A closed air-cooled fuel cell stack and a method for manufacturing the same

Abstract

This invention belongs to the field of fuel cell stacks, specifically relating to a closed-loop air-cooled fuel cell stack and its fabrication method. The fuel cell stack consists of a cathode plate, an anode plate, and upper and lower sealing rings, wherein the upper and lower sealing rings are made of hydrogen-resistant rubber. The upper and lower sealing rings have identical structures. To ensure ease of sealing, the upper sealing ring is installed by rotating 180° relative to the lower sealing ring around the central axis of the electrode plate, ensuring complete alignment of the sealing lips after rotation. Air channels and cooling channels are provided on the electrode plate, and an air manifold is provided between the air inlet and the air and cooling channels on the bipolar plate. This invention distributes the gas supplied by a blower to the cooling and heat dissipation channels, utilizing the high strength and stamping characteristics of the metal bipolar plate, and through a specific structural design, eliminates the need for a separate heat sink.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell stacks, specifically relating to a closed-loop air-cooled fuel cell stack and its preparation method. Background Technology

[0002] Hydrogen energy, as a core carrier of the zero-carbon energy system, has entered a critical stage of "diversified application scenarios." While water-cooled fuel cell stacks have achieved demonstration applications in high-power sectors such as commercial vehicles and passenger cars, they face challenges such as system complexity and insufficient adaptability, hindering their penetration into the small- and medium-power markets. In contrast, scenarios such as drones, two-wheeled vehicles, sightseeing vehicles, and distributed power sources urgently require lightweight, low-cost, and long-life energy devices—for example, drones need to balance range (requiring an energy density ≥200Wh / kg) and payload (each 1kg reduction in weight increases the effective payload by 0.5kg), while two-wheeled vehicles need to adapt to a wide temperature range of -20℃ to 45℃.

[0003] Air-cooled fuel cells, due to their simple structure and lack of a coolant circulation system, have become the preferred choice for small and medium power applications. Data shows that the global market size for air-cooled hydrogen fuel cell stacks reached several billion US dollars in 2023 and is projected to maintain an average annual growth rate of over 30% by 2030, with the proportion of closed-loop systems expected to increase from 15% in 2025 to 40%. The development of closed-loop metal plate air-cooling technology is the core support for the hydrogen energy industry's transformation from "high-power demonstration" to "small-power large-scale production." Currently, small and medium power hydrogen energy applications mainly rely on open-loop air-cooled stacks and graphite bipolar plates, but their performance defects have become an obstacle to industrialization. Traditional open-system designs couple the cathode reaction with heat dissipation, allowing ambient air to directly enter the fuel cell stack. This leads to two problems: first, the airflow required for heat dissipation (typically 5-10 times the reaction airflow) easily dries out the membrane electrode assembly (MEA), reducing proton conductivity by more than 30% and hydrogen utilization to less than 70%; second, unfiltered dust and humidity fluctuations (such as humidity exceeding 90% during the rainy season in southern China or winter humidity in northern China) can cause the MEA to be flooded or dehydrated, shortening the fuel cell stack lifespan to below 2000 hours. Some sightseeing vehicles in Shanxi Province initially used open-system designs, and due to sandstorms, the failure and repair rate reached 40% within three months. After switching to a closed-system design, the failure rate decreased by 90%.

[0004] While traditional graphite plates are corrosion-resistant, they have three major drawbacks: low power density (only 0.3-0.5 W / cm²), high processing difficulty (the success rate of irregular flow field forming is less than 60%), and high weight (more than 3 times heavier than metal plates). By replacing the graphite plates with titanium alloy metal plates, the weight of the 4kW fuel cell stack is reduced from 12kg to 5.2kg, and the volume is reduced by 40%, making it perfectly suited to the payload requirements of drones.

