JP2009087708A - Fuel battery cell body and fuel battery including fuel battery cell body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel battery cell body capable of constituting a solid electrolyte fuel battery enabled to be operated in a higher output at a lower temperature. <P>SOLUTION: The fuel battery cell body 1 provided with a fuel battery cell 6 with a pair of electrode layers and an electrolyte layer pinched by the electrode layers laminated in a tube shape, and constituted so as to be able to collect currents at both ends of the fuel battery cell 6 has an outer electrode collector layer 44a adhesively formed at least at on one of the outer periphery faces of the pair of electrode layers formed of a material formed of a palladium oxide contained with silver. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell unit and a fuel cell including the fuel cell unit.

  Conventionally, a fuel cell stack having a tubular fuel cell is known (see, for example, Patent Documents 1 and 2). First, an example of a cell stack of a conventional fuel cell described in Patent Document 1 will be described with reference to FIG. FIG. 7 is a schematic cross-sectional view of a conventional fuel cell stack.

As shown in FIG. 7, in the fuel cell stack 200 described in Patent Document 1, cylindrical fuel cells 202 are arranged side by side with respect to the longitudinal direction, and both ends thereof are supported by metal plates 204. It has a structure. In this fuel cell stack 200, fuel cells 202 are connected in parallel.

  The fuel cell 202 includes an inner electrode layer 204, an outer electrode layer 208, and an electrolyte layer 206 disposed therebetween. At one end of the fuel cell 202, a connection member 210 inserted inside the inner electrode layer 204 is provided. A connecting member 212 fitted to the outside of the outer electrode layer 208 is provided at the other end of the fuel battery cell 202. The inner electrode layer 204 or the outer electrode layer 208 and the connection members 210 and 212 are connected by brazing, spraying, or rubbing. Moreover, the connection members 210 and 212 and the metal plate 104 are connected by welding, pressure bonding, or rubbing.

Patent Document 2 describes a hollow hexagonal fuel cell, and the electrode inside the fuel cell is exposed in the longitudinal direction at the end.
JP 2002-289249 A (paragraph 0028 and FIG. 4) Japanese Patent Laid-Open No. 5-101842 (FIGS. 1 and 6)

  In the fuel cell stack 200 disclosed in Patent Document 1, it is difficult to attach the connection member 210 to the inner electrode 204, and the contact resistance tends to increase. In particular, it is difficult to attach the connecting member 210 to the inner electrode 204 of the fuel cell 202 having an outer diameter of 1 to 10 mm.

  Further, the voltage that can be generated by a single fuel cell is constant regardless of its size. Therefore, in order to obtain a high voltage, it is necessary to electrically connect the fuel cells in series. On the other hand, in order to obtain a large current, for example, it is necessary to electrically connect fuel cells in parallel. Since the number of fuel cells electrically connected in series or in parallel varies depending on the application, there is a demand for easily assembling the fuel cells with a desired electrical connection. In the fuel cell using the fuel cell stack 200 disclosed in Patent Document 1, a plurality of fuel cells 202 are electrically assembled in series, and then the assembled cells are electrically connected in parallel. 200, or a process of electrically assembling a plurality of fuel cells 202 in parallel to form the fuel cell stack 200 and then assembling them electrically in series, and assembling the entire fuel cell. It took time and effort.

  Therefore, the present inventors provide a fuel cell body that can be easily taken out from an inner electrode layer and can be easily assembled so that the fuel cell can be electrically connected, and a fuel cell including the same. Study was carried out.

