Porous metal body, method for producing porous metal body, and fuel cell
阅读说明：本技术 金属多孔体、该金属多孔体的制造方法以及燃料电池 (Porous metal body, method for producing porous metal body, and fuel cell ) 是由 平岩千寻 真岛正利 东野孝浩 水原奈保 俵山博匡 于 2019-01-09 设计创作，主要内容包括：该金属多孔体具有三维网状结构的骨架,其中：通过连接多个支柱部分构成骨架；多个支柱部分在金属多孔体的表面形成开口；多个支柱部分在金属多孔体的内部形成空隙；开口和空隙彼此连通,并且金属多孔体的孔隙率为1体积％至55体积％,并且密度为3g/cm<Sup>3</Sup>至10g/cm<Sup>3</Sup>。(The porous metal body has a skeleton of a three-dimensional network structure in which: forming a framework by connecting a plurality of strut parts; the plurality of pillar portions form openings in the surface of the porous metal body; the plurality of pillar portions form voids inside the porous metal body; the openings and the voids are communicated with each other, and the porosity of the metallic porous body is 1 volume% to 55 vol%, and a density of 3g/cm 3 To 10g/cm 3 。)
1. A porous metal body having a skeleton of a three-dimensional network structure,
the skeleton is formed of a plurality of strut parts connected to each other,
the plurality of pillar portions form openings in the surface of the porous metal body,
the plurality of pillar portions form voids inside the porous metal body,
the opening and the gap communicate with each other,
a porosity of 1 to 55 vol%,
the density was 3g/cm3To 10g/cm3。
2. The porous metal body according to claim 1, wherein the diameter of the opening is 3 μm to 55 μm.
3. The porous metal body according to claim 1 or 2, wherein the porous metal body has a sheet-like shape and a thickness of 0.05mm to 0.2 mm.
4. A method of making a metallic porous body comprising:
a first step of preparing a metal material having a skeleton of a three-dimensional network structure; and
a second step of pressing the metal material.
5. A method of making a metallic porous body as claimed in claim 4, wherein
In the second step, a plurality of the metal materials are laminated so that the metal materials are at least partially overlapped, and the thus-overlapped portions are pressed.
6. A fuel cell, comprising:
a cathode;
an anode;
an electrolyte layer interposed between the cathode and the anode; and
a porous metal body according to any one of claims 1 to 3 provided so as to oppose at least one of the cathode and the anode.
Technical Field
The present disclosure relates to a porous metal body, a method for producing the porous metal body, and a fuel cell. This application claims the benefit of priority from japanese patent application No.2018-032912, filed on 27.2.2018, the entire contents of which are incorporated herein by reference.
Background
Weight reduction of electronic devices, automobiles, and the like is a recent trend, and with this trend, porous metal bodies are receiving attention. The metal porous body has a large specific surface area, excellent gas permeability, and excellent electrical conductivity. Therefore, the porous metal body is expected to be used as a heat exchange material, a heat insulating material, a sound absorbing material, an impact absorbing material, a carrier for various chemical substances (e.g., a catalyst), a filter material, a gas passage of a fuel cell, an electrode or a current collector of various batteries, an adsorbing material, an electromagnetic wave shielding material, and the like.
As such a porous metal body, a metal mesh having a two-dimensional porous structure and a sponge metal having a three-dimensional porous structure are known. For example, the metal mesh is obtained by weaving metal fibers. The sponge metal is obtained by, for example: a method in which a foaming agent is added to a molten metal, stirred, and then cooled (precursor method); a method of sintering metal powder; and a method of mixing a metal powder and a separator powder, sintering, and then removing the separator (a separator method, for example, a method in japanese patent laid-open No.2013-082965 (patent document 1)).
Reference list
Patent document
Patent document 1: japanese patent laid-open No.2013-082965
Disclosure of Invention
One aspect of the present disclosure relates to a porous metal body having a skeleton of a three-dimensional network structure, the skeleton being composed of a plurality of pillar portions connected to each other, the plurality of pillar portions forming openings on a surface of the porous metal body, the plurality of pillar portions forming voids inside the porous metal body, the openings and the voids being in communication with each other, the porosity being 1% by volume to 55% by volume, and the density being 3g/cm3To 10g/cm3。
Another aspect of the present disclosure relates to a method of making a metallic porous body, comprising: a first step of preparing a metal material having a skeleton of a three-dimensional network structure; and a second step of pressing the metal material.
Yet another aspect of the present disclosure relates to a fuel cell, including: a cathode; an anode; an electrolyte layer interposed between the cathode and the anode; and the above-described metal porous body provided so as to oppose at least one of the cathode and the anode.
Drawings
Fig. 1 is a schematic view of an exemplary structure of a part of a skeleton of a metal material.
