Coating slurry for metal connector, coating, preparation method and application

Abstract

The invention discloses coating slurry for a metal connector, a coating as well as a preparation method and application of the coating. The preparation method of the metal connector coating comprises the steps that the surface of ferritic stainless steel is evenly coated with coating slurry, heat treatment is conducted for 5 h at the temperature of 900-1000 DEG C under the protective atmosphere, and the metal connector coating is obtained. The coating slurry for the metal connector is prepared from the following raw materials: a binding agent, terpilenol, 3-10 wt% of copper oxide and strontium iron molybdenum powder, and the mass ratio of the strontium iron molybdenum powder to the binding agent to the terpilenol is 4: 2: 1. The method has the advantages that the densification temperature of the coating is effectively reduced, and the density of the coating is improved; the prepared metal connector coating can effectively inhibit chromium diffusion; the metal connector coating is used for the solid oxide fuel cell, and the performance of the cell is effectively improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of solid oxide fuel cells, and in particular to a coating slurry, a coating, a preparation method, and an application thereof for a metal interconnect. Background Art

[0002] Solid oxide fuel cells (SOFCs) are widely used in distributed power plants and power supply applications due to their advantages, including high power generation efficiency, wide fuel source availability, flexible structure, long service life, and low power generation costs. However, the power generated by a single SOFC cell is very limited, so several cells are typically connected in series through connectors to form an SOFC stack to achieve the required power output.

[0003] The interconnects act as current collectors in the stack, and their operating environment is very demanding. They must not only have excellent high-temperature oxidation resistance, good electrical conductivity, and a suitable thermal expansion coefficient, but must also maintain sufficient stability over a wide range of oxygen partial pressures. Compared to ceramic interconnects, metal interconnects have become the current mainstream interconnect material due to their high electrical and thermal conductivity, good machinability, and lower material cost. However, oxidation of metal interconnects under long-term high-temperature SOFC operating conditions can cause irreversible performance degradation in the SOFC stack. Metal interconnects are exposed to both air and fuel atmospheres, especially in SOFCs fueled by alcohols and hydrocarbons, where the fuel gas contains a large amount of water.

[0004] Currently, the main anti-oxidation coatings are applied to the air electrode side, but existing studies have shown that oxidation is equally serious on the fuel electrode side of the metal connector. For example, the coating of Mn-Co (manganese-cobalt) spinel material applied to the air electrode side cannot exist stably on the fuel electrode side and cannot play an anti-oxidation role, causing some chromium to diffuse to the coating surface. At present, in order to suppress the diffusion of chromium inside the metal connector, the coating on the surface of the connector needs to be densified. However, the coating densification is carried out at high temperature (above 1100°C), resulting in serious diffusion of Cr (chromium) in the metal connector, which has a significant impact on the performance degradation of SOFC.

[0005] In addition, we also found that Sr2Fe 1.5 Mo 0.5 O 6-δ (abbreviated as "SFM") can be used as a high-temperature fuel cell electrode material, suitable for the temperature under the fuel electrode side atmosphere, and is a potential connector coating material, but SFM materials require very high temperatures (>1300℃) to densify. Summary of the Invention

[0006] The present disclosure provides a coating slurry, a coating, a preparation method and an application for a metal connector, so as to at least solve one of the technical problems existing in the prior art.

[0007] According to a first aspect of the present disclosure, a coating slurry for a metal connector is provided, comprising the following raw materials: a binder, terpineol, 3-10 wt% copper oxide, and strontium iron molybdenum (SFM) powder; the mass ratio of the strontium iron molybdenum powder, the binder, and the terpineol is 4:2:1.

[0008] In one embodiment, the binder is a mixture of PVB, ethyl cellulose and terpineol.

[0009] According to the second aspect of the present disclosure, a method for preparing a metal connector coating is provided, wherein the coating slurry is uniformly applied to the surface of ferritic stainless steel, and heat treated at 900-1000° C. for 4-10 hours under a protective atmosphere to obtain the metal connector coating.

[0010] In one embodiment, the ferritic stainless steel is polished to 1200 mesh with sandpaper and ultrasonically cleaned with ethanol before coating.

[0011] In one embodiment, the coating slurry is evenly coated on the surface of the ferritic stainless steel by screen printing.

[0012] In one embodiment, the ferritic stainless steel is SUS430 ferritic stainless steel.

[0013] In one embodiment, the protective atmosphere is Ar.

[0014] According to a third aspect of the present disclosure, a metal interconnect coating is provided, which is obtained by the above-mentioned preparation method.

[0015] According to a fourth aspect of the present disclosure, there is provided a use of the metal interconnect coating in a solid oxide fuel cell.

[0016] In one embodiment, the metal interconnect coating is used to secure the fuel electrode side of an oxide fuel cell.

