Cell control system

Abstract

To provide a cell control system capable of increasing the lifespan thereof.SOLUTION: A cell control system includes an electrochemical cell 2 in which a plurality of layers 20 are stacked. The plurality of layers 20 include at least a first electrode layer 21, a second electrode layer 22, and an electrolyte layer 23. The first electrode layer 21 is a layer 20 that is supplied with a reducing gas or generates a reducing gas. The electrolyte layer 23 and at least one of the layers 20 on the first electrode layer 21 side in the stacking direction Z of the plurality of layers 20 with respect to the electrolyte layer 23 is a cerium-containing layer 3. The cerium-containing layer 3 contains cerium and has a fluorite-type crystal structure. A control unit controls the temperature T of the electrochemical cell 2 and the oxygen partial pressure PO2 of a gas supplied to the first electrode layer 21 so that at least one of the stress of each layer 20, the load applied to each layer 20, and the strain of each layer 20 is less than or equal to a prescribed value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cell control system. [Background technology]

[0002] For example, as described in Patent Document 1, a fuel cell including an electrochemical cell having an electrolyte layer is known. In the fuel cell described in Patent Document 1, the electrolyte layer has a ceria-based base material, and a layer containing alkaline earth elements, cerium, oxygen, rare earth elements, etc. is formed on the surface of the ceria-based base material. This suppresses the reduction of cerium by a reducing gas at high temperatures, and prevents damage and deterioration of the electrolyte layer due to expansion associated with the reduction of cerium. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-243473 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the fuel cell described in Patent Document 1 does not fully consider the temperature and oxygen partial pressure of the electrochemical cell, which change during operation or when switching from an operating state to a stopped state, nor does it fully consider layers other than the electrolyte layer that constitute the electrochemical cell. In other words, it does not fully consider the fact that the amount of expansion of cerium contained in the electrolyte layer and the fuel electrode layer changes depending on the temperature of the electrochemical cell and the oxygen partial pressure of the gas supplied to the electrochemical cell. Therefore, it can be said that the fuel cell described in Patent Document 1 has room for further improvement in terms of suppressing damage and deterioration of the electrochemical cell due to expansion associated with the reduction of cerium and achieving a longer lifespan.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a cell control system that can achieve a longer life. [Means for solving the problem]

[0006] One aspect of the present invention is an electrochemical cell (2) including a plurality of layers (20) stacked together, the layers including at least a first electrode layer (21), a second electrode layer (22), and an electrolyte layer (23) disposed between the first electrode layer and the second electrode layer, the first electrode layer is the layer to which a reducing gas is supplied or which generates the reducing gas; at least one of the electrolyte layer and the layer located on the first electrode layer side of the electrolyte layer in the stacking direction (Z) of the plurality of layers is a cerium-containing layer (3) containing cerium and having a fluorite-type crystal structure; a control unit (6) that controls a temperature T of the electrochemical cell and an oxygen partial pressure PO2 of a gas supplied to the first electrode layer, The control unit is in a cell control system (1) that controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress of each layer, the load on each layer, and the strain of each layer is equal to or less than a predetermined value. [Effects of the Invention]

[0007] In the cell control system, the control unit controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress in each layer due to the expansion of cerium contained in the cerium-containing layer, the load on each layer, and the strain in each layer is kept below a predetermined value. This can suppress damage and deterioration of the electrochemical cell, resulting in a longer lifespan.

[0008] As described above, according to the above aspect, it is possible to provide a cell control system that can achieve a longer lifespan. In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of a cell control system according to a first embodiment. [Figure 2] FIG. 1 is a cross-sectional view of an electrochemical cell according to a first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of an electrochemical cell showing the thickness tm of each layer in the first embodiment. [Figure 4] FIG. 3 is a cross-sectional view of an electrochemical cell showing the distance t′m in the first embodiment. [Figure 5] FIG. 4 is a diagram showing the load Pm of each layer in the first embodiment. [Figure 6] 1 is a cross-sectional view of an electrochemical cell showing the radius of curvature ρ in accordance with embodiment 1. FIG. [Figure 7] FIG. 2 is a cross-sectional view of a cell stack in the first embodiment. [Figure 8] 4 is a graph showing a control region CR of the cell control system in the first embodiment. [Figure 9] 4 is a graph showing the relationship between oxygen partial pressure and the amount of expansion of a sample in Experimental Example 1. [Figure 10] 1 is a graph showing the relationship between the change in oxygen vacancies Δδ of a sample and the amount of strain Δε of the sample in Experimental Example 1. [Figure 11] 10 is a cross-sectional photograph of an electrochemical cell in Experimental Example 2, which was operated under Condition A outside the control region CR, after operation. [Figure 12] 10 is a cross-sectional photograph of an electrochemical cell in Experimental Example 2, which was operated under condition B outside the control region CR, after operation. [Figure 13] FIG. 10 is a cross-sectional view of an experimental device in Experimental Example 3. [Figure 14] 10 is a graph showing the relationship between the reduction time and the displacement of the electrolyte layer and the first electrode layer in Experimental Example 3. [Figure 15] 10 is a graph showing the relationship between the reduction time and the residual stress of the intermediate layer and the leak prevention layer in Experimental Example 3. [Figure 16] 10 is a graph showing the safety factor of the intermediate layer when only the first electrode layer is a cerium-containing layer in Experimental Example 4. [Figure 17] 10 is a graph showing the safety factor of the intermediate layer when only the electrolyte layer is a cerium-containing layer in Experimental Example 4. [Figure 18] 10 is a graph showing the safety factor of the intermediate layer when only the support layer is a cerium-containing layer in Experimental Example 4. [Figure 19] FIG. 10 is a configuration diagram of a cell control system in a second embodiment. [Figure 20] FIG. 6 is a cross-sectional view of an electrochemical cell according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) An embodiment of a cell control system will be described with reference to FIGS. 2, the cell control system 1 of this embodiment has an electrochemical cell 2 in which a plurality of layers 20 are stacked. The plurality of layers 20 includes at least a first electrode layer 21, a second electrode layer 22, and an electrolyte layer 23 disposed between the first electrode layer 21 and the second electrode layer 22. The first electrode layer 21 is the layer 20 to which a reducing gas is supplied or which generates a reducing gas.

[0011] At least one of the electrolyte layer 23 and the layer 20 on the first electrode layer 21 side of the electrolyte layer 23 in the stacking direction Z of the multiple layers 20 is a cerium-containing layer 3. The cerium-containing layer 3 contains cerium and has a fluorite-type crystal structure.

[0012] 1, the cell control system 1 also has a control unit 6. The control unit 6 controls the temperature T of the electrochemical cell 2 and the oxygen partial pressure P02 of the gas supplied to the first electrode layer 21. The control unit 6 controls the temperature T and the oxygen partial pressure P02 so that at least one of the stress of each layer 20, the load applied to each layer 20, and the strain of each layer 20 is equal to or less than a predetermined value.

[0013] The cell control system 1 can be used, for example, as a means for controlling a fuel cell that generates electricity by utilizing a reaction between a reducing gas and an oxidizing gas, or a hydrogen production device that produces hydrogen gas, a reducing gas, by electrolyzing steam or the like using supplied power. The cell control system 1 of this embodiment controls an electrochemical cell 2 that produces hydrogen gas. That is, in this embodiment, the electrochemical cell 2 electrolyzes steam, a raw material, using power supplied from a power source 19 to produce hydrogen gas, a reducing gas. In this embodiment, the control unit 6 controls the power source 19 to adjust the power supplied to the electrochemical cell 2. In this embodiment, the electrochemical cell 2 is an SOEC (Solid Oxide Electrolysis Cell). In this specification, the gas supplied to the first electrode layer 21 is referred to as a first gas, and the gas supplied to the second electrode layer 22 is referred to as a second gas. As shown in FIG. 2 , in the stacking direction Z of the multiple layers 20, the side of the first electrode layer 21 relative to the electrolyte layer 23 is referred to as a first side Z1, and the side of the second electrode layer 22 relative to the electrolyte layer 23 is referred to as a second side Z2.

