Solid oxide fuel cell, and method for manufacturing fuel cell cathode

Abstract

A solid oxide fuel cell is disclosed. The solid oxide fuel cell comprises a solid electrolyte, and an anode and a cathode that are disposed, respectively, on one surface and the other surface of the solid electrolyte, wherein the cathode includes: a cathode functional layer disposed on the solid electrolyte and formed of a first cathode material having a first coefficient of thermal expansion; and a cathode contact layer disposed on the cathode functional layer and formed of a second cathode material having a second coefficient of thermal expansion, which is greater than the first coefficient of thermal expansion, and the average thickness ratio of the cathode functional layer and the cathode contact layer is 1:0.6-2.2.

Description

Method for manufacturing a solid oxide fuel cell and an anode for a fuel cell

[0001] The present invention relates to a solid oxide fuel cell and a method for manufacturing an anode for a fuel cell.

[0002] The anode of a solid oxide fuel cell (SOFC) consists of an anode functional layer and an anode contact layer. The anode functional layer is advantageously constructed from a material with a similar coefficient of thermal expansion to the electrolyte and diffusion barrier, while the anode contact layer is preferably constructed from a material with high electrical conductivity. Since the anode functional layer and anode contact layer are composed of different materials, the differences in their coefficients of thermal expansion require each layer to be sintered at different temperatures during the cell manufacturing process, resulting in significant manufacturing costs and time. Furthermore, continuous SOFC operation at temperatures between 600 and 800°C can lead to anode delamination during operation.

[0003] One object of the present invention is to provide a solid oxide fuel cell that does not delaminate during operation.

[0004] Another object of the present invention is to provide a method for manufacturing an anode for a solid oxide fuel cell, which can reduce manufacturing process costs and time by performing sintering at once.

[0005] In order to achieve the above object, the present invention provides a solid oxide fuel cell comprising: a solid electrolyte; and a cathode and an anode respectively disposed on one surface and the other surface of the solid electrolyte; wherein the anode comprises: an anode functional layer disposed on the solid electrolyte and formed of a first anode material having a first thermal expansion coefficient; and an anode contact layer disposed on the anode functional layer and formed of a second anode material having a second thermal expansion coefficient greater than the first thermal expansion coefficient; wherein an average thickness ratio of the anode functional layer and the anode contact layer is 1:0.6 to 2.2.

[0006] In addition, the present invention provides a method for manufacturing an anode for a solid oxide fuel cell, comprising the steps of: manufacturing a first anode paste in which first anode material particles are dispersed; manufacturing a second anode paste in which second anode material particles having a larger thermal expansion coefficient than the first anode material particles are dispersed; applying the first anode paste on an electrolyte to form a first paste layer; applying the second anode paste on one surface of the first paste layer to form a second paste layer; and simultaneously sintering the first paste layer and the second paste layer to form a cathode functional layer and an anode contact layer, respectively.

[0007] According to the present invention, the solid oxide fuel cell of the present invention can have increased stability by controlling the thickness of the anode functional layer and the anode contact layer so that peeling does not occur at each interface during operation.

[0008] In addition, the method for manufacturing an anode for a solid oxide fuel cell of the present invention can reduce the time and cost of the manufacturing process by manufacturing an anode functional layer and an anode contact layer through a single sintering process.

[0009] FIG. 1 is a flowchart illustrating a method for manufacturing an anode for a solid oxide fuel cell according to one embodiment of the present invention.

[0010] Figure 2 shows the results of analyzing the LSCF particle size and LSC particle size.

[0011] Figure 3 is a scanning electron microscope side image of Example 1 of the present invention.

[0012] Figure 4 shows the peeling test results of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0013] Figure 5 is a scanning electron microscope image of a surface on which a peeling test was performed in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0014] Figure 6 is a current-voltage-power graph of Example 2 and Comparative Example 3.

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be modified in various ways and can take various forms, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0016] While terms like "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0017] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0018] Meanwhile, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0019]

[0020] FIG. 1 is a flowchart illustrating a method for manufacturing an anode for a solid oxide fuel cell according to one embodiment of the present invention.

