Solid oxide cell protective coating and method of making same

Abstract

The application discloses a solid oxide cell protective coating and a preparation method thereof. The coating comprises a dense layer directly connected with a bipolar plate or a current collector and a non-dense layer connected with the dense layer. The thickness of the dense layer is 0.1-2 microns, the thickness of the non-dense layer is 1-10 microns, the density of the non-dense layer is 85%-95%, the composition of the dense layer is spinel MN2O4, M is any one of Mn, Co, Fe, Co, Ni, Cu and Zn, and N is any one of Mn, Co, Fe, Co, Ni, Cu and Zn. The non-dense layer is a composite of spinel oxide and oxide X, X is one or more than two of TiO2, ZrO2, CeO2 and La2O3. The method comprises the steps of metal alloy layer preparation, spinel oxide modified slurry preparation and coating sintering. The prepared protective coating can form a dense film at low temperature, and effectively prevents the oxidation of the metal plate under high-temperature working conditions. The application is particularly suitable for the surface protection of the bipolar plate or the current collector of a solid oxide electrolysis cell or a solid oxide fuel cell.

Description

Technical Field

[0001] This invention relates to the field of fuel cells and electrolyzers, and specifically to a solid oxide battery protective coating and its preparation method. Background Technology

[0002] With the increasing severity of environmental pollution and energy shortages, renewable energy has developed rapidly, and the large-scale storage of renewable energy has attracted widespread attention from scientists. Hydrogen energy storage is considered an important technology for achieving large-scale storage of renewable energy. Solid oxide batteries consist of solid oxide fuel cells (SOFCs) and solid oxide electrolyzers (SOECs), which are inverse processes. In battery mode, they provide clean electricity; in electrolysis mode, they can produce hydrogen, syngas, etc. The stack is the core component of a solid oxide battery, consisting of several membrane electrodes connected in series via bipolar plates. Considering cost factors, ferritic stainless steel is currently the main material for bipolar plates, such as SUS430, ZML232L, and Crofer22 APU. However, these bipolar plate materials continuously oxidize at high temperatures, leading to the formation of a passivation layer on the surface, resulting in increased resistance and reduced electroplating performance. Furthermore, bipolar plates contain chromium (Cr), and the volatilization of Cr at high temperatures can poison the oxygen electrode, causing battery performance degradation. Therefore, a coating needs to be prepared on the surface of the bipolar plates to prevent oxidation at high temperatures and to inhibit Cr volatilization.

[0003] Methods for preparing surface coatings for bipolar plates include electrophoretic deposition and plasma spraying. However, these methods suffer from high costs, complex processes, and low production efficiency. Traditional slurry coating methods offer advantages such as simplicity and low cost, but coatings prepared by these methods are difficult to densify at low temperatures. Furthermore, increasing the sintering temperature above 1000℃ accelerates bipolar plate oxidation. Therefore, there is an urgent need for a solid oxide battery protective coating and its preparation method. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a solid oxide battery protective coating and its preparation method. The solid oxide battery protective coating comprises a dense layer directly connected to a bipolar plate or current collector and a non-dense layer connected to the dense layer. The thickness of the dense layer is 0.1–2 micrometers, and the thickness of the non-dense layer is 1–10 micrometers. The density of the non-dense layer is 85%–95%. The dense layer is composed of spinel MN₂O₄, where M is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn, and N is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn. M and N are not the same. The non-dense layer is a composite of spinel oxide and oxide X, where X is one or more of TiO₂, ZrO₂, CeO₂, and La₂O₃. The spinel MN₂O₄ in the dense layer has the same composition as the spinel oxide in the non-dense layer.

[0005] Furthermore, in the above technical solution, the molecular formula of the spinel oxide in the non-dense layer is AB2O4, where A is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn, and B is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn; A and B are not the same.

[0006] This invention provides a method for preparing the above-mentioned solid oxide battery protective coating, the method comprising the following steps:

[0007] (1) Preparation of metal alloy layer: The alloy thin film was prepared by magnetron sputtering. The sputtering atmosphere was a mixture of oxygen and argon with a flow ratio of 1 / 1 to 1 / 40. The sputtering substrate temperature was 30 to 400℃, the sputtering pressure was 0.05 Pa to 5 Pa, and the sputtering power density P = 5 to 50 W / cm³. -2 The sputtering time is 0.5–50 h; the metallic elements in the metal alloy are M and N;

[0008] (2) Preparation of spinel oxide modified slurry: spinel oxide and active component X are mixed to form a composite oxide. The composite oxide is ball-milled and mixed with anhydrous ethanol and polyvinyl butyral to form a slurry. The mass ratio of the three is 40-50:45-48:2-15. The metal elements in spinel oxide are A and B.

