阅读说明：本技术 燃料电池 (Fuel cell ) 是由 平岩千寻 小川光靖 东野孝浩 沼田昂真 真岛正利 于 2019-07-25 设计创作，主要内容包括：本发明提供一种燃料电池,其包含：单元电池结构体,其包含正极、负极和置于所述正极与所述负极之间的固体电解质层；和与所述正极接触的集电器,其中经由所述集电器将氧化剂供给到所述正极,所述集电器包含由金属材料制成的多孔体和负载在所述多孔体的孔隙内部的铬吸附剂,所述金属材料包含第一金属和第二金属,所述第一金属包含镍,并且所述第二金属包含选自由锡、铝、钴、钛、锰、钨、铜、银和金构成的组中的至少一种。(The present invention provides a fuel cell, comprising: a unit cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode; and a current collector in contact with the positive electrode, wherein an oxidant is supplied to the positive electrode via the current collector, the current collector includes a porous body made of a metal material and a chromium adsorbent supported inside pores of the porous body, the metal material includes a first metal and a second metal, the first metal includes nickel, and the second metal includes at least one selected from the group consisting of tin, aluminum, cobalt, titanium, manganese, tungsten, copper, silver, and gold.)

1. A fuel cell, comprising:

a unit cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode; and

a current collector in contact with the positive electrode, wherein

Supplying an oxidant to the positive electrode via the current collector,

the current collector comprises a porous body made of a metal material and a chromium adsorbent supported inside pores of the porous body,

the metallic material comprises a first metal and a second metal,

the first metal comprises nickel, and

the second metal includes at least one selected from the group consisting of tin, aluminum, cobalt, titanium, manganese, tungsten, copper, silver, and gold.

2. The fuel cell according to claim 1, wherein

The metallic material comprises an alloy of the first metal and the second metal.

3. The fuel cell according to claim 1 or 2, wherein

The ratio of the second metal to the total amount of the first metal and the second metal contained in the metal material is 4 mass% or more and 15 mass% or less.

4. A fuel cell according to any one of claims 1 to 3, wherein

The second metal is tin.

5. The fuel cell according to any one of claims 1 to 4, wherein

The porous body has a skeleton of a three-dimensional network structure.

Technical Field

The present disclosure relates to a fuel cell. The present application claims priority from japanese patent application No. 2018-166259 filed on 9/5/2018. The entire contents of the disclosures in said japanese patent applications are incorporated herein by reference.

Background

A fuel cell is a device that generates electricity by an electrochemical reaction between a fuel gas such as hydrogen and an oxidant such as air. Since the fuel cell can directly convert chemical energy into electric energy, it has high power generation efficiency. In particular, a solid oxide fuel cell (hereinafter referred to as SOFC) having an operating temperature of 700 ℃ or more, particularly, about 800 ℃ to about 1000 ℃ is promising because of its high reaction speed. For SOFC, a Membrane Electrode Assembly (MEA) is used in which an electrolyte layer containing a solid oxide is sandwiched between and integrated with two sheets of electrodes composed of ceramics (sintered body). That is, all the constituent elements of the MEA are solid, and therefore they are easy to handle.

As a member constituting the fuel cell, an alloy containing chromium (chromium alloy) such as stainless steel may be used because the chromium alloy is excellent in heat resistance and oxidation resistance. However, when the SOFC is operated, chromium contained in the chromium alloy is gasified and dispersed in fuel electricityIn the pool. The dispersed chromium reacts with a metal oxide constituting the positive electrode, such as Lanthanum Strontium Cobalt Ferrite (LSCF), and SrCrO is generated₄And chromium oxide. These products accumulate at the interface between the positive electrode and the electrolyte layer, and deteriorate the electrode reaction. As a result, the power generation performance deteriorates.

Patent document 1 (japanese laid-open patent publication No. 2010-519716) and patent document 2 (japanese laid-open patent publication No. 2012-500462) teach coating the inner surface of the casing of the fuel cell with a chromium adsorbent. Non-patent document 1(The 18th Annual Solid Oxide Fuel Cell (SOFC) Project reviewing, Pittsburgh, 2017, 12 th to 14 th days 6 and 7) teaches a chromium adsorbing material comprising a honeycomb structure made of ceramic and a chromium adsorbent.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication No. 2010-519716

Patent document 2: japanese Kohyo publication No. 2012-500462

Non-patent document

Non-patent document 1: the 18th Annual Solid Oxide Fuel Cell (SOFC) Project Review Meeting, Pittsburgh, 6/month 12/day to 14/day 2017

Disclosure of Invention

One aspect of the present disclosure relates to a fuel cell, comprising: a unit cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode; and a current collector in contact with the positive electrode, wherein an oxidant is supplied to the positive electrode via the current collector, the current collector includes a porous body made of a metal material and a chromium adsorbent supported inside pores of the porous body, the metal material includes a first metal and a second metal, the first metal includes nickel, and the second metal includes at least one selected from the group consisting of tin, aluminum, cobalt, titanium, manganese, tungsten, copper, silver, and gold.

