Preparation method of coating, coating and fuel cell metal bipolar plate

Abstract

The invention provides a preparation method of a coating, the coating and a fuel cell metal bipolar plate, and the preparation method of the coating comprises the following steps: step S20, feeding a substrate into a cavity of a multi-target magnetron sputtering instrument, and preparing a Ti bottom layer on the substrate in a sputtering deposition mode; s30, a transition layer is prepared on the side, away from the base body, of the Ti bottom layer in a sputtering deposition mode, and the transition layer is a TiON layer; and S40, a top layer is prepared on the side, away from the Ti bottom layer, of the transition layer in a sputtering deposition mode, and the top layer is a nitrogen-doped Magneli phase titanium oxide layer. By applying the technical scheme provided by the invention, the problem of poor corrosion resistance of the coating of the metal bipolar plate of the fuel cell in the prior art can be effectively solved.

Description

Technical Field

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

[0002] Bipolar plates are one of the core components of proton exchange membrane fuel cells, serving as a transport of reactant gases, support for the stack, and drainage. Bipolar plates made of metal materials have excellent machining properties and are low in price, making them the key to replacing traditional graphite bipolar plates. However, metal bipolar plates are not corrosion-resistant under the operating conditions of fuel cells, and the surface contact resistance of the coating increases due to the passivation of the metal. Metal ions that overflow from corrosion cause irreversible damage to the membrane electrode of the stack. In order to solve the corrosion and passivation problems of metal bipolar plates and meet the application of metal bipolar plates in fuel cells, a coating needs to be prepared on its surface to meet the requirements of corrosion resistance and conductivity.

[0003] At present, a series of modified coatings have been applied in fuel cell bipolar plates. For example, amorphous carbon, various metal nitrides and carbides have been widely studied and applied, showing excellent corrosion resistance and conductivity, making them potential bipolar plate coating materials. In addition, when proton exchange membrane fuel cells are used in passenger cars, conditions such as starting and idling may cause potentials as high as +1.6V (vs. SHE), and changes in vehicle status cause the PEMFC stack potential to fluctuate frequently between 1.5-0.9V (vs. SHE). Precious metal gold has excellent performance, but its high cost hinders its application in bipolar plates. Carbon coatings, metal nitrides and carbides are easily dissolved or detached under high potential corrosion environments for a long time due to the limitations of the properties of the coatings themselves.

[0004] Selecting coating materials that do not dissolve or fall off under long-term high-potential corrosion is a necessary condition for the development of fuel cell metal bipolar plate coating materials. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a coating, a coating and a fuel cell metal bipolar plate, so as to solve the problem of poor corrosion resistance of the coating of the fuel cell metal bipolar plate in the prior art.

[0006] In order to achieve the above-mentioned purpose, one aspect of the present application provides a method for preparing a coating, comprising: step S20, sending a substrate into a cavity of a multi-target magnetron sputtering instrument, and preparing a Ti bottom layer on the substrate by sputtering deposition; step S30, preparing a transition layer by sputtering deposition on a side of the Ti bottom layer away from the substrate, the transition layer being a TiON layer; step S40, preparing a top layer by sputtering deposition on a side of the transition layer away from the Ti bottom layer, the top layer being a nitrogen-doped Magnéli phase titanium oxide layer.

[0007] Further, step S40 includes: step S41, controlling the nitrogen flow rate between 20-40sccm, controlling the oxygen flow rate between 20-50sccm, controlling the Ti target current between 5-10A, and controlling the reaction temperature between 500-750°C within a first preset time; step S42, depositing on the TiON layer for 60-150min; step S43, after sputtering deposition, annealing at a temperature range of 550°C-750°C for 1-2.5h to form a nitrogen-doped Magnéli phase titanium oxide layer.

[0008] Furthermore, the first preset time is 300s.

[0009] Further, step S30 includes: step S31, controlling the nitrogen flow rate to 10-30 sccm, controlling the oxygen flow rate to 20-40 sccm, and controlling the Ti target current to 5-10 A within a second preset time; step S32, depositing on the Ti bottom layer for 30-60 minutes.

[0010] Furthermore, the second preset time is 300s.

