JPH02312171A - Structure of solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To obtain a high output fuel cell while reducing its current density by connecting stacks in series to each other by means of conductive plates. CONSTITUTION:An electro motive force is generated by passing an oxidizing gas and a fuel gas on both sides of each cell 1 where a solid electrolyte 6 is sandwitched. The plural cells 1 are connected in parallel to each other by means of an inner current collector 8 and an outer current collector 9 to form a stack 2. The conductive plate 11 which is electrically integrated with the inner current collector 8 and which extends between cells to the outer face side of the outer current collector 9 is brought in electric contact with the outer face of adjacent stack 2 so that the stack 2 is connected in series to adjacent stack 2, while a current generated at one stack is transmitted to another stack 2 via the conductive plate 11. The conductive plate 11 is provided along the whole length of the inner current collector 8 so its cross section is broadened and its current density is reduced. A high output fuel cell is thus obtained.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to the structure of a fuel cell in which a plurality of single cells are connected in parallel to each other and the aggregates are further connected in series, and in particular, the present invention relates to a fuel cell structure in which a plurality of unit cells are connected in parallel to each other, and an assembly of the cells is further connected in series. This relates to a fuel cell that is mainly a single cell that has an oxygen electrode and a fuel electrode provided on its inner and outer surfaces.

Conventional Technology As is well known, solid electrolyte fuel cells utilize the fact that materials such as yttria-stabilized zirconia (YSZ) exhibit oxygen ion conductivity at high temperatures of around 1000°C. *The structure consists of a porous I element electrode made of velorskite-type lanthanum-based composite oxide, etc., with a solid electrolyte such as YSZ in between, and a porous structure made of nickel, nickel alloy, Ni-Zr02 cermet, etc. A solid electrolyte is produced by flowing an oxidizing gas such as air or oxygen gas to the B element electrode side in a high temperature state, and flowing a fuel gas such as hydrogen gas or carbon monoxide gas to the fuel electrode side. Electricity is obtained through oxidation and reduction reactions.

The voltage obtained by this type of 1 dollar battery is only about 1 cm at most, so in order to put it into practical use, it is necessary to connect many cells in series and parallel.For this reason, cells have traditionally been made into cylindrical shapes. structure that forms and connects them in series and parallel,
Various structures have been developed and studied, such as a flat plate type in which a large number of single cells are formed between conductive plates serving as interconnectors and stacked in large numbers. Among these structures, the flat plate type has the advantage of making the whole structure more compact, but it also has problems such as difficulty in sealing to prevent mixing of oxidizing gas and fuel gas, as well as a lack of ease of manufacture. Therefore, the cylindrical type is highly practical.

Conventionally, a single cell was used as a structure to obtain the necessary electromotive force using a cylindrical single cell! A structure is known in which a large number of cells are arranged in a U-horizontal matrix, and each cell is connected in series in the vertical direction, and each cell is connected in parallel in the horizontal direction. However, in such a structure, if an abnormality occurs in one of the cells and that cell no longer generates an electromotive force, the entire group of cells connected in series including that cell will no longer be able to perform its R function, or its A problem arises in that the internal resistance of the unit cell group increases significantly and the power generation efficiency decreases. The applicant has already proposed a structure that can solve these problems, and its basic structure consists of arranging a large number of cylindrical cells around the outer periphery of a conductive internal current collector. 111
The electrode on the inner circumference of the battery is connected to the internal current collector through an interconnector, and the entire cell is surrounded by a cylindrical external current collector provided almost concentrically with the internal current collector, and the outer circumferential side of each cell is The electrode is electrically connected to an external current collector. It should be noted that an @reduction body in which a plurality of single cells are connected in this way is called a stack.

