Electrochemical cell stack, hot module, and hydrogen production device

Abstract

To provide an electrochemical cell stack constituted so that a sufficient amount of fuel gas can be made to flow even on the outlet side of a fuel chamber.SOLUTION: An anode current collector 312 of an electrochemical cell stack 1 includes an upper side part side 311c having an upper surface side S1 in contact with an anode layer side 312a, a lower side part side S2 having a lower surface side 312C in contact with an interconnector 313, and a pair of connecting part side 312a and side 312C formed from both side ends of the upper surface side S1 toward the lower surface side S2 so as to connect the upper side part side and the lower side part side. 312b 312b. A protrusion portion side 312A is formed by the upper side portion side 312b and the pair of coupling portion side 312b and side 312A, and an inner space side 312A surrounded by the protrusion portion side A1 and the interconnector 313 is configured such that fuel gas flows from one end to the other end in the depth direction. An opening is formed in the upper surface S1, and the opening ratio in the front half area FA of the upper surface S1 is smaller than the opening ratio in the rear half area RA.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to an electrochemical cell stack, a hot module, and a hydrogen production device. [Background technology]

[0002] An electrochemical cell is a cell that generates gases such as hydrogen and carbon monoxide or generates electricity by utilizing an electrochemical reaction. When generating gases or generating electricity using an electrochemical cell, an electrochemical cell stack is actually used, which is made up of electrochemical cell units stacked together, each of which includes an electrochemical cell, an interconnector, and an anode current collector. Patent Document 1 discloses an electrochemical cell stack made up of a plurality of electrochemical cell units stacked together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 06756549 specification Summary of the Invention

[0004] The electrochemical cell stack is supplied with fuel gas required for the electrochemical reaction. This fuel gas is supplied into a fuel chamber formed within the electrochemical cell stack. As the fuel gas supplied into the fuel chamber flows from the inlet side to the outlet side of the fuel chamber, it is used in the electrochemical reaction that takes place in the anode layer exposed to the fuel chamber. At this time, fuel gas is consumed for the electrochemical reaction from the inlet side of the fuel chamber (upstream side of the fuel gas flow), so there is less fuel gas on the outlet side of the fuel chamber (downstream side of the fuel gas flow), and in some cases there may be a shortage of fuel gas near the outlet of the fuel chamber.

[0005] When the amount of fuel gas at the inlet side of the fuel chamber is large and the amount at the outlet side is small, the electrochemical reaction is promoted near the inlet side of the fuel chamber and suppressed near the outlet side. This imbalance in the reaction causes uneven current density of the current required for the reaction or the current generated by the reaction, resulting in a decrease in the performance of the electrochemical cell.

[0006] The present disclosure aims to solve the above-mentioned problems. That is, one of the objects of the present disclosure is to provide an electrochemical cell stack configured to be able to supply a sufficient amount of fuel gas also to the outlet side of the fuel chamber, a hot module including the electrochemical cell stack, and a hydrogen production device including the hot module.

[0007] The electrochemical cell stack according to the present disclosure is an electrochemical cell stack (1) formed by stacking a plurality of electrochemical cell units (31), each of which includes an electrochemical cell (311) including a solid electrolyte layer (311a), an air electrode layer (311b) stacked on one side of the solid electrolyte layer (311a), and an anode layer (311c) stacked on the other side of the solid electrolyte layer (311a), an anode current collector (312) formed of a conductive metal stacked on the electrochemical cell (311) so as to be in contact with the anode layer (311c), and an interconnector (313) stacked on the electrochemical cell (311) so as to be in contact with the anode current collector (312). The fuel electrode current collector (312) is disposed between the electrochemical cell (311) and the interconnector (313), and includes: a first contact portion (312a) formed along a predetermined first direction (depth direction) perpendicular to the stacking direction of the electrochemical cell unit (31) and in contact with an adjacent fuel electrode layer (311c) in the stacking direction; a second contact portion (312C) formed along the first direction and in contact with an adjacent interconnector (313) in the stacking direction; and a pair of connecting portions (312b, 312b) formed from both end portions of the first contact portion (312a) along the first direction toward the second contact portion (312C) so as to connect the first contact portion (312a) and the second contact portion (312C). Furthermore, the first contact portion (312a) and the pair of connecting portions (312b, 312b) form a protrusion (312A) that protrudes from the second contact portion (312C) and extends in the first direction, and an inner space (A1) surrounded by the protrusion (312A) and the interconnector (313) is configured so that fuel gas flows from one end to the other end in the first direction. An opening is formed in the first contact portion (312a). When the first contact portion (312a) is divided into a front half region (FA) that is a half region including one end and a rear half region (RA) that is a half region including the other end, the opening ratio in the front half region (FA) is smaller than the opening ratio in the rear half region (RA).

[0008] According to the above configuration, fuel gas flowing from one end to the other end of the inner space surrounded by the protrusions and the interconnector contacts the fuel electrode layer through the openings formed in the first contact portion, thereby causing an electrochemical reaction. In this case, one end of the first contact portion is located on the inlet side of the fuel chamber, and the other end is located on the outlet side of the fuel chamber. Furthermore, because the opening ratio in the first half region, which is the half region including one end of the first contact portion, is smaller than the opening ratio in the second half region, which is the half region including the other end, consumption of fuel gas due to the electrochemical reaction at one end of the inner space (the inlet side of the fuel chamber) is suppressed. This allows a sufficient amount of fuel gas to be supplied to the other end of the inner space (the outlet side of the fuel chamber), promoting the electrochemical reaction at the other end of the inner space. This suppresses bias in the electrochemical reaction, thereby suppressing performance degradation of the electrochemical cell.

[0009] In one embodiment of the electrochemical cell stack according to the present disclosure, The first contact portion (312a) has a plurality of openings formed along the first direction, and the total opening area of ​​the openings formed in the front half region (FA) is smaller than the total opening area of ​​the openings formed in the rear half region (RA).

[0010] According to the above configuration, the opening ratio in the front half region of the first contact portion can be made smaller than the opening ratio in the rear half region.

[0011] In another embodiment of the electrochemical cell stack according to the present disclosure, The pitch (D) between the openings formed in the front half area (FA) is larger than the pitch (D) between the openings formed in the rear half area (RA).

[0012] According to the above configuration, by making the number of openings formed in the front half region of the first contact portion smaller than the number of openings formed in the rear half region, the opening ratio in the front half region of the first contact portion can be made smaller than the opening ratio in the rear half region.

[0013] In yet another embodiment of the electrochemical cell stack according to the present disclosure, The opening length (L) of the opening formed in the front half region (FA) is shorter than the opening length (L) of the opening formed in the rear half region (RA). Here, the opening length is the length in the in-plane direction of the opening surface formed in the first contact portion and in a direction parallel to the first direction.

[0014] According to the above configuration, by making the opening length of the opening formed in the front half region of the first contact portion shorter than the opening length of the opening formed in the rear half region, the opening ratio in the front half region of the first contact portion can be made smaller than the opening ratio in the rear half region.

[0015] In yet another embodiment of the electrochemical cell stack according to the present disclosure, The opening width (W) of the opening formed in the front half region (FA) is narrower than the opening width (W) of the opening formed in the rear half region (RA). Here, the opening width is the length in the in-plane direction of the opening surface formed in the first contact portion and in the direction perpendicular to the first direction.

[0016] According to the above configuration, by making the opening width of the opening formed in the front half region of the first contact portion narrower than the opening width of the opening formed in the rear half region, the opening ratio in the front half region of the first contact portion can be made smaller than the opening ratio in the rear half region.

[0017] In yet another embodiment of the electrochemical cell stack according to the present disclosure, A single opening (OPs) is formed in the first contact portion (312a), The single opening (OPs) is formed so that the opening width in the front half region (FA) of the first contact portion (312a) is narrower than the opening width in the rear half region (RA).

[0018] According to the above configuration, by forming a single opening in the first contact portion so that the opening width is narrow in the front half region of the first contact portion and wide in the rear half region, the opening ratio in the front half region of the first contact portion can be made smaller than the opening ratio in the rear half region.

[0019] In yet another embodiment of the electrochemical cell stack according to the present disclosure, No opening is formed in the front half area (FA), and an opening is formed in the rear half area (RA).

[0020] According to the above configuration, by forming the opening only in the rear region of the first contact portion, the opening ratio in the front region of the first contact portion can be made smaller than the opening ratio in the rear region.

[0021] In yet another embodiment of the electrochemical cell stack according to the present disclosure, The anode current collector (312) has a plurality of ridges (312A) arranged parallel to a first direction.

[0022] According to the above configuration, in each of the plurality of protrusions, the opening ratio of the first contact portion in the front half region can be made smaller than the opening ratio in the rear half region.

[0023] In addition, the hot module (7) according to the present disclosure includes an electrochemical cell stack (1) having the above-described configuration, a vaporizer (2) that generates water vapor to be supplied to the electrochemical cell stack (1), heating devices (3, 4) that heat the gas to be supplied to the electrochemical cell stack (1), and a thermal insulator (5) in which the electrochemical cell stack (1), the vaporizer (2), and the heating devices (3, 4) are disposed.