Fig. 2 is a schematic cross-sectional view of a section of a portion of the carcass shown in fig. 1.
Fig. 3 is a schematic cross-sectional view of a fuel cell according to an embodiment of the present disclosure.
Fig. 4 is a scanning electron micrograph of the porous metal body of example 1 taken from one surface thereof.
Fig. 5 is a scanning electron micrograph of the porous metal body of example 2 taken from one surface thereof.
Fig. 6 is a scanning electron micrograph of the porous metal body of example 3 taken from one surface thereof.
Fig. 7 is a scanning electron micrograph of the porous metal body of example 4 taken from one surface thereof.
Fig. 8 is a scanning electron micrograph of the porous metal body of example 5 taken from one surface thereof.
Detailed Description
[ problem to be solved by the present disclosure ]
In such a porous metal body, the sponge metal has many electron channels and has low resistance itself. However, when used as a current collector of a battery, the sponge metal comes into point contact with the electrode, and thus tends to increase the resistance. In particular, in a solid oxide fuel cell (hereinafter referred to as SOFC), the electrical resistance significantly increases. This is because a ceramic body (sintered body) is used as an electrode in the SOFC.
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a porous metal body having low electrical resistance and excellent fluid permeability, a method for producing the porous metal body, and a fuel cell.
[ advantageous effects of the present disclosure ]
The present disclosure can provide a metal porous body having low electrical resistance and excellent fluid permeability. The present disclosure can also provide a method of obtaining a metallic porous body in a very easy and simple manner. The present disclosure can also provide a fuel cell having excellent power generation performance.
[ description of the embodiments ]
The following sets forth and describes embodiments of the present disclosure.
(1) The porous metal body according to the present disclosure is a porous metal body having a skeleton of a three-dimensional network structure, the skeleton being composed of a plurality of pillar portions connected to each other, the plurality of pillar portions forming openings on a surface of the porous metal body, the plurality of pillar portions forming voids inside the porous metal body, the openings and the voids being in communication with each other, the porosity being 1% by volume to 55% by volume, and the density being 3g/cm3To 10g/cm3. The porous metal body has low electrical resistance and excellent fluid permeability.
(2) Preferably, the diameter of the opening is 3 μm to 55 μm. With this configuration, the electric resistance is maintained at a low level and the fluid permeability is further improved.
(3) Preferably, the metallic porous body has a sheet-like shape and a thickness of 0.05mm to 0.2 mm. With this configuration, the electronic apparatus including the metallic porous body is easily miniaturized while maintaining a required level of strength.
(4) The method for manufacturing a porous metal body according to the present disclosure includes: a first step of preparing a metal material having a skeleton of a three-dimensional network structure; and a second step of pressing the metal material. By such an easy and simple method, a porous metal body having low electrical resistance and excellent fluid permeability can be obtained.
(5) In the second step, a plurality of metal materials may be stacked such that the metal materials at least partially overlap, and the thus-overlapped portions may be pressed. By this configuration, the density and porosity of the resulting porous metal body can be controlled, so that a desired porous metal body can be easily obtained.
(6) The fuel cell according to the present disclosure includes: a cathode; an anode; an electrolyte layer interposed between the cathode and the anode; and the above-described metal porous body provided so as to oppose at least one of the cathode and the anode. The fuel cell has excellent power generation performance.
[ detailed description of the embodiments ]
Next, a specific description will be given of embodiments of the present disclosure. The scope of the present invention is intended to be defined by the claims, not by the following, and includes all modifications and variations equivalent to the meaning and scope of the claims.
(porous Metal)
The porous metal body according to the present embodiment includes a first surface and a second surface opposite to the first surface, and is formed of a fibrous metal (hereinafter referred to as metal fiber). The first and second surfaces have openings formed by the intertwined metal fibers. An interior region between the first surface and the second surface has voids formed by three-dimensional entanglement of the fibrous metal. In these terms, the metallic porous body according to the present embodiment is different from the metallic mesh or the sponge metal such as the sintered body. "fibrous" refers to a shape that extends in one direction and may be linear (rod-like) or curved. There is no limitation on the length of the fibrous metal.
In one aspect of the present embodiment, the metal porous body is a metal porous body having a skeleton of a three-dimensional network structure, the skeleton being composed of a plurality of pillar portions connected to each other, the plurality of pillar portions forming openings at a surface of the metal porous body, the plurality of pillar portions forming voids inside the metal porous body. The "three-dimensional network structure" and the "pillar portion" will be described below. The metallic porous body may include a first surface and a second surface opposite the first surface. When the metal porous body has a sheet-like shape, the first surface may be regarded as one main surface of the sheet-like shape, and the second surface may be regarded as the other main surface of the sheet-like shape.
