JP2014017065A - Solid oxide fuel cell - Google Patents

Abstract

Provided is a solid oxide fuel cell that can prevent the flow of a conductive bonding agent during baking, suppress an increase in electrical resistance between a current collector and an electrode, and increase current collection efficiency.
In a solid oxide fuel cell, a recess 10 is formed in an electrode contact portion 2A of a current collector 2 provided in contact with an electrode 4 of a power generation cell 1, and a conductive bonding material is provided in the recess 10. Fill. Since the conductive bonding material is held in the recess 10 until it is baked and sintered, the paste-like conductive bonding material is prevented from flowing out between the electrode 4 and the electrode contact portion 2A. . For this reason, the initial amount filled in the concave portion 10 is sintered as the contact portion 9 as it is, and an increase in the electric resistance value between the current collector 2 and the electrode 4 can be prevented.
[Selection] Figure 2

Description

  The present invention relates to a solid oxide fuel cell including a solid electrolyte type power generation cell.

  For example, in Patent Document 1, in order to suppress delamination caused by the difference in thermal expansion coefficient between the electrode of the power generation cell and the electrode connection corrugated plate with a conductive bonding agent, It is disclosed to use a conductive bonding agent in which platinum powder is mixed with powder of the same material as the electrode to be used.

Japanese Patent Laid-Open No. 7-235312

  However, in Patent Document 1, when the conductive bonding agent is baked and cured, the conductive bonding agent flows before reaching the sintering temperature, and the contact area between the electrode connecting corrugated plate and the electrode is reduced. Therefore, the electrical resistance value between the electrode connection corrugated plate and the electrode increases, and as a result, the current collection efficiency is deteriorated.

  Therefore, the present invention provides a solid oxide fuel cell that can prevent the flow of a conductive bonding agent during baking, suppress an increase in electrical resistance between a current collector and an electrode, and increase current collection efficiency. It is.

  The solid oxide fuel cell of the present invention has a structure in which a conductive bonding agent provided between a current collector and an electrode is baked to form a contact portion. In this invention, it has the outflow prevention means which prevents the outflow of a conductive bonding agent at the time of baking.

  According to the solid oxide fuel cell of the present invention, since the outflow prevention means prevents the conductive bonding agent from flowing out, the contact portion for electrical connection between the current collector and the electrode does not decrease, The increase in electrical resistance can be prevented.

The solid oxide fuel cell of this embodiment is shown, (a) is sectional drawing which shows a laminated structure, (b) is an expanded sectional view in the A section of Fig.1 (a). It is a principal part expanded sectional view which shows an example of the outflow prevention means which prevents the outflow of a conductive bonding agent. It is a comparative example without the outflow prevention means which prevents the outflow of an electroconductive bonding agent, (a) is sectional drawing which shows the state after application | coating of an electroconductive bonding agent, (b) is sectional drawing which shows the state after baking. is there. It is a figure which shows the relationship between temperature and time when hardening an electroconductive bonding agent. It is a principal part expanded sectional view which shows the other example of an outflow prevention means. It is a principal part expanded sectional view which shows the further another example of an outflow prevention means. It is a principal part expanded sectional view which shows the further another example of an outflow prevention means. It is a principal part expanded sectional view which shows the further another example of an outflow prevention means. The example which provided the flow-path member in the recessed part is shown, (a) is the principal part expanded sectional view after baking, (b) is the principal part expanded sectional view which shows the state before providing a flow-path member in a recessed part. FIG. 2A is a perspective view of a flow path member having a rectangular body, and FIG. 2B is a perspective view of the flow path member having a cylindrical body. It is a principal part expanded sectional view which shows a mode that the gas produced | generated by the binder removal process flows in into a flow-path member. It is a perspective view which shows a mode that the gas produced | generated by the debinding process flows in into a flow-path member, and is exhausted outside.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  As shown in FIG. 1A, the solid oxide fuel cell according to the present embodiment is formed by stacking a plurality of unit cells each having a current collector 2 on both sides of a power generation cell 1 as one unit. Has been.

