Manufacturing method for electrochemical stack and electrochemical stack

Abstract

To provide a technique that suppresses damage to an electrochemical cell during the construction of an electrochemical stack.SOLUTION: A manufacturing method disclosed herein comprises a first process for preparing a cell 1 in which a substrate 10, a hydrogen electrode 20, a solid electrolyte layer 30, and an oxygen electrode 40 are stacked in this order, a second process for measuring the warp quantity of the cell 1, a third process for determining a cell 1 as good if a convex warp that is a convex curvature toward the oxygen electrode 40 side has occurred and the warp quantity (Hmax-HS) is 0.3 mm or more and 1.3 mm or less, and a fourth process for constructing a stack using the cell 1 determined as good in the third process. The cell 1 with the convex warp having the above warp quantity is less prone to stresses that could expand the solid electrolyte layer 30, thereby suppressing damage during stack construction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrochemical stack and to an electrochemical stack. [Background technology]

[0002] Solid oxide electrolysis cells (SOECs) generate oxygen gas and hydrogen gas through the electrolysis of water. This allows them to convert electrical energy, which is difficult to store, into chemical substances that are easy to store, and they have attracted attention in fields such as solar power generation. Meanwhile, some SOEC cells can also be used as solid oxide fuel cells (SOFCs). SOFCs generate electricity by reacting hydrogen gas with oxygen gas. In this specification, cells that can be used for both SOECs and SOFCs are referred to as "electrochemical cells." This type of electrochemical cell has a porous hydrogen electrode and an oxygen electrode stacked on top of a dense solid electrolyte layer. Technologies related to this electrochemical cell are disclosed in Patent Documents 1 and 2.

[0003] Furthermore, electrochemical cells are sometimes used as an electrochemical stack in which a plurality of cells are electrically connected. In such an electrochemical stack, a plurality of electrochemical cells are typically stacked via metal connection plates (metal interconnectors). An example of an electrochemical stack having such a configuration is disclosed in Patent Document 3. Furthermore, a stack including electrochemical cells and metal connection plates may be restrained along the stacking direction by restraining members such as springs or bellows. This allows the interface between the electrochemical cells and the metal connection plate to be tightly attached. As a result, gas leakage can be suppressed and the contact resistance between the electrochemical cells and the metal connection plate can be reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-157228 [Patent Document 2] Patent Publication No. 2021-174683 [Patent Document 3] Patent Publication No. 2018-190683 Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing of the electrochemical stack with the above configuration, after stacking multiple electrochemical cells via metal connection plates, the stack of metal connection plates and electrochemical cells is constrained in the stacking direction. During this process, the weight of each component and the constraining pressure can sometimes damage the cells in the stack. In this case, the electrochemical stack under construction must be disassembled to replace the cells, which significantly reduces manufacturing efficiency and yield.

[0006] The technology disclosed herein has been made to solve the above-mentioned problems, and aims to provide a technology that suppresses damage to electrochemical cells in the construction of an electrochemical stack. [Means for solving the problem]

[0007] The present inventors conducted various experiments and studies to solve the above-mentioned problems, and as a result, came to the following findings. In the field of electrochemical cells, it has generally been considered preferable to have electrochemical cells with a small amount of warpage. For this reason, various techniques for reducing the amount of warpage of electrochemical cells have been proposed, such as in Patent Document 2 mentioned above. However, after studying the structure of the electrochemical stack, the present inventors concluded that using electrochemical cells that are warped a certain amount in a specific direction would be more effective in suppressing cell damage.

[0008] Specifically, electrochemical cells may develop either a concave warp toward the hydrogen electrode side or a convex warp toward the oxygen electrode side. Concave-warped cells are prone to outward stress in the planar direction on the dense solid electrolyte layer. When weight or pressure is applied to a cell with concave warp, the solid electrolyte layer may expand, potentially causing cracks. Even cells that are nearly flat (with a warpage of less than ±0.3 mm) may develop cracks in the solid electrolyte layer. On the other hand, convex-warped cells toward the oxygen electrode side are prone to inward stress in the planar direction on the solid electrolyte layer. Therefore, constructing a stack using electrochemical cells with a certain amount of convex warp or more is expected to adequately prevent damage to the electrochemical cells during construction. Based on this knowledge, the present inventors conducted extensive experiments and studies and came up with a method for manufacturing an electrochemical stack having the following configuration.

