Solid oxide fuel cells and their manufacturing methods

Abstract

A solid oxide fuel cell and a method for manufacturing the same are disclosed. The solid oxide fuel cell includes: a solid oxide electrolyte layer; an anode electrode layer located on a first surface of the solid oxide electrolyte layer; a first cathode electrode layer located on a second surface of the solid oxide electrolyte layer; and a second cathode electrode layer located above the first cathode electrode layer and having a lower hardness than the first cathode electrode layer.

Description

Technical Field

[0001] This invention relates to a solid oxide fuel cell that generates electricity through the reaction of hydrogen and oxygen, and a method for manufacturing the same. Background Technology

[0002] Solid oxide fuel cells are fuel cells that operate at high temperatures of approximately 600°C to 1000°C. They have many advantages, including the highest efficiency and least pollution among various types of traditional fuel cells, and the ability to generate electricity without a fuel converter.

[0003] As mentioned above, solid oxide fuel cells can be broadly classified into planar, cylindrical, and tubular types. Compared to cylindrical or tubular solid oxide fuel cells, planar solid oxide fuel cells have the advantage of higher power density in the stack itself, and therefore are the most widely used.

[0004] Planar solid oxide fuel cells are typically used in fuel cell stacks, which consist of multiple individual cells stacked using metal separators. In such fuel cell stacks, uniform contact between the electrodes of the ceramic individual cells and the metal separators is necessary to reduce contact resistance and thus improve the performance of the fuel cell stack.

[0005] Furthermore, if cracks in the ceramic cells are generated during the pressurization process that must be applied in the manufacturing of fuel cell stacks, it will have a significant adverse impact on the performance and stability of the fuel cell stacks. Therefore, it is necessary to develop technologies to prevent the formation of such cracks.

[0006] Furthermore, the fuel cell stack operates at high temperatures of approximately 600°C to 800°C, and when chromium (Cr), which is a metal component constituting the fuel cell stack, diffuses into the individual cells, the performance of the individual cells deteriorates rapidly. Therefore, there is a need to develop fuel cell stacks that can properly collect chromium.

[0007] Content of the invention

[0008] The problem the invention aims to solve

[0009] One object of the present invention is to provide a solid oxide fuel cell that has improved chromium collection capacity, prevents cracking in single cells during manufacturing, and exhibits excellent performance by improving contact characteristics with the separator plate.

[0010] Another object of the present invention is to provide a method for manufacturing the solid oxide fuel cell.

[0011] means for solving problems

[0012] A solid oxide fuel cell according to an embodiment of the present invention may include: a solid oxide electrolyte layer; an anode electrode layer located on a first surface of the solid oxide electrolyte layer; a first cathode electrode layer located on a second surface of the solid oxide electrolyte layer; and a second cathode electrode layer located above the first cathode electrode layer and having a lower hardness than the first cathode electrode layer.

[0013] In one embodiment, the solid oxide fuel cell may further include: a current collector located on the upper part of the second cathode electrode layer and in contact with the second cathode electrode layer.

[0014] In one embodiment, the first cathode electrode layer is made of lanthanum strontium cobalt ferrite (LSCF). 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) or Lanthanum strontium manganite (LSM) (La 1-x Sr x The second cathode electrode layer can be formed from lanthanum strontium cobaltite (LSC) (La). 0.6 Sr 0.4 CoO 3-δ )form.

[0015] In one embodiment, under a load of 0.01 kgf and a holding time of 10 seconds, the Vickers hardness of the first cathode electrode layer is 48 to 57, and the Vickers hardness of the second cathode electrode layer can be 10 to 20.

[0016] In one embodiment, at least a portion of the current collector may be embedded within the second cathode electrode layer.

[0017] In one embodiment, the current collector may include a separation plate, and at least a portion of the separation plate is embedded within the second cathode electrode layer.

[0018] In one embodiment, the current collector may include: a separation plate and a current collector mesh structure located between the separation plate and the second cathode electrode layer; at least a portion of the current collector mesh structure is embedded inside the second cathode electrode layer.

