JP2011228093A - Method for manufacturing fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a fuel cell, which can suppress cracking and peeling of an electrolyte layer while improving the denseness of the electrolyte layer.SOLUTION: A method for manufacturing a fuel cell includes an arrangement process for arranging a solid oxide electrolyte and an ancillary material on a metal substrate having a gas permeable property, temporally in a different process; and a firing process for firing the solid oxide electrolyte. A melting point or a glass transition point of the ancillary material is below a firing temperature of the firing process. The method is capable of suppressing such as cracking and peeling of the electrolyte layer while improving denseness of the electrolyte layer.

Description

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

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell is excellent in terms of the environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  A solid oxide fuel cell (SOFC) has a structure in which a solid oxide electrolyte is sandwiched between a fuel electrode and an oxygen electrode. In order to reduce the thickness of the solid oxide electrolyte, for example, a solid oxide fuel cell having a structure in which a fuel electrode, a solid oxide electrolyte, and an oxygen electrode are formed on a porous metal substrate as a support substrate Has been developed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 04-160761

  However, in the fuel cell according to Patent Document 1, when firing the solid oxide electrolyte, the solid oxide electrolyte cracks and peels due to the difference in thermal shrinkage between the solid oxide electrolyte and the metal substrate. Etc. may occur. Therefore, it is also conceivable to add a material that becomes liquid when firing the solid oxide electrolyte. However, even when trying to fire the solid oxide electrolyte and the material that becomes liquid at the time of firing at once, due to the difference between the melting point of the material that becomes liquid at the time of firing and the firing temperature of the solid oxide electrolyte, the denseness of the resulting electrolyte layer Decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a fuel cell that can suppress cracking, peeling, and the like of the electrolyte layer while improving the denseness of the electrolyte layer. And

  The method for producing a fuel cell according to the present invention includes a disposing step of disposing a solid oxide electrolyte and an auxiliary material on a gas-permeable metal substrate in separate steps, and firing the solid oxide electrolyte. And a melting point or a glass transition point of the auxiliary material is equal to or lower than a firing temperature of the firing step. In the method for producing a fuel cell according to the present invention, the solid oxide electrolyte and the auxiliary material are arranged in separate steps in time, so that the auxiliary material becomes a liquid phase at the time of firing, thereby reducing the density of the electrolyte layer. While improving, cracking and peeling of the electrolyte layer can be suppressed.

  In the arranging step, the auxiliary material may be arranged on the metal substrate after the arrangement of the solid oxide electrolyte. The arranging step may be a step of alternately laminating the solid oxide electrolyte and the auxiliary material on the metal substrate. The placement step and the firing step include the electrolyte placement step of placing the solid oxide electrolyte on the metal substrate, the electrolyte firing step of firing the solid oxide electrolyte, and the auxiliary in the middle of the electrolyte firing step. And an auxiliary material disposing step of disposing a material on the metal substrate.

  The arranging step may be a step of depositing the solid oxide electrolyte on the metal substrate, and arranging the auxiliary material on the upper surface and the side surface of the deposited solid electrolyte. The placement step includes an electrolyte placement step of placing the solid oxide electrolyte on the metal substrate, an addition step of adding the auxiliary material dissolved in a solvent onto the solid oxide electrolyte, and the auxiliary material. And a drying step for drying.

  The metal substrate may be ferritic stainless steel. The solid oxide electrolyte may be at least one of stabilized zirconia, stabilized ceria, and lanthanum gallate. The auxiliary material may be at least one of carbonate, chloride, fluoride, and glass.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a fuel cell which can suppress the crack of an electrolyte layer, peeling, etc. can be provided, improving the denseness of an electrolyte layer.

