JP2018098081A - Solid oxide fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell stack with high durability and a good current extraction efficiency by adopting a one-end current collector structure to avoid, e.g., the concentration of current caused in a fuel battery cell bottom-end part in a solid oxide fuel cell stack having a plurality of columnar fuel battery cells arranged therein.SOLUTION: A solid oxide fuel cell stack comprises a plurality of columnar fuel battery cells 2, which is arranged to generate an electric power by supplying a fuel gas to fuel electrode layers 7 and an oxidant gas to air electrode layers 10 from one end toward the other end. Each fuel battery cell has a fuel electrode conductive layer 8 electrically connected to the fuel electrode layer 7, and an air electrode conductive layer 11 electrically connected to the air electrode layer 10. In the solid oxide fuel cell stack, the fuel electrode conductive layers 8 of the plurality of fuel battery cells 2 arrayed therein are electrically connected in series with the air electrode conductive layers 11 of the fuel battery cells 2 adjacent thereto through current collector joining members set only on the other end side. In the power-generation part of each fuel battery cell, a one-end side electric resistance is larger than that on the other-end side in a conducting path in an axial direction.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fuel cell stack. In particular, the present invention relates to a solid oxide fuel cell stack that generates power by a reaction between a fuel gas obtained by reforming a raw material gas and an oxidant gas.

  A solid oxide fuel cell device (hereinafter also referred to as “SOFC”) uses an oxide ion conductive solid electrolyte as an electrolyte, and a fuel cell having electrodes attached to both sides thereof in a multi-module container. The fuel cell is arranged to supply a fuel gas to one electrode (fuel electrode) and supply an oxidant gas (air, oxygen, etc.) to the other electrode (air electrode) to generate power by a power generation reaction. It is a device for extracting electric power, and operates at a relatively high temperature of, for example, about 700 to 1000 ° C. with respect to other fuel cell devices such as a polymer electrolyte fuel cell device.

  As fuel cells used in such a solid oxide fuel cell device, columnar fuel cells such as a cylindrical cell and a flat cylindrical cell described in Patent Document 1 are known. In general, since a single fuel battery cell (single cell) has a small amount of electric power, a plurality of these are arranged side by side and electrically connected in series to obtain the necessary electric power.

  By the way, in a columnar fuel cell such as a cylindrical cell, since the electrode extends in the axial direction, there is a problem that the distance of movement of electrons in the electrode is long and the power generation efficiency of the fuel cell is reduced. It was. Therefore, in Patent Document 1, as an electrical series connection to adjacent fuel cells, an air electrode (+ electrode) of one fuel cell and a fuel electrode (−electrode) of an adjacent fuel cell are provided. The connection is solved by a so-called “both ends current collecting” structure in which the current collecting members are used independently at the upper end and the lower end of the fuel cell. With this configuration, the current generated in the power generation unit of the fuel cell is distributed to the upper and lower ends of the fuel cell and extracted to the outside, so that the current path is shortened to reduce the electrical resistance.

  However, in general, fuel gas containing hydrogen is supplied to the internal flow path from the lower end side of the columnar fuel cell, and the hydrogen concentration in the supplied fuel gas is gradually consumed by the power generation reaction. Therefore, the hydrogen concentration decreases from the upstream side to the downstream side in the internal flow path. For this reason, the power generation reaction is more active at the lowermost end of the fuel cell, and the amount of generated current is large. Under this circumstance, when both-end current collection is adopted, current collection on the upstream side of the fuel cell (that is, the lower end side of the fuel cell), depending on the amount of fuel gas supplied or extracted, or the fuel cell current collection mode The inventor has found that current concentration may occur in the section. That is, there is a problem in that the main current generation region and the current extraction region coincide. The current concentration in the fuel cell causes various problems such as a decrease in durability due to deterioration of the fuel cell due to local power generation promotion and a decrease in output due to hindering extraction of generated current.

  In view of this, the inventor consolidates the current collecting structure only at the upper end portion of the fuel battery cell in order to suppress and avoid the current concentration at the lower end portion of the fuel battery cell, which is caused by taking the current collecting structure at both ends. We have found that the “electric (top current collector)” structure is optimal. In Patent Document 2, a current collecting member (connector) in which current collecting terminals connected to respective electrodes of adjacent fuel cells are connected and integrated by a conductive connecting member is used to connect the upper end portions of the fuel cells. A one-end current collecting structure in which are connected in series is disclosed.

Japanese Patent No. 5578332 JP 2007-95442 A

  By adopting the one-end current collecting structure described in Patent Document 2 described above as the current collecting structure of the columnar fuel cell, an area where the power generation amount at the lower end of the cell is maximized, and an area where terminals for taking out current are arranged Can be separated. As a result, it was estimated that current concentration was suppressed and the durability of the fuel cell was greatly improved.

  However, the inventor completely eliminated the problem of current concentration occurring at the lower end of the columnar fuel cell by simply adopting the one-end current collection structure as the current collection structure instead of the conventional both-end current collection structure. I found that I can't. That is, as long as the supply of fuel gas and oxidant gas is at the lower end of the columnar fuel cell, high-concentration fuel gas is first consumed in the power generation reaction at the lower end, so the amount of current generated is mainly at the lower end. This is because there is no change in the situation. For this reason, when adopting the one-end current collecting structure for avoiding the current concentration at the lower end as the current collecting structure of the fuel cell, further reduction and improvement of the current concentration at the lower end has been demanded.

  Therefore, the present invention adopts a configuration in which a current collecting structure of the fuel cell is a one-end current collecting structure and further avoids current concentration in a solid oxide fuel cell stack in which a plurality of columnar fuel cells are arranged. Thus, the present invention provides a solid oxide fuel cell stack that solves the problem of current concentration occurring at the lower end of a fuel cell.

  This also provides a solid oxide fuel cell stack with high durability and good current extraction efficiency.

  One aspect of a solid oxide fuel cell stack according to the present invention is a columnar fuel in which a power generation unit formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell stack in which a plurality of battery cells are arranged to generate power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel electrode of a fuel cell having a plurality of fuel cell cells, each having a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell through a current collector connecting member installed only on the other end side, and the axial direction in the power generation unit of the fuel cell In the conductive path, the electrical resistance at one end is greater than the electrical resistance at the other end. It is heard things.

