JP4953692B2 - Cell stack and fuel cell - Google Patents

Description

  The present invention relates to a cell stack and a fuel cell in which a current collecting member is interposed between a plurality of fuel cells, and the plurality of fuel cells are electrically connected.

  In general, a solid oxide fuel cell is configured with a cell stack disposed in a housing case. The cell stack electrically connects fuel cells by arranging a plurality of fuel cells in a row and providing a current collecting member between adjacent fuel cells.

  Although the conventional current collecting member has a relatively rigid structure, the adhesive portion between the current collecting member and the fuel battery cell is easy to peel off because there is no followability to warp deformation due to the thermal stress of the fuel battery cell. A current collecting member having elasticity and a relatively flexible structure has come to be used.

  FIG. 8 is a plan view showing some conventional examples of current collecting members having a relatively flexible structure. FIG. 8 shows a state in which conventional current collecting members 101 to 103 are inserted and installed between two fuel cells 30. The fuel cell 30 schematically shown is a columnar shape having a pair of opposed flat side surfaces, and a plurality of reaction gas passages 31 are formed in the inside of a gas-permeable conductive support 32 along the axial direction. Has been. The reaction gas passage 31 is supplied with the first reaction gas.

  Although not shown, an inner electrode, a solid electrolyte, and an outer electrode are sequentially stacked on one flat side surface of the conductive support 32, and an interconnector (conducting with the inner electrode) made of conductive ceramics is formed on the other flat side surface. ) Are stacked. Accordingly, the current collecting members 101 to 103 are in electrical contact with the outer electrode of one fuel cell 30 and the interconnector of the other fuel cell 30. Usually, the adhesion strength is increased and the electrical resistance is reduced by adhering between the current collecting member and the flat side surface of each fuel cell with a conductive adhesive. Note that the second reaction gas is supplied from the periphery to the outer electrode of the fuel cell 30. Therefore, the current collecting member needs to have a structure that does not hinder the flow of the second reaction gas to the fuel cell.

  FIG. 8A is a diagram showing a current collecting member 101 whose section perpendicular to the axial direction (length direction) of the fuel cell 30 is U-shaped. Since the current collecting member having a U-shaped cross section has elasticity, the followability with respect to the change in the distance between the fuel cells due to thermal deformation or the like is good, and the generation of stress at the bonded portion is thereby reduced. However, since the followability to the expansion and contraction of the fuel cell in the length direction is inferior, the stress reduction effect in the axial direction is not sufficient.

  FIG. 8B shows the current collecting member 102 having a Z-shaped cross section. The current collecting member having a Z-shaped cross section also has elasticity, and has an effect of reducing the stress applied to the current collecting member with respect to both the distance variation between the fuel cells and the expansion and contraction in the length direction. However, since the Z-shape is asymmetric in the width direction of the fuel cells, when the distance between the fuel cells increases, the current collecting member tends to shift so as to rotate around the axis. As a result, the adhesive strength was reduced or peeled off.

  Further, the disadvantage of the U-shaped or Z-shaped structure of the current collecting member is that there is variation in the bending finish, that is, the bending angle, so that the portion should be parallel (the portion that contacts the flat side surface of the fuel cell). Is not parallel. Even when such a current collecting member is inserted between the fuel cells and a fixing pressure is applied to both ends of the fuel cell stack, the current collecting member does not sufficiently elastically deform. As a result, the adhesion between the current collecting member and the fuel battery cell is impaired.

  FIG. 8 (c <b> 1) is a diagram showing still another current collecting member 103. FIG. 8C2 is a partial perspective view thereof. The current collecting member 103 has a cylindrical shape with a flat cross section and has a shape in which both end portions 113a and 113b are joined. On the flat side surface, two strips 111 and 112 protrude alternately, and each of them is a fuel. It contacts the flat side surface of the battery cell 30.

  In the conductive interconnect member disclosed in Patent Document 1, a plurality of plane members with a predetermined interval are arranged between two cells so as to be parallel to the fuel cell surface. Breathability is secured by processing the projecting part and the recessed part.