  As shown in FIG. 1B, the power generation cell 1 is formed as a laminate of a solid oxide electrolyte 3, an electrode 4 on the air electrode side, and an electrode 5 on the fuel electrode side. The electrode 4 on the air electrode side and the electrode 5 on the fuel electrode side are arranged with the electrolyte 3 interposed therebetween. The power generation cell 1 has inner and outer peripheral edges supported by a support member 6 made of, for example, stainless steel. The electrode 4 may be an electrode on the fuel electrode side, and the electrode 5 may be an electrode on the air electrode side.

  The current collector 2 is formed by forming irregularities of a predetermined shape on a conductive metal plate made of, for example, stainless steel. In the current collector 2, the convex electrode contact portion 2 </ b> A is in surface contact with the electrodes 4 and 5. Moreover, the recessed part formed between the electrode contact parts 2A used as the convex of the electrical power collector 2 is made into the flow-path parts 7 and 8 (refer FIG. 1) through which an oxidizing agent or a fuel flows. An oxidizing gas flows through the flow path portion 7 corresponding to the electrode 4 on the air electrode side. The fuel gas flows through the flow path portion 8 corresponding to the electrode 5 on the fuel electrode side.

  Between the electrode contact portion 2A of the current collector 2 and the electrodes 4 and 5, as shown in FIG. 2, a contact portion 9 formed by baking a conductive bonding agent is provided. Since the conductive bonding agent is in the form of a paste containing a solvent and a binder, it easily flows due to the temperature rise during baking. Therefore, the electrode contact portion 2A is provided with outflow prevention means for preventing the conductive bonding agent from flowing out.

  The outflow prevention means comprises a recess 10 formed on the surface of the electrode contact portion 2A that contacts the electrodes 4 and 5. In FIG. 2, the concave portion 10 is a dent having a substantially inverted U-shaped cross section. If the recess 10 is filled with the conductive bonding agent, the conductive bonding agent can be prevented from flowing out of the recess 10 due to heat during baking. The recess 10 is formed to extend in a direction perpendicular to the paper surface of FIG. 1 if the power generation cell 1 is rectangular, and is formed in an annular shape if the power generation cell is disk-shaped. It shall be.

  FIG. 3 shows a comparative example of the present invention. In the comparative example, no concave portion 10 is formed in the electrode contact portion 2A, and the surface in contact with the electrode 4 is flat. In this case, as shown in FIG. 3A, when the paste-like conductive bonding agent 9a is applied between the electrode contact portion 2A and the electrode 4 and then baked, the binder component is volatilized as a gas. In the meantime, the conductive bonding agent 9a flows out from between them. Therefore, as shown in FIG.3 (b), the contact part of the contact part 9 with respect to the electrical power collector 2 reduces from an initial state (state of Fig.3 (a)). As a result, the electrical resistance value between the current collector 2 and the electrode 4 increases, and the power generation efficiency for extracting the electricity generated in the power generation cell 1 decreases.

  In contrast, in the solid oxide fuel cell of the present invention, the outflow prevention means prevents the conductive bonding agent 9a from flowing out, so that the conductive bonding agent 9a does not flow out to the outside at the time of temperature rise by baking. Therefore, the electrical resistance value between the current collector 2 and the electrode 4 does not increase.

  Further, in the solid oxide fuel cell of the present invention, since the outflow prevention means is the recess 10, the recess 10 serves as an outflow prevention wall to prevent the conductive bonding agent 9 a from flowing out, and the current collector 2 is pressed. It can be easily formed when processing.

  In order to form the contact portion 9, a paste-like conductive bonding agent containing a solvent and a binder is applied in the recess 10. Then, the current collector 2 is stacked on the power generation cell 1 and the power generation cell 1 is further stacked thereon, and then both ends of the stacked body are fastened with bolts. Then, the conductive bonding agent in the recess 10 comes into contact with the electrodes 4 and 5.

  In this state, first, it is kept at 120 ° C. for about 20 minutes in order to evaporate the solvent, and then kept at 400 ° C. for about 20 minutes in order to perform the binder removal treatment. Then, at this temperature, the binder in the paste burns and gas is released. Once the binder treatment is performed, the conductive bonding agent loses its fluidity and can secure an electrical connection at a desired baking temperature. The baking is desirably performed at, for example, 700 ° C. to 800 ° C. As shown in FIG. 4, the heating is performed at a solvent removal temperature for a predetermined time and a baking temperature for a predetermined time.

