JP2018098080A - Solid oxide fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell stack which enables the achievement of a predetermined output density as well as high durability and low cost in a solid oxide fuel cell stack with a plurality of columnar fuel battery cells arranged therein, by making a current collector structure of a fuel battery cell be a one-end current collector structure, and shortening the fuel cells in length.SOLUTION: A solid oxide fuel cell stack comprises: a plurality of columnar fuel battery cells arrayed therein, each having a power-generation part formed by a fuel electrode layer and an air electrode layer with a solid oxide type electrolyte layer disposed therebetween, and extending in an axial direction. The solid oxide fuel cell stack generates an electric power by supplying a fuel gas to the fuel electrode layers and an oxidant gas to the air electrode layers from one end of the plurality of columnar fuel battery cells toward the other end. The fuel electrode layers of the plurality of fuel battery cells arrayed in the fuel cell stack are electrically connected in series with the air electrode layers of the fuel battery cells adjacent thereto through corresponding current collector joining members set only on the other end side. Each fuel battery cells is 100 mm or less in length of the power-generation part in the axial direction thereof. The potential of the fuel battery cells is larger than 0.7 V under the condition of the current density of 0.3 A/cm.SELECTED DRAWING: Figure 2

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.

  However, in these columnar fuel cells such as cylindrical cells, since the electrodes extend in the axial direction, the movement distance of the electrons in the electrodes is long and the power generation efficiency of the fuel cells is reduced. was there. 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.

  By the way, in development of a fuel cell device for household use, downsizing and cost reduction of the fuel cell device are demanded in view of its spread. In particular, miniaturization of the fuel cell device is particularly important for installation in a limited space in an apartment house such as a condominium. For this reason, shortening (shortening) the conventional columnar fuel cell in the axial direction greatly contributes to miniaturization of the fuel cell device and also contributes to a reduction in price.

  However, the inventor has found that when the fuel cell having the current collecting structure described above is shortened, the power generation performance is adversely affected. That is, shortening the length of the fuel cell is advantageous in that the axial current path of the fuel cell is shortened and the resistance component is reduced and the output density is improved. It has been found that the maximum current density at the lower end of the fuel cell supplying the gas increases, and as a result, the deterioration rate of the fuel cell is accelerated.

  The fuel gas containing hydrogen is generally supplied to the internal flow path from the lower end side of the columnar fuel cell, but the hydrogen concentration in the supplied fuel gas is gradually consumed by the power generation reaction, In the internal flow path, the hydrogen concentration decreases from the upstream side to the downstream side. 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 these circumstances, when collecting electricity at both ends, depending on the amount of fuel gas supplied or taken out, or depending on the form of current collection of the fuel cell, the current collector on the upstream side of the fuel cell (that is, the lower end side of the fuel cell) The inventors found that current concentration may occur. This has a problem that the region where the electromotive force is high coincides with the current extraction region. Since shortening the length of the fuel cell is a shortening of the current path, the current concentration at the lower end of the fuel cell is further increased, resulting in a decrease in durability due to deterioration of the fuel cell due to local power generation promotion. In addition, various problems such as damage of the fuel cell due to thermal stress generated by local heat generation are caused.

  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

  On the other hand, adopting a single-ended current collection structure instead of the conventional double-ended current collection structure avoids the occurrence of current concentration, but the current path becomes longer than the double-ended current collection structure, so the double-ended current collection structure is shortened. It is considered that the improvement of the output density of the fuel cell, which was the superiority when performing the above, cannot be obtained.

  Therefore, the present invention provides a solid oxide fuel cell stack in which a plurality of columnar fuel cells are arranged, and the current collecting structure of the fuel cells is made to be a one-end current collecting structure, and is shortened to add high durability and low cost. The present invention provides a solid oxide fuel cell stack capable of obtaining a predetermined power density.

As described above, in the current collecting structure of the fuel cell, since the current path is increased by adopting the one-end current collecting structure with respect to the both-end current collecting structure, the output density is lowered. It has been found that the cell potential tends to increase as the electrode length (hereinafter referred to as “electrode length”) is shortened. In particular, if the electrode length of the fuel cell is 100 mm or less under the condition that the current density of the current drawn from the fuel cell is 0.3 A / cm ² , the cell potential of the fuel cell is confirmed to be larger than 0.7V. did. For this reason, it has been clarified that by designing the electrode length of the fuel cell to a predetermined short, a sufficient output density that can withstand practical use can be secured.

