WO2010067833A1

WO2010067833A1 - Electrochemical device

Info

Publication number: WO2010067833A1
Application number: PCT/JP2009/070634
Authority: WO
Inventors: 久野俊明; 高瀬尚哉
Original assignee: 日本碍子株式会社
Priority date: 2008-12-08
Filing date: 2009-12-03
Publication date: 2010-06-17
Also published as: JP5417344B2; JPWO2010067833A1

Abstract

An electrochemical device is provided with a plurality of ceramic electrochemical cells (10) and interconnectors (11). Each cell is provided with; a first electrode which has a built-in gas channel wherein a first gas flows and is in contact with the first gas; a solid electrolyte layer; a second electrode which is exposed from the main surface of the cell and is in contact with the second gas; and a plurality of conductive sections (8A, 8B) which are exposed from the main surface of the cell and are electrically connected with the first electrode. The conductive sections are arranged on the outer edge section of the cell main surface. Each interconnector is provided with a storing section which stores a part of the cell, and a plurality of connecting sections which protrude from the storing section. A second gas channel (30) is formed between the storing section and the cell. The gas is brought into contact with the second electrode, while the gas is passing through the second gas channel. Each connecting section is electrically connected to each conductive section of the adjacent cell.

Description

Electrochemical equipment

The present invention relates to an electrochemical device such as a solid oxide fuel cell.

Since the voltage per fuel cell is about 1 V, a plurality of sheets must be stacked in order to obtain a large output. Therefore, it becomes a problem how small the number of layers can be increased and a large output can be obtained.
In WO 2007/029860 A1, particularly in FIG. 14, a fuel flow path is formed inside, for example, a fuel electrode of a ceramic electrochemical cell, and a solid electrolyte membrane and an air electrode membrane are formed on the fuel electrode. A gas supply hole and a gas discharge hole are provided in the cell itself, and a plurality of cells are directly stacked to form a stack. In forming the stack, the gas supply passages are formed by connecting the gas supply holes of adjacent cells, and the gas discharge passages are formed by connecting the gas discharge holes of the cells.

In a stack (collective battery) as described in WO 2007/029860 A1, a cell having a gas flow path is attached to a fixed member, and these are stacked. However, since the cell in this structure also has a role as a structural member, stress is easily applied. In particular, since a cell having a gas flow path has a lower structural strength than a cell having no gas flow path, a structure in which no stress is applied to the cell is desirable.
The present applicant discloses in WO 2008 / 123570A1 that a fuel gas flow path is formed inside an electrochemical cell and a plurality of electrochemical cells are supported by a gas supply member and a gas discharge member in a state of being separated from each other. did.
However, in this case, the flow rate of air flowing outside the cell is large, the amount of air available for power generation on the surface of the cell is small, and the utilization efficiency is low. Further, although the adjacent cells are made conductive by the conductive gas supply member or the discharge member, the current flowing distance tends to be long, and the current loss tends to increase from this point.
Further, the present applicant disclosed in JP-A-2009-146805 that each flow path built-in cell is accommodated in an interconnector, and a plurality of interconnectors are stacked in this state to form a stack. A conductive part is formed on the surface of each cell, and the conductive part of each cell is electrically connected in series to the adjacent interconnector.
However, in this stack, on the main surface with the connection part of the interconnector, the distance from each part to the connection part and the conductive part of the adjacent cell is short, but on the opposite main surface without the connection part. Has a long distance at the connection. For this reason, it is easily affected by the material resistance of the interconnector, and the output loss in the cell is large. And since the power density differed between the main surface with a connection part and the main surface of the other side, the tendency for the durability of a cell to fall was seen.
The object of the present invention is to reduce the mechanical stress applied to the cell when stacking the electrochemical cell made of ceramic, to improve the gas utilization efficiency, and to reduce the deviation of the conduction distance between the two main surfaces of the cell. This is to reduce the difference in power density between the two main surfaces and improve the durability of the cell.
The present invention is an electrochemical device comprising a plurality of ceramic electrochemical cells and an interconnector,
The electrochemical cell has a built-in gas flow path through which the first gas flows, and is in contact with the first gas, the solid electrolyte layer, and the second gas exposed on the main surface of the cell. The second electrode, and a plurality of conductive portions that are exposed on the main surface of the cell and are electrically connected to the first electrode, and the conductive portion is provided on the outer edge portion of the main surface,
The interconnector includes an accommodating portion that accommodates a part of the cell, and a plurality of connecting portions protruding from the accommodating portion,
A second gas flow path is formed between the accommodating portion and the electrochemical cell, and the second gas contacts the second electrode while passing through the flow path, and each connection portion is adjacent to the second gas flow path. It is electrically connected to each conductive part of the cell.
In the present invention, the first gas flow path is formed in the electrochemical cell, and a part of the electrochemical cell is accommodated by the interconnector, and the second gas flow path is provided between the interconnector and the cell. Form. The second gas contacts the second electrode while passing through this flow path, and contributes to the electrochemical reaction. Accordingly, since the cells are accommodated in the interconnector to form the second gas flow path, the second gas flow path can be formed as a narrow flow path, and the utilization efficiency of the second gas is improved. be able to.
At the same time, a connection portion is provided in the interconnector, and the connection portion of the interconnector that accommodates a certain cell is electrically connected to the conductive portion of the adjacent cell. As a result, the adjacent cells are connected to the adjacent cells via the connection portions extending from the interconnector housing portions. With this structure, the compressive stress applied to the entire stack is received by each accommodating portion of each interconnector, and the stress is dispersed at each connecting portion. Therefore, damage due to excessive stress applied to the cell can be prevented.
Furthermore, a plurality of conductive portions that are electrically connected to the first electrode are provided, and are respectively positioned on the outer edge portions of the cell main surface. And each connection part is electrically connected with respect to each electroconductive part of an adjacent cell. Thereby, the deviation between the conduction distance on the principal surface on the connection part side of the cell and the conduction distance on the cell principal surface on the side without the connection part becomes small, and the deviation of the internal resistance on both principal faces becomes small. As a result, the power density is improved as a whole, and a decrease in cell durability due to a deviation in power density between both main surfaces can be prevented.