[0009] The manufacturing method disclosed herein produces an electrochemical stack including a plurality of electrochemical cells. The manufacturing method includes a first step of preparing an electrochemical cell in which a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode are stacked in this order, a second step of measuring the amount of warpage of the electrochemical cell, a third step of determining as a non-defective electrochemical cell those electrochemical cells that have a convex warp that warps convexly toward the oxygen electrode and whose amount of convex warp is 0.3 mm or more and 1.3 mm or less, and a fourth step of constructing an electrochemical stack using the electrochemical cells determined to be non-defective in the third step.

[0010] In the manufacturing method described above, an electrochemical stack is constructed using electrochemical cells in which the amount of convex warp toward the oxygen electrode is 0.3 mm or more and 1.3 mm or less, which prevents the solid electrolyte layer from being subjected to outward stress in the planar direction, thereby suppressing damage to the electrochemical cells during construction of the electrochemical stack.

[0011] Another aspect of the technology disclosed herein provides an electrochemical stack. The electrochemical stack includes a plurality of electrochemical cells. Each electrochemical cell of the electrochemical stack includes a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode stacked in this order. 90% or more of the electrochemical cells included in the electrochemical stack have a convex warp toward the oxygen electrode, and the amount of the convex warp is 0.3 mm or more and 1.3 mm or less. An electrochemical stack configured in this manner can prevent outward stress in the planar direction from being applied to the solid electrolyte layer, thereby suppressing damage to the electrochemical cells. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an electrochemical cell. [Figure 2] FIG. 2 is a diagram for explaining measurement of the amount of warpage. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an electrochemical cell having a convex warp. [Figure 4] FIG. 4 is a cross-sectional view schematically showing an electrochemical cell having a concave warpage. [Figure 5] FIG. 5 is a perspective view schematically illustrating an electrochemical stack. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the technology disclosed herein are described below. Matters necessary for implementing the technology disclosed herein, other than those specifically mentioned in this specification, can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the technical common sense in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals, and redundant explanations may be omitted or simplified. In this specification, when a numerical range is described as "A to B (A and B are arbitrary numerical values)," this means "greater than A and less than B (including a range greater than A but less than B)."

[0014] 1. Manufacturing method of electrochemical stack Hereinafter, one embodiment of the method for manufacturing an electrochemical stack disclosed herein will be described. Fig. 1 is a cross-sectional view schematically showing an electrochemical cell. Fig. 2 is a diagram illustrating measurement of the amount of warpage. Fig. 3 is a cross-sectional view schematically showing an electrochemical cell having a convex warpage. Fig. 4 is a cross-sectional view schematically showing an electrochemical cell having a concave warpage. Fig. 5 is a perspective view schematically showing an electrochemical stack.

[0015] The method for manufacturing an electrochemical stack according to this embodiment is a method for manufacturing an electrochemical stack 100 including a plurality of electrochemical cells 1. This manufacturing method includes at least the following first to fourth steps. Each step will now be described in detail.

[0016] (1) First step In this step, an electrochemical cell 1 is prepared. As shown in Fig. 1, this electrochemical cell 1 (hereinafter also simply referred to as "cell") has a support 10, a hydrogen electrode 20, a solid electrolyte layer 30, and an oxygen electrode 40 laminated in this order. Each layer will be described below.

