A bipolar plate and a fuel cell

Abstract

The application discloses a bipolar plate and a fuel cell. The bipolar plate comprises a first surface and a second surface oppositely arranged along the thickness direction of the bipolar plate. The first surface is provided with a first recessed part which is recessed inward relative to the surface of the first surface. The second surface is provided with a second recessed part which is recessed inward relative to the surface of the second surface. The density of the first recessed part distributed on the first surface is alpha 1, the density of the second recessed part distributed on the second surface is alpha 2, and alpha 1 / alpha 2 satisfies 1 <= alpha 1 / alpha 2 <= 5. The first recessed part and the second recessed part in the application can guide the flow direction of water, so that water can flow inside each flow channel. This is not only beneficial to improve the flow efficiency of water and improve the drainage capacity of the fuel cell, but also beneficial to reduce the possibility of affecting the gas diffusion in the process of water flow, so as to guarantee the reaction efficiency inside the fuel cell, thereby guaranteeing the stability and reliability of the fuel cell in the working process.

Description

Technical Field

[0001] This application relates to the field of fuel cell technology, and in particular to a bipolar plate and a fuel cell. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) consists of stacked bipolar plates and membrane electrode assemblies. During the operation of a PEMFC, hydrogen flows through the anode side of the bipolar plates and oxygen flows through the cathode side of the bipolar plates. The two undergo an electrochemical reaction within the membrane electrode assembly, producing water and heat. The generated water can be discharged through the same flow channel as the oxygen.

[0003] In existing technologies, the generated water is usually discharged from the bipolar plate along with unreacted air (or residual gases in the air, such as nitrogen). However, during the operation of a fuel cell, at least some of the generated water is at risk of remaining inside the bipolar plate, and there is even a risk of reverse osmosis, which can easily affect the performance of the fuel cell. Summary of the Invention

[0004] In view of this, this application provides a bipolar plate and a fuel cell to solve the technical problem that water is easily trapped inside the bipolar plate in the prior art.

[0005] This application provides a bipolar plate, which includes a first surface and a second surface disposed opposite to each other along a first direction. The first surface is provided with a first recessed portion, which is recessed inward relative to the surface of the first surface. The second surface is provided with a second recessed portion, which is recessed inward relative to the surface of the second surface.

[0006] The density of the first recess on the first surface is α1, and the density of the second recess on the second surface is α2, and α1 / α2 satisfies 1≤α1 / α2≤5.

[0007] In one possible implementation, both the first and second surfaces are provided with a flow field area, an inlet area, and an outlet area. The inlet area and the outlet area are distributed on both sides of the flow field area along the second direction and are connected through a flow channel within the flow field area. The first recess and the second recess are respectively provided within the flow field areas of the first and second surfaces.

[0008] In one possible implementation, the flow field region includes multiple ribs spaced apart along a third direction, with flow channels formed between adjacent ribs.

[0009] Along the first direction, the flow field region includes a first hydrophobic region and a first hydrophilic region. The first hydrophobic region is located on the top wall of the rib, and the first hydrophilic region is located on the bottom wall of the flow channel.

[0010] Each recess is provided on the top wall of the rib and the bottom wall of the flow channel. The density of the recess in the first hydrophobic region is β1, and the density of the recess in the first hydrophilic region is β2, and β1 and β2 satisfy β1<β2.

[0011] In one possible implementation, along the first direction, the flow field region further includes a first transition region disposed on the sidewall of the flow channel.

[0012] The density of the recess in the first transition region is β3, and β1, β2 and β3 satisfy β1<β3, β3<β2.

[0013] In one possible implementation, along the first direction, within the first transition zone, the density of the recess gradually increases.

[0014] In one possible implementation, β1 also satisfies 10%≤β1≤30%, β2 also satisfies 65%≤β2≤90%, and β3 also satisfies 35%≤β3≤60%.

[0015] In one possible implementation, along the fourth direction, the flow field region includes a second hydrophobic region and a second hydrophilic region, with the second hydrophobic region located at one end of the flow field region near the inlet region and the second hydrophilic region located at one end of the flow field region near the outlet region.

[0016] Each recess is provided on the side wall and bottom wall of the flow channel. The density of the recess in the second hydrophobic zone is γ1, and the density of the recess in the second hydrophilic zone is γ2. γ1 and γ2 satisfy γ1 < γ2.

[0017] In one possible implementation, along the fourth direction, the flow field region further includes a second transition region located between the second hydrophobic region and the second hydrophilic region.

[0018] The density of the recess in the second transition region is γ3, and γ1, γ2 and γ3 satisfy γ1<γ3, γ3<γ2.

[0019] In one possible implementation, along the fourth direction, the density of the depression gradually increases in at least one of the second hydrophobic region, the second transition region, and the second hydrophilic region.

[0020] In one possible implementation, γ1 also satisfies 5%≤γ1≤35%, γ2 also satisfies 70%≤γ2≤90%, and γ3 also satisfies 40%≤γ3≤65%.

[0021] In one possible implementation, the flow field region includes multiple ribs spaced apart along a third direction, with flow channels formed between adjacent ribs.

[0022] The flow field region also includes a first hydrophobic region, a first hydrophilic region, a second hydrophobic region, and a second hydrophilic region. Along the fourth direction, the second hydrophobic region is located at one end of the flow field region near the inlet region, and the second hydrophilic region is located at one end of the flow field region near the outlet region. Along the first direction, the first hydrophobic region is located on the top wall of the rib, and the first hydrophilic region is located on the bottom wall of the flow channel.

[0023] Each recess is provided on the top wall of the rib and the side and bottom walls of the flow channel. Along the first direction, the density of the recess in the first hydrophobic region is β1, and the density of the recess in the first hydrophilic region is β2, and β1 and β2 satisfy β1 < β2. Along the fourth direction, the density of the recess in the second hydrophobic region is γ1, and the density of the recess in the second hydrophilic region is γ2, and γ1 and γ2 satisfy γ1 < γ2.

[0024] In one possible implementation, the flow field region further includes a first transition region and a second transition region, the first transition region being disposed on the sidewall of the flow channel, and the second transition region being located between the second hydrophobic region and the second hydrophilic region.

[0025] The density of the recess in the first transition region is β3, and β1, β2 and β3 satisfy β1<β3, β3<β2. The density of the recess in the second transition region is γ3, and γ1, γ2 and γ3 satisfy γ1<γ3, γ3<γ2.

[0026] In one possible implementation, when the first recess and the second recess are respectively disposed on the bottom wall of the flow channel of the first surface and the second surface, the projections of the first recess and the second recess are misaligned along the first direction.

[0027] In one possible implementation, the diameter of the first recess is D1, and D1 satisfies 5μm≤D1≤20μm, and / or the depth of the first recess is H1, and H1 satisfies 3μm≤H1≤10μm.

[0028] The diameter of the second recess is D2, and D2 satisfies 5μm≤D2≤20μm, and / or the depth of the second recess is H2, and H2 satisfies 3μm≤H2≤10μm.

[0029] In one possible implementation, along the first direction, the cross-sectional shape of the first recess and the second recess is one or more of trapezoidal, rectangular, triangular and semi-circular.

[0030] This application also provides a fuel cell, which includes bipolar plates and a membrane electrode assembly, wherein the membrane electrode assembly and the bipolar plates are stacked along a first direction.

[0031] Wherein, the bipolar plate is any of the bipolar plates described above.