The openings and the voids are communicated with each other, and the porosity of the entire metallic porous body is 1 to 55 vol%. In other words, the porosity of the metallic porous body is superior to that of the metallic mesh or sponge. Therefore, the porous metal body has excellent fluid permeability.
The density of the porous metal body was 3g/cm3To 10g/cm3It is dense. Therefore, the metallic porous body has low electrical resistance while having high fluid permeability. Further, in an aspect of the present embodiment, the internal region of the metallic porous body has a structure in which the metal fibers are wound in a three-dimensional manner, and therefore the metallic porous body tends to be plastically deformed. As a result, the contact between the metal porous body and other components (e.g., electrodes) can be enhanced without damaging these other components. In other words, the metallic porous body tends to be in line contact or even in plane contact with other components. For these reasons, the metallic porous body according to the present embodiment is particularly suitable as a current collector of a fuel cell designed to be in contact with a ceramic electrode.
The porosity (void ratio) of the entire metal porous body is preferably 5 to 50 vol%, more preferably 5 to 40 vol%, and further preferably 5 to 10 vol%. The porosity (vol%) was calculated by {1- (apparent mass per unit volume of the metallic porous body)/(true specific gravity of the metallic porous body) } × 100. The "true specific gravity of the porous metal body" means the specific gravity of the metal constituting the porous metal body.
The density of the porous metal body is preferably 4g/cm3To 9g/cm3More preferably 5g/cm3To 8.5g/cm3More preferably 6g/cm3To 8.5g/cm3. By dividing the mass (g) of the porous metal body by the apparent volume (cm)3) To calculate the density (g/cm)3). The "apparent volume" may be regarded as the volume of the metallic porous body estimated from the outer shape of the metallic porous body.
The diameter of the opening (opening diameter Ds) formed on each surface of the porous metal body is not particularly limited and may be appropriately selected according to the use. Specifically, the opening diameter Ds is preferably 3 μm to 55 μm, more preferably 5 μm to 20 μm, further preferably 5 μm to 15 μm, and particularly preferably 5 μm to 12 μm. With this configuration, the electric resistance is maintained at a low level and the fluid permeability is further improved. The opening diameters Ds of the opening in the first surface and the opening in the second surface (hereinafter may be referred to as a first opening and a second opening, respectively) may be the same as or different from each other.
The opening diameter Ds is determined, for example, in the manner described below. In the SEM photograph of the first surface taken in the normal direction, the region Rs is determined so that it includes five or more complete first openings. Of all the first openings of the region Rs, five first openings are, for example, randomly selected. For each first opening, the diameter of the largest perfect circle that can be accommodated in the particular first opening is measured, and the diameter of the smallest perfect circle that can be accommodated in the particular first opening is measured, and then the average of these diameters is calculated. The result is considered to be the diameter of the particular first opening. The diameters of the five selected first openings are averaged and used as the opening diameter Ds. In the same manner, the opening diameter Ds of the second opening is determined.
The diameter Ws of the metal fibers in each surface of the porous metal body is not particularly limited. Specifically, the diameter Ws is preferably 20 μm to 200 μm, more preferably 50 μm to 100 μm, further preferably 65 μm to 100 μm, and particularly preferably 65 μm to 90 μm from the viewpoint of fluid permeability and strength. The diameter Ws is the length of the cross section of the metal fiber perpendicular to the longitudinal direction of the metal fiber. For example, the diameter Ws is the average of the diameters of any five locations of the metal fibers within the region Rs. The diameter Ws of the metal fibers in the first surface may be the same as or different from the diameter Ws of the metal fibers in the second surface. Preferably, the diameter of the strut sections described below is equal to the diameter of the metal fibers.
When the metal porous body has a sheet-like shape (e.g., as shown in fig. 3), the thickness (distance between the first surface and the second surface) of the metal porous body is not particularly limited and may be appropriately selected depending on the purpose. Specifically, the thickness of the porous metal body is preferably 0.05mm to 0.2mm, more preferably 0.1mm to 0.19mm, and further preferably 0.1mm to 0.18mm from the viewpoint of miniaturization and strength. For example, the thickness can be measured with a commercially available digital thickness gauge.
The specific surface area (BET specific surface area) of the porous metal body is not particularly limited and may be appropriately selected depending on the use. For example, the specific surface area of the metallic porous body may be 100m2/m3To 9000m2/m3And may be 200m2/m3To 6000m2/m3. For example, the specific surface area can be determined by BET measurement.
The metal constituting the metal porous body may be appropriately selected depending on the use or use environment, and the type of the metal is not particularly limited. Examples of metals include copper, copper alloys (copper alloyed with Fe, Ni, Si, Mn, and/or the like), nickel or nickel alloys (nickel alloyed with tin, chromium, tungsten, and/or the like), aluminum or aluminum alloys (aluminum alloyed with Fe, Ni, Si, Mn, and/or the like), and stainless steels.
