JP2007066583A - Fuel battery cell, cell stack, and fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery cell capable of sufficiently taking out current from an electrode layer and to provide a cell stack, and a fuel battery. <P>SOLUTION: A high conductivity layer 91 having higher conductivity than an air electrode layer 70 electrically connected to the air electrode layer 70 is installed in a solid electrolyte layer 66 in which the air electrode layer 70 is formed on the outer surface and a fuel electrode layer 66 is formed on the inner surface to form a fuel battery cell, a plurality of fuel battery cells are arranged in prescribed intervals, and an interconnector 72 of a fuel cell 62 on one side and the air electrode layer 70 of an adjoined fuel battery cell 62 on the other side are electrically connected through the high conductivity layer 91 electrically connected to the air electrode layer 70 and a current collecting member 76 between the fuel battery cell 62 on one side and the fuel battery cell 62 on the other side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a columnar fuel cell, a cell stack, and a fuel cell each having a porous electrode layer on the inner and outer surfaces of a solid electrolyte layer.

  In recent years, various fuel cells in which a stack of a plurality of fuel battery cells is housed in a container have been proposed as next-generation energy.

  FIG. 8 shows a cell stack of a conventional hollow plate type solid oxide fuel cell. This cell stack aggregates a plurality of fuel cells 223 (223a, 223b), and one fuel cell 223a A current collecting member 225 made of a metal member or the like is interposed between the other fuel battery cell 223b, and the outer electrode (air electrode layer) 228 of one fuel battery cell 223a and the inner electrode of the other fuel battery cell 223b ( The fuel electrode layer) 227 is electrically connected.

  The fuel cell 223 (223a, 223b) is configured by sequentially providing a solid electrolyte layer 229 and an outer electrode 228 on the outer peripheral surface of the flat inner electrode 227, and is exposed from the solid electrolyte layer 229 and the outer electrode 228. The inner electrode 227 is provided with an interconnector 230 so as not to be connected to the outer electrode 228. In the inner electrode 227, a plurality of gas passage holes 232 constituting a gas flow path are formed.

The electrical connection between one fuel cell 223a and the other fuel cell 223b is made by connecting the inner electrode 227 of the other fuel cell 223b via the interconnector 230 and the current collecting member 225 provided on the inner electrode 227. This is done by connecting to the outer electrode 228 of one fuel cell 223a (see, for example, Patent Documents 1 and 2).
JP-A-1-169878 JP 2003-282101 A

  However, in the conventional fuel cell described above, the outer electrode (air electrode layer) 228 is made of a porous conductive ceramic material, so that the conductivity is still low, and the current collector connected to the outer electrode 228 is low. There was a problem that the current collection characteristic by the member 225 was lowered.

  In addition, the current collecting member 225 is joined to the outer electrode 228 of the fuel cell by a joining material. However, the outer electrode 228 is porous and the outer electrode 228 is easily peeled off from the solid electrolyte layer 229 or the current collecting member. There was a problem that the member 225 was easily peeled from the outer electrode layer 228. Thereby, there existed a problem that the current collection characteristic by the current collection member 225 became low.

  An object of the present invention is to provide a fuel cell, a cell stack, and a fuel cell that can sufficiently draw current from an electrode layer.

  The fuel cell of the present invention is a columnar fuel cell having porous electrode layers on the inner and outer surfaces of the solid electrolyte layer, respectively, and is electrically connected to the electrode layer and connected to the electrode layer. The present invention is characterized in that a high conductivity layer having a higher conductivity is provided by bonding.

  In such a fuel cell, for example, a high conductivity layer connected to the oxygen electrode layer and having a higher conductivity than that of the oxygen electrode layer is joined to the solid electrolyte layer. Even if an oxygen electrode layer made of ceramics and having low conductivity is used, the generated current flows through the high conductivity layer and can be sufficiently extracted through this high conductivity.

  In the present invention, when providing a high conductivity layer that is electrically connected to the inner electrode, in addition to providing a high conductivity layer that is electrically connected to the outer electrode, both the outer electrode and the inner electrode are electrically This includes the case where a high conductivity layer to be connected is provided. In particular, it is desirable to provide a high conductivity layer connected to the oxygen electrode layer having a large electrical resistance. However, also in the fuel electrode layer, a high conductivity layer having a higher conductivity than the fuel electrode layer is electrically connected. The generated current can be effectively extracted from the fuel battery cell.

  In addition, since the high conductivity layer is joined to the solid electrolyte layer, the high conductivity layer can be prevented from being peeled off from the fuel battery cell, whereby the oxygen electrode layer can be peeled off from the solid electrolyte layer, or the current collecting member. Can be prevented from peeling.

  That is, conventionally, a current collecting member is interposed between the oxygen electrode layer of one fuel cell and the interconnector of the other fuel cell, and the current collecting member, the oxygen electrode layer, and the interconnector are joined by a joining material. However, since the oxygen electrode layer itself needs to take in oxygen, it is porous and the strength of the oxygen electrode layer is not sufficient. As a result, the current collector and the oxygen electrode layer, the oxygen electrode layer and the solid electrolyte layer There was a problem that the bonding strength with the electrode became insufficient, and the current collecting member was easily peeled off. In addition, the fuel cell may be warped or tilted during the manufacturing process or power generation, or may be displaced due to a difference in thermal expansion. In this case, the bonding strength of the current collecting member to the oxygen electrode layer is low. If insufficient, there is a problem that the current collecting member is peeled off from the cell and causes voltage degradation of the fuel cell.

  Furthermore, since the oxygen electrode layer is porous and is not sufficiently bonded to the solid electrolyte layer, for example, an Ag paste is applied to the oxygen electrode layer made of conductive ceramics, and the high conductivity layer is formed on the upper layer of the oxygen electrode layer. In this case, a porous oxygen electrode layer is joined to the solid electrolyte layer, and the high conductivity layer is easily peeled off. Since the conductivity layer is bonded to the solid electrolyte layer without interposing the air electrode layer, it is possible to prevent the high conductivity layer from peeling off from the solid electrolyte layer, thereby preventing the oxygen electrode layer from peeling off from the solid electrolyte layer. Can be prevented.

