A surface-modified fuel cell bipolar plate, method of manufacture and fuel cell

Abstract

The application provides a surface modified fuel cell bipolar plate and a preparation method thereof, wherein a bipolar plate of a fuel cell is used as a base material, a uniform C-Cr coating layer is formed on the surface of the base material by using a vacuum sputtering plating layer technology, and by using Cr element doped C, the poor adhesion between stainless steel and the C thin film and the defects that carbon deposition has some difficulties are overcome; compared with common carbon thin films, the C-Cr thin film can improve the interface conductivity and corrosion resistance of the coating layer, meanwhile, the thin film has low residual stress and good stability, and the risk of local corrosion caused by defects of the coating layer is reduced. In addition, the application further provides a fuel cell.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and in particular to a surface-modified fuel cell bipolar plate, its preparation method, and the fuel cell. Background Technology

[0002] Currently, carbon-based materials are widely used in the fabrication of bipolar plates for proton exchange membrane fuel cells (PEMFCs) both domestically and internationally. Although carbon-based materials are relatively inexpensive, the complex gas flow channels required for their fabrication result in high machining costs. Furthermore, carbon-based materials have poor bending resistance and are brittle, leading to thicker bipolar plates. Therefore, the volume, weight, and cost of carbon-based bipolar plates account for the majority of the entire fuel cell stack. In contrast, metallic bipolar plates possess superior mechanical properties, machinability, and dimensional stability. They can be rolled into thin metal sheets, significantly reducing battery weight and volume. Moreover, metallic materials have mature processing techniques, allowing for the fabrication of the necessary flow channels using precision machining, facilitating cooling and drainage. For these reasons, metallic bipolar plates are considered the ideal bipolar electrode material.

[0003] Stainless steel, with its high corrosion resistance, high thermal conductivity, good processing performance, and low price, is highly competitive among metal bipolar plate materials. However, research has found that untreated stainless steel bipolar plates are prone to forming oxide passivation films on their surfaces in PEMFC environments. The poor conductivity of these passivation films significantly increases contact resistance. Furthermore, the electrolyte becomes contaminated by nickel, chromium, and iron ions deposited from the bipolar plates, leading to a significant increase in the battery's ohmic impedance and charge transfer impedance. This directly impacts the fuel cell's lifespan and fails to meet the high-performance requirements of fuel cells. While untreated stainless steel bipolar plates offer advantages such as fast production and low processing costs, the poor corrosion resistance and susceptibility to passivation films in battery environments directly affect fuel cell performance. Therefore, improving the corrosion resistance of stainless steel bipolar plates through surface modification is a crucial approach to achieving their commercial application.

[0004] Currently, the most effective method to simultaneously address the conductivity and corrosion resistance issues of stainless steel bipolar plates is surface coating modification. Modified stainless steel bipolar plates can improve corrosion resistance while maintaining good conductivity, thus ensuring overall battery performance and lifespan. Different surface coating modifications of stainless steel bipolar plates exhibit varying performance characteristics. To meet the performance requirements of stainless steel bipolar plate coatings, researchers both domestically and internationally have conducted extensive research on stainless steel surface modification. Based on the different materials used in the coating, it can be divided into two categories: metal-based coatings and carbon-based coatings.

[0005] The advantages of carbon and metal are combined, the carbon-based coating is prepared by deposition on the surface of the stainless steel bipolar plate, the corrosion resistance of the stainless steel bipolar plate can be significantly improved on the basis of retaining the high conductivity, mechanical properties and low permeability of the stainless steel bipolar plate, the preparation is simple, and the cost is low. Meanwhile, the carbon-based coating shows good hydrophobicity, which is beneficial to timely discharge of liquid water in the fuel cell. However, for the carbon-based film, it is difficult to simultaneously improve the compactness and reduce the internal stress, and it is a technical problem to produce the carbon-based coating with no defects, low internal stress and stable performance. SUMMARY

[0006] Therefore, it is necessary to provide a surface-modified fuel cell bipolar plate, a preparation method and a fuel cell which can improve compactness and reduce internal stress in view of the defects in the prior art.

[0007] To solve the above problems, the technical scheme is as follows:

[0008] One of the purposes of the present application is to provide a surface-modified fuel cell bipolar plate, comprising a bipolar plate and a C-Cr coating formed on the surface of the bipolar plate.