Substances such as various catalysts, adsorption materials, electrode active materials, and electrolytes may be held in the voids of the metal porous body. With this configuration, the metallic porous body can exhibit various functions.
(method for producing porous Metal Material)
The metallic porous body, that is, the metallic material pressed with the skeleton having a three-dimensional network structure can be obtained by a very easy and simple method. More specifically, the metallic porous body is produced by a method comprising: a first step of preparing a metal material; and a second step of pressing the metal material. In the second step, a plurality of metal materials may be stacked such that the metal materials at least partially overlap, and the thus-overlapped portion may be pressed.
Next, the metal material will be described with reference to the drawings. Fig. 1 is a schematic view of an exemplary structure of a part of a skeleton of a metal material, and fig. 2 is a cross-sectional view of a section of the part of the skeleton.
The metal material has pores and a metal skeleton. In this case, the metal material is constituted by a plurality of cells each having a hole (void) and a metal skeleton. For example, as shown in FIG. 1, each cell may be shown as a regular dodecahedron. The
The skeleton of the cells is formed by
As shown in fig. 2, the interior of the
For example, the metal material can be formed by coating the resin porous body with the metal. For example, the metal coating may be performed by plating treatment, vapor phase methods (e.g., evaporation, plasma chemical vapor deposition, sputtering), and/or metal paste coating. The skeleton of the three-dimensional network structure is formed by metal coating treatment. Among these coating methods, plating treatment is preferable.
The plating treatment may be any plating treatment capable of forming a metal layer on the surface of the resin porous body (including the surface of the internal voids), and a known plating treatment method such as electrolytic plating and/or molten salt plating may be employed. By this plating treatment, a metal material including a three-dimensional network structure reflecting the shape of the resin porous body is formed. In the constitution in which the plating treatment is performed by electrolytic plating, it is necessary to form a conductive layer before electrolytic plating. The conductive layer may be formed on the surface of the porous resin body by electroless plating, vapor deposition, sputtering, coating with a conductive agent, dipping the porous resin body in a dispersion containing a conductive agent, and/or the like.
The porous resin body is not particularly limited as long as it has voids, and may be, for example, a resin foam and/or a resin nonwoven fabric. Among them, a resin foam is preferable because communication holes are easily formed therein. The resin constituting the porous body is preferably a resin capable of making the
It is desirable to remove the resin present inside the skeleton via degradation or dissolution by heat treatment and/or the like. After the heat treatment, residual components (resin, degradation products, unreacted monomers, additives contained in the resin, and/or the like) remaining inside the skeleton may be removed by washing and/or the like. If necessary, the resin may be removed by heat treatment while a voltage is appropriately applied to the resin. The heat treatment may be performed while applying a voltage in a state where the plated porous body is immersed in a molten salt plating bath. By thus removing the resin inside after the metal coating treatment, a cavity is formed inside the skeleton of the metal porous body, and the inside of the skeleton becomes hollow. The metal material thus obtained has a skeleton of a three-dimensional network structure reflecting the shape of the resin foam. As a commercially available metal material, "Aluminum-Celmet" (registered trademark) or "Celmet" (registered trademark) made of copper or nickel, both of which are products manufactured by sumitomo electric industry co.
(first step)
In the first step, the metal material having the skeleton of the three-dimensional network structure described above is prepared.
As described below, when a plurality of metal materials are used, the constitutions (metal type, thickness, porosity, etc.) of the metal materials may be the same as or different from each other. The number of the metal material may be any number of 1 or more, and may be appropriately selected in consideration of the density and porosity of the desired metallic porous body. Specifically, the amount of the metal material is preferably 6 or less from the viewpoint of downsizing and fluid permeability.
(second step)
In a second step, the metal material is pressed. Thereby, the metal skeleton (fiber portion 102) of the metal material is plastically deformed, so that the metal fibers are entangled with each other. Alternatively, the metal skeleton (the pillar portion 102) of the metal material is plastically deformed so that the plurality of pillar portions are in contact with each other. Thus, the obtained porous metal body has a relatively high porosity and a high density. Further, the resulting porous metal body may be thin. For example, the porosity of the metal porous body is 1 to 55 vol%. For example, a density of 3g/cm3To 10g/cm3。
In general, a fuel cell is manufactured by providing a pair of collectors and sandwiching a pair of electrodes and an electrolyte layer interposed between the electrodes between the collectors to form a unit cell, and stacking a plurality of such unit cells (for example, 50 or more unit cells). Since the conventional sponge metal is difficult to be thinned due to its manufacturing process, the thickness of each unit cell tends to be large. When the metal mesh is used, each fiber metal needs to be thick in order to maintain sufficient electronic channels, and thus the thickness of each unit cell tends to be large. In contrast, the metallic porous body obtained according to the present embodiment is thin, and therefore it is possible to miniaturize the resulting fuel cell while maintaining high power generation performance.
