A fuel cell metal bipolar plate having a conductive corrosion-resistant carbon-based coating and a method of making the same

Abstract

This invention relates to a conductive and corrosion-resistant carbon-based coating for a fuel cell metal bipolar plate and its preparation method, belonging to the field of fuel cell technology. The conductive and corrosion-resistant carbon-based coating for a fuel cell metal bipolar plate includes a metal substrate, a metal transition layer, and a conductive and corrosion-resistant composite interlayer. The conductive and corrosion-resistant composite interlayer consists of a conductive layer, a carbon interlayer, and a corrosion-resistant layer. The metal transition layer is located on the metal substrate and is used to enhance the adhesion between the coating and the substrate. The conductive layer is deposited on the metal transition layer, and the carbon interlayer is deposited on the conductive layer to reduce internal stress within the coating.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to a fuel cell metal bipolar plate with a conductive and corrosion-resistant carbon-based coating and its preparation method. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is an electrochemical device that generates electricity through an electrochemical reaction. As an emerging and prominent clean power source, PEMFC has advantages such as low temperature, low pressure, short start-up and shutdown time, low noise, and high efficiency. It is an important driver for building a green and low-carbon society and has great development prospects in the field of new energy.

[0003] Bipolar plates are crucial multifunctional components in PEMFCs, accounting for approximately 80% of the battery stack volume, 70% of the weight, and 30% of the cost. Their function includes separating reactant gases, collecting electrons generated during electrochemical reactions, and dissipating heat and waste gases. Based on the material, bipolar plates are mainly classified into graphite bipolar plates, metal bipolar plates, and composite bipolar plates. Metal bipolar plates possess advantages such as high mechanical strength, high conductivity, low airtightness, low cost, and ease of processing, making them widely used by new energy vehicle manufacturers. However, in operating environments with strong acids (pH 2-5), high temperatures (70℃), and high humidity, metal bipolar plates are highly susceptible to corrosion, and dissolved metal ions cause catalyst poisoning. Simultaneously, the passivation film on the corroded surface increases the interfacial contact resistance (ICR) between the gas diffusion layer (GDL) and the bipolar plate, reducing the stack's output power. To overcome these problems, researchers have conducted extensive research on coating technologies, such as metal carbide coatings, noble metal coatings, and conductive polymer coatings. However, the performance of existing coatings does not meet the desired performance. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a metal bipolar plate for fuel cells with a conductive and corrosion-resistant carbon-based coating and its preparation method.

[0005] The metal bipolar plate includes: a metal substrate, a metal transition layer, and a conductive and corrosion-resistant composite interlayer; wherein, the conductive and corrosion-resistant composite interlayer is composed of a conductive layer, a carbon interlayer, and a corrosion-resistant layer in sequence, and the sp2 content of the conductive layer is greater than the sp2 content of the corrosion-resistant layer; the carbon interlayer is deposited between the conductive layer and the corrosion-resistant layer, forming an interlayer structure.

[0006] Furthermore, the metal substrate is one or more of stainless steel, titanium, and aluminum.

[0007] Furthermore, the metal material in the metal transition layer is one or more of chromium, titanium, and tungsten, and its function is to enhance the adhesion between the coating and the metal substrate.

[0008] Furthermore, the conductive and corrosion-resistant composite interlayer consists of a conductive layer, a carbon interlayer, and a corrosion-resistant layer.

[0009] Furthermore, in the conductive and corrosion-resistant composite interlayer, the sp2 content of the conductive layer is greater than the sp2 content of the corrosion-resistant layer.

[0010] Furthermore, the conductive layer in the conductive and corrosion-resistant composite interlayer is one or more of chromium carbide and titanium carbide amorphous carbon layers.

[0011] Furthermore, the carbon interlayer in the conductive and corrosion-resistant composite interlayer is one or more of a graphite-like layer and a diamond-like layer.

[0012] Furthermore, the corrosion-resistant layer in the conductive and corrosion-resistant composite interlayer is one or more of chromium carbide and titanium carbide amorphous carbon layers.

[0013] Furthermore, the conductive and corrosion-resistant coating of the metal bipolar plate is prepared by magnetron sputtering.

[0014] Preferably, the thickness of the metal transition layer is 20–50 nm.

[0015] Preferably, the thickness of the conductive layer in the conductive and corrosion-resistant composite interlayer is 200nm-400nm.

