JP6836156B2 - Fuel cell - Google Patents

Description

The present invention relates to a fuel cell.

For example, in a solid oxide fuel cell operating at 600 to 800 ° C., a lanthanum cobaltite-based perovskite oxide LaSrCoO ₃ (hereinafter, also referred to as LSC) and LaSrCoFeO ₃ (hereinafter, also referred to as LSCF) are frequently used as current collecting materials. Has been done. Patent Document 1 discloses a fuel cell including a so-called horizontal stripe type fuel cell cell stack. A plurality of fuel cell cells are arranged in a flying island shape on a hollow flat tubular porous support of a fuel cell stack at predetermined intervals along the longitudinal direction. The fuel cell module is assembled by stacking the flat surfaces of a large number of fuel cell stacks so as to face each other. Further, the fuel cell is assembled by housing the fuel cell module in a predetermined housing. Patent Document 2 discloses a fuel cell formed by stacking substantially square plate-shaped battery elements and a flat plate type fuel cell formed by stacking fuel cell cells.

The fuel cell cells adjacent to each other in Patent Document 1 are connected to each other along the longitudinal direction of the porous support via a current collector (interconnector) and a porous current collector layer. Specifically, the anode layer of one fuel cell and the cathode layer of the other fuel cell are electrically connected. Further, the fuel cell stacks adjacent to each other are connected to each other via a stack connecting member arranged on one end side. Specifically, the stack connecting member electrically connects a porous current collecting layer conducting to the cathode layer of one fuel cell stack and a porous current collecting layer conducting to the anode layer of the other fuel cell stack. Connect to. As described above, in the fuel cell, a large number of fuel cell cells (hereinafter, also referred to as a single cell) are electrically connected via a predetermined current collecting member such as an interconnector, a bonding layer, a porous current collecting layer, and a stack connecting member. It is connected so that electricity can be taken out from the outside of the fuel cell device.

In Patent Document 3, a bent-molded sheet metal-shaped metal member for current collection (current collection member 76) is used as an interface between the cathode layer (oxygen electrode 70) of one single cell (fuel cell 62) and the other single cell. A configuration example is disclosed in which a fuel cell stack is formed by connecting a metal member for collecting current and both single cells using a conductive bonding agent of LSCF, which is interposed between the connector (72). See 4th grade).

Japanese Unexamined Patent Publication No. 2010-257744 Japanese Unexamined Patent Publication No. 2013-012473 Japanese Unexamined Patent Publication No. 2005-339904

However, in general, the current collecting member is expected to have a large electric conductivity in order to reduce the current collecting loss (voltage loss) due to its electric resistance. Similarly, the cathode layer is expected to have a large electrical conductivity in order to ensure electron conductivity and enhance electrode reactivity. Further, in a solid oxide fuel cell that operates at a high temperature, the material used for the current collector member and the cathode layer is also required to have heat resistance.

Among the current collector members shown in Patent Documents 1 and 2, a lanthanum chromite-based perovskite-type oxide (LaCrO ₃ ) is mentioned as a main conductive material used for an interconnector. Moreover, as a main conductive material used for a porous current collector layer, a perovskite type oxide (LSC, LSCF, etc.) of a lanthanum cobaltite type (lantern strontium cobaltite type) is mentioned. Further, as the main conductive material used for the bonding layer, silver, silver alloy, LSC, LSCF and the like are mentioned.
Further, as a main cathode material used for the cathode layer, lanthanum manganese night (LaMnO ₃ ) is typically mentioned. Further, a perovskite-type oxide represented by the general formula LnMO ₃ (Ln: La, Sr, Pr or Sm, M: Fe, Co, Mn or Ni) is mentioned. Excluding metal materials, among the above ceramic materials, LSC has a large and excellent electrical conductivity.

Further, the current collector member or the cathode layer is expected to exhibit a coefficient of thermal expansion similar to that of other constituent members of a single cell (hereinafter, may be referred to as other members). This is to prevent problems such as peeling from occurring due to thermal stress generated at the joint with other members to be joined due to the difference in the degree of thermal expansion under high temperature.
As in the example of Patent Document 3, when a current collector member (interconnector 72) made of a ceramic material and a cathode layer are mainly joined to a metal member for current collection in order to connect single cells to each other, the case is used. The coefficient of thermal expansion of each of the current collector member, the cathode layer and the current collector metal member is required to be about the same. Although LSC has a large electrical conductivity and is excellent, the coefficient of thermal expansion is larger than that of general metal materials and ceramic materials. It is expected that a conductive material or a cathode material having a large electric conductivity and a coefficient of thermal expansion similar to that of other members will appear.

The present invention has been made to solve the above-mentioned problems, and in a fuel cell having a current collecting member and a cathode layer, a large amount of electricity is generated under the condition that at least one of the current collecting member or the cathode layer operates at a high temperature. An object of the present invention is to provide a fuel cell having a conductivity and a coefficient of thermal expansion close to the coefficient of thermal expansion of other members.

The fuel cell of the present invention electrically has an electrolyte layer, a cathode layer provided on one side of the electrolyte layer, an anode layer provided on the other side of the electrolyte layer, and at least one of the cathode layer and the anode layer. A current collecting member for connecting to collect electrons or extracting electricity to the outside of the fuel cell is provided, and at least one of the current collecting member or the cathode layer is made of a perovskite type oxide represented by the _{general formula ABO 3.} The perovskite-type oxide contains La and Sr at the A site and Co at the B site, and a part of one La of the La and Sr arranged at the A site is Sm. It is substituted with (LaSmSrCoO ₃ ) and has a perovskite structure in which the molar composition ratio of Sm to the perovskite-type oxide is smaller than the molar composition ratio of La to the perobskite-type oxide before substitution.

According to the fuel cell of the present invention, the perovskite-type oxide (LaSrCoO ₃ ) before substitution is an oxide in which La and Sr are arranged at the A site and Co is arranged at the B site, and has a basic structure _{represented by LaSrCoO 3.} Has. LaSmSrCoO part of La perovskite type oxide (LaSrCoO ₃₎ is substituted with Sm ₃ shows a large electric conductivity than LaSrCoO ₃ before replacement. The thermal expansion coefficient of the LaSmSrCoO ₃ reduces than LaSrCoO _3, closer to the thermal expansion coefficient of the other member that, including metal material or ceramic material.

It is a figure which shows the SOFC cell of this Example. It is a figure for demonstrating the crystal structure of a perovskite type oxide. It is a figure for demonstrating the crystal structure after substituting the A site element of FIG. 2A. It is a graph which shows the relationship between the electric conductivity and the temperature of the oxide which concerns on Example 1. FIG. It is a graph which shows the relationship between the substitution ratio of the substitution element and the electric conductivity which concerns on Example 2. FIG. It is a graph which shows the relationship between the substitution ratio of the substitution element and the coefficient of thermal expansion which concerns on Example 2. FIG. It is a graph which shows the relationship between the substitution ratio of the substitution element and the electric conductivity which concerns on Example 3. FIG. It is a graph which shows the relationship between the substitution ratio of the substitution element and the coefficient of thermal expansion which concerns on Example 3. FIG. It is a graph which shows the relationship between the substitution ratio of the substitution element and the cell voltage which concerns on Example 4. FIG. It is sectional drawing of the coin-type cell C (disk) which concerns on Example 4. FIG. It is sectional drawing of the cylindrical cell C (cyl) which concerns on Example 4. FIG.

Hereinafter, as an example of the fuel cell of the present invention, a solid oxide fuel cell (hereinafter, also simply referred to as “SOFC (Solid Oxide Fuel Cell)”) using an oxygen ion conductive electrolyte layer will be described in detail. The fuel cell of the present invention includes a current collecting member 52 and a cathode layer 2, and the current collecting member 52 corresponds to the conductive material (material contained in the current collecting member 52) of the present embodiment described later. ), Or the cathode layer 2 contains a cathode material (corresponding to the material contained in the cathode layer 2) described later. Therefore, matters other than the conductive material forming the current collecting member 52 and necessary for carrying out the present invention (for example, the configuration and construction method of a single cell) are those skilled in the art based on the prior art in the art. It can be grasped as a design matter.

(SOFC)
The configuration of the SOFC 100 of the present embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the structure of the flat plate type SOFC 100 according to the present embodiment. As shown in the figure, in the flat plate type SOFC 100, a plurality of flat plate-shaped single cells C and a current collector E are alternately laminated along the normal direction with their respective surfaces (for example, upper surface and lower surface) facing each other. It has a multi-layer structure. The single cell C has a flat thin-film electrolyte layer 3, a similarly flat thin-film cathode layer 2 provided on one side (upper side in the drawing) of the electrolyte layer 3, and the other side (upper side in the drawing) of the electrolyte layer 3. It has a multilayer structure including a similarly flat anode layer 1 provided on the lower side in the drawing).