[0014] In this embodiment, operation of the electrochemical cell 2 means producing hydrogen gas by electrolyzing water vapor using the electrochemical cell 2. In this embodiment, the first electrode layer 21 is a layer 20 that produces hydrogen gas, which is a reducing gas.

[0015] 1, the cell control system 1 of this embodiment includes a first supply flow path 51 that supplies a first gas to the first electrode layer 21 of the electrochemical cell 2, and a second supply flow path 52 that supplies a second gas to the second electrode layer 22 of the electrochemical cell 2. In this embodiment, the first supply flow path 51 supplies a first gas containing water vapor and hydrogen gas to the first electrode layer 21 during operation, and the second supply flow path 52 supplies air as the second gas to the second electrode layer 22 during operation.

[0016] The cell control system 1 of this embodiment includes a hydrogen supply unit 55 that supplies hydrogen gas to the electrochemical cell 2. The hydrogen supply unit 55 is connected to the first supply flow path 51 and includes a reducing gas supply flow path 552 that supplies hydrogen gas to the first supply flow path 51. The reducing gas supply flow path 552 is provided with a flow rate adjuster 551 that adjusts the flow rate of hydrogen gas supplied to the first supply flow path 51. The flow rate adjuster 551 may be, for example, an electromagnetic valve. The control unit 6 controls the flow rate adjuster 551 to adjust the amount of hydrogen gas contained in the first gas. The hydrogen supply unit 55 may be, for example, a reformer that reforms methane gas or city gas containing methane as a main component through a catalytic reaction to produce a gas containing hydrogen gas and carbon monoxide. The hydrogen supply unit 55 may also be, for example, a storage tank that stores hydrogen gas. The hydrogen supply unit 55 may also be, for example, a device that recovers reducing gas discharged from the electrochemical cell 2 to a first discharge flow path 53 (described later) and supplies it again to the reducing gas supply flow path 552.

[0017] The cell control system 1 of this embodiment includes a water vapor generator 56 that generates water vapor. The water vapor generator 56 can be, for example, a bubbling-type vaporizer. The water vapor generator 56 is provided in a branch flow path 562, which is a flow path that branches off from the reducing gas supply flow path 552 and is connected to the first supply flow path 51. A portion of the gas containing hydrogen gas supplied from the hydrogen supply unit 55 is introduced into the water vapor generator 56 through the branch flow path 562 as a carrier gas, and is then supplied to the first supply flow path 51 as a gas containing a large amount of water vapor. In addition, a flow rate adjuster 561 is provided in the branch flow path 562 upstream of the water vapor generator 56. The flow rate adjuster 561 adjusts the flow rate of the gas supplied from the hydrogen supply unit 55 to be introduced into the water vapor generator 56. The flow rate adjuster 561 can be, for example, an electromagnetic valve. The control unit 6 controls the water vapor generator 56 and the flow rate adjuster 561, and adjusts the amount of water vapor contained in the first gas by adjusting the temperature of the water in the water vapor generator 56 and the amount of carrier gas supplied to the water vapor generator 56.

[0018] The second supply flow path 52 is provided with an air pump 521 for supplying air, which is the second gas, in a pressurized state to the electrochemical cell 2. The control unit 6 controls the air pump 521 to adjust the flow rate of the second gas supplied to the second electrode layer 22.

[0019] The cell control system 1 also includes a first discharge flow path 53 and a second discharge flow path 54 through which gas discharged from the electrochemical cell 2 flows. In this embodiment, gas containing a large amount of hydrogen gas generated by the electrochemical cell 2 flows through the first discharge flow path 53, and gas containing a large amount of oxygen gas generated by the electrochemical cell 2 is discharged through the second discharge flow path 54.

[0020] The cell control system 1 of this embodiment has a temperature adjustment unit (not shown) for adjusting the temperature T of the electrochemical cell 2. The control unit 6 controls the temperature adjustment unit to adjust the temperature T of the electrochemical cell 2 to a desired temperature. The temperature adjustment unit can be, for example, a combustor, an electric heating wire heater, a heat exchanger using cooling water, or the like.

[0021] For example, during operation, the control unit 6 controls the temperature adjustment unit so that the temperature T of the electrochemical cell 2 is 550 to 850° C. In this embodiment, the control unit 6 controls the temperature adjustment unit so that the temperature T is 650° C. during operation. The control unit 6 has a processor and a memory.

[0022] As shown in FIG. 7 , the cell control system 1 of this embodiment includes a cell stack 200 in which a plurality of electrochemical cells 2 are stacked. The plurality of electrochemical cells 2 are sandwiched between a pair of end plates 201 arranged at both ends of the cell stack 200 in the stacking direction Z. In the cell stack 200, interconnectors 202, frames 203, and current collectors 204 are arranged between the electrochemical cells 2, and the electrochemical cells 2 are electrically connected to each other via the interconnectors 202, frames 203, and current collectors 204. In addition, a gas seal 205 that suppresses leakage of gas to the outside is provided on the outer periphery of the cell stack 200. Note that in the cell stack 200 shown in FIG. 7 , some of the electrochemical cells 2 and the like are omitted.

[0023] The cell stack 200 has a manifold section 18 that connects the electrochemical cell 2 to the first supply flow path 51 and also connects the electrochemical cell 2 to the first exhaust flow path 53. The manifold section 18 has a supply gas distribution flow path 181 that is a flow path for supplying the first gas SG from the first supply flow path 51 to the electrochemical cell 2. The manifold section 18 also has an exhaust gas distribution flow path 182 that is a flow path for discharging the gas EG discharged from the electrochemical cell 2 to the first exhaust flow path 53.

[0024] The cell control system 1 also includes a temperature measurement unit (not shown) that measures or estimates the temperature T of the electrochemical cell 2. Information about the temperature T measured or estimated by the temperature measurement unit is transmitted to the control unit 6. The temperature measurement unit can be, for example, a thermocouple or a resistance temperature detector. The temperature measurement unit can be configured to directly measure the temperature T of the electrochemical cell 2, or can be configured to estimate the temperature T by measuring the temperature of the manifold unit 18. The temperature measurement unit can also use, for example, the temperature measuring device described in JP 2022-185259 A.

[0025] In this embodiment, the cell control system 1 includes a gas temperature measurement unit (not shown) that measures the temperature of the gas supplied to the electrochemical cell 2 or the gas discharged from the electrochemical cell 2. The cell control system 1 also includes a gas pressure measurement unit (not shown) that measures the pressure of the gas supplied to the electrochemical cell 2 or the gas discharged from the electrochemical cell 2. The gas temperature measurement unit and the gas pressure measurement unit can be provided, for example, between the steam generator 56 and the supply gas flow passage 181 of the manifold unit 18. The gas temperature measurement unit or the gas pressure measurement unit can measure, for example, the temperature or pressure of the first gas flowing through the supply gas flow passage 181. The gas temperature measurement unit can also estimate the temperature of the first gas or the temperature T of the electrochemical cell 2 by measuring, for example, the temperature of the gas in the exhaust gas flow passage 182 or the first exhaust flow passage 53. The gas temperature measurement unit can also measure, for example, the temperature of the gas flowing through the first supply flow passage 51 or the supply gas flow passage 181, and use the measured temperature as a representative temperature for the temperature T of the electrochemical cell 2. In other words, the gas temperature measurement unit can also be a temperature measurement unit that estimates the temperature T of the electrochemical cell 2.

