JP4906794B2 - Cell stack and solid oxide fuel cell - Google Patents

Description

  The present invention relates to a cell stack and a solid oxide fuel cell.

  In recent years, various fuel cells have been proposed as next-generation energy. Various types of fuel cells such as a solid polymer type, a phosphoric acid type, a molten carbonate type, and a solid electrolyte type are known. Among them, a solid electrolyte type fuel cell has an operating temperature of 1000. Although it is as high as about ℃, it has advantages such as high power generation efficiency and the ability to use waste heat, and its research and development is being promoted.

  In a solid electrolyte fuel cell, a plurality of fuel cells each having a fuel electrode and an oxygen electrode (air electrode) sandwiched between solid electrolytes are electrically connected to each other by a metal or alloy current collecting member. Thus, the current is extracted.

  By the way, in the fuel cell having the above structure, since the fuel gas is supplied to the fuel electrode and the oxygen-containing gas such as air is supplied to the oxygen electrode, the current collecting member has gas permeability. At the same time, it must have good resistance to oxidation and reduction. As a conventionally known current collecting member, a felt formed of a metal or alloy fiber has been used. However, since the felt has a large specific surface area and is easily oxidized, a perovskite type is formed on the surface of the felt fiber. It has been proposed to support an oxide (see, for example, Patent Document 1).

Japanese Patent No. 3108256

  In the current collecting member in which the perovskite oxide is supported on the fiber surface as described above, the oxidation of the fiber surface is prevented by the oxide, and an increase in resistance due to the oxidation can be suppressed, and at the portion where the fiber and the fiber cross each other. Since the perovskite oxide is attached, the reduction of the fiber gap due to the creep (plastic deformation) of the felt is suppressed, and there is an advantage that a decrease in gas permeability can be avoided.

  However, the current collector treated with the perovskite oxide has the disadvantages that the initial resistance is relatively large and the durability is low. That is, there is a drawback that the resistance increases due to long-term use, and the output of the battery is reduced.

Accordingly, an object of the present invention is to provide a cell stack using a current collecting member that has a low initial resistance, excellent durability, suppresses an increase in resistance due to long-term use, and can effectively avoid a decrease in battery output. It is to provide.
Another object of the present invention is to provide a solid oxide fuel cell in which a plurality of the cell stacks are housed and electrically connected.

According to the present invention, there is provided a cell stack in which solid oxide fuel cells are electrically connected in series via a current collecting member made of metal or alloy, and a perovskite type is formed on the surface of the current collecting member. An oxide and an oxide of at least one metal selected from Fe, Cr, Co and Mn, and a content of at least one metal selected from Fe, Cr, Co and Mn, A cell stack is provided that is 0.1 to 10 parts by mass per 100 parts by mass of the perovskite oxide.
According to the present invention, there is provided a solid oxide fuel cell characterized in that a plurality of the cell stacks are housed and electrically connected in a housing container.

  According to the present invention, the surface of a current collector made of metal or alloy has a perovskite oxide and an oxide of at least one metal selected from Fe, Cr, Co, and Mn, and the Fe A fuel cell is connected using a current collecting member in which the content of at least one metal selected from Cr, Co and Mn is 0.1 to 10 parts by mass per 100 parts by mass of the perovskite oxide Accordingly, it is possible to obtain a cell stack and a solid oxide fuel cell that have low initial resistance and excellent durability, suppress an increase in resistance due to long-term use, and effectively avoid a decrease in battery output.

  Refer to Examples and Comparative Examples described later. For example, in a comparative example of a cell stack in which fuel cells are connected using a current collector obtained by treating the surface of a metal or alloy felt only with a perovskite oxide, the initial resistance is high, and further resistance is obtained when a long-term durability test is performed. An increase is observed. That is, in a cell stack using such a current collector, micro cracks are generated at the junction between the current collector and the fuel cell and at the fiber / fiber interface inside the current collector. It is thought that it is raising. In addition, when a long-term durability test is performed, this crack develops to cause a crack, and this crack causes a decrease in the current collecting path, resulting in a significant increase in resistance and a decrease in output. is there. However, in accordance with the present invention, a current collector treated with a surface treatment agent containing at least one metal selected from Fe, Cr, Co and Mn in a predetermined amount in the perovskite oxide and fired is used. In the embodiment of the cell stack, the generation of cracks at the initial stage is effectively suppressed, so that the generation of cracks due to the progress of cracks is also effectively prevented, and therefore, the initial resistance is low and long-term durability tests are performed. However, the increase in resistance is suppressed, the decrease in output is effectively avoided, and excellent durability is exhibited.