[0005] The explosive growth of the small and medium power market has placed clear demands on fuel cell stack performance. Closed-loop metal plate technology is perfectly suited to the needs of low-altitude economic and mobile equipment, distributed energy and emergency power supplies, special equipment and agricultural machinery.

[0006] In existing technologies, air-cooled fuel cell stacks are divided into graphite bipolar plate fuel cell stacks and metal bipolar plate fuel cell stacks, each accounting for approximately 50% of the market share. They can also be divided into open-type and closed-type air-cooled fuel cell stacks. Open-type air-cooled stacks utilize both metal plate and graphite plate methods, but closed-type stacks primarily use graphite plate solutions because the traditional closed-type metal plate air-cooled stacks have a more complex structure and manufacturing process. This complexity stems from the metal plate stamping process; typical products require the addition of heat dissipation plates, resulting in metal stacks often consisting of three or more metal plates, sometimes as many as six or seven, and the assembly process is also quite complex. Traditional air-cooled stacks use fans for cooling. In open-type air-cooled stacks, the gas supplied by the fan serves as both reactant and cooling gas; in closed-type air-cooled stacks, a blower supplies the reactant gas, and the fan provides the cooling gas. Therefore, closed-type air-cooled stacks are designed with an independent heat dissipation plate to facilitate the smooth flow of gas through the stack and the removal of heat. Summary of the Invention

[0007] This invention distributes the gas supplied by the blower to the cooling and heat dissipation channels. Utilizing the high strength and stamping characteristics of the metal bipolar plate, and through a specific structural design, it eliminates the need for a separate heat sink. Therefore, a fan is also unnecessary to provide cooling gas.

[0008] The objective of this invention is achieved by at least one of the following technical solutions.

[0009] The core of this invention lies in the design of the bipolar plate structure and the design of the bipolar plate sealing scheme.

[0010] A closed-loop air-cooled fuel cell stack, the fuel cell stack including a bipolar plate structure, the bipolar plates being sealed by a sealing ring;

[0011] The specific structure is as follows: the battery stack consists of a cathode plate, an anode plate, and two sets of upper and lower sealing rings, wherein the upper and lower sealing rings are made of hydrogen-resistant rubber; the upper and lower sealing rings have the same structure, and to ensure the simplicity of sealing, the upper sealing ring is installed by rotating 180° relative to the lower sealing ring around the central axis of the electrode plate, and after rotation, the sealing lips of the sealing rings are completely aligned.

[0012] The electrode plate is provided with an air flow channel and a cooling flow channel, and an air manifold is provided between the air inlet and the air flow channel and cooling flow channel on the bipolar plate.

[0013] Furthermore, the hydrogen-resistant rubber is EPDM or fluororubber, and the Shore hardness of the hydrogen-resistant rubber is 60-70HA, with a temperature range of -40℃ to 120℃.

[0014] Furthermore, the bipolar plate is made of 316L stainless steel or titanium alloy TA2 substrate, and the surface of the substrate is formed with air manifold, air flow channel and cooling flow channel by stamping process.

[0015] Furthermore, the air manifold is located at the edge of the electrode plate as the main air inlet, and its inner wall is provided with a guide protrusion to achieve air diversion and guidance; the cross-section is rectangular or circular with a cross-sectional area of ​​8-50 mm²; the height of the guide protrusion is 0.3-0.5 mm.

[0016] Furthermore, the airflow channel is a direct flow channel or a serpentine flow channel, and both ends of the flow channel are connected to the exhaust manifold at the edge of the electrode plate; the airflow channel has a groove width of 0.8-1.2 mm, a ridge width of 0.6-1.0 mm, and a depth of 0.5-0.8 mm.

[0017] Furthermore, the air entering through the air manifold is diverted to the cooling channel and the air channel in a volume fraction of 60-70%:30-40%.

[0018] Furthermore, sealing bosses are provided in the corresponding areas of the anode plate and the cathode plate, which cooperate with the weld to form an isolation barrier between the hydrogen chamber and the cooling channel; the height of the sealing bosses is 0.2-0.3mm and the width is 1.0-1.5mm.