Problems to be Solved by the Invention The above-mentioned stack can be assembled into a fuel cell by connecting a plurality of stacks in series and parallel, but in that case, each stack has an internal current collector as one electrode and an external current collector as one electrode. Since it is considered to be an independent power generation element with the other electrode, the structure in which they are connected in series is a structure in which the internal current collector is surrounded by the external current collector, so that at least the internal current collector is One end is made to protrude in the axial direction, and a conductive connector extending radially from the protruding part is applied to the outer surface of the external current collector of the other stack by interposing a cushioning 1j electrical material such as nickel felt. An If4 construction where the two are in contact with each other is conceivable. However, in such a structure, the current generated in each stack is concentrated in the connector provided at one end, resulting in a high current density at the connector, and as a result, the current density at the connector is high. The loss is-
There are problems such as the increase in size and the length of the current flow path, which reduces the power generation efficiency of the fuel cell as a whole.

This invention was made against the background of the above-mentioned circumstances, and aims to provide a high-output fuel cell by reducing the resistance and loss associated with connecting stacks.

Means for Solving the Problems In order to achieve the above object, the present invention has a plurality of unit cells each having an oxygen electrode and a fuel electrode formed on the inner and outer peripheral surfaces of a cylindrical solid electrolyte, which are arranged approximately concentrically with each other. Between the internal current collector and the cylindrical external current collector arranged in a shape, one electrode is connected to the internal current collector and the other electrode is connected to the external current collector. A stack is constructed by arranging a conductive plate, which is in electrical contact with the internal current collector and whose other end passes through the external current collector in an insulating state, at the outer periphery of the internal current collector and between any of the cells, The stacks arranged adjacent to each other are connected by electrically contacting the other end of the conductive plate with the outer surface of the external current collector of the other stack.

Function: Even in the fuel cell having the structure according to the present invention, an electromotive force is generated by flowing the oxidizing gas and the fuel gas on both sides of the solid electrolyte of each unit cell. These plurality of cells are connected in parallel to each other by an internal current collector and an external current collector to form a stack, and the stack is electrically integrated with the internal current collector, and any of the cells are connected in parallel to each other. They are connected in series by electrically contacting the outer surface of the other adjacent stack with a conductive plate that extends through the gap to the outer surface of the external current collector, and the current generated in one stack passes through that conductive plate. sent to other stacks via Since the conductive plate is provided over almost the entire length of the internal current collector, its cross-sectional area becomes wider, lowering the current density, and the current flow path between the stacks becomes shorter, resulting in an increase in internal resistance. It is considered a high-output fuel cell because there are fewer factors that increase loss.

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

FIG. 1 is a cutaway perspective view schematically showing a part of the fuel cell according to the present invention, in which a plurality of (five in the figure) single cells 1
is one stack 2, which is connected in series. In other words, each unit cell 1 is of a so-called cylindrical type, an example of which is schematically shown in FIG.
An oxygen electrode 4 made of velorskite-type lanthanum-based composite oxide or the like is formed on the outer periphery of a ceramic support tube 3 formed with a porous M4 structure using AQ203), etc., and a part of its outer surface is coated with nickel. An interconnector 5 made of an alloy or the like is protruded, and the outer periphery of the Ml element electrode 4 is made of ittria-stabilized zirconia (YSZ).
), etc., is formed as a solid electrolyte 6. Furthermore, a fuel electrode 7 made of a nickel alloy, a cermet of nickel and zirconia, or the like is formed on the outer periphery of the solid electrolyte 6 so as to be non-conductive to the interconnector 5. Therefore, in the cell 1, an oxidizing gas such as air is allowed to flow on the inner circumferential side, while a fuel gas such as hydrogen gas is allowed to flow on the outer circumferential side. Electromotive force is generated through an electrochemical reaction.

