An ultrathin fuel cell bipolar plate

Abstract

This invention discloses an ultrathin fuel cell bipolar plate, which is formed by joining an active region assembly and distribution region assemblies located on both sides thereon. The distribution region is composed of an upper half and a lower half of the distribution region joined along the thickness direction. The inner and outer surfaces of the upper half and the lower half of the distribution region are provided with independently formed gas and cooling medium guide channels, and the flow channel depth of the distribution region is not less than the flow channel depth of the active region. This invention breaks through the process limitations of traditional one-piece stamping of ultrathin metal plates, and achieves the deep flow channel design of the distribution region through split manufacturing, which effectively improves the uniformity of fluid distribution and greatly enhances the electrochemical reaction efficiency. At the same time, it retains the advantages of ultrathin high power density of the active region, and achieves the goal of significantly improving the volumetric power density of the fuel cell stack.

Description

Technical Field

[0001] This invention relates to the field of core components technology for hydrogen fuel cells, specifically to an ultrathin fuel cell bipolar plate. Background Technology

[0002] The volumetric power density of proton exchange membrane fuel cells (PEMFCs) is a key indicator in the aerospace and automotive fields, representing the effective power output of the fuel cell stack per unit volume. A higher volumetric power density means a smaller fuel cell stack volume for the same output power, which is more advantageous for fuel cell installation and placement in aircraft, vehicles, and ships. Furthermore, a higher volumetric power density also means less material is needed for the fuel cell stack for the same output power, thus reducing the material cost of the fuel cell. Currently, in applications such as drones and electric vertical aerial vehicles (eVTOLs), the industry is still focused on reducing the thickness of bipolar plates.

[0003] Traditional technology uses two monopole plates welded back-to-back, resulting in a relatively thick layer. Improved, advanced technologies employ nested or interlocking structures, utilizing waveform phase differences to arrange air-water channels at intervals on the same layer, effectively reducing the thickness of the active zone. However, existing technologies use a single piece of material for integral processing to form the active and distribution zones; for example, metal is formed by integral stamping or graphite by integral machining. Extremely thin metal foils are difficult to stamp into distribution channels with large depth variations and complex structures. Forced stamping can easily lead to material breakage or severe springback. Furthermore, due to limitations in the stamping process, the existing ultra-thin plates have shallow distribution zone channels, smaller than the active zone channels, resulting in high flow resistance and difficulty in effectively and evenly distributing fluid from the vertical main pipe to the horizontal micro-channels, thus degrading the fuel cell stack performance. Summary of the Invention

[0004] To overcome the aforementioned technical problems, this invention provides an ultra-thin fuel cell bipolar plate. Its core advantage lies in retaining the ultra-thin nested structure of the active region, but the manufacturing method of the reconfigurable distribution region employs a pre-fabrication and then splicing approach, thus solving the problem that ultra-thin plates cannot form complex distribution channels.

[0005] The bipolar plate assembly provided by this invention consists of an active region assembly and a distribution region assembly connected together. The active region employs two corrugated monopolar plates, namely an anode plate and a cathode plate, nested together. The waveform phase difference is used to form a cooling channel in the non-contact area, achieving ultra-thinness. The distribution regions are located at both ends of the active region and are used to connect the external main pipe to the active region's flow channel.

[0006] The active region and the distribution region mentioned above are independent components, which are connected by a bonding process.

[0007] The aforementioned distribution area component is made up of an upper half and a lower half that are machined independently and joined together in the thickness direction, i.e., the Z-axis.

[0008] The flow channel depth of the aforementioned distribution zone is not less than the flow channel depth of the active zone.

[0009] Furthermore, the upper and lower halves of the distribution zone are each equipped with gas flow channels and cooling medium flow channels. Next, the upper and lower halves are connected using welding or bonding processes to form a complete fluid distribution system. One end of the joined distribution zone assembly is connected to an external hydrogen / air / coolant main pipe, and the other end is connected to the ultra-thin monopolar plate of the active zone, precisely guiding the fluid into the same-layer flow channel of the active zone.

