ELECTROCHEMICAL CELL STACK

Abstract

Stack (100) of electrochemical cells (301) containing: an electrochemical cell (301); and a manifold (200) supporting a base end (302) of the electrochemical cell (301); wherein the electrochemical cell (301) includes an electrically insulating support substrate (2) and a plurality of power generation units (11, 12, 13, 14) arranged on the support substrate (2), wherein a gas flow path (21) is provided in the support substrate (2); wherein each of the plurality of power generation units (11, 12, 13, 14) includes an anode (3), a cathode (6), and a solid electrolyte layer (4) disposed between the anode (3) and the cathode (6), which solid electrolyte layer includes a zirconium dioxide-based material as a main component; wherein in a power generation unit (11) on the base end side closest to the manifold (200) among the plurality of power generation units (11, 12, 13, 14), the solid electrolyte layer (4) includes a first region (41) covering within 3 µm of an anode-side surface and a second region (42) provided on the first region (41); wherein an intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum in the first region (41) is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region (42); and wherein an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the first region (41) is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the solid electrolyte layer (4) of another power generation unit (12, 13, 14) of the plurality of power generation units (11, 12, 13, 14) other than the power generation unit (11) on the base end side.

Description

TECHNICAL FIELD

[0001] The present invention relates to a stack of electrochemical cells. BACKGROUND

[0002] According to the prior art, fuel cell stacks containing fuel cells and a manifold supporting the base ends of the fuel cells are known as a type of electrochemical cell stack (see, for example, Patent Literature 1). Each fuel cell includes a support substrate and a power generation unit disposed on the support substrate. In addition, a gas flow path is provided in the support substrate. Furthermore, each fuel cell includes an anode, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. During operation of the fuel cell, fuel gas is supplied from within the manifold to the gas flow paths of the fuel cells.

[0003] Further prior art is also known from patent literatures 2 and 3. List of publicationsPatent literature Patent literature 1: JP 2008 -135 272 A Patent literature 2: WO 2015 / 182 527 A1 Patent literature 3: US 2013 / 0 230 788 A1 SHORT DESCRIPTIONTechnical problem

[0004] However, if the fuel gas preheating on the gas flow path side near the manifold (the base end of the fuel cell) is insufficient, the temperature of the power generation unit may decrease on the side closest to the manifold. In this case, the solid electrolyte layer is subjected to thermal stress, which may damage the solid electrolyte layer. This damage to the solid electrolyte layer may occur not only when the fuel cell is first started, but also when it is restarted after a temporary shutdown.

[0005] In view of the situation described above, it is an object of the present invention to provide a stack of electrochemical cells capable of reducing damage to the solid electrolyte layer. Solution to the problem

[0006] An electrochemical cell stack according to a first aspect of the present invention includes an electrochemical cell and a manifold supporting a base end of the electrochemical cell. The electrochemical cell includes an electrically insulating support substrate and a plurality of power generation units disposed on the support substrate. Additionally, a gas flow path is provided in the support substrate. Each of the plurality of power generation units includes an anode, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. Additionally, the solid electrolyte layer includes a zirconium dioxide-based material as its main component.In a power generation unit located on the base end side closest to the manifold among the plurality of power generation units, the solid electrolyte layer includes a first region covering within 3 μm of an anode-side surface and a second region provided on the first region. An intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum in the first region is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region.An intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the first region is larger than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the solid electrolyte layer of another power generation unit of the plurality of power generation units other than the power generation unit on the base end side.

[0007] An electrochemical cell stack according to a second aspect of the present invention includes an electrochemical cell and a manifold supporting a base end of the electrochemical cell. The electrochemical cell includes an electrically conductive support substrate and a power generation unit disposed on the support substrate. Additionally, a gas flow path is provided in the support substrate. The power generation unit includes an anode disposed on a first main surface of the support substrate, a cathode, and a solid electrolyte layer disposed between the anode and the cathode. Additionally, the solid electrolyte layer includes a zirconium dioxide-based material as its main component. The solid electrolyte layer includes a base end portion disposed on one side of the base end and a separate portion disposed separately from the base end portion.The base end portion includes a first region covering within 3 µm of an anode-side surface and a second region provided on the first region. An intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum in the first region is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region. Advantageous effects of the invention

[0008] According to the present invention, an electrochemical cell stack capable of reducing damage to the solid electrolyte layer can be provided. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a fuel cell stack; Fig. 2 is a perspective view of a manifold; Fig. 3 is a perspective view of a segmented series fuel cell; Fig. 4 is a cross-sectional view of Fig. 3 along line AA; Fig. 5 is a perspective view of a flat-tubular type fuel cell; Fig. 6 is a cross-sectional view of Fig. 5 along a line BB. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. First Embodiment Fuel Cell Stack 100

[0009] Fig. 1 is a perspective view of a fuel cell stack 100. Fig. 2 is a perspective view of a manifold 200. Fig. 3 is a perspective view of a fuel cell 301. Fig. 4 is a cross-sectional view of Fig. 3 along line AA

[0010] How Fig. 1, the fuel cell stack 100 includes the manifold 200 and a plurality of fuel cells 301. (1) Pipe distributor 200

[0011] How Fig. As shown in Figure 2, the manifold 200 is configured to supply fuel gas to each of the fuel cells 301. The manifold 200 is hollow and has an interior space. The fuel gas is supplied through an introduction line 201 into the interior of the manifold 200. The manifold 200 includes a cover plate 203 and a manifold main body 204.