[0032] The beneficial effects of this application are as follows: the bipolar plate can promote water flow towards the interior of each flow channel through the first and second recesses on its surface, thereby ensuring appropriate wettability of the membrane electrode assembly while reducing the possibility of water stagnation and blockage. This improves the stability and smoothness of fluid flow inside the fuel cell, and consequently, enhances the fuel cell's operating efficiency. Simultaneously, by designing a gradual distribution density of the first and second recesses, sequentially connected hydrophobic, transition, and hydrophilic regions can be formed. This allows the water distribution inside the fuel cell to exhibit a gradient structure along the direction from the hydrophobic to the hydrophilic region, enabling water to flow towards the hydrophilic region under capillary action for drainage. This reduces the possibility of flooding or even reverse osmosis inside the fuel cell, improving the stability and reliability of the fuel cell during operation.

[0033] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A top view of the bipolar plate provided in this application in one embodiment;

[0036] Figure 2 for Figure 1 A partial sectional view;

[0037] Figure 3 for Figure 2 The front view.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1-First page;

[0040] 11-First flow field;

[0041] 111 - First protruding rib;

[0042] 112 - First flow channel;

[0043] 113 - First recessed portion;

[0044] 12-First Import;

[0045] 13-First Exit;

[0046] 2-Second page;

[0047] 21-Second flow field;

[0048] 211 - Second rib;

[0049] 212 - Second flow channel;

[0050] 213 - Second recessed portion;

[0051] 22-Second Import;

[0052] 23-Second Exit;

[0053] 3-First hydrophobic zone;

[0054] 4-First waterfront area;

[0055] 5-First transition zone;

[0056] 6-Second hydrophobic zone;

[0057] 7-Second waterfront area;

[0058] 8-Second transition zone;

[0059] 9-Membrane electrode assembly.

[0060] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0061] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0063] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0064] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0065] Embodiments of this application provide a bipolar plate, such as Figure 1 , Figure 2 and Figure 3 As shown, the bipolar plate includes a first surface 1 and a second surface 2 disposed opposite to each other along a first direction x. The first surface 1 is provided with a first recess 113, which is recessed inward relative to the surface of the first surface 1. The second surface 2 is provided with a second recess 213, which is recessed inward relative to the surface of the second surface 2.

[0066] The density of the first recess 113 on the first surface 1 is α1, and the density of the second recess 213 on the second surface 2 is α2, and α1 / α2 satisfies 1≤α1 / α2≤5.

[0067] It should be noted that the bipolar plate in this embodiment can be used in a fuel cell, and in the fuel cell, the bipolar plate and the membrane electrode assembly 9 can be stacked along the first direction x so that the first surface 1 of the bipolar plate can serve as the cathode surface for air circulation, and the second surface 2 of the bipolar plate can serve as the anode surface for hydrogen circulation.

[0068] The membrane electrode assembly 9 may include a proton exchange membrane, a catalyst layer and a gas diffusion layer stacked together. Along the first direction x, the catalyst layer is connected to both sides of the proton exchange membrane, and the gas diffusion layer is connected to the side of the two catalyst layers opposite to the proton exchange membrane.

[0069] Meanwhile, in this embodiment, the thickness direction of the bipolar plate can be defined as the first direction x, the length direction of the bipolar plate can be defined as the second direction y, the width direction of the bipolar plate can be defined as the third direction z, and the flow direction of the fluid (including liquid and gas) can be defined as the fourth direction v.

[0070] During fuel cell operation, air and hydrogen flow through the first surface 1 and the second surface 2 of the bipolar plate, respectively. Under the action of a catalyst, they undergo a redox reaction, producing water on the first surface 1. This water is typically discharged from the bipolar plate along with unreacted air (or residual gases in the air, such as nitrogen). However, during fuel cell operation, some of the water may remain on the first surface 1 or even seep back into the second surface 2, potentially affecting the fuel cell's performance.

[0071] To address the aforementioned issues, embodiments of this application provide a first recess 113 and a second recess 213 on the first surface 1 and the second surface 2, respectively. The first recess 113 guides water generated on the first surface 1, while the second recess 213 guides water that has reversed its permeation to the second surface 2. This improves the drainage capacity of each surface of the bipolar plate, reducing the possibility of water blocking gas transport on the first and second surfaces 1 and 2, thereby ensuring the reaction efficiency inside the fuel cell and guaranteeing the stability and reliability of the fuel cell during operation. Furthermore, by limiting the distribution density ratio of the first recess 113 and the second recess 213, differentiated water treatment can be achieved on each surface of the bipolar plate to meet the different water requirements of the first and second surfaces 1 and 2, thus facilitating refined water management of the bipolar plate.

[0072] Optionally, α1 / α2 can be any other value within the range mentioned above, such as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, etc.

[0073] Specifically, by limiting α1 / α2 to satisfy α1 / α2≥1, the distribution density of the first recess 113 on the first surface 1 is equal to the distribution density of the second recess 213 on the second surface 2, or the distribution density of the first recess 113 on the first surface 1 is greater than the distribution density of the second recess 213 on the second surface 2. This design further enhances the drainage capacity of the first surface 1, which already possesses drainage capabilities on both the first and second surfaces 1. This reduces the possibility of flooding caused by a large amount of newly generated water accumulating on the first surface 1, thus avoiding the risk of water clogging the gas diffusion layer and reducing airflow efficiency. Consequently, it prioritizes ensuring the stability and smoothness of airflow on the first surface 1. Furthermore, by strengthening the drainage capacity of the first surface 1, it also reduces the possibility of water backflow into the second surface 2, thereby avoiding the risk of water clogging the gas diffusion layer and reducing hydrogen flow efficiency. This further ensures the stability and smoothness of hydrogen flow on the second surface 2.

[0074] Meanwhile, by limiting α1 / α2 to ≤ 5, the distribution density of the first recess 113 on the first surface 1 and the distribution density of the second recess 213 on the second surface 2 are moderately different. This design limits the drainage capacity of the first surface 1, preventing the risk of water being discharged before effectively wetting the membrane electrode assembly 9 due to excessive drainage capacity. This reduces the likelihood of the membrane electrode assembly 9 drying out and its performance deteriorating. Furthermore, it achieves a better balance between enhancing the drainage capacity of the first surface 1 and maintaining the wettability of the membrane electrode assembly 9, enabling rapid drainage while maintaining its own wettability. This improves the precision control of water management within the fuel cell.

[0075] In addition, by processing the first recess 113 and the second recess 213 on the surface of the bipolar plate, fine control of water management inside the fuel cell can be achieved, thus eliminating the need to coat the first surface 1 and / or the second surface 2 to improve the hydrophilic or hydrophobic properties of the bipolar plate surface. This can reduce the production cost of the bipolar plate and the fuel cell while extending their service life, which is more in line with actual production needs.

[0076] In summary, by providing the first recess 113 and the second recess 213, this embodiment ensures that both the first surface 1 and the second surface 2 of the bipolar plate have good drainage capabilities.

[0077] The first recess 113 guides the generated water, promoting its flow efficiency on the first surface 1 and reducing the possibility of water stagnation and flooding. This reduces the likelihood of water backflow onto the second surface 2, thereby improving air flow efficiency on the first surface 1. Simultaneously, the second recess 213 guides water that accidentally seeps into the second surface 2, promoting its flow efficiency and reducing the possibility of water stagnation and blockage. This improves hydrogen flow efficiency on the second surface 2, enhancing the internal reaction efficiency and overall performance of the fuel cell. Furthermore, by limiting the distribution density ratio of the first and second recesses 113, the bipolar plate can achieve rapid drainage while maintaining appropriate wettability in the membrane electrode assembly 9, ensuring proton transport efficiency and improving the stability and reliability of the membrane electrode assembly 9 during operation.

