A metal bipolar plate structure for a cathode closed hydrogen fuel cell stack

Abstract

This invention discloses a metal bipolar plate structure for a cathode closed-loop hydrogen fuel cell stack. In this structure, both the anode and cathode plates employ a U-shaped flow field. The inlet and outlet of the reactant gas are located on the same edge of the flow field and are physically adjacent. Due to the proximity of the inlet (low water concentration) and outlet (high water concentration), water is guided to spontaneously and in reverse from the high humidity region to the low humidity region within the membrane electrode plane, achieving passive self-balancing of moisture within the cathode closed-loop stack. Thus, this structure transforms the passive mode of "relying on pressure difference for longitudinal drainage" into an active mode of "using concentration gradient to drive lateral water balance." This concept perfectly aligns with the physical essence of a cathode closed-loop system where "moisture is a circulating variable within the closed system," representing a fundamental innovation for this specific application scenario.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fuel cell technology, specifically to a metal bipolar plate structure for a cathode closed-circuit hydrogen fuel cell stack, and particularly to a bipolar plate integration scheme that fundamentally solves the unique dry / flooding contradiction of cathode closed-circuit stacks by achieving passive circulation and self-balancing of water in the horizontal plane of the membrane electrode through an innovative "U-shaped flow field design with inlet and outlet on the same side". Background Technology

[0002] Based on the way air flows through the cathode, air-cooled hydrogen fuel cells are mainly divided into two configurations: open cathode and closed cathode. Their hydrothermal management strategies and bipolar plate design requirements are quite different.

[0003] The advantages and disadvantages of open-cathode, air-cooled hydrogen fuel cells are as follows: Advantages: The cathode air is directly taken from the environment and discharged back into the environment, resulting in an extremely high airflow rate. This provides extremely strong forced convection heat dissipation and water vapor removal capabilities. The water generated in the reaction can be quickly carried away by a large amount of excess air, making it difficult for liquid water to accumulate (flooding) in the flow channel.

[0004] Disadvantages: The huge airflow rate results in extremely low and uncontrollable absolute humidity of the inlet air, which can easily cause excessive drying of the proton exchange membrane in the inlet area of ​​the membrane electrode assembly (MEA), leading to membrane cracking, decreased proton conductivity, and performance degradation. At the same time, the high-flow-rate air compressor consumes a lot of power, significantly reducing the system's net output efficiency.

[0005] The advantages and disadvantages of a closed-cathode, air-cooled hydrogen fuel cell are as follows: advantage: The cathode reactant gas and cooling gas are separated, with the amount of cathode reactant gas being less than 2% of the total air intake. This allows for thorough purification of the cathode reactant gas with minimal power consumption. The small amount of reactant gas intake avoids water loss and drying of the membrane electrode assembly (MEA) caused by large air volumes, which can increase the power density of the MEA by more than 50% and reduce the possibility of mechanical failure of the MEA, thereby significantly improving the lifespan of the air-cooled fuel cell.

[0006] Disadvantages: In a closed system, the water produced in the reaction cannot be discharged to the outside of the system, but instead accumulates continuously in the closed loop. This leads to two prominent problems: Extreme longitudinal humidity gradient: From the inlet to the outlet of the flow channel, the absolute humidity of the air increases sharply along the way, and the outlet is close to or reaches saturation. This causes the membrane electrode to be subjected to a huge moisture gradient along the gas flow direction, resulting in uneven performance and material degradation. The traditional "drainage" logic of flow fields fails: Although traditional flow channels (such as Z-shaped or serpentine flow channels) can use pressure difference to "push" liquid water towards the outlet, their design logic is to discharge water from the flow channel. In a closed system, water cannot be discharged from the system. The water pushed towards the outlet actually exacerbates the flooding of the gas diffusion layer (GDL) and flow channel at the outlet, severely hindering gas transmission. Meanwhile, the inlet area remains dry because water cannot be effectively transported. The contradiction of "too dry at the inlet and too flooded at the outlet" is amplified and solidified in the cathode closed system.

[0007] The traditional Z-type / serpentine flow channel bipolar plates currently used in closed-cell cathode reactors inherently contradict the design concept of "pushing water to the outlet" from the fundamental physical requirement of closed systems that "water has no external outlet and urgently needs internal balance." Therefore, there is an urgent need for a novel bipolar plate structure specifically designed for closed-cell cathode operation that can actively guide and realize the lateral redistribution and recycling of water within the active area plane of the membrane electrode. Summary of the Invention