[0019] In one embodiment, the current collector may include: a metal component, and a coating layer, at least coated on the surface of the metal component in the region facing the second cathode electrode layer; in this case, the coating layer may be formed of the same material as the second cathode electrode layer.

[0020] In one embodiment, the hardness of the coating layer can be 0.7 to 1.2 times the hardness of the second cathode electrode layer.

[0021] In one embodiment, the current collector may further include a chromium collecting layer formed between the metal member and the coating layer.

[0022] A method for manufacturing a solid oxide fuel cell according to an embodiment of the present invention may include: a first step of manufacturing a laminated structure of an anode electrode layer, a solid oxide electrolyte layer and a first cathode electrode layer; a second step of coating a cathode slurry on the surface of the first cathode electrode layer to form a cathode slurry layer; and a third step of pre-sintering the cathode slurry layer to form a second cathode electrode layer.

[0023] In one embodiment, the cathode paste may contain LSC powder.

[0024] In one embodiment, the pre-sintering of the cathode slurry layer can be performed such that the density of the cathode slurry layer is 80% to 95% of the theoretical density of sintering at the full sintering temperature.

[0025] In one embodiment, the method for manufacturing the solid oxide fuel cell may further include the following steps: placing a current collector on the second cathode electrode layer and pressurizing it; in this case, during the pressurization step, a portion of the current collector may be embedded inside the second cathode electrode layer.

[0026] The effects of the invention

[0027] According to the solid oxide fuel cell and its manufacturing method of the present invention, the cathode electrode layer is formed of two or more layers, and the outermost cathode electrode layer is formed to have relatively low hardness and relatively high ductility, which not only improves the contact characteristics between the cathode electrode layer and the current collector, but also prevents cracks from occurring in any of the cathode electrode layer, solid oxide electrolyte layer, and anode electrode layer due to impacts applied by the current collector during the manufacturing process or operation, and can also have improved chromium collection capacity. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view used to illustrate a solid oxide fuel cell.

[0029] Figure 2This is a cross-sectional view used to illustrate a solid oxide fuel cell according to another embodiment of the present invention.

[0030] Figure 3 This is a flowchart illustrating a method for manufacturing a solid oxide fuel cell according to an embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures

[0032] 100, 200: Solid oxide fuel cells

[0033] 110, 210: Anode electrode layer

[0034] 111, 211: Anode support layer

[0035] 112, 212: Anode functional layer

[0036] 120, 220: Solid oxide electrolyte layer

[0037] 130, 230: Cathode electrode layer

[0038] 131, 231: First cathode electrode layer

[0039] 132, 232: Second cathode electrode layer

[0040] 140, 240: Current collector components Detailed Implementation

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention can be subject to various modifications and can take many forms; specific embodiments are illustrated illustratively in the drawings and described in detail herein. However, this is not intended to limit the invention to the specific forms disclosed, and it should be understood to include all modifications, equivalents, and substitutions falling within the spirit and scope of the present invention. In describing the various drawings, similar reference numerals are used for similar constituent elements. In the drawings, for clarity of the invention, the dimensions of structures are shown enlarged compared to their actual dimensions.

[0042] While terms such as "first" and "second" can be used to describe various constituent elements, the constituent elements are not limited to these terms. These terms are used only to distinguish one constituent element from others. For example, without departing from the scope of this invention, a first constituent element may be named a second constituent element, and similarly, a second constituent element may be named a first constituent element.

[0043] The terminology used in this application is for illustrative purposes only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly specifies otherwise. In this application, terms such as "comprising" or "having" are used to specify the presence of features, numbers, steps, actions, constituent elements, components, or combinations thereof as described in the specification, and do not preclude the presence or additional possibilities of more than one other feature, number, step, action, constituent element, component, or combination thereof.

[0044] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in common dictionaries shall be interpreted as having the same meaning as in the context of the relevant art, and shall not be construed as having an ideal or overly formal meaning unless expressly defined in this application.

[0045] Figure 1 This is a cross-sectional view used to illustrate a solid oxide fuel cell.