[0078] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3As shown, both the first surface 1 and the second surface 2 are provided with a flow field area, an inlet area and an outlet area. The inlet area and the outlet area are distributed on both sides of the flow field area along the second direction y and are connected through the flow channel in the flow field area. The first recess 113 and the second recess 213 are respectively provided in the flow field areas of the first surface 1 and the second surface 2.

[0079] In this embodiment of the application, the flow field region may include a first flow field 11 and a second flow field 21, the inlet region may include a first inlet 12 and a second inlet 22, the outlet region may include a first outlet 13 and a second outlet 23, and the flow channel may include a first flow channel 112 and a second flow channel 212.

[0080] A first flow field 11, a first inlet 12, and a first outlet 13 are provided on the first surface 1 of the bipolar plate. The first inlet 12 and the first outlet 13 are distributed on both sides of the first flow field 11 along the second direction y and are connected through the first flow channel 112 in the first flow field 11.

[0081] The first flow field 11 is the cathode flow field. During the operation of the fuel cell, air first flows into the first flow field 11 from the first inlet 12, then flows along the extension direction of the first flow channel 112, and participates in the oxidation-reduction reaction during the flow. Finally, air and water flow out of the first flow field 11 from the first outlet 13.

[0082] A second flow field 21, a second inlet 22, and a second outlet 23 are provided on the second surface 2 of the bipolar plate. The second inlet 22 and the second outlet 23 are distributed on both sides of the second flow field 21 along the second direction y and are connected through the second flow channel 212 in the second flow field 21.

[0083] The second flow field 21 is the anode flow field. During the operation of the fuel cell, hydrogen first flows into the second flow field 21 from the second inlet 22, and then flows along the extension direction of the second flow channel 212. During the flow, it participates in the oxidation-reduction reaction. Finally, hydrogen and water flow out of the second flow field 21 from the second outlet 23.

[0084] In this embodiment, by concentrating the first recess 113 and the second recess 213 in the first flow field 11 and the second flow field 21 respectively, the water can be directly guided, which is beneficial to promoting the flow efficiency of water in the first flow channel 112 and the second flow channel 212, so as to maximize the drainage effect and thus ensure the stability and reliability of the fuel cell during operation.

[0085] Optionally, on the bipolar plates, the first inlet 12 and the first outlet 13 can be diagonally distributed relative to the first flow field 11. This design helps to extend the airflow path within the first flow field 11, allowing for sufficient air diffusion and improving the uniformity of air distribution within the first flow field 11. This, in turn, increases the proportion of air participating in the reaction, thereby improving the performance of the fuel cell.

[0086] Optionally, on the bipolar plate, the second inlet 22 and the second outlet 23 can be diagonally distributed relative to the second flow field 21. This design helps to extend the flow path of hydrogen in the second flow field 21, allowing for sufficient hydrogen diffusion and improving the uniformity of hydrogen distribution within the second flow field 21. This, in turn, increases the proportion of hydrogen participating in the reaction, thereby improving the performance of the fuel cell.

[0087] Optionally, on the bipolar plate, along the third direction z, the first inlet 12 and the second outlet 23 are arranged adjacent to each other, and the second inlet 22 and the first outlet 13 are arranged adjacent to each other. This design ensures that the airflow direction is opposite to the hydrogen flow direction, which helps improve the reaction efficiency inside the fuel cell, thereby enhancing the fuel cell's performance.

[0088] Optionally, the first flow channel 112 and the second flow channel 212 extend in a straight line. This design reduces the flow resistance of air, hydrogen, and water during the flow process, improves flow efficiency, facilitates further optimization of the bipolar plate's exhaust and drainage capabilities, and also enhances the internal reaction efficiency of the fuel cell, thereby improving the fuel cell's performance.

[0089] Optionally, the first flow channel 112 and the second flow channel 212 extend in a curved manner. This design allows for the separation of air and water, and hydrogen and water, through the shear forces and local pressure changes generated at the bends or turns of each flow channel. This ensures the stability and smoothness of the gas and water flow. Furthermore, the bends or turns of each flow channel can introduce disturbances, further enhancing the drainage capacity of the bipolar plates and thus improving the performance of the fuel cell.

[0090] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, the flow field region includes multiple ribs spaced at intervals along the third direction z, and flow channels are formed between adjacent ribs.

[0091] Along the first direction x, the flow field region includes a first hydrophobic region 3 and a first hydrophilic region 4. The first hydrophobic region 3 is located on the top wall of the rib, and the first hydrophilic region 4 is located on the bottom wall of the flow channel.

[0092] Each recess is provided on the top wall of the rib and the bottom wall of the flow channel. The density of the recess in the first hydrophobic zone 3 is β1, and the density of the recess in the first hydrophilic zone 4 is β2, and β1 and β2 satisfy β1<β2.

[0093] In this embodiment of the application, the rib may include a first rib 111 and a second rib 211.

[0094] On the first surface 1 of the bipolar plate, the first flow field 11 includes a plurality of first ribs 111 spaced apart along the third direction z, and a first flow channel 112 is formed between adjacent first ribs 111 so that the first ribs 111 and the first flow channel 112 share the same sidewall.

[0095] In the process of stacking bipolar plates and membrane electrode assembly 9 along the first direction x, the top wall of the first rib 111 can abut against the membrane electrode assembly 9 to provide support, which is beneficial to improving the overall structural stability of the fuel cell.

[0096] Meanwhile, the top wall of the first rib 111 and the bottom wall of the first flow channel 112 are both provided with a first recess 113. The distribution density of the first recess 113 on the top wall of the first rib 111 can be β1, and the distribution density of the first recess 113 on the bottom wall of the first flow channel 112 can be β2, and β1 and β2 satisfy β1 < β2.

[0097] This design allows the distribution density of the first recess 113 on the bottom wall of the first flow channel 112 to be greater than its distribution density on the top wall of the first rib 111. This enables the top wall of the first rib 111 to serve as the first hydrophobic region 3, and the bottom wall of the first flow channel 112 to serve as the first hydrophilic region 4. Furthermore, the distribution density of the first recess 113 increases along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, forming a gradient structure that varies along the first direction x on the first surface 1 of the bipolar plate. This allows water to flow and diffuse from the membrane electrode assembly 9 towards the interior of the first flow channel 112 under capillary action, and to flow out of the bipolar plate under the guidance of the first flow channel 112. This improves the flow efficiency of water within the first flow channel 112, thereby enhancing the drainage capacity of the bipolar plate.

[0098] In addition, by setting a gradient change in the distribution density of the first recess 113 from the first hydrophobic region 3 to the first hydrophilic region 4, the possibility of water back-permeating to the second surface 2 of the bipolar plate can be reduced by using capillary force, which is conducive to further improving the working efficiency of the fuel cell.

[0099] On the second surface 2 of the bipolar plate, the second flow field 21 includes a plurality of second ribs 211 distributed at intervals along the third direction z, and a second flow channel 212 is formed between adjacent second ribs 211 so that the second ribs 211 and the second flow channel 212 share the same sidewall.