[0011] Further, step S20 includes: step S21, sending the substrate into the cavity of a multi-target magnetron sputtering instrument; step S22, controlling the Ar gas flow rate to 200 sccm and the Ti target current to be between 5-10 A within a third preset time; step S23, depositing on the substrate for 30-60 minutes.

[0012] Furthermore, the third preset time is 600s.

[0013] Furthermore, the coating preparation method further includes: step S10, cleaning the substrate.

[0014] Further, step S10 includes: step S11, placing the substrate into a vacuum chamber, evacuating to 6×10-4Pa, introducing Ar gas, the Ar gas flow rate is 200sccm, and maintaining the vacuum degree at 2-4Pa; step S12, bombarding the substrate with ions for 20-30min with a medium frequency power supply; step S20 includes: step S21, sending the substrate into a multi-target magnetron sputtering chamber; step S22, controlling the Ar gas flow rate to remain unchanged within 600s, and controlling the Ti target current to be between 5-10A; step S23, depositing on the substrate for 30-60min; step S30 includes: step S31, controlling the Ti target current to remain unchanged within 300s, and controlling The nitrogen flow rate is 10-30sccm, and the oxygen flow rate is controlled between 20-40sccm; step S32, depositing on the Ti bottom layer for 30-60min; step S40 includes: step S41, controlling the Ti target current to remain unchanged within 300s, controlling the nitrogen flow rate to be between 20-40sccm, controlling the oxygen flow rate to be between 20-50sccm, and controlling the reaction temperature to be between 500-750℃; step S42, depositing on the TiON layer for 60-150min; step S43, after sputtering deposition, annealing at a temperature range of 550℃-750℃ for 1-2.5h to form a nitrogen-doped Magnéli phase titanium oxide layer.

[0015] Another aspect of the present application provides a coating obtained by the above-mentioned coating preparation method, the coating comprising: a Ti bottom layer; a transition layer, located on one side of the Ti bottom layer, the transition layer being a TiON layer; a top layer, located on a side of the transition layer away from the Ti bottom layer, the top layer being a nitrogen-doped Magnéli phase titanium oxide layer.

[0016] Further, the thickness of the top layer is within 600 nm.

[0017] Another aspect of the present application provides a fuel cell metal bipolar plate, comprising: a bipolar plate body; a coating, disposed on the surface of the bipolar plate body, the coating being the coating prepared as described above.

[0018] The coating preparation method of the present application successfully prepares a coating having a Ti bottom layer, a TiON transition layer, and a nitrogen-doped Magnéli phase titanium oxide top layer by precisely controlling the conditions of sputtering deposition. This coating structure not only enhances the bonding force between the substrate and the coating, but also improves the corrosion resistance, electrical conductivity, and mechanical strength of the coating, thereby significantly improving the performance and service life of the fuel cell metal bipolar plate. In practical applications, the preparation method of this coating is simple, low-cost, and has low requirements for production equipment, and is suitable for large-scale production.

[0019] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0021] Figure 1 A schematic structural diagram of a coating according to an embodiment of the present invention disposed on a substrate is shown.

[0022] The above drawings include the following reference numerals:

[0023] 1. Matrix; 10. Ti bottom layer; 20. Transition layer; 30. Top layer. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] like Figure 1 As shown, in the present application, the coating preparation method includes: step S20: feeding the substrate 1 into the cavity of the multi-target magnetron sputtering instrument, and preparing the Ti bottom layer 10 on the substrate 1 by sputtering deposition; step S30: preparing the transition layer 20 by sputtering deposition on the side of the Ti bottom layer 10 away from the substrate 1, and the transition layer 20 is a TiON layer; step S40: preparing the top layer 30 by sputtering deposition on the side of the transition layer 20 away from the Ti bottom layer 10, and the top layer 30 is a nitrogen-doped Magnéli phase titanium oxide layer. On the one hand, the coating prepared by magnetron sputtering grows in columnar crystals, which often produces deeper grain boundaries. The transition layer TiON coating is used as a buffer layer to further prevent corrosion, so that it can maintain a stable state in a long-term high-potential corrosion environment; on the other hand, the introduction of the nitrogen-doped Magnéli phase titanium oxide layer significantly enhances the corrosion resistance of the coating, which is suitable for the manufacture of metal bipolar plates for fuel cells, especially in highly corrosive environments, and can effectively protect the bipolar plates and extend their service life.