  As understood from the above description, the current collecting member in the cell stack of the present invention is surface-treated with a surface treatment agent in which a predetermined amount of metal is mixed with a perovskite-type oxide and fired. The occurrence of cracks is effectively suppressed, and as a result, excellent characteristics are exhibited. That is, in the cell stack using the current collecting member surface-treated with the perovskite oxide alone, the firing shrinkage is large, and for this reason, the junction between the current collecting member and the fuel cell and the fibers / fibers inside the current collecting member Cracks occur at the interface. However, in a cell stack using a current collecting member in which at least one metal selected from a predetermined amount of Fe, Cr, Co, and Mn is mixed with a perovskite oxide, the perovskite oxide is fired and shrunk, It is believed that the firing shrinkage of the surface treatment agent is reduced by the volume expansion due to oxidation, and therefore, generation of cracks at the initial stage is prevented, and various inconveniences caused by such cracks can be effectively avoided.

  Further, since the surface treatment agent as described above contains a perovskite type oxide, the current collecting member in the cell stack of the present invention treated with such a surface treatment agent is similar to a known current collecting member, It has excellent oxidation resistance, and also suppresses a decrease in fiber gap due to fiber creep due to long-term use, and has stable gas permeability.

The present invention will be described below based on specific examples shown in the accompanying drawings.
FIG. 1 is a cross-sectional view showing a typical structure of a cell stack of a solid oxide fuel cell according to the present invention.

  In the cell stack, a plurality of solid electrolyte fuel cells 1 are assembled, and a current collecting member 20 is interposed between one fuel cell 1a and the other fuel cell 1b adjacent to each other in the vertical direction, and the two are mutually connected. It is configured by connecting in series. Further, adjacent cell stacks are connected by the conductive member 22. That is, the electrode support substrate 10 of one fuel cell 1 is electrically connected to the oxygen electrode layer 13 of the other fuel cell 1b via the interconnector 14 and the current collecting member 20. Such cell stacks are arranged side by side as shown in FIG. 1, and adjacent cell stacks are connected in series by a conductive member 22. As the conductive member 22, a metal plate or the like is usually used in consideration of strength and the like.

  In FIG. 1, a fuel battery cell generally indicated by 1 includes an electrode support substrate 10, a fuel electrode layer 11 that is an inner electrode layer, a solid electrolyte layer 12, an oxygen electrode layer 13 that is an outer electrode layer, and an interconnector. 14.

  As is apparent from FIG. 1, the electrode support substrate 10 has a flat plate shape, and a plurality of gas passages 16 are formed therein.

  The interconnector 14 is provided on one surface of the electrode support substrate 10, and the fuel electrode layer 11 is laminated on the other surface of the electrode support substrate 10, and is formed on the opposite surface. It extends to both end portions of the connector 14. Furthermore, the solid electrolyte layer 12 is provided so as to cover the fuel electrode layer 11 and is laminated on the entire surface of the fuel electrode layer 11 as shown in FIG. It is joined to the part. The oxygen electrode layer 13 is laminated on the solid electrolyte layer 12, faces the fuel electrode layer 11, and simultaneously faces the interconnector 14. Located on the surface.

  In such a fuel cell, a fuel gas (hydrogen) is supplied into the gas passage 16 in the electrode support substrate 10 and an oxygen-containing gas such as air is supplied to the outside of the oxygen electrode layer 13 and heated to a predetermined operating temperature. By doing so, power is generated. That is, power is generated by causing an electrode reaction of the following formula (1) in the oxygen electrode layer 13 and an electrode reaction of the following formula (2) in the fuel electrode layer 11.

Oxygen electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte) (1)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)

  The current generated by the power generation is collected through the interconnector 14 provided on the electrode support substrate 10.