  Further, in order to confirm the holding effect of the conductive bonding agent, the structure of the present invention was compared with the conventional structure. In the comparative example, two 10 × 10 × 1 mm Crofer22APU stainless steel substrates are used as test specimens, and a conductive bonding agent containing Ag in a paste state is applied to one substrate so that the distance between the plates becomes 0.2 mm. Baking was carried out with a gap formed between them. Firing was performed at a temperature of 5 ° C./min, held at 120 ° C. for 15 minutes, then held at 400 ° C. for 15 minutes, and finally baked at 800 ° C. for 1 hour.

  In the present invention, two 10 × 10 × 1 mm Crofer22APU stainless steel substrates are used as test specimens, and a recess of 7.5 × 7.5 × 0.2 mm is formed on one substrate, and the conductivity containing Ag is formed in the recess. Filled with bonding agent and overlaid on the other substrate. Then, a weight was placed on the specimen, and a baking process was performed in the atmosphere in an atmosphere furnace with the same firing pattern as that of the comparative example.

In order to measure the electric resistance value of the contact portion, the electric resistance was measured by a four-terminal method using a Hokuto Denko potentio / galvanostat and a KEITHLEY multimeter to measure the resistance at 750 ° C. As a result, in the comparative example, it was 4.03 × 10 ⁻⁵ Ωcm ² . Moreover, when cross-sectional observation was performed after baking processing, it was confirmed that the contact area with the upper board | substrate is small.

In contrast, in the present invention, the electric resistance value was 2.27 × 10 ⁻⁵ Ωcm ² . When the cross section was observed after the baking treatment, the conductive bonding agent filled in the recesses maintained the contact area with the substrate.

  Next, another example of the outflow prevention means will be shown. In FIG. 5, a U-shaped recess 10 that opens toward the electrode 4 is formed in the electrode contact portion 2 </ b> A, and the U-shaped recess 10 is used as an outflow prevention means. By forming the U-shaped concave portion 10 in the electrode contact portion 2A, both side portions of the opening become the protruding portions 11 having pointed tips. The protrusion 11 pierces the electrode 4 to form a space surrounded by the surface 4 a of the electrode 4 and the recess 10. Then, the sintered contact portion 9 is formed by filling and baking the conductive bonding agent in the space.

  In this example, since the protruding portion 11 pierces the electrode 4, the conductive bonding agent is surrounded by the sealed concave portion 10 during baking, and is prevented from flowing to the outside. Therefore, the area of the contact portion 9 between the electrode contact portion 2A and the electrode 4 does not decrease, and an increase in the electrical resistance value between the electrode contact portion 2A and the electrode 4 can be prevented.

  In FIG. 6, a U-shaped concave portion 10 that opens toward the electrode contact portion 2 </ b> A is formed on the surface 4 a of the electrode 4, and the concave portion 10 is used as an outflow prevention means. With respect to the recess 10, the tapered surface 12 having the side surface of the electrode contact portion 2 </ b> A inclined is brought into contact with the opening end 10 a of the recess 10 to serve as a stopper, so that the tip surface 13 of the electrode contact portion 2 </ b> A and the recess 10 A space is formed between the bottom surface 14. The sintered contact portion 9 is formed by filling and baking the conductive bonding agent in this space.

  In this example, since the concave portion 10 filled with the conductive bonding agent is covered with the electrode contact portion 2A, the conductive bonding agent is prevented from flowing out. Therefore, the area of the contact portion 9 between the electrode contact portion 2A and the electrode 4 does not decrease, and an increase in the electrical resistance value between the electrode contact portion 2A and the electrode 4 can be prevented.

