JP2021064502A - Fuel battery cell - Google Patents

Abstract

To provide a fuel battery cell which can lighten the stress concentration in a bonding material serving to bond a fuel battery cell main body and a separator.SOLUTION: A fuel battery cell comprises: a fuel battery cell main body; a separator; and a bonding material. The battery cell main body has an air electrode, a solid electrolyte layer and a fuel electrode, which are laminated in order, and it has an outer peripheral part at an edge of an outer periphery side when viewed from a lamination direction, of which the shape is a flat plate type. The separator has an opening formed thereinside when viewed from the lamination direction. In addition, the separator has an inner peripheral edge part at an edge of its inner periphery side, which overlaps with the outer peripheral part of the fuel battery cell main body, and it has, as the bonding material, a cell bonding material for bonding the fuel battery cell main body and the separator together. The cell bonding material has a bonding part which makes a region where the outer peripheral part of the fuel battery cell main body overlaps with the inner peripheral edge part of the separator when viewed from the lamination direction. The bonding part has an interface where it is in contact with the inner peripheral edge part of the separator; the interface is undulating in shape.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell.

Conventionally, a flat plate type solid oxide fuel cell (hereinafter, also simply referred to as “fuel cell”) is widely known (for example, Patent Document 1). The flat plate type fuel cell includes a fuel cell cell body having a flat solid electrolyte layer, an air electrode provided on one surface of the solid electrolyte layer, and a fuel electrode provided on the other surface. The fuel cell has a stack structure in which a plurality of fuel cell cells are stacked and connected. The fuel cell further has a separator that separates a space in which the oxidant gas located on the air electrode side exists and a space in which the fuel gas located on the fuel electrode side exists. The separator is bonded to the fuel cell main body via a bonding material.

Japanese Unexamined Patent Publication No. 2014-49324

In a flat plate type fuel cell, a difference in thermal expansion occurs between the fuel cell body made of ceramics or the like and the separator made of metal or the like as the temperature changes during operation of the fuel cell. Due to this difference in thermal expansion, stress is generated in the bonding material that is arranged between the fuel cell body and the separator and that joins the fuel cell body and the separator. In particular, since stress is concentrated in a part of the joint material, there is a problem that cracks are likely to occur in the region.

In view of such a problem, it is an object of the present invention to provide a fuel cell capable of alleviating stress concentration in a bonding material for joining a fuel cell cell body and a separator.

Hereinafter, the technical configuration and the action and effect of the present invention will be described. However, the mechanism of action of the present invention includes estimation. The scope of claims should not be limited by the correctness of the mechanism of action.

The fuel cell according to the present invention includes a fuel cell main body, a separator, and a bonding material.
The battery cell body is
It is provided with an air electrode, a solid electrolyte layer, and a fuel electrode, which are sequentially laminated.
It has an outer peripheral edge on the outer peripheral edge when viewed from the stacking direction, and its shape is a flat plate type.
The separator has an opening formed inside when viewed from the stacking direction, and has an inner peripheral edge portion that overlaps with the outer peripheral edge portion of the fuel cell main body at the edge portion on the inner peripheral side.
As the joining material, a cell joining material for joining the fuel cell main body and the separator is provided.
The cell joining material has a joining portion that is a region where the outer peripheral edge portion of the fuel cell main body and the inner peripheral edge portion of the separator overlap when viewed from the stacking direction.
The joint has an interface in contact with the inner peripheral edge of the separator.
The interface has an undulating shape.

In the fuel cell, the shape of the interface is an undulating shape. By forming the interface into an undulating shape, the stress applied to the joint is dispersed through the undulations. As a result, the concentration of stress on the joint is suppressed. As a result, the concentration of stress in the cell joining material that joins the fuel cell cell body and the separator can be relaxed.

In the fuel cell according to the present invention, when the maximum thickness of the joint is T _max and the minimum thickness is T _min , the ratio of T _{max to T min} is 1.20 or more and 20.0 or less. It may be.

In the fuel cell according to the present invention, the joint portion has a linear length of X _{1 as seen from the stacking direction between two predetermined points at the interface, and X 2} for the total length of the interface between the two points. At that time, the ratio of X _{2 to X 1} may be 1.02 or more and 2.00 or less.

According to the present invention, it is possible to provide a fuel cell that can relieve stress concentration in a bonding material that joins a fuel cell body and a separator.

FIG. 1 is a side sectional view of the fuel cell 1 according to the present embodiment. FIG. 2 is an enlarged cross-sectional view showing the cell joining material 20 shown in FIG. 1 and its vicinity. FIG. 3 is a plan view of the cell joining material 20 shown in FIG. FIG. 4 is an end view of the stretched portion 112 in the direction along the inner peripheral edge portion 31 of the separator 30. FIG. 5 is a perspective view of the solid oxide fuel cell 100. FIG. 6 is a side sectional view of the solid oxide fuel cell 100.