[0010] The beneficial effects of this invention include the following:

[0011] First, this invention fundamentally solves the problem of forming complex flow channels in ultra-thin sheets. Traditional one-piece stamping processes require the construction of complex interlaced flow channel structures through drastic material deformation on a single-layer ultra-thin sheet, which often exceeds the elongation limit of the metal foil and easily leads to breakage at corners. This invention divides the complex distribution channel's distribution area 1 structure into two relatively simple geometric planes: the upper half 13 and the lower half 14 of the distribution area. This transforms the depth deformation that originally needed to be achieved on a single sheet of material into the spatial superposition of two joined materials. The stamping depth of each material is only about half the total depth of the final flow channel, greatly alleviating stress concentration in the material, eliminating forming springback, and making it possible to manufacture complex distribution systems on ultra-thin sheets.

[0012] Secondly, through the above design, this invention provides superior hydrodynamic characteristics to address the flow resistance and distribution uniformity issues caused by the shallow distribution channel in existing technologies. The combined distribution zone 1 forms an independent cooling medium channel 10 internally, and air channels 11 and hydrogen channels 12 with a depth not less than that of the active zone 2 are formed on its surface. This increases the equivalent hydraulic diameter of the channels by more than 50% compared to traditional single-sided pressurized channels, significantly reducing local resistance losses when fluid enters the horizontal channel from the vertical main pipe. Furthermore, after the fluid enters the distribution zone 1 from the external main pipe, a uniform pressure field can be rapidly established within the deeper, low-flow-resistance distribution channel, and then it is precisely guided into the micro-channels of the active zone 2. This design effectively overcomes the uneven distribution of fluid when switching between the vertical main pipe and the horizontal micro-channels, thereby significantly improving the output performance and stability of the fuel cell stack under high current density.

[0013] In summary, this invention achieves a deep flow channel design in the distribution zone, thereby significantly reducing local flow resistance and constructing an efficient pressure-stabilizing distribution mechanism. This highly uniform fluid distribution ensures consistency in the supply of reactant gases and thermal management within the active zone, greatly improving electrochemical reaction efficiency. Combined with the ultra-thin nesting advantage of the active zone, output performance is optimized while maintaining an extremely low plate thickness, ultimately achieving a significant increase in the volumetric power density of the fuel cell stack. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the bipolar plate structure of the proton exchange membrane fuel cell of the present invention, wherein: 1-distribution area; 2-active area; 4-hydrogen inlet; 5-cooling medium outlet; 6-air outlet; 7-air inlet; 8-cooling medium inlet; 9-hydrogen outlet; 11-air flow channel.

[0015] Figure 2 This is a schematic diagram of the distribution area structure of the bipolar plate of a proton exchange membrane fuel cell, where: 7-air inlet; 8-cooling medium inlet; 9-hydrogen outlet; 11-air flow channel; 12-hydrogen flow channel; 13-upper part of the distribution area; 14-lower part of the distribution area.

[0016] Figure 3 This is a cross-sectional view of the upper and lower distribution regions of the bipolar plate of a proton exchange membrane fuel cell, where: 10 - cooling medium flow channel; 13 - upper distribution region; 14 - lower distribution region, and AA is a cross-sectional view of the upper distribution region 13, and BB is a cross-sectional view of the lower distribution region 14.

[0017] Figure 4 This is a schematic diagram of the active region structure of a bipolar plate in a proton exchange membrane fuel cell, where 2 represents the active region and 15 represents the unipolar plate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] The fuel cell bipolar plate provided by this invention is suitable for both metallic and graphite materials. The joining processes mentioned in this specification include welding and bonding. If the material is metallic, it can be joined using welding methods such as laser welding, resistance spot welding, or diffusion welding. If the material is graphite, it can be bonded using hot-pressing adhesive bonding.

[0020] like Figure 1As shown, the fuel cell bipolar plate is formed by joining an active region 2 and distribution regions 1 located on both sides of the active region. One distribution region 1 has a hydrogen inlet 4, an air outlet 6, a cooling medium outlet 5, an air flow channel 11 for air circulation, and a hydrogen flow channel for hydrogen circulation. The hydrogen flow channel for hydrogen circulation is not shown in the diagram and is located on the back side of distribution region 1. The other distribution region 1 has a hydrogen outlet 9, an air inlet 7, a cooling medium inlet 8, an air flow channel 11 for air circulation, and a hydrogen flow channel for hydrogen circulation. The active region 2 consists of two structurally matched monopolar plates, the structural details of which are shown in [the diagram]. Figure 4 The Central Committee will provide a detailed explanation.

