JP7135458B2 - Fuel cell - Google Patents

Description

The present invention relates to fuel cells.

Solid oxide fuel cells are conventionally known as fuel cells using a solid electrolyte as an electrolyte. For example, Patent Literature 1 describes a solid oxide fuel cell in which a single cell and a metal separator are sealed with a glass-based sealing material, a specific brazing material, or the like.

JP 2014-49325 A

In a fuel cell using a solid electrolyte as an electrolyte, a glass-based sealing material is usually used for gas sealing between a unit cell and a metal member. A sealing portion made of a glass-based sealing material has excellent base material strength. However, the seal portion made of a glass-based sealing material is extremely weak against a peeling force acting to peel the metal member from the seal portion at the interface between the seal portion and the metal member. When a fuel cell generates power under a high load or is started and stopped in a short period of time, uneven distortion occurs due to the temperature distribution that occurs within the cell surface, which causes the cell parts to warp and the above-mentioned peeling force to occur. Cheap. When such a peeling force is generated, interfacial breakage due to peeling from the interface between the metal member and the seal portion progresses without stopping, and the seal portion reaches final breakage, resulting in a loss of gas sealing performance.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and it is an object of the present invention to provide a fuel cell capable of delaying the final breakage of the seal portion.

One aspect of the present invention is a single cell (2) using a solid electrolyte as the electrolyte,
a metal member (3) arranged around the single cell;
a sealing part (4) made of a sealing material for gas-sealing between the single cell and the metal member;
and a fracture mode transition section (5) that changes the fracture mode from the interface fracture to the seal material fracture due to the seal material in the middle of the interface fracture due to peeling from the interface between the metal member and the seal portion. and
The single cell has an anode (21) on one side of a solid electrolyte layer (20) and a cathode (22) on the other side , and the cathode is formed to have a smaller outer shape than the solid electrolyte layer. Alternatively, the anode is arranged on one side of the solid electrolyte layer and the cathode is arranged on the other side, and an intermediate layer is provided between the solid electrolyte layer and the cathode, and the cathode is formed to have a smaller outer shape than the outer shape of the intermediate layer ,
The sealing portion gas seals a gap (40) formed between the cathode-side outer peripheral surface of the solid electrolyte layer and the metal member, or the cathode-side outer surface of the intermediate layer. A gap (40) formed between the peripheral surface and the metal member is gas-sealed,
The fracture mode transition portion has a through hole (31) penetrating the metal member and a portion (40 0 ) of the seal material entering the through hole.
in the fuel cell (1).

The fuel cell has the configuration described above. Therefore, in the above fuel cell, when the battery component is warped and a peeling force is generated so as to peel off the metal member from the sealing portion, when the peeling force exceeds the peeling strength, the sealing portion and the sealing portion are first separated. Interfacial failure occurs from the edge of the interface with the metal member. Then, as the interfacial fracture progresses, that is, as the crack propagates along the interface, the tip of the crack reaches the fracture mode transition part on the way, and the interfacial fracture is temporarily terminated (at the fracture mode transition part The peeling of the metal member stops temporarily). The macroscopic crack continues to stop growing up to the allowable stress value of the seal material forming the seal portion, and when the stress applied to the seal portion exceeds the allowable stress value of the seal material, the seal material breaks. As described above, in the fuel cell, the first interfacial failure does not progress continuously to the final failure, and the sealing material failure occurs during the process. The sealing material breaking strength of the sealing material is higher than the interfacial breaking strength between the seal portion and the metal member. Therefore, according to the above-mentioned fuel cell, it is possible to delay the final destruction of the sealing part compared to the fuel cell that does not have a destruction mode transition part and reaches the final destruction as the interfacial destruction that first occurs in the sealing part. become.

It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

2 is an explanatory view schematically showing a cross section perpendicular to the cell in-plane direction of the fuel cell of Embodiment 1. FIG. 1 is an explanatory diagram schematically showing the fuel cell of Embodiment 1 as viewed from the cathode side of a single cell; FIG. FIG. 3 is an explanatory view schematically showing a cross section taken along line III-III of FIG. 2; 3 is an explanatory view schematically showing the fuel cell of Embodiment 2 corresponding to FIG. 2; FIG. FIG. 5 is an explanatory view schematically showing a cross section taken along the line VV of FIG. 4;

(Embodiment 1)
A fuel cell according to Embodiment 1 will be described with reference to FIGS. 1 to 3. FIG. As illustrated in FIGS. 1 to 3, the fuel cell 1 of this embodiment has a unit cell 2, a metal member 3, a seal portion 4, and a fracture mode transition portion 5. FIG.