  As will be described later, a plurality of such fuel cells are arranged at a predetermined interval, and an interconnector of one fuel cell and an outer electrode of the other adjacent fuel cell are connected to the outer electrode. There is a case where a cell stack is configured by electrically connecting via an electrically connected high conductivity layer and a current collecting member between the one fuel cell and the other fuel cell. In this case, the high conductivity layer is bonded to the solid electrolyte layer, and the current collecting member is bonded to the high conductivity layer. Therefore, the high conductivity layer can be made denser than the oxygen electrode layer. It is possible to increase the bonding strength of the high conductivity layer to the solid electrolyte layer and the bonding strength to the current collecting member, and the current collecting member allows the oxygen electrode layer of one fuel cell to be connected to the other interconnector. It can be reliably joined.

  The fuel cell of the present invention is a hollow plate type or cylindrical type fuel cell, wherein an outer electrode layer is provided on the outer surface of the solid electrolyte layer, and the high conductivity layer is electrically connected to the outer electrode layer. It is characterized by being connected to.

  In such a fuel cell, a high conductivity layer can be easily provided on the outer electrode layer. In the present invention, the outer electrode layer is an oxygen electrode layer, and it is desirable that a high conductivity layer is electrically connected to the oxygen electrode layer.

  Further, the fuel cell of the present invention is a hollow flat plate type or cylindrical type fuel cell, wherein an inner electrode layer is provided on the inner surface of the solid electrolyte layer, an outer electrode layer is provided on the outer surface, and the outer electrode layer is provided with the above-mentioned An interconnector for electrically connecting the high conductivity layer and electrically connecting to the inner electrode layer is provided.

  In such a fuel cell, as described above, when configuring a cell stack, the high conductivity layer is joined to the solid electrolyte layer, and the current collecting member is joined to the high conductivity layer. The high conductivity layer can be made dense, and the bonding strength of the high conductivity layer to the solid electrolyte layer and the bonding strength to the current collecting member can be increased. The oxygen electrode layer of the battery cell and the other interconnector can be reliably bonded.

  The fuel cell of the present invention is a hollow flat plate type or cylindrical type fuel cell, and the outer electrode layer and the high electrode layer are formed on the entire circumference of the annular solid electrolyte layer so as to surround the solid electrolyte layer. A conductivity layer is provided. The present invention can also be applied to so-called interconnector-less fuel cells.

  In such an interconnector-less fuel cell, the adjacent fuel cells are electrically connected to each other at the end of the columnar fuel cell. When the current generated at one end of the fuel cell flows to the other end due to the fact that the resistance of the oxygen electrode layer is still high, Although the electric resistance was large and the power generation performance tended to decrease, in the present invention, it was generated at one end of the fuel cell by providing the axial length direction high conductivity layer formed in the axial direction. The current efficiently flows to the other end through the high conductivity layer, the electric resistance is reduced, and the power generation performance can be improved.

  Furthermore, the fuel cell of the present invention is characterized in that the high conductivity layer is an axial length direction high conductivity layer formed in the axial length direction. In such a fuel cell, the current generated at the axial end portion of the fuel cell can be effectively extracted by the high axial conductivity layer.

  Furthermore, the fuel cell of the present invention is characterized in that a circumferential high conductivity layer connected to the axial length high conductivity layer is formed in the circumferential direction of the outer electrode layer. In such a fuel cell, the current generated in the circumferential direction of the fuel cell can be effectively drawn out through the circumferential high conductivity layer and the axial length high conductivity layer.

  In the cell stack of the present invention, a plurality of the fuel cells are arranged at a predetermined interval, and an interconnector of one fuel cell and an outer electrode of the other adjacent fuel cell are electrically connected to the outer electrode. The electrically connected high conductivity layers and the current collecting member between the one fuel cell and the other fuel cell are electrically connected. In such a cell stack, as described above, it becomes possible to increase the bonding strength of the high conductivity layer to the solid electrolyte layer and the bonding strength to the current collecting member. The oxygen electrode layer and the other interconnector can be reliably bonded.

  In the cell stack of the present invention, a plurality of the fuel cells are arranged at a predetermined interval, and the inner electrode of one fuel cell and the outer electrode of the other adjacent fuel cell are connected to the outer electrode. It is electrically connected at an end portion of the fuel cell through a connected high conductivity layer and a current collecting member between the one fuel cell and the other fuel cell. And In such a cell stack, as described above, by providing an axial length direction high conductivity layer formed in the axial length direction, a current generated at one end of the fuel cell is allowed to flow through the high conductivity layer. To the other end and electrically connected via the current collecting member between one fuel cell and the other fuel cell, reducing the electrical resistance between the fuel cells and improving the power generation performance can do.

  The fuel cell of the present invention is characterized in that the cell stack is housed in a housing container. In such a fuel cell, since the electric resistance in the cell stack is small, the power generation performance can be improved.

  In the fuel cell according to the present invention, the solid electrolyte layer is provided with the high conductivity layer connected to the electrode layer and having a higher conductivity than the electrode layer. The current can be drawn out through this high conductivity layer, and the current from the electrode layer can be drawn out sufficiently.

  Hereinafter, the fuel cell of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of the fuel cell, FIG. 2 is a top plan view of the fuel cell, FIG. 3 is a perspective view showing a power generation unit assembly housed in the fuel cell, and FIG. 4 is a cross-sectional view of the cell stack.

  The fuel cell of the present invention includes a substantially rectangular parallelepiped housing (storage container) 2. The six wall surfaces of the housing 2 are heat insulating walls formed of an appropriate heat insulating material, that is, an upper heat insulating wall 4, a lower heat insulating wall 6, a right heat insulating wall 8, a left heat insulating wall 9, a front heat insulating wall 10, and a rear heat insulating wall. 11 is disposed. A power generation / combustion chamber 12 is defined in the housing 2.