FIG. 3 is a production flow diagram for explaining a method for producing a fuel cell according to Example 1; It is a figure for demonstrating the effect in the case of arrange | positioning a solid oxide electrolyte and an auxiliary material in a separate process temporally. 6 is a flowchart for explaining an arrangement process and a baking process according to Example 2. FIG. It is a flowchart for demonstrating the arrangement | positioning process and baking process which concern on Example 3. FIG. It is a flowchart for demonstrating the arrangement | positioning process and baking process which concern on Example 4.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a manufacturing flow diagram for explaining a method of manufacturing a fuel cell according to the first embodiment. As shown to Fig.1 (a), the electrode 20 is arrange | positioned on the metal base material 10 by application | coating etc. As shown in FIG. The metal substrate 10 is a metal material that has gas permeability and can support an electrolyte layer 30 described later. As the metal substrate 10, for example, a porous metal material can be used. Specifically, an iron-based alloy such as stainless steel, a nickel-based alloy, a cobalt-based alloy, or the like can be used as the metal substrate 10. However, since it is preferable that the difference in thermal expansion coefficient between the metal substrate 10 and the electrolyte layer 30 is small, it is preferable to use ferritic stainless steel as the metal substrate 10.

  The material constituting the electrode 20 is not particularly limited as long as it can be used as an anode. For example, Ni / YSZ (yttria stabilized zirconia) cermet (50/50 wt%), Ni / GDC (Gadolinium Doped Ceria) Cermet (50/50 wt%) and the like.

Next, as shown in FIG. 1B, an electrolyte layer 30 is disposed on the electrode 20 by coating or the like. In this embodiment, the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the electrode 20 in separate steps in terms of time. Specifically, the electrolyte layer 30 is disposed on the electrode 20 by alternately laminating the solid oxide electrolyte 31 and the auxiliary material 32. The solid oxide electrolyte 31 is not particularly limited as long as it has oxygen ion conductivity, but 3YSZ (3 mol% Yttrium Stabilized Zirconia), 6YSZ (6 mol% Yttrium Stabilized Zirconia), 8YSZ (8 mol% Yttrium Stabilized). Zirconia), 10YSZ (10 mol% Yttrium Stabilized Zirconia), 8ScSZ (8 mol% Calcium Stabilized Zirconia), 8CaSZ (8 mol% Calcium Stabilized Zirconia) and other stabilized zirconia, Ce _0.9 Gd _0.1 O ₂ , Ce _0.8 Stabilized ceria such as Gd _0.2 O ₂ , Ce _0.8 Sm _0.2 O ₂ , Ce _0.9 Sm _0.1 O ₂ , lanthanum gallate (La _(1-x) Sr _x Ga _{(1-y )} Mg _y O ₃ (x: 0.05 to 0.2, y: 0.05 to 0.2) and the like.

The auxiliary material 32 only needs to have a liquid phase (fluidization) when the solid oxide electrolyte 31 is fired. Accordingly, as the auxiliary material 32, a material having a melting point or a glass transition point not higher than the sintering start temperature of the solid oxide electrolyte 31 can be used. As the auxiliary material 32, for example, Na ₂ CO ₃ , Li ₂ CO ₃ , K ₂ CO ₃ , LiCl, NaCl, KCl, MgCl ₂ , CaCl ₂ , NaF, AlF ₃ , LiCO ₃ / Na ₂ CO ₃ (2/1 mol) Mixed salt), LiCl / KCl (59/41 mol mixed salt), borosilicate glass, soda glass, and the like can be used.

  Table 1 shows examples of materials that can be used as the solid oxide electrolyte 31 and their sintering start temperatures. Table 2 shows examples of materials that can be used as the auxiliary material 32 and their melting points or glass transition points.

The auxiliary material 32 preferably has ionic conductivity. This is because ions can be conducted through both the solid oxide electrolyte 31 and the auxiliary material 32. Therefore, it is preferable that the auxiliary material 32 can conduct at least one ion of O ²⁻ , H ⁺ , and OH ⁻ . Since salt generally has ionic conductivity, it is preferable to use salt in Table 2. In particular, carbonate is suitable for the auxiliary material 32 because it conducts OH ⁻ and H ⁺ .