[0029] It should be noted that the conductive mechanism of the Magnéli phase titanium oxide coating is the formation of crystal shear planes in the TiO2 lattice. The oxygen-deficient state of the crystal shear planes leads to an increase in the overlap of electron clouds between titanium atoms, thereby enhancing the mobility of electrons and further improving the conductivity, thereby providing a channel for electron transition, making this structure have excellent conductivity. At the same time, the crystal shear planes are surrounded by the TiO2 lattice and will not be easily corroded by acidic ions. Therefore, the coating has good corrosion resistance.

[0030] However, in the prior art, the Magnéli phase titanium oxide has the problems of complex preparation, high cost, and high equipment requirements when prepared on a large scale. In order to further solve the above problems, in the present application, step S40 includes: step S41: controlling the nitrogen flow rate between 20-40sccm, controlling the oxygen flow rate between 20-50sccm, controlling the Ti target current between 5-10A, and controlling the reaction temperature between 500-750°C within the first preset time; step S42: depositing on the TiON layer for 60-150min; step S43: after sputtering deposition, annealing treatment at a temperature range of 550°C-750°C for 1-2.5h to form a nitrogen-doped Magnéli phase titanium oxide layer. Specifically, the inventors propose that the formation of crystal shear planes is the key to large-scale preparation of Magnéli phase titanium oxide coatings. The technical solution of the present application gives Ti more energy by precisely controlling the O2 flow rate and the Ti target current and by high-temperature deposition; when nitrogen doping is present, highly dispersed nitrogen atoms replace the original high-energy Ti atoms or ions. This atomic replacement in the lattice introduces additional charges, allowing the Ti ions to balance the charge imbalance around the nitrogen atoms through a charge compensation mechanism, ultimately forming oxygen vacancies and inducing the formation of crystal shear planes. At the same time, later annealing makes this compensation mechanism more balanced, allowing its structure to reach equilibrium, ultimately forming pure or multi-phase Magnéli phase titanium oxide. The above-mentioned preparation method makes the preparation of Magnéli phase titanium oxide simple, low-cost, and low-equipment requirements when it is prepared on a large scale.

[0031] Furthermore, the first preset time is 300s. Setting the first preset time to 300s can ensure the deposition quality of the TiON layer, while controlling the deposition time, avoiding increased energy consumption and decreased production efficiency caused by too long deposition time, which is suitable for large-scale production environments, can effectively improve production efficiency and reduce production costs.

[0032] Further, step S30 includes: step S31, linearly increasing the nitrogen flow rate to 10-30sccm, linearly increasing the oxygen flow rate to 20-40sccm within the second preset time, and controlling the Ti target current to be between 5-10A; step S32, depositing on the Ti bottom layer 10 for 30-60min. By controlling the nitrogen and oxygen flow rates, a stable TiON transition layer can be formed on the Ti bottom layer, and the TiON transition layer serves as a buffer layer to further prevent corrosion, so that it can maintain a stable state in a long-term high-potential corrosion environment.

[0033] Furthermore, the second preset time is 300s. Setting the second preset time to 300s can ensure that the deposition process of the TiON transition layer is completed within a controllable time, avoid performance degradation caused by the transition layer being too thick or too thin, is suitable for precision manufacturing processes, and can improve the accuracy and consistency of coating preparation.

[0034] Further, step S20 includes: step S21, feeding the substrate 1 into the cavity of the multi-target magnetron sputtering instrument; step S22, controlling the Ar gas flow rate to 200 sccm within the third preset time, and controlling the Ti target current to increase linearly to between 5 and 10 A; step S23, depositing on the substrate 1 for 30 to 60 minutes. By controlling the Ar gas flow rate and the Ti target current, a dense Ti bottom layer can be formed on the substrate, providing a good foundation for subsequent coating preparation, which is suitable for coating preparation requiring high bonding strength, especially in the surface treatment of bipolar plates, which can significantly improve the bonding strength between the coating and the substrate and reduce the risk of coating shedding.

[0035] Furthermore, the third preset time is 600s. Setting the third preset time to 600s can ensure that the deposition process of the Ti bottom layer is completed within the optimal time, forming a Ti bottom layer that is neither too thick nor too thin, which is suitable for coating preparation that pursues optimal performance, especially in the manufacture of fuel cell bipolar plates that have strict requirements on coating thickness, and can provide precise thickness control to ensure optimization of coating performance.

