JPWO2018167845A1 - Flat plate type electrochemical cell stack - Google Patents

Abstract

A plurality of stacked unit electrochemical cells including a flat solid oxide electrochemical cell and a conductive separator surrounding the periphery of the electrochemical cell, a separator of the unit electrochemical cell, and an adjacent unit electricity At least one frame disposed between the separator of the chemical cell and the frame-like seal surrounding the periphery of the electrochemical cell, the separator of the unit electrochemical cell, and the separator of the adjacent unit electrochemical cell; A flat type electrochemical cell stack having an insulating portion whose portion is located on the outer peripheral side of the seal portion and having a thickness smaller than that of the seal portion.

Description

  Embodiments of the present invention relate to planar electrochemical cell stacks.

  Fuel cells that convert chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen attract attention. Fuel cells have high energy utilization efficiency, and are being developed as large-scale distributed power sources, household power sources, and mobile power sources.

  Fuel cells are classified into solid polymer type, phosphoric acid type, molten carbonate type, solid oxide type, and the like according to the temperature range and the type of material and fuel used. Among them, solid oxide fuel cells (SOFCs) that obtain electric energy by an electrochemical reaction using an electrolyte composed of solid oxide are attracting attention from the viewpoint of efficiency and the like. In addition, high-temperature steam electrolysis, in which hydrogen is produced by a solid oxide electrolytic cell (SOEC) using the reverse reaction of SOFC, has also been recently developed.

  A cell, which is the smallest constituent unit of SOFC and SOEC, is generally composed of an electrolyte and an electrode. The solid oxide electrolyte has oxygen ion conductivity. As the electrolyte of the solid oxide, for example, a compact stabilized zirconia, a perovskite type oxide, a compact of a ceria-based solid solution, or the like is used.

As for the electrodes, taking SOFC as an example, the electrodes can be roughly divided into a fuel electrode and an air electrode. At the fuel electrode, H ₂ which is a fuel gas and oxygen ions which have moved through the electrolyte react electrochemically to generate H ₂ O and electrons (e −). At the air electrode, oxygen (in air) takes up electrons (e −), and electrochemical reactions produce oxygen ions, which are transferred to the electrolyte.

  For the fuel electrode, generally, a mixed sintered body (cermet) of metal and solid oxide is used. For example, Ni-YSZ (yttria stabilized zirconia), Ni-ScSZ (scandia stabilized zirconia), etc. are used.

  On the other hand, a perovskite-type oxide or an oxide in which some of these sites are substituted is generally used for the air electrode. For example, LaSrMn oxide, LaSrCo oxide, LaSrCoFe oxide, LaSrFe oxide etc. may be mentioned. Moreover, the mixture with the solid oxide used for electrolyte etc., etc. are used, for example, LSM-YSZ, LSM-ScSZ, LSC-SDC, LSC-GDC etc. are mentioned.

  As described above, the cell is at least a laminate of the air electrode, the electrolyte and the fuel electrode. Materials having different characteristics are used for the air electrode, the electrolyte and the fuel electrode. The air electrode and the fuel electrode are porous, and different gases are supplied to the air electrode and the fuel electrode, respectively, with a dense electrolyte. The air electrode and the fuel electrode are electric conductors, and the electrolyte is an ion conductor that does not conduct electricity.

  The shape of the cell may be flat, cylindrical, cylindrical flat, or the like. For example, a flat cell has a shape in which an air electrode, an electrolyte, a fuel electrode and the like are stacked in a flat plate shape. A plurality of integrated cells are generally called a stack.

  For example, in the case of flat cells, the stack is formed by stacking a plurality of flat cells, supplying different gases to the air electrode and the fuel electrode of each cell, and the cells can be electrically connected in series. Has a simple structure. The cell and the cell are separated by a separator, which separates the gas per cell. Since the separator is conductive, it also plays a role of electrical conduction between cells. In addition, a gas supply / discharge flow path to each cell is generally formed in the separator.

  In the stack, the cell portion is separated by the dense electrolyte between the fuel electrode and the air electrode, but the other portion is separated by the dense separator between the atmospheres of adjacent cells. Moreover, about the atmosphere of the fuel electrode of the same cell, and the air electrode, the crevice etc. of the part in which the cell is not installed are closed with a precise member, and it is isolated.