[0017] (1-1) Support The support 10 is a member that supports the laminated structure (hydrogen electrode 20, solid electrolyte layer 30, and oxygen electrode 40) of the electrochemical cell 1. The material of the support 10 is a material that is conductive in a reducing atmosphere when the electrochemical cell 1 is used. The specific material of the support 10 is not particularly limited, and any conventionally known conductive material that can be used for a support of an electrochemical cell can be used without particular limitation. Examples of inorganic materials contained in the support 10 include stabilized zirconia such as yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), and scandia-stabilized zirconia (ScSZ), and cerium oxides such as gadolinia-doped ceria (GDC) and samaria-doped ceria (SDC). Furthermore, metal composite oxides such as lanthanum strontium titanium composite oxide (LST), metal oxides such as nickel oxide (NiO) and copper oxide (CuO), and alloy materials such as nickel-chromium-iron alloy (NCF) and nickel-chromium-cobalt alloy (NCC) can also be used for the support 10. Among these materials, nickel oxide (NiO) is suitable as an inorganic material for constructing a conductive support because it functions as a conductive material when reduced with hydrogen gas. Even when constructing a conductive support, a non-conductive ceramic material (e.g., YSZ) may be added. In this case, the mixing ratio (mass ratio) of the conductive material to the ceramic material is preferably within a range of 3:7 to 7:3, for example, approximately 5:5.

[0018] The support 10 according to this embodiment is a plate-like member having a rectangular planar shape. However, the planar shape of the support 10 is not particularly limited and may be circular or polygonal. Furthermore, as the thickness of the support 10 increases, the mechanical strength of the support 10 improves, thereby enabling the cell structure to be properly maintained. From this perspective, the thickness of the support 10 is preferably 150 μm or more, more preferably 200 μm or more, and particularly preferably 250 μm or more. On the other hand, as the thickness of the support 10 decreases, the air permeability to the laminated structure (typically the hydrogen electrode 20) tends to improve. From this perspective, the upper limit of the thickness of the support 10 is preferably 600 μm or less, more preferably 500 μm or less, and particularly preferably 400 μm or less.

[0019] (1-2) Hydrogen electrode The hydrogen electrode 20 is formed on the upper surface of the support 10. When the electrochemical cell 1 is used as an SOEC, the hydrogen electrode 20 functions as a layer that decomposes water (H2O) to generate hydrogen gas (H2). On the other hand, when the electrochemical cell 1 is used as an SOFC, the hydrogen electrode 20 oxidizes the hydrogen gas (H2) to generate electrons (e - The hydrogen electrode 20 functions as a layer that generates a hydrogen-containing gas. The hydrogen electrode 20 is, for example, a porous body containing a conductive material (a material having catalytic activity). The hydrogen electrode 20 preferably has a large number of pores. This improves the breathability of the hydrogen electrode 20. The material of the hydrogen electrode 20 can be any conventionally known conductive material that can be used for hydrogen electrodes in electrochemical cells, without any particular limitations. Examples of conductive materials for the hydrogen electrode 20 include metals such as nickel (Ni), copper (Cu), gold (Au), platinum (Pt), palladium (Pd), ruthenium (Ru), cobalt (Co), lanthanum (La), strontium (Sr), and titanium (Ti), as well as oxides of these metals. These conductive materials can be used alone or in combination of two or more. Nickel is particularly suitable because it is less expensive than other metals and exhibits high reaction activity. The hydrogen electrode 20 may also contain an ion-conductive ceramic material (e.g., YSZ). In this case, the mixing ratio (mass ratio) of the conductive material to the ceramic material is preferably within a range of 3:7 to 7:3, for example, about 6:4.

[0020] The porosity of the hydrogen electrode 20 is preferably 10% or more, more preferably 15% or more, even more preferably 17.5% or more, and particularly preferably 20% or more. As the porosity of the hydrogen electrode 20 increases, cells 1 (see FIG. 3) that are warped toward the oxygen electrode 40 are more likely to be produced. This increases the number of cells 1 that are determined to be non-defective in the third step, contributing to improved yield. On the other hand, if the porosity of the hydrogen electrode 20 is too high, cells 1 that are excessively warped are more likely to be produced, which may actually reduce yield. From this perspective, the porosity of the hydrogen electrode 20 is preferably 35% or less, more preferably 34% or less, even more preferably 32% or less, and particularly preferably 30% or less. The porosity in this specification is measured based on image analysis of cross-sectional SEM images.