[0021] Referring to FIG. 1, a method for manufacturing an anode for a solid oxide fuel cell may include a step of manufacturing a first anode paste in which first anode material particles are dispersed, and a step of manufacturing a second anode paste in which second anode material particles having a larger thermal expansion coefficient than the first anode material particles are dispersed (S110); a step of applying the first anode paste on an electrolyte to form a first paste layer (S120); a step of applying the second anode paste on one surface of the first paste layer to form a second paste layer (S130); and a step of simultaneously sintering the first paste layer and the second paste layer to form a cathode functional layer and an anode contact layer, respectively (S140).

[0022] In the step (S110) of manufacturing the first positive electrode paste and the second positive electrode paste, the first and second positive electrode materials may use a mixed ionic and electronic conductor (MIEC) material having ionic conductivity and electrical conductivity. For example, the first positive electrode material may be a lanthanum strontium cobalt ferrite (LSCF) particle, and the second positive electrode material may be a lanthanum strontium cobalt (LSC) particle, but is not limited thereto.

[0023] In one embodiment, the ratio of the average particle size (D50) of the LSCF particles and the LSC particles may be about 1:1.5 to 3.5. For example, the average particle size (D50) of the LSCF particles may be about 0.4 to 0.8 μm, and the average particle size (D50) of the LSC particles may be about 1 to 3 μm. If the average particle size (D50) of the LSCF particles exceeds about 0.8 μm, or the average particle size (D50) of the LSC particles exceeds about 3 μm, the driving force for sintering may decrease, so that sufficient cohesion between particles may not occur, making it difficult to secure a desirable microstructure.

[0024] In the step of forming the first paste layer (S120) and the step of forming the second paste layer (S130), the first paste and the second paste can be applied by screen printing. The thickness of the first paste layer and the second paste layer can be controlled by repeating the screen printing 1 to 3 times.

[0025] In the step (S140) of forming the anode functional layer and the anode contact layer, respectively, the sintering temperature for the first paste layer and the second paste layer may be 1000 to 1200°C. Since the first paste layer and the second paste layer can be sintered simultaneously, the time and cost of the manufacturing process can be reduced.

[0026]

[0027] The solid oxide fuel cell of the present invention may include an anode manufactured according to the method for manufacturing an anode for a solid electrolyte fuel cell, and includes a solid electrolyte; and a cathode and an anode respectively disposed on one surface and the other surface of the solid electrolyte; wherein the anode includes an anode functional layer disposed on the solid electrolyte and formed of a first anode material having a first thermal expansion coefficient; and an anode contact layer disposed on the anode functional layer and formed of a second anode material having a second thermal expansion coefficient greater than the first thermal expansion coefficient, and an average thickness ratio of the anode functional layer and the anode contact layer may be about 1:0.6 to 2.2.

[0028] In one embodiment, the average thickness of the anode functional layer may be about 10 to 16 μm. If the average thickness of the anode functional layer is less than about 10 μm, the area of ​​the region where gas is introduced and reacts with the electrode to generate ions may decrease, and thus the performance of the anode functional layer may not be maintained. If the average thickness of the anode functional layer exceeds about 16 μm, peeling may occur during the manufacture or operation of the fuel cell, thereby reducing stability.

[0029] In one embodiment, the average thickness of the anode contact layer may be about 10 to 22 μm.

[0030] In one embodiment, the first cathode material may include LSCF (Lanthanum strontium cobalt ferrite) particles, and the second cathode material may include LSC (Lanthanum strontium cobalt) particles, but is not limited thereto. Detailed descriptions of the LSCF particles and the LSC particles are substantially the same as those described in the step (S110) of manufacturing the first cathode paste and the second cathode paste, and therefore, redundant detailed descriptions thereof are omitted.

[0031] In one embodiment, the first coefficient of thermal expansion is about 16 × 10 -6 / ℃, and the second thermal expansion coefficient is about 19 × 10 -6 / ℃ may be.

[0032] In one embodiment, the solid electrolyte and the cathode may be made of materials commonly used in solid electrolyte fuel cells, and no special limitations are imposed.

