JP2014072115A - Method for manufacturing fuel cell - Google Patents

Abstract

An increase in the interface resistance of a fuel cell can be suppressed.
A method of manufacturing a fuel cell having an intermediate layer (118) between an anode layer (116) and an electrolyte layer (112), wherein the intermediate layer (118) is laminated on the anode layer (116) and then fired at 1400 degrees Celsius or higher. And a step of firing at 1300 degrees Celsius or higher after the electrolyte layer 112 is laminated on the intermediate layer 118.
[Selection] Figure 4

Description

  The present invention relates to a method for manufacturing a fuel cell.

  A fuel cell system using a fuel cell that generates power by an electrochemical reaction between an anode gas and a cathode gas as an energy source has attracted attention. This fuel cell includes a solid oxide fuel cell using an oxide film as an electrolyte membrane.

  In recent years, a technique for providing an intermediate layer between an electrolyte layer and an anode layer has been proposed. For example, in the technique described in Patent Document 1 below, an intermediate layer is provided between a lanthanum gallate electrolyte layer and a nickel anode layer. By providing this intermediate layer, generation of a layer formed of impurities or a layer that increases electrical resistance is prevented by mutual diffusion or chemical reaction of metal elements between the electrolyte layer and the anode layer.

JP 2011-142042 A JP 2011-216464 A JP 2009-016109 A

  By the way, in the said patent document 1, the anode layer, the intermediate | middle layer, and the electrolyte layer are formed with the following method. A suspension of a mixed powder of LSGM powder and LDC powder as an intermediate layer is applied on a nickel-based anode layer in a pre-sintered state and dried, and then a suspension of LSGM powder as an electrolyte layer on the coated surface. Apply liquid. This laminate is heated at 1400 degrees Celsius for 6 hours for co-sintering.

  However, in the method described in Patent Document 1, a layer containing nickel is formed between LDC and LSGM during co-sintering. This layer has a problem that the interface resistance increases. In addition, it is estimated that the mechanism in which the layer containing Ni is generated is as follows. NiO (nickel oxide) in the anode layer diffuses to the LSGM side through the grain boundary of the LDC. The NiO reacts with Mg (magnesium) of LSGM. As a result of the reaction, a layer containing Ni is formed between LDC and LSGM.

  Therefore, a technique capable of suppressing an increase in interface resistance has been desired in a method for producing a fuel cell containing LSGM and LDC. In addition, in the conventional fuel cell manufacturing method, it has been desired to save resources, facilitate manufacturing, improve manufacturing accuracy, improve workability, and the like.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one form of this invention, the manufacturing method of a fuel cell is provided. This fuel cell manufacturing method is a method of manufacturing a fuel cell having an intermediate layer between an anode layer and an electrolyte layer, and the step of firing the anode layer and the intermediate layer at 1400 degrees Celsius or higher; And, after applying the electrolyte layer to the intermediate layer, firing at 1300 degrees Celsius or higher. According to the fuel cell manufacturing method of this embodiment, the firing of LDC is advanced and the grain growth of metal particles is promoted. This increases the particle diameter of the metal particles and reduces the grain boundaries. As a result, diffusion of NiO can be suppressed and increase in interface resistance can be suppressed.

  Note that the present invention can be realized in various modes. The present invention can be realized, for example, in the form of a solid oxide fuel cell in addition to a form as a slurry for forming an intermediate layer in SOFC, a form as an MEA and a production method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows schematic structure of the fuel cell 100 as embodiment of this invention with a perspective view. Explanatory drawing which shows the schematic cross section of the membrane electrode assembly 110 along the 2-2 line in FIG. 1 with the mode of a composition of each layer. Explanatory drawing which shows the manufacture procedure of laminated body S1 which consists of the anode electrode 116 intermediate | middle layer 118 electrolyte layer 112. FIG. Explanatory drawing which shows the manufacturing procedure of laminated body S2 which consists of the anode electrode 116 intermediate | middle layer 118 electrolyte layer 112. FIG. Explanatory drawing which shows the manufacture procedure of laminated body S3 which consists of the anode electrode 116 intermediate | middle layer 118 electrolyte layer 112. FIG. 4 is an explanatory diagram showing the concentration of Ni diffused and permeated into the electrolyte layer 112 (Ni concentration) and the IR (resistance value Ω per cm ² ) between the cathode electrode 114 and the anode electrode 116. FIG.