  In FIG. 7, projections 15 and 15 are provided on the surface 4 a of the electrode 4 at a predetermined interval, and the recess 10 surrounded by the projections 15 and 15 is used as an outflow prevention means. With respect to the recess 10, the tapered surface 12 having the side surface of the electrode contact portion 2 </ b> A inclined is brought into contact with the opening end 10 a of the recess 10 to serve as a stopper, so that the tip surface 13 of the electrode contact portion 2 </ b> A and the recess 10 A space is formed between the bottom surface 14. The sintered contact portion 9 is formed by filling and baking the conductive bonding agent in this space. For example, a metal such as stainless steel is used for the protrusion 15.

  In this example, since the concave portion 10 filled with the conductive bonding agent is covered with the electrode contact portion 2A, the conductive bonding agent is prevented from flowing out. Therefore, the area of the contact portion 9 between the electrode contact portion 2A and the electrode 4 does not decrease, and an increase in the electrical resistance value between the electrode contact portion 2A and the electrode 4 can be prevented.

  In FIG. 8, a mesh member 16 is provided between the electrode contact portion 2A and the electrode 4, and the mesh member 16 is used as an outflow prevention means. The mesh member 16 is made of stainless steel for the cathode side electrode and Ni (nickel) for the anode side electrode. When the mesh member 16 is filled with a paste-like conductive bonding agent, the mesh member 16 suppresses the flow. Therefore, the area of the contact portion 9 between the electrode contact portion 2A and the electrode 4 does not decrease, and an increase in the electrical resistance value between the electrode contact portion 2A and the electrode 4 can be prevented.

  When the paste-like conductive bonding agent filled in the concave portion 10 is fired, it is necessary to efficiently release the contained binder component from the coating portion (this is called debinding treatment). Of the recesses 10, the binder component contained in the conductive bonding agent located near the center from the outside tends to be hardly released.

  Therefore, as shown in FIG. 9, a flow path member 17 that discharges gas generated during baking is provided in the recess 10. The flow path member 17 has a function of supplying a fuel gas to the electrodes 4 and 5 as well as a gas discharging function. The flow path member 17 may be, for example, either the rectangular body of FIG. 10A or the cylindrical body of FIG. 10B, and the first gas flow path 18 penetrating the center and the gas generated during baking are the first gas. A second gas flow path 19 that flows into the flow path 18 and a third gas flow path 20 that supplies fuel gas flowing through the first gas flow path 18 to the electrodes 4 and 5 when the fuel cell is operating are provided.

  The flow path member 17 of FIG. 10A is formed as a tunnel having a rectangular cross section having a first gas flow path 18 penetrating in the center. A plurality of holes communicating with the first gas flow path 18 are formed in the longitudinal direction as the second gas flow paths 19 on both side surfaces 17 a and 17 b of the flow path member 17. In addition, a plurality of holes, which are open to the electrodes 4 and 5, are formed in the longitudinal direction as third gas flow paths 20 on the bottom surface 17 c of the flow path member 17 in contact with the electrodes 4 and 5.

  The flow path member 17 in FIG. 10B is formed as a pipe that forms a tunnel with an annular cross section having a first gas flow path 18 penetrating in the center. A plurality of holes communicating with the first gas flow path 18 are formed in the longitudinal direction as the second gas flow path 19 in a portion passing through the vicinity of the center of the flow path member 17 and parallel to the electrodes 4 and 5. Yes. In addition, a plurality of holes that open to the electrodes 4 and 5 are formed in the longitudinal direction as third gas flow paths 20 at the bottom portion of the flow path member 17 in contact with the electrodes 4 and 5.

  FIG. 11 and FIG. 12 show a state in which the gas G generated by desolvation at the time of firing the conductive bonding agent flows from the second gas channel 19 into the first gas channel 18. When the binder component contained in the conductive bonding agent existing near the center of the recess 10 is released, the gas G generated by the solvent removal flows into the first gas flow path 18 through the second gas flow path 19 and the first gas. The air is exhausted from the outlet of the flow path 18 to the outside. On the other hand, during the fuel cell operation, the fuel gas is also supplied to the first gas flow path 18. As a result, the fuel gas flowing through the first gas passage 18 is supplied to the electrodes 4 and 5 through the third gas passage 20 formed on the bottom surface.

  The flow path member 17 is provided in contact with the electrodes 4 and 5 and is made of a conductive material. By doing so, it is possible to ensure conductivity with respect to the electrodes 4 and 5, and there is no fear of increasing the electric resistance value. The conductive material may be any of metal, stainless steel, and oxide.

