Electrochemical apparatus

Abstract

To provide an electrochemical apparatus that suppresses the progression of localized deterioration and easily achieves performance improvements. [Solution] The electrochemical apparatus of the embodiment includes an electrochemical cell in which an electrolyte membrane is sandwiched between a fuel electrode through which fuel electrode gas flows and an oxygen electrode through which oxygen electrode gas flows. The electrochemical apparatus has a fuel electrode side metal plate portion installed on the side of the fuel electrode and a fuel electrode side current collector interposed between the fuel electrode and the fuel electrode side metal plate portion. The fuel electrode side current collector includes at least a first fuel electrode side current collector portion located furthest upstream in the flow direction in which the fuel electrode gas flows between the fuel electrode side metal plate portion and the fuel electrode, and a second fuel electrode side current collector portion located downstream of the first fuel electrode side current collector portion in the flow direction. The porosity X11 of the first fuel electrode side current collector portion and the porosity X12 of the second fuel electrode side current collector portion satisfy the relationship shown in X11 > X12.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to an electrochemical apparatus. [Background technology]

[0002] The electrochemical apparatus has an electrochemical cell configured such that an electrolyte membrane is sandwiched between a fuel electrode and an oxygen electrode. The electrochemical cell is, for example, a solid oxide type electrochemical cell in which the electrolyte membrane is formed of a solid oxide. The solid oxide type electrochemical cell functions as at least one of a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC).

[0003] When a solid oxide electrochemical cell (SOFC) functions as a SOFC, under high operating temperatures (e.g., 600-900°C), the fuel electrode gas (hydrogen, carbon monoxide, hydrocarbons, ammonia, etc.) supplied to the fuel electrode and the oxygen electrode gas (oxygen, air, etc.) supplied to the oxygen electrode react through an electrolyte membrane to generate electrical energy.

[0004] In contrast, when functioning as a SOEC, a solid oxide electrochemical cell undergoes the reverse reaction compared to when functioning as an SOFC. For example, under high operating temperatures (e.g., above 700°C), an electrolysis reaction occurs, and water vapor is electrolyzed into hydrogen and oxygen. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-117699 [Patent Document 2] Japanese Patent Publication No. 2005-346989 [Patent Document 3] Japanese Patent Publication No. 2006-86018 [Patent Document 4] Japanese Patent Publication No. 2011-17055 [Patent Document 5] Japanese Patent Publication No. 2009-26519 [Overview of the project] [Problems that the invention aims to solve]

[0006] The electrochemical apparatus comprises a cell stack in which multiple electrochemical cells are stacked. In the cell stack, each of the multiple electrochemical cells is connected in series via current collectors, separators, etc.

[0007] To improve the efficiency of a cell stack, a large current must flow through the electrochemical cell, and electrochemical reactions must proceed within the cell. However, a large current flowing through an electrochemical cell can sometimes lead to degradation of the cell. Because there is an uneven distribution of current within the electrochemical cell, degradation may occur locally in the areas where a large current flows. As a result, the performance of the electrochemical apparatus may decrease.

[0008] Specifically, the equilibrium potential generated during operation in an electrochemical cell changes with changes in the composition of the fuel electrode gas. For example, when using a solid oxide electrochemical cell (SOEC), the equilibrium potential is lowest upstream where the mole fraction of water vapor in the fuel electrode gas is highest. As the gas moves downstream, it is electrolyzed into hydrogen and oxygen, and the mole fraction of water vapor decreases, causing the equilibrium potential to rise. The current flowing through the electrochemical cell increases in proportion to the overpotential, which is the difference between the applied voltage and the equilibrium potential, and is therefore highest upstream. Thus, in the flow direction of the fuel electrode gas, the upstream portion has a higher current density than the downstream portion, making it more susceptible to performance degradation.

