JP7649929B2 - Electrochemical Cell - Google Patents

Description

The present invention relates to an electrochemical cell.

Conventionally, electrochemical cells (electrolysis cells, fuel cells, etc.) having a structure in which a cell body is supported by a metal support are known. For example, the electrochemical cell described in Patent Document 1 has a cell body in which a first electrode layer, an electrolyte layer, and a second electrode layer are laminated in this order on the main surface of a metal support. The metal support is made of a metal material such as stainless steel.

JP 2020-155337 A

Because the heat resistance of the metal support is low, it is difficult to form the first electrode layer on the main surface of the metal support at high temperatures. Therefore, there is a limit to how much strength the porous microstructure of the first electrode layer can be improved, and the first electrode layer is prone to damage (cracks and peeling).

The object of the present invention is to provide an electrochemical cell capable of suppressing damage to the first electrode layer.

The electrochemical cell according to a first aspect of the present invention comprises a cell body and a metal support. The cell body has a first electrode layer, a second electrode layer, and an electrolyte layer disposed between the first and second electrode layers. The metal support has a first main surface, a second main surface, a recess formed in the first main surface, and a plurality of supply holes communicating with the second main surface and a bottom surface of the recess. At least a portion of the first electrode layer is disposed within the recess.

The electrochemical cell according to the second aspect of the present invention relates to the first aspect, and in a cross section along the thickness direction of the metal support, the boundary between the side peripheral surface and the bottom surface of the recess is R-shaped.

The electrochemical cell according to the third aspect of the present invention is related to the first or second aspect, and the cell main body has a catalyst layer disposed in at least one of the plurality of supply holes and connected to the first electrode layer.

The present invention provides an electrochemical cell that can suppress damage to the first electrode layer.

FIG. 1 is a plan view of an electrolysis cell according to an embodiment. FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a cross-sectional view of an electrolysis cell according to the first modification. FIG. 4 is a cross-sectional view of an electrolysis cell according to the second modification.

(Electrolytic cell 100)
Fig. 1 is a plan view of an electrolytic cell 100 according to an embodiment. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. The electrolytic cell 100 is a so-called metal-supported electrolytic cell. The electrolytic cell 100 is an example of the "electrochemical cell" according to the present invention.

The electrolytic cell 100 is formed in a plate shape extending in the X-axis direction and the Y-axis direction. In this embodiment, the electrolytic cell 100 is formed in a rectangular shape extending in the Y-axis direction in a plan view, but the planar shape of the electrolytic cell 100 is not particularly limited and may be a polygon other than a rectangle, an ellipse, a circle, etc.

As shown in FIG. 2, the electrolysis cell 100 comprises a metal support 10, a cell main body 20, and a flow path member 30.

(Metal Support 10)
The metal support 10 supports the cell main body 20. The metal support 10 is formed in a plate shape. The metal support 10 may be in a flat plate shape or a curved plate shape. The metal support 10 may have any thickness as long as it can maintain the strength of the electrolysis cell 100, and the thickness is not particularly limited, but may be, for example, 0.1 mm or more and 2.0 mm or less.

As shown in FIG. 2, the metal support 10 has a first main surface 11, a second main surface 12, a recess 13, and a plurality of supply holes 14.

The first main surface 11 is the main surface on the cell main body 20 side. The first main surface 11 is formed in a planar shape. The cell main body 20 is joined to the first main surface 11. A recess 13 is formed in the first main surface 11. Therefore, the first main surface 11 is formed in an annular shape when viewed in a plan view.

The second main surface 12 is the main surface opposite the cell main body 20 and is provided opposite the first main surface 11. The second main surface 12 is formed in a planar shape. A flow path member 30 is joined to the second main surface 12.

The recess 13 is formed in the first main surface 11. The recess 13 opens to the first main surface 11. The recess 13 is a so-called bottomed recess. The hydrogen electrode layer 1, which will be described later, is disposed within the recess 13. The recess 13 has a bottom surface S1 and a peripheral side surface S2.

