Solid oxide fuel cell and manufacturing method thereof

Abstract

Disclosed are a solid oxide fuel cell and a method of manufacturing the same. The solid oxide fuel cell includes: 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; and 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.

Description

Technical Field

[0001] The present invention relates to a solid oxide fuel cell that generates electric power through the reaction of hydrogen and oxygen, and a method for manufacturing the same. Background Art

[0002] A solid oxide fuel cell is a fuel cell that operates at a high temperature of about 600°C to 1000°C, and has many advantages such as the highest efficiency, the least pollution, and the ability to perform combined power generation without a fuel converter among various types of conventional fuel cells.

[0003] The solid oxide fuel cell as described above can be roughly classified into a flat plate type, a cylindrical type, and a flat tube type. The flat plate type solid oxide fuel cell has the advantage of a high power density of the stack itself compared to the cylindrical or flat tube type solid oxide fuel cell, and thus is the most widely used.

[0004] The flat plate type solid oxide fuel cell is usually applied in the form of a fuel cell stack in which a plurality of single cells are stacked using a metal separator plate. In such a fuel cell stack, it is necessary to reduce the contact resistance by uniformly contacting the electrodes of the single cell formed of ceramic and the metal separator plate, thereby improving the performance of the fuel cell stack.

[0005] In addition, if cracks occur in the ceramic single cell during the pressing process that must be applied during the manufacture of the fuel cell stack, it will have a significant adverse effect on the performance and stability of the fuel cell stack. Therefore, it is necessary to develop a technology to prevent the occurrence of such cracks.

[0006] In addition, the fuel cell stack operates at a high temperature of about 600°C to 800°C, and when chromium (Cr) as a metal component constituting the fuel cell stack diffuses into the single cell, the performance of the single cell deteriorates rapidly. Therefore, it is necessary to develop a fuel cell stack that can correctly collect chromium.

[0007] Contents of the Invention

[0008] Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a solid oxide fuel cell having improved chromium collection ability, capable of preventing cracks from occurring in a single cell during the manufacturing process, and capable of exhibiting excellent performance by improving the 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 the 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 disposed on a first surface of the solid oxide electrolyte layer; a first cathode electrode layer disposed on a second surface of the solid oxide electrolyte layer; and a second cathode electrode layer disposed on an upper portion of the first cathode electrode layer and having a hardness lower than that of the first cathode electrode layer.

[0013] In one embodiment, the solid oxide fuel cell may further include: a current collector member disposed on an upper portion 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 formed of lanthanum strontium cobalt ferrite (LSCF) (La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) or lanthanum strontium manganite (LSM) (La 1-x Sr x MnO 3 ), and the second cathode electrode layer may be formed of lanthanum strontium cobaltite (LSC) (La 0.6 Sr 0.4 CoO 3-δ ).

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

[0016] In one embodiment, at least a part of the current collector member may be buried inside the second cathode electrode layer.

[0017] In one embodiment, the current collector member may include a separator plate, and at least a part of the separator plate is buried inside the second cathode electrode layer.

[0018] In one embodiment, the current collector member may include: a separator plate, and a current collecting mesh structure disposed between the separator plate and the second cathode electrode layer; at least a part of the current collecting mesh structure is buried inside the second cathode electrode layer.

[0019] In one embodiment, the current collector member may include: a metal member, and a coating layer coated at least on a region of the surface of the metal member facing the second cathode electrode layer; at this time, 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 may be 0.7 times to 1.2 times the hardness of the second cathode electrode layer.

[0021] In one embodiment, the current collector member may further include: a chromium collection 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 stacked structure of an anode electrode layer, a solid oxide electrolyte layer, and a first cathode electrode layer; a second step of coating a cathode paste on the surface of the first cathode electrode layer to form a cathode paste layer; and a third step of pre-sintering the cathode paste 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 paste layer may be performed such that the density of the cathode paste layer is 80% to 95% of the theoretical density sintered at the full sintering temperature.

[0025] In one embodiment, the method for manufacturing the solid oxide fuel cell may further include the following steps: disposing a current collector member on the second cathode electrode layer and applying pressure thereto; at this time, in the pressing step, a part of the current collector member may be buried inside the second cathode electrode layer.

[0026] 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, so that not only the contact characteristics between the cathode electrode layer and the current collector member can be improved, but also cracks can be prevented from occurring in any one of the cathode electrode layer, the solid oxide electrolyte layer, and the anode electrode layer due to the impact applied by the current collector member during the manufacturing process or operation, and the chromium collection ability can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional view for explaining a solid oxide fuel cell.