A solid electrolyte is used as the electrolyte in the single cell 2 . Specifically, the single cell 2 has a structure in which an anode 21 is arranged on one side of a solid electrolyte layer 20 and a cathode 22 is arranged on the other side thereof, as shown in FIG. That is, the single cell 2 is a solid electrolyte fuel cell using a solid electrolyte as the electrolyte. In this embodiment, as the solid electrolyte forming the solid electrolyte layer 20, specifically, a solid oxide ceramic exhibiting oxygen ion conductivity is used. A fuel cell that uses solid oxide ceramics as a solid electrolyte is called a solid oxide fuel cell (SOFC).

In this embodiment, the single cell 2 has a flat battery structure, as shown in FIG. Examples of materials for the solid electrolyte layer 20 include zirconium oxide-based oxides such as yttria-stabilized zirconia. Examples of the material of the anode 21 include a mixture containing a catalyst such as Ni or NiO and the zirconium oxide-based oxide. Materials for the cathode 22 include, for example, a mixture containing a transition metal perovskite oxide such as a lanthanum-strontium-cobalt-based oxide and ceria or a ceria-based solid solution. Note that the single cell 2 may have an intermediate layer (not shown) between the solid electrolyte layer 20 and the cathode 22 . The intermediate layer is mainly a layer for suppressing reaction between the solid electrolyte layer material and the cathode material. Examples of materials for the intermediate layer include ceria and ceria-based solid solutions.

In this embodiment, the fuel cell 1 further includes a support 6 that supports the unit cells 2 . Specifically, the support 6 can be made of a metal plate. As shown in FIG. 1, the support 6 can have a cell support surface portion 60 that supports the surface of the anode 21 in the single cell 2 . The cell support surface portion 60 has a plurality of communication holes 61 communicating with a fuel gas flow path 81, which will be described later. According to this configuration, the fuel gas F can be supplied to the surface of the anode 21 through the plurality of communication holes 61 while the single cell 2 is reliably supported by the cell support surface portion 60 . Although not shown, the support 6 may also be formed in a frame shape having an opening, and may be configured to support the single cell 2 at the outer peripheral edge of the opening.

The metal member 3 is arranged around the single cell 2 . The seal portion 4 is for gas-sealing a gap 40 formed between the single cell 2 and the metal member 3 , more specifically, between the single cell 2 and the metal member 3 . Therefore, it can be said that the metal member 3 is a metal member that is arranged around the unit cell 2 and is in contact with the seal portion 4 that is in contact with the unit cell 2 . Specifically, in this embodiment, the metal member 3 is a fixing member for fixing the outer peripheral edge of the unit cell 2 to the support 6 . This type of fixing member is sometimes referred to as a retainer member.

In FIG. 1, the unit cell 2 has the cathode 22 formed to have an outer shape smaller than the outer shape of the solid electrolyte layer 20, and the outer peripheral surface of the solid electrolyte layer 20 on the cathode 22 side and the metal member 3 An example in which the seal portion 4 seals the space between is shown. When the single cell 2 has the above-described intermediate layer, the sealing portion 4 can be configured to seal the outer peripheral surface of the intermediate layer on the cathode 22 side and the metal member 3 with gas. In addition, FIG. 2 shows an example in which the seal portion 4 is arranged so as to surround the outer periphery of the cathode 22 when viewed along the thickness direction of the unit cell 2 from the cathode 22 side. Also, the metal member 3 and the support 6 are welded together.

Examples of the metal material forming the metal member 3 include ferritic stainless steel, heat-resistant Cr alloy, heat-resistant NiCr alloy, and austenitic stainless steel. A similar metal material can be used as the material of the metal plate material that constitutes the support 6 .

The sealing portion 4 for gas-sealing the gap 40 between the metal member 3 as a fixing member for fixing the outer peripheral edge of the unit cell 2 to the support 6 and the unit cell 2 has a gap 40 between the metal member 3 and the unit cell 2. Due to the difference in thermal expansion coefficient, shear stress is likely to occur due to elongation of the single cell 2 in the cell in-plane direction. Therefore, interface breakage is likely to occur from the interface end portion A between the seal portion 4 and the metal member 3 as the fixing member illustrated in FIG. 3 . However, even in such a case, according to the fuel cell 1, it is possible to delay the final destruction of the seal portion 4. FIG.

The seal portion 4 is made of a seal material. Examples of sealing materials include glass-based sealing materials and metal brazing materials.