The bottom surface S1 is in contact with the hydrogen electrode layer 1. The bottom surface S1 covers the metal support 10 side of the hydrogen electrode layer 1. The bottom surface S1 is disposed between the first main surface 11 and the second main surface 12 in the Z-axis direction. The Z-axis direction is a direction perpendicular to each of the X-axis direction and the Y-axis direction, and is an example of the "thickness direction" according to the present invention. In this embodiment, the bottom surface S1 is formed in a planar shape.

The side peripheral surface S2 is continuous with the outer edge of the bottom surface S1 and the inner edge of the first main surface 11. The side peripheral surface S2 is formed in an annular shape. The side peripheral surface S2 contacts the hydrogen electrode layer 1. The side peripheral surface S2 covers the side circumference of the hydrogen electrode layer 1.

2, in a cross section along the thickness direction of the metal support 10, the boundary 13a between the bottom surface S1 and the side peripheral surface S2 is R-shaped. Therefore, the side peripheral surface S2 is smoothly connected to the bottom surface S1. There is no inflection point between the bottom surface S1 and the side peripheral surface S2. Therefore, although the boundary between the bottom surface S1 and the side peripheral surface S2 is not clear, the area parallel to the first main surface 11 may be regarded as the bottom surface S1, and the area other than the bottom surface S1 may be regarded as the side peripheral surface S2.

2, the side peripheral surface S2 is curved outward in the surface direction. Specifically, the contour of the side peripheral surface S2 is formed to protrude outward in the surface direction. The surface direction is a direction perpendicular to the Z-axis direction (thickness direction). The outward surface direction refers to a direction away from the center of the metal support 10 in the surface direction.

The depth of the recess 13 in the Z-axis direction is not particularly limited, but can be greater than or equal to 1% and less than or equal to 50% of the thickness of the metal support 10 in the Z-axis direction.

The supply holes 14 are connected to the second main surface 12 and the bottom surface S1 of the recess 13. Each supply hole 14 penetrates the metal support 10 from the second main surface 12 to the bottom surface S1. Each supply hole 14 opens to the second main surface 12 and the bottom surface S1. The opening of the supply hole 14 on the bottom surface S1 side is covered by the hydrogen electrode layer 1. That is, each supply hole 14 is formed in the area of the bottom surface S1 where the hydrogen electrode layer 1 is joined. The opening of the supply hole 14 on the opposite side to the bottom surface S1 is connected to the flow path 30a formed between the metal support 10 and the flow path member 30. A catalyst layer 2, which will be described later, is arranged in each supply hole 14.

Each supply hole 14 can be formed by mechanical processing (e.g., punching), laser processing, or chemical processing (e.g., etching). In this embodiment, each supply hole 14 is formed linearly along the Z-axis direction, but it does not have to be along the Z-axis direction, and it does not have to be linear. For example, when the metal support 10 is made of porous metal, each supply hole 14 may be a three-dimensional mesh-like open hole formed in the porous metal.

The metal support 10 is made of a metal material. For example, the metal support 10 is made of an alloy material containing Cr (chromium). Examples of such metal materials include Fe-Cr alloy steel (stainless steel, etc.) and Ni-Cr alloy steel. The Cr content in the metal support 10 is not particularly limited, but can be 4% by mass or more and 30% by mass or less.

The metal support 10 may contain Ti (titanium) and Zr (zirconium). The Ti content in the metal support 10 is not particularly limited, but may be 0.01 mol% or more and 1.0 mol% or less. The Al content in the metal support 10 is not particularly limited, but may be 0.01 mol% or more and 0.4 mol% or less. The metal support 10 may contain Ti as _TiO2 (titania) and Zr as _ZrO2 (zirconia).

