JPH02312165A - Cylindrical solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To absorb thermal expansion and prevent excessive thermal stress by elastically deforming either an inner current collector or outer current collector of a single cell which collectors sandwiches a power generating element between them. CONSTITUTION:While a solid electrolyte 8 is heated to raise its temperature, an oxidizing gas containing oxygen gas is caused to flow to the inner periphery side of each single cell 3, and also fuel gas such as hydrogen gas is caused to flow to the outer periphery side of each single cell 3. Then an electromotive force is generated by the difference in oxygen density between the inner and outer peripheries of the solid electrolyte 8, so that in each single cell 3 an oxygen electrode 6 becomes cathode and a fuel electrode 9 becomes anode. As the whole stack 23, an inner current collector 21 therefore becomes cathode and the outer current collector 22 anode. When the whole stack 23 is heated to the operating temperature of the fuel cell, the inner current collector 21 and the single cell 3 thermally expand, and also their amounts of expansion are different but a relative displacement caused by the difference is absorbed by elastic deformation of the inner current collector 21 or outer current collector 22. Excessive thermal stress is thereby prevented from occurring in each single cell 3.

Description

[Detailed Description of the Invention] Industrial Application Field □ This invention is a module in which a plurality of cells are arranged around an internal current collector to form a stack, or a plurality of stacks are arranged around an internal current collector to form a module. The present invention relates to a cylindrical solid electrolyte fuel cell comprising a cylindrical solid electrolyte fuel cell.

As is well known in the art, a solid electrolyte fuel cell consists of an oxygen electrode made of a perovsnoite complex oxide, etc., and an oxygen electrode made of a perovsnoite type composite oxide, with a solid electrolyte such as yttria-stabilized zirconia (ysz) that is permeable to oxygen ions in between. -1r A fuel electrode made of O2 cermet etc. is provided to form a single cell, multiple cells are connected in series or in parallel to form a stack, and multiple stacks are assembled to form a module. , the required output is obtained by connecting a large number of single cells in this way. Conventionally, this type of '
Cylindrical and flat monolithic types of T'M ponds or stacks are known, but they are easy to seal between oxidizing gas such as air and fuel gas such as hydrogen gas, and are easy to manufacture. The cylindrical type is superior in this respect.

FIG. 4 is a cross-sectional view showing an example of a stack constituting a cylindrical fuel cell, and FIG. A plurality of N (in the figure, l
]) is arranged, and its outer periphery is a cylindrical exterior made of a conductive material such as Ni! It has a structure covered by J-electron 4. Here, the cell 3 is as shown in FIG.
An oxygen electrode 6 is formed on the outer periphery of a ceramic support tube 5 made of alumina (^l! 203) or the like to have a porous structure, and an interconnector 7 electrically connected to the oxygen electrode 6 is provided to protrude in the radial direction. A solid electrolyte 8 is provided on the outer periphery of the solid electrolyte 8 , and a fuel electrode 9 in a non-conducting state is further provided on the outer periphery of the solid electrolyte 8 in the interconnector 7 . This unit cell 3 is electrically connected to the internal current collector 2 by interposing a conductive felt 10 such as Ni felt at the tip of the interconnector 7, and the fuel cell 9 of each unit cell 3 is connected to the internal current collector 2 via a conductive felt 11. It is electrically connected to the external current collector 4. The reason for interposing the leW felt 10.11 is that the current collectors 2, 4 and the interconnect 7 are rigid bodies with no elasticity, and the coefficients of thermal expansion of the respective constituent members are not the same. This is because it is necessary to absorb thermal expansion while ensuring reliability.

Problems to be Solved by the Invention By the way, the voltage obtained with the above-mentioned single cells 3 is 1 volt or less, and the current density is about 100 to 3001 A. Therefore, in order to obtain the necessary power, a large number of single cells 3 must be connected in series and parallel. Therefore, the resistance at the connection point or the quality of the connection will greatly affect the power generation capacity.

