Electrical contact layer for solid oxide fuel cell, preparation method thereof and solid oxide fuel cell comprising the same

Abstract

The present invention provides an electrical contact layer for a solid oxide cell, a solid oxide fuel cell containing the same, and a method for preparing the electrical contact layer. The electrical contact layer is located between the oxygen electrode of the solid oxide cell and an interconnected substrate, wherein the electrical contact layer includes a coating of slurry A and a coating of slurry B, the coating of slurry B being adjacent to the oxygen electrode, the coating of slurry A being formed by mixing manganese-cobalt mixed metal powder and a binder, and the coating of slurry B being formed by mixing manganese-cobalt mixed metal powder with perovskite oxide and a binder.

Description

Technical Field

[0001] The present invention relates to the field of solid oxide fuel cells, and in particular to an electric contact layer for a solid oxide fuel cell, a solid oxide fuel cell comprising the electric contact layer, and a method for preparing the electric contact layer. Background Art

[0002] Solid oxide fuel cells (SOFCs) are all-solid-state power generation devices that convert the chemical energy in fuels directly into electrical energy through electrochemical reactions. They can efficiently generate electricity from fuels such as hydrogen, ammonia, or hydrocarbons. When operated in reverse mode as a solid oxide electrolysis cell (SOFC), the same device can be used to produce hydrogen or synthesis gas, which can be stored or converted into high-value-added chemicals. It is generally believed that solid oxide cells (SOCs) have the following advantages: (1) environmental compatibility, capable of absorbing carbon dioxide; (2) flexible application, with a variety of inlet compositions, and suitable for integration with various renewable energy sources; (3) powerful functions, playing an important role in energy use and storage; (4) universal applicability, able to meet different applications or local energy needs; (5) cost control, and cost competitiveness compared with other energy forms. In order to achieve the commercialization of SOC technology, its long-term stability and reliability must be guaranteed.

[0003] Planar solid oxide fuel cells or electrolyzers are the predominant structure currently used for stack manufacturing internationally. Their most prominent advantage is that they can use inexpensive alloys such as stainless steel as interconnect materials between cells while maintaining high power density. At the same time, establishing a strong contact between the cell's oxygen electrode and the stainless steel interconnect is one of the main durability challenges currently facing SOC stacks. To improve the bond between these two layers, an electrical contact layer can be prepared. The contact layer material should be physicochemically compatible with the oxygen electrode and the coating interconnect, possessing high conductivity and strength, and a thermal expansion coefficient that matches that of the other battery components.

[0004] Currently commonly used ceramic perovskite oxides have high electrical conductivity and thermal expansion coefficient, but their main disadvantage is that they require high-temperature sintering (~1100°C). Due to the use of stainless steel interconnects and glass (ceramic) seals, the upper limit of the sealing temperature of general stack components is about 900°C, which will lead to insufficient sintering of the contact layer and weak adhesion at the interface, increasing the risk of contact loss during operation and thermal cycling. Therefore, in order to achieve strong sintering of the contact layer at low sintering temperatures, a potential method is to form the contact layer through in-situ reactive oxidation bonding. In this method, the contact layer is applied in the form of metal particles and oxidized during the stack assembly / sealing process. Due to the high enthalpy of the oxidation reaction, the sintering driving force is greatly enhanced compared to the sintering driving force of traditional oxide particles.

[0005] In addition, T.H. Norby et al. have also reported on metal coatings, for example, in "Deposition of Coatings on Interconnects for Solid Oxide Battery Stacks," Chinese Patent Publication No. CN110073039A; and "Improved Contact Between Interconnects and Cells in Solid Oxide Battery Stacks," Chinese Patent Publication No. CN110088954A. However, despite the improved adhesion of the metal coating to stainless steel, the significant difference in thermal expansion coefficient between the metal coating and the perovskite-based air electrode results in poor contact with the air electrode. Summary of the Invention

[0006] The present invention solves the above technical problems and obtains a stable and reliable electrical contact layer by coating and sintering to form two or more coatings containing different substances between the oxygen electrode and the interconnected substrate of the solid oxide fuel cell.

[0007] Specifically, in one aspect, the present invention provides a method for preparing an electrical contact layer, wherein the electrical contact layer is located between an oxygen electrode of a solid oxide cell and an interconnect substrate, wherein the method comprises the following steps:

[0008] (1) preparing manganese-cobalt mixed metal powder;

[0009] (2) mixing the manganese-cobalt mixed metal powder with a binder and grinding to obtain slurry A;

[0010] (3) mixing the manganese-cobalt mixed metal powder with perovskite oxide and a binder, and grinding to obtain at least one slurry B;

[0011] (4) coating the slurry B on the surface of the oxygen electrode and drying it to form at least one layer of slurry B coating, and coating the slurry A on the slurry B coating of the oxygen electrode and / or the surface of the interconnect substrate and drying it to form a slurry A coating; or

[0012] (5) applying the slurry A and the slurry B sequentially onto the surface of the interconnect substrate and drying them to form a coating layer of slurry A and at least one coating layer of slurry B;

[0013] (6) Assembling the oxygen electrode prepared in step (4) with an interconnect substrate and sintering them in situ, or assembling the interconnect substrate prepared in step (5) with the oxygen electrode and sintering them, to form an electrical contact layer between the oxygen electrode and the interconnect substrate, wherein the electrical contact layer comprises at least one coating layer of slurry B and a coating layer of slurry A, wherein the coating layer of slurry B is adjacent to the oxygen electrode.