[0012] The cover plate 203 includes a plurality of through-holes 202. Each of the through-holes 202 communicates with the interior and exterior of the manifold 200. A base end 302 of each of the fuel cells 301 is inserted into a respective through-hole 202. The cover plate 203 is formed of an electrically conductive material. The cover plate 203 may be formed of a metal material. Stainless steel and similar materials can be used as the metal material, but the material of the cover plate 203 is not limited thereto.

[0013] The manifold main body 204 is formed in a rectangular cuboid shape with an open top. The top of the manifold main body 204 is sealed by the cover plate 203. The manifold main body 204 can be electrically conductive or non-conductive. (2) Fuel cells 301

[0014] As in the Fig. 3 and Fig. As shown in Figure 4, each of the fuel cells 301 is a so-called solid oxide fuel cell (SOFC) of the segmented series type. The base end 302 of the respective fuel cells 301 is inserted into a respective through-hole 202 of the manifold 200. Oxygen-containing gas (air) is supplied around the fuel cells 301.

[0015] The base end 302 of the respective fuel cells 301 is fixed to the respective cover plate 203 of the manifold 200 by a bonding material, with the base end 302 inserted into a respective through-hole 202. Examples of usable bonding materials include crystallized glass, amorphous glass, brazing metal, and ceramic.

[0016] The fuel cells 301 are connected to each other by current collecting elements (not shown in the drawings). Examples of materials usable for the current collecting elements include fired bodies of oxide ceramics, noble metal materials (Pt, Au, Ag), and base metal materials (Ni, Ni alloy, Ni-ceramic composites).

[0017] As in the Fig. 3 and Fig. 4, each of the fuel cells 301 includes a support substrate 2 and first to fourth power generation units 11 to 14.

[0018] Each of the first to fourth power generation units 11 to 14 includes an anode 3, a solid electrolyte layer 4, a barrier layer 5, a cathode 6, a cathode current collecting layer 7, and an interconnector 8. It should be noted that the cathode current collecting layer 7 in Fig. 3 is not shown.

[0019] The support substrate 2 has a plate-like shape that is flat and elongated in one direction. The thickness of the support substrate 2 is not particularly limited but can be adjusted between 1 mm and 5 mm. The porosity of the support substrate 2 is not particularly limited but can be adjusted between 20% and 60%.

[0020] The support substrate 2 contains an electrically insulating porous material as a main component. Examples of materials that can be used to form the support substrate 2 include MgO (magnesium oxide), mixtures of MgAl2O4 (magnesium oxide-aluminum oxide spinel) and MgO (magnesium oxide), and insulating ceramics such as CSZ (calcium-stabilized zirconia), YSZ (yttrium-stabilized zirconia), Y2O3 (yttrium oxide), and CZO (calcium zirconate).

[0021] In the present embodiment, “contains as a main component” means a content of 70 wt% or more of the component.

[0022] The support substrate 2 may contain a transition metal or an oxide thereof that acts as a catalyst to accelerate the reforming reaction of the fuel gas. Ni (nickel) is preferred as the transition metal.

[0023] Five gas flow paths 21 are provided in the support substrate 2. Each of the gas flow paths 21 extends along the longitudinal direction of the support substrate 2. During power generation, the fuel gas flowing from the manifold 200 through the respective gas flow paths 21 passes through pores in the support substrate 2 and is supplied to the anode 3. The number of gas flow paths 21 is not limited to five.

[0024] The anode 3 acts as an anode. The anode 3 contains an anode current collecting layer 31 and an anode active layer 32.

[0025] The anode current collecting layer 31 is arranged on the support substrate 2. The anode current collecting layer 31 is formed from an electrically conductive material. The anode current collecting layer 31 may contain an oxygen ion conductive material. For example, the anode current collecting layer 31 may be formed from NiO-8YSZ, NiO-Y2O3, NiO-CSZ, or the like. The thickness of the anode current collecting layer 31 is not particularly limited but can be set to between 50 µm and 500 µm. The porosity of the anode current collecting layer 31 is not particularly limited but can be set to between 25% and 50%.

[0026] The anode active layer 32 is disposed on the anode current collecting layer 31. The anode active layer 32 is formed of an electrically conductive material and an oxygen ion conductive material. For example, the anode active layer 32 can be formed of NiO-8YSZ, NiO-GDC (gadolinium-doped ceria), or the like. It is preferable that the volume ratio of the oxygen ion conductive material in the anode active layer 32 is larger than the volume ratio of the oxygen ion conductive material in the anode current collecting layer 31. The thickness of the anode active layer 32 is not particularly limited but can be set to 5 μm to 30 μm. The porosity of the anode active layer 32 is not particularly limited but can be set to 25% to 50%.

[0027] The solid electrolyte layer 4 is arranged between the anode 3 and the cathode 6. The solid electrolyte layer 4 is formed to cover the support substrate 2 and the anode 3, and is also connected to the interconnectors 8 of two adjacent power generation units. In the Fig. In the example shown in Figure 4, the solid electrolyte layer 4 of the first power generation unit 11 is connected to the intermediate connector 8 of the second power generation unit 12. Thus, the solid electrolyte layer 4 and the intermediate connector 8 are continuous in the surface direction (the direction perpendicular to the thickness direction) and form a sealing film that prevents the fuel gas from mixing with the oxygen-containing gas.