[0019] A method for fabricating a closed-loop air-cooled fuel cell stack includes the following steps:

[0020] Take a cathode plate, an anode plate, and two sets of sealing rings, with the upper and lower sealing rings having the same structure. To ensure the simplicity of sealing, the upper sealing ring is installed by rotating it 180° relative to the lower sealing ring around the central axis of the electrode plate. After rotation, the sealing lips of the sealing rings are completely aligned.

[0021] The upper and lower sealing rings have the same structure. To ensure the simplicity of sealing, the upper sealing ring is installed by rotating 180° relative to the lower sealing ring around the central axis of the electrode plate. After rotation, the sealing lips of the sealing rings are completely aligned, so that the upper and lower sealing rings form a continuous sealing surface in the bipolar plate assembly, covering the boundaries of the hydrogen chamber, air manifold, and cooling channel. Only 2 sets of sealing rings are needed to achieve multi-chamber isolation.

[0022] Specifically, the steps include the following:

[0023] (1) The anode and cathode plates are assembled into bipolar plates by laser welding. The laser power is 150-250W, the welding speed is 30-50mm / s, the focal distance is 0.5-1.0mm, the weld width is 0.2-0.4mm, and the weld depth is 0.3-0.5mm.

[0024] (2) The adhesive for bonding the electrode plate and the sealing ring is preferably liquid silicone or epoxy resin with high viscosity. Before bonding, the surface of the bipolar plate sealing groove needs to be degreased, the adhesive is coated on the inner wall of the sealing groove, the sealing ring is pasted on the surface of the sealing groove and pressed together, and finally cured and formed.

[0025] (3) After the bipolar plates are prepared, they are stacked with the membrane electrode assembly to form an air-cooled fuel cell stack: the bipolar plate assembly and the membrane electrode assembly (MEA) are stacked alternately. The stacking order is bipolar plate assembly, MEA, and bipolar plate assembly stacked in sequence. When each new bipolar plate assembly is added, it is rotated 180° around the central axis of the plate. After stacking, the end plates are pressed together. The pressing force is controlled at 1.2-1.8 MPa to ensure that the contact resistance between the bipolar plate assembly and the MEA meets the requirements for use, and at the same time, the sealing ring is fully deformed to achieve reliable sealing.

[0026] In the above method, the laser welding is a fiber laser; the wavelength of the laser is 1064nm; the degreasing is performed by ultrasonic cleaning with anhydrous ethanol for 10-15 minutes and drying at 60-80℃; the adhesive coating thickness is 0.1-0.2mm, uniformly covering the inner wall of the sealing groove.

[0027] In the above method, the pressing pressure is 0.2-0.3 MPa, and the holding time is 30-60 s; the curing temperature is 80-100℃, and the curing time is 120-180 min.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] 1) This invention eliminates the need for a fan, reducing structural complexity and improving the efficiency of the closed-loop air-cooled fuel cell stack;

[0030] 2) This invention reduces the number of heat sinks, greatly increasing the power density.

[0031] 3) This invention uses only two bipolar plates, i.e. two stamped parts, resulting in low manufacturing costs. Attached Figure Description

[0032] Figure 1 This is a diagram illustrating air distribution.

[0033] Figure 2 This is a schematic diagram of a bipolar plate assembly.

[0034] Figure 3This is a schematic diagram of the welding of a bipolar plate assembly;

[0035] Figure 4 A schematic diagram of a bipolar plate with a sealing ring (anode side);

[0036] Figure 5 A side view of a bipolar plate with a sealing ring (cathode side).

[0037] Figure 6 This is a schematic diagram of a closed-type air-cooled fuel cell stack.

