Bipolar plate having multi-flow field structure and preparation method therefor

Abstract

A bipolar plate having a multi-flow field structure and a preparation method therefor, relating to the field of fuel cells. A reaction flow field region of the bipolar plate is composed of an upper straight flow section (1), a middle blocking section (2), a lower variable-diameter flow section (3), and a bottom blocking section (4), wherein each section occupies a different proportion of the total length of the bipolar plate. The upper straight flow section (1) has a parallel flow field structure; the middle blocking section (2) has a specific boss structure; the lower variable-diameter flow section (3) has a variable-diameter flow field structure and is provided with variable-diameter flow channel ridges, contraction portions and expansion portions; and the bottom blocking section (4) has a staggered truncated cone structure. The preparation method comprises metal plate surface pretreatment and rubber pad stamping forming processes. By changing a flow field structure, a bipolar plate structure can simultaneously help to increase the reactant flow rate, promote reagent diffusion, and facilitate gas transport and water discharge in a membrane electrode assembly.

Description

A bipolar plate with a multi-flow field structure and its preparation method Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a bipolar plate with a multi-flow field structure and its preparation method. Background Technology

[0002] Fuel cell stacks and water electrolysis for hydrogen production mainly consist of membranes, catalyst layers, diffusion layers, and bipolar plates. Among these, the bipolar plates, as core components, play many important roles in fuel cells and electrolyzers, and their performance largely depends on the flow field structure. This involves the optimization of traditional flow fields (such as parallel flow fields, serpentine flow fields, and interdigitated flow fields) and the design of novel flow fields. For traditional flow fields, one approach is to improve battery performance and adjust the flow field geometry by optimizing channel parameters. However, studies have found that while reducing channel depth and width helps increase reactant / product flow rates and thus improves battery performance, it also increases pressure drop and pump parasitic power, affecting the battery's net output power. Another approach is to study flow field geometry. In fuel cells, flow fields with "trap" structures can promote reactant diffusion into the MEA, which is beneficial for battery performance. Flow fields with "convergence-diffusion" variable diameter structures can promote gas transport and water discharge in the membrane electrode assembly (MEA) due to the pressure difference between adjacent channels, thus improving the fuel cell's output power. However, these traditional flow field optimization methods still have certain limitations. In water electrolysis, when operating at high current densities, oxygen or hydrogen on the gas production side also faces problems such as low gas escape efficiency, product retention in the flow channels, and local overheating, which can lead to performance degradation and membrane degradation. Summary of the Invention

[0003] To address the aforementioned technical problem of improving the performance and output power of fuel cells and electrolyzers, this invention provides a bipolar plate with a multi-flow field structure and its fabrication method. By altering the flow field structure, this invention enables the bipolar plate structure to simultaneously increase reactant flow rate, promote reactant diffusion, and facilitate gas transport and water removal within the membrane electrode assembly.

[0004] The technical means employed in this invention are as follows:

[0005] A bipolar plate with a multi-flow field structure includes a reaction flow field region disposed on the plate. Along the length of the bipolar plate, the reaction flow field region is composed of an upper direct current section region, a middle obstruction region, a lower variable flow section region, and a bottom obstruction region. Taking the length of the bipolar plate as the total length, the upper direct current section region, the middle obstruction region, the lower variable flow section region, and the bottom obstruction region account for 25%, 15%, 50%, and 5% of the total length of the plate, respectively.

[0006] The upper DC section region has a parallel flow field structure;

[0007] The central barrier area is a boss structure, which consists of a transverse ridge and multiple longitudinal ridges perpendicular to the transverse ridge. The height of the boss structure is lower than that of the parallel flow field structure.

[0008] The lower variable-diameter flow section is a variable-diameter flow field structure with the same height as the parallel flow field structure;

[0009] The bottom barrier region is composed of multiple rows of frustums arranged along the width direction of the bipolar plate, with each row of frustums staggered. The upper surface of the frustums is flush with the upper surface of the variable diameter flow field structure.

[0010] The parallel flow field structure is composed of multiple straight flow channel ridges, and a straight flow channel groove of a bipolar plate is formed between each two adjacent straight flow channel ridges.

[0011] The variable diameter flow field structure consists of multiple variable diameter flow channel ridges, and a variable diameter flow channel groove of a bipolar plate is formed between each pair of adjacent variable diameter flow channel ridges.