[0009] In some embodiments, the bipolar plate is a 316 stainless steel foil.

[0010] In some embodiments, the thickness of the C-Cr coating is 800-1000 nm.

[0011] The second purpose of the present application is to provide a preparation method of the surface-modified fuel cell bipolar plate, comprising the following steps:

[0012] Introducing working gas in a vacuum environment;

[0013] In the above working gas environment, the bipolar plate is placed on an anode frame, and a cathode frame is arranged in the parallel direction of the anode frame, a target material is arranged on the cathode frame, the target material and the bipolar plate are oppositely arranged, and the target material is a solid C-Cr twin target.

[0014] The cathode frame is connected to a high-voltage power supply, the high-voltage power supply excites target atoms in the target material into a particle state, the excited particles move in the direction of the bipolar plate and deposit on the bipolar plate.

[0015] In some embodiments, in the step of introducing working gas in a vacuum environment, the working gas is argon or a mixture of hydrogen and argon.

[0016] In some embodiments, in the step of introducing working gas in a vacuum environment, specifically comprising: vacuumizing in a coating chamber and introducing working gas, the body pressure is maintained at 1*10 -3Pa, the quality of the workpiece is guaranteed, and after the working gas is introduced, the working pressure range is 0.3-0.8 Pa, and different effects of the workpiece are achieved by adjusting different pressures.

[0017] In some embodiments, the bipolar plate is placed on the anode frame in the environment of the working gas, and the cathode frame is arranged in the parallel direction of the anode frame, the target material is arranged on the cathode frame, the target material and the bipolar plate are arranged oppositely, and the distance between the target material and the bipolar plate is 100-150 mm in the step of arranging the solid C: Cr twin target as the target material, so that the coating growth is within the range of glow discharge, and the coating growth is uniform.

[0018] In some embodiments, the bipolar plate is placed on the anode frame in the environment of the working gas, and the cathode frame is arranged in the parallel direction of the anode frame, the target material is arranged on the cathode frame, the target material and the bipolar plate are arranged oppositely, and the distance between the target material and the bipolar plate is 100-150 mm in the step of arranging the solid C: Cr twin target as the target material, so that the coating growth is within the range of glow discharge, and the coating growth is uniform. 2 .

[0019] In some embodiments, the cathode frame is connected to a high-voltage power supply, the high-voltage power supply excites target atoms in the target material into a particle state, the excited particles move along the direction of the bipolar plate and deposit on the bipolar plate in the step of exciting the target atoms in the target material into a particle state, and the power range of the high-voltage power supply is 5-9 kW, and the power density range is 4.17-7.5 W / cm 2 .

[0020] In some embodiments, the cathode frame is connected to a high-voltage power supply, the high-voltage power supply excites target atoms in the target material into a particle state, the excited particles move along the direction of the bipolar plate and deposit on the bipolar plate in the step of exciting the target atoms in the target material into a particle state, and the temperature range of the deposition is 20-300 DEG C, and the change of the coating adhesion can be realized by adjusting the temperature.

[0021] In some embodiments, the cathode frame is connected to a high-voltage power supply, the high-voltage power supply excites target atoms in the target material into a particle state, the excited particles move along the direction of the bipolar plate and deposit on the bipolar plate in the step of exciting the target atoms in the target material into a particle state, and the deposition time is 30-40 min, the deposition time corresponds to the film thickness, and the coating with different thicknesses can be obtained.

[0022] The third object of the present application is to provide a fuel cell comprising the surface-modified fuel cell bipolar plate.

[0023] The above technical scheme is adopted in the present application, and the beneficial effects are as follows:

[0024] The surface modified fuel cell bipolar plate and the preparation method thereof provided by the application are characterized by that: a uniform C-Cr coating layer is formed on the surface of the bipolar plate of the fuel cell by vacuum sputtering coating technology, and the C-Cr thin film can improve the interface conductivity and corrosion resistance of the coating layer, and at the same time, the thin film has low residual stress and good stability, and the risk of local corrosion caused by coating defects is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiments of the application or the prior art description will be briefly introduced. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The structure schematic diagram of the surface modified fuel cell bipolar plate provided by the embodiments of the application.