[0038] Figure 7 This is a comparison diagram of the closed-type air-cooled fuel cell stack of the present invention and the conventional open-type air-cooled fuel cell stack. Detailed Implementation

[0039] The technical solutions described below, in conjunction with specific illustrations, are presented to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and similar extended embodiments made by those skilled in the art without inventive effort are all within the scope of protection of this invention.

[0040] like Figure 1 As shown, air enters the electrode plate from the air manifold and splits into two parts: one part enters the air channel to participate in the electrochemical reaction, and the other part enters the cooling channel to maintain the stack temperature. This design has two advantages. First, compared to conventional closed-loop air cooling systems that discard the cooling channel (which would require an additional cooling plate), this invention utilizes the cooling channel. This eliminates the need for a sealed design, greatly simplifying the stack components. Second, by using air from the air manifold to cool the stack, there is no need for an additional cooling fan, significantly reducing costs and simplifying the overall structure.

[0041] The bipolar plates (cathode plates / anode plates) are made of 316L stainless steel or titanium alloy TA2 substrate, and the surface of the substrate is formed by stamping to form air manifolds, air channels and cooling channels.

[0042] The air manifold has a rectangular or circular cross-section with a cross-sectional area of ​​8-50 mm². It is located at the edge of the electrode plate and serves as the main air inlet. Its inner wall is provided with guide protrusions (0.3-0.5 mm in height) to guide the air flow.

[0043] The air entering through the manifold is split into the cooling channel and the air channel at a ratio of 60-70%:30-40%. The air channel is either a direct channel or a serpentine channel (groove width 0.8-1.2mm, ridge width 0.6-1.0mm, depth 0.5-0.8mm), and both ends of the channel are connected to the exhaust manifold at the edge of the electrode plate.

[0044] Sealing bosses (0.2-0.3mm high, 1.0-1.5mm wide) are provided in corresponding areas of the anode plate and cathode plate to form an isolation barrier between the hydrogen chamber and the cooling channel in conjunction with the weld.

[0045] Figure 2 This refers to the design of the core component of the fuel cell stack—the bipolar plate assembly. It consists of a cathode plate, an anode plate, and upper and lower sets of sealing rings. The upper and lower sealing rings are made of hydrogen-resistant rubber (EPDM or fluororubber, Shore hardness 60-70 HA, temperature range -40℃ to 120℃). The upper and lower sealing rings have identical structures. To ensure ease of sealing, the upper sealing ring is installed by rotating it 180° relative to the lower sealing ring around the central axis of the electrode plate. After rotation, the sealing lips of the sealing rings are perfectly aligned.

[0046] By using "seal ring structure consistency + 180° rotation installation", the upper and lower seal rings form a continuous sealing surface within the bipolar plate assembly, covering the boundaries of the hydrogen chamber, air manifold, and cooling channel. Only two sets of seal rings are needed to achieve multi-chamber isolation.

[0047] The manufacturing process of the bipolar plate assembly is as follows: welding of the anode and cathode plates → bonding of the sealing ring.

[0048] The anode and cathode plates are assembled into bipolar plates using laser welding (preferably fiber laser, wavelength 1064nm). The laser power is 150-250W, the welding speed is 30-50mm / s, the focal distance is 0.5-1.0mm, the weld width is 0.2-0.4mm, and the weld depth is 0.03-0.05mm (ensuring complete fusion of the substrate with no incomplete penetration). The function of welding is to restrict the movement of materials within the battery to a fixed chamber; therefore, the weld must completely surround the entire gas flow area. The welding position is as follows... Figure 3 As shown. Furthermore, hydrogen needs to be isolated from air, therefore the hydrogen manifold and the bridge area need to be surrounded. This weld design ensures that the anode gas (i.e., hydrogen) cannot enter the cooling channel, while air can enter smoothly. Additionally, welding is required at the contact points in the reaction zone to reduce the contact resistance between the electrodes.

