Electrochemical device

Abstract

To provide an electrochemical device capable of achieving prevention of increase in electrical resistance and the like to easily improve the performance.SOLUTION: In an electrochemical device of an embodiment, a cell stack includes a plurality of electrochemical cells stacked to be arranged in a stack direction; each of a plurality of interconnectors is interposed between each of the plurality of electrochemical cells; and each of a plurality of gasket sealing materials is provided at a position between each of the interconnectors so as to surround a housing space for the electrochemical cell. The electrochemical cell has a hydrogen electrode current collector and an oxygen electrode current collector. At least either the hydrogen electrode current collector and the oxygen electrode current collector includes at least a first current collector layer and a second current collector layer; the first current collector layer and the second current collector layer are stacked in the stack direction; and a Young's modulus of the first current collector layer and a Young's modulus of the second current collector layer are different.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to electrochemical devices. [Background technology]

[0002] The electrochemical device has an electrochemical cell configured such that an electrolyte membrane is sandwiched between a hydrogen electrode and an oxygen electrode.

[0003] In the electrochemical cell, the electrolyte membrane is formed of, for example, a solid oxide. An electrochemical cell having a solid oxide electrolyte membrane functions as at least one of a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC).

[0004] When the electrochemical cell functions as an SOFC, a fuel cell reaction occurs at a high operating temperature (e.g., 600 to 900°C), generating electrical energy. In the fuel cell reaction, hydrogen electrode gas (reducing gas; hydrogen, hydrocarbon, ammonia, etc.) supplied to the hydrogen electrode reacts with oxygen electrode gas (oxidizing gas; oxygen, air, etc.) supplied to the oxygen electrode via the electrolyte membrane. In contrast, when the electrochemical cell functions as an SOEC, a reaction occurs in the cell that is the reverse of the reaction when the cell functions as an SOFC, in which water vapor decomposes into hydrogen and oxygen at a high operating temperature (e.g., 700°C or higher).

[0005] The electrochemical device includes a cell stack including a plurality of electrochemical cells stacked in a stacking direction. An interconnector (separator) is interposed between each of the plurality of electrochemical cells arranged in the stacking direction in the cell stack. A gasket sealant is provided between each of the plurality of interconnectors arranged in the stacking direction in the cell stack so as to surround a storage space that houses the electrochemical cells. In the storage space that houses the electrochemical cells, a hydrogen electrode current collector is interposed between the hydrogen electrode and the interconnector, and an oxygen electrode current collector is interposed between the oxygen electrode and the interconnector.

[0006] In electrochemical devices, a load is applied to the cell stack in the stacking direction. This increases the adhesion between the interconnector and the gasket sealant, making it possible to prevent gas leakage, such as from the hydrogen electrode gas and the oxygen electrode gas, in the storage space that houses the electrochemical cells. Furthermore, increased adhesion between the hydrogen electrode, the hydrogen electrode current collector, and the interconnector, and between the oxygen electrode, the oxygen electrode current collector, and the interconnector, reduces the electrical resistance between each component. However, in electrochemical devices, excessive load on the cell stack can cause damage to the electrochemical cells.

[0007] For this reason, mechanisms for adjusting the load on the cell stack have been proposed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-076996 Summary of the Invention [Problem to be solved by the invention]

[0009] However, because electrochemical cells are stacks of layers made of different types of materials, warping may occur. Therefore, the surface of the electrochemical cell that comes into contact with the oxygen electrode current collector, etc., may have irregularities, and the load applied in the stacking direction may not be uniform across the surface of the electrochemical cell. Because electrochemical cells operate at high temperatures (600°C or higher), even if the load is applied uniformly at room temperature, the load may become non-uniform at the operating temperature due to thermal expansion, etc.

[0010] Electrical resistance increases in areas of the electrochemical cell surface where a small load is applied. The likelihood of breakage increases in areas of the electrochemical cell surface where a large load is applied. Furthermore, uneven application of the load can reduce adhesion between the interconnector and the gasket seal, making it difficult to fully prevent gas leakage.

[0011] For example, let us consider a case where the central portion of the surface of the electrochemical cell is warped so as to protrude convexly in a room temperature atmosphere. In this case, the central portion of the surface of the electrochemical cell is in sufficient contact with the oxygen electrode current collector, etc., in a room temperature atmosphere, and therefore has appropriate electrical resistance. However, when the electrochemical cell is exposed to a high-temperature atmosphere that is higher than room temperature for operation of the electrochemical cell, the height of the protrusion in the central portion of the surface of the electrochemical cell decreases. As a result, the central portion of the surface of the electrochemical cell may not be in sufficient contact with the oxygen electrode current collector, etc., in a high-temperature atmosphere, resulting in high electrical resistance.

[0012] As a result, the performance of the electrochemical device may be reduced.