  As a result, the inventors have invented a fuel cell unit that can easily collect current from both ends of a cylindrical fuel cell body. An example of the fuel cell unit will be described in detail. A tubular inner electrode layer, a tubular outer electrode layer, a tubular electrolyte layer disposed between these electrode layers, and an inner electrode layer. A tubular fuel cell body having a through-flow passage configured; an inner electrode terminal fixed to one end of the fuel cell body and for taking out electricity from an inner electrode layer; and the other of the fuel cell body And an outer electrode terminal for taking out electricity from the outer electrode layer. The fuel cell body has an inner electrode layer, an electrolyte layer and an outer electrode layer at one end. An inner electrode exposed peripheral surface exposed to the inner electrode, and an outer peripheral surface of one end portion has an inner electrode outer peripheral surface that is in electrical communication with the inner electrode layer through the inner electrode exposed peripheral surface. The outer peripheral surface of the outer electrode that is in electrical communication with the outer electrode layer is formed on the outer peripheral surface of the end. The inner electrode terminal is arranged so as to cover the outer circumference of the inner electrode from the outside over the entire circumference and is electrically connected thereto, and the outer electrode terminal is arranged so as to cover the outer circumference of the outer electrode from the outer circumference over the entire circumference. In addition, the inner electrode terminal and the outer electrode terminal are electrically connected thereto, and have a connection channel that communicates with the through channel and communicates with the outside.

  Furthermore, it has been found that the outer peripheral surface of the inner electrode may be constituted by an inner electrode exposed peripheral surface, or may be constituted by an inner electrode current collecting layer provided outside thereof. Further, it has been found that the outer peripheral surface of the outer electrode may be constituted by an outer electrode layer or may be constituted by an outer electrode current collecting layer provided outside the outer electrode layer.

  By the way, when a fuel cell based on this new invention was manufactured and a power generation test was actually performed, a sufficient output could be obtained. However, the present inventors were able to obtain a higher output at a low temperature (for example, about 700 ° C.). Further studies were made to obtain a high-power solid oxide fuel cell.

  Accordingly, the present invention provides a fuel cell unit capable of constituting a solid oxide fuel cell that can be operated at a lower temperature and higher output, and a fuel cell using the fuel cell unit. Objective.

  In order to solve the above problems, a fuel cell body according to the present invention includes a tubular body in which a pair of electrode layers and an electrolyte layer sandwiched between the pair of electrode layers are respectively formed in a tubular shape, and both ends of the tubular body And a current collecting layer formed in close contact with an outer peripheral surface of at least one of the pair of electrode layers, wherein the current collecting layer comprises palladium oxide on silver. It consists of the contained material.

  According to the present invention, it is easy to assemble so that electricity can be easily taken out from the inner electrode layer and the fuel cell can be electrically connected, and a lower temperature and higher output solid oxide fuel cell is configured. It becomes possible.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  First, an embodiment of a fuel cell unit including a fuel cell body according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a fuel cell unit according to this embodiment.

  As shown in FIG. 1, the fuel cell unit 1 according to the present embodiment has a single tubular fuel cell body. In the present embodiment, the fuel cell body is composed of one fuel cell 6 (tubular body), and the fuel cell 6 has a cylindrical shape.

  The fuel cell 6 includes a cylindrical inner electrode layer 16, a cylindrical outer electrode layer 20, a cylindrical electrolyte layer 18 disposed between these electrode layers 16, 20, and an inner electrode. It has a through flow path 15 configured inside the layer 16. Further, an inner electrode exposed peripheral surface 16a in which the inner electrode layer 16 is exposed with respect to the electrolyte layer 18 and the outer electrode layer 20, and the electrolyte layer 18 on the one end portion 6a of the fuel cell 6 are disposed on the outer electrode layer. 20 is provided, and the inner electrode exposed peripheral surface 16 a and the electrolyte exposed peripheral surface 18 a constitute the outer peripheral surface of the fuel cell 6. The remaining outer peripheral surface including the other end 6b of the fuel cell 6 is constituted by an outer electrode exposed peripheral surface 20a from which the outer electrode layer 20 is exposed. In the present embodiment, the inner electrode exposed peripheral surface 16 a is also the inner electrode outer peripheral surface 21 that is in electrical communication with the inner electrode layer 16, and the outer electrode exposed peripheral surface 20 a is an outer surface that is in electrical communication with the outer electrode layer 20. It is also the electrode outer peripheral surface 22.