  According to this aspect, when the columnar fuel cell configured to flow fuel gas and oxidant gas from one end side to the other end side has a one-end current collecting structure, the axial direction in the power generation unit of the fuel cell unit Since the electrical resistance on one end side is larger than that on the other end side in the conductive path, current flow on one end side is suppressed. By slowing down the current flow on one end side, the current flow as the whole power generation unit is adjusted, and it is possible to avoid the occurrence of current concentration that may occur on the other end side from which the current is extracted. Thereby, deterioration of the fuel cell due to current concentration can be suppressed, and a highly durable solid oxide fuel cell stack can be provided.

  Here, in this specification, the “columnar fuel cell” is a fuel cell having a three-dimensional shape extending in one direction (axial direction), and has a cylindrical shape in which a gas flow path is provided. Is included. For example, a solid shape such as a cylindrical shape such as a cylindrical shape or a flat cylindrical shape, an elliptical shape, or a rectangular shape is included.

  Further, in the present specification, the “fuel cell stack” is an assembly in which at least a plurality of fuel cells are physically fixed by connecting means such as a current collector or a sealing material. For example, fuel gas is temporarily stored. In addition, a plurality of fuel cells are installed and fixed on a fuel gas manifold for supplying the fuel cells in a distributed manner.

  In one embodiment of the present invention, the fuel electrode conductive layer on one end side is more than the fuel electrode conductive layer on the other end side and / or the air on one end side in the axial conductive path in the power generation unit of the fuel cell. The electrode conductive layer preferably has a larger electric resistance than the air electrode conductive layer on the other end side.

  According to this aspect, as a countermeasure against current concentration that may occur due to the one-end current collecting structure, the durability of the solid oxide fuel cell stack can be easily improved by adjusting the electric resistance of the fuel electrode conductive layer or the air electrode conductive layer. Can be realized.

  Moreover, in one aspect of the present invention, the fuel electrode conductive layer and / or the air electrode conductive layer in the power generation unit of the fuel cell unit are divided into two regions, one having a large resistance on one end side and a region having a small resistance on the other end side. It is preferable to consist of regions.

  According to this aspect, since the adjustment of the electric resistance of the fuel electrode conductive layer or the air electrode conductive layer can be realized by forming two regions divided by the magnitude of the resistance, measures against current concentration are implemented with a simple configuration. can do.

  In one embodiment of the present invention, the fuel electrode conductive layer on one end side is more than the fuel electrode conductive layer on the other end side and / or the air on one end side in the axial conductive path in the power generation unit of the fuel cell. The electrode conductive layer is preferably thinner than the air electrode conductive layer on the other end side.

  According to this aspect, it is possible to take measures against current concentration with a simple configuration in which the film thickness of the fuel electrode conductive layer or the air electrode conductive layer is appropriately changed.

  Further, in one aspect of the present invention, the fuel electrode conductive layer and / or the air electrode conductive layer in the power generation unit of the fuel cell gradually increase in thickness so that the electric resistance gradually decreases from one end side to the other end side. It is preferable to be thick.

  According to this aspect, since the film thickness of the fuel electrode conductive layer or the air electrode conductive layer is continuously changed, generation of discontinuous current distribution can be suppressed and local current concentration can be avoided.

  In one embodiment of the present invention, the fuel electrode conductive layer on one end side is more than the fuel electrode conductive layer on the other end side and / or the air on one end side in the axial conductive path in the power generation unit of the fuel cell. The polar conductive layer preferably has a higher porosity than the air electrode conductive layer on the other end side.

  According to this aspect, by increasing the porosity of the fuel electrode conductive layer or the air electrode conductive layer and decreasing the conductivity, the electrical resistance on one end side is increased and current concentration on the other end side is prevented. Can do.

  Here, the porosity in this specification is the ratio of the volume of pores (voids) to the layer volume in the layer. The porosity can be calculated, for example, by cutting the fuel cell in which each of the layers is formed and acquiring an SEM image of the cross section.

  In one embodiment of the present invention, it is preferable that the electrolyte on one end side has a larger electric resistance than the electrolyte layer on the other end side in the axial conductive path in the power generation unit of the fuel cell.

  According to this aspect, as a countermeasure against current concentration that can occur due to the one-end current collecting structure, the durability of the solid oxide fuel cell stack can be easily improved by adjusting the electric resistance of the electrolyte layer.

  In one embodiment of the present invention, the electrolyte layer in the power generation unit of the fuel cell preferably includes two regions, a region having a large resistance on one end side and a region having a small resistance on the other end side.

  According to this aspect, since the adjustment of the electric resistance of the electrolyte layer can be realized by forming two regions divided by the magnitude of the resistance, it is possible to take measures against current concentration with a simple configuration.

  In one embodiment of the present invention, it is preferable that the electrolyte layer on one end side is thicker than the electrolyte layer on the other end side in the axial conductive path in the power generation unit of the fuel cell.

  According to this aspect, since the electrolyte layer on one end side is made thicker than the electrolyte layer on the other end side, the electrical resistance on the one end side increases, so that measures for current concentration are implemented with a simple configuration. be able to.

  Moreover, in one aspect of the present invention, it is preferable that the electrolyte layer in the power generation unit of the fuel cell is configured to be gradually thinner so that the electrical resistance gradually decreases from one end side to the other end side.

  According to this aspect, since the thickness of the electrolyte layer is continuously changed, generation of discontinuous current distribution can be suppressed, and local current concentration can be avoided.

  Also, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation section formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell in which a plurality of fuel cells are arranged and power is generated by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel of a fuel cell that is a stack and has a fuel electrode layer that is a stack and has a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The electrode conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell via the current collector connecting member installed only on the other end side, and the axial direction in the power generation unit of the fuel cell The fuel electrode layer on one end side than the fuel electrode layer on the other end side, and Or, one end of the air electrode layer is also from the other end side of the air electrode layer, but the catalytic activity is low.

  According to this aspect, since the catalytic activity (electrocatalytic action) of the fuel electrode layer and the air electrode layer on the other end side is higher than that on the one end side, the generated current increases on the other end side. Concentration can be eased.

  Moreover, in one aspect of the present invention, the fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell are divided into two regions, one having a low catalytic activity at one end and the other having a high catalytic activity at the other end. It is preferable to consist of regions.

  According to this aspect, since it is possible to realize by forming two regions divided by the level of catalyst activity in the fuel electrode layer and the air electrode layer, it is possible to implement a countermeasure for current concentration with a simple configuration. it can.