[0013] Therefore, an object of the present invention is to provide an electrochemical device that can prevent an increase in electrical resistance and easily improve performance. [Means for solving the problem]

[0014] The electrochemical device of the embodiment includes a cell stack including a plurality of electrochemical cells configured such that an electrolyte membrane is sandwiched between a hydrogen electrode and an oxygen electrode, and the plurality of electrochemical cells are stacked in a stacking direction. The cell stack includes a plurality of interconnectors and a plurality of gasket sealants. Each of the plurality of interconnectors is interposed between the plurality of electrochemical cells arranged in the stacking direction and includes a first interconnector surface on the hydrogen electrode side and a second interconnector surface on the oxygen electrode side. Each of the plurality of gasket sealants is provided between the plurality of interconnectors arranged in the stacking direction so as to surround a storage space that accommodates the electrochemical cell. Each of the plurality of electrochemical cells includes a hydrogen electrode current collector and an oxygen electrode current collector. The hydrogen electrode current collector is interposed between the hydrogen electrode and the first interconnector surface in the storage space and is in contact with the hydrogen electrode and the first interconnector surface. The oxygen electrode current collector is interposed between the oxygen electrode and the second interconnector surface in the storage space and is in contact with the oxygen electrode and the second interconnector surface. At least one of the hydrogen electrode current collector and the oxygen electrode current collector includes at least a first current collector layer and a second current collector layer, the first current collector layer and the second current collector layer being stacked in the stacking direction, and the Young's modulus of the first current collector layer and the Young's modulus of the second current collector layer being different. [Brief explanation of the drawings]

[0015] [Figure 1A] FIG. 1A is a diagram schematically illustrating an electrochemical device 1 according to an embodiment. [Figure 1B] FIG. 1B is a diagram schematically illustrating the electrochemical device 1 according to the embodiment. [Figure 2] FIG. 2 is a diagram schematically showing an oxygen electrode current collector 22 of the first modification. [Figure 3A] FIG. 3A is a diagram schematically showing an oxygen electrode current collector 22 of Modification 2. As shown in FIG. [Figure 3B] FIG. 3A is a diagram schematically showing an oxygen electrode current collector 22 of Modification 2. As shown in FIG. [Figure 4] FIG. 4 shows the IV characteristics obtained for each example. DETAILED DESCRIPTION OF THE INVENTION

[0016] An example of an embodiment will be described.

[0017] [A] Configuration of electrochemical device 1 1A and 1B are diagrams schematically illustrating an electrochemical device 1 according to an embodiment.

[0018] 1A, the longitudinal direction is the vertical direction z, the horizontal direction is the first horizontal direction x, and the direction perpendicular to the paper surface is the second horizontal direction y that is perpendicular to the vertical direction z and the first horizontal direction x. Fig. 1A is a side cross-sectional view of the electrochemical device 1, showing a portion corresponding to the plane (xz plane) of the Y1-Y1 portion in Fig. 1B.

[0019] 1B, the longitudinal direction is the second horizontal direction y, the lateral direction is the first horizontal direction x, and the direction perpendicular to the paper surface is the vertical direction z. Fig. 1B is a top view of the electrochemical device 1, showing a portion corresponding to the plane (xy plane) of the Z1-Z1 portion in Fig. 1A.

[0020] As shown in FIGS. 1A and 1B, the electrochemical device 1 includes a cell stack 80 and a load-applying mechanism 90.

[0021] [A-1] Cell Stack 80 In the electrochemical device 1, the cell stack 80 includes an electrochemical cell 10, an interconnector 30, and a gasket sealant 40. The cell stack 80 is configured so that a plurality of unit cells, each including an electrochemical cell 10, an interconnector 30, and a gasket sealant 40, are stacked in a stacking direction (here, the vertical direction z), and is configured to perform power generation and electrolysis. A pair of bus bars (not shown) are electrically connected to the cell stack 80, and a current is supplied to the cell stack 80 via the pair of bus bars when electrolysis is performed, and a current is extracted via the pair of bus bars when power generation is performed.

[0022] Each part of the cell stack 80 will be explained in turn.

[0023] [A-1-1] Electrochemical cell 10 The electrochemical cell 10 is, for example, a rectangular flat plate type and includes an electrolyte membrane 110, a hydrogen electrode 111, and an oxygen electrode 112, with the electrolyte membrane 110 interposed between the hydrogen electrode 111 and the oxygen electrode 112. The electrochemical cell 10 is, for example, a hydrogen electrode-supported type (fuel electrode-supported type) in which the electrolyte membrane 110 and the oxygen electrode 112 are sequentially stacked on top of the hydrogen electrode 111, which functions as a support. The electrochemical cell 10 is not limited to a hydrogen electrode-supported type (for example, an electrolyte-supported type), and may have a shape other than a rectangular shape (such as a circle). Furthermore, the area of ​​the hydrogen electrode 111 is the same as the area of ​​the electrolyte membrane 110, and the area of ​​the oxygen electrode 112 is smaller than the area of ​​the electrolyte membrane 110, but is not limited thereto.