  The inner electrode layer 16 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, ceria doped with Ni and at least one selected from rare earth elements, And a mixture of Ni and lanthanum gallate doped with at least one selected from Sr, Mg, Co, Fe, and Cu. The electrolyte layer 18 includes, 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 outer electrode layer 20 is made of, 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 selected from samarium cobalt and silver doped with at least one selected. In this case, the inner electrode layer 16 becomes a fuel electrode, and the outer electrode layer 20 becomes an air electrode. The thickness of the inner electrode layer 16 is, for example, 1 mm, the thickness of the electrolyte layer 18 is, for example, 30 μm, and the thickness of the outer electrode layer 20 is, for example, 30 μm.

  The fuel cell unit 1 is further fixed to one end portion 6a of the fuel cell 6 and fixed to the inner electrode terminal 24 for taking out electricity from the inner electrode layer 16, and to the other end portion 6b. It has an outer electrode terminal 26 for taking out electricity from the outer electrode layer 20.

  The inner electrode terminal 24 is disposed so as to cover the inner electrode outer peripheral surface 21 from the outside over the entire circumference and is electrically connected to the main body portion 24a, and the longitudinal direction of the fuel cell 6 so as to be away from the fuel cell 6. And a tubular portion 24b extending in the direction. Preferably, the body portion 24a and the tubular portion 24b are cylindrical and arranged concentrically, and the tube diameter of the tubular portion 24b is smaller than the tube diameter of the body portion 24a. The main body portion 24a and the tubular portion 24b have a connection channel 24c that communicates with the through channel 15 and communicates with the outside. A step portion 24d between the main body portion 24a and the tubular portion 24b is in contact with the end face 16b of the inner electrode layer 16.

  The outer electrode terminal 26 is disposed so as to cover the outer peripheral surface 22 of the outer electrode from the outside over the entire circumference and is electrically connected thereto, and the longitudinal direction of the fuel cell 2 so as to be away from the fuel cell 2 And a tubular portion 26b extending in the direction. Preferably, the body portion 26a and the tubular portion 26b are cylindrical and concentric, and the tube diameter of the tubular portion 26b is smaller than the tube diameter of the body portion 26a. The main body portion 26a and the tubular portion 26b have a connection channel 26c that communicates with the through channel 15 and communicates with the outside. A step portion 26 d between the main body portion 26 a and the tubular portion 26 b is in contact with the outer electrode layer 20, the electrolyte layer 18, and the end surface 16 c of the inner electrode layer 16 through an annular insulating member 28.

  The tubular portions 24b, 26b of the inner electrode terminal 24 and the outer electrode terminal 26 preferably have the same outer contour cross-sectional shape. More preferably, the inner electrode terminal 24 and the outer electrode terminal 26 have the same overall shape.

  The inner electrode terminal 24 and the fuel battery cell 6, and the outer electrode terminal 26 and the fuel battery cell 6 are sealed and fixed by a conductive sealing material 32 over the entire circumference.

  At one end 6a, the inner electrode exposed peripheral surface 16a and the electrolyte exposed peripheral surface 18a extend over the entire circumference of the fuel cell 6 and are adjacent to each other in the longitudinal direction A. Further, the inner electrode exposed peripheral surface 16 a is located at the front end portion 6 c of the fuel cell 6. A boundary 34 between the inner electrode exposed peripheral surface 16a and the electrolyte exposed peripheral surface 18a is inside the main body portion 24a of the inner electrode terminal 24, and a boundary between the electrolyte exposed peripheral surface 18 and the outer electrode exposed peripheral surface 20 is provided. 36 is located outside the main body portion 24a. Further, the electrolyte exposed peripheral surface 18a has a tapered portion 18b that becomes thinner toward the inner electrode exposed peripheral surface 16a.