[0046] Reference Figure 1 According to an embodiment of the present invention, a solid oxide fuel cell 100 may include an anode electrode layer 110, a solid oxide electrolyte layer 120, a cathode electrode layer 130, and a current collector 140.

[0047] The anode electrode layer 110 may have a porous structure for the movement of hydrogen-containing fuel into the interior, and may be formed of a cermet of transition metals and ion-conducting oxides. For example, the anode electrode layer 110 may be formed of a cermet of nickel (Ni) and ytria-stabilized zirconia (YSZ).

[0048] In one embodiment, the anode electrode layer 110 may include an anode support layer 111 and an anode functional layer 112.

[0049] The anode support layer 111 is a structure that increases the strength of the single cell (the laminate of the anode electrode layer 110, the solid oxide electrolyte layer 120, and the cathode electrode layer 130). Its thickness may be greater than that of the anode functional layer 112, and it has a porous structure that allows hydrogen-containing fuel gas to move into the interior. It may be formed of a cermet of nickel and YSZ. As one embodiment, the anode support layer 111 may be formed from a support raw material powder comprising approximately 30 to 60 parts by weight of the YSZ powder and approximately 40 to 70 parts by weight of the nickel oxide powder.

[0050] In one embodiment, the anode support layer 111 can be manufactured by mixing the support raw material powder with a pore-forming agent and dispersing it in a solvent, then adding a binder to it to manufacture a support molding slurry, and then using the support molding slurry for a compression molding process or a casting molding process. In this case, the pore-forming agent can be powders of polymethyl methacrylate (PMMA), activated carbon, carbon black, graphite, starch, etc., and the support molding slurry can contain about 30 to 60 parts by weight of the YSZ powder, about 40 to 70 parts by weight of the nickel oxide powder, and about 1 to 20 parts by weight of the pore-forming agent. Furthermore, the binder can be one or a mixture of two or more of polyvinyl alcohol (PVA)-based binders, methylcellulose (MC)-based binders, and sodium carboxymethylcellulose (CMC)-based binders, and the binder can be mixed in an amount of about 10% to about 50% by volume relative to the first raw material powder. In addition, water can be used as the solvent, for example, distilled water or deionized water.

[0051] The anode functional layer 112 is located on the anode support layer 111 and can be formed into a relatively dense structure compared to the anode support layer 111. As one embodiment, the anode functional layer 112 can be formed from a cermet of YSZ and nickel. For example, the anode functional layer 112 can be formed by: after forming a mixed slurry of nickel oxide powder and YSZ powder, forming a coating film on the anode support layer 111 using a dip coating method, drying, and then sintering in an air atmosphere at approximately 900°C to approximately 1200°C. Alternatively, the anode functional layer 112 can also be manufactured into a green sheet through a tape casting process and then bonded to the anode support layer 111 by sintering.

[0052] The solid oxide electrolyte layer 120 may be located on the anode functional layer 112, may be formed of YSZ, and may be formed as a denser structure compared to the anode support layer 111. For example, the YSZ of the solid oxide electrolyte layer 120 may contain about 5 mol% to 10 mol% yttrium oxide.

[0053] In one embodiment, the solid oxide electrolyte layer 120 can be formed by: manufacturing a green sheet using a YSZ slurry casting process, then stacking it with the green sheet of the anode electrode layer 110 and sintering it to form the anode electrode layer 110 and the solid oxide electrolyte layer 120 bonded thereto. Alternatively, the solid oxide electrolyte layer 120 can be formed by: forming an electrolyte coating film on the outer surface of the anode functional layer 112 using the dipcoating method of the YSZ slurry, and then sintering it in an air atmosphere at approximately 1300°C to approximately 1500°C.

[0054] The cathode electrode layer 130 is located on the solid oxide electrolyte layer 120 and has a porous structure that allows oxygen to move internally. It can be formed of a metal oxide material that has ionic and electronic conductivity.

[0055] In one embodiment, the cathode electrode layer 130 may include: a first cathode electrode layer 131 located above the solid oxide electrolyte layer 120; and a second cathode electrode layer 132 located above the first cathode electrode layer 131.

