KR20100134347A - Anode-supported electrolyte for solid oxide fuel cell and manufacturing method of the same - Google Patents

Abstract

PURPOSE: A method for manufacturing an anode-supported electrolyte is provided to lower a firing temperature of electrolyte by adding a small amount of γ-Al2O3 to YSZ powder and to reduce time and cost required for manufacturing unit cells. CONSTITUTION: A method for manufacturing an anode-supported electrolyte comprises the steps of: forming a first slurry; forming a fuel electrode support layer sheet using the first slurry; forming a second slurry; forming a reactive layer sheet using a second slurry; forming an electrolytic slurry; forming the electrolytic sheet using the electrolytic slurry; forming a laminate by successively laminating an anode support layer sheet, an anode reactive layer sheet, and the electrolytic sheet; forming a green sheet by laminating the laminate; removing a solvent and a binder through calcinations of the green sheet; and plasticizing the green sheet in which calcination is completed.

Description

Anode-supported electrolyte for a solid oxide fuel cell and a method of manufacturing the same {ANODE-SUPPORTED ELECTROLYTE FOR SOLID OXIDE FUEL CELL AND MANUFACTURING METHOD OF THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit cell constituting a stack of planar solid oxide fuel cells. The present invention relates to a fuel cell support electrolyte of a solid oxide fuel cell capable of simultaneously firing an anode support and an electrolyte at a low temperature, and It is to provide a manufacturing method.

A fuel cell is defined as a cell that has the ability to produce direct current by converting the chemical energy of fuel (hydrogen) directly into electrical energy, and through the oxide electrolyte, oxidant (eg oxygen) and gaseous fuel (eg For example, as an energy conversion device for producing direct current electricity by electrochemically reacting hydrogen), unlike the conventional battery, it is characterized by continuously producing electricity by supplying fuel and air from the outside.

Fuel cell types include molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs) operating at high temperatures, and phosphoric acid fuel cells operating at relatively low temperatures. Cell, PAFC), Alkaline Fuel Cell (AFC), Proton Exchange Membrane Fuel Cell (PEMFC), Direct Methanol Fuel Cells (DEMFC).

Solid oxide fuel cell generates electricity directly from fuel by electrochemical reaction of fuel (hydrogen) and oxygen (air) at high temperature of 600 ~ 1000 ℃. It is the highest generation efficiency among fuel cells and uses cogeneration by using waste heat. It is easy to generate power, has the potential to be a high performance, clean and efficient power supply, and is being developed for various power generation applications.

The planar solid oxide fuel cell is formed of a multilayer stack of unit cells composed of an anode, an electrolyte, and a cathode. As a unit cell of a conventional solid oxide fuel cell, a composite of nickel oxide (hereinafter referred to as 'NiO') and yttria stabilized zirconia (hereinafter referred to as 'YSZ') is used as the anode. the electrolyte is a YSZ used, the air electrode is a strontium-doped lanthanum broken (referred to as lanthanum strontium Manganite, hereinafter, 'LSM') nitro _{(La 0 .8 Sr 0 .2 MnO} 3) and YSZ of composite is used.

However, when the unit cell of the solid oxide fuel cell is manufactured, even though the anode and the electrolyte have similar firing temperatures, the thermal expansion coefficients may be different, which may cause warpage or cracks during simultaneous firing. There is difficulty. In particular, the warpage or crack of the unit cell increases as the area of the unit cell increases. Due to this problem, the conventional unit cell is manufactured by firing the anode, the electrolyte, and the cathode, respectively, or by firing the anode first and then baking the electrolyte by coating the electrolyte on the anode, and then firing the coating by applying the cathode. The existing unit cell manufacturing method has a problem that not only the process is complicated but also requires a lot of time and manpower, and the production cost increases. In particular, as the size of the unit cell increases, it is difficult to coat the electrolyte thinly and uniformly, making it difficult to manufacture a large area unit cell and deteriorating performance.