[0014] In the method for preparing the electrical contact layer of the present invention, by making the interconnect substrate adjacent to the coating of slurry A and the oxygen electrode adjacent to the coating of slurry B, the coatings on both sides of the electrical contact layer simultaneously match the thermal expansion coefficients of the interconnect substrate and the battery oxygen electrode, thereby achieving the purpose of firmly sintering the electrical contact layer to the interconnect substrate and the oxygen electrode at the same time.

[0015] The present invention achieves matching of thermal expansion coefficients by adjusting the mass fraction of perovskite oxide in slurry B (based on the total amount of manganese-cobalt mixed metal powder and perovskite oxide). Therefore, any setting of the mass fraction of perovskite oxide in slurry B that can achieve the purpose of the present invention is within the scope of protection of the present invention. The difference between each slurry B in the "at least one slurry B" of the present invention is mainly that the mass fraction of perovskite oxide therein is different. Preferably, the present invention can also achieve the purpose of the present invention by providing two or more coatings of slurries B with different mass fractions of perovskite oxide. Preferably, the coatings of the two or more slurries B are distributed in a manner with a decreasing mass fraction of perovskite oxide in the direction from the oxygen electrode to the interconnect substrate. In addition, the coating in the present application is directly sintered after coating and drying without any treatment, which simplifies the preparation process of the electrical contact layer.

[0016] Preferably, the step (1) comprises: adding manganese powder and cobalt powder to an alcohol compound, mixing, grinding, and drying to obtain a manganese-cobalt mixed metal powder; preferably, the average particle size of the manganese-cobalt mixed metal powder is 5-100 μm; preferably, the molar ratio of the manganese powder to the cobalt powder is 1:2 to 2:1; preferably, the alcohol compound comprises methanol, ethanol, propanol and / or isopropanol; preferably, the grinding comprises grinding using a planetary ball mill; preferably, the grinding speed is 100-300 rpm, and the time is 6-24 h; preferably, the drying is vacuum drying, and the vacuum drying temperature is 80-100° C., and the time is 24-48 h.

[0017] The binder in the present invention is not particularly limited, and those commonly used in the art can be used. Preferably, a cellulose binder is used, including ethyl cellulose.

[0018] Preferably, in step (2) or (3), the mass ratio of the manganese-cobalt mixed metal powder to the binder is 200:1 to 10:1 (preferably 100:1 to 10:1, more preferably 50:1 to 10:1, for example, 48:1, 42:1, 39:1, 38:1, 34:1, 30:1, 26:1, 24:1, 23:1, 19:1, 18:1 or 11:1); preferably, the binder is a cellulose binder, preferably an ethyl Cellulose, preferably, the binder is mixed in the form of a solution with a concentration of 2 to 10% by mass; preferably, the solid mass fractions in the slurries A and B are both 50 to 80%; preferably, the mixing is carried out using a vacuum mixer; preferably, the speed of the vacuum mixer is 800 to 2000 rpm, and the time is 5 to 10 minutes; preferably, the grinding includes grinding using a three-roll ball mill, and preferably, the roller spacing of the three-roll ball mill is 10 to 150 μm.

[0019] Preferably, in the step (3), based on the total amount of the manganese-cobalt mixed metal powder and the perovskite oxide, the mass fraction of the perovskite oxide is 10wt%-70wt%, for example, it can be 10wt%-60wt%, 10wt%-50wt%, 10wt%-40wt%, 10wt%-30wt%, 10wt%-20wt%, 20wt%-70wt%, 20wt%-60wt%, 20wt%-50wt%, 20wt%-40wt%, 20wt%-30wt%, 30wt%-70wt%, 30wt%-60wt%, 30wt%-50wt%, 30wt%-40wt%, 40wt%-70wt%, 40wt%-60wt% or 40wt%-50wt%.

[0020] Preferably, in step (3), the at least one slurry B comprises two or more slurries, and the mass fraction of the perovskite oxide in each of the two or more slurries is different.

[0021] Preferably, in step (3), the at least one slurry B comprises two or more slurries, and the type of perovskite oxide contained in each of the two or more slurries may be the same or different.

[0022] Preferably, the perovskite oxide comprises LSC, LSM and / or LSCF.

[0023] In the present invention, the slurry can be coated using any suitable method known in the art, including but not limited to wet coating, for example, electrospinning, inkjet printing, 3D printing, doctor blading, roller coating, spin coating, and screen printing.