However, in the fuel cell configured as described above, since the internal current collector 2 and the external current collector 4 are substantially rigid bodies, each ll1i battery 3 is
Although attempts are made to ensure continuity between the conductive felts 10 and 11 and the respective collectors 2 and 4, the amount and method of filling the conductive felts 10 and 11 must be determined in advance by design. , bias in the arrangement of the cells 3 or each collector 2, 4
If there is a dimensional error, use conductive felt 10.1.
1 becomes uneven or partially insufficient. Further, due to repeated thermal expansion and contraction of the cell 3 and the current collectors 2 and 4, the conductive felt 10.
The elastic force of 11 is lost and the contact state becomes insufficient. Therefore, in the structure of the fuel cell described above, the single cell 3 and the current collector 2,
If the 1ti batteries 3 were connected in series, the resistance at the connection between the single cells 3 would increase, and there was a high possibility that sufficient photoelectric efficiency could not be obtained.

This invention has been made in view of the above circumstances, and provides a cylindrical solid electrolyte fuel cell that can securely connect single cells or stacks to each other or to a current collector, thereby improving photoelectric efficiency. The purpose is to

Means for Solving the Problems In order to achieve the above object, the present invention provides a plurality of power generation systems that generate electromotive force due to the difference in oxygen concentration between the inner and outer circumferential sides of a cylindrical solid electrolyte that is permeable to oxygen ions. In a cylindrical solid electrolyte fuel cell in which elements are arranged on the outer periphery of an internal current collector and the outer periphery of these power generation elements is covered with an external current collector, at least one of the internal current collector and the external current collector. It is characterized by being formed of a cylindrical body whose radius increases or decreases elastically.

Note that the power generation elements here include not only single cells, but also stacks formed by forming multiple single cells around the outer periphery of a support tube, stacks formed by bundling multiple single cells, and modules formed by bundling multiple stacks. Including etc.

Function: In the fuel cell J3 of the present invention, by flowing an oxidizing gas containing oxygen gas and a fuel gas such as hydrogen gas on both sides of the solid electrolyte, the oxygen concentration on both the inside and outside of the solid electrolyte can be reduced. The difference generates an electromotive force, and the electromotive force in each power generation element is output from the internal current collector and the external current collector.

Either the internal current collector on the inner periphery side or the external current collector on the outer periphery side of each power generating element is a cylindrical body whose radius increases or decreases elastically, so each power generating element is pressed against the outer surface of the internal current collector or the inner surface of the external current collector by the elastic force of . As a result, each power generation element is brought into close contact with the internal current collector and the external current collector, and a good electrical state between them is maintained. In addition, when thermal expansion occurs, the internal current collector or external current collector deforms elastically, and this deformation absorbs the thermal expansion and prevents excessive thermal stress from occurring. Ru.

Example Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and in the example shown here, six cells 3 are equally distributed between an internal current collector 21 and an external current collector 22 to form a stack 23. This is an example of a constructed fuel cell, and since the unit cell 3 has the same construction as that described with reference to FIG. 5, the description thereof will be omitted here. The internal current collector 21 is formed into a cylindrical shape from a material that is conductive, has a high melting point, and is resistant to hydrogen embrittlement, such as N, Ni alloy, or cermet containing Ni. As shown in the perspective view, the slit 21a is formed so that the slit 21a is elastically deformed and the radius increases or decreases. The external current collector 22 is also formed into a cylindrical shape using the same abrasive material as the internal current collector 21, and is elastically deformed by forming a slit 22a as shown in a perspective view in FIG. It is configured to increase and decrease. The six single cells 3 are arranged with their interconnectors 7 facing the internal current collectors 21, and the external current collectors 22 are fitted around the outer peripheries of these lr+ batteries 3. Here, as the external current collector 22, the radius in the natural state is 6 (1) arranged around the outer periphery of the internal current collector 21.
! As a result, each cell 3 is pressed toward the internal current collector 21 and its interconnector 7 is placed on the outer surface of the internal current collector 21. Naturally, the external current collector 22 is in close contact with the outer surface of each cell 3. In this case, since the internal current collector 21 is slightly bent toward the inner circumference, each heavy electric current i1! ! 3
is also pressed toward the outer circumference by the elastic force of the internal current collector 21.