[0028] The solid electrolyte layer 4 contains a zirconia-based material as a main component. Examples of materials that can be used as the zirconia-based material include 3YSZ, 8YSZ, and ScSZ (scandium-stabilized zirconia). The configuration of the solid electrolyte layer 4 of the first power generation unit 11 will be described later.

[0029] The thickness of the anode active layer 4 is not particularly limited, but can be set between 3 µm and 50 µm. The solid electrolyte layer 4 is dense. The porosity of the solid electrolyte layer 4 is preferably 20% or lower, and more preferably 10% or lower.

[0030] The barrier layer 5 is disposed on the solid electrolyte layer 4. Examples of materials that can be used to form the barrier layer 5 include ceria and ceria-based materials containing oxides of rare earth metals dissolved in ceria. Examples of such ceria-based materials include GDC, SDC (samarium-doped ceria), or the like. The thickness of the barrier layer 5 is not particularly limited but can be set to between 3 µm and 50 µm.

[0031] The cathode 6 is disposed on the barrier layer 5. Examples of materials that can be used to form the cathode 6 include (LaSr)(CoFe)O3 (LSCF, lanthanum strontium cobalt ferrite), (La,Sr)FeO3 (LSF, lanthanum strontium ferrite), La(Ni,Fe)O3 (LNF, lanthanum nickel ferrite), (La,Sr)CoO3 (LSC, lanthanum strontium cobaltite), or the like. The thickness of the cathode 6 is not particularly limited but can be set to 10 µm to 100 µm.

[0032] The cathode current collecting layer 7 is formed on the cathode 6. In the Fig. In the example shown in Figure 4, the cathode current collecting layer 7 of the first power generation unit 11 is connected to the interconnector 8 of the second power generation unit 12. The cathode current collecting layer 7 is formed of an electrically conductive porous material. Examples of materials that can be used to form the cathode current collecting layer 7 include LSCF, LSC, Ag (silver), Ag-Pd (silver-palladium alloy), and the like. The thickness of the cathode current collecting layer 7 is not particularly limited but can be set to between 50 µm and 500 µm.

[0033] The intermediate connector 8 is arranged on the anode 3. In the Fig. In the example shown in Figure 4, the solid electrolyte layer 4 of the first power generation unit 11 is connected to a first end of the intermediate connector 8 of the second power generation unit 12, and the solid electrolyte layer 4 of the second power generation unit 12 is connected to a second end of the intermediate connector 8 of the second power generation unit 12. Furthermore, although not shown in the drawings, both ends of the intermediate connector 8 are connected to the solid electrolyte layers 4 in the longitudinal direction.

[0034] The intermediate interconnector 8 is a layer that is denser than the support substrate 2 and the anode 3. The porosity of the intermediate interconnector 8 is not particularly limited, but is preferably 20% or lower, and more preferably 10% or lower. The thickness of the intermediate interconnector 8 is not particularly limited, but can be set to 10 µm to 100 µm.

[0035] The intermediate connector 8 may contain calcium-doped lanthanum chromite (hereinafter referred to as "calcium-doped lanthanum chromite") as a main component. Calcium-doped lanthanum chromite is represented by the general formula La 1-X Ca X Cr 1-Y-Z A Y O3 (wherein A is at least one element selected from the group consisting of Ti, V, Mn, Fe, Co, Cu, Ni, Zn, Mg, and Al, 0.025 ≤ X ≤ 0.3, 0 ≤ Y ≤ 0.22, and 0 ≤ Z ≤ 0.15). Configuration of the solid electrolyte layer 4 of the first power generation unit 11

[0036] Next, the configuration of the solid electrolyte layer 4 of the first power generation unit 11 will be described. The first power generation unit 11 is an example of the "base-end side power generation unit" that is closest to the manifold 200 among the first to fourth power generation units 11 to 14. The first power generation unit 11 is closest to the base end 302 of the fuel cell 301 among the first to fourth power generation units 11 to 14.

[0037] How Fig. 4, the solid electrolyte layer 4 of the first power supply unit 11 includes a first region 41 and a second region 42.

[0038] The first region 41 is in contact with the anode 3 at an anode-side surface 4S. The first region 41 is a region of the solid electrolyte layer 4 that covers within 3 μm of the anode-side surface 4S. The anode-side surface 4S is the interface between the anode 3 and the solid electrolyte layer 4. The anode-side surface 4S is a straight line obtained by approximating a line on which the element concentration contained in the solid electrolyte layer 4 changes dramatically by the least squares method when mapping the concentration of components in a cross section of the fuel cell 301.

[0039] The first region 41 contains a zirconia-based material as a main component. The first region 41 contains cubic zirconia and tetragonal zirconia as the zirconia-based materials.

[0040] Cubic zirconia is a type of zirconia that has a predominantly cubic crystalline phase. Examples of cubic zirconia include 8YSZ and 10YSZ (10 mol% yttrium-stabilized zirconia).

[0041] Tetragonal zirconia is a type of zirconia that has a predominantly tetragonal crystalline phase. Examples of tetragonal zirconia include zirconia stabilized with 3 mol% or less yttrium, such as 2.5YSZ (2.5 mol% yttrium-stabilized zirconia) or 3YSZ (3 mol% yttrium-stabilized zirconia).

