Hydrophobic bipolar plate as well as preparation method and application thereof

Abstract

The invention provides a hydrophobic bipolar plate as well as a preparation method and application thereof, and relates to the technical field of fuel cells. The hydrophobic bipolar plate comprises a bipolar plate base material and a hydrophobic coating loaded on the bipolar plate base material, wherein a mastoid structure obtained by laser etching is arranged on one side, opposite to the hydrophobic coating, of the bipolar plate base material. According to the hydrophobic bipolar plate, water can be suspended between mastoids and cannot enter gaps of the mastoids, and rapid discharge of the water is promoted; meanwhile, as the contact area of moisture, airflow and the bipolar plate is small, moisture erosion and airflow scouring suffered by the hydrophobic coating are correspondingly reduced, the service life of the hydrophobic coating is prolonged, and the problems that the hydrophobic coating on the surface of the existing bipolar plate is easy to lose efficacy under the scouring of flow resistance, the surface microcosmic bulge structure of the bipolar plate is irregular, and the service life of the bipolar plate is prolonged are effectively solved. The hydrophobic effect is poor.

Description

Technical Field

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

[0002] The bipolar plates of fuel cells play the role of conducting electricity, conducting heat, and draining water. Especially under high current density conditions, the bipolar plates must promptly discharge the generated water from the stack to prevent flooding and affect the performance of the fuel cell. In addition to the flow channel size, the hydrophobicity of the bipolar plates will also affect the drainage capacity of the plates. In order to improve the hydrophobicity of bipolar plates for fuel cells, the prior art usually adopts the method of adding a hydrophobic coating on the surface of the bipolar plate substrate or roughening the surface of the substrate to improve the hydrophobicity of the bipolar plates for fuel cells.

[0003] However, in the prior art, the bipolar plates are basically not treated with hydrophobicity, and basically rely on the hydrophobicity of the material itself or the hydrophobicity of the deposited conductive corrosion-resistant layer itself. The hydrophobic coating added on the surface of some patents or documents is often directly deposited on the surface of the substrate or the anti-corrosion coating. Due to the relatively large flow resistance of the cathode and cathode in the working environment of the fuel cell, especially the cathode flow resistance is usually more than 60kPa, such a large flow resistance will wash the surface of the hydrophobic coating, causing the hydrophobic coating to thin rapidly and eventually fail. At the same time, the existing surface roughening treatment method of the substrate is also to roughen the surface of the substrate by means of chemical solution etching, electrochemical etching, shot blasting, sand blasting, wire drawing, grinding, etc. The microscopic protrusion structure obtained by the above method has irregularity, resulting in differences in local hydrophilicity and hydrophobicity, forming deviations.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first purpose of the present invention is to provide a hydrophobic bipolar plate, which can promote the rapid discharge of water while reducing the impact of water erosion and airflow scouring on the hydrophobic coating, effectively alleviating the problem that the hydrophobic coating on the surface of the existing bipolar plate is easy to fail under flow resistance scouring, and the microscopic protrusion structure on the surface of the bipolar plate is irregular and the hydrophobic effect is poor.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned hydrophobic bipolar plate.

[0007] The third object of the present invention is to provide an application of the above-mentioned hydrophobic bipolar plate in the preparation of a fuel cell.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention provides a hydrophobic bipolar plate, which comprises a bipolar plate substrate and a hydrophobic coating supported on the bipolar plate substrate, wherein:

[0010] The bipolar plate substrate has a papillary structure obtained by laser etching on one side opposite to the hydrophobic coating.

[0011] Furthermore, the equivalent diameter of the mastoid structure is 5 to 200 μm, and the protrusion height of the mastoid structure is 3 to 100 μm;

[0012] The mastoid structure is any one of rectangular, circular and elliptical;

[0013] The mastoid structure on the bipolar plate substrate is a regular structure, and the distance between two adjacent mastoid structures is 10 to 100 μm.

[0014] Furthermore, the laser etching time is 10 -3 ~10 -7 Seconds, laser frequency is 30kHz~100kHz;

[0015] The wavelength of the pulsed laser for laser etching is 500-1000nm, the spot diameter is 0.1-1mm, and the laser energy is ≥10w / mm 2 .

[0016] Furthermore, the bipolar plate substrate includes any one of a metal bipolar plate substrate, an engraved graphite bipolar plate substrate, and a molded graphite bipolar plate substrate.