Drawings

Fig. 1 is a schematic diagram showing an example of the structure of a part of the skeleton of the porous body.

Fig. 2 is a sectional view schematically showing a section of a part of the skeleton in fig. 1.

FIG. 3 is an SEM photograph of the Ni-Sn layer.

Fig. 4 is a sectional view schematically showing the configuration of a fuel cell according to an embodiment of the present disclosure.

Fig. 5 is a graph showing the results of measurement by XRD in the examples.

Fig. 6 is a graph showing the result of measurement by XRD in the comparative example.

Fig. 7 is a graph showing the results of the compression test in the examples and comparative examples.

Detailed Description

[ problem to be solved by the present disclosure ]

With the methods in patent documents 1 and 2, it is difficult to dispose a sufficient amount of the chromium adsorbent in the battery. Disposing the chromium adsorbent in the fuel cell as in non-patent document 1 leads to an increase in the size of the fuel cell and an increase in the number of components, and complicates the assembly process. Further, the honeycomb structure made of ceramics in non-patent document 1 has heat resistance, but is easily affected by temperature change. SOFCs operating at high temperatures of 700 ℃ to 1000 ℃ can experience wide temperature variations from room temperature to 1000 ℃ due to repeated operations and stops. Therefore, the chromium adsorbent to be disposed in the fuel cell is required to have high thermal shock resistance.

An object of the present disclosure is to provide a fuel cell having high thermal shock resistance and excellent power generation performance without increasing the number of components.

[ advantageous effects of the present disclosure ]

According to the present disclosure, a fuel cell having high thermal shock resistance and having excellent power generation performance can be provided without increasing the number of components.

[ description of embodiments of the invention ]

First, the contents of the embodiments of the present disclosure will be explained in the form of a list.

(1) The disclosed fuel cell includes: a unit cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode; and a current collector in contact with the positive electrode, wherein an oxidant is supplied to the positive electrode via the current collector, the current collector includes a porous body made of a metal material and a chromium adsorbent supported inside pores of the porous body, the metal material includes a first metal and a second metal, the first metal includes nickel, and the second metal includes at least one selected from the group consisting of tin, aluminum, cobalt, titanium, manganese, tungsten, copper, silver, and gold.

Since the current collector, which is generally used as a member constituting the fuel cell, is provided to have a chromium adsorption function, it is possible to suppress an increase in the number of parts and to suppress an increase in the size of the fuel cell. Further, although the above-described current collector (hereinafter referred to as a first current collector) is made of a metal other than chromium, it has high heat resistance and oxidation resistance, and also has thermal shock resistance. Therefore, the first current collector can exhibit excellent chromium adsorption performance over a long period of time, and maintain high power generation performance of the fuel cell.

(2) From the viewpoint of heat resistance, oxidation resistance, and electrical conductivity, it is preferable that the metal material contains an alloy of the first metal and the second metal.

(3) From the same viewpoint, it is preferable that the ratio of the second metal to the total amount of the first metal and the second metal contained in the metal material is 4 mass% or more and 15 mass% or less.

(4) Preferably, the second metal is tin. When the metal material includes nickel and tin, the porous body has particularly high heat resistance and oxidation resistance.

(5) The porous body may have a skeleton of a three-dimensional network structure. Thereby, the pressure loss is reduced, and the current collecting performance is improved.

[ details of embodiments of the present invention ]

Specific examples of the embodiments of the present disclosure will be described below with reference to the accompanying drawings as appropriate. It should be noted that the present invention is not limited to these examples, but is defined by the scope of the appended claims, and is intended to encompass any modifications within the scope and meaning equivalent to the scope of the claims.

The fuel cell includes: a unit cell structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode; and a first current collector in contact with the positive electrode. An oxidant is supplied to the positive electrode via a first current collector.

As described above, the SOFC operating at a high temperature of 700 to 1000 ℃ undergoes a wide range of temperature variation from room temperature to 1000 ℃ when it is repeatedly operated and stopped. Therefore, the current collector is required to have heat resistance and high thermal shock resistance. The positive electrode-side current collector (first current collector) in contact with air (oxidizing gas) is exposed to a high-temperature, highly oxidizing atmosphere. Therefore, the first current collector is required to have particularly high oxidation resistance.

(first Current collector)

The first current collector is a porous body, and is made of a metal material. Therefore, it has excellent thermal shock resistance. In addition to the current collecting function, the first current collector also has a function of supplying the oxidizing gas introduced from the oxidizing agent pocket (ディンプル) to the positive electrode in a diffused manner.

