Fuel cell bipolar plate coating and preparation method thereof

Abstract

The invention provides a fuel cell bipolar plate coating and a preparation method thereof, and relates to the technical field of fuel cells, the fuel cell bipolar plate coating comprises a metal bottom layer, a transition layer and a surface layer which are sequentially deposited on a bipolar plate base material, the metal bottom layer is one of Ti, Cr, Zr, Nb, Ta, W and Mo, the transition layer is one or more of metal Ti, Cr, Zr, Nb, Ta, W and Mo corresponding ions, and the surface layer is one or more of metal Ti, Cr, Zr, Nb, Ta, W and Mo corresponding ions. The surface layer is composed of one of non-metal components C, N and Si. Through the synergistic effect of all the layers, the conductivity, corrosion resistance, mechanical strength and long-term stability of the fuel cell bipolar plate are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell bipolar plate coating and a preparation method thereof. Background Art

[0002] A fuel cell is a device that converts chemical energy into electrical energy through an electrochemical reaction, boasting high efficiency and environmental friendliness. In recent years, fuel cell technology has rapidly developed globally. There are many types of fuel cells, classified by electrolyte type as proton exchange membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC), solid oxide fuel cells (SOFC), and molten carbonate fuel cells (MCFC). Proton exchange membrane fuel cells are widely used due to their high efficiency, low emissions, and rapid startup.

[0003] The basic structure of a proton exchange membrane fuel cell (PEMFC) stack consists primarily of a proton exchange membrane, a catalyst layer, a diffusion layer, and bipolar plates. The bipolar plates conduct electrons, distribute the reactant gases, and remove generated water. Functionally, these plates must be made of materials that are good conductors of electricity and heat, possessing a certain strength and gas tightness. Bipolar plates must maintain their performance in the acidic, hot, and humid environments of fuel cells, placing high demands on their corrosion resistance. Currently, the coatings applied to bipolar plates have difficulty meeting the corrosion resistance requirements necessary to maintain fuel cell performance in these environments. Summary of the Invention

[0004] The problem solved by the present invention is how to solve the problem of poor corrosion resistance of the surface coating of the bipolar plate.

[0005] In order to solve the above problems, the present invention provides a fuel cell bipolar plate coating and a preparation method thereof.

[0006] In a first aspect, the present invention provides a fuel cell bipolar plate coating, comprising a metal base layer, a transition layer, and a surface layer sequentially deposited on a bipolar plate substrate;

[0007] The metal bottom layer is one of Ti, Cr, Zr, Nb, Ta, W, and Mo, the transition layer is composed of one or more corresponding ions of metal Ti, Cr, Zr, Nb, Ta, W, and Mo, and the surface layer is composed of one of non-metallic components C, N, and Si.

[0008] Optionally, the metal bottom layer is a Ti layer, the transition layer is a TiTaNb layer, and the surface layer is a C layer.

[0009] Optionally, the thickness of the metal bottom layer is 1 to 50 nm.

[0010] Optionally, the transition layer has a thickness of 100 to 300 nm.

[0011] Optionally, the surface layer has a thickness of 50 to 200 nm.

[0012] In a second aspect, the present invention provides a method for preparing a fuel cell bipolar plate coating as described above, comprising the following steps:

[0013] S1: Using vacuum magnetron sputtering method, a metal base layer is deposited on the surface of the bipolar plate substrate;

[0014] S2: using vacuum magnetron sputtering to deposit a transition layer on the surface of the metal bottom layer away from the bipolar plate substrate;

[0015] S3: Using vacuum magnetron sputtering method, a surface layer is deposited on the surface of the transition layer away from the metal bottom layer.

[0016] Optionally, the method further comprises the steps of:

[0017] S0: The surface of the bipolar plate substrate is pretreated by plasma cleaning.

[0018] Optionally, in step S1 , the deposition temperature is 100 to 300° C., and the deposition pressure is lower than 0.1 Pa.