[0021] The distribution region 1 of the proton exchange membrane fuel cell bipolar plate provided by the present invention is formed by connecting the upper half 13 and the lower half 14 of the distribution region, as shown in the figure. Figure 2 and Figure 3 As shown. The upper half 13 and the lower half 14 of the distribution area have similar or nearly identical structures, and are two parts of the distribution area 1 that are independently manufactured and joined together in the z-direction. Furthermore, the upper half 13 of the distribution area is connected to the cathode plate, and the lower half 14 of the distribution area is connected to the anode plate.

[0022] Taking the distribution zone 1 on one side of the active zone 2 as an example, the outer surface of the upper half 13 of the distribution zone is provided with an air inlet 7, an air flow channel 11 for air circulation, a cooling medium inlet 8, and a hydrogen outlet 9, as shown below. Figure 2 As shown. Similarly, the lower half 14 of the distribution zone has a hydrogen outlet 9, a hydrogen flow channel 12 for hydrogen circulation, a cooling medium inlet 8, and an air inlet 9 on its outer surface. Furthermore, the upper half 13 and the lower half 14 of the distribution zone both have cooling medium flow channels 10 on their inner surfaces, specifically as shown... Figure 3 As shown. Figure 3 This is a structural sectional view of the distribution area, where AA is a sectional view of the upper half 13 of the distribution area and BB is a sectional view of the lower half 14 of the distribution area.

[0023] With the above configuration, after the upper half 13 and lower half 14 of the distribution area provided by the present invention are joined to form the distribution area 1, the flow channel distribution exhibits a periodic pattern of air flow channel - cooling medium flow channel - hydrogen flow channel - cooling medium flow channel. One end of the distribution area 1 is connected to the external hydrogen / air / coolant main pipe, and the other end is connected to the ultrathin monopolar plate of the active area 2, so as to accurately guide the fluid into the same layer of the flow channel of the active area 2.

[0024] Figure 4The diagram shows the structure of active region 2. Active region 2 is composed of two nested monopolar plates 15 with matching structures, that is, the outer side of the groove of one monopolar plate is correspondingly joined to the outer side of the ridge of the other monopolar plate. After the two monopolar plates are joined, a cavity is formed, which serves as the cooling medium flow channel 10. Therefore, the above-mentioned active region exhibits a periodic parallel interval arrangement of air flow channel - cooling medium flow channel - hydrogen flow channel - cooling medium flow channel on the same horizontal layer. The thickness of this bipolar plate assembly is about 1 / 2 that of a conventional bipolar plate assembly, and the volumetric power density is doubled under the condition of equal output power.

[0025] As shown in Figures 1 to 4, the bipolar plate in this embodiment is manufactured using a split-type manufacturing process.

[0026] The following describes Examples 1, 2, and 3 in detail.

[0027] Example 1: Preparation of graphite bipolar plates

[0028] Manufacturing of Active Region 2: A 0.45 mm thick graphite plate was selected, and CNC machining equipment was used to machine only the flow channels of the active region. The machined anode and cathode plates were nested and stacked, and the phase difference between the grooves and ridges was used to form cooling channels. They were then connected and fixed by adhesive bonding to form Active Region 2. After joining, the depth of the hydrogen flow channel 12 is 0.1 mm, the depth of the air flow channel 11 is 0.1 mm, and the depth of the cooling medium flow channel 10 is 0.1 mm.

[0029] Manufacturing of Distribution Zone 1: Distribution Zone 1 is manufactured independently of the active zone. The upper half 13 and lower half 14 of the distribution zone can be machined from graphite plates of the same material with a thickness of 0.4 mm. Due to their relatively small size compared to the active zone, more complex guide grooves can be machined on their upper and lower surfaces, and the machining stress is easily released due to the small size of the components. The gas flow channel groove depth of the upper half 13 and lower half 14 of the distribution zone is designed to be 0.2 mm, and the cooling medium flow channel 10 groove depth is 0.1 mm. The upper half 13 and lower half 14 of the distribution zone are then aligned in the thickness direction and connected by methods such as adhesive bonding to form an independent distribution zone 1 with a total thickness consistent with that of the active zone. After joining, the hydrogen flow channel 12 groove depth is 0.2 mm, the air flow channel 11 groove depth is 0.2 mm, and the cooling medium flow channel 10 groove depth is 0.2 mm.