The metal material includes a first metal and a second metal different from the first metal. The first metal includes nickel (Ni), and the second metal includes at least one selected from the group consisting of tin (Sn), aluminum (Al), cobalt (Co), titanium (Ti), manganese (Mn), tungsten (W), copper (Cu), silver (Ag), and gold (Au). Since the metal material contains the second metal in addition to Ni, the oxidation resistance and heat resistance of the first current collector are significantly improved. In particular, when the second metal is Sn, the oxidation resistance and heat resistance of the first current collector are further improved, and the electrical conductivity thereof is also improved.

The metal material containing the first metal and the second metal is obtained, for example, by coating at least a part of the surface of a core material containing a metal other than the first metal with a layer containing the first metal and the second metal, or by coating at least a part of the surface of a core material containing the first metal with a layer containing the second metal. In particular, the metal material obtained by the latter method is preferable from the viewpoint of heat resistance and oxidation resistance. Preferably, the ratio of the total amount of the first metal and the second metal to the total amount of the metal material is 80 mass% or more. Further, it is more preferable that the ratio of the total amount of the alloy of the first metal and the second metal to the total amount of the metal material is 80 mass% or more.

From the viewpoint of oxidation resistance and heat resistance, the ratio of the second metal to the total amount of the first metal and the second metal is preferably 4% by mass or more, and more preferably 5% by mass or more. On the other hand, from the viewpoint of heat resistance and conductivity, the ratio of the second metal to the total amount of the first metal and the second metal is preferably 15% by mass or less, and more preferably 10% by mass or less.

When the second metal is Sn, specifically, a Sn-containing layer is formed on the surface of the Ni-containing porous body (Ni porous body) using plating treatment or the like, and then heat treatment is performed under a reducing atmosphere. Thereby, Sn diffuses into the Ni porous body, and a portion of a region from the surface of the porous body to a certain depth becomes a layer made of an alloy of Ni and Sn (hereinafter may be referred to as Ni — Sn layer). The Ni — Sn layer has particularly high heat resistance, oxidation resistance, and electrical conductivity.

In the Ni — Sn layer, the first phase and the second phase may coexist. The concentration of Sn with respect to Ni in the first phase is higher than that in the second phase. In the first phase, Ni and Sn are present as intermetallic compounds (e.g. Ni)₃Sn). The second phase is a phase mainly composed of Ni, and Sn is considered to exist in a form dissolved in Ni. The first phase as the intermetallic compound phase has particularly high oxidation resistance and heat resistance. The second phase exhibits high heat resistance and electrical conductivity.

When the ratio of Sn to the Ni — Sn layer is 4 mass% or more and preferably 5 mass% or more and 15 mass% or less and preferably 10 mass% or less, two phases, i.e., mainly composed of Ni, are easily observed in the Ni — Sn layer₃Intermetallic compound phase (first phase) of Sn) And a phase (second phase) mainly composed of Ni and containing Sn dissolved in Ni. This makes it easy to further improve the heat resistance, oxidation resistance, and electrical conductivity of the Ni — Sn layer.

The form of the porous body is not particularly limited as long as the porous body is made of metal and is porous. Examples of the porous body include a honeycomb structure made of metal, a nonwoven fabric made of metal fibers, a metal mesh, a sponge metal (sintered body), a structure having a skeleton of a three-dimensional network structure made of metal, and the like. In particular, a structure having a skeleton of a three-dimensional network structure made of metal (hereinafter referred to as a three-dimensional network structure) is preferable because the pressure loss thereof is small. Since the three-dimensional network structure allows a gas (oxidant) to pass in an arbitrary direction, the degree of freedom of design increases.

The three-dimensional network structure has a skeleton formed of a fibrous or rod-like metal material forming a network. Such a skeleton may be, for example, the same skeleton as a nonwoven fabric-like or sponge-like structure. The three-dimensional network structure has a plurality of pores defined by the skeleton. Adjacent pores are interconnected. The chromium adsorbent is supported in the pores. In the three-dimensional network structure, such a skeleton made of metal and pores surrounded by the skeleton constitute one unit.

As shown in fig. 1, one cell may be represented as a regular dodecahedron model, for example. The pores 101 are defined by metal portions (fiber portions 102) in a fiber or rod shape. The plurality of pores 101 is three-dimensionally continuous. The skeleton of the unit is formed by continuously extending fiber portions 102. In the unit, substantially pentagonal openings (or windows) 103 each surrounded by the fiber part 102 are formed. Adjacent cells communicate with each other, sharing an opening 103 therebetween. That is, the skeleton of the three-dimensional network structure is constituted by the fiber part 102 extending in a network form while defining the plurality of continuous pores 101. As shown in fig. 2, the fiber part 102 may have a void 102a inside, that is, it may be hollow.