Therefore, one aspect of the solid oxide fuel cell stack according to the present invention is a columnar shape in which a power generation part 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 that generates electricity by supplying a plurality of fuel cells of the columnar fuel cells from one end to the other end of the fuel cells and supplying an oxidant gas to the air electrode layer In the battery stack, the fuel electrode layers of the plurality of fuel cells arranged in series are electrically connected in series with the air electrode layer of the adjacent fuel cells through a current collector connecting member installed only on the other end side. In the fuel cell, the cell potential of the fuel cell is 0 under the condition that the length of the power generation unit in the axial direction of the fuel cell is 100 mm or less and the current density is 0.3 A / cm ^2. It is larger than 7V.

  Here, in this specification, “the length of the power generation unit in the axial direction of the fuel cell” is the length in the axial direction of the fuel electrode layer and the air electrode layer corresponding to the power generation unit in the fuel cell. Then, it is the effective cell length of the fuel cell.

  Further, in this specification, the “columnar fuel cell” is a fuel cell having a three-dimensional shape extending in one direction (axial direction), and includes a cylindrical shape in which a gas flow path is provided. It is a waste. 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.

  Moreover, in the aspect of this invention, it is preferable that the length of an electric power generation part is 50 mm or more.

  In a solid oxide fuel cell stack in which a plurality of columnar fuel cells are arranged, the current collecting structure of the fuel cells is made to be a one-sided current collecting structure, and the length is shortened, in addition to high durability and low cost, and a predetermined output density The solid oxide fuel cell stack can be provided.

It is a figure which shows the one end current collection structure (A) concerning this invention, and the conventional both-ends current collection structure (B). It is a figure which shows the relationship between the electrode length of a fuel battery cell at the time of employ | adopting the one end current collection structure in one Embodiment of this invention, cell potential, and maximum current density. It is a perspective view which shows the fuel cell stack in one Example of this invention. It is a side view which shows the fuel cell stack in one Example of this invention. It is a figure which shows the fuel cell in one Example of this invention. It is a fragmentary sectional view showing a fuel cell in one example of the present 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.

  FIG. 1B shows a conventional current collecting structure at both ends as a current collecting structure of a columnar fuel cell. For simplicity, FIG. 1B shows only the current collecting connection of two fuel cells among the plurality of fuel cells. The fuel gas (broken arrow in the figure) supplied from the lower end side of the fuel cell 100 into the internal flow path is generated by a power generation reaction with an oxidant gas (not shown) supplied from below the side surface of the fuel cell. The consumed and unreacted fuel gas is discharged from the upper end of the fuel cell 100 to the outside of the fuel cell 100. The fuel gas contains hydrogen reformed outside the fuel cell stack, and in the internal flow path of the fuel cell 100, the hydrogen concentration is higher at the upstream side (that is, the lower end side), and the power generation reaction as it flows downstream. Concentration is reduced. For this reason, the electromotive force due to the power generation reaction is higher toward the lower end side of the fuel cell 100.

  On the other hand, a current collector 102 (current collector connecting member) is provided at the upper end and the lower end of the fuel cell 100 in order to extract current from the fuel cell 100. The fuel electrode layer is exposed at the upper end portion and the lower end portion of the fuel cell 100, and each of the fuel electrode layers is connected to the air electrode layer of the fuel cell 100 that is electrically adjacent via the current collector 102. ing. Thus, the electrical connection at both the upper end and the lower end eliminates the problem related to the high electric resistance of the current path length caused by the columnar fuel cell 100 that is long in the axial direction. It was.

  However, as described above, when the length of the fuel cell 100 is reduced, the lower end of the fuel cell 100 is a region where the region where the electromotive force increases and the current extraction region coincide with each other. As a result, it has been found that the fuel cell 100 is significantly deteriorated.