[0009] Therefore, the problem that the present invention aims to solve is to provide an electrochemical apparatus that can easily suppress the progression of localized deterioration and improve performance. [Means for solving the problem]

[0010] The electrochemical apparatus of the embodiment includes an electrochemical cell in which an electrolyte membrane is sandwiched between a fuel electrode through which fuel electrode gas flows and an oxygen electrode through which oxygen electrode gas flows. The electrochemical apparatus has a fuel electrode side metal plate portion installed on the side of the fuel electrode and a fuel electrode side current collector interposed between the fuel electrode and the fuel electrode side metal plate portion. The fuel electrode side current collector includes at least a first fuel electrode side current collector portion located furthest upstream in the flow direction in which the fuel electrode gas flows between the fuel electrode side metal plate portion and the fuel electrode, and a second fuel electrode side current collector portion located downstream of the first fuel electrode side current collector portion in the flow direction. The porosity X11 of the first fuel electrode side current collector portion and the porosity X12 of the second fuel electrode side current collector portion satisfy the relationship shown in (Equation A1) below. X11>X12...(Formula A1) [Brief explanation of the drawing]

[0011] [Figure 1A] Figure 1A is a schematic diagram (side cross-sectional view) showing an example of an electrochemical apparatus 1 according to the embodiment. [Figure 1B] Figure 1B is a schematic diagram (plan view) showing an example of an electrochemical apparatus 1 according to the embodiment. [Figure 1C] Figure 1C is a schematic diagram (plan view) showing an example of an electrochemical apparatus 1 according to the embodiment. [Figure 2A] Figure 2A is a schematic diagram (cross-sectional view) showing the fuel electrode side current collector 21 in the electrochemical apparatus 1 according to this embodiment. [Figure 2B] Figure 2B is a schematic diagram (plan view) showing the fuel electrode side current collector 21 in the electrochemical apparatus 1 according to the embodiment. [Figure 3A] Figure 3A is a line graph illustrating the results of calculations regarding the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in an embodiment of the electrochemical apparatus 1 according to the embodiment. [Figure 3B] Figure 3B is a line graph illustrating the results of calculations regarding the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in a comparative example of the electrochemical apparatus 1 according to the embodiment. [Figure 4A]FIG. 4A is a diagram (cross-sectional view) schematically showing the fuel electrode side current collector 21 in the electrochemical device 1 according to the modified example. [Figure 4B] FIG. 4B is a diagram (plan view) schematically showing the fuel electrode side current collector 21 in the electrochemical device 1 according to the modified example. [Figure 5] FIG. 5 is a line graph illustrating the result of calculating the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in the electrochemical device 1 according to the modified example.

MODE FOR CARRYING OUT THE INVENTION

[0012] [A] Configuration of Electrochemical Device 1 FIGS. 1A, 1B, and 1C are diagrams schematically showing an example of the electrochemical device 1 according to the embodiment.

[0013] In FIG. 1A, the vertical direction is the vertical direction z, the horizontal direction is the first horizontal direction x, and the direction perpendicular to the paper surface is the second horizontal direction y that is orthogonal to the vertical direction z and the first horizontal direction x. FIG. 1A is a side cross-sectional view and shows a portion corresponding to the surface (xz plane) of the Y1 - Y1 portion in FIGS. IB and 1C.

[0014] In FIGS. 1B and 1C, the vertical direction is the second horizontal direction y, the horizontal direction is the first horizontal direction x, and the direction perpendicular to the paper surface is the vertical direction z. FIG. 1B is a plan view with the lower side in the vertical direction z as the line of sight and shows a portion corresponding to the surface (xy plane) of the Z1 - Z1 portion in FIG. 1A. FIG. 1C is a plan view with the upper side in the vertical direction z as the line of sight and shows a portion corresponding to the surface (xy plane) of the Z2 - Z2 portion in FIG. 1A.

[0015] As shown in FIGS. 1A, 1B, and 1C, the electrochemical device 1 has a single cell 2 including an electrochemical cell 10, a fuel electrode side current collector 21, an oxygen electrode side current collector 22, a fuel electrode side separator portion 31 (fuel electrode side metal plate portion), an oxygen electrode side separator portion 32 (oxygen electrode side metal plate portion), and an insulating sealant 40, and is configured to perform at least one of power generation and electrolysis.