FIG. 1 is a perspective view of an electrochemical cell 10 according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view of the cell 10 of FIG.
FIG. 3 is a perspective view of the cell 1 of the comparative example.
FIG. 4A is a side view of the interconnector 11, and FIG. 4B is a front view of the interconnector 11 viewed from the IVb side.
FIG. 5A is a plan view of the interconnector 11 viewed from the Va side, and FIG. 5B is a bottom view of the interconnector 11 viewed from the Vb side.
FIG. 6 is a perspective view showing a state where the interconnector 11 is fitted in the cell 10.
FIG. 7 is a perspective view showing a state where the interconnector 11 is fitted in the cell 10.
FIG. 8 is a perspective view schematically showing a state in which the cells of FIG. 7 are stacked.
FIG. 9 is a perspective view showing a state where voltage and current lines are attached to the stack of FIG.
FIG. 10 is a cross-sectional view schematically showing a state after the stack of FIG. 9 is manufactured.
FIG. 11 is a perspective view schematically showing a stack of a comparative example.
FIG. 12 is a schematic diagram showing a current flow in the example of the present invention.
FIG. 13 is a schematic diagram showing the flow of current in the comparative example.

In the present invention, the electrochemical cell is preferably plate-shaped. However, it is not limited to a flat plate shape, and may be a curved plate or a circular arc plate. The electrochemical cell includes a first electrode that contacts the first gas, a solid electrolyte membrane, a second electrode that contacts the second gas, and a conductive portion connected to the first electrode.
Here, the first electrode and the second electrode are selected from an anode or a cathode. When one of these is an anode, the other is a cathode. Similarly, the first gas and the second gas are selected from oxidizing gas and reducing gas.
The oxidizing gas is not particularly limited as long as it is a gas that can supply oxygen ions to the solid electrolyte membrane, and examples thereof include air, diluted air, oxygen, and diluted oxygen. Examples of the reducing gas include H ₂ , CO, CH ₄ and a mixed gas thereof.
The electrochemical cell targeted by the present invention means a general cell for causing an electrochemical reaction. For example, the electrochemical cell can be used as an oxygen pump or a high temperature steam electrolysis cell. The high-temperature steam electrolysis cell can be used for a hydrogen production apparatus and a steam removal apparatus. Moreover, an electrochemical cell can be used as a decomposition cell for NOx and SOx. This decomposition cell can be used as a purification device for exhaust gas from automobiles and power generation devices. In this case, oxygen in the exhaust gas is removed through the solid electrolyte membrane, and NOx is electrolyzed and decomposed into N ₂ and O ₂ ^−, and oxygen generated by this decomposition can also be removed. Moreover, with this process, water vapor in the exhaust gas is electrolysis produced hydrogen and oxygen, the hydrogen reduces NOx into N _2. In a preferred embodiment, the electrochemical cell is a solid oxide fuel cell.
The material of the solid electrolyte is not particularly limited, and any oxygen ion conductor can be used. For example, it may be yttria stabilized zirconia or yttria partially stabilized zirconia, and in the case of a NOx decomposition cell, cerium oxide is also preferable.
The material of the cathode is preferably a perovskite complex oxide containing lanthanum, more preferably lanthanum manganite or lanthanum cobaltite, and even more preferably lanthanum manganite. Lanthanum cobaltite and lanthanum manganite may be doped with strontium, calcium, chromium, cobalt (in the case of lanthanum manganite), iron, nickel, aluminum or the like.
As a material for the anode, nickel-magnesia spinel, nickel-nickel alumina spinel, nickel-zirconia, platinum-cerium oxide, ruthenium-zirconia and the like are preferable.