[0056] As an embodiment, the first cathode electrode layer 131 can be formed of a different material than the second cathode electrode layer 132. For example, to prevent the cathode electrode 130 from separating from the solid oxide electrolyte layer 120 during sintering, the first cathode electrode layer 131 can be formed of a material with a lower coefficient of thermal expansion than the second cathode electrode layer 132. Although LSC has higher ionic conductivity and superior catalytic activity than LSCF, it has a coefficient of thermal expansion of approximately 20 × 10⁻⁶. -6 Up to 23×10 -6 The relatively large coefficient of thermal expansion of LSC (LaSZ) means that when it is laminated onto the solid oxide electrolyte layer 120 formed of YSZ and sintered, the difference in thermal expansion coefficients may cause the LSC layer to separate from the solid oxide electrolyte layer 120. To compensate for this mismatch in the thermal expansion coefficients of the LSC and the solid oxide electrolyte, the first cathode electrode layer 131 can be made of LSM (LaSZ). 1-x Sr x MnO3) or LSCF (La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ The second cathode electrode layer 132 can be formed by LSC (La) 0.6 Sr 0.4 CoO 3-δ(where x and δ are real numbers greater than 0 and less than 1). When LSCF and LSC are used as materials for the first cathode electrode layer 131 and the second cathode electrode layer 132, respectively, the problem of separation between the solid oxide electrolyte layer 120 and the cathode electrode layer 130 during the manufacturing process can be solved, and the electrode performance of the cathode electrode layer 130 can be improved.

[0057] As an embodiment, the surface hardness of the second cathode electrode layer 132 can be less than the surface hardness of the first cathode layer 131. In this case, it can prevent the formation of cracks that might occur in the single cell during the pressure manufacturing process (for ensuring the bonding of the current collector 140 and the cathode electrode layer 130), improve the surface contact uniformity of the current collector 140 and the cathode electrode layer 130, and enhance the collection capacity of chromium (Cr) accompanying airflow. For example, under a load of 0.01 kgf and a holding time of 10 seconds, the Vickers hardness of the first cathode electrode layer 131 is approximately 48 to 57, while the Vickers hardness of the second cathode electrode layer 132 under the same conditions can be approximately 10 to 20, for example, approximately 15 to 18. The hardness of the second cathode electrode layer 132 can be adjusted by changing the sintering conditions used to form the second cathode electrode layer 132. For example, by coating the first cathode electrode layer 131, made from the fully sintered body, with a cathode paste for forming the second cathode electrode layer 132 to form a cathode paste layer, and then pre-sintering the cathode paste layer, a second cathode electrode layer 132 with relatively low hardness and relatively high ductility can be formed. In this specification, "fully sintered" means sintering the object by applying sintering temperature, pressure, or time so that the density of the sintered object is 98% or more of the theoretical density. "Pre-sintering" means sintering the object by applying sintering temperature, pressure, or time so that although necking occurs between the particles of the sintered object, a large number of voids remain inside, thereby making the density of the sintered object about 70% to 95% of the theoretical density.

[0058] As one embodiment, when the first cathode electrode layer 131 is formed of LSCF and the second cathode electrode layer 132 is formed of LSC, the first cathode electrode layer 131 can be formed by coating the solid electrolyte layer 120 with LSCF slurry or stacking LSCF green sheets and then fully sintering under pressure. Then, after coating the first cathode electrode layer 131 with LSC slurry, pre-sintering can be performed at a temperature lower than the full sintering temperature of LSC, for example, at a temperature that causes the shrinkage rate of the LSC slurry layer to be about 1% to 3%, or with a sintering time shorter than the time required to complete full sintering, thereby forming the second cathode electrode layer 132. The pre-sintering temperature that causes the shrinkage rate of the LSC slurry layer to reach about 1% to 3% can be about 900°C to 1000°C.

[0059] The current collector 140 is located above the second cathode electrode layer 132 to contact the second cathode electrode layer 132, and may be formed of a conductive material, such as a metal or alloy.