[0017] The present invention provides a method for preparing the above-mentioned hydrophobic bipolar plate, the preparation method comprising the following steps:

[0018] The bipolar plate substrate is laser etched to etch a regular papillary structure on the surface of the substrate; then a hydrophobic coating is loaded on the side with the papillary structure to obtain a hydrophobic bipolar plate.

[0019] Furthermore, when the bipolar plate substrate is a metal bipolar plate substrate, after the etching of the papillary structure is completed, a vacuum coating method is used to load the conductive layer;

[0020] Preferably, the vacuum-plated coating is one of a carbon-based coating, a precious metal coating, a carbide coating, and a nitride coating.

[0021] Furthermore, the preparation method further comprises the step of surface treating the carbon-based coating, the noble metal coating, the carbide coating, and the nitride coating on the metal bipolar plate substrate;

[0022] The surface treatment steps include: spraying a layer of polytetrafluoroethylene or silane hydrophobic material on the surface of the carbon-based coating and curing it, and using laser etching to remove the hydrophobic layer on the surface of the carbon-based coating on the flow field ridge of the metal bipolar plate to achieve good conductivity on the flow field ridge and good hydrophobicity at the bottom of the flow field.

[0023] Furthermore, when the bipolar plate substrate is an engraved graphite bipolar plate substrate or a molded graphite bipolar plate substrate, a layer of polytetrafluoroethylene or silane hydrophobic material hydrophobic coating is applied by spraying after the etching of the nipple structure is completed;

[0024] Subsequently, laser etching is used to remove the coating on the mastoid structure on the flow field ridge of the bipolar plate, and the recessed parts between the mastoids are heat treated to improve the bonding strength between the coating and the substrate.

[0025] Furthermore, the spraying method includes any one of ultrasonic spraying, electrostatic spraying, and plasma spraying.

[0026] The present invention provides an application of the hydrophobic metal bipolar plate in the preparation of a fuel cell.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The hydrophobic bipolar plate provided by the present invention comprises a bipolar plate substrate and a hydrophobic coating loaded on the bipolar plate substrate, wherein the bipolar plate substrate has a nipple structure obtained by laser etching on one side relative to the hydrophobic coating. The above-mentioned hydrophobic bipolar plate adopts a structure of nipple + hydrophobic coating, which can make the water suspended between the nipples and not enter the gap between the nipples, so that the contact angle between the material surface and water is very large, which promotes the rapid discharge of water; at the same time, because the contact area between water, airflow and the bipolar plate is relatively small, the water erosion and airflow scouring of the coating are also correspondingly reduced, which prolongs the life of the hydrophobic coating, and effectively alleviates the problem that the hydrophobic coating on the surface of the existing bipolar plate is easy to fail under the scouring of flow resistance, and the microscopic protrusion structure on the surface of the bipolar plate is irregular and the hydrophobic effect is poor.

[0029] The present invention provides a method for preparing a hydrophobic bipolar plate. The method firstly performs laser etching on a bipolar plate substrate to etch a regular papillary structure on the substrate surface; then a hydrophobic coating is loaded on the side with the papillary structure to obtain a hydrophobic bipolar plate. The method has the advantages of simple processing technology and easy operation.

[0030] The hydrophobic metal bipolar plate provided by the present invention can be widely used in the preparation process of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1This is a photo of the metal bipolar plate provided in Example 1 of the present invention after being laser etched;

[0033] Figure 2 A schematic diagram of the effect of the hydrophobic bipolar plate provided in Example 1 of the present invention in contact with water;

[0034] Figure 3 Schematic diagram of the flow channel of the hydrophobic bipolar plate after laser etching provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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 are within the scope of protection of the present invention.

[0036] According to one aspect of the present invention, a hydrophobic bipolar plate comprises a bipolar plate substrate and a hydrophobic coating supported on the bipolar plate substrate, wherein:

[0037] The bipolar plate substrate has a papillary structure obtained by laser etching on one side opposite to the hydrophobic coating.