[0024] According to the above configuration, it is possible to provide a hot module including an electrochemical cell stack configured to allow a sufficient amount of fuel gas to flow to the outlet side of the fuel chamber.

[0025] The hydrogen production device (100) according to the present disclosure includes the hot module (7) having the above-described configuration.

[0026] According to the above configuration, it is possible to provide a hydrogen production device equipped with a hot module including an electrochemical cell stack configured to allow a sufficient amount of fuel gas to flow to the outlet side of the fuel chamber. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a block diagram of a hydrogen production device. [Figure 2] FIG. 1 is a schematic perspective view of an electrochemical cell stack. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view of the cell cassette shown in FIG. [Figure 5] FIG. 4 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view of the cell cassette shown in FIG. 5. [Figure 7] FIG. 2 is a cross-sectional view of an anode current collector. [Figure 8] FIG. 6 is a cross-sectional view showing the details of a portion E in FIG. 5. [Figure 9] FIG. 2 is a perspective view of one protrusion and a lower side portion connected to the protrusion of the fuel electrode current collector according to the first embodiment. [Figure 10] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of the fuel electrode current collector according to Modification 1. [Figure 11] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to a second embodiment. [Figure 12] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to Modification 2. [Figure 13] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to a third embodiment. [Figure 14] FIG. 11 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to Modification 3. [Figure 15] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to a fourth embodiment. [Figure 16] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to Modification 4. [Figure 17] FIG. 11 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to a fifth embodiment. [Figure 18] FIG. 13 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to a sixth embodiment. [Figure 19] FIG. 19 is a cross-sectional view taken along line AA in FIG. 18. [Figure 20] FIG. 10 is a perspective view of one protrusion and a lower side portion connected to the protrusion of an anode current collector according to another example. DETAILED DESCRIPTION OF THE INVENTION

[0028] (First embodiment) 1 is a block diagram of a hydrogen production device 100 according to the present disclosure. The hydrogen production device 100 is a device that produces hydrogen by electrolyzing water vapor. As shown in FIG. 1, the hydrogen production device 100 includes a hot module 7 and a condenser 8.

[0029] The hot module 7 is constructed by covering with insulating material the main components that become hot among the elements that make up the hydrogen production device 100, and is a device in which the main components are concentrated within the insulating material so that they can be kept at a high temperature. This hot module 7 includes an electrochemical cell stack 1, a vaporizer 2, a heat exchanger 3, a heater 4, and an insulating material 5.

[0030] As shown in Fig. 1, water (H2O) is supplied to the vaporizer 2. The vaporizer 2 is configured to heat the supplied water to a temperature of 100°C or higher using a heat source. Therefore, the water supplied to the vaporizer 2 evaporates within the vaporizer 2, generating water vapor. The water vapor generated in the vaporizer 2 is supplied to the heat exchanger 3.

[0031] In addition to the water vapor described above, air is supplied to the heat exchanger 3. In addition, high-temperature hydrogen (H2) and high-temperature oxygen (O2) generated in the electrochemical cell stack 1 are supplied to the heat exchanger 3. These high-temperature gases exchange heat with the water vapor and air in the heat exchanger 3, thereby heating (raising the temperature) the water vapor and air supplied from the vaporizer 2 in the heat exchanger 3.

[0032] The water vapor and air heated by the heat exchanger 3 are further heated by the heater 4 to the operating temperature of the electrochemical cell stack 1 (i.e., the temperature required to operate the electrochemical cell stack 1). The water vapor and air are then supplied to the electrochemical cell stack 1. The heat exchanger 3 and the heater 4 are temperature-raising devices for raising the temperature of the gases (water vapor and air) supplied to the electrochemical cell stack 1 to the operating temperature of the electrochemical cell stack 1.

[0033] The electrochemical cell stack 1 is formed by stacking cell cassettes, each including an electrochemical cell unit having a solid oxide electrolysis cell (hereinafter referred to as an electrolysis cell). The electrochemical cell stack 1 is heated to its operating temperature by a heat source (such as a burner), not shown. A predetermined voltage is applied to the electrochemical cell stack 1. As a result, water vapor supplied to the electrochemical cell stack 1 is electrolyzed to produce high-temperature hydrogen and oxygen. The high-temperature hydrogen produced in the electrochemical cell stack 1 is supplied to the heat exchanger 3 together with unreacted water vapor, where it is used to heat the water vapor and air supplied from the vaporizer 2 to the heat exchanger 3, and then introduced into the condenser 8. The unreacted water vapor is condensed in the condenser 8. The condensed water produced in the condenser 8 is supplied to the vaporizer 2. Meanwhile, the hydrogen separated by the condensation of the water vapor in the condenser 8 is recovered. Furthermore, the high-temperature oxygen generated in the electrochemical cell stack 1 is supplied to the heat exchanger 3 and used to heat the water vapor and air, and then supplied to the vaporizer 2 to heat the water to be supplied to the vaporizer 2. The oxygen discharged from the vaporizer 2 is then recovered (or released to the atmosphere).

[0034] The electrochemical cell stack 1, vaporizer 2, heat exchanger 3, and heater 4 are disposed inside a thermal insulation material 5. This suppresses heat radiation from each of the components 1, 2, 3, and 4. Heat-resistant fibers such as ceramic wool, refractory ceramic fiber (RCF), and biosoluble fiber (AES), and / or a heat-resistant container formed from these heat-resistant fibers, can be used for the thermal insulation material 5. The heat-resistant fibers are disposed so as to fill the gaps between the electrochemical cell stack 1, vaporizer 2, heat exchanger 3, and heater 4.

[0035] FIG. 2 is a perspective view of the electrochemical cell stack 1. When directions are used to describe the electrochemical cell stack 1 and its components, the three directions shown in FIG. 2, the up-down direction, the width direction, and the depth direction, are used. The up-down direction, the width direction, and the depth direction are perpendicular to one another. The plane extending in the width direction and the depth direction is a horizontal plane perpendicular to the up-down direction. Furthermore, one side of the depth direction is defined as the front, and the other side is defined as the rear.

[0036] As shown in Fig. 2, the electrochemical cell stack 1 includes a cell cassette group formed by stacking multiple rectangular flat cell cassettes 30 in the vertical direction, an upper insulating plate 20 stacked on the upper surface of the cell cassette group, an upper end plate 10 stacked on the upper surface of the upper insulating plate 20, a terminal plate 40 stacked on the lower surface of the cell cassette group, a lower insulating plate 50 stacked on the lower surface of the terminal plate 40, and a lower end plate 60 stacked on the lower surface of the lower insulating plate 50, and is a laminate formed by stacking these plate-like members in the thickness direction. The thickness direction of each member corresponds to the vertical direction in Fig. 2. Therefore, the above-mentioned members are stacked in the vertical direction.

[0037] Each of the above-mentioned components is formed in a rectangular plate shape with sides aligned in the width and depth directions. The components are fastened to one another by bolts B inserted through the four corners in the stacking direction and nuts (not shown). The upper end plate 10, terminal plate 40, and lower end plate 60 are rectangular flat-plate components that have the same outer shape as the cell cassette 30 when viewed from above and below, and are all made of metal (e.g., stainless steel). A rectangular opening is formed in the center of the upper end plate 10. The upper insulating plate 20 and lower insulating plate 50 also have the same outer shape as the cell cassette 30 when viewed from above and below, and are plate-shaped and made of insulating material, such as mica or resin. For ease of explanation, the proportions of the components in the drawings may differ from their actual proportions.

[0038] Two gas supply passages Pfi, Pai and two gas exhaust passages Pfo, Pao are formed in the stacking direction of the multiple cell cassettes 30, terminal plate 40, lower insulating plate 50, and lower end plate 60 that make up the cell cassette group. The gas supply passage Pfi is formed near one corner of side E1, which is one of the four sides that make up the outer periphery of the electrochemical cell stack 1. The gas exhaust passage Pfo is formed near the other corner of side E2 that faces side E1 (the corner located diagonally from one corner of side E1). The gas supply passage Pai is formed near one corner of side E2, and the gas exhaust passage Pao is formed near the other corner of side E1. The gas supply passage Pfi forms a passage through which water vapor supplied to the electrochemical cell stack 1 passes, and the gas supply passage Pai forms a passage through which air supplied to the electrochemical cell stack 1 passes. The gas exhaust passage Pfo forms a passage through which hydrogen and water vapor discharged from the electrochemical cell stack 1 pass, and the gas exhaust passage Pao forms a passage through which oxygen and air discharged from the electrochemical cell stack 1 pass.

[0039] Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 3 is a cross-sectional view of the electrochemical cell stack 1 cut along the depth direction so as to reveal cross sections of the gas supply passages Pfi and the gas discharge passages Pfo. As shown in Fig. 3, the multiple cell cassettes 30 constituting the cell cassette group are stacked between an upper end plate 10 and a lower end plate 60, with an upper insulating plate 20, a lower insulating plate 50, and a terminal plate 40 interposed therebetween.