[0021] The thickness of the hydrogen electrode 20 is preferably 20 μm or more, more preferably 35 μm or more, even more preferably 50 μm or more, and particularly preferably 65 μm or more. As the hydrogen electrode 20 becomes thicker, cells 1 having convex warpage tend to be produced, which contributes to improving yield. On the other hand, if the hydrogen electrode 20 becomes too thick, cells 1 having excessive convex warpage tend to be produced, which may reduce yield. From this perspective, the thickness of the hydrogen electrode 20 is preferably 200 μm or less, more preferably 160 μm or less, even more preferably 140 μm or less, and particularly preferably 100 μm or less.

[0022] (1-3) Solid electrolyte layer The solid electrolyte layer 30 is formed on the upper surface of the hydrogen electrode 20. This solid electrolyte layer 30 is a dense layer containing a solid electrolyte having oxygen ion conductivity. For this solid electrolyte, any conventionally known material that can be used for a solid electrolyte layer of an electrochemical cell can be used without any particular limitation. Examples of solid electrolytes include stabilized zirconia such as yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), and scandia-stabilized zirconia (ScSZ). The relative density of the solid electrolyte layer 30 is, for example, about 95 to 100(%).

[0023] The thickness of the solid electrolyte layer 30 is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 7.5 μm or more, and particularly preferably 10 μm or more. As with the hydrogen electrode 20 described above, a thicker solid electrolyte layer 30 makes it easier to manufacture cells 1 with convex warpage, which contributes to improving yield. On the other hand, if the solid electrolyte layer 30 is too thick, it also makes it easier to manufacture cells 1 with excessive convex warpage, which may reduce yield. From this perspective, the thickness of the solid electrolyte layer 30 is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less, and particularly preferably 15 μm or less.

[0024] (1-4) Oxygen electrode The oxygen electrode 40 is formed on the upper surface of the solid electrolyte layer 30. For this oxygen electrode 40, any conventionally known material that can be used for the oxygen electrode of an electrochemical cell can be used without any particular limitation. An example of the material for the oxygen electrode 40 is lanthanum strontium cobalt composite oxide (LSC, for example, La 0.6 Sr 0.4 CoO3) and lanthanum strontium cobalt iron composite oxides (LSCF, e.g., La 0.6 Sr 0.4 Co 0.2 Fe 0.8 Examples of suitable perovskite-type oxides include those containing La, Sr, and Co, such as SiO2 (O3). The substitution ratios of the A and B sites of these LSCs and LSCFs can be varied, and an appropriate substitution ratio can be selected depending on the desired ionic conductivity, reduction expansion coefficient, and the like. The oxygen electrode 40 is preferably a porous body having a plurality of pores. This allows oxygen-containing gas (air) to be supplied to the entire area of ​​the oxygen electrode 40. The thickness of the oxygen electrode 40 is not particularly limited and may be 5 μm or more and 100 μm or less.

[0025] (1-5) Other structures The electrochemical cell 1 prepared in this step is not limited to the above-mentioned configuration. For example, an intermediate layer may be interposed between any of the above-mentioned layers. An example of this intermediate layer is a reaction prevention layer interposed between the solid electrolyte layer and the oxygen electrode. This can suppress performance degradation due to a reaction between the solid electrolyte layer and the oxygen electrode. The reaction prevention layer is preferably made of cerium oxide such as gadolinia-doped ceria (GDC) or samaria-doped ceria (SDC). This intermediate layer is preferably a layer that is thinner and more porous than the solid electrolyte layer. This reduces the effect on the solid electrolyte layer, This can more effectively prevent cracks in the solid electrolyte layer. For example, the thickness of the intermediate layer is preferably 10 μm or less. The porosity of the intermediate layer is preferably 25% or less.