The current collector E is interposed between adjacent single cells C, and each layer is sandwiched between the anode layer 1 of the single cell C laminated on one side and the cathode layer 2 of the single cell C laminated on the other side. It is joined to 1 and 2. Further, the current collector E serves as a separator for separating the oxidizing gas supplied to the cathode layer 2 and the reducing fuel gas supplied to the anode layer 1. A flow path (not shown) through which fuel gas flows is formed between the anode layer 1 and the current collector E, and an oxidizing gas is formed between the cathode layer 2 and the current collector E. A flow path (not shown) is formed.
Further, the current collector E collects electrons generated as a result of the electrode reaction proceeding in the anode layer 1 of the single cell C bonded to one side and supplies them to the cathode layer 2 of the single cell C bonded to the other side. Therefore, it is electrically connected to each single cell C. _{Alternatively, the predetermined current collector E 01} on one end side of the SOFC 100 is electrically connected to the single cell C on the farthest end side of the stack, and electrons supplied via an external circuit are transmitted to the cathode layer 2. Supply. Further, the predetermined current collector E ₀₂ on the other end side is electrically connected to the single cell C on the other end side which is laminated, and supplies the electrons generated in the anode layer 1 to the external circuit.

Here, the current collector E, the cathode layer 2, and other constituent members of the single cell C (hereinafter, may be referred to as other members) and the like are expected to exhibit the same degree of thermal expansion coefficient. This is to prevent problems such as peeling from occurring due to thermal stress generated at the joint with other members to be joined due to the difference in the degree of thermal expansion under high temperature.

(Anode layer)
The anode layer 1 is a fuel electrode in which a fuel gas supplied by a predetermined method and oxygen ions that have moved in the electrolyte layer 3 come into contact with each other, and an electrode reaction in which the fuel gas is oxidized to generate electrons proceeds. Hydrogen can be typically used as the fuel gas, but hydrocarbons such as methane and propane may be used.

The anode layer 1 may have a conventionally known configuration and form, and is not particularly limited. Preferably, as the anode material forming the anode layer 1, the powder of the metal material selected in consideration of catalytic activity, stability in a reducing atmosphere, cost, etc., and the powder of the ceramic material in the appropriate electrolyte layer A known cermet mixed with the above can be used. A typical example is Ni-YSZ cermet, which is a mixture of nickel oxide (NiO) as a metal material and yttria-stabilized zirconia (YSZ) as a ceramic material. As the ceramic material, instead of YSZ, scandia-stabilized zirconia (ScSZ), gadolinium-doped ceria (GDC), samarium-doped ceria (SDC), or the like can also be used. As the metal material, Fe, Co, Ru, Pd, Pt or the like can be used instead of Ni.

The anode layer 1 is preferably composed of a porous body that can efficiently permeate fuel gas. Further, the anode layer 1 may have a function as a support for supporting the thin film-like other layer of the single cell C. The thickness of the anode layer 1 may be, for example, about 10 μm to 300 μm, but when the anode layer 1 is used as a support, the thickness of the anode layer 1 can be made larger than the thickness of the other layers.

(Electrolyte layer)
The electrolyte layer 3 can move oxygen ions generated in the cathode layer 2 to the anode layer 1. The electrolyte layer 3 is made of a material that satisfies the following conditions. The first condition is that it is stable at the operating temperature under both reducing and oxidizing atmospheres, and the second condition is that it has high oxygen ion conductivity and low electron conductivity, and facilitates a dense electrolyte membrane. It is possible to form in.

The electrolyte layer 3 may have a conventionally known structure and form, and is not particularly limited. Preferably, as the material for forming the electrolyte layer 3, zirconia (ZrO ₂ ) stabilized by adding a heteroatomic metal oxide such as Y can be used. Specifically, as the heteroatomic metal oxide, one or more selected from _{Y 2} O ₃ , Yb ₂ O ₃ , Sc ₂ O ₃ , Gd ₂ O ₃ , Sm ₂ O ₃ , CeO _{2, etc. shall be used.} Can be done. Of these, yttria-stabilized zirconia (YSZ) stabilized with _{Y 2} O _{3 can be preferably used.} The thickness of the electrolyte layer 3 may be, for example, about 30 μm.

When a cobaltite-based perovskite oxide, which will be described later, is selected as the cathode material and YSZ is selected as the electrolyte material, there is a risk that a high resistance component will be generated around the interface between the cathode layer 2 and the electrolyte layer 3. There is. In such a case, a reaction suppression layer can be provided on the side of the electrolyte layer 3 on which the cathode layer 2 is arranged. Examples of the material for forming the reaction inhibitory layer include ceria (CeO ₂ ) _{doped with gadolinia (Gd 2} O _3).

(Cathode layer)
The cathode layer 2 is an air electrode that reduces oxygen in the air by electrons conducted in the electrode and sends it as oxygen ions to the electrolyte layer 3. In the cathode layer 2, oxygen in the air receives electrons conducted in the electrode via a current collector E, which will be described later, and an electrode reaction for generating oxygen ions proceeds, causing oxygen ions to reach the electrolyte layer 3. The cathode layer 2 is preferably made of a porous body that is stable in an oxidizing atmosphere and can efficiently permeate gas. As the oxidizing gas, air can be typically used, but other oxidizing gases (for example, oxygen, etc.) may be used.

The cathode layer 2 is not particularly limited in a conventionally known configuration and form, but the cathode material _{preferably contains LSSC (LaSmSrCoO 3} ) according to the present invention. The LSSC is the same material as the material described in detail later as the conductive material for forming the current collector 52. Not only LSSC is necessarily used as the main material, but it may be added to another cathode material forming the cathode layer 2 as a functional material for enhancing electron conductivity.

As other cathode materials, at least one of La, Sr and Sm is contained in the A site, and at least one of Ca, Mn, Co, Fe, Cr and Ni is contained in the B site. Oxides having a perovskite structure can be used. As the A-site element, at least one or more of Ce, Pr, Nd, Eu lanthanoids, Ca, Ba, Ra alkaline earth metals, Na and Cd may be further contained.

By the way, a covaltite-based perovskite-type oxide containing Co as a B-site element (hereinafter, also referred to as "cobaltite-based") can be used as a cathode material that can function as a cathode layer 2 even in SOFC for lowering the temperature. Are known. Specific examples thereof include LSC, LSCF, and samarium strontium cobaltite (SSC). The Cobaltite system is highly evaluated for its electrode reaction characteristics. In particular, in terms of conductivity under SOFC operating temperature conditions, LSC is a material having excellent electrical conductivity among ceramic materials, except for metal materials. However, LSC has a larger coefficient of thermal expansion than general electrolyte materials and metal-based materials, and is under development to ensure the stability of SOFC. From the viewpoint of maintaining stability and reliability for a long period of time, a manganese-nite-based perovskite-type oxide containing Mn has been evaluated to a certain degree as a B-site element. LSCF tends to be selected comprehensively by weighing stability and electrode reactivity.

In the cathode layer 2, oxygen in the gas phase is adsorbed and dissociated on the cathode material and bonded to electrons, and an electrode reaction in which the generated oxygen ions move into the electrolyte layer 3 proceeds. Therefore, from the viewpoint of promoting the electrode reaction, the cathode layer 2 first has a catalytic activity for adsorbing and dissociating oxygen, and secondly has an oxygen ion transport function (ion conductivity). Thirdly, it is formed of a cathode material having electron conductivity and satisfying each condition.
The LSSC has the basic structure of the LSC like the LSCF. Therefore, it can be estimated that the first and second conditions are satisfied, and that the LSC and thus the LSCF exhibit the same oxygen activation catalytic function and oxygen ion conductivity. As will be described later, the LSSC exhibits an even greater electrical conductivity than the LSC, which is more conductive than the LSCF, and is excellent in electronic conductivity performance.

Further, from the viewpoint of maintaining stability and reliability for a long period of time, the cathode layer 2 is firstly thermodynamically stable in an oxidizing atmosphere, and secondly, the bonded electrolyte layer 3 and current collector. It is desired that the body E is formed of a cathode material that is chemically stable under SOFC operating temperature conditions and exhibits a coefficient of thermal expansion close to that of the body E.
It is considered that LSSC satisfies the first condition in the same manner as LSC and has chemical stability in relation to the joining member under the second condition. Further, the LSSC exhibits a coefficient of thermal expansion smaller than that of the LSC, as will be described later in the examples, and can approach the coefficient of thermal expansion of an electrolyte material or a metal-based material. Therefore, it is possible to maintain stability and reliability for a long period of time as compared with using LSC.