  At one end 6a, the sealing material 32 extends over the entire circumference across the inner electrode exposed peripheral surface 16a and the electrolyte exposed peripheral surface 18a, and is filled in the main body portion 24a of the inner electrode terminal 24, so that the electrolyte exposed peripheral surface. It is spaced from the outer electrode layer 20 via 18a. At the other end 6b, the sealing material 32 extends over the entire circumference of the outer electrode exposed peripheral surface 20a and fills the space between the main body portion 26a of the outer electrode terminal 26 and the insulating member 28. . The sealing material 32 is provided so as to partition a gas region that acts on the inner electrode layer 16, that is, a gas flow region that acts on the outer electrode layer 20 and the through flow channel 15 and the connection flow channels 24 c and 26 c. ing. The sealing material 32 is various brazing materials including, for example, silver, a mixture of silver and glass, gold, nickel, copper, and titanium.

  Subsequently, the other end of the fuel cell 6 will be described in detail with reference to FIGS. 2 and 3.

  FIG. 2 is a cross-sectional view of the other end of the fuel battery cell. As shown in FIG. 3, the outer electrode current collecting layer 44 a (current collecting layer) is arranged around the entire outer electrode 20 of the fuel cell 6 or a part thereof. The outer electrode outer peripheral surface 22 electrically connected to the outer electrode 20 is constituted by an outer electrode current collecting layer 44a. The outer electrode current collecting layer 44a is a porous conductive film containing silver, and more specifically, a layer containing silver oxide in palladium oxide. The thickness of the outer electrode current collecting layer 44a is preferably 1 to 50 μm, more preferably 5 to 30 μm. Further, the outer electrode current collecting layer 44a may be composed of silver, a heat-resistant metal wire, mesh, sheet or the like. The outer electrode current collecting layer 44a functions as an electrical path when the outer electrode layer 20 is thin and difficult to conduct electricity, or when it is made of a material having low conductivity.

  FIG. 3 is a cross-sectional view of a modification of the other end of the fuel cell. As shown in FIG. 3, after the electrolyte layer 18 is exposed to the outer peripheral surface of the fuel cell 6 at the tip 6d of the other end 6b of the fuel cell 6, the second electrolyte exposed peripheral surface 18c is formed. The outer electrode current collecting layer 44b (current collecting layer) may be disposed on the whole or a part of the outer electrode 20 and the second electrolyte exposed peripheral surface 18c. In this modification, the outer electrode outer peripheral surface 22 electrically connected to the outer electrode 20 is constituted by the outer electrode current collecting layer 44b. The material, thickness, and the like of the outer electrode current collecting layer 44b are the same as those of the outer electrode current collecting layer 44a. Since the outer electrode current collecting layer 44b reduces the possibility that the outer electrode layer 20 is exposed to the gas that acts on the inner electrode layer 16, the electrical connection can be made more reliably.

  Subsequently, the operation of the fuel cell using the fuel cell unit 1 will be described. A gas (fuel gas) acting on the inner electrode layer 16 is passed through the through flow path 15 and the connection flow paths 24c and 26c. Further, a gas (air) that acts on the outer electrode layer 20 flows around the outer electrode layer 20. Thereby, the fuel cell unit 1 operates. Further, the electricity of the inner electrode 16 is taken out via the sealing material 32 and the inner electrode terminal 24, and the electricity of the outer electrode 20 is taken out via the sealing material 32 and the outer electrode terminal 26.

  Next, an example of the manufacturing method of the fuel cell unit according to the present invention will be described. First, a tubular fuel cell is formed. Specifically, first, the tubular inner electrode layer 16 is formed, the electrolyte layer 18 is formed around the inner electrode layer 16 so as to expose the end of the inner electrode layer 16, and the electrolyte layer 18 is further formed. An outer electrode layer 20 is formed around the electrolyte layer 18 so as to expose the end of the electrode layer. Thereafter, a tapered portion 18 b is preferably formed at the end of the electrolyte layer 18.

  In this case, in order to use the inner electrode outer peripheral surface 21 as the inner electrode current collecting layer and the outer electrode outer peripheral surface 22 as the outer electrode current collecting layer, a layer containing silver oxide and palladium oxide may be formed. preferable. Specifically, the resin component includes polyvinyl butyral, acrylic resin, ethyl cellulose, etc., and the solvent component includes α-terpineol, dihydroterpineol, dihydroterpinyl acetate, etc., and additives include dispersants and antifoaming agents. Etc. A paste containing silver powder and palladium oxide powder as a solid content is applied, and the resin content is burned off at 200 to 300 ° C. to form a layer in which palladium oxide is contained in silver.