The metal support 10 may have an oxide film on its surface formed by oxidation of the constituent elements of the metal support 10. A typical example of the oxide film is a chromium oxide film. The chromium oxide film covers at least a portion of the surface of the metal support 10. The chromium oxide film may cover at least a portion of the inner circumferential surface of each supply hole 14.

(Cell body 20)
The cell main body 20 has a hydrogen electrode layer 1 (cathode), multiple catalyst layers 2, an electrolyte layer 3, a reaction prevention layer 4, and an oxygen electrode layer 5 (anode). The hydrogen electrode layer 1, the electrolyte layer 3, the reaction prevention layer 4, and the oxygen electrode layer 5 are stacked in this order from the metal support 10 side in the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction.

The hydrogen electrode layer 1 is an example of a "first electrode layer" according to the present invention. The oxygen electrode layer 5 is an example of a "second electrode layer" according to the present invention. The hydrogen electrode layer 1, electrolyte layer 3, and oxygen electrode layer 5 are essential components, while the catalyst layer 2 and reaction prevention layer 4 are optional components.

[Hydrogen electrode layer 1]
The hydrogen electrode layer 1 is disposed in the recess 13 of the metal support 10. As a result, the hydrogen electrode layer 1 is held in the recess 13 of the metal support 10. In this embodiment, the hydrogen electrode layer 1 fills the recess 13. That is, the entire hydrogen electrode layer 1 is disposed in the recess 13. Therefore, as shown in FIG. 2 , the hydrogen electrode layer 1 is formed to fit the contour of the recess 13.

The hydrogen electrode layer 1 contacts the bottom surface S1 and the side surface S2 of the recess 13. Therefore, the bottom surface S1 and the side surface S2 of the recess 13 are the interfaces between the hydrogen electrode layer 1 and the metal support 10. In this embodiment, the surface S3 of the hydrogen electrode layer 1 is formed flat, but may be partially or entirely curved or bent.

The hydrogen electrode layer 1 covers each of the supply holes 14 formed in the bottom surface S1 of the recess 13. A source gas is supplied from the flow passage 30a to the hydrogen electrode layer 1 through each of the supply holes 14. The source gas contains at least _H2O .

When the source gas contains only H ₂ O, the hydrogen electrode layer 1 produces H ₂ from the source gas in accordance with the electrochemical reaction of water electrolysis shown in the following formula (1).
Hydrogen electrode layer 1: H ₂ O+2e ⁻ →H ₂ +O ²⁻ (1)

When the source gas contains CO ₂ in addition to H ₂ O, the hydrogen electrode layer 1 produces H ₂ , CO, and O ²⁻ from the source gas in accordance with the co-electrochemical reactions shown in the following formulas (2), (3), and (4).
・Hydrogen electrode layer 1: CO ₂ +H ₂ O+4e ^- →CO+H ₂ +2O ² -...(2)
Electrochemical reaction of H ₂ O: H ₂ O + 2e ⁻ → H ₂ + O ²⁻ (3)
Electrochemical reaction of _CO2 : _CO2 + ^2e- → CO + O2 ^-... (4)

The hydrogen electrode layer 1 is made of a porous material having electronic conductivity. The hydrogen electrode layer 1 may have oxide ion conductivity. The hydrogen electrode layer 1 may be made of, for example, yttria-stabilized zirconia (YSZ), calcia-stabilized zirconia (CSZ), scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), (La,Sr)(Cr,Mn _{) O3} , (La,Sr) _TiO3 , _Sr2 (Fe,Mo) _2O6 , (La,Sr) _VO3 , (La,Sr) _FeO3 , a mixed material of two or more of these, or a composite of one or more of these and NiO.

The porosity of the hydrogen electrode layer 1 is not particularly limited, but can be, for example, 5% to 70%. The thickness of the hydrogen electrode layer 1 is not particularly limited, but can be, for example, 1 μm to 100 μm.