[0012] Furthermore, along the length of the bipolar plate, multiple contraction sections are uniformly arrayed on the variable diameter flow channel ridge, and the contraction sections of adjacent variable diameter flow channel ridges are aligned; both the variable diameter flow channel ridge and the contraction section have corresponding widening sections.

[0013] Furthermore, the width of the straight flow channel is 1-5mm; the width of the variable diameter flow channel is 1-5mm; and the width of the widened portion of the variable diameter flow channel is 2-6mm.

[0014] The depth of the straight flow channel and the variable diameter flow channel is 0.8-3mm;

[0015] The first row of the bottom partition area, adjacent to the lower variable flow section area, has frustums located at the center between the two straight flow channel ridges, and the diameter of the frustum is 1-3 mm.

[0016] Furthermore, within the flow field region, the area within which the width of the flow field region is taken as the total width, and the distance from each side of the bipolar plate and accounting for one-quarter of the total width, is the edge region of the flow field region, and the rest is the middle region. The channel ridge spacing in the middle region is 0.5-2mm; the channel ridge spacing in the edge region is 2.5-5mm; and the spacing between two adjacent channel ridges in the middle region and the edge region is 1-3mm.

[0017] Furthermore, the boss structure consists of a transverse ridge and three uniformly arranged longitudinal ridges perpendicular to the transverse ridge. The height of the boss structure is 1 mm lower than that of the parallel flow field structure. The length of the transverse ridge is flush with both ends of the upper DC section. The width of the transverse ridge and the width of the longitudinal ridge are equal to the width of the straight flow channel ridge.

[0018] Furthermore, in the boss structure, the intersection of the transverse and longitudinal protrusions is low-lying.

[0019] Furthermore, when the central blocking zone is located in the middle of the lower variable flow section, the lower variable flow section is divided by the central blocking zone to form two variable flow field regions. The reaction flow field regions are, from top to bottom, the upper direct flow section region, the lower variable flow section A region, the central blocking zone, the lower variable flow section B region, and the bottom blocking zone.

[0020] The present invention also provides a method for preparing the above-mentioned bipolar plate with a multi-flow field structure, comprising the following steps:

[0021] S1. Use metal sheet and pre-treat its surface;

[0022] S2. Using rubber pad stamping forming process, the surface of metal sheet is stamped or etched to form structures including parallel flow field structure, boss structure, variable diameter flow field structure and truncated cone structure.

[0023] Furthermore, the surface pretreatment in S1 includes grinding, removing the passivation layer, and coating the surface with an anti-corrosion protective layer; grinding is done with 50-200 grit sandpaper; removing the passivation layer involves soaking in a weak acid with pH=6.6-6.9 for 1-5 hours; and coating the surface with an anti-corrosion protective layer involves sputtering precious metals such as Pt and C using the PVD method.

[0024] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] 1. This invention provides a bipolar plate with a multi-flow field structure and its preparation method. By combining a straight flow channel groove with a boss turbulence design, the contact opportunities between the gas and the reactants can be increased while ensuring smooth airflow. The straight flow channel groove ensures stable and low-resistance airflow, while the boss, through turbulence, induces airflow turbulence, causing fluctuations in gas velocity in local areas and generating turbulence. This results in more thorough mixing of reactants and gas, especially at higher flow velocities or high reaction temperatures, increasing the probability of collisions between reactant molecules and accelerating the reaction rate. Specifically, the position and size of the boss can precisely control the degree of airflow turbulence, thereby optimizing reaction efficiency and avoiding incomplete coverage of the reaction area caused by uneven gas flow. The structure of this application, through a combination of a direct flow section (high flow rate / low pressure drop), a variable diameter section (promoting diffusion / turbulence), and a barrier section (redistribution / collection), can effectively manage the discharge of oxygen from the reaction product and the supply of reactants. Specifically, the variable diameter flow channel can accelerate the fluid flow rate and prevent oxygen accumulation on the anode side of PEMWE, while the staggered frustum structure at the bottom promotes the discharge of liquid water, solving the "dry spot" problem in PEMWE. The barrier zone optimizes diffusion efficiency and improves reaction uniformity. Therefore, it also has advantages in water electrolysis, effectively reducing gas accumulation in the flow channel, improving gas escape efficiency, thereby reducing concentration polarization (oxygen in PEMWE), and improving power density and reliability.