[0027] Figure 2 The step flow chart of the preparation method of the surface modified fuel cell bipolar plate provided by the embodiments of the application. DETAILED DESCRIPTION

[0028] The embodiments of the application will be described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0029] In the description of the application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0030] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0031] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments.

[0032] Please refer to Figure 1 A structural schematic diagram of a surface modified fuel cell bipolar plate provided by an embodiment of the present application comprises a bipolar plate 110 and a C-Cr coating layer 120 formed on the surface of the bipolar plate 110.

[0033] In some embodiments, the bipolar plate 110 is a 316 stainless steel foil.

[0034] In some embodiments, the thickness of the C-Cr coating layer 120 is 800-1000 nm, so that the required contact resistance and corrosion current can be obtained.

[0035] The surface modified fuel cell bipolar plate provided by the above embodiments of the present application uses Cr-doped C, which overcomes the defects that the adhesion between stainless steel and C film is poor and the deposition of carbon is difficult, and compared with ordinary carbon film, the C-Cr film can improve the interface conductivity and corrosion resistance of the coating layer, at the same time, the film obtains low residual stress and good stability, and reduces the risk of local corrosion caused by coating defects.

[0036] The surface modified fuel cell bipolar plate provided by the above embodiments of the present application uses a bipolar plate of a fuel cell as a substrate, and uses a vacuum sputtering coating technology to form a uniform C-Cr coating layer on the surface of the substrate. By using Cr-doped C, the defects that the adhesion between stainless steel and C film is poor and the deposition of carbon is difficult are overcome, and compared with ordinary carbon film, the C-Cr film can improve the interface conductivity and corrosion resistance of the coating layer, at the same time, the film obtains low residual stress and good stability, and reduces the risk of local corrosion caused by coating defects.

[0037] Please refer to Figure 2 The step flow chart of the preparation method of the surface modified fuel cell bipolar plate provided by the embodiments of the present application comprises the following steps S110 to S130, and the implementation mode of each step will be described in detail below.

[0038] Step S110: introduce working gas in a vacuum environment.

[0039] In some embodiments, the working gas is argon or a mixture of hydrogen and argon.

[0040] Specifically, in the step of introducing working gas in a vacuum environment, specifically comprising: vacuumizing in the coating chamber and introducing working gas, the pressure is kept at 1*10 -3Pa, the pressure is kept at 0.3-0.8 Pa after the working gas is introduced, and different pressures are adjusted to achieve different effects of the product.

[0041] Step S120: In the environment of the working gas, the bipolar plate is placed on an anode frame, and a cathode frame is arranged in the parallel direction of the anode frame, a target material is arranged on the cathode frame, the target material and the bipolar plate are oppositely arranged, and the target material is a solid C: Cr twin target.

[0042] In some embodiments, the distance between the target material and the bipolar plate is 100-150 mm, which ensures that the coating grows within the range of glow discharge and grows uniformly.

[0043] In some embodiments, the size of the target material is 600 mm*100 mm*5 mm, and the surface area of the twin target material is 1200 cm 2 .

[0044] In some embodiments, the device used is a medium-frequency magnetron sputtering device, the sputtering target material is a C-Cr (20-80% at.) twin target, the target material utilization rate can be up to more than 70%, the target material has a longer service life and a faster sputtering rate.

[0045] Step S130: The cathode frame is connected to a high-voltage power supply, the target atoms in the target material are excited into a particle state by the high-voltage power supply, the excited particles move in the direction of the bipolar plate and are deposited on the bipolar plate.

[0046] In some embodiments, the power range of the high-voltage power supply is 5-9 kW, and the power density range is 4.17-7.5 w / cm 2 .

[0047] In some embodiments, the deposition temperature is 20-300℃, and the change of the adhesion of the coating can be realized by adjusting the temperature.

[0048] In some embodiments, the deposition time is 30-40 min, the deposition time corresponds to the film thickness, and different thicknesses of the coating can be obtained.

[0049] The above embodiments of the present application adopt the principle of medium-frequency sputtering to form a C-Cr coating on the surface of the bipolar plate. Due to the use of a twin target sputtering system, the target material has a high utilization rate, a longer service life, and a faster sputtering rate, and the poisoning phenomenon of the target material can be eliminated. Moreover, medium-frequency magnetron sputtering can obtain a smooth and dense film layer with high hardness, the film thickness can be linearly grown, and multi-arc sputtering applies a small voltage and a large current to the target material to ionize the material (positively charged particles), so that the particles hit the substrate (negative) at a high speed and are deposited. The target material in the particle state reacts with the working gas, the crystal grains are nucleated and grown, and a dense C: Cr thin film is formed.