[0026] Next, the electrolysis of water vapor in the electrochemical cell 2 will be described. In this embodiment, the water vapor supplied to the electrochemical cell 2 is converted into "H2O+2e - →H2+O 2- In addition, in the second electrode layer 22, electrolysis of "O 2- →1 / 2O2+2e - That is, in the first electrode layer 21, water vapor is electrolyzed to produce hydrogen gas and oxide ions (O 2- ) occurs. The oxide ions pass through the electrolyte layer 23 and the like to move toward the second electrode layer 22, where they are oxidized to form oxygen gas, which is then discharged to the second discharge flow path 54. The hydrogen gas produced by this electrolytic reaction is discharged to the first discharge flow path 53. In addition, the first electrode layer 21 and the second electrode layer 22 each contain a catalyst for promoting the reaction in the respective layers 20.

[0027] In this embodiment, the first electrode layer 21 has electron conductivity and a porous structure. The first electrode layer 21 can be made of, for example, a material such as a metal or a metal compound. In this embodiment, the first electrode layer 21 is a cerium-containing layer 3. The first electrode layer 21 also contains Ni (i.e., nickel) as a catalyst. The first electrode layer 21 can be made, for example, mainly of ceria containing Ni and doped with 10 mol % Gd (i.e., gadolinium) (hereinafter referred to as Ni-10GDC). The first electrode layer 21 can also be made, for example, mainly of ceria containing Ni and doped with Sm (i.e., samarium) (hereinafter referred to as Ni-SDC). The first electrode layer 21 can also be made, for example, mainly of lanthanum strontium cobalt oxide (hereinafter referred to as LSC). In this embodiment, the first electrode layer 21 is made mainly of Ni-10GDC.

[0028] The electrochemical cell 2 has a support layer 25 provided on the first electrode layer 21 on the side opposite to the electrolyte layer 23. The support layer 25 is a cerium-containing layer 3. The support layer 25 is a layer 20 for supporting the electrochemical cell 2 and has a porous structure. The support layer 25 has a higher porosity than the first electrode layer 21. The support layer 25 can be made of a material such as a metal or a metal compound. The support layer 25 is electronically conductive and contains Ni as an electronic conductor. The support layer 25 can be made mainly of Ni-10GDC, for example.

[0029] The second electrode layer 22 has both electronic conductivity and oxygen ion conductivity. The second electrode layer 22 has a porous structure. The second electrode layer 22 can be made of, for example, a metal, a metal compound, or other material. The second electrode layer 22 can contain, for example, at least one of Ce (i.e., cerium) and La (i.e., lanthanum). The second electrode layer 22 can be made primarily of, for example, Gd-doped ceria (hereinafter referred to as GDC), LSC, or lanthanum strontium cobalt ferrite (hereinafter referred to as LSCF). The second electrode layer 22 can also be a composite containing both GDC and LSC.

[0030] The electrolyte layer 23 has oxygen ion conductivity. In this embodiment, the electrolyte layer 23 is a cerium-containing layer 3. The electrolyte layer 23 may be made mainly of, for example, ceria doped with 10 mol % Gd (hereinafter referred to as 10GDC). The electrolyte layer 23 may also be made mainly of, for example, ceria doped with Sm (hereinafter referred to as SDC). In this embodiment, the electrolyte layer 23 is made mainly of 10GDC.

[0031] The electrochemical cell 2 also has a leak prevention layer 71 that has oxygen ion conductivity but no electron conductivity. The leak prevention layer 71 is stacked adjacent to the electrolyte layer 23. The leak prevention layer 71 may be made mainly of yttria-stabilized zirconia (hereinafter referred to as 8YSZ) containing 8 mol % Y2O3 (i.e., yttrium oxide), for example.

[0032] An intermediate layer 72 is laminated on the second side Z2 of the leak prevention layer 71. The intermediate layer 72 is a layer 20 that suppresses a reaction between components contained in the leak prevention layer 71 and components contained in the second electrode layer 22, thereby suppressing an increase in resistance of the electrochemical cell 2. In this embodiment, the intermediate layer 72 suppresses a reaction between Sr (i.e., strontium) contained in the second electrode layer 22 and Zr (i.e., zirconium) contained in the leak prevention layer 71. The intermediate layer 72 has oxygen ion conductivity. The intermediate layer 72 can be made mainly of, for example, 10GDC or SDC.

[0033] At least one cerium-containing layer 3 may be doped with an element having a valence different from that of cerium. The element doped into the cerium-containing layer 3 may be, for example, Zn (i.e., zinc), Mg (i.e., magnesium), Ca (i.e., calcium), or Co (i.e., cobalt). The support layer 25, first electrode layer 21, and electrolyte layer 23, which are the cerium-containing layer 3, may contain, for example, at least one of Zn, Mg, Ca, and Co.

[0034] Furthermore, the first electrode layer 21 is disposed adjacent to the first side Z1 of the electrolyte layer 23, and the support layer 25 is disposed adjacent to the first side Z1 of the first electrode layer 21. Furthermore, the leak prevention layer 71 is disposed adjacent to the second side Z2 of the electrolyte layer 23, and the intermediate layer 72 is disposed adjacent to the second side Z2 of the leak prevention layer 71. Furthermore, the second electrode layer 22 is disposed adjacent to the second side Z2 of the intermediate layer 72. In this embodiment, the electrochemical cell 2 has six layers 20.

[0035] Next, the control of the electrochemical cell 2 by the control unit 6 will be described. The control unit 6 controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress of each layer 20, the load applied to each layer 20, and the strain of each layer 20 is equal to or less than a predetermined value when the electrochemical cell 2 is operating, during the reduction process described below, or when the electrochemical cell 2 is switched from an operating state to a stopped state.

[0036] The control unit 6 controls the temperature adjustment unit based on the temperature T measured or estimated by the temperature measurement unit, thereby adjusting the temperature T to a desired temperature. The control unit 6 can also calculate the oxygen partial pressure PO2 based on, for example, the temperature T, the temperature and pressure of the first gas, and the ratio of the partial pressure of water vapor to the partial pressure of hydrogen gas in the first gas. Specifically, the oxygen partial pressure PO2 can be calculated using, for example, the formula described in Non-Patent Document 1 below.

[0037] Non-patent literature 1: Hiroshi Amezawa, 9th series "Fundamentals and measurement methods of solid electrolytes 2" -Oxide ion conductors-, Electrochemistry, 85(4), 208-214 (2017)

[0038] In this embodiment, the control unit 6 adjusts the partial pressure of hydrogen gas and the partial pressure of water vapor in the first gas by controlling the flow rate adjuster 551, the flow rate adjuster 561, and the water vapor generator 56 shown in FIG. 1 . That is, the control unit 6 can control the oxygen partial pressure P02 by adjusting the ratio of the partial pressure of water vapor to the partial pressure of hydrogen gas in the first gas. Furthermore, the support layer 25, the first electrode layer 21, and the electrolyte layer 23 are exposed to the water vapor and hydrogen gas contained in the first gas. That is, the first gas is also a gas that forms the atmosphere of the support layer 25, the first electrode layer 21, and the electrolyte layer 23.