[0038] The hydrophobic bipolar plate provided by the present invention comprises a bipolar plate substrate and a hydrophobic coating loaded on the bipolar plate substrate, wherein the bipolar plate substrate has a nipple structure obtained by laser etching on one side relative to the hydrophobic coating. The above-mentioned hydrophobic bipolar plate adopts a structure of nipple + hydrophobic coating, which can make the water suspended between the nipples and not enter the gap between the nipples, so that the contact angle between the material surface and water is very large, which promotes the rapid discharge of water; at the same time, because the contact area between water, airflow and the bipolar plate is relatively small, the water erosion and airflow scouring of the coating are also correspondingly reduced, which prolongs the life of the hydrophobic coating, and effectively alleviates the problem that the hydrophobic coating on the surface of the existing bipolar plate is easy to fail under the scouring of flow resistance, and the microscopic convex structure on the surface of the bipolar plate is irregular and the hydrophobic effect is poor.

[0039] The technical effects of the hydrophobic bipolar plate of the present application can also be summarized as follows:

[0040] (1) A regular papillary structure is formed on the surface of the bipolar plate substrate through laser etching technology. The existence of the above structure forms a blocking effect on the airflow in the flow field, forming a turbulent effect, forcing the airflow from laminar flow to turbulent flow, so that more air and fuel will enter the membrane electrode through the diffusion layer to participate in the chemical reaction, reducing the diffusion and mass transfer resistance under high current density and improving the performance of the battery stack. Turbulent airflow entering the battery stack will bring out more water from the carbon fiber diffusion layer into the bipolar plate flow channel and out of the battery stack, avoiding the frequency of flooding of the battery stack under high current density.

[0041] (2) This application imitates the "lotus effect" to etch a micro-papillary structure on the surface of a metal bipolar plate, deposit a conductive corrosion-resistant layer, and then load a hydrophobic coating. That is, the structure of papilla + hydrophobic coating can make the water suspended between the papillae and will not enter the gaps between the papillae, so that the contact angle between the material surface and water is very large, which promotes the rapid discharge of water from the flow field. At the same time, since the contact area between water and the plate is relatively small, the erosion of the coating is also correspondingly reduced, extending the life of the coating. At the same time, due to the lotus effect, water does not contact the coating, or the contact area is small, and the hydrogen ions and fluoride ions in the water will not penetrate into the substrate through the gaps and defects of the coating particles, resulting in a reduced probability of corrosion and dissolution of the transition layer and peeling and failure of the coating, thereby protecting the coating and extending the life of the bipolar plate.

[0042] (3) The present application adopts a structure of a mastoid structure + a hydrophobic coating. The regular mastoid structure is integrated with the substrate, has good mechanical properties, and is not easily washed away by the airflow in a short period of time, thereby reducing the roughness. At the same time, due to the presence of the mastoid structure, the contact area between water and the substrate is very small, which can reduce the scouring effect on the coating. In addition, the turbulent effect formed by the mastoid action of the airflow changes the direction of the airflow, forces the airflow to enter the diffusion layer, reduces the airflow speed, and can also alleviate the scouring effect of the airflow on the coating, thereby maintaining the hydrophobicity of the plate flow field and the durability of the coating as a whole.

[0043] In a preferred embodiment of the present invention, the equivalent diameter of the mastoid structure is 5 to 200 μm, and the protrusion height of the mastoid structure is 3 to 100 μm;

[0044] The mastoid structure is any one of rectangular, circular and elliptical;

[0045] The mastoid structure on the bipolar plate substrate is a regular structure, and the distance between two adjacent mastoid structures is 10 to 100 μm.

[0046] As a preferred embodiment, the mastoid structure of the above-mentioned shape can effectively keep water between the mastoids during use and prevent it from entering the mastoid gap.

[0047] In a preferred embodiment of the present invention, the laser etching time is 10 -3 ~10 -7 Seconds, laser frequency is 30kHz~100kHz;

[0048] The wavelength of the pulsed laser for laser etching is 500-1000nm, the spot diameter is 0.1-1mm, and the laser energy is ≥10w / mm 2 .

[0049] As a preferred embodiment, the above-mentioned laser etching is carried out by selecting an etching laser head, setting parameters such as laser pulse time, laser spot size, etching path, and number of cycles, and then the etching laser head moves back and forth on the guide rail to etch the material surface to obtain the required papillary structure. The specific parameters such as the shape, spacing, and depth of the papillary can be obtained by adjusting the laser etching power, resolution, number of repetitions and other parameters.

[0050] In a preferred embodiment of the present invention, the bipolar plate substrate includes any one of a metal bipolar plate substrate, an engraved graphite bipolar plate substrate, and a molded graphite bipolar plate substrate.