[0049] The preferred adhesive for bonding the bipolar plate to the sealing ring is a high-viscosity liquid silicone or epoxy resin. Before bonding, the surface of the bipolar plate sealing groove needs to be degreased (using anhydrous ethanol for ultrasonic cleaning, 10-15 min, drying temperature 60-80℃), followed by applying the adhesive (coating thickness 0.1-0.2 mm, evenly covering the inner wall of the sealing groove). The sealing ring is then adhered to the surface of the sealing groove and pressed (pressure 0.2-0.3 MPa, holding time 30-60 s), and finally cured (temperature 80-100℃, curing time 120-180 min).

[0050] Figure 4 and Figure 5 This is a schematic diagram of the prepared bipolar plate assembly.

[0051] like Figure 6 As shown, after the bipolar plates are fabricated, they are stacked with the membrane electrode assembly (MEA) to form an air-cooled fuel cell stack. The bipolar plate assemblies and MEAs are stacked alternately in the order of "bipolar plate assembly → MEA → bipolar plate assembly → ...", rotating 180° around the central axis of each additional bipolar plate assembly. After stacking, end plates are used for clamping, with the clamping force controlled between 1.2-1.8 MPa to ensure that the contact resistance between the bipolar plate assembly and the MEA meets the usage requirements, while also allowing the sealing ring to deform sufficiently for a reliable seal. This invention does not use a separate cooling plate, which reduces the complexity of the stacking process and significantly increases the volumetric power density of the fuel cell stack.

[0052] The following is a specific example to illustrate this.

[0053] 1) The designed closed-loop air-cooled electrode plate has a length and width of 200mm x 65mm, and the thickness of the anode and cathode electrode plates is 0.4mm and 0.3mm, respectively.

[0054] 2) The processed monopolar plates are welded (laser power 200W, welding speed 40mm / s, focal distance 0.6mm, weld width 0.25mm, weld depth 0.03mm) and sealed (coating thickness 0.1mm; pressure 0.3MPa, holding time 30s; temperature 100℃, curing time 120min) according to the above process to prepare bipolar plates;

[0055] 3) Stack bipolar plates and membrane electrode assemblies to prepare an air-cooled fuel cell stack.

[0056] 4) The test results of this embodiment are shown in the following table and Figure 7 As shown, compared with traditional air-cooled fuel cell stacks, both performance and core volumetric power density are significantly improved.

[0057]

[0058] It should be understood that the above detailed description of the technical solutions of the present invention with reference to optimized embodiments is illustrative and not restrictive. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art, any modifications to the technical solutions described in the embodiments or equivalent substitutions of some technical features without departing from the concept of the present invention should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.

Claims

1. A closed air-cooled fuel cell stack, characterized by, The battery stack includes a bipolar plate structure, and the bipolar plates are sealed by a sealing ring. The specific structure is as follows: the battery stack consists of a cathode plate, an anode plate, and two sets of upper and lower sealing rings, wherein the upper and lower sealing rings are made of hydrogen-resistant rubber; the upper and lower sealing rings have the same structure, and to ensure the simplicity of sealing, the upper sealing ring is installed by rotating 180° relative to the lower sealing ring around the central axis of the electrode plate, and after rotation, the sealing lips of the sealing rings are completely aligned. The electrode plate is provided with an air flow channel and a cooling flow channel, and an air manifold is provided between the air inlet and the air flow channel and the cooling flow channel on the bipolar plate.

2. A closed air-cooled fuel cell stack as claimed in claim 1, wherein The hydrogen-resistant rubber is EPDM or fluororubber, and has a Shore hardness of 60-70HA and a temperature range of -40℃ to 120℃.

3. The closed air-cooled fuel cell stack of claim 1 wherein, The bipolar plate is made of 316L stainless steel or titanium alloy TA2 substrate, and the surface of the substrate is formed by stamping to form air manifolds, air channels and cooling channels.