[0042] The second region 42 is a region provided on the first region 41 of the solid electrolyte layer 4. The second region 42 is provided on the side of the first region 41 opposite the anode 3. The thickness of the second region 42 is not particularly limited but can be set to 1 μm to 50 μm. From the viewpoint of reducing damage to the solid electrolyte layer 4, the thickness of the second region 42 is preferably 80% or less of the total thickness of the solid electrolyte layer 4. From the viewpoint of reducing the decrease in ionic conductivity of the solid electrolyte layer 4, the thickness of the second region 42 is preferably 20% or more of the total thickness of the solid electrolyte layer 4.

[0043] The second region 42 contains a zirconia-based material as a main component. The second region 42 contains cubic zirconia as the zirconia-based material. The second region 42 may contain tetragonal zirconia.

[0044] Here, a ratio R1 of the peak intensity of the tetragonal zirconia to the peak intensity of the cubic zirconia in the Raman spectrum in the first region 41 (hereinafter appropriately abbreviated as "the intensity ratio R1 of the first region 41") is larger than a ratio R2 of the peak intensity of the tetragonal zirconia to the peak intensity of the cubic zirconia in the Raman spectrum in the second region 42 (hereinafter appropriately abbreviated as "intensity ratio R2 of the second region 42"). The cubic zirconia particles are thus firmly bonded to each other by the tetragonal zirconia particles, which have a smaller particle size than that of the cubic zirconia particles. As a result, the framework structure of the porous first region 41 can be strengthened.Accordingly, even when the temperature of the first power generation unit 11 decreases due to insufficient preheating of the fuel gas on the base end 302 side of the gas flow path 21 of the fuel cells 301, damage to the solid electrolyte layer 11 of the first power generation unit 11 due to thermal stress can be reduced.

[0045] The intensity ratio R1 of the first region is obtained as follows.

[0046] First, in a cross-section of the first region 41 parallel to the thickness direction, Raman spectra are obtained at five positions that evenly divide the first region 41 in a surface direction perpendicular to the thickness direction. The planes of the five positions at which the Raman spectra were acquired are preferably approximately the same in the thickness direction.

[0047] Next, the ratio of the spectral intensity of tetragonal zirconia to the spectral intensity of cubic zirconia is calculated by analyzing the Raman spectra of the five positions using the unique Raman spectra of each of the cubic zirconia and the tetragonal zirconia (known spectral data). The method that uses known spectral data to analyze the Raman spectra is the CLS method, which is a well-known method for estimating chemical species from Raman spectra.

[0048] Subsequently, the intensity ratio R1 of the first region 41 is calculated by taking the arithmetic average of the intensity ratios calculated from the Raman spectra of the five positions. The intensity ratio R1 is an index indicating the concentration percentage (excess percentage) of tetragonal zirconia to cubic zirconia in the first region 41. The intensity ratio R1 of the first region 41 is expressed as a percentage.

[0049] The intensity ratio R1 of the first region 41 is not particularly limited, but can be set between 0.5% and 10%. The intensity ratio R1 of the first region 41 is preferably 1% or greater, and more preferably 8% or less.

[0050] The intensity ratio R2 of the second region 42 is obtained in the same manner as the intensity ratio R1 of the first region 41 as described below.

[0051] First, in a cross-section of the second region 42 parallel to the thickness direction, Raman spectra are obtained at five positions that evenly divide the second region 42 in the surface direction. The planes of the five positions at which the Raman spectra were acquired are preferably approximately the same in the thickness direction.

[0052] Subsequently, the ratio of the spectral intensity of the tetragonal zirconia to the spectral intensity of the cubic zirconia is calculated by analyzing the Raman spectra of the five positions using the unique Raman spectrum of each of the cubic zirconia and the tetragonal zirconia (known spectral data).

[0053] Subsequently, the intensity ratio R2 of the second region 42 is calculated by taking the arithmetic average of the intensity ratios calculated from the Raman spectra of the five positions. The intensity ratio R2 is an index indicating the concentration percentage (excess percentage) of tetragonal zirconia to cubic zirconia in the second region 42. The intensity ratio R2 of the second region 42 is expressed as a percentage.

[0054] The intensity ratio R2 of the second region 42 is not particularly limited, provided it is less than or equal to the intensity ratio of the first region 41, and can be set to 0.1% or less. The intensity ratio R2 of the second region 42 is more preferably 0.05% or less. Fuel cell manufacturing process 301

[0055] An example of a manufacturing method of the fuel cell 301 is described below.

[0056] First, a molded body of the carrier substrate 2 having five gas flow paths 21 is formed by extrusion molding the carrier substrate material described above.

[0057] Subsequently, a molded body of the anode 3 is produced by preparing the anode material described above as a paste and screen printing the paste onto the molded body of the carrier substrate 2.

[0058] Then, a molded body of the interposer 8 is manufactured by preparing the above-described interposer material as a paste and screen printing the paste onto the anode 3.

[0059] Subsequently, a molded body of the solid electrolyte layer 4 of the first power generation unit 11 is formed by dip-molding the zirconia material for the first region 41 and then dip-molding the zirconia material for the second region 42 in the region on the molded bodies of the support substrate 2 and the anode 3 corresponding to the first power generation unit 11. At this time, the mixing ratio of the tetragonal zirconia contained in the zirconia material for the first region 41 is formulated to be higher than the mixing ratio of the tetragonal zirconia contained in the zirconia material for the second region 42. The intensity ratio R1 of the first region 41 can be adjusted by changing the mixing ratio of the tetragonal zirconia to the cubic zirconia contained in the zirconia material for the first region 41.In the same way, the intensity ratio R2 of the second region 42 can be adjusted by changing the mixing ratio of the tetragonal zirconia to the cubic zirconia contained in the zirconia material for the second region. Note that the zirconia material for the second region 42 may contain only cubic zirconia.