Further, by the pressing, the portions of the metal fibers (corresponding to the first surface and the second surface of the metallic porous body) exposed to the surface of the metallic material and in contact with the press tend to be flat. As a result, the area of the first surface and the second surface in contact with other components such as the electrodes becomes large. It should be noted that the metal material includes a skeleton of a three-dimensional network structure, whereby it is plastically deformed and has a moderate level of elasticity. Therefore, the metal material tends not to be damaged by pressing.
The method of pressing is not particularly limited, and examples thereof include rolling and flat plate pressing. The pressing may be performed while heating. In particular, it is preferable to perform bonding by performing roll pressing at normal temperature from the viewpoint of cost and production efficiency. The pressing conditions are not particularly limited, and may be appropriately set in consideration of the desired porosity, density, and the like. For example, the pressing is performed such that the thickness of the resulting metal material is 1% to 10%, 2% to 7%, or 2.5% to 5.5%. The pressing pressure during pressing may be, for example, 10kPa or more, or 100kPa or more. The pressing pressure may be 4000kPa or less, or 5000kPa or less.
In the constitution in which the metal porous body is made of the sintered body of the metal powder, it is difficult to perform pressing. This is because the sintered body tends not to be plastically deformed easily and may be damaged by pressing.
In the second step, a plurality of metal materials may be stacked so as to be at least partially overlapped, and the thus-overlapped portions may be pressed. With such a configuration, it tends to be easy to control the density and porosity of the resulting porous metal body, so that the desired porous metal body can be easily obtained. In this configuration, the metal skeleton (the
In these ways, the plurality of metal materials are firmly bonded to each other without a bonding agent therebetween. As a result, the obtained porous metal body has interconnected pores and excellent fluid permeability.
[ Fuel cell ]
The fuel cell according to the present embodiment includes a cathode, an anode, an electrolyte layer interposed between the cathode and the anode, and the above-described metal porous body provided so as to oppose at least one of the cathode and the anode.
The porous metal body serves as a current collector. The porous metal body has a high density and a high porosity, and therefore it is particularly suitable as a current collector. When a plurality of current collectors are provided so as to oppose both the cathode and the anode, at least one current collector may be the above-described metal porous body. It is particularly preferable that all the current collectors are the above-described metal porous bodies.
Fig. 3 is a schematic diagram of a cross section of the structure of the fuel cell 200. The fuel cell 200 includes a cathode 12, an anode 11, an electrolyte layer 13 interposed between the cathode 12 and the anode 11, and current collectors 110A, 110B disposed opposite to the cathode 12 and the anode 11. At least one of the collectors 110A, 110B is the porous metal body.
For example, the cathode 12, the anode 11, and the electrolyte layer 13 are sintered into an integral member and constitute the unit cell 100. The method of manufacturing the unit cell 100 is not particularly limited, and conventionally known methods may be used. For example, the unit cell 100 may be manufactured by a method including: press-forming an anode material to obtain an anode formed body; laminating an electrolyte layer material to one side of the obtained anode formed body and then sintering; and laminating a cathode material on a surface of the sintered electrolyte layer and sintering.
The fuel cell 200 further includes a fuel passage 130A for supplying fuel to the anode 11 and an oxidant passage 130B for supplying oxidant to the cathode 12.
The fuel passage 130A has a fuel gas inlet through which fuel gas enters and a fuel gas outlet through which unused fuel and H generated by the reaction are discharged2O (or when the fuel is, for example, CH)4When such a hydrocarbon is CO2) (the fuel gas inlet and the fuel gas outlet are not shown). The oxidant passage 130B has an oxidant inlet through which oxidant enters and an oxidant outlet through which water produced by the reaction, unused oxidant, and the like are discharged (the oxidant inlet and the oxidant outlet are not shown). Examples of oxidizing agents include oxygen-containing gases.
When the metal oxide contained in the electrolyte layer 13 has oxide ion conductivity, the fuel cell 200 may operate at a temperature of 800 ℃ or lower; when the metal oxide has proton conductivity, the fuel cell 200 may operate at a temperature below 700 ℃. The lower limit is not particularly limited, and may be, for example, 400 ℃ or higher. The operating temperature is preferably in the mid-temperature range of about 400 ℃ to about 600 ℃.
(Anode)
The anode 11 has an ion-conductive porous structure, and for example, a reaction occurs in the anode 11 having proton conductivity, in which a fuel such as hydrogen introduced through the fuel passage 130A is oxidized to release protons and electrons (oxidation reaction of the fuel). For example, the thickness of the anode 11 may be about 10 μm to about 1000 μm.