[0026] 2. This invention provides a bipolar plate with a multi-flow field structure and its preparation method. The design of the straight flow channel optimizes the mainstream path of the airflow, reduces the fluid friction resistance caused by bends or abrupt changes in cross-section, and ensures a low overall pressure drop. The protrusion turbulence design can generate certain flow disturbances in local areas, preventing dead zones or excessively low local flow velocities in the flow channel. The main function of the protrusion is to periodically disrupt the airflow, keeping the airflow relatively uniformly distributed, and increasing the turbulence of the airflow through local turbulence, preventing possible low-speed zones. Combining these two aspects, while maintaining a low overall pressure drop, it can avoid extreme phenomena of excessively fast or slow airflow, ensuring the stability of gas flow and efficient operation of the system.

[0027] 3. This invention provides a bipolar plate with a multi-flow field structure and its preparation method. The combination of straight flow channel grooves and boss turbulence design makes the system more adaptable to changes in operating conditions such as flow rate, temperature, and reactant composition. The boss structure divides the lower variable diameter flow section into two variable diameter flow field regions, so that the flow field structure of this bipolar plate is formed from top to bottom as an upper direct flow section region, a lower variable diameter flow section A region, a middle barrier region, a lower variable diameter flow section B region, and a bottom barrier region. That is, at this time, the straight flow field structure of the upper direct flow section is directly the same as the variable diameter flow field structure of the lower variable diameter flow section A region. At this time, the middle barrier region can allow the gas to be redistributed and reduced, reducing the difference in gas usage in different flow channel grooves. After redistribution, the gas is redistributed into the next region, increasing the gas distribution and improving performance. This design is conducive to the large-size scaling of bipolar plates, increasing the number of middle barrier regions, and increasing the consistency of large-area bipolar plates.

[0028] 4. The present invention provides a bipolar plate with a multi-flow field structure and its preparation method. The intersection of the transverse and longitudinal convex edges in the boss structure is designed to be low-lying. This allows the reactant, which passes through the straight flow field structure and directly interacts with the lower variable diameter flow section A, to have a certain "convergence" effect again in the low-lying structure. This effectively avoids the phenomenon of reaction weakening and further increases the gas distribution effect, allowing the gas to flow evenly into the variable diameter flow field of the later section.

[0029] Based on the above reasons, this invention can be promoted in the fields of fuel cells and water electrolysis technology. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 is a schematic diagram of a bipolar plate structure with a multi-flow field structure according to the present invention;

[0032] Figure 2 is a schematic diagram of a bipolar plate structure with a multi-flow field structure according to the present invention (II);

[0033] Figure 3 is a schematic diagram of a bipolar plate structure with a multi-flow field structure according to the present invention (III);

[0034] Figure 4 is a schematic diagram showing that the intersection of the transverse and longitudinal protrusions in the bipolar plate boss structure of the multi-flow field structure described in this invention is in a low-lying shape.

[0035] Figure 5 is a flowchart of the preparation method of a bipolar plate with a multi-flow field structure according to the present invention.

[0036] In the diagram: 1. Upper DC section; 2. Middle blocking section; 3. Lower variable flow section; 31. Lower variable flow section A; 32. Lower variable flow section B; 4. Bottom blocking section; 5. Lateral convex ridge; 6. Longitudinal convex ridge. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0040] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0041] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0042] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0043] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0044] Example 1

[0045] As shown in Figure 1, the present invention provides a bipolar plate with a multi-flow field structure, including a reaction flow field region disposed on the plate. Along the length of the bipolar plate, the reaction flow field region is composed of an upper DC section region 1, a middle blocking region 2, a lower variable flow section region 3, and a bottom blocking region 4. Taking the length of the bipolar plate as the total length, the upper DC section region 1, the middle blocking region 2, the lower variable flow section region 3, and the bottom blocking region 4 account for 25%, 15%, 50%, and 5% of the total length of the plate, respectively.

[0046] The upper DC section 1 has a parallel flow field structure, which consists of multiple straight flow channel ridges. Between each pair of adjacent straight flow channel ridges, a straight flow channel groove for the bipolar plate is formed. The width of the straight flow channel groove is 1 mm and the depth of the straight flow channel groove is 0.8 mm.