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

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

[0031] Explanation of reference numerals

[0032] 100, 200: Solid oxide fuel cell

[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 member Detailed description of the specific embodiment

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention can be subjected to various changes and can have various forms. Specific embodiments are illustrated in the drawings and are described in detail herein. However, this is not intended to limit the present invention to the specific disclosed form, and it should be understood to include all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. When explaining each drawing, similar reference numerals are used for similar components. In the drawings, the dimensions of the structures are shown enlarged for the clarity of the present invention.

[0042] Terms such as "first" and "second" can be used to describe various components, but the components are not limited to these terms. These terms are only used for the purpose of distinguishing one component from other components. For example, without departing from the scope of the claims of the present invention, the first component can be named the second component, and similarly, the second component can also be named the first component.

[0043] The terms used in this application are only for describing specific embodiments and are not intended to limit the present invention. Unless otherwise clearly specified in the context, singular expressions include plural expressions. In this application, terms such as "including" or "having" are used to specify the existence of features, numbers, steps, actions, components, parts, or combinations thereof recorded in the specification, and do not preclude the existence or additional possibility of one or more other features, numbers, steps, actions, components, parts, or combinations thereof in advance.

[0044] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. Terms defined in a commonly used dictionary shall be interpreted as having the same meaning as in the context of the relevant technology, and shall not be interpreted as ideal or overly formal meanings unless clearly defined in this application.

[0045] Figure 1 is a cross-sectional view for explaining a solid oxide fuel cell.

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

[0047] The anode electrode layer 110 may have a porous structure for allowing a hydrogen-containing fuel to move therein, and may be formed of a cermet of a transition metal and an ion-conductive oxide. For example, the anode electrode layer 110 may be formed of a cermet of nickel (Ni) and yttria-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 for increasing the strength of a single cell (a laminate of the anode electrode layer 110, the solid oxide electrolyte layer 120, and the cathode electrode layer 130). Its thickness may be thicker than that of the anode functional layer 112, and it has a porous structure for allowing a hydrogen-containing fuel gas to move therein, and may be formed of a cermet of nickel and YSZ. As an embodiment, the anode support layer 111 may be formed of a support raw material powder containing about 30 to 60 parts by weight of the YSZ powder and about 40 to 70 parts by weight of the nickel oxide powder.

[0050] In one embodiment, the anode support layer 111 can be manufactured in the following manner: the support raw material powder is mixed with a pore former and dispersed in a solvent, and then a binder is added thereto to manufacture a slurry for forming the support. Then, a compression molding process or a tape casting process is performed using the slurry for forming the support. In this case, powders such as polymethyl methacrylate (PMMA), activated carbon, carbon black, graphite, and starch can be used as the pore former, and the slurry for forming the support can contain approximately 30 to 60 parts by weight of the YSZ powder, approximately 40 to 70 parts by weight of the nickel oxide powder, and approximately 1 to 20 parts by weight of the pore former. In addition, a polyvinyl alcohol (PVA)-based binder, a methylcellulose (MC)-based binder, a sodium carboxymethylcellulose (CMC)-based binder, or a mixture of two or more of these can be used as the binder, and the binder can be mixed in an amount of approximately 10 vol% to approximately 50 vol% with respect to the first raw material powder. In addition, water can be used as the solvent. For example, distilled water or deionized water can be used.

[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 an embodiment, the anode functional layer 112 can be formed of a cermet of YSZ and nickel. For example, the anode functional layer 112 can be formed in the following manner: after forming a mixed slurry of nickel oxide powder and YSZ powder, a coating film is formed on the anode support layer 111 using a dip coating method, and after drying, sintering is performed 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 through sintering.

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

[0053] In one embodiment, the solid oxide electrolyte layer 120 can be formed in the following manner: a green sheet is manufactured by a doctor blade process of a YSZ slurry, and then, after being laminated with the green sheet of the anode electrode layer 110, sintering is performed to form the anode electrode layer 110 and the solid oxide electrolyte layer 120 bonded thereto. Different from this, the solid oxide electrolyte layer 120 can also be formed in the following manner: after an electrolyte coating film is formed on the outer surface of the anode functional layer 112 by a dipcoating method of the YSZ slurry, sintering is performed on it in an air atmosphere at about 1300 °C to about 1500 °C.

[0054] The cathode electrode layer 130 is located on the solid oxide electrolyte layer 120, has a porous structure through which oxygen can move inside, and can be formed of a metal oxide material having ionic conductivity and electronic conductivity.