The porous body preferably has a porosity of 70% or more. When the porous body has a porosity of 70% or more, the pressure loss is reduced, and a sufficient amount of the chromium adsorbent is easily supported. On the other hand, from the viewpoint of strength, the porous body preferably has a porosity of 98% or less.

The porosity of the porous body is defined by the formula:

porosity (%) ([ 1- { Mp/(Vp × dp) } × 100

Wherein

And Mp: the mass [ g ] of the porous body,

vp: volume [ cm ] of appearance shape in porous body³]And is and

dp: density of metal constituting porous body [ g/cm ]³]。

The pore diameter of the pores is not particularly limited. The pore diameter may be, for example, 100 to 4000 μm, or may be 200 to 1000 μm. When the pore diameter is within this range, the pressure loss is reduced, and a sufficient amount of the chromium adsorbent is easily loaded.

The pore size of the pores is determined as follows. First, any one of the pores is selected from the three-dimensional network structure, the diameter of the largest sphere (not shown) received in the pore and the diameter of the smallest sphere S (see fig. 1) receiving the pore are measured, and the average thereof is defined as the pore diameter of the selected pore. Likewise, the corresponding pore diameters of any number (e.g., nine) of other pores are determined, and the average of the pore diameters of these ten pores is defined as the pore diameter of the pores in the three-dimensional network structure.

Specifically, in the SEM photograph of the three-dimensional network structure, a region V including ten or more pores was determined. Among the pores contained in the region V, a predetermined number (e.g., 10) of pores are randomly selected and the corresponding pore diameter is determined. The average of the calculated pore diameters of these pores is determined and defined as the pore diameter of the pores in the three-dimensional network structure.

The three-dimensional network structure can be formed, for example, by coating a resin porous body (template) having interconnected pores with a metal. The metal coating can be performed, for example, by a plating treatment method, a vapor phase method (such as evaporation, plasma chemical vapor deposition, or sputtering), coating of a metal paste, or the like. By the metal coating treatment, a skeleton in the form of a three-dimensional network is formed. Among these methods, the metal coating is preferably performed using a plating treatment method.

The plating treatment method may be any plating treatment method capable of forming a metal layer on the surface of the template (the surface including the cavities inside), and a known plating treatment method such as an electroplating method, a molten salt plating method, or the like may be employed. The porous body in the form of a three-dimensional network reflecting the shape of the template is formed by the plating treatment method. That is, the pore diameter of the obtained porous body can be controlled by the pore diameter of the template.

Fig. 3 is an SEM photograph of a cross section of a hollow Ni porous body (three-dimensional network structure) obtained by providing an Sn plating layer on the surface of the porous body and then performing heat treatment in a reducing atmosphere. In the SEM photograph, the upper black portion represents a void, and the lower black portion represents a void inside the fiber portion.

In fig. 3, two phases are observed, namely a portion shown as position 1 and a portion shown as position 2 (in a darker grey color than position 1). In the position 1, Ni, Sn, and O (oxygen) are contained in atomic fractions of 75 atomic%, 18 atomic%, and 7 atomic%, respectively. Thus, position 1 is considered to be the first phase in which most of the Ni and Sn are as intermetallic compounds Ni₃Sn exists in the form of Sn. On the other hand, in position 2, Ni, Sn, and O are contained in atomic fractions of 91 atomic%, 4 atomic%, and 5 atomic%, respectively. Therefore, position 2 is considered to be a second phase in which Sn is contained in a form dissolved in Ni. As can be seen from fig. 3, the metal material as the skeleton is substantially all the Ni — Sn layer.

(chromium adsorbent)

The chromium adsorbent is not particularly limited as long as it is a material that can adsorb chromium. Examples of chromium sorbents include SrNiO₃MgO, BaO, CaO, SrO, etc. The form of the chromium adsorbent is also not particularly limited, and the chromium adsorbent may be, for example, granular or fibrous.

The chromium adsorbent is supported in the pores of the porous body, for example, by immersing the porous body in a slurry in which the chromium adsorbent is dispersed, followed by heat treatment. The loading amount of the chromium adsorbent is not particularly limited, andand is, for example, 0.1g/cm³～1g/cm³。

The size of the chromium adsorbent is not particularly limited, and may be appropriately set according to the size of the pores of the porous body, or the like. The particulate chromium adsorbent has, for example, an average particle diameter of 0.5 to 10 μm. The average particle diameter refers to a particle diameter at which a cumulative volume is 50% in a volume-based particle size distribution measured by a laser diffraction method. The average particle diameter can be calculated from an SEM photograph of a cross section of the chromium adsorbent. Specifically, in the SEM photograph of the chromium adsorbent material, a predetermined number (e.g., 10) of particles of the particulate chromium adsorbent are randomly selected and the corresponding maximum diameter is measured. The average of the measured maximum diameters is determined and defined as the average particle size of the particulate chromium adsorbent.