In the current collecting member disclosed in Patent Document 2, a single strip-like body extending in parallel with the length direction of the fuel battery cell is arranged at the center, and a plurality of current collecting pieces having a substantially U-shaped cross section are formed from the long sides on both sides. It is the form which protruded toward the width direction edge part of a cell.
Japanese translation of PCT publication No. 2004-502281 JP 2003-297396 A

  In the current collecting members 101 and 102 shown in FIGS. 8A and 8B, a part of the current collecting member exists between the cells, obstructing the gas flow between the cells, and the outer electrode of the fuel cell. However, there is a problem that the reaction gas cannot be sufficiently supplied.

  Further, the current collecting member 103 shown in FIGS. 8 (c1) and (c2) has sufficient elasticity at the center and good followability, but both ends are completely joined in the length direction. Further, the stretchability in the axial direction is hindered.

  The interconnect member of Patent Document 1 has a three-dimensional structure in which protrusions and depressions are provided on the surface member, so that it is close to a rigid member, and is considered to be inferior in followability with respect to any variation in distance between cells and expansion and contraction in the length direction. It is done.

  The current collecting member of Patent Document 2 also has a longitudinal stretchability that is hindered by the presence of a band-like body like a spine in the axial direction.

  The present invention provides a cell stack and a fuel cell that have sufficient flexibility to follow fluctuations in the distance between cells and expansion and contraction in the length direction of the cell, and can sufficiently supply a reaction gas to the outer electrode of the cell. The purpose is to do.

  The cell stack of the present invention is a cell stack in which a plurality of columnar solid electrolyte fuel cells each having a pair of opposed flat side surfaces are arranged and the adjacent fuel cells are electrically connected by a current collecting member. A pair of holding members in which the current collecting member extends in parallel with a predetermined interval in the cell width direction of the fuel cell and in the cell length direction of the fuel cell, and the pair of holding members A plurality of connecting bands that are spanned and connected at predetermined intervals in the cell length direction, and a flat side surface of the fuel cell that is provided in the connecting band and extends in the cell length direction. A plurality of joining bands to be joined, and the holding member includes a first inclined portion extending from the flat side surface of one of the fuel cells to the flat side surface of the other fuel cell. And the other said fuel A second inclined portion extending from the flat side surface of the battery cell to the flat side surface of one of the fuel cells, forming a bent portion in the first inclined portion and the second inclined portion, and connecting The bands and the joining bands are alternately joined to the flat side surfaces of the fuel cells facing each other.

  In such a cell stack, since the bent portions are formed in the first inclined portion and the second inclined portion of the holding member, the movement in the cell length direction is not strongly restricted, and the thermal stress of the fuel cell It has very good followability to expansion and contraction in the cell length direction due to the like.

  In addition, the first inclined portion and the second inclined portion ensure electrical connection between the flat side surfaces of the opposed fuel cells, while the first inclined portion and the second inclined portion are formed in the cell length direction. For this reason, the first inclined portion and the second inclined portion can be formed long, thereby ensuring good followability to the variation in distance between the fuel cells.

  Furthermore, a gas passage without any obstruction is formed by the joining band of the current collecting member joined to one fuel battery cell, the joining band of the current collecting member joined to the other fuel battery cell, and the pair of holding members. Thus, the gas permeability of the reaction gas is ensured.

  That is, it is necessary to increase the inter-cell pitch in order not to cause a remarkable gas supply shortage. However, increasing the inter-cell pitch increases the size of the power generation module, which hinders improvement in energy efficiency. On the other hand, in order to reduce the size of the power generation module and improve the energy efficiency, it is desirable to reduce the inter-cell pitch. However, when the inter-cell pitch is reduced, as shown in FIG. For example, a portion that crosses between the cells is formed in the width direction of the fuel cell, so that the gas permeability of the reaction gas is hindered. However, in the present invention, a gas passage that does not cross between the cells is formed between the junction band of the current collecting member and the holding member. Since it can be reliably formed, air permeability is ensured. As a result, the power generation module can be downsized and energy efficiency can be improved.