The method for forming the hydrogen electrode layer 1 is not particularly limited, and may be a firing method, a spray coating method (thermal spraying method, aerosol deposition method, aerosol gas deposition method, powder jet deposition method, particle jet deposition method, cold spray method, etc.), a PVD method (sputtering method, pulsed laser deposition method, etc.), a CVD method, etc.

[Catalyst layer 2]
Each of the plurality of catalyst layers 2 is disposed in a corresponding supply hole 14 and is continuous with the hydrogen electrode layer 1. Each catalyst layer 2 is engaged with the opening of each supply hole 14 on the bottom surface S1 side in the planar direction.

Each catalyst layer 2 is a porous body containing a catalyst. Nickel (Ni), iron (Fe), cobalt (Co), precious metals, etc. can be used as the catalyst. When Ni is used as the catalyst, Ni is preferable because it functions as an electronic conductor and also functions as a thermal catalyst that promotes a thermal reaction between H ₂ generated in the hydrogen electrode layer 1 and CO ₂ contained in the raw material gas to maintain an appropriate gas composition. Ni is basically present in the form of metal Ni during operation of the electrolysis cell 100, but may also be partially present in the form of NiO.

Each catalyst layer 2 may contain an oxide ion conductive material. As the oxide ion conductive material, those listed as the oxide ion conductive materials for the hydrogen electrode layer 1 can be used.

The porosity of each catalyst layer 2 is not particularly limited, but can be, for example, 5% to 70%. The depth of each catalyst layer 2 in the Z-axis direction is not particularly limited, but can be 10% to 100% of the length of each supply hole 14 in the Z-axis direction.

The method for forming each catalyst layer 2 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[Electrolyte layer 3]
The electrolyte layer 3 is disposed between the hydrogen electrode layer 1 and the oxygen electrode layer 5. In this embodiment, the reaction prevention layer 4 is disposed between the electrolyte layer 3 and the oxygen electrode layer 5, and therefore the electrolyte layer 3 is disposed between the hydrogen electrode layer 1 and the reaction prevention layer 4 and is connected to both the hydrogen electrode layer 1 and the reaction prevention layer 4.

The electrolyte layer 3 covers the surface S3 of the hydrogen electrode layer 1. In this embodiment, the hydrogen electrode layer 1 is filled in the recess 13 of the metal support 10, and therefore the electrolyte layer 3 is positioned outside the recess 13.

The outer edge of the electrolyte layer 3 is connected to the first main surface 11 of the metal support 10. In this embodiment, a portion of the first main surface 11 is exposed from the electrolyte layer 3, but the entire first main surface 11 may be covered by the electrolyte layer 3.

The electrolyte layer 3 transfers O ^2- generated in the hydrogen electrode layer 1 to the oxygen electrode layer 5. The electrolyte layer 3 is made of a dense material having oxide ion conductivity. The electrolyte layer 3 can be made of, for example, YSZ (yttria-stabilized zirconia, e.g., 8YSZ), GDC (gadolinium-doped ceria), ScSZ (scandia-stabilized zirconia), SDC (samarium-doped ceria), LSGM (lanthanum gallate), or the like.

The porosity of the electrolyte layer 3 is not particularly limited, but may be, for example, 0.1% to 7%. The thickness of the electrolyte layer 3 is not particularly limited, but may be, for example, 1 μm to 100 μm.

The method for forming the electrolyte layer 3 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[Reaction prevention layer 4]
The reaction prevention layer 4 is disposed between the electrolyte layer 3 and the oxygen electrode layer 5. The reaction prevention layer 4 is disposed on the opposite side of the electrolyte layer 3 from the hydrogen electrode layer 1. The reaction prevention layer 4 prevents the constituent elements of the electrolyte layer 3 from reacting with the constituent elements of the oxygen electrode layer 5 to form a layer with high electrical resistance.

The reaction prevention layer 4 is composed of an oxide ion conductive material. The reaction prevention layer 4 can be composed of, for example, GDC, SDC, etc.