[0060] Subsequently, molded bodies of the solid electrolyte layer 4 of the second to fourth power generation units 12 to 14 are formed by dip-molding the zirconia material in the regions on the molded bodies of the support substrate 2 and the anode 3 corresponding to the second to fourth power generation units 12 to 14. Note that the zirconia material used for the solid electrolyte layers 4 of the second to fourth power generation units 12 to 14 may not contain tetragonal zirconia. Accordingly, the same zirconia material used for the second region 42 of the solid electrolyte layer 4 of the first power generation unit 11 may also be used for the solid electrolyte layers 4 of the second to fourth power generation units 12 to 14.

[0061] Subsequently, a molded body of the barrier layer 5 is formed by dip-molding the barrier layer material on the molded body of the solid electrolyte layer 4.

[0062] Then, the mold bodies for the carrier substrate 2, the anode 3, the solid electrolyte layer 4, the barrier layer 5 and the intermediate connector 8 are fired together (at 1300 °C to 1600 °C for 2 to 20 hours).

[0063] Then, a molded body of the cathode 6 is produced by preparing the cathode material as a paste and screen printing the paste onto the barrier layer 5.

[0064] Subsequently, a molded body of the cathode current collecting layer 7 is formed by preparing the material of the cathode current collecting layer as a paste and screen printing the paste onto the molded body of the cathode 6.

[0065] Then, the molded bodies of the cathode 6 and the cathode current collecting layer 7 are fired (at 900 °C to 1100 °C for 1 to 20 hours). 2. Second embodiment

[0066] The first embodiment describes that the solid electrolyte layer according to the present invention is applied to a segmented series type fuel cell, but application to a flat tubular type fuel cell is also possible. An aspect in which the solid electrolyte layer according to the present invention is applied to a flat tubular type fuel cell will be described below. Note that the configuration of the fuel cell is different between the first embodiment and the second embodiment; thus, this point will be mainly discussed. Fuel cell configuration 401

[0067] Fig. 5 is a perspective view of a fuel cell 401. Fig. 6 is a cross-sectional view of the fuel cell 401.

[0068] The fuel cell 401 is a so-called solid oxide fuel cell (SOFC) of the flat-tubular type. Base ends 402 of the fuel cells 401 are fixed to the through holes 202 by a connecting material, and the base ends 402 are inserted into the through holes 202 of the manifold 200 (see Fig. 2). A distal end of the fuel cell 401 is a free end.

[0069] The fuel cell 401 includes a support substrate 410, a power generation unit 420, and an intermediate connector 430. (1) Carrier substrate 410

[0070] The support substrate 410 is formed in a flat, plate-like shape. The support substrate 410 supports the power generation unit 420 and the intermediate connector 430. The support substrate 410 has a first main surface 410S and a second main surface 410T. The power generation unit 420 is arranged on the first main surface 410S. The intermediate connector 430 is arranged on the second main surface 410T.

[0071] Gas flow paths 410a extending in the longitudinal direction of the fuel cell 401 are provided in the support substrate 410. During power generation, the fuel gas is supplied from the manifold 200 (see Fig. 2) to the gas flow paths 410a. The number of gas flow paths 410a can be adjusted as desired.

[0072] The support substrate 410 is gas-permeable to allow the fuel gas to pass to the anode 421 and is electrically conductive to collect current via the interconnector 430. The support substrate 410 can be formed from a ferrous metal component and a ceramic component (a rare earth oxide or the like). Examples of the ferrous metal component include Fe, Ni, and Co. Examples of the rare earth oxide include Y2O3 and Yb2O3.

[0073] The thickness of the support substrate 410 is not particularly limited, but can be adjusted between, for example, 2 mm and 35 mm. The length of the support substrate 410 is not particularly limited, but can be adjusted between, for example, 50 mm and 250 mm. (2) Power generation unit 420

[0074] The power generation unit 420 includes an anode 421, a solid electrolyte layer 422, a barrier layer 423, and a cathode 424.

[0075] The anode 421 is arranged on the first main surface 410S of the carrier substrate 410. The anode 421 can be formed, for example, from ZrO2 or CeO2, in which a rare earth oxide is dissolved in the solid, and Ni and / or NiO.

[0076] It is sufficient if the anode 421 is arranged at a position at least opposite the cathode 424. Accordingly, in the Fig. 5 and Fig. 6 the anode 421 to the two ends of the intermediate connector 430 on the second main surface 410T, but the anode 421 may also be arranged only on the first main surface 410S.

[0077] The solid electrolyte layer 422 is disposed between the anode 421 and the cathode 424. The solid electrolyte layer 422 has gas barrier properties to prevent the leakage of fuel gas and oxygen-containing gas. The relative density of the solid electrolyte layer 422 is preferably 93% or greater, and more preferably 95% or greater.

[0078] The solid electrolyte layer 422 contains a zirconia-based material as a main component. Examples of materials that can be used as the zirconia-based material include 3YSZ, 8YSZ, and ScSZ (scandium-stabilized zirconia).

[0079] The solid electrolyte layer 422 according to the present embodiment includes a base end part 422a and a separate part 422b.