Hereinafter, the fuel cell 1 according to the embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a side sectional view of the fuel cell 1 according to the present embodiment. As shown in FIG. 1, the fuel cell 1 includes a flat plate type fuel cell main body 10 having a power generation function, and a separator 30 that separates a space A in which a fuel gas exists and a space B in which an oxidant gas exists. , With a bonding material. The joining material includes a cell joining material 20 for joining the fuel cell main body 10 and the separator 30, and an interconnector joining material 60 for joining the separator 30 and the interconnector 40. Further, the fuel cell 1 includes an interconnector 40 for ensuring continuity between the fuel cell body 10 and a current collector 50 for ensuring continuity between the interconnector 40 and the fuel cell body 10. ing.

[Fuel cell body]
As shown in FIG. 1, the fuel cell main body 10 includes an air electrode 12, a solid electrolyte layer 11, and a fuel electrode 13 which are sequentially laminated. That is, an air electrode 12 is provided on one surface of the solid electrolyte layer 11, a fuel electrode 13 is provided on the other surface, and the solid electrolyte layer 11 is sandwiched between the air electrode 12 and the fuel electrode 13. There is. The fuel electrode 13 includes a fuel electrode substrate 131 and a fuel electrode active portion 132 provided on one surface of the fuel electrode substrate 131. The thickness of the fuel cell body 10 is, for example, 100 to 2100 μm. In the present specification, the direction in which each layer of the air electrode 12, the solid electrolyte layer 11 and the fuel electrode 13 is laminated is referred to as a lamination direction (Z direction in FIG. 1). That is, the stacking direction is a direction orthogonal to the main surface of each layer.

The air electrode 12, the solid electrolyte layer 11, and the fuel electrode 13 (fuel electrode substrate 131 and fuel electrode active portion 132) are each formed in a rectangular flat plate shape. That is, the fuel cell body 10 has a rectangular shape when viewed from the stacking direction. The size of the air electrode 12 seen from the stacking direction is smaller than the size of the solid electrolyte layer 11. That is, the outer peripheral portion of the solid electrolyte layer 11 is exposed from the air electrode 12. Further, the size of the solid electrolyte layer 11 as seen from the stacking direction is equal to the size of the fuel electrode active portion 132. Further, the size of the fuel electrode active portion 132 as viewed from the stacking direction is smaller than the size of the fuel electrode substrate 131. That is, the outer peripheral portion of the fuel electrode substrate 131 is exposed from the fuel electrode active portion 132.

FIG. 2 is an enlarged cross-sectional view showing the cell joining material 20 shown in FIG. 1 and its vicinity. As shown in FIG. 2, the fuel cell main body 10 has an outer peripheral edge portion 101 at an edge portion on the outer peripheral side when viewed from the stacking direction. That is, the outer peripheral edge 101 is the outer peripheral edge 12a of the air electrode 12, the outer peripheral edge 11a of the solid electrolyte layer 11, the outer peripheral edge 131a of the fuel electrode substrate 131, and the fuel electrode active portion 132. It is located at the edge 132a on the outer peripheral side of the.

The air electrode 12 is made of a porous material containing, for example, LSM (La (Sr) MnO ₃ : lanthanum strontium manganite), LSCF ((La, Sr) (Co, Fe) O ₃ : lanthanum strontium cobalt ferrite) and the like. Will be done. The porosity of the air electrode 12 can be, for example, 15 to 55%. The thickness of the air electrode 12 can be, for example, 50 to 200 μm. The coefficient of thermal expansion of the air electrode 12 can be, for example, 11 to 17 ppm / K.

The solid electrolyte layer 11 is made of a dense material containing, for example, YSZ (yttria-stabilized zirconia). The porosity of the solid electrolyte layer 11 can be, for example, 0 to 10%. The solid electrolyte layer 11 may be made of a porous material such as GDC (gadolinium-doped ceria). The thickness of the solid electrolyte layer 11 can be, for example, 1 to 50 μm. The coefficient of thermal expansion of the solid electrolyte layer 11 can be, for example, 9 to 11 ppm / K.

The fuel electrode substrate 131 is made of, for example, a porous material containing Ni and YSZ. The porosity of the fuel electrode substrate 131 can be, for example, 15 to 55%. The thickness of the fuel electrode substrate 131 can be, for example, 50 to 2000 μm. The coefficient of thermal expansion of the fuel electrode substrate 131 can be, for example, 11 to 14 ppm / K.

The fuel electrode active portion 132 is made of, for example, a porous material containing Ni and YSZ. The porosity of the fuel electrode active portion 132 can be, for example, 15 to 55%. The thickness of the fuel electrode active portion 132 can be, for example, 5 to 100 μm. The coefficient of thermal expansion of the fuel electrode active portion 132 can be, for example, 11 to 14 ppm / K.