(method of manufacturing first Current collector)

The first current collector comprising the hollow porous body having a skeleton of a three-dimensional network structure and the chromium adsorbent is manufactured, for example, by the following method.

The method of manufacturing the first current collector includes: a first step of preparing a template having a skeleton of a three-dimensional network structure; a second step of forming a first plating layer containing Ni on at least a part of the surface of the template; a third step of removing the template by heating, thereby obtaining a hollow porous body (Ni porous body) made of a first metal; a fourth step of forming a second plating layer containing a second metal on the surface of the Ni porous body, thereby obtaining a porous body; and a fifth step of causing a chromium adsorbent to be supported in the pores of the porous body.

(1) First step of

A template having a skeleton of a three-dimensional network structure is prepared. As the template, a porous material that can be easily decomposed at a temperature equal to or lower than the melting point of Ni and the second metal is used. As the porous material, a porous resin body is preferable. As the porous resin body, a resin foam, a nonwoven fabric, a felt, a woven fabric, or the like, or a combination thereof can be used.

Among these porous resin bodies, a resin foam is more preferably used as a template having a three-dimensional network structure. Examples of the resin foam include polyurethane foam, polystyrene foam, and the like. In particular, a polyurethane foam is preferable from the viewpoint of high porosity. The thickness, porosity and average pore diameter of the resin foam are appropriately set according to the characteristics of the porous body to be produced. The template is preferably subjected to a conductive treatment so that the template will be easily plated in the second step.

(2) Second step of

Performing a plating treatment on the template to form a first plating layer containing Ni on at least a part of a surface of the template. The plating method of the first metal is not particularly limited as long as it is a process of performing metal plating by a known plating method. However, the electroplating method is preferably used. The plating treatment may be performed according to a conventional method. As the plating bath for Ni plating, a known or commercially available plating bath can be used, and examples thereof include a watt bath, a chloride bath, an aminosulfonic acid bath, and the like. In particular, the nickel sulfamate plating solution has a small plating stress and good coverage, and therefore, flexibility can be ensured even in an intermediate product before heat treatment, and problems such as cracking during the manufacturing process can be suppressed.

The surface of the template is coated with a first plating layer containing Ni by immersing the template in a plating bath, connecting the template with a negative electrode and connecting a counter electrode plate of Ni with a positive electrode, and passing a direct current or a pulsed intermittent current. The coating amount of the first plating layer is not particularly limited, and may be usually set to about 100g/m²About 600g/m²And can be preferably set to about 200g/m²About 500g/m²。

(3) The third step

The template was removed to form a hollow Ni porous body. The template is removed, for example, by placing the template in an oxidizing atmosphere, such as atmosphere, of 600 ℃ or more and 800 ℃ or less, preferably 600 ℃ or more and 700 ℃ or less. Preferably, after the heat treatment in the oxidizing atmosphere, the heat treatment is performed in the reducing atmosphere. Although it is desirable to perform the heat treatment in a reducing atmosphere at as high a temperature as possible, it is only necessary to have a temperature of 750 ℃ or more and 1000 ℃ or less in consideration of the manufacturing cost and the furnace body material of the reduction furnace.

(4) The fourth step

A plating treatment is performed on the Ni porous body to form a second plating layer containing a second metal on at least a part of the surface of the Ni porous body, thereby obtaining a porous body. As in the first plating step, the plating method of the second metal is not particularly limited as long as it is a process of performing metal plating by a known plating method. However, the electroplating method is preferably used. The plating treatment may be performed according to a conventional method.

The second plating layer preferably contains Sn. When the second plating layer is formed on the first plating layer, Ni in the first plating layer diffuses into the second plating layer, and a layer made of an alloy of Ni and the second metal is formed at an interface between the first plating layer and the second plating layer. Alternatively, the first plating layer and the second plating layer as a whole become a Ni — Sn layer. The Ni — Sn layer has particularly high heat resistance and oxidation resistance. A Ni — Sn alloy layer may be plated on the Ni plating layer.

The coating amount of the second plating layer is not particularly limited, and may be usually set to about 10g/m²About 300g/m²And can be preferably set to about 20g/m²About 250g/m². In particular, since 80 mass% or more of the porous body is liable to become a layer made of an alloy of Ni and the second metal, the thickness (coating amount) of the second plating layer may be 0.5 μm to 20 μm (20 g/m)²～200g/m²) Alternatively, the thickness may be 1 μm to 10 μm. In order to promote diffusion of Ni, it is preferable to perform heat treatment after forming the second plating layer.