[0033]

[0034] Hereinafter, to aid understanding of the present invention, examples will be given in detail. However, the following examples are intended only to illustrate the scope of the present invention and are not intended to limit its scope. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0035]

[0036] <Example 1>

[0037] LSCF paste and LSC paste were prepared using LSCF particles and LSC particles. The LSCF paste was applied onto an electrolyte using a screen printer to form an LSCF paste layer. The LSC paste was applied onto the LSCF paste layer using a screen printer to form an LSC paste layer. The LSCF paste layer and the LSC paste layer were simultaneously sintered at about 1000 to 1200°C to form a cathode functional layer and a cathode contact layer.

[0038]

[0039] <Comparative Example 1>

[0040] A positive electrode for a solid oxide fuel cell was manufactured in the same manner as in Example 1, except that the LSCF paste was applied twice in Example 1.

[0041]

[0042] Comparative Example 2

[0043] A positive electrode for a solid oxide fuel cell was manufactured in the same manner as in Example 1, except that the LSCF paste was applied three times in Example 1.

[0044]

[0045] Experimental Example 1

[0046] FIG. 2 and Table 1 show the results of analyzing the LSCF particle size and LSC particle size. If the LSCF particle size and LSC particle size have particle size values ​​exceeding the ranges described in Table 1 below, the driving force for sintering becomes small, and sufficient coagulation may not occur during sintering at the same temperature, making it difficult to secure a microstructure. Therefore, it is preferable to adjust the powder particle size of the LSC (anode contact layer) to be about 1.5 to 3.5 times larger in each range (Dv10, 50, 90) than the powder particle size of the LSCF (anode functional layer). In an embodiment of the present invention, a paste was prepared using powders suitable for the particle size according to Table 1, and a screen printing process was performed using this paste.

[0047]

[0048]

[0049] Experimental Example 2

[0050] Figure 3 is a scanning electron microscope side image of Example 1 of the present invention. In Example 1, it was confirmed that the thickness of the anode functional layer was about 14.0 ㎛ and the thickness of the anode contact layer was about 14.4 ㎛.

[0051] Figure 4 shows the peeling test results of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. A physical peeling experiment was conducted by attaching and removing tape to some of Example 1, Comparative Example 1, and Comparative Example 2. Peeling occurred in Comparative Example 1 and Comparative Example 2, but no peeling occurred in Example 1.

[0052] Figure 5 is a scanning electron microscope image of the surface on which the peeling test of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention was performed. In Example 1, the anode functional layer and the anode contact layer were maintained on the electrolyte, but in Comparative Examples 1 and 2, the anode functional layer and the anode contact layer were lost on the electrolyte.

[0053]

[0054] <Example 2>

[0055] The anode of Example 1 was applied to one side of the electrolyte layer. YSZ, nickel, and carbon black were mixed on the other side of the electrolyte layer and then molded to manufacture a fuel electrode, thereby manufacturing a membrane electrode assembly (MEA).

[0056] A separator with a flow path was prepared. A sealing pattern was formed on the separator to prevent interlayer bonding and fuel mixing. A mesh-type current collecting layer was fabricated to improve current collection. Upper and lower manifolds for fuel supply were fabricated. A mesh for improving current collection was attached to the anode surface of the membrane electrode assembly and then attached to the separator. A frame was placed on the attached membrane electrode assembly and separator, and a mesh-type current collecting layer for improving cathode current collection was attached to form a stack. Upper and lower manifolds for flow supply were connected.

[0057]

[0058] <Comparative Example 3>

[0059] A fuel cell was manufactured in the same manner as in Example 2, except that the anode of Comparative Example 2 was applied as the anode in Example 2.

[0060]

[0061] Experimental Example 3

[0062] Figure 6 is a current-voltage-power graph of Example 2 and Comparative Example 3.

[0063] In conventional technology, the thickness of the anode functional layer is formed to be greater than the thickness of the anode contact layer. This is because, during fuel cell operation, reaction sites for ionization of oxygen and transfer to the electrolyte are created in the anode functional layer, and thus, a method is adopted to increase the thickness of the functional layer to increase the number of reaction sites and thereby increase cell performance.