[0047] The central barrier zone 2 is a boss structure, as shown in Figure 4. The boss structure consists of a transverse ridge 5 and three uniformly arranged longitudinal ridges 6 perpendicular to the transverse ridge 5. The height of the boss structure is 1 mm lower than that of the parallel flow field structure. The length of the transverse ridge 5 is flush with both ends of the upper DC section zone 1. The width of the transverse ridge 5 and the width of the longitudinal ridge 6 are equal to the width of the straight flow channel ridge. The intersection of the transverse ridge 5 and the longitudinal ridge 6 is a depression.

[0048] The lower variable diameter flow section 3 is a variable diameter flow field structure with the same height as the straight flow channel ridge. The variable diameter flow field structure is composed of multiple variable diameter flow channel ridges. Between each pair of adjacent variable diameter flow channel ridges, a variable diameter flow channel groove of a bipolar plate is formed. Along the length direction of the bipolar plate, multiple contraction sections are uniformly arrayed on the variable diameter flow channel ridge. The variable diameter flow channel groove and the contraction section are both accompanied by a widening section. The width of the variable diameter flow channel groove is 1 mm, the width of the widening section of the variable diameter flow channel groove is 2 mm, and the depth of the variable diameter flow channel groove is 0.8 mm.

[0049] The bottom barrier region 4 is composed of two rows of frustums arranged along the width direction of the bipolar plate. The spacing between each row of frustums is 1 mm, and the frustums are staggered. The frustums adjacent to the parallel flow field structure are all located at the center between the two straight flow channel ridges. The upper surface of the frustum is flush with the upper surface of the variable diameter flow field structure, and the diameter of the frustum is 1 mm.

[0050] Example 2

[0051] As shown in Figure 2, the present invention also provides a bipolar plate with a multi-flow field structure, including a reaction flow field region disposed on the plate. Along the length of the bipolar plate, the reaction flow field region is composed of an upper DC section region 1, a middle blocking region 2, a lower variable flow section region 3, and a bottom blocking region 4. Taking the length of the bipolar plate as the total length, the upper DC section region 1, the middle blocking region 2, the lower variable flow section region 3, and the bottom blocking region 4 account for 25%, 15%, 50%, and 5% of the total length of the plate, respectively.

[0052] The upper DC section 1 has a parallel flow field structure, which consists of multiple straight flow channel ridges. Between each pair of adjacent straight flow channel ridges, a straight flow channel groove for the bipolar plate is formed. The width of the straight flow channel groove is 1 mm and the depth of the straight flow channel groove is 0.8 mm.

[0053] The central barrier zone 2 is a boss structure, as shown in Figure 4. The boss structure consists of a transverse ridge 5 and three uniformly arranged longitudinal ridges 6 perpendicular to the transverse ridge 5. The height of the boss structure is 1 mm lower than that of the parallel flow field structure. The length of the transverse ridge 5 is flush with both ends of the upper DC section zone 1. The width of the transverse ridge 5 and the width of the longitudinal ridge 6 are equal to the width of the straight flow channel ridge. The intersection of the transverse ridge 5 and the longitudinal ridge 6 is a depression.

[0054] The lower variable diameter flow section 3 is a variable diameter flow field structure with the same height as the straight flow channel ridge. The variable diameter flow field structure is composed of multiple variable diameter flow channel ridges. Between each pair of adjacent variable diameter flow channel ridges, a variable diameter flow channel groove of a bipolar plate is formed. Along the length direction of the bipolar plate, multiple contraction sections are uniformly arrayed on the variable diameter flow channel ridge. The variable diameter flow channel groove and the contraction section are both accompanied by a widening section. The width of the variable diameter flow channel groove is 1 mm, the width of the widening section of the variable diameter flow channel groove is 2 mm, and the depth of the variable diameter flow channel groove is 0.8 mm.

[0055] The middle barrier zone 2 is located in the middle of the lower variable flow section 3. The lower variable flow section 3 is divided by the middle barrier zone 2 to form two variable flow field areas. The reaction flow field areas from top to bottom are the upper direct flow section 1, the lower variable flow section A area 31, the middle barrier zone 2, the lower variable flow section B area 32, and the bottom barrier zone 4.

[0056] The bottom barrier region 4 is composed of two rows of frustums arranged along the width direction of the bipolar plate. The spacing between each row of frustums is 1 mm, and the frustums are staggered. The frustums adjacent to the parallel flow field structure are all located at the center between the two straight flow channel ridges. The upper surface of the frustum is flush with the upper surface of the variable diameter flow field structure, and the diameter of the frustum is 1 mm.