4. The closed air-cooled fuel cell stack as claimed in claim 1 or 3, wherein The air manifold is located at the edge of the electrode plate as the main air inlet, and its inner wall is provided with a guide protrusion to achieve air diversion and guidance; the cross-section is rectangular or circular with a cross-sectional area of ​​8-50 mm²; the height of the guide protrusion is 0.3-0.5 mm.

5. The closed air-cooled fuel cell stack as claimed in claim 1 or 3, wherein The airflow channel is a direct flow channel or a serpentine flow channel, and both ends of the flow channel are connected to the exhaust manifold at the edge of the electrode plate; the airflow channel has a groove width of 0.8-1.2mm, a ridge width of 0.6-1.0mm, and a depth of 0.5-0.8mm.

6. The closed air-cooled fuel cell stack as claimed in claim 1 or 3, wherein The air entering through the manifold is split into the cooling channel and the air channel in a volume fraction of 60-70%:30-40%.

7. The closed air-cooled fuel cell stack of claim 1 wherein, Sealing bosses are provided in corresponding areas of the anode plate and cathode plate, which cooperate with the weld to form an isolation barrier between the hydrogen chamber and the cooling channel; the height of the sealing bosses is 0.2-0.3mm and the width is 1.0-1.5mm.

8. The method for preparing the closed-loop air-cooled fuel cell stack according to any one of claims 1 to 7, characterized in that: Take a cathode plate, an anode plate, and two sets of sealing rings, with the upper and lower sealing rings having the same structure. To ensure the simplicity of sealing, the upper sealing ring is installed by rotating it 180° relative to the lower sealing ring around the central axis of the electrode plate. After rotation, the sealing lips of the sealing rings are completely aligned. The upper and lower sealing rings have the same structure. To ensure the simplicity of sealing, the upper sealing ring is installed by rotating 180° relative to the lower sealing ring around the central axis of the electrode plate. After rotation, the sealing lips of the sealing rings are completely aligned, so that the upper and lower sealing rings form a continuous sealing surface in the bipolar plate assembly, covering the boundaries of the hydrogen chamber, air manifold, and cooling channel. Only 2 sets of sealing rings are needed to achieve multi-chamber isolation. Specifically, the steps include the following: (1) The anode and cathode plates are assembled into bipolar plates by laser welding. The laser power is 150-250W, the welding speed is 30-50mm / s, the focal distance is 0.5-1.0mm, the weld width is 0.2-0.4mm, and the weld depth is 0.3-0.5mm. (2) The adhesive for bonding the electrode plate and the sealing ring is preferably liquid silicone or epoxy resin with high viscosity. Before bonding, the surface of the bipolar plate sealing groove needs to be degreased, the adhesive is coated on the inner wall of the sealing groove, the sealing ring is pasted on the surface of the sealing groove and pressed together, and finally cured and formed. (3) After the bipolar plates are prepared, they are stacked with the membrane electrode assembly to form an air-cooled fuel cell stack: the bipolar plate assembly and the membrane electrode assembly (MEA) are stacked alternately. The stacking order is bipolar plate assembly, MEA, and bipolar plate assembly stacked in sequence. When each new bipolar plate assembly is added, it is rotated 180° around the central axis of the plate. After stacking, the end plates are pressed together. The pressing force is controlled at 1.2-1.8 MPa to ensure that the contact resistance between the bipolar plate assembly and the MEA meets the requirements for use, and at the same time, the sealing ring is fully deformed to achieve reliable sealing.

9. The preparation method according to claim 8, characterized in that, The laser welding is a fiber laser; the wavelength of the laser is 1064nm; the degreasing is performed by ultrasonic cleaning with anhydrous ethanol for 10-15 minutes and drying at 60-80℃; the adhesive coating thickness is 0.1-0.2mm, uniformly covering the inner wall of the sealing groove.

10. The preparation method according to claim 8, characterized in that, The pressing pressure is 0.2-0.3 MPa, and the holding time is 30-60 s; the curing temperature is 80-100℃, and the curing time is 120-180 min.

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