  Thus, if the flow path member 17 is provided in the recessed part 10, the gas G generated at the time of baking can be discharged | emitted and a binder removal process can be performed. In addition, the flow path member 17 provided in the recess 10 functions to supply fuel gas to the electrodes 4 and 5 when the fuel cell is operated, so that the reaction overvoltage can be reduced.

  The flow path member 17 provided in the recess 10 includes a first gas flow path 18 that penetrates the center and a second gas flow path 19 that allows the gas G generated during baking to flow into the first gas flow path 18. Therefore, the gas G generated by volatilization of the binder component contained in the conductive bonding agent in the recess 10 is caused to flow into the first gas channel 18 through the second gas channel 19 and finally to the outside of the recess 10. And can be released. Therefore, an efficient binder process can be performed at the time of baking.

  Further, since the flow path member 17 provided in the recess 10 is in contact with the electrodes 4 and 5, fuel gas can be supplied to the electrodes 4 and 5 during fuel cell power generation, which can reduce the reaction overvoltage. it can.

  Further, since the flow path member 17 has the third gas flow path 20 for supplying the fuel gas flowing through the first gas flow path 18 to the electrodes 4 and 5 during the fuel cell operation, Fuel gas can be supplied and the reaction overvoltage can be reduced.

  Further, since the flow path member 17 is made of a conductive material, the conductivity between the current collector 2 and the electrodes 4 and 5 can be ensured.

  The flow path member 17 is provided in the recess 10 as follows. The flow path member 17 is fixed to the surface of the electrodes 4 and 5 of the power generation cell 1 with an adhesive. At this time, the flow path member 17 is arranged in a direction in which the third gas flow path 20 faces the electrodes 4 and 5.

  Next, a paste-like conductive bonding agent is filled into the recess 10 formed in the electrode contact portion 2 </ b> A of the current collector 2. And it sticks so that channel member 17 and crevice 10 may overlap so that paste dripping may not arise. As baking conditions, the temperature was raised at 5 ° C./min in an atmospheric furnace atmosphere, held at 120 ° C. for 15 minutes, and finally baked at 800 ° C.

  The present invention can be used for a solid oxide fuel cell including a solid electrolyte type power generation cell.

DESCRIPTION OF SYMBOLS 1 Power generation cell 2 Current collector 2A Electrode contact part 3 Electrolyte 4, 5 Electrode 9 Contact part 10 Recessed part (outflow prevention means)
17 channel member 18 first gas channel 19 second gas channel 20 third gas channel

Claims (7)

A solid oxide fuel cell in which a plurality of power generation cells with electrodes stacked on both sides of an electrolyte are stacked via a current collector,
A solid oxide fuel comprising: a conductive bonding agent provided between the current collector and the electrode to be baked to form a contact portion; and an outflow prevention means for preventing the conductive bonding agent from flowing out during the baking. battery. The solid oxide fuel cell according to claim 1,
The outflow prevention means comprises a recess formed in either the current collector or the electrode, and a conductive bonding agent is provided in the recess. A solid oxide fuel cell, wherein: The solid oxide fuel cell according to claim 2, wherein
A solid oxide fuel having a gas flow path for discharging gas generated during baking and supplying fuel gas supplied during fuel cell operation to the electrode is provided in the recess. battery. A solid oxide fuel cell according to claim 3,
The flow path member is in contact with the electrode. A solid oxide fuel cell, wherein: A solid oxide fuel cell according to claim 3 or claim 4, wherein
The flow path member has a first gas flow path penetrating the center and a second gas flow path for allowing a gas generated during baking to flow into the first gas flow path. Type fuel cell. The solid oxide fuel cell according to claim 5,
The said flow path member has the 3rd gas flow path which supplies the fuel gas which flows through a 1st gas flow path to the said electrode at the time of fuel cell operation | movement. The solid oxide fuel cell characterized by the above-mentioned. The solid oxide fuel cell according to any one of claims 3 to 6,
The flow path member is made of a conductive material. A solid oxide fuel cell, wherein:

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