[0008] To address the problems existing in the prior art, especially the inherent design flaws of traditional Z-shaped / serpentine flow channels when used in closed-cell cathode fuel cell stacks, this invention provides a metal bipolar plate structure for closed-cell cathode hydrogen fuel cell stacks. This structure abandons the traditional approach of "longitudinal discharge" of water and instead innovatively guides water to spontaneously and in reverse from the high humidity area to the low humidity area within the membrane electrode plane. This achieves passive self-balancing of moisture inside the closed-cell cathode stack without relying on an external humidifier, effectively solving problems such as uneven performance, local hot spots, and accelerated membrane electrode degradation caused by large humidity gradients. The technical solution adopted to achieve the above-mentioned objective of the present invention is as follows: a metal bipolar plate structure for a cathode closed-loop hydrogen fuel cell stack, characterized in that it includes an anode seal, an anode plate, a cooling plate, a cathode plate, and a cathode seal. The anode plate, cooling plate, and cathode plate are sequentially and tightly fitted together to form a sandwich structure. The anode seal and the cathode seal are respectively disposed on both sides of the sandwich structure. The anode seal seals the periphery of the anode plate, and the cathode seal seals the periphery of the cathode plate. Furthermore, the anode seal and the cathode seal respectively seal the two sides of the cooling plate where the non-cooling fluid inlet and outlet are located. One side of the anode plate... The anode plate has an anode inlet and an anode outlet on its respective edge. The anode plate flow field area is provided with anode baffles, which divide the anode plate flow field area into a U-shaped anode flow field area. The anode inlet and anode outlet are located on both sides of the anode baffles. The cathode plate has a cathode inlet and a cathode outlet on one side edge. The cathode plate flow field area is provided with cathode baffles, which divide the cathode plate flow field area into a U-shaped cathode flow field area. The cathode inlet and cathode outlet are located on both sides of the cathode baffles. The inlet and outlet areas of the anode plate and the cathode plate are located on both sides outside the non-cooling fluid inlet and outlet areas on the cooling plate. The anode sealing component has two first through holes on its sealing cooling plate portion. The anode sealing component's sealing cooling plate portion is tightly fitted with the cathode plate's inlet and outlet areas, and the two first through holes are respectively connected to the cathode inlet and cathode outlet. The cathode sealing component has two second through holes on its sealing cooling plate portion. The cathode sealing component's sealing cooling plate portion is tightly fitted with the anode plate's inlet and outlet areas, and the two second through holes are respectively connected to the anode inlet and anode outlet.

[0009] The anode flow field region has a symmetrical structure, including an anode inlet-side transition region, an anode flow channel region, and an anode outlet-side transition region. The anode inlet is connected to the inlet end of the anode flow channel region through the anode inlet-side transition region, and the anode outlet is connected to the outlet end of the anode flow channel region through the anode outlet-side transition region. The cathode flow field region has a symmetrical structure and includes a cathode inlet-side transition region, a cathode flow channel region, and a cathode outlet-side transition region. The cathode inlet is connected to the inlet end of the cathode flow channel region through the cathode inlet-side transition region, and the cathode outlet is connected to the outlet end of the cathode flow channel region through the cathode outlet-side transition region.

[0010] The anode inlet-side transition zone, anode outlet-side transition zone, cathode inlet-side transition zone, and cathode outlet-side transition zone are all formed by a flow-equalizing lattice of multiple dot-shaped protrusions arranged in an array.

[0011] The anode flow channel region includes an anode inlet side branch region, an anode reflux region, and an anode outlet side branch region. The anode inlet side branch region includes several parallel anode inlet side trenches. The anode reflux region includes a first anode lattice reflux region, an anode reflux channel region, and a second anode lattice reflux region. The anode outlet side branch region includes several parallel anode outlet side trenches. The anode inlet side trenches are parallel to the cathode outlet side trenches. The first anode lattice reflux region is formed by several arrayed dot-shaped protrusions. The anode reflux channel region is formed by several parallel anode reflux trenches, which are perpendicular to the anode inlet side trenches. The second anode lattice reflux region is formed by several arrayed dot-shaped protrusions. The outlet end of the anode inlet side branch region is connected to the inlet end of the anode reflux channel region through the first anode lattice reflux region. The inlet end of the anode outlet side branch region is connected to the outlet end of the anode reflux channel region through the second anode lattice reflux region. The cathode flow channel region includes a cathode inlet side branch region, a cathode recirculation region, and an anode outlet side branch region. The cathode inlet side branch region includes several parallel cathode inlet side trenches. The cathode recirculation region includes a first cathode lattice recirculation region, a cathode recirculation channel region, and a second cathode lattice recirculation region. The cathode outlet side branch region includes several parallel cathode outlet side trenches. The cathode inlet side trenches are parallel to the cathode outlet side trenches. The first cathode lattice recirculation region is formed by several arrayed dot-shaped protrusions. The cathode recirculation channel region is formed by several parallel cathode recirculation trenches, which are perpendicular to the cathode inlet side trenches. The second cathode lattice recirculation region is formed by several arrayed dot-shaped protrusions. The outlet end of the cathode inlet side branch region is connected to the inlet end of the cathode recirculation channel region through the first cathode lattice recirculation region. The inlet end of the cathode outlet side branch region is connected to the outlet end of the cathode recirculation channel region through the second cathode lattice recirculation region.