  The front heat insulation wall 10 and / or the rear heat insulation wall 11 is detachably or removably attached, and the front heat insulation wall 10 and / or the rear heat insulation wall 11 is detached or opened to access the power generation / combustion chamber 12. be able to. If desired, an outer wall, which may be made of a metal plate, can be disposed on the outer surface of each heat insulating wall.

  An air chamber (gas chamber) 16 is disposed at the upper end of the housing 2. The air chamber 16 is defined in a rectangular parallelepiped case 17 having a relatively small vertical dimension. The air chamber 16 communicates with an air introduction pipe (gas supply means) 22 for sending air (oxygen-containing gas) toward the power generation / combustion chamber. There are a plurality of air introduction pipes 22 and the shape thereof may be a cylinder or a hollow plate structure. The air introduction pipe 22 is disposed between the cell stacks described later, and has an opening at the lower end portion of the cell, and air is ejected from the opening portion. The air introduction tube 22 is preferably made of a material having high heat resistance such as ceramics.

  The air chamber 16 is provided with a low-temperature gas supply means including a low-temperature gas supply pipe 18. The low-temperature gas supply pipe 18 penetrates the upper heat insulating wall 4 and extends to the outside.

  The low-temperature gas supply pipe 18 supplies the same type of gas as that supplied into the air chamber 16, that is, low-temperature air, into the air chamber 16. The air supplied through the low-temperature gas supply pipe 18 is It must be cooler than the temperature of the preheated air. In particular, about room temperature is desirable.

  As shown in FIG. 2, the low temperature gas supply pipe 18 is connected to a position of the air chamber 16 that cools the power generation units 56a, 56b, 56c, and 56d, that is, the central portion of the fuel cell assembly.

  A heat exchanger 24 having a flat plate shape as a whole is disposed on both sides of the housing 2, more specifically, inside the right heat insulating wall 8 and inside the left heat insulating wall 9. Each of the heat exchangers 24 is constituted by a case 26 having a hollow flat plate shape extending substantially vertically.

  A partition plate 28 located in the middle in the lateral direction is disposed in the case 26, and the inside of the case 26 is partitioned into a discharge path 30 positioned on the inner side and an inflow path 32 positioned on the outer side. Three partition walls 34 and 36 are arranged in the discharge path 30 at intervals in the vertical direction. More specifically, in the discharge passage 30, the front edge is located rearwardly away from the front wall (not shown) of the case 26, but the rear edge is the rear wall (not shown) of the case 26. And a partition wall 36 whose front edge is connected to the front wall of the case 26 but whose rear edge is spaced forward from the rear wall of the case 26. Are alternately arranged, and thus the combustion gas discharge passage 30 is zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  Similarly, the three partition walls 38 and 40, that is, the front edges thereof are also spaced apart from the front wall (not shown) of the case 26 in the inflow path 32 with a space in the vertical direction. The rear wall is connected to the rear wall (not shown) of the case 26, and the front edge of the partition wall 38 is connected to the front wall of the case 26. The partition walls 40 spaced apart from the front are alternately arranged, and thus the inflow passage 32 is also zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  A discharge opening 42 is formed at the upper end of the inner wall of the case 26, and the discharge path 30 is communicated with the power generation / combustion chamber 12 through the discharge opening 42. In the illustrated embodiment, a heat insulating member 44 is disposed between each of the heat exchangers 24 and the power generation / combustion chamber 12, and the upper end of the heat insulating member 44 is substantially the same as the lower edge of the discharge opening 42. The discharge opening 42 is communicated with the power generation / combustion chamber 12 through a space remaining above the heat insulating member 44.

  An inflow opening 48 is formed on the outer side of the upper wall of the case 26, and the inflow path 32 is communicated with the air chamber 16 through the inflow opening 48. A double cylinder 50 (only the upper end portion thereof is shown in FIG. 1) extending in the vertical direction is disposed behind each of the heat exchangers 24. The double cylinder 50 is an outer cylinder. The member 52 and the inner cylinder member 54 are configured. The lower end of the discharge path 30 is connected to the lower end of the discharge path defined between the outer cylinder member 52 and the inner cylinder member 54, and the lower end of the inflow path 32 is defined in the inner cylinder member 54. Connected to the inflow channel.

  Four power generation units 56a, 56b, 56c and 56d are arranged in the lower part of the above-described power generation / combustion chamber. The power generation units 56a, 56b, 56c, and 56d are respectively positioned between the air introduction pipes 22 described above. 3 together with FIGS. 1 and 2, the power generation unit 56a includes a rectangular parallelepiped fuel gas case 58a extending in the front-rear direction (direction perpendicular to the paper surface in FIG. 1).

  A cell stack 60a is mounted on the upper surface of the fuel gas case 58a that defines the fuel gas chamber. The cell stack 60a is configured by arranging a plurality of plate-like and column-like upright cells 62 extending vertically in the vertical direction in the longitudinal direction of the fuel gas case 58a (that is, the direction perpendicular to the paper surface in FIG. 1).

  As shown in FIG. 4, the cell 62 includes an electrode support substrate 64, a fuel electrode layer 66 that is an inner electrode layer, a solid electrolyte layer 68, an oxygen electrode layer 70 that is an outer electrode layer, and an interconnector 72. Has been.

  The electrode support substrate 64 has an elongated columnar shape (thin plate columnar piece), and has both flat surfaces and semicircular side surfaces. The electrode support substrate 64 is formed with a plurality (six in the illustrated example) of fuel gas passages 74 penetrating the electrode support substrate 64 in the axial direction. Each of the electrode support substrates 64 is bonded to the upper wall of the fuel gas case 58a by, for example, a ceramic adhesive having excellent heat resistance.

  On the upper wall of the fuel gas case 58a, a plurality of slits (not shown) extending in the left-right direction are formed at intervals in a direction perpendicular to the paper surface in FIG. A fuel gas passage 74 is communicated with the fuel gas chamber according to each of the slits.