Further, LSSC can be preferably selected as the cathode material in the sense that the same material as the member whose main purpose is to collect current to be bonded to the cathode layer 2 is used. For example, the current collector member 52, which will be described later, is a member that covers the surface of the current collector E, is used by joining to the cathode layer 2, and contains LSSC as a conductive material. Further, if the current collector 52 and the cathode layer 2 are made of the same material, the current collector E (current collector 52) and the single cell C (cathode layer) are formed even at a high temperature at which the SOFC operates. 2) A stable state can be maintained without any unexpected chemical interaction (reaction) occurring between them. Furthermore, since the coefficient of thermal expansion of the conductive material and the cathode material are the same, long-term stability and reliability can be maintained.

(Current collector)
The current collector E separates the oxidizing gas supplied to the cathode layer 2 and the reducing fuel gas supplied to the anode layer 1, and collects electrons generated in the adjacent anode layer 1 to collect electrons. Electrons are passed through the electrode reaction field of the adjacent cathode layer 2. The current collector E acts as a so-called interconnector. For example, in the current collector E, a current collector 52 containing the conductive material according to the present invention is laminated on the surface of a dense separator layer 51 made of a metal material for separating an oxidizing gas and a reducing gas. The separator layer 51 can be formed by sandwiching the separator layer 51 from both sides in a sandwich shape. In the current collector E, the surface of one current collector 52 is on the anode layer 1 of the single cell C adjacent to one side, and the surface of the other current collector 52 is on the cathode layer 2 of the single cell C adjacent to the other side. Are joined. The current collector 52 serves as a bonding layer for ensuring the bonding strength between the dense separator layer 51 made of a metal material and the anode layer 1 and the cathode layer 2 which are porous bodies and whose main material is ceramics. Also has. The current collector 52 is formed using the following perovskite-type oxide as a main conductive material.

That is, in the perovskite-type oxide, La and Sr are arranged at the A site, Co is arranged at the B site, and a part of one of La and Sr arranged at the A site is replaced with Sm. It has a perovskite structure in which the molar composition ratio of Sm to the perovskite-type oxide is smaller than the molar composition ratio of La to the perovskite-type oxide before substitution.

Specifically, in the perovskite-type oxide according to the present embodiment, _{a part of La of LSC represented by the composition formula “La z} Sr _1-z CoO ₃ ” was replaced with Sm by “x” in the molar composition ratio. It is an oxide and is represented by the following equation (1), which satisfies the relationship of z−x> 0.
La _z-x Sm _x Sr _1-z CoO ₃ (1)
In the SOFC 100 of the present embodiment, it is preferable that the current collector 52 (or the cathode layer 2) contains the perovskite-type oxide of the above formula (1) as the conductive material (or the cathode material).
As the conductive material, it is preferable that x and z in the formula (1) satisfy the relationship of 0.01 ≦ x / z <0.5 and 0.3 ≦ z ≦ 0.8 as described later. ..
As the cathode material, it is preferable that x and z satisfy the relationship of 0 <x / z <0.72 and z = 0.5 in the formula (1).

The perovskite-type oxide according to the present invention is an oxide derived by a method of so-called Computational Materials Design based on quantum mechanics. Here, the electronic structure of the object can be quantitatively calculated based on the electronic state theory (band theory), and the electron conductivity of the object can be estimated based on the calculated value. Specifically, a simulation is performed using a predetermined quantum calculation software to obtain the size of the band gap of the target perovskite-type oxide. As a result of the analysis, it was confirmed that the perovskite-type oxide having the basic structure of _{"LaSrCoO 3" is a promising material capable of having high electron conductivity.} On the other hand, LaSrCoO ₃ is known to have a large coefficient of thermal expansion as compared with general metals.

Therefore, in order to identify the perovskite oxide expressing better electronic conductivity, it was recalculated by replacing a part of elements arranged in the A site of the LaSrCoO ₃ to another element. Each ionic radius of La and Sr, in consideration of the coordination number to be arranged in the ion valence and A site element R ₁ substituting _La, or were selected candidate element R ₂ substituting Sr. Simulation was performed using the predetermined quantum calculation software, and the size of the band gap was calculated for the perovskite-type oxide LaR ₁ SrCoO ₃ or LaSrR ₂ CoO _{3 after being replaced with the candidate elements R 1} and R _2. From the calculation _result, the electron conductivity of LaSmSrCoO ₃ obtained by substituting La as R 1 = Sm excellent, it is expected which would exhibit large electrical conductivity was obtained. Indeed, perovskite oxide having the composition and replace kept below before replacement La to Sm in molar ratio showed a high electrical conductivity than the LaSrCoO _3.

Further, when the _{thermal expansion coefficient of LaSmSrCoO 3} was actually measured under the assumed temperature of SOFC operation, the thermal conductivity was lower than that of _{LaSrCoO 3.} It was found that the coefficient of thermal expansion approaches that of general metal materials, SOFC electrodes, and ceramic materials used for electrolytes.

The background of selecting the candidate element R ₁ for substituting La or the candidate element R _{2 for substituting Sr is captured.} "LaSrCoO ₃ " is a perovskite-type oxide having a basic structure in which a rare earth metal (ion) and an alkaline earth metal (ion) are arranged at the A site of the general formula ABO _{3 and a transition metal (ion) is arranged at the B site.} Is. The perovskite-type oxide represented by the general formula ABO ₃ is known to have the basic structure described below. Further, it is known that the electronic state changes when the metal ion arranged at the A site is changed as described below.

As shown in FIG. 2A, in the oxide having a perovskite structure, metal ions at the B site are arranged in the body center of the cubic crystal. Oxygen ions are arranged at each face-centered cubic crystal centered on the metal ion at the B site. That is, six oxygen ions regularly surround the metal ions at the B site to form a _{BO 6 octahedron.} This octahedron connects in the vertical, horizontal, and height directions while sharing the oxygen ions at the apex with the adjacent octahedron. Metal ions at the A site are placed at each vertex of the cubic crystal so as to fill the gap around the octahedron.

Therefore, as shown in FIG. 2B, when the radius of the metal ion arranged at the A site becomes smaller (the symbol R is added in FIG. 2B), the ideal cubic lattice is distorted, and the octahedron is distorted. There is a finding that the bond angle BOB between facets is smaller than 180 ° (an example is shown by a very thick straight line in FIG. 2B), and the bandwidth can be controlled. Further, there is a finding that when a part of the metal ion at the A site is replaced with a metal ion R having a different radius, the above strain in the lattice can be locally different and the effect of the local lattice strain can be introduced.

Further, when a part of the metal ion of the A site is replaced with a metal ion having a different valence, specifically, the n-valent metal ion of the A site is replaced with the (n-1) or (n + 1) -valent ion by m. When replaced, it can be understood as being the same as doping electrons or holes by m. In this way, there is a finding that the electronic state of metal ions and the interaction between electrons can be changed to enhance the electron conductivity. In other words, if LaSrCoO ₃ is found to have a certain doping effect, it can be inferred that it is preferable to maintain the current valence balance.

In this way, paying attention to the ionic radius, the ionic valence, and the coordination number, a _{plurality of candidates for the element R 1} that replaces La of _{LaSrCoO 3} or the element R ₂ that replaces Sr are selected, and the quantum calculation software is actually used. A simulation was performed using the wear. Among the plurality of candidate elements, _{LaSmSrCoO 3} (hereinafter, also referred to as “LSSC”) _{when R 1} is Sm will show a large electric conductivity.
As the quantum calculation software, a generalized gradient approximation functional (GGA method), which is a known density functional, was used. Simulation results were also obtained for predetermined candidate elements R ₁ and R ₂ other than Sm (for example, Ce, Pr, Nd as _{R 1 and Ca, Ba, Ra as R 2} ), but the best expected results for Sm. was gotten.

Further, "x" in the above formula (1) is a molar composition ratio of Sm to a perovskite type oxide. “Z” is the molar composition of one of La and Sr arranged at the A site in the perovskite-type oxide LSC before substitution having the basic structure of _{“LaSrCoO 3” with respect to the perovskite-type oxide before substitution.} The ratio. The molar composition ratio of Sr to the perovskite-type oxide before the replacement of the other is represented by "1-z".

Further, it is a parameter indicating the substitution ratio of Sm to La, and the possible range of the ratio “x / z” of the molar composition ratio “x” of Sm after substitution to the molar composition ratio “z” of La before substitution is From the viewpoint of the effect of increasing the electric conductivity and obtaining an appropriate value of the coefficient of thermal expansion, 0.01 ≦ x / z <0.5 is preferable. Furthermore, if x / z is in the range of 0.01 ≦ x / z ≦ 0.25, the electrical conductivity is clearly large and the coefficient of thermal expansion approaches an appropriate value, so from the viewpoint of ensuring the output characteristics of SOFC. Is also preferable. Hereinafter, the above "x / z" is also simply referred to as "Sm substitution ratio".