[0024] Preferably, in steps (4) and (5), the at least one coating layer of slurry B is a coating layer of slurry B, and preferably, the mass fraction of the perovskite oxide in the coating layer of slurry B is 10%-45%;

[0025] Preferably, in steps (4) and (5), the coating of slurry B comprises LSC, LSM or LSCF.

[0026] Preferably, in steps (4) and (5), the coating of slurry B contains LSC. Preferably, the mass fraction of LSC is 10 wt%-15 wt%, more preferably 10 wt%.

[0027] Preferably, in steps (4) and (5), the coating of slurry B contains LSCF. Preferably, the mass fraction of LSCF is 35 wt%-45 wt%, more preferably 40 wt%.

[0028] Preferably, in steps (4) and (5), the at least one coating layer of slurry B is two or more coating layers of slurry B, and each of the two or more coating layers of slurry B is coated in a manner with a decreasing mass fraction of perovskite oxide in the direction from the oxygen electrode to the interconnect substrate.

[0029] Preferably, in the coating of the two or more layers of slurry B, the difference in mass fraction of the perovskite oxide between adjacent coatings (△wt%) is 0%<△wt%≤30%, for example, 5%≤△wt%≤25%, 10%≤△wt%≤20%, 5%≤△wt%≤30%, 10%≤△wt%≤30% or 20%≤△wt%≤30%.

[0030] Preferably, in two or more coating layers of slurry B, the differences in mass fraction of the perovskite oxide between adjacent coating layers are the same or different.

[0031] In the coating of two or more slurry B layers of the present invention, each layer of slurry B may contain one perovskite oxide or a combination of two or more perovskite oxides; the types of perovskite oxides contained in each layer of slurry B may be the same or different.

[0032] Preferably, the coating of the two or more layers of slurry B is 2-7 layers, such as 2-4 layers.

[0033] Preferably, in steps (4) and (5), the two or more layers of slurry B coating include a coating of slurry B1 and a coating of slurry B2, the coating of slurry B1 contains LSM, preferably, the mass fraction of the LSM is 15wt%-25wt%, for example, 20wt%, the coating of slurry B2 contains LSC, preferably, the mass fraction of the LSC is 35wt%-45wt%, for example, 40wt%; preferably, the coating of slurry B2 is adjacent to the oxygen electrode.

[0034] Preferably, in steps (4) and (5), the two or more layers of slurry B coating include a coating of slurry B1, a coating of slurry B2 and a coating of slurry B3, the coating of slurry B1 contains LSM, the mass fraction of the LSM is 10wt%-15wt%, for example, 10wt%, the coating of slurry B2 contains LSCF, the mass fraction of the LSCF is 25wt%-35wt%, for example, 30wt%, and the slurry B3 contains LSC, the mass fraction of the LSC is 45wt%-55wt%, for example, 50wt%; preferably, the slurry B3 is adjacent to the oxygen electrode.

[0035] Preferably, in steps (4) and (5), the two or more layers of slurry B coating include a coating of slurry B1, a coating of slurry B2 and a coating of slurry B3, the coating of slurry B1 contains LSM, the mass fraction of the LSM is 15wt%-25wt%, for example, 20wt%, the coating of slurry B2 contains LSCF, the mass fraction of the LSCF is 40wt%-50wt%, for example, 50wt%, and the slurry B3 contains LSC, the mass fraction of the LSC is 60wt%-70wt%, for example, 70wt%; preferably, the slurry B3 is adjacent to the oxygen electrode.

[0036] Preferably, in steps (4) and (5), the thickness of the coating of slurry A is 50-450 μm, and the thickness of each layer of the at least one layer of slurry B is 50-450 μm; preferably, the total thickness of the coating of slurry A and the at least one layer of slurry B is 100-500 μm; preferably, the coating is carried out by screen printing; preferably, the mesh size of the screen used for screen printing is 100-300.

[0037] Preferably, the drying in steps (4) and (5) is performed at a temperature of 60-110° C. for 5-30 min.

[0038] Preferably, the step (6) satisfies one or more of the following conditions: 1) applying 1-20 N / cm during sintering 22) the sintering is in-situ sintering, preferably the in-situ sintering temperature is 800-900 ° C; 3) the sintering adopts a heating rate of 1-10 ° C / min and a holding time of 2-20 hours; 4) the sintering is carried out in an air atmosphere.

[0039] In the present invention, "in-situ sintering" means that after the slurry layer is dried, no other treatment is performed on it before the fuel cell stack is assembled. During the heating process of the fuel cell stack, the manganese and cobalt metals are oxidized into a manganese and cobalt spinel phase and sintered with the interconnect substrate and the battery oxygen electrode to form an electrical contact layer between the two.

[0040] Preferably, the oxygen electrode is a perovskite oxygen electrode.

[0041] Preferably, the interconnect substrate is a metal interconnect, preferably a stainless steel interconnect.

[0042] In another aspect, the present invention further provides an electrical contact layer produced by the method of the present invention.

[0043] In addition, the present invention also provides a solid oxide fuel cell comprising the above electrical contact layer.