  The interconnector 72 is disposed on one side of the electrode support substrate 64. The fuel electrode layer 66 is disposed on the other surface and both side surfaces of the electrode support substrate 64, and both ends thereof are joined to both ends of the interconnector 72. The solid electrolyte layer 68 is disposed so as to cover the entire fuel electrode layer 66, and both ends thereof are joined to both ends of the interconnector 72. The oxygen electrode layer 70 is disposed on the main part of the solid electrolyte layer 68, that is, on the portion covering the other surface of the electrode support substrate 64, and is positioned to face the interconnector 72 with the electrode support substrate plate 64 interposed therebetween. Yes.

  A current collecting member 76 is disposed between adjacent cells 62 in the cell stack 60a, and connects the interconnector 72 of one cell 62 and the oxygen electrode layer 70 of the other cell 62. Current collecting members 76 are disposed at both ends of the cell stack 60a, that is, one side and the other side of the cell 62 located at the upper end and the lower end in FIG. 4, and the current collecting members 76 located at both ends of the cell stack 60a are electrically conductive members. The cell stacks 60a, 60b, 60c and 60d are connected in series with each other by the conductive member.

  The cell 62 will be described in more detail. As shown in FIG. 5, the electrode support substrate 64 is gas permeable to allow the fuel gas to permeate to the fuel electrode layer 66, and also collects current via the interconnector 72. Therefore, it is required to be conductive, and it can be formed from a porous conductive ceramic (or cermet) that satisfies such a requirement.

  In order to manufacture the cell 62 by co-firing with the fuel electrode layer 66 and / or the solid electrolyte layer 68, it is preferable to form the electrode support substrate 64 from the iron group metal component and the specific rare earth oxide. In order to provide the required gas permeability, it is preferred that the open porosity is in the range of 30% or more, in particular 35 to 50%, and the conductivity is also 300 S / cm or more, in particular 440 S / cm or more. Is preferred.

The fuel electrode layer 66 can be formed of a porous conductive ceramic, for example, ZrO ₂ (referred to as stabilized zirconia) in which a rare earth element is dissolved and Ni and / or NiO.

The solid electrolyte layer 68 has a function as an electrolyte for bridging electrons between electrodes, and at the same time needs to have a gas barrier property in order to prevent leakage between fuel gas and air. In general, it is formed from ZrO ₂ in which ₃ to 15 mol% of a rare earth element is dissolved.

The oxygen electrode layer 70 can be formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. The oxygen electrode layer 70 needs to have gas permeability, and the open porosity is preferably 20% or more, particularly preferably in the range of 30 to 50%.

Although the interconnector 72 can be formed from a conductive ceramic, it needs to have a reduction resistance and an oxidation resistance in order to come into contact with a fuel gas and air that may be hydrogen gas. A perovskite oxide (LaCrO ₃ oxide) is preferably used. The interconnector 72 must be dense in order to prevent leakage of fuel gas passing through the fuel gas passage 74 formed in the electrode support substrate 64 and air flowing outside the electrode support substrate 64, and is 93% or more. In particular, it is desired to have a relative density of 95% or more.

  The current collecting member 76 can be constituted by a member having an appropriate shape formed from a metal or alloy having elasticity, or a member obtained by adding a required surface treatment to a felt made of metal fiber or alloy fiber.

  In the fuel cell of the present invention, the solid electrolyte layer 68 is electrically connected to the oxygen electrode layer 70, and the axial length direction high conductivity layer 91 having a higher conductivity than the oxygen electrode layer 70 is joined. Is provided. That is, as shown in FIG. 6A, the oxygen electrode layer 70 is extended on the one main surface of the support substrate 64 in the length direction (axial length direction) at a predetermined interval in the cell width direction. As shown in FIG. 6B, the axially high conductivity layer 91 is joined to the solid electrolyte layer 68 between the two oxygen electrode layers 70a. The inner part of the oxygen electrode layer 70a and the outer part of the axial-direction high conductivity layer 91 are connected and are electrically connected.

  By such an axial length direction high conductivity layer 91, the current generated in the oxygen electrode layer 70a formed on both sides of the axial length direction high conductivity layer 91 flows into the central axial length direction high conductivity layer 91, This axial length direction high conductivity layer 91 can be effectively extracted. Further, since the axial length direction high conductivity layer 91 can have sufficient strength for the solid electrolyte layer 68, for example, the material, the density, etc. can be selected, the oxygen electrode layer 70a joined to the axis length direction high conductivity layer 91 can be selected. The peeling from the solid electrolyte layer 68 can be prevented.

  In addition, as shown in FIG. 6C, the axial length direction high conductivity layer 91 may be provided on both sides of the oxygen electrode layer 70. In this case, current can be drawn from the axial length direction high conductivity layer 91 more satisfactorily, and peeling of the oxygen electrode layer 70 from the solid electrolyte layer 68 can be further prevented.

  Further, as shown in FIG. 6D, a plurality of circumferential high conductivity layers 93 are extended from both sides of the axial length high conductivity layer 91 in the circumferential direction of the fuel cell. The circumferential high conductivity layer 93 is also bonded to the solid electrolyte layer 68, and its periphery is electrically connected to the oxygen electrode layer 70. The circumferential high conductivity layer 93 can be formed on the oxygen electrode layer 70 by, for example, applying an Ag paste to the oxygen electrode layer. Accordingly, the bonding strength of the circumferential high conductivity layer 93 can be increased, and the peeling of the oxygen electrode layer 70 from the solid electrolyte layer 68 can be further prevented.

  In such a fuel cell, the current generated in the circumferential direction of the fuel cell can be effectively drawn out through the circumferential high conductivity layer 93 and the axial length high conductivity layer 91. In particular, when the oxygen electrode layer 70 formed on one main surface of the support substrate 64 extends to the other main surface, it is highly conductive in the axial direction from the oxygen electrode layer 70 on the other main surface. Since the distance to the rate layer 91 is long, current can be collected effectively by directing the circumferential high conductivity layer 93.