  Therefore, in order to shorten the length of the fuel cell 100, it has been thought that it would be effective if the current collecting structure of the fuel cell 100 is a one-end current collecting structure as shown in FIG. In the one-end current collecting structure, a current collector 102 for electrically connecting the fuel electrode layer of the fuel cell 100 and the air electrode layer of the adjacent fuel cell 100 to the conventional both-end current collecting structure is used as a fuel cell. The structure is attached only to the upper end of the cell 100. Then, since the region where the current is extracted from the fuel cell 100 is limited to the upper end portion, the region where the electromotive force is increased and the current extraction region are separated, so that current concentration at the lower end portion of the fuel cell 100 is performed. It is possible to reduce the occurrence of.

  However, since the current path of the fuel cell 100 using the single-ended current collection structure is longer than that when the double-ended current collection structure is used, it is advantageous when shortening using the double-ended current collection structure. It is considered that the output density of the fuel cell 100 cannot be improved.

However, it has been found that the cell potential tends to increase as the electrode length (hereinafter referred to as “electrode length”) in the fuel cell 100 is shortened. In particular, if the electrode length of the fuel cell is 100 mm or less under the condition that the current density of the current drawn from the fuel cell is 0.3 A / cm ² , the cell potential of the fuel cell is confirmed to be larger than 0.7V. did.

Here, a method for calculating the cell potential of the fuel cell will be described first. The cell potential V is _obtained by subtracting (1) the open circuit voltage E ₀ from (2) the resistance overvoltage η _ohm , (3) the activation overvoltage η _act , (4) the diffusion overvoltage E _diff, and (5) _Nernströs η _nerst. (Equation 1).

(1) The open circuit voltage E ₀ can be obtained by calculating the oxygen partial pressure P _{O2, ca} on the air electrode side and the oxygen partial pressure P _{O2, an} on the fuel electrode side, respectively, and substituting them into Equation 2. . Here, R is a gas constant (8.31 J / Kmol), T is a temperature (973 K.), and F is a Faraday constant (96485 C / mol).

(2) The resistance overvoltage η _ohm is the cross-sectional area S _{i of} each of the laminated films such as the fuel electrode layer, the fuel electrode conductive layer, the electrolyte layer, the air electrode conductive layer, and the air electrode layer that constitute the current path of the fuel cell 100. , conductive distances l _i and conductivity to calculate the sigma _i, by substituting the number 3 to calculate the sheet resistance R _i of each layer, summed over each current density J in the resulting sheet resistivity R _i (number 4 ) Here, the current density J was calculated as 0.3 A / cm ² .

(3) The activation overvoltage η _act can be obtained by substituting each parameter into the Butler-Volmer equation (Equation 5) for the activation overvoltage on the fuel electrode side and the activation overvoltage on the air electrode side. Where α is the transport coefficient (0.5), n is the number of electrons (2), i _0eff is the exchange current density, R is the gas constant (8.31 J / Kmol), and F is the Faraday constant (96485 C / mol). .

(4) The diffusion overvoltage E _diff can be calculated by _Equation 6 by calculating the _gas partial pressure P _{O2, gas} and the three-phase oxygen partial pressure P _{O2, TPB} , respectively. Here, R is a gas constant (8.31 J / Kmol), T is a temperature (973 K.), and F is a Faraday constant (96485 C / mol).

(5) _Nernströs η _nernst is an _average of the electromotive force E _IN calculated from the composition of the fuel gas at one end of the fuel cell and the electromotive force E _OUT calculated from the composition of the fuel gas at the other end of the cell. (Equation 7).

The electrode length (effective cell length) of the fuel cell with respect to the cell potential of the columnar fuel cell derived on the assumption of the one-end current collecting structure and the maximum current density indicating the current concentration generated in the fuel cell derived from the above calculation method. FIG. 2 shows the result of trial calculation. In this trial calculation, the current density of the entire fuel cell was set to 0.3 A / cm ² that was close to the current density at the time of drawing current during actual operation of the fuel cell.

In FIG. 2, the horizontal axis indicates the electrode length (effective cell length), and the vertical axis indicates the cell potential and the maximum current density. The fuel cell is shortened as it proceeds to the left in the horizontal axis. When the electrode length was relatively long at 200 mm, the maximum current density was as extremely high as 0.83 A / cm ² . However, as the electrode length was shortened, the maximum current density once decreased greatly and then gradually increased. On the other hand, the cell potential showed a low value of 0.49 V when the electrode length was 200 mm, but it was found that the cell potential gradually increased as the fuel cell length became shorter.

