Bipolar plate with super-hydrophobic fillets and preparation method thereof

Abstract

The invention relates to a bipolar plate with super-hydrophobic filleted corners and a preparation method thereof.The bipolar plate is arranged on a gas diffusion layer and comprises connecting parts, arching parts and bending parts, the connecting parts are arranged on the two sides of the bipolar plate and attached to the surface of the gas diffusion layer, the arching parts are arranged between the connecting parts, and the bending parts are arranged between the arching parts and the connecting parts. The bending part is arranged at the joint of the connecting part and the arching part, and a latticed structure is etched on the surface of the fillet, facing the gas diffusion layer, of the bending part to form a super-hydrophobic microstructure. Compared with the prior art, liquid can be effectively prevented from being accumulated at the fillet where the bipolar plate is in contact with the gas diffusion layer, so that pores of the gas diffusion layer are kept open, reaction gas can be ensured to smoothly pass through, and the liquid is promoted to be discharged to a flow channel.

Description

Technical Field

[0001] The invention belongs to the technical field of proton exchange membrane fuel cells and relates to a bipolar plate with super-hydrophobic fillets and a preparation method thereof. Background Art

[0002] In a proton exchange membrane fuel cell (PEMFC), the capillary effect determines how liquid water and gas flow in a porous medium. Smaller pores have higher capillary pressures, which effectively repel liquid water and allow gas to pass through. Larger pores are more easily filled with liquid water. In the catalyst reaction area, the temperature is high due to the exothermic electrochemical reaction between hydrogen and oxygen to generate water and electricity. The temperature near the flow channel area is relatively low and is affected by the cooling system or the ambient temperature. This temperature difference causes water vapor to condense into liquid water in the low-temperature area, especially where the flow channel ridges contact the gas diffusion layer. After water vapor condenses into liquid water in the lower temperature area, it gradually accumulates between the flow channel ridges and the gas diffusion layer. Due to the complex structure of the flow channel ridges, water is difficult to discharge smoothly, resulting in the gradual accumulation of water in this area. As liquid water accumulates, it diffuses laterally into the pores of the gas diffusion layer under the action of capillary pressure. Liquid water gradually fills the larger pores in the gas diffusion layer to form a continuous water phase.

[0003] When the pores of the gas diffusion layer are filled with liquid water, the reaction gases (such as hydrogen and oxygen) cannot effectively pass through the gas diffusion layer to reach the catalyst surface. This can significantly reduce the operating efficiency of the fuel cell because the rate of the electrochemical reaction depends on the effective transmission of the reaction gases. The water accumulated in the gas diffusion layer will increase the internal resistance of the battery because the conductivity of water is much lower than that of gas, resulting in a decrease in the output voltage of the battery. Long-term water accumulation can also cause corrosion and degradation of the internal materials of the fuel cell, shortening the life of the battery.

[0004] Patent CN118336012A discloses a bipolar plate and its fuel cell, as well as a sealing groove design method for the bipolar plate. By ensuring the contact pressure between the active area of ​​the membrane electrode assembly and the bipolar plate after the stack is assembled, the contact resistance is reduced, and the voltage loss of the fuel cell caused by the contact resistance is reduced. Patent CN118281250A discloses a fuel cell metal bipolar plate and its preparation method. The bipolar plate has high corrosion resistance due to the nano-precious metal particle-titanium oxide mixed coating. At the same time, the nano-precious metal particles with high conductivity and good dispersibility can provide sufficient electron channels between the plate and the gas diffusion layer (GDL), thereby reducing the interfacial contact resistance (ICR). At present, the design of metal bipolar plates rarely enhances its drainage performance by regulating the surface hydrophilicity and hydrophobicity.