[0019] Optionally, in step S2 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

[0020] Optionally, in step S3 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

[0021] The beneficial effects of the fuel cell bipolar plate coating and the preparation method thereof of the present invention are as follows: the metal bottom layer is a metal layer of a single metal, which can form a strong metallurgical bond with the metal substrate of the bipolar plate through diffusion bonding, has high adhesion, and avoids peeling; secondly, the metal bottom layer can form a dense oxide film in an acidic environment to prevent corrosion of the substrate; and, the metal bottom layer can provide a low-resistance path to ensure efficient electron transmission. The transition layer is composed of metal ions, and can form metallurgical bonds with the metal base layer and surface layer through atomic diffusion or solid solution, which is significantly stronger than mechanically bonded non-metallic mixtures; secondly, the thermal expansion coefficients of the metal base layer and the transition layer are between those of the bipolar plate metal substrate and the surface layer, gradually buffering thermal stress, avoiding cracking or peeling of the multi-layer coating, and having good density; moreover, the metal transition layer has a high degree of electronic freedom, maintains low contact resistance, and has high conductivity, which is significantly stronger than the metal / non-metallic mixed layer whose resistance is increased due to the non-metallic insulating phase; finally, multi-metal elements are co-sputtered and deposited, and the high chemical stability of the coating is achieved through multi-component synergistic passivation and microstructure optimization. Among them, the atomic radii of Ti, Ta, and Nb are similar, and it is easy to form solid solutions or nanocrystalline composite structures, reducing grain boundary defects and inhibiting corrosion channels. First, the surface layer utilizes a single non-metallic layer, resulting in a stable interface and avoiding the interface instability caused by the coexistence and competition of multiple phases in a complex mixture of multiple metals and non-metals. Second, the single non-metallic phase forms a conductive layer with higher conductivity while reducing interfacial contact resistance, thus avoiding the increased resistance of a multi-metal / multi-non-metallic mixture due to increased electron scattering caused by the dispersion of the non-metallic phase. This layered coating design of "metal base layer → transition layer → surface layer" for fuel cell bipolar plates significantly improves the conductivity, corrosion resistance, mechanical strength, and long-term stability of fuel cell bipolar plates through the synergistic effect of each layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of a fuel cell bipolar plate of this embodiment;

[0023] Figure 2 Graph showing the corrosion potential of the bipolar plates of the fuel cells of Example 1, Comparative Example 1 and Comparative Example 2 in the effect embodiment;

[0024] Figure 3 1 is a comparison diagram of the interface contact resistance of the fuel cell bipolar plates of Example 1, Comparative Example 1 and Comparative Example 2 in the effect embodiment;

[0025] Description of reference numerals:

[0026] 1. Bipolar plate substrate; 2. Metal bottom layer; 3. Transition layer; 4. Surface layer. DETAILED DESCRIPTION

[0027] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the present invention description are only for the purpose of describing specific embodiments and are not intended to limit the present invention;

[0029] As used herein, the term "including" and its variations are open-ended, i.e., "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments." The relevant definitions of other terms will be given in the following description. In the description of this application, unless otherwise specified, "a plurality" means two or more.

[0030] An embodiment of the present invention provides a fuel cell bipolar plate coating and a preparation method thereof.

[0031] A fuel cell bipolar plate coating provided in one embodiment of the present invention comprises a metal base layer 2, a transition layer 3 and a surface layer 4 deposited in sequence on a bipolar plate substrate 1;

[0032] The metal bottom layer 2 is one of Ti, Cr, Zr, Nb, Ta, W, and Mo, the transition layer 3 is composed of one or more corresponding ions of metal Ti, Cr, Zr, Nb, Ta, W, and Mo, and the surface layer 4 is composed of one of non-metallic components C, N, and Si.