[0030] Assembly: Connect the prefabricated distribution area 1 to both ends of the active area component 2. During assembly, ensure that the flow channel at the outlet of the distribution area component is precisely aligned with the flow channel inlet of the active area component on the horizontal plane. Use high-adhesion adhesive for bonding and sealing to ensure that hydrogen, air, and coolant do not cross-contaminate or leak externally.

[0031] Table 1 shows the total thickness of the distribution zone obtained using different groove depths. It should be noted that, since complex deep grooves are not involved and the process is machined, the groove depth of the distribution zone flow channel can be flexibly designed. In this embodiment, the flow channel depth of the distribution zone is 0.1–0.35 mm, thus the total thickness of the resulting distribution zone can be controlled between 0.62 and 1.07 mm.

[0032]

[0033] The total thickness of the distribution zone = material thickness x 2 + air flow channel depth + hydrogen flow channel depth + cooling medium flow channel depth.

[0034] Example 2: Preparation of a metal bipolar plate

[0035] Manufacturing of active region 2: The active region component is made of 0.2 mm thick stainless steel foil, which is precision stamped to form a nested structure. The depth of the hydrogen flow channel 12 is 0.2 mm, the depth of the air flow channel 11 is 0.2 mm, and the depth of the cooling medium flow channel 10 is 0.2 mm.

[0036] Manufacturing of Distribution Zone 1: Distribution Zone 1 is manufactured independently of the active zone. The upper half 13 and lower half 14 of the distribution zone can be precision stamped using stainless steel foil of the same material with a thickness of 0.2 mm. The gas flow channel depth of the upper half 13 and lower half 14 of the distribution zone is designed to be 0.2 mm, and the cooling medium flow channel 10 depth is 0.1 mm. The upper half 13 and lower half 14 of the distribution zone are then aligned in the thickness direction and joined using one of three welding methods: laser welding, resistance spot welding, or diffusion welding, to form an independent distribution zone 1 with a total thickness consistent with that of the active zone. After joining, the hydrogen flow channel depth is 0.2 mm, the air flow channel depth is 0.2 mm, the cooling medium flow channel 10 depth is 0.2 mm, and the material thickness of the upper half 13 and lower half 14 of the distribution zone is 0.1 mm.

[0037] Assembly: The distribution area components and the active area components are joined and assembled using one of three welding methods: laser welding, resistance spot welding, or diffusion welding.

[0038] Table 2 shows the total thickness of the distribution zone obtained using different channel depths. In this embodiment, the channel depth of the distribution zone is 0.1–0.35 mm, so the total thickness of the distribution zone can be controlled between 0.50 and 1.25 mm.

[0039]

[0040] The total thickness of the distribution zone = material thickness x 2 + air flow channel depth + hydrogen flow channel depth + cooling medium flow channel depth.

[0041] Example 3: Performance improvement of the deep channel design of the distribution area of ​​the present invention compared with the prior art.

[0042] To further verify the technical advantages of the independently manufactured distribution area and the flow channel depth not less than that of the active area flow channel disclosed in this invention, this embodiment selects the metal bipolar plate prepared in Example 2 above, hereinafter referred to as the plate of this invention, and compares it with the metal bipolar plate prepared by the prior art, hereinafter referred to as the prior art plate, for comparative testing.

[0043] 1. Test object parameter settings

[0044] The plate of this invention: the distribution area 1 is formed by joining the upper half 13 and the lower half 14 of the distribution area. The flow channel depth of the distribution area is 0.1-0.35 mm, and 0.2 mm is used as an example here. The flow channel depth of the active area is 0.2 mm.

[0045] Existing technology board: It is formed by one-piece stamping. Due to the limitation of the elongation of the metal foil, the groove depth of its distribution and guiding area is only 0.15 mm, which is less than the groove depth of its active area of ​​0.35 mm.