The formation of the second plating layer containing Sn may be performed using a plating solution containing sulfuric acid and stannous sulfate. The formation of the second plating layer comprising a Ni — Sn alloy can be performed, for example, by performing electroplating treatment using a plating solution comprising stannous chloride, nickel chloride, and potassium pyrophosphate.

(5) The fifth step

The first current collector is obtained by causing a chromium adsorbent to be supported in the pores of the porous body.

For example, the chromium adsorbent is applied to the porous body in the state of a slurry or paste thereof dispersed in a binder resin. The chromium adsorbent may be supported in the pores of the porous body by immersing the porous body in the slurry or the like and then performing heat treatment.

The binder resin is not particularly limited, and examples thereof include polymer binders such as cellulose derivatives (cellulose ethers and the like) such as ethyl cellulose, vinyl acetate-based resins (including saponified vinyl acetate-based resins such as polyvinyl alcohol), and acrylic resins; and waxes, such as paraffin wax.

The heat treatment temperature is also not particularly limited, and is desirably close to the operating temperature of the fuel cell. The heat treatment temperature is, for example, 700 ℃ to 1000 ℃.

The obtained first current collector has a shape reflecting the shape of the template used in the first step. For example, when the template has a sheet shape, a first current collector having a sheet shape is obtained. For example, a first current collector having a sheet shape is cut into a desired shape, and then a plurality of cut sheets are stacked and arranged between a first separator and a positive electrode as needed.

Fig. 4 schematically shows a sectional structure of the fuel cell 100.

The unit cell structure 10 includes a positive electrode 12, a negative electrode 13, and a solid electrolyte layer 14 interposed therebetween. The negative electrode 13 and the positive electrode 12 each have, for example, a flat plate shape, and the unit cell structure 10 also has a flat plate shape. The anode 13 and the solid electrolyte layer 14 are integrated to form an electrolyte layer-electrode assembly 15.

The thickness of the negative electrode 13 is larger than that of the positive electrode 12, and the negative electrode 13 functions as a support that supports the solid electrolyte layer 14 (and thus the unit cell structure 10). However, the thickness of the anode 13 does not necessarily have to be larger than that of the cathode 12. For example, the thickness of the anode 13 may be comparable to that of the cathode 12. Further, although an example in which the anode 13 and the solid electrolyte layer 14 are integrated is shown, the present disclosure is not limited thereto.

The fuel cell 100 also includes the first current collector 121 described above in contact with the cathode 12. The oxidant is supplied to the cathode 12 via the first current collector 121. Since the first current collector 121 has chromium adsorption performance, it is not necessary to dispose an additional chromium adsorption material within the fuel cell. Thereby, an increase in the size of the fuel cell is suppressed, and the number of components can be reduced. In addition, since the first current collector 121 has excellent oxidation resistance, heat resistance, and thermal shock resistance, it can withstand long-term use.

The fuel cell 100 may include an oxidant pocket 123 for supplying an oxidant to the cathode 12, a fuel pocket 133 for supplying a fuel to the anode 13, the first separator 122 having the oxidant pocket 123 formed therein, the second separator 132 having the fuel pocket 133 formed therein, and the second current collector 131 in contact with the anode 13. The oxidant pits 123 in the first separator 122 are arranged to face the positive electrode 12, and the fuel pits 133 in the second separator 132 are arranged to face the negative electrode 13. The fuel is supplied to the anode 13 via the second current collector 131.

Hereinafter, each constituent element of the unit cell structure other than the first current collector will be further described.

(solid electrolyte layer)

The solid electrolyte layer has proton conductivity or oxygen ion conductivity in an intermediate temperature range of 400 to 600 ℃. Due to, for example, BaCe_0.8Y_0.2O_2.9(BCY) and BaZr_0.8Y_0.2O_2.9The perovskite oxides of (BZY) exhibit high proton conductivity in the intermediate-temperature range, and therefore they can be used as solid electrolytes for intermediate-temperature type fuel cells. These solid electrolytes can be formed, for example, by sintering.

The thickness of the solid electrolyte layer is, for example, 1 μm to 50 μm, and preferably 3 μm to 20 μm. When the thickness of the solid electrolyte layer is within such a range, the resistance of the solid electrolyte layer is suppressed to be low, which is preferable. The solid electrolyte layer is sandwiched between the positive electrode and the negative electrode, and has one main surface in contact with the negative electrode and the other main surface in contact with the positive electrode.

(Positive electrode)

The positive electrode has a porous structure. When a proton-conductive solid electrolyte layer is used, a reaction (oxygen reduction reaction) between protons and oxide ions conducted through the solid electrolyte layer proceeds in the positive electrode. The oxide ions are generated by dissociation of an oxidizing agent (oxygen) introduced from the oxidizing agent pits. Examples of the oxidizing agent include a gas containing oxygen, such as air.