[0040] FIG. 4 shows a cross-sectional view of the cell cassette 30 shown in FIG. 3. Note that the gas supply passages Pfi and gas discharge passages Pfo shown in FIG. 3 are omitted in FIG. 4. As shown in FIG. 4, the cell cassette 30 includes an electrochemical cell unit 31, a separator section 32, and a frame section 33. The electrochemical cell unit 31 is a reaction section where an electrochemical reaction takes place, and includes a solid oxide electrolysis cell (hereinafter referred to as an electrolysis cell) as an electrochemical cell. Specifically, the electrochemical cell unit 31 includes an electrolysis cell 311, an anode current collector 312, and an interconnector 313.

[0041] In this embodiment, the electrolysis cell 311 is a plate-like member having a substantially rectangular shape. The electrolysis cell 311 includes a solid electrolyte layer 311a, an air electrode layer 311b stacked on the upper surface (one surface) of the solid electrolyte layer 311a, and an anode layer 311c stacked on the lower surface (other surface) of the solid electrolyte layer 311a, and is formed by stacking these in the thickness direction. The air electrode layer 311b has a smaller outer shape than the solid electrolyte layer 311a and the anode layer 311c, and is located at the center of the upper surface of the solid electrolyte layer 311a in a plan view of the electrolysis cell 311. Therefore, the upper surface of the outer periphery of the solid electrolyte layer 311a is exposed.

[0042] The solid electrolyte layer 311a is a layer made of a solid oxide electrolyte. The solid electrolyte layer 311a is a rectangular flat layer containing YSZ (yttria-stabilized zirconia) and is formed by sintering. The solid electrolyte layer 311a has high oxide ion conductivity. The solid electrolyte layer 311a is a dense layer and is designed so that the atmosphere on the air electrode layer 311b side (air atmosphere) and the atmosphere on the fuel electrode layer 311c side (reducing atmosphere) do not leak into each other through the solid electrolyte layer 311a.

[0043] The air electrode layer 311b is also a rectangular flat layer containing a perovskite oxide such as lanthanum strontium cobalt iron oxide (LSCF) and is formed by sintering. The air electrode layer 311b has a functional layer and a current collecting layer. The current collecting layer is thicker than the functional layer and is disposed on top of the functional layer. The air electrode layer 311b has high electronic conductivity and effectively collects electrons from the current collecting layer. The air electrode layer 311b is a porous layer with pores inside.

[0044] The anode layer 311c is also a rectangular flat layer. The anode layer 311c is formed to be thicker than the solid electrolyte layer 311a and the air cathode layer 311b. The anode layer 311c supports the solid electrolyte layer 311a and the air cathode layer 311b. In other words, the electrolysis cell 311 is an anode-supported electrochemical cell. The outer shape of the anode layer 311c in a plan view matches the outer shape of the solid electrolyte layer 311a. The anode layer 311c also includes an anode functional layer and an anode support layer. The anode support layer is formed to be significantly thicker than the anode functional layer, and the thickness ratio can be set to, for example, approximately 16 to 40 times. The anode functional layer and the anode support layer are stacked on the lower surface of the solid electrolyte layer 311a in this order.

[0045] The anode support layer is primarily composed of a cermet of Ni and YSZ (yttria-stabilized zirconia). The anode support layer is a porous layer configured to have a porous structure containing multiple micropores (not shown). The micropores have a diameter on the order of several micrometers, ensuring water vapor permeability (gas diffusibility). The anode functional layer is also primarily composed of a cermet of Ni and YSZ. Like the anode support layer, the anode functional layer is also a porous layer configured to have a porous structure containing multiple micropores (not shown). The anode functional layer is formed to be denser than the anode support layer. That is, the anode functional layer and the anode support layer are formed so that the porosity of the anode functional layer is smaller than that of the anode support layer. The anode layer 311c is also formed by sintering, similar to the solid electrolyte layer 311a and the air cathode layer 311b. Note that the components of the anode functional layer and the anode support layer are not limited to those described above. For example, the main components of the anode functional layer can be composed of Ni and GDC (gadolinia-doped ceria).

[0046] Anode current collector 312 is a rectangular flat member made of a conductive metal plate, and is stacked below electrolytic cell 311 so as to be in contact with anode layer 311c of electrolytic cell 311. The configuration of anode current collector 312 will be described later.

[0047] The interconnector 313 is a metal (e.g., stainless steel) member having a rectangular, flat main body 313a and a protruding portion 313b protruding downward from the underside of the main body 313a. The protruding portion 313b is formed by a plurality of ridges arranged parallel to one another in a direction perpendicular to the paper surface of Figures 3 and 4 (the width direction). As shown in Figure 3, the interconnector 313 is stacked on the electrolysis cell 311 so that the main body 313a contacts the anode current collector 312 disposed above it, and the protruding portion 313b connects to the air cathode layer 311b of the adjacent electrolysis cell 311 disposed below it.

[0048] The frame section 33 includes an anode frame 331 and a cathode frame 332. The anode frame 331 is a rectangular plate-shaped metal (e.g., stainless steel) member with a rectangular opening formed in its center. The cathode frame 332 is disposed below the anode frame 331. The cathode frame 332 is a rectangular plate-shaped insulating member and may be formed from, for example, a mica sheet. The cathode frame 332 also has a rectangular opening formed in its center, similar to that of the anode frame 331. The shape of the frame section 33 viewed from the top and bottom matches the shapes of the upper end plate 10 and the lower end plate 60.

[0049] As can be seen from FIG. 4 , the electrochemical cell unit 31 is disposed inside an opening formed in the center of the frame part 33. In other words, the frame part 33 is disposed around the electrochemical cell unit 31 so as to surround the outer periphery of the electrochemical cell unit 31. A predetermined gap is formed between the frame part 33 and the electrochemical cell unit 31, and the separator part 32 is disposed to close this gap. The separator part 32 includes a cell-side separator 321 and an interconnector-side separator 322. The cell-side separator 321 is a rectangular plate-shaped metal (e.g., stainless steel) member, and has a rectangular opening formed in its center. The periphery (i.e., inner periphery) of the opening of the cell-side separator 321 is brazed to the upper surface of the outer periphery of the solid electrolyte layer 311a of the electrolysis cell 311 with brazing material (e.g., Ag brazing), not shown. On the other hand, the outer peripheral portion of the cell-side separator 321 is disposed on the upper surface of the fuel electrode frame 331 and is joined to the fuel electrode frame 331 by, for example, welding.

[0050] Like the cell-side separator 321, the interconnector-side separator 322 is a rectangular plate-shaped metal (e.g., stainless steel) member with a rectangular opening formed in its center. The periphery (i.e., inner periphery) of the opening of the interconnector-side separator 322 is joined to the upper surface of the main body 313a of the interconnector 313, for example, by welding. The outer peripheral portion of the interconnector-side separator 322 is sandwiched between the lower surface of the anode frame 331 and the upper surface of the cathode frame 332, and is joined to the upper anode frame 331, for example, by welding. In this way, the separator section 32 (cell-side separator 321 and interconnector-side separator 322) is configured to be able to connect the electrochemical cell unit 31 and the frame section 33.

[0051] The cell cassettes 30 configured as described above are stacked on the terminal plate 40 to form an electrochemical cell stack 1 in which multiple electrochemical cell units 31 are stacked vertically. At this time, the separator sections 32 (cell-side separators 321 and interconnector-side separators 322) separate the spaces between adjacent separators. This creates multiple fuel chambers Sf and air chambers Sa within the electrochemical cell stack 1, with gas flow blocked between them. Specifically, the fuel chamber Sf is formed by the anode frame 331, the cell-side separator 321 joined to the anode frame 331, the electrolysis cell 311 connected to the cell-side separator 321, the interconnector-side separator 322 joined to the anode frame 331, and the interconnector 313 connected to the interconnector-side separator 322. The fuel chamber Sf is formed between the electrolysis cell 311 and the interconnector 313. Furthermore, the fuel electrode layer 311c of the electrolysis cell 311 is exposed to the fuel chamber Sf. An air chamber Sa is formed by the air electrode frame 332, the interconnector-side separator 322 in contact with the air electrode frame 332, the interconnector 313 connected to the interconnector-side separator 322, the cell-side separator 321 of the cell cassette 30 adjacent to the air electrode frame 332, and the electrolysis cell 311 connected to the cell-side separator 321. The air electrode layer 311b of the electrolysis cell 311 is exposed to the air chamber Sa. Steam is supplied to the fuel chamber Sf as a fuel gas. Air is supplied to the air chamber Sa.

[0052] 3, the gas supply passages Pfi and the gas discharge passages Pfo are formed to penetrate the lower end plate 60, the lower insulating plate 50, the terminal plate 40, and the frame portion 33 of each cell cassette 30 constituting the cell cassette group in the stacking direction. The gas supply passages Pfi communicate with the fuel chamber Sf via horizontal holes 331a formed in the fuel electrode frame 331 of each cell cassette 30. The gas discharge passages Pfo communicate with the fuel chamber Sf via horizontal holes 331b formed in the fuel electrode frame 331 of each cell cassette 30.