The amount of replacing La of LSC with Sm may be as small as possible, but if x / z is smaller than 0.01, the effect of increasing the electrical conductivity may not be sufficient. Further, as shown in Examples described later, the relationship between the Sm substitution ratio and the electrical conductivity is an inversely proportional relationship with a gentle downward slope (see FIGS. 4 and 6). Further, as the substitution ratio x / z of Sm increases, the coefficient of thermal expansion tends to increase (see FIGS. 5 and 7). When x / z is larger than 0.5, the remarkable effect of increasing the electric conductivity is diminished, and the possibility that the coefficient of thermal expansion becomes large increases. When x / z is in the range of 0.01 ≦ x / z ≦ 0.25, it is particularly preferable from the viewpoint that the electric conductivity is clearly increased and an appropriate value of the coefficient of thermal expansion can be obtained.
Further, from the viewpoint of obtaining a large electrical conductivity, the molar composition ratio "x" of Sm is preferably smaller than the molar composition ratio "z" of La before substitution (z-x> 0).

When used as a cathode material, the possible range of the Sm substitution ratio "x / z" is preferably 0 <x / z <0.72. Compared with the case of using as the above-mentioned conductive material, the range that "x / z" can take is different in the upper limit value. As shown in Examples described later, when x / z is 0.72 or more, it is recognized that the output characteristic (cell voltage) of SOFC tends to decrease as compared with LSC (see FIG. 8). ). Furthermore, if x / z is in the range of 0.08 ≦ x / z ≦ 0.5, the electrical conductivity is clearly large (see FIG. 6) and the coefficient of thermal expansion approaches an appropriate value (see FIG. 7). , It is also preferable from the viewpoint of ensuring the output characteristics of SOFC.

Further, if the molar composition ratio "z" of La before replacement with respect to the perovskite-type oxide is in the range of 0.3 ≦ z ≦ 0.8, “La _z Sr _1-z CoO ₃ ” before replacement is sufficient. It is preferable because it is known to exhibit a large electrical conductivity. It is particularly preferable that "z" is in the range of 0.4 ≦ z ≦ 0.7 because it is known to exhibit a more preferable electric conductivity. In other words, it is preferable that the molar composition ratio "1-z" of Sr to the perovskite-type oxide is in the range of 0.2 ≦ 1-z ≦ 0.7, and 0.3 ≦ 1-z ≦ 0. It can also be expressed that it is more preferable if it is in the range of 6.6.

As described above, the SOFC of the present invention is characterized by containing LSSC, which is a perovskite-type oxide, as a conductive material in the current collecting member 52 or as a cathode material in the cathode layer 2. To do. The conductive material or cathode material containing LSSC according to the present invention has an effect of increasing the electric conductivity and a reduced coefficient of thermal expansion as compared with the case of using the conventional material LSC, and is a general metal material or ceramics for SOFC. It has the effect of reducing the difference in the coefficient of thermal expansion of the system material. As long as this effect is recognized, the SOFC of the present invention is not limited by other auxiliary materials and elements other than the LSSC forming the current collector 52 or the cathode layer 2.

Further, in the application of using the above-mentioned conductive material which is a perovskite type oxide as the current collector 52, the separator layer 51 of the metal material is coated in order to join the single cells C to each other via the current collector E. It is not limited to the method used. For example, it is used for forming an inter-stack connecting member for connecting cell stacks S in which single cells C are laminated, or for being a component of a conductive bonding agent for adhering an inter-stack connecting member to both cell stacks S. , Can also be used as a conductive material. The inter-stack connection member is, for example, a member that joins the cathode layer of one cell stack S and the current collector of the other cell stack S. To give a specific example, in the horizontal stripe type fuel cell cell stack 1 of Patent Document 1, the cell stack-to-cell stack joining member 19 corresponds. Further, LSSC can be used as a component of the conductive bonding agent used for connecting the cell stack bonding member 19 and the porous current collecting layer 17.

Further, in the present embodiment, the suitability of the coefficient of thermal expansion is considered in consideration of the operation in the so-called medium temperature range (700 to 800 °) and the bonding between the current collector member 52 and the metal material (separator layer 51). However, the use of a conductive material (or cathode material) containing LSSC is not limited to the purpose of joining with a metal material. For example, the purpose may be to join with a lanthanum chromite-based ceramic material generally used as a dense layer for forming an interconnector. To give a specific example, in the example of the flat plate type SOFC of Patent Document 2, LSSC is used as a material for forming the bonding layer 12 (also serving as an air electrode 31) bonded to the lanthanum chromite system interconnector 1 via the protective layer 11. Can be used.

(Manufacturing of SOFC)
Next, a method for manufacturing a fuel cell according to the fuel cell of the present invention will be described. The method for producing the single cell C of the present embodiment is a known production method. For example, the anode layer precursor and the electrolyte layer precursor are laminated to obtain a half-cell laminate composed of the anode layer and the electrolyte layer obtained by co-firing in advance. A single cell C can be produced by a method of laminating a cathode layer precursor on an electrolyte layer of a half-cell laminated body and firing it.

The anode layer precursor can be prepared, for example, as follows. A slurry is prepared by adding a binder, a pore-forming agent, and a solvent to a mixed powder of a ceramic material powder and a metal material powder forming an anode layer and mixing them. Next, a green sheet is prepared from this slurry, cut into a predetermined shape, and then dried. As a result, a green sheet-like anode layer precursor is obtained. Fine particles such as polyvinyl butyral and ethyl cellulose can be preferably used as a binder for adjusting the slurry, fine particles such as polymethyl methacrylate or carbon can be preferably used as a pore-forming agent, and toluene, butanol, ethanol and the like can be preferably used as a solvent, which will be described later. The same applies to the preparation of the slurry of each layer precursor.

A slurry is prepared using the electrolyte layer material powder in the same manner as the anode layer precursor, and this slurry is laminated on the surface of the anode layer precursor by screen printing and dried. Then, the material in which the anode layer precursor and the electrolyte layer precursor are laminated is co-fired over a temperature (for example, 1300 ° C. or higher) and time suitable for sintering, and the anode layer 1 and the electrolyte layer 3 are laminated. Obtain a half-cell laminate.

Next, a cathode layer precursor is formed. Similar to the anode layer precursor, a slurry is prepared using the metal oxide powder for the cathode layer 2. When LSSC is used as the cathode material, the metal oxide powder can be synthesized. The raw material powder of LSSC can be synthesized from a predetermined compound containing each element of La, Sr, Sm, and Co. These predetermined compounds are weighed so as to have a desired molar composition ratio, mixed, and synthesized by, for example, a known solid-phase reaction method to obtain a raw material powder for LSSC. In the solid phase reaction method, oxides, carbonates, nitrates, acetates and the like of the above elements can be used as predetermined compounds. The synthesis method is not limited to the solid phase reaction method, and a known synthesis method via a liquid phase may be used. For example, known methods such as an alkaline precipitation method, a coprecipitation method, a sol-gel method, and a citrate method can be mentioned.
A slurry is prepared by adding a binder, a pore-forming agent, and a solvent to the obtained LSSC raw material powder and mixing them, and screen-printing this slurry on the surface of the half-cell laminate on the electrolyte layer 3 side. To form a cathode layer precursor and dry it.
The precursor of single cell C in which the cathode layer precursor is laminated on the upper surface of the half-cell laminate is baked by holding it at a temperature of preferably 900 ° C. or higher and 1250 ° C. or lower, preferably 1 hour or longer and 12 hours or lower. To tie. As a result, the SOFC single cell C can be manufactured. The method of laminating other precursors on each precursor in order is not particularly limited, and laminating can be performed by using a slurry coating method, a tape casting method, a doctor blade method, or the like in addition to the screen printing method.

Next, a method of manufacturing the current collector E will be described. As the separator layer 51 of the current collector E, for example, a metal plate having a predetermined shape such as Ni, Fe-Cr, or SUS can be used. Further, the raw material powder of LSSC used as the current collector 52 can be synthesized in the same manner as the raw material powder of the cathode material.

A molded body of the current collecting member 52 can be obtained by molding the raw material powder of LSSC by a known method such as uniaxial compression molding, hydrostatic pressing, or extrusion molding. Alternatively, a predetermined binder and a solvent are added to the raw material powder of LSSC and mixed to prepare a slurry. Similar to the method for producing the battery element of the single cell C described above, a precursor having a desired shape can be molded from the slurry and fired to obtain a molded body of the current collector member 52. A SOFC stack in which the current collecting member 52 is interposed between the separator layer 51 and the single cell C and stacked in order to connect the single cells C to each other can be integrally manufactured. Alternatively, the LSSC slurry is prepared in the form of a paste, and this paste is applied to predetermined positions on both surfaces of the separator layer 51 and the surface of the single cell C to connect (connect) the cells, and then dried and fired. SOFC stacks in which single cells C are connected to each other can be integrally manufactured.