[0016] Although not shown in the diagram, the electrochemical apparatus 1 has multiple single cells 2, and the multiple single cells 2 are stacked vertically in the z direction to form a cell stack. The electrochemical cells 10 that make up the single cells 2 are electrically connected in series in the cell stack to increase the power output, etc. The cell stack is sandwiched between a pair of end plates (not shown) in the vertical z direction, and the space between the pair of end plates is tightened using fastening members such as bolts. The cell stack is electrically connected to a pair of busbars (not shown), and is configured to supply current to the cell stack via the pair of busbars when electrolysis is performed, and to extract current via the pair of busbars when power generation is performed.

[0017] In Figure 1A, the fuel electrode separator section 31 and the oxygen electrode separator section 32 are shown as separate components. However, when a cell stack is constructed, they can be, for example, integrated into a single unit. They may also be separate components.

[0018] The following describes each component of the electrochemical apparatus 1 in order.

[0019] [A-1] Electrochemical cell 10 The electrochemical cell 10 is, for example, a rectangular flat plate type and includes an electrolyte membrane 110, a fuel electrode 111, and an oxygen electrode 112, with the electrolyte membrane 110 interposed between the fuel electrode 111 and the oxygen electrode 112. Here, the electrochemical cell 10 is, for example, a fuel electrode-supported type (hydrogen electrode-supported type), in which the electrolyte membrane 110 and the oxygen electrode 112 are sequentially stacked on the upper surface of the fuel electrode 111, which functions as a support (see Figure 1A). The electrochemical cell 10 may be of a type other than the fuel electrode-supported type (for example, an electrolyte-supported type), and may also have a shape other than a flat plate type (such as a cylindrical shape).

[0020] In the electrochemical cell 10, the electrolyte membrane 110 contains oxide ions (O 2-It is formed of an ion-conducting solid oxide (for example, yttria-stabilized zirconia (YSZ)) that allows the electrolyte to permeate. The electrolyte membrane 110 is configured to be denser than the fuel electrode 111 and the oxygen electrode 112.

[0021] In the electrochemical cell 10, the fuel electrode 111 is composed of a porous electrical conductor (for example, a cermet formed using nickel particles and ceramic particles such as YSZ).

[0022] In the electrochemical cell 10, the oxygen electrode 112 is composed of a porous electrical conductor (such as a perovskite oxide like LaSrMnO3).

[0023] In the electrolyte membrane 110, the region R10 sandwiched between the fuel electrode 111 and the oxygen electrode 112 is, for example, rectangular in shape, and when the electrochemical cell 10 functions as an SOFC or SOEC, oxide ions (O) are present inside the region R10. 2- ) moves.

[0024] [A-2] Fuel electrode side current collector 21 and oxygen electrode side current collector 22 The fuel electrode side current collector 21 is provided on the lower surface of the fuel electrode 111 that constitutes the electrochemical cell 10. The fuel electrode side current collector 21 has a porous structure and is configured to allow the fuel electrode gas G1 consumed or generated in the fuel electrode 111 to permeate and flow through it. The fuel electrode side current collector 21 is made of a metallic material such as nickel, and electrically connects the fuel electrode 111 to the fuel electrode side separator section 31 located below the fuel electrode 111 (see Figure 1A).

[0025] The oxygen electrode side current collector 22 is provided on the upper surface of the oxygen electrode 112 that constitutes the electrochemical cell 10. Similar to the fuel electrode side current collector 21, the oxygen electrode side current collector 22 has a porous structure and is configured to allow oxygen electrode gas consumed or generated at the oxygen electrode 112 to permeate and flow through it. The oxygen electrode side current collector 22 is made of a metallic material such as silver, and electrically connects the oxygen electrode 112 to the oxygen electrode side separator section 32 located above the oxygen electrode 112 (see Figure 1A).