[0017] Compared with the prior art, the advantages of the present application are: 1) the preparation method of the metal interconnect coating of the present application can effectively reduce the densification temperature of the coating and improve the density of the coating; 2) the metal interconnect coating prepared by the present application can effectively inhibit chromium diffusion; 3) CuO is used as a sintering aid in the method of the present application, and the prepared metal interconnect coating can achieve the densification of the low-temperature metal interconnect coating; 4) the metal interconnect coating of the present application is used for solid oxide fuel cells, especially for the metal interconnect on the fuel electrode side, and can effectively inhibit the oxidation of the metal interconnect and effectively improve the performance of the battery.

[0018] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings, in which several embodiments of the present disclosure are shown by way of example and not limitation, wherein:

[0020] In the drawings, the same or corresponding reference numerals denote the same or corresponding parts.

[0021] Figure 1 Schematic diagram of XRD test of the metal interconnect coating of Example 1 of the present disclosure is shown;

[0022] Figure 2 The SEM morphology of the metal interconnect coating prepared in Comparative Example 1 of the present disclosure is shown;

[0023] Figure 3 shows the SEM morphology of the metal interconnect coating prepared in Example 1 of the present disclosure;

[0024] Figure 4 shows the EDS spectrum of the metal interconnect coating prepared in Comparative Example 1 of the present disclosure;

[0025] Figure 5 The EDS spectrum of the metal interconnect coating prepared in Example 1 of the present disclosure is shown. DETAILED DESCRIPTION

[0026] To make the purposes, features, and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative work shall fall within the scope of protection of the present disclosure.

[0027] In a first aspect, the present disclosure provides a coating slurry for metal interconnects, comprising the following raw materials: a binder, terpineol, 3-10 wt% copper oxide, and strontium iron molybdenum powder (SFM); the mass ratio of strontium iron molybdenum powder, binder, and terpineol is 4:2:1. Preferably, the binder is a mixture of PVB (polyvinyl butyral), ethyl cellulose, and terpineol. The chemical formula of the SFM is Sr2Fe 1.5 Mo 0.5 O 6-δ .

[0028] In a second aspect, the present disclosure provides a method for preparing a metal connector coating, wherein the coating slurry is evenly applied to the surface of ferritic stainless steel, and heat treated at 900-1000°C for 4-10 hours under a protective atmosphere, thereby obtaining a metal connector coating on the surface of the ferritic stainless steel. The present application uses ferritic stainless steel as a metal connector and CuO as a sintering aid, and ultimately obtains an SFM coating on the surface of the metal connector, thereby achieving the densification of a low-temperature SFM coating (the metal connector coating of the present application). The addition of CuO effectively reduces the densification temperature of the SFM coating and increases the density of the coating; and can effectively inhibit chromium diffusion.

[0029] Preferably, the ferritic stainless steel is polished to 1200 mesh with sandpaper and ultrasonically cleaned with ethanol before coating.

[0030] Preferably, the coating slurry is evenly coated on the surface of the ferritic stainless steel by screen printing.

[0031] Preferably, the ferritic stainless steel is SUS430 ferritic stainless steel, and the protective atmosphere is Ar.

[0032] In a third aspect, the present application provides a metal interconnect coating obtained by the above-mentioned preparation method. The metal interconnect coating of the present application is applied to the fuel electrode side of the metal interconnect and maintains good electrical conductivity in the fuel atmosphere, inhibiting oxidation and chromium diffusion in the metal interconnect.

[0033] In a fourth aspect, the present application provides an application of a metal interconnect coating in a solid oxide fuel cell. Preferably, the metal interconnect coating is used on the fuel electrode side of the solid oxide fuel cell.

[0034] Unless otherwise specified, the raw materials required in this application can be obtained through commercial channels. 1.5 Mo 0.5 O 6-δ(SFM) is a common perovskite oxide, and δ represents the oxygen vacancy content. SFM can be prepared using the method disclosed in Chinese patent application (CN116666650A), specifically: 10.58g of strontium nitrate, 15.15g of ferric nitrate, and 2.21g of ammonium molybdate are weighed and dissolved in a small amount of deionized water. 29g of ethylenediaminetetraacetic acid and 42g of citric acid monohydrate are weighed as complexing agents and dissolved in deionized water in a molar ratio of 1:2:1 of ethylenediaminetetraacetic acid: citric acid monohydrate: total metal ions. The complexing agent solution is added to the metal ion solution, and an appropriate amount of ammonia is added dropwise to raise the solution pH to between 7 and 8. The solution is then stirred under magnetic stirring until the water is completely evaporated to obtain a gel-like substance. The gel-like substance is calcined in an oven at 250°C for 5 hours to obtain the desired foam precursor. The precursor was placed in a high-temperature muffle furnace and calcined at 1000°C for 5 hours to obtain the desired SFM powder.

[0035] The present application is further described in detail below with reference to specific embodiments.

[0036] Unless otherwise specified, the materials used in this application can be obtained through commercial channels.