The porosity of the reaction prevention layer 4 is not particularly limited, but can be, for example, 0.1% or more and 50% or less. The thickness of the reaction prevention layer 4 is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less.

The method for forming the reaction prevention layer 4 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[Oxygen electrode layer 5]
The oxygen electrode layer 5 is disposed on the opposite side of the hydrogen electrode layer 1 with respect to the electrolyte layer 3. In this embodiment, since the reaction prevention layer 4 is disposed between the electrolyte layer 3 and the oxygen electrode layer 5, the oxygen electrode layer 5 is connected to the reaction prevention layer 4. If the reaction prevention layer 4 is not disposed between the electrolyte layer 3 and the oxygen electrode layer 5, the oxygen electrode layer 5 is connected to the electrolyte layer 3.

The oxygen electrode layer 5 produces O ₂ from O ²⁻ transferred from the hydrogen electrode layer 1 through the electrolyte layer 3 in accordance with the chemical reaction of the following formula (5).
Oxygen electrode layer 5: 2O ²⁻ →O ₂ +4e ⁻ (5)

The oxygen electrode layer 5 is made of a porous material having oxide ion conductivity and electron conductivity, and may be made of a composite material of _one or more of (La,Sr)(Co,Fe)O3, (La,Sr) _FeO3 , La(Ni,Fe) _O3 , (La,Sr) _CoO3 , and (Sm,Sr) _CoO3 and an oxide ion conductive material (such as GDC).

The porosity of the oxygen electrode layer 5 is not particularly limited, but can be, for example, 20% to 60%. The thickness of the oxygen electrode layer 5 is not particularly limited, but can be, for example, 1 μm to 100 μm.

The method for forming the oxygen electrode layer 5 is not particularly limited, and a firing method, a spray coating method, a PVD method, a CVD method, etc. can be used.

[Flow path member 30]
The flow path member 30 is joined to the second main surface 12 of the metal support 10. The flow path member 30 forms a flow path 30a between itself and the metal support 10. A source gas is supplied to the flow path 30a. The source gas supplied to the flow path 30a is sequentially supplied to the catalyst layer 2 and the hydrogen electrode layer 1 of the cell main body 20 via each supply hole 14 of the metal support 10.

The flow path member 30 may be made of, for example, an alloy material. The flow path member 30 may be made of the same material as the metal support 10. In this case, the flow path member 30 may be substantially integral with the metal support 10.

The flow path member 30 has a frame body 31 and an interconnector 32. The frame body 31 is an annular plate member that surrounds the side periphery of the flow path 30a. The frame body 31 is joined to the second main surface 12 of the metal support 10. The interconnector 32 is a plate member for electrically connecting an external power source or another electrolytic cell in series with the electrolytic cell 100. The interconnector 32 is joined to the frame body 31.

In this embodiment, the frame body 31 and the interconnector 32 are separate components, but the frame body 31 and the interconnector 32 may also be an integral component.

(Features)

(1) The heat resistance of the metal support 10 made of a metal material is low, and it is difficult to form the hydrogen electrode layer 1 at high temperatures, so there is a limit to improving the strength of the porous microstructure of the hydrogen electrode layer 1.

Therefore, in this embodiment, the hydrogen electrode layer 1 is disposed in a recess 13 formed in the first main surface 11 of the metal support 10. This allows the hydrogen electrode layer 1 to be held in the recess 13, so that deformation of the hydrogen electrode layer 1 can be reduced even if an external force in the surface direction is applied to the hydrogen electrode layer 1. In addition, the contact area between the hydrogen electrode layer 1 and the metal support 10 can be made larger than when the hydrogen electrode layer 1 is disposed on the first main surface 11. As a result, damage (cracks and peeling) to the hydrogen electrode layer 1 can be suppressed.