[0026] [A-3] Fuel electrode side separator section 31 The fuel electrode side separator section 31 is made of a conductive material such as metal, and is installed on the side of the electrochemical cell 10 that is on the fuel electrode 111 side (see Figure 1A).

[0027] In this embodiment, the fuel electrode side separator section 31 has a housing space K31. The housing space K31 is formed in the central part of the upper surface of the fuel electrode side separator section 31. The housing space K31 is a recess with a rectangular shape in plan view and is configured to house the fuel electrode side current collector 21 and the electrochemical cell 10. In this case, the housing space K31 houses the electrolyte membrane 110 and the fuel electrode 111 of the electrochemical cell 10.

[0028] In the fuel electrode side separator section 31, the housing space K31 is configured such that when the fuel electrode side current collector 21 and the electrochemical cell 10 are housed in it, a gap is interposed between each side of the fuel electrode side current collector 21 and the electrochemical cell 10 and the side of the housing space K31.

[0029] Furthermore, the fuel electrode side separator section 31 is provided with a fuel electrode gas supply port F311, a fuel electrode gas flow path F31, and a fuel electrode gas outlet F312. The fuel electrode gas G1 supplied from the fuel electrode gas supply port F311 is configured to pass through the fuel electrode gas flow path F31 and then be discharged from the fuel electrode gas outlet F312. Here, the fuel electrode gas flow path F31 is, for example, a straight groove formed on the support surface (bottom surface) that supports the fuel electrode 111 in the containment space K31 (see Figure 1C).

[0030] The fuel electrode gas flow path F31 may be formed in the fuel electrode side current collector 21. Alternatively, the fuel electrode gas flow path F31 may not be formed, and the fuel electrode side current collector 21 may perform the function of the fuel electrode gas flow path F31. In other words, it is sufficient that the fuel electrode gas G1 flows between the fuel electrode side separator section 31 and the fuel electrode 111.

[0031] [A-4] Oxygen electrode side separator section 32 The oxygen electrode side separator section 32, like the fuel electrode side separator section 31, is made of a conductive material such as metal, and is installed on the side of the electrochemical cell 10 that is on the oxygen electrode 112 (see Figure 1A).

[0032] Furthermore, the oxygen electrode side separator section 32 is provided with an oxygen electrode gas supply port F321, an oxygen electrode gas flow path F32, and an oxygen electrode gas outlet F322. The oxygen electrode gas supplied from the oxygen electrode gas supply port F321 is configured to pass through the oxygen electrode gas flow path F32 and then be discharged from the oxygen electrode gas outlet F322. The oxygen electrode gas flow path F32 is provided on the lower surface of the oxygen electrode side separator section 32 that faces the upper surface of the oxygen electrode 112. The oxygen electrode gas flow path F32 is, for example, a straight groove, formed perpendicular to the straight groove that constitutes the fuel electrode gas flow path F31 (see Figure 1B).

[0033] The oxygen electrode gas channel F32 may be formed in the oxygen electrode side current collector 22. Alternatively, the oxygen electrode gas channel F32 may not be formed, and the oxygen electrode side current collector 22 may perform the function of the oxygen electrode gas channel F32. In other words, it is sufficient that the oxygen electrode gas flows between the oxygen electrode side separator section 32 and the oxygen electrode 112.

[0034] [A-5] Insulating sealant 40 The insulating sealant 40 is interposed between the fuel electrode side separator section 31 and the oxygen electrode side separator section 32.

[0035] The insulating seal material 40 is a frame-shaped plate with an opening K40 formed in its central portion, and the oxygen electrode 112 and the oxygen electrode-side current collector 22 are housed inside the opening K40. The insulating seal material 40 also includes a portion that protrudes inward above the housing space K31, and this protruding portion covers the gap and is in contact with the upper surface of the electrolyte membrane 110.

[0036] The insulating sealant 40 is configured to create a sealed state between the fuel electrode side separator section 31 and the oxygen electrode side separator section 32.