[0039] Δε m is the strain amount of the m-th layer 20 calculated based on the temperature T and the oxygen partial pressure PO2, and b m is the width of the m-th layer 20, and t m is the thickness of the mth layer 20, and I m is the second moment of area of ​​the m-th layer 20, and E m is the longitudinal elastic modulus of the m-th layer 20. m is the Poisson's ratio of the m-th layer 20, and P m is the load in the direction perpendicular to the cross section along the thickness direction of the m-th layer 20, ρ is the radius of curvature of the electrochemical cell 2 as shown in FIG. 6, and σ m is the stress of the m-th layer 20. Also, as shown in FIG.m is defined as the distance from the reference end face 24 to the center of the m-th layer 20 in the stacking direction Z. The reference end face 24 is an end face on one side of the electrochemical cell 2 in the stacking direction Z, and is an end face on the first electrode layer 21 side of the electrolyte layer 23. At this time, the control unit 6 controls the temperature T and the oxygen partial pressure PO2 based on the following formulas (1) to (3).

[0040]

number

[0041]

number

[0042]

number

[0043] In formulas (1) to (3), m is an integer from 1 to n, and in formula (1), n ​​is an integer and also the total number of layers 20. In this embodiment, the electrochemical cell 2 has six layers 20, so the total number n is 6.

[0044] In this embodiment, the layer 20 closest to the first side Z1 is the first layer 20, and the layer 20 closest to the second side Z2 is the sixth layer 20. That is, the first layer 20 is the support layer 25, the second layer 20 is the first electrode layer 21, the third layer 20 is the electrolyte layer 23, the fourth layer 20 is the leak prevention layer 71, the fifth layer 20 is the intermediate layer 72, and the sixth layer 20 is the second electrode layer 22. Also, in this embodiment, the reference end surface 24 is the end surface of the support layer 25 on the second side Z2.

[0045] Strain amount Δε mcan be calculated by, for example, measuring the amount of strain change in each layer 20 when the temperature and the oxygen partial pressure of the atmosphere are changed relative to air using a dilatometer, and creating a map or a calculation formula using data showing the relationship between the temperature, oxygen partial pressure, and the amount of strain change. That is, for example, a portion of each layer 20 is taken out as a sample, or a sample made of the same material as the material constituting each layer 20 is created, and the amount of strain change is measured while changing the temperature of the sample and the oxygen partial pressure of the atmosphere surrounding the sample. Then, based on the measurement data, a map or a calculation formula showing the relationship between the temperature of the sample, the oxygen partial pressure of the atmosphere surrounding the sample, and the amount of strain change can be created, thereby determining the amount of strain Δε. m In this case, the length of the sample that serves as a reference for the amount of strain displacement can be, for example, the length of the sample when the atmosphere is air.

[0046] That is, as will be described in Experimental Example 1 below, the control unit 6 determines the strain amount Δε of each layer 20 based on the temperature T and the oxygen partial pressure of the gas to which each layer 20 is exposed. m Then, the strain amount Δε m and the thickness t of each layer 20 m By using the above information and calculating the above formulas (1) and (3), the load P of each layer 20 is calculated. m The curvature radius ρ can be calculated by the above equations (1) and (3). m By calculating the above formula (2) using the radius of curvature ρ and the like, the stress σ of each layer 20 can be calculated. m can be calculated.

[0047] Also, width b m is the maximum width of each layer 20 as shown in FIG.

[0048] In addition, the thickness t of each layer 20 m 3, is also the length of each layer 20 in the stacking direction Z. The thickness t1 of the support layer 25 can be set to, for example, 50 to 1000 μm. In this embodiment, the thickness t1 is 360 μm.

[0049] The thickness t2 of the first electrode layer 21 can be set to, for example, 15 to 40 μm. In this embodiment, the thickness t2 is 25 μm.

[0050] The thickness t3 of the electrolyte layer 23, the thickness t4 of the leak prevention layer 71, and the thickness t5 of the intermediate layer 72 can each be set to, for example, 0.2 to 10 μm. The total thickness of the electrolyte layer 23, the leak prevention layer 71, and the intermediate layer 72 can be set to, for example, 6 to 12 μm.

[0051] The thickness t6 of the second electrode layer 22 can be set to, for example, 0.2 to 10 μm.

[0052] Also, the second moment of area I m is the second moment of area of ​​a cross section obtained by cutting each layer 20 in the thickness direction.

[0053] In this embodiment, the stacking direction Z is also the thickness direction of each layer 20. m As shown in FIG. 5, the load P is also a load in a direction perpendicular to the cross section 29 of each layer 20 in the stacking direction Z. m is the load generated by the expansion of the cerium-containing layer 3 due to changes in temperature T and oxygen partial pressure PO2.

[0054] As shown in Fig. 6, the radius of curvature ρ is the radius of curvature of a curve NA indicating the neutral axis of the electrochemical cell 2 in a cross section taken along the stacking direction Z of the electrochemical cell 2. For ease of explanation of the radius of curvature ρ, Fig. 6 emphasizes the electrochemical cell 2 in which the cerium-containing layer 3 has expanded and become distorted due to the relatively low oxygen partial pressure PO2.

[0055] Also, σ b,m is the breaking strength of the m-th layer 20, and S m is the safety factor of the m-th layer 20. In this case, the safety factor S m can be calculated using the following formula (4). In other words, the safety factor S m When is greater than 1, the breaking strength σ b,m is the stress σ mSince the breaking strength σ of each layer 20 exceeds σ, damage and deterioration of the m-th layer 20 can be suppressed. b,m can be obtained, for example, by performing a destructive test on a test piece made in advance from a material having the same composition as the material constituting each layer 20, or a test piece obtained by removing unnecessary layers 20 other than the layer 20 to be measured from the electrochemical cell 2. Specifically, the breaking strength σ of each layer 20 b,m can be determined by, for example, a four-point bending test in accordance with JIS R 1601:2008 or a test using the small punch method. In addition, in the case of a thin film layer 20 such as the electrolyte layer 23, the leak prevention layer 71, or the intermediate layer 72, the breaking strength σ b,m For example, as described in Non-Patent Document 2 below, the strength at fracture determined by a micro-strength test using a FIB-SEM (Focused Ion Beam-Scanning Electron Microscope) can also be used.

[0056]

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[0057] Non-patent document 2: M. Muramoto et al., Deformation behavior and bending strength of single crystal 8 mol% yttria-stabilized zirconia at microscopic scale, Journal of the European Ceramic Society, 44, 2, 1061-1069 (2024)

[0058] In this embodiment, the control unit 6 controls the temperature T and the oxygen partial pressure PO2 so that they fall within the control region CR shown in the graph of Fig. 8. In the graph of Fig. 8, the region above the curve L1 shown by the solid line is the region of the temperature T and the oxygen partial pressure PO2 where the safety factor is greater than 1, and the region above the curve L2 shown by the dashed-dotted line is the region where Ni contained in the first electrode layer 21 oxidizes. In addition, the region to the right of the straight line L3 shown by the dashed-two-dot line is the region where hydrogen gas self-combusts. The control region CR is the region surrounded by the curves L1, L2, and L3. In this embodiment, the curve L1 is the region where the temperature T and the oxygen partial pressure PO2 are within the control region CR with the lowest safety factor S among the plurality of layers 20. m 1 is a curve showing the temperature T and the oxygen partial pressure PO2 at which the safety factor S5 of the intermediate layer 72, where the temperature T is low, becomes 1. The curve L2 is obtained from the Ellingham diagram.

[0059] Furthermore, the cell control system 1 of this embodiment performs a reduction step of reducing the catalyst contained in the first electrode layer 21 by supplying a gas containing a reducing gas to the first electrode layer 21 before operating the electrochemical cell 2. The control unit 6 controls the temperature T during the reduction step so that it is lower than the temperature T during operation of the electrochemical cell 2.