  Next, as shown in FIG. 1C, the electrolyte layer 30 is subjected to a baking treatment. The firing temperature is set to be equal to or higher than the sintering start temperature of the solid oxide electrolyte 31 and lower than the melting point of the solid oxide electrolyte 31. As the solid oxide electrolyte 31 is sintered, the solid oxide electrolyte 31 is densified. In this case, stress is generated between the solid oxide electrolyte 31 and the metal substrate 10. However, since the melting point or glass transition point of the auxiliary material 32 is equal to or lower than the sintering start temperature of the solid oxide electrolyte 31, the auxiliary material 32 becomes a liquid phase during the firing process. Since the liquid phase auxiliary material 32 can flow in the electrolyte layer 30, the stress accompanying the thermal contraction of the solid oxide electrolyte 31 is relieved.

For example, a Crofer22APU (made by ThyssenKrupp) substrate having a thickness of 0.1 mm can be used as the metal base 10. Further, the electrode 20 can be formed by applying 10 μm of NiO / GDC (Gadolinium Doped Ceria) cermet (1/1 wt) on the metal substrate 10. Application of 6 μm C _0.9 Gd _0.1 O ₂ by colloidal spray method and application of 4 μm Li ₂ CO ₃ / Na ₂ CO ₃ (2/1 mol) mixed salt by screen printing method are repeated three times. Thus, the electrolyte layer 30 can be formed by preparing a green body and subjecting the green body to a firing process at 1000 ° C. for 4 hours in reduced pressure Ar (3 Torr).

Next, as shown in FIG. 1D, an electrode 40 is formed on the electrolyte layer 30. The electrode 40 is not particularly limited as long as it has electrode activity as a cathode. For example, La _0.8 Sr _0.2 CoO ₃ , La _0.8 Sr _0.2 MnO ₃ , La _{0 .8} Sr _0.2 Co _0.5 Fe _0.5 O ₃ or the like.

The fuel cell 100 is completed through the above steps. The fuel cell 100 generates power by the following action. First, hydrogen (H ₂ ) is supplied to the metal substrate 10, and oxygen (O ₂ ) is supplied to the electrode 40. In the electrode 40, oxygen supplied to the electrode 40 and electrons supplied from the external electric circuit react to become oxygen ions. The oxygen ions are transferred to the electrode 20 side through the electrolyte layer 30.

On the other hand, the hydrogen supplied to the metal substrate 10 passes through the metal substrate 10 and reaches the electrode 20. The hydrogen that has reached the electrode 20 emits electrons at the electrode 20 and reacts with oxygen ions conducted through the electrolyte layer 30 from the electrode 40 side to become water (H ₂ O). The emitted electrons are taken out by an external electric circuit. The electrons taken out to the outside are supplied to the electrode 40 after performing electrical work. Power generation is performed by the above operation.

  According to the manufacturing method according to the present embodiment, since the stress between the metal substrate 10 and the electrolyte layer 30 is relieved, cracking, peeling, and the like of the electrolyte layer 30 can be suppressed. Thereby, the power generation failure etc. accompanying the gas permeation in the electrolyte layer 30 can be suppressed.

  2 (a) to 2 (c) explain the effect when the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the metal substrate 10 in a separate process in FIG. 1 (b). It is a figure for doing.

  Here, if the firing temperature is significantly higher than the melting point or glass transition point of the auxiliary material 32, the auxiliary material 32 may corrode the metal substrate 10. Accordingly, the firing temperature is preferably as low as possible. FIG. 2A is a diagram showing firing when the solid oxide electrolyte 31 and the auxiliary material 32 are randomly arranged on the metal substrate 10 and the firing temperature is lowered.

  As shown in FIG. 2A, when the firing temperature is lowered, sintering of the solid oxide electrolyte 31 does not proceed so much, so that densification of the electrolyte layer 30 is suppressed. In the example of FIG. 2A, when the volume of the electrolyte layer 30 after the baking treatment is 100%, the volume of the solid component (solid oxide electrolyte 31) is 20%, and the liquid component (auxiliary material 32). Suppose that the volume of is 20%. In this case, the space occupies 60%. Therefore, densification of the electrolyte layer 30 is suppressed.