The current collector or cathode layer according to the present invention can be used for SOFCs having various structures, and is not limited to a structure in which flat plate-type single cells are laminated. Even a SOFC having a cylindrical type or a hollow flat tubular single cell in which the peripheral surface of the cylinder is crushed can be preferably applied. For example, in the case of a known hollow flat type single cell described in Patent Document 3 at the beginning, an interconnector 72 joined to one fuel cell 62, an oxygen electrode 70 of the other fuel cell 62, and between both cells. The LSSC is used as a conductive material or a cathode material for forming the current collecting member 76 interposed therein, the conductive bonding agent 120 for joining these, the end side current collecting member 109 arranged at the end of the power generation unit, and the like. Can be used. In the example disclosed in JP-A-2008-71712, the outer electrode (cathode) layer 20, the outer electrode terminal 22, the conductive sealing material 32, 102, 120, the connecting member 55, the outer terminal 56, the connecting member 72, LSSC can be used as the conductive material or the cathode material for forming the connection electrode terminals 96, 116 and the like. Further, the fuel cell may be an SOFC using ^{an H + conductive electrolyte layer.} The type of fuel cell is not limited to the solid oxide fuel cell, and can be used for various fuel cells such as so-called phosphoric acid type and solid polymer type.

Hereinafter, examples of the present invention will be described. The first example shows the result of mainly evaluating LSSC as the conductive material of the SOFC cell, and the second example shows the result of mainly evaluating LSSC as the cathode material. The following examples show examples of concrete implementation of the present invention, and the present invention is not limited to the following examples.

<< First Example: Conductive Material >>
As a first example, an evaluation using LSSC as a conductive material of SOFC was performed. The LSSC compacts of Examples 1 and 2 were prepared, and 1) electrical conductivity and 2) coefficient of thermal expansion were evaluated.
[Preparation of perovskite type oxide molded product]
<Example 1>
As Example 1, a molded product of LSSC was obtained by the following procedure.
(LSSC molded product)
The LSSC raw material powder was prepared by the solid phase reaction method. Powders of various metal oxides or salts used as raw materials were weighed so as to obtain LSSC having a desired molar composition ratio. Specifically, La ₂ O ₃ powder, SrCO ₃ powder, Sm ₂ O ₃ powder and Co ₃ O ₄ powder were used. The powder obtained by wet-mixing these in a solution and then removing the solvent was calcined and pulverized at 800 ° C. to obtain an LSSC raw material powder having an average particle size of 0.5 μm (D50).

The obtained raw material powder is uniaxially compression-molded, further compacted using the CIP method (cold hydrostatic press) under the condition of a pressure of 245 MPa, and further sintered at 1000 ° C. to form pellets. To obtain an LSSC molded product. In the formula (1) [La _z-x Sm _x Sr _1-z CoO ₃ ], a plurality of LSSC molded body samples in which the molar composition ratio "x" of Sm when z = 0.5 is within a predetermined range are used. It was prepared (see Nos. 1-1 and 1-2 of Example 1 in Table 1).

<Example 2>
As Example 2, a molded product of LSSC was obtained by the following procedure.
(LSSC molded product)
An LSSC molded product molded into pellets by the same manufacturing method as in Example 1 was obtained. In the formula (1) [La _z-x Sm _x Sr _1-z CoO ₃ ], when the molar composition ratio "1-z" of Sr is a predetermined value, the substitution ratio "x / z" of Sm is in a predetermined range. A plurality of LSSC molded body samples were prepared (see Nos. 1 to 3 of Example 2 in Table 1).

<Comparative example 1>
(LSC molded product)
An LSC molded product molded into pellets by the same manufacturing method as in Example 1 was obtained. In [La _z Sr _1-z CoO ₃ ], an LSC molded product sample having a molar composition ratio of La “z” of z = 0.5 was prepared (see No. 1 of Comparative Example 1 in Table 1).

<Comparative example 2>
(LSC molded product)
An LSC molded product molded into pellets by the same manufacturing method as in Example 1 was obtained. In [La _z Sr _1-z CoO ₃ ], an LSC molded product sample was prepared when the molar composition ratio of Sr “1-z” was a predetermined value (see Nos. 1 to 3 of Comparative Example 2 in Table 1). ..

[Evaluation of perovskite type oxide molded product]
(Identification of perovskite type oxide molded product)
X-ray diffraction spectrum data and ICP emission spectroscopic analysis data were acquired for each LSSC molded body sample of Example 1 and each LSSC molded body sample of Example 2 to confirm the crystal phase and composition of each molded body sample. Was identified.
It was found that each of the molded product samples obtained in Examples 1 and 2 was a molded product containing a perovskite-type oxide according to the present invention.

1) Evaluation of electrical conductivity The electrical conductivity of each of the obtained LSSC molded product samples of Examples 1 and 2 was measured under a predetermined environmental temperature. FIG. 3 shows the change in the electrical conductivity of the LSSC molded product of Example 1 (No. 1-1, 1-2 in Table 1) with respect to the environmental temperature (600 to 800 ° C.). FIG. 4 shows the change in electrical conductivity with respect to the Sm substitution ratio “x / z” at 650 ° C. for each LSSC molded product of Example 2 (Nos. 1 to 3 in Table 1). The results of comparison with the LSC compacts of Comparative Examples 1 and 2 are shown for each of FIGS. 3 and 4.
In addition, the evaluation results of the electrical conductivity of Examples 1 and 2 are shown in Table 1 in a format for relative evaluation with Comparative Examples 1 and 2. In Table 1, the symbols ◎, ○, and △ indicate the evaluation as a conductive material, ◎ is much better than the comparative example, ○ is better than the comparative example, and △ is comparable to the comparative example. Slightly inferior, meaning evaluation. The evaluation of the test results of the comparative example itself, which is the comparison standard, was omitted.

From FIG. 3, it was confirmed that the LSSC molded product had a higher electrical conductivity than the LSC even when the temperature environment changed in the range of 600 to 800 ° C. It can be inferred that the electrical conductivity is higher than that of LSC even in a wider temperature range of 600 ° C. or lower and 800 ° C. or higher. The present inventors have paid attention to the fact that the electrical conductivity tends to decrease as the environmental temperature rises. That is, the temperature dependence of the electrical conductivity shows metallic behavior. Therefore, it is understood that the material has conductive properties suitable as a metal substitute material from the viewpoint of electrical properties.

Further, as shown in FIG. 4, in the molar composition ratio (1-z) of Sr to the perovskite-type oxide in a wide range, the electric conductivity of the LSSC molded product is generally larger than that of the LSC within the range of the appropriate Sm substitution ratio. It was possible to confirm the effect of replacing a part of La of LSC with Sm. From FIG. 4, when the substitution ratio x / z of Sm is in the range of 0.01 ≦ x / z ≦ 0.25, the electric conductivity of LSSC is up to about 20% larger than that of LSC. A remarkable effect was observed by substituting a part of La with Sm. It was found that when the molar composition ratio (1-z) of Sr was 0.2 ≦ 1-z ≦ 0.7, the electric conductivity of the LSSC molded product would be higher than that of the LSC.
When z = 0.3, the substitution ratio x / z of Sm is in the range of 0.01 ≦ x / z ≦ 0.5, and the electric conductivity of LSSC is larger than that of LSC. Further, when z = 0.5, the substitution ratio x / z of Sm is in the range of 0.01 ≦ x / z ≦ 0.72, and the electric conductivity of LSSC is larger than that of LSC. Further, when z = 0.8, the substitution ratio x / z of Sm is in the range of 0.01 ≦ x / z <0.5, and the electric conductivity of LSSC is larger than that of LSC.

As described above, the SOFC100 (fuel cell) of the present invention uses the perovskite-type oxide described in the present embodiment or this embodiment, and is provided on one side of the electrolyte layer 3 and the electrolyte layer 3. Electron is electrically connected to at least one of the cathode layer 2, the anode layer 1 provided on the other side of the electrolyte layer 3, and the cathode layer 2 or the anode layer 1 to collect electrons that react with the electrodes, or a single cell C. Alternatively, a current collector E for extracting electricity to the outside of the SOFC 100 is provided, and the current collector member 52 constituting the current collector E contains a perovskite-type oxide represented by _{the general formula ABO 3 as a conductive material, and the perovskite} In the type oxide, La and Sr are arranged at the A site and Co is arranged at the B site, and of the La and Sr arranged at the A site, a part of one La is replaced with Sm, and Sm. Has a perovskite structure that is smaller than the molar composition ratio of La to the perovskite-type oxide before substitution.

Therefore, since the electric conductivity of the conductive material _{is larger than that of the conventional material LaSrCoO 3} , the voltage loss due to the electric resistance of the current collecting member 52 can be reduced, and the output characteristics of the SOFC 100 can be improved. it can. Since the SOFC 100 generally has a large number of single cells C stacked and generates electricity in a state where each single cell C is electrically connected via a current collector E, the effect of reducing the electric resistance is great. Therefore, the output characteristics of the fuel cell can be improved.