[0036] Furthermore, the method for preparing the coating also includes: step S10, cleaning the substrate 1. Cleaning the substrate is a key step before preparing the coating, which can remove impurities and oxides on the surface of the substrate and improve the bonding strength between the coating and the substrate. It is suitable for various coating preparation processes that require high surface cleanliness, especially in the manufacture of fuel cell metal bipolar plates, and can significantly improve the adhesion and corrosion resistance of the coating.

[0037] Further, step S10 includes: step S11, placing the substrate 1 into a vacuum chamber, evacuating to 6×10-4Pa, introducing Ar gas, the Ar gas flow rate is 200sccm, and maintaining the vacuum degree at 2-4Pa; step S12, using a medium frequency power supply to perform ion bombardment on the substrate 1 for 20-30min. Through ion bombardment, the substrate surface can be further cleaned, the activity of the substrate can be improved, and the atomic diffusion and bonding in the subsequent deposition process can be promoted. It is suitable for the preparation of coatings that require high surface activity, especially in the manufacture of metal bipolar plates for fuel cells, which can significantly improve the bonding strength and corrosion resistance of the coating, and provide a guarantee for the efficient operation of the fuel cell.

[0038] Specifically, in the present application, the cleaning steps are as follows: first, the polished substrate is sent into an ultrasonic cleaning machine, and cleaned in anhydrous alcohol and acetone in turn using 15kHz ultrasonic waves for 20-30 minutes; then ion cleaning is performed; the above-mentioned ion cleaning, namely: the substrate is placed in a vacuum chamber, evacuated to 6×10-4Pa, and then Ar gas is introduced, the vacuum degree is maintained at 2-4Pa, and the substrate is bombarded with ions for 30 minutes using a medium frequency power supply.

[0039] The specific coating preparation method of the present application is described in detail below:

[0040] Step S11: Place the substrate 1 into a vacuum chamber, evacuate to 6×10-4Pa, introduce Ar gas, the Ar gas flow rate is 200sccm, and maintain the vacuum degree at 2-4Pa;

[0041] Step S12: using a medium frequency power source to bombard the substrate 1 with ions for 20-30 minutes;

[0042] Step S21: sending the substrate 1 into the cavity of a multi-target magnetron sputtering apparatus;

[0043] Step S22: controlling the Ar gas flow rate to remain unchanged within 600 seconds, and controlling the Ti target current to increase linearly to between 5 and 10 A;

[0044] Step S23: Depositing on substrate 1 for 30-60 minutes;

[0045] Step S31: within 300 s, the Ti target current is controlled to remain unchanged, the nitrogen flow rate is linearly increased between 10-30 sccm, and the oxygen flow rate is linearly increased between 20-40 sccm;

[0046] Step S32: depositing on the Ti bottom layer 10 for 30-60 minutes;

[0047] Step S41: controlling the Ti target current to remain unchanged within 300 seconds, controlling the nitrogen flow rate to be between 20-40 sccm, controlling the oxygen flow rate to be between 20-50 sccm, and controlling the reaction temperature to be between 500-750° C.;

[0048] Step S42: Depositing on the TiON layer for 60-150 min;

[0049] Step S43: After sputtering deposition, annealing treatment is performed at a temperature range of 550° C. to 750° C. for 1 to 2.5 hours to form a nitrogen-doped Magnéli phase titanium oxide layer.

[0050] In this application, the specific implementation details of the coating preparation method are elaborated in detail to prove the feasibility and superiority of the technical solution. Below, this coating preparation method will be deeply analyzed and expanded according to the above parameter range to provide more examples and show the changes in coating structure and performance under different conditions.

[0051] Example 1

[0052] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the multi-target magnetron sputtering chamber, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 10A, and the deposition time is 30 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 20 sccm, the oxygen flow rate is linearly increased to 30 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate remains unchanged, the oxygen flow rate is 35 sccm, the Ti target current remains unchanged, the reaction temperature is set at 750°C, and the deposition time is 120 minutes. After the sputtering deposition is completed, it is kept at 750°C for 100 minutes and annealed for 1-2.5 hours.