The material of the anode 11 may be, for example, a known material used as an anode of a fuel cell. Specific examples include a compound containing nickel as a catalyst component (hereinafter referred to as Ni compound), or a composite oxide of a Ni compound and the metal oxide described below. For example, the anode 11 including the composite oxide can be manufactured by mixing NiO powder, a powdered metal oxide, or the like and sintering the mixture.
As the metal oxide, a known material used as a solid electrolyte of a fuel cell can be used. Specifically, from the viewpoint of proton conductivity, a preferred example of the metal oxide is a metal oxide having a chemical formula consisting of ABO3The compound having a perovskite crystal structure (hereinafter referred to as a perovskite oxide). ABO3Comprising ABO3-(indicating the oxygen vacancy concentration) crystal structure. The perovskite crystal structure is similar to CaTiO3The crystal structure of (1). The ion radius of the element contained in the a site is larger than that of the element contained in the B site. From the viewpoint of oxide ion conductivity, a preferable example of the metal oxide is a compound containing zirconium dioxide (hereinafter referred to as zirconium compound).
The metal element contained in the a site is not particularly limited, and may be, for example, a group 2 element in the periodic table, such as barium (Ba), calcium (Ca), and/or strontium (Sr). Only one of these elements may be used, or two or more of these elements may be used in combination. Among them, the a site preferably contains Ba from the viewpoint of proton conductivity.
Examples of the metal element contained in the B site include cerium (Ce), zirconium (Zr), and yttrium (Y). Among them, the B site preferably contains at least one of Zr and Ce from the viewpoint of proton conductivity. The B site is partially substituted with a trivalent rare earth element other than cerium; these dopants cause oxygen vacancies, whereby the perovskite-type oxide exhibits proton conductivity.
Examples of trivalent rare earth elements (dopants) other than cerium include yttrium (Y), scandium (Sc), neodymium (Nd), samarium (Sm), gadolinium (Gd), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Among them, from the viewpoint of proton conductivity and chemical stability, Y or an element having a smaller ion radius than Y preferably occupies a part of the B site. Examples of such elements include Sc, Ho, Er, Tm, Yb and Lu. The B site may contain an element (e.g., indium (In)) serving as a dopant other than the rare earth element.
Among perovskite-type oxides, a compound represented by the formula (1-1) is particularly preferable from the viewpoints of excellent proton conductivity and excellent power generation performance: bax1Ce1-y1Yy1O3-(0.95≤x1≤1，0<y 1. ltoreq.0.5, BCY), a compound represented by the formula (2-1): bax2Zr1-y2Yy2O3-(0.95≤x2≤1，0<y 2. ltoreq.0.5, BZY), and a compound represented by the formula (3-1): bax3Zr1-y3-y4Cey3Yy4O3-(0.95≤x3≤1，0<y3<1，0<y 4. ltoreq.0.5, BZCY), which is a solid solution of the two compounds mentioned above, is preferred. Only one of these perovskite-type oxides may be used, or two or more of these perovskite-type oxides may be used in combination. In this case, Y occupying the B site may be partially substituted with other elements (e.g., other lanthanides), and Ba occupying the a site may be partially substituted with other group 2 elements (e.g., Sr, Ca).
The zirconium compound, which is also a preferred compound of the metal oxide, comprises zirconium dioxide and at least one element selected from the group consisting of Ca, Sc and Y, wherein the at least one element selected from the group consisting of Ca, Sc and Y forms a substitutional solid solution with Zr. With this configuration, the zirconium compound exhibits oxide ion conductivity. From the viewpoint of oxide ion conductivity and cost, preferred examples of the zirconium compound include yttria-stabilized zirconia (ZrO)2-Y2O3，YSZ)。
(cathode)
The cathode 12 has a porous structure capable of adsorbing, dissociating and ionizing oxygen molecules. The material of cathode 12 can be, for example, a known material used as a fuel cell cathode. For example, the material of the cathode 12 is a compound having a perovskite structure. Specific examples include lanthanum strontium cobalt ferrite (LSCF, La)1-aSraCo1-bFebO3-0 < a < 1, 0 < b < 1, representing oxygen vacancy concentration), lanthanum strontium manganate (LSM, La)1-cSrcMnO3-0 < c < 1, indicating the oxygen vacancy concentration), lanthanum strontium cobaltite (LSC, La)1-dSrdCoO3-0 < d < 1, meansOxygen vacancy concentration), and samarium strontium cobaltate (SSC, Sm)1-eSreCoO3-And 0 < e < 1, which indicates the oxygen vacancy concentration).
Cathode 12 may contain a catalyst such as nickel, iron, and/or cobalt. The cathode containing the catalyst may be formed by mixing and sintering the catalyst and the above-described materials. The thickness of the cathode 12 is not particularly limited, and may be about 5 μm to about 100 μm.