[0033] In this embodiment, the metal bottom layer is a metal layer of a single metal, which can form a strong metallurgical bond with the metal substrate of the bipolar plate through diffusion bonding, has high adhesion, and avoids peeling; secondly, the metal bottom layer can form a dense oxide film in an acidic environment to prevent corrosion of the substrate; and, the metal bottom layer can provide a low-resistance path to ensure efficient transmission of electrons. The transition layer is composed of metal ions, and can form metallurgical bonds with the metal base layer and surface layer through atomic diffusion or solid solution, which is significantly stronger than mechanically bonded non-metallic mixtures; secondly, the thermal expansion coefficients of the metal base layer and the transition layer are between those of the bipolar plate metal substrate and the surface layer, gradually buffering thermal stress, avoiding cracking or peeling of the multi-layer coating, and having good density; moreover, the metal transition layer has a high degree of electronic freedom, maintains low contact resistance, and has high conductivity, which is significantly stronger than the metal / non-metallic mixed layer whose resistance is increased due to the non-metallic insulating phase; finally, multi-metal elements are co-sputtered and deposited, and the high chemical stability of the coating is achieved through multi-component synergistic passivation and microstructure optimization. Among them, the atomic radii of Ti, Ta, and Nb are similar, and it is easy to form solid solutions or nanocrystalline composite structures, reducing grain boundary defects and inhibiting corrosion channels. First, the surface layer utilizes a single non-metallic layer, resulting in a stable interface and avoiding the interface instability caused by the coexistence and competition of multiple phases in a complex mixture of multiple metals and non-metals. Second, the single non-metallic phase forms a conductive layer with higher conductivity while reducing interfacial contact resistance, thus avoiding the increased resistance of a multi-metal / multi-non-metallic mixture due to increased electron scattering caused by the dispersion of the non-metallic phase. This layered coating design of "metal base layer → transition layer → surface layer" for fuel cell bipolar plates significantly improves the conductivity, corrosion resistance, mechanical strength, and long-term stability of fuel cell bipolar plates through the synergistic effect of each layer.

[0034] Optionally, the metal bottom layer 2 is a Ti layer, the transition layer 3 is a TiTaNb layer, and the surface layer 4 is a C layer.

[0035] In this optional embodiment, the atomic radii of Ti, Ta, and Nb in the transition layer 3 are similar, and they are easy to form a solid solution or a nanocrystalline composite structure, thereby reducing grain boundary defects, inhibiting corrosion channels, and improving corrosion resistance.

[0036] Optionally, the thickness of the metal bottom layer 2 is 1 to 50 nm.

[0037] In this optional embodiment, the thickness of the metal bottom layer 2 can meet the requirements of mechanical strength.

[0038] Optionally, the transition layer 3 has a thickness of 100 to 300 nm.

[0039] In this optional embodiment, the thickness of the transition layer 3 can make its peeling rate low.

[0040] Optionally, the thickness of the surface layer 4 is 50 to 200 nm.

[0041] In this optional embodiment, the thickness of the surface layer 4 can meet the wear resistance requirements.

[0042] Another embodiment of the present invention provides a method for preparing the fuel cell bipolar plate coating as described above, comprising the following steps:

[0043] S1: using vacuum magnetron sputtering to deposit a metal base layer 2 on the surface of the bipolar plate substrate 1;

[0044] S2: using vacuum magnetron sputtering, depositing a transition layer 3 on the surface of the metal bottom layer 2 away from the bipolar plate substrate 1;

[0045] S3: using a vacuum magnetron sputtering method, depositing a surface layer 4 on the surface of the transition layer 3 away from the metal base layer 2 .

[0046] In this embodiment, the high energy (5-50 eV) of the sputtered particles by vacuum magnetron sputtering forms a dense structure (density > 98% of the theoretical value), which blocks the H + Penetration (permeability decreased by 90%), a pore-free coating is obtained, which makes the coating have ultra-high purity and density. By adjusting the target current, substrate bias and other process parameters to adjust the composition of each layer of the multi-layer coating, the multi-layer alloy is precisely doped to achieve nano-level component controllability, which greatly improves the bonding strength of the multi-layer coating of the metal bipolar plate.

[0047] Optionally, the method further comprises the steps of:

[0048] S0: Pre-treating the surface of the bipolar plate substrate 1 by plasma cleaning.

[0049] In this optional embodiment, the metal bipolar plate substrate 1 is placed in an ultrasonic cleaning device in advance to remove dust, impurities, oil stains and other pollutants on the product surface to improve the surface cleanliness of the sample, and then dried in a vacuum oven and wait to be loaded into the furnace cavity; the cleaned metal bipolar plate substrate 1 is placed in a vacuum coating cavity for plasma cleaning to enhance the coating adhesion.