[0024] In the electrochemical cell 10, the electrolyte membrane 110 is a 2- The electrolyte membrane 110 is made of an ion-conductive solid oxide (for example, yttria-stabilized zirconia (YSZ)) that is permeable to oxygen. The electrolyte membrane 110 is configured to be denser than the hydrogen electrode 111 and the oxygen electrode 112.

[0025] In the electrochemical cell 10, the hydrogen electrode 111 is made of a porous electrical conductor (for example, a cermet formed using nickel particles and ceramic particles such as YSZ).

[0026] In the electrochemical cell 10, the oxygen electrode 112 is made of a porous electrical conductor (such as a perovskite oxide such as LaSrMnO3).

[0027] The cell stack 80 includes a plurality of electrochemical cells 10, which are arranged in the stacking direction. The plurality of electrochemical cells 10 are connected in series via interconnectors 30 or the like to increase power generation output or the like.

[0028] [A-1-2] Interconnector 30 The interconnector 30 is, for example, a rectangular flat plate and is made of a conductive material such as metal.

[0029] In the cell stack 80, there are a plurality of interconnectors 30, and each of the plurality of interconnectors 30 is interposed between each of the plurality of electrochemical cells 10 arranged in the stacking direction.

[0030] Each of the plurality of interconnectors 30 includes a first interconnector surface S301 and a second interconnector surface S302.

[0031] In the interconnector 30, the first interconnector surface S301 is located on the hydrogen electrode 111 side and faces the hydrogen electrode 111. A flow path through which the hydrogen electrode gas passes may be formed on the first interconnector surface S301.

[0032] In the interconnector 30, the second interconnector surface S302 is located on the oxygen electrode 112 side and faces the oxygen electrode 112. A flow path through which the oxygen electrode gas passes may be formed on the second interconnector surface S302.

[0033] The surface of the interconnector 30 may be coated to improve oxidation resistance, reduce electrical resistance, or for other purposes. In the cell stack 80, the interconnectors 30 may differ from one another as appropriate in terms of material, installation position, shape, structure, etc.

[0034] [A-1-3] Gasket sealant 40 The gasket sealant 40 has a frame shape, and in its central portion is provided an accommodation space SP40 for accommodating the electrochemical cell 10. The accommodation space SP40 has a rectangular planar shape. There are multiple gasket sealants 40, and each of the multiple gasket sealants 40 is provided between each of the multiple interconnectors 30 aligned in the stacking direction so as to surround the accommodation space SP40.

[0035] Each of the plurality of gasket seal materials 40 is configured to seal the gap between each of the plurality of interconnectors 30 arranged in the stacking direction. Each of the plurality of gasket seal materials 40 is formed, for example, from an insulating material, and is configured so that the portion between each of the plurality of interconnectors 30 arranged in the stacking direction where the gasket seal material 40 is interposed is electrically insulated.

[0036] Here, the gasket seal material 40 includes a hydrogen electrode side seal portion 401, an oxygen electrode side seal portion 402, and a partition portion 45, and the accommodation space SP40 has a hydrogen electrode side accommodation portion SP401 and an oxygen electrode side accommodation portion SP402.

[0037] The hydrogen electrode side seal 401 is provided to surround the hydrogen electrode side housing portion SP401, and the electrolyte membrane 110 and hydrogen electrode 111 of the electrochemical cell 10 are housed inside the hydrogen electrode side housing portion SP401. The hydrogen electrode side seal 401 prevents hydrogen electrode gas from leaking from the hydrogen electrode side housing portion SP401. The hydrogen electrode side housing portion SP401 also houses a hydrogen electrode current collector 21. Gaps are present between the side surface of the hydrogen electrode side housing portion SP401 and the side surfaces of the electrolyte membrane 110, the hydrogen electrode 111, and the hydrogen electrode current collector 21.

[0038] The oxygen electrode side seal part 402 is provided to surround the oxygen electrode side housing part SP402, and the oxygen electrode 112 of the electrochemical cell 10 is housed inside the oxygen electrode side housing part SP402. The oxygen electrode side seal part 402 prevents the oxygen electrode gas from leaking from the oxygen electrode side housing part SP402. The oxygen electrode side housing part SP402 also houses the oxygen electrode current collector 22 inside. Gaps are provided between the side surface of the hydrogen electrode side housing part SP401 and the side surfaces of the oxygen electrode 112 and the oxygen electrode current collector 22.