  The high conductivity layers 91 and 93 have higher conductivity than the oxygen electrode layers 70 and 70 a, and constitute a noble metal material, for example, Ag, a mixed material of Ag and oxygen electrode material, or the oxygen electrode layer 70. It can be composed of a conductive ceramic made of the same component as the material and having a higher density than the oxygen electrode layer. Specifically, for the high conductivity layer 91, for example, a material in which Ag and an oxygen electrode material are mixed at a weight ratio of 1: 9 to 5: 5 can be used.

  As to whether or not the axial direction high conductivity layer 91 and the circumferential direction high conductivity layer 93 have higher conductivity than the oxygen electrode layer 70, both terminals of the resistance measuring device are connected to the oxygen electrode layer 70 of the fuel cell. Are contacted at a predetermined distance to measure the resistance of the oxygen electrode layer 70 at a predetermined interval, while the high conductivity layers 91 and 93 are similarly applied to both terminals of the resistance measuring device at a predetermined distance. By comparing the resistances of the high conductivity layers 91 and 93 in contact with each other at a predetermined interval and comparing these resistances, the conductivity can be compared.

  In the cell stack of the present invention, as shown in FIG. 4A, a plurality of the above-described fuel cells 62 of the present invention are arranged at predetermined intervals, and are adjacent to the interconnector 72 of one fuel cell. The oxygen electrode layer 70 of the other fuel battery cell 62 is configured to be electrically connected through the axial length direction high conductivity layer 91 and the current collecting member 76 between one fuel battery cell and the other fuel battery cell. Has been. That is, the rod-shaped current collecting member 76 having a rectangular cross section is interposed between the axial direction high conductivity layer 91 and the interconnector 72, and this is joined by a conductive paste. In addition, the circumferential high electrical conductivity layer 93 of one cell and the interconnector 72 of the other cell can be joined by the current collecting member 76.

  FIG. 4A shows a case where the current collecting member 76 is joined to the axial direction high conductivity layer 91 and the interconnector 72 using a conductive paste containing Ag or the like. The Ag paste is applied to the surface of the high-conductivity layer 91 in the axial length direction and the interconnector 72, and the current collecting member 76 is interposed and pressed in the portion where the Ag paste is applied, and heat treatment is performed in this state. Thus, the current collecting member 76 can be bonded to the axial direction high conductivity layers 91 and 72. As shown in FIG. 4B, a current collecting member 76 made of a conductive plate such as a metal or an alloy is used, and this current collecting member 76 is joined to the interconnector 72 and the high-conductivity layer 91 in the axial direction. You may do it.

  Furthermore, although the axial length direction high conductivity layer 91 is provided on the main surface of the support substrate 64, the axial length direction high conductivity layer can be provided on the semicircular curved surface portion of the support substrate 64 having low power generation performance. In this case, since the area of the main surface of the support substrate 64 is not reduced, the area of the oxygen electrode layer in the portion with high power generation performance can be ensured to the maximum, and the power generation performance can be improved.

  Continuing the description with reference to FIG. 3, the power generation unit 56 a also includes a reforming case 78 a that is preferably a rectangular shape (or a cylindrical shape) that is elongated in the front-rear direction above the cell stack 60 a. ing. One end, that is, the upper end of the fuel gas supply pipe 80a is connected to the front surface of the reforming case 78a.

  The fuel gas supply pipe 80a extends downward, then curves and extends rearward, and the other end of the fuel gas supply pipe 80a is connected to the front surface of the fuel gas case 58a. One end of a reformed gas supply pipe 82a is connected to the rear surface of the reforming case 78a. The to-be-reformed gas supply pipe 82 a extends downward from the reforming case, and extends under the housing 2 and out of the housing 2.

  The to-be-reformed gas supply pipe 82a is connected to a to-be-reformed gas supply source (not shown) which may be a hydrocarbon gas such as city gas, and is connected to the reforming case 78a through the to-be-reformed gas supply pipe 82a. A gas to be reformed is supplied. An appropriate reforming catalyst for reforming the fuel gas into a hydrogen-rich fuel gas is accommodated in the reforming case 78a.

  In the illustrated embodiment, the reforming case 78a is connected to the fuel gas case 58a via the fuel gas supply pipe 80a, and is thereby held in a required position. As shown in the figure, for example, an appropriate support member 84a can be provided between the lower surface of the reformed gas supply pipe 82a and the lower surface or rear surface of the rear end portion of the fuel gas case 58a.

  Referring to FIG. 3, the power generation unit 56c is substantially the same as the power generation unit 56a described above, and the power generation units 56b and 56d are disposed in the front-rear direction opposite to the power generation units 56a and 56c. Fuel gas supply pipes (not shown) connecting the quality cases 78b and 78d and the fuel gas cases 58b and 58d are arranged on the rear side, and the reformed gas supply pipes 82b and 82d are located downward from the reforming case. It extends under the housing 2 and extends out of the housing 2.

  In the fuel cell assembly as described above, the gas to be reformed is supplied to the reforming cases 78a, 78b, 78c and 78d via the gas to be reformed supply pipes 82a, 82b, 82c and 82d, and the reforming case 78a. , 78b, 78c and 78d, the fuel defined in the fuel gas cases 58a, 58b, 58c and 58d through the fuel gas supply pipes 80a, 80b, 80c and 80d after being reformed into hydrogen-rich fuel gas. It is supplied to the gas chamber and then supplied to the cell stacks 60a, 60b, 60c and 60d.

In each of the cell stacks 60a, 60b, 60c and 60d, at the oxygen electrode,
1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte)
The electrode reaction of
O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻
The electrode reaction is generated and power is generated.