[0100] In the process of stacking bipolar plates and membrane electrode assembly 9 along the first direction x, the top wall of the second rib 211 can abut against the membrane electrode assembly 9 to provide support, and can reinforce the membrane electrode assembly 9 with the first rib 111 of the adjacent bipolar plate, which is beneficial to improving the overall structural stability of the fuel cell.

[0101] Meanwhile, the top wall of the second rib 211 and the bottom wall of the second flow channel 212 are both provided with a second recess 213. The distribution density of the second recess 213 on the top wall of the second rib 211 can also be β1, and the distribution density of the second recess 213 on the bottom wall of the second flow channel 212 can also be β2, and β1 and β2 satisfy β1 < β2.

[0102] This design allows the distribution density of the second recess 213 on the bottom wall of the second flow channel 212 to be greater than its distribution density on the top wall of the second rib 211. This enables the top wall of the second rib 211 to serve as the first hydrophobic region 3, and the bottom wall of the second flow channel 212 to serve as the first hydrophilic region 4. Furthermore, the distribution density of the second recess 213 increases along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, forming a gradient structure along the first direction x on the second surface 2 of the bipolar plate. This allows water that has reversed its permeation to the second surface 2 to flow and diffuse from the membrane electrode assembly 9 toward the interior of the second flow channel 212 under capillary action, and to flow out of the bipolar plate under the guidance of the second flow channel 212. This improves the flow efficiency of water within the second flow channel 212, thereby enhancing the drainage capacity of the bipolar plate.

[0103] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the first direction x, the flow field region also includes a first transition region 5, which is disposed on the side wall of the flow channel.

[0104] The density of the recessed portion in the first transition region 5 is β3, and β1, β2 and β3 satisfy β1<β3, β3<β2.

[0105] In this embodiment of the application, the first recess 113 may also be disposed on the side wall of the first flow channel 112, and the second recess 213 may also be disposed on the side wall of the second flow channel 212.

[0106] On the first surface 1 of the bipolar plate, along the first direction x, the sidewall of the first flow channel 112 is simultaneously connected to the top wall of the first rib 111 and the bottom wall of the first flow channel 112. The distribution density of the first recess 113 in the first transition zone 5 is β3, and β1, β2 and β3 satisfy β1<β3, β3<β2.

[0107] With this design, the distribution density of the first recess 113 on the side wall of the first flow channel 112 is greater than that on the top wall of the first rib 111 and less than that on the bottom wall of the first flow channel 112, so that the side wall of the first flow channel 112 can serve as the first transition zone 5. That is, along the first direction x, one end of the first transition zone 5 is connected to the first hydrophobic zone 3, and the other end of the first transition zone 5 is connected to the first hydrophilic zone 4.

[0108] Along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, the first transition region 5 can further refine the variation trend of the distribution density of the first recess 113, so as to form a more detailed gradient structure on the first surface 1 of the bipolar plate, which is conducive to further improving the flow effect of water under capillary action, thereby improving the flow efficiency and diffusion efficiency of water in the first flow channel 112, and thus improving the drainage capacity of the bipolar plate.

[0109] On the second surface 2 of the bipolar plate, along the first direction x, the sidewall of the second flow channel 212 is simultaneously connected to the top wall of the second rib 211 and the bottom wall of the second flow channel 212. The distribution density of the second recess 213 in the first transition zone 5 is β3, and β1, β2 and β3 satisfy β1<β3, β3<β2.

[0110] With this design, the distribution density of the second recess 213 on the side wall of the second flow channel 212 is greater than that on the top wall of the second rib 211 and less than that on the bottom wall of the second flow channel 212, so that the side wall of the second flow channel 212 can serve as the first transition zone 5. That is, along the first direction x, one end of the first transition zone 5 is connected to the first hydrophobic zone 3, and the other end of the first transition zone 5 is connected to the first hydrophilic zone 4.

[0111] Along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, the first transition region 5 can further refine the variation trend of the distribution density of the second recess 213, so as to form a more detailed gradient structure on the second surface 2 of the bipolar plate, which is conducive to further improving the flow effect of water under capillary action, thereby improving the flow efficiency and diffusion efficiency of water in the second flow channel 212, and thus improving the drainage capacity of the bipolar plate.

[0112] Therefore, along the first direction x, the distribution density of the recess in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 gradually increases, so that the whole presents a gradient structure from hydrophobic to hydrophilic. This allows the construction of a flow path that guides water from the membrane electrode assembly 9 to the top wall of the rib, then to the side wall of the flow channel, and finally to the bottom wall of the flow channel. This improves the water distribution near the membrane electrode assembly 9, enhances the stability and smoothness of water during the flow diffusion process, and reduces the possibility of water stagnation in any area, which is beneficial to improving the stability and reliability of the fuel cell during operation.

[0113] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the first direction x, within the first transition zone 5, the density of the recess gradually increases.

[0114] In this embodiment, along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, the distribution density of the recessed portion in the first transition region 5 can gradually increase. This can further optimize the gradient structure of the distribution density of the recessed portion in the first transition region 5, so as to guide water to flow from the end of the first transition region 5 near the first hydrophobic region 3 to the end near the first hydrophilic region 4 by utilizing the difference in capillary force. This can reduce the possibility of water stagnation in the first transition region 5 and cause flooding, thereby improving the flow efficiency of water in the first transition region 5. This enables water to flow rapidly from the membrane electrode assembly 9 to the interior of the flow channel, which is beneficial to improving the water distribution near the membrane electrode assembly 9, improving the drainage capacity of the bipolar plate, and improving the stability and reliability of the fuel cell during operation.

[0115] At the same time, the gradual design can also improve the stability and smoothness of water flowing in the first direction x within the first transition zone 5, which is conducive to further improving the flow efficiency of water.

[0116] In one specific implementation, β1 also satisfies 10%≤β1≤30%, and β1 can be any other value within the above range, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%.

[0117] When the distribution density of the recesses in the first hydrophobic region 3 satisfies 10%≤β1≤30%, the proportion of recesses in the first hydrophobic region 3 is relatively small. A smaller number of recesses is sufficient to generate capillary action, guiding water in the membrane electrode assembly 9 towards the interior of the flow channel. This avoids the risk of water stagnation in the gas diffusion layer causing blockage, thus ensuring the stability and smoothness of gas flow. Simultaneously, it also ensures a large contact area between the first hydrophobic region 3 and the membrane electrode assembly 9, guaranteeing low contact resistance and ensuring the stability and reliability of electron transport. This, in turn, improves the drainage capacity while ensuring good electrical performance of the fuel cell.

[0118] In one specific implementation, β2 also satisfies 65%≤β2≤90%, and β2 can specifically be other values ​​within the above range such as 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%.

[0119] When the distribution density of the recesses in the first hydrophilic region 4 is 65%≤β2≤90%, the proportion of the recesses in the first hydrophilic region 4 is relatively large. A large number of recesses can maximize the water collection capacity of the flow channel, which can not only reduce the possibility of water blocking the gas diffusion layer, but also achieve preliminary gas-liquid separation, thereby reducing the flow resistance of the fluid in the flow channel and improving the flow efficiency of the fluid.

[0120] In one specific implementation, β3 also satisfies 35%≤β3≤60%, and β3 can be any other value within the above range, such as 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%.