  In the cell stack of the present invention, the gas downstream side of the joining zone is the outer electrode so that the gas flowing between the fuel cells in the cell length direction flows toward the outer electrode side of the fuel cell. It is bent toward the side. In such a cell stack, the reaction gas passing through the gas passage can be sufficiently supplied toward the outer electrode side, and the power generation performance can be improved.

  The fuel cell of the present invention is characterized in that the cell stack is housed in a housing case. Such a fuel cell can be reduced in size and energy efficiency.

  In the cell stack of the present invention, the movement of the current collecting member in the cell length direction is not strongly restricted, and very good follow-up of the expansion and contraction in the cell length direction due to the thermal stress of the fuel cell. In addition, the current collecting member can ensure good followability with respect to the variation in the distance between the fuel cells, and the current collecting member is joined to one fuel cell and the other fuel cell. A gas passage without any obstruction can be formed by the joining band of the current collecting member and the pair of holding members, and the air permeability of the reaction gas can be ensured.

  FIG. 1 is a partial cross-sectional view showing a part of a cell stack of the present invention, and shows one embodiment of two adjacent fuel cells 30 and a current collecting member 10 provided therebetween. 2 is a plan view seen from the direction along line aa in FIG. 1A, FIG. 3 is a side view of FIG. 1, and FIG. 4 is a perspective view of a current collecting member.

  The fuel cell 30 schematically shown has a hollow flat plate shape, and is a flat columnar shape having a pair of opposed flat side surfaces. The direction perpendicular to the paper surface of FIG. 1 is the axial direction (length direction H) of the fuel cell 30, and the vertical direction of FIG. 1 is the width direction B of the fuel cell 30. A plurality of reaction gas passages 31 are formed in the conductive support 32 having gas permeability along the axial direction. The reaction gas passage 31 is supplied with a first reaction gas (for example, a hydrogen-rich fuel gas).

  Although not shown in FIG. 1, a fuel electrode layer, a solid electrolyte, and an oxygen electrode thin film layer are sequentially laminated on one flat side surface of the conductive support 32, and a conductive ceramic is formed on the other flat side surface. The interconnector (conducting with the fuel electrode layer) and the thin film layer of the oxygen electrode material layer are laminated, and the oxygen electrode layer and the oxygen electrode material layer are the flat side surfaces of the fuel cell. The cell stack is configured by arranging a plurality of fuel cells 30 in a line, and the horizontal direction in FIG. 1 is the cell arrangement direction. Between the two adjacent fuel cells 30, the current collecting member 10 has an oxygen electrode layer that is a flat side surface of one fuel cell and an oxygen electrode material layer (interconnector) that is a flat side surface of the other fuel cell. Are electrically connected to each other.

  Any two adjacent fuel cells 30 in the cell stack are divided into a first fuel cell (or simply “first cell”) and a second fuel cell (or simply “second cell”) for convenience of explanation. It shall be called. In FIG. 1, a current collecting member 10 includes a pair of holding members 10a extending in parallel with a predetermined interval in the cell width direction B of the fuel cell and extending in the cell length direction H of the fuel cell, A plurality of connecting bands 10b spanned and connected to the pair of holding members 10a at predetermined intervals in the cell length direction H, and a plurality of connecting bands 10b provided in the connecting band 10b and extending in the cell length direction. And a joining band 10c.

  That is, the connecting band 10b and the bonding band 10c that are bonded to the flat side surface of the first cell, and the first inclination of the holding member 10a that extends from one flat side surface of the first cell to the other flat side surface of the second cell. Part 10a1, a second inclined part 10a2 extending obliquely from the other flat side surface of the second cell to one flat side surface of the first cell, a connecting band 10b and a bonding band 10c that are bonded to the flat side surface of the second cell It comprises.

