Cell control system

Abstract

A cell control system (1) comprises 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 crystal structure. A control unit (6) 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 the stress of each layer (20), the load applied to each layer (20), and / or the strain of each layer (20) is less than or equal to a prescribed value.

Description

Cell Control System CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-084682 filed on May 24, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a cell control system.

[0003] 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.

[0004] Japanese Patent Application Laid-Open No. 2005-243473

[0005] 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 cerium reduction and achieving a longer lifespan.

[0006] The present disclosure aims to provide a cell control system that can achieve a longer life.

[0007] One aspect of the present disclosure includes an electrochemical cell in which a plurality of layers are stacked, the electrochemical cell including at least a first electrode layer, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer, wherein the first electrode layer is a layer to which a reducing gas is supplied or which generates the reducing gas, and at least one of the electrolyte layer and the layer located on the first electrode layer side with respect to the electrolyte layer in a stacking direction of the plurality of layers is a cerium-containing layer containing cerium and having a fluorite-type crystal structure, and wherein a temperature T of the electrochemical cell and an oxygen partial pressure PO of a gas supplied to the first electrode layer are varied. ２ and a control unit that 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 It is in the cell control system that controls the

[0008] In the cell control system, the control unit controls the temperature T and the oxygen partial pressure PO so that at least one of the stress of each layer due to the expansion of cerium contained in the cerium-containing layer, the load applied to each layer, and the strain of each layer is equal to or less than a predetermined value. ２ Therefore, damage and deterioration of the electrochemical cell can be suppressed, resulting in a longer lifespan.

[0009] As described above, according to the above aspects, it is possible to provide a cell control system that can achieve a long life. Note that the reference characters in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present disclosure.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a configuration diagram of a cell control system according to a first embodiment, Fig. 2 is a cross-sectional view of an electrochemical cell according to the first embodiment, and Fig. 3 is a diagram showing the thickness t of each layer according to the first embodiment. m 4 is a cross-sectional view of an electrochemical cell showing the distance t' in embodiment 1. m5 is a cross-sectional view of an electrochemical cell showing the load P of each layer in the first embodiment. m 6 is a cross-sectional view of an electrochemical cell showing the radius of curvature ρ in the first embodiment; FIG. 7 is a cross-sectional view of a cell stack in the first embodiment; FIG. 8 is a graph showing the control region CR of the cell control system in the first embodiment; FIG. 9 is a graph showing the relationship between the oxygen partial pressure and the amount of expansion of the sample in the first experimental example; and FIG. 10 is a graph showing the relationship between the change in oxygen vacancies Δδ in the sample and the amount of distortion Δ ε 11 is a cross-sectional photograph of an electrochemical cell after operation under condition A outside the control region CR in Experimental Example 2, FIG. 12 is a cross-sectional photograph of an electrochemical cell after operation under condition B outside the control region CR in Experimental Example 2, FIG. 13 is a cross-sectional view of an experimental device in Experimental Example 3, FIG. 14 is a graph showing the relationship between reduction time and the displacement amount of the electrolyte layer and the first electrode layer in Experimental Example 3, and FIG. 15 is a graph showing the relationship between reduction time and the residual stress of the intermediate layer and the leak prevention layer in Experimental Example 3. FIG. 16 is a graph showing the relationship between the temperature and the force, FIG. 16 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, FIG. 17 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, FIG. 18 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, FIG. 19 is a configuration diagram of a cell control system in embodiment 2, and FIG. 20 is a cross-sectional view of an electrochemical cell in embodiment 2.

[0011] (Embodiment 1) An embodiment of a cell control system will be described with reference to Figures 1 to 8. As shown in Figure 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 include 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.

[0012] 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.

[0013] 1, the cell control system 1 also includes a control unit 6. The control unit 6 controls the temperature T of the electrochemical cell 2 and the oxygen partial pressure PO of the gas supplied to the first electrode layer 21. ２ The control unit 6 controls the temperature T and the oxygen partial pressure PO 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. ２ Control.

[0014] 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.

[0015] 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 the layer 20 that produces hydrogen gas, which is a reducing gas.