[0050] Optionally, in step S1 , the deposition temperature is 100 to 300° C., and the deposition pressure is lower than 0.1 Pa.

[0051] In this optional embodiment, the low-temperature process of 100 to 300°C can prevent carbide precipitation or alloy phase transformation in the metal bipolar plate substrate 1, maintain the mechanical properties of the metal bipolar plate substrate 1, limit atomic diffusion at low temperature, obtain nanocrystalline or even amorphous structure, inhibit grain coarsening, increase hardness, reduce thermal stress, and reduce the risk of warping or peeling. At less than 0.1Pa, the mean free path of Ar ions reaches 10-100cm, sputtering particle collisions are reduced, kinetic energy loss is small; density is improved, and film resistivity is reduced.

[0052] Optionally, in step S2 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

[0053] In this optional embodiment, a low-temperature process of 100 to 300°C prevents carbide precipitation or alloy phase transformation in the metal bipolar plate substrate 1, maintaining its mechanical properties. The low temperature limits atomic diffusion, resulting in a nanocrystalline or even amorphous structure, suppressing grain coarsening, improving hardness, and reducing thermal stress, while also minimizing the risk of warping or spalling. Within the 0.1-1 Pa range, the Ar gas molecular density increases, increasing the probability of electron collisions and the ionization rate, significantly boosting plasma density and improving sputtering yield, making it more suitable for the efficient deposition of refractory metals.

[0054] Optionally, in step S3 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

[0055] In this optional embodiment, a low-temperature process of 100 to 300°C prevents carbide precipitation or alloy phase transformation in the metal bipolar plate substrate 1, maintaining its mechanical properties. The low temperature limits atomic diffusion, resulting in a nanocrystalline or even amorphous structure, suppressing grain coarsening, improving hardness, and reducing thermal stress, while also minimizing the risk of warping or spalling. Within the 0.1-1 Pa range, the Ar gas molecular density increases, increasing the probability of electron collisions and the ionization rate, significantly boosting plasma density and improving sputtering yield, making it more suitable for the efficient deposition of refractory metals.

[0056] The present invention is further described below with reference to specific embodiments.

[0057] Example 1

[0058] 1. Take a 316 stainless steel metal bipolar plate substrate 1, place it in an ultrasonic cleaning device in advance to remove dust, impurities, oil and other pollutants on the product surface to improve the surface cleanliness of the sample, and then dry it in a vacuum oven before loading it into the furnace cavity; place the cleaned metal bipolar plate substrate 1 into the vacuum coating cavity for plasma cleaning.

[0059] 2. A Ti metal base layer 2 is deposited on the surface of the bipolar plate substrate 1 by using a vacuum magnetron sputtering method at a deposition temperature of 200° C. and a deposition pressure of 0.05 Pa.

[0060] 3. A TiTaNb transition layer 3 is deposited on the surface of the metal bottom layer 2 away from the bipolar plate substrate 1 by using a vacuum magnetron sputtering method with a deposition temperature of 200° C. and a deposition pressure of 0.5 Pa.

[0061] Fourth, a vacuum magnetron sputtering method is used with a deposition temperature of 200° C. and a deposition pressure of 0.5 Pa to deposit a C surface layer 4 on the surface of the transition layer 3 away from the metal base layer 2 .

[0062] Comparative Example 1

[0063] The difference from Example 1 is that the C surface layer 4 of the surface layer is replaced by a Ti metal crystal coating.

[0064] Comparative Example 2

[0065] Take a 316 stainless steel metal bipolar plate substrate 1, place the metal bipolar plate substrate 1 in an ultrasonic cleaning device in advance to remove dust, impurities, oil and other pollutants on the product surface to improve the surface cleanliness of the sample, and then dry it in a vacuum oven before loading it into the furnace cavity; place the cleaned metal bipolar plate substrate 1 in a vacuum coating cavity for plasma cleaning without depositing a coating.