[0039] The partition 45 is provided to separate the hydrogen electrode side accommodating portion SP401 from the oxygen electrode side accommodating portion SP402 when the electrochemical cell 10 is accommodated in the accommodation space SP40. The partition 45 includes a portion that protrudes inward above the hydrogen electrode side accommodating portion SP401, and this protruding portion is in contact with the upper surface of the electrolyte membrane 110. The partition 45 is provided to prevent hydrogen electrode gas from leaking from the hydrogen electrode side accommodating portion SP401 to the oxygen electrode side accommodating portion SP402, and to prevent oxygen electrode gas from leaking from the oxygen electrode side accommodating portion SP402 to the hydrogen electrode side accommodating portion SP401.

[0040] The gasket sealant 40 is not limited to the above configuration. In the cell stack 80, the gasket sealants 40 may be made of different materials, installed at different positions, etc., as appropriate, to prevent leakage. The gasket sealant 40 may also be formed using a paste, for example.

[0041] [A-1-4] Hydrogen electrode current collector 21 The hydrogen electrode current collector 21 is interposed between the hydrogen electrode 111 and the first interconnector surface S301 in the accommodation space SP40, and includes portions in contact with the hydrogen electrode 111 and the first interconnector surface S301.

[0042] The hydrogen electrode current collector 21 has a mesh or porous structure and is configured to allow permeation of hydrogen electrode gas consumed or generated at the hydrogen electrode 111. The hydrogen electrode current collector 21 is made of a conductive material that is not easily reduced in a reducing atmosphere caused by the hydrogen electrode gas, and electrically connects the hydrogen electrode 111 and the interconnector 30. Specifically, the hydrogen electrode current collector 21 is made of a metal material such as nickel.

[0043] In the cell stack 80, the hydrogen electrode current collectors 21 may differ in material, installation position, shape, structure, etc. as appropriate. Furthermore, the hydrogen electrode current collectors 21 may be formed using, for example, a paste.

[0044] [A-1-5] Oxygen electrode current collector 22 The oxygen electrode current collector 22 is interposed between the oxygen electrode 112 and the second interconnector surface S302 in the accommodation space SP40, and includes portions in contact with the oxygen electrode 112 and the second interconnector surface S302.

[0045] The oxygen electrode current collector 22, like the hydrogen electrode current collector 21, has a mesh structure or a porous structure and is configured to be permeable to the oxygen electrode gas consumed or generated at the oxygen electrode 112. The oxygen electrode current collector 22 is made of a highly conductive material that is not easily oxidized in the oxidizing atmosphere of the oxygen electrode gas, and electrically connects the oxygen electrode 112 and the interconnector 30.

[0046] In this embodiment, the oxygen electrode current collector 22 is, for example, a stack including a current collecting layer 221 and a current collecting layer 222, and the current collecting layer 221 and the current collecting layer 222 are stacked in the stacking direction of the unit cell.

[0047] In the oxygen electrode current collector 22, the current collecting layer 221 is in contact with the oxygen electrode 112. In the oxygen electrode current collector 22, the current collecting layer 222 is in contact with the second interconnector surface S302.

[0048] In the oxygen electrode current collector 22 of this embodiment, the Young's modulus E1 of the current collecting layer 221 is different from the Young's modulus E2 of the current collecting layer 222. The oxygen electrode current collector 22 is configured, for example, so that the Young's modulus E2 of the current collecting layer 222 is higher than the Young's modulus E1 of the current collecting layer 221 (i.e., E1 <E2)。

[0049] Specifically, the current collecting layer 221 is formed of a metal material such as silver. The current collecting layer 222 is made of a metal material containing at least one element selected from the group consisting of Fe, Cr, Ni, and Co. The current collecting layer 222 is made of an alloy such as stainless steel. Alternatively, the current collecting layer 222 may be made of simple Cr, simple Ni, or simple Co.

[0050] In the oxygen electrode current collector 22 of this embodiment, the porosity n1 of the current collecting layer 221 is different from the porosity n2 of the current collecting layer 222. Here, the oxygen electrode current collector 22 is configured such that the porosity n1 of the current collecting layer 221 is higher than the porosity n2 of the current collecting layer 222 (i.e., n1>n2).

[0051] The thickness of each of the multiple current collecting layers (= current collecting layer 221, current collecting layer 222) constituting the oxygen electrode current collector 22 is adjusted so that the pressure applied to the surface RC of the central portion where the oxygen electrode current collector 22, the electrochemical cell 10, and the hydrogen electrode current collector 21 are stacked in the cell stack 80, and the pressure applied to the surface of the peripheral portion RS where the gasket seal material 40 is stacked, are each appropriate. For example, the pressure applied to the surface RC of the central portion and the pressure applied to the surface of the peripheral portion RS are measured using pressure-sensitive paper. Then, the thickness of each of the multiple current collecting layers is adjusted so that the pressure applied to the surface RC of the central portion and the pressure applied to the surface of the peripheral portion RS are each set to a design value. The design value of the thickness of each of the multiple current collecting layers is set in advance, taking into account the characteristics of each portion, such as the thermal expansion coefficient.