[0016] 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.

[0017] 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 also 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 resupplies it to the reducing gas supply flow path 552.

[0018] 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 connects to the first supply flow path 51. A portion of the hydrogen-containing 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 adjustment unit 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.

[0019] 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.

[0020] 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.

[0021] 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 wire heater, a heat exchanger using cooling water, or the like.

[0022] 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.

[0023] 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 gas leakage 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.

[0024] The cell stack 200 has a manifold portion 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 portion 18 has a supply gas circulation 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 portion 18 also has an exhaust gas circulation 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.

[0025] 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 on 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 Japanese Patent Laid-Open No. 2022-185259.

[0026] 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 measuring unit may be a temperature measuring unit that estimates the temperature T of the electrochemical cell 2 .

[0027] Next, the electrolysis of water vapor in the electrochemical cell 2 will be described. In this embodiment, 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. The first electrode layer 21 and the second electrode layer 22 each contain a catalyst for promoting the reaction in the respective layers 20.

[0028] 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.

[0029] 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 electron conductor. The support layer 25 can be made of, for example, Ni-10GDC as a main component.

[0030] 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, for example, a composite containing both GDC and LSC.

[0031] 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.

[0032] The electrochemical cell 2 also includes 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 is made of, for example, 8 mol % Y. ２ O ３ The main component may be yttria-stabilized zirconia (hereinafter referred to as 8YSZ) containing yttrium oxide (i.e., yttrium oxide).

[0033] 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 may be mainly composed of, for example, 10GDC or SDC.

[0034] At least one cerium-containing layer 3 may be doped with an element having a different valence from cerium. Examples of the element doped into the cerium-containing layer 3 include Zn (i.e., zinc), Mg (i.e., magnesium), Ca (i.e., calcium), and 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 at least one of Zn, Mg, Ca, and Co, for example.

[0035] 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.

[0036] Next, the control of the electrochemical cell 2 by the control unit 6 will be described. During operation of the electrochemical cell 2, during a reduction step described below, and when the electrochemical cell 2 is switched from an operating state to a stopped state, the control unit 6 controls the temperature T and the oxygen partial pressure PO 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. ２ Control.

[0037] 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 also calculates the oxygen partial pressure PO 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. ２ Specifically, the oxygen partial pressure PO ２ can be calculated, for example, by the formula described in Non-Patent Document 1 below.

[0038] Non-patent document 1: Hiroshi Amezawa, 9th series "Fundamentals and measurement methods of solid electrolytes 2" -Oxide ion conductors-, Electrochemistry, 85(4), 208-214 (2017)

[0039] 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 adjustment unit 551, the flow rate adjustment unit 561, and the water vapor generator 56 shown in Fig. 1. In other words, the control unit 6 adjusts the ratio of the partial pressure of water vapor to the partial pressure of hydrogen gas in the first gas to adjust the oxygen partial pressure PO ２ 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.

[0040] Δε m is the temperature T and the oxygen partial pressure PO ２ The strain amount of the m-th layer 20 is calculated based on the following equation: m is the width of the mth layer 20, and as shown in FIG. 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 as shown in FIG. 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 mis 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 with respect to the electrolyte layer 23. At this time, the control unit 6 calculates the temperature T and the oxygen partial pressure PO based on the following formulas (1) to (3): ２ Control.

[0041]

[0042]

[0043]

[0044] 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 the plurality of layers 20. In this embodiment, the electrochemical cell 2 has six layers 20, so the total number n is 6.

[0045] 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. In this embodiment, the reference end surface 24 is the end surface of the support layer 25 on the second side Z2.

[0046] 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 of 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 of 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.

[0047] 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 and the radius of curvature ρ, etc., are used to calculate the above formula (2), and the stress σ of each layer 20 is calculated. m can be calculated.

[0048] Also, width b m is the maximum width of each layer 20 as shown in FIG.

[0049] 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 t of the support layer 25 １ In this embodiment, the thickness t １ is 360 μm.

[0050] Thickness t of the first electrode layer 21２ In this embodiment, the thickness t ２ is 25 μm.