[0051] According to one aspect of the present invention, a method for preparing the above-mentioned hydrophobic bipolar plate comprises the following steps:

[0052] The bipolar plate substrate is laser etched to etch a regular papillary structure on the surface of the substrate; then a hydrophobic coating is loaded on the side with the papillary structure to obtain a hydrophobic bipolar plate.

[0053] The present invention provides a method for preparing a hydrophobic bipolar plate. The method firstly performs laser etching on a bipolar plate substrate to etch a regular papillary structure on the substrate surface; then a hydrophobic coating is loaded on the side with the papillary structure to obtain a hydrophobic bipolar plate. The method has the advantages of simple processing technology and easy operation.

[0054] In a preferred embodiment of the present invention, when the bipolar plate substrate is a metal bipolar plate substrate, after the etching of the nipple structure is completed, a vacuum coating method is used to first deposit a conductive corrosion-resistant layer and then deposit a hydrophobic layer;

[0055] Preferably, the conductive corrosion-resistant layer is a carbon-based coating, and the purpose of adding the carbon-based coating is mainly to improve the conductivity and corrosion resistance of the plate. The carbon coating itself is hydrophobic, but due to differences in the preparation process, the hydrophobicity prepared under different conditions is different. Therefore, in order to further improve the hydrophobicity, hydrophobicity will be further sprayed on the surface of the carbon coating and cured to improve the hydrophobicity. Since the contact with the carbon paper on the ridge of the bipolar plate flow field requires good conductivity, and the hydrophobic layer itself has poor conductivity, the method of local laser etching is used to remove the hydrophobic layer deposited on the ridge, so that the carbon coating loaded in the early stage is exposed to improve conductivity. The bottom of the bipolar plate flow field itself has no requirements for conductivity, but has relatively high requirements for hydrophobicity, so laser etching is not required here.

[0056] In addition, it should be noted that the commonly used metal bipolar plates on the market include stainless steel bipolar plates and titanium bipolar plates. The two materials will oxidize under natural conditions to form an oxide film, resulting in very poor conductivity of the bipolar plate itself. In order to improve the conductivity of the metal bipolar plate, a conductive corrosion-resistant layer (preferably a carbon-based coating) is usually magnetron sputtered on the metal bipolar plate. Due to different specific process parameters, the hydrophobicity of the conductive corrosion-resistant layer varies greatly. Based on this, a hydrophobic layer is deposited on the basis of the metal bipolar plate + conductive corrosion-resistant layer. Since the hydrophobic layer itself has relatively good corrosion resistance, but poor conductivity, the part of the bipolar plate that contacts the carbon paper is required to have good conductivity. Therefore, after the hydrophobic coating is sprayed on the metal bipolar plate, the hydrophobic layer deposited on the surface of the bipolar plate in contact with the carbon paper (the part on the flow field ridge of the bipolar plate) is etched away by a local laser etching method to expose the conductive corrosion-resistant layer deposited in the middle.

[0057] Preferably, the size and gap of the metal bipolar plate substrate mastoid structure etching are as follows: the mastoid equivalent diameter is about 5-200 μm, the distance between two regular protrusions is 10-100 μm, and the height of the protrusion is 3-100 μm. The set parameters are imported into the laser control software. After setting, the laser parameters are adjusted for laser etching, and the etching time is 10s-20min.

[0058] Preferably, the laser etching parameters for etching the mastoid structure of the metal bipolar plate substrate are as follows: the laser etching time is 10 -3 ~10 -7 seconds, the laser frequency is 30kHz~100kHz; the wavelength of the pulsed laser for laser etching is 500~1000nm, the spot diameter is 0.1~1mm, and the laser energy is ≥150w / mm 2 .

[0059] It should be noted that the present application utilizes the adjustability of the laser power parameters to achieve the regulation of the hydrophilicity and hydrophobicity of different regions. That is, by adjusting the laser etching power and other parameters, the requirements of different regions for roughness, hydrophilicity, hydrophobicity, conductivity and other properties can be met in different regions or different papilla shapes and structural matrices. For details, please refer to the following enumerated schemes:

[0060] (i) The present application can perform surface treatment on a metal bipolar plate having a papillary structure and a carbon-based hydrophobic coating to take into account both conductive and hydrophobic properties.