[0005] Patent CN118099443A discloses a polar plate, a bipolar plate and a method for preparing a polar plate. The polar plate coating has a hydrophilic layer and a conductive layer, which is not only conducive to the drainage of the flow channel of the polar plate, but also has good conductivity and improves the power generation efficiency of the fuel cell. Patent CN110707341A discloses a hydrophilic-hydrophobic surface of a bipolar plate for a fuel cell and a preparation method thereof. Depending on the situation, whether a metal film is plated on the surface of the bipolar plate, the flow channel of the bipolar plate is laser nitrided, the valley flow channel is engraved, and then the ridge flow channel or the side flow channel of the bipolar plate is laser oxidized and UV treated, thereby forming a hydrophilic-hydrophobic surface on the surface of the bipolar plate, involving the application of n-octadecyl silicon hydrophobic agent, and the operation process is cumbersome, and different processing schemes need to be adopted for materials with different components. At present, the bipolar plate structure has not specifically considered the problem of water accumulation at the corner where the flow channel ridge contacts the gas diffusion layer, and there is no good way to solve the above-mentioned many adverse effects of water accumulation in this area on the battery and alleviate the flooding of the gas diffusion layer. Therefore, there is an urgent need for a bipolar plate structure that can avoid water accumulation at the rounded corners where the bipolar plate and the gas diffusion layer contact each other, and is suitable for most metal materials.

[0006] Patent CN111446462A discloses a fuel cell metal plate with a surface microstructure and a manufacturing method thereof, which divides the surface of the metal plate into sections and sets a protruding or concave microarray structure. Although the patent adopts a microarray structure, it improves the hydrophilicity and hydrophobicity at the flow channel to match the different requirements of the gas inlet area, flow field area and outlet area for water. The water droplets generated during the operation of the fuel cell still gather at the fillet where the bipolar plate and the gas diffusion layer are connected. The flooding phenomenon between the bipolar plate and the gas diffusion layer of the fuel cell is not solved, and the gas cannot be discharged smoothly.

[0007] Patent CN114068948A discloses a fuel cell bipolar plate and drainage method with bionic active drainage function, forming a low surface energy film with hydrophobic characteristics that imitates the low adhesion effect of the lotus leaf surface on the flow field wall, etching the low surface energy film to form a hydrophilic pattern with periodic arrangement that imitates the thorns of cactus, and etching the hydrophilic pattern on the wall after hydrophobic treatment to form a bionic surface that imitates the hydrophilic and hydrophobic coupling of the back of a desert beetle. However, this patent uses chemical hydrophobic agents to change the surface energy of the metal, and different processing schemes need to be adopted for materials with different components; although this patent uses laser engraving microstructures, the purpose is to create a hydrophilic area, and it also does not solve the flooding phenomenon between the fuel cell bipolar plate and the gas diffusion layer. Summary of the invention

[0008] The purpose of the present invention is to provide a bipolar plate with super-hydrophobic rounded corners and a preparation method thereof in order to overcome at least one defect of the above-mentioned prior art. The present invention can effectively prevent liquid from accumulating at the rounded corners where the bipolar plate and the gas diffusion layer are in contact, thereby keeping the pores of the gas diffusion layer open, ensuring that the reaction gas can pass smoothly, and promoting the discharge of water into the flow channel.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] One of the technical solutions of the present invention is to provide a bipolar plate with super-hydrophobic rounded corners, which is arranged on a gas diffusion layer, and includes a connecting portion, a raised portion and a bent portion. The connecting portions are arranged on both sides of the bipolar plate and are attached to the surface of the gas diffusion layer. The raised portion is arranged between the connecting portions and protrudes in a direction away from the surface of the gas diffusion layer. The bent portion is arranged at the connection between the connecting portion and the raised portion. The surface of the bent portion at the rounded corner facing the gas diffusion layer is etched with a grid-like structure to form a super-hydrophobic microstructure to avoid liquid accumulation at the connection between the gas diffusion layer and the bipolar plate.

[0011] As a preferred technical solution, the material of the bipolar plate includes stainless steel, titanium or nickel, etc., which are most metal materials that can be used to manufacture bipolar plates.