[0060] In one embodiment, the current collector 140 may include: a separation plate 140a; and a current collector mesh structure 140b located between the separation plate 140a and the second cathode electrode layer 132 to improve the electrical connection characteristics of the separation plate 140a and the second cathode electrode layer 132.

[0061] As one embodiment, the separation plate 140a may include a first metal member 141a and a first chromium collection layer 143a, covering at least a portion of the surface of the first metal member 141a. Furthermore, the collector mesh structure 140b may include a second metal member 141b and a coating layer 142b, coated on at least a portion of the surface of the second metal member 141b; the coating layer 142b is formed of the same material as constituting the second cathode electrode layer 132 and may have a similar hardness to the second cathode electrode layer 132. For example, the hardness of the coating layer 142b may be about 0.7 to 1.2 times the hardness of the second cathode electrode layer 132. In one embodiment, when the second cathode electrode layer 132 and the coating layer 142b are formed by LSC, the coating layer 142b may be formed by pre-sintering after applying an LSC slurry to the surface of the second metal member 141b and then heat-treating it at a temperature such as about 600°C to 800°C. When the current collector mesh structure 140b includes the coating layer 142b, the coating layer 142b, which has relatively low hardness and high ductility, can not only reduce the electrical contact resistance between the current collector 140 and the second cathode electrode layer 132, but also more stably prevent cracking in the single cell through the current collector 140. Furthermore, the coating layer 142b can prevent chromium contained in the second metal member 141b from diffusing into the cathode electrode layer 130. Alternatively, the current collector mesh structure 140b may also include a second chromium collecting layer 143b formed between the second metal member 141b and the coating layer 142b.

[0062] On the other hand, due to the relatively low hardness of the second cathode electrode layer 132, at least a portion of the current collector mesh structure 140b can be embedded inside the second cathode electrode layer 132.

[0063] Figure 2 This is a cross-sectional view used to illustrate a solid oxide fuel cell according to another embodiment of the present invention.

[0064] Reference Figure 2 According to another embodiment of the present invention, a solid oxide fuel cell 200 may include an anode electrode layer 210, a solid oxide electrolyte layer 220, a cathode electrode layer 230, and a current collector 240.

[0065] The anode electrode layer 210, the solid oxide electrolyte layer 220, and the cathode electrode layer 230 are respectively compared with a reference. Figure 1 The anode electrode layer 110, solid oxide electrolyte layer 120 and cathode electrode layer 130 of the solid oxide fuel cell 100 described herein are substantially the same, therefore repeated detailed descriptions of them will be omitted.

[0066] and Figure 1 Unlike the current collector 140 shown, the current collector 240 may only include a separator plate without the grid hole structure. As the separator plate, the current collector 240 may have a protrusion formed on one surface of the separator plate facing the second cathode electrode layer 232 to form a flow path. Due to the relatively low hardness of the second cathode electrode layer 232, the end of the protrusion may be embedded inside the second cathode electrode layer 232. For example, the protrusion may include a rib that forms a flow path for uniformly supplying air to the cathode electrode layer 230.

[0067] In one embodiment, the current collector 240 may include a metal component 241 and a coating layer 242 coated on at least a portion of the surface of the metal component 241; the coating layer 242 is formed of the same material constituting the second cathode electrode layer 232 and may have a similar hardness to the second cathode electrode layer 232. For example, the hardness of the coating layer 242 may be about 0.7 to 1.2 times the hardness of the second cathode electrode layer 232. In one embodiment, when the second cathode electrode layer 232 and the coating layer 242 are formed by LSC, the coating layer 242 may be formed by applying an LSC slurry to the surface of the metal component 241 and then heat-treating it at a temperature of about 600°C to 800°C to achieve post-sintering. When the current collector 240 includes the coating layer 242, the coating layer 242, which has relatively low hardness and high ductility, can not only reduce the electrical contact resistance between the current collector 240 and the second cathode electrode layer 232, but also more stably prevent cracking in the single cell. Furthermore, the coating layer 242 can prevent chromium contained in the metal component 241 from diffusing into the cathode electrode layer 230. Alternatively, the current collector 240 may also include a chromium collecting layer 243 formed between the metal component 241 and the coating layer 242.