[0012] The anode inlet side branch area, anode recirculation area, anode outlet side branch area, cathode inlet side branch area, cathode recirculation area, and anode outlet side branch area are all square. The anode first lattice recirculation area, anode second lattice recirculation area, cathode first lattice recirculation area, and cathode second lattice recirculation area are all right-angled triangles. The anode recirculation channel area and the cathode recirculation channel area are all isosceles triangles. The hypotenuses of the anode first lattice recirculation area and the anode second lattice recirculation area are connected to the two isosceles edges of the anode recirculation channel area, respectively. The hypotenuses of the cathode first lattice recirculation area and the cathode second lattice recirculation area are connected to the two isosceles edges of the cathode recirculation channel area, respectively.

[0013] The anode inlet, anode outlet, cathode inlet, cathode outlet, first through hole, and second through hole are all square strips. The lengths of the anode inlet, anode outlet, cathode inlet, cathode outlet, first through hole, and second through hole are matched with the length of the transition zone on the anode inlet side and the width of the branch zone on the anode inlet side.

[0014] The anode sealing element includes an anode sealing ring and an anode sealing gasket. One side of the anode sealing ring is connected to one side of the anode sealing gasket. The anode sealing ring seals the periphery of the anode plate. Two first through holes are provided on the anode sealing gasket. The anode sealing gasket is tightly fitted to the inlet and outlet areas of the cathode plate. The cathode seal includes a cathode sealing ring and a cathode sealing gasket. One side of the cathode sealing ring is connected to one side of the cathode sealing gasket. The cathode sealing ring seals the periphery of the cathode plate. Two second through holes are provided on the cathode sealing gasket. The cathode sealing gasket fits tightly with the inlet and outlet areas of the anode plate. The anode sealing gasket and the cathode sealing gasket are located on both sides of the non-cooling fluid inlet and outlet areas on the cooling plate, and the anode sealing gasket and the cathode sealing gasket seal the two sides of the non-cooling fluid inlet and outlet areas on the cooling plate, respectively.

[0015] The anode plate has an anode sealing groove on its periphery, and an anode sealing ring is installed on the anode sealing groove. The end face of the anode sealing ring facing away from the anode plate has two parallel sealing ribs. The cathode plate has a cathode sealing groove on its periphery, and a cathode sealing ring is installed on the cathode sealing groove. The end face of the cathode sealing ring facing away from the cathode plate is a plane.

[0016] The anode sealing ring and the anode sealing gasket are integrally formed to form an anode sealing component, and the cathode sealing ring and the cathode sealing gasket are integrally formed to form a cathode sealing component.

[0017] The cooling plate is corrugated.

[0018] Compared with the prior art, the beneficial effects and advantages of the present invention are as follows: 1. In this metal bipolar plate structure, both the anode and cathode plates employ a U-shaped flow field. The inlet and outlet of the reactant gas are located on the same edge of the flow field and are physically adjacent. Due to the proximity of the inlet (low water concentration) and outlet (high water concentration), water is guided to spontaneously transport from the high humidity region to the low humidity region within the membrane electrode plane, achieving passive self-balancing of moisture within the closed-loop cathode stack. This structure transforms the passive mode of "relying on pressure difference for longitudinal drainage" into an active mode of "using concentration gradient to drive lateral water balance." This concept perfectly aligns with the physical essence of a closed-loop cathode system where "moisture is a circulating variable within the closed system," representing a fundamental innovation for this specific application scenario.

[0019] 2. This structure significantly reduces or even reverses the water content gradient on the membrane electrode plane, enabling the proton exchange membrane to operate in a more uniform and fully hydrated state. This not only improves the stability and consistency of the output voltage but also greatly alleviates the expansion-contraction stress caused by periodic wet-dry cycles, thereby delaying the mechanical fatigue failure of the proton exchange membrane by a factor of two and significantly extending the lifespan of the fuel cell stack—an effect that traditional flow channel designs cannot achieve.

[0020] 3. The anode seal of this structure adopts a dual-redundant seal, providing double protection for hydrogen and ensuring a high level of safety. The cathode seal uses a wide-face seal, greatly reducing the alignment accuracy requirements and enabling large-scale automated assembly of the fuel cell stack, significantly improving production efficiency and first-pass yield. Furthermore, the required assembly clamping force is lower, which is beneficial for lightweight design of the fuel cell stack end plates and structural components.

[0021] 4. The structure uses a corrugated cooling plate, which significantly increases the contact area (convective heat transfer) with the high-temperature and high-humidity air flowing over its surface, thereby enhancing heat dissipation.

[0022] 5. This structure highly integrates the three major functions of flow field, heat dissipation, and sealing into a simple sandwich structure, with fewer components and a simple and user-friendly assembly process. This directly results in weight reduction, lower material costs, and improved production efficiency and product consistency, providing a highly competitive hardware foundation for the commercial application of closed-cathode fuel cells. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a metal bipolar plate structure used in a cathode-closed hydrogen fuel cell stack.