[0026] (2)Second process In this step, the amount of warpage of the electrochemical cell 1 is measured. The amount of warpage of the cell 1 is preferably calculated based on the height positions at the plurality of measurement points by measuring the height position of the upper surface of the oxygen electrode 40 at a plurality of measurement points. The means for measuring the height position of the upper surface of the oxygen electrode 40 is not particularly limited, and any conventionally known measuring means can be used without particular limitation. Specific measuring instruments that can be used include non-contact measuring instruments such as a laser microscope or a laser displacement meter, and contact measuring instruments such as a dial gauge or an optical flat.

[0027] A specific measurement procedure using a laser microscope will be described below with reference to FIGS. 2 to 4. First, a circular measurement line L is set along the peripheral edge 40a of the oxygen electrode 40 at a position a predetermined distance (e.g., about 5 mm) inside from the peripheral edge 40a. A pair of measurement points P1 and P2, facing each other across the center C of the oxygen electrode 40, is set on the measurement line L. Height positions H1 and H2 of the oxygen electrode 40 at these measurement points P1 and P2 are measured (see FIG. 3). The average value of these height positions H1 and H2 is defined as the reference height HS of the surface of the oxygen electrode 40. Note that multiple pairs of measurement points P1 and P2 may be set. For example, in FIG. 3, two pairs of measurement points P1 and P2 are set. In other words, in FIG. 3, four measurement points P1 and P2 are set near the four corners of the planar rectangular oxygen electrode 40, and the average value of the height positions at each point is defined as the reference height HS. However, the measurement points may be set on the measurement line L as long as they are set on the measurement line L; this is not limited to the form shown in FIG. 3. For example, when a flat circular oxygen electrode is the target, a circular measurement line having a diameter smaller than the outer periphery of the oxygen electrode is set, and a pair of measurement points are set on the circular measurement line so as to face each other across the center of the circular oxygen electrode.

[0028] Next, the height position of the upper surface of the oxygen electrode 40 is scanned over the entire surface. Then, from the scan results, the maximum height Hmax of the upper surface of the oxygen electrode 40 and the minimum height Hmin of the upper surface of the oxygen electrode 40 are extracted. Next, the difference (Hmax-HS) between the maximum height Hmax and the reference height HS and the difference (Hmin-HS) between the minimum height Hmin and the reference height HS are calculated. Next, the absolute value of the difference on the maximum side, |Hmax-HS|, is compared with the absolute value of the difference on the minimum side, |Hmin-HS|. If the absolute value of the difference on the maximum side, |Hmax-HS|, is larger as shown in FIG. 3, it is determined that the cell 1 has a convex warp toward the oxygen electrode 40 side (upper U in FIG. 3). In this case, the difference on the maximum side, (Hmax-HS), is regarded as the amount of warpage of the cell 1. On the other hand, if the absolute value of the difference on the minimum side, |Hmin-HS|, is larger as shown in FIG. 4, it is determined that the cell 1 has a concave warp toward the hydrogen electrode 20 side (lower D in FIG. 4). In this case, the difference on the minimum value side (Hmin-HS) is regarded as the amount of warpage of cell 1.

[0029] (3) Third step In this process, the quality of the cell 1 is determined based on the measurement results of the amount of warpage of the cell 1 described above. Specifically, an electrochemical cell is determined to be a good product if it has a convex warp that warps convexly toward the oxygen electrode 40 side as shown in FIG. 3 and the amount of warpage of the convex warp (Hmax-HS) satisfies a predetermined threshold. Then, in this process, the cell 1 determined to be a good product is used to construct the electrochemical stack 100. On the other hand, an electrochemical cell 1 determined to be a defective product in this process is discarded.