A. Embodiment:
A1. Fuel cell configuration:
FIG. 1 is an explanatory view showing a schematic configuration of a fuel cell 100 as an embodiment of the present invention in a perspective view. FIG. 2 is an explanatory view showing a schematic cross section of the membrane electrode assembly 110 along the line 2-2 in FIG. 1 together with the composition of each layer.

  As shown in FIG. 1, the fuel cell 100 includes a stack in which a plurality of membrane electrode assemblies 110 and separators 120 are stacked after a membrane electrode assembly 110 is sandwiched between separators 120 with a collector layer (not shown) interposed therebetween. It has a structure. The membrane electrode assembly 110 has a configuration in which an electrolyte layer 112 is sandwiched between a cathode electrode 114 and an anode electrode 116, and an intermediate layer 118 is provided between the electrolyte layer 112 and the anode electrode 116 on the anode electrode 116 side. The current collector layers (not shown) arranged above and below the membrane electrode assembly 110 in FIG. 1 have a current collecting function. Further, the current collector layer has a function of diffusing and supplying oxidizing gas or fuel gas to the cathode electrode 114 and the anode electrode 116. The anode electrode 116 can also be held by a reinforcing plate material (not shown), and the reinforcing plate material in this case has gas permeability.

As shown in FIG. 2, the electrolyte layer 112 constituting the membrane electrode assembly 110 is a lanthanum galide-based solid oxide electrolyte layer having oxygen ion conductivity. In the present embodiment, the electrolyte layer 112 is formed of a perovskite solid oxide, specifically, for example, La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O ₃ (hereinafter referred to as LSGM). The electrolyte layer 112 is formed into a thin film having a thickness of about 0.01 mm through coating, drying, and firing of a slurry in which LSGM is finely divided and dispersed in an appropriate solvent. The membrane electrode assembly 110 of the present embodiment has a relatively low temperature range of 800 ° C. or lower due to the reduction of the membrane resistance accompanying the thinning of the electrolyte layer 112 and the temperature range of oxygen ion conductivity based on the composition. It will be possible to generate electricity.

The cathode electrode 114 constituting the membrane electrode assembly 110 together with the electrolyte layer 112 is formed using, for example, a lanthanum (La) perovskite, for example, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (hereinafter referred to as LSCF). Electrode. The cathode electrode 114 is formed into a thin film having a thickness of about 0.01 mm through coating, drying and firing of a slurry in which LSCF is finely divided and dispersed in an appropriate solvent. The cathode electrode 114 diffuses oxygen contained in an oxidizing gas (for example, air) supplied from an oxidizing gas channel 121 (FIG. 1) of the separator 120 described later into the electrolyte layer 112.

The anode electrode 116 constituting the membrane electrode assembly 110 together with the electrolyte layer 112 is an electrode formed by blending nickel (Ni) in the form of nickel oxide (NiO), for example, with an electrolyte layer forming material of 60 wt%. . The electrolyte forming material in this case is composed of ceria (CeO ₂ ) doped with gadolinium (Gd) (hereinafter referred to as GDC), and NiO is blended with this GDC to form the anode electrode 116 (hereinafter referred to as NiO). -Referred to as GDC).

  This anode electrode 116 is formed into a thin film of about 0.3 mm through coating / drying and firing of a slurry obtained by finely pulverizing NiO-GDC and dispersing it in an appropriate solvent. The anode electrode 116 diffuses hydrogen contained in a fuel gas (for example, hydrogen gas) supplied from a fuel gas flow path 122 (FIG. 1) of the separator 120 described later into the electrolyte layer 112.