  In one embodiment of the present invention, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side and / or the air electrode layer on one end side is the other end in the axial direction of the power generation unit of the fuel cell. The film thickness is preferably thinner than the air electrode layer on the side.

  According to this aspect, by making the film thickness of the fuel electrode layer or the air electrode layer thicker on the other end side than on the one end side, the catalytic activity can be further increased in the portion with high catalytic activity, and the current is effectively increased. Concentration measures can be implemented.

  Further, in one aspect of the present invention, the fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell are configured to gradually increase in thickness so that the catalytic activity gradually increases from one end side to the other end side. It is preferable that

  According to this aspect, since the film thickness of the fuel electrode layer or the air electrode layer is continuously changed, generation of discontinuous current distribution due to discontinuous change in catalyst activity is suppressed, and local current concentration is suppressed. Can be avoided.

  In one embodiment of the present invention, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side and / or the air electrode layer on one end side is the other end in the axial direction of the power generation unit of the fuel cell. It is preferable that the porosity is lower than the air electrode layer on the side.

  According to this aspect, by increasing the porosity of the fuel electrode layer and the air electrode layer on the other end side rather than the one end side, the reaction field at the three-phase interface is expanded and the power generation reaction on the other end side is activated. Therefore, it is possible to effectively implement current concentration countermeasures.

  Also, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation section formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell in which a plurality of fuel cells are arranged and power is generated by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel of a fuel cell that is a stack and has a fuel electrode layer that is a stack and has a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The electrode conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell via the current collector connecting member installed only on the other end side, and the axial direction in the power generation unit of the fuel cell The fuel electrode layer on one end side than the fuel electrode layer on the other end side, and Or, one end of the air electrode layer is also from the other end side of the air electrode layer, but a low gas diffusivity.

  According to this aspect, at least one of the fuel electrode layer, the fuel electrode conductive layer, the air electrode layer, and the air electrode conductive layer is configured to have high gas diffusibility on the other end side, so that the fuel gas and the oxidant The speed at which the gas reaches the three-phase interface can be increased, the electromotive force is increased, and the current easily flows. Therefore, a state where the current easily flows can be formed on the other end side. For this reason, it is possible to effectively take measures against current concentration.

  Further, in one aspect of the present invention, the fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell includes a region having a low gas diffusivity on one end side and a region having a high gas diffusibility on the other end side. It is preferable to consist of two regions.

  According to this aspect, since it is possible to realize by forming two regions divided by high and low gas diffusivity in the fuel electrode layer and the air electrode layer, it is necessary to implement a current concentration countermeasure with a simple configuration. Can do.

  In one embodiment of the present invention, the fuel electrode layer on the other end side is more than the fuel electrode layer on the one end side and / or the air electrode layer on the other end side is one end in the axial direction of the power generation unit of the fuel cell. The film thickness is preferably thinner than the air electrode layer on the side.

  According to this aspect, by reducing the film thickness of the fuel electrode layer or the air electrode layer on the other end side rather than the one end side, the gas diffusibility can be improved, and the current concentration countermeasure is effectively implemented. be able to.

  Further, in one aspect of the present invention, the fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell are gradually thinned so that the gas diffusivity gradually increases from one end side to the other end side. It is preferable to be configured.

  According to this aspect, since the film thickness of the fuel electrode layer or the air electrode layer is continuously changed, generation of discontinuous current distribution due to discontinuous change in gas diffusibility is suppressed, and local current is suppressed. Concentration can be avoided.

  In one embodiment of the present invention, the fuel electrode layer on the other end side is more than the fuel electrode layer on the one end side and / or the air electrode layer on the other end side is one end in the axial direction of the power generation unit of the fuel cell. It is preferable that the porosity is higher than that of the air electrode layer on the side.

  According to this aspect, by increasing the porosity of the fuel electrode layer or the air electrode layer on the other end side than the porosity on the other end side, the gas diffusibility can be improved and the occurrence of current concentration can be avoided. .

  In one embodiment of the present invention, at least one of the fuel electrode layer, the fuel electrode conductive layer, the air electrode layer, and the air electrode conductive layer on the other end side in the axial direction of the power generation unit of the fuel cell is It is preferable that the degree of bending is smaller than at least one of the corresponding fuel electrode layer, fuel electrode conductive layer, air electrode layer, and air electrode conductive layer on one end side.

  According to this aspect, by reducing the bending degree of the fuel electrode layer, the fuel electrode conductive layer, the air electrode layer, and the air electrode conductive layer on the other end side, the gas diffusibility on the other end side is improved and the current concentration is reduced. Occurrence can be avoided.

  Here, in this specification, the degree of bending means the effective distance of the communication path of the pores in the air electrode layer, the air electrode conductive layer, the fuel electrode layer, and the fuel electrode conductive layer that communicate with the pores existing in each of these layers. , Divided by the shortest straight line distance. The degree of flexion can be calculated by integrating a plurality of two-dimensional images observed by three-dimensional FIB-SEM (focused ion beam-scanning electron microscopy) into a three-dimensional calculation of the pore communication path, There is a method in which the pressure is obtained from a power generation experiment and calculated backward from the diffusion coefficient.

  In one embodiment of the present invention, the fuel electrode conductive layer on the other end side is provided on at least a part of the surface of the fuel electrode conductive layer and / or the air electrode conductive layer on the one end side in the axial direction of the power generation unit of the fuel cell. It is preferable that a layer having a lower gas diffusibility than the air electrode conductive layer is provided.

  According to this aspect, by separating the gas diffusibility from each other and forming a layer, the suppression of current concentration can be finely adjusted and can be manufactured separately.

  In one embodiment of the present invention, the layer having low gas diffusibility preferably has a lower porosity than the air electrode conductive layer and / or the fuel electrode conductive layer.

  According to this aspect, a layer with low gas diffusibility can be formed on one end side by forming the fuel electrode conductive layer or the air electrode conductive layer with a reduced porosity.

  In one embodiment of the present invention, the layer having low gas diffusibility preferably has a higher degree of bending than the air electrode conductive layer and / or the fuel electrode conductive layer.

  According to this aspect, a layer with low gas diffusibility can be formed on one end side by forming the fuel electrode conductive layer and the air electrode conductive layer with a high degree of bending.

