JP2018163830A - Current collection structure for fuel battery cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current collection structure which enables achievement of satisfactory conduction between a fuel battery cell and a cap.SOLUTION: A current collection structure for a fuel battery comprises a conductive cap 50 fitted on an end part of a fuel battery cell and electrically connected to an inner electrode layer (fuel electrode layer 44). The cap has a bottom part and a cylindrical part, and is fitted in such a way that an inner face of the bottom part and an inner circumferential face of the cylindrical part surround an end face and an outer circumferential face of the end part 40a of the fuel battery cell, respectively. Between the inner face of the bottom part of the cap and the inner circumferential face of the cylindrical part of the cap and the end face and outer circumferential face of the end part of the fuel battery cell, a conductive junction layer 62 is disposed to electrically join them to each other. A current-collecting layer 64 is disposed on an inner circumferential face of an inner electrode layer and it is electrically connected to the conductive junction layer. By disposing the current-collecting layer electrically connected to the conductive junction layer on the inner circumferential face of the inner electrode layer in this way, an electrical contact area of the inner electrode layer and the conductive layer (junction layer, current-collecting layer) can be ensured sufficiently. As a result, satisfactory conduction between the fuel battery cell and the cap can achieved.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a current collecting structure for a fuel cell.

  Conventionally, a current collecting structure of this type of fuel cell includes a cylindrical inner electrode layer, a cylindrical outer electrode layer, and an electrolyte layer disposed between the inner electrode layer and the outer electrode layer. A cylindrical fuel cell has been proposed in which an inner electrode terminal (cap) for current collection is attached to an end of the fuel cell (for example, see Patent Document 1). The inner electrode layer is provided with an exposed portion that is not covered with the electrolyte layer and the outer electrode layer at the end thereof. The cap is formed in a cup shape (bottomed cylindrical member) and filled with a silver seal material between the inner peripheral surface of the cylindrical portion of the cup and the inner surface of the bottom portion, and the outer peripheral surface and end surface of the exposed portion of the inner electrode layer. Has been.

Republished patent WO2013 / 047667A1

  In the fuel cell current collection structure described above, since the clearance between the inner electrode layer and the cap is small, air tends to remain between the inner electrode layer and the cap even if an attempt is made to fill the silver sealing material. Further, when a paste is used as the silver sealing material, volume shrinkage may occur in the firing process, and sink marks (concave marks) may be generated. If such air or sink marks occur between the inner electrode layer and the cap, the contact area between the inner electrode layer and the sealing material is reduced, the electrical resistance between the inner electrode layer and the cap increases, and the cell performance decreases. Will be invited.

  The main object of the current collecting structure of the fuel cell of the present invention is to provide a current collecting structure with good conductivity between the fuel cell and the cap.

  The current collecting structure of the fuel cell according to the present invention employs the following means in order to achieve the main object described above.

  A current collecting structure for a fuel cell according to the present invention includes a cylindrical inner electrode layer, a cylindrical outer electrode layer, and an electrolyte layer disposed between the inner electrode layer and the outer electrode layer. A fuel cell current collecting structure having a conductive cap that is fitted to an end of the fuel cell and electrically connected to the inner electrode layer, the cap having an annular shape A bottom portion and a cylindrical portion extending in a cylindrical shape from an outer peripheral side of the bottom portion, and an inner surface of the bottom portion and an inner peripheral surface of the cylindrical portion are an end surface and an outer peripheral surface of an end portion of the fuel cell, respectively. Between the inner surface of the bottom portion and the inner peripheral surface of the cylindrical portion, and the end surface and outer peripheral surface of the end portion of the fuel cell, and electrically conductive bonding. And a current collecting layer electrically connected to the conductive bonding layer is disposed on the inner peripheral surface of the inner electrode layer. And summarized in that the location.

  In the current collecting structure of the fuel cell according to the present invention, the cap is fitted so that the inner surface of the bottom and the inner peripheral surface of the cylindrical portion surround the end surface and the outer peripheral surface of the end of the fuel cell, respectively. A conductive bonding layer is disposed between the inner surface of the bottom of the cap and the inner peripheral surface of the cylindrical portion, and the end surface and outer peripheral surface of the end portion of the fuel cell, and the inner electrode. A current collecting layer electrically connected to the conductive bonding layer is disposed on the inner peripheral surface of the layer. In this way, by arranging the current collecting layer electrically connected to the conductive bonding layer on the inner peripheral surface of the inner electrode layer, the electric connection between the inner electrode layer and the conductive layer (bonding layer, current collecting layer) is achieved. A sufficient contact area can be ensured. As a result, the electrical conductivity between the fuel battery cell and the cap can be improved.