[0055] In one embodiment, the cathode electrode layer 130 can include: a first cathode electrode layer 131, located on the upper part of the solid oxide electrolyte layer 120; and a second cathode electrode layer 132, located on the upper part of the first cathode electrode layer 131.

[0056] As one embodiment, the first cathode electrode layer 131 can be formed of a material different from that of the second cathode electrode layer 132. For example, in order to prevent the cathode electrode 130 from being separated from the solid oxide electrolyte layer 120 during the sintering process, the first cathode electrode layer 131 can be formed of a material having a thermal expansion coefficient smaller than that of the second cathode electrode layer 132. Although LSC has higher ionic conductivity than LSCF and has more excellent catalytic activity, because it has a relatively large thermal expansion coefficient of about 20×10 -6 to 23×10 -6 / K, when it is laminated on the solid oxide electrolyte layer 120 formed of YSZ and sintered, there may be a problem that the LSC layer is separated from the solid oxide electrolyte layer 120 due to the difference in thermal expansion coefficient. In order to compensate for this mismatch in the thermal expansion coefficients of LSC and the solid oxide electrolyte, the first cathode electrode layer 131 can be formed of LSM (La 1-x Sr x MnO 3 ) or LSCF (La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ), and the second cathode electrode layer 132 can be formed of LSC (La 0.6 Sr 0.4 CoO 3-δ)Formed (where x and δ are real numbers greater than or equal to 0 and less than 1, respectively). When LSCF and LSC are used as the materials of 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 occurring during the manufacturing process can be solved, and the electrode performance of the cathode electrode layer 130 can also be improved.

[0057] As an embodiment, the surface hardness of the second cathode electrode layer 132 may be less than the surface hardness of the first cathode layer 131. In this case, the generation of cracks that may occur in the single cell during the pressing manufacturing process (for ensuring the bonding between the current collector member 140 and the cathode electrode layer 130) can be prevented, and the surface contact uniformity between the current collector member 140 and the cathode electrode layer 130 can be improved, and the collection ability of chromium (Cr) accompanying air flow can be improved. For example, under the conditions of a load of 0.01 kgf and a holding time of 10 seconds, the Vicker Hardness of the first cathode electrode layer 131 is about 48 to 57, while the Vicker Hardness of the second cathode electrode layer 132 can be about 10 to 20 under the same conditions, for example, it can be about 15 to 18. The hardness of the second cathode electrode layer 132 can be adjusted by changing the sintering conditions for forming the second cathode electrode layer 132. For example, after forming a cathode paste layer by coating a cathode paste for forming the second cathode electrode layer 132 on the first cathode electrode layer 131 made of the fully sintered body, the cathode paste layer is pre-sintered, so that the second cathode electrode layer 132 with relatively low hardness and relatively high ductility can be formed. In this specification, "fully sintered" means that the sintering object is sintered by applying a sintering temperature, pressure or time so that the density of the sintering object becomes a density of 98% or more of the theoretical density, and "pre-sintered" means that the sintering object is sintered by applying a sintering temperature, pressure or time so that although necking occurs between the particles of the sintering object, there are many voids inside, so that the density of the sintering object becomes about 70% to 95% of the theoretical density.

[0058] As an example, 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 an LSCF paste or laminating a green sheet of LSCF on the solid electrolyte layer 120 and then completely sintering it under a pressurized state. Then, after coating an LSC paste on the first cathode electrode layer 131, pre-sintering can be performed at a temperature lower than the complete sintering temperature of LSC, for example, at a temperature that makes the shrinkage rate of the LSC paste layer about 1% to 3%, or at a sintering time shorter than the time required to complete the complete sintering, so as to form the second cathode electrode layer 132. The pre-sintering temperature at which the shrinkage rate of the LSC paste layer reaches about 1% to 3% can be about 900°C to 1000°C.