[0037] Example 1

[0038] A method for preparing a metal connector coating comprises the following steps:

[0039] Step 1) SUS430 ferritic stainless steel is polished to 1200 mesh with sandpaper and ultrasonically cleaned with ethanol before coating to obtain a metal connector substrate;

[0040] Step 2) Mixing a binder, terpineol, 3 wt% copper oxide, and strontium iron molybdenum powder (i.e., SFM powder) and grinding them thoroughly until they are evenly mixed to obtain an SFM coating slurry; wherein the mass ratio of strontium iron molybdenum powder, binder, and terpineol is 4:2:1; and the binder is a mixture of PVB, ethyl cellulose, and terpineol;

[0041] In step 3), the SFM coating slurry is evenly coated on the surface of the metal connector substrate by screen printing, and heat-treated at 950° C. for 5 h in an Ar atmosphere to obtain a metal connector coating on the surface of the metal connector substrate.

[0042] Example 1: A metal connector coating was prepared.

[0043] Comparative Example 1

[0044] The preparation of Comparative Example 1 is substantially the same as that of Example 1, except that copper oxide is not added in step 2) and heat treatment is performed in an Ar atmosphere at 1300° C. for 5 h in step 3).

[0045] Comparative Example 1 prepared a metal interconnect coating (SFM coating).

[0046] Relevant performance test tests of Example 1 and Comparative Example 1:

[0047] The phases of the powder, coating and oxide layer were identified by Davinci X-ray diffractometer (XRD) with Cu-Kα radiation. The microstructure and composition of the samples were characterized by FEI scanning electron microscope (SEM, model Quanta FEG250) and energy dispersive X-ray spectrometer (EDS).

[0048] 1: The SFM powder and the metal interconnect coating prepared in Example 1 were subjected to XRD tests respectively. The results are as follows: Figure 1 shown.

[0049] Figure 1 (a) is the XRD spectrum of SFM powder, Figure 1 (b) is the XRD spectrum of the metal interconnect coating prepared in Example 1. Figure 1 (a) Shows the typical characteristic peaks of SFM at 31.50°, 46.72°, and 57.91° 2θ. Figure 1 (b) shows that due to the addition of 3% CuO, Figure 1 There is a Cu characteristic peak in (b). This shows that the metal interconnect coating prepared in Example 1 of the present application was successfully prepared.

[0050] 2: The metal interconnect coatings prepared in Example 1 and Comparative Example 1 were subjected to SEM tests respectively. The results are as follows: Figure 2-3 shown.

[0051] Figure 2 Shown is the SEM morphology of the metal interconnect coating prepared in Comparative Example 1. Figure 2 It can be seen that the SFM coating prepared without the addition of CuO sintering aid cannot fully densify the coating surface even at 1300℃.

[0052] Figure 3 Shown is the SEM morphology of the metal interconnect coating (SFM coating) prepared in Example 1. Figure 3 As can be seen in the figure, the surface of the SFM coating prepared with CuO sintering aid is densified, indicating that SFM coating densification can be achieved at low temperatures. (The low temperature here refers to less than 1100°C, at which chromium diffusion is not serious.)

[0053] 3: The metal connector coatings prepared in Example 1 and Comparative Example 1 were subjected to EDS testing. The results are as follows: Figure 4-5 shown.

[0054] Figure 4What is shown is the EDS spectrum of the metal interconnect coating prepared in Comparative Example 1. Figure 4 It can be seen that chromium is enriched on the surface of the connector and some chromium is diffused in the coating.

[0055] Figure 5 What is shown is the EDS spectrum of the metal interconnect coating prepared in Example 1. Figure 5 It can be found that chromium is enriched on the surface of the interconnect, while chromium does not diffuse significantly in the coating. This indicates that the CuO sintering aid effectively reduces the densification temperature of the coating, increases the density of the coating, and effectively inhibits chromium diffusion.

[0056] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved. This is not a limitation herein.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0058] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A coating slurry for a metal interconnect, characterized in that: The invention is composed of the following raw materials: a binder, terpineol, 3-10 wt% of copper oxide, and strontium iron molybdenum powder; the mass ratio of the strontium iron molybdenum powder, the binder and the terpineol is 4:2:

1.

2. The coating slurry according to claim 1, characterized in that: The binder is a mixture of PVB, ethyl cellulose and terpineol.

3. A method for preparing a metal interconnect coating, characterized in that: The coating slurry according to claim 1 or 2 is evenly coated on the surface of ferritic stainless steel, and heat-treated at 900-1000° C. for 4-10 hours under a protective atmosphere to obtain the metal connector coating.

4. The preparation method according to claim 3, wherein: Before coating, the ferritic stainless steel was polished to 1200 mesh with sandpaper and ultrasonically cleaned with ethanol.

5. The preparation method according to claim 3, wherein: The coating slurry is evenly coated on the surface of the ferritic stainless steel by screen printing.

6. The preparation method according to claim 5, characterized in that: The ferritic stainless steel is SUS430 ferritic stainless steel.

7. The preparation method according to claim 3, characterized in that: The protective atmosphere is Ar.

8. A metal interconnect coating, characterized in that: It is obtained by the preparation method described in any one of claims 3 to 7.

9. Use of the metal interconnect coating according to claim 8 in a solid oxide fuel cell.

10. The use according to claim 9, characterized in that: The metal interconnect coating is used to secure the fuel electrode side in an oxide fuel cell.

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