[0016] Preferably, the carbon interlayer in the conductive and corrosion-resistant composite interlayer has a thickness of 50nm-100nm.

[0017] Preferably, the thickness of the corrosion-resistant layer in the conductive and corrosion-resistant composite interlayer is 150nm-200nm.

[0018] This invention also provides a method for preparing a conductive and corrosion-resistant coating for a metal bipolar plate, the specific steps of which are as follows:

[0019] (1) The metal bipolar plate substrate was sequentially ultrasonically cleaned in acetone, ethanol, and deionized water for 20 minutes each, dried, and then fixed on the sample holder. The vacuum level was then increased to 6.0 × 10⁻⁶. -4 ~8.0×10 -4 After Pa, a certain amount of argon gas is introduced, and the substrate is etched for 30 minutes using Ar ion glow discharge under a bias voltage of -300 to -500V.

[0020] (2) Deposit a metal transition layer on a metal bipolar plate substrate by turning on the metal target current. The metal target current is 0 to 5A, the argon flow rate is 30 to 60 sccm, the bias voltage is -70 to -150V, and the deposition time is 1 to 10 min.

[0021] (3) Turn off the metal target current, turn on the carbon target current and the chromium / titanium target current, and deposit a conductive layer on the metal transition layer. The carbon target current is 0-5A, the chromium / titanium target current is 0-5A, the argon flow rate and bias voltage remain unchanged, and the deposition time is 20-30min.

[0022] (4) Keep the carbon target current constant, turn off the chromium / titanium target current, deposit a carbon interlayer on the conductive layer, keep the argon flow rate and bias voltage constant, and the deposition time is 10-20 min.

[0023] (5) Keep the carbon target current constant, turn on the chromium / titanium target current, and deposit a conductive layer on the carbon interlayer. The chromium / titanium target current is 0-2A, the argon flow rate and bias voltage are constant, and the deposition time is 10-20min.

[0024] A metal transition layer is located on the metal substrate to enhance the adhesion between the coating and the substrate. A conductive layer is deposited on the metal transition layer, and a carbon interlayer is deposited on the conductive layer to reduce internal stress within the coating. A corrosion-resistant layer is deposited on the carbon interlayer. Both the conductive and corrosion-resistant layers are amorphous carbon coatings. The carbon atoms in the amorphous carbon coating have both sp2 and sp3 hybridization types, exhibiting properties similar to graphite and diamond. By adjusting the sp2 / sp3 content of the conductive and corrosion-resistant layers, the coating achieves excellent conductivity and corrosion resistance, while also improving the service life of the metal bipolar plate.

[0025] This invention proposes a conductive and corrosion-resistant carbon-based coating for fuel cell metal bipolar plates and its preparation method. The conductive and corrosion-resistant coating adopts a structural design of a metal transition layer, a conductive layer, a carbon interlayer, and a corrosion-resistant layer. By controlling the sp2 content of the conductive and corrosion-resistant layers, the characteristics of the amorphous carbon layer are fully utilized, achieving excellent conductivity and corrosion resistance of the coating. At the same time, the composite interlayer design of the conductive layer, carbon interlayer, and corrosion-resistant layer significantly reduces the high stress occurring inside the coating, thereby improving the service life of the metal bipolar plate. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the coating distribution of the present invention.

[0027] 1. Metal substrate, 2. Metal transition layer, 3. Conductive layer, 4. Carbon interlayer, 5. Corrosion-resistant layer. Among them, 3, 4, and 5 constitute structure A, A. Conductive and corrosion-resistant composite interlayer. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] This invention provides a conductive and corrosion-resistant carbon-based coating for a fuel cell metal bipolar plate, wherein the metal bipolar plate comprises: a metal substrate, a metal transition layer, and a conductive and corrosion-resistant composite interlayer.

[0031] Furthermore, the metal substrate is one or more of stainless steel, titanium, and aluminum.

[0032] Furthermore, the metal material in the metal transition layer is one or more of chromium, titanium, and tungsten, and its function is to enhance the adhesion between the coating and the metal substrate.

[0033] Furthermore, the conductive and corrosion-resistant composite interlayer consists of a conductive layer, a carbon interlayer, and a corrosion-resistant layer.

[0034] Furthermore, in the conductive and corrosion-resistant composite interlayer, the sp2 content of the conductive layer is greater than the sp2 content of the corrosion-resistant layer.