  In a flat cell stack, the flow of gas in the stack is prevented from flowing out of the stack, and the supply gas to the fuel electrode and the air electrode is prevented from mixing inside the stack, that is, the gas sealability It is a big issue. In order to improve the sealing performance of such gas, for example, methods using various sealing materials have been proposed.

JP-A-6-325779

  Since the cell has a dense electrolyte, it is possible to prevent mixing of the atmosphere gas of each of the fuel electrode and the air electrode. However, in stack components other than cells, measures against gas leak are necessary. For example, it is necessary to seal the gap between the cells and the stack components other than the cells, and the portion for supplying the gas to the cells.

  In addition, since the cells are stacked via conductive separators, it is necessary to insulate the separators in some form. Therefore, the structure which made sealing property and insulation be compatible is needed.

  The problem to be solved by the present invention is to provide a flat plate type electrochemical cell stack with improved gas sealability.

  A planar electrochemical cell stack according to an embodiment includes a flat solid oxide electrochemical cell and a conductive separator surrounding the electrochemical cell, and a plurality of stacked unit electrochemical cells; A frame-like seal disposed between the separator of the unit electrochemical cell and the separator of the unit electrochemical cell adjacent thereto and surrounding the periphery of the electrochemical cell; the separator of the unit electrochemical cell And the separator of the unit electrochemical cell adjacent to each other, at least a portion of which is located on the outer peripheral side of the seal portion, and has an insulating portion thinner than the seal portion.

The figure which shows typically the cross-sectional structure of a part of stack of 1st Embodiment. The figure which shows the whole structure of a stack typically. The figure which shows typically the cross-sectional structure of a part of stack of 2nd Embodiment. The figure which shows typically the cross-sectional structure of a part of stack of 3rd Embodiment. The figure which shows typically the cross-sectional structure of a part of stack of 4th Embodiment. The figure which shows typically the cross-sectional structure of a part of stack of a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a view schematically showing a cross-sectional configuration of a part of a flat plate type electrochemical cell stack (hereinafter simply referred to as a stack) 100 of the embodiment. Although FIG. 1 illustrates each component in a disassembled state (a state in which a gap is provided between components) (the same applies to FIGS. 3 to 6 described later), these respective components are stacked. It is integrally held in a pressurized state.

  In the present embodiment, the flat plate type cell 101 constituting the stack 100 is an electrode-supported flat plate type electrochemical cell. The cell 101 has a laminated structure in which a thin film electrolyte 103 is formed on a porous electrode support 102, and a counter electrode 104 is formed on the electrolyte 103. In the case of SOFC, one of the electrode support 102 or the counter electrode 104 is a fuel electrode, and the other is an air electrode.

  Conductive separators 105 and 106 are provided to surround the cell 101, and the cell 101 is accommodated and supported in these. Between the electrode support 102 and the separator 106, a current collector (not shown) for electrically connecting them is disposed. Further, a current collector (not shown) for electrically connecting these is also disposed between the counter electrode 104 and the adjacent separator 106.

  The material of the separators 105 and 106 is a dense material that is conductive even in a temperature range of 600 to 1000 ° C., which is an operating temperature, such as a metal or a ceramic. Moreover, as this material, a material having a thermal expansion coefficient close to that of the cell 101 is desirable. In the present embodiment, an example in which the separator is constituted by two separators 105 and 106 which are separate members will be described. However, the separators 105 and 106 may be integrated into one member.

  The outer shape of the flat cell 101 is, for example, square. In addition, the separator 105 is formed in a rectangular frame shape so as to surround the periphery of the cell 101. A rectangular opening 105 a is formed at the central portion of the separator 105, and the cell 101 is disposed in the opening 105 a.

  The outer shape of the separator 106 is, for example, a rectangular plate. Further, through holes are formed in the separator 105 and the separator 106 at corresponding positions, respectively, and a gas flow path 109 for circulating a gas in the stacking direction is formed by these through holes.

  The separator 105 and the separator 106 constitute a support for accommodating and supporting the cell 101 in the opening 105 a. The separators 105 and 106 and the cell 101 constitute one unit chemical cell 110. As shown in FIG. 2, a plurality of these unit chemical cells 110 are stacked, and end plates 120 and the like are disposed at both side ends (upper end and lower end in FIG. 2) in the stacking direction. Then, these are tightened and fixed by fastening means, for example, a plurality of bolts 111 and nuts 112 or the like. In addition, illustration of a part of part in which the unit chemical cell 110 of the same structure is arrange | positioned is abbreviate | omitted in FIG.