The fuel cell main body 10 may further include a reaction prevention film (not shown) between the solid electrolyte layer 11 and the air electrode 12. When the fuel cell main body 10 is provided with the reaction prevention film, the material constituting the solid electrolyte layer 11 and the material constituting the air electrode 12 react with each other, and an electric resistance is generated at the interface between the solid electrolyte layer 11 and the air electrode 12. It is possible to suppress the occurrence of a phenomenon in which a large reaction layer is formed. The anti-reaction membrane is composed of, for example, GDC. The porosity of the reaction-preventing membrane can be, for example, 10 to 30%. The thickness of the anti-reaction membrane can be, for example, 3 to 50 μm.

[Separator]
As shown in FIGS. 1 and 2, the separator 30 has an opening formed inward when viewed from the stacking direction (Z direction in FIGS. 1 and 2). As a result, the central portion of the fuel cell main body 10 is exposed from the opening when viewed from one side in the stacking direction (air electrode side in FIG. 1). That is, the separator 30 is formed in a rectangular frame shape so as to overlap a part of the outer peripheral edge portion 101 of the fuel cell main body 10 when viewed from the stacking direction.

The separator 30 includes an inner peripheral edge portion 31 that overlaps with the outer peripheral edge portion 101 of the fuel cell main body 10 and an outer peripheral edge portion 32 located on the outer peripheral edge portion on the inner peripheral side edge when viewed from the stacking direction. ing. The separator 30 is curved so that a part thereof is convex toward the other side (fuel electrode side in FIG. 1) in the stacking direction. Further, the inner peripheral edge portion 31 of the separator 30 is located on the other side in the stacking direction with respect to the outer peripheral edge portion 32, and is bonded to the surface on one side in the stacking direction of the cell bonding material 20. On the other hand, the outer peripheral edge portion 32 of the separator 30 is located on one side in the stacking direction with respect to the inner peripheral edge portion 31, and is bonded to the surface on the other side in the stacking direction of the interconnector connector 60. As a result, the separator 30 divides the space A in which the fuel gas located on the fuel electrode 13 side exists and the space B in which the oxidant gas located on the air electrode 12 side flows, and the fuel gas and the oxidant gas Prevents mixing.

The separator 30 is made of, for example, metal. As the metal constituting the separator 30, for example, ferritic stainless steel, austenitic stainless steel, and Ni-based heat-resistant alloy (for example, Inconel 600 and Hastelloy) can be used. The thickness of the separator 30 can be, for example, 10 to 1000 μm. The coefficient of thermal expansion of the separator 30 can be, for example, about 11 to 18 ppm / K.

[Joining material for cells]
As shown in FIG. 2, the cell bonding material 20 is located on the other side (fuel electrode side in FIG. 1) in the stacking direction with respect to the separator 30, and the fuel cell cell body 10 and the separator 30 are bonded to each other. There is. The cell joining material 20 joins a part of the outer peripheral edge portion 101 of the fuel cell main body 10 and the inner peripheral edge portion 31 of the separator 30. More specifically, the cell bonding material 20 is provided on the outer peripheral side edge portion 11a of the solid electrolyte layer 11 of the fuel cell main body 10, the outer peripheral side edge portion 131a of the fuel electrode substrate 131, and the outer peripheral side of the fuel electrode active portion 132. The edge portion 132a and the inner peripheral edge portion 31 of the separator 30 are joined. The cell bonding material 20 is bonded to at least the highly airtight solid electrolyte layer 11 to prevent the fuel gas existing in the space A from being mixed with the oxidant gas existing in the space B.

FIG. 3 is a plan view of the cell joining material 20 shown in FIG. As shown in FIG. 3, the cell joining material 20 has an opening formed inside when viewed from the stacking direction (Z direction in FIG. 1), and is formed in a rectangular frame shape. That is, the cell joining material 20 has an outer peripheral edge 20a provided on the outer peripheral edge when viewed from the stacking direction, and an inner peripheral edge 20b provided on the inner peripheral edge. The outer peripheral edge 20a and the inner peripheral edge 20b are each composed of two sets of substantially parallel sides (that is, a total of four sides) facing each other and four corners connecting the sides. .. Each corner is curved in an arc shape. In addition, in this specification, substantially parallel means parallelism in consideration of tolerance. Such a cell joining material 20 airtightly joins the outer peripheral edge portion 101 of the fuel cell main body 10 and the inner peripheral edge portion 31 of the separator 30 over the entire circumference. This prevents the fuel gas existing in the space A and the oxidant gas existing in the space B from being mixed.

As shown in FIG. 2, the cell joining material 20 has a joining portion 111 which is a region where the outer peripheral edge portion 101 of the fuel cell main body 10 and the inner peripheral edge portion 31 of the separator 30 overlap when viewed from the stacking direction. Specifically, the joint portion 111 is located in a region of the outer peripheral edge portion 101 of the fuel cell main body 10 where a part of the outer peripheral edge portion 131a of the fuel electrode substrate 131 and the inner peripheral edge portion 31 of the separator 30 overlap. To position. The joint 111 has four stretches 112 that extend linearly. Each stretched portion 112 is arranged so that both ends in the stretching direction overlap with adjacent stretched portions 112. Note that "extending linearly" means extending in a specific direction, and the shape of the edge portion of the extending portion 112 along the extending direction is not limited to being straight. ..