The temperature of the solid electrolyte 8 in each cell 3 is 900 to 1200°C
Since it exhibits excellent oxygen ion permeability at a temperature of about 100%, an oxidizing gas containing R gas is flowed around the inner circumferential side of each unit cell 3 while the solid electrolyte 8 is heated to this temperature, and each unit A fuel gas such as hydrogen gas is passed around the outer circumferential side of the battery 3. Accordingly, an electromotive force is generated due to the difference in oxygen concentration between the inner and outer circumferences of the solid electrolyte 8, and in each 141 cell 3, the acid 1A electrode 6 becomes the anode and the fuel electrode 9 becomes the cathode. Therefore, for the stack 23 as a whole, the internal current collector 21 serves as an anode and the external current collector 22 serves as a cathode. When the entire stack 23 is heated to the operating temperature of the fuel cell, the internal current collector 21 and the single cell 3
etc., and the amount of expansion is different, but the relative displacement caused by this is absorbed by the bony deformation of the internal current collector 21 or the external current collector 22,
Excessive thermal stress is prevented from being generated in the cell 3. Furthermore, each cell 3 is sandwiched between the respective collectors 21, 22 by the elastic force of the inner and outer collectors 21, 22, and this state is maintained even when thermal expansion or contraction occurs. , the adhesion state of each unit cell 3 to each of the internal and external current collectors 21, 22 is always good, so the resistance at the contact part is small, and as a result, the internal resistance as a fuel cell is reduced and a high output peak is achieved. can be achieved.

Incidentally, in the above embodiment, a conductive felt is not particularly provided, but in the present invention, a conductive felt may be interposed between the unit cell 3 and each current collector 21, 22, and if this is done, Since the conductive felt fills in the irregularities on the outer surface of the unit cell 3, the contact area between them is expanded, and the electrical continuity becomes even better.

Furthermore, in the above embodiment, a stack in which cylindrical cells were arranged between an internal current collector and an external B element was explained as an example, but a large number of cells were arranged mutually on the outer peripheral surface of a porous support tube. Since the stack formed by connecting in series also has a cylindrical shape and needs to be connected in parallel, the present invention connects such a stack in parallel via an internal current collector as shown in FIG. It can also be applied in cases. Furthermore, the present invention can be applied to the case where a plurality of stacks shown in FIG. 1 or 4 are combined into a module.

In the above embodiment, both the internal current collector and the external current collector are cylindrical bodies whose radii change elastically. However, the present invention is not limited to the above embodiment. It is sufficient if the radius of either one of the electrons and the electrons changes elastically.

Effects of the Invention As is clear from the above explanation, according to the fuel cell of the present invention, either the internal current collector or the external collector, which sandwich a power generating element such as a unit cell, is elastically deformed. Since the radius changes between the two current collectors, relative displacement caused by thermal expansion or contraction can be absorbed by the deformation of one of the current collectors, thereby reducing the thermal stress of the power generating element. Since the contact between the power generating element and each collector is maintained by the elastic force of the collector, the contact between the power generating element and the collector is always good even when heating and cooling occur repeatedly, and the electrical resistance at that part is low. Therefore, according to the present invention, it is possible to obtain a fuel cell that can reduce internal resistance, improve power generation efficiency, and achieve high output.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a schematic perspective view showing an internal current collector, FIG. 3 is a schematic perspective view showing an external current collector, and FIG. 4 is a conventional stack. FIG. 5 is a sectional view showing an example of a unit cell. 3...111 battery, 6...oxygen main, 7...
interconnector, 8... solid electrolyte, 9...
Fuel electrode, 21... Internal current collector, 21a... Slit, 22... External IH element, 22a... Slit, 23... Stack.

Claims (1)

[Scope of Claims] A plurality of power generating elements that generate an electromotive force due to the difference in oxygen concentration between the inner and outer circumferential sides of a cylindrical solid electrolyte that is permeable to oxygen ions are disposed on the outer circumferential side of an internal current collector, and In a cylindrical solid electrolyte fuel cell in which the outer circumferential side of a power generation element is covered with an external current collector, at least one of the internal current collector and the external current collector is formed into a cylindrical body whose radius increases or decreases elastically. A cylindrical solid electrolyte fuel cell characterized by being formed by