[0009] (3) Coating sintering: The spinel oxide slurry described in step (2) is applied to the surface of the metal alloy obtained in step (1), and then calcined in a muffle furnace at 400-850°C for 1-50 hours to obtain a coating film of 0.5-10 micrometers.

[0010] Furthermore, in the above technical solution, the composition of the metal alloy in the method is MN, where M is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn, and N is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn. M and N are not the same, and the molar ratio of M to N is 1:2 to 1:1.

[0011] Furthermore, in the above technical solution, the spinel oxide in the method has the molecular formula AB2O4, where A is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn, and B is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn; A and B are not the same; the active component is one or more of TiO2, ZrO2, CeO2, and La2O3.

[0012] Furthermore, in the above technical solution, the molar ratio of spinel oxide to active component in the method is 1:0.08 to 1:0.005.

[0013] Furthermore, in the above technical solution, the particle size of the spinel oxide in the method is 1-100 nanometers, and the particle size of the active component is 1-50 nanometers.

[0014] Furthermore, in the above technical solution, the roasting temperature in step (3) is preferably 500-800℃, and the roasting time is preferably 5-20h.

[0015] Furthermore, in the above technical solution, the roasting atmosphere in step (3) can be static air.

[0016] The present invention provides the above-mentioned solid oxide battery protective coating for surface protection of bipolar plates or current collectors in solid oxide electrolyzers or solid oxide fuel cells.

[0017] Beneficial effects of the invention

[0018] (1) The coating of the present invention comprises a dense layer directly connected to the bipolar plate or current collector and a non-dense layer connected to the dense layer. The dense layer is formed by sintering an alloy layer at high temperature, which improves the bonding force between the coating and the metal plate and effectively isolates the metal plate from oxygen, thus avoiding oxidation of the metal plate and diffusion of the metal Cr element.

[0019] (2) In this invention, spinel oxide modified slurry is applied to the surface of the alloy layer. During the co-firing process, oxygen atoms in the spinel oxide modified slurry diffuse to the surface of the alloy layer, gradually oxidizing it to obtain a dense spinel oxide layer. This forms a dense and non-dense gradient structure film with tight bonding, effectively alleviating the problem of coating peeling during hot and cold cycles.

[0020] (3) In the method of the present invention, spinel oxide modified slurry is prepared, and the active component is used to improve the oxidation sintering activity of spinel, so that the non-dense film formed during the co-firing process with the metal alloy layer has a high density (85-95%), which can effectively prevent the oxidation of metal bipolar plates.

[0021] (4) The method of the present invention is simple and easy to implement, and is particularly suitable for the protection of metal bipolar plates or metal connectors of solid oxide batteries. Detailed Implementation

[0022] Example 1

[0023] A protective coating was prepared on the surface of a SUS430 wafer with a thickness of 2.5 mm and a diameter of 25 mm. The dense layer of the protective coating had a thickness of 0.3 μm, the non-dense layer had a thickness of 4.7 μm, and the density of the non-dense layer was 90%. The specific steps for this coating process are as follows:

[0024] (1) Mn-Co alloy thin films were prepared by magnetron sputtering with a molar ratio of 1:2. The sputtering atmosphere was a mixture of oxygen and argon with a flow rate ratio of 1 / 10. The sputtering substrate temperature was 100℃, the sputtering pressure was 0.5 Pa, and the sputtering power density was P = 25 W / cm³. -2 The sputtering time is 1 hour.

[0025] (2) Preparation of spinel oxide modified slurry: 1 mol of MnCo2O4 and 0.01 mol of TiO2 were mixed with anhydrous ethanol and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. The particle size of MnCo2O4 was 20–50 nm, and the particle size of TiO2 was 5–20 nm.

[0026] (3) Coating sintering: The above slurry is applied to the surface of the metal alloy by 0.020g, and then calcined in a muffle furnace at 800℃ for 10h to obtain a coating film of 5 micrometers.

[0027] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.009 Ωcm. 2 It has good antioxidant properties.

[0028] Example 2

[0029] A protective coating was prepared on the surface of a SUS430 wafer with a thickness of 2.5 mm and a diameter of 25 mm. The dense layer of the protective coating had a thickness of 0.3 μm, the non-dense layer had a thickness of 4.7 μm, and the density of the non-dense layer was 95%. The specific steps are as follows:

[0030] (1) Mn-Co alloy thin films were prepared by magnetron sputtering with a molar ratio of 1:2. The sputtering atmosphere was a mixture of oxygen and argon with a flow rate ratio of 1 / 10. The sputtering substrate temperature was 100℃, the sputtering pressure was 0.5 Pa, and the sputtering power density was P = 25 W / cm³. -2 The sputtering time is 1 hour.