  In the holding member 10a, the first inclined portions 10a1 and the second inclined portions 10a2 are alternately formed. Between the first inclined portion 10a1 and the second inclined portion 10a2, a coupling band is provided between the pair of holding members 10a. 10b is stretched, and both ends of the connecting band 10 are connected to the holding member 10a. As shown in FIG. 3, the first inclined portion 10a1 and the second inclined portion 10a2 are each formed with two bent portions 25, whereby the current collecting member 10 in the thickness direction of the fuel cell is formed. Expansion and contraction can be easily performed, and expansion and contraction in the length direction is also facilitated.

  The joining band 10c is extended in the cell length direction, and the shape thereof is rectangular. Moreover, both ends of a pair of holding member 10a which opposes are connected by the length direction end member 10d, respectively, and the rectangular frame is comprised by the holding member 10a and the length direction end member 10d. A joining band 10c is formed on the longitudinal end member 10d toward the connecting band 10b. The current collecting member 10 is formed by pressing a single alloy plate.

  In the present invention, the width and thickness of the holding member 10a of the current collecting member 10 are appropriately set, but by reducing the width or reducing the thickness, flexibility in the thickness direction of the fuel cell, the length direction Increased flexibility. Further, the flexibility in the thickness direction of the fuel cell and the flexibility in the length direction can also be changed by the number of bent portions of the holding member 10a, the angle of the bent portions, and the like.

  In addition, the shape of the bonding band 10c is preferably a band shape as shown in the figure, but the band width and thickness thereof are appropriately determined, and the bonding bands 10c of the connection bands 10b do not necessarily have to be equal. Furthermore, the band width and band length of the joining band 10c may be changed depending on the location in the length direction of the fuel cell.

  In the cell stack of the present invention, the joining band 10c is divided in the fuel cell length direction H and joined to the flat side surface of the fuel battery cell 30 and is not joined over the entire length direction. Since the bent portion 25 is formed in the first inclined portion 10a1 and the second inclined portion 10a2 of the holding member 10a, the movement in the cell length direction H is not restricted, and the cell length due to the thermal stress of the fuel cell etc. It has very good followability with respect to stretching in the vertical direction.

  Further, the first inclined portion 10a1 and the second inclined portion 10a2 ensure electrical connection between the opposed fuel cells 30, while the first inclined portion 10a1 and the second inclined portion 10a2 are formed in the cell length direction. Therefore, unlike the prior art, the first inclined portion 10a1 and the second inclined portion 10a2 can be formed longer without being restricted by the width of the cell, thereby favorably following the distance variation between the fuel cells. (Trackability in the thickness direction of the fuel cell) is ensured.

  Further, as shown in FIG. 1, a joining band 10c joined to one fuel battery cell 30, a joining band 10c of a current collecting member 10 joined to the other fuel battery cell 30, and a pair of holding members 10a, A reaction gas passage A that penetrates between the fuel cells in the cell length direction H and has no obstruction is formed, and the gas permeability of the reaction gas is ensured. Thereby, even if the pitch between cells is narrowed, the gas passage A for the reaction gas can be reliably formed, so that air permeability is ensured. As a result, the power generation module can be downsized and the energy efficiency can be improved.

  1 (b) and 3 (b) show another embodiment of the cell stack of the present invention. As shown in FIGS. 1 (b) and 3 (b), a fuel cell unit is shown. The gas downstream side of the joining zone 10c is bent toward the oxygen electrode layer side so that the oxygen-containing gas flowing in the cell length direction H between 30 flows toward the oxygen electrode layer side of the fuel cell 30 and folded. A curved portion 10c1 is formed. Thereby, the oxygen-containing gas passing through the gas passage A can be sufficiently supplied toward the oxygen electrode layer side, and the power generation performance can be improved.

  5 and 6 show in detail the structure for joining the current collecting member 10 to the fuel battery cell 30. The current collecting member 10 is a heat-resistant alloy made of an alloy containing Cr (hereinafter referred to as a current collecting base material). .) A surface layer 202 made of a material containing Zn is provided on the surface of 201. Here, the surface layer 202 is configured such that the Cr diffusion preventing layer 202a and the covering layer 202b are laminated on the surface of the current collecting base material 201 in this order.