[0012] When other metal coatings are subsequently plated on the surface of the bipolar plate, the grid structure will not be destroyed. After subsequent annealing heat treatment, the super-hydrophobic microstructure is still effective and can continue to exert its hydrophobic function.

[0013] Furthermore, the super-hydrophobic microstructure includes a first zone and a second zone, the first zone is arranged on the surface of the bending part facing the gas diffusion layer, and the second zone is arranged on the surface of the bending part close to the gas diffusion layer. The first zone and the second zone form a continuous surface to fully cover the surface of the bending part facing the gas diffusion layer. By arranging the super-hydrophobic microstructure on the surface of the rounded corners of the connecting part and the bending part facing the gas diffusion layer, liquid is prevented from accumulating at the corners where the bipolar plate contacts the surface of the gas diffusion layer. The super-hydrophobic microstructure prevents liquid from infiltrating here, which can effectively prevent the internal resistance of the battery from increasing due to liquid accumulation, thereby reducing the output voltage of the battery.

[0014] Furthermore, the super-hydrophobic microstructure includes a plurality of grooves arranged in a matrix, and matrix-distributed terraces are formed between adjacent grooves.

[0015] Furthermore, the groove width is 10-20 μm, and the spacing between the grooves is 50-150 μm.

[0016] Furthermore, the space enclosed between the arched portion and the surface of the gas diffusion layer forms a flow channel portion, which includes a flow channel ridge and a flow channel groove. The space enclosed between the two sides of the arched portion and the surface of the gas diffusion layer forms the flow channel ridge, and the space enclosed between the middle of the arched portion, the flow channel ridge and the surface of the gas diffusion layer forms the flow channel groove. The super-hydrophobic microstructure is located on the bipolar plate near the contact between the flow channel ridge and the surface of the gas diffusion layer to avoid accumulation of liquid near the contact between the flow channel ridge and the surface of the gas diffusion layer and laterally diffusion of the accumulated liquid to the surface of the gas diffusion layer.

[0017] The accumulated liquid at the rounded corners where the bipolar plate and the gas diffusion layer are in contact is discharged through the flow channel groove. Since a super-hydrophobic microstructure with extremely strong hydrophobicity is arranged at the rounded corners where the bipolar plate and the gas diffusion layer are in contact, liquid does not stick to this corner, thereby preventing the accumulated liquid from gathering and laterally diffusing here, thereby preventing a continuous water phase from forming on the gas diffusion layer. The reaction gas can effectively pass through the gas diffusion layer to reach the catalyst surface, thereby achieving effective transmission of the reaction gas, accelerating the rate of the electrochemical reaction, and improving the working efficiency of the fuel cell and the output power of the battery.

[0018] One of the technical solutions of the present invention is to provide a method for preparing the bipolar plate with super-hydrophobic fillets, the method comprising the following steps:

[0019] S1. Use laser to etch a grid-like super-hydrophobic microstructure on the surface of the bipolar plate;

[0020] S2, annealing the etched bipolar plate and taking it out;

[0021] S3, bending the annealed bipolar plate at the super-hydrophobic microstructure to form a bent portion, and stamping between the super-hydrophobic microstructures to form an arched portion, so as to obtain a bipolar plate with super-hydrophobic rounded corners.

[0022] Furthermore, in step S1, the etching spot size is 10-20 μm, and the processing step length is 50-150 μm.

[0023] Furthermore, in step S1, the power of the laser is 2.5-5.5 W, and the frequency is 45-105 kHz.

[0024] As a preferred technical solution, the thickness of the bipolar plate in step S1 is 0.1-2 mm.

[0025] Furthermore, in step S2, annealing is performed in air or water vapor atmosphere, the annealing temperature is 80-150° C., and the time is 12-48 hours.