[0035] Furthermore, the conductive layer in the conductive and corrosion-resistant composite interlayer is one or more of chromium carbide and titanium carbide amorphous carbon layers.

[0036] Furthermore, the carbon interlayer in the conductive and corrosion-resistant composite interlayer is one or more of a graphite-like layer and a diamond-like layer.

[0037] Furthermore, the corrosion-resistant layer in the conductive and corrosion-resistant composite interlayer is one or more of chromium carbide and titanium carbide amorphous carbon layers.

[0038] Furthermore, the conductive and corrosion-resistant coating of the metal bipolar plate is prepared by magnetron sputtering.

[0039] Preferably, the thickness of the metal transition layer is 20–50 nm.

[0040] Preferably, the thickness of the conductive layer in the conductive and corrosion-resistant composite interlayer is 200nm-400nm.

[0041] Preferably, the carbon interlayer in the conductive and corrosion-resistant composite interlayer has a thickness of 50nm-100nm.

[0042] Preferably, the thickness of the corrosion-resistant layer in the conductive and corrosion-resistant composite interlayer is 150nm-200nm.

[0043] This invention also provides a method for preparing a conductive and corrosion-resistant coating for a metal bipolar plate, the specific steps of which are as follows:

[0044] S1. Pretreatment: The bipolar metal substrate 1 was sequentially ultrasonically cleaned in acetone, ethanol, and deionized water for 20 minutes each. After drying, it was fixed on the sample holder and subjected to a vacuum of 6.0 × 10⁻⁶. -4 ~8.0×10 -4 After Pa, a certain amount of argon gas is introduced, and the substrate is etched by Ar ion glow discharge for 30 minutes under a bias voltage of -300 to -500V.

[0045] S2. Preparation of metal transition layer: Turn on the chromium magnetron target and deposit the chromium layer on the surface of the metal substrate under an argon atmosphere;

[0046] S3. Prepare a conductive and corrosion-resistant composite interlayer;

[0047] S3.1. Preparation of conductive layer: Keep the chromium target current constant, while turning on the carbon target current and slowly increasing it. Under an argon atmosphere, deposit the conductive layer on the chromium transition layer.

[0048] S3.2. Preparation of carbon interlayer: Turn off the chromium target current and deposit the carbon interlayer on the conductive layer under an argon atmosphere;

[0049] S3.3. Preparation of corrosion-resistant layer: Keep the carbon target current constant, and at the same time turn on the chromium target current. The chromium target current is always less than the carbon target current. Under the argon atmosphere, the corrosion-resistant layer is deposited on the carbon interlayer.

[0050] Example 1

[0051] like Figure 1 As shown, a conductive and corrosion-resistant carbon-based coating for a fuel cell metal bipolar plate includes a metal substrate 1. Outside the metal substrate 1, a metal transition layer 2 and a conductive and corrosion-resistant composite interlayer are deposited sequentially from the inside to the outside. The conductive and corrosion-resistant composite interlayer consists of a metal transition layer 2, a conductive layer 3, a carbon interlayer 4, and a corrosion-resistant layer 5, sequentially from the inside to the outside.

[0052] The metal transition layer is a chromium layer with a thickness of 50 nm; the conductive and corrosion-resistant composite interlayer consists of a chromium carbide conductive layer, a carbon interlayer, and a chromium carbide corrosion-resistant layer. The thickness of the chromium carbide conductive layer is 300±10 nm, the thickness of the carbon interlayer is 70±10 nm, and the thickness of the chromium carbide corrosion-resistant layer is 150±10 nm.

[0053] (1) The metal bipolar plate substrate was sequentially ultrasonically cleaned in acetone, ethanol, and deionized water for 20 minutes each, dried, and then fixed on the sample holder. The vacuum level was then increased to 6.0 × 10⁻⁶. -4 ~8.0×10 -4After Pa, a certain amount of argon gas is introduced, and the substrate is etched for 30 minutes using Ar ion glow discharge under a bias voltage of -300 to -500V.

[0054] (2) Deposit a metal transition layer on a metal bipolar plate substrate by turning on the metal target current. The metal target current is 0 to 5A, the argon flow rate is 30 to 60 sccm, the bias voltage is -70 to -150V, and the deposition time is 1 to 10 min.