[0046] 2. Compare experimental data

[0047] Table 3 presents comparative data obtained through fluid dynamics simulation (CFD) and single-cell polarization curve testing:

[0048]

[0049] 3. Results Analysis and Conclusions

[0050] (1) Breakthrough in manufacturing yield: Existing technology uses integral stamping to construct complex distribution channels on ultra-thin metal foil. Due to severe local deformation, micro-cracks or uneven springback are easily generated at the corners of the channels, resulting in a yield of only 82.5%. In contrast, this invention decomposes the distribution area into two simple planar structures and processes them separately, which greatly reduces the stamping depth and stress concentration of a single piece of material, and increases the manufacturing yield to 98.2%, fundamentally solving the processing problem of complex channels in ultra-thin plates.

[0051] (2) Optimization of fluid dynamics characteristics: Due to the smaller depth of the distribution channel in the existing technology plate compared to the active zone, the local resistance is huge when the fluid enters, resulting in a pressure drop of 12.4 kPa. This invention achieves a 0.2 mm deep channel through split splicing, which allows for a smooth transition between the distribution and active zones, significantly reducing the pressure drop by 43%. More importantly, the deep channel creates a more uniform pressure field in the distribution zone, reducing the velocity distribution variance from 0.18 to 0.04, ensuring a high degree of consistency in the reactive gas obtained by the active zone channel.

[0052] (3) Improved output performance and stability of the fuel cell stack: In the polarization curve test, the plate of the present invention exhibited a higher limiting current density, namely 2.8 A / cm², which is attributed to its excellent distribution uniformity. Meanwhile, during long-term operation testing, the output power fluctuation of the plate of the present invention was controlled within ±0.9%. This is because the deep flow channel design not only reduces flow resistance but also enhances the drainage capacity of the distribution area for liquid water, avoiding flooding and voltage fluctuations caused by water accumulation in the shallow flow channels of the distribution area in existing technologies, thus significantly improving the operational stability of the fuel cell stack.

[0053] Therefore, this invention overcomes the structural defect of a deep active region and a shallow distribution region in the prior art by changing the manufacturing logic of the distribution region. Experiments have shown that the distribution region flow channel design disclosed in this invention has unexpected technical effects in reducing manufacturing difficulty, improving distribution uniformity, and enhancing the output stability of the fuel cell stack, demonstrating significant inventiveness compared to the prior art.

[0054] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An ultrathin fuel cell bipolar plate, characterized in that, The bipolar plate includes an active region (2) and distribution regions (1) located on both sides of the active region; The active region (2) and the distribution region (1) are independent components, which are connected by a bonding process; The flow channel depth of the distribution area (1) is not less than the flow channel depth of the active area (2); The distribution area (1) comprises an upper half (13) and a lower half (14) of the distribution area joined together along the thickness direction. The upper half (13) of the distribution area is joined to the cathode plate of the active area, and the lower half (14) of the distribution area is joined to the anode plate of the active area. Gas flow path guide grooves are provided on the upper surface of the upper half (13) of the distribution area and the lower surface of the lower half (14) of the distribution area; The lower surface of the upper half (13) of the distribution area and the upper surface of the lower half (14) of the distribution area are provided with cooling medium flow channel guide grooves; The fluid distribution system of the distribution area (1) is connected to an external fluid main pipe at one end and to the active area (2) at the other end.

2. The ultrathin fuel cell bipolar plate as described in claim 1, characterized in that, The aforementioned connection, For metal bipolar plates, the process includes laser welding, resistance spot welding, or diffusion welding. For graphite bipolar plates, the process involves hot-pressing and bonding.

3. The ultrathin fuel cell bipolar plate as described in claim 1 or 2, characterized in that, The active region (2) is formed by nesting and joining an anode monopole plate and a cathode monopole plate, with the outer side of the groove of one monopole plate and the outer side of the ridge of the other monopole plate correspondingly joined, and the fluid distribution system of the distribution region (1) guides the fluid to the cooling channel between the anode plate and the cathode plate or the reaction flow channel on their respective surfaces.

4. The ultrathin fuel cell bipolar plate as described in claim 1 or 2, characterized in that, The distribution area (1) presents a periodically parallel arrangement of a reaction gas channel, a cooling medium channel, an air channel and a cooling medium channel at the junction of the single electrode, and the centers of the channels are at the same horizontal position.

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