  In one embodiment of the present invention, the layer having low gas diffusibility is preferably thicker than the air electrode conductive layer and / or the fuel electrode conductive layer.

  According to this aspect, the layer having low gas diffusibility can be formed on one end side by forming the fuel electrode conductive layer and the air electrode conductive layer thick.

  Also, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation section formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell in which a plurality of fuel cells are arranged and power is generated by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel of a fuel cell that is a stack and has a fuel electrode layer that is a stack and has a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The electrode conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell via a current collector connecting member installed only on the other end side, and further, the other end side of the fuel cell. Has a fuel gas other end supply pipe for supplying a part of the fuel gas directly to It is intended.

  According to this aspect, the fuel gas is supplied from one end side to the other end side of the fuel cell, and a part of the fuel gas is directly supplied to the other end side. Uf) can be controlled low. Therefore, since the electric current easily flows when the electromotive force of one fuel cell increases, the occurrence of current concentration on one end side can be suppressed.

  Also, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation section formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell in which a plurality of fuel cells are arranged and power is generated by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel of a fuel cell that is a stack and has a fuel electrode layer that is a stack and has a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The electrode conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell via a current collector connecting member installed only on the other end side, and some of the plurality of fuel cells are The fuel gas is consumed step by step by supplying the fuel gas in order Those that are configured.

  According to this aspect, the fuel gas supplied from one end side is consumed in the power generation reaction in the process of flowing to the other end side, and the unreacted fuel gas is supplied to the other fuel cells as it is to generate the power generation reaction. Is consumed. For this reason, the fuel utilization factor (Uf) on the other end side in one fuel battery cell can be controlled to be low. Therefore, since the electric current easily flows when the electromotive force of one fuel cell increases, the occurrence of current concentration on one end side can be suppressed.

  Here, in this specification, the fuel utilization rate (Uf) refers to the ratio of the amount of fuel gas used in the power generation reaction to the amount of fuel gas supplied to the fuel cells per unit time.

  Also, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation section formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer extends in the axial direction. A solid oxide fuel cell in which a plurality of fuel cells are arranged and power is generated by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer from one end to the other end of the columnar fuel cell A fuel of a fuel cell that is a stack and has a fuel electrode layer that is a stack and has a fuel electrode conductive layer electrically connected to the fuel electrode layer and an air electrode conductive layer electrically connected to the air electrode layer The electrode conductive layer is electrically connected in series with the air electrode conductive layer of the adjacent fuel cell via a current collector connecting member installed only on the other end side, and the fuel electrode layer on one end side and / or A reforming reaction preventing layer is provided on the surface of the fuel electrode conductive layer.

  According to this aspect, in the process in which the fuel gas supplied to the fuel cell flows from one end side to the other end side, methane contained in the fuel gas is reacted by the reforming reaction prevention layer provided on the one end side. Flows to the other end side in a state where is suppressed. On the other hand, methane is reformed into hydrogen by a steam reforming reaction and consumed. For this reason, since it becomes easy for a current to flow on the other end side, occurrence of current concentration can be suppressed.

  In one embodiment of the present invention, the reforming reaction preventing layer preferably has lower gas diffusibility than the fuel electrode layer and / or the fuel electrode conductive layer.

  According to this aspect, the reforming reaction prevention layer has a lower gas diffusibility than the fuel electrode layer or the fuel electrode conductive layer, thereby suppressing the progress of the reforming reaction on one end side and the other end side. The progress of the reforming reaction can be promoted.

  When constructing a solid oxide fuel cell stack in which multiple columnar fuel cells are arranged, one-sided current collection is adopted and electric resistance in the fuel cell is adjusted to avoid current concentration and durability Provided is a solid oxide fuel cell stack having high performance and high current extraction efficiency.

It is a perspective view which shows the fuel cell stack which is one Embodiment of this invention. It is a side view which shows the fuel cell stack in one Embodiment of this invention. It is a figure which shows the fuel cell in one Embodiment of this invention. It is a fragmentary sectional view showing a fuel cell in one embodiment of the present invention. It is sectional drawing which shows the fuel battery cell in one Embodiment of this invention. It is a side view which shows the fuel cell in one Embodiment of this invention. It is a side view which shows the fuel cell in one Embodiment of this invention. It is a side view which shows the fuel cell in one Embodiment of this invention. It is a side view which shows the fuel cell in one Embodiment of this invention.

  Hereinafter, embodiments of the invention disclosed in this specification will be described in detail with reference to the drawings. From the following description, many modifications and other embodiments of the present invention are apparent to persons skilled in the art. Accordingly, the following description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. Details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

(Fuel cell stack)
First, the fuel cell stack 1 according to the embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a perspective view showing a fuel cell stack 1 according to an embodiment of the present invention. As shown in FIG. 1, the fuel cell stack 1 includes a plurality of columnar fuel cells 2 having gas flow paths provided therein, and a manifold 3. The fuel cell 2 is supported and fixed with one end side (the lower end side in FIG. 1) standing upright on one manifold 3. The fuel cell 2 is also erected on the manifold 3 via an insulating support member 14 (also referred to as a bush) and is hermetically fixed by a glass ring 15.

  Here, the plurality of fuel cells 2 are connected to each other by the current collector connecting member 4 so as to be electrically in series. The fuel cell 2 at one end and the other end that are electrically connected in series is provided with a power extraction line (thick line in FIG. 1) for extracting electric power to the outside.

  As described above, the fuel gas is supplied from one end (lower end) of the fuel battery cell 2, and the fuel gas (hydrogen contained in the fuel gas) passes through the fuel gas passage 12 while being consumed in the power generation reaction. Discharged from the top. As indicated by the dotted line arrow in FIG. 5, the fuel gas is consumed in the power generation reaction as it proceeds through the fuel gas flow path 12 from the state of the high concentration fuel gas (hydrogen concentration in the fuel gas) at one end. At the end, low concentration fuel gas is discharged.

  FIG. 2 is a side view showing the fuel cell stack 1 according to the embodiment of the present invention. When the fuel gas is supplied to the inside of the manifold 3, the fuel gas is dispersed in the manifold 3 and flows in the plurality of fuel cells 2 from one end side to the other end side, and then the other ends of the plurality of fuel cells 2. It is discharged from the fuel cell stack 1 to the outside.