[0030] The lower limit of the threshold for the amount of warpage (Hmax-HS) can be set to 0.3 mm or more. This can prevent damage to the cell 1. Specifically, in a cell 1 having a concave warpage, outward stress S2 (see FIG. 4) in the planar direction (width direction X and depth direction Y) is likely to be applied to the solid electrolyte layer 30. If a large pressure (such as a restraining load) is applied to such a cell 1, cracks may occur near the center of the solid electrolyte layer 30. On the other hand, in a cell 1 having a convex warpage of a certain degree or more, inward stress S1 (see FIG. 3) in the planar direction is likely to be applied to the solid electrolyte layer 30. In such a cell 1, cracks are unlikely to occur in the solid electrolyte layer 30 even when a large pressure is applied. From the viewpoint of more suitably preventing damage to the cell 1, the lower limit of the threshold is preferably 0.4 mm or more, and particularly preferably 0.5 mm or more. On the other hand, the upper limit of the threshold for the amount of warpage (Hmax-HS) is set to 1.3 mm or less. A cell 1 having an excessive convex warpage of more than 1.4 mm is likely to undergo excessive deformation when pressure is applied from an unloaded state, which makes the solid electrolyte layer 30 more susceptible to damage. The lower limit of the threshold is preferably 1.25 mm or less, and particularly preferably 1.2 mm or less.

[0031] (4) 4th step In this step, an electrochemical stack 100 is constructed using the electrochemical cells 1 determined to be non-defective in step 3. The electrochemical stack 100 shown in Fig. 5 includes a plurality of electrochemical cells 1, a metal connection plate 110, and a restraining member (not shown).

[0032] This electrochemical stack 100 includes a plurality of electrochemical cells 1. Although this does not limit the technology disclosed herein, the number of stacked cells 1 in the electrochemical stack 100 can be set within a range of 2 to 100. Generally, as the number of stacked cells 1 increases, the total weight of each component increases, making the cells more susceptible to damage. However, the manufacturing method disclosed herein can suppress damage to the cells 1 even when constructing a stack with a large number of stacked cells. From this perspective, the manufacturing method disclosed herein is particularly suitable for use in constructing a stack with 10 or more stacked cells 1 (more preferably 15 or more, and particularly preferably 20 or more).

[0033] Next, the metal connection plate 110 is a conductive member interposed between the multiple electrochemical cells 1. This metal connection plate 110 electrically connects each of the multiple electrochemical cells 1. The metal connection plate 110 has a gas flow path for supplying gas to the electrochemical cells 1. For example, a first gas flow path 112 extending in the depth direction Y is formed on the lower surface of the metal connection plate 110 facing the oxygen electrode 40 of the electrochemical cell 1. A plurality of first gas flow paths 112 are provided at predetermined intervals in the width direction X. The first gas flow path 112 communicates with the oxygen electrode 40 of the electrochemical cell 1. Meanwhile, a second gas flow path 114 extending in the width direction X is formed on the upper surface of the metal connection plate 110 facing the support 10. A plurality of second gas flow paths 114 are provided at predetermined intervals in the depth direction Y. The second gas flow path 114 communicates with the hydrogen electrode 20 via the support 10.

[0034] Although not shown, the electrochemical stack 100 also includes a restraining member. This restraining member restrains the stack, which is made by stacking the electrochemical cells 1 and the metal connection plates 110, along the stacking direction of the stack (height direction Z in FIG. 5). This fixes the electrochemical cells 1 and the metal connection plates 110, and the electrochemical stack 100 is constructed. By restraining the stack in this manner, it is possible to prevent gaps from occurring at the interface between the cells 1 and the metal connection plates 110. As a result, it is possible to prevent gas leakage, poor contact, and the like from occurring at the interface between the cells 1 and the metal connection plates 110.