[0060] In this embodiment, as described above, the first electrode layer 21 contains Ni as a catalyst. In this embodiment, when the electrochemical cell 2 is manufactured, the first electrode layer 21 is formed using a material containing nickel oxide powder. Therefore, before the electrochemical cell 2 is operated, the first electrode layer 21 contains nickel oxide. Therefore, before the electrochemical cell 2 is operated, a reduction step is performed to reduce the nickel oxide contained in the first electrode layer 21 to Ni having catalytic activity.

[0061] The gas supplied to the first electrode layer 21 in the reduction step has a higher proportion of reducing gas than the gas supplied to the first electrode layer 21 during operation. After the reduction step, before raising the temperature of the electrochemical cell 2 to the operating temperature T, the control unit 6 controls the proportion of water vapor in the gas supplied to the first electrode layer 21 to be higher than that during the reduction step, thereby increasing the oxygen partial pressure PO2.

[0062] As shown in the graph of FIG. 8, the reduction step is carried out under conditions within the range indicated by the diagonal lines in the control region CR.

[0063] In this embodiment, after the reduction step, the oxygen partial pressure PO2 of the first gas is increased before the temperature T of the electrochemical cell 2 is increased to the operating temperature, thereby allowing the temperature T and the oxygen partial pressure PO2 of the first gas to be raised to the operating temperature T while remaining within the control region CR.

[0064] Next, the effects of this embodiment will be described. In the cell control system 1, the control unit 6 controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress on each layer 20 due to the expansion of cerium contained in the cerium-containing layer 3, the load on each layer 20, and the strain on each layer 20 is kept below a predetermined value. This makes it possible to suppress damage and deterioration of the electrochemical cell 2. As a result, the life of the electrochemical cell 2 can be extended.

[0065] Assume that an electrochemical cell is operated while the cerium-containing layer is exposed to a first gas with a low oxygen partial pressure P O2. In this case, the cerium-containing layer may expand, potentially damaging or deteriorating the electrochemical cell. Specifically, if the oxygen partial pressure P O2 of the first gas to which the cerium-containing layer is exposed is too low, oxygen is removed from the cerium-containing layer. This causes the cerium in the crystalline structure of the cerium-containing layer to change from tetravalent to trivalent, causing the cerium-containing layer to expand. Furthermore, the expansion of the cerium-containing layer based on the oxygen partial pressure P O2 is also affected by the temperature T. Therefore, in the cell control system 1 of this embodiment, the control unit 6 controls the temperature T and the oxygen partial pressure P O2 so that the rupture strength, rupture load, and rupture strain of each layer 20 are less than the respective values. Therefore, by suppressing the expansion of Ce in the crystalline structure of the cerium-containing layer 3, damage and degradation of the electrochemical cell 2 can be suppressed. The layer 20 on the second side Z2 of the electrolyte layer 23 is exposed to the second gas having a relatively high oxygen partial pressure, similar to the atmosphere. Therefore, even if the layer 20 on the second side Z2 of the electrolyte layer 23 contains Ce, it is unlikely to expand due to the oxygen partial pressure of the atmosphere, and is unlikely to cause damage or deterioration to the electrochemical cell 2.

[0066] The control unit 6 controls the temperature T and the oxygen partial pressure PO2 based on the above formulas (1) to (3). This makes it possible to more accurately suppress the expansion of the cerium-containing layer 3, thereby further suppressing damage and deterioration of the electrochemical cell 2. As a result, it is possible to further extend the life of the electrochemical cell 2.

[0067] The control unit 6 calculates the safety factor of each layer 20 constituting the electrochemical cell 2 based on the temperature T, the oxygen partial pressure PO2, and the above formulas (1) to (4). Therefore, for example, a safety factor map can be created using the safety factor of the layer 20 with the lowest safety factor among the layers 20 as a representative value, and operation, reduction step, operation stop, etc. of the electrochemical cell 2 can be performed in a region where the safety factor is greater than 1. Furthermore, by creating this map, a control region CR where the safety factor is greater than 1 can be set in all layers 20. In other words, the safety factor S of each layer 20 can be calculated by the following formula (1). mThe electrochemical cell 2 can be operated, reduced, or stopped while controlling the temperature T and the oxygen partial pressure PO2 so that the safety factor is greater than 1. This further reduces damage and deterioration of the electrochemical cell 2. Note that the layer 20 used as the representative value of the safety factor does not necessarily have to be the cerium-containing layer 3.

[0068] In this embodiment, the control unit 6 controls the temperature T and the oxygen partial pressure PO2 so that they fall within the control region CR. This makes it possible to prevent Ni from being oxidized, and ensure the catalytic activity of the first electrode layer 21 for a long period of time.

[0069] In this embodiment, the electrolyte layer 23 is the cerium-containing layer 3. Thus, even when the electrolyte layer 23 is the cerium-containing layer 3, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed by controlling the temperature T and the oxygen partial pressure P02. Furthermore, in this embodiment, the intermediate layer 72 is subjected to a greater stress due to the expansion of the electrolyte layer 23 than the other layers 20. Therefore, by suppressing the expansion of the electrolyte layer 23 through control of the temperature T and the oxygen partial pressure P02, damage and deterioration of the intermediate layer 72, which is subjected to a relatively greater stress due to the expansion of the electrolyte layer 23, can be sufficiently suppressed.

[0070] The electrochemical cell 2 has a leak prevention layer 71. The leak prevention layer 71 is laminated adjacent to the electrolyte layer 23. Therefore, even if the electrolyte layer 23 is a cerium-containing layer 3, it is possible to suppress electron leakage between the first electrode layer 21 and the second electrode layer 22 via the electrolyte layer 23. That is, for example, during operation, the electrolyte layer is exposed to the first gas with a relatively low oxygen partial pressure PO2, and trivalent Ce in the crystal structure of the electrolyte layer is 3+ If the proportion of SiO 2 increases, electronic conductivity may appear in the electrolyte layer. This may cause a short circuit in the electrolyte layer, resulting in a decrease in the electromotive force of the electrochemical cell. Therefore, the electrochemical cell 2 of this embodiment is provided with the leak prevention layer 71. This can prevent short circuits in the electrolyte layer 23, thereby suppressing a decrease in the electromotive force of the electrochemical cell 2.

[0071] In this embodiment, the support layer 25 is the cerium-containing layer 3. Even when the support layer 25 is the cerium-containing layer 3, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed by controlling the temperature T and the oxygen partial pressure PO2.

[0072] In this embodiment, the first electrode layer 21 is a cerium-containing layer 3. Even when the first electrode layer 21 is a cerium-containing layer 3, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed by controlling the temperature T and the oxygen partial pressure PO2.

[0073] The cell control system 1 of this embodiment performs a reduction step before operating the electrochemical cell 2. The control unit 6 controls the temperature T during the reduction step so that it is lower than the temperature T during operation of the electrochemical cell 2. This allows the reduction step to be performed under conditions where the concentration of the reducing gas is relatively high, i.e., under conditions where the oxygen partial pressure P02 is relatively low, while suppressing expansion of the cerium-containing layer 3. As a result, damage and deterioration of the electrochemical cell 2 due to the reduction step can be sufficiently suppressed, while sintering of Ni contained in the first electrode layer 21 can be easily suppressed, and the catalytic activity of Ni can be sufficiently ensured.

[0074] Furthermore, the control unit 6 controls the reduction step so that the proportion of water vapor contained in the first gas is lower than that during operation. This makes it possible to suppress aggregation of Ni contained in the first electrode layer 21. As a result, it is possible to ensure sufficient catalytic activity of Ni, and therefore sufficient performance of the electrochemical cell 2.