[0053] The gas supply passages Pai and gas discharge passages Pao are also formed to penetrate the lower end plate 60, the lower insulating plate 50, the terminal plate 40, and the frame portion 33 of each cell cassette 30 constituting the cell cassette group in the stacking direction. The gas supply passages Pai and gas discharge passages Pao each communicate with the air chamber Sa via a horizontal hole (not shown) formed in the air electrode frame 332 of each cell cassette 30.

[0054] The cell cassette 30 (30A) located at the top of the cell cassette group is a dummy cell cassette provided with a metal plate PL instead of the electrolysis cell 311. The fuel electrode frame 331 of this dummy cell cassette 30A functions as a terminal plate.

[0055] The operation of the electrochemical cell stack 1 will be described. First, a voltage is applied to the electrochemical cell stack 1. In this case, the negative electrode of the power supply is connected to the terminal plate 40, and the positive electrode is connected to the fuel electrode frame 331 of the dummy cell cassette 30A. Next, high-temperature water vapor is supplied from the gas supply passage Pfi. The water vapor supplied to the gas supply passage Pfi flows into the fuel chamber Sf of each cell cassette 30 through the horizontal hole 331a. In addition, high-temperature air is supplied from the gas supply passage Pai. The air supplied to the gas supply passage Pai flows into the air chamber Sa of each cell cassette 30 through a horizontal hole (not shown). The reason for supplying high-temperature air to the air chamber Sa is to control the temperature of the electrochemical cell stack 1.

[0056] The water vapor that flows into the fuel chamber Sf flows through the fuel chamber Sf from the front side (one end) to the rear side (the other end) in the depth direction, as shown in FIG. 3 . Therefore, the front side in the depth direction is the inlet side of the fuel chamber Sf, and the rear side in the depth direction is the outlet side of the fuel chamber Sf. The water vapor in the fuel chamber Sf comes into contact with the anode layer 311c exposed to the fuel chamber Sf and reacts with electrons supplied to the anode layer 311c via the interconnector 313, the anode current collector 312, and the like. This causes the water vapor to decompose into hydrogen and oxide ions (water vapor electrolysis reaction). The hydrogen generated by the water vapor electrolysis reaction flows further to the rear side in the depth direction within the fuel chamber Sf and is discharged from the gas discharge passage Pfo via the horizontal hole 331b. At this time, unreacted water vapor is discharged from the gas discharge passage Pfo together with the hydrogen. Meanwhile, the oxide ions move through the solid electrolyte layer 311a to the air electrode layer 311b exposed to the air chamber Sa, where they release electrons in the functional layer of the air electrode layer 311b and become oxygen. The oxygen diffuses within the air chamber Sa and is discharged from the gas discharge passage Pao via a horizontal hole (not shown) together with the air that has flowed into the air chamber Sa.

[0057] Electrons emitted from the functional layer of the air electrode layer 311b are collected by the interconnector 313 via the current collecting layer, and then return to the positive electrode of the power supply device through the dummy cell cassette 30A.

[0058] Next, the anode current collector 312 will be described. Fig. 5 is a cross-sectional view taken along line VV in Fig. 3, and Fig. 5 is a cross-sectional view of the electrochemical cell stack 1 cut along the width direction. Fig. 6 shows a cross-section of one cell cassette 30 shown in Fig. 5. As shown in Figs. 5 and 6, the anode current collector 312 is disposed between the electrolysis cell 311 and the interconnector 313. Because a fuel chamber Sf is formed between the electrolysis cell 311 and the interconnector 313, the anode current collector 312 is disposed within the fuel chamber Sf.

[0059] Anode current collector 312 is constructed by forming multiple upwardly protruding ridges on a single conductive metal plate. The ridges are formed at regular intervals in the width direction and extend in the depth direction. Anode current collector 312 is disposed between electrolysis cell 311 and interconnector 313 so that the portion connecting adjacent ridges in the width direction is in surface contact with main body 313a of interconnector 313 and the upper surface of each ridge is in surface contact with anode layer 311c of electrolysis cell 311.

[0060] Fig. 7 shows a cross section of the anode current collector 312 shown in Fig. 5. As shown in Fig. 7, the anode current collector 312 has a plurality of protrusions 312A aligned in the width direction and a bottom side 312C connecting adjacent protrusions 312A in the width direction. The plurality of protrusions 312A are formed so as to be arranged parallel to each other in the depth direction at predetermined intervals in the width direction.

[0061] FIG. 8 shows a detail of portion E in FIG. 5. FIG. 8 shows a cross section of a protrusion 312A formed on an anode current collector 312 and its vicinity. As shown in FIG. 8, the protrusion 312A is formed by an upper edge portion 312a and a pair of connecting portions 312b, 312b. The upper edge portion 312a constitutes the upper end portion of the protrusion 312A. The upper edge portion 312a is formed along the depth direction. The upper surface S1 of the upper edge portion 312a is formed flat and parallel to a plane perpendicular to the up-down direction. The upper surface S1 is formed along the depth direction (first direction) and is in surface contact with the lower surface of the anode layer 311c of the electrolysis cell 311 stacked immediately above it. Therefore, the upper edge portion 312a is a first contact portion that is in surface contact with the anode layer 311c of the electrolysis cell 311 adjacent in the stacking direction.

[0062] Like the upper side portion 312a, the lower side portion 312C is also formed along the depth direction. A lower surface S2 of the lower side portion 312C is formed flat so as to be parallel to a plane perpendicular to the up-down direction. The lower surface S2 is formed along the depth direction and comes into surface contact with the upper surface of the main body portion 313a of the interconnector 313 stacked directly below it. Therefore, the lower side portion 312C is a second contact portion that comes into surface contact with the interconnector 313 adjacent in the stacking direction.

[0063] The connecting portion 312b is formed from both depthwise ends (i.e., both widthwise ends) of the upper side portion 312a toward the lower side portion 312C so as to connect the upper side portion 312a and the lower side portion 312C. The connecting portion 312b includes a first inclined portion P1, a second inclined portion P2, and a step portion P3. The first inclined portion P1 is formed so as to slope obliquely downward and widen from the side end (widthwise end) along the extension direction (depth direction) of the upper side portion 312a. The step portion P3 is connected to the lower end of the first inclined portion P1. The step portion P3 has a flat surface parallel to a plane perpendicular to the up-down direction. The upper end of the second inclined portion P2 is connected to the widthwise end of the step portion P3, which is opposite the end to which the first inclined portion P1 is connected. The second inclined portion P2 is formed so as to slope obliquely downward and widen from the end of the step portion P3. The lower end of the second inclined portion P2 is connected to the lower side portion 312C.

[0064] The protrusion 312A is formed by an upper side portion 312a and a pair of connecting portions 312b, 312b connected to both side ends of the upper side portion 312a along the extension direction (depth direction), and its cross-sectional shape is a two-tiered mountain shape that widens toward the end, as can be seen in Figure 8. The protrusion 312A is formed to protrude from the lower side portion 312C and extend in the depth direction. The pair of connecting portions 312b, 312b each connects the upper side portion 312a and the lower side portion 312C.

[0065] When the electrochemical cell stack 1 is fastened with the bolts B and nuts, the fastening force acts to compress the anode current collector 312 in the vertical direction. This fastening force is absorbed by the elastic deformation of the connecting portions 312b of the protrusions 312A of the anode current collector 312. At this time, the elastic force of the connecting portions 312b acts on the upper side portion 312a and the lower side portion 312C, so that the upper side portion 312a is pressed firmly against the anode layer 311c, and the lower side portion 312C is pressed firmly against the main body portion 313a of the interconnector 313. This makes it possible to maintain good contact between the upper surface S1 of the upper side portion 312a and the anode layer 311c, and between the lower surface S2 of the lower side portion 312C and the main body portion 313a of the interconnector 313.

[0066] During operation of the electrochemical cell stack 1, water vapor is supplied to the fuel chamber Sf as described above. As shown in FIG. 3 , the water vapor supplied to the fuel chamber Sf flows through the fuel chamber Sf from the front side in the depth direction, which is the inlet side of the fuel chamber Sf, to the rear side in the depth direction, which is the outlet side of the fuel chamber Sf. An anode current collector 312 is disposed within the fuel chamber Sf, and this anode current collector 312 is provided with a plurality of protrusions 312A extending in the depth direction. Therefore, water vapor within the fuel chamber Sf flows from the inlet side (front side in the depth direction) of the fuel chamber Sf to the outlet side (rear side in the depth direction) along the extension direction of the protrusions 312A.

[0067] 5, the fuel chamber Sf is divided into an inner space A1, which is a space surrounded by the protrusions 312A and the interconnector 313 directly below the protrusions 312A, and an outer space A2, which is surrounded by the protrusions 312A and the fuel electrode layer 311c of the electrolysis cell 311 directly above the protrusions 312A. The inner space A1 and the outer space A2 are separated by the connecting portion 312b of the protrusions 312A. Water vapor in the fuel chamber Sf flows from the front to the rear in the depth direction through either the inner space A1 or the outer space A2 within the fuel chamber Sf.