[0035] In the electrochemical stack 100 configured as described above, the weight and confining pressure of each component are applied to the cell 1. In a cell with a concave warp, stress is likely to be applied to the solid electrolyte layer 30, causing it to expand outward in the planar direction. When the weight and confining pressure of each component are applied to this cell with a concave warp, the solid electrolyte layer 30 may be damaged. On the other hand, the cell 1 with a convex warp shown in FIG. 3 is likely to be applied with stress, causing the solid electrolyte layer 30 to contract inward in the planar direction. Therefore, even if a large pressure is applied to the cell 1, cracks due to expansion of the solid electrolyte layer 30 are unlikely to occur. In contrast, in the manufacturing method according to this embodiment, in the third step, convexly warped cells 1 with a warp amount of 0.3 mm or more and 1.3 mm or less are selected, and these convexly warped cells 1 are used to construct the stack 100. This makes it possible to suppress damage to electrochemical cells during the construction of the electrochemical stack.

[0036] In this step, all (100%) of the cells 1 used to construct the stack 100 do not need to be cells that have been determined to be non-defective in the third step (the amount of convex warpage is 0.3 mm or more and 1.3 mm or less). For example, if 90% or more of the cells 1 used to construct the stack 100 are determined to be non-defective, stress concentration due to stacking of multiple cells can be sufficiently alleviated, and cell damage can be sufficiently suppressed. However, from the viewpoint of more reliably suppressing cell damage, the proportion of non-defective cells when the total number of cells 1 in the stack 100 is taken as 100% is preferably 92% or more, more preferably 95% or more, even more preferably 98% or more, and particularly preferably 100%.

[0037] [Test example] Test examples relating to the technology disclosed herein will be described below. Note that the test examples are not intended to limit the technology disclosed herein to the following content.

[0038] 1. Sample Preparation In this test, 19 types of electrochemical cells (Samples 1 to 19) were prepared. These electrochemical cells were constructed by laminating, in this order, a support made of a mixture of NiO and YSZ, a hydrogen electrode made of a mixture of NiO and GDC, a solid electrolyte layer made of YSZ, a reaction prevention layer made of GDC, and an oxygen electrode made of LSCF. In this test, the thickness of the solid electrolyte layer, the thickness of the hydrogen electrode, and the porosity of the hydrogen electrode were varied for each sample (see Table 1). In this test, the thickness of the oxygen electrode was standardized to 30 μm, and the porosity of the oxygen electrode was standardized to 50%.

[0039] 2. Measurement of warpage In this test, the warpage of the cell (H max -H S ) were measured. The measurement results are shown in Table 1. In this test, a one-shot 3D shape measuring machine (model: VR-5000) manufactured by Keyence Corporation was used as the laser microscope.

[0040] 3.Load test In this test, a universal testing machine (Shimadzu Corporation, model: AG-100kN) was used at room temperature to apply a warping pressure to the cell of each sample in the stacking direction. The load on the cell was then gradually increased to measure the stress at which the cell cracked (compressive failure stress). Samples with a compressive failure stress of 200kPa or more were evaluated as "Good," and samples with a compressive failure stress of less than 200kPa were evaluated as "Poor." The results are shown in Table 1.

[0041] [Table 1]

[0042] As shown in Table 1, samples 4-6, 8-16, and 18-19 demonstrated excellent load-bearing capacity. This indicates that cells with a convex warpage of 0.3 mm to 1.3 mm can suppress breakage during stack construction. On the other hand, it was confirmed that the thickness of the solid electrolyte layer, the thickness of the hydrogen electrode, and the porosity of the hydrogen electrode also affect load-bearing capacity. However, because various factors have a complex influence, it is difficult to use these as evaluation indices to uniformly determine the quality of electrochemical cells. From the above, it was found that in order to suppress cell breakage during stack construction, it is sufficient to use the amount of convex warpage of the cell as an evaluation index and construct a stack using cells with a specified amount of convex warpage.

[0043] The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. In other words, the technology disclosed herein encompasses the aspects described in items 1 to 6 below.