  As shown in FIG. 1, a sheet-like insulating member 107 formed in a frame shape is provided between the separator 105 and the separator 106 of the adjacent unit chemical cell 110. The insulating member 107 is provided to prevent an electrical short between the separator 105 and the separator 106 of the adjacent cell 101. The insulating member 107 constitutes an insulating portion.

  Furthermore, a sheet-like seal member 108 formed in a frame shape is provided inside the insulating member 107 between the separator 105 and the separator 106 of the adjacent unit chemical cell 110. The seal member 108 is disposed along the periphery of the cell 101. The seal member 108 is disposed across the outer peripheral edge of the cell 101 and the inner peripheral edge of the separator 105. In addition, the seal member 108 is disposed to surround the gas flow path 109. That is, the seal member 108 is in the form of a sheet, and when viewed from the upper surface or the lower surface, the outer shape is substantially rectangular, and has a substantially rectangular opening smaller than the outer shape of the cell 101 at the center portion ). Then, an opening corresponding to the shape of the gas flow passage 109 is provided in a portion corresponding to the gas flow passage 109. The seal member 108 constitutes a seal portion.

  The seal member 108 is provided to prevent the leak of gas from the gap between the cell 101 and the separators 105 and 106. Further, the seal member 108 is provided to insulate between the separator 105 and the separator 106 of the unit chemical cell 110 adjacent thereto.

  The material of the insulating member 107 is not particularly limited, but desirably has high electrical insulation (high electrical resistance). Examples of this material include alumina, zirconia, silica, and materials containing at least these. As for the density, a dense one is desirable, but a porous one may be used.

  The material of the seal member 108 is not particularly limited, but desirably has high electrical insulation. Examples of this material include alumina, zirconia, silica, and materials containing at least these. About density, precise thing is desirable. The material of the sealing member 108 may be the same as the material of the insulating member 107.

  In the present embodiment, the thicknesses of the insulating member 107 and the sealing member 108 disposed in the same plane are different. That is, the thickness of the insulating member 107 is thinner than the thickness of the seal member 108.

  As described above, in the present embodiment, the insulating portion and the seal portion are separated, and by making the thick seal member 108 and the thin insulating member 107, the contact pressure of the seal portion is increased with a simple structure. Sealability can be improved.

  In the case of a flat stack, pressure is applied in the stacking direction to increase the surface pressure of the seal portion for sealing, but in order to increase surface pressure on a large area, it is necessary to apply very large pressure. For example, as in the stack 500 of the comparative example shown in FIG. 6, one member has an insulating function and a sealing function, and the insulating seal member 508 having a large surface area, the separator 105, and the separator 106 of the adjacent unit chemical cell 110. In order to increase the surface pressure, it is necessary to apply a very large pressure. For this reason, the surface pressure can not be sufficiently increased, and the sealability may be reduced.

  On the other hand, in the present embodiment in which the insulating portion and the sealing portion are separated and the thick sealing member 108 and the thin insulating member 107 are used, compared to the case of the insulating sealing member 508 shown in FIG. The surface area of the seal member 108 can be reduced, and the surface pressure can be easily increased. Thereby, sealing performance can be improved.

  In addition, as a material of the sealing member 108, a material which is porous at room temperature and which becomes dense by being exposed to a high temperature in a compressed state can be used. A porous material at room temperature is highly compressible. For example, when there is a step or the like at the cell edge, pressure may be applied in the stack stacking direction to apply surface pressure to the seal portion, and the step may be absorbed It becomes possible. And by being exposed to high temperature in a compressed state, it becomes dense and sealability improves.

  When the seal member 108 is configured using a material as described above, the thickness of the seal member 108 changes before laminating and compressing, and after laminating and compressing. That is, the thickness of the seal member 108 after lamination and compression is thinner than that before compression. Therefore, the difference between the thickness of the seal member 108 and the thickness of the insulating member 107 is also reduced. In this case, the thickness of the seal member 108 may be slightly thicker than the thickness of the insulating member 107 after compression.

  FIG. 3 is a view schematically showing a cross-sectional configuration of a part of the stack 200 according to the second embodiment. In FIG. 3, the parts corresponding to those in FIG. 1 are given the same reference numerals.

  As shown in FIG. 3, in the stack 200, a coating film 207 formed by coating in advance an insulating material on one surface (the lower surface in FIG. 3) of the separator 106 is used as the insulating portion. The coating film 207 is formed in a frame shape so as to surround the periphery of the seal member 108.