[0075] The gas supplied to the first electrode layer 21 during the reduction process has a higher proportion of reducing gas than the gas supplied to the first electrode layer 21 during operation. After the reduction process, before raising the temperature of the electrochemical cell 2 to the operating temperature T, the control unit 6 controls the oxygen partial pressure P O2 by increasing the proportion of water vapor in the gas supplied to the first electrode layer 21 compared to that during the reduction process. That is, after the reduction process, before raising the temperature T of the electrochemical cell 2 to the operating temperature T, the oxygen partial pressure P O2 of the first gas is first raised. Then, the temperature T and the oxygen partial pressure P O2 of the first gas are raised to the operating temperature T while remaining within the control region CR. If the temperature T were raised after the reduction process before raising the oxygen partial pressure P O2 of the first gas, the temperature T would fall outside the control region CR, potentially preventing sufficient suppression of damage and degradation of the electrochemical cell 2. Therefore, the control unit 6 raises the oxygen partial pressure P O2 of the first gas before raising the temperature T. This allows the process to be shifted from the reduction step to the operation of the electrochemical cell 2 while remaining within the control region CR. As a result, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed. Furthermore, in the reduction step, by increasing the proportion of reducing gas contained in the first gas, the catalyst can be sufficiently reduced. Therefore, the catalytic activity of the first electrode layer 21 can be sufficiently ensured.

[0076] At least one cerium-containing layer 3 may be doped with an element having a different valence from cerium. In this case, expansion due to reduction of Ce contained in the cerium-containing layer 3 can be suppressed. This allows the controllable range of the oxygen partial pressure PO2 during operation or the reduction step to be widened. As a result, control by the control unit 6 during operation or the reduction step can be facilitated. Furthermore, damage and deterioration of the electrochemical cell 2 can be further suppressed.

[0077] As described above, according to this embodiment, it is possible to provide a cell control system 1 that can achieve a longer lifespan.

[0078] In the above-described first embodiment, the cell control system 1 controls the oxygen partial pressure P02 by controlling the flow rate regulator 551, the flow rate regulator 561, and the steam generator 56. However, when the hydrogen supply unit is a reformer, for example, the cell control system can also adjust the oxygen partial pressure P02 by controlling the amount of steam supplied to the reformer. Furthermore, when a bubbling-type vaporizer is used as the steam generator, the oxygen partial pressure P02 can also be controlled by the water temperature in the bubbler.

[0079] The cell control system of the present invention can be applied not only to water electrolysis but also to co-electrolysis. In other words, in addition to controlling the partial pressures of water vapor and hydrogen gas contained in the first gas, the control unit can also control the oxygen partial pressure PO2 of the first gas, for example, by controlling the partial pressures of carbon monoxide, carbon dioxide, water vapor, and hydrogen contained in the first gas. Co-electrolysis is an electrolysis reaction in which water and carbon dioxide are electrolyzed simultaneously, and the reaction "3H2O + CO2 → CO + 3H2 + 2O2" occurs in the electrochemical cell 2. When co-electrolysis is performed, the produced gas containing hydrogen and carbon monoxide can be used, for example, to generate methane.

[0080] (Experimental Example 1) In this example, similar to the electrolyte layer in embodiment 1, a sample containing 10GDC as the main component was used, and the relationship between the oxygen partial pressure and the strain amount Δε was determined while changing the oxygen partial pressure in the sample atmosphere. The strain amount Δε of the sample when the oxygen partial pressure was changed was confirmed using a dilatometer (Netsch, model number: TD5000SE). In this example, the strain amount Δε of the sample was determined using air and a gas with an oxygen partial pressure lower than that of air.

[0081] The graph in Figure 9 shows the relationship between the oxygen partial pressure in the atmosphere around the sample and the amount of expansion, which is the displacement of the sample, when the temperature of the sample is fixed using a dilatometer. O2,1 P O2,2 As shown in the graph in Figure 9, the lower the oxygen partial pressure, the more the sample expands.

[0082] The amount of expansion of the sample when the sample atmosphere is air is set to 0, and the length of the sample in this case is set to the reference length L. The oxygen partial pressure of the sample atmosphere is set to P O2,1 The expansion amount from the reference length L when the sample is heated is defined as the expansion amount λ1, and the oxygen partial pressure in the atmosphere of the sample is defined as P O2,2 When the expansion amount from the reference length L is set as the expansion amount λ2, the oxygen partial pressure is P O2,1 The strain Δε when the oxygen partial pressure is P O2,2 The amount of strain Δε when

[0083] The change in oxygen vacancies Δδ in the crystal of the sample varies depending on the temperature of the sample and the oxygen partial pressure of the sample atmosphere. The relationship between the temperature of a 10GDC sample, the oxygen partial pressure of the sample atmosphere, and the change Δδ can be expressed by the following formulas (5) and (6), based on the content described in Non-Patent Document 3 below. In formulas (5) and (6), T is the sample temperature. In formula (5), ΔG° is the Gibbs energy change, R is the gas constant, PO2 is the oxygen partial pressure of the sample atmosphere, and a is a constant. In formula (6), ΔH is the enthalpy change, and ΔS is the entropy change. In formula (5), the value of a is 115,000 J / mol. In formula (6), the value of enthalpy change ΔH is 435,209 J / mol, and the value of entropy change ΔS is 140.69 J / mol.

[0084]

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[0085]

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[0086] Non-patent document 3: K. Yashiro et al., Mass transport properties of Ce 0.9 Gd 0.1O2d at the surface and in the bulk, Solid State Ionics, 152-153, 469-476 (2002),

[0087] The graph in FIG. 10 shows the experimental relationship between the change in oxygen vacancies Δδ and the strain Δε for a sample made of 10GDC. That is, the graph in FIG. 10 shows the relationship between the change in oxygen vacancies Δδ and the strain Δε when the sample temperature T and the oxygen partial pressure of the sample atmosphere are changed. From the results of the graph in FIG. 10, it can be seen that the larger the change in oxygen vacancies Δδ, the larger the strain Δε. Here, the change in oxygen vacancies Δδ increases as the temperature T increases and as the oxygen partial pressure of the sample atmosphere decreases. Therefore, it can be said that the higher the temperature T, the larger the strain Δε, and the lower the oxygen partial pressure of the sample atmosphere. From these results, it can be said that the cell control system of embodiment 1, which controls the temperature T of the electrochemical cell and the oxygen partial pressure PO2 of the first gas, can suppress damage and degradation of the electrochemical cell by suppressing the strain of each layer.

[0088] (Experimental Example 2) In this example, the relationship between the safety factor and the occurrence of cracks in the layers constituting the electrochemical cell was investigated while changing the temperature T and the oxygen partial pressure P02 using a cell control system having the same basic configuration as in embodiment 1. Also, in this example, the oxygen partial pressure P02 of the first gas was controlled by adjusting the amounts of hydrogen gas, water vapor, and nitrogen gas contained in the first gas.

[0089] When the presence or absence of cracks in the layers constituting the electrochemical cell was investigated, it was confirmed that no cracks were observed when the temperature T and oxygen partial pressure PO2 were controlled so as to fall within the control region CR shown in Figure 8. On the other hand, when the safety factor was controlled to a region lower than 1, cracks were observed in the layers constituting the electrochemical cell, as shown in the cross-sectional photographs of the electrochemical cell in Figures 11 and 12. Specifically, when the temperature T was 800°C and the oxygen partial pressure was 10 -24At this temperature, cracks were observed in the electrolyte layer, the leak prevention layer, and the intermediate layer, as indicated by the arrows CK in Figure 11. In addition, under the condition "B" shown in the graph of Figure 8, where the temperature T was 600°C and the oxygen partial pressure was 10 -34 At a pressure of 1000 kJ / s, cracks were observed in the leak prevention layer, as indicated by the arrow CK in Figure 12. These results indicate that the cell control system of embodiment 1, which adjusts the temperature T and the oxygen partial pressure P02 so that the safety factor is greater than 1, can suppress damage and deterioration of the electrochemical cell by suppressing the expansion of cerium contained in the cerium-containing layer. In this example, the oxygen partial pressure P02 was adjusted by setting the concentration of hydrogen gas contained in the first gas to 5% under condition "A" shown in the graph of Figure 8, and by setting the concentration of hydrogen gas contained in the first gas to 50% under condition "B" shown in the graph of Figure 8.