[0044] The contact layer, preparation method thereof, and solid oxide fuel cell comprising the same of the present invention have the following advantages and beneficial effects compared to the prior art:

[0045] The present invention coats and sinters a manganese-cobalt metal mixture and a mixture of manganese-cobalt and perovskite oxide between the battery's interconnect substrate and oxygen electrode (where the interconnect substrate is adjacent to the manganese-cobalt metal mixture, and the oxygen electrode is adjacent to the manganese-cobalt and perovskite oxide mixture). This reduces the sintering temperature while allowing the coatings containing different substances in the electrical contact layer to match the thermal expansion coefficients of the interconnect substrate and the battery's oxygen electrode, respectively. The metal particles bond in situ at operating temperatures, thereby producing a securely sintered electrical contact layer. The electrical contact layer of the present invention can be prepared and securely sintered in situ during the stack assembly / sealing process, effectively ensuring the long-term stability and reliability of the stack and promising industrial applications.

[0046] The method of this invention enables precise control of the uniformity of the electrical contact layer precursor slurry, as well as the thickness and porosity of the deposited film. The reliability of the contact layer is effectively verified by simulating an in-situ sintering process in which the stack is heated to operating temperature. This method is simple, produces a stable and reliable contact layer, and is amenable to assembly-line and large-scale manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The SEM (scanning electron microscope) microstructure of the cross section of the electrical contact layer prepared in Comparative Example 1 of the present invention is shown. Figure 1a) and the surface morphology of the side adjacent to the oxygen electrode after sintering and oxidation in air ( Figure 1 b).

[0048] Figure 2 The figure shows the interconnect substrate-electrical contact layer-half cell sintering sample prepared in Comparative Example 2 of the present invention ( Figure 2 a) and cross-sectional SEM microstructure ( Figure 2 b).

[0049] Figure 3 Shown is a SEM microstructure image of a cross section of the electrical contact layer prepared in Example 3 of the present invention.

[0050] Figure 4 Shown is a SEM microstructure image of a cross section of the electrical contact layer prepared in Example 4 of the present invention.

[0051] Figure 5 Shown is a SEM microstructure image of a cross section of the electrical contact layer prepared in Example 5 of the present invention.

[0052] Figure 6 Shown are the surface resistance test curves of the electrical contact layers prepared in Examples 1-5 of the present invention, with a test temperature of 850° C., a test time of 10 h, and a heating and cooling rate of 5° C. / min. DETAILED DESCRIPTION

[0053] The present invention is described below through specific embodiments, and those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in the present invention. Although the present invention will be introduced in conjunction with a preferred embodiment in the present invention, this does not mean that the features of the present invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be expanded based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The implementation of the present invention may also not use these details. In addition, in order to avoid confusion or obscuring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0054] The present invention performs microscopic observation of the electrical contact layer by the following method:

[0055] 1) Preparation of samples to be observed: The sintered samples in the embodiment are embedded in resin, mechanically cut to expose the cross section, and then the cross section is ground and polished to obtain a smooth and flat morphology under a scanning electron microscope.

[0056] 2) The morphology of the gradient electrical contact layer and the interface sintering condition were observed by super-resolution field emission scanning electron microscopy (JEOL, model: JSM-7800F) using secondary electron mode (LED).

[0057] Example

[0058] Example 1

[0059] (1) 11.188 g of high-purity manganese powder (Mn) and 12 g of high-purity cobalt powder (Co) in a molar ratio of 1:1 were added to a ball mill, and 100 ml of anhydrous ethanol was added. The mixture was ball milled at 300 rpm for 12 h using a planetary ball mill to mix uniformly. The mixture was placed in a vacuum drying oven and dried at 100 °C for 30 h to obtain a metal powder material.

[0060] (2) 9.73 g of metal powder and 4.17 ml of diethyl ethyl acetate binder containing 5 wt% ethyl cellulose were added to a mixing tank at a solid content of 70%, and mixed at 800 rpm for 10 min using a vacuum stirrer to obtain slurry A.

[0061] (3) 9 g of dried metal powder was added to a mixing tank, 1 g of LSC powder additive was added at a ratio of 10 wt%, and 4.29 ml of diethyl ethyl acetate binder containing 5 wt% ethyl cellulose was added at a solid content of 70%. The mixture was mixed at 2000 rpm using a vacuum mixer for 10 min to obtain slurry B.

[0062] (4) Slurries A and B were ground separately on a three-roll ball mill for 10 min with a wheelbase of 30 μm. Slurries A and B were then uniformly deposited on the interconnect substrate using screen printing technology with a mesh size of 300 and a total printed thickness of 300 μm. The resulting films were dried at 90°C for 20 min.

[0063] (5) Assemble the interconnected substrate and the battery oxygen electrode relative to each other and apply 15N / cm 2 The external pressure was 1000℃ and the sintering temperature was 800℃ in air with a heating rate of 2℃ / min and the temperature was kept at this temperature for 10 hours.