As shown in FIG. 2, the cell joining material 20 is formed with an interface 111a in contact with the inner peripheral edge portion 31 of the separator 30. Although not represented in FIG. 2, the interface 111a has an undulating shape.

In the present invention, the word "undulating shape" means a shape having undulations (higher or lower).

FIG. 4 is an end view of the stretched portion 112 in the direction along the inner peripheral edge portion 31 of the separator 30 (that is, the longitudinal direction along the inner peripheral edge portion 31 of the separator 30). Here, FIG. 4 shows a stretched portion 112 which is a part when the cell joining material 20 in FIG. 3 is cut along the AA line. As shown in FIG. 4, the interface 111a in the cross section in the direction along the inner peripheral edge portion 31 has an undulating shape. Specifically, the interface 111a has an undulating shape in which convex portions and concave portions are repeatedly wavy (hereinafter, also simply referred to as “wavy”), and has an undulating shape with irregular undulations.

Referring to FIG. 4, the junction 111, the maximum thickness of the _{T max,} when the minimum thickness was _{T min,} the ratio of _{T max} for _{T min (T max / T min} ) is 1.20 It is preferably 20.0 or more, and more preferably 1.50 or more and 15.0 or less. For T _max and T _min , referring to FIG. 4, one stretched portion 112 is evenly divided into 10 equal parts along the stretching direction, and the thickness of the central portion in the width direction of the stretched portion 112 at the equal division point is measured. To do. Then, the maximum thickness is T _max , and the minimum thickness is T _min . In the present specification, the "center portion in the width direction" of the stretched portion 112 means a portion located at the center in the width direction of the stretched portion 112 in consideration of tolerance. The bonding unit 111, all of the ratio of _{T max} for _{T min} in the stretching section 112 are not required to meet the above-mentioned range, the ratio of _{T max} for _{T min} in one extension portion 112 at least one is within the above range It suffices if it satisfies. The thickness is not particularly limited, but can be confirmed by photographing the stretched portion 112 with a scanning electron microscope at a magnification of 250 to 1000 times.

_{With reference to FIG. 4, the joint portion 111 has a linear length X 1} as seen from the stacking direction between the predetermined two points L and M at the interface 111a, and the total length of the interface between the two points is X. when a _2, it is preferable that the ratio of _{X 2} with respect to _{X 1 (X 2 / X 1} ) is 1.02 to 2.00, further preferably 1.04 to 1.50. In the present specification, the "total length of the interface X ₂ " means the length when the interface 111a is extended in a straight line. With _{reference to FIG. 4, X 1} and X ₂ are measured in one stretched portion 112 with both end edges in the stretch direction in the central portion in the width direction as L and M, respectively. That is, in the present embodiment, the predetermined space between two points means the space between both ends of one stretched portion 112 in the stretch direction of the central portion in the width direction. The bonding unit 111, all ratios of X ₂ with respect to X ₁ in the extending portion 112 is not required to meet the above-mentioned range, the ratio of X ₂ with respect to X ₁ in one extension part 112 at least one is within the above range It suffices if it satisfies. X ₁ and X ₂ are not particularly limited, but can be confirmed by using a digital camera, an optical microscope, or an electron microscope depending on the magnification to be photographed. Note that X ₂ can be quantified by performing image analysis on the cross-sectional image obtained by the above method.

The average thickness of the joint portion 111 is preferably 10 μm or more and 300 μm or less, and more preferably 20 μm or more and 200 μm or less. The thickness of the joint portion 111 means the thickness in the stacking direction. For the average thickness of the joint portion 111, refer to FIG. 4, divide one stretched portion 112 evenly along the stretching direction into 10 equal parts, and determine the thickness of the central portion in the width direction of the stretched portion 112 at the equal division point. Each is measured and used as the average value of the thickness. It is not necessary for the joint portion 111 to have an average thickness of all the stretched portions 112 satisfying the above range, and it is sufficient that the average thickness of at least one of the stretched portions 112 satisfies the above range.

In the present invention, the shape of the interface 111a, the ratio of T _{max to T min,} and the ratio of X _{2 to X 1} are the mold (press) with respect to the region forming the interface in contact with the cell bonding material of the separator to be used. The above adjustment can be made by forming the undulating shape in advance by performing processing or bending.

As the cell bonding material 20, for example, crystallized glass, amorphous glass, brazing material, ceramics and the like can be used. In the present specification, the crystallized glass has a ratio (crystallinity) of "volume occupied by the crystal phase" to the total volume of 60% or more, and "volume occupied by the amorphous phase and impurities" with respect to the total volume. The ratio of "" is less than 40%. Examples of such crystallized glass include SiO _2- B ₂ O ₃ system, SiO _2- CaO system, SiO _2- Mg O system and the like. Specifically, as the crystallized glass, at least one selected from the group consisting of _{SiO 2-} MgO-B ₂ O _3- Al ₂ O ₃ system and SiO _2- MgO-Al ₂ O _{3-ZnO system can be used.} it can. The cell joining material 20 may be composed of a single material or may be composed of a plurality of materials. When the crystallized glass is composed of a plurality of materials, those materials may be in contact and integrated, or may be partially or wholly non-contact.