  Therefore, in order to form the dense electrolyte layer 30, it is conceivable to increase the volume ratio of the liquid component (auxiliary material 32). FIG. 2B is a diagram showing firing in the case where the volume ratio of the liquid component (auxiliary material 32) is higher than that in FIG. In the example of FIG. 2B, when the volume of the electrolyte layer 30 after the baking treatment is 100%, the volume of the solid component (solid oxide electrolyte 31) becomes 10%, and the liquid component (auxiliary material 32). Suppose the volume of is 30%. In this case, since the volume ratio of the solid component (solid oxide electrolyte 31) is lower than that in FIG. 2A, densification of the electrolyte layer 30 is suppressed.

  On the other hand, by arranging the solid oxide electrolyte 31 and the auxiliary material 32 in separate steps in time as shown in FIG. 1 (b), the portion consisting only of the solid oxide electrolyte 31 is locally distributed. To do. In this case, even if the firing temperature is increased, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed. In the present embodiment, the movement of the auxiliary material 32 is suppressed by the solid oxide electrolyte 31 arranged in layers.

  FIG. 2C shows an example in which the electrolyte layer 30 is baked by the manufacturing method according to this embodiment. Since the firing temperature is high, the sintering of the solid oxide electrolyte 31 proceeds sufficiently. On the other hand, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed. Therefore, the denseness of the electrolyte layer 30 can be improved.

  In order to suppress the movement of the auxiliary material 32 to the metal base material 10, it is preferable to dispose the auxiliary material 32 after the solid oxide electrolyte 31 is disposed on the electrode 20 in the step of FIG. .

  Example 2 shows the other example of the arrangement | positioning process and baking process which concern on Example 1. FIG. FIG. 3 is a flowchart for explaining the arrangement step and the firing step according to the second embodiment. Also in this embodiment, the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the electrode 20 in separate steps in terms of time.

  First, as shown in FIG. 3A, a solid oxide electrolyte 31 is disposed on the metal substrate 10 on which the electrode 20 is formed by coating or the like. Next, as shown in FIG. 3B, the first firing step is performed on the solid oxide electrolyte 31. The firing temperature in the first firing step is set to be equal to or higher than the sintering start temperature of the solid oxide electrolyte 31. Thereby, the solid oxide electrolyte 31 is sintered. The firing process is terminated before the sintering of the solid oxide electrolyte 31 is completed.

  Next, as shown in FIG. 3C, the auxiliary material 32 is added to the solid oxide electrolyte 31 at an atmospheric temperature equal to or higher than the melting point of the auxiliary material 32 or the glass transition point. In this case, the auxiliary material 32 is liquid and added to the solid oxide electrolyte 31. Next, as shown in FIG. 3D, the solid oxide electrolyte 31 is subjected to a second baking process. The firing temperature in this case is a temperature equal to or higher than the melting point of the auxiliary material 32 or the glass transition point.

  Since the solid oxide electrolyte 31 and the auxiliary material 32 are temporally arranged in separate steps, a portion consisting only of the solid oxide electrolyte 31 is locally distributed. Thereby, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed. In particular, since the solid oxide electrolyte 31 is densified by the first firing treatment, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed. As a result, the denseness of the electrolyte layer 30 can be improved. On the other hand, since the sintering of the solid oxide electrolyte 31 is not completed in the first firing treatment, the auxiliary material 32 penetrates into the gaps of the solid oxide electrolyte 31 as shown in FIG. Thereby, the stress accompanying the thermal contraction of the solid oxide electrolyte 31 is relaxed.