[0064] exist Figure 1 middle, Figure 1 a is the SEM microstructure of the contact layer cross section. The local crack between gradient coating A and gradient coating B shown in the figure is the mechanical damage caused when the sample was cut. Outside the damaged area, it can be seen that gradient coating A and gradient coating B are firmly bonded to the stainless steel interconnect and oxygen electrode, respectively. Figure 1 b is the surface morphology of the gradient coating B after the prepared contact layer was sintered and oxidized in air, from which the formation of manganese-cobalt spinel octahedral conductive phase can be seen, which indicates that the in-situ sintered contact layer can have good conductivity.

[0065] Example 2

[0066] (1) 18.646 g of high-purity manganese powder (Mn) and 10 g of high-purity cobalt powder (Co) in a molar ratio of 2:1 were added to a ball mill, and 100 ml of anhydrous ethanol was added. The mixture was ball milled at 200 rpm for 24 hours using a planetary ball mill to mix evenly. The mixture was placed in a vacuum drying oven and dried at 90°C for 48 hours to prepare a metal powder material.

[0067] (2) 9.73 g of metal powder and 4.17 ml of diethyl ethyl acetate binder containing 6 wt% ethyl cellulose were added to a mixing tank at a solid content of 70%, and mixed at 1600 rpm for 5 min using a vacuum stirrer to obtain slurry A.

[0068] (3) 6 g of dried metal powder was added to a mixing tank, 4 g of LSCF powder additive was added at a ratio of 40 wt%, and 4.29 ml of diethyl ethyl acetate binder containing 6 wt% ethyl cellulose was added at a solid content of 70%. The mixture was mixed at 2000 rpm using a vacuum mixer for 5 min to obtain slurry B.

[0069] (4) Slurries A and B were ground separately on a three-roll ball mill for 10 min with a wheelbase of 50 μm. Slurry A was uniformly deposited on the interconnect substrate, and slurry B was uniformly deposited on the oxygen electrode using screen printing technology. The mesh size of the screen used was 300, and the total printing thickness was controlled to be 200 μm. Drying was carried out at 100°C for 10 min.

[0070] (5) Assemble the interconnect substrate and the side of the battery oxygen electrode with the deposited layer opposite to each other, and apply 12N / cm 2 The external pressure was 1000℃ and the sintering temperature was 900℃ in air with a heating rate of 2℃ / min and the temperature was kept at this temperature for 2 hours.

[0071] exist Figure 2 middle, Figure 2 a is a physical picture of the interconnect substrate-contact layer-half-cell sintering sample. Figure 2 b is the SEM microstructure of the contact layer cross section, from which it can be seen that the gradient coating A and gradient coating B of the contact layer are firmly bonded to the stainless steel interconnect substrate and the battery oxygen electrode, respectively.

[0072] Example 3

[0073] (1) 18.646 g of high-purity manganese powder (Mn) and 10 g of high-purity cobalt powder (Co) in a molar ratio of 2:1 were added to a ball mill, and 100 ml of anhydrous ethanol was added. The mixture was ball milled at 300 rpm for 12 hours using a planetary ball mill to mix evenly. The mixture was placed in a vacuum drying oven and dried at 90°C for 48 hours to prepare a metal powder material.

[0074] (2) 9.73 g of metal powder and 6.49 ml of diethyl ethyl acetate binder containing 5 wt% ethyl cellulose were added to a mixing tank at a solid content of 60%, and mixed at 2000 rpm for 5 minutes using a vacuum stirrer to obtain slurry A.

[0075] (3) 8 g of dried metal powder was added to a mixing tank, 2 g of LSM powder additive was added at a ratio of 20 wt%, and 6.67 ml of diethyl ethyl acetate binder containing 5 wt% ethyl cellulose was added at a solid content of 60%. The mixture was mixed at 2000 rpm using a vacuum mixer for 5 min to obtain slurry B1.

[0076] (4) Take 6 g of dried metal powder and add it to a mixing tank. Add 4 g of LSC powder additive at a ratio of 40 wt %, add 6.67 ml of diethanol ethylene acetate binder containing 5 wt % ethyl cellulose at a solid content of 60%, and use a vacuum mixer to mix at a speed of 2000 rpm for 5 minutes to obtain slurry B2.

[0077] (5) Slurries A, B1, and B2 were ground separately on a three-roll ball mill for 10 min with a wheelbase of 30 μm. Slurries A, B1, and B2 were then uniformly deposited on the interconnect substrate using screen printing technology with a mesh size of 200 and a total printed thickness of 200 μm. The resulting films were dried at 100°C for 10 min.

[0078] (6) Assemble the side of the interconnect substrate with the deposited layer opposite to the battery oxygen electrode, and apply 5N / cm 2 The external pressure was 1000 ℃ and the sintering temperature was 850 ℃ in air with a heating rate of 2 ℃ / min and the temperature was kept at this temperature for 2 hours.