As the current collecting base material 201, an alloy containing 10 to 30% by mass of Cr having high conductivity and heat resistance, for example, Fe—Cr alloy, Ni—Cr alloy, or the like is used. The Cr diffusion preventing layer 202a is a metal oxide having at least one of a spinel structure, a corundum structure, a wurtzite structure, and a rock salt structure, or a structure similar to these. In particular, the Cr diffusion preventing layer 202a is made of Zn—Mn spinel and may contain elements such as Fe and Cr. The Cr diffusion preventing layer 202a is formed from a Zn—Mn spinel, for example, (Zn, Mn) Mn ₂ O ₄ . Since the metal oxide containing Zn and Mn hardly dissolves Cr, it has the effect of suppressing the diffusion of Cr.

A conductive layer containing zinc as an element may be provided at the interface between the Cr diffusion preventing layer 202a and the coating layer 202b. This conductive layer contains ZnO, and pure ZnO is an insulator. However, Zn _{1 + δ} O becomes a cation-rich n-type semiconductor, and by adding a high-valence impurity element, n 1 Type impurity semiconductor. Here, since Zn in ZnO is a +2 valent ion, conductivity is imparted by dissolving a metal element that becomes +3 or higher ion. As the metal element that becomes +3 or more ions, Al and Fe are particularly desirable. The conductive layer made of zinc oxide in which Al and Fe are solid-solved preferably has a conductivity of ¹ S · cm ⁻¹ or more at 550 ° C. to 900 ° C. near the power generation temperature in the atmosphere.

The coating layer 202b contains a composite oxide having a perovskite structure and zinc oxide containing at least a part of the components constituting the oxygen electrode layer of the fuel cell, and specifically includes La and Fe or Mn. It contains perovskite complex oxide and zinc oxide. More specifically, it can be composed of a perovskite complex oxide used for forming an oxygen electrode layer, for example, LaFeO ₃ system, LaMnO ₃ system, and ZnO.

Such a coating layer 202b contains LaFeO ₃ and LaMnO ₃ systems used for the oxygen electrode layer, a Cr diffusion prevention layer 202a, and ZnO used for the conductive layer, so that the coating layer 202b and the current collector are collected. It has an intermediate thermal expansion coefficient between the Cr diffusion prevention layer 202a of the base material and the conductive layer, and can improve the reliability of bonding between the fuel cell 30 and the current collecting member 10 and achieve long-term reliability with little voltage drop. An excellent fuel cell can be obtained.

  Since Cr in the current collecting base material 201 is vaporized and diffused to the outside, the Cr diffusion preventing layer 202a is preferably provided densely so as to cover at least the entire surface of the current collecting base material 201.

  If the Cr diffusion preventing layer 202a is 2 μm or less, particularly 1 μm or less, the conductivity as the current collecting member 10 is not affected even if it is insulating to some extent.

  In the case of dipping, the Cr diffusion preventing layer 202a of the present invention can be formed by immersing the current collecting base material 201 in a paste containing Zn or ZnO, and by heat treatment or heating during power generation.

That is, in the case where the Cr diffusion preventing layer 202a is made of Zn—Mn spinel, for example, a current collecting base material 201 containing Mn is used, for example, Zn or ZnO and Fe ₂ O ₃ or Al _2. By immersing in a paste containing O ₃ and performing heat treatment, a Cr diffusion prevention layer 202a made of Zn—Mn spinel is formed on the surface of the current collecting base material 201, and the surface of the Cr diffusion prevention layer 202a is made of ZnO. A conductive layer containing Fe or Al can be formed.

In the case of using the current collector substrate 201 containing no Mn, it, for example, a Zn or ZnO, and _Fe 2 _{O 3} or _Al 2 _{O 3,} it was immersed in the paste in containing Mn, by heat treatment A Cr diffusion preventing layer 202a made of Zn—Mn spinel is formed, and a conductive layer containing Fe or Al in ZnO can also be formed.