[0080] The base end portion 422a is formed integrally with the separate portion 422b. The base end portion 422a is disposed on the base end 402 side (the manifold 200 side) of the fuel cell 401. That is, the base end portion 422a is a region of the solid electrolyte layer 422 close to the base end 402. Specifically, the base end portion 422a may be disposed in a region covering 1 / 4 of the total length in the longitudinal direction of the solid electrolyte layer 422. The detailed configuration of the base end portion 422a will be described below.

[0081] The separate part 422b is the area of ​​the solid electrolyte layer 422 that is different from the base end part 422a. The separate part 422b is arranged separately from the base end 402 (the manifold 200 side) of the fuel cell 401. That is, the separate part 422b is a portion of the solid electrolyte layer 422 that is separated from the base end 402. The separate part 422b may be arranged in an area that covers 3 / 4 of the total length in the longitudinal direction of the solid electrolyte layer 422.

[0082] The barrier layer 423 is disposed between the solid electrolyte layer 422 and the cathode 424. The barrier layer 423 is provided to block the diffusion of elements from the cathode 424 to the solid electrolyte layer 422. The barrier layer 423 can be formed, for example, from a Ce-containing oxide.

[0083] The cathode 424 is disposed at a position opposite the anode 421 with the solid electrolyte layer 422 interposed therebetween. The cathode 424 may be formed from a perovskite oxide represented by the general formula ABO3. Examples of such a perovskite oxide include transition metal perovskite oxides. Examples of transition metal perovskite oxides include (La, Sr) (Co, Fe)O3 oxides, LaMnO3 oxides, LaFeO3 oxides, and LaCoO3 oxides. (3) Intermediate connector 430

[0084] The intermediate interconnect 430 is arranged on the second main surface 410T of the support substrate 410. The intermediate interconnect 430 may be formed from an electrically conductive ceramic that is reduction-resistant, oxidation-resistant, and dense. Examples of such electrically conductive ceramics include lanthanum chromite-based perovskite oxides (LaCrO3 oxides). The relative density of the intermediate interconnect 430 is, for example, preferably 93% or greater, and more preferably 95% or greater. The thickness of the intermediate interconnect 430 is not particularly limited but can be set to, for example, 10 µm to 200 µm. Configuration of the base end part 422a of the solid electrolyte layer 422

[0085] The configuration of the base end part 422a of the solid electrolyte layer 422 will be described below.

[0086] As the Fig. 5 and Fig.6, the base end portion 422a includes a first region 41 and a second region 42.

[0087] The first region 41 is a region of the base end part 422a covering within 3 μm of an anode-side surface 422S. The anode-side surface 422S is the interface between the anode 421 and the solid electrolyte layer 422. The anode-side surface 422S is a straight line obtained by approximating a line on which the element concentration contained in the solid electrolyte layer 422 changes dramatically by the least squares method when mapping the concentration of components in a cross section of the fuel cell 301.

[0088] The first region 41 contains a zirconia-based material as a main component. The first region 41 contains cubic zirconia and tetragonal zirconia as the zirconia-based materials.

[0089] Cubic zirconia is a type of zirconia that has a predominantly cubic crystalline phase. Examples of cubic zirconia include 8YSZ and 10YSZ (10 mol% yttrium-stabilized zirconia).

[0090] Tetragonal zirconia is a type of zirconia that has a predominantly tetragonal crystalline phase. Examples of tetragonal zirconia include zirconia stabilized with 3 mol% or less yttrium, such as 2.5YSZ (2.5 mol% yttrium-stabilized zirconia) or 3YSZ (3 mol% yttrium-stabilized zirconia).

[0091] The second region 42 is a region of the solid electrolyte layer 422 provided on the first region 41. The second region 42 is provided on the opposite side of the first region 41 from the anode 421. The thickness of the second region 42 is not particularly limited but can be set to 1 μm to 50 μm. From the viewpoint of reducing damage to the solid electrolyte layer 422, the thickness of the second region 42 is preferably 80% or less of the total thickness of the solid electrolyte layer 422. From the viewpoint of reducing the decrease in ionic conductivity of the solid electrolyte layer 422, the thickness of the second region 42 is preferably 20% or more of the total thickness of the solid electrolyte layer 422.

[0092] The second region 42 contains a zirconia-based material as a main component. The second region 42 contains cubic zirconia as the zirconia-based material. The second region 42 may contain tetragonal zirconia.

[0093] Here, a ratio R1 of the peak intensity of the tetragonal zirconia to the peak intensity of the cubic zirconia in the Raman spectrum in the first region 41 (hereinafter appropriately abbreviated as "the intensity ratio R1 of the first region 41") is larger than a ratio R2 of the peak intensity of the tetragonal zirconia to the peak intensity of the cubic zirconia in the Raman spectrum in the second region 42 (hereinafter appropriately abbreviated as "intensity ratio R2 of the second region 42"). The cubic zirconia particles are thus firmly bonded to each other by the tetragonal zirconia particles, which have a smaller particle size than that of the cubic zirconia particles. As a result, the framework structure of the porous first region 41 can be strengthened.Accordingly, even if the temperature of the base end 402 decreases due to insufficient preheating of the fuel gas on the base end 402 side of the gas flow path 410a of the fuel cell 401, damage to the base end part 422a of the solid electrolyte layer 422 due to thermal stress can be reduced.

[0094] The intensity ratio R1 of the first region is obtained as follows.