Further, the stack 2 is constructed by arranging a plurality of the above-mentioned IP zero ponds 1 between an internal current collector 8 and an external current collector 9 arranged substantially concentrically with respect to the internal current collector 8. The internal current collector 8 and the external current collector 9 are tubular members made of a material having high heat resistance and hydrogen embrittlement resistance, such as nickel or a nickel alloy. The nickel felts 10 are arranged in close contact with each other, and each 113 i-cell 1 has its interconnector 5 in contact with the nickel felt 10, so that one electrode, the oxygen electrode 4, is electrically connected to the internal current collector 8. They are arranged around the outer periphery of the internal current collector 8. Further, on the outer periphery of the internal current collector 8, a conductive plate 11 is arranged so as to protrude outward in the flat diameter direction. This conductive plate 11
is made of the same material as the internal current collector 8, has approximately the same length as the internal current collector 8 or the IIi battery 1, and is located at one location on the outer periphery of the internal current collector 8 where the unit cell 1 is to be placed. The internal current collector 8
Further, the other side end portion of the conductive plate 11 passes through the external We main electron in an insulating state and extends to the outside thereof. The external current collector 9 is a cylindrical member made of the same material as the internal current collector 8, and the outer surface of each unit cell 1 is covered with a conductive cushioning material such as nickel felt 12 attached to its inner peripheral surface. A plurality of single cells 1 are accommodated with fuel electrodes 7 in contact with each other. A slit 13 is formed in a part of the external current collector 9 along the axial direction, and the conductive plate 11 projects to the outside of the external current collector 9 through the slit 13.

A plurality of stacks 2 formed as described above are connected in series and parallel to form a fuel cell, and the series state is
As shown in the figure, the end of the conductive plate 11 of one stack 2 of a pair of stacks 2 adjacent to each other is interposed with a conductive MWI material, for example, nickel felt 14, on the outer surface of the external current collector 9 of the other stack 2. to make electrical contact,
Thereby, the stacks 2 are connected in series.

In each stack 2, electricity is generated by flowing an oxidizing gas such as air or oxygen gas to the inner circumference of each cell 1, and flowing a fuel gas such as hydrogen gas to the outer circumference, and the oxygen electrode 4 is electrically connected to the internal current collector 8, and the fuel electrode 7 is electrically connected to the external current collector 9, so that the internal current collector 8 is adjacent and the external current collector 9 is ll! Become the pole. Each stack 2 is connected in series by the conductive plate 11 having a length approximately equal to the length of the internal current collector 8 or the single cell 1, so that a 1 m current including the current generated in each stack 2 is transmitted to the stack 2. It flows through the conductive plate 11 to the other stack 2. Therefore, since the cross-sectional area of the conductive plate 11 is large, the resistance at this part is small, and the current from each stack 2 to the other stack 2 does not pass through one end of each internal current collector 8. Since the current flows directly through the conductive plate 11 from any point in the axial direction, the current flow path becomes short. Therefore, the resistance caused by connecting the stack 2 does not become particularly large, resulting in a high output fuel cell.

In addition, in the present invention, the stacks 2 are not only connected in series as described in the above embodiments, but also stack groups connected in series as described above may be further connected in parallel.

Effects of the Invention As is clear from the above explanation, according to the structure of the fuel cell of the present invention, the cross-sectional area of the electric circuit between the stacks is widened, so the resistance in that part is extremely small, and the connection between the stacks is Since the conductive plate is long along the axis of the internal current collector, the electrical path from the cells in one stack to the cells in the other stack is shortened, which also reduces resistance. According to the method, a fuel cell with low internal resistance and high power generation efficiency can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view schematically showing a part of an embodiment of the present invention, and FIG. 2 is a sectional view schematically showing one of the unit cells. 1...Single battery, 2...Stack, 4...i!
[! Elementary electrode, 5... Interconnector, 6... Solid electrolyte, 7... Fuel electrode, 8... Internal current collector, 9... External current collector, 11... Conductive plate, 13
...slit, 14...nickel felt.

Claims (1)

[Claims] A plurality of unit cells each having an oxygen electrode and a fuel electrode formed on the inner and outer peripheral surfaces of a cylindrical solid electrolyte are placed between an internal current collector and a cylindrical external current collector, which are arranged approximately concentrically with each other. The electrodes are arranged in such a way that they are electrically connected to the internal current collector and the other electrode is electrically connected to the external current collector, and one end is electrically integrated with the internal current collector and the other end is connected to the external current collector. A stack is constructed by placing a conductive plate that passes through the internal current collector at the outer periphery of the internal current collector and between any of the cells, and stacks that are placed adjacent to each other connect the other end of the conductive plate to the other side. A structure of a solid electrolyte fuel cell characterized in that it is connected in electrical contact with the outer surface of an external current collector of a stack.