  For example, a ZMG232L (made by Hitachi Metals) substrate having a thickness of 0.3 mm can be used as the metal base 10. Also, the electrode 20 can be formed by applying 15 μm of NiO / 8YSZ (6/4 wt) on the metal substrate 10. 8YSZ to which a binder and a solvent are added is formed on the electrode 20 by a screen printing method, formed into a 30 μm film, and subjected to a baking treatment at 1250 ° C. for 24 hours in reduced pressure Ar (2 Torr). Hold at atmospheric pressure for 3 hours. During this holding time, the electrolyte layer 30 can be formed by gently dropping molten LiCl into 8YSZ.

  Thereafter, as shown in FIG. 3E, an electrode 40 is formed on the electrolyte layer 30. The fuel cell 100 is completed through the above steps. According to the present embodiment, cracking and peeling of the electrolyte layer 30 can be suppressed while improving the denseness of the electrolyte layer 30.

  Example 3 shows another example of the arrangement step and the firing step of Example 1. FIG. 4 is a flowchart for explaining an arrangement process and a baking process according to the third embodiment. Also in this embodiment, the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the electrode 20 in separate steps in terms of time. First, as shown in FIG. 4A, the solid oxide electrolyte 31 is disposed on the metal substrate 10 on which the electrode 20 is formed by coating or the like. In this case, for example, the solid oxide electrolyte 31 is disposed so as to occupy a region where the electrolyte layer 30 should exist after firing.

  Next, as shown in FIG. 4B, the auxiliary material 32 is disposed on the upper surface and each side surface of the solid oxide electrolyte 31. Next, as shown in FIG. 4C, the solid oxide electrolyte 31 is subjected to a firing process at a temperature equal to or higher than the sintering start temperature of the solid oxide electrolyte 31. In this case, since the part consisting only of the solid oxide electrolyte 31 is locally distributed, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed, while the auxiliary material 32 in liquid phase is solid oxide. It penetrates into the gaps in the electrolyte 31. As a result, as shown in FIG. 4D, the denseness of the electrolyte layer 30 is improved, and the stress accompanying the thermal contraction of the solid oxide electrolyte 31 is relieved.

  For example, as the metal base material 10, a SUS430 substrate having a thickness of 0.2 mm can be used. Also, the electrode 20 can be obtained by applying 20 μm of NiO / 8YSZ (6/4 wt) on the metal substrate 10. Next, an 8YSZ green sheet having a thickness of 20 μm is adhered on the electrode 20 as an electrolyte, and a LiCl / KCl (59/41 mol) mixed salt is formed to a thickness of 5 μm by dip coating so as to wrap the upper surface and side surfaces of the electrolyte. The electrolyte layer 30 can be formed by subjecting the electrolyte to baking at 1300 ° C. for 10 hours in reduced pressure Ar (1 Torr).

  Thereafter, as shown in FIG. 4E, the electrode 40 is formed on the electrolyte layer 30. The fuel cell 100 is completed through the above steps. According to the present embodiment, cracking and peeling of the electrolyte layer 30 can be suppressed while improving the denseness of the electrolyte layer 30.

  Example 4 shows the other example of the arrangement | positioning process of Example 1, and a baking process. FIG. 5 is a flowchart for explaining an arrangement process and a baking process according to the fourth embodiment. Also in this embodiment, the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the electrode 20 in separate steps in terms of time. First, as shown in FIG. 5A, a solid oxide electrolyte 31 is disposed on the metal substrate 10 on which the electrode 20 is formed by coating or the like.

  Next, as shown in FIG. 5B, the auxiliary material 32 dissolved in the solvent is added to the solid oxide electrolyte 31. As a solvent in this case, the auxiliary material 32 is liquid at a temperature (for example, room temperature) when the auxiliary material 32 is added to the solid oxide electrolyte 31, and the auxiliary material 32 can be dissolved. Those which decompose into a gas phase are preferred. For example, water, ethanol, isopropyl alcohol, or the like can be used.