[0090] (Experimental Example 3) In this example, the stress of each layer of the electrochemical cell 2 is measured using an experimental device 10 shown in FIG. 13, and the measurement results and the stress σ calculated using the above formulas (1) to (3) are compared. m was compared with.

[0091] As shown in FIG. 13 , the experimental apparatus 10 includes a housing 100 for fixing an electrochemical cell 2 therein and a cylindrical heat insulating section 12 equipped with a heat insulating material. The electrochemical cell 2 is fixed so that its first electrode layer faces a first space 101, which is the space inside the heat insulating section 12, and its second electrode layer faces the outside of the housing 100. An annular second space 102 is formed between the heat insulating section 12 and the housing 100. The experimental apparatus 10 also includes a supply pipe 14 for supplying a supply gas G1 containing hydrogen gas to the first space 101. The supply gas G1 supplied to the first space 101 by the supply pipe 14 is supplied to the first electrode layer of the electrochemical cell 2. The second electrode layer faces the outside air. Supplying the supply gas G1 and air to the electrochemical cell 2 enables the electrochemical cell 2 to generate electricity, as in the second embodiment described below. Gas G2 containing a large amount of water vapor generated by power generation in the electrochemical cell 2 flows from the electrochemical cell 2 into the second space 102 and is discharged to the outside through a discharge pipe 15 provided in the housing 100.

[0092] In the experimental apparatus 10, a heating wire 13 for adjusting the temperature T of the electrochemical cell 2 is provided in the heat insulating section 12, etc. The experimental apparatus 10 also has a thermocouple 16 for measuring the temperature T of the electrochemical cell 2. A control section (not shown) controls the heating wire 13 based on the temperature T measured by the thermocouple 16, so that the electrochemical cell 2 reaches a predetermined temperature. In this example, the electrochemical cell 2 is controlled to be 600°C. Furthermore, the supply gas G1 is hydrogen gas diluted with nitrogen gas and supplied through a bubbling type vaporizer so that the oxygen partial pressure reaches a desired value.

[0093] The experimental apparatus 10 further includes an X-ray analyzer 11 (manufactured by Pulstec Industrial Co., Ltd., model number μ-X360). The X-ray analyzer 11 is configured to measure the residual stress of the electrochemical cell 2 by the cos α method.

[0094] The graph in FIG. 14 shows the reduction time of the electrolyte layer and the first electrode layer using a gas and the displacement of the electrolyte layer and the first electrode layer. The graph in FIG. 14 shows the results of an experiment in which the electrolyte layer and the first electrode layer were reduced using a gas with the same oxygen partial pressure as the supply gas G1 of the experimental apparatus 10, and the displacement was measured using a method similar to that of Experimental Example 1. In the experiment shown in FIG. 14, the temperature of each layer was the same as the temperature T in the experiment using the experimental apparatus 10. The lengths of the electrolyte layer and the first electrode layer used as the reference for the displacement in the graph in FIG. 14 are the lengths when the gas to which each layer is exposed is air. A displacement value greater than 0 indicates that the length of the electrolyte layer or the first electrode layer is longer than the reference length due to expansion. On the other hand, a displacement value less than 0 indicates that the length of the electrolyte layer or the first electrode layer is shorter than the reference length due to contraction. As shown in FIG. 14, the displacement of the electrolyte layer and the first electrode layer changes as the reduction time elapses. The displacement of the electrolyte layer gradually increased with the passage of reduction time. The displacement of the first electrode layer gradually decreased due to volume contraction accompanying the reduction reaction from nickel oxide to nickel until approximately 30 minutes of reduction time had elapsed, and then gradually increased due to reduction expansion at 10 GDC.

[0095] The graph in FIG. 15 shows the relationship between the reduction time using the first gas and the residual stress of the intermediate layer and the leak prevention layer. In the graph in FIG. 15, the white circles and white squares represent the measurement results of the residual stress when an experiment was conducted using the experimental apparatus 10 shown in FIG. 13. Since multiple experiments were conducted for each reduction time, error bars are displayed for the experimental results for each reduction time. The white circles and white squares represent the average values ​​of the experimental results for each reduction time. In addition, in the graph in FIG. 15, the black circles and black squares represent the experimental results shown in the graph in FIG. 14 and the stress values ​​calculated using the above formulas (1) to (3). That is, when calculating the stress, the strain amount of each layer was calculated based on the displacement amount measured in the experiment in the graph in FIG. 14. The graph in FIG. 15 shows that the residual stress values ​​obtained by the experiment are close to the stress values ​​calculated using the above formulas (1) to (3). From these results, it can be said that the stress in each layer constituting the electrochemical cell can be accurately estimated by using a map or calculation formula showing the relationship between the temperature T and oxygen partial pressure PO2 and the oxygen partial pressure, temperature, and strain displacement of the atmosphere in each layer, and the above formulas (1) to (3).

[0096] (Experimental Example 4) In this example, as shown in the graphs of FIGS. 16 to 18, the relationship between the temperature T and the oxygen partial pressure PO2 and the safety factor was analyzed using a cell control system having the same basic configuration as in Embodiment 1. The safety factor was calculated using the above formulas (1) to (3). In this example, the electrochemical cell was configured to have only one cerium-containing layer. Specifically, the analysis was performed using only one of the first electrode layer, electrolyte layer, and support layer as the cerium-containing layer. In addition, the graphs of FIGS. 16 to 18 are graphs in which the safety factor of the layer with the lowest safety factor is used as a representative value among the six layers constituting the electrochemical cell. In this example, the safety factor of the intermediate layer is used as a representative value in all of the graphs of FIGS. 16 to 18, and "S" represents the safety factor of the intermediate layer.

[0097] The graph in FIG. 16 shows the results when, among the layers constituting the electrochemical cell, only the first electrode layer is a cerium-containing layer. The graph in FIG. 17 shows the results when, among the layers, only the electrolyte layer is a cerium-containing layer, and the graph in FIG. 18 shows the results when, among the layers, only the support layer 25 is a cerium-containing layer. As shown in the graphs in FIGS. 17 and 18, when the cerium-containing layer is the electrolyte layer or the support layer, there are regions in the analyzed range where the safety factor is 1 or less. On the other hand, as shown in the graph in FIG. 16, when the cerium-containing layer is the first electrode layer, the safety factor is greater than 1 in all analyzed regions. Furthermore, as shown in the graph in FIG. 17, when the cerium-containing layer is the electrolyte layer, the region where the safety factor is 1 or less is larger than when the cerium-containing layer is the support layer, as shown in FIG. 18. From these results, it is inferred that using a cerium-containing layer as the electrolyte layer is more susceptible to damage and degradation of the electrochemical cell than using a cerium-containing layer as the first electrode layer or the support layer. Furthermore, it is presumed that a cerium-containing layer for the support layer is more susceptible to damage and degradation of the electrochemical cell than a cerium-containing layer for the first electrode layer. Therefore, it is presumed that when the support layer and electrolyte layer, among the layers constituting the electrochemical cell, are cerium-containing layers, damage and degradation of the electrochemical cell can be more easily suppressed by controlling the temperature T and the oxygen partial pressure PO2. Furthermore, it is presumed that, particularly when the electrolyte layer is a cerium-containing layer, damage and degradation of the electrochemical cell can be even more easily suppressed by controlling the temperature T and the oxygen partial pressure PO2 with the control unit.