[0068] The water vapor flowing through the outer space A2 comes into direct contact with the fuel electrode layer 311c exposed to the outer space A2 so as to form the upper wall of the outer space A2, and is utilized in the water vapor electrolysis reaction. As a result, the water vapor is consumed from the front side in the depth direction (the inlet side of the fuel chamber Sf), and the amount of water vapor decreases toward the rear side in the depth direction, and the amount of water vapor is small near the rear end in the depth direction (near the outlet of the fuel chamber Sf).

[0069] Meanwhile, the upper edge portion 312a of the protrusion 312A is located directly above the water vapor flowing through the inner space A1. The fuel electrode layer 311c of the electrolysis cell 311 contacts the upper surface S1 of this upper edge portion 312a, and an opening is formed through the upper edge portion 312a in the thickness direction. Therefore, the fuel electrode layer 311c is partially exposed to the inner space A1 through this opening. Therefore, the water vapor flowing through the inner space A1 comes into contact with the fuel electrode layer 311c partially exposed through the opening formed in the upper edge portion 312a and is used in the water vapor electrolysis reaction. Even in this case, water vapor is consumed by the water vapor electrolysis reaction from the front side in the depth direction (the inlet side of the fuel chamber Sf). However, in this embodiment, the opening formed in the upper edge portion 312a is adjusted so that a sufficient amount of water vapor is also supplied near the rear end in the depth direction (i.e., the outlet side of the fuel chamber Sf).

[0070] FIG. 9 is a perspective view showing one protrusion 312A formed on an anode current collector 312 according to the first embodiment and a bottom edge 312C provided on both sides of the protrusion 312A. As shown in FIG. 9, water vapor (HO) is supplied to the inner space A1 of the protrusion 312A from the front side in the depth direction. Multiple openings OP are formed in the upper edge 312a of the protrusion 312A. In this example, eight openings OP are formed. Each opening OP penetrates the upper edge 312a in the thickness direction. Each opening OP is formed along the depth direction. In this embodiment, each opening OP has a rectangular shape with sides in the width direction and depth direction. The sizes of these rectangular openings OP vary. Specifically, each opening OP is formed so that the opening area increases from the front side to the rear side in the depth direction. In this embodiment, all openings have the same opening width W. The opening width W is the length in the in-plane direction of the opening surface of the opening, perpendicular to the depth direction (e.g., the width direction). On the other hand, the openings OP are formed so that the opening length L is longer as the opening OP is formed closer to the rear. More specifically, the openings are formed so that the opening length L of the nth opening from the front in the depth direction is shorter than the opening length L of the (n+1)th opening from the front in the depth direction. The opening length L is the length in the in-plane direction of the opening surface of the opening, parallel to the depth direction. The pitch D between the openings in the depth direction (the length in the direction parallel to the depth direction between the rear end of an opening OP and the front end of an opening OP adjacent to the rear of that opening OP) is all the same.

[0071] Here, the upper side portion 312a is divided into a front half region FA, which includes the front end (one end) in the extension direction (depth direction) of the upper side portion 312a and is located forward of the midpoint of its length in the extension direction, and a rear half region RA, which includes the rear end (the other end) in the extension direction (depth direction) and is located rearward of the midpoint of its length in the extension direction. When the upper side portion 312a is divided into the front half region FA and the rear half region RA, the surface areas of the front half region FA and the rear half region RA are equal. Furthermore, since the upper side portion 312a is disposed within the fuel chamber Sf and water vapor within the fuel chamber Sf flows from the front side (one end) to the rear side (the other end) in the extension direction (depth direction) of the upper side portion 312a, the front half region FA, which includes the front end of the upper side portion 312a, is located near the inlet of the fuel chamber Sf, and the rear half region RA, which includes the rear end of the upper side portion 312a, is located near the outlet of the fuel chamber Sf.

[0072] Furthermore, the ratio of the total opening area of ​​the openings formed in the front half region FA to the surface area (area including the opening area) of the front half region FA is defined as the opening ratio in the front half region FA, and the ratio of the total opening area of ​​the openings formed in the rear half region RA to the total area (area including the opening area) of the rear half region RA is defined as the opening ratio in the rear half region RA.

[0073] The opening length L of the openings OP formed in the upper side portion 312a is longer as the openings OP are formed further rearward in the depth direction. Therefore, the opening length L of the openings OP formed in the front half region FA of the upper side portion 312a is shorter than the opening length L of the openings OP formed in the rear half region RA of the upper side portion 312a. Furthermore, the opening width W of all openings OP is equal. Therefore, the opening area of ​​each opening OP increases as the opening OP is formed further rearward in the depth direction (i.e., toward the outlet of the fuel chamber Sf). Furthermore, the pitch D between all openings is equal. Therefore, openings with smaller opening areas are formed in the front half region FA of the upper side portion 312a, and openings with larger opening areas are formed in the rear half region RA of the upper side portion 312a. Therefore, the total opening area of ​​the openings formed in the front half region FA of the upper side portion 312a is smaller than the total opening area of ​​the openings formed in the rear half region RA of the upper side portion 312a. In other words, the opening ratio in the front half region FA of the upper side portion 312a is smaller than the opening ratio in the rear half region RA of the upper side portion 312a.

[0074] Water vapor flowing from the front side to the rear side in the depth direction within the inner space A1 can contact the fuel electrode layer 311c only through the openings OP. In this embodiment, as described above, the opening ratio in the front half region FA of the upper edge portion 312a is smaller than the opening ratio in the rear half region RA, so the amount of water vapor that can contact the fuel electrode layer 311c in the front half region FA is small, thereby suppressing the steam electrolysis reaction in the front half region FA. This limits the amount of water vapor consumed by the steam electrolysis reaction in the front half region FA, allowing sufficient water vapor to flow in the rear half region RA as well. Furthermore, because the opening ratio in the rear half region RA is larger than the opening ratio in the front half region FA, a large amount of water vapor can contact the fuel electrode layer 311c in the rear half region RA. This therefore promotes the steam electrolysis reaction in the rear half region RA.

[0075] Thus, according to this embodiment, the openings are formed in the upper edge portion 312a so that the opening ratio in the front region FA of the upper edge portion 312a is smaller than the opening ratio in the rear region RA. This allows a sufficient amount of steam to flow near the rear end of the upper edge portion 312a, i.e., near the outlet of the fuel chamber Sf, and promotes the steam electrolysis reaction near the outlet of the fuel chamber Sf, thereby suppressing bias in the steam electrolysis reaction (electrochemical reaction) in the depth direction. Suppressing bias in the steam electrolysis reaction in this way suppresses performance degradation of the electrochemical cell.

[0076] Furthermore, according to this embodiment, a plurality of openings OP are formed on the top side portion 312a, and the opening length L of the openings OP formed in the front half region FA of the top side portion 312a is shorter than the opening length L of the openings OP formed in the rear half region RA. By adjusting the opening length L of each opening OP in this manner, the opening ratio in the front half region FA of the top side portion 312a can be made smaller than the opening ratio in the rear half region RA.

[0077] Furthermore, according to this embodiment, the anode current collector 312 has multiple protrusions 312A arranged parallel to the depth direction (first direction), so that the opening ratio in the front half region FA of the upper edge portion 312a of each of the multiple protrusions 312A can be made smaller than the opening ratio in the rear half region RA. This allows the water vapor flowing through the internal space A1 of each protrusion 312A to flow to the vicinity of the rear end in the depth direction (i.e., the vicinity of the outlet of the fuel chamber), further suppressing bias in the water vapor electrolysis reaction.

[0078] (Variation 1) In the above first embodiment, an example was shown in which a plurality of openings OP are formed in the upper side portion 312a of the fuel electrode current collector 312 such that the opening length L gradually increases toward the rear side in the depth direction. However, among the plurality of openings, there may be openings having the same opening length. For example, as shown in FIG. 10, a plurality of openings may be formed on the upper surface S1. According to FIG. 10, among the plurality of openings formed in the upper side portion 312a of the fuel electrode current collector 312 (ridge portion 312A), the opening lengths of the foremost and second openings OP1 and OP2 from the front are the same opening length L1, the opening lengths of the third and fourth openings OP3 and OP4 from the front are the same opening length L2, the opening lengths of the fifth and sixth openings OP5 and OP6 from the front are the same opening length L3, and the opening lengths of the seventh and eighth openings OP7 and OP8 from the front are the same opening length L4. And the opening lengths of each opening are in the relationship of L1 < L2 < L3 < L4.

[0079] Even in the case where each opening is formed in this way, the opening ratio of the front half region FA in the upper side portion 312a can be made smaller than the opening ratio in the rear half region RA.