  On the other hand, the current collecting member 20 provided between the fuel cells is connected to the interconnector 14 of one fuel cell 1a and the oxygen electrode layer 13 of the other fuel cell 1b. Current flows from the other fuel cell 1b to the one fuel cell 1a. As such a current collecting member, for example, a plate-like metal formed into a U shape or a Y shape to give elasticity, or a felt made of metal fibers is preferably used.

  A fuel cell is configured by housing the cell stack as described above in a predetermined storage container. The storage container is provided with an introduction pipe for introducing a fuel gas such as hydrogen into the fuel battery cell 1 from the outside, and an introduction pipe for introducing an oxygen-containing gas such as air into the external space of the fuel battery cell 1. The fuel cell is heated to a predetermined temperature (for example, 600 to 900 ° C.) to generate electric power, and the used fuel gas and oxygen-containing gas are discharged out of the storage container.

Electrode support substrate 10:
In the fuel cell 1 described above, the electrode support substrate 10 is gas permeable to allow the fuel gas to permeate to the fuel electrode layer 11 and is conductive to collect current via the interconnector 14. In order to manufacture the electrode support substrate 10 by co-firing with the fuel electrode layer 11 and the solid electrolyte layer 12, it is formed from a porous conductive ceramic (or cermet) that satisfies such requirements. Then, it is preferable to form the electrode support substrate 10 from an iron group metal component and a specific rare earth oxide.

  The iron group metal component is for imparting conductivity to the electrode support substrate 10 and may be an iron group metal alone, or an iron group metal oxide, an iron group metal alloy or alloy oxidation. It may be a thing. The iron group metals include iron, nickel, and cobalt, and any of them can be used, but Ni and / or NiO are contained as an iron group component because they are inexpensive and stable in fuel gas. It is preferable.

The rare earth oxide component used together with the iron group metal component is used to approximate the thermal expansion coefficient of the electrode support substrate 10 to that of the solid electrolyte layer 12, and maintains a high conductivity and is a solid electrolyte. At least one selected from the group consisting of Y, Lu, Yb, Tm, Er, Ho, Dy, Gd, Sm, and Pr in order to prevent the element from diffusing into the layer 12 and the like and to eliminate the influence of element diffusion. Oxides containing rare earth elements are preferred. Examples of such rare earth _{oxide, Y 2 O 3, Lu 2} O 3, Yb 2 O 3, Tm 2 O 3, Er 2 O 3, Ho 2 O 3, Dy 2 O 3, Gd 2 O 3 , Sm ₂ O ₃ , and Pr ₂ O ₃ , and Y ₂ O ₃ and Yb ₂ O ₃ are preferable in that they are particularly inexpensive.

  The iron group component described above is preferably included in the electrode support substrate 10 in an amount of 35 to 65% by volume, and the rare earth oxide is preferably included in the electrode support substrate 10 in an amount of 35 to 65% by volume. It is. Of course, the electrode support substrate 10 may contain other metal components and oxide components as long as required characteristics are not impaired.

  Since the electrode support substrate 10 composed of the iron group metal component and the rare earth oxide as described above needs to have fuel gas permeability, the open porosity is usually 30% or more, particularly It is preferable to be in the range of 35 to 50%. Further, the conductivity is preferably 300 S / cm or more, and particularly preferably 440 S / cm or more.

  The electrode support substrate 10 usually has a length of 15 to 35 mm and a thickness of about 2.5 to 5 mm. Further, it is preferable that curvature portions are formed at both ends in order to prevent breakage during molding and to increase mechanical strength.

Fuel electrode layer 11:
The fuel electrode layer 11 serving as the inner electrode layer causes the electrode reaction of the above-described formula (2) and is formed from a known porous conductive ceramic. For example, it is formed from ZrO ₂ in which a rare earth element is dissolved, and Ni and / or NiO. As ZrO ₂ (stabilized zirconia) in which the rare earth element is dissolved, the same one used for forming the solid electrolyte layer 12 described below may be used.