[0053] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 4.37 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 6.28mΩ·cm 2 , the constant potential polarization curve remains stable.

[0054] Example 2

[0055] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the multi-target magnetron sputtering chamber, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 8A, and the deposition time is 30 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 30 sccm, the oxygen flow rate is linearly increased to 20 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate remains unchanged, the oxygen flow rate is 45 sccm, the Ti target current remains unchanged, the reaction temperature is set at 700°C, and the deposition time is 120 minutes. After the sputtering deposition is completed, it is kept at 700°C for 90 minutes and annealed for 1-2.5 hours.

[0056] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 3.52 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 7.98mΩ·cm 2 , the constant potential polarization curve remains stable.

[0057] Example 3

[0058] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 10A, and the deposition time is 40 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 20 sccm, the oxygen flow rate is linearly increased to 20 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen and oxygen flow rates remain unchanged, the Ti target current remains unchanged, the reaction temperature is set at 750°C, and the deposition time is 120 minutes. After the sputtering deposition is completed, it is kept at 750°C for 100 minutes and annealed for 1-2.5 hours.

[0059] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 4.25 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 6.84mΩ·cm 2 , the constant potential polarization curve remains stable.

[0060] Example 4

[0061] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 5A, and the deposition time is 50 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 30 sccm, the oxygen flow rate is linearly increased to 40 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate is linearly increased to 40 sccm, the oxygen flow rate is linearly increased to 50 sccm, the Ti target current remains unchanged, the reaction temperature is set at 500°C, and the deposition time is 130 minutes. After the sputtering deposition is completed, it is kept at 500°C for 110 minutes and annealed for 1-2.5 hours.

[0062] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 3.45 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 9.48mΩ·cm 2 , the constant potential polarization curve remains stable.

[0063] Example 5

[0064] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the multi-target magnetron sputtering chamber, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200sccm, the Ti target current is linearly increased to 7A, and the deposition time is 60min. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 20sccm, the oxygen flow rate is linearly increased to 30sccm, the Ti target current remains unchanged, and the deposition time is 60min. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, with a nitrogen flow rate of 30sccm, an oxygen flow rate of 40sccm, a Ti target current remaining unchanged, a reaction temperature set at 600℃, and a deposition time of 140min. After the sputtering deposition is completed, it is kept at 600℃ for 100min and annealed for 1-2.5h.

[0065] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 2.89 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 8.56mΩ·cm 2 , the constant potential polarization curve remains stable.

[0066] It can be seen from the above examples that the coating prepared by the coating preparation method of the present invention has a constant potential polarization under high potential and maintains a stable state, and the surface contact resistance after corrosion for 10 hours is less than 10mΩ·cm 2 .

[0067] Comparative Example 1

[0068] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the multi-target magnetron sputtering chamber, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 10A, and the deposition time is 60min. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 20sccm, the oxygen flow rate is linearly increased to 10sccm, the Ti target current remains unchanged, and the deposition time is 60min. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate and oxygen flow rate remain unchanged, the Ti target current remains unchanged, the reaction temperature is set at 750℃, and the deposition time is 140min. After the sputtering deposition is completed, it is kept at 750℃ for 100min and annealed for 1-2.5h.

[0069] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 4.83 mΩ·cm.2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 22.63mΩ·cm 2 .

[0070] Comparative Example 2

[0071] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 7A, and the deposition time is 60 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 10 sccm, the oxygen flow rate is linearly increased to 30 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate remains unchanged, the oxygen flow rate is increased to 40 sccm, the Ti target current remains unchanged, the reaction temperature is set at 600°C, and the deposition time is 140 minutes. After the sputtering deposition is completed, it is kept at 600°C for 100 minutes and annealed for 1-2.5 hours.

[0072] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 5.83 mΩ·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 26.28mΩ·cm 2 .

[0073] Comparative Example 3

[0074] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 4A, and the deposition time is 60 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 10 sccm, the oxygen flow rate is linearly increased to 30 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate is increased to 30 sccm, the oxygen flow rate is increased to 40 sccm, the Ti target current remains unchanged, the reaction temperature is set at 600°C, and the deposition time is 140 minutes. After the sputtering deposition is completed, it is kept at 600°C for 100 minutes and annealed for 1-2.5 hours.