[0037] Furthermore, the insulating seal material 40 is configured to provide electrical insulation between the fuel electrode side separator section 31 and the oxygen electrode side separator section 32. It is preferable that the insulating seal material 40 can maintain its insulating performance without dielectric breakdown even when the electrochemical cell 10 is operated for tens of thousands of hours or more.

[0038] [B] Detailed configuration of the fuel electrode side current collector 21 Details of the fuel electrode side current collector 21 of this embodiment will be described.

[0039] Figures 2A and 2B schematically show the fuel electrode side current collector 21 in the electrochemical apparatus 1 according to the embodiment.

[0040] In Figure 2A, the vertical direction is the vertical direction z, the horizontal direction is the second horizontal direction y, and the direction perpendicular to the plane of the paper is the first horizontal direction x. Figure 2A is a cross-sectional view relating to the plane (zy plane) defined by the vertical direction z and the second horizontal direction y. In Figure 2A, the flow direction of the fuel electrode gas G1 is indicated by a thick arrow, with the left side being the upstream UPS and the right side being the downstream DWS.

[0041] In Figure 2B, the vertical direction is the second horizontal direction y, the horizontal direction is the first horizontal direction x, and the direction perpendicular to the plane of the paper is the vertical direction z. Figure 2B is a plan view relating to the plane (xy plane) defined by the second horizontal direction y and the first horizontal direction x. In Figure 2B, as in Figure 2A, the flow direction of the fuel electrode gas G1 is indicated by a thick arrow.

[0042] and As shown in Figures 2A and 2B, the fuel electrode side current collector 21 of this embodiment includes two fuel electrode side current collector sections 211 and 212.

[0043] The fuel electrode side current collector section 211 (first fuel electrode side current collector section) is located in the upstream UPS in the flow direction of the fuel electrode gas G1.

[0044] The fuel electrode side current collector section 212 (second fuel electrode side current collector section) is located adjacent to the downstream DWS of the fuel electrode side current collector section 211 in the flow direction of the fuel electrode gas G1, and is positioned at the furthest downstream DWS.

[0045] In this embodiment, the fuel electrode side current collector 21 is configured such that the porosity is higher in the upstream UPS than in the downstream DWS in the flow direction of the fuel electrode gas G1. Specifically, the porosity X11 of the fuel electrode side current collector 211 located at the most upstream UPS and the porosity X12 of the fuel electrode side current collector 212 located at the most downstream DWS satisfy the relationship shown in (Equation A1) below.

[0046] X11>X12...(Formula A1)

[0047] In the fuel electrode current collector 21, the fuel electrode current collector section 211 and the fuel electrode current collector section 212 can be manufactured by, for example, changing the compressive strength of a mesh-like metal to create differences in their porosity. Porosity is a value measured, for example, by the relationship between volume and weight (effective density).

[0048] Since contact resistance is inversely proportional to the contact area, it is proportional to the porosity. When the porosity of the fuel electrode gas G1 is higher upstream (inlet side) than downstream (outlet side) in the flow direction, as in the case where the relationship shown in (Equation A1) is satisfied, the contact resistance is higher upstream UPS than downstream DWS. For this reason, in this embodiment, the overvoltage, which is the difference between the applied voltage and the equilibrium potential, is reduced in the portion of the fuel electrode gas G1 located upstream UPS in the flow direction compared to the case where the relationship shown in (Equation A1) is not satisfied. As a result, in this embodiment, the current density in the portion of the fuel electrode gas G1 located upstream UPS in the flow direction is reduced compared to the case where the relationship shown in (Equation A1) is not satisfied. Consequently, in this embodiment, the difference between the current density in the portion of the fuel electrode gas G1 located upstream UPS and the current density in the portion located downstream DWS becomes smaller. Therefore, in the electrochemical apparatus 1 of this embodiment, the progression of localized degradation is suppressed, and thus improved performance can be achieved.