As the material for the positive electrode, a known material can be used. As the positive electrode material, for example, compounds containing lanthanum and having a perovskite structure (such as ferrite, manganite, and/or cobaltite) are preferable, and among these compounds, compounds further containing strontium are more preferable. Specifically, examples of the positive electrode material include lanthanum strontium cobalt ferrite (LSCF, La)_{1- x1}Sr_x1Fe_1-y1Co_y1O_3-δ1，0<x1<1，0<y1<1 and δ 1 represents oxygen deficiency), lanthanum strontium manganite (LSM, La)_{1- x2}Sr_x2MnO_3-δ1，0<x2<1, and δ 1 represents oxygen deficiency), lanthanum strontium cobaltite (LSC, La)_1-x3Sr_x3CoO_3-δ1，0<x3 ≦ 1, and δ 1 represents oxygen deficiency), and the like. The positive electrode may contain a catalyst such as Pt from the viewpoint of promoting the reaction between protons and oxide ions. When the positive electrode contains a catalyst, the positive electrode may be formed by mixing the catalyst and the above-described materials and sintering the resultant mixture.

The thickness of the positive electrode is not particularly limited, and may be appropriately set, for example, in the range of 5 μm to 2mm, and may be about 5 μm to about 40 μm.

(cathode)

The negative electrode has a porous structure. In the anode, a reaction (fuel oxidation reaction) is performed in which a fuel such as hydrogen introduced from the fuel pit is oxidized and protons and electrons are released. Examples of fuels include gases containing gases such as hydrogen, methane, ammonia, carbon monoxide, and the like.

As the material for the negative electrode, a known material can be used. Examples of the anode material include nickel oxide (NiO) as a catalyst component and a proton conductor such as yttrium oxide (Y)₂O₃) BCY, BZY, etc.).

The negative electrode can be formed by, for example, sintering the raw material. For example, the negative electrode may be formed by sintering a mixture of NiO powder and proton conductor powder or the like. The thickness of the negative electrode can be set appropriately within a range of, for example, 10 μm to 2mm, and can be 10 μm to 100 μm.

(baffle)

In terms of heat resistance, examples of the material of the first separator and the second separator may include heat-resistant alloys such as stainless steel, nickel-based alloys, chromium-based alloys, and the like. In particular, stainless steel is preferred because it is inexpensive. Since the operating temperature of a Proton Ceramic Fuel Cell (PCFC) is about 400 to about 600 ℃, stainless steel can be used as a material for the separator. When a plurality of unit cell structural bodies are stacked, each separator may contain, for example, dimples (oxidant dimples and fuel dimples) on both sides.

(second Current collector)

In addition to the current collecting function, the second current collector 131 also has a function of supplying the fuel gas introduced from the fuel pocket 133 to the anode 13 in a diffused manner. Therefore, each current collector is preferably a structure having sufficient air permeability.

Examples of the structure for the second current collector include porous bodies, metal meshes, punched metals, expanded metals, and the like containing silver, silver alloys, nickel alloys, and the like. In particular, a porous body is preferable in terms of light weight and air permeability. In particular, a three-dimensional network structure as described above is preferable.

In addition to the use of the above-described unit cell structure, a fuel cell can be manufactured by a known method.

[ examples ]

Hereinafter, the present disclosure will be specifically explained based on examples and comparative examples. However, the present invention is not limited to the following examples.

[ example 1]

(1) Manufacture of the first Current collector

A1.5 mm thick polyurethane sheet was used as a template. Then, 100g of carbon black as amorphous carbon having a particle diameter of 0.01 to 0.2 μm was dispersed in 0.5L of a 10% acrylic resin aqueous solution to prepare an adhesive coating material at this ratio. Subsequently, a template made of polyurethane is immersed in the adhesive coating, pressed between rollers, and then dried. Thereby, a conductive coating is formed on the surface of the template made of polyurethane.

Thereafter, 700g/m was deposited on the template made of polyurethane subjected to the electro-conductive treatment by the electroplating method²To form a first plated layer. As the plating solution, nickel sulfamate plating solution was used.

The nickel-plated template is heated to 650 c under an atmospheric oxidizing atmosphere to remove the template. Subsequently, a reducing atmosphere was formed with a reducing gas using a mixed gas of nitrogen and hydrogen, and reduction treatment was performed at 1000 ℃ to obtain a hollow Ni porous body.