[Interconnector]
As shown in FIG. 1, the interconnector 40 is formed in a plate shape and has a rectangular shape when viewed from the stacking direction (Z direction in FIG. 1). The interconnector 40 has an outer peripheral edge portion 41 to be joined to the interconnector connector 60 at the outer peripheral portion, and is joined to the separator 30 at the outer peripheral edge portion 41 via the interconnector connector member 60. Further, the interconnector 40 has an inner region 42 that overlaps with the fuel cell main body 10 when viewed from the stacking direction, and is joined to the current collector 50 in the inner region 42. As a result, the interconnector 40 can secure continuity between the fuel cell main bodies 10. The interconnector 40 is made of, for example, metal or the like.

[Current collector]
As shown in FIG. 1, the current collector 50 includes an air electrode side current collector 51 arranged on the air electrode 12 side of the fuel cell main body 10 and a fuel electrode side current collector 51 arranged on the fuel electrode 13 side. 52 and. The air pole side current collector 51 and the fuel pole side current collector 52 are arranged at intervals from each other, and are composed of a plurality of strip-shaped pieces extending in the length direction (X direction in FIG. 1). Between each strip-shaped piece of the air electrode side current collector 51, there is a flow path through which the oxidant gas flows. On the other hand, between each strip-shaped piece of the fuel electrode side current collector 52, there is a flow path through which the fuel gas flows. In the air electrode side current collector 51, one end in the stacking direction (Z direction in FIG. 1) is joined to the interconnector 40, and the other end is joined to the air electrode 12. On the other hand, the fuel electrode side current collector 52 is bonded to the fuel electrode substrate 131 at one end in the stacking direction and to the interconnector 40 of the adjacent fuel cell 1 at the other end. Thereby, the current collector 50 can secure the continuity between the interconnector 40 and the fuel cell main body 10. The current collector 50 is made of, for example, metal.

[Joint material for interconnector]
As shown in FIG. 1, the connector 60 joins the outer peripheral edge 32 of the separator 30 and the outer peripheral edge 41 of the interconnector 40. Such an interconnector connector 60 is formed in a rectangular frame shape when viewed from the stacking direction, and airtightly joins the outer periphery of the separator 30 and the outer periphery of the interconnector 40 over the entire circumference. .. This prevents the fuel gas existing in the space A and the oxidant gas existing in the space B from being mixed. As the interconnector bonding material 60, the same material as the cell bonding material 20 can be used.

In the fuel cell 1 described above, the air electrode 12 is formed by flowing a fuel gas (hydrogen gas or the like) through the space A located on the fuel electrode 13 side and flowing an oxidant gas through the space B located on the air electrode 12 side. The electrochemical reaction represented by the following formula (1) occurs, and the electrochemical reaction represented by the following formula (2) occurs at the fuel electrode 13, and as a result, a current flows.
(1/2) ・ O ₂ + 2e ⁻ → O ^2- … (1)
H ₂ + O ^2- → H ₂ O + 2e ⁻ … (2)

In the fuel cell 1 according to the present embodiment, the shape of the interface 111a of the joint portion 111 is an undulating shape. By forming the interface 111a into an undulating shape, the stress applied to the cell joining material 20 is dispersed through the undulations. As a result, it is possible to suppress the concentration of stress in a part of the cell joining material 20. As a result, the concentration of stress in the cell joining material 20 that joins the fuel cell cell body 10 and the separator 30 can be relaxed.

In the fuel cell 1 according to the present embodiment, when the maximum thickness of the joint portion 111 is T _max and the minimum thickness is T _min , the ratio of T _{max to T min} is 1.20 or more and 20. It is preferably 0.0 or less. When the ratio of the maximum thickness to the minimum thickness of the joint portion 111 is within the above range, the stress applied to the cell joint material 20 is more dispersed through the undulations. As a result, it is possible to further suppress the concentration of stress in a part of the cell joining material 20. As a result, the concentration of stress in the cell joining material 20 that joins the fuel cell cell body 10 and the separator 30 can be further relaxed. As long as the shape of the interface 111a has an undulating shape, the fuel cell 1 can relieve the stress in the cell bonding material 20 even when _{(T max} / T _{min) is not in the above range.}

In the fuel cell 1 according to the present embodiment, the joint portion 111 has a linear length X ₁ as seen from the stacking direction between two predetermined points at the interface 111a, and the total length of the interface between the two points. when the X _2, the ratio of _{X 2} with respect to _{X 1 (X 2 / X 1} ) is preferably not 1.02 to 2.00. When the ratio of X _{2 to X 1} is within the above range, the stress applied to the cell bonding material 20 is more dispersed through the undulations. As a result, it is possible to further suppress the concentration of stress in a part of the cell joining material 20. As a result, the concentration of stress in the cell joining material 20 that joins the fuel cell cell body 10 and the separator 30 can be further relaxed. As long as the shape of the interface 111a has an undulating shape, the fuel cell 1 can relieve the stress in the cell bonding material 20 even when _{(X 2} / X _{1) is not in the above range.}

Next, a solid oxide fuel cell 100 having a stack structure in which a plurality of fuel cell 1s according to the present embodiment are stacked and connected will be described. FIG. 5 is a perspective view of the solid oxide fuel cell 100, and FIG. 6 is a side sectional view of the solid oxide fuel cell 100.