[0051] Thickness t of the electrolyte layer 23 ３ , the thickness t of the leak prevention layer 71 ４ , the thickness t of the intermediate layer 72 ５ The total thickness of the electrolyte layer 23, the leak prevention layer 71, and the intermediate layer 72 may be, for example, 6 to 12 μm.

[0052] Thickness t of the second electrode layer 22 ６ can be, for example, 0.2 to 10 μm.

[0053] In addition, 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.

[0054] 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 temperature T and the oxygen partial pressure PO ２ This is the load generated by the expansion of the cerium-containing layer 3 due to the change in temperature.

[0055] 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 along the stacking direction Z of the electrochemical cell 2. For convenience of explanation of the radius of curvature ρ, Fig. 6 shows the radius of curvature ρ in the case of the electrochemical cell 2, where the oxygen partial pressure PO ２ 1 highlights an electrochemical cell 2 in which the cerium-containing layer 3 has expanded and become distorted due to a relatively low .DELTA..times ...

[0056] 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): 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 on 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.

[0057]

[0058] 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)

[0059] In this embodiment, the control unit 6 controls the temperature T and the oxygen partial pressure PO so that the temperature T and the oxygen partial pressure PO fall within the control region CR shown in the graph of FIG. ２ In the graph of FIG. 8, the area above the curve L1 shown by the solid line is the temperature T and oxygen partial pressure PO at which the safety factor is greater than 1. ２ The region above the curve L2 indicated by the dashed line is the region where Ni contained in the first electrode layer 21 oxidizes. The region to the right of the straight line L3 indicated by the dashed 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 with the lowest safety factor S among the multiple layers 20.m The temperature T and the oxygen partial pressure PO ２ The curve L2 is obtained from the Ellingham diagram.

[0060] Furthermore, the cell control system 1 of this embodiment performs a reduction step before operation of the electrochemical cell 2, in which a gas containing a reducing gas is supplied to the first electrode layer 21 to reduce the catalyst contained in the first electrode layer 21. 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.

[0061] 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.

[0062] 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 increases the proportion of water vapor in the gas supplied to the first electrode layer 21 compared to that during the reduction step, thereby reducing the oxygen partial pressure PO ２ is controlled to increase.

[0063] 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.

[0064] In this embodiment, after the reduction step, before the temperature T of the electrochemical cell 2 is raised to the operating temperature, the oxygen partial pressure PO ２ By increasing the temperature T and the oxygen partial pressure PO of the first gas, ２ The temperature can be raised to the operating temperature T while remaining within the control region CR.

[0065] 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 PO so that at least one of the stress of each layer 20 due to the expansion of cerium contained in the cerium-containing layer 3, the load applied to each layer 20, and the strain of each layer 20 is equal to or less than a predetermined value. ２ Therefore, damage and deterioration of the electrochemical cell 2 can be suppressed, and as a result, the life of the electrochemical cell 2 can be extended.

[0066] If the cerium-containing layer is ２ Assume that the electrochemical cell is operated in a state where it is exposed to a first gas with a low oxygen partial pressure PO. In this case, the cerium-containing layer may expand, which may damage or deteriorate the electrochemical cell. Specifically, when the oxygen partial pressure PO of the first gas to which the cerium-containing layer is exposed is low, ２ If the partial pressure of oxygen PO in the cerium-containing layer is too low, oxygen is taken away from the cerium-containing layer. As a result, the cerium in the crystal structure of the cerium-containing layer changes from tetravalent to trivalent, causing the cerium-containing layer to expand. ２ The expansion based on 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 PO so that the breaking strength, breaking load, and breaking strain of each layer 20 are less than the respective values. ２ Therefore, by suppressing the expansion of Ce in the crystal structure contained in the cerium-containing layer 3, damage and deterioration of the electrochemical cell 2 can be suppressed. The layer 20 on the second side Z2 of the electrolyte layer 23 is the layer 20 that 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 and deterioration of the electrochemical cell 2.

