 231b. The line spacing h2 of the contact members 231c indicates the spacing between the adjacent contact members 231c and 231c. Specifically, as the hydrogen flow direction B and the air flow direction C are directed in the direction of the combined vector D, the inter-line distance h1 of the contact material 231b is shorter. Further, as the hydrogen flow direction B and the direction of the combined vector D in the air flow direction C go, the inter-line distance h2 of the contact material 231c is also shorter. Even with such a configuration, the application distribution of the contact layer 231 can be made uneven, so the resistance distribution of the cathode layer 23 can be easily made uneven.

Third Embodiment
Next, a third embodiment of the fuel cell stack 1 will be described. Hereinafter, differences from the first embodiment will be mainly described.

  As shown in FIG. 9, in the fuel cell stack 1 of the present embodiment, the hydrogen flow direction B and the air flow direction C are the same. That is, in the fuel cell stack 1 of the present embodiment, a so-called coflow type supply method is employed.

  As shown in gray scale in FIG. 9, the cathode layer 23 is coated with the contact layer 231 so as to have a higher density in the hydrogen flow direction B. That is, the cathode layer 23 is provided with a non-uniform resistance distribution such that the resistance value decreases as going in the hydrogen flow direction B. Thus, the application distribution of the contact layer 231 of the present embodiment is set based on the hydrogen flow direction B.

  According to the fuel cell stack 1 of the present embodiment described above, in addition to the functions and effects shown in (3) of the first embodiment, the functions and effects shown in the following (5) can be obtained.

  (5) In the case where hydrogen and air flow as shown in FIG. 9, since hydrogen is insufficient toward the downstream side in the hydrogen flow direction B, power generation is less likely to occur. Therefore, the heat generation distribution that the temperature decreases as it goes to the downstream side in the hydrogen flow direction B is generated in the SOFC 2. Therefore, as in the present embodiment, if the cathode layer 23 is provided with a resistance distribution in which the resistance value decreases in the hydrogen flow direction B, the amount of heat generation due to the concentration of hydrogen and air, and power generation The amount of heat generated due to the magnitude of the current is inversely correlated. Therefore, since the heat generation distribution of SOFC 2 can be made uniform, it is possible to suppress the thermal stress originating from SOFC 2. As a result, damage to the fuel cell stack 1 caused by thermal stress can be suppressed. Further, since the sintering of the contact layer 231 is suppressed, the life of the fuel cell stack 1 can be extended.

Fourth Embodiment
Next, a fourth embodiment of the fuel cell stack 1 will be described. Hereinafter, differences from the first embodiment will be mainly described.

  As shown in FIG. 10, in the fuel cell stack 1 of the present embodiment, the hydrogen flow direction B and the air flow direction are opposite to each other. That is, in the fuel cell stack 1 of the present embodiment, a so-called counterflow type supply method is employed.

  As shown in gray scale in FIG. 10, the contact layer 231 is applied to the cathode layer 23 so as to be denser in the hydrogen flow direction B. That is, the cathode layer 23 is provided with a non-uniform resistance distribution such that the resistance value decreases as going in the hydrogen flow direction B. Thus, the application distribution of the contact layer 231 of the present embodiment is set based on the hydrogen flow direction B.

  According to the fuel cell stack 1 of the present embodiment described above, in addition to the functions and effects shown in (3) of the first embodiment, the functions and effects shown in the following (6) can be obtained.

  (6) In the case where hydrogen and air flow as shown in FIG. 10, since hydrogen is insufficient toward the downstream side in the hydrogen flow direction B, power generation is less likely to occur. Therefore, the heat generation distribution that the temperature decreases as it goes to the downstream side in the hydrogen flow direction B is generated in the SOFC 2. Further, since the air warmed on the downstream side in the hydrogen flow direction B flows to the upstream side in the hydrogen flow direction B, the heat of the air is transmitted to the upstream side in the hydrogen flow direction B. This also causes the SOFC 2 to generate a heat generation distribution whose temperature decreases as it goes downstream in the hydrogen flow direction B. Therefore, as in the present embodiment, if the cathode layer 23 is provided with a resistance distribution in which the resistance value decreases in the hydrogen flow direction B, the amount of heat generation due to the concentration of hydrogen and air, and power generation The amount of heat generated due to the magnitude of the current is inversely correlated. Therefore, since the heat generation distribution of SOFC 2 can be made uniform, it is possible to suppress the thermal stress originating from SOFC 2. As a result, damage to the fuel cell stack 1 caused by thermal stress can be suppressed. Further, since the sintering of the contact layer 231 is suppressed, the life of the fuel cell stack 1 can be extended.