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

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

[0061] As an embodiment, the separation plate 140a may include: a first metal member 141a, and a first chromium collection layer 143a covering at least a part of the surface of the first metal member 141a. In addition, the current collecting mesh structure 140b may include: a second metal member 141b, and a coating layer 142b coated on at least a part of the surface of the second metal member 141b; the coating layer 142b is formed of the same material as the material constituting the second cathode electrode layer 132 and may have a hardness similar to that of the second cathode electrode layer 132. For example, the hardness of the coating layer 142b may be about 0.7 times 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 of LSC, the coating layer 142b may be formed by coating an LSC slurry on the surface of the second metal member 141b and then performing heat treatment at a temperature of about 600°C to 800°C to achieve pre-sintering. When the current collecting mesh structure 140b includes the coating layer 142b, through the coating layer 142b with relatively low hardness and high ductility, not only can the electrical contact resistance between the current collecting member 140 and the second cathode electrode layer 132 be reduced, but also cracks generated in the single cell can be more stably prevented through the current collecting member 140. In addition, the coating layer 142b can prevent chromium contained in the second metal member 141b from diffusing into the cathode electrode layer 130. On the other hand, the current collecting mesh structure 140b may further include a second chromium collection layer 143b formed between the second metal member 141b and the coating layer 142b.

[0062] On the other hand, due to the physical property of the relatively low hardness of the second cathode electrode layer 132, at least a part of the current collecting mesh structure 140b may be buried inside the second cathode electrode layer 132.

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

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

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

[0066] Unlike Figure 1 the current collector member 140 shown, the current collector member 240 may include only a separator plate without a grid hole structure. As the current collector member 240 which is the separator plate, protrusions for forming a flow path may be formed on one surface of the separator plate facing the second cathode electrode layer 232, and due to the relatively low hardness physical property of the second cathode electrode layer 232, the ends of the protrusions may be buried inside the second cathode electrode layer 232. For example, the protrusions may include ribs which form a flow path for uniformly supplying air to the cathode electrode layer 230.

[0067] In one embodiment, the current collector member 240 may include: a metal member 241, and a coating layer 242 coated on at least a part of the surface of the metal member 241; the coating layer 242 is formed of the same material as the material constituting the second cathode electrode layer 232 and may have a hardness similar to that of the second cathode electrode layer 232. For example, the hardness of the coating layer 242 may be about 0.7 times 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 of LSC, the coating layer 242 may be formed by coating an LSC slurry on the surface of the metal member 241 and then performing heat treatment at a temperature of about 600 °C to 800 °C to achieve post pre-sintering. When the current collector member 240 includes the coating layer 242, through the coating layer 242 with relatively low hardness and high ductility, not only can the electrical contact resistance between the current collector member 240 and the second cathode electrode layer 232 be reduced, but also cracks generated in the single cell can be more stably prevented through the current collector member 240. In addition, the coating layer 242 can prevent chromium contained in the metal member 241 from diffusing into the cathode electrode layer 230. On the other hand, the current collector member 240 may further include a chromium collection layer 243 formed between the metal member 241 and the coating layer 242.

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

[0069] Refer to Figure 1 、 Figure 2 and Figure 3, A method for manufacturing 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 of 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 of coating a cathode paste on the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) to form a cathode paste layer; and a third step S130 of pre-sintering the cathode paste 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 method for manufacturing 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 an embodiment, the stacked structure may be manufactured by sequentially stacking an anode electrode green sheet, a solid oxide electrolyte green sheet, and a cathode electrode green sheet and then sintering them. As another embodiment, the stacked structure may also be manufactured by the following method: stacking the anode electrode green sheet and the solid oxide electrolyte green sheet and then performing a first sintering, and then stacking the cathode electrode green sheet on the solid oxide electrolyte layer (solid oxide electrolyte layer 120, solid oxide electrolyte layer 220) formed by the first sintering and then performing a second sintering to manufacture the stacked structure.

[0072] The anode electrode green sheet may be manufactured by the following method: forming a support green sheet through a doctor blade forming process of a support forming slurry containing a support raw material powder, a pore former, and a binder, and then coating a mixed slurry of nickel oxide powder and YSZ powder on the surface of the support green sheet. In addition, the solid oxide electrolyte green sheet may be manufactured through a doctor blade forming process of a YSZ powder slurry, and the cathode electrode green sheet may be manufactured through a doctor blade forming process of an LSCF or LSM powder slurry.

[0073] In the second step S120, a cathode paste layer can be formed by coating an LSC powder paste on the surface of the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) of the stacked structure. The method of coating the LSC powder paste on 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 on the surface of the first cathode electrode layer (first cathode electrode layer 131, first cathode electrode layer 231) through a coating process to form the cathode paste layer.