[0121] When the distribution density of the recessed portion in the first transition zone 5 satisfies 35%≤β3≤60%, the proportion of the recessed portion in the first transition zone 5 is relatively moderate, so that the first transition zone 5 can connect the first hydrophobic region 3 and the first hydrophilic region 4 to form a more refined gradient structure. This allows the use of capillary action to construct a flow path that guides water from the membrane electrode assembly 9 to the top wall of the rib, then to the side wall of the flow channel, and finally to the bottom wall of the flow channel. This improves the stability and smoothness of water flowing along the first direction x and ensures the stability and smoothness of gas flowing along the fourth direction v.

[0122] Therefore, by limiting the density of each recessed portion in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 to different extents, and by making the overall structure present a gradient design, it is possible to improve the fine control of water management inside the fuel cell while ensuring its electrical performance. This can optimize the water distribution state inside the fuel cell, which is beneficial to improving the stability and smoothness of gas and liquid flow, and thus improving the stability and reliability of the fuel cell during operation.

[0123] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the fourth direction v, the flow field region includes a second hydrophobic region 6 and a second hydrophilic region 7. The second hydrophobic region 6 is located at one end of the flow field region near the inlet region, and the second hydrophilic region 7 is located at one end of the flow field region near the outlet region.

[0124] Each recess is provided on the side wall and bottom wall of the flow channel. The density of the recess in the second hydrophobic zone 6 is γ1, and the density of the recess in the second hydrophilic zone 7 is γ2. γ1 and γ2 satisfy γ1 < γ2.

[0125] In this embodiment, the fourth direction v can be the direction in which air flows from the first inlet 12 along the first flow channel 112 to the first outlet 13, or it can be the direction in which hydrogen flows from the second inlet 22 along the second flow channel 212 to the second outlet 23.

[0126] On the first surface 1 of the bipolar plate, the first flow field 11 further includes a second hydrophobic region 6 and a second hydrophilic region 7. Along the second direction y, the second hydrophobic region 6 is located at the end of the first flow field 11 near the first inlet 12, and the second hydrophilic region 7 is located at the end of the first flow field 11 near the first outlet 13. The first flow field 11 also includes a plurality of first flow channels 112 extending along the second direction y and spaced apart along the third direction z to connect the first inlet 12 and the first outlet 13 for the circulation of air and water.

[0127] The first recess 113 is disposed on the side wall and bottom wall of the first flow channel 112. The density of the first recess 113 in the second hydrophobic region 6 is γ1, and the density in the second hydrophilic region 7 is γ2, and γ1 and γ2 satisfy γ1 < γ2.

[0128] With this design, the distribution density of the first recess 113 at the outlet end of the first flow channel 112 is greater than its distribution density at the inlet end of the first flow channel 112, so that the inlet end of the first flow channel 112 can serve as the second hydrophobic zone 6 and the outlet end of the first flow channel 112 can serve as the second hydrophilic zone 7.

[0129] Furthermore, along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, the distribution density of the first recess 113 tends to increase, so as to form a gradient structure that varies along the fourth direction v on the first surface 1 of the bipolar plate. This allows water in the first flow channel 112 to flow from the inlet end of the first flow channel 112 to the outlet end of the first flow channel 112 under capillary action, and to flow out of the bipolar plate under the guidance of the first flow channel 112. This is beneficial to improving the flow efficiency of water in the first flow channel 112, thereby improving the drainage capacity of the bipolar plate.

[0130] In addition, by setting a gradient change in the distribution density of the first recess 113 from the second hydrophobic region 6 to the second hydrophilic region 7, it is possible to improve the flow efficiency of air and water during the flow process, thereby further improving the working efficiency of the fuel cell.

[0131] On the second surface 2 of the bipolar plate, the second flow field 21 also includes a second hydrophobic region 6 and a second hydrophilic region 7. Along the second direction y, the second hydrophobic region 6 is located at the end of the second flow field 21 near the second inlet 22, and the second hydrophilic region 7 is located at the end of the second flow field 21 near the second outlet 23. The second flow field 21 also includes a plurality of second flow channels 212 extending along the second direction y and spaced apart along the third direction z to connect the second inlet 22 and the second outlet 23 for the flow of hydrogen and water.

[0132] The second recess 213 is disposed on the side wall and bottom wall of the second flow channel 212. The density of the second recess 213 in the second hydrophobic region 6 is γ1, and the density in the second hydrophilic region 7 is γ2, and γ1 and γ2 satisfy γ1 < γ2.

[0133] With this design, the distribution density of the second recess 213 at the outlet end of the second flow channel 212 is greater than that at the inlet end of the second flow channel 212, so that the inlet end of the second flow channel 212 can serve as the second hydrophobic zone 6 and the outlet end of the second flow channel 212 can serve as the second hydrophilic zone 7.

[0134] Furthermore, along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, the distribution density of the second recess 213 tends to increase, so as to form a gradient structure that varies along the fourth direction v on the second surface 2 of the bipolar plate. This allows water in the second flow channel 212 to flow from the inlet end of the second flow channel 212 to the outlet end of the second flow channel 212 under capillary action, and to flow out of the bipolar plate under the guidance of the second flow channel 212. This is beneficial to improving the flow efficiency of water in the second flow channel 212, thereby improving the drainage capacity of the bipolar plate.

[0135] In addition, by setting a gradient change in the distribution density of the second recess 213 from the second hydrophobic region 6 to the second hydrophilic region 7, it is possible to improve the flow efficiency of hydrogen and water during the flow process, thereby further improving the working efficiency of the fuel cell.

[0136] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the fourth direction v, the flow field region also includes a second transition region 8, which is located between the second hydrophobic region 6 and the second hydrophilic region 7.

[0137] The density of the recess in the second transition region 8 is γ3, and γ1, γ2 and γ3 satisfy γ1<γ3, γ3<γ2.

[0138] In this embodiment, along the fourth direction v, the distribution density of the recessed portion on the second transition region 8 is greater than that on the second hydrophobic region 6 and less than that on the second hydrophilic region 7. Along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, the second transition region 8 can further refine the variation trend of the distribution density of the first recessed portion 113 and the second recessed portion 213, so as to form a more detailed gradient structure on the first surface 1 and the second surface 2 of the bipolar plate, which is beneficial to further improve the flow effect of water in the first flow channel 112 and the second flow channel 212, thereby improving the flow efficiency and diffusion efficiency of water in each flow channel, and thus improving the drainage capacity of the bipolar plate.

[0139] Therefore, along the fourth direction v, the distribution density of the recess in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 gradually increases, so that the whole presents a gradient structure from hydrophobic to hydrophilic. This enables the construction of a flow path that guides water from the inlet end to the outlet end of each channel, thereby improving the water distribution in each channel, enhancing the stability and smoothness of water during the flow diffusion process, and reducing the possibility of water stagnation in any region. This is beneficial to improving the stability and reliability of the fuel cell during operation.

[0140] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the fourth direction v, the density of the depression gradually increases in at least one of the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7.

[0141] In this embodiment, along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, the distribution density of the recessed portion in the second transition region 8 can gradually increase, so that each flow channel presents a gradient structure from hydrophobic to hydrophilic. This can improve the water capture capacity of the inlet end of each flow channel, so as to ensure the wettability inside the flow channel, which is beneficial to promoting the proton transport efficiency. It can also improve the water discharge capacity of the outlet end of each flow channel, so as to reduce the possibility of water adhering inside the flow channel. This can promote the flow of water along the fourth direction v, which is beneficial to reducing the possibility of local flooding in each flow channel, thereby improving the drainage capacity of the bipolar plate and improving the working efficiency of the fuel cell.

[0142] At the same time, the gradual design can also improve the stability and smoothness of gas and water flowing in the fourth direction v in each channel, which is conducive to further improving the flow efficiency of the fluid.