  The stabilized zirconia content in the fuel electrode layer 11 is preferably in the range of 35 to 65% by volume, and the Ni or NiO content is preferably in the range of 65 to 35% by volume. Further, the open porosity of the fuel electrode layer 11 is preferably 15% or more, particularly in the range of 20 to 40%, and the thickness is preferably 1 to 30 μm. For example, if the thickness of the fuel electrode layer 11 is too thin, the current collecting performance may be lowered. If the thickness is too thick, peeling due to a difference in thermal expansion between the solid electrolyte layer 12 and the fuel electrode layer 11 may occur. There is.

Solid electrolyte layer 12:
The solid electrolyte layer 12 provided on the fuel electrode layer 11 has a function as an electrolyte that bridges electrons between the electrodes, and at the same time, in order to prevent leakage of the fuel gas and the oxygen-containing gas. It must have gas barrier properties and is generally formed from ZrO ₂ (usually called stabilized zirconia) in which 3 to 15 mol% of a rare earth element is dissolved. Examples of the rare earth element include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, but they are inexpensive. Therefore, Y and Yb are preferable.

  The stabilized zirconia ceramics forming the solid electrolyte layer 12 is desirably a dense material having a relative density (according to Archimedes method) of 93% or more, particularly 95% or more from the viewpoint of preventing gas permeation. It is desirable that the thickness is 10 to 100 μm.

Oxygen electrode layer 13:
The oxygen electrode layer 13 is formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. As such a perovskite oxide, at least one of transition metal perovskite oxides, particularly LaMnO ₃ oxides, LaFeO ₃ oxides, and LaCoO ₃ oxides having La at the A site is preferable. LaFeO ₃ -based oxides are particularly suitable because they have high electrical conductivity at an operating temperature of about 1000 ° C. In the perovskite oxide, Sr and the like may exist together with La at the A site, and Co and Mn may exist together with Fe at the B site.

  The oxygen electrode layer 13 must have gas permeability. Therefore, the conductive ceramics (perovskite oxide) has an open porosity of 20% or more, particularly in the range of 30 to 50%. It is desirable to be in The thickness of the oxygen electrode layer 13 is preferably 30 to 100 μm from the viewpoint of current collection.

Interconnector 14:
The interconnector 14 provided on one surface of the flat plate portion of the electrode support substrate 10 so as to face the oxygen electrode layer 13 is made of conductive ceramics, and includes a fuel gas (hydrogen) and an oxygen-containing gas. In order to contact, it is necessary to have reduction resistance and oxidation resistance. For this reason, lanthanum chromite perovskite oxides (LaCrO ₃ oxides) are generally used as the conductive ceramics. Further, in order to prevent leakage of the fuel gas passing through the inside of the electrode support substrate 10 and the oxygen-containing gas passing through the outside of the electrode support substrate 10, such conductive ceramics must be dense, for example 93% or more, particularly It is preferable to have a relative density of 95% or more.

  The interconnector 14 is preferably 10 to 200 μm from the viewpoint of preventing gas leakage and electrical resistance. That is, if the thickness is smaller than this range, gas leakage is likely to occur, and if the thickness is larger than this range, the electric resistance is large, and the current collecting function may be reduced due to a potential drop. .

Further, a P-type semiconductor layer (not shown) may be provided on the outer surface (upper surface) of the interconnector 14. That is, in the cell stack assembled from the fuel battery cell 1, the current collector 20 of the present invention is connected to the interconnector 14 as shown in FIG. When connected to the connector 14, the potential drop increases due to non-ohmic contact, and the current collection performance may be reduced. However, by connecting the current collecting member 20 to the interconnector 14 via the P-type semiconductor layer, the contact between the two becomes an ohmic contact, the potential drop is reduced, and the deterioration of the current collecting performance can be effectively avoided. It becomes possible. As such a P-type semiconductor, a transition metal perovskite oxide can be exemplified. Specifically, those having higher electron conductivity than LaCrO ₃ oxides constituting the interconnector 14, for example, LaMnO ₃ oxides and LaFeO ₃ oxides in which Mn, Fe, Co, etc. exist at the B site P-type semiconductor ceramics made of at least one of LaCoO ₃ -based oxides can be used. In general, the thickness of such a P-type semiconductor layer is preferably in the range of 30 to 100 μm.