Furthermore, since the deformation of the hydrogen electrode layer 1 can be reduced, the thickness of the hydrogen electrode layer 1 can be increased, improving the gas diffusion in the surface direction within the hydrogen electrode layer 1. As a result, the electrode resistance of the hydrogen electrode layer 1 can be reduced.

(2) In a cross section along the thickness direction of the metal support 10, the boundary 13a between the side peripheral surface S2 and the bottom surface S1 is rounded. Therefore, no corners are formed in the hydrogen electrode layer 1, so that chipping of the hydrogen electrode layer 1 can be suppressed.

(3) The cell body 20 has a catalyst layer 2 disposed in each supply hole 14 and connected to the hydrogen electrode layer 1. This allows the anchor effect of the catalyst layer 2 on the metal support 10 to further reduce deformation of the hydrogen electrode layer 1 in the planar direction.

(Modification of the embodiment)
Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention.

[Modification 1]
In the above embodiment, the entire hydrogen electrode layer 1 is disposed within the recess 13 of the metal support 10. However, as shown in FIG. 3, it is sufficient that at least a portion of the hydrogen electrode layer 1 is disposed within the recess 13.

[Modification 2]
In the above embodiment, the electrolyte layer 3 is disposed outside the recess 13. However, as shown in FIG. 4 , when the thickness of the hydrogen electrode layer 1 is smaller than the depth of the recess 13, the electrolyte layer 3 may be disposed inside the recess 13.

[Modification 3]
In the above embodiment, the boundary portion 13a between the side peripheral surface S2 and the bottom surface S1 has an R-shape, but this is not limited thereto. The side peripheral surface S2 may be disposed so as to be curved with respect to the bottom surface S1.

[Modification 4]
In the above embodiment, the cell body 20 has the catalyst layer 2 , but it does not have to have the catalyst layer 2 .

[Modification 5]
In the above embodiment, the catalyst layer 2 is disposed in each of the plurality of supply holes 14, but this is not limited thereto. It is sufficient that the catalyst layer 2 is disposed in at least one of the plurality of supply holes 14.

[Modification 6]
In the above embodiment, the hydrogen electrode layer 1 functions as a cathode and the oxygen electrode layer 5 functions as an anode, but the hydrogen electrode layer 1 may function as an anode and the oxygen electrode layer 5 may function as a cathode. In this case, the constituent materials of the hydrogen electrode layer 1 and the oxygen electrode layer 5 are switched, and a source gas is caused to flow over the outer surface of the hydrogen electrode layer 1.

[Modification 7]
In the above embodiment, the electrolysis cell 100 has been described as an example of an electrochemical cell, but the electrochemical cell is not limited to the electrolysis cell. An electrochemical cell is a general term for an element in which a pair of electrodes are arranged so that an electromotive force is generated from an overall oxidation-reduction reaction in order to convert electrical energy into chemical energy, and an element for converting chemical energy into electrical energy. Therefore, the electrochemical cell includes, for example, a fuel cell that uses oxide ions or protons as a carrier.

Reference Signs List 100 Electrolysis cell 10 Metal support 11 First main surface 12 Second main surface 13 Recess S1 Bottom surface S2 Side peripheral surface 13a Boundary portion 14 Supply hole 20 Cell body 1 Hydrogen electrode layer 2 Catalyst layer 3 Electrolyte layer 4 Reaction prevention layer 5 Oxygen electrode layer 30 Flow path member 30a Flow path

Claims (1)

a cell body having a first electrode layer, a second electrode layer, and an electrolyte layer disposed between the first electrode layer and the second electrode layer;
a metal support having a first main surface, a second main surface, a recess formed in the first main surface, and a plurality of supply holes communicating with the second main surface and a bottom surface of the recess;
Equipped with
At least a portion of the first electrode layer is disposed within the recess;
the cell body portion has a catalyst layer disposed in at least one of the plurality of supply holes and connected to the first electrode layer;
Electrochemical cell.

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