[0050] The surface modified fuel cell bipolar plate provided by the above embodiments of the present application uses a vacuum sputtering coating technology to form a uniform C-Cr coating layer on the surface of the bipolar plate of the fuel cell, and by using Cr-doped C, the poor adhesion between stainless steel and the C film and the difficulty in carbon deposition are overcome. Compared with ordinary carbon films, the C-Cr film can improve the interface conductivity and corrosion resistance of the coating layer, while making the film obtain low residual stress and good stability, and reducing the risk of local corrosion caused by coating defects.

[0051] The above technical solutions of the present application will be described in detail below in combination with specific embodiments.

[0052] Embodiment 1

[0053] 1. Clean the surface of the 316 stainless steel bipolar plate with a cleaning machine for a total of 5 times, 1h20min each time, and change the direction of the substrate between each cleaning to remove the dust on the surface. Then bake the stainless steel bipolar plate in an oven at 90°C for 10 minutes to remove moisture;

[0054] 2. Put the 316 stainless steel bipolar plate into an ultrasonic cleaning machine and perform ultrasonic pre-cleaning with acetone. After completion, dry the surface with nitrogen. Then place the bipolar plate on the substrate holder in the vacuum chamber, and then perform Ar plasma etching for 10 minutes to remove surface oxide contamination.

[0055] 3. Start the mechanical pump, and when the pressure is less than 1kPa, start the Roots pump, and when the pressure is less than 17Pa, start the molecular pump to evacuate the coating chamber. Place the sample on the sample holder, and after the pressure reaches below 10-3Pa, transfer the sample holder to the heating chamber and keep it in the chamber for 30min. (The sample does not need to be heated under room temperature conditions)

[0056] 4. Turn on the high-voltage power supply and adjust the power to 5kW. A large amount of Ar is introduced for a short time for 10min of pre-sputtering, and pipeline cleaning is performed at the same time. After the target surface is ignited, the Ar flow rate can be reduced to the required size for work.

[0057] 5. When the sputtering chamber pressure is maintained at 0.3-0.8Pa, transfer the sample holder to the sputtering chamber, adjust the sample movement rate, and start the control program to prepare a C:Cr film on the surface of the sample. A loose layer is prepared on the surface of the sample at a sputtering power of 5kW and an Ar flow rate of 500sccm to improve surface adhesion. A dense layer is then prepared at a sputtering power of 9kW and an Ar flow rate of 200sccm to obtain a dense C-Cr coating layer.

[0058] It should be noted that in the fourth step, the surface resistance can be adjusted by introducing different flow rates of H2 to obtain a coating with the desired electrical conductivity.

[0059] 6. The sample holder is transported into the heating chamber, and after the sample is cooled to below 120℃, the sample is transported into the sample chamber and out of the sample.

[0060] 7. The sample is characterized using a step meter, an X-ray fluorescence spectrometer, a scanning electron microscope and other instruments to obtain the thickness of the surface film of the sample, surface components, surface morphology and other parameters, so as to determine whether the obtained film meets the required standard.

[0061] 8. The sample is loaded into a labeled vacuum bag, vacuumized and sealed to protect the surface of the sample.

[0062] The surface modified fuel cell bipolar plate and the preparation method thereof provided by the above embodiments take the bipolar plate of the fuel cell as a substrate, form a uniform C-Cr coating layer on the surface of the substrate by using a vacuum sputtering plating technology, and overcome the defects that the adhesion between the stainless steel and the C film is poor and the deposition of carbon is difficult by using Cr-doped C. Compared with the ordinary carbon film, the C-Cr film can improve the interface conductivity and corrosion resistance of the coating layer, at the same time, the film obtains low residual stress and good stability, and reduces the risk of local corrosion caused by defects in the coating layer.

[0063] It can be understood that any combination of the technical features of the above embodiments can be made, and in order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0064] The above is only a preferred embodiment of the present application, and only the technical principles of the present application are specifically described, and these descriptions are only for explaining the principles of the present application, and cannot be explained as a limitation on the protection scope of the present application in any way. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principles of the present application, and other specific embodiments of the present application which can be easily thought by those skilled in the art without creative labor, should be included in the protection scope of the present application.