Furthermore, after forming the Cr diffusion prevention layer 202a made of Zn—Mn spinel on the current collection base material 201, the current collection base material 201 on which the Cr diffusion prevention layer 202a is formed is made of, for example, Zn or ZnO and Fe _2. A conductive layer containing Fe or Al in ZnO is formed on the Cr diffusion prevention layer 202a made of Zn-Mn spinel by dipping in a paste containing O ₃ or Al ₂ O ₃ and heat-treating. You can also

When the coating layer 202b is formed on the surface of the conductive layer, it is immersed in a paste containing a perovskite structure, a LaFeO ₃ system, a LaMnO ₃ system, and ZnO used for forming an oxygen electrode layer, etc., and heat-treated. Can be formed.

When forming the coating layer 202b on the surface of the Cr diffusion preventing layer 202a, the current collecting base material 201 is immersed in a paste containing Zn—Mn spinel and heat-treated to form the Cr diffusion preventing layer 202a. Then, it can be formed by dipping in a paste containing a perovskite structure, LaFeO ₃ system, LaMnO ₃ system, and ZnO used for forming an oxygen electrode layer and heat-treating.

  The Cr diffusion prevention layer 202a is formed by using a method such as plating or vapor deposition in addition to dipping (a dip coating method in which the current collecting base material is immersed in a liquid containing zinc for the Cr diffusion prevention layer). Dipping is desirable in terms of cost.

  Although the thickness of a conductive layer is based also on the lifetime of the current collection base material 201, in the case of dipping, 1-100 micrometers is preferable and 5-50 micrometers is more preferable. By setting the thickness to 5 μm or more, generation of voids due to air entrainment or the like can be prevented. Further, by setting the thickness to 50 μm or less, the internal stress due to the difference in thermal expansion from the current collecting base material 201 can be suppressed to the minimum, the decrease in conductivity can be suppressed, and the formation can be facilitated.

  As shown in FIG. 7, the fuel battery cell 30 is a hollow flat plate type, and includes a flat plate support 32, a fuel electrode layer 30 a provided around the flat plate support 32, a solid electrolyte layer 30 b, an oxygen The electrode layer 30c, the interconnector 30d, and the oxygen electrode material layer 30e are provided, and the support 32 further includes a plurality of fuel gases extending in the direction intersecting the stacking direction of the fuel cells 1 (cell length direction). It is configured to have a passage 31. In FIG. 1, the oxygen electrode layer 30c is formed as one flat side surface of the cell, and the oxygen electrode material layer 30e is formed as the other flat side surface.

The support body 32 is made of, for example, a porous and conductive material, and has a flat side surface and arcuate portions at both ends of the flat side surface as shown in FIG. A porous fuel electrode layer 30a is provided so as to cover one of the opposing flat side surfaces and arcuate portions at both ends thereof, and a dense solid electrolyte layer 30b is laminated so as to cover the fuel electrode layer 30a. Further, an oxygen electrode layer 30c made of a porous conductive ceramic is laminated on the solid electrolyte layer 30b so as to face the fuel electrode layer 30a. A dense interconnector 30d is formed on the flat side surface of the support substrate 32 that faces the surface on which the electrode layers 30a and 30c are provided. An oxygen electrode material layer 30e made of an oxygen electrode material is formed on the surface of the interconnector 30d. Here, the oxygen electrode material is made of an oxide such as La (Fe, Mn) O ₃ or (La, Sr) (Co, Fe) O ₃ having a perovskite structure. However, the oxygen electrode material layer 30e is not necessarily formed. As shown in FIG. 7, the fuel electrode layer 30a and the solid electrolyte layer 30b extend to both sides of the interconnector 30d, and are configured so that the surface of the support 32 is not exposed to the outside.

  In the fuel cell 30 having such a structure, the portion of the fuel electrode layer 30a facing the oxygen electrode layer 30c operates as a fuel electrode to generate electric power. That is, an oxygen-containing gas such as air is allowed to flow outside the oxygen electrode layer 30c, and a fuel gas (hydrogen) is allowed to flow through the gas passage 31 in the support 32, and the oxygen electrode layer 30c is heated to a predetermined operating temperature. Then, an electrode reaction of the following formula (1) occurs, and power is generated by, for example, an electrode reaction of the following formula (2) occurring in the portion that becomes the fuel electrode of the fuel electrode layer 30a.