[0061] The surface treatment step includes: magnetron sputtering a carbon-based coating on the mastoid structure on the surface of the metal bipolar plate substrate by laser etching, and then loading a hydrophilic coating on the mastoid structure. Finally, laser etching is performed on the partially loaded hydrophobic coating to adjust the contact resistance between the plate and the carbon paper.

[0062] Preferably, the supported hydrophilic coating may also be subjected to laser heat treatment to enhance the bonding strength between the hydrophilic coating and the substrate.

[0063] After the above-mentioned hydrophilic surface treatment, water can enter the flow field from the diffusion layer and be discharged from the battery stack as quickly as possible, thereby preventing the occurrence of flooding.

[0064] (ii) When the bipolar plate substrate is a carved graphite bipolar plate substrate or a molded graphite bipolar plate substrate, after the etching of the nipple structure is completed, in order to further control the hydrophobicity of the material, a layer of polytetrafluoroethylene or silane hydrophobic material is coated on the surface of the substrate by a spraying process to form a structure of nipple + hydrophobic coating;

[0065] Then, laser etching is used to remove the hydrophobic coating components on the surface of the mastoids in an etching mode to expose the carbon-based material components; the laser power is reduced for the concave parts between the mastoids, and the hydrophobic material is heat-treated to improve the bonding strength between tetrafluoroethylene or silane materials and the substrate. This ensures that the hydrophobic material has excellent conductivity and hydrophobicity when in contact with the diffusion layer.

[0066] It should be noted that the engraved graphite bipolar plates and molded graphite bipolar plates have relatively good conductivity, so there is no need to deposit an additional conductive corrosion-resistant layer. After laser etching, a papillary structure is formed on the surface of the plate, and a hydrophobic coating can be further deposited if necessary. Similar to metal bipolar plates, after spraying the hydrophobic coating, the hydrophobic layer deposited on the surface of the bipolar plate in contact with the carbon paper (the part on the flow field ridge of the bipolar plate) is etched away by local laser etching to expose the engraved graphite plate or molded graphite plate body.

[0067] Preferably, the spraying method includes any one of ultrasonic spraying, electrostatic spraying and plasma spraying.

[0068] Preferably, the laser etching parameters for etching the mastoid structure of the engraved graphite bipolar plate substrate or the molded graphite bipolar plate substrate are as follows: the laser processing time is 10 -3 ~10 -7 seconds, laser frequency 30kHz-100kHz preferably 50kHz, pulse laser wavelength 500-1000nm, spot diameter 0.1-1mm, laser energy ≥100w / mm 2 .

[0069] Preferably, the size and gap of the engraved graphite bipolar plate substrate or the molded graphite bipolar plate substrate mastoid structure etching are as follows: the mastoid equivalent diameter is about 5-200 μm, the distance between two regular protrusions is 10-100 μm, and the height of the protrusion is 3-100 μm. The set parameters are imported into the laser control software. After setting, the laser parameters are adjusted for laser etching, etching time, and etching time is 10s-20min.

[0070] According to one aspect of the present invention, the hydrophobic metal bipolar plate is used in preparing a fuel cell.

[0071] The hydrophobic metal bipolar plate provided by the present invention can be widely used in the preparation process of fuel cells.

[0072] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0073] Example 1

[0074] A method for preparing a hydrophobic bipolar plate, the method comprising:

[0075] (1) Providing a TA1 titanium bipolar plate as a substrate, etching the bare metal bipolar plate using a laser etching method, and etching a regular papillary structure on the surface of the substrate;

[0076] Specifically: Set the size and gap of the mastoid structure. The specific mastoid equivalent diameter is about 12μm, the distance between two regular protrusions is 6μm, the height of the protrusion is 3μm, and the laser etching area is 100mm×100mm. After the parameter setting is completed, import the set parameters into the laser control software. Turn on the carbon dioxide laser, set the laser spot to 0.2mm, the pulse interval to 10 milliseconds, adjust the laser power, and the spot energy to 150w / mm 2 After the setting is completed, the material surface is evenly irradiated. The laser treatment is carried out for a total of 5 minutes to etch a regular papillary structure on the surface of the substrate.

[0077] Figure 1 This is a partial effect diagram of the metal bipolar plate after laser etching in this embodiment.

[0078] Depend on Figure 1 As shown, after etching, a layer of raised portions of the papillary structure is regularly arranged on the surface of the metal bipolar plate substrate, and grooves are formed between the raised portions.