  Here, as shown in FIG. 2, the increasing tendency with the shortening of the cell potential is linear, but when the electrode length becomes 100 mm, the increasing tendency tends to accelerate. A similar tendency was also observed in the maximum current density, but the displacement of the maximum current density was small compared to the increasing tendency of the cell potential. When the electrode length of this fuel cell is 100 mm, the cell potential is 0.71 A, which is a numerical value exceeding 0.7 A that is desired to be secured as the performance of the fuel cell in configuring the fuel cell stack.

For this reason, by setting the electrode length of the fuel battery cell to 100 mm or less, it is possible to obtain a cell potential that shows an increasing tendency when the cell potential is 0.7 A or more. Moreover, the lower the maximum current density is preferable for solving the problem of durability due to current concentration, but the maximum current density is remarkably increased even if the electrode length is 100 mm or less by adopting the premise of the one-end current collecting structure. This is not a problem because it is less than 0.6 A / cm ² which greatly affects the durability of the fuel cell. On the other hand, since the maximum current density tends to increase due to the shortening of the fuel cell, the electrode length of the fuel cell is preferably set to 50 mm at the shortest.

  From the above, by designing the electrode length of the fuel cell that adopts the one-end current collecting structure to be a predetermined short, it is possible to ensure sufficient output density that can withstand practical use while avoiding current concentration Became clear.

  Next, an embodiment of a fuel cell stack according to the present invention will be described with reference to the drawings.

  A fuel cell stack 1 according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 3 is a perspective view showing the fuel cell stack 1 in the embodiment of the present invention. As shown in FIG. 3, the fuel cell stack 1 includes a plurality of columnar fuel cells 2 in which gas flow paths are provided, and a manifold 3. The fuel cell 2 is supported and fixed with one end side (the lower end side in FIG. 3) 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, each of the plurality of fuel cells 2 is connected by the current collector 4 so as to be electrically in series. The fuel cells 2 at one end and the other end that are electrically connected in series are provided with power extraction lines (thick lines in FIG. 3) 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. 4 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 fuel cell 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 plurality of fuel cell cells 2. Is discharged from the other end of the fuel cell stack 1 to the outside.

  Here, as the fuel cells 2 constituting the fuel cell stack 1, those having an axial electrode length of 100 mm or less are used. In particular, the electrode length is preferably 50 mm or more and 100 mm or less. In this way, in the solid oxide fuel cell stack 1 in which a plurality of cylindrical fuel cells 2 are arranged, the current collecting structure of the fuel cells 2 has a one-end current collecting structure and is shortened so that high durability is achieved. In addition to low cost, a predetermined power density can be obtained.

  Next, fuel cells used in the embodiments of the present invention will be described with reference to FIGS.

  FIG. 5 is a diagram showing the fuel cell 2 constituting the fuel cell stack 1 in the embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view of the end portion of the fuel battery cell 2.

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

  As shown in FIG. 6, 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 this 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. 6, 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 is coated with 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 this embodiment, the Ag current collecting 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.

  Next, electrical connection of the fuel cell stack 1 will be described with reference to FIGS.

  The current collector 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 4 is the upper end of one of the two adjacent fuel cells 2. Is electrically connected to the cap 5 provided on the surface using silver paste. Furthermore, the current collector 4 is electrically connected to the air electrode conductive layer 11 of the other 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.

100 Fuel cell 102 Current collector (current collector connecting member)
DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Fuel cell 3 Manifold 4 Current collector (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 Support member 15 Glass ring

Claims (2)

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,
The fuel electrode layers of the plurality of the fuel cells arranged in series are electrically connected in series with the air electrode layers of the adjacent fuel cells via a current collecting connection member installed only on the other end side. ,
In the fuel cell, the cell potential of the fuel cell is 0 under the condition that the length of the power generation unit in the axial direction of the fuel cell is 100 mm or less and the current density is 0.3 A / cm ^2. A solid oxide fuel cell stack characterized by being greater than .7V.   The solid oxide fuel cell stack according to claim 1, wherein the power generation unit has a length of 50 mm or more.

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