  The fuel cell 1 described above is not limited to the structure shown in FIG. 1 and can take various configurations. For example, the positional relationship between the fuel electrode layer 11 and the oxygen electrode layer 13 described above can be reversed. That is, the oxygen electrode layer 13 can be provided as the inner electrode layer, and the fuel electrode layer 11 can be provided as the outer electrode layer. In this case, oxygen-containing gas such as air is supplied into the gas passage 16 formed in the electrode support substrate 10, and fuel gas is supplied outside the cell 1 (outside the fuel electrode layer 11). Electric power is generated, and the current flow is opposite to that of the fuel cell 1 having the structure of FIG. Further, in the fuel cell 1 shown in FIG. 1, the electrode support substrate 10 and the inner electrode layer (fuel electrode layer 11) are formed separately, but the electrode support substrate 10 itself is used as the inner electrode. You can also. In this case, the fuel electrode layer 11 corresponding to the inner electrode can be omitted in FIG. Furthermore, the electrode support substrate 10 is not limited to a flat plate shape, and may have a cylindrical shape, for example.

Current collecting member 20:
The current collecting member 20 used for the connection of the battery cell 1 described above is a metal or alloy elastic current collecting member or a felt-like current collecting member made of metal or alloy fibers with a predetermined surface treatment agent. Obtained by surface treatment.

  The metal or alloy constituting the current collecting member 20 is not particularly limited as long as it has high conductivity, but generally Ni, Fe—Cr, SUS, or the like is preferably used.

  In the present invention, the surface treatment agent used for the treatment of the current collecting member comprises a mixed powder of a perovskite oxide powder and a metal powder.

Examples of the perovskite oxide include the same oxides used for the formation of the oxygen electrode layer 13, and LaFeO ₃ -based oxides are particularly preferable in terms of conductivity. For example, (La, Sr) (Co, Fe) O ₃ is most preferably used. By using such a perovskite type oxide, the oxidation of the metal or alloy constituting the current collecting member 20 can be effectively prevented, and when the current collecting member is made of felt, the fiber is made of a perovskite type oxide. Therefore, fiber creep (plastic deformation) when the fuel cell is used for a long period of time is effectively suppressed, and a decrease in fiber gap due to creep, that is, a decrease in gas permeability can be effectively prevented. .

  In addition, when the surface treatment is performed only with the perovskite oxide, the firing shrinkage when the current collecting member 20 is connected between the fuel cells 1 is large, and the junction interface or current collection between the fuel cell 1 and the current collecting member 20 is large. Cracks occur at the fiber / fiber interface inside the electric member 20, and the initial resistance increases. Further, a fuel cell in which such a crack has occurred has poor durability, and as the fuel cell is used, the crack progresses to form a crack, resulting in a large decrease in output. Such inconvenience can be avoided by using at least one metal selected from Fe, Cr, Co and Mn together with the perovskite oxide.

  That is, by coexisting such a metal, the perovskite type oxide is baked and contracted due to expansion due to oxidation of the metal, but as a whole, the calcination shrinkage is reduced, and the occurrence of cracks accompanying the calcination contraction is effectively prevented, As a result, the initial resistance is low, and crack generation due to crack propagation is effectively avoided, so it has excellent durability, and output reduction can be effectively suppressed even after long-term use, and stable output can be maintained. It becomes. In addition, these metals are desirable because they do not adversely affect the electrodes of the fuel cell 1.

  In the present invention, the amount of the at least one metal selected from Fe, Cr, Co and Mn is 0.1 to 10 parts by mass, particularly 1 to 5 parts by mass, per 100 parts by mass of the perovskite oxide. The range. That is, if blended in a larger amount than the above range, even if the firing shrinkage of the surface treatment agent can be reduced, the metal is oxidized and becomes an oxide, resulting in inconveniences such as an increase in resistance. If the amount is small, the reduction in firing shrinkage is insufficient, and there is a risk that an increase in initial resistance and a decrease in durability due to the occurrence of cracks.

  The perovskite oxide powder and at least one metal powder selected from Fe, Cr, Co, and Mn all have an average particle size in the range of about 0.2 to 5 μm. It is suitable for uniformly adhering to the surface of the member (fiber surface).