As shown in FIGS. 5 and 6, in the solid oxide fuel cell 100, the fuel cell 1 according to the present embodiment is laminated in a direction in which the stacking direction is the vertical direction and the length direction is the depth direction. There is. Such a solid oxide fuel cell 100 is a flat plate type solid oxide fuel cell. The direction in which the fuel cell 1 is stacked is also referred to as a stacking direction.

The solid oxide fuel cell 100 is a fastening member that fastens the fuel cell 1 and the holding plate 40'provided in place of the interconnector 40 in the uppermost layer and the lowermost layer, and the fuel cell 1 and the holding plate 40'. 21 to 28.

Of the eight fastening members 21 to 28 shown in FIG. 5, a flow path through which the oxidant gas or fuel gas flows is formed inside the four fastening members along the stacking direction (Z direction in FIG. 1). Has been done. Specifically, the fastening member 23 is used as a fuel gas supply pipe, the fastening member 27 is used as a fuel gas discharge pipe, the fastening member 25 is used as an oxidant gas supply pipe, and the fastening member 21 is used as an oxidant gas discharge pipe.

As shown in FIG. 6, in the solid oxide fuel cell 100, the connector 60 is also joined to the fastening members 21 to 28. That is, in the solid oxide fuel cell 100, the interconnector bonding material 60 joins the outer peripheral edge portion 32 of the separator 30, the outer peripheral edge portion 61 of the interconnector 40, and the fastening members 21 to 28.

Although the embodiments of the present invention have been described above, the present invention is not limited to the present embodiment, and various modifications can be made without departing from the gist of the present invention.

In the present embodiment, the fuel cell body 10 and the interconnector 40 are rectangular in shape when viewed from the stacking direction. However, the present invention is not limited to this configuration, and the fuel cell body 10 and the interconnector 40 may have a polygonal shape other than a rectangular shape when viewed from the stacking direction, or may have a circular shape. It may be oval.

In the present embodiment, the size of the air electrode 12 seen from the stacking direction is smaller than the size of the solid electrolyte layer 11. Further, the size of the fuel electrode active portion 132 as seen from the stacking direction is smaller than the size of the fuel electrode substrate 131. However, the present invention is not limited to this configuration, and the size of the air electrode 12 seen from the stacking direction may be formed equal to the size of the solid electrolyte layer 11, or the fuel electrode seen from the stacking direction may be formed. The size of the active portion 132 may be formed equal to the size of the fuel electrode substrate 131. Further, the air electrode 12, the solid electrolyte layer 11, the fuel electrode substrate 131, and the fuel electrode active portion 132 may all have the same size.

In the present embodiment, the region of the fuel cell main body 10 that overlaps the separator 30 of the outer peripheral edge portion 101 (that is, the joint portion 111) is located at a part of the outer peripheral edge portion 131a of the fuel electrode substrate 131. However, the present invention is not limited to this configuration, and the region overlapping the separator 30 is a part of the outer peripheral side edge portion 11a of the solid electrolyte layer 11 or the outer peripheral side edge portion 132a of the fuel electrode active portion 132. It may be located.

In the present embodiment, the shape of the separator 30, the cell joining material 20, and the interconnector joining material 60 as viewed from the stacking direction is a rectangular frame shape. However, the present invention is not limited to this configuration, and the separator 30, the cell bonding material 20, and the interconnector bonding material 60 have a polygonal shape when viewed from the stacking direction and a shape other than a rectangle when viewed from the stacking direction. It may be circular, circular, or elliptical.

In the present embodiment, the inner peripheral edge portion 31 of the separator 30 is joined to the surface of the cell joining material 20 on one side in the stacking direction. However, the present invention is not limited to this configuration, and at least a part of the inner peripheral edge portion 31 of the separator 30 may be embedded in the cell bonding material 20. Since at least a part of the inner peripheral edge portion 31 of the separator 30 is embedded in the cell bonding material 20, the bonding area between the separator 30 and the cell bonding material 20 is increased, so that the bonding strength is improved.