[0052] In the cell stack 80, the oxygen electrode current collectors 22 may differ in material, installation position, shape, structure, etc. as appropriate. Furthermore, the oxygen electrode current collectors 22 may be formed by using a paste in combination, for example.

[0053] [A-2] Load applying mechanism 90 In the electrochemical device 1, the load-applying mechanism 90 has load-receiving plates 92a, 92b, and 92c, a load-relieving member 93, and load-applying members 95a and 95b, and is configured to apply a load in the stacking direction to the cell stack 80. The load-applying members 95a and 95b may be provided together with the cell stack 80 in an environment where the temperature becomes high due to operation of the cell stack 80, or may be installed in a room temperature environment.

[0054] Each component of the load applying mechanism 90 will be described in turn.

[0055] [A-2-1] Load-receiving plates 92a, 92b, 92c Each of the load-receiving plates 92a, 92b, and 92c is, for example, a rectangular plate-like body. The load-receiving plate 92a is located on one end side of the cell stack 80 in the stacking direction (the lower side in FIG. 1A). The load-receiving plate 92b is located on the other end side of the cell stack 80 in the stacking direction (the lower side in FIG. 1B). In other words, the load-receiving plates 92a and 92b are arranged so as to sandwich the cell stack 80 in the stacking direction. The load-receiving plate 92c is located closer to the other end side of the cell stack 80 than the load-receiving plate 92b in the stacking direction. It is preferable that each of the load-receiving plates 92a, 92b, and 92c is thicker and more rigid than the interconnector 30 in order to uniformly distribute the load applied to the interconnector 30 in the cell stack 80 in its plane.

[0056] [A-2-1] Load relief member 93 The load relief member 93 is, for example, a biasing component such as a spring. The load relief member 93 is interposed between the load-receiving plate 92b and the load-receiving plate 92c in the stacking direction. The load relief member 93 is provided to relieve the load applied to the cell stack 80 in the stacking direction during the process of raising the temperature of the cell stack 80 to the operating temperature and during the process of maintaining the cell stack 80 at the operating temperature.

[0057] [A-2-1] Load-applying members 95a, 95b The load-applying members 95a and 95b are, for example, fastening parts, and are configured to fasten the load-receiving plates 92a, 92b, and 92c together to apply a load in the stacking direction to the cell stack 80. The load-applying members 95a are, for example, bolts, and the load-applying members 95b are, for example, nuts. The shafts of the bolts serving as the load-applying members 95a are inserted into insertion holes formed in the load-receiving plates 92a, 92b, and 92c, and the nuts serving as the load-applying members 95b are attached, thereby fastening the load-receiving plates 92a, 92b, and 92c together.

[0058] The load applying mechanism 90 may be a device such as a press machine in addition to the above.

[0059] [B] Summary As described above, in this embodiment, the oxygen electrode current collector 22 has a current collecting layer 221 (first current collecting layer) and a current collecting layer 222 (second current collecting layer) stacked in the stacking direction. In the oxygen electrode current collector 22, the Young's modulus E1 of the current collecting layer 221 is different from the Young's modulus E2 of the current collecting layer 222. In other words, the oxygen electrode current collector 22 is configured by stacking a plurality of current collecting layers with different rigidities.

[0060] As a result, in this embodiment, even if the electrochemical cell 10 is warped and the surface of the oxygen electrode 112 becomes a convex surface that protrudes convexly, the surface of the oxygen electrode current collector 22 follows the shape of the convex surface, thereby mitigating the load applied in the stacking direction to the surface of the electrochemical cell 10. In the oxygen electrode current collector 22 of this embodiment, the layer with a large Young's modulus (layer with high rigidity) can reduce the displacement difference of the layer with a small Young's modulus (layer with low rigidity), thereby widening the range of the allowable elastic modulus.

[0061] As a result, in this embodiment, the oxygen electrode 112 and the oxygen electrode current collector 22 are in close contact with each other, and a load is applied uniformly to the surface between the oxygen electrode 112 and the oxygen electrode current collector 22, which prevents an increase in electrical resistance between the oxygen electrode 112 and the oxygen electrode current collector 22 and also prevents breakage. In addition, the adhesion between the interconnector 30 and the gasket sealant 40, etc., is improved, which makes it possible to sufficiently prevent gas leakage.

[0062] Therefore, in this embodiment, the performance of the electrochemical device 1 can be easily improved.

[0063] In this embodiment, the oxygen electrode current collector 22 is composed of multiple current collecting layers with different Young's moduli, etc. The hydrogen electrode current collector 21 is not composed of multiple current collecting layers with different Young's moduli, etc. Stacking multiple current collecting layers with different Young's moduli makes it easier to select a more appropriate Young's modulus, and the oxygen electrode current collector 22 can be brought into contact with the cell surface with a more uniform load distribution.