[0049] In the fuel electrode side current collector 21, it is preferable that the porosity X11 of the fuel electrode side current collector portion 211 located at the upstream UPS in the fuel electrode side current collector 21 and the porosity X12 of the fuel electrode side current collector portion 212 located at the downstream DWS in the fuel electrode side current collector 21 satisfy the relationship shown in (Equation B1) below. Furthermore, it is preferable that the relationship shown in (Equation B1b) below is also satisfied. If the relationship shown in (Equation B1b) is not satisfied, problems such as local deformation due to extreme differences in rigidity may occur. This makes it possible to easily obtain the above effects.

[0050] 1.2≦X11 / X12 (Formula B1) X11 / X12≦5 (Formula B1b)

[0051] The fuel electrode side current collector 21 preferably satisfies the relationship shown in the following (Equation C1) between the length L1 (= L11 + L12) of the fuel electrode side current collector 21 in the flow direction of the fuel electrode gas G1 and the length L11 of the fuel electrode side current collector portion 211 in the flow direction of the fuel electrode gas G1. Further, it is preferable to satisfy the relationship shown in the following (Equation C1b). If the relationship shown in (Equation C1b) is not satisfied, there is a concern about a decrease in the performance of the cell stack due to an increase in the overall contact resistance, and the meaning of changing the porosity for each region becomes small.

[0052] 0.1 < L11 / L1 ···(Equation C1) L11 / L1 < 0.3 ···(Equation C1b)

[0053] FIG. 3A is a line graph illustrating the result of calculating the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in an example of the electrochemical device 1 according to the embodiment. FIG. 3B is a line graph illustrating the result of calculating the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in a comparative example of the electrochemical device 1 according to the embodiment.

[0054] In FIGS. 3A and 3B, the horizontal axis represents the position in the flow direction of the fuel electrode gas G1, and the positions divided into 10 equal parts from the upstream side to the downstream side are sequentially shown by natural numbers from 1 to 10. The left vertical axis represents the relative porosity, indicating the ratio of the porosity when the lowest porosity in the fuel electrode side current collector 21 is set to 1.0. The right vertical axis represents the current.

[0055] FIGS. 3A and 3B show the case where the conditions when the electrochemical cell 10 is operated as an SOEC are as follows. [[ID=?]]· Area Specific Resistance (ASR) of the electrochemical cell 10: 0.6 Ω·cm 2 [[ID=?]]· Area of the electrochemical cell 10: 9 cm × 9 cm = 81 cm 2 [[ID=?]]· Current density (average value) of the electrochemical cell 10: 0.5 A / cm 2 It seems there is an error in the original text where the unit for the area of the electrochemical cell in line should likely be \(cm^2\) instead of \(cm\). This has been noted in the translation with a "?".(Current: 0.5×81=40.5A) • Mole fraction of water vapor contained in fuel electrode gas G1 (inlet): 95% • Mole fraction of water vapor contained in fuel electrode gas G1 (outlet): Approximately 20%

[0056] Figure 3A illustrates a case where the fuel electrode side current collector 21 has the following relationship between the porosity X11 of the fuel electrode side current collector portion 211 and the porosity X12 of the fuel electrode side current collector portion 212, and also the following relationship between the length L1 of the fuel electrode side current collector 21 and the length L11 of the fuel electrode side current collector portion 211. In other words, Figure 3A shows the case where the relationships shown in (Equation A1), (Equation B1), (Equation C1), etc., are satisfied. In this case, the contact resistance of the fuel electrode side current collector portion 211 is 0.2 Ω·cm 2 Therefore, the contact resistance of the fuel electrode side current collector section 212 is 0.1 Ω·cm. 2 The applied voltage is 1.33V.

[0057] X11 / X12 = 2.0 L11 / L1 = 0.3

[0058] Figure 3B illustrates a case where the porosity of the fuel electrode side current collector 21 is the same as in Figure 3A, except that it is uniform in the flow direction of the fuel electrode gas G1. In other words, Figure 3B shows a case where the relationships shown in (Equation A1), (Equation B1), (Equation C1), etc., are not satisfied, unlike in Figure 3A. In the case of Figure 3B, the porosity of the fuel electrode side current collector 21 is the same as the porosity of the fuel electrode side current collector portion 211 in the case of Figure 3A. In this case, the contact resistance of the fuel electrode side current collector 21 is 0.1 Ω·cm 2 The applied voltage is 1.32V.