[0067] The control unit 6 calculates the temperature T and the oxygen partial pressure PO based on the above formulas (1) to (3). ２ Therefore, the expansion of the cerium-containing layer 3 can be more accurately suppressed, and damage and deterioration of the electrochemical cell 2 can be further suppressed. As a result, the life span can be further extended.

[0068] The control unit 6 controls the temperature T and the oxygen partial pressure PO２ The safety factor of each layer 20 constituting the electrochemical cell 2 is calculated based on 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 the operation, reduction process, 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 m The temperature T and the oxygen partial pressure PO are set so that ２ The electrochemical cell 2 can be operated, reduced, or stopped while controlling the temperature and humidity. This makes it possible to further suppress 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.

[0069] In this embodiment, the control unit 6 controls the temperature T and the oxygen partial pressure PO so that they fall within the control region CR. ２ Therefore, oxidation of Ni can be suppressed, and the catalytic activity of first electrode layer 21 can be ensured for a long period of time.

[0070] In this embodiment, the electrolyte layer 23 is a cerium-containing layer 3. In this way, even if the electrolyte layer 23 is a cerium-containing layer 3, the temperature T and the oxygen partial pressure PO ２ By controlling the temperature T and the oxygen partial pressure PO, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed. In addition, in this embodiment, the intermediate layer 72 is subjected to a larger stress caused by the expansion of the electrolyte layer 23 than the other layers 20. Therefore, ２ By suppressing the expansion of the electrolyte layer 23 through the control of (1), damage and deterioration of the intermediate layer 72, which is subjected to a relatively large stress due to the expansion of the electrolyte layer 23, can be sufficiently suppressed.

[0071] 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 ２ By exposing the electrolyte layer to a first gas having a relatively low concentration, trivalent Ce in the crystal structure of the electrolyte layer 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 suppress short circuits in the electrolyte layer 23, thereby suppressing a decrease in the electromotive force of the electrochemical cell 2.

[0072] In this embodiment, the support layer 25 is the cerium-containing layer 3. In this way, even if the support layer 25 is the cerium-containing layer 3, the temperature T and the oxygen partial pressure PO ２ By controlling the temperature, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed.

[0073] In this embodiment, the first electrode layer 21 is a cerium-containing layer 3. In this way, even if the first electrode layer 21 is a cerium-containing layer 3, the temperature T and the oxygen partial pressure PO ２ By controlling the temperature, damage and deterioration of the electrochemical cell 2 can be sufficiently suppressed.

[0074] The cell control system 1 of this embodiment performs a reduction step before the operation of the electrochemical cell 2. The control unit 6 controls the temperature T in the reduction step so that it is lower than the temperature T during operation of the electrochemical cell 2. Therefore, while suppressing expansion of the cerium-containing layer 3, the reduction step can be performed under conditions where the concentration of the reducing gas is relatively high, i.e., the oxygen partial pressure PO ２ 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.

[0075] Furthermore, the control unit 6 controls the first gas to have a lower proportion of water vapor in the reduction step than during operation, thereby suppressing aggregation of Ni contained in the first electrode layer 21. As a result, the catalytic activity of Ni can be sufficiently ensured, and the performance of the electrochemical cell 2 can be sufficiently ensured.

[0076] 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 increases the proportion of water vapor in the gas supplied to the first electrode layer 21 compared to that during the reduction step, thereby reducing the oxygen partial pressure PO ２ That is, after the reduction step, before the temperature T of the electrochemical cell 2 is raised to the operating temperature T, the oxygen partial pressure PO of the first gas is first controlled to be increased. ２ Then, the temperature T and the oxygen partial pressure PO of the first gas are increased. ２ The temperature is raised to the operating temperature T while the oxygen partial pressure PO of the first gas is kept within the control region CR. ２ If the temperature T is increased before increasing the oxygen partial pressure PO of the first gas, the temperature T will deviate from the control region CR, and there is a risk that damage and deterioration of the electrochemical cell 2 may not be sufficiently suppressed. Therefore, the control unit 6 adjusts the oxygen partial pressure PO of the first gas before increasing the temperature T. ２ 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 the 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.