  Fuel gas and air that have flown upward from the cell stacks 60a, 60b, 60c and 60d without being used for power generation are ignited by an ignition means (not shown) disposed in the power generation / combustion chamber 12 at the time of startup. It is ignited and burned. As is well known, the power generation / combustion chamber 12 has a high temperature of, for example, about 1000 ° C. due to power generation in the cell stacks 60a, 60b, 60c and 60d, and also due to combustion of fuel gas and air. The reforming cases 78a, 78b, 78c and 78d are disposed in the power generation / combustion chamber 12, and are positioned immediately above the cell stacks 60a, 60b, 60c and 60d, and are directly heated by the combustion flame. Thus, the high temperature generated in the power generation / combustion chamber 12 is effectively used for reforming the reformed gas.

  The combustion gas generated in the power generation / combustion chamber 12 flows into the discharge passage 30 from the discharge opening 42 formed in the heat exchanger 24, and flows through the discharge passage 30 extending in a zigzag shape. 50 is discharged through a discharge passage defined between the outer cylinder member 52 and the inner cylinder member 54. When the combustion gas flows through the discharge path in the double cylinder 50, air flows through the inflow path in the double cylinder 50, and heat exchange is performed between the combustion gas and air.

  Further, when the combustion gas is caused to flow in the exhaust passage 30 of the heat exchanger 24 in a zigzag manner, the air is caused to flow in the inflow passage 32 of the heat exchanger 24 in a zigzag manner. Thus, heat is effectively exchanged between the combustion gas and air to preheat the air.

  When a part or all of the cell stacks 60a, 60b, 60c and 60d deteriorates by performing power generation over a long period of time, the front wall 10 or the rear wall 11 of the housing 2 is detached or opened, and the power generation unit Part or all of 56a, 56b, 56c and 56d is taken out from the housing 2.

  Then, replace some or all of the power generation units 56a, 56b, 56c and 56d with new ones, or only the cell stacks 60a, 60b, 60c and 60d in some or all of the power generation units 56a, 56b, 56c and 56d. May be replaced with a new one and mounted again at a required position in the housing 2. Even when it is necessary to replace the reforming catalyst accommodated in the reforming cases 78a, 78b, 78c and 78d in some or all of the power generation units 56a, 56b, 56c and 56d, the power generation units 56a, 56b , 56c and 56d are removed from the housing 2, and the reforming cases 78a, 78b, 78c and 78d themselves in the power generation units 56a, 56b, 56c and 56d are replaced with new ones or reforming cases. Only the reforming catalyst in 78a, 78b, 78c and 78d may be replaced with a new one.

  In order to be able to perform the replacement of the reforming catalyst in the reforming cases 78a, 78b, 78c and 78d sufficiently easily, a part of the reforming cases 78a, 78b, 78c and 78d can be opened and closed if desired. It can be put on the door.

  On the other hand, air is supplied to the inflow path 32 of the heat exchanger 24 through the inflow path defined in the inner cylinder member 54 of the double cylinder 50, and is preheated (heated) through the heat exchanger 24. Is temporarily stored in the air chamber 16 and supplied between the cell stacks of the combustion / power generation chamber 12 through the air introduction pipe 22. At this time, the air introduction pipe 22 passes through the combustion gas atmosphere that burns in the vicinity of the fuel gas passage 74 at the upper end of the fuel cell 62 of the cell stack 60. Accordingly, the preheated air in the air chamber 16 is further heated in the combustion region above the cell stacks 60a, 60b, 60c and 60d, and the air heated to a high temperature is supplied to the cells.

  During normal operation, air preheated by the heat exchanger 24 is introduced into the air chamber 16, and air is introduced from the air chamber 16 into the combustion / power generation chamber 12 using the air introduction pipe 22. When the temperature rises more than expected, the low-temperature air that has passed through the low-temperature gas supply pipe 18 that does not pass through the heat exchanger 24 is introduced into the air chamber 16 and preheated through the heat exchanger 24. And the air temperature of the air chamber 16 is reduced to some extent. By supplying this air between the power generation chambers 12, that is, between the cell stacks, air having a lower temperature than that during normal operation is introduced between the cell stacks. Therefore, a good fuel cell assembly that can appropriately control the temperature in the power generation chamber is provided.

  Moreover, since the air temperature in the air chamber 16 is mixed with the outside air supplied from the low temperature gas supply pipe 18 and the air preheated through the heat exchanger 24, the air temperature is not as low as room temperature. Even if the fuel cell 60 is supplied to the hot fuel cell 60, it is possible to avoid problems such as cracks and thermal shock destruction of the fuel cell 60, so that the function deterioration of the entire fuel cell power generation system can be suppressed and the life can be extended. .

  FIG. 7 shows another interconnector-less type fuel cell according to the present invention, and this cell is a hollow plate type fuel cell as shown in FIGS. An oxygen electrode layer 170 is formed on the entire circumferential surface of the annular solid electrolyte layer 168 so as to surround the solid electrolyte layer 168, and an axial length direction high conductivity layer 191 is provided so as to be connected to the oxygen electrode layer 170. ing. That is, the oxygen electrode layer 170 is formed on the outer peripheral surface of the solid electrolyte layer 168 except for the portion where the axial length direction high conductivity layer 191 is formed, and the axial length direction high conductivity layer 191 is formed. Except for the part, it will generate electricity.

  In such a fuel cell, the current generated at the upper end flows to the lower end via the axial direction high conductivity layer 191 and passes through the oxygen electrode layer made of a porous conductive ceramic as in the prior art. Since no current flows to the lower end, the electric resistance is reduced, and the power generation performance can be improved.

  In the fuel cell shown in FIG. 7, since power is generated on the entire circumferential surface, if the axial length direction high conductivity layer 191 is formed only on one main surface, the current generated on the other main surface is generated. However, since it is necessary to flow through the oxygen electrode layer 170 to the high-conductivity layer 191 in the axial direction of the main surface on one side, a plurality of peripheral high-conductivity layers 93 as shown in FIG. By connecting to the axial direction high conductivity layer 191, current generated on the other main surface is passed through the circumferential high conductivity layer 93 to the axial length direction high conductivity layer 191. The electric power can be reduced and the electric resistance can be reduced to improve the power generation performance.