From the results of Example 2 above, when the range of the molar composition ratio (1-z) of Sr of LSSC is 0.2 ≦ 1-z ≦ 0.7, the range of possible substitution ratio x / z of Sm is It can be seen that when 0.01 ≦ x / z <0.5, the electrical conductivity is larger than that of the LSC before replacement with Sm, which is preferable. Further, when the substitution ratio x / z of Sm is 0.01 ≦ x / z ≦ 0.25, it is particularly preferable in that it is clear that the above effect can be obtained.

The range 0.2 ≦ 1-z ≦ 0.7 of the molar composition ratio (1-z) of Sr is 0.3 ≦ z ≦ 0.7 when the molar composition ratio “z” of La before substitution is used. Corresponds to the range of 0.8.

2) Evaluation of the coefficient of thermal expansion The coefficient of thermal expansion of each of the obtained LSSC molded body samples of Example 2 was measured under a predetermined environmental temperature. FIG. 5 shows the change in the coefficient of thermal expansion with respect to the Sm substitution ratio x / z of Example 2 (No. 2 in Table 1) at 650 ° C.
Further, in the same manner as the evaluation of the electric conductivity described above, the evaluation result of the coefficient of thermal expansion of Example 2 is shown in Table 1 in a format of relative evaluation with Comparative Example 2.

When the conductive material according to the present invention is treated as a current collecting member used by joining to a predetermined other member, it is preferably close to the coefficient of thermal expansion of the mating member to be joined. The current collector member is originally required to have a high electrical conductivity as a characteristic, and a metal material is often selected as the mating member. The coefficient of thermal expansion of the other party's metal material is ^{assumed to be about 11 to 12 × 10-6} (K ^-1 ) as a guideline (estimated coefficient of thermal expansion). From FIG. 5, it was clarified that the LSSC molded product was closer to the assumed coefficient of thermal expansion of the metal material than the LSC at 650 ° C., and favorable evaluation results were obtained.

By the way, although LSC has a large electrical conductivity and is excellent, the coefficient of thermal expansion is larger than that of general metal materials and ceramic materials. It is expected that a conductive material or a cathode material having a large electric conductivity and a coefficient of thermal expansion similar to that of other members will appear.
This embodiment was made to solve such a problem, and collect electricity having a large electric conductivity under the condition of operating at a high temperature and having a coefficient of thermal expansion close to the coefficient of thermal expansion of other members. It can be an object to provide a fuel cell with components.

As described above, in the SOFC 100 (fuel cell) of the present invention, the current collecting member 52 according to the present embodiment contains the perovskite type oxide LSSC according to the present embodiment as a conductive material. Therefore, in addition to electrical conductivity of the conductive material increases, the thermal expansion coefficient of the LaSmSrCoO ₃ is smaller than the LaSrCoO _3, the thermal expansion coefficient between the ceramic material and the metallic material at a high temperature (under operating temperature) It is possible to prevent the current collecting member 52 and the separator layer 51 containing a metal material as a main component from peeling off due to the disagreement between the two. Therefore, since the contact resistance can be reduced, the output characteristics of the fuel cell can be further improved.

Further, since the thermal expansion coefficient of the LaSmSrCoO ₃ is smaller than the LaSrCoO _3, the separator layer 51, the cathode layer 2, due to the mismatch in thermal expansion coefficient between the battery member such as the anode layer 1, the less likely the crack chipping Increased reliability.

From the results of Example 2 above, when the range of the molar composition ratio (1-z) of Sr of LSSC is 0.2 ≦ 1-z ≦ 0.7, the range in which the substitution ratio x / z of Sm can be taken is When 0.01 ≦ x / z <0.5, the electric conductivity is larger than that of the LSC before replacement with Sm, and the coefficient of thermal expansion approaches an appropriate value, which is preferable. Further, when the substitution ratio x / z of Sm is 0.01 ≦ x / z ≦ 0.25, it is particularly preferable in that it is clear that the above effect can be obtained.

<< Second Example: Cathode Material >>
As a second example, an evaluation using LSSC as a cathode material for SOFC was performed. The LSSC molded product of Example 3 is produced and the LSSC molded product is evaluated in the same manner as in the first embodiment, and the coin-shaped cell C (disk) according to Example 4 (corresponding to a single cell of SOFC) is produced. Then, the output voltage when LSSC was used as the cathode material was measured. Based on this output voltage measurement value, the output voltage of the cylindrical cell C (cyl) corresponding to the coin cell C (disk) was obtained by simulation, and the power generation performance was evaluated as the SOFC cell of Example 4.

[Preparation of perovskite type oxide molded product]
<Example 3>
As Example 3, a molded product of LSSC was obtained by the following procedure.
(LSSC molded product)
An LSSC molded product molded into pellets was obtained by the same manufacturing method as in Example 1. In the formula (1) [La _z-x Sm _x Sr _1-z CoO ₃ ], a plurality of types of LSSC raw material powders in which the molar composition ratio "x" of Sm when z = 0.5 is within a predetermined range are used. By synthesizing, a plurality of LSSC molded body samples were prepared (see Nos. 1 to 4 in Table 1).

<Comparative example 3>
(LSC molded product)
A molded product sample _{of LSC [La 0.5} Sr _0.5 CoO ₃ ] in the case of z = 0.5 molded into pellets by the same manufacturing method as in Comparative Example 1 was obtained.

[Evaluation of perovskite type oxide molded product]
1) Evaluation of electrical conductivity In the same manner as in Examples 1 and 2, each LSSC molded product sample of Example 3 obtained was identified, and each molded product sample of Example 3 was perovskite-type oxidized according to the present invention. It was confirmed that it was a molded product containing an object. Then, the electrical conductivity of each of the obtained molded article samples of LSSC of Example 3 was measured under a predetermined environmental temperature. FIG. 6 shows the change in electrical conductivity with respect to the Sm substitution ratio x / z of each LSSC of Example 3 at 700 ° C.

From FIG. 6, it was confirmed by experiments that each LSSC molded product of Example 3 had a higher electrical conductivity than the LSSC molded product of Comparative Example 3 at 700 ° C. as in Example 1. In the range where the substitution ratio x / z of Sm was 0 <x / z ≦ 0.72, the effect that the electric conductivity of each LSSC molded product was larger than that of the LSSC molded product of Comparative Example 3 was observed.

2) Evaluation of coefficient of thermal expansion The coefficient of thermal expansion at 700 ° C. was measured for each LSSC molded product sample of Example 3 obtained. FIG. 7 shows the change in the coefficient of thermal expansion with respect to the replacement ratio x / z of Sm of each LSSC molded product of Example 3.

In SOFC, it is preferable that the coefficient of thermal expansion of the cathode layer and the mating member bonded to the cathode layer are close to each other. It is assumed that the cathode layer is joined to an electrolyte layer, a reaction suppression layer or a current collector member made of a ceramic material, or a mating member such as a current collector member made of a metal material. As the coefficient of thermal expansion that can be consistent with these mating members, ^{about 11 to 12 × 10-6} (K ^-1 ) is assumed as a guideline value (assumed thermal expansion) as in Examples 1 and 2. coefficient). From the graph of FIG. 7, at 700 ° C., each LSSC compact of Example 3 had a Sm substitution ratio x / z in the range of 0 <x / z ≦ 0.5, and the LSSC compact of Comparative Example 3 was used. The effect of becoming smaller than the coefficient of thermal expansion and approaching the assumed coefficient of thermal expansion was observed.

[Creation of coin-shaped cell]
<Example 4>
In order to evaluate the output characteristics of the SOFC of Example 4, a coin-shaped cell C (disk) using LSSC as a cathode material was produced by the following procedure. That is, using a plurality of types of cathode layer pastes (cathode materials) containing LSSC powders having different molar composition ratios x in the formula (1) [La _z-x Sm _x Sr _1-z CoO _{3], FIG.} A plurality of each coin-shaped cell C (disk) shown was produced.
(Preparation of anode layer support precursor)
And commercially available nickel oxide (NiO) powder having a particle size of about 0.5 [mu] m, 8YSZ particle size of about 0.5μm _{(Y 2 O} 3: 8 [mol]%) and powder, in a weight ratio of 6: mixed with 4 To obtain a mixed powder. The mixed powder of the anode electrode support material, xylene as a solvent, polyvinyl butyral as an organic binder, acrylic resin as a pore-forming material, and phthalate ester as a plasticizer are used in a weight ratio of 48 to 58: The mixture was added at a ratio of 24: 8.5: 5 to 15: 4.5, dispersed in xylene, and kneaded with a ball mill to prepare a slurry. A sheet was formed from this slurry on a PET base sheet by the doctor blade method, and the sheet was dried to prepare an anode layer support precursor having a thickness of 0.5 to 1.0 mm.