  Next, the inner electrode terminal 24 is placed on one end 6 a of the fuel cell 6, and they are sealed and fixed to each other by a sealing material 32. Further, the outer electrode terminal 26 is placed on the other end 6b of the fuel cell via an insulating member 28, and they are sealed and fixed to each other by a sealing material 32. Thereby, the fuel cell unit 1 is formed.

  In the fuel cell unit 1, the electricity of the inner electrode layer 16 is taken out from the inner electrode terminal 16 via the inner electrode outer peripheral surface 21 which is the outer peripheral surface of the fuel cell 6. It is easy to take out electricity of the layer 16. In addition, the contact area between the sealing material 32 and the inner electrode outer peripheral surface 16a can be increased without hindering the flow of gas acting on the inner electrode 15, thereby reducing the contact resistance. In particular, it is advantageous when a fuel cell having an outer diameter of 1 to 10 mm is used.

  Moreover, since the fuel cell 6 in which the inner electrode terminal 24 and the outer electrode terminal 26 are arranged on both sides is a unit, the fuel cell 6 can be freely combined in electrical series connection and / or parallel connection. Easy to assemble.

  Further, in the fuel cell unit 1, the tubular portions 24 b and 26 b of the inner electrode terminal 24 and the outer electrode terminal 26 have the same outer contour cross-sectional shape, so that the connection to the inner electrode terminal 24 and the connection to the outer electrode terminal 26 are performed. This makes it possible to make the fuel cell assembly easier. Further, in the fuel cell unit 1, since the overall shape of the inner electrode terminal 24 and the outer electrode terminal 26 is the same, a common member can be used for the inner electrode terminal 24 and the outer electrode terminal 26, and the fuel cell unit The number of parts required for 1 can be reduced.

  Further, the fuel cell unit 1 has a function of partitioning the gas acting on the inner electrode layer 16 and the gas acting on the outer electrode layer 20 by the conductive sealing material 32, and the inner electrode layer 16 and the outer electrode layer 16. Both functions for extracting electricity from the electrode layer 20 are already incorporated. Further, since the conductive sealing material 32 has good adhesion to the inner electrode outer peripheral surface 21, the contact resistance at the interface is reduced, and the fuel cell unit 1 having excellent power generation performance and reliability can be configured. Therefore, it is possible to easily assemble the fuel cell without having to consider taking out electricity from the inner electrode layer 16 and gas sealing.

  In addition, by using the inner electrode exposed surface 16a and using the sealing material 32, the fuel cell unit 1 can be easily manufactured. In particular, it is advantageous when the fuel cell 6 having an outer diameter of 1 to 10 mm is used.

  Further, when the sealing material 32 is disposed or filled between the inner electrode member 24 and the fuel cell 6 by the tapered portion 18b of the electrolyte layer 18, it is between the inner electrode exposed peripheral surface 16a and the electrolyte exposed peripheral surface 18a. Bubbles or the like remain in the gas and the gas sealing function can be prevented from being lowered by the sealing material 32. As a result, the yield increases and stable production can be easily performed.

Further, when the current collecting layer as described above is provided, the power generation performance is improved. In order to confirm the improvement of the power generation performance, the results of measuring the power generation performance of the fuel cell unit 1 described above are shown in FIGS. In FIGS. 4 and 5, the current collecting layer composed only of silver is Comparative Example 1, the current collecting layer composed of silver and palladium is Comparative Example 2, and the current collecting layer is composed of silver and palladium oxide. The configuration is an example. In the measurement of FIGS. 4 and 5, one fuel cell unit 1 is prepared, and fuel gas is supplied to the inside of the air on the outside to measure the potential and current. The test conditions were a cell temperature of 700 ° C., a current density of 0.2 A / cm ² , air of 1.00 L / min, nitrogen of 0.04 L / min, and hydrogen of 0.03 L / min. As shown in FIG. 5, compared to Comparative Example 1, in the example, the potential increased by 2.1% when the fuel utilization rate was 70%. Further, when a fuel cell is configured by using a plurality (853) of the fuel cell units 1, the output in the comparative example 1 was 783 W, whereas the output in the example was 800 W. became. In other words, when an output of 800 W is to be obtained, 853 fuel cell units 1 are required in the case of the embodiment, and 869 fuel cell units 1 are required in the case of the comparative example 1. Therefore, in the case of the embodiment, 16 fuel cell units 1 can be reduced.