In the present embodiment, the cell bonding material 20 is formed on the outer peripheral side edge portion 11a of the solid electrolyte layer 11 of the fuel cell main body 10, the outer peripheral side edge portion 131a of the fuel electrode substrate 131, and the outer peripheral side of the fuel electrode active portion 132. It is joined to the edge portion 132a of the. However, the present invention is not limited to this configuration, and if the cell bonding material 20 is bonded to at least the outer peripheral edge portion 11a of the solid electrolyte layer 11, the outer peripheral edge of the fuel electrode substrate 131 is used. It does not have to be joined to the peripheral edge portion 132a of the portion 131a and the fuel electrode active portion 132. Further, as long as the cell bonding material 20 is bonded to at least the outer peripheral side edge portion 11a of the solid electrolyte layer 11, it may be further bonded to the outer peripheral side edge portion 12a of the air electrode 12. When a dense layer other than the solid electrolyte layer 11 is formed between the air electrode 12 and the fuel electrode 13, the cell bonding material 20 does not have to be bonded to the solid electrolyte layer 11, and at least the dense layer is not required. It suffices if it is joined to various layers. As a result, the cell bonding material 20 prevents the fuel gas existing in the space A from being mixed with the oxidant gas existing in the space B.

In the present embodiment, the outer peripheral edge 20a and the inner peripheral edge 20b of the cell joining material 20 are two sets of substantially parallel sides facing each other and a corner portion curved in an arc shape, respectively, when viewed from the stacking direction. And, including. However, the present invention is not limited to this configuration, and the side may have a curved portion. Specifically, the side may be formed in a convex shape, a concave shape, or a shape in which unevenness is repeated toward the outside in the radial direction. Since the side has a curved portion, the residual stress is dispersed and the concentration of stress is easily suppressed. Therefore, the stress in the cell joining material 20 can be further relaxed. Further, the corner portion may be formed at a right angle or an acute angle, or may be bent into a C shape.

In the present embodiment, the undulating shape of the interface 111a is an irregular shape. However, the undulating shape may be a shape in which undulations are a combination of a regular shape and an irregular shape, or all may be a regular shape. As long as the shape of the interface 111a has an undulating shape, the stress in the cell joining material 20 is relaxed regardless of any of the above-mentioned undulating shapes.

In the present embodiment, the interconnector bonding material 60 directly joins the outer peripheral edge portion 32 of the separator 30 and the outer peripheral edge portion 41 of the interconnector connector 40. However, the present invention is not limited to this configuration, and another member different from the connector 60 is arranged between the outer peripheral edge portion 32 of the separator 30 and the outer peripheral edge portion 41 of the interconnector 40. You may. Examples of other members include an insulating material and a compression sealing material. For example, by using an insulating material as another member, the insulating property between the separator 30 and the interconnector 40 can be improved, and the height of the space B located on the air electrode 12 side can be adjusted.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

No. shown in Table 1. 1-No. By stacking and combining the fuel cell cells of No. 8, the fuel cell of Test Example 1 having a stack structure was produced. The structures of the fuel cell and the fuel cell are as shown in FIGS. 1 to 6. No. 1-No. The fuel cell of No. 7 corresponds to the embodiment, and No. The fuel cell of No. 8 corresponds to a comparative example. No. 1-No. The fuel cell of No. 7 has a wavy interface shape at least in a cross section in a direction along the inner peripheral edge portion of the separator, and has an undulating shape with irregular undulations.

The air electrode is LSCF (porosity: 40%, thickness: 30 μm, coefficient of thermal expansion: 14.4 ppm / K), and the solid electrolyte layer is 8YSZ (porosity: 0.5%, thickness: 20 μm, Coefficient of thermal expansion: 10.5ppm / K), Ni-8YSZ as fuel electrode substrate (porosity: 40%, thickness: 800μm, coefficient of thermal expansion: 12.8ppm / K), Ni− as fuel electrode active part 8YSZ (porosity: 35%, thickness: 10 μm, coefficient of thermal expansion: 12.8 ppm / K) was used. Further, NCA-1 manufactured by Nissin Steel Co., Ltd. (thickness: 200 μm, coefficient of thermal expansion: 13.5 ppm / K) was used as the separator, and crystallized glass was used as the cell bonding material and the interconnector bonding material.

<Evaluation method>
[Thermodynamic cycle test]
The fuel cell of Test Example 1 was examined for the amount of gas leak and the presence or absence of cracks by a thermal cycle test. Specifically, the fuel cell of Test Example 1 was installed in an electric furnace, and after repeating raising and lowering from room temperature to 800 ° C. at an elevating temperature rate of 400 ° C./hr 10 times, it was taken out from the electric furnace to determine the amount of gas leak and the amount of gas leak. The presence or absence of cracks was investigated.

The amount of gas leak was measured by measuring the flow rate of gas leaking from the air electrode to the fuel electrode. More specifically, after sealing the outlet end of the oxidant gas discharge pipe and the inlet end of the fuel gas discharge pipe of the fuel cell, argon gas is supplied from the oxidant gas supply pipe, and the air electrode side of the fuel cell is 10 kPa. The amount of gas leak was measured by a flow meter provided at the outlet end of the fuel gas supply pipe. The results are shown in Table 1. Since the lower limit of measurement is 0.1 (cc / min), in Table 1 below, those below the lower limit of measurement are described as "<0.1 (cc / min)", and it is judged that there is no gas leak. ..