[0080] (Second Embodiment) The fuel electrode current collector according to the present embodiment also has a shape in which a plurality of ridge portions that are convex upward extend in parallel in the depth direction, similar to the fuel electrode current collector according to the first embodiment. FIG. 11 is a perspective view showing one ridge portion formed in the fuel electrode current collector according to the second embodiment and a pair of lower side portions connected to the ridge portion. The basic shape and structure of the fuel electrode current collector according to the present embodiment are the same as the shape and structure of the fuel electrode current collector according to the first embodiment, and the difference lies in the shape and pitch of the plurality of openings formed in the upper side portion of the fuel electrode current collector. Hereinafter, the description will focus on the differences.

[0081] 11 , like the anode current collector 312 according to the first embodiment, the anode current collector 312 according to this embodiment has an upper side portion 312a, a connecting portion 312b, and a lower side portion 312C. The upper side portion 312a and a pair of connecting portions 312b, 312b connected to the upper side portion 312a form a two-tiered, mountain-shaped protrusion 312A that protrudes from the lower side portion 312C and extends in the depth direction. The external shapes of these portions are the same as the external shapes of the upper side portion 312a, the connecting portion 312b, and the lower side portion 312C of the anode current collector 312 according to the first embodiment.

[0082] Additionally, multiple openings OP penetrating the upper edge portion 312a in the thickness direction are formed along the depth direction. In FIG. 11, ten openings OP1 to OP10 are formed on the upper edge portion 312a. These openings OP1 to OP10 are all identical rectangular shapes with sides in the width and depth directions. That is, all openings OP1 to OP10 have the same opening width W and opening length L. Therefore, all openings OP1 to OP10 have the same opening area. However, the pitch D between each opening decreases toward the rear. According to FIG. 11, the openings are formed so that the pitch Dn between the nth (n=1 to 8) opening OPn from the front in the depth direction and the n+1th opening OPn+1 from the front is longer than the pitch Dn+1 between the n+1th opening OPn+1 from the front and the n+2th opening OPn+2 from the front. The pitch D9 at the rearmost opening is the shortest.

[0083] According to the anode current collector 312 of this embodiment, multiple openings are formed in the top edge portion 312a so that the pitch D on the front side in the depth direction is longer than the pitch D on the rear side. Therefore, the number of openings formed in the front region FA of the top edge portion 312a is smaller than the number of openings formed in the rear region RA. Furthermore, because all openings have the same opening area, the opening ratio in the front region FA of the top edge portion 312a is smaller than the opening ratio in the rear region RA. Because the opening ratio in the front region FA is small, the amount of water vapor that can contact the anode layer 311c in the front region FA is small, thereby suppressing the steam electrolysis reaction in the front region FA. This limits the amount of water vapor consumed by the steam electrolysis reaction in the front region FA, thereby allowing sufficient water vapor to flow in the rear region RA. Furthermore, because the opening ratio in the rear region RA is larger than the opening ratio in the front region FA, the amount of water vapor that can contact the anode layer 311c in the rear region RA is large. This promotes the steam electrolysis reaction in the rear region RA.

[0084] As described above, according to this embodiment, the steam electrolysis reaction can be promoted near the outlet of the fuel chamber Sf where the rear region RA of the upper edge portion 312a is located, thereby suppressing bias in the electrochemical reaction in the depth direction, and as a result, suppressing performance degradation of the electrochemical cell.

[0085] Furthermore, according to this embodiment, a plurality of openings OP are formed in the top side portion 312a, and the pitch D between the openings formed in the front half region FA of the top side portion 312a is longer than the pitch D between the openings formed in the rear half region RA. By adjusting the pitch between the openings in this manner, the opening ratio in the front half region FA of the top side portion 312a can be made smaller than the opening ratio in the rear half region RA.

[0086] (Variation 2) In the second embodiment, a plurality of openings OP are formed in the upper edge portion 312a of the anode current collector 312 such that the pitch D between the openings gradually decreases toward the rear. However, the anode current collector 312 (protrusion 312A) may be configured as shown in FIG. 12, for example. As shown in FIG. 12, a plurality of openings OP (OP1 to OP11) are formed in the upper edge portion 312a of the anode current collector 312 (protrusion 312A). These openings are formed along the depth direction. In addition, the first and second pitches from the front in the depth direction are the same pitch D1, the third and fourth pitches are the same pitch D2, the fifth and sixth pitches are the same pitch D3, the seventh and eighth pitches are the same pitch D4, and the ninth and tenth pitches are the same pitch D5. The pitches have a relationship of D1>D2>D3>D4>D5.

[0087] Even when the openings are formed in this manner, the ratio of the openings in the front region FA of the upper side portion 312a can be made smaller than the ratio of the openings in the rear region RA.

[0088] (Third embodiment) Like the anode current collector according to the first embodiment, the anode current collector according to this embodiment also has a shape in which a plurality of upwardly protruding ridges extend parallel to each other in the depth direction. Figure 13 is a perspective view showing one ridge formed on the anode current collector according to the third embodiment and a pair of lower edge portions connected to the ridge. The basic shape and structure of the anode current collector according to this embodiment are the same as those of the anode current collector according to the first embodiment, except for the opening lengths and opening widths of the multiple openings formed on the upper surface of the upper edge portion of the anode current collector. The following description will focus on these differences.

[0089] 13, like the anode current collector 312 according to the first embodiment, the anode current collector 312 according to this embodiment has an upper side portion 312a, a connecting portion 312b, and a lower side portion 312C. The upper side portion 312a and a pair of connecting portions 312b, 312b connected to the upper side portion 312a form a two-tiered, mountain-shaped protrusion 312A that protrudes from the lower side portion 312C and extends in the depth direction. The external shapes of these portions are the same as the external shapes of the upper side portion 312a, the connecting portion 312b, and the lower side portion 312C of the anode current collector 312 according to the first embodiment.

[0090] Furthermore, a plurality of openings OP penetrating the upper side portion 312a in the thickness direction are formed along the depth direction. In FIG. 13, ten openings OP1 to OP10 are formed on the upper side portion 312a. These openings OP1 to OP10 all have the same opening length L. The pitch D between the openings is also the same. However, the opening width W of each opening gradually increases as the opening is formed further rearward in the depth direction. Specifically, the openings are formed so that the opening width of the nth opening OPn from the front in the depth direction is narrower than the opening width of the (n+1)th opening OPn+1. The opening width W of the rearmost opening OP10 is the widest.

[0091] In the anode current collector 312 according to this embodiment, the opening width W of the opening formed on the front side in the depth direction is smaller than the opening width W of the opening formed on the rear side. Therefore, the opening area of ​​the opening formed in the front half region FA of the top edge portion 312a is smaller than the opening area of ​​the opening formed in the rear half region RA. That is, the opening ratio in the front half region FA of the top edge portion 312a is smaller than the opening ratio in the rear half region RA. Because the opening ratio in the front half region FA is small, the amount of water vapor that can contact the anode layer 311c in the front half region FA is small, thereby suppressing the steam electrolysis reaction in the front half region FA. This limits the amount of water vapor consumed by the steam electrolysis reaction in the front half region FA, thereby allowing sufficient water vapor to flow in the rear half region RA. Furthermore, because the opening ratio in the rear half region RA is larger than the opening ratio in the front half region FA, the amount of water vapor that can contact the anode layer 311c in the rear half region RA is large. This promotes the steam electrolysis reaction in the rear half region RA.

[0092] As described above, according to this embodiment, the steam electrolysis reaction can be promoted near the outlet of the fuel chamber Sf where the rear region RA of the upper edge portion 312a is located, thereby suppressing bias in the electrochemical reaction in the depth direction, and as a result, suppressing performance degradation of the electrochemical cell.

[0093] Furthermore, according to this embodiment, multiple openings OP are formed on the top side portion 312a, and the opening width W of the openings formed in the front half region FA of the top side portion 312a is narrower than the opening width W of the openings formed in the rear half region RA. In this way, by adjusting the opening width W, the opening ratio in the front half region FA of the top side portion 312a can be made smaller than the opening ratio in the rear half region RA.

[0094] (Variation 3) In the third embodiment, multiple openings are formed in the upper edge portion 312a of the anode current collector 312 such that the opening width W gradually increases toward the rear. However, some of the multiple openings may have the same opening width. For example, the anode current collector 312 (protrusion 312A) may be configured as shown in FIG. 14. As shown in FIG. 14, multiple openings OP (OP1 to OP10) are formed along the depth direction in the upper edge portion 312a of the anode current collector 312 (protrusion 312A). The first and second openings (OP1, OP2) from the front in the depth direction have the same opening width, the third and fourth openings (OP3, OP4) have the same opening width, the fifth and sixth openings (OP5, OP6) have the same opening width, the seventh and eighth openings (OP7, OP8) have the same opening width, and the ninth and tenth openings (OP9, OP10) have the same opening width. The opening widths have the relationship (opening width of openings OP1, OP2)<(opening width of openings OP3, OP4)<(opening width of openings OP5, OP6)<(opening width of openings OP7, OP8)<(opening width of openings OP9, OP10).

[0095] Even when the openings are formed in this manner, the ratio of the openings in the front region FA of the upper side portion 312a can be made smaller than the ratio of the openings in the rear region RA.