[0075] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 22.45 mΩ·cm.2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 56.25mΩ·cm 2 .

[0076] Comparative Example 4

[0077] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 7A, and the deposition time is 60 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 10 sccm, the oxygen flow rate is linearly increased to 30 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate is increased to 30 sccm, the oxygen flow rate is increased to 40 sccm, the Ti target current remains unchanged, the reaction temperature is set at 450°C, and the deposition time is 140 minutes. After the sputtering deposition is completed, it is kept at 450°C for 100 minutes and annealed for 1-2.5 hours.

[0078] The surface contact resistance of the nitrogen-doped Magnéli phase titanium oxide coating before corrosion was 159.03Ω·cm. 2 After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 267.88mΩ·cm 2 .

[0079] Comparative Example 5

[0080] In this embodiment, the coating preparation method follows the following steps: First, the substrate is fed into the chamber of a multi-target magnetron sputtering instrument, and the preparation conditions of the Ti bottom layer are as follows: the Ar gas flow rate is controlled at 200 sccm, the Ti target current is linearly increased to 7A, and the deposition time is 60 minutes. Next, the preparation conditions of the transition layer TiON are as follows: within 5 minutes, the nitrogen flow rate is linearly increased to 10 sccm, the oxygen flow rate is linearly increased to 30 sccm, the Ti target current remains unchanged, and the deposition time is 60 minutes. Finally, the preparation of the nitrogen-doped Magnéli phase titanium oxide top layer requires more detailed temperature and gas control, the nitrogen flow rate is increased to 30 sccm, the oxygen flow rate is increased to 40 sccm, the Ti target current remains unchanged, the reaction temperature is set at 600°C, and the deposition time is 140 minutes. After the sputtering deposition is completed, no annealing treatment is performed.

[0081] After testing, the surface contact resistance of the nitrogen-doped titanium oxide coating before corrosion was 139.05 mΩ·cm 2After 10h of constant potential polarization at +1.6V (vs. SHE), the surface contact resistance increased to 247.81mΩ·cm 2 .

[0082] In addition, the present application also provides a coating, which is obtained by the above-mentioned preparation method. The embodiment of the coating according to the present application includes: a Ti bottom layer 10, a transition layer 20 and a top layer 30. Among them, the transition layer 20 is located on one side of the Ti bottom layer 10, and the transition layer 20 is a TiON layer; the top layer 30 is located on the side of the transition layer 20 away from the Ti bottom layer 10, and the top layer 30 is a nitrogen-doped Magnéli phase titanium oxide layer. The above-mentioned coating has the advantages of good conductivity and good corrosion resistance.

[0083] Furthermore, the thickness of the top layer 30 is within 600 nm. Among them, controlling the thickness of the top layer within 600 nm can ensure that the coating has good conductivity and avoid high resistance caused by an overly thick coating. It is suitable for the manufacture of fuel cell bipolar plates that require high conductivity, especially in fuel cell applications that pursue high power output. It can effectively reduce the internal resistance of the battery and increase the power density of the battery. At the same time, it shows excellent stability and reliability in harsh operating environments, providing a solid foundation for the commercial application of fuel cell technology.

[0084] The present application also provides a fuel cell metal bipolar plate. According to an embodiment of the fuel cell metal bipolar plate of the present application, it includes: a bipolar plate body and a coating disposed on the bipolar plate body. This bipolar plate not only improves corrosion resistance and electrical conductivity, but also enhances mechanical strength by adopting a layered coating, and is suitable for the manufacture of high-performance fuel cells, especially under extreme operating conditions, such as high temperature, high humidity and highly corrosive environments. It can effectively protect the bipolar plate, extend its service life, and reduce maintenance costs, providing reliable technical guarantees for the wide application of fuel cells in automobiles, power stations and other fields.

[0085] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0086] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0087] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a coating, characterized in that: include: Step S20: placing the substrate (1) into a multi-target magnetron sputtering chamber, and preparing a Ti bottom layer (10) on the substrate (1) by sputtering deposition; Step S30: preparing a transition layer (20) on a side of the Ti bottom layer (10) away from the substrate (1) by sputtering deposition, wherein the transition layer (20) is a TiON layer; Step S40: preparing a top layer (30) by sputtering deposition on a side of the transition layer (20) away from the Ti bottom layer (10), wherein the top layer (30) is a nitrogen-doped Magnéli phase titanium oxide layer.