[0068] Figure 3 This is a flowchart illustrating a method for manufacturing a solid oxide fuel cell according to an embodiment of the present invention.

[0069] Reference Figure 1 , Figure 2 as well as Figure 3The manufacturing method of a solid oxide fuel cell (solid oxide fuel cell 100, solid oxide fuel cell 200) according to an embodiment of the present invention may include: a first step S110, manufacturing a stacked structure of an anode electrode layer (anode electrode layer 110, anode electrode layer 210), a solid oxide electrolyte layer (solid oxide electrolyte layer 120, solid oxide electrolyte layer 220) and a first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231); a second step S120, coating the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) with cathode slurry to form a cathode slurry layer; and a third step S130, pre-sintering the cathode slurry layer to form a second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232).

[0070] In the first step S110, the manufacturing method of the stacked structure of the anode electrode layer (anode electrode layer 110, anode electrode layer 210), the solid oxide electrolyte layer (solid oxide electrolyte layer 120, solid oxide electrolyte layer 220) and the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) is not particularly limited.

[0071] As one embodiment, the stacked structure can be manufactured by sequentially stacking an anode green sheet, a solid oxide electrolyte green sheet, and a cathode green sheet, and then sintering them. As another embodiment, the stacked structure can also be manufactured by stacking the anode green sheet and the solid oxide electrolyte green sheet and then performing a first sintering, and then stacking the cathode green sheet on the solid oxide electrolyte layers (solid oxide electrolyte layer 120, solid oxide electrolyte layer 220) formed by the first sintering and then performing a second sintering, thereby manufacturing the stacked structure.

[0072] The anode electrode green sheet can be manufactured by forming a support green sheet using a casting process comprising support raw material powder, a pore-forming agent, and a binder, followed by coating the surface of the support green sheet with a mixed slurry of nickel oxide powder and YSZ powder. Furthermore, the solid oxide electrolyte green sheet can be manufactured using a casting process employing YSZ powder slurry, and the cathode electrode green sheet can be manufactured using a casting process employing LSCF or LSM powder slurry.

[0073] In the second step S120, a cathode paste layer can be formed by coating the surface of the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) of the laminated structure with LSC powder paste. The method of coating the LSC powder paste onto the surface of the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) is not particularly limited. For example, the LSC powder paste can be coated onto the surface of the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) by a coating process to form the cathode paste layer.

[0074] In the third step S130, the cathode slurry layer can be pre-sintered to form a second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) with relatively low hardness and relatively high ductility. The pre-sintering of the cathode slurry layer can be performed by controlling the sintering temperature, pressure, or time so that the density of the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) formed by pre-sintering is approximately 70% to 95% of the theoretical density. As an example, under a load of 0.01 kgf and a holding time of 10 seconds, the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) can be pre-sintered to achieve a Vickers hardness of approximately 10 to 20, for example, approximately 15 to 18.

[0075] The solid oxide fuel cell manufactured by the above method is a single cell, and a fuel cell stack can be formed by stacking multiple such single cells using current collectors (current collector 140, current collector 240). In this case, the current collectors (current collector 140, current collector 240) can be as follows: Figure 1 The combination of the separation plate 140a and the collector grid structure 140b shown can also be as follows: Figure 2 The separate separation plate 240 shown.