  The material of the coating film 207 is not particularly limited, but desirably has high electrical insulation. Examples of this material include alumina, zirconia, silica, and materials containing at least these. As for the density, a dense one is desirable, but a porous one may be used. Also, the coating method is not particularly limited, and examples thereof include a wet method, a dry method, a physical method, a chemical method and the like. The shape of the coating film 207 is not particularly limited, but it may be at least provided in a portion which needs to be insulated.

  As described above, when the insulating portion is formed of the coating film 207, the number of parts is reduced, the number of steps for stacking and assembling the stack 200 is reduced, and defects such as overlapping of the insulating member and the sealing member occur during construction. Can be prevented. Furthermore, the occurrence of local electrical leakage can be suppressed.

  FIG. 4 is a view schematically showing a cross-sectional configuration of part of the stack 300 according to the third embodiment. In FIG. 4, parts corresponding to FIG. 1 are given the same reference numerals.

  An end plate 120 or the like is installed at the end in the stacking direction of the stack 300 in order to secure the strength and the like of the stack 300. In this case, it is necessary to perform insulation and gas sealing between the end plate 120 and the separator 106. Therefore, in the stack 300, the insulating member 107 and the seal member 108 are disposed between the upper end plate 120 and the separator 106.

  In the stack 300 described above, the insulating member 107 and the sealing member 108 having the same shape as those disposed between the separators 105 and 106 are provided between the end plate 120 and the separator 106. As a result, surface pressure is applied to the same portion of the stack 300, surface pressure is uniformly applied to each seal member 108 in the stacking direction, and sealing performance can be improved.

  FIG. 5 is a view schematically showing a cross-sectional configuration of a part of a stack 400 according to the fourth embodiment. In FIG. 5, parts corresponding to FIG. 1 are given the same reference numerals.

  In the stack 400, a convex portion 401 having a smaller area than the seal member 108 is provided at a portion of the separator 106 in contact with the seal member 108. The convex portion 401 is formed in a frame shape along the shape of the seal member 108. As the shape of the convex portion 401, it is desirable that the shape of the convex portion 401 does not have a sharp portion so as to prevent breakage or the like of the seal member 108. In the stack 400 configured as described above, the surface pressure on the seal member 108 is further increased, and the sealability is improved.

  According to at least one embodiment described above, the gas sealability can be enhanced.

  While the embodiments of the present invention have been described above, the embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

  100, 200, 300, 400, 500: stack, 101: cell, 102: electrode support, 103: electrolyte, 104: counter electrode, 105: separator, 105a: opening, 106: separator, 107: insulating member, 108: seal Members, 109: gas flow path, 110: unit chemical cell, 111: bolt, 112: nut, 120: end plate, 207: coating film, 401: convex portion.

Claims (7)

A plurality of stacked unit electrochemical cells, comprising: a flat solid oxide electrochemical cell; and a conductive separator surrounding the electrochemical cell;
A frame-like seal disposed between the separator of the unit electrochemical cell and the separator of the unit electrochemical cell adjacent thereto and surrounding the periphery of the electrochemical cell;
An insulation disposed between the separator of the unit electrochemical cell and the separator of the adjacent unit electrochemical cell, at least a portion of which is located on the outer peripheral side of the seal portion, and thinner than the seal portion Department,
Plate-type electrochemical cell stack equipped with   The flat electrochemical cell stack according to claim 1, wherein the seal portion is disposed along a peripheral portion of the electrochemical cell.   The flat electrochemical cell stack according to claim 1 or 2, wherein a gas flow path for circulating gas is formed in the separator, and the seal portion is shaped to surround the gas flow path.   The flat electrochemical cell stack according to any one of claims 1 to 3, wherein the seal portion and the insulating portion are made of the same material. An end plate disposed at an end of the plurality of stacked unit electrochemical cells in the stacking direction,
The flat electrochemical cell stack according to any one of claims 1 to 4, wherein the seal portion and the insulating portion are disposed between the end plate and the separator.   The flat type electrochemical cell stack according to any one of claims 1 to 5, wherein a convex portion having a smaller area than the seal portion is formed on the surface of the separator in contact with the seal portion.   The flat electrochemical cell stack according to any one of claims 1 to 6, wherein the insulating portion comprises a coating film coated on the surface of the separator.

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