[0026] Furthermore, in step S1, a laser is used to etch a super-hydrophobic microstructure of a grid structure at two locations near the end of the surface of the bipolar plate;

[0027] In step S3, the annealed bipolar plate is bent at the center of the super-hydrophobic microstructure to form a bent portion, and a middle area between two super-hydrophobic microstructures is stamped to form a raised portion.

[0028] One of the technical solutions of the present invention is to provide an application of the bipolar plate with super-hydrophobic rounded corners, wherein the bipolar plate is applied to a proton exchange membrane fuel cell.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention designs a super-hydrophobic microstructure at the fillet where the bipolar plate and the gas diffusion layer contact, which can effectively prevent water from accumulating at the fillet where the bipolar plate and the gas diffusion layer contact, and avoid the situation where the accumulated liquid gradually diffuses laterally to cover the surface of the gas diffusion layer due to the continuous accumulation of liquid, thereby preventing air or oxygen from entering the gas diffusion layer, thereby keeping the pores of the gas diffusion layer open, ensuring that the reaction gas can pass smoothly, promoting the discharge of water to the flow channel, improving the working efficiency of the fuel cell, avoiding corrosion and degradation of the materials inside the fuel cell, and extending the life of the battery;

[0031] (2) The present invention uses a bipolar plate to manufacture a super-hydrophobic microstructure by combining laser etching technology with a heat treatment process. The process is simple and does not involve the use of a hydrophobic modifier, which is environmentally friendly and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of a bipolar plate with super-hydrophobic fillets combined with a gas diffusion layer in an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of the structure of a bipolar plate with super-hydrophobic fillets in an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of the enlarged structure of part A of a bipolar plate with super-hydrophobic fillet in an embodiment of the present invention;

[0035] Figure 4 Schematic diagram of the structure of the super-hydrophobic microstructure in an embodiment of the present invention;

[0036] Figure 5 : is a scanning electron microscope (SEM) image of a superhydrophobic microstructure in an embodiment of the present invention;

[0037] Figure 6 Graph showing contact angles at super-hydrophobic microstructures in an embodiment of the present invention;

[0038] Figure 7 Schematic diagram of the super-hydrophobic properties of the super-hydrophobic microstructure surface in an embodiment of the present invention.

[0039] Description of the markings in the figure:

[0040] 1—bipolar plate, 2—gas diffusion layer, 3—superhydrophobic microstructure, 4—liquid, 5—flow channel;

[0041] 11—connecting portion, 12—arched portion, 13—bent portion;

[0042] 31 - groove, 32 - table, 33 - first zone, 34 - second zone. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", "third", etc. are used to describe common objects, which only refer to different instances of the same object, and are not intended to imply that the objects described in this way must adopt a given order, whether in time, space, order or any other way.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0047] Example:

[0048] A bipolar plate with super hydrophobic fillets for use in proton exchange membrane fuel cells, such as Figure 1As shown, the bipolar plate 1 is arranged on the gas diffusion layer 2, and includes a connecting portion 11, an arched portion 12 and a bent portion 13. The connecting portion 11 is arranged on both sides of the bipolar plate 1 and is attached to the surface of the gas diffusion layer 2. The arched portion 12 is arranged between the two connecting portions 11 and protrudes away from the surface of the gas diffusion layer 2. The bent portion 13 is arranged at the connection between the connecting portion 11 and the arched portion 12. The surface of the curved portion 13 facing the gas diffusion layer 2 is etched with a grid-like structure to form a super-hydrophobic microstructure 3 to avoid the accumulation of liquid 4, such as liquid water, at the connection between the gas diffusion layer 2 and the bipolar plate 1.