  In the current collecting structure of the fuel battery cell of the present invention, the conductive bonding layer and the current collecting layer may be formed of the same material. It is possible to eliminate the thermal expansion difference between the conductive bonding layer and the current collecting layer with respect to the temperature change, thereby reducing the thermal stress and maintaining good electrical connection between the two.

  In the current collecting structure of the fuel battery cell of the present invention, the conductive joining layer and the current collecting layer may be formed of a conductive paste. If it carries out like this, a current collection layer can be arrange | positioned more easily on the internal peripheral surface of an inner side electrode layer.

It is a block diagram which shows the outline of a structure of the electric power generation module 10 which has the fuel cell 40 of this embodiment. It is sectional drawing which expands and shows the cross section of the circular part of the dashed-two dotted line in the electric power generation module 10 of FIG.

  Next, modes for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram showing an outline of the configuration of a power generation module 10 having a fuel cell 40 of the present embodiment, and FIG. It is sectional drawing. As shown in FIG. 1, the power generation module 10 includes a vaporizer 22 that generates water vapor, and a fuel gas (reformed gas) containing hydrogen by reforming raw fuel gas such as natural gas or LP gas through a steam reforming reaction. ), A fuel cell stack 30 in which a plurality of fuel cells 40 that generate power by reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen are stacked, and a fuel gas supply pipe 26 The fuel gas manifold 34 is connected to the reformer 24 through the fuel cell and distributes the fuel gas from the reformer 24 to each fuel cell 40, and the oxidant gas manifold 38 distributes the oxidant gas to each fuel cell 40. These are housed in the module case 11. The power generation module 10 constitutes a fuel cell system by being combined with a hot water supply unit (hot water storage tank) (not shown) that recovers and supplies hot water generated by the power generation.

  The module case 11 is formed in a box shape from a heat insulating material, and the raw fuel gas supply pipe 12, the reformed water supply pipe 14, and the air supply pipe 16 are connected. The raw fuel gas supply pipe 12 is a pipe for supplying the raw fuel gas from a supply source to the vaporizer 22, and the pipe is provided with an on-off valve, a pump, a flow meter, a pressure gauge, a desulfurizer, and the like. The reforming water supply pipe 14 is a pipe that supplies the reforming water to the vaporizer 22, and the pipe is provided with a reforming water tank, a pump, and the like. The air supply pipe 16 is a pipe that supplies air as an oxidant gas to the oxidant gas manifold 38, and an air blower, a flow meter, and the like are provided in the pipe.

  Further, the module case 11 is provided with a combustion section 28 for supplying heat necessary for the generation of water vapor by the vaporizer 22 and the steam reforming reaction by the reformer 24. The combustion unit 28 ignites and burns surplus fuel gas (anode offgas) and oxidant gas (cathode offgas) that have not been used for the power generation reaction of the fuel battery cell 40, thereby using the combustion heat to vaporize the carburetor 22. And the reformer 24 is heated. The combustion exhaust gas generated by the combustion of the combustion unit 28 is discharged out of the case through the combustion exhaust gas exhaust pipe 18 provided in the upper part of the module case 11. Note that a heat exchanger (not shown) is connected to the combustion exhaust gas discharge pipe 18, and the heat exchanger warms the hot water supplied from the hot water storage tank through the circulation pipe by heat exchange with the combustion exhaust gas. The combustion exhaust gas that has passed through the heat exchanger is condensed by heat exchange with the hot water, and the condensed water is collected in the reformed water tank.