The fracture mode transition portion 5 is a portion that changes the fracture mode from interface fracture to seal material fracture by the sealing material in the middle of interface fracture due to peeling from the interface between the metal member 3 and the seal portion 4 . In the above-described interfacial failure, separation between the metal member 3 and the seal portion 4 occurs as a crack develops in the interface between the metal member 3 and the seal portion 4 . Further, in the sealing material failure, the crack progresses in the seal portion 4, causing the seal portion 4 itself to be destroyed.

The fuel cell 1 has the above configuration. Therefore, in the fuel cell 1, when the battery component is warped and a peeling force is generated so as to peel the metal member 3 from the seal portion 4, if the peeling force exceeds the peeling strength, the seal is first removed. Interfacial failure occurs from the interface end A between the portion 4 and the metal member 3 . Then, as the interfacial fracture progresses, that is, as the crack propagates along the interface, the tip of the crack reaches the fracture mode transition portion 5 on the way, and the interfacial fracture is temporarily terminated (fracture mode transition portion 5, the peeling of the metal member 3 temporarily stops). The macroscopic crack continues to stop growing up to the allowable stress value of the seal material forming the seal portion 4, and when the stress applied to the seal portion 4 exceeds the allowable stress value of the seal material, the seal material breaks. As described above, in the fuel cell 1, the first interfacial failure does not progress continuously to the final failure, and the sealing material failure occurs on the way. The sealing material breaking strength of the sealing material is higher than the interfacial breaking strength between the seal portion 4 and the metal member 3 . Therefore, according to the fuel cell 1, the final breakage of the seal portion 4 is delayed as compared with the fuel cell that does not have the breakage mode transition portion 5 and reaches the final breakage with the interfacial breakage that first occurs in the seal portion 4. becomes possible.

The fracture mode transition portion 5 specifically has a through hole 31 penetrating the metal member 3 and a portion 400 of the sealing material entering the through hole 31 . Forming the through holes 31 in the metal member 3 leads to an increase in the number of gas leak locations, so normally such through holes 31 are not formed in the metal member 2 . However, according to the above configuration, the through hole 31 is formed in the metal member 3, and the through hole 31 is filled with the sealing material of the sealing portion 4 (it can also be said that the through hole 31 is filled with the sealing material). ), it is possible to delay the final destruction of the seal portion 4 while suppressing gas leakage. In addition, such a structure can be obtained by disposing a sealing material in the gap 40 between the single cell 2 and the metal member 3 and then heat-treating the sealing material to melt and flow the sealing material so that a part of the sealing material is put into the through hole 31 . can be formed by

Note that the shape of the through hole 31 is not particularly limited. Also, the metal member 3 can have at least one through hole 31 . In this embodiment, as illustrated in FIG. 2, an example in which the metal member 3 has a plurality of through holes 31 is shown. Further, when the seal portion 4 is arranged so as to surround the outer periphery of the cathode 22 and the metal member 3 has a plurality of through holes 31, the plurality of through holes 31 surround the outer periphery of the cathode 22. can be arranged as According to this configuration, even when interfacial failure occurs from any position on the outer circumference of the cathode 22, the function of the failure mode transition portion 5 can be easily exhibited.

As illustrated in FIG. 3, the fuel cell 1 has an exposed seal portion 400 of the seal material that has entered the through hole 31 on the surface of the metal member 3 opposite to the seal portion 4 side. A configuration having a portion 41 can be employed. According to this configuration, a peeling force for peeling off the metal member 3 from the seal portion 4 is easily applied to the portion 400 of the sealing material, and the above-described effects can be easily ensured. At this time, when the seal exposed portion 41 is in a state of protruding from the through hole 31, it is easier to ensure the above-described effects. 2, the sealing material and the exposed seal portion 41 are omitted.

Also, the maximum diameter of the seal exposed portion 41 can be configured to be equal to or larger than the minimum hole diameter of the through hole 31 , more preferably larger than the minimum hole diameter of the through hole 31 . According to this configuration, it becomes easier to prevent the seal exposed portion 41 from slipping through the through hole 31 when a peeling force acts. As a result, the peel strength (peeling strength) between the seal portion 4 and the metal member 3 is improved. Therefore, according to this configuration, it is possible to obtain the fuel cell 1 in which the final breakage of the seal portion 4 is likely to be delayed.