[0096] (Fourth embodiment) Like the anode current collector according to the first embodiment, the anode current collector according to this embodiment also has a shape in which a plurality of upwardly protruding ridges extend parallel to each other in the depth direction. FIG. 15 is a perspective view showing one ridge formed on the anode current collector according to the fourth embodiment and a pair of lower edge portions connected to the ridge. The basic shape and structure of the anode current collector according to this embodiment are the same as those of the anode current collector according to the first embodiment, except that a single opening is formed in the upper edge portion of the anode current collector. The following description will focus on these differences.

[0097] 15, like the anode current collector 312 according to the first embodiment, the anode current collector 312 according to this embodiment has an upper side portion 312a, a connecting portion 312b, and a lower side portion 312C. The upper side portion 312a and a pair of connecting portions 312b, 312b connected to the upper side portion 312a form a two-tiered, mountain-shaped protrusion 312A that protrudes from the lower side portion 312C and extends in the depth direction. The external shapes of these portions are the same as the external shapes of the upper side portion 312a, the connecting portion 312b, and the lower side portion 312C of the anode current collector 312 according to the first embodiment.

[0098] A single large opening OPs is formed in the upper side portion 312a, penetrating the upper side portion 312a in the thickness direction. The opening shape of this opening OPs is a triangle having a base BL and a pair of oblique sides SL.SL. The base BL is formed parallel to the width direction near the rear end of the upper side portion 312a. One oblique side SL extends from one widthwise end of the base BL toward the front in the depth direction, and the other oblique side SL extends from the other widthwise end of the base BL toward the front in the depth direction. The front ends of the pair of oblique sides SL meet near the front end of the upper side portion 312a to form the vertex of the triangle.

[0099] When such openings OPs are formed in the upper edge portion 312a, the opening width W of the openings OPs varies in the depth direction. Specifically, the opening width W increases toward the rear in the depth direction. Therefore, the opening ratio in the front half region FA of the upper edge portion 312a is smaller than the opening ratio in the rear half region RA. Because the opening ratio in the front half region FA is small, the amount of water vapor that can contact the fuel electrode layer 311c in the front half region FA is small, thereby suppressing the steam electrolysis reaction in the front half region FA. This limits the amount of water vapor consumed by the steam electrolysis reaction in the front half region FA, thereby allowing sufficient water vapor to flow in the rear half region RA as well. Furthermore, because the opening ratio in the rear half region RA is larger than the opening ratio in the front half region FA, the amount of water vapor that can contact the fuel electrode layer 311c in the rear half region RA is large. This promotes the steam electrolysis reaction in the rear half region RA.

[0100] As described above, according to this embodiment, the steam electrolysis reaction can be promoted near the outlet of the fuel chamber Sa where the rear region RA of the upper edge portion 312a is located, thereby suppressing bias in the electrochemical reaction in the depth direction, and as a result, suppressing performance degradation of the electrochemical cell.

[0101] (Variation 4) In the above fourth embodiment, an example was shown in which the shape of the opening OPs is triangular, but as shown in Figure 16, a single opening OPr may be formed on the upper surface S1 such that the opening width W gradually increases from the front to the rear in the depth direction.

[0102] Fifth Embodiment Like the anode current collector according to the first embodiment, the anode current collector according to this embodiment also has a shape in which a plurality of upwardly protruding ridges extend parallel to each other in the depth direction. FIG. 17 is a perspective view showing one ridge formed on the anode current collector according to the fifth embodiment and a pair of lower edge portions connected to the ridge. The basic shape and structure of the anode current collector according to this embodiment are the same as those of the anode current collector according to the first embodiment, except for the arrangement of openings formed in the upper edge portion of the anode current collector. The following description will focus on the differences.

[0103] 17, like the anode current collector 312 according to the first embodiment, the anode current collector 312 according to this embodiment has an upper side portion 312a, a connecting portion 312b, and a lower side portion 312C. The upper side portion 312a and a pair of connecting portions 312b, 312b connected to the upper side portion 312a form a two-tiered, mountain-shaped protrusion 312A that protrudes from the lower side portion 312C and extends in the depth direction. The external shapes of these portions are the same as the external shapes of the upper side portion 312a, the connecting portion 312b, and the lower side portion 312C of the anode current collector 312 according to the first embodiment.

[0104] In addition, multiple openings OP are formed in the upper side portion 312a, penetrating in the thickness direction. However, the openings OP are formed only in the rear region RA of the upper side portion 312a, and not in the front region FA. In FIG. 17, the multiple openings OP formed in the rear region RA of the upper side portion 312a all have the same shape, and the pitch between the openings is also constant. However, the shapes of the multiple openings formed in the rear region RA do not have to be the same. Furthermore, a single opening may be formed in the rear region RA.

[0105] If openings OP are formed only in the rear region RA of the upper edge portion 312a and no openings are formed in the front region FA, the opening ratio (=0) in the front region FA will be smaller than the opening ratio in the rear region RA. In particular, because the opening ratio in the front region FA is 0, there is no opportunity for water vapor to come into contact with the fuel electrode layer 311c in the front region FA, and the steam electrolysis reaction does not occur in the front region FA. As a result, water vapor is not consumed in the front region FA, and a sufficient amount of water vapor can flow into the rear region RA. Furthermore, because openings are formed in the rear region RA, water vapor comes into contact with the fuel electrode layer 311c in the rear region RA. This can promote the steam electrolysis reaction in the rear region RA.

[0106] As described above, according to this embodiment, the steam electrolysis reaction can be promoted near the outlet of the fuel chamber Sf where the rear region RA of the upper edge portion 312a is located, thereby suppressing bias in the electrochemical reaction in the depth direction, and as a result, suppressing performance degradation of the electrochemical cell.

[0107] (Sixth embodiment)

[0108] Like the anode current collector according to the first embodiment, the anode current collector according to this embodiment also has a shape in which a plurality of upwardly protruding ridges extend parallel to each other in the depth direction. Fig. 18 is a perspective view showing one ridge formed on the anode current collector according to the sixth embodiment and a pair of lower edge portions connected to the ridge. The anode current collector according to this embodiment differs from the above-described embodiments in the structure of the connecting portion. The following description will focus on these differences.

[0109] 18, like the anode current collector 312 according to the first embodiment, the anode current collector 312 according to this embodiment has an upper side portion 312a, a connecting portion 312b, and a lower side portion 312C. The upper side portion 312a and a pair of connecting portions 312b, 312b connected to the upper side portion 312a form a protrusion 312A that protrudes from the lower side portion 312C and extends in the depth direction. However, the cross-sectional shape of the protrusion 312A according to this embodiment differs from the cross-sectional shapes of the protrusions according to the above embodiments.

[0110] FIG. 19 is a cross-sectional view taken along line AA in FIG. 18. FIG. 19 also shows the anode current collector 312, the anode layer 311c located above and below it, and part of the main body 313a of the interconnector 313. As shown in FIG. 19, connecting portions 312b, 312b are connected to both ends in the width direction of the upper side portion 312a. The lower end of connecting portion 312b is connected to the lower side portion 312C. Therefore, connecting portion 312b connects the upper side portion 312a and the lower side portion 312C. The cross-sectional shape of connecting portion 312b according to this embodiment is an arc shape that bulges outward from the internal space A1.

[0111] When a fastening force acts from above or below on anode current collector 312 having the above-described shape, connecting portion 312b, which has an arc-shaped cross section, bends and elastically deforms, thereby absorbing the fastening force. At this time, the elastic force of connecting portion 312b acts on upper side portion 312a and lower side portion 312C, so that upper side portion 312a is pressed firmly against anode layer 311c, and lower side portion 312C is pressed firmly against main body portion 313a of interconnector 313. This makes it possible to maintain good contact between upper surface S1 of upper side portion 312a and anode layer 311c, and between lower surface S2 of lower side portion 312C and main body portion 313a of interconnector 313.

[0112] 18, a plurality of openings OP are formed in the upper side portion 312a along the depth direction. These openings OP are formed so that the opening length L increases toward the rear in the depth direction. The opening width W of each opening is the same, and the pitch D between each opening is also the same.

[0113] When multiple openings OP are formed in the top edge portion 312a in this manner, the opening ratio in the front region FA of the top edge portion 312a is smaller than the opening ratio in the rear region RA. Because the opening ratio in the front region FA is small, the amount of water vapor that can contact the fuel electrode layer 311c in the front region FA is small, thereby suppressing the steam electrolysis reaction in the front region FA. This limits the amount of water vapor consumed by the steam electrolysis reaction in the front region FA, allowing sufficient water vapor to flow in the rear region RA as well. Furthermore, because the opening ratio in the rear region RA is larger than the opening ratio in the front region FA, a larger amount of water vapor can contact the fuel electrode layer 311c in the rear region RA. This therefore promotes the steam electrolysis reaction in the rear region RA.

[0114] As described above, according to this embodiment, the steam electrolysis reaction can be promoted near the outlet of the fuel chamber Sa where the rear region RA of the upper edge portion 312a is located, thereby suppressing bias in the electrochemical reaction in the depth direction, and as a result, suppressing performance degradation of the electrochemical cell.