[0057] Example 3

[0058] As shown in Figure 3, the present invention also provides a bipolar plate with a multi-flow field structure, including a reaction flow field region disposed on the plate. Along the length of the bipolar plate, the reaction flow field region is composed of an upper DC section region 1, a middle blocking region 2, a lower variable flow section region 3, and a bottom blocking region 4. Taking the length of the bipolar plate as the total length, the upper DC section region 1, the middle blocking region 2, the lower variable flow section region 3, and the bottom blocking region 4 account for 25%, 15%, 50%, and 5% of the total length of the plate, respectively.

[0059] The upper DC section 1 has a parallel flow field structure, which consists of multiple straight flow channel ridges. Between each pair of adjacent straight flow channel ridges, a straight flow channel groove for the bipolar plate is formed. The width of the straight flow channel groove is 1 mm, and the depth of the straight flow channel groove is 0.8 mm. Taking the width direction of the bipolar plate as the total width, the edge region of the bipolar plate is located one-quarter of the total width from both sides of the bipolar plate, and the rest is the middle region. The straight flow channel ridges in the upper DC section 1 are arranged in a state of being dense in the middle region and sparse in the edge region, as shown in Figure 3. The spacing between the flow channel ridges in the middle region is 0.5 mm; the spacing between the flow channel ridges in the edge region is 2.5 mm; and the spacing between two adjacent flow channel ridges in the middle region and the edge region is 1 mm.

[0060] The central barrier zone 2 is a boss structure, as shown in Figure 4. The boss structure consists of a transverse ridge 5 and three uniformly arranged longitudinal ridges 6 perpendicular to the transverse ridge 5. The height of the boss structure is 1 mm lower than that of the parallel flow field structure. The length of the transverse ridge 5 is flush with both ends of the upper DC section zone 1. The width of the transverse ridge 5 and the width of the longitudinal ridge 6 are equal to the width of the straight flow channel ridge. The intersection of the transverse ridge 5 and the longitudinal ridge 6 is a depression.

[0061] The lower variable diameter flow section 3 is a variable diameter flow field structure with the same height as the straight flow channel ridge. The variable diameter flow field structure is composed of multiple variable diameter flow channel ridges. Between each pair of adjacent variable diameter flow channel ridges, a variable diameter flow channel groove of a bipolar plate is formed. Along the length direction of the bipolar plate, multiple contraction sections are uniformly arrayed on the variable diameter flow channel ridge. The variable diameter flow channel groove and the contraction section are both accompanied by a widening section. The width of the variable diameter flow channel groove is 1 mm, the width of the widening section of the variable diameter flow channel groove is 2 mm, and the depth of the variable diameter flow channel groove is 0.8 mm.

[0062] The bottom barrier region 4 is composed of two rows of frustums arranged along the width direction of the bipolar plate. The spacing between each row of frustums is 1 mm, and the frustums are staggered. The frustums adjacent to the parallel flow field structure are all located at the center between the two straight flow channel ridges. The upper surface of the frustum is flush with the upper surface of the variable diameter flow field structure, and the diameter of the frustum is 1 mm.

[0063] As shown in Figure 5, the present invention also provides a method for preparing a bipolar plate with a multi-flow field structure, comprising the following steps:

[0064] S1. Two 280×500mm metal plates are used for surface pretreatment, which includes grinding, removing the passivation layer, and coating the surface with an anti-corrosion protective layer. Grinding is done with 200-grit sandpaper. The passivation layer is removed by soaking in a weak acid with pH=6.6 for 5 hours. The surface is coated with an anti-corrosion protective layer by sputtering Pt precious metal using the PVD method.