[0049] By designing a super-hydrophobic microstructure 3 at the fillet where the bipolar plate 1 and the gas diffusion layer 2 are in contact, the liquid 4 can be effectively prevented from accumulating at the fillet where the bipolar plate 1 and the gas diffusion layer 2 are in contact, and the situation where the accumulated liquid gradually diffuses laterally to cover the surface of the gas diffusion layer 2 due to the continuous accumulation of the liquid 4 and prevents air or oxygen from entering the gas diffusion layer 2 can be further avoided, thereby keeping the pores of the gas diffusion layer 2 open, ensuring that the reaction gas can pass smoothly, promoting the discharge of the liquid 4 to the flow channel groove, improving the working efficiency of the fuel cell, avoiding corrosion and degradation of the materials inside the fuel cell, and extending the life of the battery;

[0050] The material of the bipolar plate 1 can be stainless steel or titanium, nickel or other metal materials that can be used to manufacture the bipolar plate 1. In this embodiment, stainless steel is preferred.

[0051] In addition, when other metal coatings are subsequently plated on the surface of the bipolar plate 1, the grid structure will not be destroyed. After subsequent annealing heat treatment, the super-hydrophobic microstructure 3 is still effective and can continue to exert its hydrophobic function;

[0052] The space enclosed between the arched portion 12 and the surface of the gas diffusion layer 2 forms a flow channel portion 5, and the flow channel portion 5 includes a flow channel ridge and a flow channel groove. The space enclosed between the two sides of the arched portion 12 and the surface of the gas diffusion layer 2 forms the flow channel ridge, and the space enclosed between the middle of the arched portion 12, the flow channel ridge and the surface of the gas diffusion layer 2 forms the flow channel groove. The super-hydrophobic microstructure 3 is located on the bipolar plate 1 near the contact between the flow channel ridge and the surface of the gas diffusion layer 2 to prevent the liquid 4 from accumulating near the contact between the flow channel ridge and the surface of the gas diffusion layer 2 and the accumulated liquid from diffusing laterally to the surface of the gas diffusion layer 2.

[0053] The accumulated liquid at the fillet where the bipolar plate 1 and the gas diffusion layer 2 are in contact is discharged through the flow channel groove. Since the super-hydrophobic microstructure 3 with extremely strong hydrophobicity is arranged at the fillet where the bipolar plate 1 and the gas diffusion layer 2 are in contact, the liquid does not stick to the fillet here, and the accumulated liquid is prevented from gathering and laterally diffusing here, so that a continuous water phase cannot be formed on the gas diffusion layer 2. The reaction gas can effectively pass through the gas diffusion layer 2 to reach the catalyst surface, thereby realizing the effective transmission of the reaction gas, accelerating the rate of the electrochemical reaction, and improving the working efficiency of the fuel cell and the output power of the battery;

[0054] like Figure 2 As shown, the super-hydrophobic microstructure 3 includes a first area 33 and a second area 34. The first area 33 is arranged on the surface of the bending portion 13 facing the gas diffusion layer 2, and the second area 34 is arranged on the surface of the bending portion 13 close to the gas diffusion layer 2. The first area 33 and the second area 34 form a continuous surface to fully cover the surface of the bending portion 13 facing the gas diffusion layer 2. By arranging the super-hydrophobic microstructure 3 on the surface of the fillet of the connecting portion 11 and the bending portion 13 facing the gas diffusion layer 2, the liquid 4 is prevented from accumulating at the corner where the bipolar plate 1 contacts the surface of the gas diffusion layer 2. The super-hydrophobic microstructure 3 prevents the liquid 4 from infiltrating there, which can effectively prevent the internal resistance of the battery from increasing due to the accumulation of liquid, thereby causing the output voltage of the battery to decrease.

[0055] like Figure 3 As shown, the super-hydrophobic microstructure 3 includes a plurality of grooves 31 arranged in a matrix, and a matrix-distributed terrace 32 is formed between adjacent grooves 31;

[0056] like Figure 4 As shown, the groove width of the groove 31 is 15 μm, and the interval between the grooves 31 is 100 μm.