[0143] In one specific implementation, γ1 also satisfies 5%≤γ1≤35%, and γ1 can specifically be other values ​​within the above range such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%.

[0144] When the distribution density of the recesses in the second hydrophobic region 6 meets the condition 5%≤γ1≤35%, the proportion of recesses in the second hydrophobic region 6 is relatively small. This reduces the flow resistance of the gas in the second hydrophobic region 6, allowing the gas to flow smoothly towards the interior of the flow field region. This is beneficial for improving the uniformity of gas distribution within the flow field region, thereby improving the uniformity of the reaction region. Simultaneously, fewer recesses can also capture some of the generated liquid, which is used to wet the membrane electrode assembly 9, ensuring that the membrane electrode assembly 9 is in a suitable working state. Furthermore, it avoids the risk of generated liquid stagnating at the inlet end of the flow channel, which helps to ensure the working efficiency of the fuel cell.

[0145] In one specific implementation, γ2 also satisfies 70%≤γ2≤90%, and γ2 can be any other value within the above range, such as 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%.

[0146] When the distribution density of the recesses in the second hydrophilic region 7 meets the condition of 70%≤γ2≤90%, the proportion of the recesses in the second hydrophilic region 7 is relatively large. A large number of recesses can enable the second hydrophilic region 7 to have a strong ability to capture liquid, thereby reducing the possibility of liquid backflow. This can ensure the stability and smoothness of liquid flow in the flow channel, and further promote the discharge of liquid, thereby improving the drainage capacity of the bipolar plate.

[0147] In one specific implementation, γ3 also satisfies 40%≤γ3≤65%, and γ3 can specifically be other values ​​within the above range, such as 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%.

[0148] When the distribution density of the recesses in the second transition zone 8 satisfies 40%≤γ3≤65%, the proportion of the recesses in the second transition zone 8 is relatively moderate, so that the second transition zone 8 can connect the second hydrophobic zone 6 and the second hydrophilic zone 7 to form a more refined gradient structure. This allows the use of capillary action to construct a flow path that guides water from the inlet end of each flow channel to the outlet end of each flow channel, thereby improving the stability and smoothness of water flowing along the fourth direction v and ensuring the stability and smoothness of gas flowing along the fourth direction v.

[0149] Therefore, by limiting the density of each recessed portion in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 to a different extent, and by making the overall structure present a gradient design, it is possible to improve the fine control of water management inside the fuel cell while ensuring its electrical performance. This can optimize the water distribution state inside the fuel cell, which is beneficial to improving the stability and smoothness of gas and liquid flow, and thus improving the stability and reliability of the fuel cell during operation.

[0150] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, the flow field region includes the first hydrophobic region 3, the first hydrophilic region 4, the second hydrophobic region 6, and the second hydrophilic region 7 mentioned above.

[0151] In this embodiment of the application, along the first direction x, the first hydrophobic region 3 is disposed on the top wall of the rib of each flow field region, the first hydrophilic region 4 is disposed on the bottom wall of the flow channel of each flow field region, and along the fourth direction v, the second hydrophobic region 6 is disposed at one end of each flow field region near the inlet region, and the second hydrophilic region 7 is disposed at one end of each flow field region near the outlet region.

[0152] This design allows both the first surface 1 and the second surface 2 of the bipolar plate to have a gradient structure along the first direction x, as well as a gradient structure along the fourth direction v. These two different gradient structures simultaneously guide the water flow, enabling water to flow towards both the bottom walls of each channel and the outlet area. This improves the water distribution within each channel, increases flow efficiency, and enhances the drainage capacity of each surface of the bipolar plate. Consequently, it improves the fuel cell's operating efficiency, stability, and reliability during operation.

[0153] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, the flow field region also includes the first transition region 5 and the second transition region 8 mentioned above.

[0154] In this embodiment of the application, along the first direction x, the first transition zone 5 is disposed on the flow channel sidewall of each flow field zone, and along the fourth direction v, the second transition zone 8 is disposed between the second hydrophobic zone 6 and the second hydrophilic zone 7 of each flow field zone.

[0155] This design approach allows for further refinement of the gradient structures in two different directions, resulting in a smoother change in the distribution density from hydrophobic to hydrophilic regions. This improves the stability and smoothness of water flow along the first direction (x) and the fourth direction (v), reducing the risk of adverse phenomena such as localized flooding or drying during flow. Simultaneously, the first transition region 5 and the second transition region 8 also act as buffers, reducing the possibility of water affecting gas flow or current transmission during operation, thus enhancing the stability and reliability of the fuel cell during operation.

[0156] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, when the first recess 113 and the second recess 213 are respectively disposed on the bottom wall of the flow channel of the first surface 1 and the second surface 2, the projections of the first recess 113 and the second recess 213 are misaligned along the first direction x.

[0157] In this embodiment, according to the three schemes described above, the flow field region includes only the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4; the flow field region includes only the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7; and the flow field region simultaneously includes the first hydrophobic region 3, the first transition region 5, the first hydrophilic region 4, the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7. The bottom wall and side wall of the first flow channel 112 are both provided with a first recess 113, and the bottom wall and side wall of the second flow channel 212 are both provided with a second recess 213. Since the bipolar plate is formed by stacking two monopolar plates, the bottom wall of the first flow channel 112 and the bottom wall of the second flow channel 212 can abut against each other along the first direction x, thus providing mutual support and improving the stability and reliability of the overall bipolar plate structure.

[0158] Among them, along the first direction x, the projections of the first recess 113 and the second recess 213 located on the bottom wall of each flow channel can be staggered.

[0159] This design reduces the possibility of excessively thin bipolar plates (i.e., the bottom walls of each flow channel), thereby reducing the likelihood of bipolar plates breaking or perforating under external forces. This improves the overall structural strength of the bipolar plates, enhancing their safety and reliability during subsequent lamination and / or pressing with the membrane electrode assembly 9 along the first direction x, increasing the production yield of bipolar plates, and extending the lifespan of the fuel cell.

[0160] Optionally, along the first direction x, the projections of the first recess 113 and the second recess 213 located on the bottom wall of each flow channel can at least partially overlap, or can completely overlap.

[0161] This design improves the space utilization of the bottom wall of each flow channel, thus meeting the requirement that the first recess 113 and the second recess 213 have a high distribution density in the first hydrophilic zone 4 and / or the second hydrophilic zone 7.

[0162] Optionally, along the first direction x, the projections of the first recess 113 and the second recess 213 located on the sidewalls of each flow channel can completely overlap, or at least partially overlap, or be staggered.

[0163] Optionally, along the first direction x, the projections of the first recess 113 and the second recess 213 located on the top wall of each rib can completely overlap, or at least partially overlap, or be staggered.

[0164] In one specific embodiment, the diameter of the first recess 113 is D1, and D1 satisfies 5μm≤D1≤20μm, and / or the depth of the first recess 113 is H1, and H1 satisfies 3μm≤H1≤10μm.

[0165] In this embodiment, when the diameter of the first recess 113 satisfies 5μm≤D1≤20μm and / or the depth of the first recess 113 satisfies 3μm≤H1≤10μm, the diameter and / or depth of the first recess 113 are moderate. This ensures that the bipolar plate has sufficient mechanical strength to maintain its structural stability, while also matching the pores of the gas diffusion layer to form a larger gradient structure. This allows the flow of water to be guided through capillary action, ensuring the stability and smoothness of the water flow. Consequently, it enables precise control of water management within the bipolar plate.