[0077] An element having a different valence from cerium may be added as a doping element to at least one cerium-containing layer 3. In this case, expansion due to reduction of Ce contained in the cerium-containing layer 3 can be suppressed. Therefore, the oxygen partial pressure PO ２As a result, control by the control unit 6 during operation and the reduction step can be facilitated. In addition, damage and deterioration of the electrochemical cell 2 can be further suppressed.

[0078] As described above, according to this embodiment, it is possible to provide a cell control system 1 that can achieve a longer life.

[0079] In the first embodiment, the cell control system 1 controls the flow rate adjusting unit 551, the flow rate adjusting unit 561, and the water vapor generating device 56 to adjust the oxygen partial pressure PO ２ However, when the hydrogen supply unit is a reformer, the cell control system controls the amount of steam supplied to the reformer to control the oxygen partial pressure PO ２ In addition, when a bubbling type vaporizer is used as the water vapor generator, the oxygen partial pressure PO can be adjusted by the water temperature in the bubbler. ２ can also be controlled.

[0080] The cell control system of the present disclosure can be applied not only to water electrolysis but also to co-electrolysis. In other words, the control unit controls the partial pressures of water vapor and hydrogen gas contained in the first gas, and also the partial pressures of carbon monoxide, carbon dioxide, water vapor, and hydrogen contained in the first gas, thereby controlling the oxygen partial pressure PO ２ 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 generated gas containing hydrogen and carbon monoxide can be used, for example, to generate methane.

[0081] 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 of 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.

[0082] The graph in Figure 9 shows the relationship between the oxygen partial pressure in the atmosphere of 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 More than P O2,2 As shown in the graph of FIG. 9, it can be seen that the lower the oxygen partial pressure, the more the sample expands.

[0083] 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 expanded is defined as λ1, and the oxygen partial pressure in the atmosphere of the sample is defined as P O2,2 The expansion amount from the reference length L when the oxygen partial pressure is P O2,1 The strain amount Δε when the oxygen partial pressure is P O2,2 The amount of distortion Δε when

[0084] Furthermore, the change in oxygen defects Δδ in the crystal of the sample varies depending on the temperature of the sample and the oxygen partial pressure of the atmosphere of the sample. The relationship between the temperature of a sample made of 10GDC, the oxygen partial pressure of the atmosphere of the sample, and the change Δδ can be expressed by the following formulas (5) and (6), based on the contents described in the following non-patent document 3. In the following formulas (5) and (6), T is the temperature of the sample. In the following formula (5), ΔG° is the Gibbs energy change, R is the gas constant, and PO ２ is the oxygen partial pressure in the atmosphere of the sample, and a is a constant. In the following formula (6), ΔH is the enthalpy change, and ΔS is the entropy change. In the following formula (5), the value of a is 115,000 J / mol, and in the following formula (6), the value of the enthalpy change ΔH is 435,209 J / mol, and the value of the entropy change ΔS is 140.69 J / mol.

[0085]

[0086]

[0087] Non-patent document 3: K. Yashiro et al., Mass transport properties of Ce 0.9 Gd 0.1 O2d at the surface and in the bulk, Solid State Ionics, 152-153, 469-476 (2002),

[0088] The graph in FIG. 10 is a graph showing the relationship between the change in oxygen vacancies Δδ and the strain Δε of a sample made of 10GDC, which was obtained through an experiment. In other words, the graph in FIG. 10 is a graph showing the relationship between the change in oxygen vacancies Δδ and the strain Δε when the temperature T of the sample 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, the larger the strain Δε. From these results, it can be seen that the temperature T of the electrochemical cell and the oxygen partial pressure PO of the first gas ２ The cell control system of the first embodiment, which controls the above, can suppress damage and deterioration of the electrochemical cell by suppressing the amount of strain in each layer.

[0089] (Experimental Example 2) In this example, a cell control system having the same basic configuration as in the first embodiment was used to measure the temperature T and the oxygen partial pressure PO ２ The relationship between the safety factor and the occurrence of cracks in the layers constituting the electrochemical cell was investigated while changing the oxygen partial pressure PO of the first gas. ２ was controlled.