(Fuel battery cell)
Next, the fuel cell used in the embodiment of the present invention will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a diagram showing the fuel cell 2 constituting the fuel cell stack 1 in the embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of the end portion of the fuel battery cell 2.

  As shown in FIG. 3, the fuel battery cell 2 includes a cell body 6 and caps 5 (also referred to as metal caps) that are connection electrode portions connected to both ends of the cell body 6.

  As shown in FIG. 4, the cell body 6 in the case of having a conductive support as a support is a tubular structure extending in the vertical direction, and a fuel gas flow path 12 (also referred to as an internal flow path) that is a gas path inside. A cylindrical fuel electrode conductive layer 7 having conductivity, a fuel electrode layer 8 provided on the outer periphery of the fuel electrode conductive layer 7, and a cylindrical solid electrolyte provided on the outer peripheral side of the fuel electrode layer 8 An electrolyte layer 9 as a layer, a cylindrical air electrode (oxidant gas electrode) layer 10 provided on the outer periphery of the electrolyte layer 9, and an air electrode conductive layer 11 having conductivity on the outer periphery of the air electrode layer 10. ing. The fuel electrode conductive layer 7 is a porous body that functions as a support that constitutes the cell body 6 and that constitutes a gas passage through which fuel gas flows.

  The fuel electrode conductive layer 7 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, Sc, and ceria doped with at least one selected from rare earth elements. A mixture of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe and Cu. In the present embodiment, the fuel electrode conductive layer 7 is made of Ni / YSZ. A porous insulating support can be used as the support. In this case, the fuel electrode conductive layer is formed outside the insulating support.

  A fuel electrode layer 8 is formed on the outer periphery of the fuel electrode conductive layer 7. The fuel electrode layer is a catalyst layer and is made of Ni / GDC in this embodiment.

  The electrolyte layer 9 is formed over the entire circumference along the outer peripheral surface of the fuel electrode layer 8, the lower end is terminated above the lower end of the fuel electrode conductive layer 7, and the upper end is higher than the upper end of the fuel electrode conductive layer 7. It ends at the bottom. The electrolyte layer 9 is, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

  The air electrode layer 10 is formed over the entire circumference along the outer peripheral surface of the electrolyte layer 9. The lower end terminates above the lower end of the electrolyte layer 9, and the upper end terminates below the upper end of the electrolyte layer 9. ing. The air electrode layer 10 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

  An air electrode conductive layer 11 is formed on the outer periphery of the air electrode layer 10. The air electrode conductive layer 11 contains at least Ag, and the air electrode 10 has a conductive performance.

  Next, the cap 5 will be described. Since the caps 5 attached to the upper end side and the lower end side of the cell body 6 have the same structure, here, the cap 5 attached to the lower end side of the cell body 5 is specifically described. I will explain it.

  Caps 5 (metal caps) are provided so as to surround the upper and lower ends of the cell body 6, and are electrically connected to the fuel electrode conductive layer 7 of the cell body 6 to connect the fuel electrode conductive layer 7 to the outside. Functions as an electrode. As shown in FIG. 4, the cap 5 provided at the lower end of the cell body 6 includes a cylindrical first cylindrical portion 5a and an annular ring portion extending outward from the upper end of the first cylindrical portion 5a. 5b and a second cylindrical portion 5c extending upward from the outer periphery of the annular portion 5b. A fuel gas passage 13 communicating with the fuel gas passage 12 of the fuel electrode conductive layer 7 is formed at the center of the first cylindrical portion 5 a of the cap 5. The fuel gas flow path 12 is an elongated pipe line provided so as to extend in the axial direction of the cell body 6 from the center of the cap 5.

In the cap 5, chromium oxide (Cr ₂ O _{3 in} this embodiment) is coated on the inner peripheral surface and outer peripheral surface of a main body made of ferritic stainless steel or austenitic stainless steel, and the outer peripheral surface has MnCo ₂ O. ₄ is coated. In addition, an Ag current collector film is provided on the outer peripheral surface of the coated MnCo ₂ O ₄ layer. In the present embodiment, the Ag current collector film is provided over the entire outer peripheral surface of the cap 5, but may be provided only in part.

  A silver paste 14 is disposed in the space between the inside of the second cylindrical portion 5 c of the cap 5 and the outer peripheral surface of the end portion of the fuel electrode conductive layer 7 (fuel electrode layer 8) of the cell body 6. By firing after assembling the fuel cell 2, the silver paste 14 is sintered, and the fuel electrode conductive layer 7 and the cap 5 are electrically and mechanically coupled. A glass seal 15 made of a glass material is provided between the inner peripheral surface of the second cylindrical portion 5 c of the cap 5 and the outer peripheral surface of the lower end portion of the electrolyte layer 9. With this glass seal 15, the space between the cap 5 and the fuel electrode conductive layer 7 is hermetically sealed with respect to the space outside the fuel cell 2.

(Fuel cell collection structure)
Next, a current collecting structure of the fuel cell stack 1 will be described with reference to FIGS.

  The current collector connecting member 4 is connected so that adjacent fuel cells 2 are electrically in series. The cap 5 provided at the upper end of the fuel cell 2 is electrically coupled to the fuel electrode conductive layer 7, and the current collector connecting member 4 is connected to one of the adjacent fuel cells 2. The cap 5 provided at the upper end is electrically connected using silver paste. Furthermore, the current collector connecting member 4 is electrically connected to the air electrode conductive layer 11 of the other adjacent fuel cell 2 out of two adjacent fuel cells 2 using a silver paste.

  In this way, the fuel electrode conductive layer 7 of one adjacent fuel battery cell 2 and the air electrode conductive layer 11 of the other fuel battery cell 2 are connected to a plurality of fuel battery cells, and a plurality of fuel battery cells 2 are connected. As a result, the fuel cell stack 1 in which all the plurality of fuel cells 2 are connected in series is obtained.

  Further, by disposing a reformer and an evaporator in a combustion region where off gas discharged from the fuel cell stack is combusted, an arrangement configuration equivalent to that of a conventional fuel cell module can be applied. For this reason, it can respond to a small fuel cell device having an output performance of about 1 kw, and can provide a highly efficient and highly durable fuel cell system.

(Electric resistance of fuel cell)
Next, the electrical resistance of the fuel battery cell 2 will be described with reference to FIG.