(electrolyte layer)
The electrolyte layer 13 contains an ion-conductive solid oxide. The ions moving within the electrolyte layer 13 are not particularly limited, and may be oxide ions or may be hydrogen ions (protons). Particularly preferably, the electrolyte layer 13 has proton conductivity. For example, Proton Conducting Fuel Cells (PCFCs) may operate at medium temperatures of 400 ℃ to 600 ℃. Thus, PCFCs have various uses. The thickness of the electrolyte layer 13 is not particularly limited, and in order to achieve low resistance, the thickness thereof is preferably about 5 μm to about 100 μm.
Examples of the ion-conductive solid oxide include metal oxides used in the anode 11. The electrolyte layer 13 may contain other components than the metal oxide, but the content thereof is preferably low. For example, the metal oxide preferably accounts for 99 mass% or more of the electrolyte layer 13. The other components than the metal oxide are not particularly limited, and examples thereof may include compounds known as solid electrolytes (including non-ion conductive compounds)
(Current collector)
The anode-side current collector 110A has a current collecting function and a function of diffusing the fuel gas introduced through the fuel passage 130A and supplying it to the anode 11. The cathode-side current collector 110B has a current collecting function and a function of diffusing the oxidant gas introduced through the oxidant passage 130B and supplying it to the cathode 12. Therefore, each current collector is preferably a gas permeable structure having low resistance. The porous metal body according to the present embodiment is suitable as a current collector.
Examples of the structure for the current collector include a metal mesh, a punching metal, and a metal expanded mesh containing platinum, silver, a silver alloy, Ni, a Ni alloy, and/or the like, in addition to the metal porous body.
(baffle)
The fuel passage 130A may be, for example, provided in the separator 120A, and the separator 120A is provided outside the anode 11. Likewise, the oxidant passage 130B may be, for example, provided in the separator 120B, the separator 120B being provided outside the cathode 12.
For example, in a configuration in which a plurality of unit cells 100 are stacked to form the fuel cell 200, the unit cells 100 and one current collector and one separator are regarded as a single stacked unit. For example, a plurality of unit cells 100 may be connected in series via a separator having gas channels (oxidant channels and fuel channels) on both sides.
Examples of the material of the separators 120A, 120B may include heat-resistant alloys such as stainless steel, nickel-based alloys, and chromium-based alloys from the viewpoint of electrical conductivity and heat resistance. Among them, stainless steel is preferable because of its low cost. Stainless steel may be used as the material of the separator when the operating temperature of the fuel cell 200 is about 400 c to about 600 c.
[ pay note ]
The above description includes the embodiments noted below.
(pay 1)
A porous metal body comprising a first surface and a second surface opposite to the first surface, the porous metal body being formed of a fibrous metal,
the first and second surfaces comprise openings formed by the winding of fibrous metal,
in an inner region between the first surface and the second surface, a void is formed by a three-dimensional winding of fibrous metal,
the openings and the air gaps are communicated with each other,
a porosity of 1 to 55 vol%,
the density was 3g/cm3To 10g/cm3。
(pay 2)
The porous metal body according to note 1, wherein the diameter of the opening is 3 μm to 55 μm.
(pay 3)
The porous metal body according to note 1 or note 2, wherein the thickness is 0.05mm to 0.2 mm.
(pay 4)
A method of making a metallic porous body comprising:
a first step of preparing a metal material having a skeleton of a three-dimensional network structure; and
a second step of pressing the metal material.
(pay 5)
The method of manufacturing a porous metal body according to supplementary note 4, wherein in the second step, a plurality of metal materials are laminated such that the metal materials at least partially overlap, and the thus-overlapped portions are pressed.
(note 6) a fuel cell comprising:
a cathode;
an anode;
an electrolyte layer interposed between the cathode and the anode; and
the porous metal body according to supplementary note 1 provided so as to face at least one of the cathode and the anode.
[ example ]
Next, the present disclosure will be specifically described based on embodiments. However, the following examples do not limit the scope of the present disclosure.
[ example 1]
A fuel cell was prepared by the following procedure.
(1) Preparation of metallic materials
As a metal material, Celmet (registered trademark; product No. 8; opening diameter, 450 μm; thickness, 1.4mm) made of nickel manufactured by Sumitomo electric industries, Ltd was prepared.
(2) Preparation of porous metal bodies
The metallic porous body a (thickness, 0.075mm) was prepared by rolling the metallic material to about 5% of the entire thickness of the metallic material. Fig. 4 is a Scanning Electron Microscope (SEM) photograph taken from one surface of the porous metal body a. The opening diameter Ds of the surface of the porous metal body A was 50 μm, and the diameter (i.e., pillar portion diameter) Ws of the metal fiber was 63 μm.