[0098] (Embodiment 2) In this embodiment, as shown in FIGS. 19 and 20, the electrochemical cell 2 functions as a fuel cell.

[0099] In this embodiment, the electrochemical cell 2 is configured to generate electricity by supplying air as a second gas to the second electrode layer 22 and supplying a gas containing hydrogen gas and water vapor as a first gas to the first electrode layer 21. In this embodiment, the electrochemical cell 2 is an SOFC (Solid Oxide Fuel Cell) and is electrically connected to an external load (not shown). In this embodiment, operation of the electrochemical cell 2 means that the electrochemical cell 2 generates electricity using hydrogen gas, which is a reducing gas, and oxygen gas, which is an oxidizing gas.

[0100] In this embodiment, oxygen is reduced in the second electrode layer 22 to generate oxide ions. A reaction occurs in the first electrode layer 21 to generate protons and electrons from hydrogen. The generated electrons then flow to an external load, and the protons react with oxide ions that have migrated from the second electrode layer 22 to the first electrode layer 21 through the electrolyte layer 23 and the like, generating water vapor. The generated water vapor is discharged to the first discharge flow path 53, and the air after oxygen has been consumed by the electrochemical cell 2 is discharged to the second discharge flow path 54. Other aspects are the same as those of embodiment 1. Note that, among the symbols used in embodiment 2 and onwards, the same symbols as those used in the previous embodiments represent the same components, etc. as those in the previous embodiments, unless otherwise specified.

[0101] In this embodiment, the control unit 6 also controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress of each layer 20, the load applied to each layer 20, and the strain of each layer 20 is equal to or less than a predetermined value. Therefore, by suppressing the expansion of cerium contained in the cerium-containing layer 3, damage and deterioration of the electrochemical cell 2 can be suppressed. As a result, the life of the electrochemical cell 2 can be extended. In addition, the same effects as those of the first embodiment are achieved.

[0102] In the above-mentioned embodiments 1 and 2, the safety factor S m is the stress σ m However, the safety factor can also be calculated based on the load and strain on each story.

[0103] The support layer may be made of an Fe-Cr based metal such as Crofer22APU or SUS430.

[0104] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0105] <Other> The features of the present invention are as follows. [Section 1] The electrochemical cell (2) includes a plurality of layers (20) stacked together, the layers including at least a first electrode layer (21), a second electrode layer (22), and an electrolyte layer (23) disposed between the first electrode layer and the second electrode layer, the first electrode layer is the layer to which a reducing gas is supplied or which generates the reducing gas; at least one of the electrolyte layer and the layer located on the first electrode layer side of the electrolyte layer in the stacking direction (Z) of the plurality of layers is a cerium-containing layer (3) containing cerium and having a fluorite-type crystal structure; a control unit (6) that controls a temperature T of the electrochemical cell and an oxygen partial pressure PO2 of a gas supplied to the first electrode layer, The control unit controls the temperature T and the oxygen partial pressure PO2 so that at least one of the stress of each layer, the load on each layer, and the strain of each layer is equal to or less than a predetermined value. [Section 2] Δε m is the strain amount of the m-th layer calculated based on the temperature T and the oxygen partial pressure PO2, and b m Let be the width of the mth layer, and t m is the thickness of the mth layer, and I m is the second moment of area of ​​the mth layer, and E m is the longitudinal elastic modulus of the m-th layer, and ν m Let be the Poisson's ratio of the mth layer, and P mis the load in the direction perpendicular to the cross section along the thickness direction of the mth layer, ρ is the radius of curvature of the electrochemical cell, and σ m Let be the stress of the mth layer, and t' m is the distance from a reference end face (24) that is an end face on one side in the stacking direction of the electrochemical cell and that is on the first electrode layer side with respect to the electrolyte layers to the center of the m-th layer in the stacking direction, Item 2. The cell control system according to item 1, wherein the control unit controls the temperature T and the oxygen partial pressure PO2 based on the following formulas (1) to (3).

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[0106] 1...cell control system, 2...electrochemical cell, 3...cerium-containing layer, 6...controller, 20...layer, 21...first electrode layer, 22...second electrode layer, 23...electrolyte layer, Z...stacking direction

Claims

1. The electrochemical cell (2) includes a plurality of layers (20) stacked together, the layers including at least a first electrode layer (21), a second electrode layer (22), and an electrolyte layer (23) disposed between the first electrode layer and the second electrode layer, the first electrode layer is the layer to which a reducing gas is supplied or which generates the reducing gas; At least one of the electrolyte layer and the layer located on the first electrode layer side of the electrolyte layer in the stacking direction (Z) of the plurality of layers is a cerium-containing layer (3) containing cerium and having a fluorite-type crystal structure, The temperature T of the electrochemical cell and the oxygen partial pressure PO of the gas supplied to the first electrode layer ２ and a control unit (6) for controlling the The control unit controls the temperature T and the oxygen partial pressure PO so that at least one of the stress of each layer, the load applied to each layer, and the strain of each layer is equal to or less than a predetermined value. ２ A cell control system (1) that controls the above.

2. Δε m the temperature T and the oxygen partial pressure PO ２ and b is the strain amount of the m-th layer calculated based on m Let be the width of the mth layer, and t m is the thickness of the mth layer, and I m is the second moment of area of ​​the m-th layer, and E m is the longitudinal elastic modulus of the m-th layer, and v m Let P be the Poisson's ratio of the m-th layer, m is the load in the direction perpendicular to the cross section along the thickness direction of the mth layer, ρ is the radius of curvature of the electrochemical cell, and σ m Let t' be the stress of the mth layer, m is the distance from a reference end face (24) that is an end face on one side in the stacking direction of the electrochemical cell and is on the first electrode layer side with respect to the electrolyte layers to the center of the m-th layer in the stacking direction, The control unit calculates the temperature T and the oxygen partial pressure PO based on the following formulas (1) to (3): ２ The cell control system according to claim 1 , wherein the cell control system controls: [Equation 1] [Equation 2] [Equation 3] In the formulas (1) to (3), m is an integer of 1 to n, and in the formula (1), n ​​is an integer and also the total number of the plurality of layers.

3. The cell control system according to claim 1 or 2, wherein the electrolyte layer is the cerium-containing layer.

4. 4. The cell control system of claim 3, wherein the electrochemical cell has a leak prevention layer (71) that has oxygen ion conductivity but no electron conductivity, and the leak prevention layer is stacked adjacent to the electrolyte layer.

5. 3. The cell control system according to claim 1, wherein the electrochemical cell has a support layer (25) provided on the first electrode layer on a side opposite to the electrolyte layer, and the support layer is the cerium-containing layer.

6. The cell control system according to claim 1 or 2, wherein the first electrode layer is the cerium-containing layer.

7. a reduction step of reducing a catalyst contained in the first electrode layer by supplying a gas containing the reducing gas to the first electrode layer before operation of the electrochemical cell; 3. The cell control system according to claim 1, wherein the control unit controls the temperature T in the reduction step to be lower than the temperature T during operation of the electrochemical cell.

8. the gas supplied to the first electrode layer in the reduction step has a higher proportion of the reducing gas than the gas supplied to the first electrode layer during the operation, After the reduction step, before raising the temperature of the electrochemical cell to the temperature T during operation, the control unit increases the proportion of water vapor in the gas supplied to the first electrode layer to a level higher than that during the reduction step, thereby reducing the oxygen partial pressure PO ２ The cell control system according to claim 7, wherein the control is performed to increase the temperature.

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