[0031] (2) Preparation of spinel oxide modified slurry: 1 mol of MnCo2O4 and 0.02 mol of CeO2 were mixed with anhydrous ethanol and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. The particle size of MnCo2O4 was 20–50 nm, and the particle size of CeO2 was 5–10 nm.

[0032] (3) Coating sintering: The above slurry is applied to the surface of the metal alloy by 0.020g, and then calcined in a muffle furnace at 700℃ for 10h to obtain a coating film of 5 micrometers.

[0033] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.0085 Ωcm. 2 It has good antioxidant properties.

[0034] Example 3

[0035] A protective coating was prepared on the surface of a SUS430 wafer with a thickness of 2.5 mm and a diameter of 25 mm. The dense layer of the protective coating had a thickness of 0.5 μm, the non-dense layer had a thickness of 4.7 μm, and the density of the non-dense layer was 92%. The specific steps are as follows:

[0036] (1) Mn-Co alloy thin films were prepared by magnetron sputtering with a molar ratio of 1:2. The sputtering atmosphere was a mixture of oxygen and argon with a flow rate ratio of 1 / 20. The sputtering substrate temperature was 200℃, the sputtering pressure was 0.5 Pa, and the sputtering power density was P = 40 W / cm³. -2 The sputtering time is 1 hour.

[0037] (2) Preparation of spinel oxide modified slurry: 1 mol of MnCo2O4 and 0.02 mol of CeO2 were mixed with anhydrous ethanol and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. The particle size of MnCo2O4 was 20–50 nm, and the particle size of CeO2 was 5–10 nm.

[0038] (3) Coating sintering: The above slurry is applied to the surface of the metal alloy by 0.020g, and then calcined in a muffle furnace at 700℃ for 20h to obtain a coating film of 5 micrometers.

[0039] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.009 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.010 Ωcm. 2 It has good antioxidant properties.

[0040] Example 4

[0041] A protective coating was prepared on the surface of a SUS430 wafer with a thickness of 2.5 mm and a diameter of 25 mm. The dense layer of the protective coating had a thickness of 1 μm, the non-dense layer had a thickness of 9 μm, and the density of the non-dense layer was 92%. The specific steps are as follows:

[0042] (1) Mn-Cu alloy thin films were prepared by magnetron sputtering with a molar ratio of 1:2. The sputtering atmosphere was a mixture of oxygen and argon with a flow rate ratio of 1 / 10. The sputtering substrate temperature was 300℃, the sputtering pressure was 0.5 Pa, and the sputtering power density was P = 25 W / cm³. -2 The sputtering time is 3 hours.

[0043] (2) Preparation of spinel oxide modified slurry: 1 mol of MnCu2O4 and 0.01 mol of ZrO2 were mixed with anhydrous ethanol and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. The particle size of MnCu2O4 was 20–50 nm, and the particle size of CeO2 was 5–10 nm.

[0044] (3) Coating sintering: The above slurry is applied to the surface of the metal alloy by 0.040g, and then calcined in a muffle furnace at 800℃ for 20h to obtain a coating film of 10 micrometers.

[0045] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.0083 Ωcm. 2 It has good antioxidant properties.

[0046] Comparative Example 1

[0047] A protective coating was prepared on the surface of a SUS430 disc with a thickness of 2.5 mm and a diameter of 25 mm. The specific steps are as follows:

[0048] Mn-Co alloy thin films were prepared by magnetron sputtering with a molar ratio of 1:2. The sputtering atmosphere was a mixture of oxygen and argon with a flow rate ratio of 1 / 10. The sputtering substrate temperature was 100℃, the sputtering pressure was 0.5 Pa, and the sputtering power density was P = 25 W / cm³. -2 The sputtering time was 1 hour. Then, it was calcined at 800℃ for 10 hours to obtain a 500-nanometer-thick MnCo2O4 protective coating.

[0049] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.012 Ωcm. 2 .

[0050] Comparative Example 2

[0051] A protective coating was prepared on the surface of a SUS430 disc with a thickness of 2.5 mm and a diameter of 25 mm. The specific steps are as follows:

[0052] 1 mol of MnCo2O4 was mixed with anhydrous ethanol and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. 0.020 g of this slurry was coated onto the surface of an SUS430 wafer, and then calcined in a muffle furnace at 950 °C for 10 h to obtain a 5 μm MnCo2O4 coating film.

[0053] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2 After 1000 hours, the resistance of the disc was 0.011 Ωcm. 2 .