  As shown in FIG. 2, the fuel cell 40 includes a cylindrical electrolyte layer 42 having a dense structure made of an oxygen ion conductor, and a fuel electrode layer having a porous structure as an anode laminated inside the electrolyte layer 42 ( A cylindrical solid oxide fuel cell (inner electrode layer) 44 and a porous oxidant electrode layer (outer electrode layer) 46 as a cathode laminated on the outside of the electrolyte layer 42. The cell is configured as a cell (SOFC) cell, and a current collecting cap 50 is attached to both ends in the longitudinal direction so as to be electrically connected to the fuel electrode layer 44. A fuel gas flow path 44a through which fuel gas flows is formed inside the fuel electrode layer 44. In the fuel cell 40, the fuel gas flow path 44a and the fuel gas manifold 34 communicate with each other as shown in FIG. In this manner, the fuel gas manifold 34 is erected on the support plate 36. As shown in FIG. 2, the fuel electrode layer 44 is provided with an exposed portion 44 b that is not covered with the electrolyte layer 42 and the oxidant electrode layer 46 at the end.

  The electrolyte layer 42 is, for example, one or more selected from stabilized zirconia doped with one or more selected from rare earth elements such as Y, Sc and Ce, and rare earth elements such as Gd, Y and Sm. Can be used, such as ceria doped with lanthanum gallate doped with one or more selected from Ni, Sr, Mg, Co, Fe, Cu.

  The fuel electrode layer 44 is made of, for example, a mixture of a catalytic metal such as Ni or Fe and a stabilized zirconia doped with one or more selected from rare earth elements such as Y, Sc, and Ce, and Ni and Fe. A mixture of a catalyst metal and a ceria doped with one or more rare earth elements such as Gd, Y, Sm, etc., a catalyst metal such as Ni or Fe, and Sr, Mg, Co, Fe, Cu A mixture with lanthanum gallate doped with one or more kinds can be used.

  The oxidant electrode layer 46 includes, for example, lanthanum manganite doped with one or two selected from Sr and Ca, lanthanum ferrite doped with one or more selected from Sr, Co, Ni, and Cu, Sr , Lanthanum cobaltite doped with one or more selected from Fe, Ni, Cu, barium cobaltite doped with one or two selected from Sr, Fe, silver, silver-palladium alloy, platinum, etc. Can be used.

  Between the electrolyte layer 42 and the oxidant electrode layer 46, ceria doped with rare earth such as ceria doped with gadolinium (GDC), ceria doped with yttria (YDC), ceria doped with samarium (SDC), or the like. It is also preferable to provide a reaction preventing layer using a mixture.

  The cap 50 is formed of, for example, a metal material such as ferritic stainless steel. As shown in FIG. 2, the cap 50 has an annular bottom portion 52, a cylindrical portion 54 that extends in a cylindrical shape from the outer peripheral side of the bottom portion 52, and the bottom portion 52. A projection 56 extends in a cylindrical shape in the opposite direction to the cylindrical portion 54 from the inner peripheral side. The cap 50 is fitted to the fuel cell 40 so that the inner surface of the bottom portion 52 and the inner peripheral surface of the cylindrical portion 54 surround the end surface and the outer peripheral surface of the end portion 40a of the fuel cell 40, respectively. Between the bottom portion 52 of the cap 50 and the end surface of the end portion 40a of the fuel cell 40, the inner peripheral surface of the cylindrical portion 54 of the cap 50, and the end portion 40a of the fuel cell 40 (exposed portion 44b of the fuel electrode layer 44). Is electrically connected by the conductive bonding layer 62 and the fuel gas flowing in the fuel gas flow path 44a inside the fuel electrode layer 44 leaks to the outside (oxidant electrode layer 46 side). Not sealed. A current collecting layer 64 that is electrically connected to the conductive bonding layer 62 is disposed on the inner peripheral surface of the end 40 a of the fuel battery cell 40 (the exposed portion 44 b of the fuel electrode layer 44). The conductive bonding material 62 and the current collecting layer 64 can be formed using, for example, a conductive paste such as platinum, silver, copper, or a silver-palladium alloy, or a conductive ceramic such as lanthanum chromite. In the present embodiment, the conductive bonding material 62 and the current collecting layer 64 are each formed of the same kind of material. The upper end surface of the conductive bonding layer 62 is covered with a glass seal layer 66. For the glass seal layer 66, for example, crystallized glass excellent in heat resistance and sealability such as alumina-silica crystallized glass can be used. The glass seal layer 66 may not be provided.

  The connection plate 32 is formed of, for example, a metal material such as ferritic stainless steel. As shown in FIG. 1, the cap 50 (the fuel electrode layer 44) of one of the two fuel cells 40 adjacent to each other, as shown in FIG. 1. ) And the oxidant electrode layer 46 of the other fuel cell 40 are electrically connected. The plurality of fuel cells 40 are electrically connected in series by connecting two fuel cells 40 adjacent to each other via the connection plate 32.