In addition, in the case of the existing electrolyte, since the firing temperature is higher than 1400 ° C., there is a problem in that the time is long when manufacturing the unit cell.

Embodiments of the present invention for solving the above problems in the production of a unit cell constituting a stack of a solid oxide fuel cell, to provide a cathode support type electrolyte that can simultaneously fire the anode and the electrolyte and a method for manufacturing the same will be.

In addition, embodiments of the present invention to provide a cathode support type electrolyte capable of low-temperature firing by lowering the firing temperature of the electrolyte and a method of manufacturing the same.

According to embodiments of the present invention for achieving the above object of the present invention, a method for producing a cathode support type electrolyte of a solid oxide fuel cell capable of co-firing at low temperatures, nickel oxide (NiO) and yttria stabilized zirconia (YSZ) mixing to form a first slurry, forming a cathode support layer sheet using the first slurry, mixing NiO and YSZ to form a second slurry, using the second slurry Forming a cathode reaction layer sheet, mixing YSZ and gamma aluminum oxide (γ-Al ₂ O ₃ ) to form an electrolyte slurry, forming an electrolyte sheet using the electrolyte slurry, the anode support layer sheet, Sequentially stacking the anode reaction layer sheet and the electrolyte sheet to form a laminate, and laminating the laminate. Drawn to form a sheet, and calcined (calcinations) of the green sheet may be formed of a step and the firing step of the calcination the lean sheet is completed to remove the solvent and binder.

In an embodiment, the electrolyte slurry may be formed by mixing 0.2 wt% of γ-Al ₂ O ₃ with the YSZ.

In an embodiment, the electrolyte sheet is formed to a thickness of 1 to 5㎛, the laminate may be stacked one sheet of the electrolyte sheet. In addition, the firing step may be baked by pressing the calcination is completed to a load of 35 to 40kgf / ㎠ at 1200 to 1300 ℃.

On the other hand, according to other embodiments of the present invention for achieving the above object of the present invention, the anode support type electrolyte of a solid oxide fuel cell capable of low-temperature co-fired, is formed of NiO / YSZ cermet mixed with NiO and YSZ The anode support layer, the anode reaction layer stacked on the anode support layer and formed of NiO / YSZ cermet, and the electrolyte layer stacked on the anode reaction layer and formed by mixing the YSZ and γ-Al ₂ O ₃ are formed. Here, the anode support layer, the anode reaction layer, and the electrolyte layer may be co-fired.

In an embodiment, the electrolyte may be formed by mixing γ-Al ₂ O ₃ to 0.2wt% of the YSZ. And it can be baked at 1200 to 1300 ℃.

On the other hand, according to another embodiment of the present invention for achieving the above object of the present invention, the unit cell of the solid oxide fuel cell capable of low-temperature co-fired, the anode support layer formed of NiO / YSZ Cermet, NiO / YSZ Cermet The anode reaction layer, the electrolyte layer formed by mixing the YSZ and γ-Al ₂ O ₃ , are sequentially stacked on the anode support electrolyte and the anode support electrolyte formed by co-firing, and the LSM and the YSZ It can be formed with a cathode formed of a mixed LSM / YSZ cermet.

In an embodiment, the anode support type electrolyte is formed by firing at 1200 to 1300 ° C. The cathode may be formed by mixing the LSM and the YSZ in a weight ratio of 6: 4, and may be formed by a screen printing method.

As described above, according to the embodiments of the present invention, by adding a small amount of γ-Al ₂ O ₃ to the YSZ powder can lower the firing temperature of the electrolyte, it can reduce the time and cost of the unit cell manufacturing process have.

Further, according to the embodiments of the present invention, the calcination temperature of the electrolyte and the unit cell is lowered by adding γ-Al ₂ O ₃ to the powder for forming the electrolyte, rather than changing the existing electrolyte and unit cell manufacturing process itself. The process can simplify the process and can be easily applied to the unit cell manufacturing process.