[0024] Figure 2 for Figure 1 Top view.

[0025] Figure 3 for Figure 2 Exploded view.

[0026] Figure 4 for Figure 1 The main view.

[0027] Figure 5 This is a schematic diagram of the anode plate.

[0028] Figure 6 for Figure 5 The main view.

[0029] Figure 7 This is a schematic diagram of the structure of the anode seal.

[0030] Figure 8 for Figure 7 The main view.

[0031] Figure 9 This is a schematic diagram of the cooling plate.

[0032] Among them, 1-anode seal, 2-anode sealing ring, 3-anode sealing pad, 4-sealing rib, 5-first through hole, 6-anode plate, 7-anode inlet, 8-anode outlet, 9-anode partition, 10-anode flow field area, 11-anode inlet side transition area, 12-dot protrusion, 13-anode flow channel area, 14-anode outlet side transition area, 15-anode inlet side branch area, 16-anode reflux area, 17-anode outlet side branch area, 18-anode inlet side groove, 19-anode first lattice reflux area, 20-anode reflux channel area, 21-anode second lattice reflux area, 22-anode outlet side groove, 23-anode reflux groove, 24-cooling plate, 25-cathode plate, 26-cathode seal, 27-anode sealing groove.

[0033] Since the anode plate and cathode plate have the same structure, and the anode seal and cathode seal have basically similar structures, only the anode plate and anode seal are marked. Detailed Implementation

[0034] 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. 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.

[0035] The structure of the metal bipolar plate for a cathode closed-loop hydrogen fuel cell stack provided in this embodiment is as follows: Figure 1-4 As shown, the assembly includes an anode seal 1, an anode plate 6, a cooling plate 24, a cathode plate 25, and a cathode seal 26. The anode plate 6, cooling plate 24, and cathode plate are all made of metal. They are symmetrical structures, and all are square in shape. The lengths and widths of the anode plate 6, cooling plate 24, and cathode plate 26 are matched. The anode plate 6, cooling plate 24, and cathode plate are sequentially and tightly fitted together to form a sandwich structure. The anode plate 6 is fixed to the cooling plate 24, and the cooling plate 24 is fixed to the cathode plate by welding.

[0036] like Figure 5-6 As shown, an anode inlet 7 and an anode outlet 8 are symmetrically arranged on one side edge of the anode plate 6 in the width direction. Both the anode inlet 7 and the anode outlet 8 are square strips. An anode baffle 9 is provided in the flow field region of the anode plate 6, which divides the flow field region of the anode plate 6 into a U-shaped anode flow field region 10. The anode inlet 7 and the anode outlet 8 are located on both sides of the anode baffle 9, and are separated by the anode baffle 9.

[0037] The anode flow field region 10 has a symmetrical structure and includes an anode inlet-side transition region 11, an anode flow channel region 13, and an anode outlet-side transition region 14. Both the anode inlet-side transition region 11 and the anode outlet-side transition region 14 are flow-equalizing lattices formed by a row of dotted protrusions. The anode inlet-side transition region 11, by incorporating a row of dotted protrusions 12, diverts and disturbs the hydrogen gas entering from the anode inlet, aiming to reduce pressure drop while enhancing mass transfer efficiency, thereby achieving uniform hydrogen distribution within the active region. The anode outlet-side transition region 14, by incorporating a row of dotted protrusions 12, smoothly and uniformly collects and guides the fluid flowing out of the reaction zone to the anode outlet, reducing local pressure loss while preventing gas-liquid blockage.

[0038] The anode flow channel region 13 includes an anode inlet side branch region 15, an anode reflux region 16, and an anode outlet side branch region 17. The anode inlet side branch region 15 is square and includes several parallel anode inlet side grooves 18, which are parallel to the length direction of the anode plate 6. The anode inlet 7 is connected to the inlet ends of each anode inlet side groove in the anode inlet side branch region 15 through the flow equalization lattice of the anode inlet side transition region 11.

[0039] The anode reflux region 16 includes a first anode lattice reflux region 19, an anode reflux channel region 20, and a second anode lattice reflux region 21. Both the first anode lattice reflux region 19 and the second anode lattice reflux region 21 are right-angled triangles, while the anode reflux channel region 20 is an isosceles triangle. The first anode lattice reflux region 19 is formed by a plurality of arrayed dot-shaped protrusions 12. The anode reflux channel region 20 is formed by a plurality of parallel anode reflux grooves 23, which are perpendicular to the anode inlet side groove 18. The second anode lattice reflux region 21 is formed by a plurality of arrayed dot-shaped protrusions 12. A first lattice reflux region 19 and a second lattice reflux region 21 are set on both sides of the anode reflux region 16. By setting arrayed dot-shaped protrusions, hydrogen is distributed in a secondary manner. This avoids the problem of inconsistent hydrogen path lengths in the U-shaped flow field, thereby avoiding the problems of uneven hydrogen flow distribution, local hydrogen starvation, and current density imbalance that could lead to battery performance degradation or even component damage.