  The fuel gas manifold 34 is a box-shaped member having an upper opening, and a support plate 36 is joined so as to close the upper opening and form a sealed space. The support plate 36 has a plurality of through holes 36a formed at predetermined intervals, and a plurality of fuel cells are inserted by inserting the fuel cell 40 so that the protrusions 56 of the cap 50 penetrate the respective through holes 36a. The cell 40 is supported in a standing state. As a result, the fuel gas manifold 34 communicates with the fuel gas flow path 44 a of each fuel cell 40 through the hollow cap 50, and the fuel gas supplied from the fuel gas supply pipe 26 is supplied to the fuel cell 40. Supply (distribution) to the gas flow path 44a. The fuel gas supplied to the fuel gas channel 44a passes through the fuel gas channel 44a and is discharged upward from the upper cap 50. As described above, surplus fuel gas that has passed through the fuel battery cell 40 is combusted in the combustion unit 28 together with the oxidant gas, and is discharged to the combustion exhaust gas exhaust pipe 18 as combustion exhaust gas. The support plate 36 can be formed of, for example, a metal material such as ferritic stainless steel or austenitic stainless steel, or can be formed of an insulating material such as an insulating ceramic. When the support plate 36 is formed of a metal material, an insulating seal member is provided in the through hole 36a in order to electrically insulate the lower cap 50 of the fuel cell 40 and the through hole 36a of the support plate 36. It may be provided.

  A glass seal portion 37 is formed between the fuel cell 40 and the support plate 36, that is, between the outer surface of the bottom portion 52 of the cap 50 and the upper surface of the support plate 36. The glass seal part 37 can be formed using crystallized glass excellent in heat resistance and sealability, such as alumina-silica crystallized glass.

  The oxidant gas manifold 38 is connected to the air supply pipe 16, and a plurality of supply ports 38 a for distributing the oxidant gas (air) to the oxidant electrode layer 46 of each fuel cell 40 are formed. .

  The following experiment was conducted on the conductivity between the fuel cell 40 and the cap 50.

Example A conductive paste made of a silver-palladium alloy was applied to the inner peripheral surface (the inner peripheral surface of the fuel electrode layer 44) of the end 40a of the fuel cell 40, and the fuel cell 40 (the end surface and the outer periphery of the end 40a). Surface) and the cap 50 (the inner surface of the bottom portion 52 and the inner peripheral surface of the cylindrical portion 54) are filled with a conductive paste made of a silver-palladium alloy, and the conductive paste is fired at 850 ° C. Wiring was attached to the surface and the end of the fuel cell 40 opposite to the cap 50 mounting side (fuel electrode layer 44), and the electrical resistance was measured in a reducing atmosphere. The electric resistance was 8.8 mΩ at 700 ° C.

Comparative Example A conductive paste made of a silver-palladium alloy is filled between the fuel cell 40 (the end surface and the outer peripheral surface of the end portion 40a) and the cap 50 (the inner surface of the bottom portion 52 and the inner peripheral surface of the cylindrical portion 54), The conductive paste is baked at 850 ° C., wiring is attached to the outer peripheral surface of the cap 50 and the end of the fuel cell 40 opposite to the cap 50 mounting side (fuel electrode layer 44), and electric resistance is obtained in a reducing atmosphere. Was measured. The electrical resistance was 10.3 mΩ at 700 ° C.

  According to the current collecting structure of the fuel cell 40 of the present embodiment described above, the cap 50 has the inner surface of the bottom 52 and the inner peripheral surface of the cylindrical portion 54, respectively, the end surface and the outer periphery of the end 40a of the fuel cell 40. It is fitted so as to surround the surface. And between the inner surface of the bottom part 52 of the cap 50 and the inner peripheral surface of the cylindrical part 54, and the end surface and outer peripheral surface of the end part 40a of the fuel cell 40, there is a conductive bonding layer 62 that electrically joins both. A current collecting layer 64 that is disposed and is electrically connected to the conductive bonding layer 62 is disposed on the inner peripheral surface of the fuel electrode layer 44. In this way, by arranging the current collecting layer 64 electrically connected to the conductive bonding layer 62 on the inner peripheral surface of the fuel electrode layer 44, the fuel electrode layer 44 and the conductive layer (the conductive bonding layer 62, the current collecting layer) are arranged. A sufficient electrical contact area with the electric layer 64) can be ensured. As a result, the electrical conductivity between the fuel cell 40 and the cap 50 can be improved.