(Preparation of paste for anode layer)
The same nickel oxide (NiO) powder from which the anode layer support precursor was prepared, the same 8YSZ powder, α-terpineol as a solvent, and ethyl cellulose as a binder were used in a weight ratio of 48:32:18: 2. The mixture was added in proportion and mixed, and kneaded well to prepare a paste for the anode layer.

(Preparation of paste for electrolyte layer)
_{Commercially available YSZ (Y 2} O ₃ : 8 [mol]%-ZrO ₂ : 92 [mol]%) powder having a particle size of about 0.5 μm, a terpineol solvent as a solvent, and ethyl cellulose as a binder in a weight ratio. , 65: 31: 4, and mixed, and sufficiently kneaded to prepare a paste for an electrolyte layer.

(Preparation of paste for reaction suppression layer)
_{A commercially available 10 GDC (Gd 2} O ₃ : 10 [mol]%-CeO ₂ : 90 [mol]%) powder having a particle size of about 0.5 μm, α-terpineol as a solvent, and ethyl cellulose as a binder in a weight ratio. , 65: 31: 4, and mixed, and sufficiently kneaded to prepare a reaction inhibitory layer paste.

(Preparation of paste for cathode layer)
A plurality of types of cathode layer pastes containing LSSC raw material powders having different compositions as cathode materials were prepared by the following methods. In the formula (1) [La _z-x Sm _x Sr _1-z CoO ₃ ], the molar composition ratio "x" of Sm when z = 0.5 is within a predetermined range (0 <x ≦ 0.36). The LSSC raw material powder in the above was used. Specifically, LSSC powder having the same composition as the LSSC raw material powder having the respective composition for producing each LSSC molded product of Example 3 was used (see Table 1). To each LSSC powder having a predetermined molar composition ratio x, α-terpineol as a solvent and ethyl cellulose as a binder are added and mixed at a weight ratio of 80:17: 3, and are sufficiently kneaded to form a plurality of types. A paste for the cathode layer was obtained.

(Creation of coin-shaped cell C (disk))
FIG. 9 shows that each cathode layer paste containing the above-mentioned LSSC powder having a different molar composition ratio and the above-mentioned paste for other members are used, and only the cathode material for forming the cathode layer is different by the following method. A plurality of coin-shaped cells C (disk) shown in the above were produced.
Using the above-mentioned anode layer support precursor, the above-mentioned anode layer paste is screen-printed concentrically on one side of the surface and dried, and a circular thin film-like anode layer precursor having a diameter of about 30 mm and a thickness of about 10 μm is dried. The body was laminated. Further, the above-mentioned electrolyte layer paste was screen-printed concentrically on the surface of the anode layer precursor and dried, and a circular thin film-shaped electrolyte layer precursor having a diameter of about 30 mm and a thickness of about 10 μm was laminated. Further, similarly, the above-mentioned reaction suppressing layer paste is screen-printed concentrically on the surface of the electrolyte layer precursor and dried, and a circular thin film-shaped reaction suppressing layer precursor having a diameter of about 15 mm and a thickness of about 5 μm is laminated. After that, it was cut out into a disk shape having a diameter of about 25 mm. A laminate precursor was obtained in which the anode layer support / anode layer / electrolyte layer had substantially the same diameter, and only the reaction suppression layer had a small diameter and were laminated concentrically.

Next, the laminate precursor of the anode layer support / anode layer / electrolyte layer / reaction suppression layer was calcined at 1350 ° C. for 3 hours. A disc-shaped half-cell laminate in which the anode layer support 12, the anode layer 11, the electrolyte layer 31, and the reaction suppression layer 32 were laminated in this order was produced.

Next, the cathode layer paste was screen-printed concentrically on the surface of the reaction suppression layer 32 of the half-cell laminate, dried, and the cathode layer precursor having a diameter of about 10 mm was laminated. A laminate precursor having a small diameter and being laminated concentrically in the order of half-cell laminate / cathode layer was obtained.

Next, the above-mentioned half-cell laminate / cathode layer laminate precursor was calcined at 1000 ° C. for 2 hours. As shown in FIG. 9, a coin-shaped cell C (disk) in which the anode layer support 12, the anode layer 11, the electrolyte layer 31, the reaction suppression layer 32, and the cathode layer 21 are laminated in this order was produced. In the coin-type cell C (disk), the anode layer support 12, the anode layer 11, and the electrolyte layer 31 have substantially the same diameter, and the reaction suppression layer 32 and the cathode layer 21 have smaller diameters in this order, and these layers are laminated concentrically. The anode layer 11, the electrolyte layer 31, the reaction suppression layer 32, and the cathode layer 21 as a whole have a circular flat plate type structure having a thickness of about 50 μm.

(Comparative Example 4)
(Creation of coin-shaped cell C (disk))
_{Using the LSC [La 0.5} Sr _0.5 CoO ₃ ] powder in the case of z = 0.5 in Comparative Example 3, a coin-shaped cell C (disk) having the same shape was produced by the same manufacturing method as in Example 4. Made.

[Cell voltage evaluation]
(Power generation test)
Using the coin-type cell C (disk) according to Example 4 and Comparative Example 4, a power generation test was performed under the following conditions, and the cell voltage of each coin-type cell C (disk) was actually measured.
The coin-shaped cell C (disk) of the fourth embodiment has an overall shape of a substantially circular flat plate type. In the coin-shaped cell C (disk), as shown in FIG. 9, the anode layer support 12, the anode layer 11, and the electrolyte layer 31 have substantially the same diameter, and the reaction suppression layer 32 and the cathode layer 21 have smaller diameters in this order. Each layer has a structure in which the layers are laminated concentrically upward in order in the drawing.
Using a known power generation test device, an electrode body made of a platinum mesh member is brought into contact with the exposed portion of the anode layer support 12 at an environmental temperature of 700 ° C. to collect electricity on the anode electrode side. The electrode body was brought into contact with the surface of the cathode layer 21 to collect electricity on the cathode electrode side. And _{H 2} is used as a fuel gas, using air as the oxidizing gas was flowed at flow rates of 200 (ml / min). The voltage between the electrode bodies at a predetermined current density of 0.2 (A / cm ^{2) was measured.}

(Cell voltage: Cylindrical cell)
The voltage of the cylindrical cell C (cyl) was estimated from the voltage of the coin-shaped cell C (disk) measured in this way. Specifically, using the transmission line model (equivalent circuit) of the cylindrical cell C (cyl), the cylindrical cell C (equivalent circuit) is based on the measured cell voltage of the coin cell C (disk) obtained in the power generation test. A simulation was performed to obtain the output voltage of cyl). Assuming that a predetermined virtual current collecting member (not shown) is attached to the cylindrical cell C (cyl), the voltage drop for the current collecting loss of the virtual current collecting member is calculated from the above simulation value. The voltage of the cylindrical cell C (cyl) was estimated by performing correction by subtracting the value.
As shown in FIG. 10, the cylindrical cell C (cyl) has the anode layer support 12, the anode layer 11, and the electrolyte layer 31 of the coin-shaped cell C (disk) in this order from the inside to the outside along the radial direction. The anode layer support 120, the anode layer 110, the electrolyte layer 310, the reaction suppression layer 320, and the cathode layer 210 correspond to each of the five layers of the reaction suppression layer 32 and the cathode layer 21.

The cylindrical cell C (cyl) has an electrode length of a predetermined length (for example, L = 50 mm) along the axial direction. The current collecting portions of the cylindrical cell C (cyl) connected to the external circuit are at one end and the other end along the axial direction in the anode layer 110 and the cathode layer 210. In addition, in order to perform simulation in this transmission line model, known numerical values were given as physical property values of the materials forming each layer. Among them, as the electrical conductivity of the cathode layer 210, the values actually measured in each LSSC molded product according to Example 3 were given. The electrical conductivity of the virtual cathode current collector member connected to the cathode layer 210 is a numerical value calculated as having a porosity of 30% based on the numerical values actually measured in each LSSC molded product according to the corresponding Example 3. Was given.

FIG. 8 shows the cell voltage of the cylindrical cell C (cyl). The output voltage of each cylindrical cell C (cyl) calculated based on the measured voltage value of each coin cell C (disk) according to Example 4 and Comparative Example 4 and the replacement ratio x / z of Sm of LSSC. A graph showing the relationship is shown.
From FIG. 8, each cylindrical cell C (cyl) of Example 4, which contains LSSC as the cathode material of the cathode layer 21 and assumes that LSSC is used as the conductive material of the virtual cathode current collector, has a temperature of 700 ° C. Below, it was confirmed that the cell voltage was comparable to that of the cylindrical cell C (cyl) of Comparative Example 4. In the cylindrical cell C (cyl) in which the substitution ratio x / z of Sm is in the range of 0 <x / z <0.72, a cell voltage similar to that of the cell of Comparative Example 4 is obtained and can be evaluated. did it. In particular, in the cylindrical cell C (cyl) using the LSSC in the vicinity of the Sm substitution ratio x / z of 0.08, a cell voltage larger than that of the cylindrical cell C (cyl) of Comparative Example 4 is obtained. , I was able to appreciate it.