[0040] The outlet ends of each anode inlet side trench 18 in the anode inlet side branch area 15 are connected to the right-angle edge of the anode first lattice reflux area 19, and the oblique edges of the anode first lattice reflux area 19 and the anode second lattice reflux area 21 are connected to the two isosceles edges of the anode reflux channel area 20, respectively.

[0041] The anode outlet side branch area 17 is square and includes several parallel anode outlet side trenches 22. The anode inlet side trenches 22 are parallel to the cathode outlet side trenches 18. The inlet end of each anode outlet side trench 22 in the anode outlet side branch area 17 is connected to the right-angled edge of the anode second lattice recirculation region 21. The anode outlet 8 is connected to the outlet end of each anode outlet side trench 22 in the anode outlet side branch area 17 through the flow equalization lattice of the anode outlet side transition region 14.

[0042] A cathode plate 25 has a symmetrically arranged cathode inlet and cathode outlet on one side edge along its width direction. Both the cathode inlet and cathode outlet are square strips. An anode baffle is provided within the flow field region of the cathode plate, dividing the flow field region into a U-shaped cathode flow field region. The cathode inlet and cathode outlet are located on opposite sides of the anode baffle, and are separated by the cathode baffle.

[0043] The cathode flow field region has a symmetrical structure, comprising a cathode inlet-side transition zone, a cathode flow channel zone, and a cathode outlet-side transition zone. Both the cathode inlet-side and cathode outlet-side transition zones are flow-equalizing lattices formed by a row of dot-like protrusions. The cathode inlet-side transition zone, through the arrangement of these protrusions, diverts and disturbs the oxygen or air entering from the cathode inlet. This aims to optimize fluid distribution and enhance mass transfer efficiency, particularly addressing the issue of water retention generated during the reaction, thereby ensuring that oxygen can reach the catalyst layer uniformly and smoothly to participate in the reaction. The cathode outlet-side transition zone, also with a row of protrusions, disturbs the flow field and alters the pressure distribution, promoting the efficient discharge and stripping of reaction products (such as liquid water), preventing their accumulation at the outlet and blockage of the flow channel, thus ensuring the stability of the battery operation.

[0044] The cathode flow channel region includes a cathode inlet side branch region, a cathode recirculation region, and a cathode outlet side branch region. The cathode inlet side branch region is square and includes several parallel cathode inlet side grooves, which are parallel to the length direction of the cathode plate. The cathode inlet is connected to the inlet ends of each cathode inlet side groove in the cathode inlet side branch region through the flow equalization lattice of the cathode inlet side transition region.

[0045] The cathode reflow region includes the first cathode lattice reflow region, the cathode reflow channel region, and the second cathode lattice reflow region. The first cathode lattice reflow region and the second cathode lattice reflow region are both right-angled triangles, while the cathode reflow region is an isosceles triangle.

[0046] The first cathode lattice recirculation zone is formed by several arrayed dot-shaped protrusions, and the cathode recirculation channel zone is formed by several parallel cathode recirculation channels, which are perpendicular to the cathode inlet side channel. The second cathode lattice recirculation zone is also formed by several arrayed dot-shaped protrusions. By setting the first and second cathode lattice recirculation zones on both sides of the cathode recirculation zone, and by using arrayed dot-shaped protrusions for secondary distribution of oxygen or air, the problem of inconsistent oxygen or air path lengths in the U-shaped flow field can be avoided. This prevents uneven oxygen or air distribution and pressure loss, leading to local reactant "starvation," unbalanced current density distribution, and water management failure (such as localized flooding), which can significantly degrade the overall battery performance.

[0047] The outlet ends of each cathode inlet-side trench in the cathode inlet-side branch area are connected to the right-angled edge of the first lattice recirculation area of ​​the anode, and the inclined edges of the first lattice recirculation area of ​​the cathode and the second lattice recirculation area of ​​the cathode are connected to the two isosceles edges of the cathode recirculation channel area, respectively.

[0048] The cathode outlet side branch area is square in shape and includes several parallel cathode outlet side trenches. The cathode inlet side trenches are parallel to the cathode outlet side trenches. The inlet end of each cathode outlet side trench in the cathode outlet side branch area is connected to the right-angled edge of the cathode second lattice recirculation region. The cathode outlet is connected to the outlet end of each cathode outlet side trench in the cathode outlet side branch area through the flow equalization lattice of the cathode outlet side transition region.