  Moreover, since the conductive bonding layer 62 and the current collecting layer 64 are formed of the same material, the thermal stress is reduced by eliminating the difference in thermal expansion between the conductive bonding layer 62 and the current collecting layer 64 with respect to temperature changes. Both electrical connections can be kept good.

  In the present embodiment, the conductive bonding layer 62 and the current collecting layer 64 are formed of the same kind of material, but may be formed of different materials. In this case, it is desirable to select materials having similar thermal expansion coefficients (for example, materials having a difference in coefficient of thermal expansion within 0.5 ppm).

  In the present embodiment, the fuel battery cell 40 and the cap 50 are formed in a cylindrical shape, but may be formed in any shape such as a rectangular tube shape as long as it is cylindrical.

  The correspondence between the main elements of the present embodiment and the main elements of the invention described in the column of means for solving the problem will be described. In the present embodiment, the electrolyte layer 42 corresponds to an “electrolyte layer”, the fuel electrode layer 44 corresponds to an “inner electrode layer”, the oxidant electrode layer 46 corresponds to an “outer electrode layer”, and the fuel cell 40. Corresponds to the “fuel cell”, the cap 50 corresponds to the “cap”, the bottom 52 corresponds to the “bottom”, the cylindrical portion 54 corresponds to the “tubular portion”, and the conductive bonding layer 62 “ The current collecting layer 64 corresponds to a “conductive bonding layer”, and the current collecting layer 64 corresponds to a “current collecting layer”.

  As mentioned above, although it demonstrated using the form for implementing this invention, this invention is not limited at all to such embodiment, In the range which does not deviate from the summary of this invention, it can implement with a various form. Of course.

  The present invention is applicable to the fuel cell manufacturing industry.

  DESCRIPTION OF SYMBOLS 10 Power generation module, 11 Module case, 12 Raw fuel gas supply pipe, 14 Reformed water supply pipe, 16 Air supply pipe, 18 Combustion exhaust gas discharge pipe, 22 Vaporizer, 24 Reformer, 26 Fuel gas supply pipe, 28 Combustion , 30 Fuel cell stack, 32 Connection plate, 34 Fuel gas manifold, 36 Support plate, 36a Through hole, 37 Glass seal part, 38 Oxidant gas manifold, 38a Supply port, 40 Fuel cell, 42 Electrolyte layer, 44 Fuel Electrode layer, 44a Fuel gas flow path, 44b Exposed portion, 46 Oxidant electrode layer, 50 Cap, 52 Bottom portion, 54 Cylindrical portion, 56 Protruding portion, 62 Conductive bonding layer, 64 Current collecting layer, 66 Glass seal layer

Claims (3)

A current collecting structure for a cylindrical fuel cell having a cylindrical inner electrode layer, a cylindrical outer electrode layer, and an electrolyte layer disposed between the inner electrode layer and the outer electrode layer. ,
A conductive cap fitted to an end of the fuel cell and electrically connected to the inner electrode layer;
The cap includes an annular bottom portion and a cylindrical portion extending in a cylindrical shape from the outer peripheral side of the bottom portion, and an inner surface of the bottom portion and an inner peripheral surface of the cylindrical portion are the ends of the fuel cell, respectively. It is fitted so as to surround the end surface and outer peripheral surface of the part,
Between the inner surface of the bottom portion and the inner peripheral surface of the cylindrical portion, and the end surface and outer peripheral surface of the end portion of the fuel cell, a conductive bonding layer is disposed to electrically bond both,
A current collecting layer electrically connected to the conductive bonding layer is disposed on the inner peripheral surface of the inner electrode layer.
Current collecting structure of fuel cell. A current collecting structure for a fuel cell according to claim 1,
The conductive bonding layer and the current collecting layer are formed of the same material.
Current collecting structure of fuel cell. A current collecting structure for a fuel cell according to claim 1 or 2,
The conductive bonding layer and the current collecting layer are formed of a conductive paste.
Current collecting structure of fuel cell.

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