[0090] When the presence or absence of cracks in the layers constituting the electrochemical cell was examined, it was found that the temperature T and the oxygen partial pressure PO ２On 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, under the condition "A" shown in the graph of Figure 8, where the temperature T was 800°C and the oxygen partial pressure was 10 －２４ At this temperature, cracks were observed in the electrolyte layer, the leak prevention layer, and the intermediate layer, as indicated by the arrows CK in Fig. 11. In addition, under the condition "B" shown in the graph of Fig. 8, where the temperature T was 600°C and the oxygen partial pressure was 10 －３４ At this temperature, cracks were observed in the leak prevention layer as shown by the arrow CK in FIG. 12. From these results, it is clear that the temperature T and the oxygen partial pressure PO ２ The cell control system of the first embodiment, which controls the temperature so that the safety factor is greater than 1 by adjusting the temperature, can be said to be able to suppress damage and deterioration of the electrochemical cell by suppressing the expansion of cerium contained in the cerium-containing layer. In this example, the condition "A" shown in the graph of FIG. 8 is that the concentration of hydrogen gas contained in the first gas is 5%, and the condition "B" shown in the graph of FIG. 8 is that the concentration of hydrogen gas contained in the first gas is 50%, thereby reducing the oxygen partial pressure PO ２ was adjusted.

[0091] Experimental Example 3 In this example, the stress of each layer of the electrochemical cell 2 was 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) were compared. m was compared with.

[0092] As shown in FIG. 13 , the experimental apparatus 10 includes a housing 100 for fixing the electrochemical cell 2 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 the discharge pipe 15 provided in the housing 100.

[0093] 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.

[0094] The experimental device 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.

[0095] 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 that serve 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 zero 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 zero 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 the graph 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 of 10 GDC.

[0096] 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 indicate the measurement results of 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 indicate the average values ​​of the experimental results for each reduction time. In addition, the black circles and black squares indicate the experimental results shown in the graph in FIG. 14 and the stress values ​​calculated using the above formulas (1) to (3). In other words, when calculating the stress, the strain amount of each layer was calculated based on the displacement amount measured in the experiment shown 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). These results indicate that the temperature T and oxygen partial pressure PO ２ By using the map or calculation formula showing the relationship between the oxygen partial pressure of the atmosphere, temperature, and strain displacement in each layer, and the above formulas (1) to (3), it can be said that the stress in each layer constituting the electrochemical cell can be accurately estimated.

[0097] Experimental Example 4 In this example, as shown in the graphs of FIGS. 16 to 18, a cell control system having the same basic configuration as in the first embodiment was used to measure the temperature T and the oxygen partial pressure PO ２ The relationship between the safety factor and the safety factor was analyzed. 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 a cerium-containing layer as only one of the first electrode layer, electrolyte layer, and support layer. The graphs in Figures 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 that make up the electrochemical cell. In this example, the safety factor of the intermediate layer is used as a representative value in all of the graphs in Figures 16 to 18, and "S" represents the safety factor of the intermediate layer.

[0098] 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 the electrochemical cell is more susceptible to damage and deterioration when the support layer is made of a cerium-containing layer than when the first electrode layer is made of a cerium-containing layer. Therefore, when the support layer and the electrolyte layer are made of cerium-containing layers, the temperature T and the oxygen partial pressure PO ２ It is estimated that damage and deterioration of the electrochemical cell can be easily suppressed by controlling the temperature T and the oxygen partial pressure PO. In particular, when the electrolyte layer is a cerium-containing layer, the control unit can ２ It is estimated that by controlling the above, damage and deterioration of the electrochemical cell can be more easily suppressed.

[0099] Second Embodiment In this embodiment, as shown in FIGS. 19 and 20, the electrochemical cell 2 functions as a fuel cell.

[0100] 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.

[0101] 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 other layers, generating water vapor. The generated water vapor is discharged to the first discharge flow path 53, and air after oxygen has been consumed by the electrochemical cell 2 is discharged to the second discharge flow path 54. The rest is the same as in embodiment 1. Note that, of the symbols used in embodiment 2 and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components, etc. as in the previous embodiments, unless otherwise specified.