[0049] The working principle and physical mechanism of the U-shaped flow field of the cathode plate in this metal bipolar plate structure are as follows: In the closed-loop cathode circulation, relatively dry circulating air enters from the inlet, flows along the "U"-shaped path and participates in the electrochemical reaction, becoming nearly saturated humid air by the time it reaches the outlet. Due to the proximity of the inlet (low water concentration) and the outlet (high water concentration), an extremely strong transverse water concentration (or hydrochemical potential) gradient is formed in the plane containing the gas diffusion layer (GDL) and the catalyst layer, pointing from the outlet side to the inlet side. This gradient becomes the core and sole driving force for moisture transport.

[0050] Achieving passive water balance: Driven by the aforementioned strong lateral water concentration gradient, the water (including steam and liquid water) generated and accumulated in the catalyst layer on the outlet side is spontaneously and laterally transported to the area below the inlet side through the pores of the gas diffusion layer (GDL), primarily via capillary condensation and reverse diffusion. This process achieves a triple benefit: "In-situ passive humidification of the inlet area: effectively wets the proton exchange membrane below the inlet, prevents the membrane from drying out, and reduces ohmic loss; "In-situ passive drainage" of the outlet area: reduces the accumulation of liquid water in the outlet side diffusion layer and flow channel, alleviates flooding, and improves gas mass transfer; The membrane electrode plane achieves "global water content homogenization," significantly reducing the water gradient across the entire active region. This design concept of "guiding internal water recycling" is the complete opposite of the traditional Z-shaped flow channel approach of "pushing water vertically out," and it is an effective solution to the fundamental contradiction of the cathode closed system.

[0051] like Figure 9 As shown, the cooling plate 24 is corrugated and is formed by rolling a thin metal strip. In a closed-loop air-cooled fuel cell stack, the main cooling medium is the cathode air itself, which is heated and humidified by the stack and circulates in the closed loop. The core function of this cooling plate is to significantly increase the contact area (convective heat transfer) with the high-temperature, high-humidity air flowing over its surface, thereby enhancing heat dissipation. In addition, the completely open design of the cooling plate eliminates the need for inlets and outlets and their welding seals required by traditional independent cooling channels from a physical structure perspective. For a closed-loop system requiring long-term, absolute airtightness, this fundamentally eliminates the risk of leakage at this point, greatly improves the inherent reliability of the system, and avoids the additional costs associated with welding quality inspection and rework.

[0052] The inlet and outlet areas of the anode plate 6 and the cathode plate 25 are located on both sides of the non-cooling fluid inlet and outlet areas on the cooling plate 24. The inlet and outlet areas of the anode plate 6 and the cathode plate 25, as well as the cooling fluid inlet and outlet areas of the cooling plate 24, are located around the cooling plate 24. This allows the fluid flow direction of the anode plate 6 or the cathode plate 25 to intersect with the cooling fluid flow direction of the cooling plate, further increasing the heat dissipation effect.

[0053] like Figure 7-8 As shown, the anode seal 1 is generally square in shape and includes an anode sealing ring 2 and an anode sealing gasket 3. One edge of the anode sealing ring 2 is connected to one edge of the anode sealing gasket 3, and the anode sealing ring 2 and the anode sealing gasket 3 are integrally formed. An anode sealing groove 27 is provided on the periphery of the anode plate 3, and the anode sealing ring 2 is installed on the anode sealing groove 27. Two parallel sealing ribs 4 are provided on the end face of the anode sealing ring 2 facing away from the anode plate. Two first through holes 5 are symmetrically provided on the anode sealing gasket 3. The first through holes 5 are square strips.

[0054] The cathode seal 26 is generally square in shape and includes a cathode sealing ring and a cathode sealing gasket. One edge of the cathode sealing ring is connected to one edge of the cathode sealing gasket, and the cathode sealing ring and cathode sealing gasket are integrally formed. A cathode sealing groove is provided on the periphery of the cathode plate, and the cathode sealing ring is installed in the cathode sealing groove. The end face of the cathode sealing ring facing away from the cathode plate is flat. Two second through holes are symmetrically provided on the cathode sealing gasket, and the second through holes are square strips.

[0055] The anode sealing ring 2 adopts a design with two parallel independent sealing ribs (i.e., "double-line sealing"). During fuel cell stack press-fitting, only a small unit area pressure is required to effectively deform the two sealing ribs, forming two independent sealing lines. The advantages of this design are: 1) It reduces the requirements for the overall assembly clamping force of the fuel cell stack, which is conducive to fuel cell stack weight reduction; 2) It forms a redundant seal, which greatly enhances the safety factor and long-term reliability of the hydrogen seal, and the accidental failure of a single seal will not lead to leakage.