[0066] Effect embodiment

[0067] The fuel cell bipolar plates of Example 1 and Comparative Examples 1 and 2 were subjected to potentiodynamic polarization testing to determine their corrosion resistance in a simulated proton exchange membrane fuel cell (PEMFC) environment (acidic, humid, 80°C). The test conditions included:

[0068] Electrolyte: 0.5M H2SO4+2ppm HF (simulating PEMFC environment);

[0069] Temperature: 80°C (simulated battery operating temperature);

[0070] Scan range: -0.5V to +1.0V (vs.SCE);

[0071] Scan rate: 1mV / s.

[0072] The test results are as follows Figure 2 As shown, under the constant potential polarization test potential of 0.84V, the corrosion current of Example 1 is 0.28μAcm -2 The corrosion current of comparative example 1 is 2.2 μA cm -2 The corrosion current of comparative example 2 is 12.6 μA cm -2 The corrosion current of Example 1 is lower than those of Comparative Examples 1 and 2.

[0073] The fuel cell bipolar plate of Example 1 was subjected to a 96-hour accelerated test in a simulated PEMFC environment, where air or hydrogen was introduced at a flow rate of 20 mL / min. The coating morphology remained intact, with no signs of corrosion on the surface. The contact resistance remained essentially unchanged after the corrosion test, demonstrating that the highly corrosion-resistant multi-element coating of this fuel cell bipolar plate possesses exceptional corrosion resistance at high potentials.

[0074] The interface contact resistance of the fuel cell bipolar plates of Example 1, Comparative Example 1 and Comparative Example 2 was tested. The test results are as follows: Figure 3As shown, the contact resistance of Example 1 is lower than the contact resistance of Comparative Examples 1 and 2, indicating that the highly corrosion-resistant multi-element coating of the fuel cell bipolar plate has excellent conductive properties.

[0075] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A fuel cell bipolar plate coating, characterized in that: It comprises a metal base layer (2), a transition layer (3) and a surface layer (4) deposited in sequence on a bipolar plate substrate (1); The metal bottom layer (2) is one of Ti, Cr, Zr, Nb, Ta, W, and Mo; the transition layer (3) is composed of one or more corresponding ions of the metals Ti, Cr, Zr, Nb, Ta, W, and Mo; and the surface layer (4) is composed of one of the non-metallic components C, N, and Si.

2. The fuel cell bipolar plate coating according to claim 1, characterized in that: The metal bottom layer (2) is a Ti layer, the transition layer (3) is a TiTaNb layer, and the surface layer (4) is a C layer.

3. The fuel cell bipolar plate coating according to claim 1, characterized in that: The thickness of the metal bottom layer (2) is 1 to 50 nm.

4. The fuel cell bipolar plate coating according to claim 1, characterized in that: The thickness of the transition layer (3) is 100 to 300 nm.

5. The fuel cell bipolar plate coating according to claim 1, characterized in that: The thickness of the surface layer (4) is 50 to 200 nm.

6. A method for preparing a fuel cell bipolar plate coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: using a vacuum magnetron sputtering method to deposit a metal base layer (2) on the surface of a bipolar plate substrate (1); S2: using a vacuum magnetron sputtering method to deposit a transition layer (3) on a surface of the metal bottom layer (2) away from the bipolar plate substrate (1); S3: using a vacuum magnetron sputtering method, depositing a surface layer (4) on the surface of the transition layer (3) away from the metal base layer (2).

7. The method for preparing a fuel cell bipolar plate coating according to claim 6, characterized in that: Also includes the steps: S0: Pre-treating the surface of the bipolar plate substrate (1) by plasma cleaning.

8. The method for preparing a fuel cell bipolar plate coating according to claim 6, characterized in that: In step S1 , the deposition temperature is 100 to 300° C., and the deposition pressure is lower than 0.1 Pa.

9. The method for preparing a fuel cell bipolar plate coating according to claim 6, wherein: In step S2 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

10. The method for preparing a fuel cell bipolar plate coating according to claim 6, wherein: In step S3 , the deposition temperature is 100 to 300° C., and the deposition pressure is 0.1 to 1 Pa.

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