[0115] Although the embodiments of the present disclosure have been described above, the technology according to the present disclosure is not limited to the above embodiments. For example, the technology according to the present disclosure may be applied by combining the embodiments. For example, the openings formed in the upper side portion 312a may be formed so that the opening ratio in the front region FA of the upper side portion 312a is smaller than the opening ratio in the rear region RA by adjusting the opening length, opening width, and pitch between the openings. Furthermore, although the above embodiments describe an example in which the openings are rectangular, the openings may have any shape. For example, a circular opening may be formed in the upper side portion 312a. In this case, as shown in FIG. 20, multiple circular openings OP having the same opening area may be formed in the upper side portion 312a so that the pitch between the openings becomes smaller (shorter) from the front to the rear in the depth direction. Furthermore, multiple circular openings may be formed in the upper side portion 312a at equal pitches so that the radius increases from the front to the rear in the depth direction. Furthermore, in the above embodiment, the multiple openings formed in the upper edge portion 312a are arranged in a line along the depth direction, but multiple openings may be formed in the width direction. In other words, any type of opening may be formed as long as the opening ratio in the front region FA of the upper edge portion 312a is smaller than the opening ratio in the rear region RA. Furthermore, while the above embodiment illustrates an electrochemical cell stack that generates hydrogen using steam as a fuel gas, the present technology can also be applied to electrochemical cell stacks that generate other gases, such as carbon monoxide, hydrogen and carbon monoxide, or hydrogen-based power generation. In this way, the technology disclosed herein can be modified without departing from its spirit.

[0116] Furthermore, the present disclosure may include the following aspects. [1] an electrochemical cell stack formed by stacking a plurality of electrochemical cell units, each of which includes an electrochemical cell including a solid electrolyte layer, an air cathode layer stacked on one side of the solid electrolyte layer, and an anode layer stacked on the other side of the solid electrolyte layer; an anode current collector formed of a conductive metal stacked on the electrochemical cell so as to be in contact with the anode layer; and an interconnector stacked on the electrochemical cell so as to be in contact with the anode current collector, The fuel electrode current collector is disposed between the electrochemical cell and the interconnector; a first contact portion formed along a predetermined first direction perpendicular to the stacking direction of the electrochemical cell units and in contact with the fuel electrode layer adjacent in the stacking direction; a second contact portion formed along the first direction and in contact with the interconnector adjacent in the stacking direction; and a pair of connecting portions formed from both side ends of the first contact portion along the first direction toward the second contact portion so as to connect the first contact portion and the second contact portion, a protrusion portion that protrudes from the second contact portion and extends in the first direction is formed by the first contact portion and the pair of connecting portions, and an inner space surrounded by the protrusion portion and the interconnector is configured so that a fuel gas flows from one end to the other end in the first direction, an opening is formed in the first contact portion; when the first contact portion is divided into a front half region that is a half region including the one end and a rear half region that is a half region including the other end, an opening ratio in the front half region is smaller than an opening ratio in the rear half region, Electrochemical cell stack. [2] [1] The electrochemical cell stack according to [1], a plurality of openings are formed in the first contact portion along the first direction, a total opening area of ​​the openings formed in the front half region is smaller than a total opening area of ​​the openings formed in the rear half region; Electrochemical cell stack. [3] [2] The electrochemical cell stack according to [2], the pitch between the openings formed in the front half region is larger than the pitch between the openings formed in the rear half region; Electrochemical cell stack. [4] The electrochemical cell stack according to [2] or [3], an opening length of the opening formed in the front half region is shorter than an opening length of the opening formed in the rear half region; Electrochemical cell stack. [5] The electrochemical cell stack according to any one of [2] to [4], the opening width of the opening formed in the front half region is narrower than the opening width of the opening formed in the rear half region; Electrochemical cell stack. [6] [1] The electrochemical cell stack according to [1], a single opening formed in the first contact portion; The single opening is formed such that an opening width in a front half region of the first contact portion is narrower than an opening width in a rear half region of the first contact portion. Electrochemical cell stack. [7] [1] to [6], an electrochemical cell stack according to any one of [1] to [6], No opening is formed in the front half region, and an opening is formed in the rear half region. Electrochemical cell stack. [8] [1] to [7], an electrochemical cell stack according to any one of [1] to [7], the anode current collector includes a plurality of the protrusions arranged in parallel to the first direction; Electrochemical cell stack. [9] [1] to [8], and an electrochemical cell stack according to any one of [1] to [8]. a vaporizer that generates water vapor to be supplied to the electrochemical cell stack; a heating device for heating the gas supplied to the electrochemical cell stack; a thermal insulator in which the electrochemical cell stack, the vaporizer, and the heating device are disposed; Equipped with Hot module.

[10] A hydrogen production device comprising the hot module according to [9]. [Explanation of symbols]

[0117] 1...electrochemical cell stack, 2...evaporator, 3...heat exchanger (heating device), 4...heater (heating device), 5...insulation material, 7...hot module, 8...condenser, 10...upper end plate, 20...upper insulating plate, 30...cell cassette, 31...electrochemical cell unit, 311...electrolysis cell (electrochemical cell), 311a...solid electrolyte layer, 311b...air cathode layer, 311c...fuel electrode layer, 312...fuel electrode current collector, 312A...ridge portion, 312a...upper edge portion (first contact portion), 312b...connecting portion, 312C...lower edge portion (second contact portion) contact portion), 313...interconnector, 313a...main body portion, 313b...protrusion portion, 32...separator portion, 321...cell side separator, 322...interconnector side separator, 33...frame portion, 331...fuel electrode frame, 332...air electrode frame, 40...terminal plate, 50...lower insulating plate, 60...lower end plate, 100...hydrogen production device, A1...inner space, A2...outer space, FA...first half region, RA...second half region, OP...opening, S1...upper surface, S2...lower surface, Sa...air chamber, Sf...fuel chamber,

Claims

1. an electrochemical cell stack formed by stacking a plurality of electrochemical cell units, each of which includes an electrochemical cell including a solid electrolyte layer, an air cathode layer stacked on one side of the solid electrolyte layer, and an anode layer stacked on the other side of the solid electrolyte layer; an anode current collector formed of a conductive metal stacked on the electrochemical cell so as to be in contact with the anode layer; and an interconnector stacked on the electrochemical cell so as to be in contact with the anode current collector, The fuel electrode current collector is disposed between the electrochemical cell and the interconnector; a first contact portion formed along a predetermined first direction perpendicular to the stacking direction of the electrochemical cell units and in contact with the fuel electrode layer adjacent in the stacking direction; a second contact portion formed along the first direction and in contact with the interconnector adjacent in the stacking direction; and a pair of connecting portions formed from both side ends of the first contact portion along the first direction toward the second contact portion so as to connect the first contact portion and the second contact portion, a protrusion portion that protrudes from the second contact portion and extends in the first direction is formed by the first contact portion and the pair of connecting portions, and an inner space surrounded by the protrusion portion and the interconnector is configured so that a fuel gas flows from one end to the other end in the first direction, an opening is formed in the first contact portion; when the first contact portion is divided into a front half region that is a half region including the one end and a rear half region that is a half region including the other end, an opening ratio in the front half region is smaller than an opening ratio in the rear half region, Electrochemical cell stack.

2. 10. The electrochemical cell stack of claim 1, a plurality of openings are formed in the first contact portion along the first direction, a total opening area of ​​the openings formed in the front half region is smaller than a total opening area of ​​the openings formed in the rear half region; Electrochemical cell stack.

3. 3. The electrochemical cell stack of claim 2, the pitch between the openings formed in the front half region is larger than the pitch between the openings formed in the rear half region; Electrochemical cell stack.

4. 3. The electrochemical cell stack of claim 2, an opening length of the opening formed in the front half region is shorter than an opening length of the opening formed in the rear half region; Electrochemical cell stack.

5. 3. The electrochemical cell stack of claim 2, the opening width of the opening formed in the front half region is narrower than the opening width of the opening formed in the rear half region; Electrochemical cell stack.

6. 10. The electrochemical cell stack of claim 1, a single opening formed in the first contact portion; The single opening is formed such that an opening width in a front half region of the first contact portion is narrower than an opening width in a rear half region of the first contact portion. Electrochemical cell stack.

7. 10. The electrochemical cell stack of claim 1, No opening is formed in the front half region, and an opening is formed in the rear half region. Electrochemical cell stack.

8. 10. The electrochemical cell stack of claim 1, the anode current collector includes a plurality of the protrusions arranged in parallel to the first direction; Electrochemical cell stack.

9. An electrochemical cell stack according to any one of claims 1 to 8; a vaporizer that generates water vapor to be supplied to the electrochemical cell stack; a heating device for heating the gas supplied to the electrochemical cell stack; a thermal insulator in which the electrochemical cell stack, the vaporizer, and the heating device are disposed; Equipped with Hot module.

10. A hydrogen production device comprising the hot module according to claim 9.

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