[0079] (2) After the laser etching is completed, the bipolar plate with the mastoid structure is polished with a polishing liquid to remove the laser welding slag on the metal surface.

[0080] After polishing, clean it with pure water ultrasonic cleaning and dry it with nitrogen. Hang the bipolar plate into the magnetron sputtering coating machine and evacuate it to 3×10 -3 pa, raise the temperature to 120℃; introduce argon gas, set the vacuum degree to 0.8pa, turn on the bias power supply, set the bias power supply voltage to 800v, ​​and glow etch for 10min.

[0081] Adjust the vacuum degree to 0.2 Pa, turn on the titanium target, set the current to 10 A, and the bias power supply voltage to 120 V for magnetron sputtering, and the sputtering time is 10 min; after sputtering, adjust the vacuum degree to 0.25 Pa, turn on two pairs of DC magnetron graphite plane targets, the single target current is 7 A, the bias power supply voltage is 80 V, turn on the ion source, set the current to 3.5 A for auxiliary deposition, and the deposition time is 30 min.

[0082] The carbon-based material is loaded on a bipolar plate having a papillary structure to obtain a hydrophobic bipolar plate.

[0083] Figure 2 Schematic diagram of the effect when the hydrophobic bipolar plate of this embodiment comes into contact with water.

[0084] Depend on Figure 2 It can be seen that after the bipolar plate is processed by laser etching to form a structure of papillae + hydrophobic coating, the contact angle of water on the material surface is relatively large, and water is not easy to spread on the material surface. Due to the internal micro-papillary structure and the large contact angle of water, the water is directly suspended between the two papillae structures. The contact area between the water droplet and the substrate is very small, and the hydrogen ions and fluoride ions in the water do not contact the substrate, and will not penetrate into the interior of the substrate, causing the coating peeling failure effect to occur.

[0085] Comparative Example 1

[0086] A method for preparing a hydrophobic bipolar plate, the method comprising:

[0087] (1) Provide a bare TA1 titanium bipolar plate as the same as in Example 1 as a substrate, and spray a layer of micron-sized metal particles on the surface of the substrate by electrostatic spraying. The particle size of the metal particles is D 50 Equal to 12 microns;

[0088] The sprayed micron-sized metal particles are sintered together with the substrate by high-temperature heat treatment technology to obtain a micron-sized papillary structure similar to that formed by etching in Example 1.

[0089] The temperature of the high temperature heat treatment is 1500°C.

[0090] (2) Same as Example 1.

[0091] Comparative Example 2

[0092] A method for preparing a hydrophobic bipolar plate, the method comprising:

[0093] Provide the same bare metal bipolar plate as in Example 1, hang the bare metal bipolar plate into a magnetron sputtering coating machine, and evacuate to 3×10 -3pa, raise the temperature to 120℃; introduce argon gas, set the vacuum degree to 0.8pa, turn on the bias power supply, set the bias power supply voltage to 800v, ​​and glow etch for 10min.

[0094] Adjust the vacuum degree to 0.2 Pa, turn on the titanium target, set the current to 10 A, and the bias power supply voltage to 120 V for magnetron sputtering, and the sputtering time is 10 min; after sputtering, adjust the vacuum degree to 0.25 Pa, turn on two pairs of DC magnetron graphite plane targets, the single target current is 7 A, the bias power supply voltage is 80 V, turn on the ion source, set the current to 3.5 A for auxiliary deposition, and the deposition time is 30 min.

[0095] The difference between this comparative example and Example 1 is that the hydrophobic bipolar plate prepared in this comparative example does not contain a papillary structure. Because the lotus leaf effect requires a combination of two aspects to achieve better hydrophobicity. On the one hand, a papillary structure is formed on the surface of the material, and on the other hand, the substrate or the deposited coating itself is hydrophobic. The combination of the two has a better hydrophobic effect. Therefore, the conductivity and hydrophobicity of the bipolar plate prepared in this comparative example are poor.

[0096] Example 2

[0097] A method for preparing a hydrophobic bipolar plate, the method comprising:

[0098] (1) Same as in Example 1;

[0099] (2) Same as in Example 1;

[0100] (3) Prepare 1% (w%) ethyl orthosilicate isopropanol solution, stir it evenly with magnetic force, spray a layer of solution on the etched part by ultrasonic spraying, and then put it into a muffle furnace and dry it at 400° C. for 30 minutes.