[0079] Figure 3 Figure 3 is the SEM microstructure of the contact layer cross section. It can be seen that the three contact layers of different components are tightly sintered between each layer and between the two sides of the contact layer and the interconnection substrate and the battery oxygen electrode, achieving good contact.

[0080] Example 4

[0081] (1) 6 g of high-purity manganese powder (Mn) and 12.871 g of high-purity cobalt powder (Co) in a molar ratio of 1:2 were added to a ball mill, and 100 ml of anhydrous ethanol was added. The mixture was ball milled at 200 rpm for 24 hours using a planetary ball mill to mix evenly. The mixture was placed in a vacuum drying oven and dried at 90°C for 24 hours to prepare a metal powder material.

[0082] (2) 9.73 g of metal powder and 6.49 ml of diethyl ethyl acetate binder containing 4 wt% ethyl cellulose were added to a mixing tank at a solid content of 60%, and mixed for 8 minutes using a vacuum stirrer at a speed of 1000 rpm to obtain slurry A.

[0083] (3) 9 g of dried metal powder was added to a mixing tank, 1 g of LSM powder additive was added at a rate of 10 wt%, and 6.67 ml of diethyl ethyl acetate binder containing 4 wt% ethyl cellulose was added at a solid content of 60%. The mixture was mixed for 5 min at a speed of 2000 rpm using a vacuum mixer to obtain slurry B1.

[0084] (4) 7 g of dried metal powder was added to a mixing tank, 3 g of LSCF powder additive was added at a ratio of 30 wt%, and 6.67 ml of diethanol ethylene acetate binder containing 4 wt% ethyl cellulose was added at a solid content of 60%. The mixture was mixed for 5 min at a speed of 2000 rpm using a vacuum mixer to obtain slurry B2.

[0085] (5) Take 5 g of dried metal powder and add it to a mixing tank. Add 5 g of LSC powder additive at a ratio of 50 wt %, add 6.67 ml of diethanol ethylene acetate binder containing 4 wt % ethyl cellulose at a solid content of 60%, and use a vacuum mixer at a speed of 2000 rpm to mix for 5 minutes to obtain slurry B3.

[0086] (6) Slurries A, B1, B2, and B3 were ground separately on a three-roll ball mill for 10 min with a wheelbase of 50 μm. Slurries A, B1, B2, and B3 were then uniformly deposited on the interconnect substrate using screen printing technology with a mesh size of 150 and a total printed thickness of 250 μm. The resulting films were dried at 100°C for 10 min.

[0087] (7) Assemble the interconnect substrate with the deposited layer and the battery oxygen electrode relative to each other, and apply 6N / cm 2 The external pressure was 1000℃ and the sintering temperature was 900℃ in air with a heating rate of 2℃ / min and the temperature was kept at this temperature for 5 hours.

[0088] Figure 4This is the SEM microstructure of the contact layer cross section. Due to the multi-layer gradient setting, the interface distinction is not obvious. It can be seen that the layers and the two sides of the contact layer are sintered tightly with the interconnection substrate and the battery oxygen electrode, achieving good contact.

[0089] Example 5

[0090] (1) 12 g of high-purity manganese powder (Mn) and 25.742 g of high-purity cobalt powder (Co) in a molar ratio of 1:2 were added to a ball mill, and 100 ml of anhydrous ethanol was added. The mixture was ball milled at 200 rpm for 24 hours using a planetary ball mill to mix evenly. The mixture was placed in a vacuum drying oven and dried at 90°C for 24 hours to prepare a metal powder material.

[0091] (2) 9.73 g of metal powder and 4.17 ml of diethyl ethyl acetate binder containing 5 wt% ethyl cellulose were added to a mixing tank at a solid content of 70%, and mixed at 1000 rpm for 8 minutes using a vacuum stirrer to obtain slurry A.

[0092] (3) 8 g of dried metal powder was added to a mixing tank, 2 g of LSM powder additive was added at a ratio of 20 wt%, and 6.67 ml of diethyl ethyl acetate binder containing 4 wt% ethyl cellulose was added at a solid content of 60%. The mixture was mixed at 2000 rpm using a vacuum mixer for 5 min to obtain slurry B1.

[0093] (4) Take 5 g of dried metal powder and add it to a mixing tank. Add 5 g of LSCF powder additive at a ratio of 50 wt %, add 6.67 ml of diethanol ethylene acetate binder containing 4 wt % ethyl cellulose at a solid content of 60%, and use a vacuum stirrer to mix at a speed of 2000 rpm for 5 minutes to obtain slurry B2.

[0094] (5) Take 3 g of dried metal powder and add it to a mixing tank. Add 7 g of LSC powder additive at a ratio of 70 wt %, add 6.67 ml of diethanol ethylene acetate binder containing 4 wt % ethyl cellulose at a solid content of 60%, and use a vacuum stirrer to mix at a speed of 2000 rpm for 5 minutes to obtain slurry B3.