Claims

1. A surface-modified fuel cell bipolar plate, characterized in that, Includes a bipolar plate and a C-Cr coating formed on the surface of the bipolar plate; The bipolar plate is made of 316 stainless steel foil; The thickness of the C-Cr coating is 800-1000 nm; The method for preparing the surface-modified fuel cell bipolar plate includes the following steps: The working gas is introduced into a vacuum environment; In the above-mentioned working gas environment, the bipolar plate is placed on the anode frame, and a cathode frame is arranged in the parallel direction of the anode frame. A target material is arranged on the cathode frame, and the target material and the bipolar plate are arranged opposite to each other. The target material is a solid C:Cr twin target. The cathode frame is connected to a high-voltage power supply, which excites the target atoms in the target material into a particle state. The excited particles move along the bipolar plate and are deposited on the bipolar plate. The step of introducing the working gas into a vacuum environment specifically includes: evacuating the coating chamber and introducing the working gas, maintaining the body pressure at 1*10⁻⁶. -3 Below Pa, the working pressure range after introducing working gas is 0.3-0.8 Pa; When the sputtering chamber pressure is maintained at 0.3-0.8 Pa, the sample holder is transferred into the sputtering chamber, the sample movement speed is adjusted, the control program is started, and a C:Cr thin film is prepared on the sample surface. A loose layer is prepared on the sample surface with sputtering power of 5 kW and Ar flow rate of 500 sccm to improve surface adhesion. Then, a dense layer is prepared with sputtering power of 9 kW and Ar flow rate of 200 sccm to obtain a dense C-Cr coating. The distance between the target and the bipolar plate is 100-150 mm; The target material has dimensions of 600mm*100mm*5mm, and the twin target material has a surface area of ​​1200cm². 2 ; Power density ranges from 4.17 to 7.5 W / cm². 2 ; The deposition temperature range is 20-300℃.

2. A method for preparing a surface-modified fuel cell bipolar plate as described in claim 1, characterized in that, Includes the following steps: The working gas is introduced into a vacuum environment; In the above-mentioned working gas environment, the bipolar plate is placed on the anode frame, and a cathode frame is arranged in the parallel direction of the anode frame. A target material is arranged on the cathode frame, and the target material and the bipolar plate are arranged opposite to each other. The target material is a solid C:Cr twin target. The cathode frame is connected to a high-voltage power supply, which excites the target atoms in the target material into a particle state. The excited particles move along the bipolar plate and are deposited on the bipolar plate. The step of introducing the working gas into a vacuum environment specifically includes: evacuating the coating chamber and introducing the working gas, maintaining the body pressure at 1*10⁻⁶. -3 Below Pa, the working pressure range after introducing working gas is 0.3-0.8 Pa; When the sputtering chamber pressure is maintained at 0.3-0.8 Pa, the sample holder is transferred into the sputtering chamber, the sample movement speed is adjusted, the control program is started, and a C:Cr thin film is prepared on the sample surface. A loose layer is prepared on the sample surface with sputtering power of 5 kW and Ar flow rate of 500 sccm to improve surface adhesion. Then, a dense layer is prepared with sputtering power of 9 kW and Ar flow rate of 200 sccm to obtain a dense C-Cr coating. The distance between the target and the bipolar plate is 100-150 mm; The target material has dimensions of 600mm*100mm*5mm, and the twin target material has a surface area of ​​1200cm². 2 ; Power density ranges from 4.17 to 7.5 W / cm². 2 ; The deposition temperature range is 20-300℃.

3. The method for preparing the surface-modified fuel cell bipolar plate as described in claim 2, characterized in that, In the step of introducing a working gas into a vacuum environment, the working gas is argon or a mixture of hydrogen and argon.

4. The method for preparing the surface-modified fuel cell bipolar plate as described in claim 2, characterized in that, In the step of connecting the cathode frame to a high-voltage power supply, where the high-voltage power supply excites the target atoms in the target material into a particle state, and the excited particles move along the direction of the bipolar plate and are deposited on the bipolar plate, the deposition time is 30-40 minutes.

5. A fuel cell, characterized in that, Includes the surface-modified fuel cell bipolar plate as described in any one of claims 2 to 4.

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