[0095] First, in a cross-section of the first region 41 parallel to the thickness direction, Raman spectra are obtained at five positions that evenly divide the first region 41 in a surface direction perpendicular to the thickness direction. The planes of the five positions at which the Raman spectra were acquired are preferably approximately the same in the thickness direction.

[0096] Next, the ratio of the spectral intensity of tetragonal zirconia to the spectral intensity of cubic zirconia is calculated by analyzing the Raman spectra of the five positions using the unique Raman spectra of each of the cubic zirconia and the tetragonal zirconia (known spectral data). The method that uses known spectral data to analyze the Raman spectra is the CLS method, which is a well-known method for estimating chemical species from Raman spectra.

[0097] Subsequently, the intensity ratio R1 of the first region 41 is calculated by taking the arithmetic average of the intensity ratios calculated from the Raman spectra of the five positions. The intensity ratio R1 is an index indicating the concentration ratio (excess ratio) of tetragonal zirconia to cubic zirconia in the first region 41. The intensity ratio R1 of the first region 41 is expressed as a percentage.

[0098] The intensity ratio R1 of the first region 41 is not particularly limited, but can be set between 0.5% and 10%. The intensity ratio R1 of the first region 41 is preferably 1% or greater, and more preferably 8% or less.

[0099] The intensity ratio R2 of the second region 42 is obtained in the same manner as the intensity ratio R1 of the first region 41 as described below.

[0100] First, in a cross-section of the second region 42 parallel to the thickness direction, Raman spectra are obtained at five positions that evenly divide the second region 42 in the surface direction. The planes of the five positions at which the Raman spectra were acquired are preferably approximately the same in the thickness direction.

[0101] Subsequently, the ratio of the spectral intensity of the tetragonal zirconia to the spectral intensity of the cubic zirconia is calculated by analyzing the Raman spectra of the five positions using the unique Raman spectrum of each of the cubic zirconia and the tetragonal zirconia (known spectral data).

[0102] Subsequently, the intensity ratio R2 of the second region 42 is calculated by taking the arithmetic average of the intensity ratios calculated from the Raman spectra of the five positions. The intensity ratio R2 is an index indicating the concentration ratio (excess ratio) of tetragonal zirconia to cubic zirconia in the second region 42. The intensity ratio R2 of the second region 42 is expressed as a percentage.

[0103] The intensity ratio R2 of the second region 42 is not particularly limited, provided it is less than or equal to the intensity ratio of the first region 41, and can be set to 0.1% or less. The intensity ratio R2 of the second region 42 is more preferably 0.05% or less. Fuel cell manufacturing process 401

[0104] First, a slurry is prepared by mixing a pore-forming agent, an organic binder, a solvent, and a dispersant with a mixed powder (a mixed powder containing a ferrous metal or an oxide powder thereof and a rare earth oxide powder) to form the support substrate 410. A molded body of the plate-like support substrate 410, in which gas flow paths are provided, is formed by extrusion molding this slurry.

[0105] Subsequently, a slurry is prepared by mixing an organic binder and a solvent with a powder mixture (for example, a powder mixture containing NiO powder and YSZ powder) to form the anode 421. Then, a molded body of the anode 421 is formed by placing an anode plate made of this slurry over the first main surface 410S of the molded body of the support substrate 410.

[0106] Subsequently, a molded body of the base end part 422a of the solid electrolyte layer 422 is formed by dip-molding the zirconia material for the first region 41 and then dip-molding the zirconia material for the second region 42 in a region of the molded body of the anode 421 covering from the base end 402 to 1 / 4 of the total length in the longitudinal direction of the molded body.

[0107] Here, the mixing ratio of the tetragonal zirconia contained in the zirconia material for the first region 41 is formulated to be higher than the mixing ratio of the tetragonal zirconia contained in the zirconia material for the second region 42. The intensity ratio R1 of the first region 41 can be adjusted by changing the mixing ratio of the tetragonal zirconia to the cubic zirconia contained in the zirconia material for the first region 41. In the same way, the intensity ratio R2 of the second region 42 can be adjusted by changing the mixing ratio of the tetragonal zirconia to the cubic zirconia contained in the zirconia material for the second region. Note that the zirconia material for the second region 42 can only contain cubic zirconia.

[0108] Then, a molded body of the separate part 422b of the solid electrolyte layer 422 is formed by dip-molding the zirconia material in the region covering more than 1 / 4 of the total length in the longitudinal direction of the molded body from the base end 402. Note that the zirconia material used for the separate part 422b may not contain tetragonal zirconia. Accordingly, the same zirconia material used for the second region 42 of the base end part 422a may be used for the separate part 422b.

[0109] Subsequently, a slurry is prepared by mixing an organic binder and a solvent with a powder (for example, GDC) to form the barrier layer 423. Then, a molded body of the barrier layer 423 is formed by placing a barrier plate made from this slurry over the molded body of the solid electrolyte layer 422 (the base end part 422a and the separate part 422b).

[0110] Next, a slurry is prepared by mixing an organic binder and a solvent with a powder (for example, a LaCrO3-based material) to form the interconnector 430. Then, an interconnector plate made from this slurry is placed on the second main surface 410T of the molded body of the support substrate 410.

[0111] Next, the resulting laminated body is subjected to a heat treatment to remove the binder and then fired in an oxygen-containing atmosphere at 1300 °C to 1600 °C to obtain fired bodies of the support substrate 410, the power generation unit 420 (except the cathode 424), and the interconnector 430.