  Further, in the fuel cell shown in FIG. 7, the example in which the axial length direction high conductivity layer 191 is formed only on one main surface has been described, but the axial length direction high conductivity layer is similarly formed on the other side main surface. By providing 191, the current generated on the other main surface can be passed through the high conductivity layer in the axial direction of the other main surface, and the electric resistance can be reduced and the power generation performance can be improved. .

  FIG. 7C shows a cell stack using the interconnector-less fuel cell. In this cell stack, fuel cells are inserted and fixed in through holes formed in the upper lid 121 of the fuel gas cases 58a to 58d in FIG. Then, the fuel electrode support 164 of one fuel cell and the oxygen electrode layer 170 of the other fuel cell adjacent to each other are connected to the oxygen electrode layer 170 in the axial length direction high conductivity layer 191, It is configured to be electrically connected at the lower end of the fuel cell via a current collecting member 123 between the fuel cell and the other fuel cell.

  That is, the fuel cell is inserted into the through hole of the upper lid 121 and solidified, and the current collecting member 123 formed by applying, for example, Ag paste to the upper lid 121 in the axially long high conductivity layer 191 of one cell. The current collecting member 123 is electrically connected to the fuel electrode layer 166 and the support 164 of the other fuel cell through the removed part of the solid electrolyte layer 168 of the other cell. Connected.

  The upper lid 121 and the current collecting member 123 are covered and protected by a glass layer 125. In such a cell stack, as described above, by providing the axial direction high conductivity layer 191 formed in the axial direction, the current generated at one end (upper end) of the fuel cell is It flows to the other end portion (lower end portion) through the high conductivity layer 191 and is electrically connected through the current collecting member 123 between one fuel cell and the other fuel cell. The electric resistance of the battery can be reduced, and the power generation performance can be improved.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and various modifications and corrections can be made without departing from the scope of the present invention. It goes without saying that this is possible.

  For example, the present invention has been described in relation to a fuel cell assembly having a specific reforming case above the cell stack. However, the present invention can be applied even when the reforming case is not located above the cell stack. I can do it.

  Further, in the above embodiment, a case has been described in which low temperature gas supply means is provided in the air chamber, and air is supplied to the outer surface of the fuel cell by the air supply pipe. Of course, air may be supplied to the air. In this case, it goes without saying that an air electrode is formed inside the fuel cell and a fuel electrode is formed outside.

  In the above embodiment, in order to electrically connect the side surfaces of the fuel cells with the current collecting member 76, the axially long high-conductivity layer 91 is used as shown in FIGS. 6 (a) to 6 (d). In the present invention, as shown in FIG. 6 (e), even when a plurality of circular high conductivity layers 92 are provided, the same effect as in the above embodiment can be obtained.

  In the above embodiment, the hollow flat plate fuel cell has been described, but the present invention can of course be applied to a cylindrical fuel cell.

  Further, in the above embodiment, the case where the oxygen electrode layer is provided on the outer surface of the solid electrolyte layers 68 and 168 has been described. However, in the present invention, the fuel electrode layer may be provided on the outer surface of the solid electrolyte layer.

  Furthermore, in the above embodiment, the case where the oxygen electrode layer is provided on the outer surface of the solid electrolyte layers 68 and 168 and the high conductivity layer electrically connected to the oxygen electrode layer is provided has been described. Even when a high conductivity layer electrically connected to the fuel electrode layer is provided on the inner surface of 168 so as to be joined to the inner surface of the solid electrolyte, substantially the same effect as in the above embodiment can be obtained. Further, even when a high conductivity layer that is electrically connected to the oxygen electrode layer on the outer surface and the fuel electrode layer on the inner surface of the solid electrolyte layers 68 and 168 is provided, substantially the same effect as in the above embodiment can be obtained.

  In the above example, the case where the fuel electrode layer, the solid electrolyte layer, and the oxygen electrode layer are formed on the support substrate has been described. However, the present invention can be applied even when the fuel electrode layer is a support.

  Furthermore, in the above example, the example in which the current collecting member is joined to the interconnector has been described, but an intermediate layer such as a P-type semiconductor is formed on the surface of the interconnector, and the current collecting member is joined via this intermediate layer. good.

NiO powder having an average particle size of 0.5 μm and Y ₂ O ₃ powder (average particle size is 0.6 to 0.9 μm), NiO is 48% by volume in terms of Ni, and Y ₂ O ₃ is 52% by volume. In this way, the mixed powder is extruded into a support substrate clay formed by mixing a pore agent, an organic binder, and water, dried, debindered, and flattened. A molded body for a substrate was prepared and dried. Then, it calcined at 1000 degreeC and produced the support substrate calcined body.

Next, a _ZrO 2 (YSZ) powder containing 8 _mol% Y 2 _{O 3,} and NiO powder, an organic binder, using a slurry obtained by mixing a solvent to prepare a fuel electrode layer forming sheet, it It laminated | stacked on the predetermined position of the support substrate calcined body, and calcined at 1000 degreeC, and the fuel electrode layer calcined body was formed in the surface of a support substrate calcined body.

  On the other hand, an immersion liquid in which the YSZ powder, an organic binder, and a solvent are mixed is prepared. A coating film of the material was formed and dried to form a solid electrolyte layer molded body.

Next, a sheet for an interconnector is prepared using a slurry obtained by mixing LaCrO ₃ oxide powder having an average particle diameter of 2 μm, an organic binder, and a solvent, and the support substrate calcined body is exposed to the sheet. A sintered laminated sheet comprising a support substrate calcined body, a fuel electrode layer calcined body, an interconnector sheet, and a solid electrolyte layer molded body was produced. Next, the laminated sheet for sintering was subjected to binder removal treatment and co-fired at 1500 ° C. in the air.