In addition, the anode and the electrolyte may be manufactured and co-fired using a continuous tape casting method to manufacture an anode-supported electrolyte, thereby reducing the time and cost of the unit cell manufacturing process and improving productivity. You can.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or limited by the embodiments. In describing the present invention, a detailed description of well-known functions or constructions may be omitted for clarity of the present invention.

Hereinafter, an anode-supported electrolyte, a unit cell, and a manufacturing method of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. It demonstrates in detail. For reference, FIG. 1 is a flowchart illustrating a method of manufacturing a cathode support type electrolyte of a solid oxide fuel cell according to an embodiment of the present invention, and FIG. 2 is a cathode support type electrolyte manufactured according to the method of FIG. 1. It is a schematic cross section of. 3 is a flowchart illustrating a method of manufacturing a unit cell of a solid oxide fuel cell according to an exemplary embodiment of the present invention, and FIG. 4 is a schematic cross-sectional view of a unit cell manufactured according to the method of FIG. 3.

The solid oxide fuel cell is formed by stacking a plurality of unit cells composed of an anode, an electrolyte, and a cathode. Here, the unit cell of the solid oxide fuel cell comprises a process of manufacturing a cathode support electrolyte consisting of a fuel electrode and an electrolyte and a process of forming an air electrode on the anode support electrolyte. For example, in the anode support type electrolyte, the anode and the electrolyte are formed by continuous and co-fired by using a tape casting method. The unit cell is formed by forming and firing the cathode on the anode support type electrolyte formed as described above by screen printing or the like.

As shown in FIG. 2, the anode support type electrolyte 10 has a structure in which an electrolyte layer 13 is stacked on a cathode support including the anode support layer 11 and the anode reaction layer 12. As shown in FIG. 4, the unit cell 20 has a structure in which a cathode layer 21 having a predetermined thickness is stacked on the anode support electrolyte 10.

In the unit cell 20 according to the present embodiment, a fuel electrode is mixed with nickel oxide (hereinafter referred to as 'NiO') and yttria stabilized zirconia (hereinafter referred to as 'YSZ'). NiO / YSZ cermet is formed, the electrolyte is a mixture of gamma aluminum oxide (γ-Al ₂ O ₃ ) and YSZ, the air electrode is YSZ and strontium doped lanthanum manganite (Lanthanum Strontium Manganite, hereinafter ' as LSM _{'to) (La 0 .8 Sr 0 .2} MnO 3) is formed Metro mixed LSM / YSZ standing.

Referring to FIG. 1, in the method of manufacturing the anode support-type electrolyte 10, first, NiO and YSZ are mixed to form a first NiO / YSZ slurry (S11). Here, the first NiO / YSZ slurry is formed by mixing NiO and YSZ at 60:40, adding 10 wt% of carbon black as a pore body, and adding a solvent, a dispersant, and a binder. The first mixed NiO / YSZ slurry as described above is ball milled for 48 hours.

Next, the first NiO / YSZ slurry is tape casted to form a fuel electrode supporting layer sheet (S12). For example, the anode support layer sheet is formed to a thickness of 35 to 45 µm.

Next, NiO and YSZ are mixed to form a second NiO / YSZ slurry (S13). Here, the second NiO / YSZ slurry is used to form the anode reaction layer 12. Like the first NiO / YSZ slurry, 10 wt% of carbon black, a solvent, a dispersant, and a binder are added to NiO and YSZ. Formed by ball milling for 48 hours. However, unlike the first NiO / YSZ slurry, the second NiO / YSZ slurry is mixed with NiO and YSZ at 55:45.

Next, the second NiO / YSZ slurry is tape cast to form a fuel electrode reaction layer sheet having a thickness of 10 to 30㎛ (S14).