[0112] Next, a molded body of the cathode 424 is formed by dispersing a powder (for example, a LaFeO3-based oxide powder) for forming the cathode 424 in a solvent to prepare a coating solution, and applying this coating solution on the surface of the barrier layer 423 by dip molding.

[0113] Then, the cathode 424 is formed by firing the cathode 424 mold body at 1000 °C to 1300 °C. Other embodiments

[0114] The present invention is not limited to the embodiments described above, and various kinds of changes and modifications can be made without departing from the scope of the invention.

[0115] The above embodiments describe that the solid electrolyte layer according to the present invention is applied to a solid oxide fuel cell. However, in addition to solid oxide fuel cells, the solid electrolyte layer according to the present invention can be applied to solid oxide electrochemical cells such as solid oxide electrolysis cells.

[0116] The above embodiments describe that the first to fourth power generation units 11 to 14 are arranged on the support substrate 2, but the number of power generation units can be selected as desired.

[0117] The above embodiments describe the solid electrolyte layer 4 of the "base-end side power generation unit," namely, the first power generation unit 11 closest to the manifold 200. However, the solid electrolyte layers 4 of the second to fourth power generation units may have configurations different from that of the solid electrolyte layer 4 of the first power generation unit 11. For example, the entire solid electrolyte layer 4 of the second to fourth power generation units may each have the same configuration as the second region 42 of the solid electrolyte layer 4 of the first power generation unit 11. In addition, the solid electrolyte layer 4 of the second to fourth power generation units may each have the same configuration as the solid electrolyte layer 4 of the first power generation unit 11. REFERENCE SYMBOL 2 Carrier substrate 3 Anode 4 Solid electrolyte layer 5 Barrier layer 6 Cathode 7 Cathode current collecting layer 8 intermediate connectors 11 first power generation unit (example of a base-end power generation unit) 12 second power generation unit 13 third power generation unit 14 fourth power generation unit 21 Gas flow path 41 first area 42 second area 100 stacks 200 pipe distributors 201 insertion line 202 through hole 203 Cover plate 204 pipe manifold main body 301 Fuel cell 302 Base End 401 Fuel cell 402 Base End 410 carrier substrate 410S first main surface 410T second main surface 410a Gas flow path 421 Anode 422 Solid electrolyte layer 423 barrier layer 424 Cathode 402 Power generation unit 430 intermediate connectors

Claims

[1] Stack (100) of electrochemical cells (301) containing: an electrochemical cell (301); and a manifold (200) supporting a base end (302) of the electrochemical cell (301); wherein the electrochemical cell (301) includes an electrically insulating support substrate (2) and a plurality of power generation units (11, 12, 13, 14) arranged on the support substrate (2), wherein a gas flow path (21) is provided in the support substrate (2); wherein each of the plurality of power generation units (11, 12, 13, 14) includes an anode (3), a cathode (6), and a solid electrolyte layer (4) disposed between the anode (3) and the cathode (6), which solid electrolyte layer includes a zirconium dioxide-based material as a main component; wherein in a power generation unit (11) on the base end side closest to the manifold (200) among the plurality of power generation units (11, 12, 13, 14), the solid electrolyte layer (4) includes a first region (41) covering within 3 µm of an anode-side surface and a second region (42) provided on the first region (41); wherein an intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum in the first region (41) is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region (42); and wherein an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the first region (41) is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the solid electrolyte layer (4) of another power generation unit (12, 13, 14) of the plurality of power generation units (11, 12, 13, 14) other than the power generation unit (11) on the base end side. [2] The stack (100) of electrochemical cells (301) of claim 1, wherein the intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the first region (41) is 1% or greater. [3] The stack (100) of electrochemical cells (301) according to claim 1 or 2, wherein the intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region (42) is 0.1% or less. [4] Stack (100) of electrochemical cells (401) containing: an electrochemical cell (401); and a manifold (200) supporting a base end (402) of the electrochemical cell (401); wherein the electrochemical cell (401) includes an electrically conductive support substrate (410) and a power generation unit (402) arranged on the support substrate (410), wherein a gas flow path (410a) is provided in the support substrate (410); wherein the power generation unit (402) includes an anode (421) arranged on a first main surface (410S) of the support substrate (410), a cathode (424), and a solid electrolyte layer (422) arranged between the anode (421) and the cathode (424), which solid electrolyte layer (422) includes a zirconium dioxide-based material as its main component;. wherein the solid electrolyte layer (422) includes a base end portion disposed on one side of the base end of the electrochemical cell (402) and a separate portion disposed separately from the base end (402); wherein the base end part (402) covers a first region (41) within 3 µm of an anode-side surface, and includes a second region (42) provided on the first region (41); and wherein an intensity ratio of tetragonal zirconia to cubic zirconia in a Raman spectrum in the first region (41) is greater than an intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region (42). [5] The electrochemical cell stack (100) (401) according to claim 4, wherein the base end portion is a region covering 1 / 4 of the total length of the solid electrolyte layer (422) in a direction in which the gas flow path (410a) extends. [6] Stack (100) of electrochemical cells (401) according to claim 4 or 5, wherein the intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the first (41) region is 1% or greater. [7] Stack (100) of electrochemical cells (401) according to one of claims 4 to 6, wherein the intensity ratio of tetragonal zirconia to cubic zirconia in the Raman spectrum in the second region (42) is 0.1% or less.

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