[0076] During the manufacturing process of the fuel cell stack, the bonding characteristics between the anode electrode layer (anode electrode layer 110, anode electrode layer 210) and the current collector (current collector 140, current collector 240) of the single cell and the current collector (current collector 140, current collector 240) and the cathode electrode layer (cathode electrode layer 130, cathode electrode layer 230) and the current collector (current collector 140, current collector 240) of the single cell can be improved by performing a pressurization process after alternately stacking the single cell and the current collector (current collector 140, current collector 240). In this case, as in the present invention, when the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) in contact with the current collector (current collector 140, current collector 240) is formed to have relatively low hardness and relatively high ductility, a portion of the current collector (current collector 140, current collector 240) can penetrate into the interior of the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) during the pressurization process, thereby significantly improving the bonding characteristics of the current collector (current collector 140, current collector 240) and the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232). Furthermore, when the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) is formed to have relatively low hardness and relatively high ductility, as described above, the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) absorbs part of the impact force or pressure, thereby preventing cracks from occurring at any location in the cathode electrode layer (cathode electrode layer 130, cathode electrode layer 230), the solid oxide electrolyte layer (solid oxide electrolyte layer 120, solid oxide electrolyte layer 220), and the anode electrode layer (anode electrode layer 110, anode electrode layer 210).

[0077] Although the invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and alterations can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. A solid oxide fuel cell, characterized by comprising: a solid oxide electrolyte layer; an anode electrode layer on a first surface of the solid oxide electrolyte layer; a first cathode electrode layer on a second surface of the solid oxide electrolyte layer; a second cathode electrode layer on an upper portion of the first cathode electrode layer and having a hardness lower than that of the first cathode electrode layer; and a current collecting member on an upper portion of the second cathode electrode layer and in contact with the second cathode electrode layer; the current collecting member comprising: a metal member; a coating layer applied to at least a region of a surface of the metal member facing the second cathode electrode layer; and a chromium collection layer formed between the metal member and the coating layer; the coating layer being formed of the same material as the second cathode electrode layer.

2. The solid oxide fuel cell according to claim 1, characterized in that 3. The solid oxide fuel cell according to claim 2, characterized in that the Vickers hardness of the first cathode electrode layer is 48 to 57 and the Vickers hardness of the second cathode electrode layer is 10 to 20 under a load of 0.01 kgf and a holding time of 10 seconds.

4. The solid oxide fuel cell according to claim 1, characterized in that at least a portion of the current collecting member is embedded inside the second cathode electrode layer.

5. The solid oxide fuel cell according to claim 1, characterized in that the current collecting member comprises a separator plate, and at least a portion of the separator plate is embedded inside the second cathode electrode layer.

6. The solid oxide fuel cell according to claim 1, characterized in that the current collecting member comprises: a separator plate, and a current collecting mesh structure between the separator plate and the second cathode electrode layer; the metal member is the current collecting mesh structure, at least a portion of the current collecting mesh structure is embedded inside the second cathode electrode layer.

7. The solid oxide fuel cell according to claim 1, characterized in that the hardness of the coating layer is 0.7 to 1.2 times the hardness of the second cathode electrode layer. The first cathode electrode layer is formed of LSCF or LSM, wherein the LSCF is La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ , and the LSM is La 1-x Sr x MnO3, The second cathode electrode layer is formed of LSC, wherein the LSC is La 0.6 Sr 0.4 CoO 3-δ .

8. A method for manufacturing a solid oxide fuel cell, characterized by comprising: a first step of manufacturing a laminated structure of an anode electrode layer, a solid oxide electrolyte layer, and a first cathode electrode layer; a second step of applying a cathode slurry on a surface of the first cathode electrode layer to form a cathode slurry layer; a third step of pre-sintering the cathode slurry layer to form a second cathode electrode layer; and a fourth step of disposing a current collecting member on the second cathode electrode layer and pressing it; the current collecting member comprising: a metal member; a coating layer applied to at least a region of a surface of the metal member facing the second cathode electrode layer; and a chromium collection layer formed between the metal member and the coating layer; the coating layer being formed of the same material as the second cathode electrode layer.

9. The method for manufacturing a solid oxide fuel cell according to claim 8, characterized in that the cathode slurry contains LSC powder. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. The method of manufacturing a solid oxide fuel cell according to claim 9, characterized in that, the pre-sintering of the cathode slurry layer is performed in such a manner that the density of the cathode slurry layer is 80% to 95% of the theoretical density at the full sintering temperature.

11. The method of manufacturing a solid oxide fuel cell according to claim 8, characterized in that, in the step of pressing, a part of the current collecting member is buried inside the second cathode electrode layer.

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