The form of each electrochemical cell is not particularly limited. The electrochemical cell may consist of three layers: an anode, a cathode and a solid electrolyte layer. Alternatively, the electrochemical cell may have, for example, a porous body layer in addition to the anode, the cathode, and the solid electrolyte layer.
In the present invention, a gas flow path for flowing the first gas is provided in the electrochemical cell. The form, number and location of the gas flow path are not particularly limited.
In a preferred embodiment, the adjacent electrochemical cells are connected by a connecting member having a through hole.
In this embodiment, the first through hole and the second through hole communicating with the first gas flow path can be formed in the cell. The form, number and location of each through hole are not particularly limited.
In the present invention, the method for connecting the binding member and the electrochemical cell is not particularly limited. For this connection, for example, an adhesive made of glass or ceramics, or a mechanical bonding method can be used. Further, the method for hermetically sealing the connecting member and the electrochemical cell is not particularly limited, but it is preferable to use a sealing material. The material of such a seal member is not particularly limited, but it needs to have oxidation resistance and reduction resistance at the operating temperature of the electrochemical cell. Specifically, glass mainly composed of silica, crystallized glass, metal brazing and the like can be exemplified. Also, compression seals such as O-rings, C-rings, E-rings, metal jacket gaskets, and mica gaskets can be exemplified.
When the connecting member is a tubular body or an annular body, the specific form of the tubular portion is not limited. The cross-sectional shape of the tubular portion may be, for example, a polygon such as a perfect circle, an ellipse, a triangle, a quadrangle, or a hexagon.
Hereinafter, the present invention will be described in more detail with reference to the drawings as appropriate.
FIG. 1 is a perspective view showing an electrochemical cell 10 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing the electrochemical cell 1 in an exploded manner. FIG. 3 is a perspective view showing a cell 1 of a comparative example.
A gas flow path 7 for flowing the first gas is formed inside the first electrode 16 of the electrochemical cell 10. The first electrode 16 has a flat plate shape, and the solid electrolyte layer 6 is provided so as to cover the first electrode 16. On the main surfaces 10a and 10b on both sides of the cell 10,

second electrodes

2A and 2B are formed, respectively, and the

second electrodes

2A and 2B are exposed.
In the electrochemical cell 10 of FIG. 1, a first through hole 3 and a second through hole 4 are formed at predetermined positions. As shown in FIG. 2, the first gas that has flowed into the cell from the through hole 3 flows through the gas flow path 7 as indicated by arrows A, B, and C, and is discharged from the second through hole 4. The first gas contributes to the electrochemical reaction while flowing through the flow path 7.
Here, in FIG. 3, the conductive portion 5 that is electrically connected to the first electrode 16 inside the cell is exposed at the center of the cell 1. In this case, as shown in FIG. 13, which will be described later, from the main surface on the side where the connecting portion of the interconnector 21 is present, current passes through a long conduction path as indicated by arrows E, F, and G, and is adjacent to it. Reaches the conductive portion 5 of the cell to be operated. At this time, on the main surface side where there is a connection portion, the conduction distance in the cell is short and the internal resistance is small, so the current density tends to be high. On the other hand, the upper main surface without the connection portion has a long conduction distance and also passes through the side surface and the corner portion, so that the internal resistance is large and the current density tends to be low. As a result, the durability of the cell may decrease due to the deviation of the current density between the two main surfaces.
On the other hand, in FIG. 1,