Next, γ-Al ₂ O ₃ of the nanoparticles are mixed with the YSZ powder to form an electrolyte slurry (S15). Here, γ-Al ₂ O ₃ may be added 0.1 to 0.3wt%. Then, the solvent and toluene, ethanol, a dispersant, and a binder are mixed with the YSZ powder mixed with γ-Al ₂ O ₃ and ball milled for 48 hours.

Next, the electrolyte slurry is tape cast to form an electrolyte sheet having a thickness of 1 to 5 μm (S16).

Next, the anode support layer sheet, the anode reaction layer sheet, and the electrolyte sheet are sequentially stacked (S161) to form a laminate (S17). For example, a 40-μm-thick anode support layer sheet is stacked to form a anode support layer 11, and a 20-μm-thick anode reaction layer sheet is stacked on the anode support layer 11 to form a cathode reaction layer 12. Then, one electrolyte sheet having a thickness of 5 탆 is laminated on the anode reaction layer 12 to form an electrolyte layer 13.

Next, the laminate is laminated (S171) to form a unit cell green sheet (S18). Here, the green sheet forming step is a process of pressing the laminate at a predetermined temperature so that the stacked sheets adhere well to each other to prevent them from being separated from each other, in particular, to prevent the anode and the electrolyte layer from being peeled from each other. For example, the laminate is pressed by a load of 400 kgf / cm 2 at a temperature of 70 to 90 ° C. (eg, 80 ° C.).

Next, a calcinations step is performed to remove components such as pores, solvents, binders, and dispersants mixed in the slurry forming step in the green sheet in which lamination is completed (S181). Here, the calcination step is carried out step by step according to each characteristic to be removed from the green sheet. For example, the green sheet is heat treated at 150 ° C. for 2 hours to remove the solvent, the temperature is raised to 300 ° C. to disassociate the binder through heat treatment for 2 hours, and the temperature is raised to 600 ° C. to heat the carbon for 2 hours. To remove the residual carbon through heat treatment for 2 hours at 900 ℃, and to maintain the room temperature after heat treatment for 3 hours at 1000 ℃ can remove the carbon black pore body. Here, when the calcination temperature is 1000 ° C or less, it is easy to cause breakage due to poor calcination, and when the calcination temperature is 1000 ° C or more, the bending of the green sheet occurs severely in the calcination step, so that calcination is performed at a temperature near 1000 ° C.

Next, the green sheet having the calcining step is completed (S182) to form the anode support type electrolyte 10 (S19). For example, the anode support-type electrolyte 10 is fired at about 1300 ° C. Here, in order to prevent defects such as warpage and cracks from occurring in the firing step, the green sheet is baked in a pressurized state by applying a predetermined load to the green sheet. For example, the pressurized body having a predetermined size and weight on the upper portion of the green sheet may be pressed and fired. For example, the pressing body may have a predetermined block or flat plate shape corresponding to the shape of the green sheet so as to press the green sheet under a load of 35 to 40 kgf / cm 2 and pressurize the green sheet uniformly. In addition, the press body is formed of a stable material that does not cause a chemical reaction with the green sheet in the firing step, the press body is formed of a material that does not cause physical / chemical deformation, for example, formed of a ceramic material such as zirconia Can be.

The unit cell 20 is formed by forming and firing the cathode layer 21 on the anode support electrolyte 10 formed as described above.

Referring to FIG. 3, first, an LSM / YSZ slurry in which LSM and YSZ are mixed is formed (S21). Here, the LSM / YSZ slurry is formed by mixing 60:40 LSM and YSZ.

Next, the cathode layer 21 is formed by applying the LSM / YSZ slurry screen printing (S211) method on the electrolyte layer 13 of the anode support-type electrolyte 10 (S22). Here, the LSM / YSZ slurry may be screen printed three times to form the cathode layer 21 having a thickness of about 50 μm.

Next, the anode support type electrolyte 10 in which the cathode layer 21 is formed is fired (S221) to form a unit cell 20 (S23). For example, the unit cell 20 is fired at 1100 to 1200 ℃.