[0059] As shown in Figure 3A, in embodiments that satisfy the relationship shown in (Equation A1), etc., the difference in current in the flow direction of the fuel electrode gas G1 is approximately 1.5A, and the ratio of the upstream current to the downstream current is approximately 1.45.

[0060] In contrast, as shown in Figure 3B, in the case of a comparative example that does not satisfy the relationship shown in (Equation A1), etc., the difference in current in the flow direction of the fuel electrode gas G1 is approximately 2.2A, and the ratio of the upstream current to the downstream current is approximately 1.7.

[0061] As can be seen from these results, in the case of the embodiment described above (Figure 3A), the difference in current in the flow direction of the fuel electrode gas G1 is reduced to approximately 85% compared to the comparative example (Figure 3B), and the current in the flow direction of the fuel electrode gas G1 becomes uniform. Therefore, in the embodiment described above, the progression of localized deterioration is suppressed, and performance improvement can be easily achieved.

[0062] [C] Variant Figures 4A and 4B schematically show the fuel electrode side current collector 21 in the modified electrochemical apparatus 1.

[0063] Figure 4A shows a similar part to Figure 2A, and Figure 4B shows a similar part to Figure 2B.

[0064] and As shown in Figures 4A and 4B, the fuel electrode side current collector 21 of this modified example differs from that of the above embodiment in that it includes three fuel electrode side current collector sections 211, 212, and 213.

[0065] In the modified fuel electrode current collector 21, the fuel electrode current collector section 211 (first fuel electrode current collector section) is located at the most upstream UPS in the flow direction of the fuel electrode gas G1, and the fuel electrode current collector section 212 is located adjacent to the downstream DWS of the fuel electrode current collector section 211 in the flow direction of the fuel electrode gas G1. The fuel electrode current collector section 213 (second fuel electrode current collector section) is located adjacent to the downstream DWS of the fuel electrode current collector section 212 in the flow direction of the fuel electrode gas G1, and is located at the most downstream DWS in the flow direction of the fuel electrode gas G1.

[0066] Similar to the case of the above embodiment, the fuel electrode side current collector 21 of this modified example is configured such that in the flow direction of the fuel electrode gas G1, the porosity is higher on the upstream side UPS than on the downstream side DWS, and the fuel electrode side current collector portion 211, the fuel electrode side current collector portion 212, and the fuel electrode side current collector portion 213 are formed.

[0067] As can be seen from this modified example, the fuel electrode side current collector 21 may include three or more fuel electrode side current collector portions.

[0068] FIG. 5 is a line graph illustrating the result of calculating the relationship between the porosity of the fuel electrode side current collector 21 and the current flowing through the fuel electrode side current collector 21 in the electrochemical device 1 according to the modified example.

[0069] FIG. 5 shows the result when the calculation is performed under the same conditions as in FIGS. 3A and 3B.

[0070] [[ID=​​​​​​​​​​​​​​​​​​As shown in Figure 5, in this modified example, the relationships shown in (Equation A1), (Equation B1), (Equation C1), etc., are satisfied, the difference in current in the flow direction of the fuel electrode gas G1 is approximately 1.5A, and the ratio of the upstream current to the downstream current is approximately 1.43.

[0073] In contrast, as shown in Figure 3B, in the case of comparative examples that do not satisfy the relationships shown in (Equation A1), (Equation B1), (Equation C1), etc., the difference in current in the flow direction of the fuel electrode gas G1 is approximately 2.2A, and the ratio of the upstream current to the downstream current is approximately 1.7.

[0074] As can be seen from these results, in the case of the embodiment described above (Figure 5), the difference in current in the flow direction of the fuel electrode gas G1 is reduced to approximately 84% compared to the comparative example (Figure 3B), and the current in the flow direction of the fuel electrode gas G1 becomes uniform. Therefore, in this modified example as well, the progression of localized degradation is suppressed, and performance improvement can be easily achieved, similar to the embodiment described above.