[0064] In the oxygen electrode current collector 22 of this embodiment, the porosity n1 of the current collecting layer 221 is different from the porosity of the current collecting layer 222. Generally, a difference in porosity causes a change in Young's modulus, so by providing the current collecting layer 221 and the current collecting layer 222 with different porosities, the oxygen electrode current collector 22 can be brought into contact with the cell surface with a more uniform load distribution.

[0065] [C] Variation [C-1] Variation 1 Fig. 2 is a diagram schematically showing an oxygen electrode current collector 22 of Modification 1. Fig. 2 shows only the oxygen electrode current collector 22 of the electrochemical device 1 (see Fig. 1A).

[0066] As shown in FIG. 2, the oxygen electrode current collector 22 of this modified example is a laminate in which a current collecting layer 221, a current collecting layer 222, and a current collecting layer 223 are stacked.

[0067] Although not shown, in the oxygen electrode current collector 22 of this modified example, the current collecting layer 221 is in contact with the oxygen electrode 112 (see FIG. 1A). The current collecting layer 221 and the current collecting layer 222 are formed of a metal material such as silver. The current collecting layer 223 is in contact with the second interconnector surface S302 (see FIG. 1A) and is formed of a metal material containing at least one element selected from the group consisting of Fe, Cr, Ni, and Co.

[0068] In this way, the oxygen electrode current collector 22 may be composed of three or more current collecting layers, and in this case, the same effects as those of the above embodiment can be obtained.

[0069] The oxygen electrode current collector 22 is preferably positioned on the electrochemical cell 10 side so that the current collector layer with the smallest Young's modulus among the multiple current collector layers is in contact with the oxygen electrode 112. This allows the surface of the oxygen electrode current collector 22 to adhere more closely to the warped surface of the oxygen electrode 112, even if the surface of the oxygen electrode 112 is warped, thereby further improving the performance of the electrochemical cell 10.

[0070] In the oxygen electrode current collector 22, it is preferable that the thickness of the current collector layer with the highest Young's modulus among the multiple current collector layers is thicker than the thickness of each of the other current collector layers. It is more preferable that the thickness of the current collector layer with the highest Young's modulus is 50% or more of the thickness of the oxygen electrode current collector 22. It is preferable that the current collector layer with the highest Young's modulus is made of a metal material whose composition contains at least one element selected from the group consisting of Fe, Cr, Ni, and Co. It is preferable that the oxygen electrode current collector 22 is configured to include multiple current collector layers whose Young's moduli differ by two or more. It is preferable that the oxygen electrode current collector 22 includes a current collector layer whose Young's modulus is 30 MPa or more. The multiple current collector layers that make up the oxygen electrode current collector 22 may have different Young's moduli, or may include current collector layers with the same Young's modulus.

[0071] Moreover, the oxygen electrode current collector 22 is preferably positioned on the electrochemical cell 10 side so that the current collector layer with the smallest porosity among the multiple current collector layers is in contact with the oxygen electrode 112. This allows for a smooth flow of oxygen electrode gas.

[0072] The oxygen electrode current collector 22 preferably includes a porous layer having a porosity of 10% or more as a current collecting layer, and also includes a dense layer having a porosity of 1% or less as a current collecting layer. The oxygen electrode current collector 22 may have a plurality of porous current collecting layers, and the porosities of the plurality of porous layers may be different. The thickness of the dense current collecting layer is preferably 50% or more of the thickness of the oxygen electrode current collector 22. The dense current collecting layer is preferably made of a metal material containing at least one element selected from the group consisting of Fe, Cr, Ni, and Co. The plurality of current collecting layers constituting the oxygen electrode current collector 22 may have different porosities, or may include current collecting layers with the same porosity.

[0073] [C-2] Variation 2 3A and 3B are diagrams schematically showing the oxygen electrode current collector 22 of Modification 2. In Fig. 3A and 3B, the oxygen electrode current collector 22 is selectively illustrated from the electrochemical device 1 (see Fig. 1A).

[0074] As shown in Figures 3A and 3B, the oxygen electrode current collector 22 of this modified example may be configured so that the current collecting layers 221 and 222 include portions with different thicknesses between a central portion located at the center in a plane perpendicular to the stacking direction (the xy plane in Figure 2B) and side portions located on either side of the central portion.

[0075] Specifically, as shown in FIG. 3A, current collecting layer 221 may be thicker at the center than at the sides, and current collecting layer 222 may be thicker at the sides than at the center.

[0076] As shown in FIG. 3B, current collecting layer 221 may be thinner at the center than at the sides, and current collecting layer 222 may be thinner at the sides than at the center.