[0056] The cathode sealing ring employs a single wide-face planar sealing structure. The main advantage of this design is the significant reduction in alignment accuracy requirements. During the stacking and assembly of bipolar plates and membrane electrode assemblies (MEAs), if both the anode and cathode sides use "double-line sealing," extremely high positioning accuracy is required to ensure that the multiple sealing ribs on both sides are precisely aligned and effectively compressed simultaneously. Otherwise, misalignment can easily lead to localized seal failure. This embodiment replaces the cathode side with a single wide-face seal, significantly relaxing assembly tolerances. This allows for uniform and sufficient compression of the cathode-side sealing interface under conventional manufacturing and assembly precision conditions, achieving a reliable seal. This greatly improves the friendliness of the assembly process and production yield.

[0057] Synergistic advantages: The combination of "highly reliable redundant double-line seal" on the anode side and "highly fault-tolerant and easily assembled wide-face seal" on the cathode side is an optimal design that balances the highest safety standards with the best manufacturability. The two work together to achieve reliable and durable sealing of hydrogen and air without the need for welding between the plates. Moreover, the overall assembly difficulty and precision requirements are significantly lower than the traditional solution with multiple precision seals on both sides.

[0058] The anode sealing gasket 3 and the cathode sealing gasket are located on both sides of the non-cooling fluid inlet and outlet areas on the cooling plate 24, respectively, and seal the two sides of the non-cooling fluid inlet and outlet areas on the cooling plate 24. The anode sealing gasket 3 is tightly fitted to the inlet and outlet areas of the cathode plate 25, and the two first through holes 5 are respectively connected to the cathode inlet and cathode outlet. The anode sealing gasket 3 provides a good seal for the inlet and outlet areas of the cathode plate 25, eliminating the need for welding. The cathode sealing gasket is tightly fitted to the inlet and outlet areas of the cathode plate, and the two second through holes are respectively connected to the anode inlet 7 and anode outlet 8. The cathode sealing gasket provides a good seal for the inlet and outlet areas of the cathode plate 6, eliminating the need for welding. The first through hole 5, the second through hole, the anode inlet 7, the anode outlet 8, the cathode inlet, and the cathode outlet have the same planar dimensions, but their depths may differ.

Claims

1. A metal bipolar plate structure for a cathode closed hydrogen fuel cell stack, characterized by: The device includes an anode seal, an anode plate, a cooling plate, a cathode plate, and a cathode seal. The anode plate, cooling plate, and cathode plate are tightly fitted together to form a sandwich structure. The anode seal and cathode seal are respectively located on both sides of the sandwich structure. The anode seal seals the periphery of the anode plate, and the cathode seal seals the periphery of the cathode plate. The anode seal and cathode seal also seal the two sides of the cooling plate where the non-cooling fluid inlet and outlet are located. An anode inlet and an anode outlet are respectively provided on one side edge of the anode plate. An anode baffle is provided in the flow field area of ​​the anode plate, which divides the flow field area of ​​the anode plate into a U-shaped anode flow field area. The anode inlet and anode outlet are respectively located on both sides of the anode baffle. A cathode inlet and a cathode outlet are respectively provided on one side edge of the cathode plate. A cathode baffle is provided in the flow field area of ​​the cathode plate, which divides the flow field area of ​​the cathode plate into a U-shaped cathode flow field area. The cathode inlet and cathode outlet are respectively located on both sides of the cathode baffle. The inlet and outlet areas of the anode plate and the cathode plate are respectively located outside the two sides of the non-cooling fluid inlet and outlet areas on the cooling plate. The anode sealing component has two first through holes on its sealing cooling plate portion. The anode sealing component's sealing cooling plate portion is tightly fitted with the cathode plate's inlet and outlet areas, and the two first through holes are respectively connected to the cathode inlet and cathode outlet. The cathode sealing component has two second through holes on its sealing cooling plate portion. The cathode sealing component's sealing cooling plate portion is tightly fitted with the anode plate's inlet and outlet areas, and the two second through holes are respectively connected to the anode inlet and anode outlet.

2. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack according to claim 1, characterized by: The anode flow field region has a symmetrical structure, including an anode inlet-side transition region, an anode flow channel region, and an anode outlet-side transition region. The anode inlet is connected to the inlet end of the anode flow channel region through the anode inlet-side transition region, and the anode outlet is connected to the outlet end of the anode flow channel region through the anode outlet-side transition region. The cathode flow field region has a symmetrical structure and includes a cathode inlet-side transition region, a cathode flow channel region, and a cathode outlet-side transition region. The cathode inlet is connected to the inlet end of the cathode flow channel region through the cathode inlet-side transition region, and the cathode outlet is connected to the outlet end of the cathode flow channel region through the cathode outlet-side transition region.

3. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack according to claim 2, characterized by: The anode inlet-side transition zone, anode outlet-side transition zone, cathode inlet-side transition zone, and cathode outlet-side transition zone are all formed by a flow-equalizing lattice of multiple dot-shaped protrusions arranged in an array.

4. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack according to claim 2, characterized by: The anode flow channel region includes an anode inlet side branch region, an anode reflux region, and an anode outlet side branch region. The anode inlet side branch region includes several parallel anode inlet side trenches. The anode reflux region includes a first anode lattice reflux region, an anode reflux channel region, and a second anode lattice reflux region. The anode outlet side branch region includes several parallel anode outlet side trenches. The anode inlet side trenches are parallel to the cathode outlet side trenches. The first anode lattice reflux region is formed by several arrayed dot-shaped protrusions. The anode reflux channel region is formed by several parallel anode reflux trenches, which are perpendicular to the anode inlet side trenches. The second anode lattice reflux region is formed by several arrayed dot-shaped protrusions. The outlet end of the anode inlet side branch region is connected to the inlet end of the anode reflux channel region through the first anode lattice reflux region. The inlet end of the anode outlet side branch region is connected to the outlet end of the anode reflux channel region through the second anode lattice reflux region. The cathode flow channel region includes a cathode inlet side branch region, a cathode recirculation region, and an anode outlet side branch region. The cathode inlet side branch region includes several parallel cathode inlet side trenches. The cathode recirculation region includes a first cathode lattice recirculation region, a cathode recirculation channel region, and a second cathode lattice recirculation region. The cathode outlet side branch region includes several parallel cathode outlet side trenches. The cathode inlet side trenches are parallel to the cathode outlet side trenches. The first cathode lattice recirculation region is formed by several arrayed dot-shaped protrusions. The cathode recirculation channel region is formed by several parallel cathode recirculation trenches, which are perpendicular to the cathode inlet side trenches. The second cathode lattice recirculation region is formed by several arrayed dot-shaped protrusions. The outlet end of the cathode inlet side branch region is connected to the inlet end of the cathode recirculation channel region through the first cathode lattice recirculation region. The inlet end of the cathode outlet side branch region is connected to the outlet end of the cathode recirculation channel region through the second cathode lattice recirculation region.

5. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack of claim 4, wherein: The anode inlet side branch area, anode recirculation area, anode outlet side branch area, cathode inlet side branch area, cathode recirculation area, and anode outlet side branch area are all square. The anode first lattice recirculation area, anode second lattice recirculation area, cathode first lattice recirculation area, and cathode second lattice recirculation area are all right-angled triangles. The anode recirculation channel area and the cathode recirculation channel area are all isosceles triangles. The hypotenuses of the anode first lattice recirculation area and the anode second lattice recirculation area are connected to the two isosceles edges of the anode recirculation channel area, respectively. The hypotenuses of the cathode first lattice recirculation area and the cathode second lattice recirculation area are connected to the two isosceles edges of the cathode recirculation channel area, respectively.

6. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack of claim 4, wherein: The anode inlet, anode outlet, cathode inlet, cathode outlet, first through hole, and second through hole are all square strips. The lengths of the anode inlet, anode outlet, cathode inlet, cathode outlet, first through hole, and second through hole are matched with the length of the transition zone on the anode inlet side and the width of the branch zone on the anode inlet side.

7. The metal bipolar plate structure for a cathode-closed hydrogen fuel cell stack according to claim 1, characterized in that: The anode sealing element includes an anode sealing ring and an anode sealing gasket. One side of the anode sealing ring is connected to one side of the anode sealing gasket. The anode sealing ring seals the periphery of the anode plate. Two first through holes are provided on the anode sealing gasket. The anode sealing gasket is tightly fitted to the inlet and outlet areas of the cathode plate. The cathode seal includes a cathode sealing ring and a cathode sealing gasket. One side of the cathode sealing ring is connected to one side of the cathode sealing gasket. The cathode sealing ring seals the periphery of the cathode plate. Two second through holes are provided on the cathode sealing gasket. The cathode sealing gasket fits tightly with the inlet and outlet areas of the anode plate. The anode sealing gasket and the cathode sealing gasket are located on both sides of the non-cooling fluid inlet and outlet areas on the cooling plate, and the anode sealing gasket and the cathode sealing gasket seal the two sides of the non-cooling fluid inlet and outlet areas on the cooling plate, respectively.

8. The metal bipolar plate structure for a cathode closed-loop hydrogen fuel cell stack according to claim 7, characterized in that: The anode plate has an anode sealing groove on its periphery, and an anode sealing ring is installed on the anode sealing groove. The end face of the anode sealing ring facing away from the anode plate has two parallel sealing ribs. The cathode plate has a cathode sealing groove on its periphery, and a cathode sealing ring is installed on the cathode sealing groove. The end face of the cathode sealing ring facing away from the cathode plate is a plane.

9. The metal bipolar plate structure for a cathode closed hydrogen fuel cell stack of claim 7, wherein: The anode sealing ring and the anode sealing gasket are integrally formed to form an anode sealing component, and the cathode sealing ring and the cathode sealing gasket are integrally formed to form a cathode sealing component.

10. The metal bipolar plate structure for a cathode-closed hydrogen fuel cell stack according to claim 1, characterized in that: The cooling plate is corrugated.

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