According to the embodiments of the present invention, since the anode and the electrolyte can be formed simultaneously by the continuous tape casting method and the simultaneous firing, the manufacturing process of the anode support-type electrolyte 10 and the unit cell 20 can be shortened, and the time can be reduced. It can save money, reduce costs, and improve productivity. In addition, the electrolyte of the thin film can be formed, thereby improving the performance of the unit cell 20. As the thickness of the electrolyte becomes thinner, the ohmic resistance and the polarization resistance decrease as the movement distance of oxygen ions decrease in the electrolyte, and the performance of the unit cell 20 can be improved by improving the contact and reactivity between the electrolyte and the fuel electrode. Because there is.

In addition, by adding γ-Al ₂ O ₃ , the anode support-type electrolyte 10 can be calcined at a relatively low temperature of 1200 to 1300 ° C., thereby reducing process time and cost, and compact structure such as calcining at high temperature. Can be obtained. In addition, since the calcination temperature can be lowered by adding γ-Al ₂ O ₃ to the electrolyte powder in the electrolyte and unit cell manufacturing process, the existing electrolyte and unit cell manufacturing process can be applied without adding a separate device or process. The advantage is that it can be easily applied to existing processes.

Hereinafter, the performance of a cathode support type electrolyte and a unit cell manufactured according to an embodiment of the present invention will be described with reference to FIGS. 5 to 7. Here, in order to evaluate the performance of the unit cell according to the embodiment of the present invention, a cathode support type electrolyte and a unit cell were manufactured according to the above-described manufacturing method. Hereinafter, a unit cell manufactured according to the unit cell manufacturing method of the present invention will be referred to as an 'example'. A unit cell was formed in the same manner as in the example, except that the electrolyte was formed of YSZ powder to which γ-Al ₂ O ₃ was not added, and then calcined at 1300 ° C. to prepare a cathode support-type electrolyte. A unit cell is called a "comparative example."

5 is a scanning electron microscope (SEM) image of the anode support-type electrolyte in the embodiment. As shown in FIG. 5, the embodiment can confirm that the thickness of the electrolyte layer is 10 μm or less, and the fuel electrode has good pores so that gas permeation is good, and the interface contact state between the fuel electrode and the electrolyte is very good. I can see that

6A is an SEM image of the electrolyte layer in the example, and FIG. 6B is an SEM image of the electrolyte layer in the comparative example. In order to block gas permeation between the anode and the cathode, the electrolyte must be dense. As shown in FIG. 6A, the embodiment shows that the electrolyte layer is in a dense and dense state with almost no pores. On the other hand, the electrolyte layer of the comparative example is not dense and pores are formed, it can be expected that the leakage of gas through the electrolyte layer (leak) can occur. In the comparative example, performance evaluation could not be performed due to gas leakage.

7 is a graph showing the results of performance evaluation of the example. Here, in the comparative example, the performance evaluation was not properly performed due to the outflow of gas as described above, and thus, only the performance evaluation results for the example are described in FIG. 7.

First, for the performance evaluation of the embodiment, hydrogen gas (H ₂ ) containing 3% water (H ₂ O) at 800 ° C. was flowed to the anode at a rate of 400 mL / min, and air was flowed at a rate of 500 mL / min. After 8 hours of reduction, the current voltage (IV) curve was measured, and at the same time, the impedance was measured in the open circuit state.

Referring to Figure 7, the embodiment shows a high performance of 0.58W / ㎠ output performance. Although the embodiment is fired at a low temperature, it can be seen that the electrolyte can be densely manufactured, a thin film of electrolyte can be formed, and the electrolyte surface uniformity is excellent, so that the microstructure of the unit cell and the gas leakage prevention effect are large.

As described above, the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided only to help a more general understanding of the present invention, and the present invention is limited to the above-described embodiments. In other words, various modifications and variations are possible to those skilled in the art to which the present invention pertains. Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and all the things that are equivalent to or equivalent to the scope of the claims as well as the claims to be described later belong to the scope of the present invention.