conductive portions

8A, 8B, 8C, and 8D are provided, for example, at four locations on the outer peripheral edge portion of the main surface of the cell 1. As will be described later, through-holes 14 corresponding to the conductive portions are formed in the interconnector 11 (see FIG. 12), and through the through-holes, the conductive portions are connected to the corresponding connecting portions 12A, It is electrically connected to 12B.
Therefore, the current reaches the conductive portion of the adjacent cell as indicated by the arrow D from the main surface on the side where the

cell connection portions

12A and 12B are present. On the upper main surface where there is no connection portion, as indicated by an arrow H, the current reaches the conductive portion of the adjacent cell. Therefore, the deviation of the conduction distance on both main surfaces of the interconnector is small, the deviation of the current density is also small, and the durability of the cell is improved.
In the present invention, a plurality of conductive portions are provided on the outer edge portion of the cell main surface. Here, the cell main surface refers to a surface having a large area in the cell, and is usually two opposing surfaces. The outer edge portion of the main surface refers to a region within 10 mm from the outer edge of the main surface. The conductive portion of the present invention does not need to be entirely included in the outer edge portion, and only part of the conductive portion may be included in the outer edge portion.
The number of conductive parts per cell is 2 or more, preferably 3 or more, and more preferably 4 or more. There is no particular upper limit on the number of conductive parts, but eight or less are practical.
The interconnector of the present invention includes a housing portion that houses a part of the electrochemical cell and a connection portion that protrudes from the housing portion. The accommodating part can be inserted from the outside of the cell, sandwiches the cell from both sides thereof, and forms a second gas flow path between the cell and the accommodating part. Moreover, a through-hole is formed in the accommodating part at a position corresponding to each conductive part.
The interconnector material must be conductive and must be durable to the second gas at the cell operating temperature. Specifically, it may be a pure metal or an alloy, but nickel-based alloys such as nickel, inconel and nichrome, iron-based alloys such as stainless steel, and cobalt-based alloys such as stellite are preferable.
The connecting portion is preferably elastically deformable, and is particularly preferably formed from a metal plate. Examples of the metal material include the above-described interconnector materials.
Fig.4 (a) is a side view of the interconnector 11 which concerns on one Embodiment, FIG.4 (b) is the front view which looked at Fig.4 (a) from the IVb side. 5A is a plan view of the interconnector of FIG. 4A viewed from the upper side (Va side), and FIG. 5B is the lower side of the interconnector of FIG. 4A (Vb side). It is the bottom view seen from.
The accommodating portion 25 includes an upper plate 11a and a lower plate 11b, and a space 13 is formed between the upper plate 11a and the lower plate 11b.

Connection portions

12A and 12B protrude from the lower plate 11b. In this example, the

connection parts

12A and 12B are a combination of a plurality of elongated flat plates.

Such connection parts

12A and 12B are formed by processing a metal flat plate.
In particular, as shown in FIG. 5A, a through hole 14 is formed in the upper plate 11a at a position corresponding to the conductive portion. Two through holes 14 are formed in one interconnector, and one cell is accommodated in the two interconnectors. Thus, the four conductive portions of each cell can be aligned with each penetrator 14 respectively. As shown in FIG. 5A, since the through hole 14 is larger than the

connection parts

12A and 12B, the

connection parts

12A and 12B can be seen through the through hole 14 from above.
For example, the interconnector 11 as described above is put on each cell 10 and fixed. As shown in FIG. 6, the accommodating portion of the interconnector 11 is fitted from the side as indicated by an arrow J and fixed so as to cover each electrode 2 </ b> A of each cell 10. In addition, the accommodating portion of the interconnector 11 is fitted from the side as indicated by an arrow J so as to cover each electrode 2B of each cell 10 and fixed. In this state, the state shown in FIG. 7 is obtained.
Also, as shown in FIG. 8, a plurality of cells 10 are stacked (arrow B). And each through-