[0054] Comparative Example 3

[0055] A protective coating was prepared on the surface of a SUS430 disc with a thickness of 2.5 mm and a diameter of 25 mm. The specific steps are as follows:

[0056] 1 mol of MnCo₂O₄, 0.01 mol of TiO₂, and anhydrous ethanol were mixed and ball-milled for 5 h. 45 g of the dried mixture was then ball-milled with 47 g of anhydrous ethanol and 8 g of polyvinyl butyral for 24 h to form a slurry. 0.020 g of this slurry was coated onto the surface of an SUS430 disc, and then calcined in a muffle furnace at 800 °C for 10 h to obtain a 5 μm coating film.

[0057] The coated SUS430 wafer resistors were prepared using AC impedance spectroscopy. At 750°C and in a static air atmosphere, the initial resistance of the wafers was 0.008 Ωcm. 2After 1000 hours, the resistance of the disc was 0.010 Ωcm. 2 .

Claims

1. A protective coating for solid oxide batteries, characterized in that, The coating comprises a dense layer and a non-dense layer. The thickness of the dense layer is 0.1-2 micrometers, and the thickness of the non-dense layer is 1-10 micrometers. The density of the non-dense layer is 85%-95%. The dense layer is composed of spinel MN2O4, where M is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn, and N is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn. M and N are not the same. The non-dense layer is a composite of spinel oxide and oxide X, where X is one or more of TiO2, ZrO2, CeO2, and La2O3. The dense layer, spinel MN2O4, has the same composition as the non-dense layer, which is spinel oxide. The method for preparing the protective coating for the solid oxide battery includes the following steps: (1) Preparation of metal alloy layer: The alloy thin film was prepared by magnetron sputtering. The sputtering atmosphere was a mixture of oxygen and argon with a flow ratio of 1 / 1 to 1 / 40. The sputtering substrate temperature was 30 to 400℃, the sputtering pressure was 0.05 Pa to 5 Pa, the sputtering power density was 5 to 50 W cm⁻², and the sputtering time was 0.5 to 50 h. The metal elements in the metal alloy were M and N. (2) Preparation of spinel oxide modified slurry: spinel oxide is mixed with active component X to form a composite oxide, and the composite oxide is ball-milled and mixed with anhydrous ethanol and polyvinyl butyral to form a slurry. The mass ratio of the three is 40~50:45~48:2~15; the metal elements in spinel oxide are A and B. (3) Coating sintering: The spinel oxide slurry described in step (2) is applied to the surface of the metal alloy obtained in step (1), and then calcined in a muffle furnace at 400~850℃ for 1~50h to obtain a coating film of 0.5~10 micrometers.

2. The solid oxide battery protective coating according to claim 1, characterized in that, The spinel oxide in the non-dense layer has the molecular formula AB2O4, where A is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn, and B is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn; A and B are not the same.

3. The method for preparing the solid oxide battery protective coating as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Preparation of metal alloy layer: The alloy thin film was prepared by magnetron sputtering. The sputtering atmosphere was a mixture of oxygen and argon with a flow ratio of 1 / 1 to 1 / 40. The sputtering substrate temperature was 30 to 400℃, the sputtering pressure was 0.05 Pa to 5 Pa, and the sputtering power density was P = 5 to 50 W / cm³. -2 The sputtering time is 0.5~50h; the metallic elements in the metal alloy are M and N; (2) Preparation of spinel oxide modified slurry: spinel oxide is mixed with active component X to form a composite oxide, and the composite oxide is ball-milled and mixed with anhydrous ethanol and polyvinyl butyral to form a slurry. The mass ratio of the three is 40~50:45~48:2~15; the metal elements in spinel oxide are A and B. (3) Coating sintering: The spinel oxide slurry described in step (2) is applied to the surface of the metal alloy obtained in step (1), and then calcined in a muffle furnace at 400~850℃ for 1~50h to obtain a coating film of 0.5~10 micrometers.

4. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, The composition of the metal alloy in the method is MN, where M is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn, and N is any one of Mn, Co, Fe, Co, Ni, Cu, and Zn. M and N are not the same, and the molar ratio of M to N is 1:2 to 1:

1.

5. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, The spinel oxide in the method has the molecular formula AB2O4, where A is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn, and B is one or more of Mn, Co, Fe, Co, Ni, Cu, and Zn; the active component is one or more of TiO2, ZrO2, CeO2, and La2O3; and A and B are not the same.

6. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, In step (2), the molar ratio of spinel oxide to active component is 1:0.08~1:0.

005.

7. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, In step (2), the particle size of spinel oxide is 1~100 nanometers, and the particle size of active component is 1~50 nanometers.

8. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, In step (3), the roasting temperature is 500~800℃ and the roasting time is 5~20h.

9. The method for preparing the solid oxide battery protective coating according to claim 3, characterized in that, In step (3), the roasting atmosphere is static air.

10. The solid oxide battery protective coating as described in claim 1 or 2 is applied to the surface protection of bipolar plates or current collectors in solid oxide electrolyzers or solid oxide fuel cells.