2. The method for preparing the coating according to claim 1, characterized in that: The step S40 comprises: Step S41: controlling the nitrogen flow rate to be between 20-40 sccm, the oxygen flow rate to be between 20-50 sccm, the Ti target current to be between 5-10 A, and the reaction temperature to be between 500-750° C. within the first preset time; Step S42: depositing on the TiON layer for 60-150 min; Step S43: After the sputtering deposition, annealing is performed at a temperature range of 550° C. to 750° C. for 1 to 2.5 hours to form the nitrogen-doped Magnéli phase titanium oxide layer.

3. The method for preparing the coating according to claim 2, characterized in that: The first preset time is 300s.

4. The method for preparing the coating according to claim 1, characterized in that: The step S30 comprises: Step S31: linearly increase the nitrogen flow rate between 10-30 sccm, linearly increase the oxygen flow rate between 20-40 sccm, and control the Ti target current between 5-10 A within the second preset time; Step S32: Depositing on the Ti bottom layer (10) for 30-60 minutes.

5. The method for preparing the coating according to claim 4, characterized in that: The second preset time is 300s.

6. The method for preparing the coating according to claim 1, characterized in that: The step S20 comprises: Step S21: feeding the substrate (1) into a cavity of a multi-target magnetron sputtering apparatus; Step S22: controlling the Ar gas flow rate to 200 sccm within a third preset time, and controlling the Ti target current to increase linearly to between 5-10 A; Step S23: Depositing on the substrate (1) for 30-60 minutes.

7. The method for preparing the coating according to claim 6, characterized in that: The third preset time is 600s.

8. The method for preparing a coating according to claim 1, characterized in that: The method for preparing the coating further comprises: Step S10: cleaning the substrate (1).

9. The method for preparing the coating according to claim 8, characterized in that: The step S10 comprises: Step S11: placing the substrate (1) into a vacuum chamber, evacuating the chamber to 6×10-4Pa, and then introducing Ar gas with a flow rate of 200 sccm to maintain the vacuum degree at 2-4Pa; Step S12: using a medium frequency power source to bombard the substrate (1) with ions for 20-30 minutes; Step S20 includes: Step S21: placing the substrate (1) into a cavity of a multi-target magnetron sputtering apparatus; Step S22: controlling the Ar gas flow rate to remain unchanged within 600 seconds, and linearly increasing the Ti target current to between 5 and 10 A; Step S23: Depositing on the substrate (1) for 30-60 minutes; Step S30 includes: Step S31: within 300 seconds, the Ti target current is controlled to remain unchanged, the nitrogen flow rate is linearly increased between 10-30 sccm, and the oxygen flow rate is linearly increased between 20-40 sccm; Step S32: depositing on the Ti bottom layer (10) for 30-60 minutes; the step S40 comprises: Step S41: controlling the Ti target current to remain unchanged within 300 seconds, controlling the nitrogen flow rate to be between 20-40 sccm, controlling the oxygen flow rate to be between 20-50 sccm, and controlling the reaction temperature to be between 500-750° C.; Step S42: depositing on the TiON layer for 60-150 min; Step S43: After the sputtering deposition, annealing is performed at a temperature range of 550° C. to 750° C. for 1 to 2.5 hours to form the nitrogen-doped Magnéli phase titanium oxide layer.

10. A coating, characterized in that: The coating is obtained by the method for preparing the coating according to any one of claims 1 to 9, wherein the coating comprises: Ti bottom layer (10); A transition layer (20), located on one side of the Ti bottom layer (10), wherein the transition layer (20) is a TiON layer; The top layer (30) is located on a side of the transition layer (20) away from the Ti bottom layer (10), and the top layer (30) is a nitrogen-doped Magnéli phase titanium oxide layer.

11. The coating according to claim 10, characterized in that The thickness of the top layer (30) is within 600 nm.

12. A fuel cell metal bipolar plate, comprising: Bipolar plate body; A coating is arranged on the surface of the bipolar plate body, characterized in that the coating is a coating prepared according to any one of claims 1 to 9.

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