The obtained sintered body was immersed in a paste made of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (referred to as LSCF) powder having an average particle diameter of 2 μm and a solvent, and sintered. On the surface of the solid electrolyte layer formed on the body, as shown in FIG. 6 (a), two coating layers for the oxygen electrode layer are provided, and the paste is formed on the sintered body. It is applied to the outer surface, provided with a P-type semiconductor coating layer, baked at 1150 ° C., and then Ag—Pd (9: 9) so that the side portions of these oxygen electrode layers overlap each other between the two oxygen electrode layers. A conductive paste containing 1) and the above LSCF powder in a weight ratio of 1: 1 was applied and baked at 900 ° C. to produce a fuel cell as shown in FIG.

  The produced fuel cell has a length of 145 mm, a width of 26 mm, a thickness of 3.2 mm, a fuel electrode layer thickness of 10 μm, an oxygen electrode layer thickness of 120 μm, an interconnector thickness of 50 μm, and a P-type semiconductor layer thickness. Was 100 μm. Further, the axially long high conductivity layer had a thickness of 120 μm, a width of 3 mm and a length of 125 mm, and the oxygen electrode layers on both sides thereof had a width of 11 mm and a length of 125 mm.

  With respect to the produced fuel cell, the resistance between both ends in the length direction of the high conductivity layer was measured using a resistance measuring instrument, and found to be 0.083Ω. Similarly, the resistance between both ends in the length direction of the oxygen electrode layer was 4.2Ω.

A cell stack as shown in FIG. 4 (a) was prepared using five of these fuel cells and a rectangular rod-shaped current collecting member, and the amount of power generation in this cell stack was measured. The power generation conditions were such that the current density per 1 cm ² of the air electrode was 0.3 A, and the total output of 5 cells was 33.0 W.

  Also, after 1000 hours of power generation, when the axial length direction high conductivity layer and the current collecting member, the joining state of the solid electrolyte layer and the joining state of the solid electrolyte and the air electrode layer were confirmed, no peeled portion was found. .

  On the other hand, it is produced in the same manner as FIG. 4A except that the high conductivity layer in the axial direction is not formed, the width of the air electrode layer is 25 mm, the length is 125 mm, and the current collecting member and the air electrode layer are joined. In the cell stack of the comparative example, the amount of power generation under the above conditions is 30.0 W, and after 300 hours of power generation, a part of the junction between the current collecting member and the air electrode layer, and part between the air electrode and the solid electrolyte Peeling was observed.

The longitudinal cross-sectional view which shows the fuel cell of this invention. The top view of FIG. FIG. 2 is a perspective view showing a power generation unit assembly used in the fuel cell of FIG. 1. The cell stack which shows a cell stack, (a) The cell stack using a rectangular rod-shaped current collection member, (b) is a cross-sectional view which shows the cell stack using the current collection member which shape | molded the electroconductive board in the ribbon shape. The perspective view which shows the fuel battery cell of this invention. It is a side view of a fuel cell, (a) shows the state where the air electrode layer is divided into two, (b) shows the axial length direction high conductivity layer between the two divided air electrode layers. (C) shows the state where the axial length direction high conductivity layer is provided on both sides of the air electrode layer, and (d) shows the state where the axial length direction high conductivity layer and the circumferential direction high conductivity layer are provided. The side view which shows the state which showed the state, (e) is a side view which shows the state which scattered the high electrical conductivity layer. 1 shows a fuel cell of an interconnector-less type, in which (a) is a cross-sectional view of the fuel cell, (b) is a side view of (a), and (c) is a plurality of (a) fuel cells. The longitudinal cross-sectional view which shows the state connected electrically. The cross-sectional view which shows the conventional cell stack.

Explanation of symbols

2: Housing (storage container)
60a, 60b, 60c and 60d: cell stack 62: fuel cell 66, 166: fuel electrode layer 68, 168: solid electrolyte layer 70, 70a, 170: air electrode layer 72: interconnector 76, 123: current collecting member 91 , 92, 93, 191: High conductivity layer

Claims (9)

Columnar fuel cells each having a porous electrode layer on the inner and outer surfaces of the solid electrolyte layer, wherein the solid electrolyte layer is electrically connected to the electrode layer and has a higher conductivity than the electrode layer. A fuel cell having a conductive layer bonded thereto. 2. A hollow flat plate type or a cylindrical type, wherein an outer electrode layer is provided on an outer surface of the solid electrolyte layer, and the high conductivity layer is electrically connected to the outer electrode layer. Fuel cell. A hollow flat plate type or a cylindrical type, wherein an inner electrode layer is provided on an inner surface of the solid electrolyte layer, an outer electrode layer is provided on an outer surface, the high conductivity layer is electrically connected to the outer electrode layer, and The fuel cell according to claim 2, wherein an interconnector is electrically connected to the inner electrode layer. A hollow flat plate type or a cylindrical type, wherein the outer electrode layer and the high conductivity layer are provided on the entire circumferential surface of the annular solid electrolyte layer so as to surround the solid electrolyte layer. Item 3. The fuel cell according to Item 2. The fuel cell according to any one of claims 1 to 4, wherein the high conductivity layer is an axial length direction high conductivity layer formed in an axial length direction. The fuel cell according to claim 5, wherein a circumferential high conductivity layer connected to the axial length high conductivity layer is formed in a circumferential direction of the outer electrode layer. A plurality of fuel cells according to claim 3 are arranged at predetermined intervals, and an interconnector of one fuel cell and an outer electrode layer of the other fuel cell adjacent to the fuel cell are electrically connected to the outer electrode layer. A cell stack comprising: a high-conductivity layer connected to the substrate; and a current collecting member between the one fuel cell and the other fuel cell. 5. A plurality of fuel cells according to claim 4 are arranged at predetermined intervals, and an inner electrode layer of one fuel cell and an outer electrode layer of the other adjacent fuel cell are connected to the outer electrode layer. And an electrical connection at the end of the fuel cell via a current collecting member between the one fuel cell and the other fuel cell. Cell stack. A fuel cell comprising the cell stack according to claim 7 or 8 stored in a storage container.

Images