Other Embodiments
In addition, the said embodiment can also be implemented with the following forms.
The hydrogen flow direction B and the air flow direction C in the first embodiment are not limited to directions orthogonal to each other, and may be directions intersecting each other at a predetermined angle.

  In the fuel cell stack 1 of the third embodiment and the fourth embodiment, the method of making the application distribution of the contact layer 231 uneven is not limited to the method of changing the dot diameter d of the contact material 231a, and the first embodiment The methods of the first to third modified examples, and the methods of the second embodiment and the modified examples thereof can also be adopted.

  The contact layer 231 may be applied to the surface of the functional layer 230 in order to reduce the contact resistance of the contact portion with the metal member other than the separator 3.

  The method of making the resistance distribution of the cathode layer 23 uneven is not limited to the method of making the application distribution of the contact layer 231 uneven, and any appropriate method can be adopted. The point is that the cathode layer 23 should have a non-uniform resistance distribution.

  The fuel cell stack 1 of each embodiment may use a fuel gas other than hydrogen. Further, the fuel cell stack 1 of each embodiment may use an oxidant gas other than air.

  The present invention is not limited to the above specific example. That is, to the above specific examples, those skilled in the art may appropriately modify the design as long as the features of the present invention are included in the scope of the present invention. For example, each element included in each specific example described above and its arrangement, material, conditions, shape, size, and the like are not limited to those illustrated, and can be appropriately changed. Moreover, each element with which the above-mentioned embodiment is equipped can be combined as much as technically possible, and what combined these is also included in the scope of the present invention as long as the feature of the present invention is included.

1: Fuel cell stack 2: Solid oxide fuel cell (SOFC)
3: Separator (metal member)
20: anode layer 21: solid electrolyte layer 23: cathode layer 230: functional layer 231: contact layer 231a, 231b, 231c: contact material

Claims (5)

A fuel cell stack (1) in which a plurality of fuel cells (2) are stacked and disposed,
A metal member (3) disposed between the adjacent fuel cells;
The fuel cell includes a solid electrolyte layer (21), an anode layer (20) disposed on one side of the solid electrolyte layer, and a cathode layer (23) disposed on the other side of the solid electrolyte layer. Have
The cathode layer is
A functional layer (230) that functions as an electrode;
And a contact layer (231) applied to the surface of the functional layer to reduce contact resistance at the contact portion with the metal member.
The contact layer is made of only a contact material linearly applied to the surface of the functional layer,
A plurality of lines are formed on the contact material so as to extend in a direction along a composite vector of the flow direction of the fuel gas supplied to the anode layer and the flow direction of the oxidant gas supplied to the cathode layer Contact material (231b) is included,
The line spacing of the linear contact material becomes narrower toward the downstream side in the direction of the composite vector, whereby the application distribution of the contact layer becomes uneven.
A fuel cell stack in which the resistance distribution of the cathode layer is uneven due to the uneven application distribution of the contact layer. The fuel cell stack according to claim 1, wherein the linear contact material is formed in a straight line without break from the upstream end to the downstream end in the direction of the combined vector. The fuel cell stack according to claim 1, wherein the plurality of linear contact members are radially arranged on the surface of the functional layer. When the linear contact material is a first linear contact material,
The contact material is
A plurality of the first linear contacts;
A plurality of second linear contact members (231c) which are formed to extend in a direction intersecting the composite vector and which are provided to intersect the first linear contact members. The fuel cell stack according to any one of 1 to 3. 5. The fuel cell stack according to claim 4, wherein an inter-line interval of the plurality of second linear contact members becomes narrower toward the downstream side in the direction of the combined vector.