[0055] (3) Turn off the metal target current, turn on the carbon target current and the chromium / titanium target current, and deposit a conductive layer on the metal transition layer. The carbon target current is 0-5A, the chromium / titanium target current is 0-5A, the argon flow rate and bias voltage remain unchanged, and the deposition time is 20-30min.

[0056] (4) Keep the carbon target current constant, turn off the chromium / titanium target current, deposit a carbon interlayer on the conductive layer, keep the argon flow rate and bias voltage constant, and the deposition time is 10-20 min.

[0057] (5) Keep the carbon target current constant, turn on the chromium / titanium target current, and deposit a conductive layer on the carbon interlayer. The chromium / titanium target current is 0-2A, the argon flow rate and bias voltage are constant, and the deposition time is 10-20min.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A fuel cell metal bipolar plate with a conductive and corrosion-resistant carbon-based coating, characterized in that, The metal bipolar plate includes: a metal substrate, a metal transition layer, and a conductive and corrosion-resistant composite interlayer; wherein, the conductive and corrosion-resistant composite interlayer consists of a conductive layer, a carbon interlayer, and a corrosion-resistant layer from the inside out; the sp2 content of the conductive layer is greater than the sp2 content of the corrosion-resistant layer; the carbon interlayer is deposited between the conductive layer and the corrosion-resistant layer, forming an interlayer structure; A metal transition layer is located on a metal substrate to enhance the adhesion between the coating and the substrate; a conductive layer is deposited on the metal transition layer, and a carbon interlayer is deposited on the conductive layer to reduce internal stress in the coating. The carbon interlayer in the conductive and corrosion-resistant composite interlayer is one or more of a graphite-like layer and a diamond-like layer; The metal bipolar plate fabrication steps include the following: S3.

1. Turn on the metal target current and deposit a metal transition layer on the bipolar metal substrate; S3.

2. Turn off the metal target current, turn on the carbon target current and chromium / titanium target current, and deposit a conductive layer on the metal transition layer. S3.

3. Keep the carbon target current constant, turn off the chromium / titanium target current, deposit a carbon interlayer on the conductive layer, and keep the argon flow rate and bias voltage constant. S3.

4. Keep the carbon target current constant, turn on the chromium / titanium target current, and deposit a conductive layer on the carbon interlayer.

2. The bipolar plate according to claim 1, characterized in that, The thickness of the metal transition layer is 20–50 nm.

3. The bipolar plate according to claim 1, characterized in that, The thickness of the metal transition layer is 200nm-400nm, which is the same as the thickness of the conductive layer in the conductive and corrosion-resistant composite interlayer.

4. The bipolar plate according to claim 1, characterized in that, The carbon interlayer in the conductive and corrosion-resistant composite interlayer has a thickness of 50nm-100nm.

5. The bipolar plate according to claim 1, characterized in that, The thickness of the corrosion-resistant layer in the conductive and corrosion-resistant composite interlayer is 150nm-200nm.

6. The bipolar plate according to claim 1, characterized in that, The metal material in the metal transition layer is one or more of chromium, titanium, and tungsten.

7. The bipolar plate according to claim 1, characterized in that, The conductive layer in the conductive and corrosion-resistant composite interlayer is one or more of chromium carbide and titanium carbide amorphous carbon layers.

8. A method for preparing a bipolar plate according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Pretreatment: The bipolar metal substrate was ultrasonically cleaned in acetone, ethanol and deionized water for 20 minutes each, dried and fixed on the sample holder. After the vacuum reached 6.0×10-4~8.0×10-4Pa, a certain amount of argon gas was introduced and the substrate was etched by Ar ion glow discharge for 30 minutes under a bias voltage of -300~-500V. S2. Preparation of metal transition layer: Turn on the chromium magnetron target and deposit the chromium layer on the surface of the metal substrate under an argon atmosphere; S3. Prepare a conductive and corrosion-resistant composite interlayer.

9. The method according to claim 8, characterized in that, The preparation steps specifically include the following: S3.

1. The metal target current is 0-5A, the argon flow rate is 30-60sccm, the bias voltage is -70--150V, and the deposition time is 1-10min; S3.

2. The carbon target current is 0-5A, the chromium / titanium target current is 0-5A, the argon flow rate and bias voltage are constant, and the deposition time is 20-30 min; S3.

3. The deposition time is 10–20 min; S3.

4. The chromium / titanium target current is 0-2A, the argon flow rate and bias voltage remain constant, and the deposition time is 10-20min.

Images