[0101] (4) After step (3) is completed, the plate is laser etched again according to the method of step (1). This laser etching only etches the protruding part of the mastoid, and etches away the hydrophilic silicon dioxide layer loaded on the surface of the mastoid, ensuring that the plate and the GDL diffusion layer have good conductivity.

[0102] Example 3

[0103] A method for preparing a hydrophobic bipolar plate, the method comprising:

[0104] (1) Provide engraved graphite bipolar plate as substrate, set the size and gap of the mastoid structure, the specific mastoid equivalent diameter is about 20μm, the distance between two regular protrusions is 10μm, and the height of the protrusion is 3μm. After the parameter setting is completed, import the set parameters into the laser control software. Turn on the carbon dioxide laser, set the laser spot to 0.2mm, the pulse interval to 2 milliseconds, adjust the laser power, the spot energy to 50w / mm2, and evenly irradiate the material surface after the setting is completed. The laser treatment is carried out for a total of 15 minutes.

[0105] (2) Prepare a 0.5% (w%) polytetrafluoroethylene aqueous solution, stir it evenly with a magnetic force, spray a layer of the solution on the engraved graphite plate by ultrasonic spraying, and then put it in an oven for drying at 250° C. for 10 minutes.

[0106] (3) After step (2) is completed, the plate is laser etched again according to the method of step (1). This laser etching only etches the protruding part of the mastoid, and etches away the polytetrafluoroethylene hydrophobic layer loaded on the surface of the mastoid, ensuring that the plate and the GDL diffusion layer have good conductivity.

[0107] Figure 3 Schematic diagram of the flow channel of the hydrophobic bipolar plate after laser etching in this embodiment.

[0108] Depend on Figure 3 It can be seen that a layer of hydrophobic material is coated on the surface of the bipolar plate, and different treatment methods are performed on different parts using a laser processor. The etching mode is used on the ridge, and the etching power and time are precisely controlled to ensure that the hydrophobic layer on the ridge is completely cleaned evenly, leaking the conductive part of the bipolar plate, and ensuring that the bipolar plate and the diffusion layer have good conductivity. In the groove part, the power of the laser processor is adjusted, and the heat treatment mode is used to cure the coating, so that the coating and the substrate have a stable and firm bonding force, forming a stable hydrophobic structure. The water generated in the fuel cell passes through the hydrophobic layer in the flow channel and is quickly discharged from the stack to avoid flooding.

[0109] Experimental Example 1

[0110] In order to show that the hydrophobic bipolar plate prepared in the present application has good electrical conductivity and hydrophobicity, the hydrophobic bipolar plates prepared in the above Examples 1 and 2 and Comparative Examples 1 and 2 are subjected to performance testing.

[0111] The specific detection method is as follows: the contact resistance test of the prepared bipolar plate is carried out at 0.6MPa according to the national standard, and the contact angle measurement is tested using a contact angle meter. The prepared plates are assembled into a battery stack and activated, and then the polarization performance test is carried out to measure the rated working condition of 1.7A / cm 2 Order the battery voltage value.

[0112] The specific test results are shown in the following table:

[0113]

[0114]

[0115] It can be seen from the above table that the hydrophobic bipolar plate prepared in Example 1 of the present application, after the bipolar plate is treated with laser etching to form a structure of papilla + hydrophobic coating, has a relatively large contact angle of water on the surface of the material, and water is not easy to spread on the surface of the material; at the same time, it has better conductivity.

[0116] The hydrophobic bipolar plate prepared in Example 2 is based on the bipolar plate in Example 1 through surface modification, which effectively improves the conductivity of the bipolar plate.

[0117] The hydrophobic graphite bipolar plate prepared in Example 3 can evenly clean the hydrophobic layer on the ridge by using the etching mode, leaking the conductive part of the bipolar plate, ensuring that the bipolar plate and the diffusion layer have good conductivity. In the groove part, the power of the laser processor is adjusted, and the coating is cured by the heat treatment mode, so that the coating and the substrate have a stable and firm bonding force, forming a stable hydrophobic structure. The water generated in the fuel cell passes through the hydrophobic layer in the flow channel and is quickly discharged from the stack to avoid flooding.