(Air electrode conductive layer)
FIG. 5A is a cross-sectional view of the air electrode conductive layer 11 of the fuel battery cell 2 according to the present embodiment. The A1 region is configured to have a high electrical resistance on one end side, and the electrical resistance is configured to be low on the other end side. The fuel cell 2 provided with the made A2 area | region is shown.

  The air electrode conductive layer 11 is formed so that the film thickness is thin on one end side and thick on the other end side in the axial conductive path. That is, in the air electrode conductive layer 11, the film thickness on one end side is formed thin, so that the electrical resistance is increased in the conductive path in the axial direction, and the film thickness on the other end side is formed thick. In the axial direction, the electrical resistance is reduced. In other words, the air electrode conductive layer 11 has two regions, a region having a large resistance on one end side and a region having a small resistance on the other end side. Thereby, the flow of current on one end side is suppressed, and the flow of current from one end to the other end is adjusted by the slowing of the current flow on one end side.

  Further, in the fuel battery cell 2 shown in FIG. 5A, an inclination is formed in the film thickness so that the film thickness gradually changes from one end to the other end in the axial direction, and the film thickness continuously changes. It may be configured.

(Fuel electrode conductive layer)
FIG. 5B is a cross-sectional view of the anode current collecting layer 7 of the fuel battery cell 2 according to the present embodiment. The A1 region is configured to have a high electrical resistance on one end side, and has a low electrical resistance on the other end side. The fuel cell 2 provided with the made A2 area | region is shown. FIG.5 (b) shows sectional drawing of the fuel cell 2 in embodiment of this invention. The fuel electrode conductive layer 7 is formed so that the film thickness is thin at one end and thick at the other end in the axial conductive path. That is, in the fuel electrode conductive layer 7, the film thickness on one end side is formed thin, so that the electric resistance is increased in the axial conductive path, and the film thickness on the other end side is formed thick. In the axial direction, the electrical resistance is reduced. In other words, the fuel electrode conductive layer 7 has two regions, a region where the resistance on one end side is large and a region where the resistance on the other end side is small. Thereby, the flow of current on one end side is suppressed, and the flow of current from one end to the other end is adjusted by the slowing of the current flow on one end side. The fuel electrode conductive layer 7 may be configured such that the film thickness is inclined so that the film thickness gradually changes from one end to the other end in the axial direction, and the film thickness changes continuously.

(Electrolyte layer)
FIG.5 (c) is sectional drawing of the electrolyte layer 9 of the fuel cell 2 in this embodiment, and was comprised by A1 area | region where the electrical resistance of one end side was comprised high, and low electrical resistance in the other end side. The fuel cell 2 provided with A2 area | region is shown. FIG.5 (c) shows sectional drawing of the fuel cell 2 in embodiment of this invention. The electrolyte layer 9 is formed such that the film thickness is thicker at one end side and thinner at the other end side in the axial conductive path. That is, in the electrolyte layer 9 having low electronic conductivity, the film thickness on one end side is formed thick, so that the electric resistance is increased in the conductive path in the axial direction, and the film thickness on the other end side is formed thin. Therefore, the electric resistance is configured to be small in the conductive path in the axial direction. In other words, the electrolyte layer 9 has two regions, a region having a large resistance on one end side and a region having a small resistance on the other end side. Thereby, the flow of current on one end side is suppressed, and the flow of current from one end to the other end is adjusted by the slowing of the current flow on one end side. It should be noted that the electrolyte layer 9 may be configured such that the film thickness is changed so that the film thickness gradually changes from one end to the other end in the axial direction, and the film thickness changes continuously.

  5 (a), (b), and (c), in the functional layer (air electrode conductive layer 11, fuel electrode conductive layer 7, and electrolyte layer) of the fuel cell 2, one end side of the other end side is provided. It is also preferable to make the porosity high. In this case, since the porosity on the one end side is configured to be high, the conductivity on the one end side is decreased, so that the electrical resistance on the one end side is increased.

(Catalytic activity)
6 (a) and 6 (b) are cross-sectional views of the fuel battery cell 2 according to the embodiment of the present invention. The B1 region having low catalytic activity (electrocatalytic action) on one end side and the other end The fuel cell 2 provided with B2 area | region with high catalyst activity on the side is shown.

  The air electrode layer 10 of the fuel battery cell 2 in FIG. 6A is formed such that the film thickness on the other end side (upper end side) is thicker than that on one end side (lower end side), and the film thickness on one end side of the air electrode layer 10 is Thinly formed. In the B1 region where the film thickness on one end side is thin, the catalyst activity is configured to be low, and the power generation current on one end side is suppressed. On the other hand, in the B2 region where the film thickness on the other end side of the air electrode layer 10 is configured to be thick, the catalyst activity is increased, and the generated current on the other end side increases. For this reason, as described above, the fuel gas flowing through the fuel gas passage 12 is in a high concentration state at one end side, but the distribution of the generated current is made uniform by adjusting the film thickness of the air electrode layer 10. be able to.

  The fuel electrode layer 8 of the fuel cell 2 in FIG. 6B is formed such that the film thickness on the other end side (upper end side) is thicker than that on the one end side (lower end side). The fuel electrode layer 8 is formed so that the film thickness on one end side is thin and the catalytic activity is low, and the power generation current on one end side is suppressed. On the other hand, the film thickness on the other end side of the fuel electrode layer 8 is formed thick so that the catalytic activity is increased, and the generated current on the other end side increases. For this reason, the fuel gas flowing through the fuel gas passage 12 is in a high concentration state at one end as shown by the dotted arrow, but the distribution of the generated current is made uniform by adjusting the film thickness of the fuel electrode layer 8. be able to.

  In FIGS. 6A and 6B, the air electrode layer 10 or the fuel electrode layer 8 is inclined so that the film thickness gradually changes from one end to the other end in the axial direction. Is preferably configured to change continuously. In this case, generation of a discontinuous current distribution due to a discontinuous change in the catalyst activity can be suppressed.

  Further, in FIGS. 6A and 6B, it is preferable that the porosity on the other end side is higher than the one end side of the air electrode layer 10 or the fuel electrode layer 8, and the porosity on the other end side is preferable. Is increased so that the reaction field at the three-phase interface is expanded and the catalytic activity at the other end is increased.