[0077] The thickness of each part is optimized, for example, by checking the performance of the electrochemical device 1. In this case, the same effect as in the above embodiment can be obtained. Note that, although this modification illustrates a case where the thickness of the central part is different from the overall thickness of the side parts surrounding the central part, if necessary, the thickness of a part of the side parts surrounding the central part may be different from the thickness of the central part.

[0078] [C-3] Other variations In the above embodiment and the like, the oxygen electrode current collector 22 is described as being configured such that the current collecting layer 221 contacts the oxygen electrode 112 in each of the plurality of unit cells that make up the cell stack 80, but this is not limiting. Unlike the above embodiment, Modification 2, and Modification 3, the current collecting layer 222 and the current collecting layer 221 may be arranged in this order from the oxygen electrode 112 side. Also, unlike Modification 1, the current collecting layer 223, the current collecting layer 222, and the current collecting layer 221 may be arranged in this order from the oxygen electrode 112 side. In other words, the arrangement of the plurality of current collecting layers with different Young's moduli that make up the oxygen electrode current collector 22 is not particularly limited.

[0079] The oxygen electrode current collector 22 may also include, as current collecting layers, multiple porous layers with a porosity of 10% or more. In this case, the difference in porosity between the multiple porous layers is preferably 5% or more. The current collecting layers that are porous layers in the oxygen electrode current collector 22 may have different porosities between a central portion located at the center of a plane perpendicular to the stacking direction and side portions located to the sides of the central portion. In this case, the difference in porosity between the central portion and the side portions is preferably 5% or more.

[0080] As described above, the case where the oxygen electrode current collector 22 is composed of multiple current collecting layers has been described, but this is not limiting. Like the oxygen electrode current collector 22, the hydrogen electrode current collector 21 may also be composed of multiple current collecting layers. In other words, it is sufficient that at least one of the hydrogen electrode current collector 21 and the oxygen electrode current collector 22 is composed of multiple current collecting layers. [Example]

[0081] Examples and comparative examples will be explained below with reference to Table 1. In Table 1, (Example 1) and (Example 2) correspond to examples, and (Example C1) corresponds to a comparative example.

[0082] [Table 1]

[0083] [a] Sample preparation Regarding the procedure for fabricating samples of the oxygen electrode current collector 22 according to each example, it will be sequentially described using Table 1.

[0084] (Example 1) (In Example 1), as shown in Table 1, a laminate of the current collector layer 221 and the current collector layer 222 was fabricated as the oxygen electrode current collector 22. Here, the oxygen electrode current collector 22 was fabricated by laminating each layer under the conditions shown in Table 1. That is, in (Example 1), while the Young's modulus E1 of the current collector layer 221 and the Young's modulus E2 of the current collector layer 222 are in the relationship shown in the following (Equation 1a), the porosity n1 of the current collector layer 221 and the porosity n2 of the current collector layer 222 are in the relationship shown in the following (Equation 1b).

[0085] E1 < E2 ···(Equation 1a) n1 > n2 ···(Equation 1b)

[0086] Then, using the oxygen electrode current collector 22 fabricated as described above, the electrochemical device 1 was assembled as shown in FIG. 1B. That is, the electrochemical device 1 of (Example 1) corresponds to the electrochemical device 1 of the embodiment.

[0087] (Example 2) [[ID=二十]](In Example 2), as shown in Table 1, a laminate of the current collector layer 221, the current collector layer 222, and the current collector layer 223 was fabricated as the oxygen electrode current collector 22. Here, the oxygen electrode current collector 22 was fabricated by laminating each layer under the conditions shown in Table 1. That is, in (Example 2), while the Young's modulus E1 of the current collector layer 221, the Young's modulus E2 of the current collector layer 222, and the Young's modulus E3 of the current collector layer 223 are in the relationship shown in the following (Equation 2a), the porosity n1 of the current collector layer 221, the porosity n2 of the current collector layer 222, and the porosity n3 of the current collector layer 223 are in the relationship shown in the following (Equation 2b).

[0088] E3 > E1 > E2 ···(Equation 2a) n2 > n1 > n3 ···(Equation 2b)

[0089] The oxygen electrode current collector 22 prepared as described above corresponds to the oxygen electrode current collector 22 of Modification 1 shown in FIG. 2. Then, the electrochemical device 1 was assembled using the oxygen electrode current collector 22 prepared as described above, as shown in FIG. 1B. That is, the electrochemical device 1 of (Example 2) corresponds to the electrochemical device 1 of Modification 1. The electrochemical device 1 of (Example 2) is substantially the same as (Example 1) except that the oxygen electrode current collector 22 is different from that of (Example 1).