[0166] Optionally, the diameter of the first recess 113 can be any of the values ​​within the range of 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, etc.

[0167] Optionally, the depth of the first recess 113 can be any of the values ​​within the range of 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, 8μm, 8.2μm, 8.4μm, 8.6μm, 8.8μm, 9μm, 9.2μm, 9.4μm, 9.6μm, 9.8μm, 10μm, etc.

[0168] Optionally, the diameters of the first recess 113 in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 can all be different.

[0169] The diameter of the first recess 113 in the first hydrophobic region 3 can be larger than its diameter in the first transition region 5. The diameter of the first recess 113 in the first transition region 5 can be larger than its diameter in the first hydrophilic region 4. Alternatively, the diameter of the first recess 113 can gradually decrease along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, so that the first hydrophilic region 4 has a strong capillary force, so as to attract water in the first hydrophobic region 3 and the first transition region 5 to flow towards the first hydrophilic region 4, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0170] Optionally, the diameters of the first recess 113 in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 can all be different.

[0171] The diameter of the first recess 113 in the second hydrophobic region 6 can be larger than its diameter in the second transition region 8. The diameter of the first recess 113 in the second transition region 8 can be larger than its diameter in the second hydrophilic region 7. Alternatively, the diameter of the first recess 113 can gradually decrease along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, so that the second hydrophilic region 7 has a strong capillary force, so as to attract water in the second hydrophobic region 6 and the second transition region 8 to flow towards the second hydrophilic region 7, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0172] Optionally, the depth of the first recess 113 in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 can all be different.

[0173] The diameter of the first recess 113 in the first hydrophobic region 3 can be smaller than its depth in the first transition region 5, and the depth of the first recess 113 in the first transition region 5 can be smaller than its depth in the first hydrophilic region 4. Alternatively, the depth of the first recess 113 can gradually increase along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, so that the first hydrophilic region 4 has a strong capillary force, so as to attract water in the first hydrophobic region 3 and the first transition region 5 to flow towards the first hydrophilic region 4, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0174] Optionally, the depths of the first recess 113 in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 can all be different.

[0175] The depth of the first recess 113 in the second hydrophobic region 6 can be smaller than its depth in the second transition region 8. The depth of the first recess 113 in the second transition region 8 can be smaller than its depth in the second hydrophilic region 7. Alternatively, the depth of the first recess 113 can gradually increase along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, so that the second hydrophilic region 7 has a strong capillary force, so as to attract water in the second hydrophobic region 6 and the second transition region 8 to flow towards the second hydrophilic region 7, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0176] In one specific embodiment, the diameter of the second recess 213 is D2, and D2 satisfies 5μm≤D2≤20μm, and / or the depth of the second recess 213 is H2, and H2 satisfies 3μm≤H2≤10μm.

[0177] In this embodiment, when the diameter of the second recess 213 satisfies 5μm≤D2≤20μm and / or the depth of the second recess 213 satisfies 3μm≤H2≤10μm, the diameter and / or depth of the second recess 213 are moderate. This ensures that the bipolar plate has sufficient mechanical strength to maintain its structural stability, while also matching the pores of the gas diffusion layer to form a larger gradient structure. This allows the flow of water to be guided through capillary action, ensuring the stability and smoothness of the water flow, and thus enabling precise control of water management within the bipolar plate.

[0178] The diameter of the second recess 213 can be any of the following values ​​within the range: 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, etc.

[0179] The depth of the second recess 213 can be any of the values ​​within the range mentioned above, such as 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, 8μm, 8.2μm, 8.4μm, 8.6μm, 8.8μm, 9μm, 9.2μm, 9.4μm, 9.6μm, 9.8μm, 10μm, etc.

[0180] Optionally, the diameters of the second recess 213 in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 can all be different.

[0181] The diameter of the second recess 213 in the first hydrophobic region 3 can be larger than its diameter in the first transition region 5. The diameter of the second recess 213 in the first transition region 5 can be larger than its diameter in the first hydrophilic region 4. Alternatively, the diameter of the second recess 213 can gradually decrease along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, so that the first hydrophilic region 4 has a strong capillary force, so as to attract water in the first hydrophobic region 3 and the first transition region 5 to flow towards the first hydrophilic region 4, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0182] Optionally, the diameters of the second recess 213 in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 can all be different.

[0183] The diameter of the second recess 213 in the second hydrophobic region 6 can be larger than its diameter in the second transition region 8. The diameter of the second recess 213 in the second transition region 8 can be larger than its diameter in the second hydrophilic region 7. Alternatively, the diameter of the second recess 213 can gradually decrease along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, so that the second hydrophilic region 7 has a strong capillary force, so as to attract water in the second hydrophobic region 6 and the second transition region 8 to flow towards the second hydrophilic region 7, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0184] Optionally, the depth of the second recess 213 in the first hydrophobic region 3, the first transition region 5, and the first hydrophilic region 4 can all be different.

[0185] The diameter of the second recess 213 in the first hydrophobic region 3 can be smaller than its depth in the first transition region 5, and the depth of the second recess 213 in the first transition region 5 can be smaller than its depth in the first hydrophilic region 4. Alternatively, the depth of the second recess 213 can gradually increase along the direction from the first hydrophobic region 3 to the first hydrophilic region 4, so that the first hydrophilic region 4 has a strong capillary force, so as to attract water in the first hydrophobic region 3 and the first transition region 5 to flow towards the first hydrophilic region 4, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0186] Optionally, the depth of the second recess 213 in the second hydrophobic region 6, the second transition region 8, and the second hydrophilic region 7 can all be different.

[0187] The depth of the second recess 213 in the second hydrophobic region 6 can be smaller than its depth in the second transition region 8. The depth of the second recess 213 in the second transition region 8 can be smaller than its depth in the second hydrophilic region 7. Alternatively, the depth of the second recess 213 can gradually increase along the direction from the second hydrophobic region 6 to the second hydrophilic region 7, so that the second hydrophilic region 7 has a strong capillary force, so as to attract water in the second hydrophobic region 6 and the second transition region 8 to flow towards the second hydrophilic region 7, which is beneficial to improving the drainage efficiency of the bipolar plate.

[0188] In one specific implementation, such as Figure 1 , Figure 2 and Figure 3 As shown, along the first direction x, the cross-sectional shape of the first recess 113 and the second recess 213 is one or more of trapezoidal, rectangular, triangular and semi-circular.

[0189] In this embodiment, the water-guiding effect varies depending on the cross-sectional shape of the recess. For example, when the cross-sectional shape of the recess is trapezoidal, the sidewalls of the recess are inclined relative to its bottom wall, which not only facilitates the inflow and outflow of water but also reduces dead angles and provides higher structural strength and a larger capacity. When the cross-sectional shape of the recess is rectangular, it has a larger capacity. When the cross-sectional shape of the recess is triangular, it can further form a gradient structure along the first direction x to improve the capillary effect. When the cross-sectional shape of the recess is semi-circular, it can reduce the flow resistance of water during flow and also reduce the disturbance experienced by gas during flow. Moreover, the above structures are simple in structure and easy to process, which helps to reduce the processing difficulty of bipolar plates, thereby reducing production costs and improving the production efficiency of bipolar plates.

[0190] Optionally, the first recess 113 and the second recess 213 can be formed on the first surface 1 and the second surface 2 of the bipolar plate by laser processing.