[0074] In the third step S130, the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) having a relatively low hardness and a relatively high ductility can be formed by pre-sintering the cathode paste layer. The pre-sintering of the cathode paste 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 becomes about 70% to 95% of the theoretical density. As an example, under the conditions of 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 have a Vickers hardness of about 10 to 20, for example, about 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 a plurality of the single cells using current collecting members (current collecting members 140, current collecting members 240). In this case, the current collecting members (current collecting members 140, current collecting members 240) can be a combination of a separator plate 140a and a current collecting mesh structure 140b as shown in Figure 1 or a single separator plate 240 as shown in Figure 2

[0076] ​In the process of manufacturing the fuel cell stack, the bonding characteristics between the anode electrode layers (anode electrode layer 110, anode electrode layer 210) of the single cells and the current collector members (current collector member 140, current collector member 240) and between the cathode electrode layers (cathode electrode layer 130, cathode electrode layer 230) of the single cells and the current collector members (current collector member 140, current collector member 240) can be improved by alternately laminating the single cells and the current collector members (current collector member 140, current collector member 240) and then performing a pressing process. At this time, 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 members (current collector member 140, current collector member 240) is formed to have a relatively low hardness and a relatively high ductility, a part of the current collector members (current collector member 140, current collector member 240) can penetrate into the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) during the pressing process, thereby significantly improving the bonding characteristics between the current collector members (current collector member 140, current collector member 240) and the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232). In addition, when the second cathode electrode layer (second cathode electrode layer 132, second cathode electrode layer 232) is formed to have a relatively low hardness and a 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 position 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 above has been described with reference to the preferred embodiments of the present invention, those of ordinary skill in the art can understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention described in the following claims.

Claims

1. A solid oxide fuel cell, characterized in that: include: solid oxide electrolyte layer; an anode electrode layer, located on the first surface of the solid oxide electrolyte layer; a first cathode electrode layer disposed on the second surface of the solid oxide electrolyte layer; and The second cathode electrode layer is located on the first cathode electrode layer and has a lower hardness than the first cathode electrode layer.

2. The solid oxide fuel cell according to claim 1, characterized in that: Also includes: The current collecting member is located on the second cathode electrode layer and in contact with the second cathode electrode layer.

3. The solid oxide fuel cell according to claim 2, characterized in that: 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 , the LSM is La 1-x Sr x MnO3, The second cathode electrode layer is formed by LSC, wherein the LSC is La 0.6 Sr 0.4 CoO 3-δ .

4. The solid oxide fuel cell according to claim 3, characterized in that: Under the conditions of 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 is 10 to 20.

5. The solid oxide fuel cell according to claim 2, characterized in that: At least a portion of the current collecting member is buried inside the second cathode electrode layer.

6. The solid oxide fuel cell according to claim 2, characterized in that: The current collecting member includes a separator plate, and at least a portion of the separator plate is buried inside the second cathode electrode layer.

7. The solid oxide fuel cell according to claim 2, characterized in that: The current collecting member comprises: Separator plate, and A collector grid hole structure is located between the separator plate and the second cathode electrode layer; At least a portion of the collector grid structure is buried inside the second cathode electrode layer.

8. The solid oxide fuel cell according to claim 5, characterized in that: The current collecting member comprises: Metal components, and A coating layer, coated at least on a region of the surface of the metal component facing the second cathode electrode layer; The coating layer is formed of the same material as that of the second cathode electrode layer.

9. The solid oxide fuel cell according to claim 8, characterized in that: The hardness of the coating layer is 0.7 to 1.2 times the hardness of the second cathode electrode layer.

10. The solid oxide fuel cell according to claim 8, characterized in that: The current collecting member further includes a chromium collection layer formed between the metal member and the coating layer.

11. A method for manufacturing a solid oxide fuel cell, characterized in that: include: The first step is to manufacture a stacked structure of an anode electrode layer, a solid oxide electrolyte layer and a first cathode electrode layer; A second step is to coat a cathode slurry on the surface of the first cathode electrode layer to form a cathode slurry layer; and The third step is to pre-sinter the cathode slurry layer to form a second cathode electrode layer.

12. The method for manufacturing a solid oxide fuel cell according to claim 11, characterized in that: The cathode slurry comprises LSC powder.

13. The method for manufacturing a solid oxide fuel cell according to claim 12, characterized in that: The pre-sintering of the cathode slurry layer is performed in such a way that the density of the cathode slurry layer is 80% to 95% of the theoretical density sintered at the full sintering temperature.

14. The method for manufacturing a solid oxide fuel cell according to claim 11, characterized in that: The method further comprises a pressurizing step of placing a current collecting member on the second cathode electrode layer and pressurizing the current collecting member. In the pressurizing step, a portion of the current collecting member is buried inside the second cathode electrode layer.

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