[0064] Comparative Example 3 is a fuel cell manufactured using conventional technology, and it was confirmed that there was almost no difference in cell performance compared to Example 2. Through Example 2, the thickness of the anode functional layer was controlled while maintaining cell performance, and the number of processes and the required time were reduced by simultaneously sintering the anode functional layer and the anode contact layer at a temperature of 1000 to 1200 ℃. At the same time, it was confirmed that the anode structure could be maintained in which no peeling occurred during sintering and operation despite the difference in the thermal expansion coefficient of each sintered anode layer. As a result, the performance of the cell was maintained constant even when the structure of the anode was changed, and the effect of saving time and cost by simplifying the process was confirmed.

[0065]

[0066] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. Solid electrolyte; and It includes a cathode and an anode respectively disposed on one side and the other side of the solid electrolyte; The above anode is, A cathode functional layer formed of a first cathode material having a first thermal expansion coefficient and disposed on top of the solid electrolyte; and It includes an anode contact layer formed of a second anode material having a second thermal expansion coefficient greater than the first thermal expansion coefficient and disposed on the upper portion of the anode functional layer, A solid oxide fuel cell, wherein the average thickness ratio of the anode functional layer and the anode contact layer is 1:0.6 to 2.

2.

2. In paragraph 1, The average thickness of the above bipolar functional layer is 10 to 16 ㎛, A solid oxide fuel cell, wherein the average thickness of the anode contact layer is 10 to 22 ㎛.

3. In paragraph 1, A solid oxide fuel cell, wherein the anode functional layer comprises LSCF (Lanthanum strontium cobalt ferrite) particles, and the anode contact layer comprises LSC (Lanthanum strontium cobalt) particles.

4. In paragraph 3, A solid oxide fuel cell, wherein the ratio of the average particle size (D50) of the LSCF and LSC particles is 1:1.5 to 3.

5.

5. In paragraph 4, The average particle size (D50) of the above LSCF is 0.4 to 0.8 ㎛, A solid oxide fuel cell, wherein the average particle size (D50) of the above LSC is 1 to 3 ㎛.

6. In paragraph 1, A solid oxide fuel cell, wherein the anode contact layer is arranged to form an interface with the anode functional layer.

7. A step of manufacturing a first positive electrode paste in which first positive electrode material particles are dispersed, and manufacturing a second positive electrode paste in which second positive electrode material particles having a larger thermal expansion coefficient than the first positive electrode material particles are dispersed; A step of forming a first paste layer by applying the first positive electrode paste onto an electrolyte; A step of forming a second paste layer by applying the second positive electrode paste to one surface of the first paste layer; A method for manufacturing an anode for a solid oxide fuel cell, comprising a step of simultaneously sintering the first paste layer and the second paste layer to form a cathode functional layer and a cathode contact layer, respectively.

8. In paragraph 7, A method for manufacturing an anode for a solid oxide fuel cell, wherein the first and second anode material particles each include LSCF particles and LSC particles.

9. In paragraph 8, A method for manufacturing a cathode for a solid oxide fuel cell, wherein the ratio of the average particle size (D50) of the LSCF particles and the LSC particles is 1:1.5 to 3.

5.

10. In paragraph 8, The average particle size (D50) of the above LSCF particles is 0.4 to 0.8 ㎛, A method for manufacturing a positive electrode for a solid oxide fuel cell, wherein the average particle size (D50) of the above LSC particles is 1 to 3 ㎛.

11. In paragraph 7, A method for manufacturing a cathode for a solid oxide fuel cell, wherein the LSCF paste and the LSCF paste are applied by repeatedly using a screen printer 1 to 3 times.

12. In paragraph 11, The average thickness of the above bipolar functional layer is 10 to 16 ㎛, A method for manufacturing an anode for a solid oxide fuel cell, wherein the average thickness of the anode contact layer is 10 to 22 ㎛.

13. In paragraph 8, A method for manufacturing an anode for a solid oxide fuel cell, wherein the sintering temperature for the first paste layer and the second paste layer is 1000 to 1200°C.

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