[0191] Optionally, the first recess 113 and the second recess 213 are distributed in a point-like or line-like manner within the flow field regions of the first surface 1 and the second surface 2, respectively.

[0192] Embodiments of this application also provide a fuel cell, such as Figure 1 , Figure 2 and Figure 3 As shown, the fuel cell includes bipolar plates and a membrane electrode assembly 9, which are stacked along a first direction x.

[0193] Wherein, the bipolar plate is any of the bipolar plates described above.

[0194] In this embodiment of the application, when the fuel cell adopts the above-mentioned bipolar plate, the bipolar plate can promote the flow of water toward the interior of each flow channel through the first recess 113 and the second recess 213 on its surface, so as to ensure that the membrane electrode assembly 9 has a suitable wettability while reducing the possibility of water stagnation inside and causing blockage, thereby improving the stability and smoothness of fluid flow inside the fuel cell, and thus improving the working efficiency of the fuel cell.

[0195] Simultaneously, by gradually varying the distribution density of the first recess 113 and the second recess 213 along the first direction x and / or the fourth direction v, a sequentially connected hydrophobic region, a transition region, and a hydrophilic region can be formed. Furthermore, during fuel cell operation, the distribution of water within the fuel cell can be designed in a gradient structure along the direction from the hydrophobic region to the hydrophilic region. This allows water inside the fuel cell to flow towards the hydrophilic region under capillary action, facilitating its discharge. This, in turn, helps reduce the possibility of flooding or even reverse osmosis inside the fuel cell, improving the stability and reliability of the fuel cell during operation.

[0196] The above description, based on the embodiments shown in the drawings, details the structure, features, and effects of this application. The above description is only a preferred embodiment of this application, but this application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of this application, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and drawings, should be within the protection scope of this application.

Claims

1. A bipolar plate, characterized in that, The bipolar plate includes a first surface and a second surface disposed opposite to each other along a first direction. The first surface is provided with a first recessed portion, which is recessed inward relative to the surface of the first surface. The second surface is provided with a second recessed portion, which is recessed inward relative to the surface of the second surface. Wherein, the density of the first recessed portion on the first surface is α1, the density of the second recessed portion on the second surface is α2, and α1 / α2 satisfies 1<α1 / α2≤5; Both the first surface and the second surface are provided with a flow field area, an inlet area and an outlet area. The inlet area and the outlet area are distributed on both sides of the flow field area along the second direction and are connected through the flow channel in the flow field area. The first recess and the second recess are respectively provided in the flow field area of ​​the first surface and the second surface. The flow field region includes multiple ribs spaced apart along a third direction, and the flow channel is formed between adjacent ribs; Along the first direction, the flow field region includes a first hydrophobic region and a first hydrophilic region, wherein the first hydrophobic region is disposed on the top wall of the rib and the first hydrophilic region is disposed on the bottom wall of the flow channel; Each recess is provided on the top wall of the rib and the bottom wall of the flow channel. The density of the recess in the first hydrophobic region is β1, and the density of the recess in the first hydrophilic region is β2, and β1 and β2 satisfy β1 < β2.

2. The bipolar plate according to claim 1, characterized in that, Along the first direction, the flow field region further includes a first transition region, which is disposed on the side wall of the flow channel; The density of the recessed portion in the first transition region is β3, and β1, β2 and β3 satisfy β1 < β3, β3 < β2.

3. The bipolar plate according to claim 2, characterized in that, Along the first direction, within the first transition region, the density of the recess gradually increases.

4. The bipolar plate according to claim 2, characterized in that, β1 also satisfies 10%≤β1≤30%, β2 also satisfies 65%≤β2≤90%, and β3 also satisfies 35%≤β3≤60%.

5. The bipolar plate according to claim 1, characterized in that, Along the fourth direction, the flow field region includes a second hydrophobic region and a second hydrophilic region. The second hydrophobic region is located at one end of the flow field region near the inlet region, and the second hydrophilic region is located at one end of the flow field region near the outlet region. Each recess is disposed on the side wall and bottom wall of the flow channel. The density of the recess in the second hydrophobic region is γ1, and the density of the recess in the second hydrophilic region is γ2, and γ1 and γ2 satisfy γ1 < γ2.

6. The bipolar plate according to claim 5, characterized in that, Along the fourth direction, the flow field region further includes a second transition region, which is located between the second hydrophobic region and the second hydrophilic region; The density of the recessed portion in the second transition region is γ3, and γ1, γ2 and γ3 satisfy γ1<γ3, γ3<γ2.

7. The bipolar plate according to claim 6, characterized in that, Along the fourth direction, the density of the recess gradually increases in at least one of the second hydrophobic region, the second transition region, and the second hydrophilic region.

8. The bipolar plate according to claim 6, characterized in that, γ1 also satisfies 5%≤γ1≤35%, γ2 also satisfies 70%≤γ2≤90%, and γ3 also satisfies 40%≤γ3≤65%.

9. The bipolar plate according to claim 1, characterized in that, The flow field region includes multiple ribs spaced apart along a third direction, and the flow channel is formed between adjacent ribs; The flow field region further includes a first hydrophobic region, a first hydrophilic region, a second hydrophobic region, and a second hydrophilic region. Along the fourth direction, the second hydrophobic region is located at one end of the flow field region near the inlet region, and the second hydrophilic region is located at one end of the flow field region near the outlet region. Along the first direction, the first hydrophobic region is located on the top wall of the rib, and the first hydrophilic region is located on the bottom wall of the flow channel. Each recess is disposed on the top wall of the rib and the side and bottom walls of the flow channel. Along the first direction, the density of the recess in the first hydrophobic region is β1, and the density of the recess in the first hydrophilic region is β2, and β1 and β2 satisfy β1 < β2. Along the fourth direction, the density of the recess in the second hydrophobic region is γ1, and the density of the recess in the second hydrophilic region is γ2, and γ1 and γ2 satisfy γ1 < γ2.

10. The bipolar plate according to claim 9, characterized in that, The flow field region further includes a first transition region and a second transition region. The first transition region is disposed on the side wall of the flow channel, and the second transition region is located between the second hydrophobic region and the second hydrophilic region. The density of the recessed portion in the first transition region is β3, and β1, β2 and β3 satisfy β1 < β3, β3 < β2. The density of the recessed portion in the second transition region is γ3, and γ1, γ2 and γ3 satisfy γ1 < γ3, γ3 < γ2.

11. The bipolar plate according to claim 1, characterized in that, When the first recess and the second recess are respectively disposed on the bottom wall of the flow channel on the first surface and the second surface, the projections of the first recess and the second recess are misaligned along the first direction.

12. The bipolar plate according to any one of claims 1-11, characterized in that, The diameter of the first recess is D1, and D1 satisfies 5μm≤D1≤20μm, and / or the depth of the first recess is H1, and H1 satisfies 3μm≤H1≤10μm; The diameter of the second recess is D2, and D2 satisfies 5μm≤D2≤20μm, and / or the depth of the second recess is H2, and H2 satisfies 3μm≤H2≤10μm.

13. The bipolar plate according to any one of claims 1-11, characterized in that, Along the first direction, the cross-sectional shape of the first recess and the second recess is one or more of trapezoidal, rectangular, triangular and semi-circular.

14. A fuel cell, characterized in that, The fuel cell includes a bipolar plate and a membrane electrode assembly, wherein the membrane electrode assembly and the bipolar plate are stacked along a first direction; The bipolar plate is any one of claims 1-13.

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