hole

3 and 4 of an adjacent cell is connected by interposing the connection member 18 between the adjacent cells 10, respectively. Each connecting member 18 is formed with a through hole 18a. Each through hole 18a and each through hole 3 communicate with each other to form a gas supply path. Moreover, a gas exhaust path is formed when each through-hole 18a and each through-hole 4 are connected.
The material of the connecting member is not particularly limited as long as it has higher mechanical strength than the ceramics constituting the cell. However, the material having a difference in thermal expansion coefficient from the cell of 2 × 10 ⁻⁶ (/ K), for example, zirconia, magnesia, spinel Examples thereof include ceramics and a composite material of these. Further, it may be a metal as long as it has oxidation resistance and reduction resistance at the operating temperature of the electrochemical cell, and may be a pure metal or an alloy, such as nickel, inconel, nichrome, etc. Nickel-based alloys, iron-based alloys such as stainless steel, and cobalt-based alloys such as stellite are preferred.
At this time, a second gas flow path is formed between each interconnector and the opposing electrode 2A (2B). A predetermined conductive connecting member is accommodated in the gas flow path, and the electrode and the accommodating portion are electrically connected by bringing the conductive connecting member into contact with the electrode and the accommodating portion. The material and form of the conductive connecting member are not particularly limited, and known materials can be used, but metal felts and meshes can be exemplified.
When the stack is formed, as shown in FIG. 9, the conductive portion of the uppermost cell 11 and the interconnector of the lowermost cell are connected. Thereby, a plurality of cells are connected in series.
The connection state of adjacent cells is schematically shown in FIG. First, the accommodating portion of the interconnector 11 is fitted over the cell 10 from the side. At this time, the conductive paste 20 is interposed between the

connection portions

12A and 12B and the

conductive portions

8A and 8B of the adjacent cells. 30 is a second gas flow path.

[Example of the present invention]
According to the method described with reference to FIGS. 1 to 10, a stack according to an example of the present invention was manufactured.
(Production of power generation cell)
A solid oxide fuel cell (cell) having a fuel electrode as a substrate was produced (see FIGS. 1 and 2).
(Fabrication of fuel electrode substrate)
Nickel oxide powder and yttria-stabilized zirconia (YSZ) were mixed to obtain a fuel electrode substrate powder. This powder was press-molded to produce two fuel electrode substrate compacts.
(Installation of flow path forming member and integration with fuel electrode substrate + electrolyte membrane formation)
The flow path forming member was sandwiched between the fuel electrode substrate molded bodies and integrated by pressing.
A slurry obtained by adding a binder to YSZ powder was used as the electrolyte. After coating and drying on the fuel electrode substrate compact, it was fired in air at 1400 ° C. for 2 hours to obtain a solid electrolyte / fuel electrode support substrate.
(Formation of air electrode and conductive plate)
A paste was prepared by adding a binder and a solvent to LaMnO ₃ powder. This paste was screen printed on the two main surfaces of the substrate, dried, and then fired in an electric furnace at 1200 ° C. for 1 hour to form an air electrode. Also, a part of the electrolyte is peeled off, the fuel electrode substrate is exposed on the surface, and a lanthanum chromite 0.3 mm thick conductive plate, which is separately manufactured, is attached to the exposed portion with a conductive paste. The periphery was fixed with a sealing material.
Fuel supply holes and discharge holes were formed in the sintered body thus obtained by machining to obtain a power generation cell. The shape of the produced cell was 110 mm long, 100 mm wide, and 3 mm thick.
(Production of metal interconnector)
A plate made of material SUS430 was processed into the shapes of FIGS. 4 and 5 having a length of 60 mm, a width of 105 mm, and a thickness of 0.5 mm.
(Stack production)
A 20-stage stack consisting of cells and metal interconnectors was made.
(Installation of metal interconnector)
An embossed current collecting mesh was placed in the metal interconnector described above, and a conductive paste was applied to the protrusions of the metal interconnector and fitted from the left and right of each cell (see FIGS. 6 and 7).
(Bonding of cell and ceramic connecting parts)
A ceramic connecting part 18 having an outer diameter of φ24 mm, an inner diameter of φ9 mm, and a thickness of 2 mm is attached to the fuel supply hole and discharge hole of the cell produced above using a glass paste that softens at 1000 ° C., stacked in 20 layers, and in the air in an electric furnace It joined by heating at 1000 ° C. for 1 hour.
[Comparative example]
A stack was manufactured in the same manner as in the example. However, as the cell, as shown in FIG. 3, one conductive portion 5 was provided. Further, a plate made of material SUS430 was formed into the form shown in FIG. This dimension is 60 mm long, 105 mm wide, and 0.5 mm thick. A 20-stage stack was produced.
(Power generation performance evaluation)
To evaluate the performance, the stack is set in an electric furnace, and the voltage and current lines are connected as shown in FIGS. 10 and 11, and the temperature is raised to 800 ° C. while flowing N ₂ on the fuel electrode side and Air on the air electrode side. When the temperature reached 800 ° C., reduction treatment was performed by flowing H ₂ to the fuel electrode side. After the reduction treatment for 3 hours, the current-voltage characteristics of the stack were evaluated.
Table 1 shows the power generation characteristics at 800 ° C. The power generation output indicates the output per unit volume of the stack and the output per cell.