[0065] S2. Using a rubber pad stamping forming process, a parallel flow field structure, a boss structure, a variable diameter flow field structure, and a frustum structure are formed on the surface of a metal sheet by stamping or etching. The total length of the parallel flow field structure is 100mm, the total length of the boss structure is 60mm, the total length of the variable diameter flow field structure is 200mm, the total length of the frustum structure is 20mm, and the total length of the remaining parts is 100mm, thereby forming an anode plate and a cathode plate.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bipolar plate with a multi-flow field structure, characterized in that, The bipolar plate includes a reaction flow field region disposed on the plate. Along the length of the bipolar plate, the reaction flow field region is composed of an upper DC section region, a middle blocking region, a lower variable flow section region, and a bottom blocking region. Taking the length of the bipolar plate as the total length, the upper DC section region, the middle blocking region, the lower variable flow section region, and the bottom blocking region account for 25%, 15%, 50%, and 5% of the total length of the plate, respectively. The upper DC section region has a parallel flow field structure; The central barrier area is a boss structure, which consists of a transverse ridge and multiple longitudinal ridges perpendicular to the transverse ridge. The height of the boss structure is lower than that of the parallel flow field structure. The lower variable-diameter flow section is a variable-diameter flow field structure with the same height as the parallel flow field structure; The bottom barrier region is composed of multiple rows of frustums arranged along the width direction of the bipolar plate, with each row of frustums staggered. The upper surface of the frustums is flush with the upper surface of the variable diameter flow field structure. The parallel flow field structure is composed of multiple straight flow channel ridges, and a straight flow channel groove of a bipolar plate is formed between each two adjacent straight flow channel ridges. The variable diameter flow field structure consists of multiple variable diameter flow channel ridges, and a variable diameter flow channel groove of a bipolar plate is formed between each pair of adjacent variable diameter flow channel ridges.

2. The bipolar plate with a multi-flow field structure according to claim 1, characterized in that, Along the length of the bipolar plate, multiple contraction sections are uniformly arrayed on the variable diameter flow channel ridge, and the contraction sections of adjacent variable diameter flow channel ridges are aligned; both the variable diameter flow channel ridge and the contraction section have corresponding widening sections.

3. The bipolar plate with a multi-flow field structure according to claim 1, characterized in that, The width of the straight flow channel is 1-5mm; the width of the variable diameter flow channel is 1-5mm; the width of the widened portion of the variable diameter flow channel is 2-6mm. The depth of the straight flow channel and the variable diameter flow channel is 0.8-3mm; A row of frustums adjacent to the lower variable flow section is located at the center between the two variable flow channel ridges, and the diameter of the frustums is 1-3 mm.

4. The bipolar plate with a multi-flow field structure according to claim 1, characterized in that, Within the flow field region, the area within the width direction of the flow field region is defined as the edge region, which is a distance of one-quarter of the total width from both sides of the bipolar plate. The remaining area is the middle region. The channel ridge spacing in the middle region is 0.5-2 mm; the channel ridge spacing in the edge region is 2.5-5 mm; and the spacing between two adjacent channel ridges in the middle and edge regions is 1-3 mm.

5. A bipolar plate with a multi-flow field structure according to claim 1, characterized in that, The boss structure consists of a transverse ridge and three uniformly arranged longitudinal ridges perpendicular to the transverse ridge. The height of the boss structure is 1 mm lower than that of the parallel flow field structure. The length of the transverse ridge is flush with both ends of the upper DC section. The width of the transverse ridge and the width of the longitudinal ridge are equal to the width of the straight flow channel ridge.

6. A bipolar plate with a multi-flow field structure according to claim 5, characterized in that, In the boss structure, the intersection of the transverse and longitudinal protrusions is low-lying.

7. A bipolar plate with a multi-flow field structure according to any one of claims 1 to 6, characterized in that, When the central blocking zone is located in the middle of the lower variable flow section, the lower variable flow section is divided by the central blocking zone to form two variable flow field areas. The reaction flow field areas are, from top to bottom, the upper direct flow section area, the lower variable flow section A area, the central blocking zone, the lower variable flow section B area, and the bottom blocking zone.

8. The method for preparing a bipolar plate with a multi-flow field structure as described in claim 1, characterized in that, Includes the following steps: S1. Use metal sheet and pre-treat its surface; S2. Using rubber pad stamping forming process, the surface of metal sheet is stamped or etched to form structures including parallel flow field structure, boss structure, variable diameter flow field structure and truncated cone structure.

9. The method for preparing a bipolar plate with a multi-flow field structure according to claim 8, characterized in that, The surface pretreatment in S1 includes grinding, removing the passivation layer, and coating the surface with an anti-corrosion protective layer; grinding is done with 50-200 grit sandpaper; removing the passivation layer involves soaking in a weak acid with pH=6.6-6.9 for 1-5 hours; and coating the surface with an anti-corrosion protective layer involves sputtering precious metals such as Pt and C using the PVD method.

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