(3) Preparation of the Battery
The battery was prepared by the following procedure.
First, NiO and BZY (BaZr)0.8Y0.2O2.9) Mixing was performed to achieve a Ni (catalyst component) content of 70 vol%, followed by pulverization and kneading in a ball mill. Then, press forming was performed to obtain an anode formed body (thickness, 550 μm), followed by pre-sintering at 1000 ℃. Subsequently, BZY (BaZr) was coated on one side of the resulting formed body by screen printing0.8Y0.2O2.9) Mixed paste with water-soluble binder resin (ethyl cellulose), and then water-soluble binder resin was removed at 750 ℃. Subsequently, co-sintering was performed by performing heat treatment at 1400 ℃ in an oxygen atmosphere to form an anode and an electrolyte layer (thickness, 10 μm).
Subsequently, cathode material LSCF (La) was used by screen printing0.6Sr0.4Co0.2Fe0.8O3-) The LSCF paste of the powder and the above organic solvent coated the surface of the resulting electrolyte layer, and then sintered at 1000 c for 2 hours in an oxygen atmosphere to prepare a unit cell. The thickness of the cathode was 10 μm.
(4) Preparation of Fuel cells
On the surface of the anode of the resulting unit cell, a metal porous body a was laminated, and an anode-side interconnect made of stainless steel having a smooth surface was further laminated. On the surface of the cathode, a cathode-side interconnect made of stainless steel having a gas channel is laminated. Thus, a fuel cell a was prepared. One ends of the leads are connected to the anode-side interconnect and the cathode-side interconnect, respectively. The other end of each lead wire is led out from the fuel cell and connected to a measuring instrument for measuring current and voltage between the lead wires.
(5) Evaluation of Power Generation Performance
Hydrogen was introduced as a fuel gas at 0.3L/min into the anode of the fuel cell a prepared above, and air was introduced at 1.0L/min into the cathode at an operating temperature of 600 c, so that the maximum power density was obtained. The results are shown in Table 1.
[ example 2]
A metallic porous body B (thickness, 0.117mm) and a fuel cell B were produced and evaluated in the same manner as in example 1, except that two sheets of metallic materials were produced in the above-described manner, and the two sheets of metallic materials were laminated and pressed. The results are shown in Table 1. Fig. 5 is an SEM photograph of the porous metal body B taken from one surface of the porous metal body B. The opening diameter Ds of the surface of the porous metal body B was 12 μm, and the diameter Ws of the metal fiber was 66 μm.
[ example 3]
A metallic porous body C (thickness, 0.117mm) and a fuel cell C were produced and evaluated in the same manner as in example 1, except that three sheets of metallic materials were produced in the above manner, and the three sheets of metallic materials were laminated and pressed. The results are shown in Table 1. Fig. 6 is an SEM photograph of the porous metal body C taken from one surface of the porous metal body C. The opening diameter Ds of the surface of the porous metal body C was 5 μm, and the diameter Ws of the metal fiber was 83 μm.
[ example 4]
A metallic porous body D (thickness, 0.160mm) and a fuel cell D were produced and evaluated in the same manner as in example 1, except that four pieces of metallic materials were produced in the above-described manner, and the four pieces of metallic materials were laminated and pressed. The results are shown in Table 1. Fig. 7 is an SEM photograph of the porous metal body D taken from one surface of the porous metal body D. The opening diameter Ds of the surface of the porous metal body D was 10 μm, and the diameter Ws of the metal fiber was 86 μm.
[ example 5]
A metallic porous body E (thickness, 0.187mm) and a fuel cell E were produced and evaluated in the same manner as in example 1, except that five pieces of metallic materials were produced in the above manner, and the five pieces of metallic materials were laminated and pressed. The results are shown in Table 1. Fig. 8 is an SEM photograph of the porous metal body E taken from one surface of the porous metal body E. The opening diameter Ds of the surface of the porous metal body E was 4 μm, and the diameter Ws of the metal fiber was 95 μm.
Comparative example 1
A fuel cell was produced and evaluated in the same manner as in example 1 except that the above-described metallic material before pressing was used in place of the metallic porous body a. The results are shown in Table 1.
[ Table 1]
As for the fuel cells a to E including the metal porous bodies obtained by pressing the metal material, they had excellent power generation performance as compared with the fuel cell a. The metallic porous body has sufficient porosity and high density, and can be plastically deformed. Therefore, using the porous metal body as a current collector can reduce the electrical resistance and improve the fluid permeability.
List of reference numerals
101: hole (void), 102: fiber portion (pillar portion), 102 a: cavity, 103: window (opening), 11: anode, 12: cathode, 13: electrolyte layer, 100: unit cell, 110A, 110B: current collector, 120A, 120B: separator, 130A: fuel passage, 130B: oxidant passage, 200: a fuel cell.
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