The presence or absence of cracks was determined by disassembling the fuel cell of Test Example 1, applying a penetrant flaw detector to the surface of the cell bonding material, and observing with a microscope. The results are shown in Table 1.

Each fuel cell was comprehensively evaluated based on the following criteria based on the above-mentioned gas leak amount and the presence / absence of cracks.
⊚: There were no cracks and no gas leak.
◯: A slight crack occurred and there was no gas leak.
Δ: Minor cracks were generated and the amount of gas leak was small (less than 1.0 cc / min).
X: Large cracks were generated and the amount of gas leak was large (1.0 cc / min or more).

<Evaluation result>
As shown in Table 1, the shape of the interface 111a is not an undulating shape. Since a large crack was confirmed in the fuel cell according to No. 8, the amount of gas leak was large. On the other hand, No. 1 in which the shape of the interface 111a is an undulating shape. 1-No. In the fuel cell according to No. 7, no cracks were confirmed in the cell bonding material 20, or even if cracks were confirmed, the cracks were minor. Therefore, there was no gas leak, or even if there was a gas leak, the amount of gas leak was small. That is, No. that satisfies all the constituent requirements of the present invention. 1-No. It was shown that in the fuel cell according to No. 7, the occurrence of cracks was suppressed and the stress concentration in the cell bonding material 20 was alleviated. In particular, No. 1-No. It can be said that the fuel cell according to No. 3 had no cracks confirmed and no gas leak, so that the occurrence of cracks was remarkably suppressed.

It is considered that the stress applied to the cell joining material 20 was dispersed through the undulations by forming the interface 111a into an undulating shape. It is considered that this suppressed the concentration of stress in a part of the cell joining material 20. As a result, it is considered that the stress concentration in the cell joining material 20 for joining the fuel cell cell body 10 and the separator 30 is relaxed.

No. 4 and No. In the fuel cell according to No. 5, although minor cracks were confirmed, there was no gas leak. That is, as long as the shape of the interface 111a has an undulating shape, the occurrence of cracks is suppressed even when the ratio of X _{2 to X 1} is not in the range of 1.02 or more and 2.00 or less, and the stress in the cell bonding material 20 is suppressed. It has been shown that can be alleviated.

No. 6 and No. Although minor cracks were confirmed in the fuel cell according to No. 7, the amount of gas leak was small. That is, as long as the shape of the interface 111a has an undulating shape, the ratio of T _{max to T min} is not in the range of 1.20 or more and 20.0 or less, and the ratio of X _{2 to X 1} is 1.02 or more. It was shown that the occurrence of cracks was suppressed even when the ratio was not in the range of 00 or less, and the stress in the cell bonding material 20 could be relaxed.

1 Fuel cell, 10 Fuel cell body, 11 Solid electrolyte layer, 11a Outer edge of solid electrolyte layer, 12 Air pole, 12a Outer edge of air pole, 13 Fuel pole, 20 cell bonding material , 20a outer peripheral edge of cell joining material, inner peripheral edge of 20b cell joining material, 21,22,23,24,25,26,27,28 fastening member, 30 separator, 31 inner peripheral edge of separator, 32 Outer peripheral edge of separator, 40 interconnector, 40'holding plate, 41 outer peripheral edge of interconnector, 42 inner area of interconnector, 50 current collector, 51 air pole side current collector, 52 fuel pole side current collector Body, 60 joint material, 100 solid oxide fuel cell, 101 outer peripheral edge of fuel cell body, 111 joint, 111a interface, 112 extension, 131 fuel electrode substrate, 131a outer peripheral edge of fuel cell substrate , 132 Fuel electrode active part, 132a Outer peripheral edge of fuel electrode active part A Space where fuel gas exists, B Space where oxidant gas exists.

Claims (3)

It is equipped with a fuel cell cell body, a separator, and a bonding material.
The fuel cell body is
It is provided with an air electrode, a solid electrolyte layer, and a fuel electrode, which are sequentially laminated.
It has an outer peripheral edge on the outer peripheral edge when viewed from the stacking direction, and its shape is a flat plate type.
The separator has an opening formed inside when viewed from the stacking direction, and has an inner peripheral edge portion that overlaps with the outer peripheral edge portion of the fuel cell main body at the edge portion on the inner peripheral side.
As the joining material, a cell joining material for joining the fuel cell main body and the separator is provided.
The cell joining material has a joining portion that is a region where the outer peripheral edge portion of the fuel cell main body and the inner peripheral edge portion of the separator overlap when viewed from the stacking direction.
The joint has an interface in contact with the inner peripheral edge of the separator.
The interface has an undulating shape.
Fuel cell. The first aspect of the present invention, wherein the ratio of T _{max to T min} is 1.20 or more and 20.0 or less when the _{maximum thickness of the joint is T max} and the minimum thickness is T _min. Fuel cell. The joint, X ₁ a linear length as viewed from the stacking direction between two predetermined points in the _interface, when the total length of the interface between the two points was X _2, for X ₁ in X ₂ The fuel cell according to claim 1 or 2, wherein the ratio is 1.02 or more and 2.00 or less.

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