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 electrode reaction is collected through an interconnector 30d attached to the support 32.

  As shown in FIGS. 1 and 3, a current collecting member 10 is interposed and electrically connected between the plurality of fuel cells 30, thereby forming a cell stack. That is, the connecting band 10b and the joining band 10c of the current collecting member 10 are joined to the oxygen electrode layer 30c of one fuel cell 30 and joined to the oxygen electrode material layer 30e of the other adjacent fuel cell 30. Thereby, the plurality of fuel cells 30 are electrically connected in series to form a cell stack.

  The oxygen electrode layer 30c includes a first oxygen electrode layer 30c1 formed on the solid electrolyte layer 30b and a second oxygen electrode layer 30c2 provided on the first oxygen electrode layer 30c1. . The first oxygen electrode layer 30c1 is formed of finer conductive ceramic particles than the second oxygen electrode layer 30c2, and one side main surface of the plate-like current collecting member 10 (the connection band 10b and the bonding band 10c) is the first surface. The first oxygen electrode layer 30c1 is bonded, and the side surfaces of the current collecting member 10 (the coupling band 10b and the bonding band 10c) are bonded to the second oxygen electrode layer 30c2.

  The first oxygen electrode layer 30c1 is composed of conductive ceramic particles having an average particle diameter of 1 μm or less, and has a thickness of 20 μm or less. The density of the first oxygen electrode layer 30c1 is set higher than that of the second oxygen electrode layer 30c2, in other words, the porosity of the first oxygen electrode layer 30c1 is lower than that of the second oxygen electrode layer 30c2. Has been.

  In such a cell stack, the first oxygen electrode layer 30c1 made of fine conductive ceramic particles is firmly bonded on the dense solid electrolyte layer 30b, and the current collector is collected on the first oxygen electrode layer 30c1. Since the main surfaces of the member 10 are bonded, the bonding strength of the current collecting member 10 to the solid electrolyte layer 30b can be improved. When the thickness of the oxygen electrode layer 30c is insufficient, an intermediate layer made of the same material as the second oxygen electrode layer 30c2 is formed between the first oxygen electrode layer 30c1 and the second oxygen electrode layer 30c2. You can also.

  In addition, the side surface of the current collecting member is joined to the second oxygen electrode layer 30c2, thereby further improving the joining strength of the plate-like current collecting member to the solid electrolyte layer. In addition, although the meniscus of the 2nd oxygen electrode layer 30c2 is formed in the side surface of a current collection member, it simplified and described in FIG. This meniscus can also improve the bonding strength of the current collecting member 10 to the oxygen electrode layer 30c. In FIG. 6, the thickness of the current collecting member 10 is exaggerated for easy understanding.

As the first oxygen electrode layer 30c1 and the second oxygen electrode layer 30c2, a perovskite complex oxide containing La and Fe, for example, (La, Sr) (Co, Fe) O ₃ having a perovskite structure can be used. By using this composite oxide, even if the first oxygen electrode layer 30c1 is somewhat dense, it can have a function as an oxygen electrode.

  The current collecting member 10 is joined to the oxygen electrode layer 30c of one fuel battery cell 30, but is also joined to the oxygen electrode material layer 30e of the other fuel battery cell 30 adjacent thereto. The current collecting member 10 is bonded to the oxygen electrode material layer 30e by embedding the current collecting member 10 in the same bonding layer 45 as the second oxygen electrode layer 30c2 formed on the surface of the oxygen electrode material layer 30e. This is performed by bonding to the bonding layer 45.

Here, the thermal expansion coefficient of each member will be described. At 750 ° C., the thermal expansion coefficient of LaFeO ₃ system generally used as the oxygen electrode material of the fuel cell is 15-17 × 10 ⁻⁶ / ° C., and LaMnO ₃ system is 10 to 11 × 10 ⁻⁶ / ° C., LaCrO ₃ system used as an interconnector is about 14 × 10 ⁻⁶ / ° C., and for the current collecting member 10, the current collecting substrate 201 is 11 × 10 ^−6. The Cr diffusion prevention layer 202a made of Zn—Mn spinel and the conductive layer containing Fe or Al in ZnO are 6 to 8 × 10 ⁻⁶ / ° C.