  Due to the above gas supply on the anode side and cathode side and the reaction of the fuel component at the anode electrode 116, the membrane electrode assembly 110 causes an electrochemical reaction between hydrogen and oxygen using the oxygen ion conductivity of the electrolyte layer 112. Generate electricity. A catalyst layer containing a carrier carrying a catalyst such as platinum may be formed at the anode electrode interface on the electrolyte layer 112 side, and a carrier carrying a catalyst may be blended in the electrolyte layer 112. Also good. The same applies to the cathode electrode 114.

The intermediate layer 118 formed between the membrane electrode assembly 110 and the anode electrode 116 is an intermediate layer formed from ceria (CeO ₂ ) (hereinafter referred to as LDC) doped with lanthanum (La). The intermediate layer 118 is formed into a thin film having a thickness of about 0.005 mm through coating / drying of a slurry dispersed in an appropriate solvent and firing thereof. The formation of the intermediate layer 118, the electrolyte layer 112, and the anode electrode 116 will be further described later.

  Since the electrolyte layer 112 has MgO that has a high solid solubility with nickel oxide, Ni that is a constituent element of the anode electrode 116 is solid-solution trapped in the firing process described later. For this reason, the intermediate layer 118 includes an LDC layer and a (Ni, Mg) O layer as a state after Ni solid solution trapping in FIG.

The separator 120 (FIG. 1) has one surface in contact with the cathode electrode 114 of one membrane electrode assembly 110 and the other surface bonded to the anode electrode 116 of the other membrane electrode assembly 110. The separator 120 includes an oxidizing gas channel 121 on the cathode electrode 114 side and a fuel gas channel 122 on the anode electrode 116 side, and these two channels intersect each other as shown in FIG. The separator 120 is required to have a function of electrically connecting the membrane electrode assembly 110 in series and a function of physically separating the fuel gas and the oxidizing gas. For this reason, it is comprised with the dense material which has electrical conductivity. Specifically, a ceramic material such as LaCrO ₃ or a metal material such as SUS is used. However, in order to reduce contact resistance, it is desirable to form the same material as the current collector in contact with the separator 120. In addition, a coolant channel may be provided in the separator 120. The fuel cell 100 includes a single cell serving as a power generation unit including the upper and lower separators 120 in FIG.

  Although not shown in FIG. 1, a fuel gas supply manifold, a fuel gas discharge manifold, an oxidizing gas supply manifold, and an oxidizing gas discharge manifold that penetrate the fuel cell stack in the stacking direction are provided in the fuel cell stack. It has been. When fuel gas is supplied to the fuel cell stack, the fuel gas is distributed to the fuel gas flow path through the fuel gas supply manifold and used for the electrochemical reaction, and then gathers in the fuel gas discharge manifold. Guided outside. Further, when the oxidizing gas is supplied to the fuel cell stack, the oxidizing gas is distributed to the oxidizing gas flow path via the oxidizing gas supply manifold and used for the electrochemical reaction, and then gathers in the oxidizing gas discharge manifold. To the outside. As the fuel gas, for example, high purity hydrogen gas can be used, and as the oxidizing gas, for example, air can be used.

  FIG. 3 is an explanatory diagram showing a manufacturing procedure of the laminate S1 including the anode electrode 116, the intermediate layer 118, and the electrolyte layer 112.

  First, the slurry of the anode electrode 116 made of the above-described forming material is applied to, for example, one surface of a reinforcing plate. Next, the slurry of the intermediate layer 118 is applied so as to be laminated on the anode electrode 116. The laminated body in this state is referred to as a laminated body S1a and is shown in FIG. About this laminated body, 1st baking is performed in a baking apparatus at 2300 degrees Celsius for 2 hours. The state after this processing is referred to as a stacked body S1b in FIG. Thereafter, after the multilayer body S1b is cooled, the slurry of the electrolyte layer 112 is applied to the intermediate layer 118 side in the multilayer body S1b. The laminated body in this state is referred to as a laminated body S1c and is shown in FIG.