Furthermore, the result of having examined the electric power generation performance of the fuel cell unit 1 mentioned above in relation to the film thickness of a current collection layer is shown in FIG. In FIG. 6, the current collecting layer is composed only of silver and the film thickness is 10 μm as Comparative Example 1, and the current collecting layer is composed of silver and palladium and the film thickness is 10 μm as Comparative Example 2. The current collecting layer is composed of silver and palladium oxide and the film thickness is 10 μm, and the current collecting layer is composed of silver and palladium oxide, and the film thickness is 5 μm. Example 2 In Example 3, the current collecting layer was made of silver and palladium oxide, and the film thickness was 20 μm. In the measurement of FIG. 6, one fuel cell unit 1 is prepared, fuel gas is supplied to the inside of the air outside, and the potential and current are measured. The test conditions were a cell temperature of 700 ° C., a current density of 0.2 A / cm ² , air of 1.00 L / min, nitrogen of 0.04 L / min, and hydrogen of 0.03 L / min. The film thickness is measured by measuring the weight before and after applying the paste to the fuel cell body 6 and converting the weight into a film thickness. As shown in FIG. 6, the power generation performance is improved by increasing the film thickness.

  As described above, the present inventors consider that the performance of the example is improved as compared with Comparative Example 2 in which the current collecting layer contains silver and palladium for the following reason. Comparing the TG / DTA profiles of palladium oxide and palladium, although palladium oxide is stable at 700 ° C., which is the power generation temperature, palladium is not stabilized at that temperature and the oxidation reaction continues up to 800 ° C. Therefore, it is considered that the cell of Comparative Example 2 does not use all oxygen for the reaction of the power generation system but uses it for the oxidation reaction of the current collecting layer. On the other hand, in the cell of the example, oxygen is not used for the oxidation reaction of the current collecting layer, and all of the cells are used for the reaction of the air electrode.

It is a figure which shows the fuel cell unit which concerns on this embodiment. It is a figure which shows the fuel cell unit which concerns on this embodiment. It is a figure which shows the fuel cell unit which concerns on this embodiment. It is a figure which shows the electric power generation performance of the fuel cell unit which concerns on this embodiment. It is a figure which shows the electric power generation performance of the fuel cell unit which concerns on this embodiment. It is a figure which shows the electric power generation performance of the fuel cell unit which concerns on this embodiment. It is a figure which shows the conventional fuel cell unit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell unit, 6 ... Fuel cell (fuel cell body), 6a ... One end part, 6b ... Other end part, 15 ... Through-flow path, 16 ... Inner electrode layer, 16a ... Inner electrode Exposed peripheral surface, 18 ... electrolyte layer, 20 ... outer electrode layer, 21 ... inner electrode outer peripheral surface, 22 ... outer electrode outer peripheral surface, 24 ... inner electrode terminal, 24b ... tubular portion, 24c ... connection channel, 26 ... outer Electrode terminal, 26b ... tubular portion, 26c ... connection channel, 32 ... sealing material, 44a, 44b ... outer electrode current collecting layer.

Claims (2)

A fuel cell unit comprising a tubular body in which a pair of electrode layers and an electrolyte layer sandwiched between the pair of electrode layers are each formed in a tubular shape, and configured to collect current at both ends of the tubular body,
A current collecting layer formed in close contact with at least one outer peripheral surface of the pair of electrode layers;
The current collecting layer is made of a material containing palladium oxide in silver. A fuel cell comprising the fuel cell unit according to claim 1.

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