[0095] (6) Slurries A, B1, B2, and B3 were ground separately on a three-roll ball mill for 10 min with a wheelbase of 50 μm. Slurries A, B1, B2, and B3 were then uniformly deposited on the interconnect substrate using screen printing technology with a mesh size of 150 and a total printed thickness of 250 μm. The resulting films were dried at 100°C for 10 min.

[0096] (7) Assemble the interconnect substrate with the deposited layer and the battery oxygen electrode relative to each other, and apply 6N / cm 2The external pressure was 1000℃ and the sintering temperature was 900℃ in air with a heating rate of 2℃ / min and the temperature was kept at this temperature for 5 hours.

[0097] Figure 5 This is the SEM microstructure of the contact layer cross section. Due to the multi-layer gradient setting, the interface distinction is not obvious. It can be seen that the layers and the two sides of the contact layer are sintered tightly with the interconnection substrate and the battery oxygen electrode, achieving good contact.

[0098] Surface resistance test

[0099] Test conditions: The contact layer was sintered at 800-900°C in a muffle furnace. The samples were aged and tested for surface resistance using the four-electrode method in a tube furnace at 850°C with a ramp rate of 5°C / min.

[0100] Figure 6 The surface resistance test curves of the contact layers prepared in Examples 1-5 are shown in Table 1. During the test period, the surface resistance of the contact layers prepared in Examples 3-5 was relatively low (always below 100 mΩ.cm). 2 ), after stabilization for 10 hours, the final surface resistance is 31~41mΩ.cm 2 , indicating that these contact layers have good performance at working temperature and can be further improved after stabilization for a period of time. The initial sheet resistance of Examples 1 and 2 is slightly different from the stable sheet resistance, which may be due to the fact that there are fewer gradient layers. However, after high temperature stabilization, the interface sintering condition is improved (e.g. Figure 6 As shown in the figure, after the contact layers of Examples 1 and 2 were stabilized for 10 hours, the surface resistance was stabilized at 171 to 200 mΩ.cm. 2 ), and its performance also meets the application requirements of this field. In summary, the performance of the contact layers prepared in Examples 1 to 5 all meet the application requirements of this field. Furthermore, as the number of gradient layers increases, the performance of the contact layer tends to be better.

[0101] It should be noted that all technical features described in the present invention can be freely combined or combined in any way unless there is a contradiction between them. Various modifications and variations can be made to the present invention without departing from the scope of the present invention, which will be apparent to those skilled in the art. For example, a feature shown or described as part of one embodiment can be used together with another embodiment to produce yet another embodiment. Therefore, the present invention is intended to cover these modifications that fall within the scope of the appended claims and their equivalents.

Claims

1. A method for preparing an electrical contact layer, wherein the electrical contact layer is located between an oxygen electrode of a solid oxide cell and an interconnect substrate, characterized in that: The method comprises the following steps: (1) preparing a manganese-cobalt mixed metal powder, wherein the molar ratio of manganese powder to cobalt powder is 1:2 to 2:1; (2) mixing the manganese-cobalt mixed metal powder with a binder and grinding the mixture to obtain slurry A; (3) mixing the manganese-cobalt mixed metal powder with perovskite oxide and a binder, and grinding to obtain at least one slurry B, wherein the mass fraction of the perovskite oxide is 10%-70% based on the total amount of the manganese-cobalt mixed metal powder and the perovskite oxide; (4) applying the slurry B onto the surface of the oxygen electrode and drying it to form at least one layer of the slurry B coating, and applying the slurry A onto the slurry B coating of the oxygen electrode and / or the surface of the interconnect substrate and drying it to form a slurry A coating; or (5) applying the slurry A and the slurry B sequentially onto the surface of the interconnect substrate and drying them to form a coating layer of slurry A and at least one layer of slurry B; (6) Assembling the oxygen electrode prepared in step (4) with the interconnect substrate and sintering them, or assembling the interconnect substrate prepared in step (5) with the oxygen electrode and sintering them, to form an electrical contact layer between the oxygen electrode and the interconnect substrate, wherein the electrical contact layer comprises at least one coating layer of slurry B and a coating layer of slurry A, wherein the coating layer of slurry B is adjacent to the oxygen electrode; the sintering is performed in an air atmosphere, the sintering is in-situ sintering, and the in-situ sintering temperature is 800-900°C; The interconnect substrate is a stainless steel interconnect substrate, and the oxygen electrode is a perovskite oxygen electrode.

2. The method according to claim 1, wherein The step (1) comprises: adding manganese powder and cobalt powder into an alcohol compound, mixing, grinding, and drying to obtain manganese-cobalt mixed metal powder.

3. The method according to claim 2, wherein: The particle size of the manganese-cobalt mixed metal powder is 5-100 μm.

4. The method according to claim 2, wherein: The alcohol compound includes methanol, ethanol, propanol and / or isopropanol.

5. The method according to claim 2, wherein: The grinding includes grinding using a planetary ball mill.

6. The method according to claim 2, wherein: The grinding speed is 100-300 rpm, and the grinding time is 6-24 hours.

7. The method according to claim 2, wherein: The drying is vacuum drying, and the temperature of the vacuum drying is 80-100° C. and the time is 24-48 hours.