  Next, the stacked body S1c is subjected to second baking at 1300 degrees Celsius for 2 hours in a baking apparatus. Let the laminated body produced in this method be the laminated body S1. In the intermediate layer 118 of the stacked body S1, in addition to the LDC layer 118a, a (Ni, Mg) O layer 118b is formed on the electrolyte layer 112 side. The electrolyte layer 112 has MgO having high solid solubility with nickel oxide. For this reason, Ni, which is a constituent element of the anode electrode 116, is solid-solved as (Ni, Mg) O at the grain boundary that occurs as the electrolyte layer 112 is fired, so that the (Ni, Mg) O layer 118b is formed. Is done.

  FIG. 4 is an explanatory diagram showing a manufacturing procedure of the laminate S2 including the anode electrode 116, the intermediate layer 118, and the electrolyte layer 112.

  First, similarly to the laminated body S1, a slurry of the anode electrode 116 made of the above-described forming material is applied to one surface of a reinforcing plate, for example. Next, the slurry of the intermediate layer 118 is applied so as to be laminated on the anode electrode 116. The laminated body in this state is referred to as a laminated body S2a and is shown in FIG.

  The stacked body S2a is subjected to first baking at 1400 degrees Celsius for 2 hours in a baking apparatus. The state after the completion of this process is referred to as a stacked body S2b in FIG. Thereafter, after the multilayer body S2b is cooled, the slurry of the electrolyte layer 112 is applied to the intermediate layer 118 side in the multilayer body S2b. The laminated body in this state is referred to as a laminated body S2c and is shown in FIG.

  Next, the stacked body S2c is subjected to second baking at 1300 degrees Celsius for 2 hours in a baking apparatus. Let the laminated body produced in this method be the laminated body S2. Also in the intermediate layer 118 of the stacked body S2, the (Ni, Mg) O layer 118b is formed on the electrolyte layer 112 side. The stacked body S1 and the stacked body S2 have different temperatures in the first firing.

  FIG. 5 is an explanatory diagram showing a manufacturing procedure of the laminate S3 including the anode electrode 116, the intermediate layer 118, and the electrolyte layer 112.

  First, similarly to the laminated body S1, a slurry of the anode electrode 116 made of the above-described forming material is applied to one surface of a reinforcing plate, for example. Thereafter, the slurry of the intermediate layer 118 is applied so as to be laminated on the anode electrode 116.

  Next, in the laminated body of the anode electrode 116 and the intermediate layer 118, the slurry of the electrolyte layer 112 is applied to the intermediate layer 118 side. The state after the completion of this process is referred to as a laminate S3a in FIG.

  The stacked body S3a is fired at 1400 degrees Celsius for 2 hours in a firing apparatus. Let the laminated body produced in this method be the laminated body S3. Also in the intermediate layer 118 of the stacked body S3, the (Ni, Mg) O layer 118b is formed on the electrolyte layer 112 side. Note that the number of firings is different between the stacked body S2 and the stacked body S3. In the laminate S2, firing is performed twice, but in the laminate S3, firing is performed only once.

  Thereafter, the laminates S1, S2, and S3 are coated with the slurry of the cathode electrode 114 on the electrolyte layer 112 side and fired at 1300 degrees Celsius for 2 hours. The membrane electrode assemblies 110 formed from the stacked bodies S1, S2, and S3 are referred to as cell A, cell B, and cell C, respectively.

  The manufacturing procedure of the fuel cell 100 is as follows. First, current collector layers (not shown) are disposed on both sides of the membrane electrode assembly 110 as shown in FIG. Then, this and the separator 120 are arrange | positioned alternately. Then, end plates (not shown) are arranged above and below. Finally, these are fastened with a fastener in the stacking direction to obtain the fuel cell 100.