[0075] In this modified example, the fuel electrode side current collector 21 is formed such that the porosity decreases sequentially in the flow direction of the fuel electrode gas G1, as in the above embodiment. The fuel electrode side current collector portion 211, the fuel electrode side current collector portion 212, and the fuel electrode side current collector portion 213 are each formed in this manner. As a result, the component ratio of the fuel electrode gas G1 changes in the flow direction of the fuel electrode gas G1 (for example, the mole fraction of water vapor decreases), and the current collection performance increases, so the current distribution is made even more uniform. However, unlike this modified example and the above embodiment, it is not necessary for the porosity to decrease sequentially in the flow direction of the fuel electrode gas G1. For example, the porosity X12a of the fuel electrode side current collector portion 212 may be higher than the porosity X11 of the fuel electrode side current collector portion 211.

[0076] As already explained, grooves may be formed in the fuel electrode side current collector 21 as fuel electrode gas flow paths F31, etc. Even in such cases, it is sufficient that the porosity of the fuel electrode side current collector 21 is configured such that the porosity is as shown in (Equation A1), etc., at the contact surface between the fuel electrode side current collector 21 and the fuel electrode 111 of the electrochemical cell 10, and at the contact surface between the fuel electrode side current collector 21 and the fuel electrode side separator portion 31. In other words, it is sufficient that the fuel electrode side current collector 21 is configured such that the porosity is as shown in (Equation A1), etc., with respect to the portion of the fuel electrode side current collector 21 that contributes to contact resistance.

[0077] <Other> While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0078] 1: Electrochemical apparatus, 2: Single cell, 10: Electrochemical cell, 21: Fuel electrode side current collector, 22: Oxygen electrode side current collector, 31: Fuel electrode side separator section, 32: Oxygen electrode side separator section, 40: Insulating sealant, 110: Electrolyte membrane, 111: Fuel electrode, 112: Oxygen electrode, 211: Fuel electrode side current collector section, F31: Fuel electrode gas flow path, F311: Fuel electrode gas supply port, F312: Fuel electrode gas outlet, F32: Oxygen electrode gas flow path, F321: Oxygen electrode gas supply port, F322: Oxygen electrode gas outlet, G1: Fuel electrode gas, K31: Containment space, K40: Opening

Claims

1. An electrochemical apparatus comprising an electrochemical cell in which an electrolyte membrane is sandwiched between a fuel electrode through which fuel electrode gas flows and an oxygen electrode through which oxygen electrode gas flows, A fuel electrode side metal plate portion is installed on the side of the fuel electrode, A fuel electrode side current collector is interposed between the fuel electrode and the fuel electrode side metal plate portion. It has, The fuel electrode side current collector is The first fuel electrode side current collector is located on the upstream side in the flow direction in which the fuel electrode gas flows between the fuel electrode side metal plate portion and the fuel electrode, A second fuel electrode side current collector is located downstream of the first fuel electrode side current collector in the flow direction, and It includes at least, The porosity X11 of the first fuel electrode side current collector and the porosity X12 of the second fuel electrode side current collector satisfy the relationship shown in (Equation A1) below. Electrochemical apparatus. X11>X12...(Formula A1)

2. The second fuel electrode side current collector section is located furthest downstream in the flow direction, The porosity X11 of the first fuel electrode side current collector and the porosity X12 of the second fuel electrode side current collector satisfy the relationship shown in (Equation B1) below. The electrochemical apparatus according to claim 1. 1.2≦X11 / X12...(Formula B1)

3. The length L1 of the fuel electrode side current collector in the flow direction and the length L11 of the first fuel electrode side current collector portion in the flow direction satisfy the relationship shown in (Equation C1) below. The electrochemical apparatus according to claim 1. 0.1<L11 / L1...(Formula C1)

4. In the aforementioned flow direction, the porosity is configured to be higher upstream than downstream. The electrochemical apparatus according to claim 1.

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