[0102] In this embodiment, the control unit 6 also controls the temperature T and the oxygen partial pressure PO 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. ２ 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.

[0103] In the above-mentioned first and second embodiments, 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.

[0104] The support layer may be made of an Fe-Cr based metal such as Crofer 22APU or SUS430.

[0105] The present disclosure is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the spirit of the present disclosure.

[0106] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0107] <Others> Features of the present disclosure are as follows: [Item 1] An electrochemical cell (2) including a plurality of layers (20) stacked together, the plurality of 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, wherein the first electrode layer is a layer to which a reducing gas is supplied or which generates the reducing gas, and at least one of the electrolyte layer and the layer located on the first electrode layer side relative to the electrolyte layer in a stacking direction (Z) of the plurality of layers is a cerium-containing layer (3) containing cerium and having a fluorite-type crystal structure, wherein a temperature T of the electrochemical cell and an oxygen partial pressure PO of a gas supplied to the first electrode layer are varied. ２ and a control unit (6) for controlling 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 The cell control system (1) controls 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 t be the width of the mth layer, m is the thickness of the mth layer, and I m is the second moment of area of ​​the m-th layer, and E mis 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 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, the control unit calculates the temperature T and the oxygen partial pressure PO based on the following formulas (1) to (3): ２ Item 2. The cell control system according to item 1, which controls the above. In the formulas (1) to (3), m is an integer from 1 to n, and in the formula (1), n ​​is an integer and the total number of the plurality of layers. [Item 3] The cell control system according to Item 1 or 2, wherein the electrolyte layer is the cerium-containing layer. [Item 4] The cell control system according to Item 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. [Item 5] The cell control system according to any one of Items 1 to 4, wherein a support layer (25) is provided on the side of the first electrode layer opposite to the electrolyte layer side, and the support layer is the cerium-containing layer. [Item 6] The cell control system according to any one of Items 1 to 5, wherein the first electrode layer is the cerium-containing layer. [Item 7] The cell control system according to any one of Items 1 to 6, wherein a reduction step is performed before operation of the electrochemical cell, by supplying a gas containing the reducing gas to the first electrode layer, to reduce a catalyst contained in the first electrode layer, and the control unit controls the temperature T in the reduction step to be lower than the temperature T during operation of the electrochemical cell. [Item 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 operation, and the control unit, after the reduction step, and before raising the temperature of the electrochemical cell to the temperature T during operation, increases the proportion of water vapor in the gas supplied to the first electrode layer compared to that during the reduction step, thereby reducing the oxygen partial pressure PO ２ Item 8. The cell control system according to item 7, wherein the cell control system controls the temperature to increase.

Claims

1. An electrochemical cell (2) having a plurality of layers (20) stacked, the plurality of 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, wherein the first electrode layer is a layer to which a reducing gas is supplied or which generates the reducing gas, and at least one of the electrolyte layer and the layer located on the first electrode layer side relative to 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, wherein the temperature T of the electrochemical cell and the oxygen partial pressure PO of the gas supplied to the first electrode layer are controlled by a temperature T of the electrochemical cell and a temperature T of the second electrode layer. ２ and a control unit (6) for controlling 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 t be the width of the mth layer, 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 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, 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: 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. The cell control system according to 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 laminated adjacent to the electrolyte layer.

5. The cell control system according to claim 1 or 2, wherein the electrochemical cell has a support layer (25) on the side of the first electrode layer opposite 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 cell control system as described in claim 1 or 2, wherein, before operation of the electrochemical cell, a reduction step is carried out to reduce a catalyst contained in the first electrode layer by supplying a gas containing the reducing gas to the first electrode layer, and the control unit controls the temperature T during 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, and the control unit, after the reduction step and before raising the temperature of the electrochemical cell to the temperature T during the operation, increases the proportion of water vapor in the gas supplied to the first electrode layer compared to that during the reduction step, thereby reducing the oxygen partial pressure PO ２ The cell control system according to claim 7, wherein the temperature is controlled to increase.

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