Therefore, when the fuel cell 30 and the current collecting member 10 are joined, a stress based on a difference in thermal expansion occurs at the interface, but the coating layer 202b has a perovskite structure used for forming the oxygen electrode layer 30c, Since it contains LaFeO ₃ , LaMnO ₃ , and ZnO, it can have a desired coefficient of thermal expansion intermediate between the oxygen electrode layer 30c and the current collector 201 by changing the ratio thereof, and the fuel The joining reliability between the battery cell 30 and the current collecting member 10 can be improved.

A method for manufacturing the cell stack will be described. First, a slurry containing an air electrode material such as (La, Sr) (Co, Fe) O ₃ is applied to the surface of the solid electrolyte layer of the fuel cell by screen printing, and baked at a predetermined temperature to form the first oxygen The polar layer 30c1 is formed. Thereafter, a slurry containing an air electrode material such as (La, Sr) (Co, Fe) O ₃ is screen printed on the surface of the first oxygen electrode layer 30c1 and the surface of the oxygen electrode material layer 30e of the interconnector 30d. In this state, the current collecting member 10 is disposed between the plurality of fuel cells and pressed from both sides, so that the current collecting member 10 contacts the first oxygen electrode layer 30c1 and the second oxygen electrode In this state, the second oxygen electrode layer and the bonding layer are baked at a temperature lower than the baking temperature of the first oxygen electrode layer 30c1 to form the cell stack of the present invention. be able to.

  Although not shown, such a cell stack is arranged in a manifold to which fuel gas is supplied, and the fuel gas supplied into the manifold passes through the gas passage 31 of the fuel cell 30.

  In the fuel cell, the cell stack is accommodated in a storage container, and a fuel gas introduction pipe for supplying fuel gas such as city gas and an air introduction pipe for supplying air are disposed in the storage container. Composed.

It is sectional drawing which shows a part of cell stack of this invention, and is sectional drawing which follows the bb line of FIG. It is a top view along the aa line of Fig.1 (a). It is a side view of FIG. It is a perspective view of a current collection member. It is a partial expanded sectional view of a current collection member. It is a longitudinal cross-sectional view of the cell stack which shows the state by which the current collection member is joined to the fuel cell. It is a cross-sectional perspective view of a fuel battery cell. It is explanatory drawing which shows the conventional cell stack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Current collection member 10a Holding member 10b Connection zone 10c Joint zone 30 Fuel cell

Claims (3)

In a cell stack in which a plurality of columnar solid electrolyte fuel cells having a pair of opposed flat side surfaces are arranged and the adjacent fuel cells are electrically connected by a current collecting member, the current collecting member comprises: A pair of holding members extending in parallel with a predetermined interval in the cell width direction of the fuel cell and extending in the cell length direction of the fuel cell, and the cell length direction of the pair of holding members A plurality of connection bands that are spanned and connected to each other at a predetermined interval, and a plurality of connection bands that are provided on the connection bands and that extend in the cell length direction and are joined to the flat side surface of the fuel cell. And the holding member includes a first inclined portion that extends from the flat side surface of one of the fuel cells to the flat side surface of the other fuel cell, and the other fuel. From the flat side of the battery cell A second inclined portion extending on the flat side surface of the fuel cell, and a bent portion is formed in the first inclined portion and the second inclined portion, and the connecting band and the joining band are A cell stack characterized by being alternately joined to flat side surfaces of the opposed fuel cells. The gas downstream side of the joining zone is bent toward the outer electrode side so that the gas flowing between the fuel cells in the cell length direction flows toward the outer electrode side of the fuel cell. The cell stack according to claim 1. A fuel cell comprising the cell stack according to claim 1 or 2 stored in a storage case.

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