1 is a flowchart illustrating a method of manufacturing a cathode support type electrolyte of a solid oxide fuel cell according to an embodiment of the present invention;

2 is a schematic cross-sectional view of an anode support type electrolyte according to the manufacturing method of FIG. 1;

3 is a flowchart illustrating a method of manufacturing a unit cell of a solid oxide fuel cell according to an embodiment of the present invention;

4 is a schematic cross-sectional view of a unit cell according to the manufacturing method of FIG.

5 is a scanning electron microscope (SEM) image of the anode support-type electrolyte in the embodiment;

6A is an SEM image of an electrolyte layer in an embodiment;

6B is an SEM image of the electrolyte layer in the comparative example;

7 is a graph showing the results of performance evaluation of the example.

<Explanation of symbols for the main parts of the drawings>

10: anode support type electrolyte 11: anode support layer

12: anode reaction layer 13: electrolyte layer

20: cell 21: air cathode layer

Claims (10)

Mixing nickel oxide (NiO) and yttria stabilized zirconia (YSZ) to form a first slurry; Forming a anode support layer sheet using the first slurry; Mixing NiO and YSZ to form a second slurry; Forming a cathode reaction layer sheet using the second slurry; Mixing YSZ and gamma aluminum oxide (γ-Al ₂ O ₃ ) to form an electrolyte slurry; Forming an electrolyte sheet using the electrolyte slurry; Sequentially stacking the anode support layer sheet, the anode reaction layer sheet, and the electrolyte sheet to form a laminate; Laminating the laminate to form a green sheet; Calcining the green sheet to remove solvent and binder; And Firing the calcined green sheet; A method of manufacturing a cathode support type electrolyte of a solid oxide fuel cell comprising a. The method of claim 1, The electrolyte slurry is a cathode support-type electrolyte manufacturing method of the solid oxide fuel cell is formed by mixing the γ-Al ₂ O ₃ to 0.2wt% of the YSZ. The method of claim 1, The electrolyte sheet is formed to a thickness of 1 to 5㎛, The laminate is a cathode support-type electrolyte manufacturing method of a solid oxide fuel cell in which one sheet of the electrolyte sheet is laminated. The method of claim 1, The firing step is a method for producing a cathode support type electrolyte of a solid oxide fuel cell is calcined by pressing the calcined laminate at a load of 35 to 40kgf / ㎠ at 1200 ~ 1300 ℃. An anode support layer formed of NiO / YSZ cermet mixed with NiO and YSZ; A cathode reaction layer stacked on the anode support layer and formed of NiO / YSZ cermet; And An electrolyte layer laminated on the anode reaction layer and formed by mixing the YSZ and γ-Al ₂ O ₃ ; And a cathode support layer, the anode reaction layer, and the electrolyte layer are co-fired. The method of claim 5, The electrolyte is a cathode support type electrolyte of a solid oxide fuel cell in which the γ-Al ₂ O ₃ is mixed at 0.2 wt% of the YSZ. The method of claim 5, A cathode support type electrolyte of a solid oxide fuel cell formed by firing at 1200 to 1300 ° C. An anode support type electrolyte formed by laminating and co-firing an anode support layer formed of NiO / YSZ cermet, an anode reaction layer formed of NiO / YSZ cermet, and an electrolyte layer formed by mixing the YSZ and γ-Al ₂ O ₃ ; And An air electrode formed of an LSM / YSZ cermet in which an LSM and an YSZ are mixed and stacked on the anode support-type electrolyte; Unit cell of a solid oxide fuel cell comprising a. The method of claim 8, The anode support type electrolyte is a unit cell of a solid oxide fuel cell formed by firing at 1200 to 1300 ℃. The method of claim 8, The cathode is a unit cell of a solid oxide fuel cell in which the LSM and the YSZ are mixed at a weight ratio of 6: 4, and formed by a screen printing method.

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