(Gas diffusivity)
Here, the fuel electrode conductive layer 7, the fuel electrode layer 8, the air electrode layer 10, and the air electrode conductive layer 11 may be configured to have high diffusibility on the other end side (upper end side) of the fuel cell 2. preferable. When fuel gas or air (oxidant gas) is supplied to each electrode, the passing speed of the electrode having a high diffusibility increases, so that the speed of reaching the three-phase interface increases. As a result, the electromotive force increases on the other end side, so that a state in which current easily flows on the other end side is formed.

  The gas diffusibility in the electrode layer may be adjusted by the film thickness. In this case, by making the film thickness on the other end side (upper end side) thinner than the one end side (lower end side) of the fuel battery cell 2, gas diffusibility on the other end side is enhanced, and electromotive force is increased on the other end side. Therefore, a state in which current easily flows on the other end side is formed. As another means for adjusting gas diffusivity, it is also preferable to provide a layer having low gas diffusibility in the electrode layer.

  Moreover, the gas diffusibility in the electrode layer may be adjusted by the porosity. In this case, by lowering the porosity of the electrode layer on the other end side than the porosity on the one end side, the gas diffusibility on the other end side is increased and the electromotive force is increased on the other end side. A state in which current easily flows is formed.

  Moreover, the gas diffusibility in the electrode layer may be adjusted by the degree of bending. In this case, by increasing the bending degree of the electrode layer on the other end side than the bending degree on the one end side, the gas diffusibility on the other end side is increased and the electromotive force is increased on the other end side. A state in which current easily flows is formed.

  Note that the degree of bending is a value obtained by dividing the effective distance of the pore communication path through which the pores existing in the electrode layer communicate with each other by the shortest linear distance. The degree of flexion can be calculated by integrating a plurality of two-dimensional images observed by three-dimensional FIB-SEM (focused ion beam-scanning electron microscopy) into a three-dimensional calculation of the pore communication path, There is a method in which the pressure is obtained from a power generation experiment and calculated backward from the diffusion coefficient.

(Fuel gas other end supply pipe)
FIG. 7 shows a cross-sectional view of the fuel cell 2 in the embodiment of the present invention. The fuel gas is supplied to the fuel gas passage 12 from one end side of the fuel battery cell 2. The fuel gas passage 12 is provided with a fuel gas other end supply pipe 17, and the fuel gas that has passed through the fuel gas other end supply pipe 17 passes through the fuel gas passage 12 on the other end side of the fuel cell 2. Supplied directly. The fuel gas supplied from one end side to the fuel gas passage 12 merges with the fuel gas that has passed through the fuel gas other end supply pipe 17 on the other end side, and is discharged from the other end of the fuel cell 2. That is, the fuel gas is supplied from one end side of the fuel cell 2 toward the other end side, and a part of the fuel gas is directly supplied to the other end side.

(Connecting member)
FIG. 8 shows a cross-sectional view of the fuel cell according to the embodiment of the present invention. The first fuel cell C1 to which fuel gas is first supplied and the second fuel cell C2 are connected to each other. 18 is connected. The fuel gas passage 12 formed in each of the first fuel cell C1 and the second fuel cell C2 is communicated by the connecting member 18.

  The fuel gas supplied from one end (lower end) side of the first fuel cell C1 is consumed in the power generation reaction in the process of flowing to the other end side, and the unreacted fuel gas passes through the connecting member, and then the second It is supplied to one end (lower end) side of the fuel battery cell C2 and consumed in the power generation reaction. Although not shown, the first fuel cell C1 and the second fuel cell C2 are electrically connected, and may be connected by a separate current collecting member, or the connecting member 18 may be electrically conductive. You may comprise so that it may have.

(Modification reaction layer)
FIG. 9 shows a cross-sectional view of the fuel cell 2 according to the embodiment of the present invention. The fuel cell 2 is composed of D1 provided with the reforming reaction preventing layer 19 and D2 on the other end side. ing. The fuel gas passage 12 constituted by the fuel electrode conductive layer 7 is provided with a reforming reaction preventing layer 19 that suppresses a reforming reaction between methane contained in the fuel gas and the fuel electrode conductive layer 7. The fuel gas (methane) supplied from one end of the fuel cell 2 and the fuel electrode conductive layer cause an electrode reaction, thereby generating hydrogen, increasing the hydrogen concentration on one end side, and increasing the hydrogen concentration on one end side. Generates a generated current, which causes current concentration. However, according to the present embodiment, the fuel gas supplied to one end side is supplied to the other end side while the reforming reaction is suppressed by the reforming reaction preventing layer 19, and hydrogen is reformed on the other end side by the reforming reaction. Produced and consumed for power generation reaction. This makes it easier for the generated current to flow on the other end side, thereby suppressing power concentration.

  Further, the reforming reaction preventing layer 19 provided on one end side of the fuel cell 2 is configured to have a gas diffusibility lower than that of the fuel electrode conductive layer 7 and / or the fuel electrode layer 8, and one end side of the fuel cell. The progress of the reforming reaction is suppressed, and the reforming reaction on the other end side is promoted.

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Fuel cell 3 Manifold 4 Current collection connection member 5 Cap (metal cap)
5a 1st cylindrical part 5b annular part 5c 2nd cylindrical part 6 Cell body 7 Fuel electrode layer 8 Fuel electrode conductive layer 9 Electrolyte layer 10 Air electrode layer 11 Air electrode conductive layer 12 Fuel gas flow path 13 Fuel gas flow path 14 Insulation Supporting member 15 Glass ring 17 Fuel gas other end supply pipe 18 Connecting member 19 Reforming reaction preventing layer

Claims (29)