Furthermore, the amount of the surface treatment agent is usually preferably in the range of 50 to 200 g / m ² . If the treatment amount is more than necessary, gas permeability may be impaired or resistance may be increased, and if the treatment amount is too small, the surface treatment effect is dilute.

  In the surface treatment using the surface treatment agent described above, for example, a mixed powder of the surface treatment agent is dispersed in an appropriate organic solvent such as isopropanol to prepare a paste, and this paste is applied to the surface of the plate-like current collecting member. The surface treatment is usually performed in the step of connecting the current collecting member 20 between the fuel cells 1, although it is performed by applying or impregnating a felt-shaped current collecting member and drying.

  That is, the paste of the surface treatment agent is applied to the entire surface of the current collecting member 20 and dried. The current collecting members 20 thus surface-treated are alternately superposed on the fuel cells 1 prepared in advance to form an array structure as shown in FIG. 1, and then fired to produce a perovskite type oxidation on the surface. A cell stack is obtained which is connected by a current collecting member 20 having an oxide and an oxide of at least one metal selected from Fe, Cr, Co and Mn. The firing is usually performed in the atmosphere at a temperature of 950 to 1200 ° C. for about 1 to 5 hours.

  The cell stacks obtained in this manner are connected to each other by the conductive member 22 and are stored in a predetermined storage container to be used as a solid oxide fuel cell.

Example 1
First, to 100 parts by mass of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder having an average particle size of 0.5 μm, an amount of metal shown in Table 1 was added, and polyvinyl alcohol was added thereto. Then, isopropyl alcohol is added, this is formed into a length of 2 mm, a width of 5 mm, and a length of 40 mm, fired in the atmosphere at 1050 ° C. for 2 hours, the length is measured, and the sintered body is sintered to the length. The ratio of body length was determined, and the firing shrinkage rate was calculated. The results are listed in Table 1.

この表１から、Ｌａ_０．６Ｓｒ_０．４Ｃｏ_０．２Ｆｅ_０．８Ｏ_３粉末のみからなる比較例の試料Ｎｏ．１７の焼成収縮率は４０％であるのに対して、本発明の試料では、焼成収縮率が３０％以下と低減され、しかも、Ｌａ_０．６Ｓｒ_０．４Ｃｏ_０．２Ｆｅ_０．８Ｏ_３粉末１００質量部に対して、金属の添加量が多くなるほど収縮率を小さくできることが判る。

From Table _1, the samples of Comparative Examples comprising only _{La 0.6 Sr 0.4 Co 0.2 Fe 0.8} O 3 powder No. The firing shrinkage rate of 17 is 40%, whereas in the sample of the present invention, the firing shrinkage rate is reduced to 30% or less, and La _0.6 Sr _0.4 Co _0.2 Fe _0.8. It can be seen that the shrinkage rate can be reduced as the amount of added metal increases with respect to 100 parts by mass of the O ₃ powder.

  Therefore, using such a surface treatment agent, for example, even when a current collecting member made of a metal plate is joined to an interconnector or an oxygen electrode of a fuel cell, generation of cracks due to firing shrinkage of the surface treatment agent is suppressed. I understand that

Example 2
First, NiO powder having an average particle size of 0.5 μm and Y ₂ O ₃ powder having an average particle size of 0.8 μm were mixed such that the volume ratio in terms of Ni after firing was 50%. A support substrate material formed by mixing this mixed powder with an organic binder composed of a pore agent and PVA and a solvent composed of water is extruded to produce a flat support substrate molded body, which is then dried. The temperature was raised to 1000 ° C., and degreasing and calcination were performed to prepare a support substrate molded body.

Next, ZrO ₂ (YSZ) powder containing 8 mol% Y ₂ O ₃ having an average particle diameter of 0.8 μm, the above-described NiO powder, an organic binder made of acrylic resin, and a solvent made of toluene were mixed. A slurry to be a fuel electrode was prepared.
A sheet-like molded body is produced using a solid electrolyte material in which the YSZ powder, an organic binder made of an acrylic resin, and a solvent made of toluene are mixed, and the slurry for the fuel electrode is placed on one side of the sheet-like molded body. This was printed and spread on the support substrate molded body so that the solid electrolyte sheet-shaped molded body was on the outer side and spaced apart at a predetermined interval on the flat portion of the support substrate molded body, and dried.