[0057] The method for preparing the bipolar plate with super-hydrophobic fillets comprises the following specific steps:

[0058] S1, using nanosecond laser to etch a grid-like super-hydrophobic microstructure 3 at two locations near the end of the surface of the bipolar plate 1;

[0059] like Figure 4 As shown, the etching spot size b is 15 μm, and the processing step length a is 100 μm;

[0060] The laser power is 4W and the frequency is 75kHz;

[0061] The thickness of the bipolar plate 1 is 0.1 mm;

[0062] S2, placing the etched bipolar plate 1 in a heat treatment furnace, annealing it in an air atmosphere at 120° C. for 24 hours, and then taking it out;

[0063] S3, bending the annealed bipolar plate 1 at the center of the super-hydrophobic microstructure 3 to form a bent portion 13, and stamping the middle area between two super-hydrophobic microstructures 3 to form a raised portion 12, to obtain a bipolar plate 1 with super-hydrophobic rounded corners.

[0064] like Figure 5 As shown, it can be seen that the super-hydrophobic microstructure 3 in this embodiment has a grid-like microscopic morphology, the processing step length is 100 μm, and the width of the grid depression is 15 μm, which is consistent with the spot size.

[0065] like Figure 6 As shown, by dropping water on the super-hydrophobic microstructure 3 in this embodiment, it can be seen that the contact angles on both sides of the water drop are 155.8° and 155.6° respectively, and the water drop cannot fall off from the end of the needle tube. The surface of the super-hydrophobic microstructure 3 in this embodiment exhibits extremely strong hydrophobicity, which can achieve the effect of not getting wet by dripping water.

[0066] like Figure 7 As shown, the hydrophobic principle of the superhydrophobic microstructure 3 in the present application is that after the metal is exposed to ambient air for nearly a month, carboxylic acids such as formic acid and acetic acid in the air are absorbed, and the non-polar chains containing CC (H) groups will adhere to the outer layer of the surface, thereby reducing the total surface free energy. The laser ablation surface becomes superhydrophobic due to the non-polar organic chains chemically absorbed from the moisture in the air, and low-temperature air annealing or wet heat testing will accelerate this process. Due to the generation of solid-gas composite interfaces, the allocated water droplets cannot fill the grooves, so the surface can be modeled with the Cassie-Baxter state, in which case the rough structure has an amplified effect on the hydrophobicity.

[0067] The method for preparing a bipolar plate with super-hydrophobic fillets in the present application uses a bipolar plate to manufacture a super-hydrophobic microstructure by combining laser etching technology with a heat treatment process. The process is simple, does not involve the use of a hydrophobic modifier, and is environmentally friendly and practical.

[0068] Experimental studies have shown that when an acidic solution, such as a sulfuric acid solution with a pH of 1, is dropped on the super-hydrophobic microstructure 3 in this embodiment, the surface of the super-hydrophobic microstructure 3 does not wet. When an alcohol solvent, such as a 75% ethanol solution, is dropped on the super-hydrophobic microstructure 3 in this embodiment, the ethanol solution completely wets the surface of the super-hydrophobic microstructure 3.

[0069] In this embodiment, the bipolar plate with super-hydrophobic rounded corners is stable under the acidic conditions of the fuel cell. Removing the hydrophobic layer requires cleaning with an alcohol solvent or heating to above 350°C to destroy the surface organic matter. The operating temperature of the proton exchange membrane fuel cell is lower than 100°C, and the working environment does not contain organic matter that can destroy the hydrophobic layer. Therefore, it can be ensured that the super-hydrophobic microstructure 3 is stable under the acidic conditions of the fuel cell.

[0070] Due to the large surface roughness, the simple microstructure itself is hydrophilic or even super hydrophilic, but after air annealing, the surface forms a stable hydrophobicity due to the adsorption of organic matter in the air. This property will only be destroyed by high temperature or organic solvents. The acidic solution simulates the working environment of the fuel cell, which shows that the hydrophobic property of the super hydrophobic microstructure 3 can exist stably in the fuel cell environment.