[0118] In contrast, since the papillary structure of Comparative Example 1 is prepared by high-temperature heat treatment technology, the metal particles prepared by this spraying and sintering process have poor consistency and a relatively large particle size distribution range, resulting in inconsistent papillary sizes and local differences in hydrophobicity on the plate.

[0119] On the other hand, the metal particles used in the spray sintering process are usually round or irregular in shape. When in contact with the diffusion layer carbon paper, the contact area is small, resulting in a larger overall contact resistance (while the laser-etched size of the present application is uniform and the upper surface is flat). At the same time, the nipple structure obtained by spray sintering can easily pierce the carbon paper fibers and cause damage to the carbon paper. The laser-etched nipple structure of the present application is integrated with the substrate and has good bonding strength. The sintered particles have poor bonding strength with the substrate and also have certain disadvantages in terms of resistance to flow resistance erosion, which can easily cause the sintered particles to fall off.

[0120] However, the hydrophobic bipolar plate prepared in Comparative Example 2 does not contain a papillary structure and cannot effectively discharge water from the surface of the material. Therefore, the bipolar plate prepared in this comparative example has poor conductivity and hydrophobicity.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hydrophobic bipolar plate, characterized in that: The hydrophobic bipolar plate comprises a bipolar plate substrate and a hydrophobic coating supported on the bipolar plate substrate, wherein: The bipolar plate substrate has a papillary structure obtained by laser etching on one side opposite to the hydrophobic coating.

2. The hydrophobic bipolar plate according to claim 1, characterized in that: The equivalent diameter of the mastoid structure is 5 to 200 μm, and the protrusion height of the mastoid structure is 3 to 100 μm; The mastoid structure is any one of rectangular, circular and elliptical; The mastoid structure on the bipolar plate substrate is a regular structure, and the distance between two adjacent mastoid structures is 10 to 100 μm.

3. The hydrophobic bipolar plate according to claim 1, characterized in that: The laser etching time is 10 -3 ~10 -7 Seconds, laser frequency is 30kHz~100kHz; The wavelength of the pulsed laser for laser etching is 500-1000nm, the spot diameter is 0.1-1mm, and the laser energy is ≥10w / mm 2 .

4. The hydrophobic bipolar plate according to claim 1, characterized in that: The bipolar plate substrate includes any one of a metal bipolar plate substrate, an engraved graphite bipolar plate substrate, and a molded graphite bipolar plate substrate.

5. A method for preparing a hydrophobic bipolar plate according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: The bipolar plate substrate is laser etched to etch a regular papillary structure on the surface of the substrate; then a hydrophobic coating is loaded on the side with the papillary structure to obtain a hydrophobic bipolar plate.

6. The method for preparing a hydrophobic bipolar plate according to claim 5, characterized in that: When the bipolar plate substrate is a metal bipolar plate substrate, the conductive layer is loaded by a vacuum coating method after the etching of the nipple structure is completed.

7. The method for preparing a hydrophobic bipolar plate according to claim 6, characterized in that: The preparation method further comprises the step of surface treating the carbon-based coating on the metal bipolar plate substrate; The surface treatment step comprises: spraying a layer of polytetrafluoroethylene or silane hydrophobic material on the surface of the carbon-based coating on the metal bipolar plate substrate and curing the layer to obtain a hydrophobic coating; Subsequently, laser etching is used to remove the hydrophobic layer on the surface of the carbon-based coating on the flow field ridges of the metal bipolar plate, thereby achieving good conductivity on the flow field ridges and better hydrophobicity at the bottom of the flow field.

8. The method for preparing a hydrophobic bipolar plate according to claim 5, characterized in that: When the bipolar plate substrate is a carved graphite bipolar plate substrate or a molded graphite bipolar plate substrate, a layer of polytetrafluoroethylene or silane hydrophobic material hydrophobic coating is applied by spraying after the etching of the nipple structure is completed; Subsequently, laser etching was used to remove the hydrophobic coating on the nipple structure on the flow field ridge of the bipolar plate, and the recessed parts between the nipples were heat treated to improve the bonding strength between the coating and the substrate.

9. The method for preparing a hydrophobic bipolar plate according to claim 8, characterized in that: The spraying method includes any one of ultrasonic spraying, electrostatic spraying and plasma spraying.

10. Use of the hydrophobic bipolar plate according to any one of claims 1 to 4 in the preparation of a fuel cell.

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