[0090] (Example C1) In (Example C1), as shown in Table 1, a single layer of the current collecting layer 221 was produced as the oxygen electrode current collector 22. Then, the oxygen electrode current collector 22 produced as described above was used to assemble the electrochemical device 1. That is, the electrochemical device 1 of (Example C1) is substantially the same as (Example 1) except that the oxygen electrode current collector 22 is different from that of (Example 1).

[0091] [b] Characterization The IV characteristics were determined for the electrochemical device 1 of each example. The IV characteristics were obtained by passing a current through the electrochemical cell 10 so as to perform electrolysis of water vapor in a high-temperature environment and evaluating the electrolysis voltage relative to the current.

[0092] FIG. 4 shows the IV characteristics obtained for each example.

[0093] As can be seen from Figure 4, (Example 1) and (Example 2) have lower electrolysis voltages than (Example C1) and have better performance. Specifically, it was found that (Example 1) exhibits better performance than (Example C1) when the electrolysis voltage is around 1.3 V. Furthermore, it was found that (Example 2) exhibits better performance when the electrolysis voltage is around 1.2 V under current conditions where the electrolysis voltage of (Example C1) is around 1.3 V.

[0094] 4, the electrolysis voltage at the same current value is lower in (Example 1) and (Example 2) than in (Example C1). This indicates that there is sufficient contact between the oxygen electrode current collector 22 and the oxygen electrode 112 of the electrochemical cell 10, and the electrical resistance between them is sufficiently low.

[0095] The oxygen electrode current collector 22 in (Example 1) and (Example 2) is a laminate of multiple current collector layers with different Young's moduli, and therefore is more elastic than (Example C1), which is presumably why a decrease in the load applied to the electrochemical cell 10 due to deformation of the component when the temperature rises is prevented.

[0096] Although not shown in Table 1, the electrochemical device 1 was assembled using an oxygen electrode current collector 22 fabricated under the same conditions as in Example C1, except that the total thickness of the oxygen electrode current collector 22 was the same as in Examples 1 and 2. However, in this case, cracks occurred in the electrochemical cell 10, and therefore, the IV characteristics could not be obtained.

[0097] <Other> Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0098] 1: electrochemical device, 10: electrochemical cell, 21: hydrogen electrode current collector, 22: oxygen electrode current collector, 30: interconnector, 40: gasket seal material, 45: partition, 80: cell stack, 90: load application mechanism, 92a: load receiving plate, 92b: load receiving plate, 92c: load receiving plate, 93: load relaxation member, 95a: load application member, 95b: load application member, 110 : electrolyte membrane, 111: hydrogen electrode, 112: oxygen electrode, 221: current collecting layer (first current collecting layer), 222: current collecting layer (second current collecting layer), 223: current collecting layer (third current collecting layer), 401: hydrogen electrode side seal part, 402: oxygen electrode side seal part, S301: first interconnector surface, S302: second interconnector surface, SP40: accommodation space, SP401: hydrogen electrode side accommodation part, SP402: oxygen electrode side accommodation part

Claims

1. An electrochemical device comprising a cell stack including a plurality of electrochemical cells configured such that an electrolyte membrane is sandwiched between a hydrogen electrode and an oxygen electrode, the plurality of electrochemical cells being stacked in a stacking direction, The cell stack comprises: a plurality of interconnectors interposed between each of the plurality of electrochemical cells arranged in the stacking direction, the interconnectors including a first interconnector surface on the hydrogen electrode side and a second interconnector surface on the oxygen electrode side; a plurality of gasket seals provided between the plurality of interconnectors arranged in the stacking direction so as to surround an accommodation space that accommodates the electrochemical cell; and Equipped with Each of the plurality of electrochemical cells comprises: a hydrogen electrode current collector interposed between the hydrogen electrode and the first interconnector surface in the accommodation space and in contact with the hydrogen electrode and the first interconnector surface; an oxygen electrode current collector interposed between the oxygen electrode and the second interconnector surface in the accommodation space and in contact with the oxygen electrode and the second interconnector surface; and At least one of the hydrogen electrode current collector and the oxygen electrode current collector is A first current collecting layer; A second current collecting layer; the first current collecting layer and the second current collecting layer are stacked in the stacking direction, the Young's modulus of the first current collecting layer is different from the Young's modulus of the second current collecting layer; Electrochemical equipment.

2. the first current collecting layer and the second current collecting layer are configured to include portions whose thicknesses vary between a central portion and a side portion in a plane perpendicular to the stacking direction. The electrochemical device of claim 1 .

3. the porosity of the first current collecting layer is different from the porosity of the second current collecting layer; The electrochemical device of claim 1 .

4. The oxygen electrode current collector is configured by laminating at least the first current collecting layer and the second current collecting layer. The electrochemical device of claim 1 .

5. the second current collecting layer is made of a material containing at least one element selected from the group consisting of Fe, Cr, Ni, and Co; The electrochemical device of claim 1 .

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