[0071] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A bipolar plate with super-hydrophobic fillets, characterized in that: The bipolar plate (1) is arranged on a gas diffusion layer (2), and comprises a connecting portion (11), a bulging portion (12) and a bent portion (13); the connecting portion (11) is arranged on both sides of the bipolar plate (1) and is attached to the surface of the gas diffusion layer (2); the bulging portion (12) is arranged between the connecting portions (11) and protrudes in a direction away from the surface of the gas diffusion layer (2); the bent portion (13) is arranged at the connection between the connecting portion (11) and the bulging portion (12); and a grid-like structure is etched on the surface of the bulging portion (13) facing the gas diffusion layer (2) to form a super-hydrophobic microstructure (3).

2. A bipolar plate with super hydrophobic fillets according to claim 1, characterized in that: The super-hydrophobic microstructure (3) comprises a first region (33) and a second region (34); the first region (33) is arranged on a surface of the bent portion (13) facing the gas diffusion layer (2); the second region (34) is arranged on a surface of the bent portion (13) close to the gas diffusion layer (2); the first region (33) and the second region (34) form a continuous surface.

3. The bipolar plate with super hydrophobic fillet according to claim 1, characterized in that: The super-hydrophobic microstructure (3) comprises a plurality of grooves (31) arranged in a matrix, and terraces (32) distributed in a matrix are formed between adjacent grooves (31).

4. The bipolar plate with super hydrophobic fillet according to claim 3, characterized in that: The groove width of the groove (31) is 10-20 μm, and the spacing between the grooves (31) is 50-150 μm.

5. The bipolar plate with super hydrophobic fillet according to claim 1, characterized in that: The space enclosed between the arched portion (12) and the surface of the gas diffusion layer (2) forms a flow channel portion (5), and the flow channel portion (5) includes a flow channel ridge and a flow channel groove. The space enclosed between the two sides of the arched portion (12) and the surface of the gas diffusion layer (2) forms the flow channel ridge, and the space enclosed between the middle of the arched portion (12), the flow channel ridge and the surface of the gas diffusion layer (2) forms the flow channel groove. The super-hydrophobic microstructure (3) is located on the bipolar plate (1) near the contact between the flow channel ridge and the surface of the gas diffusion layer (2).

6. A method for preparing a bipolar plate with super-hydrophobic fillets as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: S1, using a laser to etch a grid-like super-hydrophobic microstructure (3) on the surface of a bipolar plate (1); S2, annealing the etched bipolar plate (1) and then taking it out; S3, bending the annealed bipolar plate (1) at the super-hydrophobic microstructure (3) to form a bent portion (13), and stamping between the super-hydrophobic microstructures (3) to form a raised portion (12), thereby obtaining a bipolar plate with super-hydrophobic rounded corners.

7. The method for preparing a bipolar plate with super-hydrophobic fillets according to claim 6, characterized in that: The etching spot size in step S1 is 10-20 μm, and the processing step length is 50-150 μm.

8. The method for preparing a bipolar plate with super-hydrophobic fillets according to claim 6, characterized in that: In step S1, the power of the laser is 2.5-5.5 W, and the frequency is 45-105 kHz.

9. The method for preparing a bipolar plate with super-hydrophobic fillets according to claim 6, characterized in that: In step S2, annealing is performed in air or water vapor atmosphere at a temperature of 80-150° C. for 12-48 hours.

10. The method for preparing a bipolar plate with super-hydrophobic fillets according to claim 6, characterized in that: In step S1, a laser is used to etch a super-hydrophobic microstructure (3) having a grid structure at two locations near the end of the surface of the bipolar plate (1); In step S3, the annealed bipolar plate (1) is bent at the center of the super-hydrophobic microstructure (3) to form a bent portion (13), and a middle area between two super-hydrophobic microstructures (3) is stamped to form a raised portion (12).

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