In the present invention, in the present invention, a reduction in ohmic resistance was observed in the present invention as compared with the comparative example, and the output per unit volume was greatly improved to 310 W / L or more. This is because in the comparative example, the electrical connection with the next cell is at the center, so that the current generated on the opposite side must pass through the outer periphery of the cell on the metal interconnector. This is because the influence of the material resistance on the interconnector is reduced because the electrical connections at the outer periphery of the cell are at the four corners of the cell, and the distance that the current generated on the opposite surface flows over the metal interconnector is reduced. It is done.
Further, in the present invention, the power generation performance deterioration rate was reduced as compared with the comparative example, and the power generation performance deterioration in 100 hours was 0.005% or less, which was less than half of the comparative example. In the comparative example, in the comparative example, the distance in which the current flows on the metal interconnector is greatly different, so that the ohmic resistance is greatly different on the front and back, whereas in the present invention, the distance in which the current flows on the metal interconnector is substantially the same. Therefore, there is no big difference in ohmic resistance. For this reason, in the comparative example, there are places where the current density is greatly different on the front and back sides and there is a large power generation performance deterioration rate, whereas in the comparative example there is no large difference in current density, so there is no place where the power generation performance deterioration rate is large It is considered that the deterioration of power generation performance has decreased.
Thus, the present invention brings the electrical connection with the next cell to the outer periphery of the cell, thereby reducing the influence of the material resistance of the metal interconnector, reducing ohmic resistance, and reducing power generation performance deterioration. It is a shape that can be performed.
Although specific embodiments of the present invention have been described, the present invention is not limited to these specific embodiments and can be implemented with various changes and modifications without departing from the scope of the claims.

Claims

An electrochemical device comprising a plurality of ceramic electrochemical cells and an interconnector,
The electrochemical cell incorporates a gas flow path for flowing a first gas, and is exposed to the first electrode in contact with the first gas, the solid electrolyte layer, and the main surface of the electrochemical cell. A second electrode that is in contact with a second gas, and a plurality of conductive portions that are exposed to the main surface of the electrochemical cell and are electrically connected to the first electrode, wherein the conductive portion is It is provided at the outer edge of the main surface,
The interconnector includes a housing portion that houses a part of the electrochemical cell, and a plurality of connection portions that protrude from the housing portion,
A flow path of the second gas is formed between the accommodating portion and the electrochemical cell, and the second gas is in contact with the second electrode while passing through the flow path; The electrochemical device characterized in that each connection portion is electrically connected to each conductive portion of the adjacent electrochemical cell.
The through hole is provided at a position corresponding to each conductive portion of the housing portion, and the conductive portion and the connection portion are electrically connected through the through hole. 1. The electrochemical device according to 1.
The electrochemical device according to claim 1 or 2, wherein the connecting portion is a protrusion protruding toward the adjacent electrochemical cell.
The electrochemical device according to any one of claims 1 to 3, wherein the connection portion and the conductive portion are connected by a conductive paste.
The electrochemical device according to any one of claims 1 to 4, wherein the adjacent electrochemical cells are connected by a connecting member having a through hole.