[0044] <Item 1> 1. A method of manufacturing an electrochemical stack comprising a plurality of electrochemical cells, comprising: a first step of preparing an electrochemical cell in which a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode are stacked in this order; a second step of measuring the amount of warpage of the electrochemical cell; a third step of determining that an electrochemical cell has a convex warp that is warped convexly toward the oxygen electrode side and the warp amount of the convex warp is 0.3 mm or more and 1.3 mm or less as a non-defective product; a fourth step of constructing an electrochemical stack using the electrochemical cells determined to be non-defective in the third step; A method for manufacturing an electrochemical stack, comprising:

[0045] <Item 2> 2. The method for manufacturing an electrochemical stack according to item 1, wherein in the first step, an electrochemical cell is prepared that includes a hydrogen electrode having a porosity of 20% or more based on cross-sectional SEM observation.

[0046] <Item 3> 3. The method for manufacturing an electrochemical stack according to item 1 or 2, wherein the second step measures the amount of warpage of the electrochemical cell using a laser microscope.

[0047] <Item 4> The fourth step is a step of producing a stack in which a plurality of the electrochemical cells are stacked via a metal connection plate; constructing the electrochemical stack by attaching a restraining member that restrains the stack in a stacking direction; 4. A method for manufacturing an electrochemical stack according to any one of items 1 to 3, comprising:

[0048] <Item 5> 1. An electrochemical stack comprising a plurality of electrochemical cells, the electrochemical cell comprises a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode stacked in this order; An electrochemical stack, wherein 90% or more of the plurality of electrochemical cells have a convex warp that is warped convexly toward the oxygen electrode side, and the amount of warp of the convex warp is 0.3 mm or more and 1.3 mm or less.

[0049] <Item 6> a metal connection plate interposed between the plurality of electrochemical cells; a restraining member that restrains a stack in which the plurality of electrochemical cells are stacked via the metal connection plate along a stacking direction of the plurality of electrochemical cells; 6. The electrochemical stack of claim 5, further comprising: [Explanation of symbols]

[0050] 1. Electrochemical cell (cell) 10 Support 20 Hydrogen electrode 30 Solid electrolyte layer 40 Oxygen electrode 100 Electrochemical Stacks (Stacks) 110 Metallic connecting plate 112 first gas flow path 114 Second gas flow path

Claims

1. 1. A method of manufacturing an electrochemical stack comprising a plurality of electrochemical cells, comprising: a first step of preparing an electrochemical cell in which a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode are stacked in this order; a second step of measuring the amount of warpage of the electrochemical cell; a third step of determining that an electrochemical cell has a convex warp that is warped convexly toward the oxygen electrode side and the warp amount of the convex warp is 0.3 mm or more and 1.3 mm or less as a non-defective product; a fourth step of constructing an electrochemical stack using the electrochemical cells determined to be non-defective in the third step; A method for manufacturing an electrochemical stack, comprising:

2. 3. The method for manufacturing an electrochemical stack according to claim 1, wherein the first step comprises preparing an electrochemical cell having a hydrogen electrode with a porosity of 20% or more based on cross-sectional SEM observation.

3. The method for manufacturing an electrochemical stack according to claim 1 or 2, wherein the second step includes measuring the amount of warpage of the electrochemical cell using a laser microscope.

4. The fourth step is a step of producing a stack in which a plurality of the electrochemical cells are stacked via a metal connection plate; constructing the electrochemical stack by attaching a restraining member that restrains the stack in a stacking direction; 3. A method for manufacturing an electrochemical stack according to claim 1 or 2, comprising:

5. 1. An electrochemical stack comprising a plurality of electrochemical cells, the electrochemical cell comprises a support, a hydrogen electrode, a solid electrolyte layer, and an oxygen electrode stacked in this order; an electrochemical stack, wherein 90% or more of the plurality of electrochemical cells have a convex warp that is warped convexly toward the oxygen electrode side, and the amount of warp of the convex warp is 0.3 mm or more and 1.3 mm or less.

6. a metal connection plate interposed between the plurality of electrochemical cells; a restraining member that restrains a stack in which the plurality of electrochemical cells are stacked via the metal connection plate along a stacking direction of the plurality of electrochemical cells; The electrochemical stack of claim 5 further comprising:

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