A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
The solid oxide fuel cell stack, wherein an electric resistance on one end side is larger than an electric resistance on the other end side in an axial conductive path in the power generation unit of the fuel cell.   In the conductive path in the axial direction in the power generation section of the fuel cell, the fuel electrode conductive layer on one end side is different from the fuel electrode conductive layer on the other end side and / or the air electrode conductive layer on the one end side is other. 2. The solid oxide fuel cell stack according to claim 1, wherein the electric resistance is larger than that of the air electrode conductive layer on the end side.   The fuel electrode conductive layer and / or the air electrode conductive layer in the power generation unit of the fuel cell is composed of two regions, a region having a large resistance on one end side and a region having a small resistance on the other end side. The solid oxide fuel cell stack according to claim 2.   In the conductive path in the axial direction in the power generation unit of the fuel cell, the fuel electrode conductive layer on one end side is more than the fuel electrode conductive layer on the other end side, and / or the air electrode conductive layer on one end side is on the other end side. 4. The solid oxide fuel cell stack according to claim 2, wherein a film thickness is thinner than that of the air electrode conductive layer.   The fuel electrode conductive layer and / or the air electrode conductive layer in the power generation unit of the fuel cell are configured to gradually increase in thickness so that the electrical resistance gradually decreases from one end side to the other end side. The solid oxide fuel cell stack according to claim 2, wherein:   In the conductive path in the axial direction in the power generation section of the fuel cell, the fuel electrode conductive layer on one end side is different from the fuel electrode conductive layer on the other end side and / or the air electrode conductive layer on the one end side is other. 4. The solid oxide fuel cell stack according to claim 2, wherein the porosity is higher than that of the air electrode conductive layer on the end side.   2. The solid oxide fuel cell according to claim 1, wherein an electrolyte on one end side has a larger electric resistance than an electrolyte layer on the other end side in an axial conductive path in the power generation unit of the fuel cell. stack.   8. The solid according to claim 7, wherein the electrolyte layer in the power generation unit of the fuel cell includes two regions, a region having a large resistance on one end side and a region having a small resistance on the other end side. Oxide fuel cell stack.   9. The solid according to claim 7, wherein the electrolyte layer on one end side is thicker than the electrolyte layer on the other end side in the axial conductive path in the power generation unit of the fuel cell. Oxide fuel cell stack.   The electrolyte layer in the power generation unit of the fuel battery cell is configured such that the thickness is gradually reduced so that the electric resistance gradually decreases from one end side to the other end side. Solid oxide fuel cell stack. A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side, and / or the air electrode layer on one end side is the air electrode on the other end side. A solid oxide fuel cell stack characterized by having lower catalytic activity than a layer.   The fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel cell is composed of two regions, a region having a low catalytic activity on one end side and a region having a high catalytic activity on the other end side. The solid oxide fuel cell stack according to claim 11.   In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side, and / or the air electrode layer on one end side is more than the air electrode layer on the other end side. The solid oxide fuel cell stack according to claim 11, wherein the film thickness is thin.   The fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell are configured to gradually increase in thickness so that the catalytic activity gradually increases from one end side to the other end side. The solid oxide fuel cell stack according to any one of claims 11 to 13.   In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side, and / or the air electrode layer on one end side is the air electrode on the other end side. The solid oxide fuel cell stack according to any one of claims 11 to 14, wherein the porosity is lower than that of the layer. A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on one end side is more than the fuel electrode layer on the other end side, and / or the air electrode layer on one end side is the air electrode on the other end side. A solid oxide fuel cell stack characterized by having a lower gas diffusivity than a layer.   The fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel battery cell includes two regions, a region having a low gas diffusibility on one end side and a region having a high gas diffusibility on the other end side. The solid oxide fuel cell stack according to claim 16, wherein:   In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on the other end side is more than the fuel electrode layer on one end side, and / or the air electrode layer on the other end side is more than the air electrode layer on one end side. The solid oxide fuel cell stack according to claim 16 or 17, wherein the film thickness is thin.   The fuel electrode layer and / or the air electrode layer in the power generation unit of the fuel cell are configured to be gradually thin so that gas diffusivity gradually increases from one end side to the other end side. The solid oxide fuel cell stack according to claim 16 or 18, characterized by the above.   In the axial direction of the power generation unit of the fuel cell, the fuel electrode layer on the other end side is more than the fuel electrode layer on one end side, and / or the air electrode layer on the other end side is the air electrode on one end side. The solid oxide fuel cell stack according to any one of claims 16 to 19, wherein the porosity is higher than that of the layer.   At least one of the fuel electrode layer, the fuel electrode conductive layer, the air electrode layer, and the air electrode conductive layer on the other end side in the axial direction of the power generation unit of the fuel battery cell corresponds to one end side corresponding thereto. 21. The degree of flexure is smaller than at least one of the fuel electrode layer, the fuel electrode conductive layer, the air electrode layer, and the air electrode conductive layer. 2. A solid oxide fuel cell stack according to 1.   In the axial direction of the power generation unit of the fuel cell, at least part of the surface of the fuel electrode conductive layer and / or the air electrode conductive layer on one end side, the fuel electrode conductive layer and / or the air on the other end side. The solid oxide fuel cell stack according to any one of claims 16 to 21, wherein a layer having a lower gas diffusibility than the polar conductive layer is provided.   The solid oxide fuel cell stack according to claim 22, wherein the layer having low gas diffusibility has a lower porosity than the air electrode conductive layer and / or the fuel electrode conductive layer.   The solid oxide fuel cell stack according to claim 22 or 23, wherein the layer having low gas diffusivity has a higher degree of bending than the air electrode conductive layer and / or the fuel electrode conductive layer.   The solid oxide according to any one of claims 22 to 24, wherein the layer having low gas diffusivity is thicker than the air electrode conductive layer and / or the fuel electrode conductive layer. Fuel cell stack. A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
The solid oxide fuel cell stack further comprises a fuel gas other end supply pipe for directly supplying a part of the fuel gas to the other end side of the fuel cell. A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
A solid oxide fuel cell stack, wherein a part of the plurality of fuel cells is configured so that the fuel gas is consumed in stages by sequentially supplying the fuel gas. A plurality of columnar fuel cells each having an axially extending power generation part formed by a fuel electrode layer and an air electrode layer sandwiching a solid oxide electrolyte layer are arranged, and from one end of the columnar fuel cell A solid oxide fuel cell stack that generates power by supplying fuel gas to the fuel electrode layer and oxidant gas to the air electrode layer toward the other end,
A fuel electrode conductive layer electrically connected to the fuel electrode layer;
An air electrode conductive layer electrically connected to the air electrode layer,
The fuel electrode conductive layers of the plurality of the fuel cells arranged in series are electrically connected in series to the air electrode conductive layers of the adjacent fuel cells via a current collector connecting member installed only on the other end side. And
A solid oxide fuel cell stack, wherein a reforming reaction preventing layer is provided on a surface of the fuel electrode layer and / or the fuel electrode conductive layer on one end side.   30. The solid oxide fuel cell stack according to claim 28, wherein the reforming reaction preventing layer has a lower gas diffusibility than the fuel electrode layer and / or the fuel electrode conductive layer.

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