[Comprehensive evaluation of cathode materials]
Table 1 shows the evaluation results of Examples 3 and 4 in which LSSC was used as the cathode material of the SOFC cell in the second example in a format for relative evaluation with the comparative example.

From Table 1 and FIGS. 6 to 8, it can be judged comprehensively as follows. That is, if the possible range of the substitution ratio x / z of Sm with respect to the perovskite-type oxide is 0 <x / z <0.72, the electrical conductivity is large and the coefficient of thermal expansion approaches an appropriate value, and the comparative example It is preferable because a cell voltage comparable to that in the case of using LSC can be obtained. Further, when the possible range of the substitution ratio x / z is 0.08 ≦ x / z ≦ 0.5, it is particularly preferable in that it is clear that the above effect can be obtained.

Further, in order to evaluate the output characteristics of the SOFC cell, a cylindrical cell C (cyl) having a structure in which a virtual cathode current collector member is laminated on the cathode layer 21 and both the cathode material and the conductive material contain LSSC is provided. Although the study was carried out on the assumption, this embodiment is not limited to the configuration. Even if the SOFC cell has a structure in which at least the cathode material contains LSSC, the effect of improving the electrical conductivity can be obtained. However, since the SOFC cell is composed of different ceramics or a junction of different materials such as metal-ceramics, an insulating reactant is generated at the interface of different materials, and mutual diffusion of component elements progresses, so that the electrode There is a risk that the reaction activity may be inhibited. If the cathode layer and the cathode current collector or current collector bonded to the cathode layer are made of the same material, it is preferable because the occurrence of such a failure can be suppressed.

Although LSC has a large electrical conductivity and is excellent, the coefficient of thermal expansion is larger than that of general metal materials and ceramic materials. The emergence of cathode materials with large electrical conductivity and a coefficient of thermal expansion comparable to that of other members is expected. This embodiment was carried out in view of such a problem, and includes a cathode layer having a large coefficient of electrical conductivity under conditions of operation at a high temperature and having a coefficient of thermal expansion close to the coefficient of thermal expansion of other members. The purpose is to provide a fuel cell.

As described in detail above, the SOFC100 (fuel cell) of the present invention uses the perovskite-type oxide described in the present embodiment or this embodiment, and is provided on one side of the electrolyte layer 3 and the electrolyte layer 3. The cathode layer 2 and the anode layer 1 provided on the other side of the electrolyte layer 3 are electrically connected to at least one of the cathode layer 2 or the anode layer 1 to collect electrons that react with electrodes, or a single cell. A current collector E that extracts electricity to the outside of C to SOFC 100 is provided, and at least one of the current collector member 52 or the cathode layer 2 that constitutes the current collector E has a perovskite-type oxide represented by the _{general formula ABO 3.} One of La and Sr contained as a conductive material or a cathode material, in which a perovskite-type oxide has La and Sr arranged at the A site and Co at the B site and arranged at the A site. A part of La is substituted with Sm, and the molar composition ratio of Sm to the perovskite-type oxide is smaller than the molar composition ratio of La to the perobskite-type oxide before substitution, and has a perovskite structure.

Therefore, since the electric conductivity of the conductive material _{is larger than that of the conventional material LaSrCoO 3} , the voltage loss due to the electric resistance of the current collecting member 52 can be reduced, and the output characteristics of the SOFC 100 can be improved. it can. Since the SOFC 100 generally has a large number of single cells C stacked and generates electricity in a state where each single cell C is electrically connected via a current collector E, the effect of reducing the electric resistance is great. Sonouede, the thermal expansion coefficient of LaSmSrCoO ₃ reduces than LaSrCoO _3, closer to the thermal expansion coefficient of the other member that, including metal material or ceramic material. In other words. Since the thermal expansion coefficient of the LaSmSrCoO ₃ is smaller than the LaSrCoO _3, due to the mismatch in thermal expansion coefficient between the ceramic material and the metallic material at a high temperature (under operating temperature), mainly current collecting member 52 and the metal material It is possible to prevent the separator layer 51, which is a component, from peeling off. Therefore, since the contact resistance can be reduced, the output characteristics of the fuel cell can be further improved.

Therefore, in addition to the effect described in the first embodiment, the electric conductivity of the cathode material becomes larger than _{that of the conventional material LaSrCoO 3.} Like LaSrCoO ₃ , LaSmSrCoO ₃ has an oxygen activation catalyst function, oxygen ion conductivity, and electron conductivity. Sonouede, the thermal expansion coefficient of the LaSmSrCoO ₃ is smaller than the LaSrCoO _3, with other ceramic material at a high temperature (under operating temperature), or due to mismatch in thermal expansion coefficient between the metallic material, the cathode layer It is possible to prevent the 2 and the separator layer 51 containing a metal material as a main component, or the cathode layer 2 and the electrolyte layer 3 containing a ceramic material as a main component and the current collector E from peeling off. The coefficient of thermal expansion of the conventionally known LaSrCoO ₃ is considerably larger than that of other materials such as metals and ceramics generally used for SOFCs, and it tends to be difficult to obtain the consistency of the coefficient of thermal expansion. The effect of reducing the coefficient of thermal expansion while utilizing the conductive performance stands out. Therefore, since the contact resistance can be reduced, the output characteristics of the fuel cell can be further improved.
In the embodiment described above, the composition of preferred LaSrCoO ₃ as the cathode material has been specifically described with reference to a preferred range of the substitution ratio x / z of the Sm as a parameter, with a molar composition ratio x of the Sm as a parameter Can have a similar preferred range.

Further, the cylindrical cell C (cyl) provided with the virtual current collector member using _{LaSmSrCoO 3 as the conductive material and the cathode material and the cathode layer 210 is more than the conventional material LaSrCoO 3 used} as the conductive material and the cathode material. , The output characteristics can be improved. Further, _{the cylindrical cell C (cyl) provided with the virtual current collecting member using LaSmSrCoO 3} as the conductive material and the cathode material and the cathode layer 210 is a (virtual) cathode current collecting member bonded to the cathode layer and the cathode layer. However, since they are made of the same material, it is possible to suppress the occurrence of a disorder in which the above-mentioned electrode reaction activity is inhibited, and it is possible to suppress deterioration of the output characteristics of the SOFC cell.

Further, since the thermal expansion coefficient of the LaSmSrCoO ₃ is smaller than the LaSrCoO _3, the separator layer 51, the collector E (current collecting member 52), by reducing the mismatch of thermal expansion coefficient between the battery member 3 such electrolyte layer , Since cracking and chipping are less likely to occur, reliability can be improved.

1,11,110 ... Anode layer, 2,21,210 ... Cathode layer, 3,31,310 ... Electrolyte layer, 51 ... Separator layer, 52 ... Current collector, 100 ... SOFC (fuel cell), C ... Single cell , C (disk) ... Coin-type cell (single cell), C (cyl) ... Cylindrical cell (single cell), E ... Current collector.

Claims (3)

With the electrolyte layer,
A cathode layer provided on one side of the electrolyte layer and
An anode layer provided on the other side of the electrolyte layer and
A current collecting member that is electrically connected to at least one of the cathode layer or the anode layer to collect electrons or to take out electricity to the outside of the fuel cell.
With
At least one of the current collector member and the cathode layer contains a perovskite-type oxide represented by _{the general formula ABO 3 as a material.}
The perovskite-type oxide
La and Sr are arranged at the A site, and Co is arranged at the B site.
Of the La and Sr arranged at the A site, a part of one La is replaced with Sm.
The molar composition ratio of Sm to the perovskite oxide is smaller than the molar composition ratio of La before substitution to the perovskite oxide.
A fuel cell having a perovskite structure. The material contained in the current collector is the perovskite-type oxide having a composition represented by the following formula (1).
La _z-x Sm _x Sr _1-z CoO ₃ (1)
In the formula (1), x / z indicating the ratio of the molar composition ratio x of Sm in the perovskite-type oxide to the molar composition ratio z of La in the perovskite-type oxide before substitution is 0.01 ≦. In the range of x / z <0.5,
The fuel cell according to claim 1, wherein the molar composition ratio (1-z) of Sr in the perovskite-type oxide is in the range of 0.2 ≦ 1-z ≦ 0.7. The fuel cell according to claim 2, wherein the ratio x / z, which is the ratio of the x to the z, is in the range of 0.01 ≦ x / z ≦ 0.25.

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