Further, a sheet-like molded body was prepared using an interconnector material in which an La (MgCr) O ₃ based material having an average particle size of 0.9 μm, an organic binder made of an acrylic resin, and a solvent made of toluene were mixed. The interconnector sheet-like molded body was laminated on the exposed surface of the support substrate molded body, and a laminated molded body in which a fuel electrode molded body, a solid electrolyte molded body, and an interconnector molded body were laminated on the support substrate molded body was produced.
Next, this laminated molded body was degreased and further fired at 1500 ° C. in the air.

Thereafter, a slurry containing La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder and 50% by mass of a solvent composed of IPA was prepared, and this slurry was 30 cm high from the surface of the solid electrolyte. The spray was sprayed with a commercially available spray gun apparatus arranged in (1) to form coarse particles during dropping, and the coarse particles were deposited on the solid electrolyte surface of the sintered body.
After that, it was baked (heat treatment) in the atmosphere at 1150 ° C. for 2 hours to produce a fuel cell.

On the other hand, with respect to 100 parts by mass of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder having an average particle size of 0.5 μm, an amount of metal shown in Table 1 was added, and an acrylic system was added thereto. An organic binder made of resin and toluene are added to prepare a slurry of a surface treatment agent, and a current collecting member in which a ferrite metal plate is formed in a U shape is immersed in this slurry. A surface treatment agent was applied to the surface with a thickness of 50 μm.

  The current collecting member is interposed between the oxygen electrode of one fuel cell and the other interconnector, and is heat-treated at 1050 ° C. for 2 hours in the atmosphere. It joined to the interconnector of this through the surface treating agent.

Thereafter, hydrogen was introduced into the fuel cell and air was introduced into the fuel cell, and a power generation test was performed at 850 ° C. and a current density of 0.6 A / cm ² . The contact resistance between the interconnector and the oxygen electrode present on the opposing surfaces of the adjacent fuel cells to which the current collecting member was joined was measured. The contact resistance was measured by measuring the contact resistance at the initial stage when the power generation amount reached a steady state and after 1000 hours from the steady state. Moreover, the crack of the cross section between the oxygen electrode at that time, an interconnector, and a current collection member was observed with the scanning electron microscope (SEM), and the result was described in Table 2.

From Table 2, it can be seen that as the amount of metal in the surface treatment agent increases, the contact resistance increases, but if it is 10 parts by mass or less, the contact resistance is low.
Therefore, as the amount of added metal is increased, the amount of firing shrinkage is decreased, but the contact resistance tends to be increased. From this point, it can be seen that 0.1 to 10 parts by mass of the added metal is desirable.

  The inventor used a metal felt made of Ni having a wire diameter of 30 μm as a current collecting member. 2 and 3 were impregnated with the surface treatment agent, the power was generated in the same manner as described above, and the contact resistance was measured. 35, 36. As a result, substantially the same effect was obtained even in the case of a current collecting member made of metal felt.

  Furthermore, sample No. 1 in Table 1 was added to the metal felt. No. 17 surface treatment agent was impregnated, and electric power was generated in the same manner as described above, and contact resistance was measured. 37. As a result, the contact resistance at the initial stage and after 1000 hours was large, and cracks were also generated.

1 is a cross-sectional view showing a typical structure of a cell stack of a solid oxide fuel cell according to the present invention.

Explanation of symbols

1: Fuel cell 10: Electrode support substrate 11: Fuel electrode layer 12: Solid electrolyte layer 13: Oxygen electrode layer 14: Interconnector

Claims (2)

  A cell stack electrically connected in series via a current collecting member made of metal or alloy between solid oxide fuel cells, and on the surface of the current collecting member, a perovskite oxide, Fe, An oxide of at least one metal selected from Cr, Co, and Mn, and a content of at least one metal selected from Fe, Cr, Co, and Mn is the perovskite oxide 100. A cell stack characterized by 0.1 to 10 parts by mass per part by mass.   A solid oxide fuel cell comprising: a plurality of cell stacks according to claim 1 housed in a storage container and electrically connected thereto.

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