8. The method according to claim 1 or 2, wherein: In the step (2) or (3), the mass ratio of the manganese-cobalt mixed metal powder to the binder is 200:1 to 10:

1.

9. The method according to claim 8, wherein The binder is a cellulose binder.

10. The method according to claim 8, wherein The binder is ethyl cellulose.

11. The method according to claim 8, wherein The binder is mixed in the form of a solution with a concentration of 2 to 10% by mass.

12. The method according to claim 8, wherein The solid mass fractions in the slurries A and B are both 50-80%.

13. The method according to claim 8, wherein The mixing is performed using a vacuum mixer.

14. The method according to claim 13, wherein The rotation speed of the vacuum mixer is 800-2000 rpm, and the stirring time is 5-10 minutes.

15. The method according to claim 8, wherein The grinding includes grinding using a three-roll ball mill.

16. The method according to claim 15, wherein The roller spacing of the three-roller ball mill is 10-150 μm.

17. The method according to claim 1 or 2, wherein: The perovskite oxide includes LSC, LSM and / or LSCF.

18. The method according to claim 1 or 2, wherein: In the step (3), the at least one slurry B includes two or more slurries with different mass fractions of perovskite oxide.

19. The method according to claim 1 or 2, wherein: In steps (4) and (5), the at least one coating layer of slurry B is a coating layer of slurry B.

20. The method according to claim 19, wherein The mass fraction of the perovskite oxide in the coating of the slurry B is 10%-45%.

21. The method according to claim 19, wherein The coating of slurry B comprises LSC; or, The coating of slurry B contained LSCF.

22. The method according to claim 21, wherein The mass fraction of the LSC is 10 wt % to 15 wt %.

23. The method according to claim 21, wherein The mass fraction of the LSCF is 35 wt%-45 wt%.

24. The method according to claim 1 or 2, wherein: In steps (4) and (5), the at least one coating layer of slurry B is composed of two or more coating layers of slurry B, and each of the two or more coating layers of slurry B is coated in a manner in which the mass fraction of perovskite oxide decreases in the direction from the oxygen electrode to the interconnect substrate.

25. The method according to claim 24, wherein In the two or more coating layers of slurry B, the difference in mass fraction of the perovskite oxide between adjacent coating layers, Δwt%, is 0%<Δwt%≤30%.

26. The method according to claim 24, wherein In the two or more coating layers of slurry B, the difference in mass fraction of the perovskite oxide between adjacent coating layers, Δwt%, is 5%≤Δwt%≤25%.

27. The method according to claim 24, wherein In the two or more coating layers of slurry B, the difference in mass fraction of the perovskite oxide between adjacent coating layers, Δwt%, is 10%≤Δwt%≤20%.

28. The method according to claim 24, wherein The two or more slurry B coating layers include a slurry B1 coating layer and a slurry B2 coating layer, wherein the slurry B1 coating layer contains LSM, and the mass fraction of the LSM is 15wt%-25wt%; and the slurry B2 coating layer contains LSC, and the mass fraction of the LSC is 35wt%-45wt%; or The two or more slurry B coating layers include a slurry B1 coating layer, a slurry B2 coating layer, and a slurry B3 coating layer, wherein the slurry B1 coating layer contains LSM, the mass fraction of the LSM is 10wt%-15wt%, the slurry B2 coating layer contains LSCF, the mass fraction of the LSCF is 25wt%-35wt%, and the slurry B3 contains LSC, the mass fraction of the LSC is 45wt%-55wt%; or The two or more slurry B coatings include a slurry B1 coating, a slurry B2 coating and a slurry B3 coating, wherein the slurry B1 coating contains LSM, and the mass fraction of the LSM is 10wt%-30wt%; the slurry B2 coating contains LSCF, and the mass fraction of the LSCF is 40wt%-50wt%; the slurry B3 contains LSC, and the mass fraction of the LSC is 60wt%-70wt%.

29. The method according to claim 1 or 2, wherein In steps (4) and (5), the thickness of the coating of slurry A is 50-450 μm, and the thickness of each layer of the at least one layer of slurry B is 50-450 μm.

30. The method according to claim 29, wherein The total thickness of the coating layer of slurry A and the at least one coating layer of slurry B is 100-500 μm.

31. The method according to claim 29, wherein The coating was performed by screen printing.

32. The method according to claim 31, wherein The mesh number of the screen printing is 100-300.

33. The method according to claim 1 or 2, wherein The drying in steps (4) and (5) is performed at a temperature of 60-110° C. for 5-30 minutes.

34. The method according to claim 1 or 2, wherein The step (6) satisfies one or more of the following conditions: 1) 1-20 N / cm is applied during sintering 2 2) the sintering adopts a heating rate of 1-10 ℃ / min and a holding time of 2-20 hours.

35. An electrical contact layer produced by the method of any one of claims 1 to 34.

36. A solid oxide fuel cell comprising the electrical contact layer of claim 35.

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