The characteristics of the fuel cell 100 thus obtained, specifically, the membrane electrode assembly 110 will be described. FIG. 6 shows the concentration of Ni diffused and permeated into the electrolyte layer 112 (Ni concentration) and the IR (resistance value Ω per cm ² ) between the cathode electrode 114 and the anode electrode 116 in an unloaded state for each cell. It shows.

Ni concentration and IR were measured as follows. First, the membrane electrode assembly 110 is used as a measurement cell sandwiched between upper and lower separators 120. The measurement cell is placed at an operating temperature of 600 ° C., and then fuel gas and oxidizing gas are supplied to the cathode electrode 114 and the anode electrode 116. The operation was continued for 3 hours. Then, IR (resistance value Ω per cm ² ) between the cathode electrode 114 and the anode electrode 116 was measured. After the operation was completed, the electrolyte layer 112 was disassembled and taken out, and the Ni concentration was determined using an element analyzer. The Ni concentration was obtained by dividing the number of Ni atoms contained in the electrolyte layer 112 by the total number of atoms of La, Sr, Ga, and Mg that are constituent elements of the electrolyte layer 112.

  By this measurement, the cell B which is an embodiment of the present invention showed lower results for the Ni concentration and IR than the cell A and cell C. From this result, the following can be said. That is, according to the manufacturing method of the cells A and B, unlike the manufacturing method of the cell C, the anode electrode 116 and the intermediate layer 118 are fired before the electrolyte layer 112 is applied. For this reason, the firing of the intermediate layer 118 proceeds, and the grain growth of the metal particles is promoted.

  In addition, the manufacturing method of the cell B has a higher firing temperature for the first firing than the manufacturing method of the cell A. For this reason, the grain growth of the metal particles due to the firing of the intermediate layer 118 is further promoted than the cell A. By promoting the grain growth of the metal particles, the particle diameter of the metal particles becomes larger and the grain boundaries decrease. Thereby, it is presumed that the movement of Ni is suppressed, the ratio of the (Ni, Mg) O layer is reduced, and the IR is reduced.

  The “step of firing at 1400 ° C. or higher” described in the means for solving the problem corresponds to “first firing” in the present embodiment. The “step of firing at 1300 degrees Celsius or higher” corresponds to “second firing”. The “anode layer” corresponds to an “anode electrode”.

B. Variations:
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and can be implemented in various modes without departing from the scope of the present invention. For example, the following modifications are possible.

B1. Modification 1:
In the above embodiment, the firing time is 2 hours, but the present invention is not limited to this. That is, the firing time can be changed because it varies depending on the volume and form of the material to be fired.

B2. Modification 2:
In the above embodiment, after the step of firing the anode electrode 116 and the intermediate layer 118, the step of firing the intermediate layer 118 and the electrolyte layer 112 is performed. However, the present invention is not limited to this. That is, after the step of firing the intermediate layer 118 and the electrolyte layer 112, the step of firing the anode electrode 116 and the intermediate layer 118 may be performed.

DESCRIPTION OF SYMBOLS 100 ... Fuel cell 110 ... Membrane electrode assembly 112 ... Electrolyte layer 114 ... Cathode electrode 116 ... Anode electrode 118 ... Intermediate layer 118a ... LDC layer 118b ... (Ni, Mg) O layer 120 ... Separator 121 ... Oxidation gas flow path 122 ... Fuel gas flow path A ... cell B ... cell C ... cell S1 ... laminate S1a ... laminate S1b ... laminate S1c ... laminate S2 ... laminate S2a ... laminate S2b ... laminate S2c ... laminate S3 ... laminate S3a ... Laminated body

Claims (1)

A method of manufacturing a fuel cell having an intermediate layer between an anode layer and an electrolyte layer,
After laminating the intermediate layer on the anode layer, firing at 1400 degrees Celsius or higher,
And a step of firing at 1300 degrees Celsius or higher after laminating the electrolyte layer on the intermediate layer.

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