On the surface of the Ni porous body, a second plating layer (70 g/m) containing Sn was formed by an electroplating method²). As the plating solution, a plating solution containing stannous sulfate, sulfuric acid, cresolsulfonic acid, gelatin, and β -naphthol was used. Thereafter, heat treatment was performed at 1000 ℃ for 2 hours under a hydrogen atmosphere. Thereby, a hollow porous body having a skeleton with a three-dimensional network structure including a Ni — Sn layer was obtained. The ratio of Sn in the Ni — Sn layer was 10 mass%. The skeleton of the porous body is substantially entirely composed of the Ni-Sn layer.

Thereafter, the porous body was impregnated with a solution containing SrNiO serving as a chromium adsorbent₃SrO and MnO, and a binder resin, and then dried. Thereafter, heat treatment was performed at 700 ℃ for 2 hours in an atmospheric atmosphere to cause the chromium adsorbent to be supported in the porous body (supporting amount: 0.5 g/cm)³). Thereby, a first current collector (Ni — Sn current collector) was obtained. The mass ratio of the chromium adsorbent was set to SrNiO₃:SrO:MnO＝8:1:1。

(2) Preparation of Fuel cells

NiO (catalyst raw material) is mixed to form ZrO₂And Y₂O₃The YSZ powder of the solid solution of (a) so that 70 mass% of NiO is contained therein, and the mixture is ground and kneaded using a ball mill. The ratio (atomic composition ratio) between Zr and Y in YSZ was set to 90: 10. A slurry containing the obtained mixture (55 mass%) and a binder resin was processed into a 1.0mm thick sheet by a doctor blade methodTo obtain a precursor sheet for the negative electrode. Similarly, a slurry containing the above-described YSZ powder (55 mass%) and a binder resin was processed into a sheet shape of 12 μm thickness by a doctor blade method to obtain a precursor sheet of a solid electrolyte layer.

These precursor sheets were stacked and laminated to obtain a stacked sheet having a total thickness of about 1.0 mm. Then, the obtained stack was heated at 600 ℃ for 1 hour in the atmosphere to remove the binder. Subsequently, co-sintering was performed by performing a heating treatment at 1300 ℃ for 2 hours under an oxygen atmosphere to form an assembly of the anode and the solid electrolyte layer.

Subsequently, on the surface of the solid electrolyte layer, an LSCF paste, which is LSCF (La) as a material for a positive electrode, was screen-printed_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ) And an organic solvent, and firing at 1000 ℃ for 2 hours under an oxygen atmosphere. The formed positive electrode had a thickness of 10 μm.

A first current collector was stacked on the surface of the positive electrode, and a second current collector made of a nickel porous body (Celmet manufactured by sumitomo electrical industries co., thickness: 1mm, porosity: 95 vol%) was stacked on the surface of the negative electrode. Further, a separator made of stainless steel having dimples was stacked on each current collector to manufacture a fuel cell X having the configuration shown in fig. 4.

(3) Evaluation of Oxidation resistance and thermal shock resistance of first Current collector

The first current collector is heat-treated. The heat treatment was performed in five cycles, each cycle including the following temperature increase and decrease.

(temperature increase) the temperature was increased to 600 ℃ at 8 ℃/min and then held for 3 hours.

(temperature reduction) the first current collector was furnace-cooled to 200 ℃, and then the temperature was maintained for 3 hours.

The first current collector (Ni — Sn current collector) before and after the heat treatment was evaluated using an X-ray diffraction (XRD) apparatus. Fig. 5 shows the results. Further, the Ni — Sn current collector before and after the heat treatment was subjected to a compression test according to JIS K7018. Fig. 7 shows the results. Fig. 5 and fig. 6 described later also show peaks of Ni and NiO.

Comparative example 1

A current collector (Ni current collector) and a fuel cell Y were manufactured in the same manner as in example 1, except that the second plating layer was not formed in (1) the manufacture of the first current collector. The obtained Ni current collector was evaluated in the same manner as in example 1. Fig. 6 and 7 show the results.

As can be seen from fig. 5 and 6, when compared with the Ni current collector manufactured in comparative example 1, oxidation of the Ni — Sn current collector manufactured in example 1 was suppressed even after the heat treatment. In addition, in the Ni — Sn current collector, deformation after heat treatment is also suppressed. On the other hand, large deformation (buckling deformation) was observed in the Ni current collector after heat treatment. This is considered to be because the skeleton of the current collector becomes brittle and cracks due to oxidation of Ni to NiO.

Industrial applicability

Current collectors according to embodiments of the present disclosure are particularly suitable for use in SOFCs.

Description of the reference symbols

100: a fuel cell; 10: a unit cell structure; 12: a positive electrode; 13: a negative electrode; 14: a solid electrolyte layer; 15: an electrolyte layer-electrode assembly; 121: a first current collector; 122: a first separator; 123: an oxidant pit; 131: a second current collector; 132: a second separator; 133: a fuel pit; 101: a pore; 102: a fiber part; 102 a: a void; 103: and (4) opening.