The through-hole 31 has a protrusion 311 on the periphery of the hole, and the protrusion 311 can be arranged so that the tip thereof faces the seal section 4 side. According to this configuration, the tip of the protrusion 311 bites into the sealing material forming the sealing portion 4 . As a result, the peel strength between the seal portion 4 and the metal member 3 is improved. Therefore, according to this configuration, it is possible to obtain the fuel cell 1 in which the final breakage of the seal portion 4 is likely to be delayed.

In this embodiment, as exemplified in FIG. 3, the protrusion 311 can be specifically composed of a burr formed on the periphery of the hole. According to this configuration, burrs formed when the through holes 311 are formed in the metal member 3 by punching or the like can be used as the protrusions 311 as they are. Therefore, according to this configuration, since it is not necessary to remove burrs when forming the through hole 31, the manufacturability of the fuel cell 1 can be improved.

In this embodiment, a cell stack can be configured by alternately stacking the fuel cells 1 in which the unit cells 2 are supported by the supports 6 and fixed by the metal members 3, and the separators 7. . A fuel gas channel 81 for supplying the fuel gas F to the anode 21 can be formed between the support 6 and the separator 7 . An oxidant gas flow path (not shown) for supplying an oxidant gas (not shown) to the cathode 22 is provided between the cathode 22 and the separator 7 (the separator 7 on the cathode 22 side is not shown in FIG. 1). can be formed into

(Embodiment 2)
A fuel cell according to Embodiment 2 will be described with reference to FIGS. 4 and 5. FIG. It should be noted that, of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the previously described embodiments represent the same components and the like as those in the previously described embodiments, unless otherwise specified.

As exemplified in FIGS. 4 and 5, in the fuel cell 1 of the present embodiment, the through hole 31 has a projection 311 on the periphery of the hole. are arranged so that

In this embodiment, as exemplified in FIGS. 4 and 5, the protrusion 311 can be specifically composed of a projecting piece formed on the periphery of the hole. The projecting piece is formed by, for example, cutting and raising a cut formed in the metal member 3 (for example, a cut in the shape of "U", "U", or "V") toward the seal portion 3. It can be formed relatively easily by, for example. According to this configuration, the direction of the tip portion of the protrusion 311 can be freely oriented in a desired direction on the seal portion 4 side, as compared with the case where the protrusion 311 is formed of burrs. Moreover, as illustrated in FIGS. 4 and 5, when the tip of the protrusion 311 is directed toward the cathode 22, the peel strength between the seal portion 4 and the metal member 3 is improved. easier. Other configurations and effects are the same as those of the first embodiment.

The present invention is not limited to the above-described embodiments and experimental examples, and various modifications can be made without departing from the scope of the invention.

1 fuel cell 2 single cell 3 metal member 4 sealing portion 5 fracture mode transition portion

Claims (5)

A single cell (2) using a solid electrolyte as the electrolyte;
a metal member (3) arranged around the single cell;
a sealing part (4) made of a sealing material for gas-sealing between the single cell and the metal member;
and a fracture mode transition section (5) that changes the fracture mode from the interface fracture to the seal material fracture due to the seal material in the middle of the interface fracture due to peeling from the interface between the metal member and the seal portion. and
The single cell has an anode (21) on one side of a solid electrolyte layer (20) and a cathode (22) on the other side , and the cathode is formed to have a smaller outer shape than the solid electrolyte layer. Alternatively, the anode is arranged on one side of the solid electrolyte layer and the cathode is arranged on the other side, and an intermediate layer is provided between the solid electrolyte layer and the cathode, and the cathode is formed to have a smaller outer shape than the outer shape of the intermediate layer ,
The sealing portion gas seals a gap (40) formed between the cathode-side outer peripheral surface of the solid electrolyte layer and the metal member, or the cathode-side outer surface of the intermediate layer. A gap (40) formed between the peripheral surface and the metal member is gas-sealed,
The fracture mode transition portion has a through hole (31) penetrating the metal member and a portion (40 0 ) of the seal material entering the through hole.
Fuel cell (1). 2. The fuel cell according to claim 1, wherein the surface of the metal member opposite to the seal portion has a seal exposed portion (41) in which a portion of the seal material that has entered the through hole is exposed. 3. The fuel cell according to claim 2, wherein the maximum diameter of the exposed seal portion is equal to or greater than the minimum diameter of the through hole. The through hole has a protrusion (311) on the periphery of the hole,
4. The fuel cell according to any one of claims 1 to 3, wherein the protruding portion is arranged so that the tip thereof faces the seal portion. further comprising a support (6) that supports the single cell,
5. The fuel cell according to claim 1, wherein said metal member is a fixing member for fixing the outer peripheral edge of said unit cell to said support.

Images