  Next, as shown in FIG. 5C, the auxiliary material 32 is dried. In the present embodiment, since the solid oxide electrolyte 31 and the auxiliary material 32 are arranged on the electrode 20 in separate steps in time, the portion consisting only of the solid oxide electrolyte 31 is locally distributed. Thereby, the movement of the auxiliary material 32 to the metal substrate 10 is suppressed, while the auxiliary material 32 in the liquid phase penetrates into the gaps of the solid oxide electrolyte 31. Next, the solid oxide electrolyte 31 is baked. In this case, as shown in FIG. 5 (d), the denseness of the electrolyte layer 30 is improved and the stress accompanying the thermal contraction of the solid oxide electrolyte 31 is relieved.

For example, a Crofer22APU (made by ThyssenKrupp) substrate having a thickness of 0.1 mm can be used as the metal base 10. Further, the electrode 20 can be formed by applying 10 μm of NiO / GDC (Gadolinium Doped Ceria) cermet (1/1 wt) on the metal substrate 10. 20 μm C _0.9 Gd _0.1 O ₂ is applied as an electrolyte by a colloidal spray method, and an NaCl (5 wt%) aqueous solution is dropped / impregnated into the electrolyte and dried at 120 ° C. for 1 hour. This impregnation / drying treatment is repeated three times, and the treated electrolyte is subjected to a baking treatment at 1000 ° C. for 10 hours in the air. Thereby, the electrolyte layer 30 can be formed.

  Thereafter, as shown in FIG. 5E, the electrode 40 is formed on the electrolyte layer 30. The fuel cell 100 is completed through the above steps. According to the present embodiment, cracking and peeling of the electrolyte layer 30 can be suppressed while improving the denseness of the electrolyte layer 30.

  In addition, although the fuel cell which concerns on each said Example has a structure where the anode, the electrolyte membrane, and the cathode were arrange | positioned in order on the metal base material, you may have the structure of reverse arrangement | positioning. Even in this case, cracking and peeling of the electrolyte membrane can be suppressed while suppressing the corrosion of the oxide film of the metal material during the firing of the electrolyte membrane.

DESCRIPTION OF SYMBOLS 10 Metal base material 20 Electrode 30 Electrolyte layer 31 Solid oxide electrolyte 32 Auxiliary material 40 Electrode 100 Fuel cell

Claims (9)

An arrangement step of disposing a solid oxide electrolyte and an auxiliary material in a separate process in time on a metal substrate having gas permeability,
A firing step of firing the solid oxide electrolyte,
The auxiliary material has a melting point or glass transition point which is not higher than a firing temperature in the firing step.   2. The method of manufacturing a fuel cell according to claim 1, wherein, in the arranging step, the auxiliary material is arranged on the metal substrate after the arrangement of the solid oxide electrolyte.   3. The method of manufacturing a fuel cell according to claim 1, wherein the arranging step is a step of alternately laminating the solid oxide electrolyte and the auxiliary material on the metal substrate. The arranging step and the firing step are:
An electrolyte disposing step of disposing the solid oxide electrolyte on the metal substrate;
An electrolyte firing step of firing the solid oxide electrolyte;
The method for manufacturing a fuel cell according to claim 1, further comprising an auxiliary material arranging step of arranging the auxiliary material on the metal substrate in the middle of the electrolyte baking step.   2. The arranging step is a step of depositing the solid oxide electrolyte on the metal substrate and disposing the auxiliary material on the upper surface and side surfaces of the deposited solid electrolyte. Or the manufacturing method of the fuel cell of 2. The arrangement step includes
An electrolyte disposing step of disposing the solid oxide electrolyte on the metal substrate;
An addition step of adding the auxiliary material dissolved in a solvent onto the solid oxide electrolyte;
The method for producing a fuel cell according to claim 1, further comprising a drying step of drying the auxiliary material.   The method for manufacturing a fuel cell according to claim 1, wherein the metal base material is ferritic stainless steel.   The method for producing a fuel cell according to claim 1, wherein the solid oxide electrolyte is at least one of stabilized zirconia, stabilized ceria, and lanthanum gallate.   The fuel cell manufacturing method according to claim 1, wherein the auxiliary material is at least one of carbonate, chloride salt, fluoride salt, and glass.

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